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Revision 1.235 by root, Thu Apr 16 07:50:39 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
389		409
390	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	418	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	419	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	420	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
405		428
406	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	430	all kernel versions tested so far.
408		431
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	433	C<EVBACKEND_POLL>.
411		434
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		436
414	Kqueue deserves special mention, as at the time of this writing, it was	437	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	440	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	441	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	442	without API changes to existing programs. For this reason it's not being
		443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
420		446
421	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
424		450
425	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
431		458
432	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
433		460
434	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
440		467
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	470	C<NOTE_EOF>.
444		471
…		…
464	might perform better.	491	might perform better.
465		492
466	On the positive side, with the exception of the spurious readiness	493	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	494	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	495	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	496	OS-specific backends (I vastly prefer correctness over speed hacks).
470		497
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
473		500
474	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	557	for example).
531		558
532	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
535		562
536	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
607	very long time without entering the event loop, updating libev's idea of	634	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	635	the current time is a good idea.
609		636
610	See also "The special problem of time updates" in the C<ev_timer> section.	637	See also "The special problem of time updates" in the C<ev_timer> section.
611		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
612	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
613		666
614	Finally, this is it, the event handler. This function usually is called	667	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	668	after you initialised all your watchers and you want to start handling
616	events.	669	events.
…		…
631	the loop.	684	the loop.
632		685
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	687	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	688	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	689	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	690	user-registered callback will be called), and will return after one
638	iteration of the loop.	691	iteration of the loop.
639		692
640	This is useful if you are waiting for some external event in conjunction	693	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	694	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		752
700	If you have a watcher you never unregister that should not keep C<ev_loop>	753	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	754	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	755	stopping it.
703		756
704	As an example, libev itself uses this for its internal signal pipe: It is	757	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	758	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	759	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	760	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	761	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	762	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
711		766
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	768	running when nothing else is active.
714		769
715	struct ev_signal exitsig;	770	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	773	evf_unref (loop);
719		774
720	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
…		…
768	they fire on, say, one-second boundaries only.	823	they fire on, say, one-second boundaries only.
769		824
770	=item ev_loop_verify (loop)	825	=item ev_loop_verify (loop)
771		826
772	This function only does something when C<EV_VERIFY> support has been	827	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	828	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	829	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	830	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	831	error and call C<abort ()>.
777		832
778	This can be used to catch bugs inside libev itself: under normal	833	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	837	=back
783		838
784		839
785	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
786		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
		845
787	A watcher is a structure that you create and register to record your	846	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	847	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	848	become readable, you would create an C<ev_io> watcher for that:
790		849
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	851	{
793	ev_io_stop (w);	852	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
795	}	854	}
796		855
797	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
798	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
799	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
802	ev_loop (loop, 0);	864	ev_loop (loop, 0);
803		865
804	As you can see, you are responsible for allocating the memory for your	866	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	867	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		872
808	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	874	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	875	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	876	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	877	is readable and/or writable).
813		878
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	880	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	881	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
818		883
819	To make the watcher actually watch out for events, you have to start it	884	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	885	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	886	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		888
824	As long as your watcher is active (has been started but not stopped) you	889	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	890	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
827		892
828	Each and every callback receives the event loop pointer as first, the	893	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	894	registered watcher structure as second, and a bitset of received events as
830	third argument.	895	third argument.
831		896
…		…
889		954
890	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
891		956
892	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
893		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
894	=item C<EV_ERROR>	964	=item C<EV_ERROR>
895		965
896	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	967	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
899	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
901		975
902	Libev will usually signal a few "dummy" events together with an error, for	976	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	977	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	978	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	979	the error from read() or write(). This will not work in multi-threaded
…		…
908		982
909	=back	983	=back
910		984
911	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
912		986
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	987	=over 4
917		988
918	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
919		990
920	This macro initialises the generic portion of a watcher. The contents	991	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	996	which rolls both calls into one.
926		997
927	You can reinitialise a watcher at any time as long as it has been stopped	998	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
929		1000
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1002	int revents)>.
932		1003
933	Example: Initialise an C<ev_io> watcher in two steps.	1004	Example: Initialise an C<ev_io> watcher in two steps.
934		1005
935	ev_io w;	1006	ev_io w;
…		…
969		1040
970	ev_io_start (EV_DEFAULT_UC, &w);	1041	ev_io_start (EV_DEFAULT_UC, &w);
971		1042
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
973		1044
974	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
975	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1049	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1050	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1051	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1053
981	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
982		1055
983	Returns a true value iff the watcher is active (i.e. it has been started	1056	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1057	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1010	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1011	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
1012	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
1013	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
1014		1087
1015	This means that priorities are I<only> used for ordering callback
1016	invocation after new events have been received. This is useful, for
1017	example, to reduce latency after idling, or more often, to bind two
1018	watchers on the same event and make sure one is called first.
1019
1020	If you need to suppress invocation when higher priority events are pending	1088	If you need to suppress invocation when higher priority events are pending
1021	you need to look at C<ev_idle> watchers, which provide this functionality.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
1022		1090
1023	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
1024	pending.	1092	pending.
1025		1093
		1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1095	fine, as long as you do not mind that the priority value you query might
		1096	or might not have been clamped to the valid range.
		1097
1026	The default priority used by watchers when no priority has been set is	1098	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1099	always C<0>, which is supposed to not be too high and not be too low :).
1028		1100
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1101	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1030	fine, as long as you do not mind that the priority value you query might	1102	priorities.
1031	or might not have been adjusted to be within valid range.
1032		1103
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1105
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1058	member, you can also "subclass" the watcher type and provide your own	1129	member, you can also "subclass" the watcher type and provide your own
1059	data:	1130	data:
1060		1131
1061	struct my_io	1132	struct my_io
1062	{	1133	{
1063	struct ev_io io;	1134	ev_io io;
1064	int otherfd;	1135	int otherfd;
1065	void *somedata;	1136	void *somedata;
1066	struct whatever *mostinteresting;	1137	struct whatever *mostinteresting;
1067	};	1138	};
1068		1139
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1142	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1143
1073	And since your callback will be called with a pointer to the watcher, you	1144	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1145	can cast it back to your own type:
1075		1146
1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1147	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1077	{	1148	{
1078	struct my_io *w = (struct my_io *)w_;	1149	struct my_io *w = (struct my_io *)w_;
1079	...	1150	...
1080	}	1151	}
1081		1152
…		…
1099	programmers):	1170	programmers):
1100		1171
1101	#include <stddef.h>	1172	#include <stddef.h>
1102		1173
1103	static void	1174	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1175	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1176	{
1106	struct my_biggy big = (struct my_biggy *	1177	struct my_biggy big = (struct my_biggy *
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1178	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1179	}
1109		1180
1110	static void	1181	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1183	{
1113	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1116		1290
1117		1291
1118	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1119		1293
1120	This section describes each watcher in detail, but will not repeat	1294	This section describes each watcher in detail, but will not repeat
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1425	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1426	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1427	attempt to read a whole line in the callback.
1254		1428
1255	static void	1429	static void
1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1430	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1257	{	1431	{
1258	ev_io_stop (loop, w);	1432	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1433	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1434	}
1261		1435
1262	...	1436	...
1263	struct ev_loop *loop = ev_default_init (0);	1437	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1438	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1439	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1440	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1441	ev_loop (loop, 0);
1268		1442
1269		1443
…		…
1277	year, it will still time out after (roughly) one hour. "Roughly" because	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1279	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
1280		1454
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1455	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1456	passed. If multiple timers become ready during the same loop iteration
1283	then order of execution is undefined.	1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
		1460
		1461	=head3 Be smart about timeouts
		1462
		1463	Many real-world problems involve some kind of timeout, usually for error
		1464	recovery. A typical example is an HTTP request - if the other side hangs,
		1465	you want to raise some error after a while.
		1466
		1467	What follows are some ways to handle this problem, from obvious and
		1468	inefficient to smart and efficient.
		1469
		1470	In the following, a 60 second activity timeout is assumed - a timeout that
		1471	gets reset to 60 seconds each time there is activity (e.g. each time some
		1472	data or other life sign was received).
		1473
		1474	=over 4
		1475
		1476	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1477
		1478	This is the most obvious, but not the most simple way: In the beginning,
		1479	start the watcher:
		1480
		1481	ev_timer_init (timer, callback, 60., 0.);
		1482	ev_timer_start (loop, timer);
		1483
		1484	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1485	and start it again:
		1486
		1487	ev_timer_stop (loop, timer);
		1488	ev_timer_set (timer, 60., 0.);
		1489	ev_timer_start (loop, timer);
		1490
		1491	This is relatively simple to implement, but means that each time there is
		1492	some activity, libev will first have to remove the timer from its internal
		1493	data structure and then add it again. Libev tries to be fast, but it's
		1494	still not a constant-time operation.
		1495
		1496	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1497
		1498	This is the easiest way, and involves using C<ev_timer_again> instead of
		1499	C<ev_timer_start>.
		1500
		1501	To implement this, configure an C<ev_timer> with a C<repeat> value
		1502	of C<60> and then call C<ev_timer_again> at start and each time you
		1503	successfully read or write some data. If you go into an idle state where
		1504	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1505	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1506
		1507	That means you can ignore both the C<ev_timer_start> function and the
		1508	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1509	member and C<ev_timer_again>.
		1510
		1511	At start:
		1512
		1513	ev_timer_init (timer, callback);
		1514	timer->repeat = 60.;
		1515	ev_timer_again (loop, timer);
		1516
		1517	Each time there is some activity:
		1518
		1519	ev_timer_again (loop, timer);
		1520
		1521	It is even possible to change the time-out on the fly, regardless of
		1522	whether the watcher is active or not:
		1523
		1524	timer->repeat = 30.;
		1525	ev_timer_again (loop, timer);
		1526
		1527	This is slightly more efficient then stopping/starting the timer each time
		1528	you want to modify its timeout value, as libev does not have to completely
		1529	remove and re-insert the timer from/into its internal data structure.
		1530
		1531	It is, however, even simpler than the "obvious" way to do it.
		1532
		1533	=item 3. Let the timer time out, but then re-arm it as required.
		1534
		1535	This method is more tricky, but usually most efficient: Most timeouts are
		1536	relatively long compared to the intervals between other activity - in
		1537	our example, within 60 seconds, there are usually many I/O events with
		1538	associated activity resets.
		1539
		1540	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1541	but remember the time of last activity, and check for a real timeout only
		1542	within the callback:
		1543
		1544	ev_tstamp last_activity; // time of last activity
		1545
		1546	static void
		1547	callback (EV_P_ ev_timer *w, int revents)
		1548	{
		1549	ev_tstamp now = ev_now (EV_A);
		1550	ev_tstamp timeout = last_activity + 60.;
		1551
		1552	// if last_activity + 60. is older than now, we did time out
		1553	if (timeout < now)
		1554	{
		1555	// timeout occured, take action
		1556	}
		1557	else
		1558	{
		1559	// callback was invoked, but there was some activity, re-arm
		1560	// the watcher to fire in last_activity + 60, which is
		1561	// guaranteed to be in the future, so "again" is positive:
		1562	w->repeat = timeout - now;
		1563	ev_timer_again (EV_A_ w);
		1564	}
		1565	}
		1566
		1567	To summarise the callback: first calculate the real timeout (defined
		1568	as "60 seconds after the last activity"), then check if that time has
		1569	been reached, which means something I<did>, in fact, time out. Otherwise
		1570	the callback was invoked too early (C<timeout> is in the future), so
		1571	re-schedule the timer to fire at that future time, to see if maybe we have
		1572	a timeout then.
		1573
		1574	Note how C<ev_timer_again> is used, taking advantage of the
		1575	C<ev_timer_again> optimisation when the timer is already running.
		1576
		1577	This scheme causes more callback invocations (about one every 60 seconds
		1578	minus half the average time between activity), but virtually no calls to
		1579	libev to change the timeout.
		1580
		1581	To start the timer, simply initialise the watcher and set C<last_activity>
		1582	to the current time (meaning we just have some activity :), then call the
		1583	callback, which will "do the right thing" and start the timer:
		1584
		1585	ev_timer_init (timer, callback);
		1586	last_activity = ev_now (loop);
		1587	callback (loop, timer, EV_TIMEOUT);
		1588
		1589	And when there is some activity, simply store the current time in
		1590	C<last_activity>, no libev calls at all:
		1591
		1592	last_actiivty = ev_now (loop);
		1593
		1594	This technique is slightly more complex, but in most cases where the
		1595	time-out is unlikely to be triggered, much more efficient.
		1596
		1597	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1598	callback :) - just change the timeout and invoke the callback, which will
		1599	fix things for you.
		1600
		1601	=item 4. Wee, just use a double-linked list for your timeouts.
		1602
		1603	If there is not one request, but many thousands (millions...), all
		1604	employing some kind of timeout with the same timeout value, then one can
		1605	do even better:
		1606
		1607	When starting the timeout, calculate the timeout value and put the timeout
		1608	at the I<end> of the list.
		1609
		1610	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1611	the list is expected to fire (for example, using the technique #3).
		1612
		1613	When there is some activity, remove the timer from the list, recalculate
		1614	the timeout, append it to the end of the list again, and make sure to
		1615	update the C<ev_timer> if it was taken from the beginning of the list.
		1616
		1617	This way, one can manage an unlimited number of timeouts in O(1) time for
		1618	starting, stopping and updating the timers, at the expense of a major
		1619	complication, and having to use a constant timeout. The constant timeout
		1620	ensures that the list stays sorted.
		1621
		1622	=back
		1623
		1624	So which method the best?
		1625
		1626	Method #2 is a simple no-brain-required solution that is adequate in most
		1627	situations. Method #3 requires a bit more thinking, but handles many cases
		1628	better, and isn't very complicated either. In most case, choosing either
		1629	one is fine, with #3 being better in typical situations.
		1630
		1631	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1632	rather complicated, but extremely efficient, something that really pays
		1633	off after the first million or so of active timers, i.e. it's usually
		1634	overkill :)
1284		1635
1285	=head3 The special problem of time updates	1636	=head3 The special problem of time updates
1286		1637
1287	Establishing the current time is a costly operation (it usually takes at	1638	Establishing the current time is a costly operation (it usually takes at
1288	least two system calls): EV therefore updates its idea of the current	1639	least two system calls): EV therefore updates its idea of the current
…		…
1332	If the timer is started but non-repeating, stop it (as if it timed out).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1684
1334	If the timer is repeating, either start it if necessary (with the	1685	If the timer is repeating, either start it if necessary (with the
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1687
1337	This sounds a bit complicated, but here is a useful and typical	1688	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1338	example: Imagine you have a TCP connection and you want a so-called idle	1689	usage example.
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346
1347	That means you can ignore the C<after> value and C<ev_timer_start>
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1349
1350	ev_timer_init (timer, callback, 0., 5.);
1351	ev_timer_again (loop, timer);
1352	...
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358
1359	This is more slightly efficient then stopping/starting the timer each time
1360	you want to modify its timeout value.
1361
1362	Note, however, that it is often even more efficient to remember the
1363	time of the last activity and let the timer time-out naturally. In the
1364	callback, you then check whether the time-out is real, or, if there was
1365	some activity, you reschedule the watcher to time-out in "last_activity +
1366	timeout - ev_now ()" seconds.
1367		1690
1368	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1369		1692
1370	The current C<repeat> value. Will be used each time the watcher times out	1693	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	1694	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1699	=head3 Examples
1377		1700
1378	Example: Create a timer that fires after 60 seconds.	1701	Example: Create a timer that fires after 60 seconds.
1379		1702
1380	static void	1703	static void
1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1704	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1382	{	1705	{
1383	.. one minute over, w is actually stopped right here	1706	.. one minute over, w is actually stopped right here
1384	}	1707	}
1385		1708
1386	struct ev_timer mytimer;	1709	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1710	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1711	ev_timer_start (loop, &mytimer);
1389		1712
1390	Example: Create a timeout timer that times out after 10 seconds of	1713	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1714	inactivity.
