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Revision 1.179 by root, Sat Sep 13 19:14:21 2008 UTC vs.
Revision 1.202 by root, Fri Oct 24 08:30:01 2008 UTC

…		…
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
14	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
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<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
396	Please note that epoll sometimes generates spurious notifications, so you	400	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	401	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.	402	(or space) is available.
399		403
400	Best performance from this backend is achieved by not unregistering all	404	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.	405	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	406	i.e. keep at least one watcher active per fd at all times. Stopping and
		407	starting a watcher (without re-setting it) also usually doesn't cause
		408	extra overhead.
403		409
404	While nominally embeddable in other event loops, this feature is broken in	410	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	411	all kernel versions tested so far.
406		412
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
408	C<EVBACKEND_POLL>.	414	C<EVBACKEND_POLL>.
409		415
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		417
412	Kqueue deserves special mention, as at the time of this writing, it	418	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	419	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	420	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"	421	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	422	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)	423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
418	system like NetBSD.
419		424
420	You still can embed kqueue into a normal poll or select backend and use it	425	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	426	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.	427	the target platform). See C<ev_embed> watchers for more info.
423		428
424	It scales in the same way as the epoll backend, but the interface to the	429	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	430	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	431	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	432	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	433	two event changes per incident. Support for C<fork ()> is very bad and it
429	drops fds silently in similarly hard-to-detect cases.	434	drops fds silently in similarly hard-to-detect cases.
430		435
431	This backend usually performs well under most conditions.	436	This backend usually performs well under most conditions.
432		437
433	While nominally embeddable in other event loops, this doesn't work	438	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	439	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	440	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	441	(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	442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
438	sockets.	443	using it only for sockets.
439		444
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	445	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	446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	447	C<NOTE_EOF>.
443		448
…		…
460	While this backend scales well, it requires one system call per active	465	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	466	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	468	might perform better.
464		469
465	On the positive side, ignoring the spurious readiness notifications, this	470	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	471	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	472	in all tests and is fully embeddable, which is a rare feat among the
		473	OS-specific backends.
468		474
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	476	C<EVBACKEND_POLL>.
471		477
472	=item C<EVBACKEND_ALL>	478	=item C<EVBACKEND_ALL>
…		…
481		487
482	If one or more of these are or'ed into the flags value, then only these	488	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	489	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.	490	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		491
486	The most typical usage is like this:	492	Example: This is the most typical usage.
487		493
488	if (!ev_default_loop (0))	494	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		496
491	Restrict libev to the select and poll backends, and do not allow	497	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	498	environment settings to be taken into account:
493		499
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		501
496	Use whatever libev has to offer, but make sure that kqueue is used if	502	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	503	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):	504	private event loop and only if you know the OS supports your types of
		505	fds):
499		506
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		508
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	509	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		510
…		…
561		568
562	=item ev_loop_fork (loop)	569	=item ev_loop_fork (loop)
563		570
564	Like C<ev_default_fork>, but acts on an event loop created by	571	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	572	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.	573	after fork that you want to re-use in the child, and how you do this is
		574	entirely your own problem.
567		575
568	=item int ev_is_default_loop (loop)	576	=item int ev_is_default_loop (loop)
569		577
570	Returns true when the given loop actually is the default loop, false otherwise.	578	Returns true when the given loop is, in fact, the default loop, and false
		579	otherwise.
571		580
572	=item unsigned int ev_loop_count (loop)	581	=item unsigned int ev_loop_count (loop)
573		582
574	Returns the count of loop iterations for the loop, which is identical to	583	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	584	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	622	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.	623	either no event watchers are active anymore or C<ev_unloop> was called.
615		624
616	Please note that an explicit C<ev_unloop> is usually better than	625	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	626	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	627	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	628	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.	629	of relying on its watchers stopping correctly, that is truly a thing of
		630	beauty.
621		631
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	632	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	633	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.	634	process in case there are no events and will return after one iteration of
		635	the loop.
625		636
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	637	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	638	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	639	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	640	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	641	user-registered callback will be called), and will return after one
		642	iteration of the loop.
		643
		644	This is useful if you are waiting for some external event in conjunction
		645	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	646	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.	647	usually a better approach for this kind of thing.
633		648
634	Here are the gory details of what C<ev_loop> does:	649	Here are the gory details of what C<ev_loop> does:
635		650
636	- Before the first iteration, call any pending watchers.	651	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	661	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	662	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	663	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	664	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	666	- Queue all expired timers.
652	- Queue all outstanding periodics.	667	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	668	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	669	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	670	- 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	671	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	672	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	689	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.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		691
677	This "unloop state" will be cleared when entering C<ev_loop> again.	692	This "unloop state" will be cleared when entering C<ev_loop> again.
678		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
679	=item ev_ref (loop)	696	=item ev_ref (loop)
680		697
681	=item ev_unref (loop)	698	=item ev_unref (loop)
682		699
683	Ref/unref can be used to add or remove a reference count on the event	700	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	701	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	702	count is nonzero, C<ev_loop> will not return on its own.
		703
686	a watcher you never unregister that should not keep C<ev_loop> from	704	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	705	from returning, call ev_unref() after starting, and ev_ref() before
		706	stopping it.
		707
688	example, libev itself uses this for its internal signal pipe: It is not	708	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	709	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	710	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	711	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>	712	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,	713	(but only if the watcher wasn't active before, or was active before,
694	respectively).	714	respectively).
695		715
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	717	running when nothing else is active.
698		718
699	struct ev_signal exitsig;	719	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	722	evf_unref (loop);
703		723
704	Example: For some weird reason, unregister the above signal handler again.	724	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>)	738	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	739	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	740	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	741	opportunities).
722		742
723	The background is that sometimes your program runs just fast enough to	743	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	744	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	745	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	746	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	747	overhead for the actual polling but can deliver many events at once.
728		748
729	By setting a higher I<io collect interval> you allow libev to spend more	749	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,	750	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	752	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.	753	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		754
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	755	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	756	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	757	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	758	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	759	value will not introduce any overhead in libev.
740		760
741	Many (busy) programs can usually benefit by setting the I/O collect	761	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	762	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	763	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>,	764	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.	772	they fire on, say, one-second boundaries only.
753		773
754	=item ev_loop_verify (loop)	774	=item ev_loop_verify (loop)
755		775
756	This function only does something when C<EV_VERIFY> support has been	776	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	777	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	778	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	779	is found to be inconsistent, it will print an error message to standard
		780	error and call C<abort ()>.
760		781
761	This can be used to catch bugs inside libev itself: under normal	782	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	783	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	784	data structures consistent.
