[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.203 by root, Sun Oct 26 00:52:51 2008 UTC vs.
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC

…		…
8		8
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
		14	#include <stdio.h> // for puts
13		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;
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
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
…		…
108	name C<loop> (which is always of type C<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
…		…
298	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
299	function.	313	function.
300		314
301	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
302	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,
303	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
304		318
305	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
306	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
307	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
308	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
…		…
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		399
386	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,
387	but it scales phenomenally better. While poll and select usually scale	401	but it scales phenomenally better. While poll and select usually scale
388	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),
389	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).
390	of shortcomings, such as silently dropping events in some hard-to-detect	404
391	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
392	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.
393		421
394	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
395	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
396	(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
397	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
398	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
399		427	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		428
404	Best performance from this backend is achieved by not unregistering all	429	Best performance from this backend is achieved by not unregistering all
405	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,
406	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
407	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
408	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.
409		440
410	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
411	all kernel versions tested so far.	442	all kernel versions tested so far.
412		443
413	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
414	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
415		446
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		448
418	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
419	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
420	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
421	completely useless). For this reason it's not being "auto-detected" unless	452	it's completely useless). Unlike epoll, however, whose brokenness
422	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
423	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.
424		458
425	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
426	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
427	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
428		462
429	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
430	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
431	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
432	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
433	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
434	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
435		470
436	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
437		472
438	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
439	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
440	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
441	(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
442	(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
443	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
444		479
445	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
446	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
447	C<NOTE_EOF>.	482	C<NOTE_EOF>.
448		483
…		…
468	might perform better.	503	might perform better.
469		504
470	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
472	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
473	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
474		509
475	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
476	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
477		512
478	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
586		621
587	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
588	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
590		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
		637
591	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
592		639
593	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
594	use.	641	use.
595		642
…		…
609		656
610	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
611	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	659	the current time is a good idea.
613		660
614	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
615		688
616	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
617		690
618	Finally, this is it, the event handler. This function usually is called	691	Finally, this is it, the event handler. This function usually is called
619	after you initialised all your watchers and you want to start handling	692	after you initialised all your watchers and you want to start handling
…		…
635	the loop.	708	the loop.
636		709
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	711	necessary) and will handle those and any already outstanding ones. It
639	will block your process until at least one new event arrives (which could	712	will block your process until at least one new event arrives (which could
640	be an event internal to libev itself, so there is no guarentee that a	713	be an event internal to libev itself, so there is no guarantee that a
641	user-registered callback will be called), and will return after one	714	user-registered callback will be called), and will return after one
642	iteration of the loop.	715	iteration of the loop.
643		716
644	This is useful if you are waiting for some external event in conjunction	717	This is useful if you are waiting for some external event in conjunction
645	with something not expressible using other libev watchers (i.e. "roll your	718	with something not expressible using other libev watchers (i.e. "roll your
…		…
703		776
704	If you have a watcher you never unregister that should not keep C<ev_loop>	777	If you have a watcher you never unregister that should not keep C<ev_loop>
705	from returning, call ev_unref() after starting, and ev_ref() before	778	from returning, call ev_unref() after starting, and ev_ref() before
706	stopping it.	779	stopping it.
707		780
708	As an example, libev itself uses this for its internal signal pipe: It is	781	As an example, libev itself uses this for its internal signal pipe: It
709	not visible to the libev user and should not keep C<ev_loop> from exiting	782	is not visible to the libev user and should not keep C<ev_loop> from
710	if no event watchers registered by it are active. It is also an excellent	783	exiting if no event watchers registered by it are active. It is also an
711	way to do this for generic recurring timers or from within third-party	784	excellent way to do this for generic recurring timers or from within
712	libraries. Just remember to I<unref after start> and I<ref before stop>	785	third-party libraries. Just remember to I<unref after start> and I<ref
713	(but only if the watcher wasn't active before, or was active before,	786	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
715		790
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
717	running when nothing else is active.	792	running when nothing else is active.
