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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	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
103	Libev is very configurable. In this manual the default (and most common)	117	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	118	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	119	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	120	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	121	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	122	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	123	this argument.
110		124
111	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
112		126
113	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	129	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	130	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	131	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	132	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	133	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	134	throughout libev.
121		135
122	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
123		137
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	229	recommended ones.
216		230
217	See the description of C<ev_embed> watchers for more info.	231	See the description of C<ev_embed> watchers for more info.
218		232
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		234
221	Sets the allocation function to use (the prototype is similar - the	235	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	236	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	237	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	238	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	264	}
251		265
252	...	266	...
253	ev_set_allocator (persistent_realloc);	267	ev_set_allocator (persistent_realloc);
254		268
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		270
257	Set the callback function to call on a retryable system call error (such	271	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	272	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	273	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	274	callback is set, then libev will expect it to remedy the situation, no
…		…
276		290
277	=back	291	=back
278		292
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		294
281	An event loop is described by a C<struct ev_loop *>. The library knows two	295	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	296	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	297	I<function>).
		298
		299	The library knows two types of such loops, the I<default> loop, which
		300	supports signals and child events, and dynamically created loops which do
		301	not.
284		302
285	=over 4	303	=over 4
286		304
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	305	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		306
…		…
294	If you don't know what event loop to use, use the one returned from this	312	If you don't know what event loop to use, use the one returned from this
295	function.	313	function.
296		314
297	Note that this function is I<not> thread-safe, so if you want to use it	315	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,	316	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	317	as loops cannot be shared easily between threads anyway).
300		318
301	The default loop is the only loop that can handle C<ev_signal> and	319	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	320	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	321	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	322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	398	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		399
382	For few fds, this backend is a bit little slower than poll and select,	400	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	401	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),	402	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	403	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	404
387	cases and requiring a system call per fd change, no fork support and bad	405	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	406	of the more advanced event mechanisms: mere annoyances include silently
		407	dropping file descriptors, requiring a system call per change per file
		408	descriptor (and unnecessary guessing of parameters), problems with dup and
		409	so on. The biggest issue is fork races, however - if a program forks then
		410	I<both> parent and child process have to recreate the epoll set, which can
		411	take considerable time (one syscall per file descriptor) and is of course
		412	hard to detect.
		413
		414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		415	of course I<doesn't>, and epoll just loves to report events for totally
		416	I<different> file descriptors (even already closed ones, so one cannot
		417	even remove them from the set) than registered in the set (especially
		418	on SMP systems). Libev tries to counter these spurious notifications by
		419	employing an additional generation counter and comparing that against the
		420	events to filter out spurious ones, recreating the set when required.
389		421
390	While stopping, setting and starting an I/O watcher in the same iteration	422	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	423	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	424	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	425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	426	file descriptors might not work very well if you register events for both
395		427	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		428
400	Best performance from this backend is achieved by not unregistering all	429	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.	430	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	431	i.e. keep at least one watcher active per fd at all times. Stopping and
		432	starting a watcher (without re-setting it) also usually doesn't cause
		433	extra overhead. A fork can both result in spurious notifications as well
		434	as in libev having to destroy and recreate the epoll object, which can
		435	take considerable time and thus should be avoided.
		436
		437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		438	faster than epoll for maybe up to a hundred file descriptors, depending on
		439	the usage. So sad.
403		440
404	While nominally embeddable in other event loops, this feature is broken in	441	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	442	all kernel versions tested so far.
406		443
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	444	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)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		448
412	Kqueue deserves special mention, as at the time of this writing, it	449	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	450	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	451	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"	452	it's completely useless). Unlike epoll, however, whose brokenness
		453	is by design, these kqueue bugs can (and eventually will) be fixed
		454	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	455	"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)	456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	457	system like NetBSD.
419		458
420	You still can embed kqueue into a normal poll or select backend and use it	459	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	460	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		462
424	It scales in the same way as the epoll backend, but the interface to the	463	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	464	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	465	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	466	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	467	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		469	cases
430		470
431	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
432		472
433	While nominally embeddable in other event loops, this doesn't work	473	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	474	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	475	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	476	(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	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
439		479
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	480	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	481	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	482	C<NOTE_EOF>.
443		483
…		…
460	While this backend scales well, it requires one system call per active	500	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	501	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	503	might perform better.
464		504
465	On the positive side, ignoring the spurious readiness notifications, this	505	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	506	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	507	in all tests and is fully embeddable, which is a rare feat among the
		508	OS-specific backends (I vastly prefer correctness over speed hacks).
468		509
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
471		512
472	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
481		522
482	If one or more of these are or'ed into the flags value, then only these	523	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	524	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.	525	specified, all backends in C<ev_recommended_backends ()> will be tried.
485		526
486	The most typical usage is like this:	527	Example: This is the most typical usage.
487		528
488	if (!ev_default_loop (0))	529	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		531
491	Restrict libev to the select and poll backends, and do not allow	532	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	533	environment settings to be taken into account:
493		534
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		536
496	Use whatever libev has to offer, but make sure that kqueue is used if	537	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	538	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):	539	private event loop and only if you know the OS supports your types of
		540	fds):
499		541
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		543
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	544	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		545
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	567	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	568	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	569	for example).
528		570
529	Note that certain global state, such as signal state, will not be freed by	571	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
532		574
533	In general it is not advisable to call this function except in the	575	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	576	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	577	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
561		603
562	=item ev_loop_fork (loop)	604	=item ev_loop_fork (loop)
563		605
564	Like C<ev_default_fork>, but acts on an event loop created by	606	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	607	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.	608	after fork that you want to re-use in the child, and how you do this is
		609	entirely your own problem.
567		610
568	=item int ev_is_default_loop (loop)	611	=item int ev_is_default_loop (loop)
569		612
570	Returns true when the given loop actually is the default loop, false otherwise.	613	Returns true when the given loop is, in fact, the default loop, and false
		614	otherwise.
571		615
572	=item unsigned int ev_loop_count (loop)	616	=item unsigned int ev_loop_count (loop)
573		617
574	Returns the count of loop iterations for the loop, which is identical to	618	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	619	the number of times libev did poll for new events. It starts at C<0> and
576	happily wraps around with enough iterations.	620	happily wraps around with enough iterations.
577		621
578	This value can sometimes be useful as a generation counter of sorts (it	622	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
581		637
582	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
583		639
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	641	use.
…		…
600		656
601	This function is rarely useful, but when some event callback runs for a	657	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	658	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	659	the current time is a good idea.
604		660
605	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
		662
		663	=item ev_suspend (loop)
		664
		665	=item ev_resume (loop)
		666
		667	These two functions suspend and resume a loop, for use when the loop is
		668	not used for a while and timeouts should not be processed.
		669
		670	A typical use case would be an interactive program such as a game: When
		671	the user presses C<^Z> to suspend the game and resumes it an hour later it
		672	would be best to handle timeouts as if no time had actually passed while
		673	the program was suspended. This can be achieved by calling C<ev_suspend>
		674	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		675	C<ev_resume> directly afterwards to resume timer processing.
		676
		677	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		679	will be rescheduled (that is, they will lose any events that would have
		680	occured while suspended).
		681
		682	After calling C<ev_suspend> you B<must not> call I<any> function on the
		683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		684	without a previous call to C<ev_suspend>.
		685
		686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		687	event loop time (see C<ev_now_update>).
606		688
607	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
608		690
609	Finally, this is it, the event handler. This function usually is called	691	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	692	after you initialised all your watchers and you want to start handling
…		…
613	If the flags argument is specified as C<0>, it will not return until	695	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.	696	either no event watchers are active anymore or C<ev_unloop> was called.
615		697
616	Please note that an explicit C<ev_unloop> is usually better than	698	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	699	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	700	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	701	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.	702	of relying on its watchers stopping correctly, that is truly a thing of
		703	beauty.
621		704
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	705	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	706	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.	707	process in case there are no events and will return after one iteration of
		708	the loop.
625		709
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	710	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	711	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	712	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	713	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	714	user-registered callback will be called), and will return after one
		715	iteration of the loop.
		716
		717	This is useful if you are waiting for some external event in conjunction
		718	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	719	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.	720	usually a better approach for this kind of thing.
633		721
634	Here are the gory details of what C<ev_loop> does:	722	Here are the gory details of what C<ev_loop> does:
635		723
636	- Before the first iteration, call any pending watchers.	724	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	734	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	735	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	736	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	737	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	739	- Queue all expired timers.
652	- Queue all outstanding periodics.	740	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	741	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	742	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	743	- 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	744	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	745	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	762	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.	763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		764
677	This "unloop state" will be cleared when entering C<ev_loop> again.	765	This "unloop state" will be cleared when entering C<ev_loop> again.
678		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
679	=item ev_ref (loop)	769	=item ev_ref (loop)
680		770
681	=item ev_unref (loop)	771	=item ev_unref (loop)
682		772
683	Ref/unref can be used to add or remove a reference count on the event	773	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	774	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	775	count is nonzero, C<ev_loop> will not return on its own.
		776
686	a watcher you never unregister that should not keep C<ev_loop> from	777	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	778	from returning, call ev_unref() after starting, and ev_ref() before
		779	stopping it.
		780
688	example, libev itself uses this for its internal signal pipe: It is not	781	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	782	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	783	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	784	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>	785	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,	786	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	787	before, respectively. Note also that libev might stop watchers itself
		788	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		789	in the callback).
695		790
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	792	running when nothing else is active.
698		793
699	struct ev_signal exitsig;	794	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	797	evf_unref (loop);
703		798
704	Example: For some weird reason, unregister the above signal handler again.	799	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>)	813	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	814	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	815	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	816	opportunities).
722		817
723	The background is that sometimes your program runs just fast enough to	818	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	819	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	820	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	821	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	822	overhead for the actual polling but can deliver many events at once.
728		823
729	By setting a higher I<io collect interval> you allow libev to spend more	824	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,	825	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	827	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.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
734		831
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	834	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	836	value will not introduce any overhead in libev.
740		837
741	Many (busy) programs can usually benefit by setting the I/O collect	838	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	839	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	840	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>,	841	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
746		847
747	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	850	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	851	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
753		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		868
		869	This overrides the invoke pending functionality of the loop: Instead of
		870	invoking all pending watchers when there are any, C<ev_loop> will call
		871	this callback instead. This is useful, for example, when you want to
		872	invoke the actual watchers inside another context (another thread etc.).
		873
		874	If you want to reset the callback, use C<ev_invoke_pending> as new
		875	callback.
		876
		877	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		878
		879	Sometimes you want to share the same loop between multiple threads. This
		880	can be done relatively simply by putting mutex_lock/unlock calls around
		881	each call to a libev function.
		882
		883	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		884	wait for it to return. One way around this is to wake up the loop via
		885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		886	and I<acquire> callbacks on the loop.
		887
		888	When set, then C<release> will be called just before the thread is
		889	suspended waiting for new events, and C<acquire> is called just
		890	afterwards.
		891
		892	Ideally, C<release> will just call your mutex_unlock function, and
		893	C<acquire> will just call the mutex_lock function again.
		894
		895	=item ev_set_userdata (loop, void *data)
		896
		897	=item ev_userdata (loop)
		898
		899	Set and retrieve a single C<void *> associated with a loop. When
		900	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		901	C<0.>
		902
		903	These two functions can be used to associate arbitrary data with a loop,
		904	and are intended solely for the C<invoke_pending_cb>, C<release> and
		905	C<acquire> callbacks described above, but of course can be (ab-)used for
		906	any other purpose as well.