764		785
765	=back	786	=back
766		787
767		788
768	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
769		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
		794
770	A watcher is a structure that you create and register to record your	795	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	796	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:	797	become readable, you would create an C<ev_io> watcher for that:
773		798
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	800	{
776	ev_io_stop (w);	801	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
778	}	803	}
779		804
780	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
781	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
782	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
785	ev_loop (loop, 0);	813	ev_loop (loop, 0);
786		814
787	As you can see, you are responsible for allocating the memory for your	815	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	816	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		821
791	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	823	(watcher *, callback)>, which expects a callback to be provided. This
793	callback gets invoked each time the event occurs (or, in the case of I/O	824	callback gets invoked each time the event occurs (or, in the case of I/O
794	watchers, each time the event loop detects that the file descriptor given	825	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	826	is readable and/or writable).
796		827
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	829	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	830	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
801		832
802	To make the watcher actually watch out for events, you have to start it	833	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	834	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	835	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		837
807	As long as your watcher is active (has been started but not stopped) you	838	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	839	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
810		841
811	Each and every callback receives the event loop pointer as first, the	842	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	843	registered watcher structure as second, and a bitset of received events as
813	third argument.	844	third argument.
814		845
…		…
877	=item C<EV_ERROR>	908	=item C<EV_ERROR>
878		909
879	An unspecified error has occurred, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	911	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	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
882	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
884		919
885	Libev will usually signal a few "dummy" events together with an error,	920	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	921	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	922	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	923	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	924	programs, though, as the fd could already be closed and reused for another
		925	thing, so beware.
890		926
891	=back	927	=back
892		928
893	=head2 GENERIC WATCHER FUNCTIONS	929	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		930
898	=over 4	931	=over 4
899		932
900	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
901		934
…		…
907	which rolls both calls into one.	940	which rolls both calls into one.
908		941
909	You can reinitialise a watcher at any time as long as it has been stopped	942	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.	943	(or never started) and there are no pending events outstanding.
911		944
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	945	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	946	int revents)>.
		947
		948	Example: Initialise an C<ev_io> watcher in two steps.
		949
		950	ev_io w;
		951	ev_init (&w, my_cb);
		952	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		953
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	954	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		955
917	This macro initialises the type-specific parts of a watcher. You need to	956	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	957	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	960	difference to the C<ev_init> macro).
922		961
923	Although some watcher types do not have type-specific arguments	962	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.	963	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		964
		965	See C<ev_init>, above, for an example.
		966
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	967	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		968
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	969	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	970	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	971	a watcher. The same limitations apply, of course.
931		972
		973	Example: Initialise and set an C<ev_io> watcher in one step.
		974
		975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		976
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		978
934	Starts (activates) the given watcher. Only active watchers will receive	979	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	980	events. If the watcher is already active nothing will happen.
936		981
		982	Example: Start the C<ev_io> watcher that is being abused as example in this
		983	whole section.
		984
		985	ev_io_start (EV_DEFAULT_UC, &w);
		986
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		988
939	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
940	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	993	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	994	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	995	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.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		997
946	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
947		999
948	Returns a true value iff the watcher is active (i.e. it has been started	1000	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	1001	and not yet been stopped). As long as a watcher is active you must not modify
…		…
991	The default priority used by watchers when no priority has been set is	1043	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1044	always C<0>, which is supposed to not be too high and not be too low :).
993		1045
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
995	fine, as long as you do not mind that the priority value you query might	1047	fine, as long as you do not mind that the priority value you query might
996	or might not have been adjusted to be within valid range.	1048	or might not have been clamped to the valid range.
997		1049
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1051
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1052	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	1053	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1054	can deal with that fact, as both are simply passed through to the
		1055	callback.
1003		1056
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1057	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1058
1006	If the watcher is pending, this function returns clears its pending status	1059	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	1060	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>.	1061	watcher isn't pending it does nothing and returns C<0>.
1009		1062
		1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1064	callback to be invoked, which can be accomplished with this function.
		1065
1010	=back	1066	=back
1011		1067
1012		1068
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1070
1015	Each watcher has, by default, a member C<void *data> that you can change	1071	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	1072	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	1073	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	1074	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	1075	member, you can also "subclass" the watcher type and provide your own
1020	data:	1076	data:
1021		1077
1022	struct my_io	1078	struct my_io
1023	{	1079	{
1024	struct ev_io io;	1080	ev_io io;
1025	int otherfd;	1081	int otherfd;
1026	void *somedata;	1082	void *somedata;
1027	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
1028	};	1084	};
1029		1085
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1089
1034	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1091	can cast it back to your own type:
1036		1092
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1094	{
1039	struct my_io *w = (struct my_io *)w_;	1095	struct my_io *w = (struct my_io *)w_;
1040	...	1096	...
1041	}	1097	}
1042		1098
…		…
1053	ev_timer t2;	1109	ev_timer t2;
1054	}	1110	}
1055		1111
1056	In this case getting the pointer to C<my_biggy> is a bit more	1112	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	1113	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	1114	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1116	programmers):
1060		1117
1061	#include <stddef.h>	1118	#include <stddef.h>
1062		1119
1063	static void	1120	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1122	{
1066	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1125	}
1069		1126
1070	static void	1127	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1129	{
1073	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1132	}
1076		1133
…		…
1104	In general you can register as many read and/or write event watchers per	1161	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	1162	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	1163	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1164	required if you know what you are doing).
1108		1165
1109	If you must do this, then force the use of a known-to-be-good backend	1166	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	1167	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1169
1113	Another thing you have to watch out for is that it is quite easy to	1170	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	1171	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	1172	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	1173	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	1174	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	1175	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	1176	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.	1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1178
1122	If you cannot run the fd in non-blocking mode (for example you should not	1179	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	1180	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	1181	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	1182	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1183	does this on its own, so its quite safe to use). Some people additionally
		1184	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1185	indefinitely.
		1186
		1187	But really, best use non-blocking mode.
1127		1188
1128	=head3 The special problem of disappearing file descriptors	1189	=head3 The special problem of disappearing file descriptors
1129		1190
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1191	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,	1192	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	1193	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	1194	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	1195	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	1196	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1197	fact, a different file descriptor.
1137		1198
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1230	C<EVBACKEND_POLL>.
