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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	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,	391	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	392	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	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		418
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
382	For few fds, this backend is a bit little slower than poll and select,	424	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	425	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),	426	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	427	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	428
387	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
389		445
390	While stopping, setting and starting an I/O watcher in the same iteration	446	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	447	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	448	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	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
395		451	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		452
400	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	454	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	455	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	456	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
405		464
406	While nominally embeddable in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	466	all kernel versions tested so far.
408		467
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	469	C<EVBACKEND_POLL>.
411		470
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		472
414	Kqueue deserves special mention, as at the time of this writing, it was	473	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	474	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	475	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	476	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	477	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.	478	without API changes to existing programs. For this reason it's not being
		479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		481	system like NetBSD.
420		482
421	You still can embed kqueue into a normal poll or select backend and use it	483	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	484	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.	485	the target platform). See C<ev_embed> watchers for more info.
424		486
425	It scales in the same way as the epoll backend, but the interface to the	487	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	488	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	489	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	490	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	491	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
431		494
432	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
433		496
434	While nominally embeddable in other event loops, this doesn't work	497	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	498	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	499	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	500	(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,	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
440		503
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	504	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	505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	506	C<NOTE_EOF>.
444		507
…		…
464	might perform better.	527	might perform better.
465		528
466	On the positive side, with the exception of the spurious readiness	529	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	530	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	531	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	532	OS-specific backends (I vastly prefer correctness over speed hacks).
470		533
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	535	C<EVBACKEND_POLL>.
473		536
474	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
…		…
479		542
480	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
481		544
482	=back	545	=back
483		546
484	If one or more of these are or'ed into the flags value, then only these	547	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	548	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.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
487		551
488	Example: This is the most typical usage.	552	Example: This is the most typical usage.
489		553
490	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	591	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	592	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	593	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	594	for example).
531		595
532	Note that certain global state, such as signal state, will not be freed by	596	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	597	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
535		599
536	In general it is not advisable to call this function except in the	600	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	601	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	602	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
540		604
541	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
542		606
543	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
582		646
583	This value can sometimes be useful as a generation counter of sorts (it	647	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	648	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	649	C<ev_prepare> and C<ev_check> calls.
586		650
		651	=item unsigned int ev_loop_depth (loop)
		652
		653	Returns the number of times C<ev_loop> was entered minus the number of
		654	times C<ev_loop> was exited, in other words, the recursion depth.
		655
		656	Outside C<ev_loop>, this number is zero. In a callback, this number is
		657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		658	in which case it is higher.
		659
		660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		661	etc.), doesn't count as exit.
		662
587	=item unsigned int ev_backend (loop)	663	=item unsigned int ev_backend (loop)
588		664
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	666	use.
591		667
…		…
605		681
606	This function is rarely useful, but when some event callback runs for a	682	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	683	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	684	the current time is a good idea.
609		685
610	See also "The special problem of time updates" in the C<ev_timer> section.	686	See also L<The special problem of time updates> in the C<ev_timer> section.
		687
		688	=item ev_suspend (loop)
		689
		690	=item ev_resume (loop)
		691
		692	These two functions suspend and resume a loop, for use when the loop is
		693	not used for a while and timeouts should not be processed.
		694
		695	A typical use case would be an interactive program such as a game: When
		696	the user presses C<^Z> to suspend the game and resumes it an hour later it
		697	would be best to handle timeouts as if no time had actually passed while
		698	the program was suspended. This can be achieved by calling C<ev_suspend>
		699	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		700	C<ev_resume> directly afterwards to resume timer processing.
		701
		702	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		704	will be rescheduled (that is, they will lose any events that would have
		705	occured while suspended).
		706
		707	After calling C<ev_suspend> you B<must not> call I<any> function on the
		708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		709	without a previous call to C<ev_suspend>.
		710
		711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		712	event loop time (see C<ev_now_update>).
611		713
612	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
613		715
614	Finally, this is it, the event handler. This function usually is called	716	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	717	after you have initialised all your watchers and you want to start
616	events.	718	handling events.
617		719
618	If the flags argument is specified as C<0>, it will not return until	720	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.	721	either no event watchers are active anymore or C<ev_unloop> was called.
620		722
621	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	733	the loop.
632		734
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	735	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	736	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	737	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	738	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	739	user-registered callback will be called), and will return after one
638	iteration of the loop.	740	iteration of the loop.
639		741
640	This is useful if you are waiting for some external event in conjunction	742	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	743	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		789
688	This "unloop state" will be cleared when entering C<ev_loop> again.	790	This "unloop state" will be cleared when entering C<ev_loop> again.
689		791
		792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		793
690	=item ev_ref (loop)	794	=item ev_ref (loop)
691		795
692	=item ev_unref (loop)	796	=item ev_unref (loop)
693		797
694	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
695	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
696	count is nonzero, C<ev_loop> will not return on its own.	800	count is nonzero, C<ev_loop> will not return on its own.
697		801
698	If you have a watcher you never unregister that should not keep C<ev_loop>	802	This is useful when you have a watcher that you never intend to
699	from returning, call ev_unref() after starting, and ev_ref() before	803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
700	stopping it.	805	before stopping it.
701		806
702	As an example, libev itself uses this for its internal signal pipe: It is	807	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	808	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	809	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	810	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	811	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	812	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	813	before, respectively. Note also that libev might stop watchers itself
		814	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		815	in the callback).
709		816
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	818	running when nothing else is active.
712		819
713	struct ev_signal exitsig;	820	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	821	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	822	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	823	evf_unref (loop);
717		824
718	Example: For some weird reason, unregister the above signal handler again.	825	Example: For some weird reason, unregister the above signal handler again.
…		…
742		849
743	By setting a higher I<io collect interval> you allow libev to spend more	850	By setting a higher I<io collect interval> you allow libev to spend more
744	time collecting I/O events, so you can handle more events per iteration,	851	time collecting I/O events, so you can handle more events per iteration,
745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
746	C<ev_timer>) will be not affected. Setting this to a non-null value will	853	C<ev_timer>) will be not affected. Setting this to a non-null value will
747	introduce an additional C<ev_sleep ()> call into most loop iterations.	854	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		855	sleep time ensures that libev will not poll for I/O events more often then
		856	once per this interval, on average.
748		857
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	858	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	859	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	860	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	861	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		863
755	Many (busy) programs can usually benefit by setting the I/O collect	864	Many (busy) programs can usually benefit by setting the I/O collect
756	interval to a value near C<0.1> or so, which is often enough for	865	interval to a value near C<0.1> or so, which is often enough for
757	interactive servers (of course not for games), likewise for timeouts. It	866	interactive servers (of course not for games), likewise for timeouts. It
758	usually doesn't make much sense to set it to a lower value than C<0.01>,	867	usually doesn't make much sense to set it to a lower value than C<0.01>,
759	as this approaches the timing granularity of most systems.	868	as this approaches the timing granularity of most systems. Note that if
		869	you do transactions with the outside world and you can't increase the
		870	parallelity, then this setting will limit your transaction rate (if you
		871	need to poll once per transaction and the I/O collect interval is 0.01,
		872	then you can't do more than 100 transations per second).
760		873
761	Setting the I<timeout collect interval> can improve the opportunity for	874	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	875	saving power, as the program will "bundle" timer callback invocations that
763	are "near" in time together, by delaying some, thus reducing the number of	876	are "near" in time together, by delaying some, thus reducing the number of
764	times the process sleeps and wakes up again. Another useful technique to	877	times the process sleeps and wakes up again. Another useful technique to
765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	878	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	879	they fire on, say, one-second boundaries only.
767		880
		881	Example: we only need 0.1s timeout granularity, and we wish not to poll
		882	more often than 100 times per second:
		883
		884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
		951
768	=item ev_loop_verify (loop)	952	=item ev_loop_verify (loop)
769		953
770	This function only does something when C<EV_VERIFY> support has been	954	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	955	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	956	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	957	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	958	error and call C<abort ()>.
775		959
776	This can be used to catch bugs inside libev itself: under normal	960	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	964	=back
781		965
782		966
783	=head1 ANATOMY OF A WATCHER	967	=head1 ANATOMY OF A WATCHER
784		968
		969	In the following description, uppercase C<TYPE> in names stands for the
		970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		971	watchers and C<ev_io_start> for I/O watchers.
		972
785	A watcher is a structure that you create and register to record your	973	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	974	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	975	become readable, you would create an C<ev_io> watcher for that:
788		976
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	978	{
791	ev_io_stop (w);	979	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	980	ev_unloop (loop, EVUNLOOP_ALL);
793	}	981	}
794		982
795	struct ev_loop *loop = ev_default_loop (0);	983	struct ev_loop *loop = ev_default_loop (0);
		984
796	struct ev_io stdin_watcher;	985	ev_io stdin_watcher;
		986
797	ev_init (&stdin_watcher, my_cb);	987	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	989	ev_io_start (loop, &stdin_watcher);
		990
800	ev_loop (loop, 0);	991	ev_loop (loop, 0);
801		992
802	As you can see, you are responsible for allocating the memory for your	993	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	994	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	995	stack).
		996
		997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		999
806	Each watcher structure must be initialised by a call to C<ev_init	1000	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	1001	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	1002	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	1003	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	1004	is readable and/or writable).
811		1005
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1007	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1008	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1009	ev_TYPE_init (watcher *, callback, ...) >>.
816		1010
817	To make the watcher actually watch out for events, you have to start it	1011	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1012	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1013	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1014	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1015
822	As long as your watcher is active (has been started but not stopped) you	1016	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1017	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1018	reinitialise it or call its C<ev_TYPE_set> macro.
825		1019
826	Each and every callback receives the event loop pointer as first, the	1020	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1021	registered watcher structure as second, and a bitset of received events as
828	third argument.	1022	third argument.
829		1023
…		…
887		1081
888	=item C<EV_ASYNC>	1082	=item C<EV_ASYNC>
889		1083
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1084	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1085
		1086	=item C<EV_CUSTOM>
		1087
		1088	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1089	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1090
892	=item C<EV_ERROR>	1091	=item C<EV_ERROR>
893		1092
894	An unspecified error has occurred, the watcher has been stopped. This might	1093	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1094	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1095	ran out of memory, a file descriptor was found to be closed or any other
		1096	problem. Libev considers these application bugs.
		1097
897	problem. You best act on it by reporting the problem and somehow coping	1098	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1099	watcher being stopped. Note that well-written programs should not receive
		1100	an error ever, so when your watcher receives it, this usually indicates a
		1101	bug in your program.
899		1102
900	Libev will usually signal a few "dummy" events together with an error, for	1103	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1104	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1105	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1106	the error from read() or write(). This will not work in multi-threaded
…		…
906		1109
907	=back	1110	=back
908		1111
909	=head2 GENERIC WATCHER FUNCTIONS	1112	=head2 GENERIC WATCHER FUNCTIONS
910		1113
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1114	=over 4
915		1115
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1116	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1117
918	This macro initialises the generic portion of a watcher. The contents	1118	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1123	which rolls both calls into one.
924		1124
925	You can reinitialise a watcher at any time as long as it has been stopped	1125	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1126	(or never started) and there are no pending events outstanding.
927		1127
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1128	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1129	int revents)>.
930		1130
931	Example: Initialise an C<ev_io> watcher in two steps.	1131	Example: Initialise an C<ev_io> watcher in two steps.
932		1132
933	ev_io w;	1133	ev_io w;
934	ev_init (&w, my_cb);	1134	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1136
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1138
939	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
940	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
941	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
942	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
…		…
955		1155
956	Example: Initialise and set an C<ev_io> watcher in one step.	1156	Example: Initialise and set an C<ev_io> watcher in one step.
957		1157
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1159
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1161
962	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
964		1164
965	Example: Start the C<ev_io> watcher that is being abused as example in this	1165	Example: Start the C<ev_io> watcher that is being abused as example in this
966	whole section.	1166	whole section.
967		1167
968	ev_io_start (EV_DEFAULT_UC, &w);	1168	ev_io_start (EV_DEFAULT_UC, &w);
969		1169
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1171
972	Stops the given watcher again (if active) and clears the pending	1172	Stops the given watcher if active, and clears the pending status (whether
		1173	the watcher was active or not).
		1174
973	status. It is possible that stopped watchers are pending (for example,	1175	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1176	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1177	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1178	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1179	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1180
979	=item bool ev_is_active (ev_TYPE *watcher)	1181	=item bool ev_is_active (ev_TYPE *watcher)
980		1182
981	Returns a true value iff the watcher is active (i.e. it has been started	1183	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1184	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1201
1000	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
1001	(modulo threads).	1203	(modulo threads).
