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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
…		…
699		796
700	If you have a watcher you never unregister that should not keep C<ev_loop>	797	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	798	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	799	stopping it.
703		800
704	As an example, libev itself uses this for its internal signal pipe: It is	801	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	802	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	803	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	804	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>	805	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,	806	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	807	before, respectively. Note also that libev might stop watchers itself
		808	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		809	in the callback).
711		810
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	812	running when nothing else is active.
714		813
715	struct ev_signal exitsig;	814	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	815	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	816	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	817	evf_unref (loop);
719		818
720	Example: For some weird reason, unregister the above signal handler again.	819	Example: For some weird reason, unregister the above signal handler again.
…		…
744		843
745	By setting a higher I<io collect interval> you allow libev to spend more	844	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,	845	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	846	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	847	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.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
750		851
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	854	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	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		857
757	Many (busy) programs can usually benefit by setting the I/O collect	858	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	859	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	860	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>,	861	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.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
762		867
763	Setting the I<timeout collect interval> can improve the opportunity for	868	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	869	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	870	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	871	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	872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	873	they fire on, say, one-second boundaries only.
769		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
		945
770	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
771		947
772	This function only does something when C<EV_VERIFY> support has been	948	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	949	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	950	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	951	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	952	error and call C<abort ()>.
777		953
778	This can be used to catch bugs inside libev itself: under normal	954	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	958	=back
783		959
784		960
785	=head1 ANATOMY OF A WATCHER	961	=head1 ANATOMY OF A WATCHER
786		962
		963	In the following description, uppercase C<TYPE> in names stands for the
		964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		965	watchers and C<ev_io_start> for I/O watchers.
		966
787	A watcher is a structure that you create and register to record your	967	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	968	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:	969	become readable, you would create an C<ev_io> watcher for that:
790		970
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	972	{
793	ev_io_stop (w);	973	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	974	ev_unloop (loop, EVUNLOOP_ALL);
795	}	975	}
796		976
797	struct ev_loop *loop = ev_default_loop (0);	977	struct ev_loop *loop = ev_default_loop (0);
		978
798	struct ev_io stdin_watcher;	979	ev_io stdin_watcher;
		980
799	ev_init (&stdin_watcher, my_cb);	981	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	983	ev_io_start (loop, &stdin_watcher);
		984
802	ev_loop (loop, 0);	985	ev_loop (loop, 0);
803		986
804	As you can see, you are responsible for allocating the memory for your	987	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,	988	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	989	stack).
		990
		991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		993
808	Each watcher structure must be initialised by a call to C<ev_init	994	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	995	(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	996	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	997	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	998	is readable and/or writable).
813		999
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1000	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	1001	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	1002	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1003	ev_TYPE_init (watcher *, callback, ...) >>.
818		1004
819	To make the watcher actually watch out for events, you have to start it	1005	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	1006	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	1007	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1008	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1009
824	As long as your watcher is active (has been started but not stopped) you	1010	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	1011	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1012	reinitialise it or call its C<ev_TYPE_set> macro.
827		1013
828	Each and every callback receives the event loop pointer as first, the	1014	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	1015	registered watcher structure as second, and a bitset of received events as
830	third argument.	1016	third argument.
831		1017
…		…
889		1075
890	=item C<EV_ASYNC>	1076	=item C<EV_ASYNC>
891		1077
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1078	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1079
		1080	=item C<EV_CUSTOM>
		1081
		1082	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1083	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1084
894	=item C<EV_ERROR>	1085	=item C<EV_ERROR>
895		1086
896	An unspecified error has occurred, the watcher has been stopped. This might	1087	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1088	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	1089	ran out of memory, a file descriptor was found to be closed or any other
…		…
912		1103
913	=back	1104	=back
914		1105
915	=head2 GENERIC WATCHER FUNCTIONS	1106	=head2 GENERIC WATCHER FUNCTIONS
916		1107
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1108	=over 4
921		1109
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1110	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1111
924	This macro initialises the generic portion of a watcher. The contents	1112	This macro initialises the generic portion of a watcher. The contents
…		…
929	which rolls both calls into one.	1117	which rolls both calls into one.
930		1118
931	You can reinitialise a watcher at any time as long as it has been stopped	1119	You can reinitialise a watcher at any time as long as it has been stopped
932	(or never started) and there are no pending events outstanding.	1120	(or never started) and there are no pending events outstanding.
933		1121
934	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1122	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
935	int revents)>.	1123	int revents)>.
936		1124
937	Example: Initialise an C<ev_io> watcher in two steps.	1125	Example: Initialise an C<ev_io> watcher in two steps.
938		1126
939	ev_io w;	1127	ev_io w;
940	ev_init (&w, my_cb);	1128	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1129	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1130
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1131	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1132
945	This macro initialises the type-specific parts of a watcher. You need to	1133	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1134	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1135	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1136	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1149
962	Example: Initialise and set an C<ev_io> watcher in one step.	1150	Example: Initialise and set an C<ev_io> watcher in one step.
963		1151
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1153
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1154	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1155
968	Starts (activates) the given watcher. Only active watchers will receive	1156	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1157	events. If the watcher is already active nothing will happen.
970		1158
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1159	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1160	whole section.
973		1161
974	ev_io_start (EV_DEFAULT_UC, &w);	1162	ev_io_start (EV_DEFAULT_UC, &w);
975		1163
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1165
978	Stops the given watcher if active, and clears the pending status (whether	1166	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1167	the watcher was active or not).
980		1168
981	It is possible that stopped watchers are pending - for example,	1169	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1194	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1195
1008	Change the callback. You can change the callback at virtually any time	1196	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1197	(modulo threads).
1010		1198
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1199	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1200
1013	=item int ev_priority (ev_TYPE *watcher)	1201	=item int ev_priority (ev_TYPE *watcher)
1014		1202
1015	Set and query the priority of the watcher. The priority is a small	1203	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
1020		1208
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1211
1029	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1213	pending.
1031		1214
		1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1216	fine, as long as you do not mind that the priority value you query might
		1217	or might not have been clamped to the valid range.
		1218
1032	The default priority used by watchers when no priority has been set is	1219	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1220	always C<0>, which is supposed to not be too high and not be too low :).
1034		1221
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1223	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1224
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1226
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1049	returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
1050	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1051		1237
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
1054		1254
1055	=back	1255	=back
1056		1256
1057		1257
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1064	member, you can also "subclass" the watcher type and provide your own	1264	member, you can also "subclass" the watcher type and provide your own
1065	data:	1265	data:
1066		1266
1067	struct my_io	1267	struct my_io
1068	{	1268	{
1069	struct ev_io io;	1269	ev_io io;
1070	int otherfd;	1270	int otherfd;
1071	void *somedata;	1271	void *somedata;
1072	struct whatever *mostinteresting;	1272	struct whatever *mostinteresting;
1073	};	1273	};
1074		1274
…		…
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);	1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078		1278
1079	And since your callback will be called with a pointer to the watcher, you	1279	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:	1280	can cast it back to your own type:
1081		1281
1082	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1283	{
1084	struct my_io *w = (struct my_io *)w_;	1284	struct my_io *w = (struct my_io *)w_;
1085	...	1285	...
1086	}	1286	}
1087		1287
…		…
1105	programmers):	1305	programmers):
1106		1306
1107	#include <stddef.h>	1307	#include <stddef.h>
1108		1308
1109	static void	1309	static void
1110	t1_cb (EV_P_ struct ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1311	{
1112	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1314	}
1115		1315
1116	static void	1316	static void
1117	t2_cb (EV_P_ struct ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1318	{
1119	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1122		1425
1123		1426
1124	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1125		1428
1126	This section describes each watcher in detail, but will not repeat	1429	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1455	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1456	required if you know what you are doing).
1154		1457
1155	If you cannot use non-blocking mode, then force the use of a	1458	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1459	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1158		1463
1159	Another thing you have to watch out for is that it is quite easy to	1464	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1465	receive "spurious" readiness notifications, that is your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1467	because there is no data. Not only are some backends known to create a
…		…
1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1562	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1258	readable, but only once. Since it is likely line-buffered, you could	1563	readable, but only once. Since it is likely line-buffered, you could
1259	attempt to read a whole line in the callback.	1564	attempt to read a whole line in the callback.
1260		1565
1261	static void	1566	static void
1262	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1567	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1263	{	1568	{
1264	ev_io_stop (loop, w);	1569	ev_io_stop (loop, w);
1265	.. read from stdin here (or from w->fd) and handle any I/O errors	1570	.. read from stdin here (or from w->fd) and handle any I/O errors
1266	}	1571	}
1267		1572
1268	...	1573	...
1269	struct ev_loop *loop = ev_default_init (0);	1574	struct ev_loop *loop = ev_default_init (0);
1270	struct ev_io stdin_readable;	1575	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1577	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1274		1579
1275		1580
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
1286		1591
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1592	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1593	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1594	might introduce a small delay). If multiple timers become ready during the
		1595	same loop iteration then the ones with earlier time-out values are invoked
		1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
		1598
		1599	=head3 Be smart about timeouts
		1600
		1601	Many real-world problems involve some kind of timeout, usually for error
		1602	recovery. A typical example is an HTTP request - if the other side hangs,
		1603	you want to raise some error after a while.
		1604
		1605	What follows are some ways to handle this problem, from obvious and
		1606	inefficient to smart and efficient.
		1607
		1608	In the following, a 60 second activity timeout is assumed - a timeout that
		1609	gets reset to 60 seconds each time there is activity (e.g. each time some
		1610	data or other life sign was received).
		1611
		1612	=over 4
		1613
		1614	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1615
		1616	This is the most obvious, but not the most simple way: In the beginning,
		1617	start the watcher:
		1618
		1619	ev_timer_init (timer, callback, 60., 0.);
		1620	ev_timer_start (loop, timer);
		1621
		1622	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1623	and start it again:
		1624
		1625	ev_timer_stop (loop, timer);
		1626	ev_timer_set (timer, 60., 0.);
		1627	ev_timer_start (loop, timer);
		1628
		1629	This is relatively simple to implement, but means that each time there is
		1630	some activity, libev will first have to remove the timer from its internal
		1631	data structure and then add it again. Libev tries to be fast, but it's
		1632	still not a constant-time operation.
