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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
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	121	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	320	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	321	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		399
382	For few fds, this backend is a bit little slower than poll and select,	400	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	401	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),	402	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	403	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	404
387	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
389		421
390	While stopping, setting and starting an I/O watcher in the same iteration	422	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	423	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	424	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	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
395		427	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		428
400	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	430	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	431	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	432	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
405		440
406	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	442	all kernel versions tested so far.
408		443
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
411		446
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		448
414	Kqueue deserves special mention, as at the time of this writing, it was	449	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	450	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	451	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	452	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	453	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.	454	without API changes to existing programs. For this reason it's not being
		455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		457	system like NetBSD.
420		458
421	You still can embed kqueue into a normal poll or select backend and use it	459	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	460	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.	461	the target platform). See C<ev_embed> watchers for more info.
424		462
425	It scales in the same way as the epoll backend, but the interface to the	463	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	464	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	465	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	466	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	467	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
431		470
432	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
433		472
434	While nominally embeddable in other event loops, this doesn't work	473	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	474	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	475	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	476	(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,	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
440		479
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	480	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	481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	482	C<NOTE_EOF>.
444		483
…		…
464	might perform better.	503	might perform better.
465		504
466	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	507	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
470		509
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
473		512
474	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	567	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	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	569	for example).
531		570
532	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
535		574
536	In general it is not advisable to call this function except in the	575	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	576	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	577	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
605		644
606	This function is rarely useful, but when some event callback runs for a	645	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	646	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	647	the current time is a good idea.
609		648
610	See also "The special problem of time updates" in the C<ev_timer> section.	649	See also L<The special problem of time updates> in the C<ev_timer> section.
		650
		651	=item ev_suspend (loop)
		652
		653	=item ev_resume (loop)
		654
		655	These two functions suspend and resume a loop, for use when the loop is
		656	not used for a while and timeouts should not be processed.
		657
		658	A typical use case would be an interactive program such as a game: When
		659	the user presses C<^Z> to suspend the game and resumes it an hour later it
		660	would be best to handle timeouts as if no time had actually passed while
		661	the program was suspended. This can be achieved by calling C<ev_suspend>
		662	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		663	C<ev_resume> directly afterwards to resume timer processing.
		664
		665	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		667	will be rescheduled (that is, they will lose any events that would have
		668	occured while suspended).
		669
		670	After calling C<ev_suspend> you B<must not> call I<any> function on the
		671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		672	without a previous call to C<ev_suspend>.
		673
		674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		675	event loop time (see C<ev_now_update>).
611		676
612	=item ev_loop (loop, int flags)	677	=item ev_loop (loop, int flags)
613		678
614	Finally, this is it, the event handler. This function usually is called	679	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	680	after you initialised all your watchers and you want to start handling
…		…
631	the loop.	696	the loop.
632		697
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	698	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	699	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	700	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	701	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	702	user-registered callback will be called), and will return after one
638	iteration of the loop.	703	iteration of the loop.
639		704
640	This is useful if you are waiting for some external event in conjunction	705	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	706	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		764
700	If you have a watcher you never unregister that should not keep C<ev_loop>	765	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	766	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	767	stopping it.
703		768
704	As an example, libev itself uses this for its internal signal pipe: It is	769	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	770	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	771	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	772	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	773	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	774	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	775	before, respectively. Note also that libev might stop watchers itself
		776	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		777	in the callback).
711		778
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	780	running when nothing else is active.
714		781
715	struct ev_signal exitsig;	782	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	783	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	784	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	785	evf_unref (loop);
719		786
720	Example: For some weird reason, unregister the above signal handler again.	787	Example: For some weird reason, unregister the above signal handler again.
…		…
768	they fire on, say, one-second boundaries only.	835	they fire on, say, one-second boundaries only.
769		836
770	=item ev_loop_verify (loop)	837	=item ev_loop_verify (loop)
771		838
772	This function only does something when C<EV_VERIFY> support has been	839	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	840	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	841	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	842	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	843	error and call C<abort ()>.
777		844
778	This can be used to catch bugs inside libev itself: under normal	845	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	849	=back
783		850
784		851
785	=head1 ANATOMY OF A WATCHER	852	=head1 ANATOMY OF A WATCHER
786		853
		854	In the following description, uppercase C<TYPE> in names stands for the
		855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		856	watchers and C<ev_io_start> for I/O watchers.
		857
787	A watcher is a structure that you create and register to record your	858	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	859	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	860	become readable, you would create an C<ev_io> watcher for that:
790		861
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	863	{
793	ev_io_stop (w);	864	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	865	ev_unloop (loop, EVUNLOOP_ALL);
795	}	866	}
796		867
797	struct ev_loop *loop = ev_default_loop (0);	868	struct ev_loop *loop = ev_default_loop (0);
		869
798	struct ev_io stdin_watcher;	870	ev_io stdin_watcher;
		871
799	ev_init (&stdin_watcher, my_cb);	872	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	874	ev_io_start (loop, &stdin_watcher);
		875
802	ev_loop (loop, 0);	876	ev_loop (loop, 0);
803		877
804	As you can see, you are responsible for allocating the memory for your	878	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	879	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	880	stack).
		881
		882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		884
808	Each watcher structure must be initialised by a call to C<ev_init	885	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	886	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	887	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	888	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	889	is readable and/or writable).
813		890
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	892	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	893	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	894	ev_TYPE_init (watcher *, callback, ...) >>.
818		895
819	To make the watcher actually watch out for events, you have to start it	896	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	897	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	898	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	899	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		900
824	As long as your watcher is active (has been started but not stopped) you	901	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	902	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	903	reinitialise it or call its C<ev_TYPE_set> macro.
827		904
828	Each and every callback receives the event loop pointer as first, the	905	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	906	registered watcher structure as second, and a bitset of received events as
830	third argument.	907	third argument.
831		908
…		…
889		966
890	=item C<EV_ASYNC>	967	=item C<EV_ASYNC>
891		968
892	The given async watcher has been asynchronously notified (see C<ev_async>).	969	The given async watcher has been asynchronously notified (see C<ev_async>).
893		970
		971	=item C<EV_CUSTOM>
		972
		973	Not ever sent (or otherwise used) by libev itself, but can be freely used
		974	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		975
894	=item C<EV_ERROR>	976	=item C<EV_ERROR>
895		977
896	An unspecified error has occurred, the watcher has been stopped. This might	978	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	979	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	980	ran out of memory, a file descriptor was found to be closed or any other
		981	problem. Libev considers these application bugs.
		982
899	problem. You best act on it by reporting the problem and somehow coping	983	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	984	watcher being stopped. Note that well-written programs should not receive
		985	an error ever, so when your watcher receives it, this usually indicates a
		986	bug in your program.
901		987
902	Libev will usually signal a few "dummy" events together with an error, for	988	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	989	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	990	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	991	the error from read() or write(). This will not work in multi-threaded
…		…
908		994
909	=back	995	=back
910		996
911	=head2 GENERIC WATCHER FUNCTIONS	997	=head2 GENERIC WATCHER FUNCTIONS
912		998
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	999	=over 4
917		1000
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1001	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1002
920	This macro initialises the generic portion of a watcher. The contents	1003	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1008	which rolls both calls into one.
