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Revision 1.180 by root, Fri Sep 19 03:45:55 2008 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC

…		…
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<ev_loop *>. The library knows two
282	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
283	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
284		284
285	=over 4	285	=over 4
286		286
…		…
396	Please note that epoll sometimes generates spurious notifications, so you	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	397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.	398	(or space) is available.
399		399
400	Best performance from this backend is achieved by not unregistering all	400	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	401	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	402	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
		404	extra overhead.
403		405
404	While nominally embeddable in other event loops, this feature is broken in	406	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	407	all kernel versions tested so far.
406		408
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
408	C<EVBACKEND_POLL>.	410	C<EVBACKEND_POLL>.
409		411
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		413
412	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
414	with anything but sockets and pipes, except on Darwin, where of course	416	anything but sockets and pipes, except on Darwin, where of course it's
415	it's completely useless). For this reason it's not being "auto-detected"	417	completely useless). For this reason it's not being "auto-detected" unless
416	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
418	system like NetBSD.
419		420
420	You still can embed kqueue into a normal poll or select backend and use it	421	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	422	only for sockets (after having made sure that sockets work with kqueue on
422	the target platform). See C<ev_embed> watchers for more info.	423	the target platform). See C<ev_embed> watchers for more info.
423		424
424	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	427	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	429	two event changes per incident. Support for C<fork ()> is very bad and it
429	drops fds silently in similarly hard-to-detect cases.	430	drops fds silently in similarly hard-to-detect cases.
430		431
431	This backend usually performs well under most conditions.	432	This backend usually performs well under most conditions.
432		433
433	While nominally embeddable in other event loops, this doesn't work	434	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	435	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	436	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	437	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
438	sockets.	439	using it only for sockets.
439		440
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	443	C<NOTE_EOF>.
443		444
…		…
460	While this backend scales well, it requires one system call per active	461	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	462	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	464	might perform better.
464		465
465	On the positive side, ignoring the spurious readiness notifications, this	466	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	467	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
468		470
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	472	C<EVBACKEND_POLL>.
471		473
472	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
…		…
481		483
482	If one or more of these are or'ed into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
483	backends will be tried (in the reverse order as listed here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		487
486	The most typical usage is like this:	488	Example: This is the most typical usage.
487		489
488	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		492
491	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	494	environment settings to be taken into account:
493		495
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		497
496	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
499		502
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		504
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		506
…		…
561		564
562	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
563		566
564	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
567		571
568	=item int ev_is_default_loop (loop)	572	=item int ev_is_default_loop (loop)
569		573
570	Returns true when the given loop actually is the default loop, false otherwise.	574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
571		576
572	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
573		578
574	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
575	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
613	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
614	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
615		620
616	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
621		627
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
624	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
625		632
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
630	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	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
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
633		644
634	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
635		646
636	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	657	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	658	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	662	- Queue all expired timers.
652	- Queue all outstanding periodics.	663	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	665	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
…		…
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		687
677	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
678		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
679	=item ev_ref (loop)	692	=item ev_ref (loop)
680		693
681	=item ev_unref (loop)	694	=item ev_unref (loop)
682		695
683	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	697	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	698	count is nonzero, C<ev_loop> will not return on its own.
		699
686	a watcher you never unregister that should not keep C<ev_loop> from	700	If you have a watcher you never unregister that should not keep C<ev_loop>
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
688	example, libev itself uses this for its internal signal pipe: It is not	704	As an example, libev itself uses this for its internal signal pipe: It is
689	visible to the libev user and should not keep C<ev_loop> from exiting if	705	not visible to the libev user and should not keep C<ev_loop> from exiting
690	no event watchers registered by it are active. It is also an excellent	706	if no event watchers registered by it are active. It is also an excellent
691	way to do this for generic recurring timers or from within third-party	707	way to do this for generic recurring timers or from within third-party
692	libraries. Just remember to I<unref after start> and I<ref before stop>	708	libraries. Just remember to I<unref after start> and I<ref before stop>
693	(but only if the watcher wasn't active before, or was active before,	709	(but only if the watcher wasn't active before, or was active before,
694	respectively).	710	respectively).
695		711
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	713	running when nothing else is active.
698		714
699	struct ev_signal exitsig;	715	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	718	evf_unref (loop);
703		719
704	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	735	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	736	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	737	opportunities).
722		738
723	The background is that sometimes your program runs just fast enough to	739	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	740	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	741	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	742	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	743	overhead for the actual polling but can deliver many events at once.
728		744
729	By setting a higher I<io collect interval> you allow libev to spend more	745	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	746	time collecting I/O events, so you can handle more events per iteration,
…		…
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	748	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	749	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		750
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	751	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	752	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	753	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	755	value will not introduce any overhead in libev.
740		756
741	Many (busy) programs can usually benefit by setting the I/O collect	757	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	758	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	759	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	760	usually doesn't make much sense to set it to a lower value than C<0.01>,
…		…
752	they fire on, say, one-second boundaries only.	768	they fire on, say, one-second boundaries only.
753		769
754	=item ev_loop_verify (loop)	770	=item ev_loop_verify (loop)
755		771
756	This function only does something when C<EV_VERIFY> support has been	772	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	773	compiled in. which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	774	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
760		777
761	This can be used to catch bugs inside libev itself: under normal	778	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	779	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	780	data structures consistent.
764		781
…		…
769		786
770	A watcher is a structure that you create and register to record your	787	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	788	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	789	become readable, you would create an C<ev_io> watcher for that:
773		790
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	792	{
776	ev_io_stop (w);	793	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
778	}	795	}
779		796
780	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
781	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
782	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
785	ev_loop (loop, 0);	802	ev_loop (loop, 0);
786		803
…		…
877	=item C<EV_ERROR>	894	=item C<EV_ERROR>
878		895
879	An unspecified error has occurred, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
882	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
884		905
885	Libev will usually signal a few "dummy" events together with an error,	906	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	907	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	908	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	909	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
890		912
891	=back	913	=back
892		914
893	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
894		916
…		…
907	which rolls both calls into one.	929	which rolls both calls into one.
908		930
909	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
911		933
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	935	int revents)>.
		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		942
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		944
917	This macro initialises the type-specific parts of a watcher. You need to	945	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	946	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
922		950
923	Although some watcher types do not have type-specific arguments	951	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		953
		954	See C<ev_init>, above, for an example.
		955
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		957
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	959	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
931		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		965
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		967
934	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
936		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		977
939	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
940	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		986
946	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
947		988
948	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
997		1038
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1040
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
1003		1045
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1047
1006	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
1009		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
1010	=back	1055	=back
1011		1056
1012		1057
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1059
1015	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
1020	data:	1065	data:
1021		1066
1022	struct my_io	1067	struct my_io
1023	{	1068	{
1024	struct ev_io io;	1069	ev_io io;
1025	int otherfd;	1070	int otherfd;
1026	void *somedata;	1071	void *somedata;
1027	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
1028	};	1073	};
1029		1074
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1078
1034	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1080	can cast it back to your own type:
1036		1081
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1083	{
1039	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
1040	...	1085	...
