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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,	430	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	431	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	432	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	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.
405		440
406	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
407	all kernel versions tested so far.	442	all kernel versions tested so far.
408		443
409	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	C<EVBACKEND_POLL>.	445	C<EVBACKEND_POLL>.
411		446
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		448
414	Kqueue deserves special mention, as at the time of this writing, it was	449	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	450	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	451	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	452	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	453	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	454	without API changes to existing programs. For this reason it's not being
		455	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		456	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		457	system like NetBSD.
420		458
421	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
422	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	the target platform). See C<ev_embed> watchers for more info.	461	the target platform). See C<ev_embed> watchers for more info.
424		462
425	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
426	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
427	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
428	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
429	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
430	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
431		470
432	This backend usually performs well under most conditions.	471	This backend usually performs well under most conditions.
433		472
434	While nominally embeddable in other event loops, this doesn't work	473	While nominally embeddable in other event loops, this doesn't work
435	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
436	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
437	(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
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	477	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	478	also broken on OS X)) and, did I mention it, using it only for sockets.
440		479
441	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
442	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
443	C<NOTE_EOF>.	482	C<NOTE_EOF>.
444		483
…		…
464	might perform better.	503	might perform better.
465		504
466	On the positive side, with the exception of the spurious readiness	505	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	506	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	507	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	508	OS-specific backends (I vastly prefer correctness over speed hacks).
470		509
471	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
472	C<EVBACKEND_POLL>.	511	C<EVBACKEND_POLL>.
473		512
474	=item C<EVBACKEND_ALL>	513	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	566	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	569	for example).
531		570
532	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
533	this function, and related watchers (such as signal and child watchers)	572	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	573	as signal and child watchers) would need to be stopped manually.
535		574
536	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
537	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
538	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
539	C<ev_loop_new> and C<ev_loop_destroy>).	578	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
582		621
583	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
584	"ticks" the number of loop iterations), as it roughly corresponds with	623	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
586		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.
		637
587	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
588		639
589	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
590	use.	641	use.
591		642
…		…
605		656
606	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
607	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
608	the current time is a good idea.	659	the current time is a good idea.
609		660
610	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>).
611		688
612	=item ev_loop (loop, int flags)	689	=item ev_loop (loop, int flags)
613		690
614	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
615	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
…		…
631	the loop.	708	the loop.
632		709
633	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
634	necessary) and will handle those and any already outstanding ones. It	711	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	712	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	713	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	714	user-registered callback will be called), and will return after one
638	iteration of the loop.	715	iteration of the loop.
639		716
640	This is useful if you are waiting for some external event in conjunction	717	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	718	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	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
686	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.
687		764
688	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.
689		766
		767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		768
690	=item ev_ref (loop)	769	=item ev_ref (loop)
691		770
692	=item ev_unref (loop)	771	=item ev_unref (loop)
693		772
694	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
…		…
697		776
698	If you have a watcher you never unregister that should not keep C<ev_loop>	777	If you have a watcher you never unregister that should not keep C<ev_loop>
699	from returning, call ev_unref() after starting, and ev_ref() before	778	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	779	stopping it.
701		780
702	As an example, libev itself uses this for its internal signal pipe: It is	781	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	782	is not visible to the libev user and should not keep C<ev_loop> from
704	if 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
705	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
706	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
707	(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
708	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).
709		790
710	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>
711	running when nothing else is active.	792	running when nothing else is active.
712		793
713	struct ev_signal exitsig;	794	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	795	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	796	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	797	evf_unref (loop);
717		798
718	Example: For some weird reason, unregister the above signal handler again.	799	Example: For some weird reason, unregister the above signal handler again.
…		…
742		823
743	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
744	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,
745	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
746	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
747	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.
748		831
749	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
750	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	834	latency/jitter/inexactness (the watcher callback will be called
752	later). C<ev_io> watchers will not be affected. Setting this to a non-null	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		837
755	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
756	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
757	interactive servers (of course not for games), likewise for timeouts. It	840	interactive servers (of course not for games), likewise for timeouts. It
758	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>,
759	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).
