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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
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	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.
984
985	If you need to suppress invocation when higher priority events are pending	1088	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1090
988	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1092	pending.
990		1093
		1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1095	fine, as long as you do not mind that the priority value you query might
		1096	or might not have been clamped to the valid range.
		1097
991	The default priority used by watchers when no priority has been set is	1098	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 :).	1099	always C<0>, which is supposed to not be too high and not be too low :).
993		1100
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1101	See L<WATCHER PRIORITIES>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1102	priorities.
996	or might not have been adjusted to be within valid range.
997		1103
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1105
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	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	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1108	can deal with that fact, as both are simply passed through to the
		1109	callback.
1003		1110
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1111	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1112
1006	If the watcher is pending, this function returns clears its pending status	1113	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	1114	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>.	1115	watcher isn't pending it does nothing and returns C<0>.
1009		1116
		1117	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1118	callback to be invoked, which can be accomplished with this function.
		1119
1010	=back	1120	=back
1011		1121
1012		1122
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1123	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1124
1015	Each watcher has, by default, a member C<void *data> that you can change	1125	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	1126	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	1127	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	1128	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	1129	member, you can also "subclass" the watcher type and provide your own
1020	data:	1130	data:
1021		1131
1022	struct my_io	1132	struct my_io
1023	{	1133	{
1024	struct ev_io io;	1134	ev_io io;
1025	int otherfd;	1135	int otherfd;
1026	void *somedata;	1136	void *somedata;
1027	struct whatever *mostinteresting;	1137	struct whatever *mostinteresting;
1028	};	1138	};
1029		1139
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1142	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1143
1034	And since your callback will be called with a pointer to the watcher, you	1144	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1145	can cast it back to your own type:
1036		1146
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1147	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1148	{
1039	struct my_io *w = (struct my_io *)w_;	1149	struct my_io *w = (struct my_io *)w_;
1040	...	1150	...
1041	}	1151	}
1042		1152
…		…
1053	ev_timer t2;	1163	ev_timer t2;
1054	}	1164	}
1055		1165
1056	In this case getting the pointer to C<my_biggy> is a bit more	1166	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	1167	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	1168	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1169	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1170	programmers):
1060		1171
1061	#include <stddef.h>	1172	#include <stddef.h>
1062		1173
1063	static void	1174	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1175	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1176	{
1066	struct my_biggy big = (struct my_biggy *	1177	struct my_biggy big = (struct my_biggy *
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1178	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1179	}
1069		1180
1070	static void	1181	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1183	{
1073	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1076		1290
1077		1291
1078	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1079		1293
1080	This section describes each watcher in detail, but will not repeat	1294	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1318	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	1319	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	1320	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1321	required if you know what you are doing).
1108		1322
1109	If you must do this, then force the use of a known-to-be-good backend	1323	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	1324	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1325	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1112		1326
1113	Another thing you have to watch out for is that it is quite easy to	1327	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	1328	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	1329	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	1330	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	1331	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	1332	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	1333	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.	1334	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1335
1122	If you cannot run the fd in non-blocking mode (for example you should not	1336	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	1337	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	1338	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	1339	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1340	does this on its own, so its quite safe to use). Some people additionally
		1341	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1342	indefinitely.
		1343
		1344	But really, best use non-blocking mode.
1127		1345
1128	=head3 The special problem of disappearing file descriptors	1346	=head3 The special problem of disappearing file descriptors
1129		1347
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1348	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,	1349	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	1350	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	1351	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	1352	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	1353	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1354	fact, a different file descriptor.
1137		1355
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1386	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1387	C<EVBACKEND_POLL>.
1170		1388
1171	=head3 The special problem of SIGPIPE	1389	=head3 The special problem of SIGPIPE
1172		1390
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1391	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	1392	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	1393	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1394	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1395
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1396	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	1397	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).	1398	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1405	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1406
1189	=item ev_io_set (ev_io *, int fd, int events)	1407	=item ev_io_set (ev_io *, int fd, int events)
1190		1408
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1409	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	1410	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.	1411	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1412
1195	=item int fd [read-only]	1413	=item int fd [read-only]
1196		1414
1197	The file descriptor being watched.	1415	The file descriptor being watched.
1198		1416
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1425	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	1426	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1427	attempt to read a whole line in the callback.
1210		1428
1211	static void	1429	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1430	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1431	{
1214	ev_io_stop (loop, w);	1432	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1433	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1434	}
1217		1435
1218	...	1436	...
1219	struct ev_loop *loop = ev_default_init (0);	1437	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1438	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1439	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1440	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1441	ev_loop (loop, 0);
1224		1442
1225		1443
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1446	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1447	given time, and optionally repeating in regular intervals after that.
1230		1448
1231	The timers are based on real time, that is, if you register an event that	1449	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	1450	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	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
1236		1454
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1455	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	1456	passed. If multiple timers become ready during the same loop iteration
1239	order of execution is undefined.	1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
		1460
		1461	=head3 Be smart about timeouts
		1462
		1463	Many real-world problems involve some kind of timeout, usually for error
		1464	recovery. A typical example is an HTTP request - if the other side hangs,
		1465	you want to raise some error after a while.
		1466
		1467	What follows are some ways to handle this problem, from obvious and
		1468	inefficient to smart and efficient.
		1469
		1470	In the following, a 60 second activity timeout is assumed - a timeout that
		1471	gets reset to 60 seconds each time there is activity (e.g. each time some
		1472	data or other life sign was received).
		1473
		1474	=over 4
		1475
		1476	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1477
		1478	This is the most obvious, but not the most simple way: In the beginning,
		1479	start the watcher:
		1480
		1481	ev_timer_init (timer, callback, 60., 0.);
		1482	ev_timer_start (loop, timer);
		1483
		1484	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1485	and start it again:
		1486
		1487	ev_timer_stop (loop, timer);
		1488	ev_timer_set (timer, 60., 0.);
		1489	ev_timer_start (loop, timer);
		1490
		1491	This is relatively simple to implement, but means that each time there is
		1492	some activity, libev will first have to remove the timer from its internal
		1493	data structure and then add it again. Libev tries to be fast, but it's
		1494	still not a constant-time operation.
		1495
		1496	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1497
		1498	This is the easiest way, and involves using C<ev_timer_again> instead of
		1499	C<ev_timer_start>.
		1500
		1501	To implement this, configure an C<ev_timer> with a C<repeat> value
		1502	of C<60> and then call C<ev_timer_again> at start and each time you
		1503	successfully read or write some data. If you go into an idle state where
		1504	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1505	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1506
		1507	That means you can ignore both the C<ev_timer_start> function and the
		1508	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1509	member and C<ev_timer_again>.
		1510
		1511	At start:
		1512
		1513	ev_timer_init (timer, callback);
		1514	timer->repeat = 60.;
		1515	ev_timer_again (loop, timer);
		1516
		1517	Each time there is some activity:
		1518
		1519	ev_timer_again (loop, timer);
		1520
		1521	It is even possible to change the time-out on the fly, regardless of
		1522	whether the watcher is active or not:
		1523
		1524	timer->repeat = 30.;
		1525	ev_timer_again (loop, timer);
		1526
		1527	This is slightly more efficient then stopping/starting the timer each time
		1528	you want to modify its timeout value, as libev does not have to completely
		1529	remove and re-insert the timer from/into its internal data structure.