1041	}	1086	}
1042		1087
…		…
1053	ev_timer t2;	1098	ev_timer t2;
1054	}	1099	}
1055		1100
1056	In this case getting the pointer to C<my_biggy> is a bit more	1101	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1102	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1103	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
1060		1106
1061	#include <stddef.h>	1107	#include <stddef.h>
1062		1108
1063	static void	1109	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1111	{
1066	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1114	}
1069		1115
1070	static void	1116	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1118	{
1073	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1121	}
1076		1122
…		…
1104	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1153	required if you know what you are doing).
1108		1154
1109	If you must do this, then force the use of a known-to-be-good backend	1155	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1156	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1158
1113	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1167
1122	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1169	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
1127		1177
1128	=head3 The special problem of disappearing file descriptors	1178	=head3 The special problem of disappearing file descriptors
1129		1179
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1181	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1182	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1183	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1184	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1185	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1186	fact, a different file descriptor.
1137		1187
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1219	C<EVBACKEND_POLL>.
1170		1220
1171	=head3 The special problem of SIGPIPE	1221	=head3 The special problem of SIGPIPE
1172		1222
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1224	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1226	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1227
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1228	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1230	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1238
1189	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
1190		1240
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1244
1195	=item int fd [read-only]	1245	=item int fd [read-only]
1196		1246
1197	The file descriptor being watched.	1247	The file descriptor being watched.
1198		1248
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
1210		1260
1211	static void	1261	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1263	{
1214	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1266	}
1217		1267
1218	...	1268	...
1219	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
1224		1274
1225		1275
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
1230		1280
1231	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1282	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
1236		1286
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1287	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1288	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1289	then order of execution is undefined.
		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems invole some kind of time-out, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	Here are some ways on how to handle this problem, from simple and
		1298	inefficient to very efficient.
		1299
		1300	In the following examples a 60 second activity timeout is assumed - a
		1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")
		1302	was received.
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise, start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> the timer,
		1315	initialise it again, and start it:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there
		1322	is some activity, libev will first have to remove the timer from it's
		1323	internal data strcuture and then add it again.
		1324
		1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1326
		1327	This is the easiest way, and involves using C<ev_timer_again> instead of
		1328	C<ev_timer_start>.
		1329
		1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and
		1331	then call C<ev_timer_again> at start and each time you successfully read
		1332	or write some data. If you go into an idle state where you do not expect
		1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and
		1334	C<ev_timer_again> will automatically restart it if need be.
		1335
		1336	That means you can ignore the C<after> value and C<ev_timer_start>
		1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.
		1338
		1339	At start:
		1340
		1341	ev_timer_init (timer, callback, 0., 60.);
		1342	ev_timer_again (loop, timer);
		1343
		1344	Each time you receive some data:
		1345
		1346	ev_timer_again (loop, timer);
		1347
		1348	It is even possible to change the time-out on the fly:
		1349
		1350	timer->repeat = 30.;
		1351	ev_timer_again (loop, timer);
		1352
		1353	This is slightly more efficient then stopping/starting the timer each time
		1354	you want to modify its timeout value, as libev does not have to completely
		1355	remove and re-insert the timer from/into it's internal data structure.
		1356
		1357	=item 3. Let the timer time out, but then re-arm it as required.
		1358
		1359	This method is more tricky, but usually most efficient: Most timeouts are
		1360	relatively long compared to the loop iteration time - in our example,
		1361	within 60 seconds, there are usually many I/O events with associated
		1362	activity resets.
		1363
		1364	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1365	but remember the time of last activity, and check for a real timeout only
		1366	within the callback:
		1367
		1368	ev_tstamp last_activity; // time of last activity
		1369
		1370	static void
		1371	callback (EV_P_ ev_timer *w, int revents)
		1372	{
		1373	ev_tstamp now = ev_now (EV_A);
		1374	ev_tstamp timeout = last_activity + 60.;
		1375
		1376	// if last_activity is older than now - timeout, we did time out
		1377	if (timeout < now)
		1378	{
		1379	// timeout occured, take action
		1380	}
		1381	else
		1382	{
		1383	// callback was invoked, but there was some activity, re-arm
		1384	// to fire in last_activity + 60.
		1385	w->again = timeout - now;
		1386	ev_timer_again (EV_A_ w);
		1387	}
		1388	}
		1389
		1390	To summarise the callback: first calculate the real time-out (defined as
		1391	"60 seconds after the last activity"), then check if that time has been
		1392	reached, which means there was a real timeout. Otherwise the callback was
		1393	invoked too early (timeout is in the future), so re-schedule the timer to
		1394	fire at that future time.
		1395
		1396	Note how C<ev_timer_again> is used, taking advantage of the
		1397	C<ev_timer_again> optimisation when the timer is already running.
		1398
		1399	This scheme causes more callback invocations (about one every 60 seconds),
		1400	but virtually no calls to libev to change the timeout.
		1401
		1402	To start the timer, simply intiialise the watcher and C<last_activity>,
		1403	then call the callback:
		1404
		1405	ev_timer_init (timer, callback);
		1406	last_activity = ev_now (loop);
		1407	callback (loop, timer, EV_TIMEOUT);
		1408
		1409	And when there is some activity, simply remember the time in
		1410	C<last_activity>:
		1411
		1412	last_actiivty = ev_now (loop);
		1413
		1414	This technique is slightly more complex, but in most cases where the
		1415	time-out is unlikely to be triggered, much more efficient.
		1416
		1417	=back
1240		1418
1241	=head3 The special problem of time updates	1419	=head3 The special problem of time updates
1242		1420
1243	Establishing the current time is a costly operation (it usually takes at	1421	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1422	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1423	time only before and after C<ev_loop> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1425	lots of events in one iteration.
1248		1426
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1427	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1428	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1429	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1430	you suspect event processing to be delayed and you I<need> to base the
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1466	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1467
1290	If the timer is repeating, either start it if necessary (with the	1468	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1469	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1470
1293	This sounds a bit complicated, but here is a useful and typical	1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1472	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302
1303	That means you can ignore the C<after> value and C<ev_timer_start>
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305
1306	ev_timer_init (timer, callback, 0., 5.);
1307	ev_timer_again (loop, timer);
1308	...
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314
1315	This is more slightly efficient then stopping/starting the timer each time
1316	you want to modify its timeout value.
1317		1473
1318	=item ev_tstamp repeat [read-write]	1474	=item ev_tstamp repeat [read-write]
1319		1475
1320	The current C<repeat> value. Will be used each time the watcher times out	1476	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	1477	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	1478	which is also when any modifications are taken into account.