1002		1204
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1206
1005	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
1006		1208
1007	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1211	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1212	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1213	from being executed (except for C<ev_idle> watchers).
1012		1214
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1215	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1216	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1217
1021	You I<must not> change the priority of a watcher as long as it is active or	1218	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1219	pending.
1023		1220
		1221	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1222	fine, as long as you do not mind that the priority value you query might
		1223	or might not have been clamped to the valid range.
		1224
1024	The default priority used by watchers when no priority has been set is	1225	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1226	always C<0>, which is supposed to not be too high and not be too low :).
1026		1227
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1229	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1230
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1232
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1234	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1041	returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
1042	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
1043		1243
1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1045	callback to be invoked, which can be accomplished with this function.	1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
1046		1260
1047	=back	1261	=back
1048		1262
1049		1263
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1270	member, you can also "subclass" the watcher type and provide your own
1057	data:	1271	data:
1058		1272
1059	struct my_io	1273	struct my_io
1060	{	1274	{
1061	struct ev_io io;	1275	ev_io io;
1062	int otherfd;	1276	int otherfd;
1063	void *somedata;	1277	void *somedata;
1064	struct whatever *mostinteresting;	1278	struct whatever *mostinteresting;
1065	};	1279	};
1066		1280
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1284
1071	And since your callback will be called with a pointer to the watcher, you	1285	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1286	can cast it back to your own type:
1073		1287
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1289	{
1076	struct my_io *w = (struct my_io *)w_;	1290	struct my_io *w = (struct my_io *)w_;
1077	...	1291	...
1078	}	1292	}
1079		1293
…		…
1097	programmers):	1311	programmers):
1098		1312
1099	#include <stddef.h>	1313	#include <stddef.h>
1100		1314
1101	static void	1315	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1316	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1317	{
1104	struct my_biggy big = (struct my_biggy *	1318	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1319	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1320	}
1107		1321
1108	static void	1322	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1323	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1324	{
1111	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1326	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1327	}
		1328
		1329	=head2 WATCHER PRIORITY MODELS
		1330
		1331	Many event loops support I<watcher priorities>, which are usually small
		1332	integers that influence the ordering of event callback invocation
		1333	between watchers in some way, all else being equal.
		1334
		1335	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1336	description for the more technical details such as the actual priority
		1337	range.
		1338
		1339	There are two common ways how these these priorities are being interpreted
		1340	by event loops:
		1341
		1342	In the more common lock-out model, higher priorities "lock out" invocation
		1343	of lower priority watchers, which means as long as higher priority
		1344	watchers receive events, lower priority watchers are not being invoked.
		1345
		1346	The less common only-for-ordering model uses priorities solely to order
		1347	callback invocation within a single event loop iteration: Higher priority
		1348	watchers are invoked before lower priority ones, but they all get invoked
		1349	before polling for new events.
		1350
		1351	Libev uses the second (only-for-ordering) model for all its watchers
		1352	except for idle watchers (which use the lock-out model).
		1353
		1354	The rationale behind this is that implementing the lock-out model for
		1355	watchers is not well supported by most kernel interfaces, and most event
		1356	libraries will just poll for the same events again and again as long as
		1357	their callbacks have not been executed, which is very inefficient in the
		1358	common case of one high-priority watcher locking out a mass of lower
		1359	priority ones.
		1360
		1361	Static (ordering) priorities are most useful when you have two or more
		1362	watchers handling the same resource: a typical usage example is having an
		1363	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1364	timeouts. Under load, data might be received while the program handles
		1365	other jobs, but since timers normally get invoked first, the timeout
		1366	handler will be executed before checking for data. In that case, giving
		1367	the timer a lower priority than the I/O watcher ensures that I/O will be
		1368	handled first even under adverse conditions (which is usually, but not
		1369	always, what you want).
		1370
		1371	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1372	will only be executed when no same or higher priority watchers have
		1373	received events, they can be used to implement the "lock-out" model when
		1374	required.
		1375
		1376	For example, to emulate how many other event libraries handle priorities,
		1377	you can associate an C<ev_idle> watcher to each such watcher, and in
		1378	the normal watcher callback, you just start the idle watcher. The real
		1379	processing is done in the idle watcher callback. This causes libev to
		1380	continously poll and process kernel event data for the watcher, but when
		1381	the lock-out case is known to be rare (which in turn is rare :), this is
		1382	workable.
		1383
		1384	Usually, however, the lock-out model implemented that way will perform
		1385	miserably under the type of load it was designed to handle. In that case,
		1386	it might be preferable to stop the real watcher before starting the
		1387	idle watcher, so the kernel will not have to process the event in case
		1388	the actual processing will be delayed for considerable time.
		1389
		1390	Here is an example of an I/O watcher that should run at a strictly lower
		1391	priority than the default, and which should only process data when no
		1392	other events are pending:
		1393
		1394	ev_idle idle; // actual processing watcher
		1395	ev_io io; // actual event watcher
		1396
		1397	static void
		1398	io_cb (EV_P_ ev_io *w, int revents)
		1399	{
		1400	// stop the I/O watcher, we received the event, but
		1401	// are not yet ready to handle it.
		1402	ev_io_stop (EV_A_ w);
		1403
		1404	// start the idle watcher to ahndle the actual event.
		1405	// it will not be executed as long as other watchers
		1406	// with the default priority are receiving events.
		1407	ev_idle_start (EV_A_ &idle);
		1408	}
		1409
		1410	static void
		1411	idle_cb (EV_P_ ev_idle *w, int revents)
		1412	{
		1413	// actual processing
		1414	read (STDIN_FILENO, ...);
		1415
		1416	// have to start the I/O watcher again, as
		1417	// we have handled the event
		1418	ev_io_start (EV_P_ &io);
		1419	}
		1420
		1421	// initialisation
		1422	ev_idle_init (&idle, idle_cb);
		1423	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1424	ev_io_start (EV_DEFAULT_ &io);
		1425
		1426	In the "real" world, it might also be beneficial to start a timer, so that
		1427	low-priority connections can not be locked out forever under load. This
		1428	enables your program to keep a lower latency for important connections
		1429	during short periods of high load, while not completely locking out less
		1430	important ones.
1114		1431
1115		1432
1116	=head1 WATCHER TYPES	1433	=head1 WATCHER TYPES
1117		1434
1118	This section describes each watcher in detail, but will not repeat	1435	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1461	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1462	required if you know what you are doing).
1146		1463
1147	If you cannot use non-blocking mode, then force the use of a	1464	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1465	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1467	descriptors for which non-blocking operation makes no sense (such as
		1468	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1469
1151	Another thing you have to watch out for is that it is quite easy to	1470	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1471	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1473	because there is no data. Not only are some backends known to create a
…		…
1219		1538
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1539	So when you encounter spurious, unexplained daemon exits, make sure you
1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1222	somewhere, as that would have given you a big clue).	1541	somewhere, as that would have given you a big clue).
1223		1542
		1543	=head3 The special problem of accept()ing when you can't
		1544
		1545	Many implementations of the POSIX C<accept> function (for example,
		1546	found in port-2004 Linux) have the peculiar behaviour of not removing a
		1547	connection from the pending queue in all error cases.
		1548
		1549	For example, larger servers often run out of file descriptors (because
		1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1551	rejecting the connection, leading to libev signalling readiness on
		1552	the next iteration again (the connection still exists after all), and
		1553	typically causing the program to loop at 100% CPU usage.
		1554
		1555	Unfortunately, the set of errors that cause this issue differs between
		1556	operating systems, there is usually little the app can do to remedy the
		1557	situation, and no known thread-safe method of removing the connection to
		1558	cope with overload is known (to me).
		1559
		1560	One of the easiest ways to handle this situation is to just ignore it
		1561	- when the program encounters an overload, it will just loop until the
		1562	situation is over. While this is a form of busy waiting, no OS offers an
		1563	event-based way to handle this situation, so it's the best one can do.
		1564
		1565	A better way to handle the situation is to log any errors other than
		1566	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1567	messages, and continue as usual, which at least gives the user an idea of
		1568	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1569	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1570	usage.
		1571
		1572	If your program is single-threaded, then you could also keep a dummy file
		1573	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1574	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1575	close that fd, and create a new dummy fd. This will gracefully refuse
		1576	clients under typical overload conditions.
		1577
		1578	The last way to handle it is to simply log the error and C<exit>, as
		1579	is often done with C<malloc> failures, but this results in an easy
		1580	opportunity for a DoS attack.
1224		1581
1225	=head3 Watcher-Specific Functions	1582	=head3 Watcher-Specific Functions
1226		1583
1227	=over 4	1584	=over 4
1228		1585
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1606	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1607	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1608	attempt to read a whole line in the callback.
1252		1609
1253	static void	1610	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1611	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1612	{
1256	ev_io_stop (loop, w);	1613	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1614	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1615	}
1259		1616
1260	...	1617	...
1261	struct ev_loop *loop = ev_default_init (0);	1618	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1619	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1620	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1621	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1622	ev_loop (loop, 0);
1266		1623
1267		1624
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1632	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1633	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1634	monotonic clock option helps a lot here).
1278		1635
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1636	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1637	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1638	might introduce a small delay). If multiple timers become ready during the
		1639	same loop iteration then the ones with earlier time-out values are invoked
		1640	before ones of the same priority with later time-out values (but this is
		1641	no longer true when a callback calls C<ev_loop> recursively).
		1642
		1643	=head3 Be smart about timeouts
		1644
		1645	Many real-world problems involve some kind of timeout, usually for error
		1646	recovery. A typical example is an HTTP request - if the other side hangs,
		1647	you want to raise some error after a while.
		1648
		1649	What follows are some ways to handle this problem, from obvious and
		1650	inefficient to smart and efficient.
		1651
		1652	In the following, a 60 second activity timeout is assumed - a timeout that
		1653	gets reset to 60 seconds each time there is activity (e.g. each time some
		1654	data or other life sign was received).
		1655
		1656	=over 4
		1657
		1658	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1659
		1660	This is the most obvious, but not the most simple way: In the beginning,
		1661	start the watcher:
		1662
		1663	ev_timer_init (timer, callback, 60., 0.);
		1664	ev_timer_start (loop, timer);
		1665
		1666	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1667	and start it again:
		1668
		1669	ev_timer_stop (loop, timer);
		1670	ev_timer_set (timer, 60., 0.);
		1671	ev_timer_start (loop, timer);
		1672
		1673	This is relatively simple to implement, but means that each time there is
		1674	some activity, libev will first have to remove the timer from its internal
		1675	data structure and then add it again. Libev tries to be fast, but it's
		1676	still not a constant-time operation.
		1677
		1678	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1679
		1680	This is the easiest way, and involves using C<ev_timer_again> instead of
		1681	C<ev_timer_start>.
		1682
		1683	To implement this, configure an C<ev_timer> with a C<repeat> value
		1684	of C<60> and then call C<ev_timer_again> at start and each time you
		1685	successfully read or write some data. If you go into an idle state where
		1686	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1687	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1688
		1689	That means you can ignore both the C<ev_timer_start> function and the
		1690	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1691	member and C<ev_timer_again>.
		1692
		1693	At start:
		1694
		1695	ev_init (timer, callback);
		1696	timer->repeat = 60.;
		1697	ev_timer_again (loop, timer);
		1698
		1699	Each time there is some activity:
		1700
		1701	ev_timer_again (loop, timer);
		1702
		1703	It is even possible to change the time-out on the fly, regardless of
		1704	whether the watcher is active or not:
		1705
		1706	timer->repeat = 30.;
		1707	ev_timer_again (loop, timer);
		1708
		1709	This is slightly more efficient then stopping/starting the timer each time
		1710	you want to modify its timeout value, as libev does not have to completely
		1711	remove and re-insert the timer from/into its internal data structure.
		1712
		1713	It is, however, even simpler than the "obvious" way to do it.
		1714
		1715	=item 3. Let the timer time out, but then re-arm it as required.
		1716
		1717	This method is more tricky, but usually most efficient: Most timeouts are
		1718	relatively long compared to the intervals between other activity - in
		1719	our example, within 60 seconds, there are usually many I/O events with
		1720	associated activity resets.