		1530
		1531	It is, however, even simpler than the "obvious" way to do it.
		1532
		1533	=item 3. Let the timer time out, but then re-arm it as required.
		1534
		1535	This method is more tricky, but usually most efficient: Most timeouts are
		1536	relatively long compared to the intervals between other activity - in
		1537	our example, within 60 seconds, there are usually many I/O events with
		1538	associated activity resets.
		1539
		1540	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1541	but remember the time of last activity, and check for a real timeout only
		1542	within the callback:
		1543
		1544	ev_tstamp last_activity; // time of last activity
		1545
		1546	static void
		1547	callback (EV_P_ ev_timer *w, int revents)
		1548	{
		1549	ev_tstamp now = ev_now (EV_A);
		1550	ev_tstamp timeout = last_activity + 60.;
		1551
		1552	// if last_activity + 60. is older than now, we did time out
		1553	if (timeout < now)
		1554	{
		1555	// timeout occured, take action
		1556	}
		1557	else
		1558	{
		1559	// callback was invoked, but there was some activity, re-arm
		1560	// the watcher to fire in last_activity + 60, which is
		1561	// guaranteed to be in the future, so "again" is positive:
		1562	w->repeat = timeout - now;
		1563	ev_timer_again (EV_A_ w);
		1564	}
		1565	}
		1566
		1567	To summarise the callback: first calculate the real timeout (defined
		1568	as "60 seconds after the last activity"), then check if that time has
		1569	been reached, which means something I<did>, in fact, time out. Otherwise
		1570	the callback was invoked too early (C<timeout> is in the future), so
		1571	re-schedule the timer to fire at that future time, to see if maybe we have
		1572	a timeout then.
		1573
		1574	Note how C<ev_timer_again> is used, taking advantage of the
		1575	C<ev_timer_again> optimisation when the timer is already running.
		1576
		1577	This scheme causes more callback invocations (about one every 60 seconds
		1578	minus half the average time between activity), but virtually no calls to
		1579	libev to change the timeout.
		1580
		1581	To start the timer, simply initialise the watcher and set C<last_activity>
		1582	to the current time (meaning we just have some activity :), then call the
		1583	callback, which will "do the right thing" and start the timer:
		1584
		1585	ev_timer_init (timer, callback);
		1586	last_activity = ev_now (loop);
		1587	callback (loop, timer, EV_TIMEOUT);
		1588
		1589	And when there is some activity, simply store the current time in
		1590	C<last_activity>, no libev calls at all:
		1591
		1592	last_actiivty = ev_now (loop);
		1593
		1594	This technique is slightly more complex, but in most cases where the
		1595	time-out is unlikely to be triggered, much more efficient.
		1596
		1597	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1598	callback :) - just change the timeout and invoke the callback, which will
		1599	fix things for you.
		1600
		1601	=item 4. Wee, just use a double-linked list for your timeouts.
		1602
		1603	If there is not one request, but many thousands (millions...), all
		1604	employing some kind of timeout with the same timeout value, then one can
		1605	do even better:
		1606
		1607	When starting the timeout, calculate the timeout value and put the timeout
		1608	at the I<end> of the list.
		1609
		1610	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1611	the list is expected to fire (for example, using the technique #3).
		1612
		1613	When there is some activity, remove the timer from the list, recalculate
		1614	the timeout, append it to the end of the list again, and make sure to
		1615	update the C<ev_timer> if it was taken from the beginning of the list.
		1616
		1617	This way, one can manage an unlimited number of timeouts in O(1) time for
		1618	starting, stopping and updating the timers, at the expense of a major
		1619	complication, and having to use a constant timeout. The constant timeout
		1620	ensures that the list stays sorted.
		1621
		1622	=back
		1623
		1624	So which method the best?
		1625
		1626	Method #2 is a simple no-brain-required solution that is adequate in most
		1627	situations. Method #3 requires a bit more thinking, but handles many cases
		1628	better, and isn't very complicated either. In most case, choosing either
		1629	one is fine, with #3 being better in typical situations.
		1630
		1631	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1632	rather complicated, but extremely efficient, something that really pays
		1633	off after the first million or so of active timers, i.e. it's usually
		1634	overkill :)
1240		1635
1241	=head3 The special problem of time updates	1636	=head3 The special problem of time updates
1242		1637
1243	Establishing the current time is a costly operation (it usually takes at	1638	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	1639	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	1640	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	1641	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1642	lots of events in one iteration.
1248		1643
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1644	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	1645	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	1646	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	1647	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).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1684
1290	If the timer is repeating, either start it if necessary (with the	1685	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.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1687
1293	This sounds a bit complicated, but here is a useful and typical	1688	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	1689	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		1690
1318	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1319		1692
1320	The current C<repeat> value. Will be used each time the watcher times out	1693	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),	1694	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.	1695	which is also when any modifications are taken into account.
1323		1696
1324	=back	1697	=back
1325		1698
1326	=head3 Examples	1699	=head3 Examples
1327		1700
1328	Example: Create a timer that fires after 60 seconds.	1701	Example: Create a timer that fires after 60 seconds.
1329		1702
1330	static void	1703	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1704	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1705	{
1333	.. one minute over, w is actually stopped right here	1706	.. one minute over, w is actually stopped right here
1334	}	1707	}
1335		1708
1336	struct ev_timer mytimer;	1709	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1710	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1711	ev_timer_start (loop, &mytimer);
1339		1712
1340	Example: Create a timeout timer that times out after 10 seconds of	1713	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1714	inactivity.
1342		1715
1343	static void	1716	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1717	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1718	{
1346	.. ten seconds without any activity	1719	.. ten seconds without any activity
1347	}	1720	}
1348		1721
1349	struct ev_timer mytimer;	1722	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1723	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1724	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1725	ev_loop (loop, 0);
1353		1726
1354	// and in some piece of code that gets executed on any "activity":	1727	// and in some piece of code that gets executed on any "activity":
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1360		1733
1361	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1363		1736
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	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	1738	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	1739	(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 ()	1740	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	1741	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	1742	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		1743
		1744	You can tell a periodic watcher to trigger after some specific point
		1745	in time: for example, if you tell a periodic watcher to trigger "in 10
		1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
		1751
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1752	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	1753	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
1376		1756
1377	As with timers, the callback is guaranteed to be invoked only when the	1757	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	1758	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.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1380		1762
1381	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1382		1764
1383	=over 4	1765	=over 4
1384		1766
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		1768
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		1770
1389	Lots of arguments, lets sort it out... There are basically three modes of	1771	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:	1772	operation, and we will explain them from simplest to most complex:
1391		1773
1392	=over 4	1774	=over 4
1393		1775
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		1777
1396	In this configuration the watcher triggers an event after the wall clock	1778	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	1779	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	1780	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.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1400		1783
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		1785
1403	In this mode the watcher will always be scheduled to time out at the next	1786	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)	1787	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1406		1790
1407	This can be used to create timers that do not drift with respect to system	1791	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	1792	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	1793	hour, on the hour (with respect to UTC):
1410		1794
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1796
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1797	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	1798	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	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	1800	by 3600.