		907
754	=item ev_loop_verify (loop)	908	=item ev_loop_verify (loop)
755		909
756	This function only does something when C<EV_VERIFY> support has been	910	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	911	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	912	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	913	is found to be inconsistent, it will print an error message to standard
		914	error and call C<abort ()>.
760		915
761	This can be used to catch bugs inside libev itself: under normal	916	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	917	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	918	data structures consistent.
764		919
765	=back	920	=back
766		921
767		922
768	=head1 ANATOMY OF A WATCHER	923	=head1 ANATOMY OF A WATCHER
769		924
		925	In the following description, uppercase C<TYPE> in names stands for the
		926	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		927	watchers and C<ev_io_start> for I/O watchers.
		928
770	A watcher is a structure that you create and register to record your	929	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	930	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:	931	become readable, you would create an C<ev_io> watcher for that:
773		932
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	933	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	934	{
776	ev_io_stop (w);	935	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	936	ev_unloop (loop, EVUNLOOP_ALL);
778	}	937	}
779		938
780	struct ev_loop *loop = ev_default_loop (0);	939	struct ev_loop *loop = ev_default_loop (0);
		940
781	struct ev_io stdin_watcher;	941	ev_io stdin_watcher;
		942
782	ev_init (&stdin_watcher, my_cb);	943	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	944	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	945	ev_io_start (loop, &stdin_watcher);
		946
785	ev_loop (loop, 0);	947	ev_loop (loop, 0);
786		948
787	As you can see, you are responsible for allocating the memory for your	949	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,	950	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	951	stack).
		952
		953	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		954	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		955
791	Each watcher structure must be initialised by a call to C<ev_init	956	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	957	(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	958	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	959	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	960	is readable and/or writable).
796		961
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	962	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	963	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	964	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	965	ev_TYPE_init (watcher *, callback, ...) >>.
801		966
802	To make the watcher actually watch out for events, you have to start it	967	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	968	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	969	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	970	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		971
807	As long as your watcher is active (has been started but not stopped) you	972	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	973	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	974	reinitialise it or call its C<ev_TYPE_set> macro.
810		975
811	Each and every callback receives the event loop pointer as first, the	976	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	977	registered watcher structure as second, and a bitset of received events as
813	third argument.	978	third argument.
814		979
…		…
872		1037
873	=item C<EV_ASYNC>	1038	=item C<EV_ASYNC>
874		1039
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1040	The given async watcher has been asynchronously notified (see C<ev_async>).
876		1041
		1042	=item C<EV_CUSTOM>
		1043
		1044	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1045	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1046
877	=item C<EV_ERROR>	1047	=item C<EV_ERROR>
878		1048
879	An unspecified error has occurred, the watcher has been stopped. This might	1049	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1050	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	1051	ran out of memory, a file descriptor was found to be closed or any other
		1052	problem. Libev considers these application bugs.
		1053
882	problem. You best act on it by reporting the problem and somehow coping	1054	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1055	watcher being stopped. Note that well-written programs should not receive
		1056	an error ever, so when your watcher receives it, this usually indicates a
		1057	bug in your program.
884		1058
885	Libev will usually signal a few "dummy" events together with an error,	1059	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	1060	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	1061	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	1062	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1063	programs, though, as the fd could already be closed and reused for another
		1064	thing, so beware.
890		1065
891	=back	1066	=back
892		1067
893	=head2 GENERIC WATCHER FUNCTIONS	1068	=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		1069
898	=over 4	1070	=over 4
899		1071
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1072	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1073
…		…
907	which rolls both calls into one.	1079	which rolls both calls into one.
908		1080
909	You can reinitialise a watcher at any time as long as it has been stopped	1081	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.	1082	(or never started) and there are no pending events outstanding.
911		1083
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1084	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1085	int revents)>.
		1086
		1087	Example: Initialise an C<ev_io> watcher in two steps.
		1088
		1089	ev_io w;
		1090	ev_init (&w, my_cb);
		1091	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		1092
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1093	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		1094
917	This macro initialises the type-specific parts of a watcher. You need to	1095	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	1096	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	1099	difference to the C<ev_init> macro).
922		1100
923	Although some watcher types do not have type-specific arguments	1101	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.	1102	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1103
		1104	See C<ev_init>, above, for an example.
		1105
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1106	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1107
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1108	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	1109	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1110	a watcher. The same limitations apply, of course.
931		1111
		1112	Example: Initialise and set an C<ev_io> watcher in one step.
		1113
		1114	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1115
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1116	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		1117
934	Starts (activates) the given watcher. Only active watchers will receive	1118	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1119	events. If the watcher is already active nothing will happen.
936		1120
		1121	Example: Start the C<ev_io> watcher that is being abused as example in this
		1122	whole section.
		1123
		1124	ev_io_start (EV_DEFAULT_UC, &w);
		1125
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1126	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1127
939	Stops the given watcher again (if active) and clears the pending	1128	Stops the given watcher if active, and clears the pending status (whether
		1129	the watcher was active or not).
		1130
940	status. It is possible that stopped watchers are pending (for example,	1131	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1132	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	1133	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	1134	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.	1135	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1136
946	=item bool ev_is_active (ev_TYPE *watcher)	1137	=item bool ev_is_active (ev_TYPE *watcher)
947		1138
948	Returns a true value iff the watcher is active (i.e. it has been started	1139	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	1140	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>	1166	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1167	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1168	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1169	from being executed (except for C<ev_idle> watchers).
979		1170
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	1171	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.	1172	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1173
988	You I<must not> change the priority of a watcher as long as it is active or	1174	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1175	pending.
990		1176
		1177	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1178	fine, as long as you do not mind that the priority value you query might
		1179	or might not have been clamped to the valid range.
		1180
991	The default priority used by watchers when no priority has been set is	1181	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 :).	1182	always C<0>, which is supposed to not be too high and not be too low :).
993		1183
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1184	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1185	priorities.
996	or might not have been adjusted to be within valid range.
997		1186
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1187	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1188
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1189	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	1190	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1191	can deal with that fact, as both are simply passed through to the
		1192	callback.
1003		1193
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1194	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1195
1006	If the watcher is pending, this function returns clears its pending status	1196	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	1197	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>.	1198	watcher isn't pending it does nothing and returns C<0>.
1009		1199
		1200	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1201	callback to be invoked, which can be accomplished with this function.
		1202
1010	=back	1203	=back
1011		1204
1012		1205
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1206	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1207
1015	Each watcher has, by default, a member C<void *data> that you can change	1208	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	1209	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	1210	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	1211	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	1212	member, you can also "subclass" the watcher type and provide your own
1020	data:	1213	data:
1021		1214
1022	struct my_io	1215	struct my_io
1023	{	1216	{
1024	struct ev_io io;	1217	ev_io io;
1025	int otherfd;	1218	int otherfd;
1026	void *somedata;	1219	void *somedata;
1027	struct whatever *mostinteresting;	1220	struct whatever *mostinteresting;
1028	};	1221	};
1029		1222
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1225	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1226
1034	And since your callback will be called with a pointer to the watcher, you	1227	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1228	can cast it back to your own type:
1036		1229
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1230	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1231	{
1039	struct my_io *w = (struct my_io *)w_;	1232	struct my_io *w = (struct my_io *)w_;
1040	...	1233	...
1041	}	1234	}
1042		1235
…		…
1053	ev_timer t2;	1246	ev_timer t2;
1054	}	1247	}
1055		1248
1056	In this case getting the pointer to C<my_biggy> is a bit more	1249	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	1250	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	1251	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1252	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1253	programmers):
1060		1254
1061	#include <stddef.h>	1255	#include <stddef.h>
1062		1256
1063	static void	1257	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1258	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1259	{
1066	struct my_biggy big = (struct my_biggy *	1260	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1261	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1262	}
1069		1263
1070	static void	1264	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1265	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1266	{
1073	struct my_biggy big = (struct my_biggy *	1267	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1268	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1269	}
		1270
		1271	=head2 WATCHER PRIORITY MODELS
		1272
		1273	Many event loops support I<watcher priorities>, which are usually small
		1274	integers that influence the ordering of event callback invocation
		1275	between watchers in some way, all else being equal.
		1276
		1277	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1278	description for the more technical details such as the actual priority
		1279	range.
		1280
		1281	There are two common ways how these these priorities are being interpreted
		1282	by event loops:
		1283
		1284	In the more common lock-out model, higher priorities "lock out" invocation
		1285	of lower priority watchers, which means as long as higher priority
		1286	watchers receive events, lower priority watchers are not being invoked.
		1287
		1288	The less common only-for-ordering model uses priorities solely to order
		1289	callback invocation within a single event loop iteration: Higher priority
		1290	watchers are invoked before lower priority ones, but they all get invoked
		1291	before polling for new events.
		1292
		1293	Libev uses the second (only-for-ordering) model for all its watchers
		1294	except for idle watchers (which use the lock-out model).
		1295
		1296	The rationale behind this is that implementing the lock-out model for
		1297	watchers is not well supported by most kernel interfaces, and most event
		1298	libraries will just poll for the same events again and again as long as
		1299	their callbacks have not been executed, which is very inefficient in the
		1300	common case of one high-priority watcher locking out a mass of lower
		1301	priority ones.
		1302
		1303	Static (ordering) priorities are most useful when you have two or more
		1304	watchers handling the same resource: a typical usage example is having an
		1305	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1306	timeouts. Under load, data might be received while the program handles
		1307	other jobs, but since timers normally get invoked first, the timeout
		1308	handler will be executed before checking for data. In that case, giving
		1309	the timer a lower priority than the I/O watcher ensures that I/O will be
		1310	handled first even under adverse conditions (which is usually, but not
		1311	always, what you want).
		1312
		1313	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1314	will only be executed when no same or higher priority watchers have
		1315	received events, they can be used to implement the "lock-out" model when
		1316	required.
		1317
		1318	For example, to emulate how many other event libraries handle priorities,
		1319	you can associate an C<ev_idle> watcher to each such watcher, and in
		1320	the normal watcher callback, you just start the idle watcher. The real
		1321	processing is done in the idle watcher callback. This causes libev to
		1322	continously poll and process kernel event data for the watcher, but when
		1323	the lock-out case is known to be rare (which in turn is rare :), this is
		1324	workable.
		1325
		1326	Usually, however, the lock-out model implemented that way will perform
		1327	miserably under the type of load it was designed to handle. In that case,
		1328	it might be preferable to stop the real watcher before starting the
		1329	idle watcher, so the kernel will not have to process the event in case
		1330	the actual processing will be delayed for considerable time.
		1331
		1332	Here is an example of an I/O watcher that should run at a strictly lower
		1333	priority than the default, and which should only process data when no
		1334	other events are pending:
		1335
		1336	ev_idle idle; // actual processing watcher
		1337	ev_io io; // actual event watcher
		1338
		1339	static void
		1340	io_cb (EV_P_ ev_io *w, int revents)
		1341	{
		1342	// stop the I/O watcher, we received the event, but
		1343	// are not yet ready to handle it.
		1344	ev_io_stop (EV_A_ w);
		1345
		1346	// start the idle watcher to ahndle the actual event.