1170		1231
1171	=head3 The special problem of SIGPIPE	1232	=head3 The special problem of SIGPIPE
1172		1233
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1234	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	1235	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	1236	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1237	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1238
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1239	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	1240	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).	1241	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1248	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1249
1189	=item ev_io_set (ev_io *, int fd, int events)	1250	=item ev_io_set (ev_io *, int fd, int events)
1190		1251
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1252	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	1253	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.	1254	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1255
1195	=item int fd [read-only]	1256	=item int fd [read-only]
1196		1257
1197	The file descriptor being watched.	1258	The file descriptor being watched.
1198		1259
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	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	1269	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
1210		1271
1211	static void	1272	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1273	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1274	{
1214	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1277	}
1217		1278
1218	...	1279	...
1219	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
1224		1285
1225		1286
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1289	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1290	given time, and optionally repeating in regular intervals after that.
1230		1291
1231	The timers are based on real time, that is, if you register an event that	1292	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	1293	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	1294	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1296	monotonic clock option helps a lot here).
1236		1297
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1298	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	1299	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1300	then order of execution is undefined.
		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
1240		1476
1241	=head3 The special problem of time updates	1477	=head3 The special problem of time updates
1242		1478
1243	Establishing the current time is a costly operation (it usually takes at	1479	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	1480	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	1481	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	1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1483	lots of events in one iteration.
1248		1484
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1485	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	1486	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	1487	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	1488	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).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1525
1290	If the timer is repeating, either start it if necessary (with the	1526	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.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1528
1293	This sounds a bit complicated, but here is a useful and typical	1529	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	1530	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		1531
1318	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1319		1533
1320	The current C<repeat> value. Will be used each time the watcher times out	1534	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),	1535	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.	1536	which is also when any modifications are taken into account.
1323		1537
1324	=back	1538	=back
1325		1539
1326	=head3 Examples	1540	=head3 Examples
1327		1541
1328	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1329		1543
1330	static void	1544	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1545	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1546	{
1333	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1334	}	1548	}
1335		1549
1336	struct ev_timer mytimer;	1550	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1339		1553
1340	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1555	inactivity.
1342		1556
1343	static void	1557	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1558	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1559	{
1346	.. ten seconds without any activity	1560	.. ten seconds without any activity
1347	}	1561	}
1348		1562
1349	struct ev_timer mytimer;	1563	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1353		1567
1354	// and in some piece of code that gets executed on any "activity":	1568	// 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	1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1585	roughly 10 seconds later as it uses a relative timeout).
1372		1586
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1587	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	1588	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1589	complicated rules.
1376		1590
1377	As with timers, the callback is guaranteed to be invoked only when the	1591	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	1592	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1593	during the same loop iteration, then order of execution is undefined.
1380		1594
1381	=head3 Watcher-Specific Functions and Data Members	1595	=head3 Watcher-Specific Functions and Data Members
1382		1596
1383	=over 4	1597	=over 4
1384		1598
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1600
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1388		1602
1389	Lots of arguments, lets sort it out... There are basically three modes of	1603	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1604	operation, and we will explain them from simplest to most complex:
1391		1605
1392	=over 4	1606	=over 4
1393		1607
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1609
1396	In this configuration the watcher triggers an event after the wall clock	1610	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	1611	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	1612	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.	1613	only run when the system clock reaches or surpasses this time.
1400		1614
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1616
1403	In this mode the watcher will always be scheduled to time out at the next	1617	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)	1618	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1619	and then repeat, regardless of any time jumps.
1406		1620
1407	This can be used to create timers that do not drift with respect to system	1621	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	1622	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1623	hour, on the hour:
1410		1624
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1625	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1626
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1627	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	1628	but only that the callback will be called when the system time shows a
…		…
1440		1654
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1655	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	1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1657	only event loop modification you are allowed to do).
1444		1658
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1447		1661
		1662	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1664	{
1450	return now + 60.;	1665	return now + 60.;
1451	}	1666	}
1452		1667
1453	It must return the next time to trigger, based on the passed time value	1668	It must return the next time to trigger, based on the passed time value
…		…
1490		1705
1491	The current interval value. Can be modified any time, but changes only	1706	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	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1708	called.
1494		1709
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1711
1497	The current reschedule callback, or C<0>, if this functionality is	1712	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	1713	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.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1715
1501	=back	1716	=back
1502		1717
1503	=head3 Examples	1718	=head3 Examples
1504		1719
1505	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1508		1723
1509	static void	1724	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1726	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1728	}
1514		1729
1515	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1518		1733
1519	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1520		1735
1521	#include <math.h>	1736	#include <math.h>
1522		1737
1523	static ev_tstamp	1738	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1740	{
1526	return fmod (now, 3600.) + 3600.;	1741	return now + (3600. - fmod (now, 3600.));
1527	}	1742	}
1528		1743
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1745
1531	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1532		1747
1533	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1537		1752
1538		1753
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1756	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	1757	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	1758	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1759	normal event processing, like any other event.
1545		1760
		1761	If you want signals asynchronously, just use C<sigaction> as you would
		1762	do without libev and forget about sharing the signal. You can even use
		1763	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1764
1546	You can configure as many watchers as you like per signal. Only when the	1765	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	1766	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	1767	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	1768	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	1769	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1770	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1771
1553	If possible and supported, libev will install its handlers with	1772	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1773	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	1774	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	1775	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1792
1574	=back	1793	=back
1575		1794
1576	=head3 Examples	1795	=head3 Examples
1577		1796
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1797	Example: Try to exit cleanly on SIGINT.
1579		1798
1580	static void	1799	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1801	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1802	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1803	}
1585		1804
1586	struct ev_signal signal_watcher;	1805	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1807	ev_signal_start (loop, &signal_watcher);
1589		1808
1590		1809
1591	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1592		1811
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1812	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	1813	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	1814	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	1815	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1816	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1817	forking and then immediately registering a watcher for the child is fine,
		1818	but forking and registering a watcher a few event loop iterations later is
		1819	not.
1598		1820
1599	Only the default event loop is capable of handling signals, and therefore	1821	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1822	you can only register child watchers in the default event loop.
1601		1823
1602	=head3 Process Interaction	1824	=head3 Process Interaction
…		…
1663	its completion.	1885	its completion.
1664		1886
1665	ev_child cw;	1887	ev_child cw;
1666		1888
1667	static void	1889	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1891	{
1670	ev_child_stop (EV_A_ w);	1892	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1894	}
1673		1895
…		…
1700	the stat buffer having unspecified contents.	1922	the stat buffer having unspecified contents.
1701		1923
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1924	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.	1925	relative and your working directory changes, the behaviour is undefined.