1417		1801
1418	Another way to think about it (for the mathematically inclined) is that	1802	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	1803	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.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		1805
1422	For numerical stability it is preferable that the C<at> value is near	1806	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	1807	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	1808	this value, and in fact is often specified as zero.
1425		1809
1426	Note also that there is an upper limit to how often a timer can fire (CPU	1810	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	1811	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	1812	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).	1813	millisecond (if the OS supports it and the machine is fast enough).
1430		1814
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		1816
1433	In this mode the values for C<interval> and C<at> are both being	1817	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	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	1820	current time as second argument.
1437		1821
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	1823	or make ANY other event loop modifications whatsoever, unless explicitly
		1824	allowed by documentation here>.
1440		1825
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1826	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	1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1828	only event loop modification you are allowed to do).
1444		1829
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1830	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1831	*w, ev_tstamp now)>, e.g.:
1447		1832
		1833	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1834	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1835	{
1450	return now + 60.;	1836	return now + 60.;
1451	}	1837	}
1452		1838
1453	It must return the next time to trigger, based on the passed time value	1839	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	1859	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	1860	program when the crontabs have changed).
1475		1861
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		1863
1478	When active, returns the absolute time that the watcher is supposed to	1864	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
1480		1868
1481	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1482		1870
1483	When repeating, this contains the offset value, otherwise this is the	1871	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>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1485		1874
1486	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1488		1877
1489	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
1490		1879
1491	The current interval value. Can be modified any time, but changes only	1880	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	1881	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1882	called.
1494		1883
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1884	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1885
1497	The current reschedule callback, or C<0>, if this functionality is	1886	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	1887	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.	1888	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1889
1501	=back	1890	=back
1502		1891
1503	=head3 Examples	1892	=head3 Examples
1504		1893
1505	Example: Call a callback every hour, or, more precisely, whenever the	1894	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1895	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1896	potentially a lot of jitter, but good long-term stability.
1508		1897
1509	static void	1898	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1899	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1900	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1901	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1902	}
1514		1903
1515	struct ev_periodic hourly_tick;	1904	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1905	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1906	ev_periodic_start (loop, &hourly_tick);
1518		1907
1519	Example: The same as above, but use a reschedule callback to do it:	1908	Example: The same as above, but use a reschedule callback to do it:
1520		1909
1521	#include <math.h>	1910	#include <math.h>
1522		1911
1523	static ev_tstamp	1912	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1913	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	1914	{
1526	return fmod (now, 3600.) + 3600.;	1915	return now + (3600. - fmod (now, 3600.));
1527	}	1916	}
1528		1917
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1918	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		1919
1531	Example: Call a callback every hour, starting now:	1920	Example: Call a callback every hour, starting now:
1532		1921
1533	struct ev_periodic hourly_tick;	1922	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	1923	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	1924	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	1925	ev_periodic_start (loop, &hourly_tick);
1537		1926
1538		1927
…		…
1541	Signal watchers will trigger an event when the process receives a specific	1930	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	1931	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	1932	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	1933	normal event processing, like any other event.
1545		1934
		1935	If you want signals asynchronously, just use C<sigaction> as you would
		1936	do without libev and forget about sharing the signal. You can even use
		1937	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1938
1546	You can configure as many watchers as you like per signal. Only when the	1939	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	1940	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	1941	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	1942	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	1943	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	1944	signal handler to SIG_DFL (regardless of what it was set to before).
1552		1945
1553	If possible and supported, libev will install its handlers with	1946	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1947	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	1948	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	1949	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		1966
1574	=back	1967	=back
1575		1968
1576	=head3 Examples	1969	=head3 Examples
1577		1970
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	1971	Example: Try to exit cleanly on SIGINT.
1579		1972
1580	static void	1973	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1974	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	1975	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	1976	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	1977	}
1585		1978
1586	struct ev_signal signal_watcher;	1979	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1980	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	1981	ev_signal_start (loop, &signal_watcher);
1589		1982
1590		1983
1591	=head2 C<ev_child> - watch out for process status changes	1984	=head2 C<ev_child> - watch out for process status changes
1592		1985
1593	Child watchers trigger when your process receives a SIGCHLD in response to	1986	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	1987	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	1988	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	1989	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	1990	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1991	forking and then immediately registering a watcher for the child is fine,
		1992	but forking and registering a watcher a few event loop iterations later is
		1993	not.
1598		1994
1599	Only the default event loop is capable of handling signals, and therefore	1995	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	1996	you can only register child watchers in the default event loop.
1601		1997
1602	=head3 Process Interaction	1998	=head3 Process Interaction
…		…
1663	its completion.	2059	its completion.
1664		2060
1665	ev_child cw;	2061	ev_child cw;
1666		2062
1667	static void	2063	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2064	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2065	{
1670	ev_child_stop (EV_A_ w);	2066	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2067	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2068	}
1673		2069
…		…
1688		2084
1689		2085
1690	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1691		2087
1692	This watches a file system path for attribute changes. That is, it calls	2088	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	2089	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.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1695		2092
1696	The path does not need to exist: changing from "path exists" to "path does	2093	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	2094	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	2095	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	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1701		2099
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	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.	2102	your working directory changes, then the behaviour is undefined.
1704		2103
1705	Since there is no standard to do this, the portable implementation simply	2104	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	2105	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2106	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,	2107	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	2108	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2109	(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	2110	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1713		2112
1714	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2115	resource-intensive.
1717		2116
1718	At the time of this writing, only the Linux inotify interface is	2117	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2118	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	2119	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	2120	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		2121
1727	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1728		2123
1729	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2125	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2126	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	2127	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	2128	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	2129	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	2130	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.	2131	most noticeably displayed with ev_stat and large file support.
1737		2132
1738	The solution for this is to lobby your distribution maker to make large	2133	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	2134	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	2135	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2136	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2137	default compilation environment.
1743		2138
1744	=head3 Inotify	2139	=head3 Inotify and Kqueue
1745		2140
1746	When C<inotify (7)> support has been compiled into libev (generally only	2141	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	2142	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	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2144	watcher is being started.
1750		2145
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2146	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	2147	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	2148	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.	2149	there are many cases where libev has to resort to regular C<stat> polling,
		2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1755		2154
1756	(There is no support for kqueue, as apparently it cannot be used to	2155	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	2156	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2157	descriptor open on the object at all times, and detecting renames, unlinks
		2158	etc. is difficult.
		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
1759		2177
1760	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1761		2179
1762	The C<stat ()> system call only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2181	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2182	still only support whole seconds.
1765		2183
1766	That means that, if the time is the only thing that changes, you can	2184	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	2185	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	2186	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	2187	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2188	stat data does change in other ways (e.g. file size).
1771		2189
1772	The solution to this is to delay acting on a change for slightly more	2190	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	2191	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);	2192	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2193	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2213	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	2214	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	2215	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.	2216	path for as long as the watcher is active.
1799		2217
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2218	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	2219	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2220	last change was detected).