		1347	// it will not be executed as long as other watchers
		1348	// with the default priority are receiving events.
		1349	ev_idle_start (EV_A_ &idle);
		1350	}
		1351
		1352	static void
		1353	idle_cb (EV_P_ ev_idle *w, int revents)
		1354	{
		1355	// actual processing
		1356	read (STDIN_FILENO, ...);
		1357
		1358	// have to start the I/O watcher again, as
		1359	// we have handled the event
		1360	ev_io_start (EV_P_ &io);
		1361	}
		1362
		1363	// initialisation
		1364	ev_idle_init (&idle, idle_cb);
		1365	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1366	ev_io_start (EV_DEFAULT_ &io);
		1367
		1368	In the "real" world, it might also be beneficial to start a timer, so that
		1369	low-priority connections can not be locked out forever under load. This
		1370	enables your program to keep a lower latency for important connections
		1371	during short periods of high load, while not completely locking out less
		1372	important ones.
1076		1373
1077		1374
1078	=head1 WATCHER TYPES	1375	=head1 WATCHER TYPES
1079		1376
1080	This section describes each watcher in detail, but will not repeat	1377	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	1401	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	1402	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	1403	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1404	required if you know what you are doing).
1108		1405
1109	If you must do this, then force the use of a known-to-be-good backend	1406	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	1407	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1408	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1409	descriptors for which non-blocking operation makes no sense (such as
		1410	files) - libev doesn't guarentee any specific behaviour in that case.
1112		1411
1113	Another thing you have to watch out for is that it is quite easy to	1412	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	1413	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	1414	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	1415	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	1416	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	1417	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	1418	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.	1419	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1420
1122	If you cannot run the fd in non-blocking mode (for example you should not	1421	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	1422	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	1423	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	1424	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1425	does this on its own, so its quite safe to use). Some people additionally
		1426	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1427	indefinitely.
		1428
		1429	But really, best use non-blocking mode.
1127		1430
1128	=head3 The special problem of disappearing file descriptors	1431	=head3 The special problem of disappearing file descriptors
1129		1432
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1433	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,	1434	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	1435	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	1436	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	1437	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	1438	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1439	fact, a different file descriptor.
1137		1440
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1471	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1472	C<EVBACKEND_POLL>.
1170		1473
1171	=head3 The special problem of SIGPIPE	1474	=head3 The special problem of SIGPIPE
1172		1475
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1476	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	1477	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	1478	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1479	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1480
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1481	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	1482	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).	1483	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1490	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1491
1189	=item ev_io_set (ev_io *, int fd, int events)	1492	=item ev_io_set (ev_io *, int fd, int events)
1190		1493
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1494	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	1495	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.	1496	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1497
1195	=item int fd [read-only]	1498	=item int fd [read-only]
1196		1499
1197	The file descriptor being watched.	1500	The file descriptor being watched.
1198		1501
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1510	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	1511	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1512	attempt to read a whole line in the callback.
1210		1513
1211	static void	1514	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1515	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1516	{
1214	ev_io_stop (loop, w);	1517	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1518	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1519	}
1217		1520
1218	...	1521	...
1219	struct ev_loop *loop = ev_default_init (0);	1522	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1523	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1524	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1525	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1526	ev_loop (loop, 0);
1224		1527
1225		1528
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1531	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1532	given time, and optionally repeating in regular intervals after that.
1230		1533
1231	The timers are based on real time, that is, if you register an event that	1534	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	1535	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	1536	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1537	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1538	monotonic clock option helps a lot here).
1236		1539
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1540	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	1541	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1542	might introduce a small delay). If multiple timers become ready during the
		1543	same loop iteration then the ones with earlier time-out values are invoked
		1544	before ones of the same priority with later time-out values (but this is
		1545	no longer true when a callback calls C<ev_loop> recursively).
		1546
		1547	=head3 Be smart about timeouts
		1548
		1549	Many real-world problems involve some kind of timeout, usually for error
		1550	recovery. A typical example is an HTTP request - if the other side hangs,
		1551	you want to raise some error after a while.
		1552
		1553	What follows are some ways to handle this problem, from obvious and
		1554	inefficient to smart and efficient.
		1555
		1556	In the following, a 60 second activity timeout is assumed - a timeout that
		1557	gets reset to 60 seconds each time there is activity (e.g. each time some
		1558	data or other life sign was received).
		1559
		1560	=over 4
		1561
		1562	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1563
		1564	This is the most obvious, but not the most simple way: In the beginning,
		1565	start the watcher:
		1566
		1567	ev_timer_init (timer, callback, 60., 0.);
		1568	ev_timer_start (loop, timer);
		1569
		1570	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1571	and start it again:
		1572
		1573	ev_timer_stop (loop, timer);
		1574	ev_timer_set (timer, 60., 0.);
		1575	ev_timer_start (loop, timer);
		1576
		1577	This is relatively simple to implement, but means that each time there is
		1578	some activity, libev will first have to remove the timer from its internal
		1579	data structure and then add it again. Libev tries to be fast, but it's
		1580	still not a constant-time operation.
		1581
		1582	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1583
		1584	This is the easiest way, and involves using C<ev_timer_again> instead of
		1585	C<ev_timer_start>.
		1586
		1587	To implement this, configure an C<ev_timer> with a C<repeat> value
		1588	of C<60> and then call C<ev_timer_again> at start and each time you
		1589	successfully read or write some data. If you go into an idle state where
		1590	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1591	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1592
		1593	That means you can ignore both the C<ev_timer_start> function and the
		1594	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1595	member and C<ev_timer_again>.
		1596
		1597	At start:
		1598
		1599	ev_init (timer, callback);
		1600	timer->repeat = 60.;
		1601	ev_timer_again (loop, timer);
		1602
		1603	Each time there is some activity:
		1604
		1605	ev_timer_again (loop, timer);
		1606
		1607	It is even possible to change the time-out on the fly, regardless of
		1608	whether the watcher is active or not:
		1609
		1610	timer->repeat = 30.;
		1611	ev_timer_again (loop, timer);
		1612
		1613	This is slightly more efficient then stopping/starting the timer each time
		1614	you want to modify its timeout value, as libev does not have to completely
		1615	remove and re-insert the timer from/into its internal data structure.
		1616
		1617	It is, however, even simpler than the "obvious" way to do it.
		1618
		1619	=item 3. Let the timer time out, but then re-arm it as required.
		1620
		1621	This method is more tricky, but usually most efficient: Most timeouts are
		1622	relatively long compared to the intervals between other activity - in
		1623	our example, within 60 seconds, there are usually many I/O events with
		1624	associated activity resets.
		1625
		1626	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1627	but remember the time of last activity, and check for a real timeout only
		1628	within the callback:
		1629
		1630	ev_tstamp last_activity; // time of last activity
		1631
		1632	static void
		1633	callback (EV_P_ ev_timer *w, int revents)
		1634	{
		1635	ev_tstamp now = ev_now (EV_A);
		1636	ev_tstamp timeout = last_activity + 60.;
		1637
		1638	// if last_activity + 60. is older than now, we did time out
		1639	if (timeout < now)
		1640	{
		1641	// timeout occured, take action
		1642	}
		1643	else
		1644	{
		1645	// callback was invoked, but there was some activity, re-arm
		1646	// the watcher to fire in last_activity + 60, which is
		1647	// guaranteed to be in the future, so "again" is positive:
		1648	w->repeat = timeout - now;
		1649	ev_timer_again (EV_A_ w);
		1650	}
		1651	}
		1652
		1653	To summarise the callback: first calculate the real timeout (defined
		1654	as "60 seconds after the last activity"), then check if that time has
		1655	been reached, which means something I<did>, in fact, time out. Otherwise
		1656	the callback was invoked too early (C<timeout> is in the future), so
		1657	re-schedule the timer to fire at that future time, to see if maybe we have
		1658	a timeout then.
		1659
		1660	Note how C<ev_timer_again> is used, taking advantage of the
		1661	C<ev_timer_again> optimisation when the timer is already running.
		1662
		1663	This scheme causes more callback invocations (about one every 60 seconds
		1664	minus half the average time between activity), but virtually no calls to
		1665	libev to change the timeout.
		1666
		1667	To start the timer, simply initialise the watcher and set C<last_activity>
		1668	to the current time (meaning we just have some activity :), then call the
		1669	callback, which will "do the right thing" and start the timer:
		1670
		1671	ev_init (timer, callback);
		1672	last_activity = ev_now (loop);
		1673	callback (loop, timer, EV_TIMEOUT);
		1674
		1675	And when there is some activity, simply store the current time in
		1676	C<last_activity>, no libev calls at all:
		1677
		1678	last_actiivty = ev_now (loop);
		1679
		1680	This technique is slightly more complex, but in most cases where the
		1681	time-out is unlikely to be triggered, much more efficient.
		1682
		1683	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1684	callback :) - just change the timeout and invoke the callback, which will
		1685	fix things for you.
		1686
		1687	=item 4. Wee, just use a double-linked list for your timeouts.
		1688
		1689	If there is not one request, but many thousands (millions...), all
		1690	employing some kind of timeout with the same timeout value, then one can
		1691	do even better:
		1692
		1693	When starting the timeout, calculate the timeout value and put the timeout
		1694	at the I<end> of the list.
		1695
		1696	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1697	the list is expected to fire (for example, using the technique #3).
		1698
		1699	When there is some activity, remove the timer from the list, recalculate
		1700	the timeout, append it to the end of the list again, and make sure to
		1701	update the C<ev_timer> if it was taken from the beginning of the list.
		1702
		1703	This way, one can manage an unlimited number of timeouts in O(1) time for
		1704	starting, stopping and updating the timers, at the expense of a major
		1705	complication, and having to use a constant timeout. The constant timeout
		1706	ensures that the list stays sorted.
		1707
		1708	=back
		1709
		1710	So which method the best?
		1711
		1712	Method #2 is a simple no-brain-required solution that is adequate in most
		1713	situations. Method #3 requires a bit more thinking, but handles many cases
		1714	better, and isn't very complicated either. In most case, choosing either
		1715	one is fine, with #3 being better in typical situations.
		1716
		1717	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1718	rather complicated, but extremely efficient, something that really pays
		1719	off after the first million or so of active timers, i.e. it's usually
		1720	overkill :)
1240		1721
1241	=head3 The special problem of time updates	1722	=head3 The special problem of time updates
1242		1723
1243	Establishing the current time is a costly operation (it usually takes at	1724	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	1725	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	1726	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	1727	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1728	lots of events in one iteration.
1248		1729
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1730	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	1731	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	1732	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	1733	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).	1769	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1770
1290	If the timer is repeating, either start it if necessary (with the	1771	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.	1772	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1773
1293	This sounds a bit complicated, but here is a useful and typical	1774	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	1775	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		1776
1318	=item ev_tstamp repeat [read-write]	1777	=item ev_tstamp repeat [read-write]
1319		1778
1320	The current C<repeat> value. Will be used each time the watcher times out	1779	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),	1780	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.	1781	which is also when any modifications are taken into account.
