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Revision 1.182 by root, Fri Sep 19 03:52:56 2008 UTC vs.
Revision 1.206 by root, Tue Oct 28 12:31:38 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
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		385
382	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	387	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	388	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	389	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	390
387	cases and requiring a system call per fd change, no fork support and bad	391	The epoll syscalls are the most misdesigned of the more advanced event
388	support for dup.	392	mechanisms: problems include silently dropping fds, requiring a system
		393	call per change per fd (and unnecessary guessing of parameters), problems
		394	with dup and so on. The biggest issue is fork races, however - if a
		395	program forks then I<both> parent and child process have to recreate the
		396	epoll set, which can take considerable time (one syscall per fd) and is of
		397	course hard to detect.
		398
		399	Epoll is also notoriously buggy - embedding epoll fds should work, but
		400	of course doesn't, and epoll just loves to report events for totally
		401	I<different> file descriptors (even already closed ones, so one cannot
		402	even remove them from the set) than registered in the set (especially
		403	on SMP systems). Libev tries to counter these spurious notifications by
		404	employing an additional generation counter and comparing that against the
		405	events to filter out spurious ones.
389		406
390	While stopping, setting and starting an I/O watcher in the same iteration	407	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	408	will result in some caching, there is still a system call per such incident
392	(because the fd could point to a different file description now), so its	409	(because the fd could point to a different file description now), so its
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	410	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
394	very well if you register events for both fds.	411	very well if you register events for both fds.
395		412
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399
400	Best performance from this backend is achieved by not unregistering all	413	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.	414	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	415	i.e. keep at least one watcher active per fd at all times. Stopping and
		416	starting a watcher (without re-setting it) also usually doesn't cause
		417	extra overhead. A fork can both result in spurious notifications as well
		418	as in libev having to destroy and recreate the epoll object, which can
		419	take considerable time and thus should be avoided.
403		420
404	While nominally embeddable in other event loops, this feature is broken in	421	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	422	all kernel versions tested so far.
406		423
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
408	C<EVBACKEND_POLL>.	425	C<EVBACKEND_POLL>.
409		426
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		428
412	Kqueue deserves special mention, as at the time of this writing, it	429	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	430	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	431	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"	432	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	433	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)	434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
418	system like NetBSD.
419		435
420	You still can embed kqueue into a normal poll or select backend and use it	436	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	437	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.	438	the target platform). See C<ev_embed> watchers for more info.
423		439
424	It scales in the same way as the epoll backend, but the interface to the	440	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	441	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	442	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	443	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	444	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		446	cases
430		447
431	This backend usually performs well under most conditions.	448	This backend usually performs well under most conditions.
432		449
433	While nominally embeddable in other event loops, this doesn't work	450	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	451	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	452	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	453	(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	454	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
438	sockets.	455	using it only for sockets.
439		456
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	457	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	458	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	459	C<NOTE_EOF>.
443		460
…		…
460	While this backend scales well, it requires one system call per active	477	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	478	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	480	might perform better.
464		481
465	On the positive side, ignoring the spurious readiness notifications, this	482	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	483	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	484	in all tests and is fully embeddable, which is a rare feat among the
		485	OS-specific backends (I vastly prefer correctness over speed hacks).
468		486
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	488	C<EVBACKEND_POLL>.
471		489
472	=item C<EVBACKEND_ALL>	490	=item C<EVBACKEND_ALL>
…		…
481		499
482	If one or more of these are or'ed into the flags value, then only these	500	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	501	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.	502	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		503
486	The most typical usage is like this:	504	Example: This is the most typical usage.
487		505
488	if (!ev_default_loop (0))	506	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		508
491	Restrict libev to the select and poll backends, and do not allow	509	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	510	environment settings to be taken into account:
493		511
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		513
496	Use whatever libev has to offer, but make sure that kqueue is used if	514	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	515	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):	516	private event loop and only if you know the OS supports your types of
		517	fds):
499		518
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		520
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	521	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		522
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	543	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	544	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	545	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	546	for example).
528		547
529	Note that certain global state, such as signal state, will not be freed by	548	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	549	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	550	as signal and child watchers) would need to be stopped manually.
532		551
533	In general it is not advisable to call this function except in the	552	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	553	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	554	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	555	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		580
562	=item ev_loop_fork (loop)	581	=item ev_loop_fork (loop)
563		582
564	Like C<ev_default_fork>, but acts on an event loop created by	583	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	584	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.	585	after fork that you want to re-use in the child, and how you do this is
		586	entirely your own problem.
567		587
568	=item int ev_is_default_loop (loop)	588	=item int ev_is_default_loop (loop)
569		589
570	Returns true when the given loop actually is the default loop, false otherwise.	590	Returns true when the given loop is, in fact, the default loop, and false
		591	otherwise.
571		592
572	=item unsigned int ev_loop_count (loop)	593	=item unsigned int ev_loop_count (loop)
573		594
574	Returns the count of loop iterations for the loop, which is identical to	595	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	596	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	634	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.	635	either no event watchers are active anymore or C<ev_unloop> was called.
615		636
616	Please note that an explicit C<ev_unloop> is usually better than	637	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	638	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	639	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	640	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.	641	of relying on its watchers stopping correctly, that is truly a thing of
		642	beauty.
621		643
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	644	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	645	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.	646	process in case there are no events and will return after one iteration of
		647	the loop.
625		648
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	649	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	650	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	651	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	652	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	653	user-registered callback will be called), and will return after one
		654	iteration of the loop.
		655
		656	This is useful if you are waiting for some external event in conjunction
		657	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	658	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.	659	usually a better approach for this kind of thing.
633		660
634	Here are the gory details of what C<ev_loop> does:	661	Here are the gory details of what C<ev_loop> does:
635		662
636	- Before the first iteration, call any pending watchers.	663	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	673	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	674	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	675	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	676	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	678	- Queue all expired timers.
652	- Queue all outstanding periodics.	679	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	680	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	681	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	682	- 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	683	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	684	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	701	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.	702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		703
677	This "unloop state" will be cleared when entering C<ev_loop> again.	704	This "unloop state" will be cleared when entering C<ev_loop> again.
678		705
		706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		707
679	=item ev_ref (loop)	708	=item ev_ref (loop)
680		709
681	=item ev_unref (loop)	710	=item ev_unref (loop)
682		711
683	Ref/unref can be used to add or remove a reference count on the event	712	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	713	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	714	count is nonzero, C<ev_loop> will not return on its own.
		715
686	a watcher you never unregister that should not keep C<ev_loop> from	716	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	717	from returning, call ev_unref() after starting, and ev_ref() before
		718	stopping it.
		719
688	example, libev itself uses this for its internal signal pipe: It is not	720	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	721	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	722	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	723	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>	724	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,	725	(but only if the watcher wasn't active before, or was active before,
694	respectively).	726	respectively).
695		727
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	729	running when nothing else is active.
698		730
699	struct ev_signal exitsig;	731	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	732	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	733	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	734	evf_unref (loop);
703		735
704	Example: For some weird reason, unregister the above signal handler again.	736	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>)	750	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	751	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	752	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	753	opportunities).
722		754
723	The background is that sometimes your program runs just fast enough to	755	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	756	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	757	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	758	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	759	overhead for the actual polling but can deliver many events at once.
728		760
729	By setting a higher I<io collect interval> you allow libev to spend more	761	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,	762	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	764	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.	765	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		766
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	767	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	768	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	769	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	770	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	771	value will not introduce any overhead in libev.
740		772
741	Many (busy) programs can usually benefit by setting the I/O collect	773	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	774	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	775	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>,	776	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.	784	they fire on, say, one-second boundaries only.
753		785
754	=item ev_loop_verify (loop)	786	=item ev_loop_verify (loop)
755		787
756	This function only does something when C<EV_VERIFY> support has been	788	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	789	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	790	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	791	is found to be inconsistent, it will print an error message to standard
		792	error and call C<abort ()>.