		1633
		1634	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1635
		1636	This is the easiest way, and involves using C<ev_timer_again> instead of
		1637	C<ev_timer_start>.
		1638
		1639	To implement this, configure an C<ev_timer> with a C<repeat> value
		1640	of C<60> and then call C<ev_timer_again> at start and each time you
		1641	successfully read or write some data. If you go into an idle state where
		1642	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1643	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1644
		1645	That means you can ignore both the C<ev_timer_start> function and the
		1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1647	member and C<ev_timer_again>.
		1648
		1649	At start:
		1650
		1651	ev_init (timer, callback);
		1652	timer->repeat = 60.;
		1653	ev_timer_again (loop, timer);
		1654
		1655	Each time there is some activity:
		1656
		1657	ev_timer_again (loop, timer);
		1658
		1659	It is even possible to change the time-out on the fly, regardless of
		1660	whether the watcher is active or not:
		1661
		1662	timer->repeat = 30.;
		1663	ev_timer_again (loop, timer);
		1664
		1665	This is slightly more efficient then stopping/starting the timer each time
		1666	you want to modify its timeout value, as libev does not have to completely
		1667	remove and re-insert the timer from/into its internal data structure.
		1668
		1669	It is, however, even simpler than the "obvious" way to do it.
		1670
		1671	=item 3. Let the timer time out, but then re-arm it as required.
		1672
		1673	This method is more tricky, but usually most efficient: Most timeouts are
		1674	relatively long compared to the intervals between other activity - in
		1675	our example, within 60 seconds, there are usually many I/O events with
		1676	associated activity resets.
		1677
		1678	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1679	but remember the time of last activity, and check for a real timeout only
		1680	within the callback:
		1681
		1682	ev_tstamp last_activity; // time of last activity
		1683
		1684	static void
		1685	callback (EV_P_ ev_timer *w, int revents)
		1686	{
		1687	ev_tstamp now = ev_now (EV_A);
		1688	ev_tstamp timeout = last_activity + 60.;
		1689
		1690	// if last_activity + 60. is older than now, we did time out
		1691	if (timeout < now)
		1692	{
		1693	// timeout occured, take action
		1694	}
		1695	else
		1696	{
		1697	// callback was invoked, but there was some activity, re-arm
		1698	// the watcher to fire in last_activity + 60, which is
		1699	// guaranteed to be in the future, so "again" is positive:
		1700	w->repeat = timeout - now;
		1701	ev_timer_again (EV_A_ w);
		1702	}
		1703	}
		1704
		1705	To summarise the callback: first calculate the real timeout (defined
		1706	as "60 seconds after the last activity"), then check if that time has
		1707	been reached, which means something I<did>, in fact, time out. Otherwise
		1708	the callback was invoked too early (C<timeout> is in the future), so
		1709	re-schedule the timer to fire at that future time, to see if maybe we have
		1710	a timeout then.
		1711
		1712	Note how C<ev_timer_again> is used, taking advantage of the
		1713	C<ev_timer_again> optimisation when the timer is already running.
		1714
		1715	This scheme causes more callback invocations (about one every 60 seconds
		1716	minus half the average time between activity), but virtually no calls to
		1717	libev to change the timeout.
		1718
		1719	To start the timer, simply initialise the watcher and set C<last_activity>
		1720	to the current time (meaning we just have some activity :), then call the
		1721	callback, which will "do the right thing" and start the timer:
		1722
		1723	ev_init (timer, callback);
		1724	last_activity = ev_now (loop);
		1725	callback (loop, timer, EV_TIMEOUT);
		1726
		1727	And when there is some activity, simply store the current time in
		1728	C<last_activity>, no libev calls at all:
		1729
		1730	last_actiivty = ev_now (loop);
		1731
		1732	This technique is slightly more complex, but in most cases where the
		1733	time-out is unlikely to be triggered, much more efficient.
		1734
		1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1736	callback :) - just change the timeout and invoke the callback, which will
		1737	fix things for you.
		1738
		1739	=item 4. Wee, just use a double-linked list for your timeouts.
		1740
		1741	If there is not one request, but many thousands (millions...), all
		1742	employing some kind of timeout with the same timeout value, then one can
		1743	do even better:
		1744
		1745	When starting the timeout, calculate the timeout value and put the timeout
		1746	at the I<end> of the list.
		1747
		1748	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1749	the list is expected to fire (for example, using the technique #3).
		1750
		1751	When there is some activity, remove the timer from the list, recalculate
		1752	the timeout, append it to the end of the list again, and make sure to
		1753	update the C<ev_timer> if it was taken from the beginning of the list.
		1754
		1755	This way, one can manage an unlimited number of timeouts in O(1) time for
		1756	starting, stopping and updating the timers, at the expense of a major
		1757	complication, and having to use a constant timeout. The constant timeout
		1758	ensures that the list stays sorted.
		1759
		1760	=back
		1761
		1762	So which method the best?
		1763
		1764	Method #2 is a simple no-brain-required solution that is adequate in most
		1765	situations. Method #3 requires a bit more thinking, but handles many cases
		1766	better, and isn't very complicated either. In most case, choosing either
		1767	one is fine, with #3 being better in typical situations.
		1768
		1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1770	rather complicated, but extremely efficient, something that really pays
		1771	off after the first million or so of active timers, i.e. it's usually
		1772	overkill :)
1290		1773
1291	=head3 The special problem of time updates	1774	=head3 The special problem of time updates
1292		1775
1293	Establishing the current time is a costly operation (it usually takes at	1776	Establishing the current time is a costly operation (it usually takes at
1294	least two system calls): EV therefore updates its idea of the current	1777	least two system calls): EV therefore updates its idea of the current
…		…
1306		1789
1307	If the event loop is suspended for a long time, you can also force an	1790	If the event loop is suspended for a long time, you can also force an
1308	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1309	()>.	1792	()>.
1310		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
		1823
1311	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1312		1825
1313	=over 4	1826	=over 4
1314		1827
1315	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1828	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1338	If the timer is started but non-repeating, stop it (as if it timed out).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1339		1852
1340	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1341	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1342		1855
1343	This sounds a bit complicated, but here is a useful and typical	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1344	example: Imagine you have a TCP connection and you want a so-called idle	1857	usage example.
1345	timeout, that is, you want to be called when there have been, say, 60
1346	seconds of inactivity on the socket. The easiest way to do this is to
1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1348	C<ev_timer_again> each time you successfully read or write some data. If
1349	you go into an idle state where you do not expect data to travel on the
1350	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1351	automatically restart it if need be.
1352		1858
1353	That means you can ignore the C<after> value and C<ev_timer_start>	1859	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1354	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1355		1860
1356	ev_timer_init (timer, callback, 0., 5.);	1861	Returns the remaining time until a timer fires. If the timer is active,
1357	ev_timer_again (loop, timer);	1862	then this time is relative to the current event loop time, otherwise it's
1358	...	1863	the timeout value currently configured.
1359	timer->again = 17.;
1360	ev_timer_again (loop, timer);
1361	...
1362	timer->again = 10.;
1363	ev_timer_again (loop, timer);
1364		1864
1365	This is more slightly efficient then stopping/starting the timer each time	1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1366	you want to modify its timeout value.	1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1367		1867	will return C<4>. When the timer expires and is restarted, it will return
1368	Note, however, that it is often even more efficient to remember the	1868	roughly C<7> (likely slightly less as callback invocation takes some time,
1369	time of the last activity and let the timer time-out naturally. In the	1869	too), and so on.
1370	callback, you then check whether the time-out is real, or, if there was
1371	some activity, you reschedule the watcher to time-out in "last_activity +
1372	timeout - ev_now ()" seconds.
1373		1870
1374	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1375		1872
1376	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1377	or C<ev_timer_again> is called, and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1382	=head3 Examples	1879	=head3 Examples
1383		1880
1384	Example: Create a timer that fires after 60 seconds.	1881	Example: Create a timer that fires after 60 seconds.
1385		1882
1386	static void	1883	static void
1387	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1884	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1388	{	1885	{
1389	.. one minute over, w is actually stopped right here	1886	.. one minute over, w is actually stopped right here
1390	}	1887	}
1391		1888
1392	struct ev_timer mytimer;	1889	ev_timer mytimer;
1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1394	ev_timer_start (loop, &mytimer);	1891	ev_timer_start (loop, &mytimer);
1395		1892
1396	Example: Create a timeout timer that times out after 10 seconds of	1893	Example: Create a timeout timer that times out after 10 seconds of
1397	inactivity.	1894	inactivity.
1398		1895
1399	static void	1896	static void
1400	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1897	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1401	{	1898	{
1402	.. ten seconds without any activity	1899	.. ten seconds without any activity
1403	}	1900	}
1404		1901
1405	struct ev_timer mytimer;	1902	ev_timer mytimer;
1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1407	ev_timer_again (&mytimer); /* start timer */	1904	ev_timer_again (&mytimer); /* start timer */
1408	ev_loop (loop, 0);	1905	ev_loop (loop, 0);
1409		1906
1410	// and in some piece of code that gets executed on any "activity":	1907	// and in some piece of code that gets executed on any "activity":
…		…
1415	=head2 C<ev_periodic> - to cron or not to cron?	1912	=head2 C<ev_periodic> - to cron or not to cron?
1416		1913
1417	Periodic watchers are also timers of a kind, but they are very versatile	1914	Periodic watchers are also timers of a kind, but they are very versatile
1418	(and unfortunately a bit complex).	1915	(and unfortunately a bit complex).
1419		1916
1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1917	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1421	but on wall clock time (absolute time). You can tell a periodic watcher	1918	relative time, the physical time that passes) but on wall clock time
1422	to trigger after some specific point in time. For example, if you tell a	1919	(absolute time, the thing you can read on your calender or clock). The
1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1920	difference is that wall clock time can run faster or slower than real
1424	+ 10.>, that is, an absolute time not a delay) and then reset your system	1921	time, and time jumps are not uncommon (e.g. when you adjust your
1425	clock to January of the previous year, then it will take more than year	1922	wrist-watch).