718		793
719	ev_signal exitsig;	794	ev_signal exitsig;
…		…
748		823
749	By setting a higher I<io collect interval> you allow libev to spend more	824	By setting a higher I<io collect interval> you allow libev to spend more
750	time collecting I/O events, so you can handle more events per iteration,	825	time collecting I/O events, so you can handle more events per iteration,
751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
752	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	C<ev_timer>) will be not affected. Setting this to a non-null value will
753	introduce an additional C<ev_sleep ()> call into most loop iterations.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
754		831
755	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
756	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	834	latency/jitter/inexactness (the watcher callback will be called
758	later). C<ev_io> watchers will not be affected. Setting this to a non-null	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		837
761	Many (busy) programs can usually benefit by setting the I/O collect	838	Many (busy) programs can usually benefit by setting the I/O collect
762	interval to a value near C<0.1> or so, which is often enough for	839	interval to a value near C<0.1> or so, which is often enough for
763	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
764	usually doesn't make much sense to set it to a lower value than C<0.01>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
765	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
766		847
767	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
769	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
770	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
773		860
774	=item ev_loop_verify (loop)	861	=item ev_loop_verify (loop)
775		862
776	This function only does something when C<EV_VERIFY> support has been	863	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	864	compiled in, which is the default for non-minimal builds. It tries to go
…		…
903		990
904	=item C<EV_ASYNC>	991	=item C<EV_ASYNC>
905		992
906	The given async watcher has been asynchronously notified (see C<ev_async>).	993	The given async watcher has been asynchronously notified (see C<ev_async>).
907		994
		995	=item C<EV_CUSTOM>
		996
		997	Not ever sent (or otherwise used) by libev itself, but can be freely used
		998	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		999
908	=item C<EV_ERROR>	1000	=item C<EV_ERROR>
909		1001
910	An unspecified error has occurred, the watcher has been stopped. This might	1002	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1003	happen because the watcher could not be properly started because libev
912	ran out of memory, a file descriptor was found to be closed or any other	1004	ran out of memory, a file descriptor was found to be closed or any other
…		…
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1120	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1121	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1122	from being executed (except for C<ev_idle> watchers).
1031		1123
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1124	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1125	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1126
1040	You I<must not> change the priority of a watcher as long as it is active or	1127	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1128	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1129
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1130	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1131	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1132	or might not have been clamped to the valid range.
		1133
		1134	The default priority used by watchers when no priority has been set is
		1135	always C<0>, which is supposed to not be too high and not be too low :).
		1136
		1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1138	priorities.
1049		1139
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1141
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1142	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1143	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1118	#include <stddef.h>	1208	#include <stddef.h>
1119		1209
1120	static void	1210	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1211	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1212	{
1123	struct my_biggy big = (struct my_biggy *	1213	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1214	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1215	}
1126		1216
1127	static void	1217	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1218	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1219	{
1130	struct my_biggy big = (struct my_biggy *	1220	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1221	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1222	}
		1223
		1224	=head2 WATCHER PRIORITY MODELS
		1225
		1226	Many event loops support I<watcher priorities>, which are usually small
		1227	integers that influence the ordering of event callback invocation
		1228	between watchers in some way, all else being equal.
		1229
		1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1231	description for the more technical details such as the actual priority
		1232	range.
		1233
		1234	There are two common ways how these these priorities are being interpreted
		1235	by event loops:
		1236
		1237	In the more common lock-out model, higher priorities "lock out" invocation
		1238	of lower priority watchers, which means as long as higher priority
		1239	watchers receive events, lower priority watchers are not being invoked.
		1240
		1241	The less common only-for-ordering model uses priorities solely to order
		1242	callback invocation within a single event loop iteration: Higher priority
		1243	watchers are invoked before lower priority ones, but they all get invoked
		1244	before polling for new events.
		1245
		1246	Libev uses the second (only-for-ordering) model for all its watchers
		1247	except for idle watchers (which use the lock-out model).
		1248
		1249	The rationale behind this is that implementing the lock-out model for
		1250	watchers is not well supported by most kernel interfaces, and most event
		1251	libraries will just poll for the same events again and again as long as
		1252	their callbacks have not been executed, which is very inefficient in the
		1253	common case of one high-priority watcher locking out a mass of lower
		1254	priority ones.
		1255
		1256	Static (ordering) priorities are most useful when you have two or more
		1257	watchers handling the same resource: a typical usage example is having an
		1258	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1259	timeouts. Under load, data might be received while the program handles
		1260	other jobs, but since timers normally get invoked first, the timeout
		1261	handler will be executed before checking for data. In that case, giving
		1262	the timer a lower priority than the I/O watcher ensures that I/O will be
		1263	handled first even under adverse conditions (which is usually, but not
		1264	always, what you want).
		1265
		1266	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1267	will only be executed when no same or higher priority watchers have
		1268	received events, they can be used to implement the "lock-out" model when
		1269	required.
		1270
		1271	For example, to emulate how many other event libraries handle priorities,
		1272	you can associate an C<ev_idle> watcher to each such watcher, and in
		1273	the normal watcher callback, you just start the idle watcher. The real
		1274	processing is done in the idle watcher callback. This causes libev to
		1275	continously poll and process kernel event data for the watcher, but when
		1276	the lock-out case is known to be rare (which in turn is rare :), this is
		1277	workable.