760		793
761	This can be used to catch bugs inside libev itself: under normal	794	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	795	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	796	data structures consistent.
764		797
765	=back	798	=back
766		799
767		800
768	=head1 ANATOMY OF A WATCHER	801	=head1 ANATOMY OF A WATCHER
769		802
		803	In the following description, uppercase C<TYPE> in names stands for the
		804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		805	watchers and C<ev_io_start> for I/O watchers.
		806
770	A watcher is a structure that you create and register to record your	807	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	808	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:	809	become readable, you would create an C<ev_io> watcher for that:
773		810
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	812	{
776	ev_io_stop (w);	813	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	814	ev_unloop (loop, EVUNLOOP_ALL);
778	}	815	}
779		816
780	struct ev_loop *loop = ev_default_loop (0);	817	struct ev_loop *loop = ev_default_loop (0);
		818
781	struct ev_io stdin_watcher;	819	ev_io stdin_watcher;
		820
782	ev_init (&stdin_watcher, my_cb);	821	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	823	ev_io_start (loop, &stdin_watcher);
		824
785	ev_loop (loop, 0);	825	ev_loop (loop, 0);
786		826
787	As you can see, you are responsible for allocating the memory for your	827	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,	828	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	829	stack).
		830
		831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		833
791	Each watcher structure must be initialised by a call to C<ev_init	834	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	835	(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	836	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	837	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	838	is readable and/or writable).
796		839
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	840	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	841	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	842	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	843	ev_TYPE_init (watcher *, callback, ...) >>.
801		844
802	To make the watcher actually watch out for events, you have to start it	845	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	846	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	847	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		849
807	As long as your watcher is active (has been started but not stopped) you	850	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	851	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	852	reinitialise it or call its C<ev_TYPE_set> macro.
810		853
811	Each and every callback receives the event loop pointer as first, the	854	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	855	registered watcher structure as second, and a bitset of received events as
813	third argument.	856	third argument.
814		857
…		…
877	=item C<EV_ERROR>	920	=item C<EV_ERROR>
878		921
879	An unspecified error has occurred, the watcher has been stopped. This might	922	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	923	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	924	ran out of memory, a file descriptor was found to be closed or any other
		925	problem. Libev considers these application bugs.
		926
882	problem. You best act on it by reporting the problem and somehow coping	927	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	928	watcher being stopped. Note that well-written programs should not receive
		929	an error ever, so when your watcher receives it, this usually indicates a
		930	bug in your program.
884		931
885	Libev will usually signal a few "dummy" events together with an error,	932	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	933	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	934	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	935	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	936	programs, though, as the fd could already be closed and reused for another
		937	thing, so beware.
890		938
891	=back	939	=back
892		940
893	=head2 GENERIC WATCHER FUNCTIONS	941	=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		942
898	=over 4	943	=over 4
899		944
900	=item C<ev_init> (ev_TYPE *watcher, callback)	945	=item C<ev_init> (ev_TYPE *watcher, callback)
901		946
…		…
907	which rolls both calls into one.	952	which rolls both calls into one.
908		953
909	You can reinitialise a watcher at any time as long as it has been stopped	954	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.	955	(or never started) and there are no pending events outstanding.
911		956
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	957	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	958	int revents)>.
		959
		960	Example: Initialise an C<ev_io> watcher in two steps.
		961
		962	ev_io w;
		963	ev_init (&w, my_cb);
		964	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		965
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	966	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		967
917	This macro initialises the type-specific parts of a watcher. You need to	968	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	969	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	972	difference to the C<ev_init> macro).
922		973
923	Although some watcher types do not have type-specific arguments	974	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.	975	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		976
		977	See C<ev_init>, above, for an example.
		978
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	979	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		980
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	981	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	982	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	983	a watcher. The same limitations apply, of course.
931		984
		985	Example: Initialise and set an C<ev_io> watcher in one step.
		986
		987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		988
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		990
934	Starts (activates) the given watcher. Only active watchers will receive	991	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	992	events. If the watcher is already active nothing will happen.
936		993
		994	Example: Start the C<ev_io> watcher that is being abused as example in this
		995	whole section.
		996
		997	ev_io_start (EV_DEFAULT_UC, &w);
		998
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1000
939	Stops the given watcher again (if active) and clears the pending	1001	Stops the given watcher if active, and clears the pending status (whether
		1002	the watcher was active or not).
		1003
940	status. It is possible that stopped watchers are pending (for example,	1004	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1005	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	1006	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	1007	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.	1008	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1009
946	=item bool ev_is_active (ev_TYPE *watcher)	1010	=item bool ev_is_active (ev_TYPE *watcher)
947		1011
948	Returns a true value iff the watcher is active (i.e. it has been started	1012	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	1013	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	1055	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 :).	1056	always C<0>, which is supposed to not be too high and not be too low :).
993		1057
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1058	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	1059	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.	1060	or might not have been clamped to the valid range.
997		1061
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1063
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1064	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	1065	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1066	can deal with that fact, as both are simply passed through to the
		1067	callback.
1003		1068
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1069	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1070
1006	If the watcher is pending, this function returns clears its pending status	1071	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	1072	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>.	1073	watcher isn't pending it does nothing and returns C<0>.
1009		1074
		1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1076	callback to be invoked, which can be accomplished with this function.
		1077
1010	=back	1078	=back
1011		1079
1012		1080
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1082
1015	Each watcher has, by default, a member C<void *data> that you can change	1083	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	1084	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	1085	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	1086	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	1087	member, you can also "subclass" the watcher type and provide your own
1020	data:	1088	data:
1021		1089
1022	struct my_io	1090	struct my_io
1023	{	1091	{
1024	struct ev_io io;	1092	ev_io io;
1025	int otherfd;	1093	int otherfd;
1026	void *somedata;	1094	void *somedata;
1027	struct whatever *mostinteresting;	1095	struct whatever *mostinteresting;
1028	};	1096	};
1029		1097
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1101
1034	And since your callback will be called with a pointer to the watcher, you	1102	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1103	can cast it back to your own type:
1036		1104
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1105	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1106	{
1039	struct my_io *w = (struct my_io *)w_;	1107	struct my_io *w = (struct my_io *)w_;
1040	...	1108	...
1041	}	1109	}
1042		1110
…		…
1053	ev_timer t2;	1121	ev_timer t2;
1054	}	1122	}
1055		1123
1056	In this case getting the pointer to C<my_biggy> is a bit more	1124	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	1125	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	1126	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1127	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1128	programmers):
1060		1129
1061	#include <stddef.h>	1130	#include <stddef.h>
1062		1131
1063	static void	1132	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1133	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1134	{
1066	struct my_biggy big = (struct my_biggy *	1135	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1136	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1137	}
1069		1138
1070	static void	1139	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1140	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1141	{
1073	struct my_biggy big = (struct my_biggy *	1142	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1143	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1144	}
1076		1145
…		…
1104	In general you can register as many read and/or write event watchers per	1173	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	1174	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	1175	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1176	required if you know what you are doing).
1108		1177
1109	If you must do this, then force the use of a known-to-be-good backend	1178	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	1179	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1181
1113	Another thing you have to watch out for is that it is quite easy to	1182	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	1183	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	1184	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	1185	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	1186	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	1187	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	1188	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.	1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1190
1122	If you cannot run the fd in non-blocking mode (for example you should not	1191	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	1192	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	1193	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	1194	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1195	does this on its own, so its quite safe to use). Some people additionally
		1196	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1197	indefinitely.
		1198
		1199	But really, best use non-blocking mode.
1127		1200
1128	=head3 The special problem of disappearing file descriptors	1201	=head3 The special problem of disappearing file descriptors
1129		1202
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1203	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,	1204	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	1205	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	1206	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	1207	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	1208	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1209	fact, a different file descriptor.
1137		1210
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1242	C<EVBACKEND_POLL>.