1803		2221
1804	=item ev_stat_stat (loop, ev_stat *)	2222	=item ev_stat_stat (loop, ev_stat *)
1805		2223
1806	Updates the stat buffer immediately with new values. If you change the	2224	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	2225	watched path in your callback, you could call this function to avoid
…		…
1890		2308
1891		2309
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2310	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2311
1894	Idle watchers trigger events when no other events of the same or higher	2312	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	2313	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2314	as receiving "events").
1897		2315
1898	That is, as long as your process is busy handling sockets or timeouts	2316	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	2317	(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	2318	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	2319	are pending), the idle watchers are being called once per event loop
…		…
1912		2330
1913	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
1914		2332
1915	=over 4	2333	=over 4
1916		2334
1917	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
1918		2336
1919	Initialises and configures the idle watcher - it has no parameters of any	2337	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,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2339	believe me.
1922		2340
…		…
1926		2344
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2346	callback, free it. Also, use no error checking, as usual.
1929		2347
1930	static void	2348	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2349	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2350	{
1933	free (w);	2351	free (w);
1934	// now do something you wanted to do when the program has	2352	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2353	// no longer anything immediate to do.
1936	}	2354	}
1937		2355
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2356	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2357	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2358	ev_idle_start (loop, idle_cb);
1941		2359
1942		2360
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2362
1945	Prepare and check watchers are usually (but not always) used in tandem:	2363	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2364	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2365	afterwards.
1948		2366
1949	You I<must not> call C<ev_loop> or similar functions that enter	2367	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>	2368	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,	2371	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	2372	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2373	called in pairs bracketing the blocking call.
1956		2374
1957	Their main purpose is to integrate other event mechanisms into libev and	2375	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	2376	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	2377	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2378	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,	2379	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>	2380	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2381	watcher).
1964		2382
1965	This is done by examining in each prepare call which file descriptors need	2383	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	2384	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	2385	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	2386	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2387	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	2388	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,	2389	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2390	nevertheless, because you never know, you know?).
1973		2391
1974	As another example, the Perl Coro module uses these hooks to integrate	2392	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2393	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2394	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	2395	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	2398	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2399	low-priority coroutines to idle/background tasks).
1982		2400
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2401	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	2402	priority, to ensure that they are being run before any other watchers
		2403	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2404
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2405	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	2406	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2407	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	2408	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	2409	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	2410	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2411	others).
1992		2412
1993	=head3 Watcher-Specific Functions and Data Members	2413	=head3 Watcher-Specific Functions and Data Members
1994		2414
1995	=over 4	2415	=over 4
1996		2416
…		…
1998		2418
1999	=item ev_check_init (ev_check *, callback)	2419	=item ev_check_init (ev_check *, callback)
2000		2420
2001	Initialises and configures the prepare or check watcher - they have no	2421	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>	2422	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.	2423	macros, but using them is utterly, utterly, utterly and completely
		2424	pointless.
2004		2425
2005	=back	2426	=back
2006		2427
2007	=head3 Examples	2428	=head3 Examples
2008		2429
…		…
2021		2442
2022	static ev_io iow [nfd];	2443	static ev_io iow [nfd];
2023	static ev_timer tw;	2444	static ev_timer tw;
2024		2445
2025	static void	2446	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2447	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2448	{
2028	}	2449	}
2029		2450
2030	// create io watchers for each fd and a timer before blocking	2451	// create io watchers for each fd and a timer before blocking
2031	static void	2452	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2453	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2454	{
2034	int timeout = 3600000;	2455	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2456	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2457	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2458	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2052	}	2473	}
2053	}	2474	}
2054		2475
2055	// stop all watchers after blocking	2476	// stop all watchers after blocking
2056	static void	2477	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2478	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2479	{
2059	ev_timer_stop (loop, &tw);	2480	ev_timer_stop (loop, &tw);
2060		2481
2061	for (int i = 0; i < nfd; ++i)	2482	for (int i = 0; i < nfd; ++i)
2062	{	2483	{
…		…
2101	}	2522	}
2102		2523
2103	// do not ever call adns_afterpoll	2524	// do not ever call adns_afterpoll
2104		2525
2105	Method 4: Do not use a prepare or check watcher because the module you	2526	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	2527	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	2528	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	2529	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2530	this approach, effectively embedding EV as a client into the horrible
		2531	libglib event loop.
2110		2532
2111	static gint	2533	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2534	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2535	{
2114	int got_events = 0;	2536	int got_events = 0;
…		…
2145	prioritise I/O.	2567	prioritise I/O.
2146		2568
2147	As an example for a bug workaround, the kqueue backend might only support	2569	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	2570	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	2571	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	2572	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	2573	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	2574	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.	2575	C<kevent>, but at least you can use both mechanisms for what they are
		2576	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2577
2155	As for prioritising I/O: rarely you have the case where some fds have	2578	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	2579	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	2580	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	2581	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.	2582	the rest in a second one, and embed the second one in the first.
2160		2583
2161	As long as the watcher is active, the callback will be invoked every time	2584	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	2585	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	2586	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	2587	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	2588	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	2589	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2590
2169	As long as the watcher is started it will automatically handle events. The	2591	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	2592	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		2593
2174	Also, there have not currently been made special provisions for forking:	2594	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,	2595	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	2596	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2597	C<ev_loop_fork> on the embedded loop.
2178		2598
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2601	portable one.
2182		2602
2183	So when you want to use this feature you will always have to be prepared	2603	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	2604	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	2605	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.	2606	create it, and if that fails, use the normal loop for everything.
		2607
		2608	=head3 C<ev_embed> and fork
		2609
		2610	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2611	automatically be applied to the embedded loop as well, so no special
		2612	fork handling is required in that case. When the watcher is not running,
		2613	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2614	as applicable.
2187		2615
2188	=head3 Watcher-Specific Functions and Data Members	2616	=head3 Watcher-Specific Functions and Data Members
2189		2617
2190	=over 4	2618	=over 4
2191		2619
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2647	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2648	used).
2221		2649
2222	struct ev_loop *loop_hi = ev_default_init (0);	2650	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2651	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2652	ev_embed embed;
2225		2653
2226	// see if there is a chance of getting one that works	2654	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2655	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2656	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2657	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2671	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2672	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2673
2246	struct ev_loop *loop = ev_default_init (0);	2674	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2675	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2676	ev_embed embed;
2249		2677
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2678	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2679	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2680	{
2253	ev_embed_init (&embed, 0, loop_socket);	2681	ev_embed_init (&embed, 0, loop_socket);
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2737	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	2738	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2739	need elaborate support such as pthreads.
2312		2740
2313	That means that if you want to queue data, you have to provide your own	2741	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	2742	queue. But at least I can tell you how to implement locking around your
2315	queue:	2743	queue:
2316		2744
2317	=over 4	2745	=over 4
2318		2746
2319	=item queueing from a signal handler context	2747	=item queueing from a signal handler context
2320		2748
2321	To implement race-free queueing, you simply add to the queue in the signal	2749	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	2750	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2751	an example that does that for some fictitious SIGUSR1 handler:
2324		2752
2325	static ev_async mysig;	2753	static ev_async mysig;
2326		2754
2327	static void	2755	static void
2328	sigusr1_handler (void)	2756	sigusr1_handler (void)
…		…
2394	=over 4	2822	=over 4
2395		2823
2396	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2397		2825
2398	Initialises and configures the async watcher - it has no parameters of any	2826	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,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2828	trust me.