760		847
761	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	849	saving power, as the program will "bundle" timer callback invocations that
763	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
764	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
765	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
766	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
767		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	While event loop modifications are allowed between invocations of
		896	C<release> and C<acquire> (that's their only purpose after all), no
		897	modifications done will affect the event loop, i.e. adding watchers will
		898	have no effect on the set of file descriptors being watched, or the time
		899	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		900	to take note of any changes you made.
		901
		902	In theory, threads executing C<ev_loop> will be async-cancel safe between
		903	invocations of C<release> and C<acquire>.
		904
		905	See also the locking example in the C<THREADS> section later in this
		906	document.
		907
		908	=item ev_set_userdata (loop, void *data)
		909
		910	=item ev_userdata (loop)
		911
		912	Set and retrieve a single C<void *> associated with a loop. When
		913	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		914	C<0.>
		915
		916	These two functions can be used to associate arbitrary data with a loop,
		917	and are intended solely for the C<invoke_pending_cb>, C<release> and
		918	C<acquire> callbacks described above, but of course can be (ab-)used for
		919	any other purpose as well.
		920
768	=item ev_loop_verify (loop)	921	=item ev_loop_verify (loop)
769		922
770	This function only does something when C<EV_VERIFY> support has been	923	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	924	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	925	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	926	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	927	error and call C<abort ()>.
775		928
776	This can be used to catch bugs inside libev itself: under normal	929	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	933	=back
781		934
782		935
783	=head1 ANATOMY OF A WATCHER	936	=head1 ANATOMY OF A WATCHER
784		937
		938	In the following description, uppercase C<TYPE> in names stands for the
		939	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		940	watchers and C<ev_io_start> for I/O watchers.
		941
785	A watcher is a structure that you create and register to record your	942	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	943	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	944	become readable, you would create an C<ev_io> watcher for that:
788		945
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	946	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	947	{
791	ev_io_stop (w);	948	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	949	ev_unloop (loop, EVUNLOOP_ALL);
793	}	950	}
794		951
795	struct ev_loop *loop = ev_default_loop (0);	952	struct ev_loop *loop = ev_default_loop (0);
		953
796	struct ev_io stdin_watcher;	954	ev_io stdin_watcher;
		955
797	ev_init (&stdin_watcher, my_cb);	956	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	957	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	958	ev_io_start (loop, &stdin_watcher);
		959
800	ev_loop (loop, 0);	960	ev_loop (loop, 0);
801		961
802	As you can see, you are responsible for allocating the memory for your	962	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	963	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	964	stack).
		965
		966	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		967	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		968
806	Each watcher structure must be initialised by a call to C<ev_init	969	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	970	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	971	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	972	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	973	is readable and/or writable).
811		974
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	975	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	976	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	977	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	978	ev_TYPE_init (watcher *, callback, ...) >>.
816		979
817	To make the watcher actually watch out for events, you have to start it	980	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	981	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	982	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	983	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		984
822	As long as your watcher is active (has been started but not stopped) you	985	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	986	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	987	reinitialise it or call its C<ev_TYPE_set> macro.
825		988
826	Each and every callback receives the event loop pointer as first, the	989	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	990	registered watcher structure as second, and a bitset of received events as
828	third argument.	991	third argument.
829		992
…		…
887		1050
888	=item C<EV_ASYNC>	1051	=item C<EV_ASYNC>
889		1052
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1053	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1054
		1055	=item C<EV_CUSTOM>
		1056
		1057	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1058	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1059
892	=item C<EV_ERROR>	1060	=item C<EV_ERROR>
893		1061
894	An unspecified error has occurred, the watcher has been stopped. This might	1062	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1063	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1064	ran out of memory, a file descriptor was found to be closed or any other
		1065	problem. Libev considers these application bugs.
		1066
897	problem. You best act on it by reporting the problem and somehow coping	1067	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1068	watcher being stopped. Note that well-written programs should not receive
		1069	an error ever, so when your watcher receives it, this usually indicates a
		1070	bug in your program.