1170		1243
1171	=head3 The special problem of SIGPIPE	1244	=head3 The special problem of SIGPIPE
1172		1245
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1246	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	1247	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	1248	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1249	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1250
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1251	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	1252	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).	1253	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1260	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1261
1189	=item ev_io_set (ev_io *, int fd, int events)	1262	=item ev_io_set (ev_io *, int fd, int events)
1190		1263
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1264	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	1265	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.	1266	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1267
1195	=item int fd [read-only]	1268	=item int fd [read-only]
1196		1269
1197	The file descriptor being watched.	1270	The file descriptor being watched.
1198		1271
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1280	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	1281	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1282	attempt to read a whole line in the callback.
1210		1283
1211	static void	1284	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1285	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1286	{
1214	ev_io_stop (loop, w);	1287	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1288	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1289	}
1217		1290
1218	...	1291	...
1219	struct ev_loop *loop = ev_default_init (0);	1292	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1293	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1295	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1296	ev_loop (loop, 0);
1224		1297
1225		1298
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1301	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1302	given time, and optionally repeating in regular intervals after that.
1230		1303
1231	The timers are based on real time, that is, if you register an event that	1304	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	1305	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	1306	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1308	monotonic clock option helps a lot here).
1236		1309
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1310	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	1311	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1312	then order of execution is undefined.
		1313
		1314	=head3 Be smart about timeouts
		1315
		1316	Many real-world problems involve some kind of timeout, usually for error
		1317	recovery. A typical example is an HTTP request - if the other side hangs,
		1318	you want to raise some error after a while.
		1319
		1320	What follows are some ways to handle this problem, from obvious and
		1321	inefficient to smart and efficient.
		1322
		1323	In the following, a 60 second activity timeout is assumed - a timeout that
		1324	gets reset to 60 seconds each time there is activity (e.g. each time some
		1325	data or other life sign was received).
		1326
		1327	=over 4
		1328
		1329	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1330
		1331	This is the most obvious, but not the most simple way: In the beginning,
		1332	start the watcher:
		1333
		1334	ev_timer_init (timer, callback, 60., 0.);
		1335	ev_timer_start (loop, timer);
		1336
		1337	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1338	and start it again:
		1339
		1340	ev_timer_stop (loop, timer);
		1341	ev_timer_set (timer, 60., 0.);
		1342	ev_timer_start (loop, timer);
		1343
		1344	This is relatively simple to implement, but means that each time there is
		1345	some activity, libev will first have to remove the timer from its internal
		1346	data structure and then add it again. Libev tries to be fast, but it's
		1347	still not a constant-time operation.
		1348
		1349	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1350
		1351	This is the easiest way, and involves using C<ev_timer_again> instead of
		1352	C<ev_timer_start>.
		1353
		1354	To implement this, configure an C<ev_timer> with a C<repeat> value
		1355	of C<60> and then call C<ev_timer_again> at start and each time you
		1356	successfully read or write some data. If you go into an idle state where
		1357	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1358	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1359
		1360	That means you can ignore both the C<ev_timer_start> function and the
		1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1362	member and C<ev_timer_again>.
		1363
		1364	At start:
		1365
		1366	ev_timer_init (timer, callback);
		1367	timer->repeat = 60.;
		1368	ev_timer_again (loop, timer);
		1369
		1370	Each time there is some activity:
		1371
		1372	ev_timer_again (loop, timer);
		1373
		1374	It is even possible to change the time-out on the fly, regardless of
		1375	whether the watcher is active or not:
		1376
		1377	timer->repeat = 30.;
		1378	ev_timer_again (loop, timer);
		1379
		1380	This is slightly more efficient then stopping/starting the timer each time
		1381	you want to modify its timeout value, as libev does not have to completely
		1382	remove and re-insert the timer from/into its internal data structure.
		1383
		1384	It is, however, even simpler than the "obvious" way to do it.
		1385
		1386	=item 3. Let the timer time out, but then re-arm it as required.
		1387
		1388	This method is more tricky, but usually most efficient: Most timeouts are
		1389	relatively long compared to the intervals between other activity - in
		1390	our example, within 60 seconds, there are usually many I/O events with
		1391	associated activity resets.
		1392
		1393	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1394	but remember the time of last activity, and check for a real timeout only
		1395	within the callback:
		1396
		1397	ev_tstamp last_activity; // time of last activity
		1398
		1399	static void
		1400	callback (EV_P_ ev_timer *w, int revents)
		1401	{
		1402	ev_tstamp now = ev_now (EV_A);
		1403	ev_tstamp timeout = last_activity + 60.;
		1404
		1405	// if last_activity + 60. is older than now, we did time out
		1406	if (timeout < now)
		1407	{
		1408	// timeout occured, take action
		1409	}
		1410	else
		1411	{
		1412	// callback was invoked, but there was some activity, re-arm
		1413	// the watcher to fire in last_activity + 60, which is
		1414	// guaranteed to be in the future, so "again" is positive:
		1415	w->again = timeout - now;
		1416	ev_timer_again (EV_A_ w);
		1417	}
		1418	}
		1419
		1420	To summarise the callback: first calculate the real timeout (defined
		1421	as "60 seconds after the last activity"), then check if that time has
		1422	been reached, which means something I<did>, in fact, time out. Otherwise
		1423	the callback was invoked too early (C<timeout> is in the future), so
		1424	re-schedule the timer to fire at that future time, to see if maybe we have
		1425	a timeout then.
		1426
		1427	Note how C<ev_timer_again> is used, taking advantage of the
		1428	C<ev_timer_again> optimisation when the timer is already running.
		1429
		1430	This scheme causes more callback invocations (about one every 60 seconds
		1431	minus half the average time between activity), but virtually no calls to
		1432	libev to change the timeout.
		1433
		1434	To start the timer, simply initialise the watcher and set C<last_activity>
		1435	to the current time (meaning we just have some activity :), then call the
		1436	callback, which will "do the right thing" and start the timer:
		1437
		1438	ev_timer_init (timer, callback);
		1439	last_activity = ev_now (loop);
		1440	callback (loop, timer, EV_TIMEOUT);
		1441
		1442	And when there is some activity, simply store the current time in
		1443	C<last_activity>, no libev calls at all:
		1444
		1445	last_actiivty = ev_now (loop);
		1446
		1447	This technique is slightly more complex, but in most cases where the
		1448	time-out is unlikely to be triggered, much more efficient.
		1449
		1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1451	callback :) - just change the timeout and invoke the callback, which will
		1452	fix things for you.
		1453
		1454	=item 4. Wee, just use a double-linked list for your timeouts.
		1455
		1456	If there is not one request, but many thousands (millions...), all
		1457	employing some kind of timeout with the same timeout value, then one can
		1458	do even better:
		1459
		1460	When starting the timeout, calculate the timeout value and put the timeout
		1461	at the I<end> of the list.
		1462
		1463	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1464	the list is expected to fire (for example, using the technique #3).
		1465
		1466	When there is some activity, remove the timer from the list, recalculate
		1467	the timeout, append it to the end of the list again, and make sure to
		1468	update the C<ev_timer> if it was taken from the beginning of the list.
		1469
		1470	This way, one can manage an unlimited number of timeouts in O(1) time for
		1471	starting, stopping and updating the timers, at the expense of a major
		1472	complication, and having to use a constant timeout. The constant timeout
		1473	ensures that the list stays sorted.
		1474
		1475	=back
		1476
		1477	So which method the best?
		1478
		1479	Method #2 is a simple no-brain-required solution that is adequate in most
		1480	situations. Method #3 requires a bit more thinking, but handles many cases
		1481	better, and isn't very complicated either. In most case, choosing either
		1482	one is fine, with #3 being better in typical situations.
		1483
		1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1485	rather complicated, but extremely efficient, something that really pays
		1486	off after the first million or so of active timers, i.e. it's usually
		1487	overkill :)
1240		1488
1241	=head3 The special problem of time updates	1489	=head3 The special problem of time updates
1242		1490
1243	Establishing the current time is a costly operation (it usually takes at	1491	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	1492	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	1493	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	1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1495	lots of events in one iteration.