1323		1782
1324	=back	1783	=back
1325		1784
1326	=head3 Examples	1785	=head3 Examples
1327		1786
1328	Example: Create a timer that fires after 60 seconds.	1787	Example: Create a timer that fires after 60 seconds.
1329		1788
1330	static void	1789	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1790	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1791	{
1333	.. one minute over, w is actually stopped right here	1792	.. one minute over, w is actually stopped right here
1334	}	1793	}
1335		1794
1336	struct ev_timer mytimer;	1795	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1796	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1797	ev_timer_start (loop, &mytimer);
1339		1798
1340	Example: Create a timeout timer that times out after 10 seconds of	1799	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1800	inactivity.
1342		1801
1343	static void	1802	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1804	{
1346	.. ten seconds without any activity	1805	.. ten seconds without any activity
1347	}	1806	}
1348		1807
1349	struct ev_timer mytimer;	1808	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1809	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1810	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1811	ev_loop (loop, 0);
1353		1812
1354	// and in some piece of code that gets executed on any "activity":	1813	// and in some piece of code that gets executed on any "activity":
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	1818	=head2 C<ev_periodic> - to cron or not to cron?
1360		1819
1361	Periodic watchers are also timers of a kind, but they are very versatile	1820	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	1821	(and unfortunately a bit complex).
1363		1822
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1823	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	1824	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	1825	(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 ()	1826	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	1827	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	1828	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		1829
		1830	You can tell a periodic watcher to trigger after some specific point
		1831	in time: for example, if you tell a periodic watcher to trigger "in 10
		1832	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1833	not a delay) and then reset your system clock to January of the previous
		1834	year, then it will take a year or more to trigger the event (unlike an
		1835	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1836	it, as it uses a relative timeout).
		1837
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1838	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	1839	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	1840	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1841	those cannot react to time jumps.
1376		1842
1377	As with timers, the callback is guaranteed to be invoked only when the	1843	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	1844	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.	1845	timers become ready during the same loop iteration then the ones with
		1846	earlier time-out values are invoked before ones with later time-out values
		1847	(but this is no longer true when a callback calls C<ev_loop> recursively).
1380		1848
1381	=head3 Watcher-Specific Functions and Data Members	1849	=head3 Watcher-Specific Functions and Data Members
1382		1850
1383	=over 4	1851	=over 4
1384		1852
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1853	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		1854
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1855	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		1856
1389	Lots of arguments, lets sort it out... There are basically three modes of	1857	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:	1858	operation, and we will explain them from simplest to most complex:
1391		1859
1392	=over 4	1860	=over 4
1393		1861
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1862	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		1863
1396	In this configuration the watcher triggers an event after the wall clock	1864	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	1865	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	1866	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.	1867	will be stopped and invoked when the system clock reaches or surpasses
		1868	this point in time.
1400		1869
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1870	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		1871
1403	In this mode the watcher will always be scheduled to time out at the next	1872	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)	1873	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	1874	negative) and then repeat, regardless of any time jumps. The C<offset>
		1875	argument is merely an offset into the C<interval> periods.
1406		1876
1407	This can be used to create timers that do not drift with respect to system	1877	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	1878	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	1879	hour, on the hour (with respect to UTC):
1410		1880
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1881	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1882
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1883	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	1884	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	1885	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	1886	by 3600.
1417		1887
1418	Another way to think about it (for the mathematically inclined) is that	1888	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	1889	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.	1890	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		1891
1422	For numerical stability it is preferable that the C<at> value is near	1892	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	1893	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	1894	this value, and in fact is often specified as zero.
1425		1895
1426	Note also that there is an upper limit to how often a timer can fire (CPU	1896	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	1897	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	1898	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).	1899	millisecond (if the OS supports it and the machine is fast enough).
1430		1900
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1901	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		1902
1433	In this mode the values for C<interval> and C<at> are both being	1903	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	1904	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	1905	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	1906	current time as second argument.
1437		1907
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1908	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	1909	or make ANY other event loop modifications whatsoever, unless explicitly
		1910	allowed by documentation here>.
1440		1911
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1912	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	1913	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	1914	only event loop modification you are allowed to do).
1444		1915
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1916	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	1917	*w, ev_tstamp now)>, e.g.:
1447		1918
		1919	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1920	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	1921	{
1450	return now + 60.;	1922	return now + 60.;
1451	}	1923	}
1452		1924
1453	It must return the next time to trigger, based on the passed time value	1925	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	1945	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	1946	program when the crontabs have changed).
1475		1947
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	1948	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		1949
1478	When active, returns the absolute time that the watcher is supposed to	1950	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	1951	to trigger next. This is not the same as the C<offset> argument to
		1952	C<ev_periodic_set>, but indeed works even in interval and manual
		1953	rescheduling modes.
1480		1954
1481	=item ev_tstamp offset [read-write]	1955	=item ev_tstamp offset [read-write]
1482		1956
1483	When repeating, this contains the offset value, otherwise this is the	1957	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>).	1958	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1959	although libev might modify this value for better numerical stability).
1485		1960
1486	Can be modified any time, but changes only take effect when the periodic	1961	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	1962	timer fires or C<ev_periodic_again> is being called.
1488		1963
1489	=item ev_tstamp interval [read-write]	1964	=item ev_tstamp interval [read-write]
1490		1965
1491	The current interval value. Can be modified any time, but changes only	1966	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	1967	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	1968	called.
1494		1969
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1970	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		1971
1497	The current reschedule callback, or C<0>, if this functionality is	1972	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	1973	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.	1974	the periodic timer fires or C<ev_periodic_again> is being called.
1500		1975
1501	=back	1976	=back
1502		1977
1503	=head3 Examples	1978	=head3 Examples
1504		1979
1505	Example: Call a callback every hour, or, more precisely, whenever the	1980	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	1981	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	1982	potentially a lot of jitter, but good long-term stability.
1508		1983
1509	static void	1984	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1985	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	1986	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	1987	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	1988	}
1514		1989
1515	struct ev_periodic hourly_tick;	1990	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1991	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	1992	ev_periodic_start (loop, &hourly_tick);
1518		1993
1519	Example: The same as above, but use a reschedule callback to do it:	1994	Example: The same as above, but use a reschedule callback to do it:
1520		1995
1521	#include <math.h>	1996	#include <math.h>
1522		1997
1523	static ev_tstamp	1998	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1999	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2000	{
1526	return fmod (now, 3600.) + 3600.;	2001	return now + (3600. - fmod (now, 3600.));
1527	}	2002	}
1528		2003
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2005
1531	Example: Call a callback every hour, starting now:	2006	Example: Call a callback every hour, starting now:
1532		2007
1533	struct ev_periodic hourly_tick;	2008	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2009	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2010	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2011	ev_periodic_start (loop, &hourly_tick);
1537		2012
1538		2013
…		…
1541	Signal watchers will trigger an event when the process receives a specific	2016	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	2017	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	2018	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2019	normal event processing, like any other event.
1545		2020
		2021	If you want signals asynchronously, just use C<sigaction> as you would
		2022	do without libev and forget about sharing the signal. You can even use
		2023	C<ev_async> from a signal handler to synchronously wake up an event loop.
		2024
1546	You can configure as many watchers as you like per signal. Only when the	2025	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	2026	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	2027	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	2028	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	2029	the last signal watcher for a signal is stopped, libev will reset the
1551	SIG_DFL (regardless of what it was set to before).	2030	signal handler to SIG_DFL (regardless of what it was set to before).
1552		2031
1553	If possible and supported, libev will install its handlers with	2032	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2033	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	2034	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	2035	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1573		2052
1574	=back	2053	=back
1575		2054
1576	=head3 Examples	2055	=head3 Examples
1577		2056
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2057	Example: Try to exit cleanly on SIGINT.
1579		2058
1580	static void	2059	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2060	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2061	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2062	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	2063	}
1585		2064
1586	struct ev_signal signal_watcher;	2065	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2066	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2067	ev_signal_start (loop, &signal_watcher);
1589		2068
1590		2069
1591	=head2 C<ev_child> - watch out for process status changes	2070	=head2 C<ev_child> - watch out for process status changes
1592		2071
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2072	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	2073	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	2074	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	2075	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2076	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2077	forking and then immediately registering a watcher for the child is fine,
		2078	but forking and registering a watcher a few event loop iterations later or
		2079	in the next callback invocation is not.
1598		2080
1599	Only the default event loop is capable of handling signals, and therefore	2081	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2082	you can only register child watchers in the default event loop.
		2083
		2084	Due to some design glitches inside libev, child watchers will always be
		2085	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2086	libev)
1601		2087
1602	=head3 Process Interaction	2088	=head3 Process Interaction
1603		2089
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2090	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2091	initialised. This is necessary to guarantee proper behaviour even if
…		…
1663	its completion.	2149	its completion.
1664		2150
1665	ev_child cw;	2151	ev_child cw;
1666		2152
1667	static void	2153	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2154	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2155	{
1670	ev_child_stop (EV_A_ w);	2156	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2157	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2158	}
1673		2159
…		…
1688		2174
1689		2175
1690	=head2 C<ev_stat> - did the file attributes just change?	2176	=head2 C<ev_stat> - did the file attributes just change?
1691		2177
1692	This watches a file system path for attribute changes. That is, it calls	2178	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	2179	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.	2180	and sees if it changed compared to the last time, invoking the callback if
		2181	it did.
1695		2182
1696	The path does not need to exist: changing from "path exists" to "path does	2183	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	2184	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	2185	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	2186	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2187	least one) and all the other fields of the stat buffer having unspecified
		2188	contents.
1701		2189
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2190	The path I<must not> end in a slash or contain special components such as
		2191	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.	2192	your working directory changes, then the behaviour is undefined.
1704		2193
1705	Since there is no standard to do this, the portable implementation simply	2194	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	2195	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2196	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,	2197	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	2198	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2199	(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	2200	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2201	currently around C<0.1>, but that's usually overkill.
1713		2202
1714	This watcher type is not meant for massive numbers of stat watchers,	2203	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2204	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2205	resource-intensive.
1717		2206
1718	At the time of this writing, only the Linux inotify interface is	2207	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2208	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	2209	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	2210	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		2211
1727	=head3 ABI Issues (Largefile Support)	2212	=head3 ABI Issues (Largefile Support)
1728		2213
1729	Libev by default (unless the user overrides this) uses the default	2214	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2215	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2216	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	2217	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	2218	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	2219	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	2220	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.	2221	most noticeably displayed with ev_stat and large file support.
1737		2222
1738	The solution for this is to lobby your distribution maker to make large	2223	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	2224	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	2225	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2226	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2227	default compilation environment.
1743		2228
1744	=head3 Inotify	2229	=head3 Inotify and Kqueue
1745		2230
1746	When C<inotify (7)> support has been compiled into libev (generally only	2231	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	2232	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	2233	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2234	watcher is being started.
1750		2235
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2236	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	2237	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	2238	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.	2239	there are many cases where libev has to resort to regular C<stat> polling,
		2240	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2241	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2242	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2243	xfs are fully working) libev usually gets away without polling.
1755		2244
1756	(There is no support for kqueue, as apparently it cannot be used to	2245	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	2246	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2247	descriptor open on the object at all times, and detecting renames, unlinks
		2248	etc. is difficult.
		2249
		2250	=head3 C<stat ()> is a synchronous operation
		2251
		2252	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2253	the process. The exception are C<ev_stat> watchers - those call C<stat
		2254	()>, which is a synchronous operation.