926		1009
927	You can reinitialise a watcher at any time as long as it has been stopped	1010	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1011	(or never started) and there are no pending events outstanding.
929		1012
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1013	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1014	int revents)>.
932		1015
933	Example: Initialise an C<ev_io> watcher in two steps.	1016	Example: Initialise an C<ev_io> watcher in two steps.
934		1017
935	ev_io w;	1018	ev_io w;
…		…
969		1052
970	ev_io_start (EV_DEFAULT_UC, &w);	1053	ev_io_start (EV_DEFAULT_UC, &w);
971		1054
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
973		1056
974	Stops the given watcher again (if active) and clears the pending	1057	Stops the given watcher if active, and clears the pending status (whether
		1058	the watcher was active or not).
		1059
975	status. It is possible that stopped watchers are pending (for example,	1060	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1061	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1062	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1063	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1064	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1065
981	=item bool ev_is_active (ev_TYPE *watcher)	1066	=item bool ev_is_active (ev_TYPE *watcher)
982		1067
983	Returns a true value iff the watcher is active (i.e. it has been started	1068	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1069	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1010	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1011	(default: C<-2>). Pending watchers with higher priority will be invoked	1096	(default: C<-2>). Pending watchers with higher priority will be invoked
1012	before watchers with lower priority, but priority will not keep watchers	1097	before watchers with lower priority, but priority will not keep watchers
1013	from being executed (except for C<ev_idle> watchers).	1098	from being executed (except for C<ev_idle> watchers).
1014		1099
1015	This means that priorities are I<only> used for ordering callback
1016	invocation after new events have been received. This is useful, for
1017	example, to reduce latency after idling, or more often, to bind two
1018	watchers on the same event and make sure one is called first.
1019
1020	If you need to suppress invocation when higher priority events are pending	1100	If you need to suppress invocation when higher priority events are pending
1021	you need to look at C<ev_idle> watchers, which provide this functionality.	1101	you need to look at C<ev_idle> watchers, which provide this functionality.
1022		1102
1023	You I<must not> change the priority of a watcher as long as it is active or	1103	You I<must not> change the priority of a watcher as long as it is active or
1024	pending.	1104	pending.
1025		1105
		1106	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1107	fine, as long as you do not mind that the priority value you query might
		1108	or might not have been clamped to the valid range.
		1109
1026	The default priority used by watchers when no priority has been set is	1110	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1111	always C<0>, which is supposed to not be too high and not be too low :).
1028		1112
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1030	fine, as long as you do not mind that the priority value you query might	1114	priorities.
1031	or might not have been adjusted to be within valid range.
1032		1115
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1117
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1119	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1058	member, you can also "subclass" the watcher type and provide your own	1141	member, you can also "subclass" the watcher type and provide your own
1059	data:	1142	data:
1060		1143
1061	struct my_io	1144	struct my_io
1062	{	1145	{
1063	struct ev_io io;	1146	ev_io io;
1064	int otherfd;	1147	int otherfd;
1065	void *somedata;	1148	void *somedata;
1066	struct whatever *mostinteresting;	1149	struct whatever *mostinteresting;
1067	};	1150	};
1068		1151
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1155
1073	And since your callback will be called with a pointer to the watcher, you	1156	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1157	can cast it back to your own type:
1075		1158
1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1077	{	1160	{
1078	struct my_io *w = (struct my_io *)w_;	1161	struct my_io *w = (struct my_io *)w_;
1079	...	1162	...
1080	}	1163	}
1081		1164
…		…
1099	programmers):	1182	programmers):
1100		1183
1101	#include <stddef.h>	1184	#include <stddef.h>
1102		1185
1103	static void	1186	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1187	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1188	{
1106	struct my_biggy big = (struct my_biggy *	1189	struct my_biggy big = (struct my_biggy *)
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1190	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1191	}
1109		1192
1110	static void	1193	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1194	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1195	{
1113	struct my_biggy big = (struct my_biggy *	1196	struct my_biggy big = (struct my_biggy *)
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1197	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1198	}
		1199
		1200	=head2 WATCHER PRIORITY MODELS
		1201
		1202	Many event loops support I<watcher priorities>, which are usually small
		1203	integers that influence the ordering of event callback invocation
		1204	between watchers in some way, all else being equal.
		1205
		1206	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1207	description for the more technical details such as the actual priority
		1208	range.
		1209
		1210	There are two common ways how these these priorities are being interpreted
		1211	by event loops:
		1212
		1213	In the more common lock-out model, higher priorities "lock out" invocation
		1214	of lower priority watchers, which means as long as higher priority
		1215	watchers receive events, lower priority watchers are not being invoked.
		1216
		1217	The less common only-for-ordering model uses priorities solely to order
		1218	callback invocation within a single event loop iteration: Higher priority
		1219	watchers are invoked before lower priority ones, but they all get invoked
		1220	before polling for new events.
		1221
		1222	Libev uses the second (only-for-ordering) model for all its watchers
		1223	except for idle watchers (which use the lock-out model).
		1224
		1225	The rationale behind this is that implementing the lock-out model for
		1226	watchers is not well supported by most kernel interfaces, and most event
		1227	libraries will just poll for the same events again and again as long as
		1228	their callbacks have not been executed, which is very inefficient in the
		1229	common case of one high-priority watcher locking out a mass of lower
		1230	priority ones.
		1231
		1232	Static (ordering) priorities are most useful when you have two or more
		1233	watchers handling the same resource: a typical usage example is having an
		1234	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1235	timeouts. Under load, data might be received while the program handles
		1236	other jobs, but since timers normally get invoked first, the timeout
		1237	handler will be executed before checking for data. In that case, giving
		1238	the timer a lower priority than the I/O watcher ensures that I/O will be
		1239	handled first even under adverse conditions (which is usually, but not
		1240	always, what you want).
		1241
		1242	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1243	will only be executed when no same or higher priority watchers have
		1244	received events, they can be used to implement the "lock-out" model when
		1245	required.
		1246
		1247	For example, to emulate how many other event libraries handle priorities,
		1248	you can associate an C<ev_idle> watcher to each such watcher, and in
		1249	the normal watcher callback, you just start the idle watcher. The real
		1250	processing is done in the idle watcher callback. This causes libev to
		1251	continously poll and process kernel event data for the watcher, but when
		1252	the lock-out case is known to be rare (which in turn is rare :), this is
		1253	workable.
		1254
		1255	Usually, however, the lock-out model implemented that way will perform
		1256	miserably under the type of load it was designed to handle. In that case,
		1257	it might be preferable to stop the real watcher before starting the
		1258	idle watcher, so the kernel will not have to process the event in case
		1259	the actual processing will be delayed for considerable time.
		1260
		1261	Here is an example of an I/O watcher that should run at a strictly lower
		1262	priority than the default, and which should only process data when no
		1263	other events are pending:
		1264
		1265	ev_idle idle; // actual processing watcher
		1266	ev_io io; // actual event watcher
		1267
		1268	static void
		1269	io_cb (EV_P_ ev_io *w, int revents)
		1270	{
		1271	// stop the I/O watcher, we received the event, but
		1272	// are not yet ready to handle it.