1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1427	roughly 10 seconds later as it uses a relative timeout).
1428		1923
		1924	You can tell a periodic watcher to trigger after some specific point
		1925	in time: for example, if you tell a periodic watcher to trigger "in 10
		1926	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1927	not a delay) and then reset your system clock to January of the previous
		1928	year, then it will take a year or more to trigger the event (unlike an
		1929	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1930	it, as it uses a relative timeout).
		1931
1429	C<ev_periodic>s can also be used to implement vastly more complex timers,	1932	C<ev_periodic> watchers can also be used to implement vastly more complex
1430	such as triggering an event on each "midnight, local time", or other	1933	timers, such as triggering an event on each "midnight, local time", or
1431	complicated rules.	1934	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1935	those cannot react to time jumps.
1432		1936
1433	As with timers, the callback is guaranteed to be invoked only when the	1937	As with timers, the callback is guaranteed to be invoked only when the
1434	time (C<at>) has passed, but if multiple periodic timers become ready	1938	point in time where it is supposed to trigger has passed. If multiple
1435	during the same loop iteration, then order of execution is undefined.	1939	timers become ready during the same loop iteration then the ones with
		1940	earlier time-out values are invoked before ones with later time-out values
		1941	(but this is no longer true when a callback calls C<ev_loop> recursively).
1436		1942
1437	=head3 Watcher-Specific Functions and Data Members	1943	=head3 Watcher-Specific Functions and Data Members
1438		1944
1439	=over 4	1945	=over 4
1440		1946
1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1947	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1442		1948
1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1949	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1444		1950
1445	Lots of arguments, lets sort it out... There are basically three modes of	1951	Lots of arguments, let's sort it out... There are basically three modes of
1446	operation, and we will explain them from simplest to most complex:	1952	operation, and we will explain them from simplest to most complex:
1447		1953
1448	=over 4	1954	=over 4
1449		1955
1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1956	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1451		1957
1452	In this configuration the watcher triggers an event after the wall clock	1958	In this configuration the watcher triggers an event after the wall clock
1453	time C<at> has passed. It will not repeat and will not adjust when a time	1959	time C<offset> has passed. It will not repeat and will not adjust when a
1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1960	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1455	only run when the system clock reaches or surpasses this time.	1961	will be stopped and invoked when the system clock reaches or surpasses
		1962	this point in time.
1456		1963
1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1964	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1458		1965
1459	In this mode the watcher will always be scheduled to time out at the next	1966	In this mode the watcher will always be scheduled to time out at the next
1460	C<at + N * interval> time (for some integer N, which can also be negative)	1967	C<offset + N * interval> time (for some integer N, which can also be
1461	and then repeat, regardless of any time jumps.	1968	negative) and then repeat, regardless of any time jumps. The C<offset>
		1969	argument is merely an offset into the C<interval> periods.
1462		1970
1463	This can be used to create timers that do not drift with respect to the	1971	This can be used to create timers that do not drift with respect to the
1464	system clock, for example, here is a C<ev_periodic> that triggers each	1972	system clock, for example, here is an C<ev_periodic> that triggers each
1465	hour, on the hour:	1973	hour, on the hour (with respect to UTC):
1466		1974
1467	ev_periodic_set (&periodic, 0., 3600., 0);	1975	ev_periodic_set (&periodic, 0., 3600., 0);
1468		1976
1469	This doesn't mean there will always be 3600 seconds in between triggers,	1977	This doesn't mean there will always be 3600 seconds in between triggers,
1470	but only that the callback will be called when the system time shows a	1978	but only that the callback will be called when the system time shows a
1471	full hour (UTC), or more correctly, when the system time is evenly divisible	1979	full hour (UTC), or more correctly, when the system time is evenly divisible
1472	by 3600.	1980	by 3600.
1473		1981
1474	Another way to think about it (for the mathematically inclined) is that	1982	Another way to think about it (for the mathematically inclined) is that
1475	C<ev_periodic> will try to run the callback in this mode at the next possible	1983	C<ev_periodic> will try to run the callback in this mode at the next possible
1476	time where C<time = at (mod interval)>, regardless of any time jumps.	1984	time where C<time = offset (mod interval)>, regardless of any time jumps.
1477		1985
1478	For numerical stability it is preferable that the C<at> value is near	1986	For numerical stability it is preferable that the C<offset> value is near
1479	C<ev_now ()> (the current time), but there is no range requirement for	1987	C<ev_now ()> (the current time), but there is no range requirement for
1480	this value, and in fact is often specified as zero.	1988	this value, and in fact is often specified as zero.
1481		1989
1482	Note also that there is an upper limit to how often a timer can fire (CPU	1990	Note also that there is an upper limit to how often a timer can fire (CPU
1483	speed for example), so if C<interval> is very small then timing stability	1991	speed for example), so if C<interval> is very small then timing stability
1484	will of course deteriorate. Libev itself tries to be exact to be about one	1992	will of course deteriorate. Libev itself tries to be exact to be about one
1485	millisecond (if the OS supports it and the machine is fast enough).	1993	millisecond (if the OS supports it and the machine is fast enough).
1486		1994
1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1995	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1488		1996
1489	In this mode the values for C<interval> and C<at> are both being	1997	In this mode the values for C<interval> and C<offset> are both being
1490	ignored. Instead, each time the periodic watcher gets scheduled, the	1998	ignored. Instead, each time the periodic watcher gets scheduled, the
1491	reschedule callback will be called with the watcher as first, and the	1999	reschedule callback will be called with the watcher as first, and the
1492	current time as second argument.	2000	current time as second argument.
1493		2001
1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2002	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1495	ever, or make ANY event loop modifications whatsoever>.	2003	or make ANY other event loop modifications whatsoever, unless explicitly
		2004	allowed by documentation here>.
1496		2005
1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2006	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2007	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1499	only event loop modification you are allowed to do).	2008	only event loop modification you are allowed to do).
1500		2009
1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2010	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1502	*w, ev_tstamp now)>, e.g.:	2011	*w, ev_tstamp now)>, e.g.:
1503		2012
		2013	static ev_tstamp
1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2014	my_rescheduler (ev_periodic *w, ev_tstamp now)
1505	{	2015	{
1506	return now + 60.;	2016	return now + 60.;
1507	}	2017	}
1508		2018
1509	It must return the next time to trigger, based on the passed time value	2019	It must return the next time to trigger, based on the passed time value
…		…
1529	a different time than the last time it was called (e.g. in a crond like	2039	a different time than the last time it was called (e.g. in a crond like
1530	program when the crontabs have changed).	2040	program when the crontabs have changed).
1531		2041
1532	=item ev_tstamp ev_periodic_at (ev_periodic *)	2042	=item ev_tstamp ev_periodic_at (ev_periodic *)
1533		2043
1534	When active, returns the absolute time that the watcher is supposed to	2044	When active, returns the absolute time that the watcher is supposed
1535	trigger next.	2045	to trigger next. This is not the same as the C<offset> argument to
		2046	C<ev_periodic_set>, but indeed works even in interval and manual
		2047	rescheduling modes.
1536		2048
1537	=item ev_tstamp offset [read-write]	2049	=item ev_tstamp offset [read-write]
1538		2050
1539	When repeating, this contains the offset value, otherwise this is the	2051	When repeating, this contains the offset value, otherwise this is the
1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2052	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2053	although libev might modify this value for better numerical stability).
1541		2054
1542	Can be modified any time, but changes only take effect when the periodic	2055	Can be modified any time, but changes only take effect when the periodic
1543	timer fires or C<ev_periodic_again> is being called.	2056	timer fires or C<ev_periodic_again> is being called.
1544		2057
1545	=item ev_tstamp interval [read-write]	2058	=item ev_tstamp interval [read-write]
1546		2059
1547	The current interval value. Can be modified any time, but changes only	2060	The current interval value. Can be modified any time, but changes only
1548	take effect when the periodic timer fires or C<ev_periodic_again> is being	2061	take effect when the periodic timer fires or C<ev_periodic_again> is being
1549	called.	2062	called.
1550		2063
1551	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2064	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1552		2065
1553	The current reschedule callback, or C<0>, if this functionality is	2066	The current reschedule callback, or C<0>, if this functionality is
1554	switched off. Can be changed any time, but changes only take effect when	2067	switched off. Can be changed any time, but changes only take effect when
1555	the periodic timer fires or C<ev_periodic_again> is being called.	2068	the periodic timer fires or C<ev_periodic_again> is being called.
1556		2069
…		…
1561	Example: Call a callback every hour, or, more precisely, whenever the	2074	Example: Call a callback every hour, or, more precisely, whenever the
1562	system time is divisible by 3600. The callback invocation times have	2075	system time is divisible by 3600. The callback invocation times have
1563	potentially a lot of jitter, but good long-term stability.	2076	potentially a lot of jitter, but good long-term stability.
1564		2077
1565	static void	2078	static void
1566	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1567	{	2080	{
1568	... its now a full hour (UTC, or TAI or whatever your clock follows)	2081	... its now a full hour (UTC, or TAI or whatever your clock follows)
1569	}	2082	}
1570		2083
1571	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2085	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1573	ev_periodic_start (loop, &hourly_tick);	2086	ev_periodic_start (loop, &hourly_tick);
1574		2087
1575	Example: The same as above, but use a reschedule callback to do it:	2088	Example: The same as above, but use a reschedule callback to do it:
1576		2089
1577	#include <math.h>	2090	#include <math.h>
1578		2091
1579	static ev_tstamp	2092	static ev_tstamp
1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2093	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1581	{	2094	{
1582	return now + (3600. - fmod (now, 3600.));	2095	return now + (3600. - fmod (now, 3600.));
1583	}	2096	}
1584		2097
1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2098	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1586		2099
1587	Example: Call a callback every hour, starting now:	2100	Example: Call a callback every hour, starting now:
1588		2101
1589	struct ev_periodic hourly_tick;	2102	ev_periodic hourly_tick;
1590	ev_periodic_init (&hourly_tick, clock_cb,	2103	ev_periodic_init (&hourly_tick, clock_cb,
1591	fmod (ev_now (loop), 3600.), 3600., 0);	2104	fmod (ev_now (loop), 3600.), 3600., 0);
1592	ev_periodic_start (loop, &hourly_tick);	2105	ev_periodic_start (loop, &hourly_tick);
1593		2106
1594		2107
…		…
1597	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1598	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1599	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1600	normal event processing, like any other event.	2113	normal event processing, like any other event.