		1278
		1279	Usually, however, the lock-out model implemented that way will perform
		1280	miserably under the type of load it was designed to handle. In that case,
		1281	it might be preferable to stop the real watcher before starting the
		1282	idle watcher, so the kernel will not have to process the event in case
		1283	the actual processing will be delayed for considerable time.
		1284
		1285	Here is an example of an I/O watcher that should run at a strictly lower
		1286	priority than the default, and which should only process data when no
		1287	other events are pending:
		1288
		1289	ev_idle idle; // actual processing watcher
		1290	ev_io io; // actual event watcher
		1291
		1292	static void
		1293	io_cb (EV_P_ ev_io *w, int revents)
		1294	{
		1295	// stop the I/O watcher, we received the event, but
		1296	// are not yet ready to handle it.
		1297	ev_io_stop (EV_A_ w);
		1298
		1299	// start the idle watcher to ahndle the actual event.
		1300	// it will not be executed as long as other watchers
		1301	// with the default priority are receiving events.
		1302	ev_idle_start (EV_A_ &idle);
		1303	}
		1304
		1305	static void
		1306	idle_cb (EV_P_ ev_idle *w, int revents)
		1307	{
		1308	// actual processing
		1309	read (STDIN_FILENO, ...);
		1310
		1311	// have to start the I/O watcher again, as
		1312	// we have handled the event
		1313	ev_io_start (EV_P_ &io);
		1314	}
		1315
		1316	// initialisation
		1317	ev_idle_init (&idle, idle_cb);
		1318	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1319	ev_io_start (EV_DEFAULT_ &io);
		1320
		1321	In the "real" world, it might also be beneficial to start a timer, so that
		1322	low-priority connections can not be locked out forever under load. This
		1323	enables your program to keep a lower latency for important connections
		1324	during short periods of high load, while not completely locking out less
		1325	important ones.
1133		1326
1134		1327
1135	=head1 WATCHER TYPES	1328	=head1 WATCHER TYPES
1136		1329
1137	This section describes each watcher in detail, but will not repeat	1330	This section describes each watcher in detail, but will not repeat
…		…
1163	descriptors to non-blocking mode is also usually a good idea (but not	1356	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1357	required if you know what you are doing).
1165		1358
1166	If you cannot use non-blocking mode, then force the use of a	1359	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only	1360	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1362	descriptors for which non-blocking operation makes no sense (such as
		1363	files) - libev doesn't guarentee any specific behaviour in that case.
1169		1364
1170	Another thing you have to watch out for is that it is quite easy to	1365	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1366	receive "spurious" readiness notifications, that is your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1368	because there is no data. Not only are some backends known to create a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1489	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1491	monotonic clock option helps a lot here).
1297		1492
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1493	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1494	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1495	might introduce a small delay). If multiple timers become ready during the
		1496	same loop iteration then the ones with earlier time-out values are invoked
		1497	before ones of the same priority with later time-out values (but this is
		1498	no longer true when a callback calls C<ev_loop> recursively).
1301		1499
1302	=head3 Be smart about timeouts	1500	=head3 Be smart about timeouts
1303		1501
1304	Many real-world problems involve some kind of timeout, usually for error	1502	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1503	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1547	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1548	member and C<ev_timer_again>.
1351		1549
1352	At start:	1550	At start:
1353		1551
1354	ev_timer_init (timer, callback);	1552	ev_init (timer, callback);
1355	timer->repeat = 60.;	1553	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1554	ev_timer_again (loop, timer);
1357		1555
1358	Each time there is some activity:	1556	Each time there is some activity:
1359		1557
…		…
1398	else	1596	else
1399	{	1597	{
1400	// callback was invoked, but there was some activity, re-arm	1598	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1599	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1600	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1601	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1602	ev_timer_again (EV_A_ w);
1405	}	1603	}
1406	}	1604	}
1407		1605
1408	To summarise the callback: first calculate the real timeout (defined	1606	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1619
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1620	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1621	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1622	callback, which will "do the right thing" and start the timer:
1425		1623
1426	ev_timer_init (timer, callback);	1624	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1625	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1626	callback (loop, timer, EV_TIMEOUT);
1429		1627
1430	And when there is some activity, simply store the current time in	1628	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1629	C<last_activity>, no libev calls at all:
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	1722	If the timer is started but non-repeating, stop it (as if it timed out).
1525		1723
1526	If the timer is repeating, either start it if necessary (with the	1724	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	1725	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		1726
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1728	usage example.
1531		1729
1532	=item ev_tstamp repeat [read-write]	1730	=item ev_tstamp repeat [read-write]
1533		1731
1534	The current C<repeat> value. Will be used each time the watcher times out	1732	The current C<repeat> value. Will be used each time the watcher times out
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	1771	=head2 C<ev_periodic> - to cron or not to cron?
