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Revision 1.180 by root, Fri Sep 19 03:45:55 2008 UTC vs.
Revision 1.210 by root, Thu Oct 30 08:09:30 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
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	306	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	307	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
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 mechanism deserves honorable mention as the most misdesigned
388	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
389		407
390	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	410	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
395		413	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		414
400	Best performance from this backend is achieved by not unregistering all	415	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.	416	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	417	i.e. keep at least one watcher active per fd at all times. Stopping and
		418	starting a watcher (without re-setting it) also usually doesn't cause
		419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
403		422
404	While nominally embeddable in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	424	all kernel versions tested so far.
406		425
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		430
412	Kqueue deserves special mention, as at the time of this writing, it	431	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	432	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	433	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	439	system like NetBSD.
419		440
420	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		444
424	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
430		452
431	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
432		454
433	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
438	sockets.	460	using it only for sockets.
439		461
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	462	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	463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	464	C<NOTE_EOF>.
443		465
…		…
460	While this backend scales well, it requires one system call per active	482	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	483	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	485	might perform better.
464		486
465	On the positive side, ignoring the spurious readiness notifications, this	487	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
468		491
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	493	C<EVBACKEND_POLL>.
471		494
472	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
…		…
481		504
482	If one or more of these are or'ed into the flags value, then only these	505	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	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		508
486	The most typical usage is like this:	509	Example: This is the most typical usage.
487		510
488	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		513
491	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	515	environment settings to be taken into account:
493		516
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		518
496	Use whatever libev has to offer, but make sure that kqueue is used if	519	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	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
499		523
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		525
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		527
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	551	for example).
528		552
529	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
532		556
533	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		585
562	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
563		587
564	Like C<ev_default_fork>, but acts on an event loop created by	588	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	589	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.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
567		592
568	=item int ev_is_default_loop (loop)	593	=item int ev_is_default_loop (loop)
569		594
570	Returns true when the given loop actually is the default loop, false otherwise.	595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
571		597
572	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
573		599
574	Returns the count of loop iterations for the loop, which is identical to	600	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	601	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	639	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.	640	either no event watchers are active anymore or C<ev_unloop> was called.
615		641
616	Please note that an explicit C<ev_unloop> is usually better than	642	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	643	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	645	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.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
621		648
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	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	650	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.	651	process in case there are no events and will return after one iteration of
		652	the loop.
625		653
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	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	663	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.	664	usually a better approach for this kind of thing.
633		665
634	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
635		667
636	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	683	- Queue all expired timers.
652	- Queue all outstanding periodics.	684	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	686	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- 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	688	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	689	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	706	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.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		708
677	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
678		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
679	=item ev_ref (loop)	713	=item ev_ref (loop)
680		714
681	=item ev_unref (loop)	715	=item ev_unref (loop)
682		716
683	Ref/unref can be used to add or remove a reference count on the event	717	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	718	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	719	count is nonzero, C<ev_loop> will not return on its own.
		720
686	a watcher you never unregister that should not keep C<ev_loop> from	721	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	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
688	example, libev itself uses this for its internal signal pipe: It is not	725	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	726	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	727	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	728	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>	729	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,	730	(but only if the watcher wasn't active before, or was active before,
694	respectively).	731	respectively).
695		732
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	734	running when nothing else is active.
698		735
699	struct ev_signal exitsig;	736	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	739	evf_unref (loop);
703		740
704	Example: For some weird reason, unregister the above signal handler again.	741	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>)	755	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	756	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	757	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	758	opportunities).
722		759
723	The background is that sometimes your program runs just fast enough to	760	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	761	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	762	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	763	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
728		765
729	By setting a higher I<io collect interval> you allow libev to spend more	766	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,	767	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	769	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.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		771
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	776	value will not introduce any overhead in libev.
740		777
741	Many (busy) programs can usually benefit by setting the I/O collect	778	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	779	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	780	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>,	781	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.	789	they fire on, say, one-second boundaries only.
753		790
754	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
755		792
756	This function only does something when C<EV_VERIFY> support has been	793	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	794	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	795	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
760		798
761	This can be used to catch bugs inside libev itself: under normal	799	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	800	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	801	data structures consistent.
764		802
765	=back	803	=back
766		804
767		805
768	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
769		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
770	A watcher is a structure that you create and register to record your	812	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	813	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:	814	become readable, you would create an C<ev_io> watcher for that:
773		815
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	817	{
776	ev_io_stop (w);	818	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
778	}	820	}
779		821
780	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
781	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
782	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
785	ev_loop (loop, 0);	830	ev_loop (loop, 0);
786		831
787	As you can see, you are responsible for allocating the memory for your	832	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,	833	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		838
791	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	840	(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	841	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	842	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	843	is readable and/or writable).
796		844
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	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	846	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	847	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
801		849
802	To make the watcher actually watch out for events, you have to start it	850	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	851	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	852	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		854
807	As long as your watcher is active (has been started but not stopped) you	855	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	856	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
810		858
811	Each and every callback receives the event loop pointer as first, the	859	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	860	registered watcher structure as second, and a bitset of received events as
813	third argument.	861	third argument.
814		862
…		…
877	=item C<EV_ERROR>	925	=item C<EV_ERROR>
878		926
879	An unspecified error has occurred, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	928	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	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
882	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
884		936
885	Libev will usually signal a few "dummy" events together with an error,	937	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	938	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	939	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	940	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
890		943
891	=back	944	=back
892		945
893	=head2 GENERIC WATCHER FUNCTIONS	946	=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		947
898	=over 4	948	=over 4
899		949
900	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
901		951
…		…
907	which rolls both calls into one.	957	which rolls both calls into one.
908		958
909	You can reinitialise a watcher at any time as long as it has been stopped	959	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.	960	(or never started) and there are no pending events outstanding.