		1721
		1722	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1723	but remember the time of last activity, and check for a real timeout only
		1724	within the callback:
		1725
		1726	ev_tstamp last_activity; // time of last activity
		1727
		1728	static void
		1729	callback (EV_P_ ev_timer *w, int revents)
		1730	{
		1731	ev_tstamp now = ev_now (EV_A);
		1732	ev_tstamp timeout = last_activity + 60.;
		1733
		1734	// if last_activity + 60. is older than now, we did time out
		1735	if (timeout < now)
		1736	{
		1737	// timeout occured, take action
		1738	}
		1739	else
		1740	{
		1741	// callback was invoked, but there was some activity, re-arm
		1742	// the watcher to fire in last_activity + 60, which is
		1743	// guaranteed to be in the future, so "again" is positive:
		1744	w->repeat = timeout - now;
		1745	ev_timer_again (EV_A_ w);
		1746	}
		1747	}
		1748
		1749	To summarise the callback: first calculate the real timeout (defined
		1750	as "60 seconds after the last activity"), then check if that time has
		1751	been reached, which means something I<did>, in fact, time out. Otherwise
		1752	the callback was invoked too early (C<timeout> is in the future), so
		1753	re-schedule the timer to fire at that future time, to see if maybe we have
		1754	a timeout then.
		1755
		1756	Note how C<ev_timer_again> is used, taking advantage of the
		1757	C<ev_timer_again> optimisation when the timer is already running.
		1758
		1759	This scheme causes more callback invocations (about one every 60 seconds
		1760	minus half the average time between activity), but virtually no calls to
		1761	libev to change the timeout.
		1762
		1763	To start the timer, simply initialise the watcher and set C<last_activity>
		1764	to the current time (meaning we just have some activity :), then call the
		1765	callback, which will "do the right thing" and start the timer:
		1766
		1767	ev_init (timer, callback);
		1768	last_activity = ev_now (loop);
		1769	callback (loop, timer, EV_TIMEOUT);
		1770
		1771	And when there is some activity, simply store the current time in
		1772	C<last_activity>, no libev calls at all:
		1773
		1774	last_actiivty = ev_now (loop);
		1775
		1776	This technique is slightly more complex, but in most cases where the
		1777	time-out is unlikely to be triggered, much more efficient.
		1778
		1779	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1780	callback :) - just change the timeout and invoke the callback, which will
		1781	fix things for you.
		1782
		1783	=item 4. Wee, just use a double-linked list for your timeouts.
		1784
		1785	If there is not one request, but many thousands (millions...), all
		1786	employing some kind of timeout with the same timeout value, then one can
		1787	do even better:
		1788
		1789	When starting the timeout, calculate the timeout value and put the timeout
		1790	at the I<end> of the list.
		1791
		1792	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1793	the list is expected to fire (for example, using the technique #3).
		1794
		1795	When there is some activity, remove the timer from the list, recalculate
		1796	the timeout, append it to the end of the list again, and make sure to
		1797	update the C<ev_timer> if it was taken from the beginning of the list.
		1798
		1799	This way, one can manage an unlimited number of timeouts in O(1) time for
		1800	starting, stopping and updating the timers, at the expense of a major
		1801	complication, and having to use a constant timeout. The constant timeout
		1802	ensures that the list stays sorted.
		1803
		1804	=back
		1805
		1806	So which method the best?
		1807
		1808	Method #2 is a simple no-brain-required solution that is adequate in most
		1809	situations. Method #3 requires a bit more thinking, but handles many cases
		1810	better, and isn't very complicated either. In most case, choosing either
		1811	one is fine, with #3 being better in typical situations.
		1812
		1813	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1814	rather complicated, but extremely efficient, something that really pays
		1815	off after the first million or so of active timers, i.e. it's usually
		1816	overkill :)
1282		1817
1283	=head3 The special problem of time updates	1818	=head3 The special problem of time updates
1284		1819
1285	Establishing the current time is a costly operation (it usually takes at	1820	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1821	least two system calls): EV therefore updates its idea of the current
…		…
1298		1833
1299	If the event loop is suspended for a long time, you can also force an	1834	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1835	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1836	()>.
1302		1837
		1838	=head3 The special problems of suspended animation
		1839
		1840	When you leave the server world it is quite customary to hit machines that
		1841	can suspend/hibernate - what happens to the clocks during such a suspend?
		1842
		1843	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1844	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1845	to run until the system is suspended, but they will not advance while the
		1846	system is suspended. That means, on resume, it will be as if the program
		1847	was frozen for a few seconds, but the suspend time will not be counted
		1848	towards C<ev_timer> when a monotonic clock source is used. The real time
		1849	clock advanced as expected, but if it is used as sole clocksource, then a
		1850	long suspend would be detected as a time jump by libev, and timers would
		1851	be adjusted accordingly.
		1852
		1853	I would not be surprised to see different behaviour in different between
		1854	operating systems, OS versions or even different hardware.
		1855
		1856	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1857	time jump in the monotonic clocks and the realtime clock. If the program
		1858	is suspended for a very long time, and monotonic clock sources are in use,
		1859	then you can expect C<ev_timer>s to expire as the full suspension time
		1860	will be counted towards the timers. When no monotonic clock source is in
		1861	use, then libev will again assume a timejump and adjust accordingly.
		1862
		1863	It might be beneficial for this latter case to call C<ev_suspend>
		1864	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1865	deterministic behaviour in this case (you can do nothing against
		1866	C<SIGSTOP>).
		1867
1303	=head3 Watcher-Specific Functions and Data Members	1868	=head3 Watcher-Specific Functions and Data Members
1304		1869
1305	=over 4	1870	=over 4
1306		1871
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1872	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1895	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1896
1332	If the timer is repeating, either start it if necessary (with the	1897	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1898	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1899
1335	This sounds a bit complicated, but here is a useful and typical	1900	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1901	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		1902
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1903	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		1904
1348	ev_timer_init (timer, callback, 0., 5.);	1905	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1906	then this time is relative to the current event loop time, otherwise it's
1350	...	1907	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		1908
1357	This is more slightly efficient then stopping/starting the timer each time	1909	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1910	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		1911	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	1912	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	1913	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1914
1366	=item ev_tstamp repeat [read-write]	1915	=item ev_tstamp repeat [read-write]
1367		1916
1368	The current C<repeat> value. Will be used each time the watcher times out	1917	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1918	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1923	=head3 Examples
1375		1924
1376	Example: Create a timer that fires after 60 seconds.	1925	Example: Create a timer that fires after 60 seconds.
1377		1926
1378	static void	1927	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1928	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1929	{
1381	.. one minute over, w is actually stopped right here	1930	.. one minute over, w is actually stopped right here
1382	}	1931	}
1383		1932
1384	struct ev_timer mytimer;	1933	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1934	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1935	ev_timer_start (loop, &mytimer);
1387		1936
1388	Example: Create a timeout timer that times out after 10 seconds of	1937	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1938	inactivity.
1390		1939
1391	static void	1940	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1941	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1942	{
1394	.. ten seconds without any activity	1943	.. ten seconds without any activity
1395	}	1944	}
1396		1945
1397	struct ev_timer mytimer;	1946	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1947	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1948	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1949	ev_loop (loop, 0);
1401		1950
1402	// and in some piece of code that gets executed on any "activity":	1951	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1956	=head2 C<ev_periodic> - to cron or not to cron?
1408		1957
1409	Periodic watchers are also timers of a kind, but they are very versatile	1958	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1959	(and unfortunately a bit complex).
1411		1960
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1961	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1962	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1963	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1964	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1965	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1966	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1967
		1968	You can tell a periodic watcher to trigger after some specific point
		1969	in time: for example, if you tell a periodic watcher to trigger "in 10
		1970	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1971	not a delay) and then reset your system clock to January of the previous
		1972	year, then it will take a year or more to trigger the event (unlike an
		1973	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1974	it, as it uses a relative timeout).
		1975
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1976	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1977	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1978	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1979	those cannot react to time jumps.
1424		1980
1425	As with timers, the callback is guaranteed to be invoked only when the	1981	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1982	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1983	timers become ready during the same loop iteration then the ones with
		1984	earlier time-out values are invoked before ones with later time-out values
		1985	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1986
1429	=head3 Watcher-Specific Functions and Data Members	1987	=head3 Watcher-Specific Functions and Data Members
1430		1988
1431	=over 4	1989	=over 4
1432		1990
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1991	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1992
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1993	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1994
1437	Lots of arguments, lets sort it out... There are basically three modes of	1995	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1996	operation, and we will explain them from simplest to most complex:
1439		1997
1440	=over 4	1998	=over 4
1441		1999
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2000	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2001
1444	In this configuration the watcher triggers an event after the wall clock	2002	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	2003	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2004	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	2005	will be stopped and invoked when the system clock reaches or surpasses
		2006	this point in time.
1448		2007
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2008	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		2009
1451	In this mode the watcher will always be scheduled to time out at the next	2010	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	2011	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	2012	negative) and then repeat, regardless of any time jumps. The C<offset>
		2013	argument is merely an offset into the C<interval> periods.
1454		2014
1455	This can be used to create timers that do not drift with respect to the	2015	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	2016	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	2017	hour, on the hour (with respect to UTC):
1458		2018
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2019	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2020
1461	This doesn't mean there will always be 3600 seconds in between triggers,	2021	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	2022	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	2023	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	2024	by 3600.
1465		2025
1466	Another way to think about it (for the mathematically inclined) is that	2026	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	2027	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	2028	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		2029
1470	For numerical stability it is preferable that the C<at> value is near	2030	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	2031	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	2032	this value, and in fact is often specified as zero.
1473		2033
1474	Note also that there is an upper limit to how often a timer can fire (CPU	2034	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	2035	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	2036	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	2037	millisecond (if the OS supports it and the machine is fast enough).
1478		2038
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2039	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2040
1481	In this mode the values for C<interval> and C<at> are both being	2041	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2042	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	2043	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	2044	current time as second argument.
1485		2045
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2046	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	2047	or make ANY other event loop modifications whatsoever, unless explicitly
		2048	allowed by documentation here>.
1488		2049
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2050	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2051	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	2052	only event loop modification you are allowed to do).
1492		2053
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2054	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2055	*w, ev_tstamp now)>, e.g.:
1495		2056
		2057	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2058	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2059	{
1498	return now + 60.;	2060	return now + 60.;
1499	}	2061	}
1500		2062
1501	It must return the next time to trigger, based on the passed time value	2063	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	2083	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2084	program when the crontabs have changed).
1523		2085
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2086	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2087
1526	When active, returns the absolute time that the watcher is supposed to	2088	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2089	to trigger next. This is not the same as the C<offset> argument to
		2090	C<ev_periodic_set>, but indeed works even in interval and manual
		2091	rescheduling modes.
1528		2092
1529	=item ev_tstamp offset [read-write]	2093	=item ev_tstamp offset [read-write]
1530		2094
1531	When repeating, this contains the offset value, otherwise this is the	2095	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2096	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2097	although libev might modify this value for better numerical stability).
1533		2098
1534	Can be modified any time, but changes only take effect when the periodic	2099	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2100	timer fires or C<ev_periodic_again> is being called.
1536		2101
1537	=item ev_tstamp interval [read-write]	2102	=item ev_tstamp interval [read-write]
1538		2103
1539	The current interval value. Can be modified any time, but changes only	2104	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2105	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2106	called.
1542		2107
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2108	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2109
1545	The current reschedule callback, or C<0>, if this functionality is	2110	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2111	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2112	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2113
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2118	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2119	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2120	potentially a lot of jitter, but good long-term stability.
1556		2121
1557	static void	2122	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2123	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	2124	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2125	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2126	}
1562		2127
1563	struct ev_periodic hourly_tick;	2128	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2129	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2130	ev_periodic_start (loop, &hourly_tick);
1566		2131
1567	Example: The same as above, but use a reschedule callback to do it:	2132	Example: The same as above, but use a reschedule callback to do it:
1568		2133
1569	#include <math.h>	2134	#include <math.h>
1570		2135
1571	static ev_tstamp	2136	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2137	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2138	{
1574	return now + (3600. - fmod (now, 3600.));	2139	return now + (3600. - fmod (now, 3600.));
1575	}	2140	}
1576		2141
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2142	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2143
1579	Example: Call a callback every hour, starting now:	2144	Example: Call a callback every hour, starting now:
1580		2145
1581	struct ev_periodic hourly_tick;	2146	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2147	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2148	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2149	ev_periodic_start (loop, &hourly_tick);
1585		2150
1586		2151
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2154	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2155	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2156	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2157	normal event processing, like any other event.
1593		2158
1594	If you want signals asynchronously, just use C<sigaction> as you would	2159	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2160	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2161	the signal. You can even use C<ev_async> from a signal handler to
		2162	synchronously wake up an event loop.