		2255
		2256	For local paths, this usually doesn't matter: unless the system is very
		2257	busy or the intervals between stat's are large, a stat call will be fast,
		2258	as the path data is usually in memory already (except when starting the
		2259	watcher).
		2260
		2261	For networked file systems, calling C<stat ()> can block an indefinite
		2262	time due to network issues, and even under good conditions, a stat call
		2263	often takes multiple milliseconds.
		2264
		2265	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2266	paths, although this is fully supported by libev.
1759		2267
1760	=head3 The special problem of stat time resolution	2268	=head3 The special problem of stat time resolution
1761		2269
1762	The C<stat ()> system call only supports full-second resolution portably, and	2270	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2271	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2272	still only support whole seconds.
1765		2273
1766	That means that, if the time is the only thing that changes, you can	2274	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	2275	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	2276	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	2277	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2278	stat data does change in other ways (e.g. file size).
1771		2279
1772	The solution to this is to delay acting on a change for slightly more	2280	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	2281	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);	2282	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2283	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2303	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	2304	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	2305	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.	2306	path for as long as the watcher is active.
1799		2307
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2308	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	2309	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2310	last change was detected).
1803		2311
1804	=item ev_stat_stat (loop, ev_stat *)	2312	=item ev_stat_stat (loop, ev_stat *)
1805		2313
1806	Updates the stat buffer immediately with new values. If you change the	2314	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	2315	watched path in your callback, you could call this function to avoid
…		…
1890		2398
1891		2399
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2400	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2401
1894	Idle watchers trigger events when no other events of the same or higher	2402	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	2403	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2404	as receiving "events").
1897		2405
1898	That is, as long as your process is busy handling sockets or timeouts	2406	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	2407	(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	2408	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	2409	are pending), the idle watchers are being called once per event loop
…		…
1912		2420
1913	=head3 Watcher-Specific Functions and Data Members	2421	=head3 Watcher-Specific Functions and Data Members
1914		2422
1915	=over 4	2423	=over 4
1916		2424
1917	=item ev_idle_init (ev_signal *, callback)	2425	=item ev_idle_init (ev_idle *, callback)
1918		2426
1919	Initialises and configures the idle watcher - it has no parameters of any	2427	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,	2428	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2429	believe me.
1922		2430
…		…
1926		2434
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2435	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2436	callback, free it. Also, use no error checking, as usual.
1929		2437
1930	static void	2438	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2439	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2440	{
1933	free (w);	2441	free (w);
1934	// now do something you wanted to do when the program has	2442	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2443	// no longer anything immediate to do.
1936	}	2444	}
1937		2445
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2446	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2447	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2448	ev_idle_start (loop, idle_watcher);
1941		2449
1942		2450
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2451	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2452
1945	Prepare and check watchers are usually (but not always) used in tandem:	2453	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2454	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2455	afterwards.
1948		2456
1949	You I<must not> call C<ev_loop> or similar functions that enter	2457	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>	2458	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,	2461	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	2462	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2463	called in pairs bracketing the blocking call.
1956		2464
1957	Their main purpose is to integrate other event mechanisms into libev and	2465	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	2466	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	2467	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2468	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,	2469	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>	2470	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2471	watcher).
1964		2472
1965	This is done by examining in each prepare call which file descriptors need	2473	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	2474	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	2475	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	2476	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2477	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	2478	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,	2479	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2480	nevertheless, because you never know, you know?).
1973		2481
1974	As another example, the Perl Coro module uses these hooks to integrate	2482	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2483	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2484	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	2485	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	2488	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2489	low-priority coroutines to idle/background tasks).
1982		2490
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2491	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	2492	priority, to ensure that they are being run before any other watchers
		2493	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2494
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2495	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	2496	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2497	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	2498	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	2499	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	2500	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2501	others).
1992		2502
1993	=head3 Watcher-Specific Functions and Data Members	2503	=head3 Watcher-Specific Functions and Data Members
1994		2504
1995	=over 4	2505	=over 4
1996		2506
…		…
1998		2508
1999	=item ev_check_init (ev_check *, callback)	2509	=item ev_check_init (ev_check *, callback)
2000		2510
2001	Initialises and configures the prepare or check watcher - they have no	2511	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>	2512	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.	2513	macros, but using them is utterly, utterly, utterly and completely
		2514	pointless.
2004		2515
2005	=back	2516	=back
2006		2517
2007	=head3 Examples	2518	=head3 Examples
2008		2519
…		…
2021		2532
2022	static ev_io iow [nfd];	2533	static ev_io iow [nfd];
2023	static ev_timer tw;	2534	static ev_timer tw;
2024		2535
2025	static void	2536	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2537	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2538	{
2028	}	2539	}
2029		2540
2030	// create io watchers for each fd and a timer before blocking	2541	// create io watchers for each fd and a timer before blocking
2031	static void	2542	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2543	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2544	{
2034	int timeout = 3600000;	2545	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2546	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2547	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2548	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2549
2039	/* the callback is illegal, but won't be called as we stop during check */	2550	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2551	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2552	ev_timer_start (loop, &tw);
2042		2553
2043	// create one ev_io per pollfd	2554	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2555	for (int i = 0; i < nfd; ++i)
2045	{	2556	{
…		…
2052	}	2563	}
2053	}	2564	}
2054		2565
2055	// stop all watchers after blocking	2566	// stop all watchers after blocking
2056	static void	2567	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2568	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2569	{
2059	ev_timer_stop (loop, &tw);	2570	ev_timer_stop (loop, &tw);
2060		2571
2061	for (int i = 0; i < nfd; ++i)	2572	for (int i = 0; i < nfd; ++i)
2062	{	2573	{
…		…
2101	}	2612	}
2102		2613
2103	// do not ever call adns_afterpoll	2614	// do not ever call adns_afterpoll
2104		2615
2105	Method 4: Do not use a prepare or check watcher because the module you	2616	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	2617	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	2618	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	2619	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2620	this approach, effectively embedding EV as a client into the horrible
		2621	libglib event loop.
2110		2622
2111	static gint	2623	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2625	{
2114	int got_events = 0;	2626	int got_events = 0;
…		…
2145	prioritise I/O.	2657	prioritise I/O.
2146		2658
2147	As an example for a bug workaround, the kqueue backend might only support	2659	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	2660	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	2661	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	2662	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	2663	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	2664	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.	2665	C<kevent>, but at least you can use both mechanisms for what they are
		2666	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2667
2155	As for prioritising I/O: rarely you have the case where some fds have	2668	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	2669	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	2670	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	2671	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.	2672	the rest in a second one, and embed the second one in the first.
2160		2673
2161	As long as the watcher is active, the callback will be invoked every time	2674	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	2675	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	2676	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	2677	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	2678	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	2679	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2680
2169	As long as the watcher is started it will automatically handle events. The	2681	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	2682	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		2683
2174	Also, there have not currently been made special provisions for forking:	2684	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,	2685	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	2686	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2687	C<ev_loop_fork> on the embedded loop.
2178		2688
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2689	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2690	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2691	portable one.
2182		2692
2183	So when you want to use this feature you will always have to be prepared	2693	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	2694	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	2695	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.	2696	create it, and if that fails, use the normal loop for everything.
		2697
		2698	=head3 C<ev_embed> and fork
		2699
		2700	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2701	automatically be applied to the embedded loop as well, so no special
		2702	fork handling is required in that case. When the watcher is not running,
		2703	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2704	as applicable.
2187		2705
2188	=head3 Watcher-Specific Functions and Data Members	2706	=head3 Watcher-Specific Functions and Data Members
2189		2707
2190	=over 4	2708	=over 4
2191		2709
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2737	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2738	used).
2221		2739
2222	struct ev_loop *loop_hi = ev_default_init (0);	2740	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2741	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2742	ev_embed embed;
2225		2743
2226	// see if there is a chance of getting one that works	2744	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2745	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2746	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2747	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2761	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2762	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2763
2246	struct ev_loop *loop = ev_default_init (0);	2764	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2765	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2766	ev_embed embed;
2249		2767
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2768	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2769	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2770	{
2253	ev_embed_init (&embed, 0, loop_socket);	2771	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	2786	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	2787	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2788	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	2789	handlers will be invoked, too, of course.
2272		2790
		2791	=head3 The special problem of life after fork - how is it possible?
		2792
		2793	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2794	up/change the process environment, followed by a call to C<exec()>. This
		2795	sequence should be handled by libev without any problems.
		2796
		2797	This changes when the application actually wants to do event handling
		2798	in the child, or both parent in child, in effect "continuing" after the
		2799	fork.
		2800
		2801	The default mode of operation (for libev, with application help to detect
		2802	forks) is to duplicate all the state in the child, as would be expected
		2803	when I<either> the parent I<or> the child process continues.
		2804
		2805	When both processes want to continue using libev, then this is usually the
		2806	wrong result. In that case, usually one process (typically the parent) is
		2807	supposed to continue with all watchers in place as before, while the other
		2808	process typically wants to start fresh, i.e. without any active watchers.
		2809
		2810	The cleanest and most efficient way to achieve that with libev is to
		2811	simply create a new event loop, which of course will be "empty", and
		2812	use that for new watchers. This has the advantage of not touching more
		2813	memory than necessary, and thus avoiding the copy-on-write, and the
		2814	disadvantage of having to use multiple event loops (which do not support
		2815	signal watchers).
		2816
		2817	When this is not possible, or you want to use the default loop for
		2818	other reasons, then in the process that wants to start "fresh", call
		2819	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2820	the default loop will "orphan" (not stop) all registered watchers, so you
		2821	have to be careful not to execute code that modifies those watchers. Note
		2822	also that in that case, you have to re-register any signal watchers.
		2823
2273	=head3 Watcher-Specific Functions and Data Members	2824	=head3 Watcher-Specific Functions and Data Members
2274		2825
2275	=over 4	2826	=over 4
2276		2827
2277	=item ev_fork_init (ev_signal *, callback)	2828	=item ev_fork_init (ev_signal *, callback)
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2860	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	2861	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2862	need elaborate support such as pthreads.
2312		2863
2313	That means that if you want to queue data, you have to provide your own	2864	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	2865	queue. But at least I can tell you how to implement locking around your
2315	queue:	2866	queue:
2316		2867
2317	=over 4	2868	=over 4
2318		2869
2319	=item queueing from a signal handler context	2870	=item queueing from a signal handler context
2320		2871
2321	To implement race-free queueing, you simply add to the queue in the signal	2872	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	2873	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2874	an example that does that for some fictitious SIGUSR1 handler:
2324		2875
2325	static ev_async mysig;	2876	static ev_async mysig;
2326		2877
2327	static void	2878	static void
2328	sigusr1_handler (void)	2879	sigusr1_handler (void)
…		…
2394	=over 4	2945	=over 4
2395		2946
2396	=item ev_async_init (ev_async *, callback)	2947	=item ev_async_init (ev_async *, callback)
2397		2948
2398	Initialises and configures the async watcher - it has no parameters of any	2949	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,	2950	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	2951	trust me.
2401		2952
2402	=item ev_async_send (loop, ev_async *)	2953	=item ev_async_send (loop, ev_async *)
2403		2954
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2955	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	2956	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	2957	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	2958	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	2959	section below on what exactly this means).
2409		2960
		2961	Note that, as with other watchers in libev, multiple events might get
		2962	compressed into a single callback invocation (another way to look at this
		2963	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2964	reset when the event loop detects that).