911		961
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		970
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		972
917	This macro initialises the type-specific parts of a watcher. You need to	973	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	974	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
922		978
923	Although some watcher types do not have type-specific arguments	979	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.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		981
		982	See C<ev_init>, above, for an example.
		983
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		985
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	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	987	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
931		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		993
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		995
934	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
936		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1005
939	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
940	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1010	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	1011	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	1012	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.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1014
946	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
947		1016
948	Returns a true value iff the watcher is active (i.e. it has been started	1017	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	1018	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	1060	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 :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
993		1062
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	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	1064	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.	1065	or might not have been clamped to the valid range.
997		1066
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1068
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	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	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
1003		1073
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1075
1006	If the watcher is pending, this function returns clears its pending status	1076	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	1077	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>.	1078	watcher isn't pending it does nothing and returns C<0>.
1009		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
1010	=back	1083	=back
1011		1084
1012		1085
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1087
1015	Each watcher has, by default, a member C<void *data> that you can change	1088	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	1089	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	1090	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	1091	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	1092	member, you can also "subclass" the watcher type and provide your own
1020	data:	1093	data:
1021		1094
1022	struct my_io	1095	struct my_io
1023	{	1096	{
1024	struct ev_io io;	1097	ev_io io;
1025	int otherfd;	1098	int otherfd;
1026	void *somedata;	1099	void *somedata;
1027	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
1028	};	1101	};
1029		1102
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1106
1034	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1108	can cast it back to your own type:
1036		1109
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1111	{
1039	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
1040	...	1113	...
1041	}	1114	}
1042		1115
…		…
1053	ev_timer t2;	1126	ev_timer t2;
1054	}	1127	}
1055		1128
1056	In this case getting the pointer to C<my_biggy> is a bit more	1129	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	1130	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	1131	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
1060		1134
1061	#include <stddef.h>	1135	#include <stddef.h>
1062		1136
1063	static void	1137	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1139	{
1066	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1142	}
1069		1143
1070	static void	1144	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1146	{
1073	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1149	}
1076		1150
…		…
1104	In general you can register as many read and/or write event watchers per	1178	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	1179	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	1180	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1181	required if you know what you are doing).
1108		1182
1109	If you must do this, then force the use of a known-to-be-good backend	1183	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	1184	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1186
1113	Another thing you have to watch out for is that it is quite easy to	1187	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	1188	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	1189	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	1190	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	1191	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	1192	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	1193	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.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1195
1122	If you cannot run the fd in non-blocking mode (for example you should not	1196	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	1197	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	1198	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	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1127		1205
1128	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1129		1207
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	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,	1209	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	1210	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	1211	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	1212	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	1213	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1214	fact, a different file descriptor.
1137		1215
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1170		1248
1171	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1172		1250
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1251	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	1252	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	1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1255
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1256	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	1257	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).	1258	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1266
1189	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1190		1268
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	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	1270	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.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1272
1195	=item int fd [read-only]	1273	=item int fd [read-only]
1196		1274
1197	The file descriptor being watched.	1275	The file descriptor being watched.
1198		1276
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	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	1286	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1210		1288
1211	static void	1289	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1291	{
1214	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1294	}
1217		1295
1218	...	1296	...
1219	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1224		1302
1225		1303
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1230		1308
1231	The timers are based on real time, that is, if you register an event that	1309	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	1310	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	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
1236		1314
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1315	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	1316	passed, but if multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
1240		1493
1241	=head3 The special problem of time updates	1494	=head3 The special problem of time updates
1242		1495
1243	Establishing the current time is a costly operation (it usually takes at	1496	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	1497	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	1498	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	1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1500	lots of events in one iteration.
1248		1501
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1502	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	1503	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	1504	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	1505	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).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1542
1290	If the timer is repeating, either start it if necessary (with the	1543	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.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1545
1293	This sounds a bit complicated, but here is a useful and typical	1546	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	1547	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		1548
1318	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1319		1550
1320	The current C<repeat> value. Will be used each time the watcher times out	1551	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),	1552	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.	1553	which is also when any modifications are taken into account.
1323		1554
1324	=back	1555	=back
1325		1556
1326	=head3 Examples	1557	=head3 Examples
1327		1558
1328	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1329		1560
1330	static void	1561	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1563	{
1333	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1334	}	1565	}
1335		1566
1336	struct ev_timer mytimer;	1567	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1339		1570
1340	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1572	inactivity.
1342		1573
1343	static void	1574	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1576	{
1346	.. ten seconds without any activity	1577	.. ten seconds without any activity
1347	}	1578	}
1348		1579
1349	struct ev_timer mytimer;	1580	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1353		1584
1354	// and in some piece of code that gets executed on any "activity":	1585	// 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	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1372		1603
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1604	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	1605	such as triggering an event on each "midnight, local time", or other
1375	complicated, rules.	1606	complicated rules.
1376		1607
1377	As with timers, the callback is guaranteed to be invoked only when the	1608	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	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1379	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1380		1611
1381	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1382		1613
1383	=over 4	1614	=over 4
1384		1615
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1386		1617
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1388		1619
1389	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1391		1622
1392	=over 4	1623	=over 4
1393		1624
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1395		1626
1396	In this configuration the watcher triggers an event after the wall clock	1627	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	1628	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	1629	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.	1630	only run when the system clock reaches or surpasses this time.
1400		1631
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1402		1633
1403	In this mode the watcher will always be scheduled to time out at the next	1634	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)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1405	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1406		1637
1407	This can be used to create timers that do not drift with respect to system	1638	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	1639	system clock, for example, here is a C<ev_periodic> that triggers each
1409	the hour:	1640	hour, on the hour:
1410		1641
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1643
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1644	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	1645	but only that the callback will be called when the system time shows a
…		…
1440		1671
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	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	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1444		1675
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1447		1678
		1679	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1681	{
1450	return now + 60.;	1682	return now + 60.;
1451	}	1683	}
1452		1684
1453	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1490		1722
1491	The current interval value. Can be modified any time, but changes only	1723	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	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1725	called.