1597		2163
1598	You can configure as many watchers as you like per signal. Only when the	2164	You can configure as many watchers as you like for the same signal, but
		2165	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2166	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2167	C<SIGINT> in both the default loop and another loop at the same time. At
		2168	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2169
1599	first watcher gets started will libev actually register a signal handler	2170	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2171	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2172	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2173
1605	If possible and supported, libev will install its handlers with	2174	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2175	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2176	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2177	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2178	and unblock them in an C<ev_prepare> watcher.
		2179
		2180	=head3 The special problem of inheritance over fork/execve/pthread_create
		2181
		2182	Both the signal mask (C<sigprocmask>) and the signal disposition
		2183	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2184	stopping it again), that is, libev might or might not block the signal,
		2185	and might or might not set or restore the installed signal handler.
		2186
		2187	While this does not matter for the signal disposition (libev never
		2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2189	C<execve>), this matters for the signal mask: many programs do not expect
		2190	certain signals to be blocked.
		2191
		2192	This means that before calling C<exec> (from the child) you should reset
		2193	the signal mask to whatever "default" you expect (all clear is a good
		2194	choice usually).
		2195
		2196	The simplest way to ensure that the signal mask is reset in the child is
		2197	to install a fork handler with C<pthread_atfork> that resets it. That will
		2198	catch fork calls done by libraries (such as the libc) as well.
		2199
		2200	In current versions of libev, the signal will not be blocked indefinitely
		2201	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2202	the window of opportunity for problems, it will not go away, as libev
		2203	I<has> to modify the signal mask, at least temporarily.
		2204
		2205	So I can't stress this enough: I<If you do not reset your signal mask when
		2206	you expect it to be empty, you have a race condition in your code>. This
		2207	is not a libev-specific thing, this is true for most event libraries.
1610		2208
1611	=head3 Watcher-Specific Functions and Data Members	2209	=head3 Watcher-Specific Functions and Data Members
1612		2210
1613	=over 4	2211	=over 4
1614		2212
…		…
1625		2223
1626	=back	2224	=back
1627		2225
1628	=head3 Examples	2226	=head3 Examples
1629		2227
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2228	Example: Try to exit cleanly on SIGINT.
1631		2229
1632	static void	2230	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2231	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2232	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2233	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2234	}
1637		2235
1638	struct ev_signal signal_watcher;	2236	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2237	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2238	ev_signal_start (loop, &signal_watcher);
1641		2239
1642		2240
1643	=head2 C<ev_child> - watch out for process status changes	2241	=head2 C<ev_child> - watch out for process status changes
1644		2242
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2243	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2244	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2245	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2246	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2247	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2248	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2249	but forking and registering a watcher a few event loop iterations later or
1652	not.	2250	in the next callback invocation is not.
1653		2251
1654	Only the default event loop is capable of handling signals, and therefore	2252	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2253	you can only register child watchers in the default event loop.
1656		2254
		2255	Due to some design glitches inside libev, child watchers will always be
		2256	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2257	libev)
		2258
1657	=head3 Process Interaction	2259	=head3 Process Interaction
1658		2260
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2261	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2262	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2263	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2264	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2265	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2266	children, even ones not watched.
1665		2267
1666	=head3 Overriding the Built-In Processing	2268	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2278	=head3 Stopping the Child Watcher
1677		2279
1678	Currently, the child watcher never gets stopped, even when the	2280	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2281	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2282	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2283	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2284	problem).
1682		2285
1683	=head3 Watcher-Specific Functions and Data Members	2286	=head3 Watcher-Specific Functions and Data Members
1684		2287
1685	=over 4	2288	=over 4
1686		2289
…		…
1718	its completion.	2321	its completion.
1719		2322
1720	ev_child cw;	2323	ev_child cw;
1721		2324
1722	static void	2325	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2326	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2327	{
1725	ev_child_stop (EV_A_ w);	2328	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2329	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2330	}
1728		2331
…		…
1743		2346
1744		2347
1745	=head2 C<ev_stat> - did the file attributes just change?	2348	=head2 C<ev_stat> - did the file attributes just change?
1746		2349
1747	This watches a file system path for attribute changes. That is, it calls	2350	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2351	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2352	and sees if it changed compared to the last time, invoking the callback if
		2353	it did.
1750		2354
1751	The path does not need to exist: changing from "path exists" to "path does	2355	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2356	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2357	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2358	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2359	least one) and all the other fields of the stat buffer having unspecified
		2360	contents.
1756		2361
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2362	The path I<must not> end in a slash or contain special components such as
		2363	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2364	your working directory changes, then the behaviour is undefined.
1759		2365
1760	Since there is no standard kernel interface to do this, the portable	2366	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2367	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2368	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2369	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2370	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2371	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2372	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2373	currently around C<0.1>, but that's usually overkill.
1768		2374
1769	This watcher type is not meant for massive numbers of stat watchers,	2375	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2376	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2377	resource-intensive.
1772		2378
1773	At the time of this writing, the only OS-specific interface implemented	2379	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2380	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2381	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2382	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2383
1778	=head3 ABI Issues (Largefile Support)	2384	=head3 ABI Issues (Largefile Support)
1779		2385
1780	Libev by default (unless the user overrides this) uses the default	2386	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2387	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2388	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2389	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2390	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2391	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2392	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2393	most noticeably displayed with ev_stat and large file support.
1788		2394
1789	The solution for this is to lobby your distribution maker to make large	2395	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2396	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2397	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2398	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2399	default compilation environment.
1794		2400
1795	=head3 Inotify and Kqueue	2401	=head3 Inotify and Kqueue
1796		2402
1797	When C<inotify (7)> support has been compiled into libev (generally only	2403	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2404	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2405	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2406	watcher is being started.
1801		2407
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2408	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2409	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2410	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2411	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2412	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2413	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2414	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2415	xfs are fully working) libev usually gets away without polling.
1807		2416
1808	There is no support for kqueue, as apparently it cannot be used to	2417	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2418	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2419	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2420	etc. is difficult.
1812		2421
		2422	=head3 C<stat ()> is a synchronous operation
		2423
		2424	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2425	the process. The exception are C<ev_stat> watchers - those call C<stat
		2426	()>, which is a synchronous operation.
		2427
		2428	For local paths, this usually doesn't matter: unless the system is very
		2429	busy or the intervals between stat's are large, a stat call will be fast,
		2430	as the path data is usually in memory already (except when starting the
		2431	watcher).
		2432
		2433	For networked file systems, calling C<stat ()> can block an indefinite
		2434	time due to network issues, and even under good conditions, a stat call
		2435	often takes multiple milliseconds.
		2436
		2437	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2438	paths, although this is fully supported by libev.
		2439
1813	=head3 The special problem of stat time resolution	2440	=head3 The special problem of stat time resolution
1814		2441
1815	The C<stat ()> system call only supports full-second resolution portably, and	2442	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2443	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2444	still only support whole seconds.
1818		2445
1819	That means that, if the time is the only thing that changes, you can	2446	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2447	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2448	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2449	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2592
1966	=head3 Watcher-Specific Functions and Data Members	2593	=head3 Watcher-Specific Functions and Data Members
1967		2594
1968	=over 4	2595	=over 4
1969		2596
1970	=item ev_idle_init (ev_signal *, callback)	2597	=item ev_idle_init (ev_idle *, callback)
1971		2598
1972	Initialises and configures the idle watcher - it has no parameters of any	2599	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2600	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2601	believe me.
1975		2602
…		…
1979		2606
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2607	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2608	callback, free it. Also, use no error checking, as usual.
1982		2609
1983	static void	2610	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2611	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2612	{
1986	free (w);	2613	free (w);
1987	// now do something you wanted to do when the program has	2614	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2615	// no longer anything immediate to do.
1989	}	2616	}
1990		2617
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2618	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2619	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2620	ev_idle_start (loop, idle_watcher);
1994		2621
1995		2622
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2623	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2624
1998	Prepare and check watchers are usually (but not always) used in pairs:	2625	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2704
2078	static ev_io iow [nfd];	2705	static ev_io iow [nfd];
2079	static ev_timer tw;	2706	static ev_timer tw;
2080		2707
2081	static void	2708	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2709	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2710	{
2084	}	2711	}
2085		2712
2086	// create io watchers for each fd and a timer before blocking	2713	// create io watchers for each fd and a timer before blocking
2087	static void	2714	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2715	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2716	{
2090	int timeout = 3600000;	2717	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2718	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2719	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2720	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2721
2095	/* the callback is illegal, but won't be called as we stop during check */	2722	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2723	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2724	ev_timer_start (loop, &tw);
2098		2725
2099	// create one ev_io per pollfd	2726	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2727	for (int i = 0; i < nfd; ++i)
2101	{	2728	{
…		…
2108	}	2735	}
2109	}	2736	}
2110		2737
2111	// stop all watchers after blocking	2738	// stop all watchers after blocking
2112	static void	2739	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2740	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2741	{
2115	ev_timer_stop (loop, &tw);	2742	ev_timer_stop (loop, &tw);
2116		2743
2117	for (int i = 0; i < nfd; ++i)	2744	for (int i = 0; i < nfd; ++i)
2118	{	2745	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2841	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2842	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2843	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2844	the rest in a second one, and embed the second one in the first.
2218		2845
2219	As long as the watcher is active, the callback will be invoked every time	2846	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2847	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2848	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2849	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2850	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2851	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2852
2227	As long as the watcher is started it will automatically handle events. The	2853	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2854	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2855
2232	Also, there have not currently been made special provisions for forking:	2856	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2857	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2858	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2859	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2860
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2861	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2862	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2863	portable one.
2241		2864
2242	So when you want to use this feature you will always have to be prepared	2865	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2866	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2867	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2868	create it, and if that fails, use the normal loop for everything.
		2869
		2870	=head3 C<ev_embed> and fork
		2871
		2872	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2873	automatically be applied to the embedded loop as well, so no special
		2874	fork handling is required in that case. When the watcher is not running,
		2875	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2876	as applicable.
2246		2877
2247	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2248		2879
2249	=over 4	2880	=over 4
2250		2881
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2909	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2910	used).
2280		2911
2281	struct ev_loop *loop_hi = ev_default_init (0);	2912	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2913	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2914	ev_embed embed;
2284		2915
2285	// see if there is a chance of getting one that works	2916	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2917	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2918	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2919	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2933	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2934	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2935
2305	struct ev_loop *loop = ev_default_init (0);	2936	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2937	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2938	ev_embed embed;
2308		2939
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2940	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2941	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2942	{
2312	ev_embed_init (&embed, 0, loop_socket);	2943	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	event loop blocks next and before C<ev_check> watchers are being called,	2958	event loop blocks next and before C<ev_check> watchers are being called,
2328	and only in the child after the fork. If whoever good citizen calling	2959	and only in the child after the fork. If whoever good citizen calling
2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2960	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2330	handlers will be invoked, too, of course.	2961	handlers will be invoked, too, of course.
2331		2962
		2963	=head3 The special problem of life after fork - how is it possible?
		2964
		2965	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2966	up/change the process environment, followed by a call to C<exec()>. This
		2967	sequence should be handled by libev without any problems.
		2968
		2969	This changes when the application actually wants to do event handling
		2970	in the child, or both parent in child, in effect "continuing" after the
		2971	fork.
		2972
		2973	The default mode of operation (for libev, with application help to detect
		2974	forks) is to duplicate all the state in the child, as would be expected
		2975	when I<either> the parent I<or> the child process continues.
		2976
		2977	When both processes want to continue using libev, then this is usually the
		2978	wrong result. In that case, usually one process (typically the parent) is
		2979	supposed to continue with all watchers in place as before, while the other
		2980	process typically wants to start fresh, i.e. without any active watchers.
		2981
		2982	The cleanest and most efficient way to achieve that with libev is to
		2983	simply create a new event loop, which of course will be "empty", and
		2984	use that for new watchers. This has the advantage of not touching more
		2985	memory than necessary, and thus avoiding the copy-on-write, and the
		2986	disadvantage of having to use multiple event loops (which do not support
		2987	signal watchers).
		2988
		2989	When this is not possible, or you want to use the default loop for
		2990	other reasons, then in the process that wants to start "fresh", call
		2991	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2992	the default loop will "orphan" (not stop) all registered watchers, so you
		2993	have to be careful not to execute code that modifies those watchers. Note
		2994	also that in that case, you have to re-register any signal watchers.