		2965
2410	This call incurs the overhead of a system call only once per loop iteration,	2966	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	2967	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	2968	repeated calls to C<ev_async_send> for the same event loop.
2413		2969
2414	=item bool = ev_async_pending (ev_async *)	2970	=item bool = ev_async_pending (ev_async *)
2415		2971
2416	Returns a non-zero value when C<ev_async_send> has been called on the	2972	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	2973	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	2976	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,	2977	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	2978	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.	2979	quickly check whether invoking the loop might be a good idea.
2424		2980
2425	Not that this does I<not> check whether the watcher itself is pending, only	2981	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	2982	only whether it has been requested to make this watcher pending: there
		2983	is a time window between the event loop checking and resetting the async
		2984	notification, and the callback being invoked.
2427		2985
2428	=back	2986	=back
2429		2987
2430		2988
2431	=head1 OTHER FUNCTIONS	2989	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	2993	=over 4
2436		2994
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2995	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		2996
2439	This function combines a simple timer and an I/O watcher, calls your	2997	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	2998	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	2999	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	3000	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3001	more watchers yourself.
2444		3002
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3003	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	3004	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3005	the given C<fd> and C<events> set will be created and started.
2448		3006
2449	If C<timeout> is less than 0, then no timeout watcher will be	3007	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	3008	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	3009	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3010
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3011	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	3012	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>	3013	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	3014	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3015	a timeout and an io event at the same time - you probably should give io
		3016	events precedence.
		3017
		3018	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3019
2459	static void stdin_ready (int revents, void *arg)	3020	static void stdin_ready (int revents, void *arg)
2460	{	3021	{
		3022	if (revents & EV_READ)
		3023	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3024	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	3025	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3026	}
2466		3027
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3028	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3029
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)	3030	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2470		3031
2471	Feeds the given event set into the event loop, as if the specified event	3032	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	3033	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).	3034	initialised but not necessarily started event watcher).
2474		3035
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3036	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		3037
2477	Feed an event on the given fd, as if a file descriptor backend detected	3038	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3039	the given events it.
2479		3040
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3041	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		3042
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3043	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	3044	loop!).
2484		3045
2485	=back	3046	=back
…		…
2607		3168
2608	myclass obj;	3169	myclass obj;
2609	ev::io iow;	3170	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3171	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3172
		3173	=item w->set (object *)
		3174
		3175	This is an B<experimental> feature that might go away in a future version.
		3176
		3177	This is a variation of a method callback - leaving out the method to call
		3178	will default the method to C<operator ()>, which makes it possible to use
		3179	functor objects without having to manually specify the C<operator ()> all
		3180	the time. Incidentally, you can then also leave out the template argument
		3181	list.
		3182
		3183	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3184	int revents)>.
		3185
		3186	See the method-C<set> above for more details.
		3187
		3188	Example: use a functor object as callback.
		3189
		3190	struct myfunctor
		3191	{
		3192	void operator() (ev::io &w, int revents)
		3193	{
		3194	...
		3195	}
		3196	}
		3197
		3198	myfunctor f;
		3199
		3200	ev::io w;
		3201	w.set (&f);
		3202
2612	=item w->set<function> (void *data = 0)	3203	=item w->set<function> (void *data = 0)
2613		3204
2614	Also sets a callback, but uses a static method or plain function as	3205	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	3206	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3207	C<data> member and is free for you to use.
2617		3208
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3209	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3210
2620	See the method-C<set> above for more details.	3211	See the method-C<set> above for more details.
2621		3212
2622	Example:	3213	Example: Use a plain function as callback.
2623		3214
2624	static void io_cb (ev::io &w, int revents) { }	3215	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3216	iow.set <io_cb> ();
2626		3217
2627	=item w->set (struct ev_loop *)	3218	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	3256	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	3257	the constructor.
2667		3258
2668	class myclass	3259	class myclass
2669	{	3260	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3261	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3262	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3263
2673	myclass (int fd)	3264	myclass (int fd)
2674	{	3265	{
2675	io .set <myclass, &myclass::io_cb > (this);	3266	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3267	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3283	=item Perl
2693		3284
2694	The EV module implements the full libev API and is actually used to test	3285	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,	3286	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3287	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	3288	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>).	3289	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3290	and C<EV::Glib>).
2699		3291
2700	It can be found and installed via CPAN, its homepage is at	3292	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3293	L<http://software.schmorp.de/pkg/EV>.
2702		3294
2703	=item Python	3295	=item Python
2704		3296
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3297	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	3298	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		3299
2712	=item Ruby	3300	=item Ruby
2713		3301
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3302	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	3303	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	3304	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3305	L<http://rev.rubyforge.org/>.
2718		3306
		3307	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3308	makes rev work even on mingw.
		3309
		3310	=item Haskell
		3311
		3312	A haskell binding to libev is available at
		3313	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3314
2719	=item D	3315	=item D
2720		3316
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3317	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>.	3318	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3319
		3320	=item Ocaml
		3321
		3322	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2723		3324
2724	=back	3325	=back
2725		3326
2726		3327
2727	=head1 MACRO MAGIC	3328	=head1 MACRO MAGIC
…		…
2828		3429
2829	#define EV_STANDALONE 1	3430	#define EV_STANDALONE 1
2830	#include "ev.h"	3431	#include "ev.h"
2831		3432
2832	Both header files and implementation files can be compiled with a C++	3433	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	3434	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3435	as a bug).
2835		3436
2836	You need the following files in your source tree, or in a directory	3437	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):	3438	in your include path (e.g. in libev/ when using -Ilibev):
2838		3439
…		…
2882		3483
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3484	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3485
2885	Libev can be configured via a variety of preprocessor symbols you have to	3486	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	3487	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3488	autoconf is documented for every option.
2888		3489
2889	=over 4	3490	=over 4
2890		3491
2891	=item EV_STANDALONE	3492	=item EV_STANDALONE
2892		3493
…		…
2894	keeps libev from including F<config.h>, and it also defines dummy	3495	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3496	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	3497	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.	3498	F<event.h> that are not directly supported by the libev core alone.
2898		3499
		3500	In stanbdalone mode, libev will still try to automatically deduce the
		3501	configuration, but has to be more conservative.
		3502
2899	=item EV_USE_MONOTONIC	3503	=item EV_USE_MONOTONIC
2900		3504
2901	If defined to be C<1>, libev will try to detect the availability of the	3505	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	3506	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	3507	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	3508	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3509	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>	3510	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3511	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3512
2909	=item EV_USE_REALTIME	3513	=item EV_USE_REALTIME
2910		3514
2911	If defined to be C<1>, libev will try to detect the availability of the	3515	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	3516	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	3517	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3518	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3519	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3520	correctness. See the note about libraries in the description of
		3521	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3522	C<EV_USE_CLOCK_SYSCALL>.
		3523
		3524	=item EV_USE_CLOCK_SYSCALL
		3525
		3526	If defined to be C<1>, libev will try to use a direct syscall instead
		3527	of calling the system-provided C<clock_gettime> function. This option
		3528	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3529	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3530	programs needlessly. Using a direct syscall is slightly slower (in
		3531	theory), because no optimised vdso implementation can be used, but avoids
		3532	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3533	higher, as it simplifies linking (no need for C<-lrt>).
2917		3534
2918	=item EV_USE_NANOSLEEP	3535	=item EV_USE_NANOSLEEP
2919		3536
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3537	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 ()>.	3538	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3554
2938	=item EV_SELECT_USE_FD_SET	3555	=item EV_SELECT_USE_FD_SET
2939		3556
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3557	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	3558	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	3559	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	3560	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	3561	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	3562	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3563	configures the maximum size of the C<fd_set>.
2947		3564
2948	=item EV_SELECT_IS_WINSOCKET	3565	=item EV_SELECT_IS_WINSOCKET
2949		3566
2950	When defined to C<1>, the select backend will assume that	3567	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3568	select/socket/connect etc. don't understand file descriptors but
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3679	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	3680	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	3681	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3682	fine.
3066		3683
3067	If your embedding application does not need any priorities, defining these both to	3684	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3685	both to C<0> will save some memory and CPU.
3069		3686
3070	=item EV_PERIODIC_ENABLE	3687	=item EV_PERIODIC_ENABLE
3071		3688
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3689	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	3690	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3697	code.
3081		3698
3082	=item EV_EMBED_ENABLE	3699	=item EV_EMBED_ENABLE
3083		3700
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3701	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3702	defined to be C<0>, then they are not. Embed watchers rely on most other
		3703	watcher types, which therefore must not be disabled.
3086		3704
3087	=item EV_STAT_ENABLE	3705	=item EV_STAT_ENABLE
3088		3706
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3707	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3708	defined to be C<0>, then they are not.
…		…
3100	defined to be C<0>, then they are not.	3718	defined to be C<0>, then they are not.
3101		3719
3102	=item EV_MINIMAL	3720	=item EV_MINIMAL
3103		3721
3104	If you need to shave off some kilobytes of code at the expense of some	3722	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	3723	speed (but with the full API), define this symbol to C<1>. Currently this
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3724	is used to override some inlining decisions, saves roughly 30% code size
3107	much smaller 2-heap for timer management over the default 4-heap.	3725	on amd64. It also selects a much smaller 2-heap for timer management over
		3726	the default 4-heap.
		3727
		3728	You can save even more by disabling watcher types you do not need
		3729	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3730	(C<-DNDEBUG>) will usually reduce code size a lot.
		3731
		3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3733	provide a bare-bones event library. See C<ev.h> for details on what parts
		3734	of the API are still available, and do not complain if this subset changes
		3735	over time.
3108		3736
3109	=item EV_PID_HASHSIZE	3737	=item EV_PID_HASHSIZE
3110		3738
3111	C<ev_child> watchers use a small hash table to distribute workload by	3739	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3122	two).	3750	two).
3123		3751
3124	=item EV_USE_4HEAP	3752	=item EV_USE_4HEAP
3125		3753
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3754	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	3755	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	3756	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3757	faster performance with many (thousands) of watchers.
3130		3758
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3759	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3760	(disabled).
3133		3761
3134	=item EV_HEAP_CACHE_AT	3762	=item EV_HEAP_CACHE_AT
3135		3763
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3764	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	3765	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>),	3766	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,	3767	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	3768	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3769	noticeably with many (hundreds) of watchers.
3142		3770
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3771	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3772	(disabled).
3145		3773
3146	=item EV_VERIFY	3774	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3780	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	3781	verification code will be called very frequently, which will slow down
3154	libev considerably.	3782	libev considerably.
3155		3783
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3784	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3785	C<0>.
3158		3786
3159	=item EV_COMMON	3787	=item EV_COMMON
3160		3788
3161	By default, all watchers have a C<void *data> member. By redefining	3789	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	3790	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	3807	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	3808	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	3809	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	3810	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++.	3811	method calls instead of plain function calls in C++.
		3812
		3813	=back
3184		3814
3185	=head2 EXPORTED API SYMBOLS	3815	=head2 EXPORTED API SYMBOLS
3186		3816
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3817	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	3818	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:	3865	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		3866
3237	#include "ev_cpp.h"	3867	#include "ev_cpp.h"
3238	#include "ev.c"	3868	#include "ev.c"
3239		3869
		3870	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		3871
3241	=head1 THREADS AND COROUTINES	3872	=head2 THREADS AND COROUTINES
3242		3873
3243	=head2 THREADS	3874	=head3 THREADS
3244		3875
3245	Libev itself is thread-safe (unless the opposite is specifically	3876	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	3877	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	3878	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	3879	are no concurrent calls into any libev function with the same loop
		3880	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	3881	of course): libev guarantees that different event loops share no data
3250	need locking.	3882	structures that need any locking.