1494		1726
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1728
1497	The current reschedule callback, or C<0>, if this functionality is	1729	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	1730	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.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1732
1501	=back	1733	=back
1502		1734
1503	=head3 Examples	1735	=head3 Examples
1504		1736
1505	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1508		1740
1509	static void	1741	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1743	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1745	}
1514		1746
1515	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1518		1750
1519	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1520		1752
1521	#include <math.h>	1753	#include <math.h>
1522		1754
1523	static ev_tstamp	1755	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1757	{
1526	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1527	}	1759	}
1528		1760
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1762
1531	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1532		1764
1533	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1537		1769
1538		1770
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1773	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	1774	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	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1776	normal event processing, like any other event.
1545		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1546	You can configure as many watchers as you like per signal. Only when the	1782	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	1783	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	1784	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	1785	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	1786	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1788
1553	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1790	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	1791	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	1792	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1809
1574	=back	1810	=back
1575		1811
1576	=head3 Examples	1812	=head3 Examples
1577		1813
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1579		1815
1580	static void	1816	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1818	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1820	}
1585		1821
1586	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1589		1825
1590		1826
1591	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1592		1828
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1829	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	1830	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	1831	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	1832	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
1598		1837
1599	Only the default event loop is capable of handling signals, and therefore	1838	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1601		1840
1602	=head3 Process Interaction	1841	=head3 Process Interaction
…		…
1663	its completion.	1902	its completion.
1664		1903
1665	ev_child cw;	1904	ev_child cw;
1666		1905
1667	static void	1906	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1908	{
1670	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1911	}
1673		1912
…		…
1688		1927
1689		1928
1690	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1691		1930
1692	This watches a file system path for attribute changes. That is, it calls	1931	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	1932	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1695		1935
1696	The path does not need to exist: changing from "path exists" to "path does	1936	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	1937	not exist" is a status change like any other. The condition "path does
1698	not exist" is signified by the C<st_nlink> field being zero (which is	1938	not exist" is signified by the C<st_nlink> field being zero (which is
1699	otherwise always forced to be at least one) and all the other fields of	1939	otherwise always forced to be at least one) and all the other fields of
1700	the stat buffer having unspecified contents.	1940	the stat buffer having unspecified contents.
1701		1941
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	1942	The path I<must not> end in a slash or contain special components such as
		1943	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	1944	your working directory changes, then the behaviour is undefined.
1704		1945
1705	Since there is no standard to do this, the portable implementation simply	1946	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1947	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	1948	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	1949	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	1950	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	1951	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	1952	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	1953	currently around C<0.1>, but that's usually overkill.
1713		1954
1714	This watcher type is not meant for massive numbers of stat watchers,	1955	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	1956	as even with OS-supported change notifications, this can be
1716	resource-intensive.	1957	resource-intensive.
1717		1958
1718	At the time of this writing, only the Linux inotify interface is	1959	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	1960	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	1961	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	1962	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		1963
1727	=head3 ABI Issues (Largefile Support)	1964	=head3 ABI Issues (Largefile Support)
1728		1965
1729	Libev by default (unless the user overrides this) uses the default	1966	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	1967	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	1968	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	1969	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	1970	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	1971	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	1972	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	1973	most noticeably displayed with ev_stat and large file support.
1737		1974
1738	The solution for this is to lobby your distribution maker to make large	1975	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	1976	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	1977	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	1978	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	1979	default compilation environment.
1743		1980
1744	=head3 Inotify	1981	=head3 Inotify and Kqueue
1745		1982
1746	When C<inotify (7)> support has been compiled into libev (generally only	1983	When C<inotify (7)> support has been compiled into libev (generally
		1984	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	1985	implementations) and present at runtime, it will be used to speed up
1748	change detection where possible. The inotify descriptor will be created lazily	1986	change detection where possible. The inotify descriptor will be created
1749	when the first C<ev_stat> watcher is being started.	1987	lazily when the first C<ev_stat> watcher is being started.
1750		1988
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	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	1990	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	1991	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.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as the path exists, libev usually gets away without polling.
1755		1994
1756	(There is no support for kqueue, as apparently it cannot be used to	1995	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	1996	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	1997	descriptor open on the object at all times, and detecting renames, unlinks
		1998	etc. is difficult.
1759		1999
1760	=head3 The special problem of stat time resolution	2000	=head3 The special problem of stat time resolution
1761		2001
1762	The C<stat ()> system call only supports full-second resolution portably, and	2002	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2003	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2004	still only support whole seconds.
1765		2005
1766	That means that, if the time is the only thing that changes, you can	2006	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	2007	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	2008	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	2009	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2010	stat data does change in other ways (e.g. file size).
1771		2011
1772	The solution to this is to delay acting on a change for slightly more	2012	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	2013	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);	2014	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2015	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2035	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	2036	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	2037	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.	2038	path for as long as the watcher is active.
1799		2039
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2040	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	2041	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2042	last change was detected).
1803		2043
1804	=item ev_stat_stat (loop, ev_stat *)	2044	=item ev_stat_stat (loop, ev_stat *)
1805		2045
1806	Updates the stat buffer immediately with new values. If you change the	2046	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	2047	watched path in your callback, you could call this function to avoid
…		…
1890		2130
1891		2131
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2132	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2133
1894	Idle watchers trigger events when no other events of the same or higher	2134	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	2135	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2136	as receiving "events").
1897		2137
1898	That is, as long as your process is busy handling sockets or timeouts	2138	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	2139	(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	2140	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	2141	are pending), the idle watchers are being called once per event loop
…		…
1926		2166
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2167	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2168	callback, free it. Also, use no error checking, as usual.
1929		2169
1930	static void	2170	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2171	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2172	{
1933	free (w);	2173	free (w);
1934	// now do something you wanted to do when the program has	2174	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2175	// no longer anything immediate to do.
1936	}	2176	}
1937		2177
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2178	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2179	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2180	ev_idle_start (loop, idle_cb);
1941		2181
1942		2182
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2183	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2184
1945	Prepare and check watchers are usually (but not always) used in tandem:	2185	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2186	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2187	afterwards.