1323		1479
1324	=back	1480	=back
1325		1481
1326	=head3 Examples	1482	=head3 Examples
1327		1483
1328	Example: Create a timer that fires after 60 seconds.	1484	Example: Create a timer that fires after 60 seconds.
1329		1485
1330	static void	1486	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1487	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1488	{
1333	.. one minute over, w is actually stopped right here	1489	.. one minute over, w is actually stopped right here
1334	}	1490	}
1335		1491
1336	struct ev_timer mytimer;	1492	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1493	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1494	ev_timer_start (loop, &mytimer);
1339		1495
1340	Example: Create a timeout timer that times out after 10 seconds of	1496	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1497	inactivity.
1342		1498
1343	static void	1499	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1500	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1501	{
1346	.. ten seconds without any activity	1502	.. ten seconds without any activity
1347	}	1503	}
1348		1504
1349	struct ev_timer mytimer;	1505	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1507	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1508	ev_loop (loop, 0);
1353		1509
1354	// and in some piece of code that gets executed on any "activity":	1510	// and in some piece of code that gets executed on any "activity":
…		…
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger	1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1527	roughly 10 seconds later as it uses a relative timeout).
1372		1528
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1529	C<ev_periodic>s can also be used to implement vastly more complex timers,
1374	such as triggering an event on each "midnight, local time", or other	1530	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1531	complicated rules.
1376		1532
1377	As with timers, the callback is guaranteed to be invoked only when the	1533	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	1534	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1535	during the same loop iteration, then order of execution is undefined.
1380		1536
1381	=head3 Watcher-Specific Functions and Data Members	1537	=head3 Watcher-Specific Functions and Data Members
1382		1538
1383	=over 4	1539	=over 4
1384		1540
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1542
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1388		1544
1389	Lots of arguments, lets sort it out... There are basically three modes of	1545	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1546	operation, and we will explain them from simplest to most complex:
1391		1547
1392	=over 4	1548	=over 4
1393		1549
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1551
1396	In this configuration the watcher triggers an event after the wall clock	1552	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	1553	time C<at> has passed. It will not repeat and will not adjust when a time
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1399	run when the system time reaches or surpasses this time.	1555	only run when the system clock reaches or surpasses this time.
1400		1556
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1558
1403	In this mode the watcher will always be scheduled to time out at the next	1559	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	1560	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1561	and then repeat, regardless of any time jumps.
1406		1562
1407	This can be used to create timers that do not drift with respect to system	1563	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	1564	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1565	hour, on the hour:
1410		1566
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1567	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1568
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1569	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	1570	but only that the callback will be called when the system time shows a
…		…
1440		1596
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1599	only event loop modification you are allowed to do).
1444		1600
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1601	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1602	*w, ev_tstamp now)>, e.g.:
1447		1603
		1604	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1605	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1606	{
1450	return now + 60.;	1607	return now + 60.;
1451	}	1608	}
1452		1609
1453	It must return the next time to trigger, based on the passed time value	1610	It must return the next time to trigger, based on the passed time value
…		…
1490		1647
1491	The current interval value. Can be modified any time, but changes only	1648	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	1649	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1650	called.
1494		1651
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1652	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1653
1497	The current reschedule callback, or C<0>, if this functionality is	1654	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	1655	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	1656	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1657
1501	=back	1658	=back
1502		1659
1503	=head3 Examples	1660	=head3 Examples
1504		1661
1505	Example: Call a callback every hour, or, more precisely, whenever the	1662	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1663	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1664	potentially a lot of jitter, but good long-term stability.
1508		1665
1509	static void	1666	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1668	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1669	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1670	}
1514		1671
1515	struct ev_periodic hourly_tick;	1672	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1673	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1674	ev_periodic_start (loop, &hourly_tick);
1518		1675
1519	Example: The same as above, but use a reschedule callback to do it:	1676	Example: The same as above, but use a reschedule callback to do it:
1520		1677
1521	#include <math.h>	1678	#include <math.h>
1522		1679
1523	static ev_tstamp	1680	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1681	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1682	{
1526	return fmod (now, 3600.) + 3600.;	1683	return now + (3600. - fmod (now, 3600.));
1527	}	1684	}
1528		1685
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1686	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1687
1531	Example: Call a callback every hour, starting now:	1688	Example: Call a callback every hour, starting now:
1532		1689
1533	struct ev_periodic hourly_tick;	1690	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1691	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1692	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1693	ev_periodic_start (loop, &hourly_tick);
1537		1694
1538		1695
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1698	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	1699	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	1700	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1701	normal event processing, like any other event.
1545		1702
		1703	If you want signals asynchronously, just use C<sigaction> as you would
		1704	do without libev and forget about sharing the signal. You can even use
		1705	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1706
1546	You can configure as many watchers as you like per signal. Only when the	1707	You can configure as many watchers as you like per signal. Only when the
1547	first watcher gets started will libev actually register a signal watcher	1708	first watcher gets started will libev actually register a signal handler
1548	with the kernel (thus it coexists with your own signal handlers as long	1709	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	1710	you don't register any with libev for the same signal). Similarly, when
1550	watcher for a signal is stopped libev will reset the signal handler to	1711	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1712	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1713
1553	If possible and supported, libev will install its handlers with	1714	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1555	interrupted. If you have a problem with system calls getting interrupted by	1716	interrupted. If you have a problem with system calls getting interrupted by
1556	signals you can block all signals in an C<ev_check> watcher and unblock	1717	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1734
1574	=back	1735	=back
1575		1736
1576	=head3 Examples	1737	=head3 Examples
1577		1738
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1739	Example: Try to exit cleanly on SIGINT.
1579		1740
1580	static void	1741	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1743	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1744	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1745	}
1585		1746
1586	struct ev_signal signal_watcher;	1747	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1749	ev_signal_start (loop, &signal_watcher);
1589		1750
1590		1751
1591	=head2 C<ev_child> - watch out for process status changes	1752	=head2 C<ev_child> - watch out for process status changes
1592		1753
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1754	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	1755	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	1756	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	1757	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1758	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1759	forking and then immediately registering a watcher for the child is fine,
		1760	but forking and registering a watcher a few event loop iterations later is
		1761	not.
1598		1762
1599	Only the default event loop is capable of handling signals, and therefore	1763	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1764	you can only register child watchers in the default event loop.
1601		1765
1602	=head3 Process Interaction	1766	=head3 Process Interaction
…		…
1663	its completion.	1827	its completion.
1664		1828
1665	ev_child cw;	1829	ev_child cw;
1666		1830
1667	static void	1831	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1832	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1833	{
1670	ev_child_stop (EV_A_ w);	1834	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1835	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1836	}
1673		1837
…		…
1700	the stat buffer having unspecified contents.	1864	the stat buffer having unspecified contents.