		2995
2332	=head3 Watcher-Specific Functions and Data Members	2996	=head3 Watcher-Specific Functions and Data Members
2333		2997
2334	=over 4	2998	=over 4
2335		2999
2336	=item ev_fork_init (ev_signal *, callback)	3000	=item ev_fork_init (ev_signal *, callback)
…		…
2365	=head3 Queueing	3029	=head3 Queueing
2366		3030
2367	C<ev_async> does not support queueing of data in any way. The reason	3031	C<ev_async> does not support queueing of data in any way. The reason
2368	is that the author does not know of a simple (or any) algorithm for a	3032	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	3033	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	3034	need elaborate support such as pthreads or unportable memory access
		3035	semantics.
2371		3036
2372	That means that if you want to queue data, you have to provide your own	3037	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you how to implement locking around your	3038	queue. But at least I can tell you how to implement locking around your
2374	queue:	3039	queue:
2375		3040
2376	=over 4	3041	=over 4
2377		3042
2378	=item queueing from a signal handler context	3043	=item queueing from a signal handler context
2379		3044
2380	To implement race-free queueing, you simply add to the queue in the signal	3045	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3046	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	3047	an example that does that for some fictitious SIGUSR1 handler:
2383		3048
2384	static ev_async mysig;	3049	static ev_async mysig;
2385		3050
2386	static void	3051	static void
2387	sigusr1_handler (void)	3052	sigusr1_handler (void)
…		…
2453	=over 4	3118	=over 4
2454		3119
2455	=item ev_async_init (ev_async *, callback)	3120	=item ev_async_init (ev_async *, callback)
2456		3121
2457	Initialises and configures the async watcher - it has no parameters of any	3122	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3123	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	3124	trust me.
2460		3125
2461	=item ev_async_send (loop, ev_async *)	3126	=item ev_async_send (loop, ev_async *)
2462		3127
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3128	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3129	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	3130	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3131	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	3132	section below on what exactly this means).
2468		3133
		3134	Note that, as with other watchers in libev, multiple events might get
		3135	compressed into a single callback invocation (another way to look at this
		3136	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3137	reset when the event loop detects that).
		3138
2469	This call incurs the overhead of a system call only once per loop iteration,	3139	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	3140	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	3141	repeated calls to C<ev_async_send> for the same event loop.
2472		3142
2473	=item bool = ev_async_pending (ev_async *)	3143	=item bool = ev_async_pending (ev_async *)
2474		3144
2475	Returns a non-zero value when C<ev_async_send> has been called on the	3145	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	3146	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3149	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	3150	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	3151	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	3152	quickly check whether invoking the loop might be a good idea.
2483		3153
2484	Not that this does I<not> check whether the watcher itself is pending, only	3154	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	3155	only whether it has been requested to make this watcher pending: there
		3156	is a time window between the event loop checking and resetting the async
		3157	notification, and the callback being invoked.
2486		3158
2487	=back	3159	=back
2488		3160
2489		3161
2490	=head1 OTHER FUNCTIONS	3162	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3166	=over 4
2495		3167
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3168	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3169
2498	This function combines a simple timer and an I/O watcher, calls your	3170	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3171	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3172	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3173	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3174	more watchers yourself.
2503		3175
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3176	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3177	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3178	the given C<fd> and C<events> set will be created and started.
2507		3179
2508	If C<timeout> is less than 0, then no timeout watcher will be	3180	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3181	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3182	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3183
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3184	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	3185	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3186	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	3187	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3188	a timeout and an io event at the same time - you probably should give io
		3189	events precedence.
		3190
		3191	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3192
2518	static void stdin_ready (int revents, void *arg)	3193	static void stdin_ready (int revents, void *arg)
2519	{	3194	{
		3195	if (revents & EV_READ)
		3196	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3197	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	3198	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3199	}
2525		3200
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3202
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2529
2530	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).
2533
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3203	=item ev_feed_fd_event (loop, int fd, int revents)
2535		3204
2536	Feed an event on the given fd, as if a file descriptor backend detected	3205	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	3206	the given events it.
2538		3207
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3208	=item ev_feed_signal_event (loop, int signum)
2540		3209
2541	Feed an event as if the given signal occurred (C<loop> must be the default	3210	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	3211	loop!).
2543		3212
2544	=back	3213	=back
…		…
2624		3293
2625	=over 4	3294	=over 4
2626		3295
2627	=item ev::TYPE::TYPE ()	3296	=item ev::TYPE::TYPE ()
2628		3297
2629	=item ev::TYPE::TYPE (struct ev_loop *)	3298	=item ev::TYPE::TYPE (loop)
2630		3299
2631	=item ev::TYPE::~TYPE	3300	=item ev::TYPE::~TYPE
2632		3301
2633	The constructor (optionally) takes an event loop to associate the watcher	3302	The constructor (optionally) takes an event loop to associate the watcher
2634	with. If it is omitted, it will use C<EV_DEFAULT>.	3303	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2666		3335
2667	myclass obj;	3336	myclass obj;
2668	ev::io iow;	3337	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3338	iow.set <myclass, &myclass::io_cb> (&obj);
2670		3339
		3340	=item w->set (object *)
		3341
		3342	This is an B<experimental> feature that might go away in a future version.
		3343
		3344	This is a variation of a method callback - leaving out the method to call
		3345	will default the method to C<operator ()>, which makes it possible to use
		3346	functor objects without having to manually specify the C<operator ()> all
		3347	the time. Incidentally, you can then also leave out the template argument
		3348	list.
		3349
		3350	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3351	int revents)>.
		3352
		3353	See the method-C<set> above for more details.
		3354
		3355	Example: use a functor object as callback.
		3356
		3357	struct myfunctor
		3358	{
		3359	void operator() (ev::io &w, int revents)
		3360	{
		3361	...
		3362	}
		3363	}
		3364
		3365	myfunctor f;
		3366
		3367	ev::io w;
		3368	w.set (&f);
		3369
2671	=item w->set<function> (void *data = 0)	3370	=item w->set<function> (void *data = 0)
2672		3371
2673	Also sets a callback, but uses a static method or plain function as	3372	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3373	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	3374	C<data> member and is free for you to use.
…		…
2681	Example: Use a plain function as callback.	3380	Example: Use a plain function as callback.
2682		3381
2683	static void io_cb (ev::io &w, int revents) { }	3382	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3383	iow.set <io_cb> ();
2685		3384
2686	=item w->set (struct ev_loop *)	3385	=item w->set (loop)
2687		3386
2688	Associates a different C<struct ev_loop> with this watcher. You can only	3387	Associates a different C<struct ev_loop> with this watcher. You can only
2689	do this when the watcher is inactive (and not pending either).	3388	do this when the watcher is inactive (and not pending either).
2690		3389
2691	=item w->set ([arguments])	3390	=item w->set ([arguments])
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3460	L<http://software.schmorp.de/pkg/EV>.
2762		3461
2763	=item Python	3462	=item Python
2764		3463
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3464	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3465	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3466
2772	=item Ruby	3467	=item Ruby
2773		3468
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3469	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3470	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3471	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3472	L<http://rev.rubyforge.org/>.
2778		3473
		3474	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3475	makes rev work even on mingw.
		3476
		3477	=item Haskell
		3478
		3479	A haskell binding to libev is available at
		3480	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3481
2779	=item D	3482	=item D
2780		3483
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3484	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3485	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3486
		3487	=item Ocaml
		3488
		3489	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3490	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3491
		3492	=item Lua
		3493
		3494	Brian Maher has written a partial interface to libev for lua (at the
		3495	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3496	L<http://github.com/brimworks/lua-ev>.
2783		3497
2784	=back	3498	=back
2785		3499
2786		3500
2787	=head1 MACRO MAGIC	3501	=head1 MACRO MAGIC
…		…
2888		3602
2889	#define EV_STANDALONE 1	3603	#define EV_STANDALONE 1
2890	#include "ev.h"	3604	#include "ev.h"
2891		3605
2892	Both header files and implementation files can be compiled with a C++	3606	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3607	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3608	as a bug).
2895		3609
2896	You need the following files in your source tree, or in a directory	3610	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3611	in your include path (e.g. in libev/ when using -Ilibev):
2898		3612
…		…
2941	libev.m4	3655	libev.m4
2942		3656
2943	=head2 PREPROCESSOR SYMBOLS/MACROS	3657	=head2 PREPROCESSOR SYMBOLS/MACROS
2944		3658
2945	Libev can be configured via a variety of preprocessor symbols you have to	3659	Libev can be configured via a variety of preprocessor symbols you have to
2946	define before including any of its files. The default in the absence of	3660	define before including (or compiling) any of its files. The default in
2947	autoconf is documented for every option.	3661	the absence of autoconf is documented for every option.
		3662
		3663	Symbols marked with "(h)" do not change the ABI, and can have different
		3664	values when compiling libev vs. including F<ev.h>, so it is permissible
		3665	to redefine them before including F<ev.h> without breakign compatibility
		3666	to a compiled library. All other symbols change the ABI, which means all
		3667	users of libev and the libev code itself must be compiled with compatible
		3668	settings.
2948		3669
2949	=over 4	3670	=over 4
2950		3671
2951	=item EV_STANDALONE	3672	=item EV_STANDALONE (h)
2952		3673
2953	Must always be C<1> if you do not use autoconf configuration, which	3674	Must always be C<1> if you do not use autoconf configuration, which
2954	keeps libev from including F<config.h>, and it also defines dummy	3675	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3676	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3677	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3678	F<event.h> that are not directly supported by the libev core alone.
2958		3679
		3680	In standalone mode, libev will still try to automatically deduce the
		3681	configuration, but has to be more conservative.
		3682
2959	=item EV_USE_MONOTONIC	3683	=item EV_USE_MONOTONIC
2960		3684
2961	If defined to be C<1>, libev will try to detect the availability of the	3685	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3686	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3687	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3688	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3689	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3690	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3691	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3692
2969	=item EV_USE_REALTIME	3693	=item EV_USE_REALTIME
2970		3694
2971	If defined to be C<1>, libev will try to detect the availability of the	3695	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3696	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3697	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3698	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3699	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3700	correctness. See the note about libraries in the description of
		3701	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3702	C<EV_USE_CLOCK_SYSCALL>.
		3703
		3704	=item EV_USE_CLOCK_SYSCALL
		3705
		3706	If defined to be C<1>, libev will try to use a direct syscall instead
		3707	of calling the system-provided C<clock_gettime> function. This option
		3708	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3709	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3710	programs needlessly. Using a direct syscall is slightly slower (in
		3711	theory), because no optimised vdso implementation can be used, but avoids
		3712	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3713	higher, as it simplifies linking (no need for C<-lrt>).
2977		3714
2978	=item EV_USE_NANOSLEEP	3715	=item EV_USE_NANOSLEEP
2979		3716
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3717	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3718	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3734
2998	=item EV_SELECT_USE_FD_SET	3735	=item EV_SELECT_USE_FD_SET
2999		3736
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3737	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3738	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3739	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3740	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3741	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3742	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3743	configures the maximum size of the C<fd_set>.
3007		3744
3008	=item EV_SELECT_IS_WINSOCKET	3745	=item EV_SELECT_IS_WINSOCKET
3009		3746
3010	When defined to C<1>, the select backend will assume that	3747	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3748	select/socket/connect etc. don't understand file descriptors but
…		…
3013	be used is the winsock select). This means that it will call	3750	be used is the winsock select). This means that it will call
3014	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3751	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3015	it is assumed that all these functions actually work on fds, even	3752	it is assumed that all these functions actually work on fds, even
3016	on win32. Should not be defined on non-win32 platforms.	3753	on win32. Should not be defined on non-win32 platforms.
3017		3754
3018	=item EV_FD_TO_WIN32_HANDLE	3755	=item EV_FD_TO_WIN32_HANDLE(fd)
3019		3756
3020	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3757	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3021	file descriptors to socket handles. When not defining this symbol (the	3758	file descriptors to socket handles. When not defining this symbol (the
3022	default), then libev will call C<_get_osfhandle>, which is usually	3759	default), then libev will call C<_get_osfhandle>, which is usually
3023	correct. In some cases, programs use their own file descriptor management,	3760	correct. In some cases, programs use their own file descriptor management,
3024	in which case they can provide this function to map fds to socket handles.	3761	in which case they can provide this function to map fds to socket handles.
		3762
		3763	=item EV_WIN32_HANDLE_TO_FD(handle)
		3764
		3765	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3766	using the standard C<_open_osfhandle> function. For programs implementing
		3767	their own fd to handle mapping, overwriting this function makes it easier
		3768	to do so. This can be done by defining this macro to an appropriate value.