1704		1926
1705	Since there is no standard to do this, the portable implementation simply	1927	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	1928	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	1929	it changed somehow. You can specify a recommended polling interval for
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1930	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	1931	then a I<suitable, unspecified default> value will be used (which
1710	five seconds, although this might change dynamically). Libev will also	1932	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	1933	dynamically). Libev will also impose a minimum interval which is currently
1712	usually overkill.	1934	around C<0.1>, but thats usually overkill.
1713		1935
1714	This watcher type is not meant for massive numbers of stat watchers,	1936	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1937	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1938	resource-intensive.
1717		1939
1718	At the time of this writing, only the Linux inotify interface is	1940	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1941	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	1942	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	1943	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		1944
1727	=head3 ABI Issues (Largefile Support)	1945	=head3 ABI Issues (Largefile Support)
1728		1946
1729	Libev by default (unless the user overrides this) uses the default	1947	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1948	compilation environment, which means that on systems with large file
…		…
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1957	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	1958	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1959	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1960	default compilation environment.
1743		1961
1744	=head3 Inotify	1962	=head3 Inotify and Kqueue
1745		1963
1746	When C<inotify (7)> support has been compiled into libev (generally only	1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	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	1966	implementations) and present at runtime, it will be used to speed up
1748	change detection where possible. The inotify descriptor will be created lazily	1967	change detection where possible. The inotify descriptor will be created
1749	when the first C<ev_stat> watcher is being started.	1968	lazily when the first C<ev_stat> watcher is being started.
1750		1969
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1970	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	1971	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	1972	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.	1973	there are many cases where libev has to resort to regular C<stat> polling,
		1974	but as long as the path exists, libev usually gets away without polling.
1755		1975
1756	(There is no support for kqueue, as apparently it cannot be used to	1976	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	1977	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	1978	descriptor open on the object at all times, and detecting renames, unlinks
		1979	etc. is difficult.
1759		1980
1760	=head3 The special problem of stat time resolution	1981	=head3 The special problem of stat time resolution
1761		1982
1762	The C<stat ()> system call only supports full-second resolution portably, and	1983	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	1984	even on systems where the resolution is higher, most file systems still
1764	only support whole seconds.	1985	only support whole seconds.
1765		1986
1766	That means that, if the time is the only thing that changes, you can	1987	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	1988	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	1989	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	1990	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	1991	stat data does change in other ways (e.g. file size).
1771		1992
1772	The solution to this is to delay acting on a change for slightly more	1993	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	1994	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);	1995	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	1996	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2016	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	2017	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	2018	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.	2019	path for as long as the watcher is active.
1799		2020
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2021	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	2022	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2023	last change was detected).
1803		2024
1804	=item ev_stat_stat (loop, ev_stat *)	2025	=item ev_stat_stat (loop, ev_stat *)
1805		2026
1806	Updates the stat buffer immediately with new values. If you change the	2027	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	2028	watched path in your callback, you could call this function to avoid
…		…
1890		2111
1891		2112
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2113	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2114
1894	Idle watchers trigger events when no other events of the same or higher	2115	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	2116	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2117	as receiving "events").
1897		2118
1898	That is, as long as your process is busy handling sockets or timeouts	2119	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	2120	(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	2121	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	2122	are pending), the idle watchers are being called once per event loop
…		…
1926		2147
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1929		2150
1930	static void	2151	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2152	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2153	{
1933	free (w);	2154	free (w);
1934	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2156	// no longer anything immediate to do.
1936	}	2157	}
1937		2158
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1941		2162
1942		2163
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2165
1945	Prepare and check watchers are usually (but not always) used in tandem:	2166	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2167	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2168	afterwards.
1948		2169
1949	You I<must not> call C<ev_loop> or similar functions that enter	2170	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>	2171	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,	2174	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	2175	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2176	called in pairs bracketing the blocking call.
1956		2177
1957	Their main purpose is to integrate other event mechanisms into libev and	2178	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	2179	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	2180	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2181	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,	2182	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>	2183	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2184	watcher).
1964		2185
1965	This is done by examining in each prepare call which file descriptors need	2186	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	2187	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	2188	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	2189	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2190	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	2191	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,	2192	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2193	nevertheless, because you never know, you know?).
1973		2194
1974	As another example, the Perl Coro module uses these hooks to integrate	2195	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2196	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2197	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	2198	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	2201	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2202	low-priority coroutines to idle/background tasks).
1982		2203
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2204	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	2205	priority, to ensure that they are being run before any other watchers
		2206	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2207
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2208	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	2209	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2210	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	2211	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	2212	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	2213	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2214	others).
1992		2215
1993	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
1994		2217
1995	=over 4	2218	=over 4
1996		2219
…		…
1998		2221
1999	=item ev_check_init (ev_check *, callback)	2222	=item ev_check_init (ev_check *, callback)
2000		2223
2001	Initialises and configures the prepare or check watcher - they have no	2224	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>	2225	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.	2226	macros, but using them is utterly, utterly, utterly and completely
		2227	pointless.
2004		2228
2005	=back	2229	=back
2006		2230
2007	=head3 Examples	2231	=head3 Examples
2008		2232
…		…
2021		2245
2022	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
2023	static ev_timer tw;	2247	static ev_timer tw;
2024		2248
2025	static void	2249	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2250	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2251	{
2028	}	2252	}
2029		2253
2030	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
2031	static void	2255	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2256	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2257	{
2034	int timeout = 3600000;	2258	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2276	}
2053	}	2277	}
2054		2278
2055	// stop all watchers after blocking	2279	// stop all watchers after blocking
2056	static void	2280	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2281	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2282	{
2059	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
2060		2284
2061	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
2062	{	2286	{
…		…
2101	}	2325	}
2102		2326
2103	// do not ever call adns_afterpoll	2327	// do not ever call adns_afterpoll
2104		2328
2105	Method 4: Do not use a prepare or check watcher because the module you	2329	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	2330	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	2331	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	2332	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2333	this approach, effectively embedding EV as a client into the horrible
		2334	libglib event loop.
2110		2335
2111	static gint	2336	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2337	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2338	{
2114	int got_events = 0;	2339	int got_events = 0;
…		…
2145	prioritise I/O.	2370	prioritise I/O.
2146		2371
2147	As an example for a bug workaround, the kqueue backend might only support	2372	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	2373	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	2374	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	2375	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	2376	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	2377	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.	2378	C<kevent>, but at least you can use both mechanisms for what they are
		2379	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2380
2155	As for prioritising I/O: rarely you have the case where some fds have	2381	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	2382	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	2383	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	2384	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.	2385	the rest in a second one, and embed the second one in the first.