1248		1496
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1497	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	1498	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	1499	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	1500	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).	1536	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1537
1290	If the timer is repeating, either start it if necessary (with the	1538	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.	1539	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1540
1293	This sounds a bit complicated, but here is a useful and typical	1541	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	1542	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		1543
1318	=item ev_tstamp repeat [read-write]	1544	=item ev_tstamp repeat [read-write]
1319		1545
1320	The current C<repeat> value. Will be used each time the watcher times out	1546	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),	1547	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.	1548	which is also when any modifications are taken into account.
1323		1549
1324	=back	1550	=back
1325		1551
1326	=head3 Examples	1552	=head3 Examples
1327		1553
1328	Example: Create a timer that fires after 60 seconds.	1554	Example: Create a timer that fires after 60 seconds.
1329		1555
1330	static void	1556	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1557	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1558	{
1333	.. one minute over, w is actually stopped right here	1559	.. one minute over, w is actually stopped right here
1334	}	1560	}
1335		1561
1336	struct ev_timer mytimer;	1562	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1563	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1564	ev_timer_start (loop, &mytimer);
1339		1565
1340	Example: Create a timeout timer that times out after 10 seconds of	1566	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1567	inactivity.
1342		1568
1343	static void	1569	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1570	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1571	{
1346	.. ten seconds without any activity	1572	.. ten seconds without any activity
1347	}	1573	}
1348		1574
1349	struct ev_timer mytimer;	1575	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1577	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1353		1579
1354	// and in some piece of code that gets executed on any "activity":	1580	// 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	1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1597	roughly 10 seconds later as it uses a relative timeout).
1372		1598
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1599	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	1600	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1601	complicated rules.
1376		1602
1377	As with timers, the callback is guaranteed to be invoked only when the	1603	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	1604	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1605	during the same loop iteration, then order of execution is undefined.
1380		1606
1381	=head3 Watcher-Specific Functions and Data Members	1607	=head3 Watcher-Specific Functions and Data Members
1382		1608
1383	=over 4	1609	=over 4
1384		1610
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1612
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1388		1614
1389	Lots of arguments, lets sort it out... There are basically three modes of	1615	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1616	operation, and we will explain them from simplest to most complex:
1391		1617
1392	=over 4	1618	=over 4
1393		1619
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1621
1396	In this configuration the watcher triggers an event after the wall clock	1622	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	1623	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	1624	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.	1625	only run when the system clock reaches or surpasses this time.
1400		1626
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1628
1403	In this mode the watcher will always be scheduled to time out at the next	1629	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)	1630	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1631	and then repeat, regardless of any time jumps.
1406		1632
1407	This can be used to create timers that do not drift with respect to system	1633	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	1634	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1635	hour, on the hour:
1410		1636
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1637	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1638
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1639	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	1640	but only that the callback will be called when the system time shows a
…		…
1440		1666
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1667	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	1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1669	only event loop modification you are allowed to do).
1444		1670
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1671	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1672	*w, ev_tstamp now)>, e.g.:
1447		1673
		1674	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1675	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1676	{
1450	return now + 60.;	1677	return now + 60.;
1451	}	1678	}
1452		1679
1453	It must return the next time to trigger, based on the passed time value	1680	It must return the next time to trigger, based on the passed time value
…		…
1490		1717
1491	The current interval value. Can be modified any time, but changes only	1718	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	1719	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1720	called.
1494		1721
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1722	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1723
1497	The current reschedule callback, or C<0>, if this functionality is	1724	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	1725	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.	1726	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1727
1501	=back	1728	=back
1502		1729
1503	=head3 Examples	1730	=head3 Examples
1504		1731
1505	Example: Call a callback every hour, or, more precisely, whenever the	1732	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1733	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1734	potentially a lot of jitter, but good long-term stability.
1508		1735
1509	static void	1736	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1738	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1739	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1740	}
1514		1741
1515	struct ev_periodic hourly_tick;	1742	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1743	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1744	ev_periodic_start (loop, &hourly_tick);
1518		1745
1519	Example: The same as above, but use a reschedule callback to do it:	1746	Example: The same as above, but use a reschedule callback to do it:
1520		1747
1521	#include <math.h>	1748	#include <math.h>
1522		1749
1523	static ev_tstamp	1750	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1751	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1752	{
1526	return fmod (now, 3600.) + 3600.;	1753	return now + (3600. - fmod (now, 3600.));
1527	}	1754	}
1528		1755
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1756	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1757
1531	Example: Call a callback every hour, starting now:	1758	Example: Call a callback every hour, starting now:
1532		1759
1533	struct ev_periodic hourly_tick;	1760	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1761	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1762	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1763	ev_periodic_start (loop, &hourly_tick);
1537		1764
1538		1765
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1768	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	1769	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	1770	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1771	normal event processing, like any other event.
1545		1772
		1773	If you want signals asynchronously, just use C<sigaction> as you would
		1774	do without libev and forget about sharing the signal. You can even use
		1775	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1776
1546	You can configure as many watchers as you like per signal. Only when the	1777	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	1778	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	1779	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	1780	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	1781	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1782	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1783
1553	If possible and supported, libev will install its handlers with	1784	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1785	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	1786	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	1787	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1804
1574	=back	1805	=back
1575		1806
1576	=head3 Examples	1807	=head3 Examples
1577		1808
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1809	Example: Try to exit cleanly on SIGINT.
1579		1810
1580	static void	1811	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1813	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1814	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1815	}
1585		1816
1586	struct ev_signal signal_watcher;	1817	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1819	ev_signal_start (loop, &signal_watcher);
1589		1820
1590		1821
1591	=head2 C<ev_child> - watch out for process status changes	1822	=head2 C<ev_child> - watch out for process status changes
1592		1823
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1824	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	1825	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	1826	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	1827	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1828	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1829	forking and then immediately registering a watcher for the child is fine,
		1830	but forking and registering a watcher a few event loop iterations later is
		1831	not.
1598		1832
1599	Only the default event loop is capable of handling signals, and therefore	1833	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1834	you can only register child watchers in the default event loop.
1601		1835
1602	=head3 Process Interaction	1836	=head3 Process Interaction
…		…
1663	its completion.	1897	its completion.
1664		1898
1665	ev_child cw;	1899	ev_child cw;
1666		1900
1667	static void	1901	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1902	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1903	{
1670	ev_child_stop (EV_A_ w);	1904	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1905	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1906	}
1673		1907
…		…
1700	the stat buffer having unspecified contents.	1934	the stat buffer having unspecified contents.
1701		1935
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1936	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.	1937	relative and your working directory changes, the behaviour is undefined.
1704		1938
1705	Since there is no standard to do this, the portable implementation simply	1939	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	1940	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	1941	it changed somehow. You can specify a recommended polling interval for
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1942	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	1943	then a I<suitable, unspecified default> value will be used (which
1710	five seconds, although this might change dynamically). Libev will also	1944	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	1945	dynamically). Libev will also impose a minimum interval which is currently
1712	usually overkill.	1946	around C<0.1>, but thats usually overkill.
1713		1947
1714	This watcher type is not meant for massive numbers of stat watchers,	1948	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1949	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1950	resource-intensive.
1717		1951
1718	At the time of this writing, only the Linux inotify interface is	1952	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1953	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	1954	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	1955	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		1956
1727	=head3 ABI Issues (Largefile Support)	1957	=head3 ABI Issues (Largefile Support)
1728		1958
1729	Libev by default (unless the user overrides this) uses the default	1959	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1960	compilation environment, which means that on systems with large file
…		…
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1969	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	1970	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1971	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1972	default compilation environment.