1574		1772
1575	Periodic watchers are also timers of a kind, but they are very versatile	1773	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	1774	(and unfortunately a bit complex).
1577		1775
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	1777	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	1778	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1779	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	1780	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	1781	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		1782
		1783	You can tell a periodic watcher to trigger after some specific point
		1784	in time: for example, if you tell a periodic watcher to trigger "in 10
		1785	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1786	not a delay) and then reset your system clock to January of the previous
		1787	year, then it will take a year or more to trigger the event (unlike an
		1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1789	it, as it uses a relative timeout).
		1790
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	1791	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	1792	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1794	those cannot react to time jumps.
1590		1795
1591	As with timers, the callback is guaranteed to be invoked only when the	1796	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	1797	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	1798	timers become ready during the same loop iteration then the ones with
		1799	earlier time-out values are invoked before ones with later time-out values
		1800	(but this is no longer true when a callback calls C<ev_loop> recursively).
1594		1801
1595	=head3 Watcher-Specific Functions and Data Members	1802	=head3 Watcher-Specific Functions and Data Members
1596		1803
1597	=over 4	1804	=over 4
1598		1805
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1806	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		1807
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1808	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		1809
1603	Lots of arguments, lets sort it out... There are basically three modes of	1810	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	1811	operation, and we will explain them from simplest to most complex:
1605		1812
1606	=over 4	1813	=over 4
1607		1814
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1815	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		1816
1610	In this configuration the watcher triggers an event after the wall clock	1817	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	1818	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1819	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	1820	will be stopped and invoked when the system clock reaches or surpasses
		1821	this point in time.
1614		1822
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1823	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		1824
1617	In this mode the watcher will always be scheduled to time out at the next	1825	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	1826	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	1827	negative) and then repeat, regardless of any time jumps. The C<offset>
		1828	argument is merely an offset into the C<interval> periods.
1620		1829
1621	This can be used to create timers that do not drift with respect to the	1830	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	1831	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	1832	hour, on the hour (with respect to UTC):
1624		1833
1625	ev_periodic_set (&periodic, 0., 3600., 0);	1834	ev_periodic_set (&periodic, 0., 3600., 0);
1626		1835
1627	This doesn't mean there will always be 3600 seconds in between triggers,	1836	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	1837	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	1838	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	1839	by 3600.
1631		1840
1632	Another way to think about it (for the mathematically inclined) is that	1841	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	1842	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	1843	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		1844
1636	For numerical stability it is preferable that the C<at> value is near	1845	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	1846	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	1847	this value, and in fact is often specified as zero.
1639		1848
1640	Note also that there is an upper limit to how often a timer can fire (CPU	1849	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	1850	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	1851	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	1852	millisecond (if the OS supports it and the machine is fast enough).
1644		1853
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1854	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		1855
1647	In this mode the values for C<interval> and C<at> are both being	1856	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	1857	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	1858	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	1859	current time as second argument.
1651		1860
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1861	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	1862	or make ANY other event loop modifications whatsoever, unless explicitly
		1863	allowed by documentation here>.
1654		1864
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1865	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1866	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	1867	only event loop modification you are allowed to do).
1658		1868
…		…
1688	a different time than the last time it was called (e.g. in a crond like	1898	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	1899	program when the crontabs have changed).
1690		1900
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	1901	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		1902
1693	When active, returns the absolute time that the watcher is supposed to	1903	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	1904	to trigger next. This is not the same as the C<offset> argument to
		1905	C<ev_periodic_set>, but indeed works even in interval and manual
		1906	rescheduling modes.
1695		1907
1696	=item ev_tstamp offset [read-write]	1908	=item ev_tstamp offset [read-write]
1697		1909
1698	When repeating, this contains the offset value, otherwise this is the	1910	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1911	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1912	although libev might modify this value for better numerical stability).
1700		1913
1701	Can be modified any time, but changes only take effect when the periodic	1914	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	1915	timer fires or C<ev_periodic_again> is being called.
1703		1916
1704	=item ev_tstamp interval [read-write]	1917	=item ev_tstamp interval [read-write]
…		…
1813	some child status changes (most typically when a child of yours dies or	2026	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2027	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2028	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2029	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2030	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2031	but forking and registering a watcher a few event loop iterations later or
1819	not.	2032	in the next callback invocation is not.
1820		2033
1821	Only the default event loop is capable of handling signals, and therefore	2034	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2035	you can only register child watchers in the default event loop.