		1273	ev_io_stop (EV_A_ w);
		1274
		1275	// start the idle watcher to ahndle the actual event.
		1276	// it will not be executed as long as other watchers
		1277	// with the default priority are receiving events.
		1278	ev_idle_start (EV_A_ &idle);
		1279	}
		1280
		1281	static void
		1282	idle_cb (EV_P_ ev_idle *w, int revents)
		1283	{
		1284	// actual processing
		1285	read (STDIN_FILENO, ...);
		1286
		1287	// have to start the I/O watcher again, as
		1288	// we have handled the event
		1289	ev_io_start (EV_P_ &io);
		1290	}
		1291
		1292	// initialisation
		1293	ev_idle_init (&idle, idle_cb);
		1294	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1295	ev_io_start (EV_DEFAULT_ &io);
		1296
		1297	In the "real" world, it might also be beneficial to start a timer, so that
		1298	low-priority connections can not be locked out forever under load. This
		1299	enables your program to keep a lower latency for important connections
		1300	during short periods of high load, while not completely locking out less
		1301	important ones.
1116		1302
1117		1303
1118	=head1 WATCHER TYPES	1304	=head1 WATCHER TYPES
1119		1305
1120	This section describes each watcher in detail, but will not repeat	1306	This section describes each watcher in detail, but will not repeat
…		…
1146	descriptors to non-blocking mode is also usually a good idea (but not	1332	descriptors to non-blocking mode is also usually a good idea (but not
1147	required if you know what you are doing).	1333	required if you know what you are doing).
1148		1334
1149	If you cannot use non-blocking mode, then force the use of a	1335	If you cannot use non-blocking mode, then force the use of a
1150	known-to-be-good backend (at the time of this writing, this includes only	1336	known-to-be-good backend (at the time of this writing, this includes only
1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1338	descriptors for which non-blocking operation makes no sense (such as
		1339	files) - libev doesn't guarentee any specific behaviour in that case.
1152		1340
1153	Another thing you have to watch out for is that it is quite easy to	1341	Another thing you have to watch out for is that it is quite easy to
1154	receive "spurious" readiness notifications, that is your callback might	1342	receive "spurious" readiness notifications, that is your callback might
1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1343	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1156	because there is no data. Not only are some backends known to create a	1344	because there is no data. Not only are some backends known to create a
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1439	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1440	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1441	attempt to read a whole line in the callback.
1254		1442
1255	static void	1443	static void
1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1444	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1257	{	1445	{
1258	ev_io_stop (loop, w);	1446	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1447	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1448	}
1261		1449
1262	...	1450	...
1263	struct ev_loop *loop = ev_default_init (0);	1451	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1452	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1453	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1454	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1455	ev_loop (loop, 0);
1268		1456
1269		1457
…		…
1277	year, it will still time out after (roughly) one hour. "Roughly" because	1465	year, it will still time out after (roughly) one hour. "Roughly" because
1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1466	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1279	monotonic clock option helps a lot here).	1467	monotonic clock option helps a lot here).
1280		1468
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1469	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1470	passed (not I<at>, so on systems with very low-resolution clocks this
1283	then order of execution is undefined.	1471	might introduce a small delay). If multiple timers become ready during the
		1472	same loop iteration then the ones with earlier time-out values are invoked
		1473	before ones with later time-out values (but this is no longer true when a
		1474	callback calls C<ev_loop> recursively).
		1475
		1476	=head3 Be smart about timeouts
		1477
		1478	Many real-world problems involve some kind of timeout, usually for error
		1479	recovery. A typical example is an HTTP request - if the other side hangs,
		1480	you want to raise some error after a while.
		1481
		1482	What follows are some ways to handle this problem, from obvious and
		1483	inefficient to smart and efficient.
		1484
		1485	In the following, a 60 second activity timeout is assumed - a timeout that
		1486	gets reset to 60 seconds each time there is activity (e.g. each time some
		1487	data or other life sign was received).
		1488
		1489	=over 4
		1490
		1491	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1492
		1493	This is the most obvious, but not the most simple way: In the beginning,
		1494	start the watcher:
		1495
		1496	ev_timer_init (timer, callback, 60., 0.);
		1497	ev_timer_start (loop, timer);
		1498
		1499	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1500	and start it again:
		1501
		1502	ev_timer_stop (loop, timer);
		1503	ev_timer_set (timer, 60., 0.);
		1504	ev_timer_start (loop, timer);
		1505
		1506	This is relatively simple to implement, but means that each time there is
		1507	some activity, libev will first have to remove the timer from its internal
		1508	data structure and then add it again. Libev tries to be fast, but it's
		1509	still not a constant-time operation.
		1510
		1511	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1512
		1513	This is the easiest way, and involves using C<ev_timer_again> instead of
		1514	C<ev_timer_start>.
		1515
		1516	To implement this, configure an C<ev_timer> with a C<repeat> value
		1517	of C<60> and then call C<ev_timer_again> at start and each time you
		1518	successfully read or write some data. If you go into an idle state where
		1519	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1520	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1521
		1522	That means you can ignore both the C<ev_timer_start> function and the
		1523	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1524	member and C<ev_timer_again>.
		1525
		1526	At start:
		1527
		1528	ev_timer_init (timer, callback);
		1529	timer->repeat = 60.;
		1530	ev_timer_again (loop, timer);
		1531
		1532	Each time there is some activity:
		1533
		1534	ev_timer_again (loop, timer);
		1535
		1536	It is even possible to change the time-out on the fly, regardless of
		1537	whether the watcher is active or not:
		1538
		1539	timer->repeat = 30.;
		1540	ev_timer_again (loop, timer);
		1541
		1542	This is slightly more efficient then stopping/starting the timer each time
		1543	you want to modify its timeout value, as libev does not have to completely
		1544	remove and re-insert the timer from/into its internal data structure.
		1545
		1546	It is, however, even simpler than the "obvious" way to do it.
		1547
		1548	=item 3. Let the timer time out, but then re-arm it as required.
		1549
		1550	This method is more tricky, but usually most efficient: Most timeouts are
		1551	relatively long compared to the intervals between other activity - in
		1552	our example, within 60 seconds, there are usually many I/O events with
		1553	associated activity resets.
		1554
		1555	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1556	but remember the time of last activity, and check for a real timeout only
		1557	within the callback:
		1558
		1559	ev_tstamp last_activity; // time of last activity
		1560
		1561	static void
		1562	callback (EV_P_ ev_timer *w, int revents)
		1563	{
		1564	ev_tstamp now = ev_now (EV_A);
		1565	ev_tstamp timeout = last_activity + 60.;
		1566
		1567	// if last_activity + 60. is older than now, we did time out
		1568	if (timeout < now)
		1569	{
		1570	// timeout occured, take action
		1571	}
		1572	else
		1573	{
		1574	// callback was invoked, but there was some activity, re-arm
		1575	// the watcher to fire in last_activity + 60, which is
		1576	// guaranteed to be in the future, so "again" is positive:
		1577	w->repeat = timeout - now;
		1578	ev_timer_again (EV_A_ w);
		1579	}
		1580	}
		1581
		1582	To summarise the callback: first calculate the real timeout (defined
		1583	as "60 seconds after the last activity"), then check if that time has
		1584	been reached, which means something I<did>, in fact, time out. Otherwise
		1585	the callback was invoked too early (C<timeout> is in the future), so
		1586	re-schedule the timer to fire at that future time, to see if maybe we have
		1587	a timeout then.