1601		2114
1602	If you want signals asynchronously, just use C<sigaction> as you would	2115	If you want signals to be delivered truly asynchronously, just use
1603	do without libev and forget about sharing the signal. You can even use	2116	C<sigaction> as you would do without libev and forget about sharing
1604	C<ev_async> from a signal handler to synchronously wake up an event loop.	2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
1605		2119
1606	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1607	first watcher gets started will libev actually register a signal handler	2126	When the first watcher gets started will libev actually register something
1608	with the kernel (thus it coexists with your own signal handlers as long as	2127	with the kernel (thus it coexists with your own signal handlers as long as
1609	you don't register any with libev for the same signal). Similarly, when	2128	you don't register any with libev for the same signal).
1610	the last signal watcher for a signal is stopped, libev will reset the
1611	signal handler to SIG_DFL (regardless of what it was set to before).
1612		2129
1613	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1614	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1615	interrupted. If you have a problem with system calls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1616	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1617	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1618		2160
1619	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1620		2162
1621	=over 4	2163	=over 4
1622		2164
…		…
1636	=head3 Examples	2178	=head3 Examples
1637		2179
1638	Example: Try to exit cleanly on SIGINT.	2180	Example: Try to exit cleanly on SIGINT.
1639		2181
1640	static void	2182	static void
1641	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1642	{	2184	{
1643	ev_unloop (loop, EVUNLOOP_ALL);	2185	ev_unloop (loop, EVUNLOOP_ALL);
1644	}	2186	}
1645		2187
1646	struct ev_signal signal_watcher;	2188	ev_signal signal_watcher;
1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1648	ev_signal_start (loop, &signal_watcher);	2190	ev_signal_start (loop, &signal_watcher);
1649		2191
1650		2192
1651	=head2 C<ev_child> - watch out for process status changes	2193	=head2 C<ev_child> - watch out for process status changes
…		…
1654	some child status changes (most typically when a child of yours dies or	2196	some child status changes (most typically when a child of yours dies or
1655	exits). It is permissible to install a child watcher I<after> the child	2197	exits). It is permissible to install a child watcher I<after> the child
1656	has been forked (which implies it might have already exited), as long	2198	has been forked (which implies it might have already exited), as long
1657	as the event loop isn't entered (or is continued from a watcher), i.e.,	2199	as the event loop isn't entered (or is continued from a watcher), i.e.,
1658	forking and then immediately registering a watcher for the child is fine,	2200	forking and then immediately registering a watcher for the child is fine,
1659	but forking and registering a watcher a few event loop iterations later is	2201	but forking and registering a watcher a few event loop iterations later or
1660	not.	2202	in the next callback invocation is not.
1661		2203
1662	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1663	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
1664		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
1665	=head3 Process Interaction	2211	=head3 Process Interaction
1666		2212
1667	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1668	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1669	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
1670	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1671	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1672	children, even ones not watched.	2218	children, even ones not watched.
1673		2219
1674	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1684	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
1685		2231
1686	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
1687	child terminates, so normally one needs to stop the watcher in the	2233	child terminates, so normally one needs to stop the watcher in the
1688	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
1689	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1690		2237
1691	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1692		2239
1693	=over 4	2240	=over 4
1694		2241
…		…
1726	its completion.	2273	its completion.
1727		2274
1728	ev_child cw;	2275	ev_child cw;
1729		2276
1730	static void	2277	static void
1731	child_cb (EV_P_ struct ev_child *w, int revents)	2278	child_cb (EV_P_ ev_child *w, int revents)
1732	{	2279	{
1733	ev_child_stop (EV_A_ w);	2280	ev_child_stop (EV_A_ w);
1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2281	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1735	}	2282	}
1736		2283
…		…
1751		2298
1752		2299
1753	=head2 C<ev_stat> - did the file attributes just change?	2300	=head2 C<ev_stat> - did the file attributes just change?
1754		2301
1755	This watches a file system path for attribute changes. That is, it calls	2302	This watches a file system path for attribute changes. That is, it calls
1756	C<stat> regularly (or when the OS says it changed) and sees if it changed	2303	C<stat> on that path in regular intervals (or when the OS says it changed)
1757	compared to the last time, invoking the callback if it did.	2304	and sees if it changed compared to the last time, invoking the callback if
		2305	it did.
1758		2306
1759	The path does not need to exist: changing from "path exists" to "path does	2307	The path does not need to exist: changing from "path exists" to "path does
1760	not exist" is a status change like any other. The condition "path does	2308	not exist" is a status change like any other. The condition "path does not
1761	not exist" is signified by the C<st_nlink> field being zero (which is	2309	exist" (or more correctly "path cannot be stat'ed") is signified by the
1762	otherwise always forced to be at least one) and all the other fields of	2310	C<st_nlink> field being zero (which is otherwise always forced to be at
1763	the stat buffer having unspecified contents.	2311	least one) and all the other fields of the stat buffer having unspecified
		2312	contents.
1764		2313
1765	The path I<should> be absolute and I<must not> end in a slash. If it is	2314	The path I<must not> end in a slash or contain special components such as
		2315	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1766	relative and your working directory changes, the behaviour is undefined.	2316	your working directory changes, then the behaviour is undefined.
1767		2317
1768	Since there is no standard kernel interface to do this, the portable	2318	Since there is no portable change notification interface available, the
1769	implementation simply calls C<stat (2)> regularly on the path to see if	2319	portable implementation simply calls C<stat(2)> regularly on the path
1770	it changed somehow. You can specify a recommended polling interval for	2320	to see if it changed somehow. You can specify a recommended polling
1771	this case. If you specify a polling interval of C<0> (highly recommended!)	2321	interval for this case. If you specify a polling interval of C<0> (highly
1772	then a I<suitable, unspecified default> value will be used (which	2322	recommended!) then a I<suitable, unspecified default> value will be used
1773	you can expect to be around five seconds, although this might change	2323	(which you can expect to be around five seconds, although this might
1774	dynamically). Libev will also impose a minimum interval which is currently	2324	change dynamically). Libev will also impose a minimum interval which is
1775	around C<0.1>, but thats usually overkill.	2325	currently around C<0.1>, but that's usually overkill.
1776		2326
1777	This watcher type is not meant for massive numbers of stat watchers,	2327	This watcher type is not meant for massive numbers of stat watchers,
1778	as even with OS-supported change notifications, this can be	2328	as even with OS-supported change notifications, this can be
1779	resource-intensive.	2329	resource-intensive.
1780		2330
1781	At the time of this writing, the only OS-specific interface implemented	2331	At the time of this writing, the only OS-specific interface implemented
1782	is the Linux inotify interface (implementing kqueue support is left as	2332	is the Linux inotify interface (implementing kqueue support is left as an
1783	an exercise for the reader. Note, however, that the author sees no way	2333	exercise for the reader. Note, however, that the author sees no way of
1784	of implementing C<ev_stat> semantics with kqueue).	2334	implementing C<ev_stat> semantics with kqueue, except as a hint).
1785		2335
1786	=head3 ABI Issues (Largefile Support)	2336	=head3 ABI Issues (Largefile Support)
1787		2337
1788	Libev by default (unless the user overrides this) uses the default	2338	Libev by default (unless the user overrides this) uses the default
1789	compilation environment, which means that on systems with large file	2339	compilation environment, which means that on systems with large file
1790	support disabled by default, you get the 32 bit version of the stat	2340	support disabled by default, you get the 32 bit version of the stat
1791	structure. When using the library from programs that change the ABI to	2341	structure. When using the library from programs that change the ABI to
1792	use 64 bit file offsets the programs will fail. In that case you have to	2342	use 64 bit file offsets the programs will fail. In that case you have to
1793	compile libev with the same flags to get binary compatibility. This is	2343	compile libev with the same flags to get binary compatibility. This is
1794	obviously the case with any flags that change the ABI, but the problem is	2344	obviously the case with any flags that change the ABI, but the problem is
1795	most noticeably disabled with ev_stat and large file support.	2345	most noticeably displayed with ev_stat and large file support.
1796		2346
1797	The solution for this is to lobby your distribution maker to make large	2347	The solution for this is to lobby your distribution maker to make large
1798	file interfaces available by default (as e.g. FreeBSD does) and not	2348	file interfaces available by default (as e.g. FreeBSD does) and not
1799	optional. Libev cannot simply switch on large file support because it has	2349	optional. Libev cannot simply switch on large file support because it has
1800	to exchange stat structures with application programs compiled using the	2350	to exchange stat structures with application programs compiled using the
1801	default compilation environment.	2351	default compilation environment.
1802		2352
1803	=head3 Inotify and Kqueue	2353	=head3 Inotify and Kqueue
1804		2354
1805	When C<inotify (7)> support has been compiled into libev (generally	2355	When C<inotify (7)> support has been compiled into libev and present at
1806	only available with Linux 2.6.25 or above due to bugs in earlier	2356	runtime, it will be used to speed up change detection where possible. The
1807	implementations) and present at runtime, it will be used to speed up	2357	inotify descriptor will be created lazily when the first C<ev_stat>
1808	change detection where possible. The inotify descriptor will be created	2358	watcher is being started.
1809	lazily when the first C<ev_stat> watcher is being started.
1810		2359
1811	Inotify presence does not change the semantics of C<ev_stat> watchers	2360	Inotify presence does not change the semantics of C<ev_stat> watchers
1812	except that changes might be detected earlier, and in some cases, to avoid	2361	except that changes might be detected earlier, and in some cases, to avoid
1813	making regular C<stat> calls. Even in the presence of inotify support	2362	making regular C<stat> calls. Even in the presence of inotify support
1814	there are many cases where libev has to resort to regular C<stat> polling,	2363	there are many cases where libev has to resort to regular C<stat> polling,
1815	but as long as the path exists, libev usually gets away without polling.	2364	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2365	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2366	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2367	xfs are fully working) libev usually gets away without polling.