1701		1865
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1866	The path I<should> be absolute and I<must not> end in a slash. If it is
1703	relative and your working directory changes, the behaviour is undefined.	1867	relative and your working directory changes, the behaviour is undefined.
1704		1868
1705	Since there is no standard to do this, the portable implementation simply	1869	Since there is no standard kernel interface to do this, the portable
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1870	implementation simply calls C<stat (2)> regularly on the path to see if
1707	can specify a recommended polling interval for this case. If you specify	1871	it changed somehow. You can specify a recommended polling interval for
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1872	this case. If you specify a polling interval of C<0> (highly recommended!)
1709	unspecified default> value will be used (which you can expect to be around	1873	then a I<suitable, unspecified default> value will be used (which
1710	five seconds, although this might change dynamically). Libev will also	1874	you can expect to be around five seconds, although this might change
1711	impose a minimum interval which is currently around C<0.1>, but thats	1875	dynamically). Libev will also impose a minimum interval which is currently
1712	usually overkill.	1876	around C<0.1>, but thats usually overkill.
1713		1877
1714	This watcher type is not meant for massive numbers of stat watchers,	1878	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1879	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1880	resource-intensive.
1717		1881
1718	At the time of this writing, only the Linux inotify interface is	1882	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1883	is the Linux inotify interface (implementing kqueue support is left as
1720	reader, note, however, that the author sees no way of implementing ev_stat	1884	an exercise for the reader. Note, however, that the author sees no way
1721	semantics with kqueue). Inotify will be used to give hints only and should	1885	of implementing C<ev_stat> semantics with kqueue).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		1886
1727	=head3 ABI Issues (Largefile Support)	1887	=head3 ABI Issues (Largefile Support)
1728		1888
1729	Libev by default (unless the user overrides this) uses the default	1889	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1890	compilation environment, which means that on systems with large file
…		…
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1899	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	1900	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1901	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1902	default compilation environment.
1743		1903
1744	=head3 Inotify	1904	=head3 Inotify and Kqueue
1745		1905
1746	When C<inotify (7)> support has been compiled into libev (generally only	1906	When C<inotify (7)> support has been compiled into libev (generally
		1907	only available with Linux 2.6.25 or above due to bugs in earlier
1747	available on Linux) and present at runtime, it will be used to speed up	1908	implementations) and present at runtime, it will be used to speed up
1748	change detection where possible. The inotify descriptor will be created lazily	1909	change detection where possible. The inotify descriptor will be created
1749	when the first C<ev_stat> watcher is being started.	1910	lazily when the first C<ev_stat> watcher is being started.
1750		1911
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1912	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	1913	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	1914	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	1915	there are many cases where libev has to resort to regular C<stat> polling,
		1916	but as long as the path exists, libev usually gets away without polling.
1755		1917
1756	(There is no support for kqueue, as apparently it cannot be used to	1918	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	1919	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	1920	descriptor open on the object at all times, and detecting renames, unlinks
		1921	etc. is difficult.
1759		1922
1760	=head3 The special problem of stat time resolution	1923	=head3 The special problem of stat time resolution
1761		1924
1762	The C<stat ()> system call only supports full-second resolution portably, and	1925	The C<stat ()> system call only supports full-second resolution portably, and
1763	even on systems where the resolution is higher, many file systems still	1926	even on systems where the resolution is higher, most file systems still
1764	only support whole seconds.	1927	only support whole seconds.
1765		1928
1766	That means that, if the time is the only thing that changes, you can	1929	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	1930	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	1931	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	1932	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	1933	stat data does change in other ways (e.g. file size).
1771		1934
1772	The solution to this is to delay acting on a change for slightly more	1935	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	1936	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	1937	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	1938	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	1958	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	1959	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	1960	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	1961	path for as long as the watcher is active.
1799		1962
1800	The callback will receive C<EV_STAT> when a change was detected, relative	1963	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	1964	relative to the attributes at the time the watcher was started (or the
1802	was detected).	1965	last change was detected).
1803		1966
1804	=item ev_stat_stat (loop, ev_stat *)	1967	=item ev_stat_stat (loop, ev_stat *)
1805		1968
1806	Updates the stat buffer immediately with new values. If you change the	1969	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	1970	watched path in your callback, you could call this function to avoid
…		…
1890		2053
1891		2054
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2055	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2056
1894	Idle watchers trigger events when no other events of the same or higher	2057	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2058	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2059	as receiving "events").
1897		2060
1898	That is, as long as your process is busy handling sockets or timeouts	2061	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2062	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2063	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2064	are pending), the idle watchers are being called once per event loop
…		…
1926		2089
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2090	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2091	callback, free it. Also, use no error checking, as usual.
1929		2092
1930	static void	2093	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2095	{
1933	free (w);	2096	free (w);
1934	// now do something you wanted to do when the program has	2097	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2098	// no longer anything immediate to do.
1936	}	2099	}
1937		2100
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2102	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2103	ev_idle_start (loop, idle_cb);
1941		2104
1942		2105
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2107
1945	Prepare and check watchers are usually (but not always) used in tandem:	2108	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2109	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2110	afterwards.
1948		2111
1949	You I<must not> call C<ev_loop> or similar functions that enter	2112	You I<must not> call C<ev_loop> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2113	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2117	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2118	called in pairs bracketing the blocking call.
1956		2119
1957	Their main purpose is to integrate other event mechanisms into libev and	2120	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2121	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2122	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2123	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2124	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2125	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2126	watcher).
1964		2127
1965	This is done by examining in each prepare call which file descriptors need	2128	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2129	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2130	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2131	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2132	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2133	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2134	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2135	nevertheless, because you never know, you know?).
1973		2136
1974	As another example, the Perl Coro module uses these hooks to integrate	2137	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2138	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2139	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2140	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2143	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2144	low-priority coroutines to idle/background tasks).
1982		2145
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2147	priority, to ensure that they are being run before any other watchers
		2148	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2149
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2151	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2152	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2153	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2154	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2156	others).
1992		2157
1993	=head3 Watcher-Specific Functions and Data Members	2158	=head3 Watcher-Specific Functions and Data Members
1994		2159
1995	=over 4	2160	=over 4
1996		2161
…		…
1998		2163
1999	=item ev_check_init (ev_check *, callback)	2164	=item ev_check_init (ev_check *, callback)
2000		2165
2001	Initialises and configures the prepare or check watcher - they have no	2166	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2167	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2168	macros, but using them is utterly, utterly, utterly and completely
		2169	pointless.