3251		3883
3252	Or to put it differently: calls with different loop parameters can be done	3884	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	3885	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	3886	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	3887	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	3888	a mutex per loop).
3257		3889
3258	Specifically to support threads (and signal handlers), libev implements	3890	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	3891	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	3892	concurrency on the same event loop, namely waking it up "from the
		3893	outside".
3261		3894
3262	If you want to know which design (one loop, locking, or multiple loops	3895	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	3896	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	3897	help you, but here is some generic advice:
3265		3898
3266	=over 4	3899	=over 4
3267		3900
3268	=item * most applications have a main thread: use the default libev loop	3901	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	3902	in that thread, or create a separate thread running only the default loop.
…		…
3293	default loop and triggering an C<ev_async> watcher from the default loop	3926	default loop and triggering an C<ev_async> watcher from the default loop
3294	watcher callback into the event loop interested in the signal.	3927	watcher callback into the event loop interested in the signal.
3295		3928
3296	=back	3929	=back
3297		3930
		3931	=head4 THREAD LOCKING EXAMPLE
		3932
3298	=head2 COROUTINES	3933	=head3 COROUTINES
3299		3934
3300	Libev is much more accommodating to coroutines ("cooperative threads"):	3935	Libev is very accommodating to coroutines ("cooperative threads"):
3301	libev fully supports nesting calls to it's functions from different	3936	libev fully supports nesting calls to its functions from different
3302	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3303	different coroutines and switch freely between both coroutines running the	3938	different coroutines, and switch freely between both coroutines running the
3304	loop, as long as you don't confuse yourself). The only exception is that	3939	loop, as long as you don't confuse yourself). The only exception is that
3305	you must not do this from C<ev_periodic> reschedule callbacks.	3940	you must not do this from C<ev_periodic> reschedule callbacks.
3306		3941
3307	Care has been taken to ensure that libev does not keep local state inside	3942	Care has been taken to ensure that libev does not keep local state inside
3308	C<ev_loop>, and other calls do not usually allow coroutine switches.	3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3944	they do not call any callbacks.
3309		3945
		3946	=head2 COMPILER WARNINGS
3310		3947
3311	=head1 COMPLEXITIES	3948	Depending on your compiler and compiler settings, you might get no or a
		3949	lot of warnings when compiling libev code. Some people are apparently
		3950	scared by this.
3312		3951
3313	In this section the complexities of (many of) the algorithms used inside	3952	However, these are unavoidable for many reasons. For one, each compiler
3314	libev will be explained. For complexity discussions about backends see the	3953	has different warnings, and each user has different tastes regarding
3315	documentation for C<ev_default_init>.	3954	warning options. "Warn-free" code therefore cannot be a goal except when
		3955	targeting a specific compiler and compiler-version.
3316		3956
3317	All of the following are about amortised time: If an array needs to be	3957	Another reason is that some compiler warnings require elaborate
3318	extended, libev needs to realloc and move the whole array, but this	3958	workarounds, or other changes to the code that make it less clear and less
3319	happens asymptotically never with higher number of elements, so O(1) might	3959	maintainable.
3320	mean it might do a lengthy realloc operation in rare cases, but on average
3321	it is much faster and asymptotically approaches constant time.
3322		3960
3323	=over 4	3961	And of course, some compiler warnings are just plain stupid, or simply
		3962	wrong (because they don't actually warn about the condition their message
		3963	seems to warn about). For example, certain older gcc versions had some
		3964	warnings that resulted an extreme number of false positives. These have
		3965	been fixed, but some people still insist on making code warn-free with
		3966	such buggy versions.
3324		3967
3325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3968	While libev is written to generate as few warnings as possible,
		3969	"warn-free" code is not a goal, and it is recommended not to build libev
		3970	with any compiler warnings enabled unless you are prepared to cope with
		3971	them (e.g. by ignoring them). Remember that warnings are just that:
		3972	warnings, not errors, or proof of bugs.
3326		3973
3327	This means that, when you have a watcher that triggers in one hour and
3328	there are 100 watchers that would trigger before that then inserting will
3329	have to skip roughly seven (C<ld 100>) of these watchers.
3330		3974
3331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3975	=head2 VALGRIND
3332		3976
3333	That means that changing a timer costs less than removing/adding them	3977	Valgrind has a special section here because it is a popular tool that is
3334	as only the relative motion in the event queue has to be paid for.	3978	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3335		3979
3336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3980	If you think you found a bug (memory leak, uninitialised data access etc.)
		3981	in libev, then check twice: If valgrind reports something like:
3337		3982
3338	These just add the watcher into an array or at the head of a list.	3983	==2274== definitely lost: 0 bytes in 0 blocks.
		3984	==2274== possibly lost: 0 bytes in 0 blocks.
		3985	==2274== still reachable: 256 bytes in 1 blocks.
3339		3986
3340	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3987	Then there is no memory leak, just as memory accounted to global variables
		3988	is not a memleak - the memory is still being referenced, and didn't leak.
3341		3989
3342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3990	Similarly, under some circumstances, valgrind might report kernel bugs
		3991	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3992	although an acceptable workaround has been found here), or it might be
		3993	confused.
3343		3994
3344	These watchers are stored in lists then need to be walked to find the	3995	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3345	correct watcher to remove. The lists are usually short (you don't usually	3996	make it into some kind of religion.
3346	have many watchers waiting for the same fd or signal).
3347		3997
3348	=item Finding the next timer in each loop iteration: O(1)	3998	If you are unsure about something, feel free to contact the mailing list
		3999	with the full valgrind report and an explanation on why you think this
		4000	is a bug in libev (best check the archives, too :). However, don't be
		4001	annoyed when you get a brisk "this is no bug" answer and take the chance
		4002	of learning how to interpret valgrind properly.
3349		4003
3350	By virtue of using a binary or 4-heap, the next timer is always found at a	4004	If you need, for some reason, empty reports from valgrind for your project
3351	fixed position in the storage array.	4005	I suggest using suppression lists.
3352		4006
3353	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3354		4007
3355	A change means an I/O watcher gets started or stopped, which requires	4008	=head1 PORTABILITY NOTES
3356	libev to recalculate its status (and possibly tell the kernel, depending
3357	on backend and whether C<ev_io_set> was used).
3358		4009
3359	=item Activating one watcher (putting it into the pending state): O(1)
3360
3361	=item Priority handling: O(number_of_priorities)
3362
3363	Priorities are implemented by allocating some space for each
3364	priority. When doing priority-based operations, libev usually has to
3365	linearly search all the priorities, but starting/stopping and activating
3366	watchers becomes O(1) w.r.t. priority handling.
3367
3368	=item Sending an ev_async: O(1)
3369
3370	=item Processing ev_async_send: O(number_of_async_watchers)
3371
3372	=item Processing signals: O(max_signal_number)
3373
3374	Sending involves a system call I<iff> there were no other C<ev_async_send>
3375	calls in the current loop iteration. Checking for async and signal events
3376	involves iterating over all running async watchers or all signal numbers.
3377
3378	=back
3379
3380
3381	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4010	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3382		4011
3383	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4012	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3384	requires, and its I/O model is fundamentally incompatible with the POSIX	4013	requires, and its I/O model is fundamentally incompatible with the POSIX
3385	model. Libev still offers limited functionality on this platform in	4014	model. Libev still offers limited functionality on this platform in
3386	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4015	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3393	way (note also that glib is the slowest event library known to man).	4022	way (note also that glib is the slowest event library known to man).
3394		4023
3395	There is no supported compilation method available on windows except	4024	There is no supported compilation method available on windows except
3396	embedding it into other applications.	4025	embedding it into other applications.
3397		4026
		4027	Sensible signal handling is officially unsupported by Microsoft - libev
		4028	tries its best, but under most conditions, signals will simply not work.
		4029
3398	Not a libev limitation but worth mentioning: windows apparently doesn't	4030	Not a libev limitation but worth mentioning: windows apparently doesn't
3399	accept large writes: instead of resulting in a partial write, windows will	4031	accept large writes: instead of resulting in a partial write, windows will
3400	either accept everything or return C<ENOBUFS> if the buffer is too large,	4032	either accept everything or return C<ENOBUFS> if the buffer is too large,
3401	so make sure you only write small amounts into your sockets (less than a	4033	so make sure you only write small amounts into your sockets (less than a
3402	megabyte seems safe, but thsi apparently depends on the amount of memory	4034	megabyte seems safe, but this apparently depends on the amount of memory
3403	available).	4035	available).
3404		4036
3405	Due to the many, low, and arbitrary limits on the win32 platform and	4037	Due to the many, low, and arbitrary limits on the win32 platform and
3406	the abysmal performance of winsockets, using a large number of sockets	4038	the abysmal performance of winsockets, using a large number of sockets
3407	is not recommended (and not reasonable). If your program needs to use	4039	is not recommended (and not reasonable). If your program needs to use
3408	more than a hundred or so sockets, then likely it needs to use a totally	4040	more than a hundred or so sockets, then likely it needs to use a totally
3409	different implementation for windows, as libev offers the POSIX readiness	4041	different implementation for windows, as libev offers the POSIX readiness
3410	notification model, which cannot be implemented efficiently on windows	4042	notification model, which cannot be implemented efficiently on windows
3411	(Microsoft monopoly games).	4043	(due to Microsoft monopoly games).
3412		4044
3413	A typical way to use libev under windows is to embed it (see the embedding	4045	A typical way to use libev under windows is to embed it (see the embedding
3414	section for details) and use the following F<evwrap.h> header file instead	4046	section for details) and use the following F<evwrap.h> header file instead
3415	of F<ev.h>:	4047	of F<ev.h>:
3416		4048
…		…
3418	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4050	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3419		4051
3420	#include "ev.h"	4052	#include "ev.h"
3421		4053
3422	And compile the following F<evwrap.c> file into your project (make sure	4054	And compile the following F<evwrap.c> file into your project (make sure
3423	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4055	you do I<not> compile the F<ev.c> or any other embedded source files!):
3424		4056
3425	#include "evwrap.h"	4057	#include "evwrap.h"
3426	#include "ev.c"	4058	#include "ev.c"
3427		4059
3428	=over 4	4060	=over 4
…		…
3452		4084
3453	Early versions of winsocket's select only supported waiting for a maximum	4085	Early versions of winsocket's select only supported waiting for a maximum
3454	of C<64> handles (probably owning to the fact that all windows kernels	4086	of C<64> handles (probably owning to the fact that all windows kernels
3455	can only wait for C<64> things at the same time internally; Microsoft	4087	can only wait for C<64> things at the same time internally; Microsoft
3456	recommends spawning a chain of threads and wait for 63 handles and the	4088	recommends spawning a chain of threads and wait for 63 handles and the
3457	previous thread in each. Great).	4089	previous thread in each. Sounds great!).