2160		2386
2161	As long as the watcher is active, the callback will be invoked every time	2387	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	2388	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	2389	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	2390	their callbacks (you could also start an idle watcher to give the embedded
…		…
2172	interested in that.	2398	interested in that.
2173		2399
2174	Also, there have not currently been made special provisions for forking:	2400	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,	2401	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	2402	but you will also have to stop and restart any C<ev_embed> watchers
2177	yourself.	2403	yourself - but you can use a fork watcher to handle this automatically,
		2404	and future versions of libev might do just that.
2178		2405
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2408	portable one.
2182		2409
2183	So when you want to use this feature you will always have to be prepared	2410	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	2411	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	2412	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.	2413	create it, and if that fails, use the normal loop for everything.
		2414
		2415	=head3 C<ev_embed> and fork
		2416
		2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2418	automatically be applied to the embedded loop as well, so no special
		2419	fork handling is required in that case. When the watcher is not running,
		2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2421	as applicable.
2187		2422
2188	=head3 Watcher-Specific Functions and Data Members	2423	=head3 Watcher-Specific Functions and Data Members
2189		2424
2190	=over 4	2425	=over 4
2191		2426
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2455	used).
2221		2456
2222	struct ev_loop *loop_hi = ev_default_init (0);	2457	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2458	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2459	ev_embed embed;
2225		2460
2226	// see if there is a chance of getting one that works	2461	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2462	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2478	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2480
2246	struct ev_loop *loop = ev_default_init (0);	2481	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2482	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2483	ev_embed embed;
2249		2484
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2487	{
2253	ev_embed_init (&embed, 0, loop_socket);	2488	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2544	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	2545	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2546	need elaborate support such as pthreads.
2312		2547
2313	That means that if you want to queue data, you have to provide your own	2548	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	2549	queue. But at least I can tell you how to implement locking around your
2315	queue:	2550	queue:
2316		2551
2317	=over 4	2552	=over 4
2318		2553
2319	=item queueing from a signal handler context	2554	=item queueing from a signal handler context
2320		2555
2321	To implement race-free queueing, you simply add to the queue in the signal	2556	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	2557	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2558	an example that does that for some fictitious SIGUSR1 handler:
2324		2559
2325	static ev_async mysig;	2560	static ev_async mysig;
2326		2561
2327	static void	2562	static void
2328	sigusr1_handler (void)	2563	sigusr1_handler (void)
…		…
2395		2630
2396	=item ev_async_init (ev_async *, callback)	2631	=item ev_async_init (ev_async *, callback)
2397		2632
2398	Initialises and configures the async watcher - it has no parameters of any	2633	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,	2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2400	believe me.	2635	trust me.
2401		2636
2402	=item ev_async_send (loop, ev_async *)	2637	=item ev_async_send (loop, ev_async *)
2403		2638
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2639	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	2640	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	2641	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	2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2643	section below on what exactly this means).
2409		2644
2410	This call incurs the overhead of a system call only once per loop iteration,	2645	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	2646	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2670	=over 4
2436		2671
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2673
2439	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2675	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	2676	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	2677	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2678	more watchers yourself.
2444		2679
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	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	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2682	the given C<fd> and C<events> set will be created and started.
2448		2683
2449	If C<timeout> is less than 0, then no timeout watcher will be	2684	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	2685	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	2686	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2687
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2688	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	2689	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>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2696
2459	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
2460	{	2698	{
		2699	if (revents & EV_READ)
		2700	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2701	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2702	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2703	}
2466		2704
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2706
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2708
2471	Feeds the given event set into the event loop, as if the specified event	2709	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	2710	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
2474		2712
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2714
2477	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2716	the given events it.
2479		2717
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2719
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2721	loop!).
2484		2722
2485	=back	2723	=back
…		…
2617		2855
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2857
2620	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
2621		2859
2622	Example:	2860	Example: Use a plain function as callback.
2623		2861
2624	static void io_cb (ev::io &w, int revents) { }	2862	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2863	iow.set <io_cb> ();
2626		2864
2627	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2904	the constructor.
2667		2905
2668	class myclass	2906	class myclass
2669	{	2907	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2910
2673	myclass (int fd)	2911	myclass (int fd)
2674	{	2912	{
2675	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	2930	=item Perl
2693		2931
2694	The EV module implements the full libev API and is actually used to test	2932	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,	2933	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	2934	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	2935	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>).	2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
2699		2938
2700	It can be found and installed via CPAN, its homepage is at	2939	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	2940	L<http://software.schmorp.de/pkg/EV>.
2702		2941
2703	=item Python	2942	=item Python
…		…
2719	=item D	2958	=item D
2720		2959
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2723		2962
		2963	=item Ocaml
		2964
		2965	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2967
2724	=back	2968	=back
2725		2969
2726		2970
2727	=head1 MACRO MAGIC	2971	=head1 MACRO MAGIC
2728		2972
…		…
2882		3126
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3127	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3128
2885	Libev can be configured via a variety of preprocessor symbols you have to	3129	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	3130	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3131	autoconf is documented for every option.
2888		3132
2889	=over 4	3133	=over 4
2890		3134
2891	=item EV_STANDALONE	3135	=item EV_STANDALONE
2892		3136
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3306	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	3307	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	3308	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3309	fine.
3066		3310
3067	If your embedding application does not need any priorities, defining these both to	3311	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3312	both to C<0> will save some memory and CPU.
3069		3313
3070	=item EV_PERIODIC_ENABLE	3314	=item EV_PERIODIC_ENABLE
3071		3315
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3316	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	3317	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3324	code.
3081		3325
3082	=item EV_EMBED_ENABLE	3326	=item EV_EMBED_ENABLE
3083		3327
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3329	defined to be C<0>, then they are not. Embed watchers rely on most other
		3330	watcher types, which therefore must not be disabled.
3086		3331
3087	=item EV_STAT_ENABLE	3332	=item EV_STAT_ENABLE
3088		3333
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not.
…		…
3122	two).	3367	two).
3123		3368
3124	=item EV_USE_4HEAP	3369	=item EV_USE_4HEAP
3125		3370
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3371	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	3372	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	3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3374	faster performance with many (thousands) of watchers.
3130		3375
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3377	(disabled).
3133		3378
3134	=item EV_HEAP_CACHE_AT	3379	=item EV_HEAP_CACHE_AT
3135		3380
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3381	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	3382	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>),	3383	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,	3384	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	3385	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3386	noticeably with many (hundreds) of watchers.
3142		3387
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3389	(disabled).
3145		3390
3146	=item EV_VERIFY	3391	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3397	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	3398	verification code will be called very frequently, which will slow down
3154	libev considerably.	3399	libev considerably.