2401		2829
2402	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2403		2831
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	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	2833	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	2834	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	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2836	section below on what exactly this means).
2409		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2410	This call incurs the overhead of a system call only once per loop iteration,	2843	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	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2413		2846
2414	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2415		2848
2416	Returns a non-zero value when C<ev_async_send> has been called on the	2849	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	2850	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	2853	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,	2854	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	2855	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.	2856	quickly check whether invoking the loop might be a good idea.
2424		2857
2425	Not that this does I<not> check whether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2427		2862
2428	=back	2863	=back
2429		2864
2430		2865
2431	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	2870	=over 4
2436		2871
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2872	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2873
2439	This function combines a simple timer and an I/O watcher, calls your	2874	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2875	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	2876	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	2877	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	2878	more watchers yourself.
2444		2879
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	2880	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	2881	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	2882	the given C<fd> and C<events> set will be created and started.
2448		2883
2449	If C<timeout> is less than 0, then no timeout watcher will be	2884	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	2885	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	2886	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		2887
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2888	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	2889	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>	2890	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	2891	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2892	a timeout and an io event at the same time - you probably should give io
		2893	events precedence.
		2894
		2895	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		2896
2459	static void stdin_ready (int revents, void *arg)	2897	static void stdin_ready (int revents, void *arg)
2460	{	2898	{
		2899	if (revents & EV_READ)
		2900	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	2901	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	2902	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	2903	}
2466		2904
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2905	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		2906
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	2907	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		2908
2471	Feeds the given event set into the event loop, as if the specified event	2909	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	2910	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	2911	initialised but not necessarily started event watcher).
2474		2912
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2913	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		2914
2477	Feed an event on the given fd, as if a file descriptor backend detected	2915	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	2916	the given events it.
2479		2917
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	2918	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		2919
2482	Feed an event as if the given signal occurred (C<loop> must be the default	2920	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	2921	loop!).
2484		2922
2485	=back	2923	=back
…		…
2607		3045
2608	myclass obj;	3046	myclass obj;
2609	ev::io iow;	3047	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
		3079
2612	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2613		3081
2614	Also sets a callback, but uses a static method or plain function as	3082	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	3083	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3084	C<data> member and is free for you to use.
2617		3085
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3086	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3087
2620	See the method-C<set> above for more details.	3088	See the method-C<set> above for more details.
2621		3089
2622	Example:	3090	Example: Use a plain function as callback.
2623		3091
2624	static void io_cb (ev::io &w, int revents) { }	3092	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3093	iow.set <io_cb> ();
2626		3094
2627	=item w->set (struct ev_loop *)	3095	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	3133	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	3134	the constructor.
2667		3135
2668	class myclass	3136	class myclass
2669	{	3137	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3138	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3139	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3140
2673	myclass (int fd)	3141	myclass (int fd)
2674	{	3142	{
2675	io .set <myclass, &myclass::io_cb > (this);	3143	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3144	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3160	=item Perl
2693		3161
2694	The EV module implements the full libev API and is actually used to test	3162	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,	3163	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3164	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	3165	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>).	3166	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3167	and C<EV::Glib>).
2699		3168
2700	It can be found and installed via CPAN, its homepage is at	3169	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2702		3171
2703	=item Python	3172	=item Python
2704		3173
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3174	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	3175	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		3176
2712	=item Ruby	3177	=item Ruby
2713		3178
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3179	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	3180	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	3181	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
2718		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3191
2719	=item D	3192	=item D
2720		3193
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	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>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3196
		3197	=item Ocaml
		3198
		3199	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3200	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2723		3201
2724	=back	3202	=back
2725		3203
2726		3204
2727	=head1 MACRO MAGIC	3205	=head1 MACRO MAGIC
…		…
2828		3306
2829	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
2830	#include "ev.h"	3308	#include "ev.h"
2831		3309
2832	Both header files and implementation files can be compiled with a C++	3310	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	3311	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3312	as a bug).
2835		3313
2836	You need the following files in your source tree, or in a directory	3314	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):	3315	in your include path (e.g. in libev/ when using -Ilibev):
2838		3316
…		…
2882		3360
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3361	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3362
2885	Libev can be configured via a variety of preprocessor symbols you have to	3363	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	3364	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3365	autoconf is documented for every option.
2888		3366
2889	=over 4	3367	=over 4
2890		3368
2891	=item EV_STANDALONE	3369	=item EV_STANDALONE
2892		3370
…		…
2894	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3373	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	3374	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.	3375	F<event.h> that are not directly supported by the libev core alone.
2898		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
2899	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
2900		3381
2901	If defined to be C<1>, libev will try to detect the availability of the	3382	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	3383	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	3384	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	3385	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3386	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>	3387	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3389
2909	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
2910		3391
2911	If defined to be C<1>, libev will try to detect the availability of the	3392	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	3393	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	3394	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
2917		3411
2918	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
2919		3413
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	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 ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3431
2938	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
2939		3433
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	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	3435	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	3436	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	3437	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	3438	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	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
2947		3441
2948	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
2949		3443
2950	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3556	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	3557	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	3558	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3559	fine.
3066		3560
3067	If your embedding application does not need any priorities, defining these both to	3561	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3562	both to C<0> will save some memory and CPU.
3069		3563
3070	=item EV_PERIODIC_ENABLE	3564	=item EV_PERIODIC_ENABLE
3071		3565
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3566	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	3567	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3574	code.
3081		3575
3082	=item EV_EMBED_ENABLE	3576	=item EV_EMBED_ENABLE
3083		3577
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3578	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3579	defined to be C<0>, then they are not. Embed watchers rely on most other
		3580	watcher types, which therefore must not be disabled.
3086		3581
3087	=item EV_STAT_ENABLE	3582	=item EV_STAT_ENABLE
3088		3583
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3584	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3585	defined to be C<0>, then they are not.
…		…
3122	two).	3617	two).
3123		3618
3124	=item EV_USE_4HEAP	3619	=item EV_USE_4HEAP
3125		3620
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3621	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	3622	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	3623	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3624	faster performance with many (thousands) of watchers.
3130		3625
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3626	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3627	(disabled).
3133		3628
3134	=item EV_HEAP_CACHE_AT	3629	=item EV_HEAP_CACHE_AT
3135		3630
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3631	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	3632	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>),	3633	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,	3634	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	3635	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3636	noticeably with many (hundreds) of watchers.
3142		3637
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3638	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3639	(disabled).
3145		3640
3146	=item EV_VERIFY	3641	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3647	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	3648	verification code will be called very frequently, which will slow down
3154	libev considerably.	3649	libev considerably.
3155		3650
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3651	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3652	C<0>.
3158		3653
3159	=item EV_COMMON	3654	=item EV_COMMON
3160		3655
3161	By default, all watchers have a C<void *data> member. By redefining	3656	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	3657	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	3674	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	3675	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	3676	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	3677	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++.	3678	method calls instead of plain function calls in C++.