1948		2188
1949	You I<must not> call C<ev_loop> or similar functions that enter	2189	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>	2190	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,	2193	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	2194	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2195	called in pairs bracketing the blocking call.
1956		2196
1957	Their main purpose is to integrate other event mechanisms into libev and	2197	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	2198	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	2199	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2200	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,	2201	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>	2202	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2203	watcher).
1964		2204
1965	This is done by examining in each prepare call which file descriptors need	2205	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	2206	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	2207	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	2208	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2209	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	2210	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,	2211	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2212	nevertheless, because you never know, you know?).
1973		2213
1974	As another example, the Perl Coro module uses these hooks to integrate	2214	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2215	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2216	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	2217	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	2220	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2221	low-priority coroutines to idle/background tasks).
1982		2222
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2223	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	2224	priority, to ensure that they are being run before any other watchers
		2225	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2226
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2227	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	2228	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2229	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	2230	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	2231	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	2232	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2233	others).
1992		2234
1993	=head3 Watcher-Specific Functions and Data Members	2235	=head3 Watcher-Specific Functions and Data Members
1994		2236
1995	=over 4	2237	=over 4
1996		2238
…		…
1998		2240
1999	=item ev_check_init (ev_check *, callback)	2241	=item ev_check_init (ev_check *, callback)
2000		2242
2001	Initialises and configures the prepare or check watcher - they have no	2243	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>	2244	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.	2245	macros, but using them is utterly, utterly, utterly and completely
		2246	pointless.
2004		2247
2005	=back	2248	=back
2006		2249
2007	=head3 Examples	2250	=head3 Examples
2008		2251
…		…
2021		2264
2022	static ev_io iow [nfd];	2265	static ev_io iow [nfd];
2023	static ev_timer tw;	2266	static ev_timer tw;
2024		2267
2025	static void	2268	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2269	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2270	{
2028	}	2271	}
2029		2272
2030	// create io watchers for each fd and a timer before blocking	2273	// create io watchers for each fd and a timer before blocking
2031	static void	2274	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2275	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2276	{
2034	int timeout = 3600000;	2277	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2278	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2279	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2280	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2295	}
2053	}	2296	}
2054		2297
2055	// stop all watchers after blocking	2298	// stop all watchers after blocking
2056	static void	2299	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2300	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2301	{
2059	ev_timer_stop (loop, &tw);	2302	ev_timer_stop (loop, &tw);
2060		2303
2061	for (int i = 0; i < nfd; ++i)	2304	for (int i = 0; i < nfd; ++i)
2062	{	2305	{
…		…
2101	}	2344	}
2102		2345
2103	// do not ever call adns_afterpoll	2346	// do not ever call adns_afterpoll
2104		2347
2105	Method 4: Do not use a prepare or check watcher because the module you	2348	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	2349	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	2350	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	2351	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2352	this approach, effectively embedding EV as a client into the horrible
		2353	libglib event loop.
2110		2354
2111	static gint	2355	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2356	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2357	{
2114	int got_events = 0;	2358	int got_events = 0;
…		…
2145	prioritise I/O.	2389	prioritise I/O.
2146		2390
2147	As an example for a bug workaround, the kqueue backend might only support	2391	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	2392	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	2393	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	2394	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	2395	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	2396	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.	2397	C<kevent>, but at least you can use both mechanisms for what they are
		2398	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2399
2155	As for prioritising I/O: rarely you have the case where some fds have	2400	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	2401	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	2402	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	2403	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.	2404	the rest in a second one, and embed the second one in the first.
2160		2405
2161	As long as the watcher is active, the callback will be invoked every time	2406	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	2407	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	2408	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	2409	their callbacks (you could also start an idle watcher to give the embedded
…		…
2172	interested in that.	2417	interested in that.
2173		2418
2174	Also, there have not currently been made special provisions for forking:	2419	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,	2420	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	2421	but you will also have to stop and restart any C<ev_embed> watchers
2177	yourself.	2422	yourself - but you can use a fork watcher to handle this automatically,
		2423	and future versions of libev might do just that.
2178		2424
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2425	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2426	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2427	portable one.
2182		2428
2183	So when you want to use this feature you will always have to be prepared	2429	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	2430	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	2431	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.	2432	create it, and if that fails, use the normal loop for everything.
		2433
		2434	=head3 C<ev_embed> and fork
		2435
		2436	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2437	automatically be applied to the embedded loop as well, so no special
		2438	fork handling is required in that case. When the watcher is not running,
		2439	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2440	as applicable.
2187		2441
2188	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
2189		2443
2190	=over 4	2444	=over 4
2191		2445
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2473	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2474	used).
2221		2475
2222	struct ev_loop *loop_hi = ev_default_init (0);	2476	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2477	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2478	ev_embed embed;
2225		2479
2226	// see if there is a chance of getting one that works	2480	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2481	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2482	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2483	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2497	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2498	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2499
2246	struct ev_loop *loop = ev_default_init (0);	2500	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2501	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2502	ev_embed embed;
2249		2503
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2504	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2505	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2506	{
2253	ev_embed_init (&embed, 0, loop_socket);	2507	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2563	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	2564	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2565	need elaborate support such as pthreads.
2312		2566
2313	That means that if you want to queue data, you have to provide your own	2567	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	2568	queue. But at least I can tell you how to implement locking around your
2315	queue:	2569	queue:
2316		2570
2317	=over 4	2571	=over 4
2318		2572
2319	=item queueing from a signal handler context	2573	=item queueing from a signal handler context
2320		2574
2321	To implement race-free queueing, you simply add to the queue in the signal	2575	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	2576	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2577	an example that does that for some fictitious SIGUSR1 handler:
2324		2578
2325	static ev_async mysig;	2579	static ev_async mysig;
2326		2580
2327	static void	2581	static void
2328	sigusr1_handler (void)	2582	sigusr1_handler (void)
…		…
2394	=over 4	2648	=over 4
2395		2649
2396	=item ev_async_init (ev_async *, callback)	2650	=item ev_async_init (ev_async *, callback)
2397		2651
2398	Initialises and configures the async watcher - it has no parameters of any	2652	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,	2653	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2654	trust me.