		3769
		3770	=item EV_WIN32_CLOSE_FD(fd)
		3771
		3772	If programs implement their own fd to handle mapping on win32, then this
		3773	macro can be used to override the C<close> function, useful to unregister
		3774	file descriptors again. Note that the replacement function has to close
		3775	the underlying OS handle.
3025		3776
3026	=item EV_USE_POLL	3777	=item EV_USE_POLL
3027		3778
3028	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3779	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3029	backend. Otherwise it will be enabled on non-win32 platforms. It	3780	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3076	as well as for signal and thread safety in C<ev_async> watchers.	3827	as well as for signal and thread safety in C<ev_async> watchers.
3077		3828
3078	In the absence of this define, libev will use C<sig_atomic_t volatile>	3829	In the absence of this define, libev will use C<sig_atomic_t volatile>
3079	(from F<signal.h>), which is usually good enough on most platforms.	3830	(from F<signal.h>), which is usually good enough on most platforms.
3080		3831
3081	=item EV_H	3832	=item EV_H (h)
3082		3833
3083	The name of the F<ev.h> header file used to include it. The default if	3834	The name of the F<ev.h> header file used to include it. The default if
3084	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3835	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3085	used to virtually rename the F<ev.h> header file in case of conflicts.	3836	used to virtually rename the F<ev.h> header file in case of conflicts.
3086		3837
3087	=item EV_CONFIG_H	3838	=item EV_CONFIG_H (h)
3088		3839
3089	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3840	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3090	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3841	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3091	C<EV_H>, above.	3842	C<EV_H>, above.
3092		3843
3093	=item EV_EVENT_H	3844	=item EV_EVENT_H (h)
3094		3845
3095	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3846	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3096	of how the F<event.h> header can be found, the default is C<"event.h">.	3847	of how the F<event.h> header can be found, the default is C<"event.h">.
3097		3848
3098	=item EV_PROTOTYPES	3849	=item EV_PROTOTYPES (h)
3099		3850
3100	If defined to be C<0>, then F<ev.h> will not define any function	3851	If defined to be C<0>, then F<ev.h> will not define any function
3101	prototypes, but still define all the structs and other symbols. This is	3852	prototypes, but still define all the structs and other symbols. This is
3102	occasionally useful if you want to provide your own wrapper functions	3853	occasionally useful if you want to provide your own wrapper functions
3103	around libev functions.	3854	around libev functions.
…		…
3125	fine.	3876	fine.
3126		3877
3127	If your embedding application does not need any priorities, defining these	3878	If your embedding application does not need any priorities, defining these
3128	both to C<0> will save some memory and CPU.	3879	both to C<0> will save some memory and CPU.
3129		3880
3130	=item EV_PERIODIC_ENABLE	3881	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3131		3884
3132	If undefined or defined to be C<1>, then periodic timers are supported. If	3885	If undefined or defined to be C<1> (and the platform supports it), then
3133	defined to be C<0>, then they are not. Disabling them saves a few kB of	3886	the respective watcher type is supported. If defined to be C<0>, then it
3134	code.	3887	is not. Disabling watcher types mainly saves codesize.
3135		3888
3136	=item EV_IDLE_ENABLE	3889	=item EV_FEATURES
3137
3138	If undefined or defined to be C<1>, then idle watchers are supported. If
3139	defined to be C<0>, then they are not. Disabling them saves a few kB of
3140	code.
3141
3142	=item EV_EMBED_ENABLE
3143
3144	If undefined or defined to be C<1>, then embed watchers are supported. If
3145	defined to be C<0>, then they are not. Embed watchers rely on most other
3146	watcher types, which therefore must not be disabled.
3147
3148	=item EV_STAT_ENABLE
3149
3150	If undefined or defined to be C<1>, then stat watchers are supported. If
3151	defined to be C<0>, then they are not.
3152
3153	=item EV_FORK_ENABLE
3154
3155	If undefined or defined to be C<1>, then fork watchers are supported. If
3156	defined to be C<0>, then they are not.
3157
3158	=item EV_ASYNC_ENABLE
3159
3160	If undefined or defined to be C<1>, then async watchers are supported. If
3161	defined to be C<0>, then they are not.
3162
3163	=item EV_MINIMAL
3164		3890
3165	If you need to shave off some kilobytes of code at the expense of some	3891	If you need to shave off some kilobytes of code at the expense of some
3166	speed, define this symbol to C<1>. Currently this is used to override some	3892	speed (but with the full API), you can define this symbol to request
3167	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3893	certain subsets of functionality. The default is to enable all features
3168	much smaller 2-heap for timer management over the default 4-heap.	3894	that can be enabled on the platform.
		3895
		3896	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3897	with some broad features you want) and then selectively re-enable
		3898	additional parts you want, for example if you want everything minimal,
		3899	but multiple event loop support, async and child watchers and the poll
		3900	backend, use this:
		3901
		3902	#define EV_FEATURES 0
		3903	#define EV_MULTIPLICITY 1
		3904	#define EV_USE_POLL 1
		3905	#define EV_CHILD_ENABLE 1
		3906	#define EV_ASYNC_ENABLE 1
		3907
		3908	The actual value is a bitset, it can be a combination of the following
		3909	values:
		3910
		3911	=over 4
		3912
		3913	=item C<1> - faster/larger code
		3914
		3915	Use larger code to speed up some operations.
		3916
		3917	Currently this is used to override some inlining decisions (enlarging the roughly
		3918	30% code size on amd64.
		3919
		3920	When optimising for size, use of compiler flags such as C<-Os> with
		3921	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3922	assertions.
		3923
		3924	=item C<2> - faster/larger data structures
		3925
		3926	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3927	hash table sizes and so on. This will usually further increase codesize
		3928	and can additionally have an effect on the size of data structures at
		3929	runtime.
		3930
		3931	=item C<4> - full API configuration
		3932
		3933	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3934	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3935
		3936	=item C<8> - full API
		3937
		3938	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3939	details on which parts of the API are still available without this
		3940	feature, and do not complain if this subset changes over time.
		3941
		3942	=item C<16> - enable all optional watcher types
		3943
		3944	Enables all optional watcher types. If you want to selectively enable
		3945	only some watcher types other than I/O and timers (e.g. prepare,
		3946	embed, async, child...) you can enable them manually by defining
		3947	C<EV_watchertype_ENABLE> to C<1> instead.
		3948
		3949	=item C<32> - enable all backends
		3950
		3951	This enables all backends - without this feature, you need to enable at
		3952	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3953
		3954	=item C<64> - enable OS-specific "helper" APIs
		3955
		3956	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3957	default.
		3958
		3959	=back
		3960
		3961	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3962	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3963	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3964	watchers, timers and monotonic clock support.
		3965
		3966	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3967	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3968	your program might be left out as well - a binary starting a timer and an
		3969	I/O watcher then might come out at only 5Kb.
		3970
		3971	=item EV_AVOID_STDIO
		3972
		3973	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3974	functions (printf, scanf, perror etc.). This will increase the codesize
		3975	somewhat, but if your program doesn't otherwise depend on stdio and your
		3976	libc allows it, this avoids linking in the stdio library which is quite
		3977	big.
		3978
		3979	Note that error messages might become less precise when this option is
		3980	enabled.
		3981
		3982	=item EV_NSIG
		3983
		3984	The highest supported signal number, +1 (or, the number of
		3985	signals): Normally, libev tries to deduce the maximum number of signals
		3986	automatically, but sometimes this fails, in which case it can be
		3987	specified. Also, using a lower number than detected (C<32> should be
		3988	good for about any system in existance) can save some memory, as libev
		3989	statically allocates some 12-24 bytes per signal number.
3169		3990
3170	=item EV_PID_HASHSIZE	3991	=item EV_PID_HASHSIZE
3171		3992
3172	C<ev_child> watchers use a small hash table to distribute workload by	3993	C<ev_child> watchers use a small hash table to distribute workload by
3173	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3994	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3174	than enough. If you need to manage thousands of children you might want to	3995	usually more than enough. If you need to manage thousands of children you
3175	increase this value (I<must> be a power of two).	3996	might want to increase this value (I<must> be a power of two).
3176		3997
3177	=item EV_INOTIFY_HASHSIZE	3998	=item EV_INOTIFY_HASHSIZE
3178		3999
3179	C<ev_stat> watchers use a small hash table to distribute workload by	4000	C<ev_stat> watchers use a small hash table to distribute workload by
3180	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4001	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3181	usually more than enough. If you need to manage thousands of C<ev_stat>	4002	disabled), usually more than enough. If you need to manage thousands of
3182	watchers you might want to increase this value (I<must> be a power of	4003	C<ev_stat> watchers you might want to increase this value (I<must> be a
3183	two).	4004	power of two).
3184		4005
3185	=item EV_USE_4HEAP	4006	=item EV_USE_4HEAP
3186		4007
3187	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4008	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3188	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4009	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3189	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4010	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3190	faster performance with many (thousands) of watchers.	4011	faster performance with many (thousands) of watchers.
3191		4012
3192	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4013	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3193	(disabled).	4014	will be C<0>.
3194		4015
3195	=item EV_HEAP_CACHE_AT	4016	=item EV_HEAP_CACHE_AT
3196		4017
3197	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4018	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3198	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4019	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3199	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4020	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3200	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4021	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3201	but avoids random read accesses on heap changes. This improves performance	4022	but avoids random read accesses on heap changes. This improves performance
3202	noticeably with many (hundreds) of watchers.	4023	noticeably with many (hundreds) of watchers.
3203		4024
3204	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4025	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3205	(disabled).	4026	will be C<0>.
3206		4027
3207	=item EV_VERIFY	4028	=item EV_VERIFY
3208		4029
3209	Controls how much internal verification (see C<ev_loop_verify ()>) will	4030	Controls how much internal verification (see C<ev_loop_verify ()>) will
3210	be done: If set to C<0>, no internal verification code will be compiled	4031	be done: If set to C<0>, no internal verification code will be compiled
…		…
3212	called. If set to C<2>, then the internal verification code will be	4033	called. If set to C<2>, then the internal verification code will be
3213	called once per loop, which can slow down libev. If set to C<3>, then the	4034	called once per loop, which can slow down libev. If set to C<3>, then the
3214	verification code will be called very frequently, which will slow down	4035	verification code will be called very frequently, which will slow down
3215	libev considerably.	4036	libev considerably.
3216		4037
3217	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4038	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3218	C<0>.	4039	will be C<0>.
3219		4040
3220	=item EV_COMMON	4041	=item EV_COMMON
3221		4042
3222	By default, all watchers have a C<void *data> member. By redefining	4043	By default, all watchers have a C<void *data> member. By redefining
3223	this macro to a something else you can include more and other types of	4044	this macro to a something else you can include more and other types of
…		…
3281	file.	4102	file.
3282		4103
3283	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4104	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3284	that everybody includes and which overrides some configure choices:	4105	that everybody includes and which overrides some configure choices:
3285		4106
3286	#define EV_MINIMAL 1	4107	#define EV_FEATURES 8
3287	#define EV_USE_POLL 0	4108	#define EV_USE_SELECT 1
3288	#define EV_MULTIPLICITY 0
3289	#define EV_PERIODIC_ENABLE 0	4109	#define EV_PREPARE_ENABLE 1
		4110	#define EV_IDLE_ENABLE 1
3290	#define EV_STAT_ENABLE 0	4111	#define EV_SIGNAL_ENABLE 1
3291	#define EV_FORK_ENABLE 0	4112	#define EV_CHILD_ENABLE 1
		4113	#define EV_USE_STDEXCEPT 0
3292	#define EV_CONFIG_H <config.h>	4114	#define EV_CONFIG_H <config.h>
3293	#define EV_MINPRI 0
3294	#define EV_MAXPRI 0
3295		4115
3296	#include "ev++.h"	4116	#include "ev++.h"
3297		4117
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4118	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		4119
3300	#include "ev_cpp.h"	4120	#include "ev_cpp.h"
3301	#include "ev.c"	4121	#include "ev.c"
3302		4122
		4123	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		4124
3304	=head1 THREADS AND COROUTINES	4125	=head2 THREADS AND COROUTINES
3305		4126
3306	=head2 THREADS	4127	=head3 THREADS
3307		4128
3308	All libev functions are reentrant and thread-safe unless explicitly	4129	All libev functions are reentrant and thread-safe unless explicitly
3309	documented otherwise, but it uses no locking itself. This means that you	4130	documented otherwise, but libev implements no locking itself. This means
3310	can use as many loops as you want in parallel, as long as there are no	4131	that you can use as many loops as you want in parallel, as long as there
3311	concurrent calls into any libev function with the same loop parameter	4132	are no concurrent calls into any libev function with the same loop
3312	(C<ev_default_*> calls have an implicit default loop parameter, of	4133	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3313	course): libev guarantees that different event loops share no data	4134	of course): libev guarantees that different event loops share no data
3314	structures that need any locking.	4135	structures that need any locking.