1743		1973
1744	=head3 Inotify	1974	=head3 Inotify and Kqueue
1745		1975
1746	When C<inotify (7)> support has been compiled into libev (generally only	1976	When C<inotify (7)> support has been compiled into libev (generally
		1977	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	1978	implementations) and present at runtime, it will be used to speed up
1748	change detection where possible. The inotify descriptor will be created lazily	1979	change detection where possible. The inotify descriptor will be created
1749	when the first C<ev_stat> watcher is being started.	1980	lazily when the first C<ev_stat> watcher is being started.
1750		1981
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1982	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	1983	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	1984	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.	1985	there are many cases where libev has to resort to regular C<stat> polling,
		1986	but as long as the path exists, libev usually gets away without polling.
1755		1987
1756	(There is no support for kqueue, as apparently it cannot be used to	1988	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	1989	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	1990	descriptor open on the object at all times, and detecting renames, unlinks
		1991	etc. is difficult.
1759		1992
1760	=head3 The special problem of stat time resolution	1993	=head3 The special problem of stat time resolution
1761		1994
1762	The C<stat ()> system call only supports full-second resolution portably, and	1995	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	1996	even on systems where the resolution is higher, most file systems still
1764	only support whole seconds.	1997	only support whole seconds.
1765		1998
1766	That means that, if the time is the only thing that changes, you can	1999	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	2000	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	2001	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	2002	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2003	stat data does change in other ways (e.g. file size).
1771		2004
1772	The solution to this is to delay acting on a change for slightly more	2005	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	2006	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);	2007	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2008	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2028	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	2029	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	2030	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.	2031	path for as long as the watcher is active.
1799		2032
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2033	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	2034	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2035	last change was detected).
1803		2036
1804	=item ev_stat_stat (loop, ev_stat *)	2037	=item ev_stat_stat (loop, ev_stat *)
1805		2038
1806	Updates the stat buffer immediately with new values. If you change the	2039	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	2040	watched path in your callback, you could call this function to avoid
…		…
1890		2123
1891		2124
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2125	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2126
1894	Idle watchers trigger events when no other events of the same or higher	2127	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	2128	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2129	as receiving "events").
1897		2130
1898	That is, as long as your process is busy handling sockets or timeouts	2131	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	2132	(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	2133	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	2134	are pending), the idle watchers are being called once per event loop
…		…
1926		2159
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2160	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2161	callback, free it. Also, use no error checking, as usual.
1929		2162
1930	static void	2163	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2164	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2165	{
1933	free (w);	2166	free (w);
1934	// now do something you wanted to do when the program has	2167	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2168	// no longer anything immediate to do.
1936	}	2169	}
1937		2170
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2171	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2172	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2173	ev_idle_start (loop, idle_cb);
1941		2174
1942		2175
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2176	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2177
1945	Prepare and check watchers are usually (but not always) used in tandem:	2178	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2179	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2180	afterwards.
1948		2181
1949	You I<must not> call C<ev_loop> or similar functions that enter	2182	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>	2183	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,	2186	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	2187	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2188	called in pairs bracketing the blocking call.
1956		2189
1957	Their main purpose is to integrate other event mechanisms into libev and	2190	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	2191	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	2192	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2193	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,	2194	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>	2195	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2196	watcher).
1964		2197
1965	This is done by examining in each prepare call which file descriptors need	2198	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	2199	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	2200	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	2201	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2202	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	2203	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,	2204	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2205	nevertheless, because you never know, you know?).
1973		2206
1974	As another example, the Perl Coro module uses these hooks to integrate	2207	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2208	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2209	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	2210	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	2213	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2214	low-priority coroutines to idle/background tasks).
1982		2215
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2216	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	2217	priority, to ensure that they are being run before any other watchers
		2218	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2219
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2220	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	2221	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2222	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	2223	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	2224	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	2225	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2226	others).
1992		2227
1993	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1994		2229
1995	=over 4	2230	=over 4
1996		2231
…		…
1998		2233
1999	=item ev_check_init (ev_check *, callback)	2234	=item ev_check_init (ev_check *, callback)
2000		2235
2001	Initialises and configures the prepare or check watcher - they have no	2236	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>	2237	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.	2238	macros, but using them is utterly, utterly, utterly and completely
		2239	pointless.
2004		2240
2005	=back	2241	=back
2006		2242
2007	=head3 Examples	2243	=head3 Examples
2008		2244
…		…
2021		2257
2022	static ev_io iow [nfd];	2258	static ev_io iow [nfd];
2023	static ev_timer tw;	2259	static ev_timer tw;
2024		2260
2025	static void	2261	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2262	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2263	{
2028	}	2264	}
2029		2265
2030	// create io watchers for each fd and a timer before blocking	2266	// create io watchers for each fd and a timer before blocking
2031	static void	2267	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2268	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2269	{
2034	int timeout = 3600000;	2270	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2271	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2272	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2273	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2288	}
2053	}	2289	}
2054		2290
2055	// stop all watchers after blocking	2291	// stop all watchers after blocking
2056	static void	2292	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2293	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2294	{
2059	ev_timer_stop (loop, &tw);	2295	ev_timer_stop (loop, &tw);
2060		2296
2061	for (int i = 0; i < nfd; ++i)	2297	for (int i = 0; i < nfd; ++i)
2062	{	2298	{
…		…
2101	}	2337	}
2102		2338
2103	// do not ever call adns_afterpoll	2339	// do not ever call adns_afterpoll
2104		2340
2105	Method 4: Do not use a prepare or check watcher because the module you	2341	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	2342	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	2343	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	2344	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2345	this approach, effectively embedding EV as a client into the horrible
		2346	libglib event loop.
2110		2347
2111	static gint	2348	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2349	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2350	{
2114	int got_events = 0;	2351	int got_events = 0;
…		…
2145	prioritise I/O.	2382	prioritise I/O.
2146		2383
2147	As an example for a bug workaround, the kqueue backend might only support	2384	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	2385	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	2386	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	2387	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	2388	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	2389	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.	2390	C<kevent>, but at least you can use both mechanisms for what they are
		2391	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2392
2155	As for prioritising I/O: rarely you have the case where some fds have	2393	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	2394	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	2395	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	2396	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.	2397	the rest in a second one, and embed the second one in the first.
2160		2398
2161	As long as the watcher is active, the callback will be invoked every time	2399	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	2400	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	2401	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	2402	their callbacks (you could also start an idle watcher to give the embedded
…		…
2172	interested in that.	2410	interested in that.
2173		2411
2174	Also, there have not currently been made special provisions for forking:	2412	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,	2413	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	2414	but you will also have to stop and restart any C<ev_embed> watchers
2177	yourself.	2415	yourself - but you can use a fork watcher to handle this automatically,
		2416	and future versions of libev might do just that.
2178		2417
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2418	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2419	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2420	portable one.
2182		2421
2183	So when you want to use this feature you will always have to be prepared	2422	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	2423	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	2424	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.	2425	create it, and if that fails, use the normal loop for everything.
		2426
		2427	=head3 C<ev_embed> and fork
		2428
		2429	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2430	automatically be applied to the embedded loop as well, so no special
		2431	fork handling is required in that case. When the watcher is not running,
		2432	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2433	as applicable.
2187		2434
2188	=head3 Watcher-Specific Functions and Data Members	2435	=head3 Watcher-Specific Functions and Data Members
2189		2436
2190	=over 4	2437	=over 4
2191		2438
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2466	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2467	used).
2221		2468
2222	struct ev_loop *loop_hi = ev_default_init (0);	2469	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2470	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2471	ev_embed embed;
2225		2472
2226	// see if there is a chance of getting one that works	2473	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2474	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2475	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2476	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2490	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2491	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2492
2246	struct ev_loop *loop = ev_default_init (0);	2493	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2494	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2495	ev_embed embed;
2249		2496
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2497	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2498	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2499	{
2253	ev_embed_init (&embed, 0, loop_socket);	2500	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2556	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	2557	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2558	need elaborate support such as pthreads.