		1588
		1589	Note how C<ev_timer_again> is used, taking advantage of the
		1590	C<ev_timer_again> optimisation when the timer is already running.
		1591
		1592	This scheme causes more callback invocations (about one every 60 seconds
		1593	minus half the average time between activity), but virtually no calls to
		1594	libev to change the timeout.
		1595
		1596	To start the timer, simply initialise the watcher and set C<last_activity>
		1597	to the current time (meaning we just have some activity :), then call the
		1598	callback, which will "do the right thing" and start the timer:
		1599
		1600	ev_timer_init (timer, callback);
		1601	last_activity = ev_now (loop);
		1602	callback (loop, timer, EV_TIMEOUT);
		1603
		1604	And when there is some activity, simply store the current time in
		1605	C<last_activity>, no libev calls at all:
		1606
		1607	last_actiivty = ev_now (loop);
		1608
		1609	This technique is slightly more complex, but in most cases where the
		1610	time-out is unlikely to be triggered, much more efficient.
		1611
		1612	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1613	callback :) - just change the timeout and invoke the callback, which will
		1614	fix things for you.
		1615
		1616	=item 4. Wee, just use a double-linked list for your timeouts.
		1617
		1618	If there is not one request, but many thousands (millions...), all
		1619	employing some kind of timeout with the same timeout value, then one can
		1620	do even better:
		1621
		1622	When starting the timeout, calculate the timeout value and put the timeout
		1623	at the I<end> of the list.
		1624
		1625	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1626	the list is expected to fire (for example, using the technique #3).
		1627
		1628	When there is some activity, remove the timer from the list, recalculate
		1629	the timeout, append it to the end of the list again, and make sure to
		1630	update the C<ev_timer> if it was taken from the beginning of the list.
		1631
		1632	This way, one can manage an unlimited number of timeouts in O(1) time for
		1633	starting, stopping and updating the timers, at the expense of a major
		1634	complication, and having to use a constant timeout. The constant timeout
		1635	ensures that the list stays sorted.
		1636
		1637	=back
		1638
		1639	So which method the best?
		1640
		1641	Method #2 is a simple no-brain-required solution that is adequate in most
		1642	situations. Method #3 requires a bit more thinking, but handles many cases
		1643	better, and isn't very complicated either. In most case, choosing either
		1644	one is fine, with #3 being better in typical situations.
		1645
		1646	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1647	rather complicated, but extremely efficient, something that really pays
		1648	off after the first million or so of active timers, i.e. it's usually
		1649	overkill :)
1284		1650
1285	=head3 The special problem of time updates	1651	=head3 The special problem of time updates
1286		1652
1287	Establishing the current time is a costly operation (it usually takes at	1653	Establishing the current time is a costly operation (it usually takes at
1288	least two system calls): EV therefore updates its idea of the current	1654	least two system calls): EV therefore updates its idea of the current
…		…
1332	If the timer is started but non-repeating, stop it (as if it timed out).	1698	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1699
1334	If the timer is repeating, either start it if necessary (with the	1700	If the timer is repeating, either start it if necessary (with the
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	1701	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1702
1337	This sounds a bit complicated, but here is a useful and typical	1703	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1338	example: Imagine you have a TCP connection and you want a so-called idle	1704	usage example.
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346
1347	That means you can ignore the C<after> value and C<ev_timer_start>
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1349
1350	ev_timer_init (timer, callback, 0., 5.);
1351	ev_timer_again (loop, timer);
1352	...
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358
1359	This is more slightly efficient then stopping/starting the timer each time
1360	you want to modify its timeout value.
1361
1362	Note, however, that it is often even more efficient to remember the
1363	time of the last activity and let the timer time-out naturally. In the
1364	callback, you then check whether the time-out is real, or, if there was
1365	some activity, you reschedule the watcher to time-out in "last_activity +
1366	timeout - ev_now ()" seconds.
1367		1705
1368	=item ev_tstamp repeat [read-write]	1706	=item ev_tstamp repeat [read-write]
1369		1707
1370	The current C<repeat> value. Will be used each time the watcher times out	1708	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	1709	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1714	=head3 Examples
1377		1715
1378	Example: Create a timer that fires after 60 seconds.	1716	Example: Create a timer that fires after 60 seconds.
1379		1717
1380	static void	1718	static void
1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1719	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1382	{	1720	{
1383	.. one minute over, w is actually stopped right here	1721	.. one minute over, w is actually stopped right here
1384	}	1722	}
1385		1723
1386	struct ev_timer mytimer;	1724	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1725	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1726	ev_timer_start (loop, &mytimer);
1389		1727
1390	Example: Create a timeout timer that times out after 10 seconds of	1728	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1729	inactivity.
1392		1730
1393	static void	1731	static void
1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1732	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1395	{	1733	{
1396	.. ten seconds without any activity	1734	.. ten seconds without any activity
1397	}	1735	}
1398		1736
1399	struct ev_timer mytimer;	1737	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1738	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1739	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1740	ev_loop (loop, 0);
1403		1741
1404	// and in some piece of code that gets executed on any "activity":	1742	// and in some piece of code that gets executed on any "activity":
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	1747	=head2 C<ev_periodic> - to cron or not to cron?
1410		1748
1411	Periodic watchers are also timers of a kind, but they are very versatile	1749	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	1750	(and unfortunately a bit complex).
1413		1751
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1752	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	1753	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	1754	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1755	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	1756	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	1757	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		1758
		1759	You can tell a periodic watcher to trigger after some specific point
		1760	in time: for example, if you tell a periodic watcher to trigger "in 10
		1761	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1762	not a delay) and then reset your system clock to January of the previous
		1763	year, then it will take a year or more to trigger the event (unlike an
		1764	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1765	it, as it uses a relative timeout).
		1766
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	1767	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	1768	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	1769	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1770	those cannot react to time jumps.
1426		1771
1427	As with timers, the callback is guaranteed to be invoked only when the	1772	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	1773	point in time where it is supposed to trigger has passed. If multiple
1429	during the same loop iteration, then order of execution is undefined.	1774	timers become ready during the same loop iteration then the ones with
		1775	earlier time-out values are invoked before ones with later time-out values
		1776	(but this is no longer true when a callback calls C<ev_loop> recursively).
1430		1777
1431	=head3 Watcher-Specific Functions and Data Members	1778	=head3 Watcher-Specific Functions and Data Members
1432		1779
1433	=over 4	1780	=over 4
1434		1781
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1782	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1783
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1784	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1785
1439	Lots of arguments, lets sort it out... There are basically three modes of	1786	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	1787	operation, and we will explain them from simplest to most complex:
1441		1788
1442	=over 4	1789	=over 4
1443		1790
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1791	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		1792
1446	In this configuration the watcher triggers an event after the wall clock	1793	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	1794	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1795	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	1796	will be stopped and invoked when the system clock reaches or surpasses
		1797	this point in time.