3315		4136
3316	Or to put it differently: calls with different loop parameters can be done	4137	Or to put it differently: calls with different loop parameters can be done
3317	concurrently from multiple threads, calls with the same loop parameter	4138	concurrently from multiple threads, calls with the same loop parameter
3318	must be done serially (but can be done from different threads, as long as	4139	must be done serially (but can be done from different threads, as long as
…		…
3358	default loop and triggering an C<ev_async> watcher from the default loop	4179	default loop and triggering an C<ev_async> watcher from the default loop
3359	watcher callback into the event loop interested in the signal.	4180	watcher callback into the event loop interested in the signal.
3360		4181
3361	=back	4182	=back
3362		4183
		4184	=head4 THREAD LOCKING EXAMPLE
		4185
		4186	Here is a fictitious example of how to run an event loop in a different
		4187	thread than where callbacks are being invoked and watchers are
		4188	created/added/removed.
		4189
		4190	For a real-world example, see the C<EV::Loop::Async> perl module,
		4191	which uses exactly this technique (which is suited for many high-level
		4192	languages).
		4193
		4194	The example uses a pthread mutex to protect the loop data, a condition
		4195	variable to wait for callback invocations, an async watcher to notify the
		4196	event loop thread and an unspecified mechanism to wake up the main thread.
		4197
		4198	First, you need to associate some data with the event loop:
		4199
		4200	typedef struct {
		4201	mutex_t lock; /* global loop lock */
		4202	ev_async async_w;
		4203	thread_t tid;
		4204	cond_t invoke_cv;
		4205	} userdata;
		4206
		4207	void prepare_loop (EV_P)
		4208	{
		4209	// for simplicity, we use a static userdata struct.
		4210	static userdata u;
		4211
		4212	ev_async_init (&u->async_w, async_cb);
		4213	ev_async_start (EV_A_ &u->async_w);
		4214
		4215	pthread_mutex_init (&u->lock, 0);
		4216	pthread_cond_init (&u->invoke_cv, 0);
		4217
		4218	// now associate this with the loop
		4219	ev_set_userdata (EV_A_ u);
		4220	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4221	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4222
		4223	// then create the thread running ev_loop
		4224	pthread_create (&u->tid, 0, l_run, EV_A);
		4225	}
		4226
		4227	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4228	solely to wake up the event loop so it takes notice of any new watchers
		4229	that might have been added:
		4230
		4231	static void
		4232	async_cb (EV_P_ ev_async *w, int revents)
		4233	{
		4234	// just used for the side effects
		4235	}
		4236
		4237	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4238	protecting the loop data, respectively.
		4239
		4240	static void
		4241	l_release (EV_P)
		4242	{
		4243	userdata *u = ev_userdata (EV_A);
		4244	pthread_mutex_unlock (&u->lock);
		4245	}
		4246
		4247	static void
		4248	l_acquire (EV_P)
		4249	{
		4250	userdata *u = ev_userdata (EV_A);
		4251	pthread_mutex_lock (&u->lock);
		4252	}
		4253
		4254	The event loop thread first acquires the mutex, and then jumps straight
		4255	into C<ev_loop>:
		4256
		4257	void *
		4258	l_run (void *thr_arg)
		4259	{
		4260	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4261
		4262	l_acquire (EV_A);
		4263	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4264	ev_loop (EV_A_ 0);
		4265	l_release (EV_A);
		4266
		4267	return 0;
		4268	}
		4269
		4270	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4271	signal the main thread via some unspecified mechanism (signals? pipe
		4272	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4273	have been called (in a while loop because a) spurious wakeups are possible
		4274	and b) skipping inter-thread-communication when there are no pending
		4275	watchers is very beneficial):
		4276
		4277	static void
		4278	l_invoke (EV_P)
		4279	{
		4280	userdata *u = ev_userdata (EV_A);
		4281
		4282	while (ev_pending_count (EV_A))
		4283	{
		4284	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4285	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4286	}
		4287	}
		4288
		4289	Now, whenever the main thread gets told to invoke pending watchers, it
		4290	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4291	thread to continue:
		4292
		4293	static void
		4294	real_invoke_pending (EV_P)
		4295	{
		4296	userdata *u = ev_userdata (EV_A);
		4297
		4298	pthread_mutex_lock (&u->lock);
		4299	ev_invoke_pending (EV_A);
		4300	pthread_cond_signal (&u->invoke_cv);
		4301	pthread_mutex_unlock (&u->lock);
		4302	}
		4303
		4304	Whenever you want to start/stop a watcher or do other modifications to an
		4305	event loop, you will now have to lock:
		4306
		4307	ev_timer timeout_watcher;
		4308	userdata *u = ev_userdata (EV_A);
		4309
		4310	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4311
		4312	pthread_mutex_lock (&u->lock);
		4313	ev_timer_start (EV_A_ &timeout_watcher);
		4314	ev_async_send (EV_A_ &u->async_w);
		4315	pthread_mutex_unlock (&u->lock);
		4316
		4317	Note that sending the C<ev_async> watcher is required because otherwise
		4318	an event loop currently blocking in the kernel will have no knowledge
		4319	about the newly added timer. By waking up the loop it will pick up any new
		4320	watchers in the next event loop iteration.
		4321
3363	=head2 COROUTINES	4322	=head3 COROUTINES
3364		4323
3365	Libev is much more accommodating to coroutines ("cooperative threads"):	4324	Libev is very accommodating to coroutines ("cooperative threads"):
3366	libev fully supports nesting calls to it's functions from different	4325	libev fully supports nesting calls to its functions from different
3367	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4326	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3368	different coroutines and switch freely between both coroutines running the	4327	different coroutines, and switch freely between both coroutines running
3369	loop, as long as you don't confuse yourself). The only exception is that	4328	the loop, as long as you don't confuse yourself). The only exception is
3370	you must not do this from C<ev_periodic> reschedule callbacks.	4329	that you must not do this from C<ev_periodic> reschedule callbacks.
3371		4330
3372	Care has been taken to ensure that libev does not keep local state inside	4331	Care has been taken to ensure that libev does not keep local state inside
3373	C<ev_loop>, and other calls do not usually allow coroutine switches.	4332	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4333	they do not call any callbacks.
3374		4334
		4335	=head2 COMPILER WARNINGS
3375		4336
3376	=head1 COMPLEXITIES	4337	Depending on your compiler and compiler settings, you might get no or a
		4338	lot of warnings when compiling libev code. Some people are apparently
		4339	scared by this.
3377		4340
3378	In this section the complexities of (many of) the algorithms used inside	4341	However, these are unavoidable for many reasons. For one, each compiler
3379	libev will be explained. For complexity discussions about backends see the	4342	has different warnings, and each user has different tastes regarding
3380	documentation for C<ev_default_init>.	4343	warning options. "Warn-free" code therefore cannot be a goal except when
		4344	targeting a specific compiler and compiler-version.
3381		4345
3382	All of the following are about amortised time: If an array needs to be	4346	Another reason is that some compiler warnings require elaborate
3383	extended, libev needs to realloc and move the whole array, but this	4347	workarounds, or other changes to the code that make it less clear and less
3384	happens asymptotically never with higher number of elements, so O(1) might	4348	maintainable.
3385	mean it might do a lengthy realloc operation in rare cases, but on average
3386	it is much faster and asymptotically approaches constant time.
3387		4349
3388	=over 4	4350	And of course, some compiler warnings are just plain stupid, or simply
		4351	wrong (because they don't actually warn about the condition their message
		4352	seems to warn about). For example, certain older gcc versions had some
		4353	warnings that resulted an extreme number of false positives. These have
		4354	been fixed, but some people still insist on making code warn-free with
		4355	such buggy versions.
3389		4356
3390	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4357	While libev is written to generate as few warnings as possible,
		4358	"warn-free" code is not a goal, and it is recommended not to build libev
		4359	with any compiler warnings enabled unless you are prepared to cope with
		4360	them (e.g. by ignoring them). Remember that warnings are just that:
		4361	warnings, not errors, or proof of bugs.
3391		4362
3392	This means that, when you have a watcher that triggers in one hour and
3393	there are 100 watchers that would trigger before that then inserting will
3394	have to skip roughly seven (C<ld 100>) of these watchers.
3395		4363
3396	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4364	=head2 VALGRIND
3397		4365
3398	That means that changing a timer costs less than removing/adding them	4366	Valgrind has a special section here because it is a popular tool that is
3399	as only the relative motion in the event queue has to be paid for.	4367	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3400		4368
3401	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4369	If you think you found a bug (memory leak, uninitialised data access etc.)
		4370	in libev, then check twice: If valgrind reports something like:
3402		4371
3403	These just add the watcher into an array or at the head of a list.	4372	==2274== definitely lost: 0 bytes in 0 blocks.
		4373	==2274== possibly lost: 0 bytes in 0 blocks.
		4374	==2274== still reachable: 256 bytes in 1 blocks.
3404		4375
3405	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4376	Then there is no memory leak, just as memory accounted to global variables
		4377	is not a memleak - the memory is still being referenced, and didn't leak.
3406		4378
3407	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4379	Similarly, under some circumstances, valgrind might report kernel bugs
		4380	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4381	although an acceptable workaround has been found here), or it might be
		4382	confused.
3408		4383
3409	These watchers are stored in lists then need to be walked to find the	4384	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3410	correct watcher to remove. The lists are usually short (you don't usually	4385	make it into some kind of religion.
3411	have many watchers waiting for the same fd or signal).
3412		4386
3413	=item Finding the next timer in each loop iteration: O(1)	4387	If you are unsure about something, feel free to contact the mailing list
		4388	with the full valgrind report and an explanation on why you think this
		4389	is a bug in libev (best check the archives, too :). However, don't be
		4390	annoyed when you get a brisk "this is no bug" answer and take the chance
		4391	of learning how to interpret valgrind properly.
3414		4392
3415	By virtue of using a binary or 4-heap, the next timer is always found at a	4393	If you need, for some reason, empty reports from valgrind for your project
3416	fixed position in the storage array.	4394	I suggest using suppression lists.
3417		4395
3418	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3419		4396
3420	A change means an I/O watcher gets started or stopped, which requires	4397	=head1 PORTABILITY NOTES
3421	libev to recalculate its status (and possibly tell the kernel, depending
3422	on backend and whether C<ev_io_set> was used).
3423		4398
3424	=item Activating one watcher (putting it into the pending state): O(1)
3425
3426	=item Priority handling: O(number_of_priorities)
3427
3428	Priorities are implemented by allocating some space for each
3429	priority. When doing priority-based operations, libev usually has to
3430	linearly search all the priorities, but starting/stopping and activating
3431	watchers becomes O(1) with respect to priority handling.
3432
3433	=item Sending an ev_async: O(1)
3434
3435	=item Processing ev_async_send: O(number_of_async_watchers)
3436
3437	=item Processing signals: O(max_signal_number)
3438
3439	Sending involves a system call I<iff> there were no other C<ev_async_send>
3440	calls in the current loop iteration. Checking for async and signal events
3441	involves iterating over all running async watchers or all signal numbers.
3442
3443	=back
3444
3445
3446	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4399	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3447		4400
3448	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4401	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3449	requires, and its I/O model is fundamentally incompatible with the POSIX	4402	requires, and its I/O model is fundamentally incompatible with the POSIX
3450	model. Libev still offers limited functionality on this platform in	4403	model. Libev still offers limited functionality on this platform in
3451	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4404	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3458	way (note also that glib is the slowest event library known to man).	4411	way (note also that glib is the slowest event library known to man).
3459		4412
3460	There is no supported compilation method available on windows except	4413	There is no supported compilation method available on windows except
3461	embedding it into other applications.	4414	embedding it into other applications.
3462		4415
		4416	Sensible signal handling is officially unsupported by Microsoft - libev
		4417	tries its best, but under most conditions, signals will simply not work.