2312		2559
2313	That means that if you want to queue data, you have to provide your own	2560	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	2561	queue. But at least I can tell you how to implement locking around your
2315	queue:	2562	queue:
2316		2563
2317	=over 4	2564	=over 4
2318		2565
2319	=item queueing from a signal handler context	2566	=item queueing from a signal handler context
2320		2567
2321	To implement race-free queueing, you simply add to the queue in the signal	2568	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	2569	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2570	an example that does that for some fictitious SIGUSR1 handler:
2324		2571
2325	static ev_async mysig;	2572	static ev_async mysig;
2326		2573
2327	static void	2574	static void
2328	sigusr1_handler (void)	2575	sigusr1_handler (void)
…		…
2395		2642
2396	=item ev_async_init (ev_async *, callback)	2643	=item ev_async_init (ev_async *, callback)
2397		2644
2398	Initialises and configures the async watcher - it has no parameters of any	2645	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,	2646	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2400	believe me.	2647	trust me.
2401		2648
2402	=item ev_async_send (loop, ev_async *)	2649	=item ev_async_send (loop, ev_async *)
2403		2650
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2651	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	2652	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	2653	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	2654	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2655	section below on what exactly this means).
2409		2656
2410	This call incurs the overhead of a system call only once per loop iteration,	2657	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	2658	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2682	=over 4
2436		2683
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2684	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2685
2439	This function combines a simple timer and an I/O watcher, calls your	2686	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2687	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	2688	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	2689	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2690	more watchers yourself.
2444		2691
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2692	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	2693	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2694	the given C<fd> and C<events> set will be created and started.
2448		2695
2449	If C<timeout> is less than 0, then no timeout watcher will be	2696	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	2697	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	2698	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2699
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2700	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	2701	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>	2702	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2703	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2704	a timeout and an io event at the same time - you probably should give io
		2705	events precedence.
		2706
		2707	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2708
2459	static void stdin_ready (int revents, void *arg)	2709	static void stdin_ready (int revents, void *arg)
2460	{	2710	{
		2711	if (revents & EV_READ)
		2712	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2713	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2714	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2715	}
2466		2716
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2717	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2718
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2719	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2720
2471	Feeds the given event set into the event loop, as if the specified event	2721	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	2722	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2723	initialised but not necessarily started event watcher).
2474		2724
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2725	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2726
2477	Feed an event on the given fd, as if a file descriptor backend detected	2727	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2728	the given events it.
2479		2729
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2730	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2731
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2732	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2733	loop!).
2484		2734
2485	=back	2735	=back
…		…
2617		2867
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2868	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2869
2620	See the method-C<set> above for more details.	2870	See the method-C<set> above for more details.
2621		2871
2622	Example:	2872	Example: Use a plain function as callback.
2623		2873
2624	static void io_cb (ev::io &w, int revents) { }	2874	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2875	iow.set <io_cb> ();
2626		2876
2627	=item w->set (struct ev_loop *)	2877	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2915	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2916	the constructor.
2667		2917
2668	class myclass	2918	class myclass
2669	{	2919	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2920	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2921	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2922
2673	myclass (int fd)	2923	myclass (int fd)
2674	{	2924	{
2675	io .set <myclass, &myclass::io_cb > (this);	2925	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2926	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	2942	=item Perl
2693		2943
2694	The EV module implements the full libev API and is actually used to test	2944	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,	2945	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	2946	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	2947	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>).	2948	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2949	and C<EV::Glib>).
2699		2950
2700	It can be found and installed via CPAN, its homepage is at	2951	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	2952	L<http://software.schmorp.de/pkg/EV>.
2702		2953
2703	=item Python	2954	=item Python
…		…
2719	=item D	2970	=item D
2720		2971
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2972	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>.	2973	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2723		2974
		2975	=item Ocaml
		2976
		2977	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2978	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2979
2724	=back	2980	=back
2725		2981
2726		2982
2727	=head1 MACRO MAGIC	2983	=head1 MACRO MAGIC
2728		2984
…		…
2882		3138
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3139	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3140
2885	Libev can be configured via a variety of preprocessor symbols you have to	3141	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	3142	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3143	autoconf is documented for every option.
2888		3144
2889	=over 4	3145	=over 4
2890		3146
2891	=item EV_STANDALONE	3147	=item EV_STANDALONE
2892		3148
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3318	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	3319	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	3320	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3321	fine.
3066		3322
3067	If your embedding application does not need any priorities, defining these both to	3323	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3324	both to C<0> will save some memory and CPU.
3069		3325
3070	=item EV_PERIODIC_ENABLE	3326	=item EV_PERIODIC_ENABLE
3071		3327
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3328	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	3329	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3336	code.
3081		3337
3082	=item EV_EMBED_ENABLE	3338	=item EV_EMBED_ENABLE
3083		3339
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3340	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3341	defined to be C<0>, then they are not. Embed watchers rely on most other
		3342	watcher types, which therefore must not be disabled.
3086		3343
3087	=item EV_STAT_ENABLE	3344	=item EV_STAT_ENABLE
3088		3345
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3346	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3347	defined to be C<0>, then they are not.
…		…
3122	two).	3379	two).
3123		3380
3124	=item EV_USE_4HEAP	3381	=item EV_USE_4HEAP
3125		3382
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3383	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	3384	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	3385	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3386	faster performance with many (thousands) of watchers.
3130		3387
3131	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>
3132	(disabled).	3389	(disabled).
3133		3390
3134	=item EV_HEAP_CACHE_AT	3391	=item EV_HEAP_CACHE_AT
3135		3392
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3393	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	3394	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>),	3395	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,	3396	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	3397	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3398	noticeably with many (hundreds) of watchers.
3142		3399
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3400	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3401	(disabled).
3145		3402
3146	=item EV_VERIFY	3403	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3409	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	3410	verification code will be called very frequently, which will slow down
3154	libev considerably.	3411	libev considerably.
3155		3412
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3413	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3414	C<0>.
3158		3415
3159	=item EV_COMMON	3416	=item EV_COMMON
3160		3417
3161	By default, all watchers have a C<void *data> member. By redefining	3418	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	3419	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	3436	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	3437	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	3438	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	3439	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++.	3440	method calls instead of plain function calls in C++.
		3441
		3442	=back
3184		3443
3185	=head2 EXPORTED API SYMBOLS	3444	=head2 EXPORTED API SYMBOLS
3186		3445
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3446	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	3447	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:	3494	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3495
3237	#include "ev_cpp.h"	3496	#include "ev_cpp.h"
3238	#include "ev.c"	3497	#include "ev.c"
3239		3498
		3499	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3500
3241	=head1 THREADS AND COROUTINES	3501	=head2 THREADS AND COROUTINES
3242		3502
3243	=head2 THREADS	3503	=head3 THREADS
3244		3504
3245	Libev itself is thread-safe (unless the opposite is specifically	3505	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	3506	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	3507	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	3508	are no concurrent calls into any libev function with the same loop
		3509	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	3510	of course): libev guarantees that different event loops share no data
3250	need locking.	3511	structures that need any locking.
3251		3512
3252	Or to put it differently: calls with different loop parameters can be done	3513	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	3514	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	3515	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	3516	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	3517	a mutex per loop).
3257		3518
3258	Specifically to support threads (and signal handlers), libev implements	3519	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	3520	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	3521	concurrency on the same event loop, namely waking it up "from the
		3522	outside".
3261		3523
3262	If you want to know which design (one loop, locking, or multiple loops	3524	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	3525	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	3526	help you, but here is some generic advice:
3265		3527
3266	=over 4	3528	=over 4
3267		3529
3268	=item * most applications have a main thread: use the default libev loop	3530	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	3531	in that thread, or create a separate thread running only the default loop.
…		…
3293	default loop and triggering an C<ev_async> watcher from the default loop	3555	default loop and triggering an C<ev_async> watcher from the default loop
3294	watcher callback into the event loop interested in the signal.	3556	watcher callback into the event loop interested in the signal.