		2036
		2037	Due to some design glitches inside libev, child watchers will always be
		2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)
1823		2039
1824	=head3 Process Interaction	2040	=head3 Process Interaction
1825		2041
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2042	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2043	initialised. This is necessary to guarantee proper behaviour even if
…		…
1910		2126
1911		2127
1912	=head2 C<ev_stat> - did the file attributes just change?	2128	=head2 C<ev_stat> - did the file attributes just change?
1913		2129
1914	This watches a file system path for attribute changes. That is, it calls	2130	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2131	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2132	and sees if it changed compared to the last time, invoking the callback if
		2133	it did.
1917		2134
1918	The path does not need to exist: changing from "path exists" to "path does	2135	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2136	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2137	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2138	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2139	least one) and all the other fields of the stat buffer having unspecified
		2140	contents.
1923		2141
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2142	The path I<must not> end in a slash or contain special components such as
		2143	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2144	your working directory changes, then the behaviour is undefined.
1926		2145
1927	Since there is no standard kernel interface to do this, the portable	2146	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2147	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2148	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2149	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2150	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2151	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2152	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2153	currently around C<0.1>, but that's usually overkill.
1935		2154
1936	This watcher type is not meant for massive numbers of stat watchers,	2155	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2156	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2157	resource-intensive.
1939		2158
1940	At the time of this writing, the only OS-specific interface implemented	2159	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2160	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2161	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2162	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2163
1945	=head3 ABI Issues (Largefile Support)	2164	=head3 ABI Issues (Largefile Support)
1946		2165
1947	Libev by default (unless the user overrides this) uses the default	2166	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2167	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2168	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2169	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2170	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2171	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2172	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2173	most noticeably displayed with ev_stat and large file support.
1955		2174
1956	The solution for this is to lobby your distribution maker to make large	2175	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2176	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2177	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2178	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2179	default compilation environment.
1961		2180
1962	=head3 Inotify and Kqueue	2181	=head3 Inotify and Kqueue
1963		2182
1964	When C<inotify (7)> support has been compiled into libev (generally	2183	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2184	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2185	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2186	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2187
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2188	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2189	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2190	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2191	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2192	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2193	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2194	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2195	xfs are fully working) libev usually gets away without polling.
1975		2196
1976	There is no support for kqueue, as apparently it cannot be used to	2197	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2198	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2199	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2200	etc. is difficult.
1980		2201
		2202	=head3 C<stat ()> is a synchronous operation
		2203
		2204	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2205	the process. The exception are C<ev_stat> watchers - those call C<stat
		2206	()>, which is a synchronous operation.
		2207
		2208	For local paths, this usually doesn't matter: unless the system is very
		2209	busy or the intervals between stat's are large, a stat call will be fast,
		2210	as the path data is usually in memory already (except when starting the
		2211	watcher).
		2212
		2213	For networked file systems, calling C<stat ()> can block an indefinite
		2214	time due to network issues, and even under good conditions, a stat call
		2215	often takes multiple milliseconds.
		2216
		2217	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2218	paths, although this is fully supported by libev.
		2219
1981	=head3 The special problem of stat time resolution	2220	=head3 The special problem of stat time resolution
1982		2221
1983	The C<stat ()> system call only supports full-second resolution portably, and	2222	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2223	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2224	still only support whole seconds.
1986		2225
1987	That means that, if the time is the only thing that changes, you can	2226	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2227	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2228	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2229	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2372
2134	=head3 Watcher-Specific Functions and Data Members	2373	=head3 Watcher-Specific Functions and Data Members
2135		2374
2136	=over 4	2375	=over 4
2137		2376
2138	=item ev_idle_init (ev_signal *, callback)	2377	=item ev_idle_init (ev_idle *, callback)
2139		2378
2140	Initialises and configures the idle watcher - it has no parameters of any	2379	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2380	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2381	believe me.
2143		2382
…		…
2156	// no longer anything immediate to do.	2395	// no longer anything immediate to do.
2157	}	2396	}
2158		2397
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2399	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2400	ev_idle_start (loop, idle_watcher);
2162		2401
2163		2402
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2404
2166	Prepare and check watchers are usually (but not always) used in pairs:	2405	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2259	struct pollfd fds [nfd];	2498	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2499	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2500	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2501
2263	/* the callback is illegal, but won't be called as we stop during check */	2502	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2503	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2504	ev_timer_start (loop, &tw);
2266		2505
2267	// create one ev_io per pollfd	2506	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2507	for (int i = 0; i < nfd; ++i)
2269	{	2508	{
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2621	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2622	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2623	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	2624	the rest in a second one, and embed the second one in the first.
2386		2625
2387	As long as the watcher is active, the callback will be invoked every time	2626	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	2627	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2628	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	2629	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	2630	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	2631	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2632
2395	As long as the watcher is started it will automatically handle events. The	2633	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	2634	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2635
2400	Also, there have not currently been made special provisions for forking:	2636	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2637	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2638	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2639	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2640
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2641	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2642	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2643	portable one.