		4418
3463	Not a libev limitation but worth mentioning: windows apparently doesn't	4419	Not a libev limitation but worth mentioning: windows apparently doesn't
3464	accept large writes: instead of resulting in a partial write, windows will	4420	accept large writes: instead of resulting in a partial write, windows will
3465	either accept everything or return C<ENOBUFS> if the buffer is too large,	4421	either accept everything or return C<ENOBUFS> if the buffer is too large,
3466	so make sure you only write small amounts into your sockets (less than a	4422	so make sure you only write small amounts into your sockets (less than a
3467	megabyte seems safe, but this apparently depends on the amount of memory	4423	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3471	the abysmal performance of winsockets, using a large number of sockets	4427	the abysmal performance of winsockets, using a large number of sockets
3472	is not recommended (and not reasonable). If your program needs to use	4428	is not recommended (and not reasonable). If your program needs to use
3473	more than a hundred or so sockets, then likely it needs to use a totally	4429	more than a hundred or so sockets, then likely it needs to use a totally
3474	different implementation for windows, as libev offers the POSIX readiness	4430	different implementation for windows, as libev offers the POSIX readiness
3475	notification model, which cannot be implemented efficiently on windows	4431	notification model, which cannot be implemented efficiently on windows
3476	(Microsoft monopoly games).	4432	(due to Microsoft monopoly games).
3477		4433
3478	A typical way to use libev under windows is to embed it (see the embedding	4434	A typical way to use libev under windows is to embed it (see the embedding
3479	section for details) and use the following F<evwrap.h> header file instead	4435	section for details) and use the following F<evwrap.h> header file instead
3480	of F<ev.h>:	4436	of F<ev.h>:
3481		4437
…		…
3517		4473
3518	Early versions of winsocket's select only supported waiting for a maximum	4474	Early versions of winsocket's select only supported waiting for a maximum
3519	of C<64> handles (probably owning to the fact that all windows kernels	4475	of C<64> handles (probably owning to the fact that all windows kernels
3520	can only wait for C<64> things at the same time internally; Microsoft	4476	can only wait for C<64> things at the same time internally; Microsoft
3521	recommends spawning a chain of threads and wait for 63 handles and the	4477	recommends spawning a chain of threads and wait for 63 handles and the
3522	previous thread in each. Great).	4478	previous thread in each. Sounds great!).
3523		4479
3524	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4480	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3525	to some high number (e.g. C<2048>) before compiling the winsocket select	4481	to some high number (e.g. C<2048>) before compiling the winsocket select
3526	call (which might be in libev or elsewhere, for example, perl does its own	4482	call (which might be in libev or elsewhere, for example, perl and many
3527	select emulation on windows).	4483	other interpreters do their own select emulation on windows).
3528		4484
3529	Another limit is the number of file descriptors in the Microsoft runtime	4485	Another limit is the number of file descriptors in the Microsoft runtime
3530	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4486	libraries, which by default is C<64> (there must be a hidden I<64>
3531	or something like this inside Microsoft). You can increase this by calling	4487	fetish or something like this inside Microsoft). You can increase this
3532	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4488	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3533	arbitrary limit), but is broken in many versions of the Microsoft runtime	4489	(another arbitrary limit), but is broken in many versions of the Microsoft
3534	libraries.
3535
3536	This might get you to about C<512> or C<2048> sockets (depending on	4490	runtime libraries. This might get you to about C<512> or C<2048> sockets
3537	windows version and/or the phase of the moon). To get more, you need to	4491	(depending on windows version and/or the phase of the moon). To get more,
3538	wrap all I/O functions and provide your own fd management, but the cost of	4492	you need to wrap all I/O functions and provide your own fd management, but
3539	calling select (O(n²)) will likely make this unworkable.	4493	the cost of calling select (O(n²)) will likely make this unworkable.
3540		4494
3541	=back	4495	=back
3542		4496
3543
3544	=head1 PORTABILITY REQUIREMENTS	4497	=head2 PORTABILITY REQUIREMENTS
3545		4498
3546	In addition to a working ISO-C implementation, libev relies on a few	4499	In addition to a working ISO-C implementation and of course the
3547	additional extensions:	4500	backend-specific APIs, libev relies on a few additional extensions:
3548		4501
3549	=over 4	4502	=over 4
3550		4503
3551	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4504	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3552	calling conventions regardless of C<ev_watcher_type *>.	4505	calling conventions regardless of C<ev_watcher_type *>.
…		…
3577	except the initial one, and run the default loop in the initial thread as	4530	except the initial one, and run the default loop in the initial thread as
3578	well.	4531	well.
3579		4532
3580	=item C<long> must be large enough for common memory allocation sizes	4533	=item C<long> must be large enough for common memory allocation sizes
3581		4534
3582	To improve portability and simplify using libev, libev uses C<long>	4535	To improve portability and simplify its API, libev uses C<long> internally
3583	internally instead of C<size_t> when allocating its data structures. On	4536	instead of C<size_t> when allocating its data structures. On non-POSIX
3584	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4537	systems (Microsoft...) this might be unexpectedly low, but is still at
3585	is still at least 31 bits everywhere, which is enough for hundreds of	4538	least 31 bits everywhere, which is enough for hundreds of millions of
3586	millions of watchers.	4539	watchers.
3587		4540
3588	=item C<double> must hold a time value in seconds with enough accuracy	4541	=item C<double> must hold a time value in seconds with enough accuracy
3589		4542
3590	The type C<double> is used to represent timestamps. It is required to	4543	The type C<double> is used to represent timestamps. It is required to
3591	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4544	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3592	enough for at least into the year 4000. This requirement is fulfilled by	4545	enough for at least into the year 4000. This requirement is fulfilled by
3593	implementations implementing IEEE 754 (basically all existing ones).	4546	implementations implementing IEEE 754, which is basically all existing
		4547	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4548	2200.
3594		4549
3595	=back	4550	=back
3596		4551
3597	If you know of other additional requirements drop me a note.	4552	If you know of other additional requirements drop me a note.
3598		4553
3599		4554
3600	=head1 COMPILER WARNINGS	4555	=head1 ALGORITHMIC COMPLEXITIES
3601		4556
3602	Depending on your compiler and compiler settings, you might get no or a	4557	In this section the complexities of (many of) the algorithms used inside
3603	lot of warnings when compiling libev code. Some people are apparently	4558	libev will be documented. For complexity discussions about backends see
3604	scared by this.	4559	the documentation for C<ev_default_init>.
3605		4560
3606	However, these are unavoidable for many reasons. For one, each compiler	4561	All of the following are about amortised time: If an array needs to be
3607	has different warnings, and each user has different tastes regarding	4562	extended, libev needs to realloc and move the whole array, but this
3608	warning options. "Warn-free" code therefore cannot be a goal except when	4563	happens asymptotically rarer with higher number of elements, so O(1) might
3609	targeting a specific compiler and compiler-version.	4564	mean that libev does a lengthy realloc operation in rare cases, but on
		4565	average it is much faster and asymptotically approaches constant time.
3610		4566
3611	Another reason is that some compiler warnings require elaborate	4567	=over 4
3612	workarounds, or other changes to the code that make it less clear and less
3613	maintainable.
3614		4568
3615	And of course, some compiler warnings are just plain stupid, or simply	4569	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3616	wrong (because they don't actually warn about the condition their message
3617	seems to warn about).
3618		4570
3619	While libev is written to generate as few warnings as possible,	4571	This means that, when you have a watcher that triggers in one hour and
3620	"warn-free" code is not a goal, and it is recommended not to build libev	4572	there are 100 watchers that would trigger before that, then inserting will
3621	with any compiler warnings enabled unless you are prepared to cope with	4573	have to skip roughly seven (C<ld 100>) of these watchers.
3622	them (e.g. by ignoring them). Remember that warnings are just that:
3623	warnings, not errors, or proof of bugs.
3624		4574
		4575	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3625		4576
3626	=head1 VALGRIND	4577	That means that changing a timer costs less than removing/adding them,
		4578	as only the relative motion in the event queue has to be paid for.
3627		4579
3628	Valgrind has a special section here because it is a popular tool that is	4580	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3629	highly useful, but valgrind reports are very hard to interpret.
3630		4581
3631	If you think you found a bug (memory leak, uninitialised data access etc.)	4582	These just add the watcher into an array or at the head of a list.
3632	in libev, then check twice: If valgrind reports something like:
3633		4583
3634	==2274== definitely lost: 0 bytes in 0 blocks.	4584	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3635	==2274== possibly lost: 0 bytes in 0 blocks.
3636	==2274== still reachable: 256 bytes in 1 blocks.
3637		4585
3638	Then there is no memory leak. Similarly, under some circumstances,	4586	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3639	valgrind might report kernel bugs as if it were a bug in libev, or it
3640	might be confused (it is a very good tool, but only a tool).
3641		4587
3642	If you are unsure about something, feel free to contact the mailing list	4588	These watchers are stored in lists, so they need to be walked to find the
3643	with the full valgrind report and an explanation on why you think this is	4589	correct watcher to remove. The lists are usually short (you don't usually
3644	a bug in libev. However, don't be annoyed when you get a brisk "this is	4590	have many watchers waiting for the same fd or signal: one is typical, two
3645	no bug" answer and take the chance of learning how to interpret valgrind	4591	is rare).
3646	properly.
3647		4592
3648	If you need, for some reason, empty reports from valgrind for your project	4593	=item Finding the next timer in each loop iteration: O(1)
3649	I suggest using suppression lists.
3650		4594
		4595	By virtue of using a binary or 4-heap, the next timer is always found at a
		4596	fixed position in the storage array.
		4597
		4598	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4599
		4600	A change means an I/O watcher gets started or stopped, which requires
		4601	libev to recalculate its status (and possibly tell the kernel, depending
		4602	on backend and whether C<ev_io_set> was used).
		4603
		4604	=item Activating one watcher (putting it into the pending state): O(1)
		4605
		4606	=item Priority handling: O(number_of_priorities)
		4607
		4608	Priorities are implemented by allocating some space for each
		4609	priority. When doing priority-based operations, libev usually has to
		4610	linearly search all the priorities, but starting/stopping and activating
		4611	watchers becomes O(1) with respect to priority handling.
		4612
		4613	=item Sending an ev_async: O(1)
		4614
		4615	=item Processing ev_async_send: O(number_of_async_watchers)
		4616
		4617	=item Processing signals: O(max_signal_number)
		4618
		4619	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4620	calls in the current loop iteration. Checking for async and signal events
		4621	involves iterating over all running async watchers or all signal numbers.
		4622
		4623	=back
		4624
		4625
		4626	=head1 GLOSSARY
		4627
		4628	=over 4
		4629
		4630	=item active
		4631
		4632	A watcher is active as long as it has been started (has been attached to
		4633	an event loop) but not yet stopped (disassociated from the event loop).
		4634
		4635	=item application
		4636
		4637	In this document, an application is whatever is using libev.
		4638
		4639	=item callback
		4640
		4641	The address of a function that is called when some event has been
		4642	detected. Callbacks are being passed the event loop, the watcher that
		4643	received the event, and the actual event bitset.
		4644
		4645	=item callback invocation
		4646
		4647	The act of calling the callback associated with a watcher.
		4648
		4649	=item event
		4650
		4651	A change of state of some external event, such as data now being available
		4652	for reading on a file descriptor, time having passed or simply not having
		4653	any other events happening anymore.
		4654
		4655	In libev, events are represented as single bits (such as C<EV_READ> or
		4656	C<EV_TIMEOUT>).
		4657
		4658	=item event library
		4659
		4660	A software package implementing an event model and loop.
		4661
		4662	=item event loop
		4663
		4664	An entity that handles and processes external events and converts them
		4665	into callback invocations.
		4666
		4667	=item event model
		4668
		4669	The model used to describe how an event loop handles and processes
		4670	watchers and events.
		4671
		4672	=item pending
		4673
		4674	A watcher is pending as soon as the corresponding event has been detected,
		4675	and stops being pending as soon as the watcher will be invoked or its
		4676	pending status is explicitly cleared by the application.
		4677
		4678	A watcher can be pending, but not active. Stopping a watcher also clears
		4679	its pending status.
		4680
		4681	=item real time
		4682
		4683	The physical time that is observed. It is apparently strictly monotonic :)
		4684
		4685	=item wall-clock time
		4686
		4687	The time and date as shown on clocks. Unlike real time, it can actually
		4688	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4689	clock.
		4690
		4691	=item watcher
		4692
		4693	A data structure that describes interest in certain events. Watchers need
		4694	to be started (attached to an event loop) before they can receive events.
		4695
		4696	=item watcher invocation
		4697
		4698	The act of calling the callback associated with a watcher.
		4699
		4700	=back
3651		4701
3652	=head1 AUTHOR	4702	=head1 AUTHOR
3653		4703
3654	Marc Lehmann <libev@schmorp.de>.	4704	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3655		4705

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