2004		2170
2005	=back	2171	=back
2006		2172
2007	=head3 Examples	2173	=head3 Examples
2008		2174
…		…
2021		2187
2022	static ev_io iow [nfd];	2188	static ev_io iow [nfd];
2023	static ev_timer tw;	2189	static ev_timer tw;
2024		2190
2025	static void	2191	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2192	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2193	{
2028	}	2194	}
2029		2195
2030	// create io watchers for each fd and a timer before blocking	2196	// create io watchers for each fd and a timer before blocking
2031	static void	2197	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2198	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2199	{
2034	int timeout = 3600000;	2200	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2201	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2202	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2218	}
2053	}	2219	}
2054		2220
2055	// stop all watchers after blocking	2221	// stop all watchers after blocking
2056	static void	2222	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2223	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2224	{
2059	ev_timer_stop (loop, &tw);	2225	ev_timer_stop (loop, &tw);
2060		2226
2061	for (int i = 0; i < nfd; ++i)	2227	for (int i = 0; i < nfd; ++i)
2062	{	2228	{
…		…
2101	}	2267	}
2102		2268
2103	// do not ever call adns_afterpoll	2269	// do not ever call adns_afterpoll
2104		2270
2105	Method 4: Do not use a prepare or check watcher because the module you	2271	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2272	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2273	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2274	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2275	this approach, effectively embedding EV as a client into the horrible
		2276	libglib event loop.
2110		2277
2111	static gint	2278	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2279	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2280	{
2114	int got_events = 0;	2281	int got_events = 0;
…		…
2145	prioritise I/O.	2312	prioritise I/O.
2146		2313
2147	As an example for a bug workaround, the kqueue backend might only support	2314	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2315	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2316	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2317	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2318	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2319	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2320	C<kevent>, but at least you can use both mechanisms for what they are
		2321	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2322
2155	As for prioritising I/O: rarely you have the case where some fds have	2323	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2324	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2325	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2326	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2327	the rest in a second one, and embed the second one in the first.
2160		2328
2161	As long as the watcher is active, the callback will be invoked every time	2329	As long as the watcher is active, the callback will be invoked every time
2162	there might be events pending in the embedded loop. The callback must then	2330	there might be events pending in the embedded loop. The callback must then
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2164	their callbacks (you could also start an idle watcher to give the embedded	2332	their callbacks (you could also start an idle watcher to give the embedded
…		…
2172	interested in that.	2340	interested in that.
2173		2341
2174	Also, there have not currently been made special provisions for forking:	2342	Also, there have not currently been made special provisions for forking:
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2176	but you will also have to stop and restart any C<ev_embed> watchers	2344	but you will also have to stop and restart any C<ev_embed> watchers
2177	yourself.	2345	yourself - but you can use a fork watcher to handle this automatically,
		2346	and future versions of libev might do just that.
2178		2347
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2348	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2350	portable one.
2182		2351
2183	So when you want to use this feature you will always have to be prepared	2352	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2353	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2354	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2355	create it, and if that fails, use the normal loop for everything.
		2356
		2357	=head3 C<ev_embed> and fork
		2358
		2359	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2360	automatically be applied to the embedded loop as well, so no special
		2361	fork handling is required in that case. When the watcher is not running,
		2362	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2363	as applicable.
2187		2364
2188	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2189		2366
2190	=over 4	2367	=over 4
2191		2368
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2396	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2397	used).
2221		2398
2222	struct ev_loop *loop_hi = ev_default_init (0);	2399	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2400	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2401	ev_embed embed;
2225		2402
2226	// see if there is a chance of getting one that works	2403	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2404	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2420	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2422
2246	struct ev_loop *loop = ev_default_init (0);	2423	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2424	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2425	ev_embed embed;
2249		2426
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2429	{
2253	ev_embed_init (&embed, 0, loop_socket);	2430	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2486	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	2487	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2488	need elaborate support such as pthreads.
2312		2489
2313	That means that if you want to queue data, you have to provide your own	2490	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	2491	queue. But at least I can tell you how to implement locking around your
2315	queue:	2492	queue:
2316		2493
2317	=over 4	2494	=over 4
2318		2495
2319	=item queueing from a signal handler context	2496	=item queueing from a signal handler context
2320		2497
2321	To implement race-free queueing, you simply add to the queue in the signal	2498	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2499	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2500	an example that does that for some fictitious SIGUSR1 handler:
2324		2501
2325	static ev_async mysig;	2502	static ev_async mysig;
2326		2503
2327	static void	2504	static void
2328	sigusr1_handler (void)	2505	sigusr1_handler (void)
…		…
2395		2572
2396	=item ev_async_init (ev_async *, callback)	2573	=item ev_async_init (ev_async *, callback)
2397		2574
2398	Initialises and configures the async watcher - it has no parameters of any	2575	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2400	believe me.	2577	trust me.
2401		2578
2402	=item ev_async_send (loop, ev_async *)	2579	=item ev_async_send (loop, ev_async *)
2403		2580
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	2583	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2585	section below on what exactly this means).
2409		2586
2410	This call incurs the overhead of a system call only once per loop iteration,	2587	This call incurs the overhead of a system call only once per loop iteration,
2411	so while the overhead might be noticeable, it doesn't apply to repeated	2588	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2612	=over 4
2436		2613
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2614	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2615
2439	This function combines a simple timer and an I/O watcher, calls your	2616	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2617	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	2618	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	2619	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2620	more watchers yourself.
2444		2621
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2622	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2623	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2624	the given C<fd> and C<events> set will be created and started.
2448		2625
2449	If C<timeout> is less than 0, then no timeout watcher will be	2626	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2628	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2629
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2455	passed an C<revents> set like normal event callbacks (a combination of	2631	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2633	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2634	a timeout and an io event at the same time - you probably should give io
		2635	events precedence.
		2636
		2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2638
2459	static void stdin_ready (int revents, void *arg)	2639	static void stdin_ready (int revents, void *arg)
2460	{	2640	{
		2641	if (revents & EV_READ)
		2642	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2643	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2644	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2645	}
2466		2646
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2648
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2650
2471	Feeds the given event set into the event loop, as if the specified event	2651	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an	2652	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2653	initialised but not necessarily started event watcher).
2474		2654
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2656
2477	Feed an event on the given fd, as if a file descriptor backend detected	2657	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2658	the given events it.
2479		2659
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2661
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2662	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2663	loop!).
2484		2664
2485	=back	2665	=back
…		…
2617		2797
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2798	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2799
2620	See the method-C<set> above for more details.	2800	See the method-C<set> above for more details.
2621		2801
2622	Example:	2802	Example: Use a plain function as callback.
2623		2803
2624	static void io_cb (ev::io &w, int revents) { }	2804	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2805	iow.set <io_cb> ();
2626		2806
2627	=item w->set (struct ev_loop *)	2807	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2845	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2846	the constructor.
2667		2847
2668	class myclass	2848	class myclass
2669	{	2849	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2850	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2852
2673	myclass (int fd)	2853	myclass (int fd)
2674	{	2854	{
2675	io .set <myclass, &myclass::io_cb > (this);	2855	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2856	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	2872	=item Perl
2693		2873
2694	The EV module implements the full libev API and is actually used to test	2874	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	2875	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	2876	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2877	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2878	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2879	and C<EV::Glib>).
2699		2880
2700	It can be found and installed via CPAN, its homepage is at	2881	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	2882	L<http://software.schmorp.de/pkg/EV>.
2702		2883
2703	=item Python	2884	=item Python
…		…
2882		3063
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3064	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3065
2885	Libev can be configured via a variety of preprocessor symbols you have to	3066	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3067	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3068	autoconf is documented for every option.
2888		3069
2889	=over 4	3070	=over 4
2890		3071
2891	=item EV_STANDALONE	3072	=item EV_STANDALONE
2892		3073
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3243	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3244	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3245	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3246	fine.
3066		3247
3067	If your embedding application does not need any priorities, defining these both to	3248	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3249	both to C<0> will save some memory and CPU.
3069		3250
3070	=item EV_PERIODIC_ENABLE	3251	=item EV_PERIODIC_ENABLE
3071		3252
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3253	If undefined or defined to be C<1>, then periodic timers are supported. If
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3254	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3261	code.
3081		3262
3082	=item EV_EMBED_ENABLE	3263	=item EV_EMBED_ENABLE
3083		3264
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3266	defined to be C<0>, then they are not. Embed watchers rely on most other
		3267	watcher types, which therefore must not be disabled.
3086		3268
3087	=item EV_STAT_ENABLE	3269	=item EV_STAT_ENABLE
3088		3270
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3272	defined to be C<0>, then they are not.
…		…
3122	two).	3304	two).
3123		3305
3124	=item EV_USE_4HEAP	3306	=item EV_USE_4HEAP
3125		3307
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3311	faster performance with many (thousands) of watchers.
3130		3312
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3314	(disabled).
3133		3315
3134	=item EV_HEAP_CACHE_AT	3316	=item EV_HEAP_CACHE_AT
3135		3317
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	3322	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3323	noticeably with many (hundreds) of watchers.
3142		3324
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3326	(disabled).
3145		3327
3146	=item EV_VERIFY	3328	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3334	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	3335	verification code will be called very frequently, which will slow down
3154	libev considerably.	3336	libev considerably.
3155		3337
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3339	C<0>.
3158		3340
3159	=item EV_COMMON	3341	=item EV_COMMON
3160		3342
3161	By default, all watchers have a C<void *data> member. By redefining	3343	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	3344	this macro to a something else you can include more and other types of
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	3361	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	3362	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	3363	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3364	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	3365	method calls instead of plain function calls in C++.
		3366
		3367	=back
3184		3368
3185	=head2 EXPORTED API SYMBOLS	3369	=head2 EXPORTED API SYMBOLS
3186		3370
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3371	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	3372	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3420
3237	#include "ev_cpp.h"	3421	#include "ev_cpp.h"
3238	#include "ev.c"	3422	#include "ev.c"
3239		3423
		3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3425
3241	=head1 THREADS AND COROUTINES	3426	=head2 THREADS AND COROUTINES
3242		3427
3243	=head2 THREADS	3428	=head3 THREADS
3244		3429
3245	Libev itself is thread-safe (unless the opposite is specifically	3430	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	3431	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	3432	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	3433	are no concurrent calls into any libev function with the same loop
		3434	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	3435	of course): libev guarantees that different event loops share no data
3250	need locking.	3436	structures that need any locking.
3251		3437
3252	Or to put it differently: calls with different loop parameters can be done	3438	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	3439	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	3440	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	3441	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	3442	a mutex per loop).
3257		3443
3258	Specifically to support threads (and signal handlers), libev implements	3444	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	3445	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	3446	concurrency on the same event loop, namely waking it up "from the
		3447	outside".
3261		3448
3262	If you want to know which design (one loop, locking, or multiple loops	3449	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	3450	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	3451	help you, but here is some generic advice:
3265		3452
3266	=over 4	3453	=over 4
3267		3454
3268	=item * most applications have a main thread: use the default libev loop	3455	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	3456	in that thread, or create a separate thread running only the default loop.
…		…
3281		3468
3282	Choosing a model is hard - look around, learn, know that usually you can do	3469	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	3470	better than you currently do :-)
3284		3471
3285	=item * often you need to talk to some other thread which blocks in the	3472	=item * often you need to talk to some other thread which blocks in the
		3473	event loop.
		3474
3286	event loop - C<ev_async> watchers can be used to wake them up from other	3475	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	3476	(or from signal contexts...).
3288		3477
3289	=item * some watcher types are only supported in the default loop - use	3478	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	3479	work in the default loop by registering the signal watcher with the
		3480	default loop and triggering an C<ev_async> watcher from the default loop
		3481	watcher callback into the event loop interested in the signal.
3291		3482
3292	=back	3483	=back
3293		3484
3294	=head2 COROUTINES	3485	=head3 COROUTINES
3295		3486
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	3487	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	3488	libev fully supports nesting calls to its functions from different
3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3299	different coroutines and switch freely between both coroutines running the	3490	different coroutines, and switch freely between both coroutines running the
3300	loop, as long as you don't confuse yourself). The only exception is that	3491	loop, as long as you don't confuse yourself). The only exception is that
3301	you must not do this from C<ev_periodic> reschedule callbacks.	3492	you must not do this from C<ev_periodic> reschedule callbacks.
3302		3493
3303	Care has been invested into making sure that libev does not keep local	3494	Care has been taken to ensure that libev does not keep local state inside
3304	state inside C<ev_loop>, and other calls do not usually allow coroutine	3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3305	switches.	3496	they do not clal any callbacks.
3306		3497
		3498	=head2 COMPILER WARNINGS
3307		3499
3308	=head1 COMPLEXITIES	3500	Depending on your compiler and compiler settings, you might get no or a
		3501	lot of warnings when compiling libev code. Some people are apparently
		3502	scared by this.
3309		3503
3310	In this section the complexities of (many of) the algorithms used inside	3504	However, these are unavoidable for many reasons. For one, each compiler
3311	libev will be explained. For complexity discussions about backends see the	3505	has different warnings, and each user has different tastes regarding
3312	documentation for C<ev_default_init>.	3506	warning options. "Warn-free" code therefore cannot be a goal except when
		3507	targeting a specific compiler and compiler-version.
3313		3508
3314	All of the following are about amortised time: If an array needs to be	3509	Another reason is that some compiler warnings require elaborate
3315	extended, libev needs to realloc and move the whole array, but this	3510	workarounds, or other changes to the code that make it less clear and less
3316	happens asymptotically never with higher number of elements, so O(1) might	3511	maintainable.
3317	mean it might do a lengthy realloc operation in rare cases, but on average
3318	it is much faster and asymptotically approaches constant time.
3319		3512
3320	=over 4	3513	And of course, some compiler warnings are just plain stupid, or simply
		3514	wrong (because they don't actually warn about the condition their message
		3515	seems to warn about). For example, certain older gcc versions had some
		3516	warnings that resulted an extreme number of false positives. These have
		3517	been fixed, but some people still insist on making code warn-free with
		3518	such buggy versions.
3321		3519
3322	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3520	While libev is written to generate as few warnings as possible,
		3521	"warn-free" code is not a goal, and it is recommended not to build libev
		3522	with any compiler warnings enabled unless you are prepared to cope with
		3523	them (e.g. by ignoring them). Remember that warnings are just that:
		3524	warnings, not errors, or proof of bugs.
3323		3525
3324	This means that, when you have a watcher that triggers in one hour and
3325	there are 100 watchers that would trigger before that then inserting will
3326	have to skip roughly seven (C<ld 100>) of these watchers.
3327		3526
3328	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3527	=head2 VALGRIND
3329		3528
3330	That means that changing a timer costs less than removing/adding them	3529	Valgrind has a special section here because it is a popular tool that is
3331	as only the relative motion in the event queue has to be paid for.	3530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3332		3531
3333	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3532	If you think you found a bug (memory leak, uninitialised data access etc.)
		3533	in libev, then check twice: If valgrind reports something like:
3334		3534
3335	These just add the watcher into an array or at the head of a list.	3535	==2274== definitely lost: 0 bytes in 0 blocks.
		3536	==2274== possibly lost: 0 bytes in 0 blocks.
		3537	==2274== still reachable: 256 bytes in 1 blocks.
3336		3538
3337	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3539	Then there is no memory leak, just as memory accounted to global variables
		3540	is not a memleak - the memory is still being refernced, and didn't leak.
3338		3541
3339	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3542	Similarly, under some circumstances, valgrind might report kernel bugs
		3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3544	although an acceptable workaround has been found here), or it might be
		3545	confused.
3340		3546
3341	These watchers are stored in lists then need to be walked to find the	3547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3342	correct watcher to remove. The lists are usually short (you don't usually	3548	make it into some kind of religion.
3343	have many watchers waiting for the same fd or signal).
3344		3549
3345	=item Finding the next timer in each loop iteration: O(1)	3550	If you are unsure about something, feel free to contact the mailing list
		3551	with the full valgrind report and an explanation on why you think this
		3552	is a bug in libev (best check the archives, too :). However, don't be
		3553	annoyed when you get a brisk "this is no bug" answer and take the chance
		3554	of learning how to interpret valgrind properly.
3346		3555
3347	By virtue of using a binary or 4-heap, the next timer is always found at a	3556	If you need, for some reason, empty reports from valgrind for your project
3348	fixed position in the storage array.	3557	I suggest using suppression lists.
3349		3558
3350	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3351		3559
3352	A change means an I/O watcher gets started or stopped, which requires	3560	=head1 PORTABILITY NOTES
3353	libev to recalculate its status (and possibly tell the kernel, depending
3354	on backend and whether C<ev_io_set> was used).
3355		3561
3356	=item Activating one watcher (putting it into the pending state): O(1)
3357
3358	=item Priority handling: O(number_of_priorities)
3359
3360	Priorities are implemented by allocating some space for each
3361	priority. When doing priority-based operations, libev usually has to
3362	linearly search all the priorities, but starting/stopping and activating
3363	watchers becomes O(1) w.r.t. priority handling.
3364
3365	=item Sending an ev_async: O(1)
3366
3367	=item Processing ev_async_send: O(number_of_async_watchers)
3368
3369	=item Processing signals: O(max_signal_number)
3370
3371	Sending involves a system call I<iff> there were no other C<ev_async_send>
3372	calls in the current loop iteration. Checking for async and signal events
3373	involves iterating over all running async watchers or all signal numbers.
3374
3375	=back
3376
3377
3378	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3379		3563
3380	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3381	requires, and its I/O model is fundamentally incompatible with the POSIX	3565	requires, and its I/O model is fundamentally incompatible with the POSIX
3382	model. Libev still offers limited functionality on this platform in	3566	model. Libev still offers limited functionality on this platform in
3383	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3394		3578
3395	Not a libev limitation but worth mentioning: windows apparently doesn't	3579	Not a libev limitation but worth mentioning: windows apparently doesn't
3396	accept large writes: instead of resulting in a partial write, windows will	3580	accept large writes: instead of resulting in a partial write, windows will
3397	either accept everything or return C<ENOBUFS> if the buffer is too large,	3581	either accept everything or return C<ENOBUFS> if the buffer is too large,
3398	so make sure you only write small amounts into your sockets (less than a	3582	so make sure you only write small amounts into your sockets (less than a
3399	megabyte seems safe, but thsi apparently depends on the amount of memory	3583	megabyte seems safe, but this apparently depends on the amount of memory
3400	available).	3584	available).
3401		3585
3402	Due to the many, low, and arbitrary limits on the win32 platform and	3586	Due to the many, low, and arbitrary limits on the win32 platform and
3403	the abysmal performance of winsockets, using a large number of sockets	3587	the abysmal performance of winsockets, using a large number of sockets
3404	is not recommended (and not reasonable). If your program needs to use	3588	is not recommended (and not reasonable). If your program needs to use
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3599	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3416		3600
3417	#include "ev.h"	3601	#include "ev.h"
3418		3602
3419	And compile the following F<evwrap.c> file into your project (make sure	3603	And compile the following F<evwrap.c> file into your project (make sure
3420	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3604	you do I<not> compile the F<ev.c> or any other embedded source files!):
3421		3605
3422	#include "evwrap.h"	3606	#include "evwrap.h"
3423	#include "ev.c"	3607	#include "ev.c"
3424		3608
3425	=over 4	3609	=over 4
…		…
3470	wrap all I/O functions and provide your own fd management, but the cost of	3654	wrap all I/O functions and provide your own fd management, but the cost of
3471	calling select (O(n²)) will likely make this unworkable.	3655	calling select (O(n²)) will likely make this unworkable.
3472		3656
3473	=back	3657	=back
3474		3658
3475
3476	=head1 PORTABILITY REQUIREMENTS	3659	=head2 PORTABILITY REQUIREMENTS
3477		3660
3478	In addition to a working ISO-C implementation, libev relies on a few	3661	In addition to a working ISO-C implementation and of course the
3479	additional extensions:	3662	backend-specific APIs, libev relies on a few additional extensions:
3480		3663
3481	=over 4	3664	=over 4
3482		3665
3483	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3666	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3484	calling conventions regardless of C<ev_watcher_type *>.	3667	calling conventions regardless of C<ev_watcher_type *>.
…		…
3490	calls them using an C<ev_watcher *> internally.	3673	calls them using an C<ev_watcher *> internally.