2409		2644
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	2738	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	2739	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	2741	handlers will be invoked, too, of course.
2507		2742
		2743	=head3 The special problem of life after fork - how is it possible?
		2744
		2745	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2746	up/change the process environment, followed by a call to C<exec()>. This
		2747	sequence should be handled by libev without any problems.
		2748
		2749	This changes when the application actually wants to do event handling
		2750	in the child, or both parent in child, in effect "continuing" after the
		2751	fork.
		2752
		2753	The default mode of operation (for libev, with application help to detect
		2754	forks) is to duplicate all the state in the child, as would be expected
		2755	when I<either> the parent I<or> the child process continues.
		2756
		2757	When both processes want to continue using libev, then this is usually the
		2758	wrong result. In that case, usually one process (typically the parent) is
		2759	supposed to continue with all watchers in place as before, while the other
		2760	process typically wants to start fresh, i.e. without any active watchers.
		2761
		2762	The cleanest and most efficient way to achieve that with libev is to
		2763	simply create a new event loop, which of course will be "empty", and
		2764	use that for new watchers. This has the advantage of not touching more
		2765	memory than necessary, and thus avoiding the copy-on-write, and the
		2766	disadvantage of having to use multiple event loops (which do not support
		2767	signal watchers).
		2768
		2769	When this is not possible, or you want to use the default loop for
		2770	other reasons, then in the process that wants to start "fresh", call
		2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2772	the default loop will "orphan" (not stop) all registered watchers, so you
		2773	have to be careful not to execute code that modifies those watchers. Note
		2774	also that in that case, you have to re-register any signal watchers.
		2775
2508	=head3 Watcher-Specific Functions and Data Members	2776	=head3 Watcher-Specific Functions and Data Members
2509		2777
2510	=over 4	2778	=over 4
2511		2779
2512	=item ev_fork_init (ev_signal *, callback)	2780	=item ev_fork_init (ev_signal *, callback)
…		…
2629	=over 4	2897	=over 4
2630		2898
2631	=item ev_async_init (ev_async *, callback)	2899	=item ev_async_init (ev_async *, callback)
2632		2900
2633	Initialises and configures the async watcher - it has no parameters of any	2901	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2902	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	2903	trust me.
2636		2904
2637	=item ev_async_send (loop, ev_async *)	2905	=item ev_async_send (loop, ev_async *)
2638		2906
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	2909	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	2911	section below on what exactly this means).
2644		2912
		2913	Note that, as with other watchers in libev, multiple events might get
		2914	compressed into a single callback invocation (another way to look at this
		2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2916	reset when the event loop detects that).
		2917
2645	This call incurs the overhead of a system call only once per loop iteration,	2918	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	2919	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	2920	repeated calls to C<ev_async_send> for the same event loop.
2648		2921
2649	=item bool = ev_async_pending (ev_async *)	2922	=item bool = ev_async_pending (ev_async *)
2650		2923
2651	Returns a non-zero value when C<ev_async_send> has been called on the	2924	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	2925	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2928	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	2929	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	2930	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	2931	quickly check whether invoking the loop might be a good idea.
2659		2932
2660	Not that this does I<not> check whether the watcher itself is pending, only	2933	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	2934	only whether it has been requested to make this watcher pending: there
		2935	is a time window between the event loop checking and resetting the async
		2936	notification, and the callback being invoked.
2662		2937
2663	=back	2938	=back
2664		2939
2665		2940
2666	=head1 OTHER FUNCTIONS	2941	=head1 OTHER FUNCTIONS
…		…
2845		3120
2846	myclass obj;	3121	myclass obj;
2847	ev::io iow;	3122	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3123	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3124
		3125	=item w->set (object *)
		3126
		3127	This is an B<experimental> feature that might go away in a future version.
		3128
		3129	This is a variation of a method callback - leaving out the method to call
		3130	will default the method to C<operator ()>, which makes it possible to use
		3131	functor objects without having to manually specify the C<operator ()> all
		3132	the time. Incidentally, you can then also leave out the template argument
		3133	list.
		3134
		3135	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3136	int revents)>.
		3137
		3138	See the method-C<set> above for more details.
		3139
		3140	Example: use a functor object as callback.
		3141
		3142	struct myfunctor
		3143	{
		3144	void operator() (ev::io &w, int revents)
		3145	{
		3146	...