		3679
		3680	=back
3184		3681
3185	=head2 EXPORTED API SYMBOLS	3682	=head2 EXPORTED API SYMBOLS
3186		3683
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3684	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	3685	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:	3732	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3733
3237	#include "ev_cpp.h"	3734	#include "ev_cpp.h"
3238	#include "ev.c"	3735	#include "ev.c"
3239		3736
		3737	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3738
3241	=head1 THREADS AND COROUTINES	3739	=head2 THREADS AND COROUTINES
3242		3740
3243	=head2 THREADS	3741	=head3 THREADS
3244		3742
3245	Libev itself is completely thread-safe, but it uses no locking. This	3743	All libev functions are reentrant and thread-safe unless explicitly
		3744	documented otherwise, but libev implements no locking itself. This means
3246	means that you can use as many loops as you want in parallel, as long as	3745	that you can use as many loops as you want in parallel, as long as there
3247	only one thread ever calls into one libev function with the same loop	3746	are no concurrent calls into any libev function with the same loop
3248	parameter.	3747	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3748	of course): libev guarantees that different event loops share no data
		3749	structures that need any locking.
3249		3750
3250	Or put differently: calls with different loop parameters can be done in	3751	Or to put it differently: calls with different loop parameters can be done
3251	parallel from multiple threads, calls with the same loop parameter must be	3752	concurrently from multiple threads, calls with the same loop parameter
3252	done serially (but can be done from different threads, as long as only one	3753	must be done serially (but can be done from different threads, as long as
3253	thread ever is inside a call at any point in time, e.g. by using a mutex	3754	only one thread ever is inside a call at any point in time, e.g. by using
3254	per loop).	3755	a mutex per loop).
		3756
		3757	Specifically to support threads (and signal handlers), libev implements
		3758	so-called C<ev_async> watchers, which allow some limited form of
		3759	concurrency on the same event loop, namely waking it up "from the
		3760	outside".
3255		3761
3256	If you want to know which design (one loop, locking, or multiple loops	3762	If you want to know which design (one loop, locking, or multiple loops
3257	without or something else still) is best for your problem, then I cannot	3763	without or something else still) is best for your problem, then I cannot
3258	help you. I can give some generic advice however:	3764	help you, but here is some generic advice:
3259		3765
3260	=over 4	3766	=over 4
3261		3767
3262	=item * most applications have a main thread: use the default libev loop	3768	=item * most applications have a main thread: use the default libev loop
3263	in that thread, or create a separate thread running only the default loop.	3769	in that thread, or create a separate thread running only the default loop.
…		…
3275		3781
3276	Choosing a model is hard - look around, learn, know that usually you can do	3782	Choosing a model is hard - look around, learn, know that usually you can do
3277	better than you currently do :-)	3783	better than you currently do :-)
3278		3784
3279	=item * often you need to talk to some other thread which blocks in the	3785	=item * often you need to talk to some other thread which blocks in the
		3786	event loop.
		3787
3280	event loop - C<ev_async> watchers can be used to wake them up from other	3788	C<ev_async> watchers can be used to wake them up from other threads safely
3281	threads safely (or from signal contexts...).	3789	(or from signal contexts...).
		3790
		3791	An example use would be to communicate signals or other events that only
		3792	work in the default loop by registering the signal watcher with the
		3793	default loop and triggering an C<ev_async> watcher from the default loop
		3794	watcher callback into the event loop interested in the signal.
3282		3795
3283	=back	3796	=back
3284		3797
3285	=head2 COROUTINES	3798	=head3 COROUTINES
3286		3799
3287	Libev is much more accommodating to coroutines ("cooperative threads"):	3800	Libev is very accommodating to coroutines ("cooperative threads"):
3288	libev fully supports nesting calls to it's functions from different	3801	libev fully supports nesting calls to its functions from different
3289	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3802	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3290	different coroutines and switch freely between both coroutines running the	3803	different coroutines, and switch freely between both coroutines running the
3291	loop, as long as you don't confuse yourself). The only exception is that	3804	loop, as long as you don't confuse yourself). The only exception is that
3292	you must not do this from C<ev_periodic> reschedule callbacks.	3805	you must not do this from C<ev_periodic> reschedule callbacks.
3293		3806
3294	Care has been invested into making sure that libev does not keep local	3807	Care has been taken to ensure that libev does not keep local state inside
3295	state inside C<ev_loop>, and other calls do not usually allow coroutine	3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3296	switches.	3809	they do not call any callbacks.
3297		3810
		3811	=head2 COMPILER WARNINGS
3298		3812
3299	=head1 COMPLEXITIES	3813	Depending on your compiler and compiler settings, you might get no or a
		3814	lot of warnings when compiling libev code. Some people are apparently
		3815	scared by this.
3300		3816
3301	In this section the complexities of (many of) the algorithms used inside	3817	However, these are unavoidable for many reasons. For one, each compiler
3302	libev will be explained. For complexity discussions about backends see the	3818	has different warnings, and each user has different tastes regarding
3303	documentation for C<ev_default_init>.	3819	warning options. "Warn-free" code therefore cannot be a goal except when
		3820	targeting a specific compiler and compiler-version.
3304		3821
3305	All of the following are about amortised time: If an array needs to be	3822	Another reason is that some compiler warnings require elaborate
3306	extended, libev needs to realloc and move the whole array, but this	3823	workarounds, or other changes to the code that make it less clear and less
3307	happens asymptotically never with higher number of elements, so O(1) might	3824	maintainable.
3308	mean it might do a lengthy realloc operation in rare cases, but on average
3309	it is much faster and asymptotically approaches constant time.
3310		3825
3311	=over 4	3826	And of course, some compiler warnings are just plain stupid, or simply
		3827	wrong (because they don't actually warn about the condition their message
		3828	seems to warn about). For example, certain older gcc versions had some
		3829	warnings that resulted an extreme number of false positives. These have
		3830	been fixed, but some people still insist on making code warn-free with
		3831	such buggy versions.
3312		3832
3313	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3833	While libev is written to generate as few warnings as possible,
		3834	"warn-free" code is not a goal, and it is recommended not to build libev
		3835	with any compiler warnings enabled unless you are prepared to cope with
		3836	them (e.g. by ignoring them). Remember that warnings are just that:
		3837	warnings, not errors, or proof of bugs.
3314		3838
3315	This means that, when you have a watcher that triggers in one hour and
3316	there are 100 watchers that would trigger before that then inserting will
3317	have to skip roughly seven (C<ld 100>) of these watchers.
3318		3839
3319	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3840	=head2 VALGRIND
3320		3841
3321	That means that changing a timer costs less than removing/adding them	3842	Valgrind has a special section here because it is a popular tool that is
3322	as only the relative motion in the event queue has to be paid for.	3843	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3323		3844
3324	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3845	If you think you found a bug (memory leak, uninitialised data access etc.)
		3846	in libev, then check twice: If valgrind reports something like:
3325		3847
3326	These just add the watcher into an array or at the head of a list.	3848	==2274== definitely lost: 0 bytes in 0 blocks.
		3849	==2274== possibly lost: 0 bytes in 0 blocks.
		3850	==2274== still reachable: 256 bytes in 1 blocks.