2401		2655
2402	=item ev_async_send (loop, ev_async *)	2656	=item ev_async_send (loop, ev_async *)
2403		2657
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2658	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	2659	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	2660	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	2661	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2662	section below on what exactly this means).
2409		2663
2410	This call incurs the overhead of a system call only once per loop iteration,	2664	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	2665	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2435	=over 4	2689	=over 4
2436		2690
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2691	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2692
2439	This function combines a simple timer and an I/O watcher, calls your	2693	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2694	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	2695	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	2696	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2697	more watchers yourself.
2444		2698
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2699	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	2700	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2701	the given C<fd> and C<events> set will be created and started.
2448		2702
2449	If C<timeout> is less than 0, then no timeout watcher will be	2703	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	2704	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	2705	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2706
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2707	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	2708	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>	2709	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2710	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2711	a timeout and an io event at the same time - you probably should give io
		2712	events precedence.
		2713
		2714	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2715
2459	static void stdin_ready (int revents, void *arg)	2716	static void stdin_ready (int revents, void *arg)
2460	{	2717	{
		2718	if (revents & EV_READ)
		2719	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2720	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2721	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2722	}
2466		2723
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2724	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2725
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2726	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2727
2471	Feeds the given event set into the event loop, as if the specified event	2728	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	2729	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2730	initialised but not necessarily started event watcher).
2474		2731
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2732	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2733
2477	Feed an event on the given fd, as if a file descriptor backend detected	2734	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2735	the given events it.
2479		2736
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2737	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2738
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2739	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2740	loop!).
2484		2741
2485	=back	2742	=back
…		…
2617		2874
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2875	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2876
2620	See the method-C<set> above for more details.	2877	See the method-C<set> above for more details.
2621		2878
2622	Example:	2879	Example: Use a plain function as callback.
2623		2880
2624	static void io_cb (ev::io &w, int revents) { }	2881	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2882	iow.set <io_cb> ();
2626		2883
2627	=item w->set (struct ev_loop *)	2884	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	2922	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	2923	the constructor.
2667		2924
2668	class myclass	2925	class myclass
2669	{	2926	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	2927	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	2928	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		2929
2673	myclass (int fd)	2930	myclass (int fd)
2674	{	2931	{
2675	io .set <myclass, &myclass::io_cb > (this);	2932	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	2933	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	2949	=item Perl
2693		2950
2694	The EV module implements the full libev API and is actually used to test	2951	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,	2952	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	2953	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	2954	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>).	2955	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2956	and C<EV::Glib>).
2699		2957
2700	It can be found and installed via CPAN, its homepage is at	2958	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	2959	L<http://software.schmorp.de/pkg/EV>.
2702		2960
2703	=item Python	2961	=item Python
…		…
2719	=item D	2977	=item D
2720		2978
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2979	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>.	2980	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2723		2981
		2982	=item Ocaml
		2983
		2984	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2985	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2986
2724	=back	2987	=back
2725		2988
2726		2989
2727	=head1 MACRO MAGIC	2990	=head1 MACRO MAGIC
2728		2991
…		…
2828		3091
2829	#define EV_STANDALONE 1	3092	#define EV_STANDALONE 1
2830	#include "ev.h"	3093	#include "ev.h"
2831		3094
2832	Both header files and implementation files can be compiled with a C++	3095	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3096	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3097	as a bug).
2835		3098
2836	You need the following files in your source tree, or in a directory	3099	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3100	in your include path (e.g. in libev/ when using -Ilibev):
2838		3101
…		…
2882		3145
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3146	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3147
2885	Libev can be configured via a variety of preprocessor symbols you have to	3148	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	3149	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3150	autoconf is documented for every option.
2888		3151
2889	=over 4	3152	=over 4
2890		3153
2891	=item EV_STANDALONE	3154	=item EV_STANDALONE
2892		3155
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3325	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	3326	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	3327	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3328	fine.
3066		3329
3067	If your embedding application does not need any priorities, defining these both to	3330	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3331	both to C<0> will save some memory and CPU.
3069		3332
3070	=item EV_PERIODIC_ENABLE	3333	=item EV_PERIODIC_ENABLE
3071		3334
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3335	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	3336	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3343	code.
3081		3344
3082	=item EV_EMBED_ENABLE	3345	=item EV_EMBED_ENABLE
3083		3346
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3347	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3348	defined to be C<0>, then they are not. Embed watchers rely on most other
		3349	watcher types, which therefore must not be disabled.
3086		3350
3087	=item EV_STAT_ENABLE	3351	=item EV_STAT_ENABLE
3088		3352
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3353	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3354	defined to be C<0>, then they are not.
…		…
3122	two).	3386	two).
3123		3387
3124	=item EV_USE_4HEAP	3388	=item EV_USE_4HEAP
3125		3389
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3390	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	3391	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	3392	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3393	faster performance with many (thousands) of watchers.
3130		3394
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3395	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3396	(disabled).
3133		3397
3134	=item EV_HEAP_CACHE_AT	3398	=item EV_HEAP_CACHE_AT
3135		3399
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3400	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	3401	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>),	3402	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,	3403	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	3404	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3405	noticeably with many (hundreds) of watchers.
3142		3406
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3407	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3408	(disabled).
3145		3409
3146	=item EV_VERIFY	3410	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3416	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	3417	verification code will be called very frequently, which will slow down
3154	libev considerably.	3418	libev considerably.
3155		3419
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3420	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3421	C<0>.
3158		3422
3159	=item EV_COMMON	3423	=item EV_COMMON
3160		3424
3161	By default, all watchers have a C<void *data> member. By redefining	3425	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	3426	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	3443	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	3444	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	3445	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	3446	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++.	3447	method calls instead of plain function calls in C++.
		3448
		3449	=back
3184		3450
3185	=head2 EXPORTED API SYMBOLS	3451	=head2 EXPORTED API SYMBOLS
3186		3452
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3453	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	3454	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:	3501	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3502
3237	#include "ev_cpp.h"	3503	#include "ev_cpp.h"
3238	#include "ev.c"	3504	#include "ev.c"
3239		3505
		3506	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3507
3241	=head1 THREADS AND COROUTINES	3508	=head2 THREADS AND COROUTINES
3242		3509
3243	=head2 THREADS	3510	=head3 THREADS
3244		3511
3245	Libev itself is thread-safe (unless the opposite is specifically	3512	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	3513	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	3514	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:	3515	are no concurrent calls into any libev function with the same loop
		3516	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	3517	of course): libev guarantees that different event loops share no data
3250	need locking.	3518	structures that need any locking.
3251		3519
3252	Or to put it differently: calls with different loop parameters can be done	3520	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	3521	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	3522	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	3523	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	3524	a mutex per loop).
3257		3525
3258	Specifically to support threads (and signal handlers), libev implements	3526	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	3527	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	3528	concurrency on the same event loop, namely waking it up "from the
		3529	outside".
3261		3530
3262	If you want to know which design (one loop, locking, or multiple loops	3531	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	3532	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	3533	help you, but here is some generic advice:
3265		3534
3266	=over 4	3535	=over 4
3267		3536
3268	=item * most applications have a main thread: use the default libev loop	3537	=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.	3538	in that thread, or create a separate thread running only the default loop.
…		…
3281		3550
3282	Choosing a model is hard - look around, learn, know that usually you can do	3551	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	3552	better than you currently do :-)
3284		3553
3285	=item * often you need to talk to some other thread which blocks in the	3554	=item * often you need to talk to some other thread which blocks in the
		3555	event loop.
		3556
3286	event loop - C<ev_async> watchers can be used to wake them up from other	3557	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	3558	(or from signal contexts...).
3288		3559
3289	=item * some watcher types are only supported in the default loop - use	3560	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	3561	work in the default loop by registering the signal watcher with the
		3562	default loop and triggering an C<ev_async> watcher from the default loop
		3563	watcher callback into the event loop interested in the signal.
3291		3564
3292	=back	3565	=back
3293		3566
3294	=head2 COROUTINES	3567	=head3 COROUTINES
3295		3568
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	3569	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	3570	libev fully supports nesting calls to its functions from different
3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3571	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3299	different coroutines and switch freely between both coroutines running the	3572	different coroutines, and switch freely between both coroutines running the
3300	loop, as long as you don't confuse yourself). The only exception is that	3573	loop, as long as you don't confuse yourself). The only exception is that
3301	you must not do this from C<ev_periodic> reschedule callbacks.	3574	you must not do this from C<ev_periodic> reschedule callbacks.
3302		3575
3303	Care has been invested into making sure that libev does not keep local	3576	Care has been taken to ensure that libev does not keep local state inside
3304	state inside C<ev_loop>, and other calls do not usually allow coroutine	3577	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3305	switches.	3578	they do not call any callbacks.
3306		3579
		3580	=head2 COMPILER WARNINGS
3307		3581
3308	=head1 COMPLEXITIES	3582	Depending on your compiler and compiler settings, you might get no or a
		3583	lot of warnings when compiling libev code. Some people are apparently
		3584	scared by this.
3309		3585
3310	In this section the complexities of (many of) the algorithms used inside	3586	However, these are unavoidable for many reasons. For one, each compiler
3311	libev will be explained. For complexity discussions about backends see the	3587	has different warnings, and each user has different tastes regarding
3312	documentation for C<ev_default_init>.	3588	warning options. "Warn-free" code therefore cannot be a goal except when
		3589	targeting a specific compiler and compiler-version.
3313		3590
3314	All of the following are about amortised time: If an array needs to be	3591	Another reason is that some compiler warnings require elaborate
3315	extended, libev needs to realloc and move the whole array, but this	3592	workarounds, or other changes to the code that make it less clear and less
3316	happens asymptotically never with higher number of elements, so O(1) might	3593	maintainable.
3317	mean it might do a lengthy realloc operation in rare cases, but on average
3318	it is much faster and asymptotically approaches constant time.
3319		3594
3320	=over 4	3595	And of course, some compiler warnings are just plain stupid, or simply
		3596	wrong (because they don't actually warn about the condition their message
		3597	seems to warn about). For example, certain older gcc versions had some
		3598	warnings that resulted an extreme number of false positives. These have
		3599	been fixed, but some people still insist on making code warn-free with
		3600	such buggy versions.
3321		3601
3322	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3602	While libev is written to generate as few warnings as possible,
		3603	"warn-free" code is not a goal, and it is recommended not to build libev
		3604	with any compiler warnings enabled unless you are prepared to cope with
		3605	them (e.g. by ignoring them). Remember that warnings are just that:
		3606	warnings, not errors, or proof of bugs.
3323		3607
3324	This means that, when you have a watcher that triggers in one hour and
3325	there are 100 watchers that would trigger before that then inserting will
3326	have to skip roughly seven (C<ld 100>) of these watchers.
3327		3608
3328	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3609	=head2 VALGRIND
3329		3610
3330	That means that changing a timer costs less than removing/adding them	3611	Valgrind has a special section here because it is a popular tool that is
3331	as only the relative motion in the event queue has to be paid for.	3612	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3332		3613
3333	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3614	If you think you found a bug (memory leak, uninitialised data access etc.)
		3615	in libev, then check twice: If valgrind reports something like:
3334		3616
3335	These just add the watcher into an array or at the head of a list.	3617	==2274== definitely lost: 0 bytes in 0 blocks.
		3618	==2274== possibly lost: 0 bytes in 0 blocks.
		3619	==2274== still reachable: 256 bytes in 1 blocks.
3336		3620
3337	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3621	Then there is no memory leak, just as memory accounted to global variables
		3622	is not a memleak - the memory is still being referenced, and didn't leak.
3338		3623
3339	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3624	Similarly, under some circumstances, valgrind might report kernel bugs
		3625	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3626	although an acceptable workaround has been found here), or it might be
		3627	confused.
3340		3628
3341	These watchers are stored in lists then need to be walked to find the	3629	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3342	correct watcher to remove. The lists are usually short (you don't usually	3630	make it into some kind of religion.
3343	have many watchers waiting for the same fd or signal).
3344		3631
3345	=item Finding the next timer in each loop iteration: O(1)	3632	If you are unsure about something, feel free to contact the mailing list
		3633	with the full valgrind report and an explanation on why you think this
		3634	is a bug in libev (best check the archives, too :). However, don't be
		3635	annoyed when you get a brisk "this is no bug" answer and take the chance
		3636	of learning how to interpret valgrind properly.
3346		3637
3347	By virtue of using a binary or 4-heap, the next timer is always found at a	3638	If you need, for some reason, empty reports from valgrind for your project
3348	fixed position in the storage array.	3639	I suggest using suppression lists.
3349		3640
3350	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3351		3641
3352	A change means an I/O watcher gets started or stopped, which requires	3642	=head1 PORTABILITY NOTES
3353	libev to recalculate its status (and possibly tell the kernel, depending
3354	on backend and whether C<ev_io_set> was used).
3355		3643
3356	=item Activating one watcher (putting it into the pending state): O(1)
3357
3358	=item Priority handling: O(number_of_priorities)
3359
3360	Priorities are implemented by allocating some space for each
3361	priority. When doing priority-based operations, libev usually has to
3362	linearly search all the priorities, but starting/stopping and activating
3363	watchers becomes O(1) w.r.t. priority handling.
3364
3365	=item Sending an ev_async: O(1)
3366
3367	=item Processing ev_async_send: O(number_of_async_watchers)
3368
3369	=item Processing signals: O(max_signal_number)
3370
3371	Sending involves a system call I<iff> there were no other C<ev_async_send>
3372	calls in the current loop iteration. Checking for async and signal events
3373	involves iterating over all running async watchers or all signal numbers.
3374
3375	=back
3376
3377
3378	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3644	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3379		3645
3380	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3646	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3381	requires, and its I/O model is fundamentally incompatible with the POSIX	3647	requires, and its I/O model is fundamentally incompatible with the POSIX
3382	model. Libev still offers limited functionality on this platform in	3648	model. Libev still offers limited functionality on this platform in
3383	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3649	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3394		3660
3395	Not a libev limitation but worth mentioning: windows apparently doesn't	3661	Not a libev limitation but worth mentioning: windows apparently doesn't
3396	accept large writes: instead of resulting in a partial write, windows will	3662	accept large writes: instead of resulting in a partial write, windows will
3397	either accept everything or return C<ENOBUFS> if the buffer is too large,	3663	either accept everything or return C<ENOBUFS> if the buffer is too large,
3398	so make sure you only write small amounts into your sockets (less than a	3664	so make sure you only write small amounts into your sockets (less than a
3399	megabyte seems safe, but thsi apparently depends on the amount of memory	3665	megabyte seems safe, but this apparently depends on the amount of memory
3400	available).	3666	available).
3401		3667
3402	Due to the many, low, and arbitrary limits on the win32 platform and	3668	Due to the many, low, and arbitrary limits on the win32 platform and
3403	the abysmal performance of winsockets, using a large number of sockets	3669	the abysmal performance of winsockets, using a large number of sockets
3404	is not recommended (and not reasonable). If your program needs to use	3670	is not recommended (and not reasonable). If your program needs to use
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3681	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3416		3682
3417	#include "ev.h"	3683	#include "ev.h"
3418		3684
3419	And compile the following F<evwrap.c> file into your project (make sure	3685	And compile the following F<evwrap.c> file into your project (make sure
3420	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3686	you do I<not> compile the F<ev.c> or any other embedded source files!):
3421		3687
3422	#include "evwrap.h"	3688	#include "evwrap.h"
3423	#include "ev.c"	3689	#include "ev.c"
3424		3690
3425	=over 4	3691	=over 4
…		…
3470	wrap all I/O functions and provide your own fd management, but the cost of	3736	wrap all I/O functions and provide your own fd management, but the cost of
3471	calling select (O(n²)) will likely make this unworkable.	3737	calling select (O(n²)) will likely make this unworkable.
3472		3738
3473	=back	3739	=back
3474		3740
3475
3476	=head1 PORTABILITY REQUIREMENTS	3741	=head2 PORTABILITY REQUIREMENTS
3477		3742
3478	In addition to a working ISO-C implementation, libev relies on a few	3743	In addition to a working ISO-C implementation and of course the
3479	additional extensions:	3744	backend-specific APIs, libev relies on a few additional extensions:
3480		3745
3481	=over 4	3746	=over 4
3482		3747
3483	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3748	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3484	calling conventions regardless of C<ev_watcher_type *>.	3749	calling conventions regardless of C<ev_watcher_type *>.
…		…
3490	calls them using an C<ev_watcher *> internally.	3755	calls them using an C<ev_watcher *> internally.
3491		3756
3492	=item C<sig_atomic_t volatile> must be thread-atomic as well	3757	=item C<sig_atomic_t volatile> must be thread-atomic as well
3493		3758
3494	The type C<sig_atomic_t volatile> (or whatever is defined as	3759	The type C<sig_atomic_t volatile> (or whatever is defined as
3495	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3760	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3496	threads. This is not part of the specification for C<sig_atomic_t>, but is	3761	threads. This is not part of the specification for C<sig_atomic_t>, but is
3497	believed to be sufficiently portable.	3762	believed to be sufficiently portable.
3498		3763
3499	=item C<sigprocmask> must work in a threaded environment	3764	=item C<sigprocmask> must work in a threaded environment
3500		3765
…		…
3509	except the initial one, and run the default loop in the initial thread as	3774	except the initial one, and run the default loop in the initial thread as
3510	well.	3775	well.
3511		3776
3512	=item C<long> must be large enough for common memory allocation sizes	3777	=item C<long> must be large enough for common memory allocation sizes
3513		3778
3514	To improve portability and simplify using libev, libev uses C<long>	3779	To improve portability and simplify its API, libev uses C<long> internally
3515	internally instead of C<size_t> when allocating its data structures. On	3780	instead of C<size_t> when allocating its data structures. On non-POSIX
3516	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3781	systems (Microsoft...) this might be unexpectedly low, but is still at
3517	is still at least 31 bits everywhere, which is enough for hundreds of	3782	least 31 bits everywhere, which is enough for hundreds of millions of
3518	millions of watchers.	3783	watchers.
3519		3784
3520	=item C<double> must hold a time value in seconds with enough accuracy	3785	=item C<double> must hold a time value in seconds with enough accuracy
3521		3786
3522	The type C<double> is used to represent timestamps. It is required to	3787	The type C<double> is used to represent timestamps. It is required to
3523	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3788	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3527	=back	3792	=back
3528		3793
3529	If you know of other additional requirements drop me a note.	3794	If you know of other additional requirements drop me a note.
3530		3795
3531		3796
3532	=head1 COMPILER WARNINGS	3797	=head1 ALGORITHMIC COMPLEXITIES
3533		3798
3534	Depending on your compiler and compiler settings, you might get no or a	3799	In this section the complexities of (many of) the algorithms used inside
3535	lot of warnings when compiling libev code. Some people are apparently	3800	libev will be documented. For complexity discussions about backends see
3536	scared by this.	3801	the documentation for C<ev_default_init>.
3537		3802
3538	However, these are unavoidable for many reasons. For one, each compiler	3803	All of the following are about amortised time: If an array needs to be
3539	has different warnings, and each user has different tastes regarding	3804	extended, libev needs to realloc and move the whole array, but this
3540	warning options. "Warn-free" code therefore cannot be a goal except when	3805	happens asymptotically rarer with higher number of elements, so O(1) might
3541	targeting a specific compiler and compiler-version.	3806	mean that libev does a lengthy realloc operation in rare cases, but on
		3807	average it is much faster and asymptotically approaches constant time.
3542		3808
3543	Another reason is that some compiler warnings require elaborate	3809	=over 4
3544	workarounds, or other changes to the code that make it less clear and less
3545	maintainable.
3546		3810
3547	And of course, some compiler warnings are just plain stupid, or simply	3811	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3548	wrong (because they don't actually warn about the condition their message
3549	seems to warn about).
3550		3812
3551	While libev is written to generate as few warnings as possible,	3813	This means that, when you have a watcher that triggers in one hour and
3552	"warn-free" code is not a goal, and it is recommended not to build libev	3814	there are 100 watchers that would trigger before that, then inserting will
3553	with any compiler warnings enabled unless you are prepared to cope with	3815	have to skip roughly seven (C<ld 100>) of these watchers.
3554	them (e.g. by ignoring them). Remember that warnings are just that:
3555	warnings, not errors, or proof of bugs.
3556		3816
		3817	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3557		3818
3558	=head1 VALGRIND	3819	That means that changing a timer costs less than removing/adding them,
		3820	as only the relative motion in the event queue has to be paid for.
3559		3821
3560	Valgrind has a special section here because it is a popular tool that is	3822	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3561	highly useful, but valgrind reports are very hard to interpret.
3562		3823
3563	If you think you found a bug (memory leak, uninitialised data access etc.)	3824	These just add the watcher into an array or at the head of a list.
3564	in libev, then check twice: If valgrind reports something like:
3565		3825
3566	==2274== definitely lost: 0 bytes in 0 blocks.	3826	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3567	==2274== possibly lost: 0 bytes in 0 blocks.
3568	==2274== still reachable: 256 bytes in 1 blocks.
3569		3827
3570	Then there is no memory leak. Similarly, under some circumstances,	3828	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3571	valgrind might report kernel bugs as if it were a bug in libev, or it
3572	might be confused (it is a very good tool, but only a tool).
3573		3829
3574	If you are unsure about something, feel free to contact the mailing list	3830	These watchers are stored in lists, so they need to be walked to find the
3575	with the full valgrind report and an explanation on why you think this is	3831	correct watcher to remove. The lists are usually short (you don't usually
3576	a bug in libev. However, don't be annoyed when you get a brisk "this is	3832	have many watchers waiting for the same fd or signal: one is typical, two
3577	no bug" answer and take the chance of learning how to interpret valgrind	3833	is rare).
3578	properly.
3579		3834
3580	If you need, for some reason, empty reports from valgrind for your project	3835	=item Finding the next timer in each loop iteration: O(1)
3581	I suggest using suppression lists.	3836
		3837	By virtue of using a binary or 4-heap, the next timer is always found at a
		3838	fixed position in the storage array.
		3839
		3840	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3841
		3842	A change means an I/O watcher gets started or stopped, which requires
		3843	libev to recalculate its status (and possibly tell the kernel, depending
		3844	on backend and whether C<ev_io_set> was used).
		3845
		3846	=item Activating one watcher (putting it into the pending state): O(1)
		3847
		3848	=item Priority handling: O(number_of_priorities)
		3849
		3850	Priorities are implemented by allocating some space for each
		3851	priority. When doing priority-based operations, libev usually has to
		3852	linearly search all the priorities, but starting/stopping and activating
		3853	watchers becomes O(1) with respect to priority handling.
		3854
		3855	=item Sending an ev_async: O(1)
		3856
		3857	=item Processing ev_async_send: O(number_of_async_watchers)
		3858
		3859	=item Processing signals: O(max_signal_number)
		3860
		3861	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3862	calls in the current loop iteration. Checking for async and signal events
		3863	involves iterating over all running async watchers or all signal numbers.
		3864
		3865	=back
3582		3866
3583		3867
3584	=head1 AUTHOR	3868	=head1 AUTHOR
3585		3869
3586	Marc Lehmann <libev@schmorp.de>.	3870	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3587		3871

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