3155		3400
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3402	C<0>.
3158		3403
3159	=item EV_COMMON	3404	=item EV_COMMON
3160		3405
3161	By default, all watchers have a C<void *data> member. By redefining	3406	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	3407	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	3424	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	3425	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	3426	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	3427	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++.	3428	method calls instead of plain function calls in C++.
		3429
		3430	=back
3184		3431
3185	=head2 EXPORTED API SYMBOLS	3432	=head2 EXPORTED API SYMBOLS
3186		3433
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3434	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	3435	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:	3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3483
3237	#include "ev_cpp.h"	3484	#include "ev_cpp.h"
3238	#include "ev.c"	3485	#include "ev.c"
3239		3486
		3487	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3488
3241	=head1 THREADS AND COROUTINES	3489	=head2 THREADS AND COROUTINES
3242		3490
3243	=head2 THREADS	3491	=head3 THREADS
3244		3492
3245	Libev itself is completely thread-safe, but it uses no locking. This	3493	All libev functions are reentrant and thread-safe unless explicitly
		3494	documented otherwise, but libev implements no locking itself. This means
3246	means that you can use as many loops as you want in parallel, as long as	3495	that you can use as many loops as you want in parallel, as long as there
3247	only one thread ever calls into one libev function with the same loop	3496	are no concurrent calls into any libev function with the same loop
3248	parameter.	3497	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3498	of course): libev guarantees that different event loops share no data
		3499	structures that need any locking.
3249		3500
3250	Or put differently: calls with different loop parameters can be done in	3501	Or to put it differently: calls with different loop parameters can be done
3251	parallel from multiple threads, calls with the same loop parameter must be	3502	concurrently from multiple threads, calls with the same loop parameter
3252	done serially (but can be done from different threads, as long as only one	3503	must be done serially (but can be done from different threads, as long as
3253	thread ever is inside a call at any point in time, e.g. by using a mutex	3504	only one thread ever is inside a call at any point in time, e.g. by using
3254	per loop).	3505	a mutex per loop).
		3506
		3507	Specifically to support threads (and signal handlers), libev implements
		3508	so-called C<ev_async> watchers, which allow some limited form of
		3509	concurrency on the same event loop, namely waking it up "from the
		3510	outside".
3255		3511
3256	If you want to know which design (one loop, locking, or multiple loops	3512	If you want to know which design (one loop, locking, or multiple loops
3257	without or something else still) is best for your problem, then I cannot	3513	without or something else still) is best for your problem, then I cannot
3258	help you. I can give some generic advice however:	3514	help you, but here is some generic advice:
3259		3515
3260	=over 4	3516	=over 4
3261		3517
3262	=item * most applications have a main thread: use the default libev loop	3518	=item * most applications have a main thread: use the default libev loop
3263	in that thread, or create a separate thread running only the default loop.	3519	in that thread, or create a separate thread running only the default loop.
…		…
3275		3531
3276	Choosing a model is hard - look around, learn, know that usually you can do	3532	Choosing a model is hard - look around, learn, know that usually you can do
3277	better than you currently do :-)	3533	better than you currently do :-)
3278		3534
3279	=item * often you need to talk to some other thread which blocks in the	3535	=item * often you need to talk to some other thread which blocks in the
		3536	event loop.
		3537
3280	event loop - C<ev_async> watchers can be used to wake them up from other	3538	C<ev_async> watchers can be used to wake them up from other threads safely
3281	threads safely (or from signal contexts...).	3539	(or from signal contexts...).
		3540
		3541	An example use would be to communicate signals or other events that only
		3542	work in the default loop by registering the signal watcher with the
		3543	default loop and triggering an C<ev_async> watcher from the default loop
		3544	watcher callback into the event loop interested in the signal.
3282		3545
3283	=back	3546	=back
3284		3547
3285	=head2 COROUTINES	3548	=head3 COROUTINES
3286		3549
3287	Libev is much more accommodating to coroutines ("cooperative threads"):	3550	Libev is very accommodating to coroutines ("cooperative threads"):
3288	libev fully supports nesting calls to it's functions from different	3551	libev fully supports nesting calls to its functions from different
3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3290	different coroutines and switch freely between both coroutines running the	3553	different coroutines, and switch freely between both coroutines running the
3291	loop, as long as you don't confuse yourself). The only exception is that	3554	loop, as long as you don't confuse yourself). The only exception is that
3292	you must not do this from C<ev_periodic> reschedule callbacks.	3555	you must not do this from C<ev_periodic> reschedule callbacks.
3293		3556
3294	Care has been invested into making sure that libev does not keep local	3557	Care has been taken to ensure that libev does not keep local state inside
3295	state inside C<ev_loop>, and other calls do not usually allow coroutine	3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3296	switches.	3559	they do not clal any callbacks.
3297		3560
		3561	=head2 COMPILER WARNINGS
3298		3562
3299	=head1 COMPLEXITIES	3563	Depending on your compiler and compiler settings, you might get no or a
		3564	lot of warnings when compiling libev code. Some people are apparently
		3565	scared by this.
3300		3566
3301	In this section the complexities of (many of) the algorithms used inside	3567	However, these are unavoidable for many reasons. For one, each compiler
3302	libev will be explained. For complexity discussions about backends see the	3568	has different warnings, and each user has different tastes regarding
3303	documentation for C<ev_default_init>.	3569	warning options. "Warn-free" code therefore cannot be a goal except when
		3570	targeting a specific compiler and compiler-version.
3304		3571
3305	All of the following are about amortised time: If an array needs to be	3572	Another reason is that some compiler warnings require elaborate
3306	extended, libev needs to realloc and move the whole array, but this	3573	workarounds, or other changes to the code that make it less clear and less
3307	happens asymptotically never with higher number of elements, so O(1) might	3574	maintainable.
3308	mean it might do a lengthy realloc operation in rare cases, but on average
3309	it is much faster and asymptotically approaches constant time.
3310		3575
3311	=over 4	3576	And of course, some compiler warnings are just plain stupid, or simply
		3577	wrong (because they don't actually warn about the condition their message
		3578	seems to warn about). For example, certain older gcc versions had some
		3579	warnings that resulted an extreme number of false positives. These have
		3580	been fixed, but some people still insist on making code warn-free with
		3581	such buggy versions.
3312		3582
3313	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3583	While libev is written to generate as few warnings as possible,
		3584	"warn-free" code is not a goal, and it is recommended not to build libev
		3585	with any compiler warnings enabled unless you are prepared to cope with
		3586	them (e.g. by ignoring them). Remember that warnings are just that:
		3587	warnings, not errors, or proof of bugs.