3327		3851
3328	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3852	Then there is no memory leak, just as memory accounted to global variables
		3853	is not a memleak - the memory is still being referenced, and didn't leak.
3329		3854
3330	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3855	Similarly, under some circumstances, valgrind might report kernel bugs
		3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3857	although an acceptable workaround has been found here), or it might be
		3858	confused.
3331		3859
3332	These watchers are stored in lists then need to be walked to find the	3860	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3333	correct watcher to remove. The lists are usually short (you don't usually	3861	make it into some kind of religion.
3334	have many watchers waiting for the same fd or signal).
3335		3862
3336	=item Finding the next timer in each loop iteration: O(1)	3863	If you are unsure about something, feel free to contact the mailing list
		3864	with the full valgrind report and an explanation on why you think this
		3865	is a bug in libev (best check the archives, too :). However, don't be
		3866	annoyed when you get a brisk "this is no bug" answer and take the chance
		3867	of learning how to interpret valgrind properly.
3337		3868
3338	By virtue of using a binary or 4-heap, the next timer is always found at a	3869	If you need, for some reason, empty reports from valgrind for your project
3339	fixed position in the storage array.	3870	I suggest using suppression lists.
3340		3871
3341	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3342		3872
3343	A change means an I/O watcher gets started or stopped, which requires	3873	=head1 PORTABILITY NOTES
3344	libev to recalculate its status (and possibly tell the kernel, depending
3345	on backend and whether C<ev_io_set> was used).
3346		3874
3347	=item Activating one watcher (putting it into the pending state): O(1)
3348
3349	=item Priority handling: O(number_of_priorities)
3350
3351	Priorities are implemented by allocating some space for each
3352	priority. When doing priority-based operations, libev usually has to
3353	linearly search all the priorities, but starting/stopping and activating
3354	watchers becomes O(1) w.r.t. priority handling.
3355
3356	=item Sending an ev_async: O(1)
3357
3358	=item Processing ev_async_send: O(number_of_async_watchers)
3359
3360	=item Processing signals: O(max_signal_number)
3361
3362	Sending involves a system call I<iff> there were no other C<ev_async_send>
3363	calls in the current loop iteration. Checking for async and signal events
3364	involves iterating over all running async watchers or all signal numbers.
3365
3366	=back
3367
3368
3369	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3370		3876
3371	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3877	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3372	requires, and its I/O model is fundamentally incompatible with the POSIX	3878	requires, and its I/O model is fundamentally incompatible with the POSIX
3373	model. Libev still offers limited functionality on this platform in	3879	model. Libev still offers limited functionality on this platform in
3374	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3385		3891
3386	Not a libev limitation but worth mentioning: windows apparently doesn't	3892	Not a libev limitation but worth mentioning: windows apparently doesn't
3387	accept large writes: instead of resulting in a partial write, windows will	3893	accept large writes: instead of resulting in a partial write, windows will
3388	either accept everything or return C<ENOBUFS> if the buffer is too large,	3894	either accept everything or return C<ENOBUFS> if the buffer is too large,
3389	so make sure you only write small amounts into your sockets (less than a	3895	so make sure you only write small amounts into your sockets (less than a
3390	megabyte seems safe, but thsi apparently depends on the amount of memory	3896	megabyte seems safe, but this apparently depends on the amount of memory
3391	available).	3897	available).
3392		3898
3393	Due to the many, low, and arbitrary limits on the win32 platform and	3899	Due to the many, low, and arbitrary limits on the win32 platform and
3394	the abysmal performance of winsockets, using a large number of sockets	3900	the abysmal performance of winsockets, using a large number of sockets
3395	is not recommended (and not reasonable). If your program needs to use	3901	is not recommended (and not reasonable). If your program needs to use
…		…
3406	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3912	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3407		3913
3408	#include "ev.h"	3914	#include "ev.h"
3409		3915
3410	And compile the following F<evwrap.c> file into your project (make sure	3916	And compile the following F<evwrap.c> file into your project (make sure
3411	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3917	you do I<not> compile the F<ev.c> or any other embedded source files!):
3412		3918
3413	#include "evwrap.h"	3919	#include "evwrap.h"
3414	#include "ev.c"	3920	#include "ev.c"
3415		3921
3416	=over 4	3922	=over 4
…		…
3461	wrap all I/O functions and provide your own fd management, but the cost of	3967	wrap all I/O functions and provide your own fd management, but the cost of
3462	calling select (O(n²)) will likely make this unworkable.	3968	calling select (O(n²)) will likely make this unworkable.
3463		3969
3464	=back	3970	=back
3465		3971
3466
3467	=head1 PORTABILITY REQUIREMENTS	3972	=head2 PORTABILITY REQUIREMENTS
3468		3973
3469	In addition to a working ISO-C implementation, libev relies on a few	3974	In addition to a working ISO-C implementation and of course the
3470	additional extensions:	3975	backend-specific APIs, libev relies on a few additional extensions:
3471		3976
3472	=over 4	3977	=over 4
3473		3978
3474	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3979	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3475	calling conventions regardless of C<ev_watcher_type *>.	3980	calling conventions regardless of C<ev_watcher_type *>.
…		…
3481	calls them using an C<ev_watcher *> internally.	3986	calls them using an C<ev_watcher *> internally.
3482		3987
3483	=item C<sig_atomic_t volatile> must be thread-atomic as well	3988	=item C<sig_atomic_t volatile> must be thread-atomic as well
3484		3989
3485	The type C<sig_atomic_t volatile> (or whatever is defined as	3990	The type C<sig_atomic_t volatile> (or whatever is defined as
3486	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3991	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3487	threads. This is not part of the specification for C<sig_atomic_t>, but is	3992	threads. This is not part of the specification for C<sig_atomic_t>, but is
3488	believed to be sufficiently portable.	3993	believed to be sufficiently portable.
3489		3994
3490	=item C<sigprocmask> must work in a threaded environment	3995	=item C<sigprocmask> must work in a threaded environment
3491		3996
…		…
3500	except the initial one, and run the default loop in the initial thread as	4005	except the initial one, and run the default loop in the initial thread as
3501	well.	4006	well.
3502		4007
3503	=item C<long> must be large enough for common memory allocation sizes	4008	=item C<long> must be large enough for common memory allocation sizes
3504		4009
3505	To improve portability and simplify using libev, libev uses C<long>	4010	To improve portability and simplify its API, libev uses C<long> internally
3506	internally instead of C<size_t> when allocating its data structures. On	4011	instead of C<size_t> when allocating its data structures. On non-POSIX
3507	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4012	systems (Microsoft...) this might be unexpectedly low, but is still at
3508	is still at least 31 bits everywhere, which is enough for hundreds of	4013	least 31 bits everywhere, which is enough for hundreds of millions of
3509	millions of watchers.	4014	watchers.
3510		4015
3511	=item C<double> must hold a time value in seconds with enough accuracy	4016	=item C<double> must hold a time value in seconds with enough accuracy
3512		4017
3513	The type C<double> is used to represent timestamps. It is required to	4018	The type C<double> is used to represent timestamps. It is required to
3514	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4019	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3518	=back	4023	=back
3519		4024
3520	If you know of other additional requirements drop me a note.	4025	If you know of other additional requirements drop me a note.