1450		1798
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1799	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		1800
1453	In this mode the watcher will always be scheduled to time out at the next	1801	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	1802	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	1803	negative) and then repeat, regardless of any time jumps. The C<offset>
		1804	argument is merely an offset into the C<interval> periods.
1456		1805
1457	This can be used to create timers that do not drift with respect to the	1806	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	1807	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	1808	hour, on the hour (with respect to UTC):
1460		1809
1461	ev_periodic_set (&periodic, 0., 3600., 0);	1810	ev_periodic_set (&periodic, 0., 3600., 0);
1462		1811
1463	This doesn't mean there will always be 3600 seconds in between triggers,	1812	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	1813	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	1814	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	1815	by 3600.
1467		1816
1468	Another way to think about it (for the mathematically inclined) is that	1817	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	1818	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	1819	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		1820
1472	For numerical stability it is preferable that the C<at> value is near	1821	For numerical stability it is preferable that the C<offset> value is near
1473	C<ev_now ()> (the current time), but there is no range requirement for	1822	C<ev_now ()> (the current time), but there is no range requirement for
1474	this value, and in fact is often specified as zero.	1823	this value, and in fact is often specified as zero.
1475		1824
1476	Note also that there is an upper limit to how often a timer can fire (CPU	1825	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	1826	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	1827	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	1828	millisecond (if the OS supports it and the machine is fast enough).
1480		1829
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1830	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		1831
1483	In this mode the values for C<interval> and C<at> are both being	1832	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	1833	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	1834	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	1835	current time as second argument.
1487		1836
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1837	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	1838	or make ANY other event loop modifications whatsoever, unless explicitly
		1839	allowed by documentation here>.
1490		1840
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1841	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1842	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	1843	only event loop modification you are allowed to do).
1494		1844
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1845	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	1846	*w, ev_tstamp now)>, e.g.:
1497		1847
		1848	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1849	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	1850	{
1500	return now + 60.;	1851	return now + 60.;
1501	}	1852	}
1502		1853
1503	It must return the next time to trigger, based on the passed time value	1854	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	1874	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	1875	program when the crontabs have changed).
1525		1876
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	1877	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		1878
1528	When active, returns the absolute time that the watcher is supposed to	1879	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	1880	to trigger next. This is not the same as the C<offset> argument to
		1881	C<ev_periodic_set>, but indeed works even in interval and manual
		1882	rescheduling modes.
1530		1883
1531	=item ev_tstamp offset [read-write]	1884	=item ev_tstamp offset [read-write]
1532		1885
1533	When repeating, this contains the offset value, otherwise this is the	1886	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1887	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1888	although libev might modify this value for better numerical stability).
1535		1889
1536	Can be modified any time, but changes only take effect when the periodic	1890	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	1891	timer fires or C<ev_periodic_again> is being called.
1538		1892
1539	=item ev_tstamp interval [read-write]	1893	=item ev_tstamp interval [read-write]
1540		1894
1541	The current interval value. Can be modified any time, but changes only	1895	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	1896	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	1897	called.
1544		1898
1545	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1899	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1546		1900
1547	The current reschedule callback, or C<0>, if this functionality is	1901	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	1902	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	1903	the periodic timer fires or C<ev_periodic_again> is being called.
1550		1904
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	1909	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	1910	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	1911	potentially a lot of jitter, but good long-term stability.
1558		1912
1559	static void	1913	static void
1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1914	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1561	{	1915	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	1916	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	1917	}
1564		1918
1565	struct ev_periodic hourly_tick;	1919	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1920	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	1921	ev_periodic_start (loop, &hourly_tick);
1568		1922
1569	Example: The same as above, but use a reschedule callback to do it:	1923	Example: The same as above, but use a reschedule callback to do it:
1570		1924
1571	#include <math.h>	1925	#include <math.h>
1572		1926
1573	static ev_tstamp	1927	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1928	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	1929	{
1576	return now + (3600. - fmod (now, 3600.));	1930	return now + (3600. - fmod (now, 3600.));
1577	}	1931	}
1578		1932
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1933	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		1934
1581	Example: Call a callback every hour, starting now:	1935	Example: Call a callback every hour, starting now:
1582		1936
1583	struct ev_periodic hourly_tick;	1937	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	1938	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	1939	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	1940	ev_periodic_start (loop, &hourly_tick);
1587		1941
1588		1942
…		…
1630	=head3 Examples	1984	=head3 Examples
1631		1985
1632	Example: Try to exit cleanly on SIGINT.	1986	Example: Try to exit cleanly on SIGINT.
1633		1987
1634	static void	1988	static void
1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1989	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1636	{	1990	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	1991	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	1992	}
1639		1993
1640	struct ev_signal signal_watcher;	1994	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1995	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	1996	ev_signal_start (loop, &signal_watcher);
1643		1997
1644		1998
1645	=head2 C<ev_child> - watch out for process status changes	1999	=head2 C<ev_child> - watch out for process status changes
…		…
1720	its completion.	2074	its completion.
1721		2075
1722	ev_child cw;	2076	ev_child cw;
1723		2077
1724	static void	2078	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	2079	child_cb (EV_P_ ev_child *w, int revents)
1726	{	2080	{
1727	ev_child_stop (EV_A_ w);	2081	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2082	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	2083	}
1730		2084
…		…
1745		2099
1746		2100
1747	=head2 C<ev_stat> - did the file attributes just change?	2101	=head2 C<ev_stat> - did the file attributes just change?
1748		2102
1749	This watches a file system path for attribute changes. That is, it calls	2103	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	2104	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	2105	and sees if it changed compared to the last time, invoking the callback if
		2106	it did.
1752		2107
1753	The path does not need to exist: changing from "path exists" to "path does	2108	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	2109	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	2110	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	2111	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	2112	least one) and all the other fields of the stat buffer having unspecified
		2113	contents.
1758		2114
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	2115	The path I<must not> end in a slash or contain special components such as
		2116	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	2117	your working directory changes, then the behaviour is undefined.
1761		2118
1762	Since there is no standard kernel interface to do this, the portable	2119	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	2120	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	2121	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	2122	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	2123	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	2124	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	2125	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	2126	currently around C<0.1>, but that's usually overkill.
1770		2127
1771	This watcher type is not meant for massive numbers of stat watchers,	2128	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	2129	as even with OS-supported change notifications, this can be
1773	resource-intensive.	2130	resource-intensive.
1774		2131
1775	At the time of this writing, the only OS-specific interface implemented	2132	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	2133	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	2134	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	2135	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		2136
1780	=head3 ABI Issues (Largefile Support)	2137	=head3 ABI Issues (Largefile Support)
1781		2138
1782	Libev by default (unless the user overrides this) uses the default	2139	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	2140	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	2141	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	2142	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	2143	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	2144	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	2145	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	2146	most noticeably displayed with ev_stat and large file support.
1790		2147
1791	The solution for this is to lobby your distribution maker to make large	2148	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	2149	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	2150	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	2151	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2152	default compilation environment.