1816		2368
1817	There is no support for kqueue, as apparently it cannot be used to	2369	There is no support for kqueue, as apparently it cannot be used to
1818	implement this functionality, due to the requirement of having a file	2370	implement this functionality, due to the requirement of having a file
1819	descriptor open on the object at all times, and detecting renames, unlinks	2371	descriptor open on the object at all times, and detecting renames, unlinks
1820	etc. is difficult.	2372	etc. is difficult.
1821		2373
		2374	=head3 C<stat ()> is a synchronous operation
		2375
		2376	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2377	the process. The exception are C<ev_stat> watchers - those call C<stat
		2378	()>, which is a synchronous operation.
		2379
		2380	For local paths, this usually doesn't matter: unless the system is very
		2381	busy or the intervals between stat's are large, a stat call will be fast,
		2382	as the path data is usually in memory already (except when starting the
		2383	watcher).
		2384
		2385	For networked file systems, calling C<stat ()> can block an indefinite
		2386	time due to network issues, and even under good conditions, a stat call
		2387	often takes multiple milliseconds.
		2388
		2389	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2390	paths, although this is fully supported by libev.
		2391
1822	=head3 The special problem of stat time resolution	2392	=head3 The special problem of stat time resolution
1823		2393
1824	The C<stat ()> system call only supports full-second resolution portably, and	2394	The C<stat ()> system call only supports full-second resolution portably,
1825	even on systems where the resolution is higher, most file systems still	2395	and even on systems where the resolution is higher, most file systems
1826	only support whole seconds.	2396	still only support whole seconds.
1827		2397
1828	That means that, if the time is the only thing that changes, you can	2398	That means that, if the time is the only thing that changes, you can
1829	easily miss updates: on the first update, C<ev_stat> detects a change and	2399	easily miss updates: on the first update, C<ev_stat> detects a change and
1830	calls your callback, which does something. When there is another update	2400	calls your callback, which does something. When there is another update
1831	within the same second, C<ev_stat> will be unable to detect unless the	2401	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1974		2544
1975	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1976		2546
1977	=over 4	2547	=over 4
1978		2548
1979	=item ev_idle_init (ev_signal *, callback)	2549	=item ev_idle_init (ev_idle *, callback)
1980		2550
1981	Initialises and configures the idle watcher - it has no parameters of any	2551	Initialises and configures the idle watcher - it has no parameters of any
1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2552	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1983	believe me.	2553	believe me.
1984		2554
…		…
1988		2558
1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2559	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1990	callback, free it. Also, use no error checking, as usual.	2560	callback, free it. Also, use no error checking, as usual.
1991		2561
1992	static void	2562	static void
1993	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1994	{	2564	{
1995	free (w);	2565	free (w);
1996	// now do something you wanted to do when the program has	2566	// now do something you wanted to do when the program has
1997	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
1998	}	2568	}
1999		2569
2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2001	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
2002	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
2003		2573
2004		2574
2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2006		2576
2007	Prepare and check watchers are usually (but not always) used in pairs:	2577	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2086		2656
2087	static ev_io iow [nfd];	2657	static ev_io iow [nfd];
2088	static ev_timer tw;	2658	static ev_timer tw;
2089		2659
2090	static void	2660	static void
2091	io_cb (ev_loop *loop, ev_io *w, int revents)	2661	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2092	{	2662	{
2093	}	2663	}
2094		2664
2095	// create io watchers for each fd and a timer before blocking	2665	// create io watchers for each fd and a timer before blocking
2096	static void	2666	static void
2097	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2667	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2098	{	2668	{
2099	int timeout = 3600000;	2669	int timeout = 3600000;
2100	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
2101	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2103		2673
2104	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
2105	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2106	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
2107		2677
2108	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
2109	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
2110	{	2680	{
…		…
2117	}	2687	}
2118	}	2688	}
2119		2689
2120	// stop all watchers after blocking	2690	// stop all watchers after blocking
2121	static void	2691	static void
2122	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2692	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2123	{	2693	{
2124	ev_timer_stop (loop, &tw);	2694	ev_timer_stop (loop, &tw);
2125		2695
2126	for (int i = 0; i < nfd; ++i)	2696	for (int i = 0; i < nfd; ++i)
2127	{	2697	{
…		…
2223	some fds have to be watched and handled very quickly (with low latency),	2793	some fds have to be watched and handled very quickly (with low latency),
2224	and even priorities and idle watchers might have too much overhead. In	2794	and even priorities and idle watchers might have too much overhead. In
2225	this case you would put all the high priority stuff in one loop and all	2795	this case you would put all the high priority stuff in one loop and all
2226	the rest in a second one, and embed the second one in the first.	2796	the rest in a second one, and embed the second one in the first.
2227		2797
2228	As long as the watcher is active, the callback will be invoked every time	2798	As long as the watcher is active, the callback will be invoked every
2229	there might be events pending in the embedded loop. The callback must then	2799	time there might be events pending in the embedded loop. The callback
2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2800	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2231	their callbacks (you could also start an idle watcher to give the embedded	2801	sweep and invoke their callbacks (the callback doesn't need to invoke the
2232	loop strictly lower priority for example). You can also set the callback	2802	C<ev_embed_sweep> function directly, it could also start an idle watcher
2233	to C<0>, in which case the embed watcher will automatically execute the	2803	to give the embedded loop strictly lower priority for example).
2234	embedded loop sweep.
2235		2804
2236	As long as the watcher is started it will automatically handle events. The	2805	You can also set the callback to C<0>, in which case the embed watcher
2237	callback will be invoked whenever some events have been handled. You can	2806	will automatically execute the embedded loop sweep whenever necessary.
2238	set the callback to C<0> to avoid having to specify one if you are not
2239	interested in that.
2240		2807
2241	Also, there have not currently been made special provisions for forking:	2808	Fork detection will be handled transparently while the C<ev_embed> watcher
2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2809	is active, i.e., the embedded loop will automatically be forked when the
2243	but you will also have to stop and restart any C<ev_embed> watchers	2810	embedding loop forks. In other cases, the user is responsible for calling
2244	yourself - but you can use a fork watcher to handle this automatically,	2811	C<ev_loop_fork> on the embedded loop.
2245	and future versions of libev might do just that.
2246		2812
2247	Unfortunately, not all backends are embeddable: only the ones returned by	2813	Unfortunately, not all backends are embeddable: only the ones returned by
2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2814	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2249	portable one.	2815	portable one.
2250		2816
…		…
2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2861	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2296	used).	2862	used).
2297		2863
2298	struct ev_loop *loop_hi = ev_default_init (0);	2864	struct ev_loop *loop_hi = ev_default_init (0);
2299	struct ev_loop *loop_lo = 0;	2865	struct ev_loop *loop_lo = 0;
2300	struct ev_embed embed;	2866	ev_embed embed;
2301		2867
2302	// see if there is a chance of getting one that works	2868	// see if there is a chance of getting one that works
2303	// (remember that a flags value of 0 means autodetection)	2869	// (remember that a flags value of 0 means autodetection)
2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2870	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2871	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2319	kqueue implementation). Store the kqueue/socket-only event loop in	2885	kqueue implementation). Store the kqueue/socket-only event loop in
2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2886	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2321		2887
2322	struct ev_loop *loop = ev_default_init (0);	2888	struct ev_loop *loop = ev_default_init (0);
2323	struct ev_loop *loop_socket = 0;	2889	struct ev_loop *loop_socket = 0;
2324	struct ev_embed embed;	2890	ev_embed embed;
2325		2891
2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2892	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2893	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2328	{	2894	{
2329	ev_embed_init (&embed, 0, loop_socket);	2895	ev_embed_init (&embed, 0, loop_socket);
…		…
2344	event loop blocks next and before C<ev_check> watchers are being called,	2910	event loop blocks next and before C<ev_check> watchers are being called,
2345	and only in the child after the fork. If whoever good citizen calling	2911	and only in the child after the fork. If whoever good citizen calling
2346	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2347	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2348		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2349	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2350		2949
2351	=over 4	2950	=over 4
2352		2951
2353	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2382	=head3 Queueing	2981	=head3 Queueing
2383		2982
2384	C<ev_async> does not support queueing of data in any way. The reason	2983	C<ev_async> does not support queueing of data in any way. The reason
2385	is that the author does not know of a simple (or any) algorithm for a	2984	is that the author does not know of a simple (or any) algorithm for a
2386	multiple-writer-single-reader queue that works in all cases and doesn't	2985	multiple-writer-single-reader queue that works in all cases and doesn't
2387	need elaborate support such as pthreads.	2986	need elaborate support such as pthreads or unportable memory access
		2987	semantics.
2388		2988
2389	That means that if you want to queue data, you have to provide your own	2989	That means that if you want to queue data, you have to provide your own
2390	queue. But at least I can tell you how to implement locking around your	2990	queue. But at least I can tell you how to implement locking around your
2391	queue:	2991	queue:
2392		2992
…		…
2470	=over 4	3070	=over 4
2471		3071
2472	=item ev_async_init (ev_async *, callback)	3072	=item ev_async_init (ev_async *, callback)
2473		3073
2474	Initialises and configures the async watcher - it has no parameters of any	3074	Initialises and configures the async watcher - it has no parameters of any
2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3075	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2476	trust me.	3076	trust me.
2477		3077
2478	=item ev_async_send (loop, ev_async *)	3078	=item ev_async_send (loop, ev_async *)
2479		3079
2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3080	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3081	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2482	C<ev_feed_event>, this call is safe to do from other threads, signal or	3082	C<ev_feed_event>, this call is safe to do from other threads, signal or
2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3083	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2484	section below on what exactly this means).	3084	section below on what exactly this means).
2485		3085
		3086	Note that, as with other watchers in libev, multiple events might get
		3087	compressed into a single callback invocation (another way to look at this
		3088	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3089	reset when the event loop detects that).