3458		4090
3459	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4091	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3460	to some high number (e.g. C<2048>) before compiling the winsocket select	4092	to some high number (e.g. C<2048>) before compiling the winsocket select
3461	call (which might be in libev or elsewhere, for example, perl does its own	4093	call (which might be in libev or elsewhere, for example, perl and many
3462	select emulation on windows).	4094	other interpreters do their own select emulation on windows).
3463		4095
3464	Another limit is the number of file descriptors in the Microsoft runtime	4096	Another limit is the number of file descriptors in the Microsoft runtime
3465	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4097	libraries, which by default is C<64> (there must be a hidden I<64>
3466	or something like this inside Microsoft). You can increase this by calling	4098	fetish or something like this inside Microsoft). You can increase this
3467	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4099	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3468	arbitrary limit), but is broken in many versions of the Microsoft runtime	4100	(another arbitrary limit), but is broken in many versions of the Microsoft
3469	libraries.
3470
3471	This might get you to about C<512> or C<2048> sockets (depending on	4101	runtime libraries. This might get you to about C<512> or C<2048> sockets
3472	windows version and/or the phase of the moon). To get more, you need to	4102	(depending on windows version and/or the phase of the moon). To get more,
3473	wrap all I/O functions and provide your own fd management, but the cost of	4103	you need to wrap all I/O functions and provide your own fd management, but
3474	calling select (O(n²)) will likely make this unworkable.	4104	the cost of calling select (O(n²)) will likely make this unworkable.
3475		4105
3476	=back	4106	=back
3477		4107
3478
3479	=head1 PORTABILITY REQUIREMENTS	4108	=head2 PORTABILITY REQUIREMENTS
3480		4109
3481	In addition to a working ISO-C implementation, libev relies on a few	4110	In addition to a working ISO-C implementation and of course the
3482	additional extensions:	4111	backend-specific APIs, libev relies on a few additional extensions:
3483		4112
3484	=over 4	4113	=over 4
3485		4114
3486	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4115	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3487	calling conventions regardless of C<ev_watcher_type *>.	4116	calling conventions regardless of C<ev_watcher_type *>.
…		…
3493	calls them using an C<ev_watcher *> internally.	4122	calls them using an C<ev_watcher *> internally.
3494		4123
3495	=item C<sig_atomic_t volatile> must be thread-atomic as well	4124	=item C<sig_atomic_t volatile> must be thread-atomic as well
3496		4125
3497	The type C<sig_atomic_t volatile> (or whatever is defined as	4126	The type C<sig_atomic_t volatile> (or whatever is defined as
3498	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4127	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3499	threads. This is not part of the specification for C<sig_atomic_t>, but is	4128	threads. This is not part of the specification for C<sig_atomic_t>, but is
3500	believed to be sufficiently portable.	4129	believed to be sufficiently portable.
3501		4130
3502	=item C<sigprocmask> must work in a threaded environment	4131	=item C<sigprocmask> must work in a threaded environment
3503		4132
…		…
3512	except the initial one, and run the default loop in the initial thread as	4141	except the initial one, and run the default loop in the initial thread as
3513	well.	4142	well.
3514		4143
3515	=item C<long> must be large enough for common memory allocation sizes	4144	=item C<long> must be large enough for common memory allocation sizes
3516		4145
3517	To improve portability and simplify using libev, libev uses C<long>	4146	To improve portability and simplify its API, libev uses C<long> internally
3518	internally instead of C<size_t> when allocating its data structures. On	4147	instead of C<size_t> when allocating its data structures. On non-POSIX
3519	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4148	systems (Microsoft...) this might be unexpectedly low, but is still at
3520	is still at least 31 bits everywhere, which is enough for hundreds of	4149	least 31 bits everywhere, which is enough for hundreds of millions of
3521	millions of watchers.	4150	watchers.
3522		4151
3523	=item C<double> must hold a time value in seconds with enough accuracy	4152	=item C<double> must hold a time value in seconds with enough accuracy
3524		4153
3525	The type C<double> is used to represent timestamps. It is required to	4154	The type C<double> is used to represent timestamps. It is required to
3526	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4155	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3527	enough for at least into the year 4000. This requirement is fulfilled by	4156	enough for at least into the year 4000. This requirement is fulfilled by
3528	implementations implementing IEEE 754 (basically all existing ones).	4157	implementations implementing IEEE 754, which is basically all existing
		4158	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4159	2200.
3529		4160
3530	=back	4161	=back
3531		4162
3532	If you know of other additional requirements drop me a note.	4163	If you know of other additional requirements drop me a note.
3533		4164
3534		4165
3535	=head1 COMPILER WARNINGS	4166	=head1 ALGORITHMIC COMPLEXITIES
3536		4167
3537	Depending on your compiler and compiler settings, you might get no or a	4168	In this section the complexities of (many of) the algorithms used inside
3538	lot of warnings when compiling libev code. Some people are apparently	4169	libev will be documented. For complexity discussions about backends see
3539	scared by this.	4170	the documentation for C<ev_default_init>.
3540		4171
3541	However, these are unavoidable for many reasons. For one, each compiler	4172	All of the following are about amortised time: If an array needs to be
3542	has different warnings, and each user has different tastes regarding	4173	extended, libev needs to realloc and move the whole array, but this
3543	warning options. "Warn-free" code therefore cannot be a goal except when	4174	happens asymptotically rarer with higher number of elements, so O(1) might
3544	targeting a specific compiler and compiler-version.	4175	mean that libev does a lengthy realloc operation in rare cases, but on
		4176	average it is much faster and asymptotically approaches constant time.
3545		4177
3546	Another reason is that some compiler warnings require elaborate	4178	=over 4
3547	workarounds, or other changes to the code that make it less clear and less
3548	maintainable.
3549		4179
3550	And of course, some compiler warnings are just plain stupid, or simply	4180	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3551	wrong (because they don't actually warn about the condition their message
3552	seems to warn about).
3553		4181
3554	While libev is written to generate as few warnings as possible,	4182	This means that, when you have a watcher that triggers in one hour and
3555	"warn-free" code is not a goal, and it is recommended not to build libev	4183	there are 100 watchers that would trigger before that, then inserting will
3556	with any compiler warnings enabled unless you are prepared to cope with	4184	have to skip roughly seven (C<ld 100>) of these watchers.
3557	them (e.g. by ignoring them). Remember that warnings are just that:
3558	warnings, not errors, or proof of bugs.
3559		4185
		4186	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3560		4187
3561	=head1 VALGRIND	4188	That means that changing a timer costs less than removing/adding them,
		4189	as only the relative motion in the event queue has to be paid for.
3562		4190
3563	Valgrind has a special section here because it is a popular tool that is	4191	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3564	highly useful, but valgrind reports are very hard to interpret.
3565		4192
3566	If you think you found a bug (memory leak, uninitialised data access etc.)	4193	These just add the watcher into an array or at the head of a list.
3567	in libev, then check twice: If valgrind reports something like:
3568		4194
3569	==2274== definitely lost: 0 bytes in 0 blocks.	4195	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3570	==2274== possibly lost: 0 bytes in 0 blocks.
3571	==2274== still reachable: 256 bytes in 1 blocks.
3572		4196
3573	Then there is no memory leak. Similarly, under some circumstances,	4197	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3574	valgrind might report kernel bugs as if it were a bug in libev, or it
3575	might be confused (it is a very good tool, but only a tool).
3576		4198
3577	If you are unsure about something, feel free to contact the mailing list	4199	These watchers are stored in lists, so they need to be walked to find the
3578	with the full valgrind report and an explanation on why you think this is	4200	correct watcher to remove. The lists are usually short (you don't usually
3579	a bug in libev. However, don't be annoyed when you get a brisk "this is	4201	have many watchers waiting for the same fd or signal: one is typical, two
3580	no bug" answer and take the chance of learning how to interpret valgrind	4202	is rare).
3581	properly.
3582		4203
3583	If you need, for some reason, empty reports from valgrind for your project	4204	=item Finding the next timer in each loop iteration: O(1)
3584	I suggest using suppression lists.
3585		4205
		4206	By virtue of using a binary or 4-heap, the next timer is always found at a
		4207	fixed position in the storage array.
		4208
		4209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4210
		4211	A change means an I/O watcher gets started or stopped, which requires
		4212	libev to recalculate its status (and possibly tell the kernel, depending
		4213	on backend and whether C<ev_io_set> was used).
		4214
		4215	=item Activating one watcher (putting it into the pending state): O(1)
		4216
		4217	=item Priority handling: O(number_of_priorities)
		4218
		4219	Priorities are implemented by allocating some space for each
		4220	priority. When doing priority-based operations, libev usually has to
		4221	linearly search all the priorities, but starting/stopping and activating
		4222	watchers becomes O(1) with respect to priority handling.
		4223
		4224	=item Sending an ev_async: O(1)
		4225
		4226	=item Processing ev_async_send: O(number_of_async_watchers)
		4227
		4228	=item Processing signals: O(max_signal_number)
		4229
		4230	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4231	calls in the current loop iteration. Checking for async and signal events
		4232	involves iterating over all running async watchers or all signal numbers.
		4233
		4234	=back
		4235
		4236
		4237	=head1 GLOSSARY
		4238
		4239	=over 4
		4240
		4241	=item active
		4242
		4243	A watcher is active as long as it has been started (has been attached to
		4244	an event loop) but not yet stopped (disassociated from the event loop).
		4245
		4246	=item application
		4247
		4248	In this document, an application is whatever is using libev.
		4249
		4250	=item callback
		4251
		4252	The address of a function that is called when some event has been
		4253	detected. Callbacks are being passed the event loop, the watcher that
		4254	received the event, and the actual event bitset.
		4255
		4256	=item callback invocation
		4257
		4258	The act of calling the callback associated with a watcher.
		4259
		4260	=item event
		4261
		4262	A change of state of some external event, such as data now being available
		4263	for reading on a file descriptor, time having passed or simply not having
		4264	any other events happening anymore.
		4265
		4266	In libev, events are represented as single bits (such as C<EV_READ> or
		4267	C<EV_TIMEOUT>).
		4268
		4269	=item event library
		4270
		4271	A software package implementing an event model and loop.
		4272
		4273	=item event loop
		4274
		4275	An entity that handles and processes external events and converts them
		4276	into callback invocations.
		4277
		4278	=item event model
		4279
		4280	The model used to describe how an event loop handles and processes
		4281	watchers and events.
		4282
		4283	=item pending
		4284
		4285	A watcher is pending as soon as the corresponding event has been detected,
		4286	and stops being pending as soon as the watcher will be invoked or its
		4287	pending status is explicitly cleared by the application.
		4288
		4289	A watcher can be pending, but not active. Stopping a watcher also clears
		4290	its pending status.
		4291
		4292	=item real time
		4293
		4294	The physical time that is observed. It is apparently strictly monotonic :)
		4295
		4296	=item wall-clock time
		4297
		4298	The time and date as shown on clocks. Unlike real time, it can actually
		4299	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4300	clock.
		4301
		4302	=item watcher
		4303
		4304	A data structure that describes interest in certain events. Watchers need
		4305	to be started (attached to an event loop) before they can receive events.
		4306
		4307	=item watcher invocation
		4308
		4309	The act of calling the callback associated with a watcher.
		4310
		4311	=back
3586		4312
3587	=head1 AUTHOR	4313	=head1 AUTHOR
3588		4314
3589	Marc Lehmann <libev@schmorp.de>.	4315	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3590		4316

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