3295		3557
3296	=back	3558	=back
3297		3559
3298	=head2 COROUTINES	3560	=head3 COROUTINES
3299		3561
3300	Libev is much more accommodating to coroutines ("cooperative threads"):	3562	Libev is very accommodating to coroutines ("cooperative threads"):
3301	libev fully supports nesting calls to it's functions from different	3563	libev fully supports nesting calls to its functions from different
3302	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3564	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3303	different coroutines and switch freely between both coroutines running the	3565	different coroutines, and switch freely between both coroutines running the
3304	loop, as long as you don't confuse yourself). The only exception is that	3566	loop, as long as you don't confuse yourself). The only exception is that
3305	you must not do this from C<ev_periodic> reschedule callbacks.	3567	you must not do this from C<ev_periodic> reschedule callbacks.
3306		3568
3307	Care has been taken to ensure that libev does not keep local state inside	3569	Care has been taken to ensure that libev does not keep local state inside
3308	C<ev_loop>, and other calls do not usually allow coroutine switches.	3570	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3571	they do not clal any callbacks.
3309		3572
		3573	=head2 COMPILER WARNINGS
3310		3574
3311	=head1 COMPLEXITIES	3575	Depending on your compiler and compiler settings, you might get no or a
		3576	lot of warnings when compiling libev code. Some people are apparently
		3577	scared by this.
3312		3578
3313	In this section the complexities of (many of) the algorithms used inside	3579	However, these are unavoidable for many reasons. For one, each compiler
3314	libev will be explained. For complexity discussions about backends see the	3580	has different warnings, and each user has different tastes regarding
3315	documentation for C<ev_default_init>.	3581	warning options. "Warn-free" code therefore cannot be a goal except when
		3582	targeting a specific compiler and compiler-version.
3316		3583
3317	All of the following are about amortised time: If an array needs to be	3584	Another reason is that some compiler warnings require elaborate
3318	extended, libev needs to realloc and move the whole array, but this	3585	workarounds, or other changes to the code that make it less clear and less
3319	happens asymptotically never with higher number of elements, so O(1) might	3586	maintainable.
3320	mean it might do a lengthy realloc operation in rare cases, but on average
3321	it is much faster and asymptotically approaches constant time.
3322		3587
3323	=over 4	3588	And of course, some compiler warnings are just plain stupid, or simply
		3589	wrong (because they don't actually warn about the condition their message
		3590	seems to warn about). For example, certain older gcc versions had some
		3591	warnings that resulted an extreme number of false positives. These have
		3592	been fixed, but some people still insist on making code warn-free with
		3593	such buggy versions.
3324		3594
3325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3595	While libev is written to generate as few warnings as possible,
		3596	"warn-free" code is not a goal, and it is recommended not to build libev
		3597	with any compiler warnings enabled unless you are prepared to cope with
		3598	them (e.g. by ignoring them). Remember that warnings are just that:
		3599	warnings, not errors, or proof of bugs.
3326		3600
3327	This means that, when you have a watcher that triggers in one hour and
3328	there are 100 watchers that would trigger before that then inserting will
3329	have to skip roughly seven (C<ld 100>) of these watchers.
3330		3601
3331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3602	=head2 VALGRIND
3332		3603
3333	That means that changing a timer costs less than removing/adding them	3604	Valgrind has a special section here because it is a popular tool that is
3334	as only the relative motion in the event queue has to be paid for.	3605	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3335		3606
3336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3607	If you think you found a bug (memory leak, uninitialised data access etc.)
		3608	in libev, then check twice: If valgrind reports something like:
3337		3609
3338	These just add the watcher into an array or at the head of a list.	3610	==2274== definitely lost: 0 bytes in 0 blocks.
		3611	==2274== possibly lost: 0 bytes in 0 blocks.
		3612	==2274== still reachable: 256 bytes in 1 blocks.
3339		3613
3340	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3614	Then there is no memory leak, just as memory accounted to global variables
		3615	is not a memleak - the memory is still being refernced, and didn't leak.
3341		3616
3342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3617	Similarly, under some circumstances, valgrind might report kernel bugs
		3618	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3619	although an acceptable workaround has been found here), or it might be
		3620	confused.
3343		3621
3344	These watchers are stored in lists then need to be walked to find the	3622	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3345	correct watcher to remove. The lists are usually short (you don't usually	3623	make it into some kind of religion.
3346	have many watchers waiting for the same fd or signal).
3347		3624
3348	=item Finding the next timer in each loop iteration: O(1)	3625	If you are unsure about something, feel free to contact the mailing list
		3626	with the full valgrind report and an explanation on why you think this
		3627	is a bug in libev (best check the archives, too :). However, don't be
		3628	annoyed when you get a brisk "this is no bug" answer and take the chance
		3629	of learning how to interpret valgrind properly.
3349		3630
3350	By virtue of using a binary or 4-heap, the next timer is always found at a	3631	If you need, for some reason, empty reports from valgrind for your project
3351	fixed position in the storage array.	3632	I suggest using suppression lists.
3352		3633
3353	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3354		3634
3355	A change means an I/O watcher gets started or stopped, which requires	3635	=head1 PORTABILITY NOTES
3356	libev to recalculate its status (and possibly tell the kernel, depending
3357	on backend and whether C<ev_io_set> was used).
3358		3636
3359	=item Activating one watcher (putting it into the pending state): O(1)
3360
3361	=item Priority handling: O(number_of_priorities)
3362
3363	Priorities are implemented by allocating some space for each
3364	priority. When doing priority-based operations, libev usually has to
3365	linearly search all the priorities, but starting/stopping and activating
3366	watchers becomes O(1) w.r.t. priority handling.
3367
3368	=item Sending an ev_async: O(1)
3369
3370	=item Processing ev_async_send: O(number_of_async_watchers)
3371
3372	=item Processing signals: O(max_signal_number)
3373
3374	Sending involves a system call I<iff> there were no other C<ev_async_send>
3375	calls in the current loop iteration. Checking for async and signal events
3376	involves iterating over all running async watchers or all signal numbers.
3377
3378	=back
3379
3380
3381	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3637	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3382		3638
3383	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3639	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3384	requires, and its I/O model is fundamentally incompatible with the POSIX	3640	requires, and its I/O model is fundamentally incompatible with the POSIX
3385	model. Libev still offers limited functionality on this platform in	3641	model. Libev still offers limited functionality on this platform in
3386	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3642	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3397		3653
3398	Not a libev limitation but worth mentioning: windows apparently doesn't	3654	Not a libev limitation but worth mentioning: windows apparently doesn't
3399	accept large writes: instead of resulting in a partial write, windows will	3655	accept large writes: instead of resulting in a partial write, windows will
3400	either accept everything or return C<ENOBUFS> if the buffer is too large,	3656	either accept everything or return C<ENOBUFS> if the buffer is too large,
3401	so make sure you only write small amounts into your sockets (less than a	3657	so make sure you only write small amounts into your sockets (less than a
3402	megabyte seems safe, but thsi apparently depends on the amount of memory	3658	megabyte seems safe, but this apparently depends on the amount of memory
3403	available).	3659	available).
3404		3660
3405	Due to the many, low, and arbitrary limits on the win32 platform and	3661	Due to the many, low, and arbitrary limits on the win32 platform and
3406	the abysmal performance of winsockets, using a large number of sockets	3662	the abysmal performance of winsockets, using a large number of sockets
3407	is not recommended (and not reasonable). If your program needs to use	3663	is not recommended (and not reasonable). If your program needs to use
…		…
3418	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3674	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3419		3675
3420	#include "ev.h"	3676	#include "ev.h"
3421		3677
3422	And compile the following F<evwrap.c> file into your project (make sure	3678	And compile the following F<evwrap.c> file into your project (make sure
3423	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3679	you do I<not> compile the F<ev.c> or any other embedded source files!):
3424		3680
3425	#include "evwrap.h"	3681	#include "evwrap.h"
3426	#include "ev.c"	3682	#include "ev.c"
3427		3683
3428	=over 4	3684	=over 4
…		…
3473	wrap all I/O functions and provide your own fd management, but the cost of	3729	wrap all I/O functions and provide your own fd management, but the cost of
3474	calling select (O(n²)) will likely make this unworkable.	3730	calling select (O(n²)) will likely make this unworkable.