		3090
2486	This call incurs the overhead of a system call only once per loop iteration,	3091	This call incurs the overhead of a system call only once per event loop
2487	so while the overhead might be noticeable, it doesn't apply to repeated	3092	iteration, so while the overhead might be noticeable, it doesn't apply to
2488	calls to C<ev_async_send>.	3093	repeated calls to C<ev_async_send> for the same event loop.
2489		3094
2490	=item bool = ev_async_pending (ev_async *)	3095	=item bool = ev_async_pending (ev_async *)
2491		3096
2492	Returns a non-zero value when C<ev_async_send> has been called on the	3097	Returns a non-zero value when C<ev_async_send> has been called on the
2493	watcher but the event has not yet been processed (or even noted) by the	3098	watcher but the event has not yet been processed (or even noted) by the
…		…
2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3101	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2497	the loop iterates next and checks for the watcher to have become active,	3102	the loop iterates next and checks for the watcher to have become active,
2498	it will reset the flag again. C<ev_async_pending> can be used to very	3103	it will reset the flag again. C<ev_async_pending> can be used to very
2499	quickly check whether invoking the loop might be a good idea.	3104	quickly check whether invoking the loop might be a good idea.
2500		3105
2501	Not that this does I<not> check whether the watcher itself is pending, only	3106	Not that this does I<not> check whether the watcher itself is pending,
2502	whether it has been requested to make this watcher pending.	3107	only whether it has been requested to make this watcher pending: there
		3108	is a time window between the event loop checking and resetting the async
		3109	notification, and the callback being invoked.
2503		3110
2504	=back	3111	=back
2505		3112
2506		3113
2507	=head1 OTHER FUNCTIONS	3114	=head1 OTHER FUNCTIONS
…		…
2543	/* doh, nothing entered */;	3150	/* doh, nothing entered */;
2544	}	3151	}
2545		3152
2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2547		3154
2548	=item ev_feed_event (ev_loop *, watcher *, int revents)
2549
2550	Feeds the given event set into the event loop, as if the specified event
2551	had happened for the specified watcher (which must be a pointer to an
2552	initialised but not necessarily started event watcher).
2553
2554	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3155	=item ev_feed_fd_event (loop, int fd, int revents)
2555		3156
2556	Feed an event on the given fd, as if a file descriptor backend detected	3157	Feed an event on the given fd, as if a file descriptor backend detected
2557	the given events it.	3158	the given events it.
2558		3159
2559	=item ev_feed_signal_event (ev_loop *loop, int signum)	3160	=item ev_feed_signal_event (loop, int signum)
2560		3161
2561	Feed an event as if the given signal occurred (C<loop> must be the default	3162	Feed an event as if the given signal occurred (C<loop> must be the default
2562	loop!).	3163	loop!).
2563		3164
2564	=back	3165	=back
…		…
2644		3245
2645	=over 4	3246	=over 4
2646		3247
2647	=item ev::TYPE::TYPE ()	3248	=item ev::TYPE::TYPE ()
2648		3249
2649	=item ev::TYPE::TYPE (struct ev_loop *)	3250	=item ev::TYPE::TYPE (loop)
2650		3251
2651	=item ev::TYPE::~TYPE	3252	=item ev::TYPE::~TYPE
2652		3253
2653	The constructor (optionally) takes an event loop to associate the watcher	3254	The constructor (optionally) takes an event loop to associate the watcher
2654	with. If it is omitted, it will use C<EV_DEFAULT>.	3255	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2686		3287
2687	myclass obj;	3288	myclass obj;
2688	ev::io iow;	3289	ev::io iow;
2689	iow.set <myclass, &myclass::io_cb> (&obj);	3290	iow.set <myclass, &myclass::io_cb> (&obj);
2690		3291
		3292	=item w->set (object *)
		3293
		3294	This is an B<experimental> feature that might go away in a future version.
		3295
		3296	This is a variation of a method callback - leaving out the method to call
		3297	will default the method to C<operator ()>, which makes it possible to use
		3298	functor objects without having to manually specify the C<operator ()> all
		3299	the time. Incidentally, you can then also leave out the template argument
		3300	list.
		3301
		3302	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3303	int revents)>.
		3304
		3305	See the method-C<set> above for more details.
		3306
		3307	Example: use a functor object as callback.
		3308
		3309	struct myfunctor
		3310	{
		3311	void operator() (ev::io &w, int revents)
		3312	{
		3313	...
		3314	}
		3315	}
		3316
		3317	myfunctor f;
		3318
		3319	ev::io w;
		3320	w.set (&f);
		3321
2691	=item w->set<function> (void *data = 0)	3322	=item w->set<function> (void *data = 0)
2692		3323
2693	Also sets a callback, but uses a static method or plain function as	3324	Also sets a callback, but uses a static method or plain function as
2694	callback. The optional C<data> argument will be stored in the watcher's	3325	callback. The optional C<data> argument will be stored in the watcher's
2695	C<data> member and is free for you to use.	3326	C<data> member and is free for you to use.
…		…
2701	Example: Use a plain function as callback.	3332	Example: Use a plain function as callback.
2702		3333
2703	static void io_cb (ev::io &w, int revents) { }	3334	static void io_cb (ev::io &w, int revents) { }
2704	iow.set <io_cb> ();	3335	iow.set <io_cb> ();
2705		3336
2706	=item w->set (struct ev_loop *)	3337	=item w->set (loop)
2707		3338
2708	Associates a different C<struct ev_loop> with this watcher. You can only	3339	Associates a different C<struct ev_loop> with this watcher. You can only
2709	do this when the watcher is inactive (and not pending either).	3340	do this when the watcher is inactive (and not pending either).
2710		3341
2711	=item w->set ([arguments])	3342	=item w->set ([arguments])
…		…
2781	L<http://software.schmorp.de/pkg/EV>.	3412	L<http://software.schmorp.de/pkg/EV>.
2782		3413
2783	=item Python	3414	=item Python
2784		3415
2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3416	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2786	seems to be quite complete and well-documented. Note, however, that the	3417	seems to be quite complete and well-documented.
2787	patch they require for libev is outright dangerous as it breaks the ABI
2788	for everybody else, and therefore, should never be applied in an installed
2789	libev (if python requires an incompatible ABI then it needs to embed
2790	libev).
2791		3418
2792	=item Ruby	3419	=item Ruby
2793		3420
2794	Tony Arcieri has written a ruby extension that offers access to a subset	3421	Tony Arcieri has written a ruby extension that offers access to a subset
2795	of the libev API and adds file handle abstractions, asynchronous DNS and	3422	of the libev API and adds file handle abstractions, asynchronous DNS and
2796	more on top of it. It can be found via gem servers. Its homepage is at	3423	more on top of it. It can be found via gem servers. Its homepage is at
2797	L<http://rev.rubyforge.org/>.	3424	L<http://rev.rubyforge.org/>.
2798		3425
		3426	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3427	makes rev work even on mingw.
		3428
		3429	=item Haskell
		3430
		3431	A haskell binding to libev is available at
		3432	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3433
2799	=item D	3434	=item D
2800		3435
2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3436	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3437	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3438
		3439	=item Ocaml
		3440
		3441	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3443
		3444	=item Lua
		3445
		3446	Brian Maher has written a partial interface to libev
		3447	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3448	L<http://github.com/brimworks/lua-ev>.
2803		3449
2804	=back	3450	=back
2805		3451
2806		3452
2807	=head1 MACRO MAGIC	3453	=head1 MACRO MAGIC
…		…
2908		3554
2909	#define EV_STANDALONE 1	3555	#define EV_STANDALONE 1
2910	#include "ev.h"	3556	#include "ev.h"
2911		3557
2912	Both header files and implementation files can be compiled with a C++	3558	Both header files and implementation files can be compiled with a C++
2913	compiler (at least, thats a stated goal, and breakage will be treated	3559	compiler (at least, that's a stated goal, and breakage will be treated
2914	as a bug).	3560	as a bug).
2915		3561
2916	You need the following files in your source tree, or in a directory	3562	You need the following files in your source tree, or in a directory
2917	in your include path (e.g. in libev/ when using -Ilibev):	3563	in your include path (e.g. in libev/ when using -Ilibev):
2918		3564
…		…
2974	keeps libev from including F<config.h>, and it also defines dummy	3620	keeps libev from including F<config.h>, and it also defines dummy
2975	implementations for some libevent functions (such as logging, which is not	3621	implementations for some libevent functions (such as logging, which is not
2976	supported). It will also not define any of the structs usually found in	3622	supported). It will also not define any of the structs usually found in
2977	F<event.h> that are not directly supported by the libev core alone.	3623	F<event.h> that are not directly supported by the libev core alone.
2978		3624
		3625	In standalone mode, libev will still try to automatically deduce the
		3626	configuration, but has to be more conservative.
		3627
2979	=item EV_USE_MONOTONIC	3628	=item EV_USE_MONOTONIC
2980		3629
2981	If defined to be C<1>, libev will try to detect the availability of the	3630	If defined to be C<1>, libev will try to detect the availability of the
2982	monotonic clock option at both compile time and runtime. Otherwise no use	3631	monotonic clock option at both compile time and runtime. Otherwise no
2983	of the monotonic clock option will be attempted. If you enable this, you	3632	use of the monotonic clock option will be attempted. If you enable this,
2984	usually have to link against librt or something similar. Enabling it when	3633	you usually have to link against librt or something similar. Enabling it
2985	the functionality isn't available is safe, though, although you have	3634	when the functionality isn't available is safe, though, although you have
2986	to make sure you link against any libraries where the C<clock_gettime>	3635	to make sure you link against any libraries where the C<clock_gettime>
2987	function is hiding in (often F<-lrt>).	3636	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2988		3637
2989	=item EV_USE_REALTIME	3638	=item EV_USE_REALTIME
2990		3639
2991	If defined to be C<1>, libev will try to detect the availability of the	3640	If defined to be C<1>, libev will try to detect the availability of the
2992	real-time clock option at compile time (and assume its availability at	3641	real-time clock option at compile time (and assume its availability
2993	runtime if successful). Otherwise no use of the real-time clock option will	3642	at runtime if successful). Otherwise no use of the real-time clock
2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3643	option will be attempted. This effectively replaces C<gettimeofday>
2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3644	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3645	correctness. See the note about libraries in the description of
		3646	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3647	C<EV_USE_CLOCK_SYSCALL>.