		3147	}
		3148	}
		3149
		3150	myfunctor f;
		3151
		3152	ev::io w;
		3153	w.set (&f);
		3154
2850	=item w->set<function> (void *data = 0)	3155	=item w->set<function> (void *data = 0)
2851		3156
2852	Also sets a callback, but uses a static method or plain function as	3157	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3158	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3159	C<data> member and is free for you to use.
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3245	L<http://software.schmorp.de/pkg/EV>.
2941		3246
2942	=item Python	3247	=item Python
2943		3248
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3249	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3250	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3251
2951	=item Ruby	3252	=item Ruby
2952		3253
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3254	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3255	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3256	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3257	L<http://rev.rubyforge.org/>.
		3258
		3259	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3260	makes rev work even on mingw.
		3261
		3262	=item Haskell
		3263
		3264	A haskell binding to libev is available at
		3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
2957		3266
2958	=item D	3267	=item D
2959		3268
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.
…		…
3072		3381
3073	#define EV_STANDALONE 1	3382	#define EV_STANDALONE 1
3074	#include "ev.h"	3383	#include "ev.h"
3075		3384
3076	Both header files and implementation files can be compiled with a C++	3385	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	3386	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3387	as a bug).
3079		3388
3080	You need the following files in your source tree, or in a directory	3389	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	3390	in your include path (e.g. in libev/ when using -Ilibev):
3082		3391
…		…
3138	keeps libev from including F<config.h>, and it also defines dummy	3447	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3448	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3449	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3450	F<event.h> that are not directly supported by the libev core alone.
3142		3451
		3452	In stanbdalone mode, libev will still try to automatically deduce the
		3453	configuration, but has to be more conservative.
		3454
3143	=item EV_USE_MONOTONIC	3455	=item EV_USE_MONOTONIC
3144		3456
3145	If defined to be C<1>, libev will try to detect the availability of the	3457	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3458	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3459	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3460	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3461	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3462	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3463	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3464
3153	=item EV_USE_REALTIME	3465	=item EV_USE_REALTIME
3154		3466
3155	If defined to be C<1>, libev will try to detect the availability of the	3467	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	3468	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3469	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3470	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3471	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3472	correctness. See the note about libraries in the description of
		3473	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3474	C<EV_USE_CLOCK_SYSCALL>.
		3475
		3476	=item EV_USE_CLOCK_SYSCALL
		3477
		3478	If defined to be C<1>, libev will try to use a direct syscall instead
		3479	of calling the system-provided C<clock_gettime> function. This option
		3480	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3481	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3482	programs needlessly. Using a direct syscall is slightly slower (in
		3483	theory), because no optimised vdso implementation can be used, but avoids
		3484	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3485	higher, as it simplifies linking (no need for C<-lrt>).
3161		3486
3162	=item EV_USE_NANOSLEEP	3487	=item EV_USE_NANOSLEEP
3163		3488
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3489	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	3490	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		3506
3182	=item EV_SELECT_USE_FD_SET	3507	=item EV_SELECT_USE_FD_SET
3183		3508
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	3509	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	3510	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3511	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	3512	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	3513	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3514	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	3515	configures the maximum size of the C<fd_set>.
3191		3516
3192	=item EV_SELECT_IS_WINSOCKET	3517	=item EV_SELECT_IS_WINSOCKET
3193		3518
3194	When defined to C<1>, the select backend will assume that	3519	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3520	select/socket/connect etc. don't understand file descriptors but
…		…
3554	loop, as long as you don't confuse yourself). The only exception is that	3879	loop, as long as you don't confuse yourself). The only exception is that
3555	you must not do this from C<ev_periodic> reschedule callbacks.	3880	you must not do this from C<ev_periodic> reschedule callbacks.
3556		3881
3557	Care has been taken to ensure that libev does not keep local state inside	3882	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	3884	they do not call any callbacks.
3560		3885
3561	=head2 COMPILER WARNINGS	3886	=head2 COMPILER WARNINGS
3562		3887
3563	Depending on your compiler and compiler settings, you might get no or a	3888	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	3889	lot of warnings when compiling libev code. Some people are apparently
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	3923	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	3924	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	3925	==2274== still reachable: 256 bytes in 1 blocks.
3601		3926
3602	Then there is no memory leak, just as memory accounted to global variables	3927	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	3928	is not a memleak - the memory is still being referenced, and didn't leak.
3604		3929
3605	Similarly, under some circumstances, valgrind might report kernel bugs	3930	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3931	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	3932	although an acceptable workaround has been found here), or it might be
3608	confused.	3933	confused.
…		…
3637	way (note also that glib is the slowest event library known to man).	3962	way (note also that glib is the slowest event library known to man).
3638		3963
3639	There is no supported compilation method available on windows except	3964	There is no supported compilation method available on windows except
3640	embedding it into other applications.	3965	embedding it into other applications.