3521		4026
3522		4027
3523	=head1 COMPILER WARNINGS	4028	=head1 ALGORITHMIC COMPLEXITIES
3524		4029
3525	Depending on your compiler and compiler settings, you might get no or a	4030	In this section the complexities of (many of) the algorithms used inside
3526	lot of warnings when compiling libev code. Some people are apparently	4031	libev will be documented. For complexity discussions about backends see
3527	scared by this.	4032	the documentation for C<ev_default_init>.
3528		4033
3529	However, these are unavoidable for many reasons. For one, each compiler	4034	All of the following are about amortised time: If an array needs to be
3530	has different warnings, and each user has different tastes regarding	4035	extended, libev needs to realloc and move the whole array, but this
3531	warning options. "Warn-free" code therefore cannot be a goal except when	4036	happens asymptotically rarer with higher number of elements, so O(1) might
3532	targeting a specific compiler and compiler-version.	4037	mean that libev does a lengthy realloc operation in rare cases, but on
		4038	average it is much faster and asymptotically approaches constant time.
3533		4039
3534	Another reason is that some compiler warnings require elaborate	4040	=over 4
3535	workarounds, or other changes to the code that make it less clear and less
3536	maintainable.
3537		4041
3538	And of course, some compiler warnings are just plain stupid, or simply	4042	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3539	wrong (because they don't actually warn about the condition their message
3540	seems to warn about).
3541		4043
3542	While libev is written to generate as few warnings as possible,	4044	This means that, when you have a watcher that triggers in one hour and
3543	"warn-free" code is not a goal, and it is recommended not to build libev	4045	there are 100 watchers that would trigger before that, then inserting will
3544	with any compiler warnings enabled unless you are prepared to cope with	4046	have to skip roughly seven (C<ld 100>) of these watchers.
3545	them (e.g. by ignoring them). Remember that warnings are just that:
3546	warnings, not errors, or proof of bugs.
3547		4047
		4048	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3548		4049
3549	=head1 VALGRIND	4050	That means that changing a timer costs less than removing/adding them,
		4051	as only the relative motion in the event queue has to be paid for.
3550		4052
3551	Valgrind has a special section here because it is a popular tool that is	4053	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3552	highly useful, but valgrind reports are very hard to interpret.
3553		4054
3554	If you think you found a bug (memory leak, uninitialised data access etc.)	4055	These just add the watcher into an array or at the head of a list.
3555	in libev, then check twice: If valgrind reports something like:
3556		4056
3557	==2274== definitely lost: 0 bytes in 0 blocks.	4057	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3558	==2274== possibly lost: 0 bytes in 0 blocks.
3559	==2274== still reachable: 256 bytes in 1 blocks.
3560		4058
3561	Then there is no memory leak. Similarly, under some circumstances,	4059	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3562	valgrind might report kernel bugs as if it were a bug in libev, or it
3563	might be confused (it is a very good tool, but only a tool).
3564		4060
3565	If you are unsure about something, feel free to contact the mailing list	4061	These watchers are stored in lists, so they need to be walked to find the
3566	with the full valgrind report and an explanation on why you think this is	4062	correct watcher to remove. The lists are usually short (you don't usually
3567	a bug in libev. However, don't be annoyed when you get a brisk "this is	4063	have many watchers waiting for the same fd or signal: one is typical, two
3568	no bug" answer and take the chance of learning how to interpret valgrind	4064	is rare).
3569	properly.
3570		4065
3571	If you need, for some reason, empty reports from valgrind for your project	4066	=item Finding the next timer in each loop iteration: O(1)
3572	I suggest using suppression lists.
3573		4067
		4068	By virtue of using a binary or 4-heap, the next timer is always found at a
		4069	fixed position in the storage array.
		4070
		4071	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4072
		4073	A change means an I/O watcher gets started or stopped, which requires
		4074	libev to recalculate its status (and possibly tell the kernel, depending
		4075	on backend and whether C<ev_io_set> was used).
		4076
		4077	=item Activating one watcher (putting it into the pending state): O(1)
		4078
		4079	=item Priority handling: O(number_of_priorities)
		4080
		4081	Priorities are implemented by allocating some space for each
		4082	priority. When doing priority-based operations, libev usually has to
		4083	linearly search all the priorities, but starting/stopping and activating
		4084	watchers becomes O(1) with respect to priority handling.
		4085
		4086	=item Sending an ev_async: O(1)
		4087
		4088	=item Processing ev_async_send: O(number_of_async_watchers)
		4089
		4090	=item Processing signals: O(max_signal_number)
		4091
		4092	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4093	calls in the current loop iteration. Checking for async and signal events
		4094	involves iterating over all running async watchers or all signal numbers.
		4095
		4096	=back
		4097
		4098
		4099	=head1 GLOSSARY
		4100
		4101	=over 4
		4102
		4103	=item active
		4104
		4105	A watcher is active as long as it has been started (has been attached to
		4106	an event loop) but not yet stopped (disassociated from the event loop).
		4107
		4108	=item application
		4109
		4110	In this document, an application is whatever is using libev.
		4111
		4112	=item callback
		4113
		4114	The address of a function that is called when some event has been
		4115	detected. Callbacks are being passed the event loop, the watcher that
		4116	received the event, and the actual event bitset.
		4117
		4118	=item callback invocation
		4119
		4120	The act of calling the callback associated with a watcher.
		4121
		4122	=item event
		4123
		4124	A change of state of some external event, such as data now being available
		4125	for reading on a file descriptor, time having passed or simply not having
		4126	any other events happening anymore.
		4127
		4128	In libev, events are represented as single bits (such as C<EV_READ> or
		4129	C<EV_TIMEOUT>).
		4130
		4131	=item event library
		4132
		4133	A software package implementing an event model and loop.
		4134
		4135	=item event loop
		4136
		4137	An entity that handles and processes external events and converts them
		4138	into callback invocations.
		4139
		4140	=item event model
		4141
		4142	The model used to describe how an event loop handles and processes
		4143	watchers and events.
		4144
		4145	=item pending
		4146
		4147	A watcher is pending as soon as the corresponding event has been detected,
		4148	and stops being pending as soon as the watcher will be invoked or its
		4149	pending status is explicitly cleared by the application.
		4150
		4151	A watcher can be pending, but not active. Stopping a watcher also clears
		4152	its pending status.
		4153
		4154	=item real time
		4155
		4156	The physical time that is observed. It is apparently strictly monotonic :)
		4157
		4158	=item wall-clock time
		4159
		4160	The time and date as shown on clocks. Unlike real time, it can actually
		4161	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4162	clock.
		4163
		4164	=item watcher
		4165
		4166	A data structure that describes interest in certain events. Watchers need
		4167	to be started (attached to an event loop) before they can receive events.
		4168
		4169	=item watcher invocation
		4170
		4171	The act of calling the callback associated with a watcher.
		4172
		4173	=back
3574		4174
3575	=head1 AUTHOR	4175	=head1 AUTHOR
3576		4176
3577	Marc Lehmann <libev@schmorp.de>.	4177	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3578		4178

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