		3648
		3649	=item EV_USE_CLOCK_SYSCALL
		3650
		3651	If defined to be C<1>, libev will try to use a direct syscall instead
		3652	of calling the system-provided C<clock_gettime> function. This option
		3653	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3654	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3655	programs needlessly. Using a direct syscall is slightly slower (in
		3656	theory), because no optimised vdso implementation can be used, but avoids
		3657	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3658	higher, as it simplifies linking (no need for C<-lrt>).
2997		3659
2998	=item EV_USE_NANOSLEEP	3660	=item EV_USE_NANOSLEEP
2999		3661
3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3662	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3001	and will use it for delays. Otherwise it will use C<select ()>.	3663	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3017		3679
3018	=item EV_SELECT_USE_FD_SET	3680	=item EV_SELECT_USE_FD_SET
3019		3681
3020	If defined to C<1>, then the select backend will use the system C<fd_set>	3682	If defined to C<1>, then the select backend will use the system C<fd_set>
3021	structure. This is useful if libev doesn't compile due to a missing	3683	structure. This is useful if libev doesn't compile due to a missing
3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3684	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3023	exotic systems. This usually limits the range of file descriptors to some	3685	on exotic systems. This usually limits the range of file descriptors to
3024	low limit such as 1024 or might have other limitations (winsocket only	3686	some low limit such as 1024 or might have other limitations (winsocket
3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3687	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3026	influence the size of the C<fd_set> used.	3688	configures the maximum size of the C<fd_set>.
3027		3689
3028	=item EV_SELECT_IS_WINSOCKET	3690	=item EV_SELECT_IS_WINSOCKET
3029		3691
3030	When defined to C<1>, the select backend will assume that	3692	When defined to C<1>, the select backend will assume that
3031	select/socket/connect etc. don't understand file descriptors but	3693	select/socket/connect etc. don't understand file descriptors but
…		…
3033	be used is the winsock select). This means that it will call	3695	be used is the winsock select). This means that it will call
3034	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3696	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3035	it is assumed that all these functions actually work on fds, even	3697	it is assumed that all these functions actually work on fds, even
3036	on win32. Should not be defined on non-win32 platforms.	3698	on win32. Should not be defined on non-win32 platforms.
3037		3699
3038	=item EV_FD_TO_WIN32_HANDLE	3700	=item EV_FD_TO_WIN32_HANDLE(fd)
3039		3701
3040	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3702	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3041	file descriptors to socket handles. When not defining this symbol (the	3703	file descriptors to socket handles. When not defining this symbol (the
3042	default), then libev will call C<_get_osfhandle>, which is usually	3704	default), then libev will call C<_get_osfhandle>, which is usually
3043	correct. In some cases, programs use their own file descriptor management,	3705	correct. In some cases, programs use their own file descriptor management,
3044	in which case they can provide this function to map fds to socket handles.	3706	in which case they can provide this function to map fds to socket handles.
		3707
		3708	=item EV_WIN32_HANDLE_TO_FD(handle)
		3709
		3710	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3711	using the standard C<_open_osfhandle> function. For programs implementing
		3712	their own fd to handle mapping, overwriting this function makes it easier
		3713	to do so. This can be done by defining this macro to an appropriate value.
		3714
		3715	=item EV_WIN32_CLOSE_FD(fd)
		3716
		3717	If programs implement their own fd to handle mapping on win32, then this
		3718	macro can be used to override the C<close> function, useful to unregister
		3719	file descriptors again. Note that the replacement function has to close
		3720	the underlying OS handle.
3045		3721
3046	=item EV_USE_POLL	3722	=item EV_USE_POLL
3047		3723
3048	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3724	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3049	backend. Otherwise it will be enabled on non-win32 platforms. It	3725	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3181	defined to be C<0>, then they are not.	3857	defined to be C<0>, then they are not.
3182		3858
3183	=item EV_MINIMAL	3859	=item EV_MINIMAL
3184		3860
3185	If you need to shave off some kilobytes of code at the expense of some	3861	If you need to shave off some kilobytes of code at the expense of some
3186	speed, define this symbol to C<1>. Currently this is used to override some	3862	speed (but with the full API), define this symbol to C<1>. Currently this
3187	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3863	is used to override some inlining decisions, saves roughly 30% code size
3188	much smaller 2-heap for timer management over the default 4-heap.	3864	on amd64. It also selects a much smaller 2-heap for timer management over
		3865	the default 4-heap.
		3866
		3867	You can save even more by disabling watcher types you do not need
		3868	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3869	(C<-DNDEBUG>) will usually reduce code size a lot.
		3870
		3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3872	provide a bare-bones event library. See C<ev.h> for details on what parts
		3873	of the API are still available, and do not complain if this subset changes
		3874	over time.
		3875
		3876	=item EV_NSIG
		3877
		3878	The highest supported signal number, +1 (or, the number of
		3879	signals): Normally, libev tries to deduce the maximum number of signals
		3880	automatically, but sometimes this fails, in which case it can be
		3881	specified. Also, using a lower number than detected (C<32> should be
		3882	good for about any system in existance) can save some memory, as libev
		3883	statically allocates some 12-24 bytes per signal number.
3189		3884
3190	=item EV_PID_HASHSIZE	3885	=item EV_PID_HASHSIZE
3191		3886
3192	C<ev_child> watchers use a small hash table to distribute workload by	3887	C<ev_child> watchers use a small hash table to distribute workload by
3193	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3888	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3379	default loop and triggering an C<ev_async> watcher from the default loop	4074	default loop and triggering an C<ev_async> watcher from the default loop
3380	watcher callback into the event loop interested in the signal.	4075	watcher callback into the event loop interested in the signal.
3381		4076
3382	=back	4077	=back
3383		4078
		4079	=head4 THREAD LOCKING EXAMPLE
		4080
		4081	Here is a fictitious example of how to run an event loop in a different
		4082	thread than where callbacks are being invoked and watchers are
		4083	created/added/removed.
		4084
		4085	For a real-world example, see the C<EV::Loop::Async> perl module,
		4086	which uses exactly this technique (which is suited for many high-level
		4087	languages).
		4088
		4089	The example uses a pthread mutex to protect the loop data, a condition
		4090	variable to wait for callback invocations, an async watcher to notify the
		4091	event loop thread and an unspecified mechanism to wake up the main thread.
		4092
		4093	First, you need to associate some data with the event loop:
		4094
		4095	typedef struct {
		4096	mutex_t lock; /* global loop lock */
		4097	ev_async async_w;
		4098	thread_t tid;
		4099	cond_t invoke_cv;
		4100	} userdata;
		4101
		4102	void prepare_loop (EV_P)
		4103	{
		4104	// for simplicity, we use a static userdata struct.
		4105	static userdata u;
		4106
		4107	ev_async_init (&u->async_w, async_cb);
		4108	ev_async_start (EV_A_ &u->async_w);
		4109
		4110	pthread_mutex_init (&u->lock, 0);
		4111	pthread_cond_init (&u->invoke_cv, 0);
		4112
		4113	// now associate this with the loop
		4114	ev_set_userdata (EV_A_ u);
		4115	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4116	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4117
		4118	// then create the thread running ev_loop
		4119	pthread_create (&u->tid, 0, l_run, EV_A);
		4120	}
		4121
		4122	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4123	solely to wake up the event loop so it takes notice of any new watchers
		4124	that might have been added:
		4125
		4126	static void
		4127	async_cb (EV_P_ ev_async *w, int revents)
		4128	{
		4129	// just used for the side effects
		4130	}
		4131
		4132	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4133	protecting the loop data, respectively.
		4134
		4135	static void
		4136	l_release (EV_P)
		4137	{
		4138	userdata *u = ev_userdata (EV_A);
		4139	pthread_mutex_unlock (&u->lock);
		4140	}
		4141
		4142	static void
		4143	l_acquire (EV_P)
		4144	{
		4145	userdata *u = ev_userdata (EV_A);
		4146	pthread_mutex_lock (&u->lock);
		4147	}
		4148
		4149	The event loop thread first acquires the mutex, and then jumps straight
		4150	into C<ev_loop>:
		4151
		4152	void *
		4153	l_run (void *thr_arg)
		4154	{
		4155	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4156
		4157	l_acquire (EV_A);
		4158	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4159	ev_loop (EV_A_ 0);
		4160	l_release (EV_A);
		4161
		4162	return 0;
		4163	}
		4164
		4165	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4166	signal the main thread via some unspecified mechanism (signals? pipe
		4167	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4168	have been called (in a while loop because a) spurious wakeups are possible
		4169	and b) skipping inter-thread-communication when there are no pending
		4170	watchers is very beneficial):
		4171
		4172	static void
		4173	l_invoke (EV_P)
		4174	{
		4175	userdata *u = ev_userdata (EV_A);
		4176
		4177	while (ev_pending_count (EV_A))
		4178	{
		4179	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4180	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4181	}
		4182	}
		4183
		4184	Now, whenever the main thread gets told to invoke pending watchers, it
		4185	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4186	thread to continue:
		4187
		4188	static void
		4189	real_invoke_pending (EV_P)
		4190	{
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	pthread_mutex_lock (&u->lock);
		4194	ev_invoke_pending (EV_A);
		4195	pthread_cond_signal (&u->invoke_cv);
		4196	pthread_mutex_unlock (&u->lock);
		4197	}
		4198
		4199	Whenever you want to start/stop a watcher or do other modifications to an
		4200	event loop, you will now have to lock:
		4201
		4202	ev_timer timeout_watcher;
		4203	userdata *u = ev_userdata (EV_A);
		4204
		4205	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4206
		4207	pthread_mutex_lock (&u->lock);
		4208	ev_timer_start (EV_A_ &timeout_watcher);
		4209	ev_async_send (EV_A_ &u->async_w);
		4210	pthread_mutex_unlock (&u->lock);
		4211
		4212	Note that sending the C<ev_async> watcher is required because otherwise
		4213	an event loop currently blocking in the kernel will have no knowledge
		4214	about the newly added timer. By waking up the loop it will pick up any new
		4215	watchers in the next event loop iteration.