3641		3966
		3967	Sensible signal handling is officially unsupported by Microsoft - libev
		3968	tries its best, but under most conditions, signals will simply not work.
		3969
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	3970	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	3971	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	3972	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	3973	so make sure you only write small amounts into your sockets (less than a
3646	megabyte seems safe, but this apparently depends on the amount of memory	3974	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	3978	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	3979	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	3980	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	3981	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	3982	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	3983	(due to Microsoft monopoly games).
3656		3984
3657	A typical way to use libev under windows is to embed it (see the embedding	3985	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	3986	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	3987	of F<ev.h>:
3660		3988
…		…
3696		4024
3697	Early versions of winsocket's select only supported waiting for a maximum	4025	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4026	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4027	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4028	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4029	previous thread in each. Sounds great!).
3702		4030
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4031	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4032	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4033	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4034	other interpreters do their own select emulation on windows).
3707		4035
3708	Another limit is the number of file descriptors in the Microsoft runtime	4036	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4037	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4038	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4039	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4040	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4041	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4042	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4043	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4044	the cost of calling select (O(n²)) will likely make this unworkable.
3719		4045
3720	=back	4046	=back
3721		4047
3722	=head2 PORTABILITY REQUIREMENTS	4048	=head2 PORTABILITY REQUIREMENTS
3723		4049
…		…
3766	=item C<double> must hold a time value in seconds with enough accuracy	4092	=item C<double> must hold a time value in seconds with enough accuracy
3767		4093
3768	The type C<double> is used to represent timestamps. It is required to	4094	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3770	enough for at least into the year 4000. This requirement is fulfilled by	4096	enough for at least into the year 4000. This requirement is fulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	4097	implementations implementing IEEE 754, which is basically all existing
		4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4099	2200.
3772		4100
3773	=back	4101	=back
3774		4102
3775	If you know of other additional requirements drop me a note.	4103	If you know of other additional requirements drop me a note.
3776		4104
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4172	involves iterating over all running async watchers or all signal numbers.
3845		4173
3846	=back	4174	=back
3847		4175
3848		4176
		4177	=head1 GLOSSARY
		4178
		4179	=over 4
		4180
		4181	=item active
		4182
		4183	A watcher is active as long as it has been started (has been attached to
		4184	an event loop) but not yet stopped (disassociated from the event loop).
		4185
		4186	=item application
		4187
		4188	In this document, an application is whatever is using libev.
		4189
		4190	=item callback
		4191
		4192	The address of a function that is called when some event has been
		4193	detected. Callbacks are being passed the event loop, the watcher that
		4194	received the event, and the actual event bitset.
		4195
		4196	=item callback invocation
		4197
		4198	The act of calling the callback associated with a watcher.
		4199
		4200	=item event
		4201
		4202	A change of state of some external event, such as data now being available
		4203	for reading on a file descriptor, time having passed or simply not having
		4204	any other events happening anymore.
		4205
		4206	In libev, events are represented as single bits (such as C<EV_READ> or
		4207	C<EV_TIMEOUT>).
		4208
		4209	=item event library
		4210
		4211	A software package implementing an event model and loop.
		4212
		4213	=item event loop
		4214
		4215	An entity that handles and processes external events and converts them
		4216	into callback invocations.
		4217
		4218	=item event model
		4219
		4220	The model used to describe how an event loop handles and processes
		4221	watchers and events.
		4222
		4223	=item pending
		4224
		4225	A watcher is pending as soon as the corresponding event has been detected,
		4226	and stops being pending as soon as the watcher will be invoked or its
		4227	pending status is explicitly cleared by the application.
		4228
		4229	A watcher can be pending, but not active. Stopping a watcher also clears
		4230	its pending status.
		4231
		4232	=item real time
		4233
		4234	The physical time that is observed. It is apparently strictly monotonic :)
		4235
		4236	=item wall-clock time
		4237
		4238	The time and date as shown on clocks. Unlike real time, it can actually
		4239	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4240	clock.
		4241
		4242	=item watcher
		4243
		4244	A data structure that describes interest in certain events. Watchers need
		4245	to be started (attached to an event loop) before they can receive events.
		4246
		4247	=item watcher invocation
		4248
		4249	The act of calling the callback associated with a watcher.
		4250
		4251	=back
		4252
3849	=head1 AUTHOR	4253	=head1 AUTHOR
3850		4254
3851	Marc Lehmann <libev@schmorp.de>.	4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4256

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Comparing libev/ev.pod (file contents): Revision 1.203 by root, Sun Oct 26 00:52:51 2008 UTC vs. Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.203 by root, Sun Oct 26 00:52:51 2008 UTC vs.
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC