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

Comparing libev/ev.pod (file contents):
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC vs.
Revision 1.231 by root, Wed Apr 15 19:35:53 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
…		…
912		982
913	=back	983	=back
914		984
915	=head2 GENERIC WATCHER FUNCTIONS	985	=head2 GENERIC WATCHER FUNCTIONS
916		986
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	987	=over 4
921		988
922	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
923		990
924	This macro initialises the generic portion of a watcher. The contents	991	This macro initialises the generic portion of a watcher. The contents
…		…
929	which rolls both calls into one.	996	which rolls both calls into one.
930		997
931	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
932	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
933		1000
934	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,
935	int revents)>.	1002	int revents)>.
936		1003
937	Example: Initialise an C<ev_io> watcher in two steps.	1004	Example: Initialise an C<ev_io> watcher in two steps.
938		1005
939	ev_io w;	1006	ev_io w;
…		…
1032	The default priority used by watchers when no priority has been set is	1099	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1100	always C<0>, which is supposed to not be too high and not be too low :).
1034		1101
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1036	fine, as long as you do not mind that the priority value you query might	1103	fine, as long as you do not mind that the priority value you query might
1037	or might not have been adjusted to be within valid range.	1104	or might not have been clamped to the valid range.
1038		1105
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1107
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1109	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1064	member, you can also "subclass" the watcher type and provide your own	1131	member, you can also "subclass" the watcher type and provide your own
1065	data:	1132	data:
1066		1133
1067	struct my_io	1134	struct my_io
1068	{	1135	{
1069	struct ev_io io;	1136	ev_io io;
1070	int otherfd;	1137	int otherfd;
1071	void *somedata;	1138	void *somedata;
1072	struct whatever *mostinteresting;	1139	struct whatever *mostinteresting;
1073	};	1140	};
1074		1141
…		…
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);	1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078		1145
1079	And since your callback will be called with a pointer to the watcher, you	1146	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:	1147	can cast it back to your own type:
1081		1148
1082	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1149	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1083	{	1150	{
1084	struct my_io w = (struct my_io )w_;	1151	struct my_io w = (struct my_io )w_;
1085	...	1152	...
1086	}	1153	}
1087		1154
…		…
1105	programmers):	1172	programmers):
1106		1173
1107	#include <stddef.h>	1174	#include <stddef.h>
1108		1175
1109	static void	1176	static void
1110	t1_cb (EV_P_ struct ev_timer *w, int revents)	1177	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1178	{
1112	struct my_biggy big = (struct my_biggy *	1179	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1180	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1181	}
1115		1182
1116	static void	1183	static void
1117	t2_cb (EV_P_ struct ev_timer *w, int revents)	1184	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1185	{
1119	struct my_biggy big = (struct my_biggy *	1186	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1187	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1188	}
1122		1189
…		…
1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1324	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1258	readable, but only once. Since it is likely line-buffered, you could	1325	readable, but only once. Since it is likely line-buffered, you could
1259	attempt to read a whole line in the callback.	1326	attempt to read a whole line in the callback.
1260		1327
1261	static void	1328	static void
1262	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1329	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1263	{	1330	{
1264	ev_io_stop (loop, w);	1331	ev_io_stop (loop, w);
1265	.. read from stdin here (or from w->fd) and handle any I/O errors	1332	.. read from stdin here (or from w->fd) and handle any I/O errors
1266	}	1333	}
1267		1334
1268	...	1335	...
1269	struct ev_loop *loop = ev_default_init (0);	1336	struct ev_loop *loop = ev_default_init (0);
1270	struct ev_io stdin_readable;	1337	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1339	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1340	ev_loop (loop, 0);
1274		1341
1275		1342
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1350	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1352	monotonic clock option helps a lot here).
1286		1353
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1354	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1355	passed. If multiple timers become ready during the same loop iteration
1289	then order of execution is undefined.	1356	then the ones with earlier time-out values are invoked before ones with
		1357	later time-out values (but this is no longer true when a callback calls
		1358	C<ev_loop> recursively).
		1359
		1360	=head3 Be smart about timeouts
		1361
		1362	Many real-world problems involve some kind of timeout, usually for error
		1363	recovery. A typical example is an HTTP request - if the other side hangs,
		1364	you want to raise some error after a while.
		1365
		1366	What follows are some ways to handle this problem, from obvious and
		1367	inefficient to smart and efficient.
		1368
		1369	In the following, a 60 second activity timeout is assumed - a timeout that
		1370	gets reset to 60 seconds each time there is activity (e.g. each time some
		1371	data or other life sign was received).
		1372
		1373	=over 4
		1374
		1375	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1376
		1377	This is the most obvious, but not the most simple way: In the beginning,
		1378	start the watcher:
		1379
		1380	ev_timer_init (timer, callback, 60., 0.);
		1381	ev_timer_start (loop, timer);
		1382
		1383	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1384	and start it again:
		1385
		1386	ev_timer_stop (loop, timer);
		1387	ev_timer_set (timer, 60., 0.);
		1388	ev_timer_start (loop, timer);
		1389
		1390	This is relatively simple to implement, but means that each time there is
		1391	some activity, libev will first have to remove the timer from its internal
		1392	data structure and then add it again. Libev tries to be fast, but it's
		1393	still not a constant-time operation.
		1394
		1395	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1396
		1397	This is the easiest way, and involves using C<ev_timer_again> instead of
		1398	C<ev_timer_start>.
		1399
		1400	To implement this, configure an C<ev_timer> with a C<repeat> value
		1401	of C<60> and then call C<ev_timer_again> at start and each time you
		1402	successfully read or write some data. If you go into an idle state where
		1403	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1404	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1405
		1406	That means you can ignore both the C<ev_timer_start> function and the
		1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1408	member and C<ev_timer_again>.
		1409
		1410	At start:
		1411
		1412	ev_timer_init (timer, callback);
		1413	timer->repeat = 60.;
		1414	ev_timer_again (loop, timer);
		1415
		1416	Each time there is some activity:
		1417
		1418	ev_timer_again (loop, timer);
		1419
		1420	It is even possible to change the time-out on the fly, regardless of
		1421	whether the watcher is active or not:
		1422
		1423	timer->repeat = 30.;
		1424	ev_timer_again (loop, timer);
		1425
		1426	This is slightly more efficient then stopping/starting the timer each time
		1427	you want to modify its timeout value, as libev does not have to completely
		1428	remove and re-insert the timer from/into its internal data structure.
		1429
		1430	It is, however, even simpler than the "obvious" way to do it.
		1431
		1432	=item 3. Let the timer time out, but then re-arm it as required.
		1433
		1434	This method is more tricky, but usually most efficient: Most timeouts are
		1435	relatively long compared to the intervals between other activity - in
		1436	our example, within 60 seconds, there are usually many I/O events with
		1437	associated activity resets.
		1438
		1439	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1440	but remember the time of last activity, and check for a real timeout only
		1441	within the callback:
		1442
		1443	ev_tstamp last_activity; // time of last activity
		1444
		1445	static void
		1446	callback (EV_P_ ev_timer *w, int revents)
		1447	{
		1448	ev_tstamp now = ev_now (EV_A);
		1449	ev_tstamp timeout = last_activity + 60.;
		1450
		1451	// if last_activity + 60. is older than now, we did time out
		1452	if (timeout < now)
		1453	{
		1454	// timeout occured, take action
		1455	}
		1456	else
		1457	{
		1458	// callback was invoked, but there was some activity, re-arm
		1459	// the watcher to fire in last_activity + 60, which is
		1460	// guaranteed to be in the future, so "again" is positive:
		1461	w->repeat = timeout - now;
		1462	ev_timer_again (EV_A_ w);
		1463	}
		1464	}
		1465
		1466	To summarise the callback: first calculate the real timeout (defined
		1467	as "60 seconds after the last activity"), then check if that time has
		1468	been reached, which means something I<did>, in fact, time out. Otherwise
		1469	the callback was invoked too early (C<timeout> is in the future), so
		1470	re-schedule the timer to fire at that future time, to see if maybe we have
		1471	a timeout then.
		1472
		1473	Note how C<ev_timer_again> is used, taking advantage of the
		1474	C<ev_timer_again> optimisation when the timer is already running.
		1475
		1476	This scheme causes more callback invocations (about one every 60 seconds
		1477	minus half the average time between activity), but virtually no calls to
		1478	libev to change the timeout.
		1479
		1480	To start the timer, simply initialise the watcher and set C<last_activity>
		1481	to the current time (meaning we just have some activity :), then call the
		1482	callback, which will "do the right thing" and start the timer:
		1483
		1484	ev_timer_init (timer, callback);
		1485	last_activity = ev_now (loop);
		1486	callback (loop, timer, EV_TIMEOUT);
		1487
		1488	And when there is some activity, simply store the current time in
		1489	C<last_activity>, no libev calls at all:
		1490
		1491	last_actiivty = ev_now (loop);
		1492
		1493	This technique is slightly more complex, but in most cases where the
		1494	time-out is unlikely to be triggered, much more efficient.
		1495
		1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1497	callback :) - just change the timeout and invoke the callback, which will
		1498	fix things for you.
		1499
		1500	=item 4. Wee, just use a double-linked list for your timeouts.
		1501
		1502	If there is not one request, but many thousands (millions...), all
		1503	employing some kind of timeout with the same timeout value, then one can
		1504	do even better:
		1505
		1506	When starting the timeout, calculate the timeout value and put the timeout
		1507	at the I<end> of the list.
		1508
		1509	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1510	the list is expected to fire (for example, using the technique #3).
		1511
		1512	When there is some activity, remove the timer from the list, recalculate
		1513	the timeout, append it to the end of the list again, and make sure to
		1514	update the C<ev_timer> if it was taken from the beginning of the list.
		1515
		1516	This way, one can manage an unlimited number of timeouts in O(1) time for
		1517	starting, stopping and updating the timers, at the expense of a major
		1518	complication, and having to use a constant timeout. The constant timeout
		1519	ensures that the list stays sorted.
		1520
		1521	=back
		1522
		1523	So which method the best?
		1524
		1525	Method #2 is a simple no-brain-required solution that is adequate in most
		1526	situations. Method #3 requires a bit more thinking, but handles many cases
		1527	better, and isn't very complicated either. In most case, choosing either
		1528	one is fine, with #3 being better in typical situations.
		1529
		1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1531	rather complicated, but extremely efficient, something that really pays
		1532	off after the first million or so of active timers, i.e. it's usually
		1533	overkill :)
1290		1534
1291	=head3 The special problem of time updates	1535	=head3 The special problem of time updates
1292		1536
1293	Establishing the current time is a costly operation (it usually takes at	1537	Establishing the current time is a costly operation (it usually takes at
1294	least two system calls): EV therefore updates its idea of the current	1538	least two system calls): EV therefore updates its idea of the current
…		…
1338	If the timer is started but non-repeating, stop it (as if it timed out).	1582	If the timer is started but non-repeating, stop it (as if it timed out).
1339		1583
1340	If the timer is repeating, either start it if necessary (with the	1584	If the timer is repeating, either start it if necessary (with the
1341	C<repeat> value), or reset the running timer to the C<repeat> value.	1585	C<repeat> value), or reset the running timer to the C<repeat> value.
1342		1586
1343	This sounds a bit complicated, but here is a useful and typical	1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1344	example: Imagine you have a TCP connection and you want a so-called idle	1588	usage example.
1345	timeout, that is, you want to be called when there have been, say, 60
1346	seconds of inactivity on the socket. The easiest way to do this is to
1347	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1348	C<ev_timer_again> each time you successfully read or write some data. If
1349	you go into an idle state where you do not expect data to travel on the
1350	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1351	automatically restart it if need be.
1352
1353	That means you can ignore the C<after> value and C<ev_timer_start>
1354	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1355
1356	ev_timer_init (timer, callback, 0., 5.);
1357	ev_timer_again (loop, timer);
1358	...
1359	timer->again = 17.;
1360	ev_timer_again (loop, timer);
1361	...
1362	timer->again = 10.;
1363	ev_timer_again (loop, timer);
1364
1365	This is more slightly efficient then stopping/starting the timer each time
1366	you want to modify its timeout value.
1367
1368	Note, however, that it is often even more efficient to remember the
1369	time of the last activity and let the timer time-out naturally. In the
1370	callback, you then check whether the time-out is real, or, if there was
1371	some activity, you reschedule the watcher to time-out in "last_activity +
1372	timeout - ev_now ()" seconds.
1373		1589
1374	=item ev_tstamp repeat [read-write]	1590	=item ev_tstamp repeat [read-write]
1375		1591
1376	The current C<repeat> value. Will be used each time the watcher times out	1592	The current C<repeat> value. Will be used each time the watcher times out
1377	or C<ev_timer_again> is called, and determines the next timeout (if any),	1593	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1382	=head3 Examples	1598	=head3 Examples
1383		1599
1384	Example: Create a timer that fires after 60 seconds.	1600	Example: Create a timer that fires after 60 seconds.
1385		1601
1386	static void	1602	static void
1387	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1603	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1388	{	1604	{
1389	.. one minute over, w is actually stopped right here	1605	.. one minute over, w is actually stopped right here
1390	}	1606	}
1391		1607
1392	struct ev_timer mytimer;	1608	ev_timer mytimer;
1393	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1609	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1394	ev_timer_start (loop, &mytimer);	1610	ev_timer_start (loop, &mytimer);
1395		1611
1396	Example: Create a timeout timer that times out after 10 seconds of	1612	Example: Create a timeout timer that times out after 10 seconds of
1397	inactivity.	1613	inactivity.
1398		1614
1399	static void	1615	static void
1400	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1616	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1401	{	1617	{
1402	.. ten seconds without any activity	1618	.. ten seconds without any activity
1403	}	1619	}
1404		1620
1405	struct ev_timer mytimer;	1621	ev_timer mytimer;
1406	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1407	ev_timer_again (&mytimer); /* start timer */	1623	ev_timer_again (&mytimer); /* start timer */
1408	ev_loop (loop, 0);	1624	ev_loop (loop, 0);
1409		1625
1410	// and in some piece of code that gets executed on any "activity":	1626	// and in some piece of code that gets executed on any "activity":
…		…
1415	=head2 C<ev_periodic> - to cron or not to cron?	1631	=head2 C<ev_periodic> - to cron or not to cron?
1416		1632
1417	Periodic watchers are also timers of a kind, but they are very versatile	1633	Periodic watchers are also timers of a kind, but they are very versatile
1418	(and unfortunately a bit complex).	1634	(and unfortunately a bit complex).
1419		1635
1420	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1636	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1421	but on wall clock time (absolute time). You can tell a periodic watcher	1637	relative time, the physical time that passes) but on wall clock time
1422	to trigger after some specific point in time. For example, if you tell a	1638	(absolute time, the thing you can read on your calender or clock). The
1423	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1639	difference is that wall clock time can run faster or slower than real
1424	+ 10.>, that is, an absolute time not a delay) and then reset your system	1640	time, and time jumps are not uncommon (e.g. when you adjust your
1425	clock to January of the previous year, then it will take more than year	1641	wrist-watch).
1426	to trigger the event (unlike an C<ev_timer>, which would still trigger
1427	roughly 10 seconds later as it uses a relative timeout).
1428		1642
		1643	You can tell a periodic watcher to trigger after some specific point
		1644	in time: for example, if you tell a periodic watcher to trigger "in 10
		1645	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1646	not a delay) and then reset your system clock to January of the previous
		1647	year, then it will take a year or more to trigger the event (unlike an
		1648	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1649	it, as it uses a relative timeout).
		1650
1429	C<ev_periodic>s can also be used to implement vastly more complex timers,	1651	C<ev_periodic> watchers can also be used to implement vastly more complex
1430	such as triggering an event on each "midnight, local time", or other	1652	timers, such as triggering an event on each "midnight, local time", or
1431	complicated rules.	1653	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1654	those cannot react to time jumps.
1432		1655
1433	As with timers, the callback is guaranteed to be invoked only when the	1656	As with timers, the callback is guaranteed to be invoked only when the
1434	time (C<at>) has passed, but if multiple periodic timers become ready	1657	point in time where it is supposed to trigger has passed. If multiple
1435	during the same loop iteration, then order of execution is undefined.	1658	timers become ready during the same loop iteration then the ones with
		1659	earlier time-out values are invoked before ones with later time-out values
		1660	(but this is no longer true when a callback calls C<ev_loop> recursively).
1436		1661
1437	=head3 Watcher-Specific Functions and Data Members	1662	=head3 Watcher-Specific Functions and Data Members
1438		1663
1439	=over 4	1664	=over 4
1440		1665
1441	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1666	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1442		1667
1443	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1668	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1444		1669
1445	Lots of arguments, lets sort it out... There are basically three modes of	1670	Lots of arguments, let's sort it out... There are basically three modes of
1446	operation, and we will explain them from simplest to most complex:	1671	operation, and we will explain them from simplest to most complex:
1447		1672
1448	=over 4	1673	=over 4
1449		1674
1450	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1675	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1451		1676
1452	In this configuration the watcher triggers an event after the wall clock	1677	In this configuration the watcher triggers an event after the wall clock
1453	time C<at> has passed. It will not repeat and will not adjust when a time	1678	time C<offset> has passed. It will not repeat and will not adjust when a
1454	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1679	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1455	only run when the system clock reaches or surpasses this time.	1680	will be stopped and invoked when the system clock reaches or surpasses
		1681	this point in time.
1456		1682
1457	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1683	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1458		1684
1459	In this mode the watcher will always be scheduled to time out at the next	1685	In this mode the watcher will always be scheduled to time out at the next
1460	C<at + N * interval> time (for some integer N, which can also be negative)	1686	C<offset + N * interval> time (for some integer N, which can also be
1461	and then repeat, regardless of any time jumps.	1687	negative) and then repeat, regardless of any time jumps. The C<offset>
		1688	argument is merely an offset into the C<interval> periods.
1462		1689
1463	This can be used to create timers that do not drift with respect to the	1690	This can be used to create timers that do not drift with respect to the
1464	system clock, for example, here is a C<ev_periodic> that triggers each	1691	system clock, for example, here is an C<ev_periodic> that triggers each
1465	hour, on the hour:	1692	hour, on the hour (with respect to UTC):
1466		1693
1467	ev_periodic_set (&periodic, 0., 3600., 0);	1694	ev_periodic_set (&periodic, 0., 3600., 0);
1468		1695
1469	This doesn't mean there will always be 3600 seconds in between triggers,	1696	This doesn't mean there will always be 3600 seconds in between triggers,
1470	but only that the callback will be called when the system time shows a	1697	but only that the callback will be called when the system time shows a
1471	full hour (UTC), or more correctly, when the system time is evenly divisible	1698	full hour (UTC), or more correctly, when the system time is evenly divisible
1472	by 3600.	1699	by 3600.
1473		1700
1474	Another way to think about it (for the mathematically inclined) is that	1701	Another way to think about it (for the mathematically inclined) is that
1475	C<ev_periodic> will try to run the callback in this mode at the next possible	1702	C<ev_periodic> will try to run the callback in this mode at the next possible
1476	time where C<time = at (mod interval)>, regardless of any time jumps.	1703	time where C<time = offset (mod interval)>, regardless of any time jumps.
1477		1704
1478	For numerical stability it is preferable that the C<at> value is near	1705	For numerical stability it is preferable that the C<offset> value is near
1479	C<ev_now ()> (the current time), but there is no range requirement for	1706	C<ev_now ()> (the current time), but there is no range requirement for
1480	this value, and in fact is often specified as zero.	1707	this value, and in fact is often specified as zero.
1481		1708
1482	Note also that there is an upper limit to how often a timer can fire (CPU	1709	Note also that there is an upper limit to how often a timer can fire (CPU
1483	speed for example), so if C<interval> is very small then timing stability	1710	speed for example), so if C<interval> is very small then timing stability
1484	will of course deteriorate. Libev itself tries to be exact to be about one	1711	will of course deteriorate. Libev itself tries to be exact to be about one
1485	millisecond (if the OS supports it and the machine is fast enough).	1712	millisecond (if the OS supports it and the machine is fast enough).
1486		1713
1487	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1714	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1488		1715
1489	In this mode the values for C<interval> and C<at> are both being	1716	In this mode the values for C<interval> and C<offset> are both being
1490	ignored. Instead, each time the periodic watcher gets scheduled, the	1717	ignored. Instead, each time the periodic watcher gets scheduled, the
1491	reschedule callback will be called with the watcher as first, and the	1718	reschedule callback will be called with the watcher as first, and the
1492	current time as second argument.	1719	current time as second argument.
1493		1720
1494	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1721	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1495	ever, or make ANY event loop modifications whatsoever>.	1722	or make ANY other event loop modifications whatsoever, unless explicitly
		1723	allowed by documentation here>.
1496		1724
1497	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1725	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1498	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1726	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1499	only event loop modification you are allowed to do).	1727	only event loop modification you are allowed to do).
1500		1728
1501	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1729	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1502	*w, ev_tstamp now)>, e.g.:	1730	*w, ev_tstamp now)>, e.g.:
1503		1731
		1732	static ev_tstamp
1504	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1733	my_rescheduler (ev_periodic *w, ev_tstamp now)
1505	{	1734	{
1506	return now + 60.;	1735	return now + 60.;
1507	}	1736	}
1508		1737
1509	It must return the next time to trigger, based on the passed time value	1738	It must return the next time to trigger, based on the passed time value
…		…
1529	a different time than the last time it was called (e.g. in a crond like	1758	a different time than the last time it was called (e.g. in a crond like
1530	program when the crontabs have changed).	1759	program when the crontabs have changed).
1531		1760
1532	=item ev_tstamp ev_periodic_at (ev_periodic *)	1761	=item ev_tstamp ev_periodic_at (ev_periodic *)
1533		1762
1534	When active, returns the absolute time that the watcher is supposed to	1763	When active, returns the absolute time that the watcher is supposed
1535	trigger next.	1764	to trigger next. This is not the same as the C<offset> argument to
		1765	C<ev_periodic_set>, but indeed works even in interval and manual
		1766	rescheduling modes.
1536		1767
1537	=item ev_tstamp offset [read-write]	1768	=item ev_tstamp offset [read-write]
1538		1769
1539	When repeating, this contains the offset value, otherwise this is the	1770	When repeating, this contains the offset value, otherwise this is the
1540	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1771	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1772	although libev might modify this value for better numerical stability).
1541		1773
1542	Can be modified any time, but changes only take effect when the periodic	1774	Can be modified any time, but changes only take effect when the periodic
1543	timer fires or C<ev_periodic_again> is being called.	1775	timer fires or C<ev_periodic_again> is being called.
1544		1776
1545	=item ev_tstamp interval [read-write]	1777	=item ev_tstamp interval [read-write]
1546		1778
1547	The current interval value. Can be modified any time, but changes only	1779	The current interval value. Can be modified any time, but changes only
1548	take effect when the periodic timer fires or C<ev_periodic_again> is being	1780	take effect when the periodic timer fires or C<ev_periodic_again> is being
1549	called.	1781	called.
1550		1782
1551	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1783	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1552		1784
1553	The current reschedule callback, or C<0>, if this functionality is	1785	The current reschedule callback, or C<0>, if this functionality is
1554	switched off. Can be changed any time, but changes only take effect when	1786	switched off. Can be changed any time, but changes only take effect when
1555	the periodic timer fires or C<ev_periodic_again> is being called.	1787	the periodic timer fires or C<ev_periodic_again> is being called.
1556		1788
…		…
1561	Example: Call a callback every hour, or, more precisely, whenever the	1793	Example: Call a callback every hour, or, more precisely, whenever the
1562	system time is divisible by 3600. The callback invocation times have	1794	system time is divisible by 3600. The callback invocation times have
1563	potentially a lot of jitter, but good long-term stability.	1795	potentially a lot of jitter, but good long-term stability.
1564		1796
1565	static void	1797	static void
1566	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1798	clock_cb (struct ev_loop loop, ev_io w, int revents)
1567	{	1799	{
1568	... its now a full hour (UTC, or TAI or whatever your clock follows)	1800	... its now a full hour (UTC, or TAI or whatever your clock follows)
1569	}	1801	}
1570		1802
1571	struct ev_periodic hourly_tick;	1803	ev_periodic hourly_tick;
1572	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1804	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1573	ev_periodic_start (loop, &hourly_tick);	1805	ev_periodic_start (loop, &hourly_tick);
1574		1806
1575	Example: The same as above, but use a reschedule callback to do it:	1807	Example: The same as above, but use a reschedule callback to do it:
1576		1808
1577	#include <math.h>	1809	#include <math.h>
1578		1810
1579	static ev_tstamp	1811	static ev_tstamp
1580	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1812	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1581	{	1813	{
1582	return now + (3600. - fmod (now, 3600.));	1814	return now + (3600. - fmod (now, 3600.));
1583	}	1815	}
1584		1816
1585	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1817	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1586		1818
1587	Example: Call a callback every hour, starting now:	1819	Example: Call a callback every hour, starting now:
1588		1820
1589	struct ev_periodic hourly_tick;	1821	ev_periodic hourly_tick;
1590	ev_periodic_init (&hourly_tick, clock_cb,	1822	ev_periodic_init (&hourly_tick, clock_cb,
1591	fmod (ev_now (loop), 3600.), 3600., 0);	1823	fmod (ev_now (loop), 3600.), 3600., 0);
1592	ev_periodic_start (loop, &hourly_tick);	1824	ev_periodic_start (loop, &hourly_tick);
1593		1825
1594		1826
…		…
1636	=head3 Examples	1868	=head3 Examples
1637		1869
1638	Example: Try to exit cleanly on SIGINT.	1870	Example: Try to exit cleanly on SIGINT.
1639		1871
1640	static void	1872	static void
1641	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1873	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1642	{	1874	{
1643	ev_unloop (loop, EVUNLOOP_ALL);	1875	ev_unloop (loop, EVUNLOOP_ALL);
1644	}	1876	}
1645		1877
1646	struct ev_signal signal_watcher;	1878	ev_signal signal_watcher;
1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1648	ev_signal_start (loop, &signal_watcher);	1880	ev_signal_start (loop, &signal_watcher);
1649		1881
1650		1882
1651	=head2 C<ev_child> - watch out for process status changes	1883	=head2 C<ev_child> - watch out for process status changes
…		…
1726	its completion.	1958	its completion.
1727		1959
1728	ev_child cw;	1960	ev_child cw;
1729		1961
1730	static void	1962	static void
1731	child_cb (EV_P_ struct ev_child *w, int revents)	1963	child_cb (EV_P_ ev_child *w, int revents)
1732	{	1964	{
1733	ev_child_stop (EV_A_ w);	1965	ev_child_stop (EV_A_ w);
1734	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1966	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1735	}	1967	}
1736		1968
…		…
1751		1983
1752		1984
1753	=head2 C<ev_stat> - did the file attributes just change?	1985	=head2 C<ev_stat> - did the file attributes just change?
1754		1986
1755	This watches a file system path for attribute changes. That is, it calls	1987	This watches a file system path for attribute changes. That is, it calls
1756	C<stat> regularly (or when the OS says it changed) and sees if it changed	1988	C<stat> on that path in regular intervals (or when the OS says it changed)
1757	compared to the last time, invoking the callback if it did.	1989	and sees if it changed compared to the last time, invoking the callback if
		1990	it did.
1758		1991
1759	The path does not need to exist: changing from "path exists" to "path does	1992	The path does not need to exist: changing from "path exists" to "path does
1760	not exist" is a status change like any other. The condition "path does	1993	not exist" is a status change like any other. The condition "path does not
1761	not exist" is signified by the C<st_nlink> field being zero (which is	1994	exist" (or more correctly "path cannot be stat'ed") is signified by the
1762	otherwise always forced to be at least one) and all the other fields of	1995	C<st_nlink> field being zero (which is otherwise always forced to be at
1763	the stat buffer having unspecified contents.	1996	least one) and all the other fields of the stat buffer having unspecified
		1997	contents.
1764		1998
1765	The path I<should> be absolute and I<must not> end in a slash. If it is	1999	The path I<must not> end in a slash or contain special components such as
		2000	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1766	relative and your working directory changes, the behaviour is undefined.	2001	your working directory changes, then the behaviour is undefined.
1767		2002
1768	Since there is no standard kernel interface to do this, the portable	2003	Since there is no portable change notification interface available, the
1769	implementation simply calls C<stat (2)> regularly on the path to see if	2004	portable implementation simply calls C<stat(2)> regularly on the path
1770	it changed somehow. You can specify a recommended polling interval for	2005	to see if it changed somehow. You can specify a recommended polling
1771	this case. If you specify a polling interval of C<0> (highly recommended!)	2006	interval for this case. If you specify a polling interval of C<0> (highly
1772	then a I<suitable, unspecified default> value will be used (which	2007	recommended!) then a I<suitable, unspecified default> value will be used
1773	you can expect to be around five seconds, although this might change	2008	(which you can expect to be around five seconds, although this might
1774	dynamically). Libev will also impose a minimum interval which is currently	2009	change dynamically). Libev will also impose a minimum interval which is
1775	around C<0.1>, but thats usually overkill.	2010	currently around C<0.1>, but that's usually overkill.
1776		2011
1777	This watcher type is not meant for massive numbers of stat watchers,	2012	This watcher type is not meant for massive numbers of stat watchers,
1778	as even with OS-supported change notifications, this can be	2013	as even with OS-supported change notifications, this can be
1779	resource-intensive.	2014	resource-intensive.
1780		2015
1781	At the time of this writing, the only OS-specific interface implemented	2016	At the time of this writing, the only OS-specific interface implemented
1782	is the Linux inotify interface (implementing kqueue support is left as	2017	is the Linux inotify interface (implementing kqueue support is left as an
1783	an exercise for the reader. Note, however, that the author sees no way	2018	exercise for the reader. Note, however, that the author sees no way of
1784	of implementing C<ev_stat> semantics with kqueue).	2019	implementing C<ev_stat> semantics with kqueue, except as a hint).
1785		2020
1786	=head3 ABI Issues (Largefile Support)	2021	=head3 ABI Issues (Largefile Support)
1787		2022
1788	Libev by default (unless the user overrides this) uses the default	2023	Libev by default (unless the user overrides this) uses the default
1789	compilation environment, which means that on systems with large file	2024	compilation environment, which means that on systems with large file
1790	support disabled by default, you get the 32 bit version of the stat	2025	support disabled by default, you get the 32 bit version of the stat
1791	structure. When using the library from programs that change the ABI to	2026	structure. When using the library from programs that change the ABI to
1792	use 64 bit file offsets the programs will fail. In that case you have to	2027	use 64 bit file offsets the programs will fail. In that case you have to
1793	compile libev with the same flags to get binary compatibility. This is	2028	compile libev with the same flags to get binary compatibility. This is
1794	obviously the case with any flags that change the ABI, but the problem is	2029	obviously the case with any flags that change the ABI, but the problem is
1795	most noticeably disabled with ev_stat and large file support.	2030	most noticeably displayed with ev_stat and large file support.
1796		2031
1797	The solution for this is to lobby your distribution maker to make large	2032	The solution for this is to lobby your distribution maker to make large
1798	file interfaces available by default (as e.g. FreeBSD does) and not	2033	file interfaces available by default (as e.g. FreeBSD does) and not
1799	optional. Libev cannot simply switch on large file support because it has	2034	optional. Libev cannot simply switch on large file support because it has
1800	to exchange stat structures with application programs compiled using the	2035	to exchange stat structures with application programs compiled using the
1801	default compilation environment.	2036	default compilation environment.
1802		2037
1803	=head3 Inotify and Kqueue	2038	=head3 Inotify and Kqueue
1804		2039
1805	When C<inotify (7)> support has been compiled into libev (generally	2040	When C<inotify (7)> support has been compiled into libev and present at
1806	only available with Linux 2.6.25 or above due to bugs in earlier	2041	runtime, it will be used to speed up change detection where possible. The
1807	implementations) and present at runtime, it will be used to speed up	2042	inotify descriptor will be created lazily when the first C<ev_stat>
1808	change detection where possible. The inotify descriptor will be created	2043	watcher is being started.
1809	lazily when the first C<ev_stat> watcher is being started.
1810		2044
1811	Inotify presence does not change the semantics of C<ev_stat> watchers	2045	Inotify presence does not change the semantics of C<ev_stat> watchers
1812	except that changes might be detected earlier, and in some cases, to avoid	2046	except that changes might be detected earlier, and in some cases, to avoid
1813	making regular C<stat> calls. Even in the presence of inotify support	2047	making regular C<stat> calls. Even in the presence of inotify support
1814	there are many cases where libev has to resort to regular C<stat> polling,	2048	there are many cases where libev has to resort to regular C<stat> polling,
1815	but as long as the path exists, libev usually gets away without polling.	2049	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2050	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2051	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2052	xfs are fully working) libev usually gets away without polling.
1816		2053
1817	There is no support for kqueue, as apparently it cannot be used to	2054	There is no support for kqueue, as apparently it cannot be used to
1818	implement this functionality, due to the requirement of having a file	2055	implement this functionality, due to the requirement of having a file
1819	descriptor open on the object at all times, and detecting renames, unlinks	2056	descriptor open on the object at all times, and detecting renames, unlinks
1820	etc. is difficult.	2057	etc. is difficult.
1821		2058
		2059	=head3 C<stat ()> is a synchronous operation
		2060
		2061	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2062	the process. The exception are C<ev_stat> watchers - those call C<stat
		2063	()>, which is a synchronous operation.
		2064
		2065	For local paths, this usually doesn't matter: unless the system is very
		2066	busy or the intervals between stat's are large, a stat call will be fast,
		2067	as the path data is usually in memory already (except when starting the
		2068	watcher).
		2069
		2070	For networked file systems, calling C<stat ()> can block an indefinite
		2071	time due to network issues, and even under good conditions, a stat call
		2072	often takes multiple milliseconds.
		2073
		2074	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2075	paths, although this is fully supported by libev.