3491		3674
3492	=item C<sig_atomic_t volatile> must be thread-atomic as well	3675	=item C<sig_atomic_t volatile> must be thread-atomic as well
3493		3676
3494	The type C<sig_atomic_t volatile> (or whatever is defined as	3677	The type C<sig_atomic_t volatile> (or whatever is defined as
3495	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3496	threads. This is not part of the specification for C<sig_atomic_t>, but is	3679	threads. This is not part of the specification for C<sig_atomic_t>, but is
3497	believed to be sufficiently portable.	3680	believed to be sufficiently portable.
3498		3681
3499	=item C<sigprocmask> must work in a threaded environment	3682	=item C<sigprocmask> must work in a threaded environment
3500		3683
…		…
3509	except the initial one, and run the default loop in the initial thread as	3692	except the initial one, and run the default loop in the initial thread as
3510	well.	3693	well.
3511		3694
3512	=item C<long> must be large enough for common memory allocation sizes	3695	=item C<long> must be large enough for common memory allocation sizes
3513		3696
3514	To improve portability and simplify using libev, libev uses C<long>	3697	To improve portability and simplify its API, libev uses C<long> internally
3515	internally instead of C<size_t> when allocating its data structures. On	3698	instead of C<size_t> when allocating its data structures. On non-POSIX
3516	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3699	systems (Microsoft...) this might be unexpectedly low, but is still at
3517	is still at least 31 bits everywhere, which is enough for hundreds of	3700	least 31 bits everywhere, which is enough for hundreds of millions of
3518	millions of watchers.	3701	watchers.
3519		3702
3520	=item C<double> must hold a time value in seconds with enough accuracy	3703	=item C<double> must hold a time value in seconds with enough accuracy
3521		3704
3522	The type C<double> is used to represent timestamps. It is required to	3705	The type C<double> is used to represent timestamps. It is required to
3523	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3527	=back	3710	=back
3528		3711
3529	If you know of other additional requirements drop me a note.	3712	If you know of other additional requirements drop me a note.
3530		3713
3531		3714
3532	=head1 COMPILER WARNINGS	3715	=head1 ALGORITHMIC COMPLEXITIES
3533		3716
3534	Depending on your compiler and compiler settings, you might get no or a	3717	In this section the complexities of (many of) the algorithms used inside
3535	lot of warnings when compiling libev code. Some people are apparently	3718	libev will be documented. For complexity discussions about backends see
3536	scared by this.	3719	the documentation for C<ev_default_init>.
3537		3720
3538	However, these are unavoidable for many reasons. For one, each compiler	3721	All of the following are about amortised time: If an array needs to be
3539	has different warnings, and each user has different tastes regarding	3722	extended, libev needs to realloc and move the whole array, but this
3540	warning options. "Warn-free" code therefore cannot be a goal except when	3723	happens asymptotically rarer with higher number of elements, so O(1) might
3541	targeting a specific compiler and compiler-version.	3724	mean that libev does a lengthy realloc operation in rare cases, but on
		3725	average it is much faster and asymptotically approaches constant time.
3542		3726
3543	Another reason is that some compiler warnings require elaborate	3727	=over 4
3544	workarounds, or other changes to the code that make it less clear and less
3545	maintainable.
3546		3728
3547	And of course, some compiler warnings are just plain stupid, or simply	3729	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3548	wrong (because they don't actually warn about the condition their message
3549	seems to warn about).
3550		3730
3551	While libev is written to generate as few warnings as possible,	3731	This means that, when you have a watcher that triggers in one hour and
3552	"warn-free" code is not a goal, and it is recommended not to build libev	3732	there are 100 watchers that would trigger before that, then inserting will
3553	with any compiler warnings enabled unless you are prepared to cope with	3733	have to skip roughly seven (C<ld 100>) of these watchers.
3554	them (e.g. by ignoring them). Remember that warnings are just that:
3555	warnings, not errors, or proof of bugs.
3556		3734
		3735	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3557		3736
3558	=head1 VALGRIND	3737	That means that changing a timer costs less than removing/adding them,
		3738	as only the relative motion in the event queue has to be paid for.
3559		3739
3560	Valgrind has a special section here because it is a popular tool that is	3740	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3561	highly useful, but valgrind reports are very hard to interpret.
3562		3741
3563	If you think you found a bug (memory leak, uninitialised data access etc.)	3742	These just add the watcher into an array or at the head of a list.
3564	in libev, then check twice: If valgrind reports something like:
3565		3743
3566	==2274== definitely lost: 0 bytes in 0 blocks.	3744	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3567	==2274== possibly lost: 0 bytes in 0 blocks.
3568	==2274== still reachable: 256 bytes in 1 blocks.
3569		3745
3570	Then there is no memory leak. Similarly, under some circumstances,	3746	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3571	valgrind might report kernel bugs as if it were a bug in libev, or it
3572	might be confused (it is a very good tool, but only a tool).
3573		3747
3574	If you are unsure about something, feel free to contact the mailing list	3748	These watchers are stored in lists, so they need to be walked to find the
3575	with the full valgrind report and an explanation on why you think this is	3749	correct watcher to remove. The lists are usually short (you don't usually
3576	a bug in libev. However, don't be annoyed when you get a brisk "this is	3750	have many watchers waiting for the same fd or signal: one is typical, two
3577	no bug" answer and take the chance of learning how to interpret valgrind	3751	is rare).
3578	properly.
3579		3752
3580	If you need, for some reason, empty reports from valgrind for your project	3753	=item Finding the next timer in each loop iteration: O(1)
3581	I suggest using suppression lists.	3754
		3755	By virtue of using a binary or 4-heap, the next timer is always found at a
		3756	fixed position in the storage array.
		3757
		3758	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3759
		3760	A change means an I/O watcher gets started or stopped, which requires
		3761	libev to recalculate its status (and possibly tell the kernel, depending
		3762	on backend and whether C<ev_io_set> was used).
		3763
		3764	=item Activating one watcher (putting it into the pending state): O(1)
		3765
		3766	=item Priority handling: O(number_of_priorities)
		3767
		3768	Priorities are implemented by allocating some space for each
		3769	priority. When doing priority-based operations, libev usually has to
		3770	linearly search all the priorities, but starting/stopping and activating
		3771	watchers becomes O(1) with respect to priority handling.
		3772
		3773	=item Sending an ev_async: O(1)
		3774
		3775	=item Processing ev_async_send: O(number_of_async_watchers)
		3776
		3777	=item Processing signals: O(max_signal_number)
		3778
		3779	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3780	calls in the current loop iteration. Checking for async and signal events
		3781	involves iterating over all running async watchers or all signal numbers.
		3782
		3783	=back
3582		3784
3583		3785
3584	=head1 AUTHOR	3786	=head1 AUTHOR
3585		3787
3586	Marc Lehmann <libev@schmorp.de>.	3788	Marc Lehmann <libev@schmorp.de>.

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