3314		3588
3315	This means that, when you have a watcher that triggers in one hour and
3316	there are 100 watchers that would trigger before that then inserting will
3317	have to skip roughly seven (C<ld 100>) of these watchers.
3318		3589
3319	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3590	=head2 VALGRIND
3320		3591
3321	That means that changing a timer costs less than removing/adding them	3592	Valgrind has a special section here because it is a popular tool that is
3322	as only the relative motion in the event queue has to be paid for.	3593	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3323		3594
3324	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3595	If you think you found a bug (memory leak, uninitialised data access etc.)
		3596	in libev, then check twice: If valgrind reports something like:
3325		3597
3326	These just add the watcher into an array or at the head of a list.	3598	==2274== definitely lost: 0 bytes in 0 blocks.
		3599	==2274== possibly lost: 0 bytes in 0 blocks.
		3600	==2274== still reachable: 256 bytes in 1 blocks.
3327		3601
3328	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3602	Then there is no memory leak, just as memory accounted to global variables
		3603	is not a memleak - the memory is still being refernced, and didn't leak.
3329		3604
3330	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3605	Similarly, under some circumstances, valgrind might report kernel bugs
		3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3607	although an acceptable workaround has been found here), or it might be
		3608	confused.
3331		3609
3332	These watchers are stored in lists then need to be walked to find the	3610	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3333	correct watcher to remove. The lists are usually short (you don't usually	3611	make it into some kind of religion.
3334	have many watchers waiting for the same fd or signal).
3335		3612
3336	=item Finding the next timer in each loop iteration: O(1)	3613	If you are unsure about something, feel free to contact the mailing list
		3614	with the full valgrind report and an explanation on why you think this
		3615	is a bug in libev (best check the archives, too :). However, don't be
		3616	annoyed when you get a brisk "this is no bug" answer and take the chance
		3617	of learning how to interpret valgrind properly.
3337		3618
3338	By virtue of using a binary or 4-heap, the next timer is always found at a	3619	If you need, for some reason, empty reports from valgrind for your project
3339	fixed position in the storage array.	3620	I suggest using suppression lists.
3340		3621
3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3342		3622
3343	A change means an I/O watcher gets started or stopped, which requires	3623	=head1 PORTABILITY NOTES
3344	libev to recalculate its status (and possibly tell the kernel, depending
3345	on backend and whether C<ev_io_set> was used).
3346		3624
3347	=item Activating one watcher (putting it into the pending state): O(1)
3348
3349	=item Priority handling: O(number_of_priorities)
3350
3351	Priorities are implemented by allocating some space for each
3352	priority. When doing priority-based operations, libev usually has to
3353	linearly search all the priorities, but starting/stopping and activating
3354	watchers becomes O(1) w.r.t. priority handling.
3355
3356	=item Sending an ev_async: O(1)
3357
3358	=item Processing ev_async_send: O(number_of_async_watchers)
3359
3360	=item Processing signals: O(max_signal_number)
3361
3362	Sending involves a system call I<iff> there were no other C<ev_async_send>
3363	calls in the current loop iteration. Checking for async and signal events
3364	involves iterating over all running async watchers or all signal numbers.
3365
3366	=back
3367
3368
3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3370		3626
3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3372	requires, and its I/O model is fundamentally incompatible with the POSIX	3628	requires, and its I/O model is fundamentally incompatible with the POSIX
3373	model. Libev still offers limited functionality on this platform in	3629	model. Libev still offers limited functionality on this platform in
3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3385		3641
3386	Not a libev limitation but worth mentioning: windows apparently doesn't	3642	Not a libev limitation but worth mentioning: windows apparently doesn't
3387	accept large writes: instead of resulting in a partial write, windows will	3643	accept large writes: instead of resulting in a partial write, windows will
3388	either accept everything or return C<ENOBUFS> if the buffer is too large,	3644	either accept everything or return C<ENOBUFS> if the buffer is too large,
3389	so make sure you only write small amounts into your sockets (less than a	3645	so make sure you only write small amounts into your sockets (less than a
3390	megabyte seems safe, but thsi apparently depends on the amount of memory	3646	megabyte seems safe, but this apparently depends on the amount of memory
3391	available).	3647	available).
3392		3648
3393	Due to the many, low, and arbitrary limits on the win32 platform and	3649	Due to the many, low, and arbitrary limits on the win32 platform and
3394	the abysmal performance of winsockets, using a large number of sockets	3650	the abysmal performance of winsockets, using a large number of sockets
3395	is not recommended (and not reasonable). If your program needs to use	3651	is not recommended (and not reasonable). If your program needs to use
…		…
3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3662	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3407		3663
3408	#include "ev.h"	3664	#include "ev.h"
3409		3665
3410	And compile the following F<evwrap.c> file into your project (make sure	3666	And compile the following F<evwrap.c> file into your project (make sure
3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3667	you do I<not> compile the F<ev.c> or any other embedded source files!):
3412		3668
3413	#include "evwrap.h"	3669	#include "evwrap.h"
3414	#include "ev.c"	3670	#include "ev.c"
3415		3671
3416	=over 4	3672	=over 4
…		…
3461	wrap all I/O functions and provide your own fd management, but the cost of	3717	wrap all I/O functions and provide your own fd management, but the cost of
3462	calling select (O(n²)) will likely make this unworkable.	3718	calling select (O(n²)) will likely make this unworkable.
3463		3719
3464	=back	3720	=back
3465		3721
3466
3467	=head1 PORTABILITY REQUIREMENTS	3722	=head2 PORTABILITY REQUIREMENTS
3468		3723
3469	In addition to a working ISO-C implementation, libev relies on a few	3724	In addition to a working ISO-C implementation and of course the
3470	additional extensions:	3725	backend-specific APIs, libev relies on a few additional extensions:
3471		3726
3472	=over 4	3727	=over 4
3473		3728
3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3729	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3475	calling conventions regardless of C<ev_watcher_type *>.	3730	calling conventions regardless of C<ev_watcher_type *>.
…		…
3481	calls them using an C<ev_watcher *> internally.	3736	calls them using an C<ev_watcher *> internally.
3482		3737
3483	=item C<sig_atomic_t volatile> must be thread-atomic as well	3738	=item C<sig_atomic_t volatile> must be thread-atomic as well
3484		3739
3485	The type C<sig_atomic_t volatile> (or whatever is defined as	3740	The type C<sig_atomic_t volatile> (or whatever is defined as
3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3741	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3487	threads. This is not part of the specification for C<sig_atomic_t>, but is	3742	threads. This is not part of the specification for C<sig_atomic_t>, but is
3488	believed to be sufficiently portable.	3743	believed to be sufficiently portable.
3489		3744
3490	=item C<sigprocmask> must work in a threaded environment	3745	=item C<sigprocmask> must work in a threaded environment
3491		3746
…		…
3500	except the initial one, and run the default loop in the initial thread as	3755	except the initial one, and run the default loop in the initial thread as
3501	well.	3756	well.
3502		3757
3503	=item C<long> must be large enough for common memory allocation sizes	3758	=item C<long> must be large enough for common memory allocation sizes
3504		3759
3505	To improve portability and simplify using libev, libev uses C<long>	3760	To improve portability and simplify its API, libev uses C<long> internally
3506	internally instead of C<size_t> when allocating its data structures. On	3761	instead of C<size_t> when allocating its data structures. On non-POSIX
3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3762	systems (Microsoft...) this might be unexpectedly low, but is still at
3508	is still at least 31 bits everywhere, which is enough for hundreds of	3763	least 31 bits everywhere, which is enough for hundreds of millions of
3509	millions of watchers.	3764	watchers.
3510		3765
3511	=item C<double> must hold a time value in seconds with enough accuracy	3766	=item C<double> must hold a time value in seconds with enough accuracy
3512		3767
3513	The type C<double> is used to represent timestamps. It is required to	3768	The type C<double> is used to represent timestamps. It is required to
3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3518	=back	3773	=back
3519		3774
3520	If you know of other additional requirements drop me a note.	3775	If you know of other additional requirements drop me a note.
3521		3776
3522		3777
3523	=head1 COMPILER WARNINGS	3778	=head1 ALGORITHMIC COMPLEXITIES
3524		3779
3525	Depending on your compiler and compiler settings, you might get no or a	3780	In this section the complexities of (many of) the algorithms used inside
3526	lot of warnings when compiling libev code. Some people are apparently	3781	libev will be documented. For complexity discussions about backends see
3527	scared by this.	3782	the documentation for C<ev_default_init>.
3528		3783
3529	However, these are unavoidable for many reasons. For one, each compiler	3784	All of the following are about amortised time: If an array needs to be
3530	has different warnings, and each user has different tastes regarding	3785	extended, libev needs to realloc and move the whole array, but this
3531	warning options. "Warn-free" code therefore cannot be a goal except when	3786	happens asymptotically rarer with higher number of elements, so O(1) might
3532	targeting a specific compiler and compiler-version.	3787	mean that libev does a lengthy realloc operation in rare cases, but on
		3788	average it is much faster and asymptotically approaches constant time.
3533		3789
3534	Another reason is that some compiler warnings require elaborate	3790	=over 4
3535	workarounds, or other changes to the code that make it less clear and less
3536	maintainable.
3537		3791
3538	And of course, some compiler warnings are just plain stupid, or simply	3792	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3539	wrong (because they don't actually warn about the condition their message
3540	seems to warn about).
3541		3793
3542	While libev is written to generate as few warnings as possible,	3794	This means that, when you have a watcher that triggers in one hour and
3543	"warn-free" code is not a goal, and it is recommended not to build libev	3795	there are 100 watchers that would trigger before that, then inserting will
3544	with any compiler warnings enabled unless you are prepared to cope with	3796	have to skip roughly seven (C<ld 100>) of these watchers.
3545	them (e.g. by ignoring them). Remember that warnings are just that:
3546	warnings, not errors, or proof of bugs.
3547		3797
		3798	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3548		3799
3549	=head1 VALGRIND	3800	That means that changing a timer costs less than removing/adding them,
		3801	as only the relative motion in the event queue has to be paid for.
3550		3802
3551	Valgrind has a special section here because it is a popular tool that is	3803	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3552	highly useful, but valgrind reports are very hard to interpret.
3553		3804
3554	If you think you found a bug (memory leak, uninitialised data access etc.)	3805	These just add the watcher into an array or at the head of a list.
3555	in libev, then check twice: If valgrind reports something like:
3556		3806
3557	==2274== definitely lost: 0 bytes in 0 blocks.	3807	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3558	==2274== possibly lost: 0 bytes in 0 blocks.
3559	==2274== still reachable: 256 bytes in 1 blocks.
3560		3808
3561	Then there is no memory leak. Similarly, under some circumstances,	3809	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3562	valgrind might report kernel bugs as if it were a bug in libev, or it
3563	might be confused (it is a very good tool, but only a tool).
3564		3810
3565	If you are unsure about something, feel free to contact the mailing list	3811	These watchers are stored in lists, so they need to be walked to find the
3566	with the full valgrind report and an explanation on why you think this is	3812	correct watcher to remove. The lists are usually short (you don't usually
3567	a bug in libev. However, don't be annoyed when you get a brisk "this is	3813	have many watchers waiting for the same fd or signal: one is typical, two
3568	no bug" answer and take the chance of learning how to interpret valgrind	3814	is rare).
3569	properly.
3570		3815
3571	If you need, for some reason, empty reports from valgrind for your project	3816	=item Finding the next timer in each loop iteration: O(1)
3572	I suggest using suppression lists.	3817
		3818	By virtue of using a binary or 4-heap, the next timer is always found at a
		3819	fixed position in the storage array.
		3820
		3821	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3822
		3823	A change means an I/O watcher gets started or stopped, which requires
		3824	libev to recalculate its status (and possibly tell the kernel, depending
		3825	on backend and whether C<ev_io_set> was used).
		3826
		3827	=item Activating one watcher (putting it into the pending state): O(1)
		3828
		3829	=item Priority handling: O(number_of_priorities)
		3830
		3831	Priorities are implemented by allocating some space for each
		3832	priority. When doing priority-based operations, libev usually has to
		3833	linearly search all the priorities, but starting/stopping and activating
		3834	watchers becomes O(1) with respect to priority handling.
		3835
		3836	=item Sending an ev_async: O(1)
		3837
		3838	=item Processing ev_async_send: O(number_of_async_watchers)
		3839
		3840	=item Processing signals: O(max_signal_number)
		3841
		3842	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3843	calls in the current loop iteration. Checking for async and signal events
		3844	involves iterating over all running async watchers or all signal numbers.
		3845
		3846	=back
3573		3847
3574		3848
3575	=head1 AUTHOR	3849	=head1 AUTHOR
3576		3850
3577	Marc Lehmann <libev@schmorp.de>.	3851	Marc Lehmann <libev@schmorp.de>.

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