		2076
1822	=head3 The special problem of stat time resolution	2077	=head3 The special problem of stat time resolution
1823		2078
1824	The C<stat ()> system call only supports full-second resolution portably, and	2079	The C<stat ()> system call only supports full-second resolution portably,
1825	even on systems where the resolution is higher, most file systems still	2080	and even on systems where the resolution is higher, most file systems
1826	only support whole seconds.	2081	still only support whole seconds.
1827		2082
1828	That means that, if the time is the only thing that changes, you can	2083	That means that, if the time is the only thing that changes, you can
1829	easily miss updates: on the first update, C<ev_stat> detects a change and	2084	easily miss updates: on the first update, C<ev_stat> detects a change and
1830	calls your callback, which does something. When there is another update	2085	calls your callback, which does something. When there is another update
1831	within the same second, C<ev_stat> will be unable to detect unless the	2086	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1974		2229
1975	=head3 Watcher-Specific Functions and Data Members	2230	=head3 Watcher-Specific Functions and Data Members
1976		2231
1977	=over 4	2232	=over 4
1978		2233
1979	=item ev_idle_init (ev_signal *, callback)	2234	=item ev_idle_init (ev_idle *, callback)
1980		2235
1981	Initialises and configures the idle watcher - it has no parameters of any	2236	Initialises and configures the idle watcher - it has no parameters of any
1982	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2237	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1983	believe me.	2238	believe me.
1984		2239
…		…
1988		2243
1989	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2244	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1990	callback, free it. Also, use no error checking, as usual.	2245	callback, free it. Also, use no error checking, as usual.
1991		2246
1992	static void	2247	static void
1993	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2248	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1994	{	2249	{
1995	free (w);	2250	free (w);
1996	// now do something you wanted to do when the program has	2251	// now do something you wanted to do when the program has
1997	// no longer anything immediate to do.	2252	// no longer anything immediate to do.
1998	}	2253	}
1999		2254
2000	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2001	ev_idle_init (idle_watcher, idle_cb);	2256	ev_idle_init (idle_watcher, idle_cb);
2002	ev_idle_start (loop, idle_cb);	2257	ev_idle_start (loop, idle_cb);
2003		2258
2004		2259
2005	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2086		2341
2087	static ev_io iow [nfd];	2342	static ev_io iow [nfd];
2088	static ev_timer tw;	2343	static ev_timer tw;
2089		2344
2090	static void	2345	static void
2091	io_cb (ev_loop loop, ev_io w, int revents)	2346	io_cb (struct ev_loop loop, ev_io w, int revents)
2092	{	2347	{
2093	}	2348	}
2094		2349
2095	// create io watchers for each fd and a timer before blocking	2350	// create io watchers for each fd and a timer before blocking
2096	static void	2351	static void
2097	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2352	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2098	{	2353	{
2099	int timeout = 3600000;	2354	int timeout = 3600000;
2100	struct pollfd fds [nfd];	2355	struct pollfd fds [nfd];
2101	// actual code will need to loop here and realloc etc.	2356	// actual code will need to loop here and realloc etc.
2102	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2117	}	2372	}
2118	}	2373	}
2119		2374
2120	// stop all watchers after blocking	2375	// stop all watchers after blocking
2121	static void	2376	static void
2122	adns_check_cb (ev_loop loop, ev_check w, int revents)	2377	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2123	{	2378	{
2124	ev_timer_stop (loop, &tw);	2379	ev_timer_stop (loop, &tw);
2125		2380
2126	for (int i = 0; i < nfd; ++i)	2381	for (int i = 0; i < nfd; ++i)
2127	{	2382	{
…		…
2223	some fds have to be watched and handled very quickly (with low latency),	2478	some fds have to be watched and handled very quickly (with low latency),
2224	and even priorities and idle watchers might have too much overhead. In	2479	and even priorities and idle watchers might have too much overhead. In
2225	this case you would put all the high priority stuff in one loop and all	2480	this case you would put all the high priority stuff in one loop and all
2226	the rest in a second one, and embed the second one in the first.	2481	the rest in a second one, and embed the second one in the first.
2227		2482
2228	As long as the watcher is active, the callback will be invoked every time	2483	As long as the watcher is active, the callback will be invoked every
2229	there might be events pending in the embedded loop. The callback must then	2484	time there might be events pending in the embedded loop. The callback
2230	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2485	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2231	their callbacks (you could also start an idle watcher to give the embedded	2486	sweep and invoke their callbacks (the callback doesn't need to invoke the
2232	loop strictly lower priority for example). You can also set the callback	2487	C<ev_embed_sweep> function directly, it could also start an idle watcher
2233	to C<0>, in which case the embed watcher will automatically execute the	2488	to give the embedded loop strictly lower priority for example).
2234	embedded loop sweep.
2235		2489
2236	As long as the watcher is started it will automatically handle events. The	2490	You can also set the callback to C<0>, in which case the embed watcher
2237	callback will be invoked whenever some events have been handled. You can	2491	will automatically execute the embedded loop sweep whenever necessary.
2238	set the callback to C<0> to avoid having to specify one if you are not
2239	interested in that.
2240		2492
2241	Also, there have not currently been made special provisions for forking:	2493	Fork detection will be handled transparently while the C<ev_embed> watcher
2242	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2494	is active, i.e., the embedded loop will automatically be forked when the
2243	but you will also have to stop and restart any C<ev_embed> watchers	2495	embedding loop forks. In other cases, the user is responsible for calling
2244	yourself - but you can use a fork watcher to handle this automatically,	2496	C<ev_loop_fork> on the embedded loop.
2245	and future versions of libev might do just that.
2246		2497
2247	Unfortunately, not all backends are embeddable: only the ones returned by	2498	Unfortunately, not all backends are embeddable: only the ones returned by
2248	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2499	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2249	portable one.	2500	portable one.
2250		2501
…		…
2295	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2546	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2296	used).	2547	used).
2297		2548
2298	struct ev_loop *loop_hi = ev_default_init (0);	2549	struct ev_loop *loop_hi = ev_default_init (0);
2299	struct ev_loop *loop_lo = 0;	2550	struct ev_loop *loop_lo = 0;
2300	struct ev_embed embed;	2551	ev_embed embed;
2301		2552
2302	// see if there is a chance of getting one that works	2553	// see if there is a chance of getting one that works
2303	// (remember that a flags value of 0 means autodetection)	2554	// (remember that a flags value of 0 means autodetection)
2304	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2555	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2305	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2556	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2319	kqueue implementation). Store the kqueue/socket-only event loop in	2570	kqueue implementation). Store the kqueue/socket-only event loop in
2320	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2571	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2321		2572
2322	struct ev_loop *loop = ev_default_init (0);	2573	struct ev_loop *loop = ev_default_init (0);
2323	struct ev_loop *loop_socket = 0;	2574	struct ev_loop *loop_socket = 0;
2324	struct ev_embed embed;	2575	ev_embed embed;
2325		2576
2326	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2577	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2327	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2578	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2328	{	2579	{
2329	ev_embed_init (&embed, 0, loop_socket);	2580	ev_embed_init (&embed, 0, loop_socket);
…		…
2470	=over 4	2721	=over 4
2471		2722
2472	=item ev_async_init (ev_async *, callback)	2723	=item ev_async_init (ev_async *, callback)
2473		2724
2474	Initialises and configures the async watcher - it has no parameters of any	2725	Initialises and configures the async watcher - it has no parameters of any
2475	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2726	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2476	trust me.	2727	trust me.
2477		2728
2478	=item ev_async_send (loop, ev_async *)	2729	=item ev_async_send (loop, ev_async *)
2479		2730
2480	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2481	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2482	C<ev_feed_event>, this call is safe to do from other threads, signal or	2733	C<ev_feed_event>, this call is safe to do from other threads, signal or
2483	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2484	section below on what exactly this means).	2735	section below on what exactly this means).
2485		2736
		2737	Note that, as with other watchers in libev, multiple events might get
		2738	compressed into a single callback invocation (another way to look at this
		2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2740	reset when the event loop detects that).
		2741
2486	This call incurs the overhead of a system call only once per loop iteration,	2742	This call incurs the overhead of a system call only once per event loop
2487	so while the overhead might be noticeable, it doesn't apply to repeated	2743	iteration, so while the overhead might be noticeable, it doesn't apply to
2488	calls to C<ev_async_send>.	2744	repeated calls to C<ev_async_send> for the same event loop.
2489		2745
2490	=item bool = ev_async_pending (ev_async *)	2746	=item bool = ev_async_pending (ev_async *)
2491		2747
2492	Returns a non-zero value when C<ev_async_send> has been called on the	2748	Returns a non-zero value when C<ev_async_send> has been called on the
2493	watcher but the event has not yet been processed (or even noted) by the	2749	watcher but the event has not yet been processed (or even noted) by the
…		…
2496	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2752	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2497	the loop iterates next and checks for the watcher to have become active,	2753	the loop iterates next and checks for the watcher to have become active,
2498	it will reset the flag again. C<ev_async_pending> can be used to very	2754	it will reset the flag again. C<ev_async_pending> can be used to very
2499	quickly check whether invoking the loop might be a good idea.	2755	quickly check whether invoking the loop might be a good idea.
2500		2756
2501	Not that this does I<not> check whether the watcher itself is pending, only	2757	Not that this does I<not> check whether the watcher itself is pending,
2502	whether it has been requested to make this watcher pending.	2758	only whether it has been requested to make this watcher pending: there
		2759	is a time window between the event loop checking and resetting the async
		2760	notification, and the callback being invoked.
2503		2761
2504	=back	2762	=back
2505		2763
2506		2764
2507	=head1 OTHER FUNCTIONS	2765	=head1 OTHER FUNCTIONS
…		…
2543	/* doh, nothing entered */;	2801	/* doh, nothing entered */;
2544	}	2802	}
2545		2803
2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2547		2805
2548	=item ev_feed_event (ev_loop , watcher , int revents)	2806	=item ev_feed_event (struct ev_loop , watcher , int revents)
2549		2807
2550	Feeds the given event set into the event loop, as if the specified event	2808	Feeds the given event set into the event loop, as if the specified event
2551	had happened for the specified watcher (which must be a pointer to an	2809	had happened for the specified watcher (which must be a pointer to an
2552	initialised but not necessarily started event watcher).	2810	initialised but not necessarily started event watcher).
2553		2811
2554	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2555		2813
2556	Feed an event on the given fd, as if a file descriptor backend detected	2814	Feed an event on the given fd, as if a file descriptor backend detected
2557	the given events it.	2815	the given events it.
2558		2816
2559	=item ev_feed_signal_event (ev_loop *loop, int signum)	2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2560		2818
2561	Feed an event as if the given signal occurred (C<loop> must be the default	2819	Feed an event as if the given signal occurred (C<loop> must be the default
2562	loop!).	2820	loop!).
2563		2821
2564	=back	2822	=back
…		…
2685	}	2943	}
2686		2944
2687	myclass obj;	2945	myclass obj;
2688	ev::io iow;	2946	ev::io iow;
2689	iow.set <myclass, &myclass::io_cb> (&obj);	2947	iow.set <myclass, &myclass::io_cb> (&obj);
		2948
		2949	=item w->set (object *)
		2950
		2951	This is an B<experimental> feature that might go away in a future version.
		2952
		2953	This is a variation of a method callback - leaving out the method to call
		2954	will default the method to C<operator ()>, which makes it possible to use
		2955	functor objects without having to manually specify the C<operator ()> all
		2956	the time. Incidentally, you can then also leave out the template argument
		2957	list.
		2958
		2959	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2960	int revents)>.
		2961
		2962	See the method-C<set> above for more details.
		2963
		2964	Example: use a functor object as callback.
		2965
		2966	struct myfunctor
		2967	{
		2968	void operator() (ev::io &w, int revents)
		2969	{
		2970	...
		2971	}
		2972	}
		2973
		2974	myfunctor f;
		2975
		2976	ev::io w;
		2977	w.set (&f);
2690		2978
2691	=item w->set<function> (void *data = 0)	2979	=item w->set<function> (void *data = 0)
2692		2980
2693	Also sets a callback, but uses a static method or plain function as	2981	Also sets a callback, but uses a static method or plain function as
2694	callback. The optional C<data> argument will be stored in the watcher's	2982	callback. The optional C<data> argument will be stored in the watcher's
…		…
2781	L<http://software.schmorp.de/pkg/EV>.	3069	L<http://software.schmorp.de/pkg/EV>.
2782		3070
2783	=item Python	3071	=item Python
2784		3072
2785	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3073	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2786	seems to be quite complete and well-documented. Note, however, that the	3074	seems to be quite complete and well-documented.
2787	patch they require for libev is outright dangerous as it breaks the ABI
2788	for everybody else, and therefore, should never be applied in an installed
2789	libev (if python requires an incompatible ABI then it needs to embed
2790	libev).
2791		3075
2792	=item Ruby	3076	=item Ruby
2793		3077
2794	Tony Arcieri has written a ruby extension that offers access to a subset	3078	Tony Arcieri has written a ruby extension that offers access to a subset
2795	of the libev API and adds file handle abstractions, asynchronous DNS and	3079	of the libev API and adds file handle abstractions, asynchronous DNS and
2796	more on top of it. It can be found via gem servers. Its homepage is at	3080	more on top of it. It can be found via gem servers. Its homepage is at
2797	L<http://rev.rubyforge.org/>.	3081	L<http://rev.rubyforge.org/>.
2798		3082
		3083	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3084	makes rev work even on mingw.
		3085
		3086	=item Haskell
		3087
		3088	A haskell binding to libev is available at
		3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3090
2799	=item D	3091	=item D
2800		3092
2801	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2802	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3095
		3096	=item Ocaml
		3097
		3098	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2803		3100
2804	=back	3101	=back
2805		3102
2806		3103
2807	=head1 MACRO MAGIC	3104	=head1 MACRO MAGIC
…		…
2908		3205
2909	#define EV_STANDALONE 1	3206	#define EV_STANDALONE 1
2910	#include "ev.h"	3207	#include "ev.h"
2911		3208
2912	Both header files and implementation files can be compiled with a C++	3209	Both header files and implementation files can be compiled with a C++
2913	compiler (at least, thats a stated goal, and breakage will be treated	3210	compiler (at least, that's a stated goal, and breakage will be treated
2914	as a bug).	3211	as a bug).