1392		1715
1393	static void	1716	static void
1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1717	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1395	{	1718	{
1396	.. ten seconds without any activity	1719	.. ten seconds without any activity
1397	}	1720	}
1398		1721
1399	struct ev_timer mytimer;	1722	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1723	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1724	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1725	ev_loop (loop, 0);
1403		1726
1404	// and in some piece of code that gets executed on any "activity":	1727	// and in some piece of code that gets executed on any "activity":
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1410		1733
1411	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1413		1736
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	1738	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	1739	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1740	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	1741	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	1742	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		1743
		1744	You can tell a periodic watcher to trigger after some specific point
		1745	in time: for example, if you tell a periodic watcher to trigger "in 10
		1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
		1751
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	1752	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	1753	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
1426		1756
1427	As with timers, the callback is guaranteed to be invoked only when the	1757	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	1758	point in time where it is supposed to trigger has passed. If multiple
1429	during the same loop iteration, then order of execution is undefined.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1430		1762
1431	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1432		1764
1433	=over 4	1765	=over 4
1434		1766
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1768
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1770
1439	Lots of arguments, lets sort it out... There are basically three modes of	1771	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	1772	operation, and we will explain them from simplest to most complex:
1441		1773
1442	=over 4	1774	=over 4
1443		1775
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		1777
1446	In this configuration the watcher triggers an event after the wall clock	1778	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	1779	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1780	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1450		1783
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		1785
1453	In this mode the watcher will always be scheduled to time out at the next	1786	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	1787	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1456		1790
1457	This can be used to create timers that do not drift with respect to the	1791	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	1792	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	1793	hour, on the hour (with respect to UTC):
1460		1794
1461	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1462		1796
1463	This doesn't mean there will always be 3600 seconds in between triggers,	1797	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	1798	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	1800	by 3600.
1467		1801
1468	Another way to think about it (for the mathematically inclined) is that	1802	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	1803	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		1805
1472	For numerical stability it is preferable that the C<at> value is near	1806	For numerical stability it is preferable that the C<offset> value is near
1473	C<ev_now ()> (the current time), but there is no range requirement for	1807	C<ev_now ()> (the current time), but there is no range requirement for
1474	this value, and in fact is often specified as zero.	1808	this value, and in fact is often specified as zero.
1475		1809
1476	Note also that there is an upper limit to how often a timer can fire (CPU	1810	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	1811	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	1812	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	1813	millisecond (if the OS supports it and the machine is fast enough).
1480		1814
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		1816
1483	In this mode the values for C<interval> and C<at> are both being	1817	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	1820	current time as second argument.
1487		1821
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	1823	or make ANY other event loop modifications whatsoever, unless explicitly
		1824	allowed by documentation here>.
1490		1825
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1826	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	1828	only event loop modification you are allowed to do).
1494		1829
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1830	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	1831	*w, ev_tstamp now)>, e.g.:
1497		1832
		1833	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1834	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	1835	{
1500	return now + 60.;	1836	return now + 60.;
1501	}	1837	}
1502		1838
1503	It must return the next time to trigger, based on the passed time value	1839	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	1859	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	1860	program when the crontabs have changed).
1525		1861
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		1863
1528	When active, returns the absolute time that the watcher is supposed to	1864	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
1530		1868
1531	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1532		1870
1533	When repeating, this contains the offset value, otherwise this is the	1871	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1535		1874
1536	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1538		1877
1539	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
1540		1879
1541	The current interval value. Can be modified any time, but changes only	1880	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	1881	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	1882	called.
1544		1883
1545	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1884	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1546		1885
1547	The current reschedule callback, or C<0>, if this functionality is	1886	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	1887	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	1888	the periodic timer fires or C<ev_periodic_again> is being called.
1550		1889
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	1894	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	1895	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	1896	potentially a lot of jitter, but good long-term stability.
1558		1897
1559	static void	1898	static void
1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1899	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1561	{	1900	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	1901	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	1902	}
1564		1903
1565	struct ev_periodic hourly_tick;	1904	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1905	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	1906	ev_periodic_start (loop, &hourly_tick);
1568		1907
1569	Example: The same as above, but use a reschedule callback to do it:	1908	Example: The same as above, but use a reschedule callback to do it:
1570		1909
1571	#include <math.h>	1910	#include <math.h>
1572		1911
1573	static ev_tstamp	1912	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1913	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	1914	{
1576	return now + (3600. - fmod (now, 3600.));	1915	return now + (3600. - fmod (now, 3600.));
1577	}	1916	}
1578		1917
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1918	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		1919
1581	Example: Call a callback every hour, starting now:	1920	Example: Call a callback every hour, starting now:
1582		1921
1583	struct ev_periodic hourly_tick;	1922	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	1923	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	1924	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	1925	ev_periodic_start (loop, &hourly_tick);
1587		1926
1588		1927
…		…
1630	=head3 Examples	1969	=head3 Examples
1631		1970
1632	Example: Try to exit cleanly on SIGINT.	1971	Example: Try to exit cleanly on SIGINT.
1633		1972
1634	static void	1973	static void
1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1974	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1636	{	1975	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	1976	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	1977	}
1639		1978
1640	struct ev_signal signal_watcher;	1979	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1980	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	1981	ev_signal_start (loop, &signal_watcher);
1643		1982
1644		1983
1645	=head2 C<ev_child> - watch out for process status changes	1984	=head2 C<ev_child> - watch out for process status changes
…		…
1720	its completion.	2059	its completion.
1721		2060
1722	ev_child cw;	2061	ev_child cw;
1723		2062
1724	static void	2063	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	2064	child_cb (EV_P_ ev_child *w, int revents)
1726	{	2065	{
1727	ev_child_stop (EV_A_ w);	2066	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2067	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	2068	}
1730		2069
…		…
1745		2084
1746		2085
1747	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1748		2087
1749	This watches a file system path for attribute changes. That is, it calls	2088	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	2089	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1752		2092
1753	The path does not need to exist: changing from "path exists" to "path does	2093	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	2094	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	2095	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1758		2099
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	2102	your working directory changes, then the behaviour is undefined.
1761		2103
1762	Since there is no standard kernel interface to do this, the portable	2104	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	2105	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	2106	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	2107	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	2108	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	2109	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	2110	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1770		2112
1771	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1773	resource-intensive.	2115	resource-intensive.
1774		2116
1775	At the time of this writing, the only OS-specific interface implemented	2117	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	2118	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	2119	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	2120	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		2121
1780	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1781		2123
1782	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	2125	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	2126	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	2127	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	2128	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	2129	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	2130	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	2131	most noticeably displayed with ev_stat and large file support.
1790		2132
1791	The solution for this is to lobby your distribution maker to make large	2133	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	2134	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	2135	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	2136	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2137	default compilation environment.
1796		2138
1797	=head3 Inotify and Kqueue	2139	=head3 Inotify and Kqueue
1798		2140
1799	When C<inotify (7)> support has been compiled into libev (generally only	2141	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2142	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2144	watcher is being started.
1803		2145
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2146	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2147	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2148	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2149	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1809		2154
1810	There is no support for kqueue, as apparently it cannot be used to	2155	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2156	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2157	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2158	etc. is difficult.
1814		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
		2177
1815	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1816		2179
1817	The C<stat ()> system call only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2181	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2182	still only support whole seconds.
1820		2183
1821	That means that, if the time is the only thing that changes, you can	2184	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2185	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2186	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2187	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1967		2330
1968	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
1969		2332
1970	=over 4	2333	=over 4
1971		2334
1972	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
1973		2336
1974	Initialises and configures the idle watcher - it has no parameters of any	2337	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2339	believe me.
1977		2340
…		…
1981		2344
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2346	callback, free it. Also, use no error checking, as usual.
1984		2347
1985	static void	2348	static void
1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2349	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1987	{	2350	{
1988	free (w);	2351	free (w);
1989	// now do something you wanted to do when the program has	2352	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2353	// no longer anything immediate to do.
1991	}	2354	}
1992		2355
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2356	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2357	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2358	ev_idle_start (loop, idle_cb);
1996		2359
1997		2360
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2079		2442
2080	static ev_io iow [nfd];	2443	static ev_io iow [nfd];
2081	static ev_timer tw;	2444	static ev_timer tw;
2082		2445
2083	static void	2446	static void
2084	io_cb (ev_loop *loop, ev_io *w, int revents)	2447	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2085	{	2448	{
2086	}	2449	}
2087		2450
2088	// create io watchers for each fd and a timer before blocking	2451	// create io watchers for each fd and a timer before blocking
2089	static void	2452	static void
2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2453	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2091	{	2454	{
2092	int timeout = 3600000;	2455	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2456	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2457	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2458	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2110	}	2473	}
2111	}	2474	}
2112		2475
2113	// stop all watchers after blocking	2476	// stop all watchers after blocking
2114	static void	2477	static void
2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2478	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2116	{	2479	{
2117	ev_timer_stop (loop, &tw);	2480	ev_timer_stop (loop, &tw);
2118		2481
2119	for (int i = 0; i < nfd; ++i)	2482	for (int i = 0; i < nfd; ++i)
2120	{	2483	{
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	2579	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	2580	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	2581	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	2582	the rest in a second one, and embed the second one in the first.
2220		2583
2221	As long as the watcher is active, the callback will be invoked every time	2584	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	2585	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2586	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	2587	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	2588	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	2589	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		2590
2229	As long as the watcher is started it will automatically handle events. The	2591	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	2592	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		2593
2234	Also, there have not currently been made special provisions for forking:	2594	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2595	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	2596	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	2597	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		2598
2240	Unfortunately, not all backends are embeddable: only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	2601	portable one.
2243		2602
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2647	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2648	used).
2290		2649
2291	struct ev_loop *loop_hi = ev_default_init (0);	2650	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2651	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2652	ev_embed embed;
2294		2653
2295	// see if there is a chance of getting one that works	2654	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2655	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2656	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2657	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2671	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2672	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2673
2315	struct ev_loop *loop = ev_default_init (0);	2674	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2675	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2676	ev_embed embed;
2318		2677
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2678	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2679	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2680	{
2322	ev_embed_init (&embed, 0, loop_socket);	2681	ev_embed_init (&embed, 0, loop_socket);
…		…
2463	=over 4	2822	=over 4
2464		2823
2465	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2466		2825
2467	Initialises and configures the async watcher - it has no parameters of any	2826	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	2828	trust me.
2470		2829
2471	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2472		2831
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2833	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	2834	C<ev_feed_event>, this call is safe to do from other threads, signal or
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2477	section below on what exactly this means).	2836	section below on what exactly this means).
2478		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2479	This call incurs the overhead of a system call only once per loop iteration,	2843	This call incurs the overhead of a system call only once per event loop
2480	so while the overhead might be noticeable, it doesn't apply to repeated	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2481	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2482		2846
2483	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2484		2848
2485	Returns a non-zero value when C<ev_async_send> has been called on the	2849	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	2850	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2853	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	2854	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	2855	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	2856	quickly check whether invoking the loop might be a good idea.
2493		2857
2494	Not that this does I<not> check whether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2496		2862
2497	=back	2863	=back
2498		2864
2499		2865
2500	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2536	/* doh, nothing entered */;	2902	/* doh, nothing entered */;
2537	}	2903	}
2538		2904
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2905	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		2906
2541	=item ev_feed_event (ev_loop *, watcher *, int revents)	2907	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2542		2908
2543	Feeds the given event set into the event loop, as if the specified event	2909	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an	2910	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).	2911	initialised but not necessarily started event watcher).
2546		2912
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2913	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2548		2914
2549	Feed an event on the given fd, as if a file descriptor backend detected	2915	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	2916	the given events it.
2551		2917
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	2918	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2553		2919
2554	Feed an event as if the given signal occurred (C<loop> must be the default	2920	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	2921	loop!).
2556		2922
2557	=back	2923	=back
…		…
2678	}	3044	}
2679		3045
2680	myclass obj;	3046	myclass obj;
2681	ev::io iow;	3047	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
2683		3079
2684	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2685		3081
2686	Also sets a callback, but uses a static method or plain function as	3082	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	3083	callback. The optional C<data> argument will be stored in the watcher's
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2775		3171
2776	=item Python	3172	=item Python
2777		3173
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3174	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	3175	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		3176
2785	=item Ruby	3177	=item Ruby
2786		3178
2787	Tony Arcieri has written a ruby extension that offers access to a subset	3179	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	3180	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	3181	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
2791		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3191
2792	=item D	3192	=item D
2793		3193
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3196
		3197	=item Ocaml
		3198
		3199	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3200	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2796		3201
2797	=back	3202	=back
2798		3203
2799		3204
2800	=head1 MACRO MAGIC	3205	=head1 MACRO MAGIC
…		…
2901		3306
2902	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
2903	#include "ev.h"	3308	#include "ev.h"
2904		3309
2905	Both header files and implementation files can be compiled with a C++	3310	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	3311	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3312	as a bug).
2908		3313
2909	You need the following files in your source tree, or in a directory	3314	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	3315	in your include path (e.g. in libev/ when using -Ilibev):
2911		3316
…		…
2967	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	3373	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	3374	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	3375	F<event.h> that are not directly supported by the libev core alone.