3475		3731
3476	=back	3732	=back
3477		3733
3478
3479	=head1 PORTABILITY REQUIREMENTS	3734	=head2 PORTABILITY REQUIREMENTS
3480		3735
3481	In addition to a working ISO-C implementation, libev relies on a few	3736	In addition to a working ISO-C implementation and of course the
3482	additional extensions:	3737	backend-specific APIs, libev relies on a few additional extensions:
3483		3738
3484	=over 4	3739	=over 4
3485		3740
3486	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3741	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3487	calling conventions regardless of C<ev_watcher_type *>.	3742	calling conventions regardless of C<ev_watcher_type *>.
…		…
3493	calls them using an C<ev_watcher *> internally.	3748	calls them using an C<ev_watcher *> internally.
3494		3749
3495	=item C<sig_atomic_t volatile> must be thread-atomic as well	3750	=item C<sig_atomic_t volatile> must be thread-atomic as well
3496		3751
3497	The type C<sig_atomic_t volatile> (or whatever is defined as	3752	The type C<sig_atomic_t volatile> (or whatever is defined as
3498	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3753	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3499	threads. This is not part of the specification for C<sig_atomic_t>, but is	3754	threads. This is not part of the specification for C<sig_atomic_t>, but is
3500	believed to be sufficiently portable.	3755	believed to be sufficiently portable.
3501		3756
3502	=item C<sigprocmask> must work in a threaded environment	3757	=item C<sigprocmask> must work in a threaded environment
3503		3758
…		…
3512	except the initial one, and run the default loop in the initial thread as	3767	except the initial one, and run the default loop in the initial thread as
3513	well.	3768	well.
3514		3769
3515	=item C<long> must be large enough for common memory allocation sizes	3770	=item C<long> must be large enough for common memory allocation sizes
3516		3771
3517	To improve portability and simplify using libev, libev uses C<long>	3772	To improve portability and simplify its API, libev uses C<long> internally
3518	internally instead of C<size_t> when allocating its data structures. On	3773	instead of C<size_t> when allocating its data structures. On non-POSIX
3519	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3774	systems (Microsoft...) this might be unexpectedly low, but is still at
3520	is still at least 31 bits everywhere, which is enough for hundreds of	3775	least 31 bits everywhere, which is enough for hundreds of millions of
3521	millions of watchers.	3776	watchers.
3522		3777
3523	=item C<double> must hold a time value in seconds with enough accuracy	3778	=item C<double> must hold a time value in seconds with enough accuracy
3524		3779
3525	The type C<double> is used to represent timestamps. It is required to	3780	The type C<double> is used to represent timestamps. It is required to
3526	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3781	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3530	=back	3785	=back
3531		3786
3532	If you know of other additional requirements drop me a note.	3787	If you know of other additional requirements drop me a note.
3533		3788
3534		3789
3535	=head1 COMPILER WARNINGS	3790	=head1 ALGORITHMIC COMPLEXITIES
3536		3791
3537	Depending on your compiler and compiler settings, you might get no or a	3792	In this section the complexities of (many of) the algorithms used inside
3538	lot of warnings when compiling libev code. Some people are apparently	3793	libev will be documented. For complexity discussions about backends see
3539	scared by this.	3794	the documentation for C<ev_default_init>.
3540		3795
3541	However, these are unavoidable for many reasons. For one, each compiler	3796	All of the following are about amortised time: If an array needs to be
3542	has different warnings, and each user has different tastes regarding	3797	extended, libev needs to realloc and move the whole array, but this
3543	warning options. "Warn-free" code therefore cannot be a goal except when	3798	happens asymptotically rarer with higher number of elements, so O(1) might
3544	targeting a specific compiler and compiler-version.	3799	mean that libev does a lengthy realloc operation in rare cases, but on
		3800	average it is much faster and asymptotically approaches constant time.
3545		3801
3546	Another reason is that some compiler warnings require elaborate	3802	=over 4
3547	workarounds, or other changes to the code that make it less clear and less
3548	maintainable.
3549		3803
3550	And of course, some compiler warnings are just plain stupid, or simply	3804	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3551	wrong (because they don't actually warn about the condition their message
3552	seems to warn about).
3553		3805
3554	While libev is written to generate as few warnings as possible,	3806	This means that, when you have a watcher that triggers in one hour and
3555	"warn-free" code is not a goal, and it is recommended not to build libev	3807	there are 100 watchers that would trigger before that, then inserting will
3556	with any compiler warnings enabled unless you are prepared to cope with	3808	have to skip roughly seven (C<ld 100>) of these watchers.
3557	them (e.g. by ignoring them). Remember that warnings are just that:
3558	warnings, not errors, or proof of bugs.
3559		3809
		3810	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3560		3811
3561	=head1 VALGRIND	3812	That means that changing a timer costs less than removing/adding them,
		3813	as only the relative motion in the event queue has to be paid for.
3562		3814
3563	Valgrind has a special section here because it is a popular tool that is	3815	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3564	highly useful, but valgrind reports are very hard to interpret.
3565		3816
3566	If you think you found a bug (memory leak, uninitialised data access etc.)	3817	These just add the watcher into an array or at the head of a list.
3567	in libev, then check twice: If valgrind reports something like:
3568		3818
3569	==2274== definitely lost: 0 bytes in 0 blocks.	3819	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3570	==2274== possibly lost: 0 bytes in 0 blocks.
3571	==2274== still reachable: 256 bytes in 1 blocks.
3572		3820
3573	Then there is no memory leak. Similarly, under some circumstances,	3821	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3574	valgrind might report kernel bugs as if it were a bug in libev, or it
3575	might be confused (it is a very good tool, but only a tool).
3576		3822
3577	If you are unsure about something, feel free to contact the mailing list	3823	These watchers are stored in lists, so they need to be walked to find the
3578	with the full valgrind report and an explanation on why you think this is	3824	correct watcher to remove. The lists are usually short (you don't usually
3579	a bug in libev. However, don't be annoyed when you get a brisk "this is	3825	have many watchers waiting for the same fd or signal: one is typical, two
3580	no bug" answer and take the chance of learning how to interpret valgrind	3826	is rare).
3581	properly.
3582		3827
3583	If you need, for some reason, empty reports from valgrind for your project	3828	=item Finding the next timer in each loop iteration: O(1)
3584	I suggest using suppression lists.	3829
		3830	By virtue of using a binary or 4-heap, the next timer is always found at a
		3831	fixed position in the storage array.
		3832
		3833	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3834
		3835	A change means an I/O watcher gets started or stopped, which requires
		3836	libev to recalculate its status (and possibly tell the kernel, depending
		3837	on backend and whether C<ev_io_set> was used).
		3838
		3839	=item Activating one watcher (putting it into the pending state): O(1)
		3840
		3841	=item Priority handling: O(number_of_priorities)
		3842
		3843	Priorities are implemented by allocating some space for each
		3844	priority. When doing priority-based operations, libev usually has to
		3845	linearly search all the priorities, but starting/stopping and activating
		3846	watchers becomes O(1) with respect to priority handling.
		3847
		3848	=item Sending an ev_async: O(1)
		3849
		3850	=item Processing ev_async_send: O(number_of_async_watchers)
		3851
		3852	=item Processing signals: O(max_signal_number)
		3853
		3854	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3855	calls in the current loop iteration. Checking for async and signal events
		3856	involves iterating over all running async watchers or all signal numbers.
		3857
		3858	=back
3585		3859
3586		3860
3587	=head1 AUTHOR	3861	=head1 AUTHOR
3588		3862
3589	Marc Lehmann <libev@schmorp.de>.	3863	Marc Lehmann <libev@schmorp.de>.

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