2915		3212
2916	You need the following files in your source tree, or in a directory	3213	You need the following files in your source tree, or in a directory
2917	in your include path (e.g. in libev/ when using -Ilibev):	3214	in your include path (e.g. in libev/ when using -Ilibev):
2918		3215
…		…
2974	keeps libev from including F<config.h>, and it also defines dummy	3271	keeps libev from including F<config.h>, and it also defines dummy
2975	implementations for some libevent functions (such as logging, which is not	3272	implementations for some libevent functions (such as logging, which is not
2976	supported). It will also not define any of the structs usually found in	3273	supported). It will also not define any of the structs usually found in
2977	F<event.h> that are not directly supported by the libev core alone.	3274	F<event.h> that are not directly supported by the libev core alone.
2978		3275
		3276	In stanbdalone mode, libev will still try to automatically deduce the
		3277	configuration, but has to be more conservative.
		3278
2979	=item EV_USE_MONOTONIC	3279	=item EV_USE_MONOTONIC
2980		3280
2981	If defined to be C<1>, libev will try to detect the availability of the	3281	If defined to be C<1>, libev will try to detect the availability of the
2982	monotonic clock option at both compile time and runtime. Otherwise no use	3282	monotonic clock option at both compile time and runtime. Otherwise no
2983	of the monotonic clock option will be attempted. If you enable this, you	3283	use of the monotonic clock option will be attempted. If you enable this,
2984	usually have to link against librt or something similar. Enabling it when	3284	you usually have to link against librt or something similar. Enabling it
2985	the functionality isn't available is safe, though, although you have	3285	when the functionality isn't available is safe, though, although you have
2986	to make sure you link against any libraries where the C<clock_gettime>	3286	to make sure you link against any libraries where the C<clock_gettime>
2987	function is hiding in (often F<-lrt>).	3287	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2988		3288
2989	=item EV_USE_REALTIME	3289	=item EV_USE_REALTIME
2990		3290
2991	If defined to be C<1>, libev will try to detect the availability of the	3291	If defined to be C<1>, libev will try to detect the availability of the
2992	real-time clock option at compile time (and assume its availability at	3292	real-time clock option at compile time (and assume its availability
2993	runtime if successful). Otherwise no use of the real-time clock option will	3293	at runtime if successful). Otherwise no use of the real-time clock
2994	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3294	option will be attempted. This effectively replaces C<gettimeofday>
2995	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3295	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2996	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3296	correctness. See the note about libraries in the description of
		3297	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3298	C<EV_USE_CLOCK_SYSCALL>.
		3299
		3300	=item EV_USE_CLOCK_SYSCALL
		3301
		3302	If defined to be C<1>, libev will try to use a direct syscall instead
		3303	of calling the system-provided C<clock_gettime> function. This option
		3304	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3305	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3306	programs needlessly. Using a direct syscall is slightly slower (in
		3307	theory), because no optimised vdso implementation can be used, but avoids
		3308	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3309	higher, as it simplifies linking (no need for C<-lrt>).
2997		3310
2998	=item EV_USE_NANOSLEEP	3311	=item EV_USE_NANOSLEEP
2999		3312
3000	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3313	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3001	and will use it for delays. Otherwise it will use C<select ()>.	3314	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3017		3330
3018	=item EV_SELECT_USE_FD_SET	3331	=item EV_SELECT_USE_FD_SET
3019		3332
3020	If defined to C<1>, then the select backend will use the system C<fd_set>	3333	If defined to C<1>, then the select backend will use the system C<fd_set>
3021	structure. This is useful if libev doesn't compile due to a missing	3334	structure. This is useful if libev doesn't compile due to a missing
3022	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3335	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3023	exotic systems. This usually limits the range of file descriptors to some	3336	on exotic systems. This usually limits the range of file descriptors to
3024	low limit such as 1024 or might have other limitations (winsocket only	3337	some low limit such as 1024 or might have other limitations (winsocket
3025	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3338	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3026	influence the size of the C<fd_set> used.	3339	configures the maximum size of the C<fd_set>.
3027		3340
3028	=item EV_SELECT_IS_WINSOCKET	3341	=item EV_SELECT_IS_WINSOCKET
3029		3342
3030	When defined to C<1>, the select backend will assume that	3343	When defined to C<1>, the select backend will assume that
3031	select/socket/connect etc. don't understand file descriptors but	3344	select/socket/connect etc. don't understand file descriptors but
…		…
3390	loop, as long as you don't confuse yourself). The only exception is that	3703	loop, as long as you don't confuse yourself). The only exception is that
3391	you must not do this from C<ev_periodic> reschedule callbacks.	3704	you must not do this from C<ev_periodic> reschedule callbacks.
3392		3705
3393	Care has been taken to ensure that libev does not keep local state inside	3706	Care has been taken to ensure that libev does not keep local state inside
3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as	3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3395	they do not clal any callbacks.	3708	they do not call any callbacks.
3396		3709
3397	=head2 COMPILER WARNINGS	3710	=head2 COMPILER WARNINGS
3398		3711
3399	Depending on your compiler and compiler settings, you might get no or a	3712	Depending on your compiler and compiler settings, you might get no or a
3400	lot of warnings when compiling libev code. Some people are apparently	3713	lot of warnings when compiling libev code. Some people are apparently
…		…
3434	==2274== definitely lost: 0 bytes in 0 blocks.	3747	==2274== definitely lost: 0 bytes in 0 blocks.
3435	==2274== possibly lost: 0 bytes in 0 blocks.	3748	==2274== possibly lost: 0 bytes in 0 blocks.
3436	==2274== still reachable: 256 bytes in 1 blocks.	3749	==2274== still reachable: 256 bytes in 1 blocks.
3437		3750
3438	Then there is no memory leak, just as memory accounted to global variables	3751	Then there is no memory leak, just as memory accounted to global variables
3439	is not a memleak - the memory is still being refernced, and didn't leak.	3752	is not a memleak - the memory is still being referenced, and didn't leak.
3440		3753
3441	Similarly, under some circumstances, valgrind might report kernel bugs	3754	Similarly, under some circumstances, valgrind might report kernel bugs
3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,	3755	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3443	although an acceptable workaround has been found here), or it might be	3756	although an acceptable workaround has been found here), or it might be
3444	confused.	3757	confused.
…		…
3682	=back	3995	=back
3683		3996
3684		3997
3685	=head1 AUTHOR	3998	=head1 AUTHOR
3686		3999
3687	Marc Lehmann <libev@schmorp.de>.	4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3688		4001

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Comparing libev/ev.pod (file contents): Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC vs. Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC vs.
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC