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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	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	224	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	225	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	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	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	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	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	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
389		409
390	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	418	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
403		428
404	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	430	all kernel versions tested so far.
406		431
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		436
412	Kqueue deserves special mention, as at the time of this writing, it	437	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	438	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	439	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"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	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	443	"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)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	445	system like NetBSD.
419		446
420	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		450
424	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
430		458
431	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
432		460
433	While nominally embeddable in other event loops, this doesn't work	461	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	462	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	463	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	464	(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	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
439		467
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	470	C<NOTE_EOF>.
443		471
…		…
460	While this backend scales well, it requires one system call per active	488	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	489	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	491	might perform better.
464		492
465	On the positive side, ignoring the spurious readiness notifications, this	493	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
468		497
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
471		500
472	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
481		510
482	If one or more of these are or'ed into the flags value, then only these	511	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	512	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.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		514
486	The most typical usage is like this:	515	Example: This is the most typical usage.
487		516
488	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		519
491	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	521	environment settings to be taken into account:
493		522
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		524
496	Use whatever libev has to offer, but make sure that kqueue is used if	525	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	526	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):	527	private event loop and only if you know the OS supports your types of
		528	fds):
499		529
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		531
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		533
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	557	for example).
528		558
529	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
532		562
533	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		591
562	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
563		593
564	Like C<ev_default_fork>, but acts on an event loop created by	594	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	595	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.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
567		598
568	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
569		600
570	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
571		603
572	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
573		605
574	Returns the count of loop iterations for the loop, which is identical to	606	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	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
602	very long time without entering the event loop, updating libev's idea of	634	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	635	the current time is a good idea.
604		636
605	See also "The special problem of time updates" in the C<ev_timer> section.	637	See also "The special problem of time updates" in the C<ev_timer> section.
606		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
607	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
608		666
609	Finally, this is it, the event handler. This function usually is called	667	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	668	after you initialised all your watchers and you want to start handling
611	events.	669	events.
…		…
613	If the flags argument is specified as C<0>, it will not return until	671	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.	672	either no event watchers are active anymore or C<ev_unloop> was called.
615		673
616	Please note that an explicit C<ev_unloop> is usually better than	674	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	675	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	677	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.	678	of relying on its watchers stopping correctly, that is truly a thing of
		679	beauty.
621		680
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	681	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	682	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.	683	process in case there are no events and will return after one iteration of
		684	the loop.
625		685
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	687	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	688	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	689	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	690	user-registered callback will be called), and will return after one
		691	iteration of the loop.
		692
		693	This is useful if you are waiting for some external event in conjunction
		694	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	695	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.	696	usually a better approach for this kind of thing.
633		697
634	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
635		699
636	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	715	- Queue all expired timers.
652	- Queue all outstanding periodics.	716	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	718	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	719	- 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	720	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	721	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	738	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.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		740
677	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
678		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
679	=item ev_ref (loop)	745	=item ev_ref (loop)
680		746
681	=item ev_unref (loop)	747	=item ev_unref (loop)
682		748
683	Ref/unref can be used to add or remove a reference count on the event	749	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	750	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	751	count is nonzero, C<ev_loop> will not return on its own.
		752
686	a watcher you never unregister that should not keep C<ev_loop> from	753	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	754	from returning, call ev_unref() after starting, and ev_ref() before
		755	stopping it.
		756
688	example, libev itself uses this for its internal signal pipe: It is not	757	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	758	is not visible to the libev user and should not keep C<ev_loop> from
690	no event watchers registered by it are active. It is also an excellent	759	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	760	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	761	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	762	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
695		766
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	768	running when nothing else is active.
698		769
699	struct ev_signal exitsig;	770	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	773	evf_unref (loop);
703		774
704	Example: For some weird reason, unregister the above signal handler again.	775	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>)	789	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	790	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	791	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	792	opportunities).
722		793
723	The background is that sometimes your program runs just fast enough to	794	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	795	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	796	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	797	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	798	overhead for the actual polling but can deliver many events at once.
728		799
729	By setting a higher I<io collect interval> you allow libev to spend more	800	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,	801	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	803	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.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
734		805
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	806	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	810	value will not introduce any overhead in libev.
740		811
741	Many (busy) programs can usually benefit by setting the I/O collect	812	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	813	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	814	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>,	815	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.	823	they fire on, say, one-second boundaries only.
753		824
754	=item ev_loop_verify (loop)	825	=item ev_loop_verify (loop)
755		826
756	This function only does something when C<EV_VERIFY> support has been	827	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	828	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	829	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	830	is found to be inconsistent, it will print an error message to standard
		831	error and call C<abort ()>.
760		832
761	This can be used to catch bugs inside libev itself: under normal	833	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	834	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	835	data structures consistent.
764		836
765	=back	837	=back
766		838
767		839
768	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
769		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
		845
770	A watcher is a structure that you create and register to record your	846	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	847	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	848	become readable, you would create an C<ev_io> watcher for that:
773		849
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	851	{
776	ev_io_stop (w);	852	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
778	}	854	}
779		855
780	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
781	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
782	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
785	ev_loop (loop, 0);	864	ev_loop (loop, 0);
786		865
787	As you can see, you are responsible for allocating the memory for your	866	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	867	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		872
791	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	874	(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	875	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	876	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	877	is readable and/or writable).
796		878
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	880	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	881	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
801		883
802	To make the watcher actually watch out for events, you have to start it	884	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	885	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	886	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		888
807	As long as your watcher is active (has been started but not stopped) you	889	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	890	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
810		892
811	Each and every callback receives the event loop pointer as first, the	893	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	894	registered watcher structure as second, and a bitset of received events as
813	third argument.	895	third argument.
814		896
…		…
872		954
873	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
874		956
875	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
876		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
877	=item C<EV_ERROR>	964	=item C<EV_ERROR>
878		965
879	An unspecified error has occurred, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	967	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	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
882	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
884		975
885	Libev will usually signal a few "dummy" events together with an error,	976	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	977	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	978	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	979	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
890		982
891	=back	983	=back
892		984
893	=head2 GENERIC WATCHER FUNCTIONS	985	=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		986
898	=over 4	987	=over 4
899		988
900	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
901		990
…		…
907	which rolls both calls into one.	996	which rolls both calls into one.
908		997
909	You can reinitialise a watcher at any time as long as it has been stopped	998	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	999	(or never started) and there are no pending events outstanding.
911		1000
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1002	int revents)>.
		1003
		1004	Example: Initialise an C<ev_io> watcher in two steps.
		1005
		1006	ev_io w;
		1007	ev_init (&w, my_cb);
		1008	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		1009
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		1011
917	This macro initialises the type-specific parts of a watcher. You need to	1012	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	1013	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
922		1017
923	Although some watcher types do not have type-specific arguments	1018	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.	1019	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1020
		1021	See C<ev_init>, above, for an example.
		1022
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1024
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1025	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	1026	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1027	a watcher. The same limitations apply, of course.
931		1028
		1029	Example: Initialise and set an C<ev_io> watcher in one step.
		1030
		1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1032
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		1034
934	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
936		1037
		1038	Example: Start the C<ev_io> watcher that is being abused as example in this
		1039	whole section.
		1040
		1041	ev_io_start (EV_DEFAULT_UC, &w);
		1042
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1044
939	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
940	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1049	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	1050	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	1051	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.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1053
946	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
947		1055
948	Returns a true value iff the watcher is active (i.e. it has been started	1056	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	1057	and not yet been stopped). As long as a watcher is active you must not modify
…		…
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
979		1087
		1088	See L<
		1089
980	This means that priorities are I<only> used for ordering callback	1090	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for	1091	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two	1092	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.	1093	watchers on the same event and make sure one is called first.
984		1094
…		…
991	The default priority used by watchers when no priority has been set is	1101	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 :).	1102	always C<0>, which is supposed to not be too high and not be too low :).
993		1103
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1104	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	1105	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.	1106	or might not have been clamped to the valid range.
997		1107
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1108	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1109
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1110	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	1111	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1112	can deal with that fact, as both are simply passed through to the
		1113	callback.
1003		1114
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1115	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1116
1006	If the watcher is pending, this function returns clears its pending status	1117	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	1118	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>.	1119	watcher isn't pending it does nothing and returns C<0>.
1009		1120
		1121	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1122	callback to be invoked, which can be accomplished with this function.
		1123
1010	=back	1124	=back
1011		1125
1012		1126
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1127	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1128
1015	Each watcher has, by default, a member C<void *data> that you can change	1129	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	1130	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	1131	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	1132	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	1133	member, you can also "subclass" the watcher type and provide your own
1020	data:	1134	data:
1021		1135
1022	struct my_io	1136	struct my_io
1023	{	1137	{
1024	struct ev_io io;	1138	ev_io io;
1025	int otherfd;	1139	int otherfd;
1026	void *somedata;	1140	void *somedata;
1027	struct whatever *mostinteresting;	1141	struct whatever *mostinteresting;
1028	};	1142	};
1029		1143
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1146	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1147
1034	And since your callback will be called with a pointer to the watcher, you	1148	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1149	can cast it back to your own type:
1036		1150
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1151	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1152	{
1039	struct my_io *w = (struct my_io *)w_;	1153	struct my_io *w = (struct my_io *)w_;
1040	...	1154	...
1041	}	1155	}
1042		1156
…		…
1053	ev_timer t2;	1167	ev_timer t2;
1054	}	1168	}
1055		1169
1056	In this case getting the pointer to C<my_biggy> is a bit more	1170	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	1171	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	1172	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1173	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1174	programmers):
1060		1175
1061	#include <stddef.h>	1176	#include <stddef.h>
1062		1177
1063	static void	1178	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1179	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1180	{
1066	struct my_biggy big = (struct my_biggy *	1181	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1182	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1183	}
1069		1184
1070	static void	1185	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1186	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1187	{
1073	struct my_biggy big = (struct my_biggy *	1188	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1189	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1190	}
1076		1191
…		…
1104	In general you can register as many read and/or write event watchers per	1219	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	1220	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	1221	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1222	required if you know what you are doing).
1108		1223
1109	If you must do this, then force the use of a known-to-be-good backend	1224	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	1225	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1226	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1227
1113	Another thing you have to watch out for is that it is quite easy to	1228	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	1229	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	1230	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	1231	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	1232	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	1233	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	1234	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.	1235	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1236
1122	If you cannot run the fd in non-blocking mode (for example you should not	1237	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	1238	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	1239	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	1240	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1241	does this on its own, so its quite safe to use). Some people additionally
		1242	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1243	indefinitely.
		1244
		1245	But really, best use non-blocking mode.
1127		1246
1128	=head3 The special problem of disappearing file descriptors	1247	=head3 The special problem of disappearing file descriptors
1129		1248
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1249	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,	1250	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	1251	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	1252	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	1253	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	1254	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1255	fact, a different file descriptor.
1137		1256
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1287	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1288	C<EVBACKEND_POLL>.
1170		1289
1171	=head3 The special problem of SIGPIPE	1290	=head3 The special problem of SIGPIPE
1172		1291
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1292	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	1293	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	1294	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1295	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1296
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1297	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	1298	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).	1299	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1306	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1307
1189	=item ev_io_set (ev_io *, int fd, int events)	1308	=item ev_io_set (ev_io *, int fd, int events)
1190		1309
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1310	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	1311	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.	1312	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1313
1195	=item int fd [read-only]	1314	=item int fd [read-only]
1196		1315
1197	The file descriptor being watched.	1316	The file descriptor being watched.
1198		1317
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1326	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	1327	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1328	attempt to read a whole line in the callback.
1210		1329
1211	static void	1330	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1331	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1332	{
1214	ev_io_stop (loop, w);	1333	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1334	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1335	}
1217		1336
1218	...	1337	...
1219	struct ev_loop *loop = ev_default_init (0);	1338	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1339	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1340	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1341	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1342	ev_loop (loop, 0);
1224		1343
1225		1344
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1347	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1348	given time, and optionally repeating in regular intervals after that.
1230		1349
1231	The timers are based on real time, that is, if you register an event that	1350	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	1351	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	1352	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1353	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1354	monotonic clock option helps a lot here).
1236		1355
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1356	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	1357	passed. If multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1358	then the ones with earlier time-out values are invoked before ones with
		1359	later time-out values (but this is no longer true when a callback calls
		1360	C<ev_loop> recursively).
		1361
		1362	=head3 Be smart about timeouts
		1363
		1364	Many real-world problems involve some kind of timeout, usually for error
		1365	recovery. A typical example is an HTTP request - if the other side hangs,
		1366	you want to raise some error after a while.
		1367
		1368	What follows are some ways to handle this problem, from obvious and
		1369	inefficient to smart and efficient.
		1370
		1371	In the following, a 60 second activity timeout is assumed - a timeout that
		1372	gets reset to 60 seconds each time there is activity (e.g. each time some
		1373	data or other life sign was received).
		1374
		1375	=over 4
		1376
		1377	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1378
		1379	This is the most obvious, but not the most simple way: In the beginning,
		1380	start the watcher:
		1381
		1382	ev_timer_init (timer, callback, 60., 0.);
		1383	ev_timer_start (loop, timer);
		1384
		1385	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1386	and start it again:
		1387
		1388	ev_timer_stop (loop, timer);
		1389	ev_timer_set (timer, 60., 0.);
		1390	ev_timer_start (loop, timer);
		1391
		1392	This is relatively simple to implement, but means that each time there is
		1393	some activity, libev will first have to remove the timer from its internal
		1394	data structure and then add it again. Libev tries to be fast, but it's
		1395	still not a constant-time operation.
		1396
		1397	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1398
		1399	This is the easiest way, and involves using C<ev_timer_again> instead of
		1400	C<ev_timer_start>.
		1401
		1402	To implement this, configure an C<ev_timer> with a C<repeat> value
		1403	of C<60> and then call C<ev_timer_again> at start and each time you
		1404	successfully read or write some data. If you go into an idle state where
		1405	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1406	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1407
		1408	That means you can ignore both the C<ev_timer_start> function and the
		1409	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1410	member and C<ev_timer_again>.
		1411
		1412	At start:
		1413
		1414	ev_timer_init (timer, callback);
		1415	timer->repeat = 60.;
		1416	ev_timer_again (loop, timer);
		1417
		1418	Each time there is some activity:
		1419
		1420	ev_timer_again (loop, timer);
		1421
		1422	It is even possible to change the time-out on the fly, regardless of
		1423	whether the watcher is active or not:
		1424
		1425	timer->repeat = 30.;
		1426	ev_timer_again (loop, timer);
		1427
		1428	This is slightly more efficient then stopping/starting the timer each time
		1429	you want to modify its timeout value, as libev does not have to completely
		1430	remove and re-insert the timer from/into its internal data structure.
		1431
		1432	It is, however, even simpler than the "obvious" way to do it.
		1433
		1434	=item 3. Let the timer time out, but then re-arm it as required.
		1435
		1436	This method is more tricky, but usually most efficient: Most timeouts are
		1437	relatively long compared to the intervals between other activity - in
		1438	our example, within 60 seconds, there are usually many I/O events with
		1439	associated activity resets.
		1440
		1441	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1442	but remember the time of last activity, and check for a real timeout only
		1443	within the callback:
		1444
		1445	ev_tstamp last_activity; // time of last activity
		1446
		1447	static void
		1448	callback (EV_P_ ev_timer *w, int revents)
		1449	{
		1450	ev_tstamp now = ev_now (EV_A);
		1451	ev_tstamp timeout = last_activity + 60.;
		1452
		1453	// if last_activity + 60. is older than now, we did time out
		1454	if (timeout < now)
		1455	{
		1456	// timeout occured, take action
		1457	}
		1458	else
		1459	{
		1460	// callback was invoked, but there was some activity, re-arm
		1461	// the watcher to fire in last_activity + 60, which is
		1462	// guaranteed to be in the future, so "again" is positive:
		1463	w->repeat = timeout - now;
		1464	ev_timer_again (EV_A_ w);
		1465	}
		1466	}
		1467
		1468	To summarise the callback: first calculate the real timeout (defined
		1469	as "60 seconds after the last activity"), then check if that time has
		1470	been reached, which means something I<did>, in fact, time out. Otherwise
		1471	the callback was invoked too early (C<timeout> is in the future), so
		1472	re-schedule the timer to fire at that future time, to see if maybe we have
		1473	a timeout then.
		1474
		1475	Note how C<ev_timer_again> is used, taking advantage of the
		1476	C<ev_timer_again> optimisation when the timer is already running.
		1477
		1478	This scheme causes more callback invocations (about one every 60 seconds
		1479	minus half the average time between activity), but virtually no calls to
		1480	libev to change the timeout.
		1481
		1482	To start the timer, simply initialise the watcher and set C<last_activity>
		1483	to the current time (meaning we just have some activity :), then call the
		1484	callback, which will "do the right thing" and start the timer:
		1485
		1486	ev_timer_init (timer, callback);
		1487	last_activity = ev_now (loop);
		1488	callback (loop, timer, EV_TIMEOUT);
		1489
		1490	And when there is some activity, simply store the current time in
		1491	C<last_activity>, no libev calls at all:
		1492
		1493	last_actiivty = ev_now (loop);
		1494
		1495	This technique is slightly more complex, but in most cases where the
		1496	time-out is unlikely to be triggered, much more efficient.
		1497
		1498	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1499	callback :) - just change the timeout and invoke the callback, which will
		1500	fix things for you.
		1501
		1502	=item 4. Wee, just use a double-linked list for your timeouts.
		1503
		1504	If there is not one request, but many thousands (millions...), all
		1505	employing some kind of timeout with the same timeout value, then one can
		1506	do even better:
		1507
		1508	When starting the timeout, calculate the timeout value and put the timeout
		1509	at the I<end> of the list.
		1510
		1511	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1512	the list is expected to fire (for example, using the technique #3).
		1513
		1514	When there is some activity, remove the timer from the list, recalculate
		1515	the timeout, append it to the end of the list again, and make sure to
		1516	update the C<ev_timer> if it was taken from the beginning of the list.
		1517
		1518	This way, one can manage an unlimited number of timeouts in O(1) time for
		1519	starting, stopping and updating the timers, at the expense of a major
		1520	complication, and having to use a constant timeout. The constant timeout
		1521	ensures that the list stays sorted.
		1522
		1523	=back
		1524
		1525	So which method the best?
		1526
		1527	Method #2 is a simple no-brain-required solution that is adequate in most
		1528	situations. Method #3 requires a bit more thinking, but handles many cases
		1529	better, and isn't very complicated either. In most case, choosing either
		1530	one is fine, with #3 being better in typical situations.
		1531
		1532	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1533	rather complicated, but extremely efficient, something that really pays
		1534	off after the first million or so of active timers, i.e. it's usually
		1535	overkill :)
1240		1536
1241	=head3 The special problem of time updates	1537	=head3 The special problem of time updates
1242		1538
1243	Establishing the current time is a costly operation (it usually takes at	1539	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	1540	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	1541	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	1542	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1543	lots of events in one iteration.
1248		1544
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1545	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	1546	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	1547	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	1548	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).	1584	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1585
1290	If the timer is repeating, either start it if necessary (with the	1586	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.	1587	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1588
1293	This sounds a bit complicated, but here is a useful and typical	1589	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1590	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		1591
1318	=item ev_tstamp repeat [read-write]	1592	=item ev_tstamp repeat [read-write]
1319		1593
1320	The current C<repeat> value. Will be used each time the watcher times out	1594	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),	1595	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.	1596	which is also when any modifications are taken into account.
1323		1597
1324	=back	1598	=back
1325		1599
1326	=head3 Examples	1600	=head3 Examples
1327		1601
1328	Example: Create a timer that fires after 60 seconds.	1602	Example: Create a timer that fires after 60 seconds.
1329		1603
1330	static void	1604	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1605	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1606	{
1333	.. one minute over, w is actually stopped right here	1607	.. one minute over, w is actually stopped right here
1334	}	1608	}
1335		1609
1336	struct ev_timer mytimer;	1610	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1611	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1612	ev_timer_start (loop, &mytimer);
1339		1613
1340	Example: Create a timeout timer that times out after 10 seconds of	1614	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1615	inactivity.
1342		1616
1343	static void	1617	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1618	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1619	{
1346	.. ten seconds without any activity	1620	.. ten seconds without any activity
1347	}	1621	}
1348		1622
1349	struct ev_timer mytimer;	1623	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1624	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1625	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1626	ev_loop (loop, 0);
1353		1627
1354	// and in some piece of code that gets executed on any "activity":	1628	// and in some piece of code that gets executed on any "activity":
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	1633	=head2 C<ev_periodic> - to cron or not to cron?
1360		1634
1361	Periodic watchers are also timers of a kind, but they are very versatile	1635	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	1636	(and unfortunately a bit complex).
1363		1637
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1638	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	1639	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	1640	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1641	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	1642	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	1643	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		1644
		1645	You can tell a periodic watcher to trigger after some specific point
		1646	in time: for example, if you tell a periodic watcher to trigger "in 10
		1647	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1648	not a delay) and then reset your system clock to January of the previous
		1649	year, then it will take a year or more to trigger the event (unlike an
		1650	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1651	it, as it uses a relative timeout).
		1652
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1653	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	1654	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	1655	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1656	those cannot react to time jumps.
1376		1657
1377	As with timers, the callback is guaranteed to be invoked only when the	1658	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	1659	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	1660	timers become ready during the same loop iteration then the ones with
		1661	earlier time-out values are invoked before ones with later time-out values
		1662	(but this is no longer true when a callback calls C<ev_loop> recursively).
1380		1663
1381	=head3 Watcher-Specific Functions and Data Members	1664	=head3 Watcher-Specific Functions and Data Members
1382		1665
1383	=over 4	1666	=over 4
1384		1667
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1668	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		1669
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1670	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		1671
1389	Lots of arguments, lets sort it out... There are basically three modes of	1672	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1673	operation, and we will explain them from simplest to most complex:
1391		1674
1392	=over 4	1675	=over 4
1393		1676
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1677	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		1678
1396	In this configuration the watcher triggers an event after the wall clock	1679	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	1680	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1681	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	1682	will be stopped and invoked when the system clock reaches or surpasses
		1683	this point in time.
1400		1684
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1685	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		1686
1403	In this mode the watcher will always be scheduled to time out at the next	1687	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)	1688	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	1689	negative) and then repeat, regardless of any time jumps. The C<offset>
		1690	argument is merely an offset into the C<interval> periods.
1406		1691
1407	This can be used to create timers that do not drift with respect to system	1692	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	1693	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	1694	hour, on the hour (with respect to UTC):
1410		1695
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1696	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1697
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1698	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	1699	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	1700	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	1701	by 3600.
1417		1702
1418	Another way to think about it (for the mathematically inclined) is that	1703	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	1704	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	1705	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		1706
1422	For numerical stability it is preferable that the C<at> value is near	1707	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	1708	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	1709	this value, and in fact is often specified as zero.
1425		1710
1426	Note also that there is an upper limit to how often a timer can fire (CPU	1711	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	1712	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	1713	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	1714	millisecond (if the OS supports it and the machine is fast enough).
1430		1715
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1716	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		1717
1433	In this mode the values for C<interval> and C<at> are both being	1718	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	1719	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	1720	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	1721	current time as second argument.
1437		1722
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1723	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	1724	or make ANY other event loop modifications whatsoever, unless explicitly
		1725	allowed by documentation here>.
1440		1726
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1727	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	1728	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1729	only event loop modification you are allowed to do).
1444		1730
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1731	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1732	*w, ev_tstamp now)>, e.g.:
1447		1733
		1734	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1735	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1736	{
1450	return now + 60.;	1737	return now + 60.;
1451	}	1738	}
1452		1739
1453	It must return the next time to trigger, based on the passed time value	1740	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	1760	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	1761	program when the crontabs have changed).
1475		1762
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	1763	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		1764
1478	When active, returns the absolute time that the watcher is supposed to	1765	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	1766	to trigger next. This is not the same as the C<offset> argument to
		1767	C<ev_periodic_set>, but indeed works even in interval and manual
		1768	rescheduling modes.
1480		1769
1481	=item ev_tstamp offset [read-write]	1770	=item ev_tstamp offset [read-write]
1482		1771
1483	When repeating, this contains the offset value, otherwise this is the	1772	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1773	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1774	although libev might modify this value for better numerical stability).
1485		1775
1486	Can be modified any time, but changes only take effect when the periodic	1776	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	1777	timer fires or C<ev_periodic_again> is being called.
1488		1778
1489	=item ev_tstamp interval [read-write]	1779	=item ev_tstamp interval [read-write]
1490		1780
1491	The current interval value. Can be modified any time, but changes only	1781	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	1782	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1783	called.
1494		1784
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1785	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1786
1497	The current reschedule callback, or C<0>, if this functionality is	1787	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	1788	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.	1789	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1790
1501	=back	1791	=back
1502		1792
1503	=head3 Examples	1793	=head3 Examples
1504		1794
1505	Example: Call a callback every hour, or, more precisely, whenever the	1795	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1796	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1797	potentially a lot of jitter, but good long-term stability.
1508		1798
1509	static void	1799	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1800	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1801	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1802	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1803	}
1514		1804
1515	struct ev_periodic hourly_tick;	1805	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1806	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1807	ev_periodic_start (loop, &hourly_tick);
1518		1808
1519	Example: The same as above, but use a reschedule callback to do it:	1809	Example: The same as above, but use a reschedule callback to do it:
1520		1810
1521	#include <math.h>	1811	#include <math.h>
1522		1812
1523	static ev_tstamp	1813	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1814	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1815	{
1526	return fmod (now, 3600.) + 3600.;	1816	return now + (3600. - fmod (now, 3600.));
1527	}	1817	}
1528		1818
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1819	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1820
1531	Example: Call a callback every hour, starting now:	1821	Example: Call a callback every hour, starting now:
1532		1822
1533	struct ev_periodic hourly_tick;	1823	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1824	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1825	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1826	ev_periodic_start (loop, &hourly_tick);
1537		1827
1538		1828
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1831	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	1832	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	1833	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1834	normal event processing, like any other event.
1545		1835
		1836	If you want signals asynchronously, just use C<sigaction> as you would
		1837	do without libev and forget about sharing the signal. You can even use
		1838	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1839
1546	You can configure as many watchers as you like per signal. Only when the	1840	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	1841	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	1842	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	1843	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	1844	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1845	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1846
1553	If possible and supported, libev will install its handlers with	1847	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1848	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	1849	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	1850	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1867
1574	=back	1868	=back
1575		1869
1576	=head3 Examples	1870	=head3 Examples
1577		1871
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1872	Example: Try to exit cleanly on SIGINT.
1579		1873
1580	static void	1874	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1875	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1876	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1877	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1878	}
1585		1879
1586	struct ev_signal signal_watcher;	1880	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1881	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1882	ev_signal_start (loop, &signal_watcher);
1589		1883
1590		1884
1591	=head2 C<ev_child> - watch out for process status changes	1885	=head2 C<ev_child> - watch out for process status changes
1592		1886
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1887	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	1888	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	1889	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	1890	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1891	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1892	forking and then immediately registering a watcher for the child is fine,
		1893	but forking and registering a watcher a few event loop iterations later is
		1894	not.
1598		1895
1599	Only the default event loop is capable of handling signals, and therefore	1896	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1897	you can only register child watchers in the default event loop.
1601		1898
1602	=head3 Process Interaction	1899	=head3 Process Interaction
…		…
1663	its completion.	1960	its completion.
1664		1961
1665	ev_child cw;	1962	ev_child cw;
1666		1963
1667	static void	1964	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	1965	child_cb (EV_P_ ev_child *w, int revents)
1669	{	1966	{
1670	ev_child_stop (EV_A_ w);	1967	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1968	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	1969	}
1673		1970
…		…
1688		1985
1689		1986
1690	=head2 C<ev_stat> - did the file attributes just change?	1987	=head2 C<ev_stat> - did the file attributes just change?
1691		1988
1692	This watches a file system path for attribute changes. That is, it calls	1989	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	1990	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.	1991	and sees if it changed compared to the last time, invoking the callback if
		1992	it did.
1695		1993
1696	The path does not need to exist: changing from "path exists" to "path does	1994	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	1995	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	1996	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	1997	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	1998	least one) and all the other fields of the stat buffer having unspecified
		1999	contents.
1701		2000
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2001	The path I<must not> end in a slash or contain special components such as
		2002	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.	2003	your working directory changes, then the behaviour is undefined.
1704		2004
1705	Since there is no standard to do this, the portable implementation simply	2005	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	2006	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2007	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,	2008	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	2009	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2010	(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	2011	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2012	currently around C<0.1>, but that's usually overkill.
1713		2013
1714	This watcher type is not meant for massive numbers of stat watchers,	2014	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2015	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2016	resource-intensive.
1717		2017
1718	At the time of this writing, only the Linux inotify interface is	2018	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2019	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2020	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2021	implementing C<ev_stat> semantics with kqueue, except as a hint).
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		2022
1727	=head3 ABI Issues (Largefile Support)	2023	=head3 ABI Issues (Largefile Support)
1728		2024
1729	Libev by default (unless the user overrides this) uses the default	2025	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2026	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2027	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	2028	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	2029	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	2030	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	2031	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.	2032	most noticeably displayed with ev_stat and large file support.
1737		2033
1738	The solution for this is to lobby your distribution maker to make large	2034	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	2035	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	2036	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2037	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2038	default compilation environment.
1743		2039
1744	=head3 Inotify	2040	=head3 Inotify and Kqueue
1745		2041
1746	When C<inotify (7)> support has been compiled into libev (generally only	2042	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2043	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2044	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2045	watcher is being started.
1750		2046
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2047	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	2048	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	2049	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.	2050	there are many cases where libev has to resort to regular C<stat> polling,
		2051	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2052	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2053	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2054	xfs are fully working) libev usually gets away without polling.
1755		2055
1756	(There is no support for kqueue, as apparently it cannot be used to	2056	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	2057	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2058	descriptor open on the object at all times, and detecting renames, unlinks
		2059	etc. is difficult.
		2060
		2061	=head3 C<stat ()> is a synchronous operation
		2062
		2063	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2064	the process. The exception are C<ev_stat> watchers - those call C<stat
		2065	()>, which is a synchronous operation.
		2066
		2067	For local paths, this usually doesn't matter: unless the system is very
		2068	busy or the intervals between stat's are large, a stat call will be fast,
		2069	as the path data is usually in memory already (except when starting the
		2070	watcher).
		2071
		2072	For networked file systems, calling C<stat ()> can block an indefinite
		2073	time due to network issues, and even under good conditions, a stat call
		2074	often takes multiple milliseconds.
		2075
		2076	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2077	paths, although this is fully supported by libev.
1759		2078
1760	=head3 The special problem of stat time resolution	2079	=head3 The special problem of stat time resolution
1761		2080
1762	The C<stat ()> system call only supports full-second resolution portably, and	2081	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2082	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2083	still only support whole seconds.
1765		2084
1766	That means that, if the time is the only thing that changes, you can	2085	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	2086	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	2087	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	2088	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2089	stat data does change in other ways (e.g. file size).
1771		2090
1772	The solution to this is to delay acting on a change for slightly more	2091	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	2092	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);	2093	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2094	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2114	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	2115	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	2116	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.	2117	path for as long as the watcher is active.
1799		2118
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2119	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	2120	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2121	last change was detected).
1803		2122
1804	=item ev_stat_stat (loop, ev_stat *)	2123	=item ev_stat_stat (loop, ev_stat *)
1805		2124
1806	Updates the stat buffer immediately with new values. If you change the	2125	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	2126	watched path in your callback, you could call this function to avoid
…		…
1890		2209
1891		2210
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2211	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2212
1894	Idle watchers trigger events when no other events of the same or higher	2213	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	2214	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2215	as receiving "events").
1897		2216
1898	That is, as long as your process is busy handling sockets or timeouts	2217	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	2218	(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	2219	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	2220	are pending), the idle watchers are being called once per event loop
…		…
1912		2231
1913	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1914		2233
1915	=over 4	2234	=over 4
1916		2235
1917	=item ev_idle_init (ev_signal *, callback)	2236	=item ev_idle_init (ev_idle *, callback)
1918		2237
1919	Initialises and configures the idle watcher - it has no parameters of any	2238	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2239	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2240	believe me.
1922		2241
…		…
1926		2245
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2246	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2247	callback, free it. Also, use no error checking, as usual.
1929		2248
1930	static void	2249	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2250	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2251	{
1933	free (w);	2252	free (w);
1934	// now do something you wanted to do when the program has	2253	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2254	// no longer anything immediate to do.
1936	}	2255	}
1937		2256
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2257	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2258	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2259	ev_idle_start (loop, idle_cb);
1941		2260
1942		2261
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2262	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2263
1945	Prepare and check watchers are usually (but not always) used in tandem:	2264	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2265	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2266	afterwards.
1948		2267
1949	You I<must not> call C<ev_loop> or similar functions that enter	2268	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>	2269	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,	2272	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	2273	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2274	called in pairs bracketing the blocking call.
1956		2275
1957	Their main purpose is to integrate other event mechanisms into libev and	2276	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	2277	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	2278	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2279	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,	2280	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>	2281	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2282	watcher).
1964		2283
1965	This is done by examining in each prepare call which file descriptors need	2284	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	2285	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	2286	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	2287	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2288	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	2289	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,	2290	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2291	nevertheless, because you never know, you know?).
1973		2292
1974	As another example, the Perl Coro module uses these hooks to integrate	2293	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2294	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2295	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	2296	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	2299	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2300	low-priority coroutines to idle/background tasks).
1982		2301
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2302	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	2303	priority, to ensure that they are being run before any other watchers
		2304	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2305
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2306	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	2307	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2308	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	2309	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	2310	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	2311	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2312	others).
1992		2313
1993	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1994		2315
1995	=over 4	2316	=over 4
1996		2317
…		…
1998		2319
1999	=item ev_check_init (ev_check *, callback)	2320	=item ev_check_init (ev_check *, callback)
2000		2321
2001	Initialises and configures the prepare or check watcher - they have no	2322	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>	2323	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.	2324	macros, but using them is utterly, utterly, utterly and completely
		2325	pointless.
2004		2326
2005	=back	2327	=back
2006		2328
2007	=head3 Examples	2329	=head3 Examples
2008		2330
…		…
2021		2343
2022	static ev_io iow [nfd];	2344	static ev_io iow [nfd];
2023	static ev_timer tw;	2345	static ev_timer tw;
2024		2346
2025	static void	2347	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2348	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2349	{
2028	}	2350	}
2029		2351
2030	// create io watchers for each fd and a timer before blocking	2352	// create io watchers for each fd and a timer before blocking
2031	static void	2353	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2354	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2355	{
2034	int timeout = 3600000;	2356	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2357	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2358	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2374	}
2053	}	2375	}
2054		2376
2055	// stop all watchers after blocking	2377	// stop all watchers after blocking
2056	static void	2378	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2379	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2380	{
2059	ev_timer_stop (loop, &tw);	2381	ev_timer_stop (loop, &tw);
2060		2382
2061	for (int i = 0; i < nfd; ++i)	2383	for (int i = 0; i < nfd; ++i)
2062	{	2384	{
…		…
2101	}	2423	}
2102		2424
2103	// do not ever call adns_afterpoll	2425	// do not ever call adns_afterpoll
2104		2426
2105	Method 4: Do not use a prepare or check watcher because the module you	2427	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	2428	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	2429	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	2430	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2431	this approach, effectively embedding EV as a client into the horrible
		2432	libglib event loop.
2110		2433
2111	static gint	2434	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2435	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2436	{
2114	int got_events = 0;	2437	int got_events = 0;
…		…
2145	prioritise I/O.	2468	prioritise I/O.
2146		2469
2147	As an example for a bug workaround, the kqueue backend might only support	2470	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	2471	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	2472	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	2473	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	2474	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	2475	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.	2476	C<kevent>, but at least you can use both mechanisms for what they are
		2477	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2478
2155	As for prioritising I/O: rarely you have the case where some fds have	2479	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	2480	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	2481	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	2482	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.	2483	the rest in a second one, and embed the second one in the first.
2160		2484
2161	As long as the watcher is active, the callback will be invoked every time	2485	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2486	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2487	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2488	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2489	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2490	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2491
2169	As long as the watcher is started it will automatically handle events. The	2492	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2493	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2494
2174	Also, there have not currently been made special provisions for forking:	2495	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2496	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2497	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2498	C<ev_loop_fork> on the embedded loop.
2178		2499
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2500	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2501	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2502	portable one.
2182		2503
2183	So when you want to use this feature you will always have to be prepared	2504	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	2505	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	2506	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.	2507	create it, and if that fails, use the normal loop for everything.
		2508
		2509	=head3 C<ev_embed> and fork
		2510
		2511	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2512	automatically be applied to the embedded loop as well, so no special
		2513	fork handling is required in that case. When the watcher is not running,
		2514	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2515	as applicable.
2187		2516
2188	=head3 Watcher-Specific Functions and Data Members	2517	=head3 Watcher-Specific Functions and Data Members
2189		2518
2190	=over 4	2519	=over 4
2191		2520
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2548	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2549	used).
2221		2550
2222	struct ev_loop *loop_hi = ev_default_init (0);	2551	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2552	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2553	ev_embed embed;
2225		2554
2226	// see if there is a chance of getting one that works	2555	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2556	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2557	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2558	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2572	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2573	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2574
2246	struct ev_loop *loop = ev_default_init (0);	2575	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2576	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2577	ev_embed embed;
2249		2578
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2579	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2580	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2581	{
2253	ev_embed_init (&embed, 0, loop_socket);	2582	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2638	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	2639	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2640	need elaborate support such as pthreads.
2312		2641
2313	That means that if you want to queue data, you have to provide your own	2642	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	2643	queue. But at least I can tell you how to implement locking around your
2315	queue:	2644	queue:
2316		2645
2317	=over 4	2646	=over 4
2318		2647
2319	=item queueing from a signal handler context	2648	=item queueing from a signal handler context
2320		2649
2321	To implement race-free queueing, you simply add to the queue in the signal	2650	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	2651	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2652	an example that does that for some fictitious SIGUSR1 handler:
2324		2653
2325	static ev_async mysig;	2654	static ev_async mysig;
2326		2655
2327	static void	2656	static void
2328	sigusr1_handler (void)	2657	sigusr1_handler (void)
…		…
2394	=over 4	2723	=over 4
2395		2724
2396	=item ev_async_init (ev_async *, callback)	2725	=item ev_async_init (ev_async *, callback)
2397		2726
2398	Initialises and configures the async watcher - it has no parameters of any	2727	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,	2728	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2729	trust me.
2401		2730
2402	=item ev_async_send (loop, ev_async *)	2731	=item ev_async_send (loop, ev_async *)
2403		2732
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2733	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	2734	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	2735	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	2736	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2737	section below on what exactly this means).
2409		2738
		2739	Note that, as with other watchers in libev, multiple events might get
		2740	compressed into a single callback invocation (another way to look at this
		2741	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2742	reset when the event loop detects that).
		2743
2410	This call incurs the overhead of a system call only once per loop iteration,	2744	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	2745	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	2746	repeated calls to C<ev_async_send> for the same event loop.
2413		2747
2414	=item bool = ev_async_pending (ev_async *)	2748	=item bool = ev_async_pending (ev_async *)
2415		2749
2416	Returns a non-zero value when C<ev_async_send> has been called on the	2750	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	2751	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2754	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	2755	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	2756	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	2757	quickly check whether invoking the loop might be a good idea.
2424		2758
2425	Not that this does I<not> check whether the watcher itself is pending, only	2759	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	2760	only whether it has been requested to make this watcher pending: there
		2761	is a time window between the event loop checking and resetting the async
		2762	notification, and the callback being invoked.
2427		2763
2428	=back	2764	=back
2429		2765
2430		2766
2431	=head1 OTHER FUNCTIONS	2767	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	2771	=over 4
2436		2772
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2773	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2774
2439	This function combines a simple timer and an I/O watcher, calls your	2775	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2776	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	2777	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	2778	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2779	more watchers yourself.
2444		2780
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2781	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	2782	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2783	the given C<fd> and C<events> set will be created and started.
2448		2784
2449	If C<timeout> is less than 0, then no timeout watcher will be	2785	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	2786	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	2787	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2788
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2789	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	2790	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>	2791	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2792	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2793	a timeout and an io event at the same time - you probably should give io
		2794	events precedence.
		2795
		2796	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2797
2459	static void stdin_ready (int revents, void *arg)	2798	static void stdin_ready (int revents, void *arg)
2460	{	2799	{
		2800	if (revents & EV_READ)
		2801	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2802	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2803	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2804	}
2466		2805
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2806	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2807
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2808	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2809
2471	Feeds the given event set into the event loop, as if the specified event	2810	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	2811	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2812	initialised but not necessarily started event watcher).
2474		2813
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2814	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2815
2477	Feed an event on the given fd, as if a file descriptor backend detected	2816	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2817	the given events it.
2479		2818
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2819	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2820
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2821	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2822	loop!).
2484		2823
2485	=back	2824	=back
…		…
2607		2946
2608	myclass obj;	2947	myclass obj;
2609	ev::io iow;	2948	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	2949	iow.set <myclass, &myclass::io_cb> (&obj);
2611		2950
		2951	=item w->set (object *)
		2952
		2953	This is an B<experimental> feature that might go away in a future version.
		2954
		2955	This is a variation of a method callback - leaving out the method to call
		2956	will default the method to C<operator ()>, which makes it possible to use
		2957	functor objects without having to manually specify the C<operator ()> all
		2958	the time. Incidentally, you can then also leave out the template argument
		2959	list.
		2960
		2961	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2962	int revents)>.
		2963
		2964	See the method-C<set> above for more details.
		2965
		2966	Example: use a functor object as callback.
		2967
		2968	struct myfunctor
		2969	{
		2970	void operator() (ev::io &w, int revents)
		2971	{
		2972	...
		2973	}
		2974	}
		2975
		2976	myfunctor f;
		2977
		2978	ev::io w;
		2979	w.set (&f);
		2980
2612	=item w->set<function> (void *data = 0)	2981	=item w->set<function> (void *data = 0)
2613		2982
2614	Also sets a callback, but uses a static method or plain function as	2983	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	2984	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	2985	C<data> member and is free for you to use.
2617		2986
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2987	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		2988
2620	See the method-C<set> above for more details.	2989	See the method-C<set> above for more details.
2621		2990
2622	Example:	2991	Example: Use a plain function as callback.
2623		2992
2624	static void io_cb (ev::io &w, int revents) { }	2993	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	2994	iow.set <io_cb> ();
2626		2995
2627	=item w->set (struct ev_loop *)	2996	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	3034	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	3035	the constructor.
2667		3036
2668	class myclass	3037	class myclass
2669	{	3038	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3039	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3040	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3041
2673	myclass (int fd)	3042	myclass (int fd)
2674	{	3043	{
2675	io .set <myclass, &myclass::io_cb > (this);	3044	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3045	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3061	=item Perl
2693		3062
2694	The EV module implements the full libev API and is actually used to test	3063	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,	3064	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3065	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	3066	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>).	3067	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3068	and C<EV::Glib>).
2699		3069
2700	It can be found and installed via CPAN, its homepage is at	3070	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3071	L<http://software.schmorp.de/pkg/EV>.
2702		3072
2703	=item Python	3073	=item Python
2704		3074
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3075	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3076	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3077
2712	=item Ruby	3078	=item Ruby
2713		3079
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3080	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3081	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3082	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3083	L<http://rev.rubyforge.org/>.
2718		3084
		3085	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3086	makes rev work even on mingw.
		3087
		3088	=item Haskell
		3089
		3090	A haskell binding to libev is available at
		3091	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3092
2719	=item D	3093	=item D
2720		3094
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3095	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>.	3096	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3097
		3098	=item Ocaml
		3099
		3100	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3101	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2723		3102
2724	=back	3103	=back
2725		3104
2726		3105
2727	=head1 MACRO MAGIC	3106	=head1 MACRO MAGIC
…		…
2828		3207
2829	#define EV_STANDALONE 1	3208	#define EV_STANDALONE 1
2830	#include "ev.h"	3209	#include "ev.h"
2831		3210
2832	Both header files and implementation files can be compiled with a C++	3211	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	3212	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3213	as a bug).
2835		3214
2836	You need the following files in your source tree, or in a directory	3215	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):	3216	in your include path (e.g. in libev/ when using -Ilibev):
2838		3217
…		…
2882		3261
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3262	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3263
2885	Libev can be configured via a variety of preprocessor symbols you have to	3264	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	3265	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3266	autoconf is documented for every option.
2888		3267
2889	=over 4	3268	=over 4
2890		3269
2891	=item EV_STANDALONE	3270	=item EV_STANDALONE
2892		3271
…		…
2894	keeps libev from including F<config.h>, and it also defines dummy	3273	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3274	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3275	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3276	F<event.h> that are not directly supported by the libev core alone.
2898		3277
		3278	In stanbdalone mode, libev will still try to automatically deduce the
		3279	configuration, but has to be more conservative.
		3280
2899	=item EV_USE_MONOTONIC	3281	=item EV_USE_MONOTONIC
2900		3282
2901	If defined to be C<1>, libev will try to detect the availability of the	3283	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3284	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3285	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3286	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3287	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3288	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3289	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3290
2909	=item EV_USE_REALTIME	3291	=item EV_USE_REALTIME
2910		3292
2911	If defined to be C<1>, libev will try to detect the availability of the	3293	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3294	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3295	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3296	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3297	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3298	correctness. See the note about libraries in the description of
		3299	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3300	C<EV_USE_CLOCK_SYSCALL>.
		3301
		3302	=item EV_USE_CLOCK_SYSCALL
		3303
		3304	If defined to be C<1>, libev will try to use a direct syscall instead
		3305	of calling the system-provided C<clock_gettime> function. This option
		3306	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3307	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3308	programs needlessly. Using a direct syscall is slightly slower (in
		3309	theory), because no optimised vdso implementation can be used, but avoids
		3310	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3311	higher, as it simplifies linking (no need for C<-lrt>).
2917		3312
2918	=item EV_USE_NANOSLEEP	3313	=item EV_USE_NANOSLEEP
2919		3314
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3315	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3316	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3332
2938	=item EV_SELECT_USE_FD_SET	3333	=item EV_SELECT_USE_FD_SET
2939		3334
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3335	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3336	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3337	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3338	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3339	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3340	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3341	configures the maximum size of the C<fd_set>.
2947		3342
2948	=item EV_SELECT_IS_WINSOCKET	3343	=item EV_SELECT_IS_WINSOCKET
2949		3344
2950	When defined to C<1>, the select backend will assume that	3345	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3346	select/socket/connect etc. don't understand file descriptors but
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3457	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	3458	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	3459	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3460	fine.
3066		3461
3067	If your embedding application does not need any priorities, defining these both to	3462	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3463	both to C<0> will save some memory and CPU.
3069		3464
3070	=item EV_PERIODIC_ENABLE	3465	=item EV_PERIODIC_ENABLE
3071		3466
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3467	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	3468	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3475	code.
3081		3476
3082	=item EV_EMBED_ENABLE	3477	=item EV_EMBED_ENABLE
3083		3478
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3479	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3480	defined to be C<0>, then they are not. Embed watchers rely on most other
		3481	watcher types, which therefore must not be disabled.
3086		3482
3087	=item EV_STAT_ENABLE	3483	=item EV_STAT_ENABLE
3088		3484
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3485	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3486	defined to be C<0>, then they are not.
…		…
3122	two).	3518	two).
3123		3519
3124	=item EV_USE_4HEAP	3520	=item EV_USE_4HEAP
3125		3521
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3522	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	3523	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	3524	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3525	faster performance with many (thousands) of watchers.
3130		3526
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3527	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3528	(disabled).
3133		3529
3134	=item EV_HEAP_CACHE_AT	3530	=item EV_HEAP_CACHE_AT
3135		3531
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3532	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	3533	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>),	3534	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,	3535	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	3536	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3537	noticeably with many (hundreds) of watchers.
3142		3538
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3539	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3540	(disabled).
3145		3541
3146	=item EV_VERIFY	3542	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3548	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	3549	verification code will be called very frequently, which will slow down
3154	libev considerably.	3550	libev considerably.
3155		3551
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3552	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3553	C<0>.
3158		3554
3159	=item EV_COMMON	3555	=item EV_COMMON
3160		3556
3161	By default, all watchers have a C<void *data> member. By redefining	3557	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	3558	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	3575	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	3576	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	3577	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	3578	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++.	3579	method calls instead of plain function calls in C++.
		3580
		3581	=back
3184		3582
3185	=head2 EXPORTED API SYMBOLS	3583	=head2 EXPORTED API SYMBOLS
3186		3584
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3585	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	3586	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:	3633	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3634
3237	#include "ev_cpp.h"	3635	#include "ev_cpp.h"
3238	#include "ev.c"	3636	#include "ev.c"
3239		3637
		3638	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3639
3241	=head1 THREADS AND COROUTINES	3640	=head2 THREADS AND COROUTINES
3242		3641
3243	=head2 THREADS	3642	=head3 THREADS
3244		3643
3245	Libev itself is thread-safe (unless the opposite is specifically	3644	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	3645	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	3646	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:	3647	are no concurrent calls into any libev function with the same loop
		3648	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	3649	of course): libev guarantees that different event loops share no data
3250	need locking.	3650	structures that need any locking.
3251		3651
3252	Or to put it differently: calls with different loop parameters can be done	3652	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	3653	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	3654	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	3655	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	3656	a mutex per loop).
3257		3657
3258	Specifically to support threads (and signal handlers), libev implements	3658	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	3659	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	3660	concurrency on the same event loop, namely waking it up "from the
		3661	outside".
3261		3662
3262	If you want to know which design (one loop, locking, or multiple loops	3663	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	3664	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	3665	help you, but here is some generic advice:
3265		3666
3266	=over 4	3667	=over 4
3267		3668
3268	=item * most applications have a main thread: use the default libev loop	3669	=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.	3670	in that thread, or create a separate thread running only the default loop.
…		…
3293	default loop and triggering an C<ev_async> watcher from the default loop	3694	default loop and triggering an C<ev_async> watcher from the default loop
3294	watcher callback into the event loop interested in the signal.	3695	watcher callback into the event loop interested in the signal.
3295		3696
3296	=back	3697	=back
3297		3698
3298	=head2 COROUTINES	3699	=head3 COROUTINES
3299		3700
3300	Libev is much more accommodating to coroutines ("cooperative threads"):	3701	Libev is very accommodating to coroutines ("cooperative threads"):
3301	libev fully supports nesting calls to it's functions from different	3702	libev fully supports nesting calls to its functions from different
3302	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3703	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3303	different coroutines and switch freely between both coroutines running the	3704	different coroutines, and switch freely between both coroutines running the
3304	loop, as long as you don't confuse yourself). The only exception is that	3705	loop, as long as you don't confuse yourself). The only exception is that
3305	you must not do this from C<ev_periodic> reschedule callbacks.	3706	you must not do this from C<ev_periodic> reschedule callbacks.
3306		3707
3307	Care has been taken to ensure that libev does not keep local state inside	3708	Care has been taken to ensure that libev does not keep local state inside
3308	C<ev_loop>, and other calls do not usually allow coroutine switches.	3709	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3710	they do not call any callbacks.
3309		3711
		3712	=head2 COMPILER WARNINGS
3310		3713
3311	=head1 COMPLEXITIES	3714	Depending on your compiler and compiler settings, you might get no or a
		3715	lot of warnings when compiling libev code. Some people are apparently
		3716	scared by this.
3312		3717
3313	In this section the complexities of (many of) the algorithms used inside	3718	However, these are unavoidable for many reasons. For one, each compiler
3314	libev will be explained. For complexity discussions about backends see the	3719	has different warnings, and each user has different tastes regarding
3315	documentation for C<ev_default_init>.	3720	warning options. "Warn-free" code therefore cannot be a goal except when
		3721	targeting a specific compiler and compiler-version.
3316		3722
3317	All of the following are about amortised time: If an array needs to be	3723	Another reason is that some compiler warnings require elaborate
3318	extended, libev needs to realloc and move the whole array, but this	3724	workarounds, or other changes to the code that make it less clear and less
3319	happens asymptotically never with higher number of elements, so O(1) might	3725	maintainable.
3320	mean it might do a lengthy realloc operation in rare cases, but on average
3321	it is much faster and asymptotically approaches constant time.
3322		3726
3323	=over 4	3727	And of course, some compiler warnings are just plain stupid, or simply
		3728	wrong (because they don't actually warn about the condition their message
		3729	seems to warn about). For example, certain older gcc versions had some
		3730	warnings that resulted an extreme number of false positives. These have
		3731	been fixed, but some people still insist on making code warn-free with
		3732	such buggy versions.
3324		3733
3325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3734	While libev is written to generate as few warnings as possible,
		3735	"warn-free" code is not a goal, and it is recommended not to build libev
		3736	with any compiler warnings enabled unless you are prepared to cope with
		3737	them (e.g. by ignoring them). Remember that warnings are just that:
		3738	warnings, not errors, or proof of bugs.
3326		3739
3327	This means that, when you have a watcher that triggers in one hour and
3328	there are 100 watchers that would trigger before that then inserting will
3329	have to skip roughly seven (C<ld 100>) of these watchers.
3330		3740
3331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3741	=head2 VALGRIND
3332		3742
3333	That means that changing a timer costs less than removing/adding them	3743	Valgrind has a special section here because it is a popular tool that is
3334	as only the relative motion in the event queue has to be paid for.	3744	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3335		3745
3336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3746	If you think you found a bug (memory leak, uninitialised data access etc.)
		3747	in libev, then check twice: If valgrind reports something like:
3337		3748
3338	These just add the watcher into an array or at the head of a list.	3749	==2274== definitely lost: 0 bytes in 0 blocks.
		3750	==2274== possibly lost: 0 bytes in 0 blocks.
		3751	==2274== still reachable: 256 bytes in 1 blocks.
3339		3752
3340	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3753	Then there is no memory leak, just as memory accounted to global variables
		3754	is not a memleak - the memory is still being referenced, and didn't leak.
3341		3755
3342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3756	Similarly, under some circumstances, valgrind might report kernel bugs
		3757	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3758	although an acceptable workaround has been found here), or it might be
		3759	confused.
3343		3760
3344	These watchers are stored in lists then need to be walked to find the	3761	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3345	correct watcher to remove. The lists are usually short (you don't usually	3762	make it into some kind of religion.
3346	have many watchers waiting for the same fd or signal).
3347		3763
3348	=item Finding the next timer in each loop iteration: O(1)	3764	If you are unsure about something, feel free to contact the mailing list
		3765	with the full valgrind report and an explanation on why you think this
		3766	is a bug in libev (best check the archives, too :). However, don't be
		3767	annoyed when you get a brisk "this is no bug" answer and take the chance
		3768	of learning how to interpret valgrind properly.
3349		3769
3350	By virtue of using a binary or 4-heap, the next timer is always found at a	3770	If you need, for some reason, empty reports from valgrind for your project
3351	fixed position in the storage array.	3771	I suggest using suppression lists.
3352		3772
3353	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3354		3773
3355	A change means an I/O watcher gets started or stopped, which requires	3774	=head1 PORTABILITY NOTES
3356	libev to recalculate its status (and possibly tell the kernel, depending
3357	on backend and whether C<ev_io_set> was used).
3358		3775
3359	=item Activating one watcher (putting it into the pending state): O(1)
3360
3361	=item Priority handling: O(number_of_priorities)
3362
3363	Priorities are implemented by allocating some space for each
3364	priority. When doing priority-based operations, libev usually has to
3365	linearly search all the priorities, but starting/stopping and activating
3366	watchers becomes O(1) w.r.t. priority handling.
3367
3368	=item Sending an ev_async: O(1)
3369
3370	=item Processing ev_async_send: O(number_of_async_watchers)
3371
3372	=item Processing signals: O(max_signal_number)
3373
3374	Sending involves a system call I<iff> there were no other C<ev_async_send>
3375	calls in the current loop iteration. Checking for async and signal events
3376	involves iterating over all running async watchers or all signal numbers.
3377
3378	=back
3379
3380
3381	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3776	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3382		3777
3383	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3778	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3384	requires, and its I/O model is fundamentally incompatible with the POSIX	3779	requires, and its I/O model is fundamentally incompatible with the POSIX
3385	model. Libev still offers limited functionality on this platform in	3780	model. Libev still offers limited functionality on this platform in
3386	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3781	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3397		3792
3398	Not a libev limitation but worth mentioning: windows apparently doesn't	3793	Not a libev limitation but worth mentioning: windows apparently doesn't
3399	accept large writes: instead of resulting in a partial write, windows will	3794	accept large writes: instead of resulting in a partial write, windows will
3400	either accept everything or return C<ENOBUFS> if the buffer is too large,	3795	either accept everything or return C<ENOBUFS> if the buffer is too large,
3401	so make sure you only write small amounts into your sockets (less than a	3796	so make sure you only write small amounts into your sockets (less than a
3402	megabyte seems safe, but thsi apparently depends on the amount of memory	3797	megabyte seems safe, but this apparently depends on the amount of memory
3403	available).	3798	available).
3404		3799
3405	Due to the many, low, and arbitrary limits on the win32 platform and	3800	Due to the many, low, and arbitrary limits on the win32 platform and
3406	the abysmal performance of winsockets, using a large number of sockets	3801	the abysmal performance of winsockets, using a large number of sockets
3407	is not recommended (and not reasonable). If your program needs to use	3802	is not recommended (and not reasonable). If your program needs to use
…		…
3418	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3813	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3419		3814
3420	#include "ev.h"	3815	#include "ev.h"
3421		3816
3422	And compile the following F<evwrap.c> file into your project (make sure	3817	And compile the following F<evwrap.c> file into your project (make sure
3423	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3818	you do I<not> compile the F<ev.c> or any other embedded source files!):
3424		3819
3425	#include "evwrap.h"	3820	#include "evwrap.h"
3426	#include "ev.c"	3821	#include "ev.c"
3427		3822
3428	=over 4	3823	=over 4
…		…
3473	wrap all I/O functions and provide your own fd management, but the cost of	3868	wrap all I/O functions and provide your own fd management, but the cost of
3474	calling select (O(n²)) will likely make this unworkable.	3869	calling select (O(n²)) will likely make this unworkable.
3475		3870
3476	=back	3871	=back
3477		3872
3478
3479	=head1 PORTABILITY REQUIREMENTS	3873	=head2 PORTABILITY REQUIREMENTS
3480		3874
3481	In addition to a working ISO-C implementation, libev relies on a few	3875	In addition to a working ISO-C implementation and of course the
3482	additional extensions:	3876	backend-specific APIs, libev relies on a few additional extensions:
3483		3877
3484	=over 4	3878	=over 4
3485		3879
3486	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3880	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3487	calling conventions regardless of C<ev_watcher_type *>.	3881	calling conventions regardless of C<ev_watcher_type *>.
…		…
3493	calls them using an C<ev_watcher *> internally.	3887	calls them using an C<ev_watcher *> internally.
3494		3888
3495	=item C<sig_atomic_t volatile> must be thread-atomic as well	3889	=item C<sig_atomic_t volatile> must be thread-atomic as well
3496		3890
3497	The type C<sig_atomic_t volatile> (or whatever is defined as	3891	The type C<sig_atomic_t volatile> (or whatever is defined as
3498	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3892	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3499	threads. This is not part of the specification for C<sig_atomic_t>, but is	3893	threads. This is not part of the specification for C<sig_atomic_t>, but is
3500	believed to be sufficiently portable.	3894	believed to be sufficiently portable.
3501		3895
3502	=item C<sigprocmask> must work in a threaded environment	3896	=item C<sigprocmask> must work in a threaded environment
3503		3897
…		…
3512	except the initial one, and run the default loop in the initial thread as	3906	except the initial one, and run the default loop in the initial thread as
3513	well.	3907	well.
3514		3908
3515	=item C<long> must be large enough for common memory allocation sizes	3909	=item C<long> must be large enough for common memory allocation sizes
3516		3910
3517	To improve portability and simplify using libev, libev uses C<long>	3911	To improve portability and simplify its API, libev uses C<long> internally
3518	internally instead of C<size_t> when allocating its data structures. On	3912	instead of C<size_t> when allocating its data structures. On non-POSIX
3519	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3913	systems (Microsoft...) this might be unexpectedly low, but is still at
3520	is still at least 31 bits everywhere, which is enough for hundreds of	3914	least 31 bits everywhere, which is enough for hundreds of millions of
3521	millions of watchers.	3915	watchers.
3522		3916
3523	=item C<double> must hold a time value in seconds with enough accuracy	3917	=item C<double> must hold a time value in seconds with enough accuracy
3524		3918
3525	The type C<double> is used to represent timestamps. It is required to	3919	The type C<double> is used to represent timestamps. It is required to
3526	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3920	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3530	=back	3924	=back
3531		3925
3532	If you know of other additional requirements drop me a note.	3926	If you know of other additional requirements drop me a note.
3533		3927
3534		3928
3535	=head1 COMPILER WARNINGS	3929	=head1 ALGORITHMIC COMPLEXITIES
3536		3930
3537	Depending on your compiler and compiler settings, you might get no or a	3931	In this section the complexities of (many of) the algorithms used inside
3538	lot of warnings when compiling libev code. Some people are apparently	3932	libev will be documented. For complexity discussions about backends see
3539	scared by this.	3933	the documentation for C<ev_default_init>.
3540		3934
3541	However, these are unavoidable for many reasons. For one, each compiler	3935	All of the following are about amortised time: If an array needs to be
3542	has different warnings, and each user has different tastes regarding	3936	extended, libev needs to realloc and move the whole array, but this
3543	warning options. "Warn-free" code therefore cannot be a goal except when	3937	happens asymptotically rarer with higher number of elements, so O(1) might
3544	targeting a specific compiler and compiler-version.	3938	mean that libev does a lengthy realloc operation in rare cases, but on
		3939	average it is much faster and asymptotically approaches constant time.
3545		3940
3546	Another reason is that some compiler warnings require elaborate	3941	=over 4
3547	workarounds, or other changes to the code that make it less clear and less
3548	maintainable.
3549		3942
3550	And of course, some compiler warnings are just plain stupid, or simply	3943	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3551	wrong (because they don't actually warn about the condition their message
3552	seems to warn about).
3553		3944
3554	While libev is written to generate as few warnings as possible,	3945	This means that, when you have a watcher that triggers in one hour and
3555	"warn-free" code is not a goal, and it is recommended not to build libev	3946	there are 100 watchers that would trigger before that, then inserting will
3556	with any compiler warnings enabled unless you are prepared to cope with	3947	have to skip roughly seven (C<ld 100>) of these watchers.
3557	them (e.g. by ignoring them). Remember that warnings are just that:
3558	warnings, not errors, or proof of bugs.
3559		3948
		3949	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3560		3950
3561	=head1 VALGRIND	3951	That means that changing a timer costs less than removing/adding them,
		3952	as only the relative motion in the event queue has to be paid for.
3562		3953
3563	Valgrind has a special section here because it is a popular tool that is	3954	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3564	highly useful, but valgrind reports are very hard to interpret.
3565		3955
3566	If you think you found a bug (memory leak, uninitialised data access etc.)	3956	These just add the watcher into an array or at the head of a list.
3567	in libev, then check twice: If valgrind reports something like:
3568		3957
3569	==2274== definitely lost: 0 bytes in 0 blocks.	3958	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3570	==2274== possibly lost: 0 bytes in 0 blocks.
3571	==2274== still reachable: 256 bytes in 1 blocks.
3572		3959
3573	Then there is no memory leak. Similarly, under some circumstances,	3960	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3574	valgrind might report kernel bugs as if it were a bug in libev, or it
3575	might be confused (it is a very good tool, but only a tool).
3576		3961
3577	If you are unsure about something, feel free to contact the mailing list	3962	These watchers are stored in lists, so they need to be walked to find the
3578	with the full valgrind report and an explanation on why you think this is	3963	correct watcher to remove. The lists are usually short (you don't usually
3579	a bug in libev. However, don't be annoyed when you get a brisk "this is	3964	have many watchers waiting for the same fd or signal: one is typical, two
3580	no bug" answer and take the chance of learning how to interpret valgrind	3965	is rare).
3581	properly.
3582		3966
3583	If you need, for some reason, empty reports from valgrind for your project	3967	=item Finding the next timer in each loop iteration: O(1)
3584	I suggest using suppression lists.	3968
		3969	By virtue of using a binary or 4-heap, the next timer is always found at a
		3970	fixed position in the storage array.
		3971
		3972	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3973
		3974	A change means an I/O watcher gets started or stopped, which requires
		3975	libev to recalculate its status (and possibly tell the kernel, depending
		3976	on backend and whether C<ev_io_set> was used).
		3977
		3978	=item Activating one watcher (putting it into the pending state): O(1)
		3979
		3980	=item Priority handling: O(number_of_priorities)
		3981
		3982	Priorities are implemented by allocating some space for each
		3983	priority. When doing priority-based operations, libev usually has to
		3984	linearly search all the priorities, but starting/stopping and activating
		3985	watchers becomes O(1) with respect to priority handling.
		3986
		3987	=item Sending an ev_async: O(1)
		3988
		3989	=item Processing ev_async_send: O(number_of_async_watchers)
		3990
		3991	=item Processing signals: O(max_signal_number)
		3992
		3993	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3994	calls in the current loop iteration. Checking for async and signal events
		3995	involves iterating over all running async watchers or all signal numbers.
		3996
		3997	=back
3585		3998
3586		3999
3587	=head1 AUTHOR	4000	=head1 AUTHOR
3588		4001
3589	Marc Lehmann <libev@schmorp.de>.	4002	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3590		4003

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