1796		2153
1797	=head3 Inotify and Kqueue	2154	=head3 Inotify and Kqueue
1798		2155
1799	When C<inotify (7)> support has been compiled into libev (generally only	2156	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2157	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2158	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2159	watcher is being started.
1803		2160
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2161	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2162	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2163	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2164	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2165	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2166	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2167	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2168	xfs are fully working) libev usually gets away without polling.
1809		2169
1810	There is no support for kqueue, as apparently it cannot be used to	2170	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2171	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2172	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2173	etc. is difficult.
1814		2174
		2175	=head3 C<stat ()> is a synchronous operation
		2176
		2177	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2178	the process. The exception are C<ev_stat> watchers - those call C<stat
		2179	()>, which is a synchronous operation.
		2180
		2181	For local paths, this usually doesn't matter: unless the system is very
		2182	busy or the intervals between stat's are large, a stat call will be fast,
		2183	as the path data is usually in memory already (except when starting the
		2184	watcher).
		2185
		2186	For networked file systems, calling C<stat ()> can block an indefinite
		2187	time due to network issues, and even under good conditions, a stat call
		2188	often takes multiple milliseconds.
		2189
		2190	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2191	paths, although this is fully supported by libev.
		2192
1815	=head3 The special problem of stat time resolution	2193	=head3 The special problem of stat time resolution
1816		2194
1817	The C<stat ()> system call only supports full-second resolution portably, and	2195	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2196	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2197	still only support whole seconds.
1820		2198
1821	That means that, if the time is the only thing that changes, you can	2199	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2200	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2201	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2202	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1967		2345
1968	=head3 Watcher-Specific Functions and Data Members	2346	=head3 Watcher-Specific Functions and Data Members
1969		2347
1970	=over 4	2348	=over 4
1971		2349
1972	=item ev_idle_init (ev_signal *, callback)	2350	=item ev_idle_init (ev_idle *, callback)
1973		2351
1974	Initialises and configures the idle watcher - it has no parameters of any	2352	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2353	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2354	believe me.
1977		2355
…		…
1981		2359
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2360	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2361	callback, free it. Also, use no error checking, as usual.
1984		2362
1985	static void	2363	static void
1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2364	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1987	{	2365	{
1988	free (w);	2366	free (w);
1989	// now do something you wanted to do when the program has	2367	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2368	// no longer anything immediate to do.
1991	}	2369	}
1992		2370
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2371	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2372	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2373	ev_idle_start (loop, idle_watcher);
1996		2374
1997		2375
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2376	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1999		2377
2000	Prepare and check watchers are usually (but not always) used in pairs:	2378	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2079		2457
2080	static ev_io iow [nfd];	2458	static ev_io iow [nfd];
2081	static ev_timer tw;	2459	static ev_timer tw;
2082		2460
2083	static void	2461	static void
2084	io_cb (ev_loop *loop, ev_io *w, int revents)	2462	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2085	{	2463	{
2086	}	2464	}
2087		2465
2088	// create io watchers for each fd and a timer before blocking	2466	// create io watchers for each fd and a timer before blocking
2089	static void	2467	static void
2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2468	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2091	{	2469	{
2092	int timeout = 3600000;	2470	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2471	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2472	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2473	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2110	}	2488	}
2111	}	2489	}
2112		2490
2113	// stop all watchers after blocking	2491	// stop all watchers after blocking
2114	static void	2492	static void
2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2493	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2116	{	2494	{
2117	ev_timer_stop (loop, &tw);	2495	ev_timer_stop (loop, &tw);
2118		2496
2119	for (int i = 0; i < nfd; ++i)	2497	for (int i = 0; i < nfd; ++i)
2120	{	2498	{
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	2594	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	2595	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	2596	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	2597	the rest in a second one, and embed the second one in the first.
2220		2598
2221	As long as the watcher is active, the callback will be invoked every time	2599	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	2600	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2601	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	2602	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	2603	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	2604	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		2605
2229	As long as the watcher is started it will automatically handle events. The	2606	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	2607	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		2608
2234	Also, there have not currently been made special provisions for forking:	2609	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2610	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	2611	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	2612	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		2613
2240	Unfortunately, not all backends are embeddable: only the ones returned by	2614	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2615	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	2616	portable one.
2243		2617
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2662	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2663	used).
2290		2664
2291	struct ev_loop *loop_hi = ev_default_init (0);	2665	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2666	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2667	ev_embed embed;
2294		2668
2295	// see if there is a chance of getting one that works	2669	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2670	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2671	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2672	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2686	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2687	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2688
2315	struct ev_loop *loop = ev_default_init (0);	2689	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2690	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2691	ev_embed embed;
2318		2692
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2693	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2694	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2695	{
2322	ev_embed_init (&embed, 0, loop_socket);	2696	ev_embed_init (&embed, 0, loop_socket);
…		…
2337	event loop blocks next and before C<ev_check> watchers are being called,	2711	event loop blocks next and before C<ev_check> watchers are being called,
2338	and only in the child after the fork. If whoever good citizen calling	2712	and only in the child after the fork. If whoever good citizen calling
2339	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2713	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2340	handlers will be invoked, too, of course.	2714	handlers will be invoked, too, of course.
2341		2715
		2716	=head3 The special problem of life after fork - how is it possible?
		2717
		2718	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2719	up/change the process environment, followed by a call to C<exec()>. This
		2720	sequence should be handled by libev without any problems.
		2721
		2722	This changes when the application actually wants to do event handling
		2723	in the child, or both parent in child, in effect "continuing" after the
		2724	fork.
		2725
		2726	The default mode of operation (for libev, with application help to detect
		2727	forks) is to duplicate all the state in the child, as would be expected
		2728	when I<either> the parent I<or> the child process continues.
		2729
		2730	When both processes want to continue using libev, then this is usually the
		2731	wrong result. In that case, usually one process (typically the parent) is
		2732	supposed to continue with all watchers in place as before, while the other
		2733	process typically wants to start fresh, i.e. without any active watchers.
		2734
		2735	The cleanest and most efficient way to achieve that with libev is to
		2736	simply create a new event loop, which of course will be "empty", and
		2737	use that for new watchers. This has the advantage of not touching more
		2738	memory than necessary, and thus avoiding the copy-on-write, and the
		2739	disadvantage of having to use multiple event loops (which do not support
		2740	signal watchers).
		2741
		2742	When this is not possible, or you want to use the default loop for
		2743	other reasons, then in the process that wants to start "fresh", call
		2744	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2745	the default loop will "orphan" (not stop) all registered watchers, so you
		2746	have to be careful not to execute code that modifies those watchers. Note
		2747	also that in that case, you have to re-register any signal watchers.
		2748
2342	=head3 Watcher-Specific Functions and Data Members	2749	=head3 Watcher-Specific Functions and Data Members
2343		2750
2344	=over 4	2751	=over 4
2345		2752
2346	=item ev_fork_init (ev_signal *, callback)	2753	=item ev_fork_init (ev_signal *, callback)
…		…
2463	=over 4	2870	=over 4
2464		2871
2465	=item ev_async_init (ev_async *, callback)	2872	=item ev_async_init (ev_async *, callback)
2466		2873
2467	Initialises and configures the async watcher - it has no parameters of any	2874	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2875	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	2876	trust me.