		4216
3384	=head3 COROUTINES	4217	=head3 COROUTINES
3385		4218
3386	Libev is very accommodating to coroutines ("cooperative threads"):	4219	Libev is very accommodating to coroutines ("cooperative threads"):
3387	libev fully supports nesting calls to its functions from different	4220	libev fully supports nesting calls to its functions from different
3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4221	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3389	different coroutines, and switch freely between both coroutines running the	4222	different coroutines, and switch freely between both coroutines running
3390	loop, as long as you don't confuse yourself). The only exception is that	4223	the loop, as long as you don't confuse yourself). The only exception is
3391	you must not do this from C<ev_periodic> reschedule callbacks.	4224	that you must not do this from C<ev_periodic> reschedule callbacks.
3392		4225
3393	Care has been taken to ensure that libev does not keep local state inside	4226	Care has been taken to ensure that libev does not keep local state inside
3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3395	they do not clal any callbacks.	4228	they do not call any callbacks.
3396		4229
3397	=head2 COMPILER WARNINGS	4230	=head2 COMPILER WARNINGS
3398		4231
3399	Depending on your compiler and compiler settings, you might get no or a	4232	Depending on your compiler and compiler settings, you might get no or a
3400	lot of warnings when compiling libev code. Some people are apparently	4233	lot of warnings when compiling libev code. Some people are apparently
…		…
3434	==2274== definitely lost: 0 bytes in 0 blocks.	4267	==2274== definitely lost: 0 bytes in 0 blocks.
3435	==2274== possibly lost: 0 bytes in 0 blocks.	4268	==2274== possibly lost: 0 bytes in 0 blocks.
3436	==2274== still reachable: 256 bytes in 1 blocks.	4269	==2274== still reachable: 256 bytes in 1 blocks.
3437		4270
3438	Then there is no memory leak, just as memory accounted to global variables	4271	Then there is no memory leak, just as memory accounted to global variables
3439	is not a memleak - the memory is still being refernced, and didn't leak.	4272	is not a memleak - the memory is still being referenced, and didn't leak.
3440		4273
3441	Similarly, under some circumstances, valgrind might report kernel bugs	4274	Similarly, under some circumstances, valgrind might report kernel bugs
3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4275	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3443	although an acceptable workaround has been found here), or it might be	4276	although an acceptable workaround has been found here), or it might be
3444	confused.	4277	confused.
…		…
3473	way (note also that glib is the slowest event library known to man).	4306	way (note also that glib is the slowest event library known to man).
3474		4307
3475	There is no supported compilation method available on windows except	4308	There is no supported compilation method available on windows except
3476	embedding it into other applications.	4309	embedding it into other applications.
3477		4310
		4311	Sensible signal handling is officially unsupported by Microsoft - libev
		4312	tries its best, but under most conditions, signals will simply not work.
		4313
3478	Not a libev limitation but worth mentioning: windows apparently doesn't	4314	Not a libev limitation but worth mentioning: windows apparently doesn't
3479	accept large writes: instead of resulting in a partial write, windows will	4315	accept large writes: instead of resulting in a partial write, windows will
3480	either accept everything or return C<ENOBUFS> if the buffer is too large,	4316	either accept everything or return C<ENOBUFS> if the buffer is too large,
3481	so make sure you only write small amounts into your sockets (less than a	4317	so make sure you only write small amounts into your sockets (less than a
3482	megabyte seems safe, but this apparently depends on the amount of memory	4318	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3486	the abysmal performance of winsockets, using a large number of sockets	4322	the abysmal performance of winsockets, using a large number of sockets
3487	is not recommended (and not reasonable). If your program needs to use	4323	is not recommended (and not reasonable). If your program needs to use
3488	more than a hundred or so sockets, then likely it needs to use a totally	4324	more than a hundred or so sockets, then likely it needs to use a totally
3489	different implementation for windows, as libev offers the POSIX readiness	4325	different implementation for windows, as libev offers the POSIX readiness
3490	notification model, which cannot be implemented efficiently on windows	4326	notification model, which cannot be implemented efficiently on windows
3491	(Microsoft monopoly games).	4327	(due to Microsoft monopoly games).
3492		4328
3493	A typical way to use libev under windows is to embed it (see the embedding	4329	A typical way to use libev under windows is to embed it (see the embedding
3494	section for details) and use the following F<evwrap.h> header file instead	4330	section for details) and use the following F<evwrap.h> header file instead
3495	of F<ev.h>:	4331	of F<ev.h>:
3496		4332
…		…
3532		4368
3533	Early versions of winsocket's select only supported waiting for a maximum	4369	Early versions of winsocket's select only supported waiting for a maximum
3534	of C<64> handles (probably owning to the fact that all windows kernels	4370	of C<64> handles (probably owning to the fact that all windows kernels
3535	can only wait for C<64> things at the same time internally; Microsoft	4371	can only wait for C<64> things at the same time internally; Microsoft
3536	recommends spawning a chain of threads and wait for 63 handles and the	4372	recommends spawning a chain of threads and wait for 63 handles and the
3537	previous thread in each. Great).	4373	previous thread in each. Sounds great!).
3538		4374
3539	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4375	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3540	to some high number (e.g. C<2048>) before compiling the winsocket select	4376	to some high number (e.g. C<2048>) before compiling the winsocket select
3541	call (which might be in libev or elsewhere, for example, perl does its own	4377	call (which might be in libev or elsewhere, for example, perl and many
3542	select emulation on windows).	4378	other interpreters do their own select emulation on windows).
3543		4379
3544	Another limit is the number of file descriptors in the Microsoft runtime	4380	Another limit is the number of file descriptors in the Microsoft runtime
3545	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4381	libraries, which by default is C<64> (there must be a hidden I<64>
3546	or something like this inside Microsoft). You can increase this by calling	4382	fetish or something like this inside Microsoft). You can increase this
3547	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4383	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3548	arbitrary limit), but is broken in many versions of the Microsoft runtime	4384	(another arbitrary limit), but is broken in many versions of the Microsoft
3549	libraries.
3550
3551	This might get you to about C<512> or C<2048> sockets (depending on	4385	runtime libraries. This might get you to about C<512> or C<2048> sockets
3552	windows version and/or the phase of the moon). To get more, you need to	4386	(depending on windows version and/or the phase of the moon). To get more,
3553	wrap all I/O functions and provide your own fd management, but the cost of	4387	you need to wrap all I/O functions and provide your own fd management, but
3554	calling select (O(n²)) will likely make this unworkable.	4388	the cost of calling select (O(n²)) will likely make this unworkable.
3555		4389
3556	=back	4390	=back
3557		4391
3558	=head2 PORTABILITY REQUIREMENTS	4392	=head2 PORTABILITY REQUIREMENTS
3559		4393
…		…
3602	=item C<double> must hold a time value in seconds with enough accuracy	4436	=item C<double> must hold a time value in seconds with enough accuracy
3603		4437
3604	The type C<double> is used to represent timestamps. It is required to	4438	The type C<double> is used to represent timestamps. It is required to
3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4439	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3606	enough for at least into the year 4000. This requirement is fulfilled by	4440	enough for at least into the year 4000. This requirement is fulfilled by
3607	implementations implementing IEEE 754 (basically all existing ones).	4441	implementations implementing IEEE 754, which is basically all existing
		4442	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4443	2200.
3608		4444
3609	=back	4445	=back
3610		4446
3611	If you know of other additional requirements drop me a note.	4447	If you know of other additional requirements drop me a note.
3612		4448
…		…
3680	involves iterating over all running async watchers or all signal numbers.	4516	involves iterating over all running async watchers or all signal numbers.
3681		4517
3682	=back	4518	=back
3683		4519
3684		4520
		4521	=head1 GLOSSARY
		4522
		4523	=over 4
		4524
		4525	=item active
		4526
		4527	A watcher is active as long as it has been started (has been attached to
		4528	an event loop) but not yet stopped (disassociated from the event loop).
		4529
		4530	=item application
		4531
		4532	In this document, an application is whatever is using libev.
		4533
		4534	=item callback
		4535
		4536	The address of a function that is called when some event has been
		4537	detected. Callbacks are being passed the event loop, the watcher that
		4538	received the event, and the actual event bitset.
		4539
		4540	=item callback invocation
		4541
		4542	The act of calling the callback associated with a watcher.
		4543
		4544	=item event
		4545
		4546	A change of state of some external event, such as data now being available
		4547	for reading on a file descriptor, time having passed or simply not having
		4548	any other events happening anymore.
		4549
		4550	In libev, events are represented as single bits (such as C<EV_READ> or
		4551	C<EV_TIMEOUT>).
		4552
		4553	=item event library
		4554
		4555	A software package implementing an event model and loop.
		4556
		4557	=item event loop
		4558
		4559	An entity that handles and processes external events and converts them
		4560	into callback invocations.
		4561
		4562	=item event model
		4563
		4564	The model used to describe how an event loop handles and processes
		4565	watchers and events.
		4566
		4567	=item pending
		4568
		4569	A watcher is pending as soon as the corresponding event has been detected,
		4570	and stops being pending as soon as the watcher will be invoked or its
		4571	pending status is explicitly cleared by the application.
		4572
		4573	A watcher can be pending, but not active. Stopping a watcher also clears
		4574	its pending status.
		4575
		4576	=item real time
		4577
		4578	The physical time that is observed. It is apparently strictly monotonic :)
		4579
		4580	=item wall-clock time
		4581
		4582	The time and date as shown on clocks. Unlike real time, it can actually
		4583	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4584	clock.
		4585
		4586	=item watcher
		4587
		4588	A data structure that describes interest in certain events. Watchers need
		4589	to be started (attached to an event loop) before they can receive events.
		4590
		4591	=item watcher invocation
		4592
		4593	The act of calling the callback associated with a watcher.
		4594
		4595	=back
		4596
3685	=head1 AUTHOR	4597	=head1 AUTHOR
3686		4598
3687	Marc Lehmann <libev@schmorp.de>.	4599	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3688		4600

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