2971		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
2972	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
2973		3381
2974	If defined to be C<1>, libev will try to detect the availability of the	3382	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	3383	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	3384	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	3385	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	3386	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	3387	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		3389
2982	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
2983		3391
2984	If defined to be C<1>, libev will try to detect the availability of the	3392	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	3393	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	3394	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
2990		3411
2991	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
2992		3413
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		3431
3011	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
3012		3433
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	3435	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3436	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	3437	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	3438	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
3020		3441
3021	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
3022		3443
3023	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
3383	loop, as long as you don't confuse yourself). The only exception is that	3804	loop, as long as you don't confuse yourself). The only exception is that
3384	you must not do this from C<ev_periodic> reschedule callbacks.	3805	you must not do this from C<ev_periodic> reschedule callbacks.
3385		3806
3386	Care has been taken to ensure that libev does not keep local state inside	3807	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	3809	they do not call any callbacks.
3389		3810
3390	=head2 COMPILER WARNINGS	3811	=head2 COMPILER WARNINGS
3391		3812
3392	Depending on your compiler and compiler settings, you might get no or a	3813	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	3814	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	3848	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	3849	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	3850	==2274== still reachable: 256 bytes in 1 blocks.
3430		3851
3431	Then there is no memory leak, just as memory accounted to global variables	3852	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	3853	is not a memleak - the memory is still being referenced, and didn't leak.
3433		3854
3434	Similarly, under some circumstances, valgrind might report kernel bugs	3855	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	3857	although an acceptable workaround has been found here), or it might be
3437	confused.	3858	confused.
…		…
3673	involves iterating over all running async watchers or all signal numbers.	4094	involves iterating over all running async watchers or all signal numbers.
3674		4095
3675	=back	4096	=back
3676		4097
3677		4098
		4099	=head1 GLOSSARY
		4100
		4101	=over 4
		4102
		4103	=item active
		4104
		4105	A watcher is active as long as it has been started (has been attached to
		4106	an event loop) but not yet stopped (disassociated from the event loop).
		4107
		4108	=item application
		4109
		4110	In this document, an application is whatever is using libev.
		4111
		4112	=item callback
		4113
		4114	The address of a function that is called when some event has been
		4115	detected. Callbacks are being passed the event loop, the watcher that
		4116	received the event, and the actual event bitset.
		4117
		4118	=item callback invocation
		4119
		4120	The act of calling the callback associated with a watcher.
		4121
		4122	=item event
		4123
		4124	A change of state of some external event, such as data now being available
		4125	for reading on a file descriptor, time having passed or simply not having
		4126	any other events happening anymore.
		4127
		4128	In libev, events are represented as single bits (such as C<EV_READ> or
		4129	C<EV_TIMEOUT>).
		4130
		4131	=item event library
		4132
		4133	A software package implementing an event model and loop.
		4134
		4135	=item event loop
		4136
		4137	An entity that handles and processes external events and converts them
		4138	into callback invocations.
		4139
		4140	=item event model
		4141
		4142	The model used to describe how an event loop handles and processes
		4143	watchers and events.
		4144
		4145	=item pending
		4146
		4147	A watcher is pending as soon as the corresponding event has been detected,
		4148	and stops being pending as soon as the watcher will be invoked or its
		4149	pending status is explicitly cleared by the application.
		4150
		4151	A watcher can be pending, but not active. Stopping a watcher also clears
		4152	its pending status.
		4153
		4154	=item real time
		4155
		4156	The physical time that is observed. It is apparently strictly monotonic :)
		4157
		4158	=item wall-clock time
		4159
		4160	The time and date as shown on clocks. Unlike real time, it can actually
		4161	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4162	clock.
		4163
		4164	=item watcher
		4165
		4166	A data structure that describes interest in certain events. Watchers need
		4167	to be started (attached to an event loop) before they can receive events.
		4168
		4169	=item watcher invocation
		4170
		4171	The act of calling the callback associated with a watcher.
		4172
		4173	=back
		4174
3678	=head1 AUTHOR	4175	=head1 AUTHOR
3679		4176
3680	Marc Lehmann <libev@schmorp.de>.	4177	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		4178

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