2470		2877
2471	=item ev_async_send (loop, ev_async *)	2878	=item ev_async_send (loop, ev_async *)
2472		2879
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2880	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2881	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	2882	C<ev_feed_event>, this call is safe to do from other threads, signal or
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2883	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2477	section below on what exactly this means).	2884	section below on what exactly this means).
2478		2885
		2886	Note that, as with other watchers in libev, multiple events might get
		2887	compressed into a single callback invocation (another way to look at this
		2888	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2889	reset when the event loop detects that).
		2890
2479	This call incurs the overhead of a system call only once per loop iteration,	2891	This call incurs the overhead of a system call only once per event loop
2480	so while the overhead might be noticeable, it doesn't apply to repeated	2892	iteration, so while the overhead might be noticeable, it doesn't apply to
2481	calls to C<ev_async_send>.	2893	repeated calls to C<ev_async_send> for the same event loop.
2482		2894
2483	=item bool = ev_async_pending (ev_async *)	2895	=item bool = ev_async_pending (ev_async *)
2484		2896
2485	Returns a non-zero value when C<ev_async_send> has been called on the	2897	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	2898	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2901	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	2902	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	2903	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	2904	quickly check whether invoking the loop might be a good idea.
2493		2905
2494	Not that this does I<not> check whether the watcher itself is pending, only	2906	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	2907	only whether it has been requested to make this watcher pending: there
		2908	is a time window between the event loop checking and resetting the async
		2909	notification, and the callback being invoked.
2496		2910
2497	=back	2911	=back
2498		2912
2499		2913
2500	=head1 OTHER FUNCTIONS	2914	=head1 OTHER FUNCTIONS
…		…
2536	/* doh, nothing entered */;	2950	/* doh, nothing entered */;
2537	}	2951	}
2538		2952
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2953	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		2954
2541	=item ev_feed_event (ev_loop *, watcher *, int revents)	2955	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2542		2956
2543	Feeds the given event set into the event loop, as if the specified event	2957	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an	2958	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).	2959	initialised but not necessarily started event watcher).
2546		2960
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2961	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2548		2962
2549	Feed an event on the given fd, as if a file descriptor backend detected	2963	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	2964	the given events it.
2551		2965
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	2966	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2553		2967
2554	Feed an event as if the given signal occurred (C<loop> must be the default	2968	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	2969	loop!).
2556		2970
2557	=back	2971	=back
…		…
2678	}	3092	}
2679		3093
2680	myclass obj;	3094	myclass obj;
2681	ev::io iow;	3095	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	3096	iow.set <myclass, &myclass::io_cb> (&obj);
		3097
		3098	=item w->set (object *)
		3099
		3100	This is an B<experimental> feature that might go away in a future version.
		3101
		3102	This is a variation of a method callback - leaving out the method to call
		3103	will default the method to C<operator ()>, which makes it possible to use
		3104	functor objects without having to manually specify the C<operator ()> all
		3105	the time. Incidentally, you can then also leave out the template argument
		3106	list.
		3107
		3108	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3109	int revents)>.
		3110
		3111	See the method-C<set> above for more details.
		3112
		3113	Example: use a functor object as callback.
		3114
		3115	struct myfunctor
		3116	{
		3117	void operator() (ev::io &w, int revents)
		3118	{
		3119	...
		3120	}
		3121	}
		3122
		3123	myfunctor f;
		3124
		3125	ev::io w;
		3126	w.set (&f);
2683		3127
2684	=item w->set<function> (void *data = 0)	3128	=item w->set<function> (void *data = 0)
2685		3129
2686	Also sets a callback, but uses a static method or plain function as	3130	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	3131	callback. The optional C<data> argument will be stored in the watcher's
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	3218	L<http://software.schmorp.de/pkg/EV>.
2775		3219
2776	=item Python	3220	=item Python
2777		3221
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3222	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	3223	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		3224
2785	=item Ruby	3225	=item Ruby
2786		3226
2787	Tony Arcieri has written a ruby extension that offers access to a subset	3227	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	3228	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	3229	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	3230	L<http://rev.rubyforge.org/>.
2791		3231
		3232	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3233	makes rev work even on mingw.
		3234
		3235	=item Haskell
		3236
		3237	A haskell binding to libev is available at
		3238	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3239
2792	=item D	3240	=item D
2793		3241
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3242	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3243	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3244
		3245	=item Ocaml
		3246
		3247	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3248	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2796		3249
2797	=back	3250	=back
2798		3251
2799		3252
2800	=head1 MACRO MAGIC	3253	=head1 MACRO MAGIC
…		…
2901		3354
2902	#define EV_STANDALONE 1	3355	#define EV_STANDALONE 1
2903	#include "ev.h"	3356	#include "ev.h"
2904		3357
2905	Both header files and implementation files can be compiled with a C++	3358	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	3359	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3360	as a bug).
2908		3361
2909	You need the following files in your source tree, or in a directory	3362	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	3363	in your include path (e.g. in libev/ when using -Ilibev):
2911		3364
…		…
2967	keeps libev from including F<config.h>, and it also defines dummy	3420	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	3421	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	3422	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	3423	F<event.h> that are not directly supported by the libev core alone.
2971		3424
		3425	In stanbdalone mode, libev will still try to automatically deduce the
		3426	configuration, but has to be more conservative.
		3427
2972	=item EV_USE_MONOTONIC	3428	=item EV_USE_MONOTONIC
2973		3429
2974	If defined to be C<1>, libev will try to detect the availability of the	3430	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	3431	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	3432	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	3433	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	3434	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	3435	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	3436	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		3437
2982	=item EV_USE_REALTIME	3438	=item EV_USE_REALTIME
2983		3439
2984	If defined to be C<1>, libev will try to detect the availability of the	3440	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	3441	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	3442	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3443	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3444	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3445	correctness. See the note about libraries in the description of
		3446	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3447	C<EV_USE_CLOCK_SYSCALL>.
		3448
		3449	=item EV_USE_CLOCK_SYSCALL
		3450
		3451	If defined to be C<1>, libev will try to use a direct syscall instead
		3452	of calling the system-provided C<clock_gettime> function. This option
		3453	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3454	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3455	programs needlessly. Using a direct syscall is slightly slower (in
		3456	theory), because no optimised vdso implementation can be used, but avoids
		3457	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3458	higher, as it simplifies linking (no need for C<-lrt>).
2990		3459
2991	=item EV_USE_NANOSLEEP	3460	=item EV_USE_NANOSLEEP
2992		3461
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3462	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	3463	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		3479
3011	=item EV_SELECT_USE_FD_SET	3480	=item EV_SELECT_USE_FD_SET
3012		3481
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	3482	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	3483	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3484	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	3485	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	3486	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3487	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	3488	configures the maximum size of the C<fd_set>.
3020		3489
3021	=item EV_SELECT_IS_WINSOCKET	3490	=item EV_SELECT_IS_WINSOCKET
3022		3491
3023	When defined to C<1>, the select backend will assume that	3492	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	3493	select/socket/connect etc. don't understand file descriptors but
…		…
3383	loop, as long as you don't confuse yourself). The only exception is that	3852	loop, as long as you don't confuse yourself). The only exception is that
3384	you must not do this from C<ev_periodic> reschedule callbacks.	3853	you must not do this from C<ev_periodic> reschedule callbacks.
3385		3854
3386	Care has been taken to ensure that libev does not keep local state inside	3855	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3856	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	3857	they do not call any callbacks.
3389		3858
3390	=head2 COMPILER WARNINGS	3859	=head2 COMPILER WARNINGS
3391		3860
3392	Depending on your compiler and compiler settings, you might get no or a	3861	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	3862	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	3896	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	3897	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	3898	==2274== still reachable: 256 bytes in 1 blocks.
3430		3899
3431	Then there is no memory leak, just as memory accounted to global variables	3900	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	3901	is not a memleak - the memory is still being referenced, and didn't leak.
3433		3902
3434	Similarly, under some circumstances, valgrind might report kernel bugs	3903	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3904	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	3905	although an acceptable workaround has been found here), or it might be
3437	confused.	3906	confused.
…		…
3466	way (note also that glib is the slowest event library known to man).	3935	way (note also that glib is the slowest event library known to man).
3467		3936
3468	There is no supported compilation method available on windows except	3937	There is no supported compilation method available on windows except
3469	embedding it into other applications.	3938	embedding it into other applications.
3470		3939
		3940	Sensible signal handling is officially unsupported by Microsoft - libev
		3941	tries its best, but under most conditions, signals will simply not work.
		3942
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	3943	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	3944	accept large writes: instead of resulting in a partial write, windows will
3473	either accept everything or return C<ENOBUFS> if the buffer is too large,	3945	either accept everything or return C<ENOBUFS> if the buffer is too large,
3474	so make sure you only write small amounts into your sockets (less than a	3946	so make sure you only write small amounts into your sockets (less than a
3475	megabyte seems safe, but this apparently depends on the amount of memory	3947	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	3951	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	3952	is not recommended (and not reasonable). If your program needs to use
3481	more than a hundred or so sockets, then likely it needs to use a totally	3953	more than a hundred or so sockets, then likely it needs to use a totally
3482	different implementation for windows, as libev offers the POSIX readiness	3954	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	3955	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	3956	(due to Microsoft monopoly games).
3485		3957
3486	A typical way to use libev under windows is to embed it (see the embedding	3958	A typical way to use libev under windows is to embed it (see the embedding
3487	section for details) and use the following F<evwrap.h> header file instead	3959	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	3960	of F<ev.h>:
3489		3961
…		…
3525		3997
3526	Early versions of winsocket's select only supported waiting for a maximum	3998	Early versions of winsocket's select only supported waiting for a maximum
3527	of C<64> handles (probably owning to the fact that all windows kernels	3999	of C<64> handles (probably owning to the fact that all windows kernels
3528	can only wait for C<64> things at the same time internally; Microsoft	4000	can only wait for C<64> things at the same time internally; Microsoft
3529	recommends spawning a chain of threads and wait for 63 handles and the	4001	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	4002	previous thread in each. Sounds great!).
3531		4003
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4004	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3533	to some high number (e.g. C<2048>) before compiling the winsocket select	4005	to some high number (e.g. C<2048>) before compiling the winsocket select
3534	call (which might be in libev or elsewhere, for example, perl does its own	4006	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	4007	other interpreters do their own select emulation on windows).
3536		4008
3537	Another limit is the number of file descriptors in the Microsoft runtime	4009	Another limit is the number of file descriptors in the Microsoft runtime
3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4010	libraries, which by default is C<64> (there must be a hidden I<64>
3539	or something like this inside Microsoft). You can increase this by calling	4011	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4012	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	arbitrary limit), but is broken in many versions of the Microsoft runtime	4013	(another arbitrary limit), but is broken in many versions of the Microsoft
3542	libraries.
3543
3544	This might get you to about C<512> or C<2048> sockets (depending on	4014	runtime libraries. This might get you to about C<512> or C<2048> sockets
3545	windows version and/or the phase of the moon). To get more, you need to	4015	(depending on windows version and/or the phase of the moon). To get more,
3546	wrap all I/O functions and provide your own fd management, but the cost of	4016	you need to wrap all I/O functions and provide your own fd management, but
3547	calling select (O(n²)) will likely make this unworkable.	4017	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4018
3549	=back	4019	=back
3550		4020
3551	=head2 PORTABILITY REQUIREMENTS	4021	=head2 PORTABILITY REQUIREMENTS
3552		4022
…		…
3673	involves iterating over all running async watchers or all signal numbers.	4143	involves iterating over all running async watchers or all signal numbers.
3674		4144
3675	=back	4145	=back
3676		4146
3677		4147
		4148	=head1 GLOSSARY
		4149
		4150	=over 4
		4151
		4152	=item active
		4153
		4154	A watcher is active as long as it has been started (has been attached to
		4155	an event loop) but not yet stopped (disassociated from the event loop).
		4156
		4157	=item application
		4158
		4159	In this document, an application is whatever is using libev.
		4160
		4161	=item callback
		4162
		4163	The address of a function that is called when some event has been
		4164	detected. Callbacks are being passed the event loop, the watcher that
		4165	received the event, and the actual event bitset.
		4166
		4167	=item callback invocation
		4168
		4169	The act of calling the callback associated with a watcher.
		4170
		4171	=item event
		4172
		4173	A change of state of some external event, such as data now being available
		4174	for reading on a file descriptor, time having passed or simply not having
		4175	any other events happening anymore.
		4176
		4177	In libev, events are represented as single bits (such as C<EV_READ> or
		4178	C<EV_TIMEOUT>).
		4179
		4180	=item event library
		4181
		4182	A software package implementing an event model and loop.
		4183
		4184	=item event loop
		4185
		4186	An entity that handles and processes external events and converts them
		4187	into callback invocations.
		4188
		4189	=item event model
		4190
		4191	The model used to describe how an event loop handles and processes
		4192	watchers and events.
		4193
		4194	=item pending
		4195
		4196	A watcher is pending as soon as the corresponding event has been detected,
		4197	and stops being pending as soon as the watcher will be invoked or its
		4198	pending status is explicitly cleared by the application.
		4199
		4200	A watcher can be pending, but not active. Stopping a watcher also clears
		4201	its pending status.
		4202
		4203	=item real time
		4204
		4205	The physical time that is observed. It is apparently strictly monotonic :)
		4206
		4207	=item wall-clock time
		4208
		4209	The time and date as shown on clocks. Unlike real time, it can actually
		4210	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4211	clock.
		4212
		4213	=item watcher
		4214
		4215	A data structure that describes interest in certain events. Watchers need
		4216	to be started (attached to an event loop) before they can receive events.
		4217
		4218	=item watcher invocation
		4219
		4220	The act of calling the callback associated with a watcher.
		4221
		4222	=back
		4223
3678	=head1 AUTHOR	4224	=head1 AUTHOR
3679		4225
3680	Marc Lehmann <libev@schmorp.de>.	4226	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		4227

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