899		1071
900	Libev will usually signal a few "dummy" events together with an error, for	1072	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1073	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1074	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1075	the error from read() or write(). This will not work in multi-threaded
…		…
906		1078
907	=back	1079	=back
908		1080
909	=head2 GENERIC WATCHER FUNCTIONS	1081	=head2 GENERIC WATCHER FUNCTIONS
910		1082
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	1083	=over 4
915		1084
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1085	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1086
918	This macro initialises the generic portion of a watcher. The contents	1087	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1092	which rolls both calls into one.
924		1093
925	You can reinitialise a watcher at any time as long as it has been stopped	1094	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1095	(or never started) and there are no pending events outstanding.
927		1096
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1097	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1098	int revents)>.
930		1099
931	Example: Initialise an C<ev_io> watcher in two steps.	1100	Example: Initialise an C<ev_io> watcher in two steps.
932		1101
933	ev_io w;	1102	ev_io w;
…		…
967		1136
968	ev_io_start (EV_DEFAULT_UC, &w);	1137	ev_io_start (EV_DEFAULT_UC, &w);
969		1138
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1139	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1140
972	Stops the given watcher again (if active) and clears the pending	1141	Stops the given watcher if active, and clears the pending status (whether
		1142	the watcher was active or not).
		1143
973	status. It is possible that stopped watchers are pending (for example,	1144	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1145	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1146	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1147	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1148	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1149
979	=item bool ev_is_active (ev_TYPE *watcher)	1150	=item bool ev_is_active (ev_TYPE *watcher)
980		1151
981	Returns a true value iff the watcher is active (i.e. it has been started	1152	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1153	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1008	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1179	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1180	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1181	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1182	from being executed (except for C<ev_idle> watchers).
1012		1183
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	If you need to suppress invocation when higher priority events are pending	1184	If you need to suppress invocation when higher priority events are pending
1019	you need to look at C<ev_idle> watchers, which provide this functionality.	1185	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1186
1021	You I<must not> change the priority of a watcher as long as it is active or	1187	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1188	pending.
1023		1189
		1190	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1191	fine, as long as you do not mind that the priority value you query might
		1192	or might not have been clamped to the valid range.
		1193
1024	The default priority used by watchers when no priority has been set is	1194	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1195	always C<0>, which is supposed to not be too high and not be too low :).
1026		1196
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1197	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1198	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1199
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1200	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1201
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1202	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1203	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1225	member, you can also "subclass" the watcher type and provide your own
1057	data:	1226	data:
1058		1227
1059	struct my_io	1228	struct my_io
1060	{	1229	{
1061	struct ev_io io;	1230	ev_io io;
1062	int otherfd;	1231	int otherfd;
1063	void *somedata;	1232	void *somedata;
1064	struct whatever *mostinteresting;	1233	struct whatever *mostinteresting;
1065	};	1234	};
1066		1235
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1238	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1239
1071	And since your callback will be called with a pointer to the watcher, you	1240	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1241	can cast it back to your own type:
1073		1242
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1243	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1244	{
1076	struct my_io *w = (struct my_io *)w_;	1245	struct my_io *w = (struct my_io *)w_;
1077	...	1246	...
1078	}	1247	}
1079		1248
…		…
1097	programmers):	1266	programmers):
1098		1267
1099	#include <stddef.h>	1268	#include <stddef.h>
1100		1269
1101	static void	1270	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1271	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1272	{
1104	struct my_biggy big = (struct my_biggy *	1273	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1274	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1275	}
1107		1276
1108	static void	1277	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1278	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1279	{
1111	struct my_biggy big = (struct my_biggy *	1280	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1281	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1282	}
		1283
		1284	=head2 WATCHER PRIORITY MODELS
		1285
		1286	Many event loops support I<watcher priorities>, which are usually small
		1287	integers that influence the ordering of event callback invocation
		1288	between watchers in some way, all else being equal.
		1289
		1290	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1291	description for the more technical details such as the actual priority
		1292	range.
		1293
		1294	There are two common ways how these these priorities are being interpreted
		1295	by event loops:
		1296
		1297	In the more common lock-out model, higher priorities "lock out" invocation
		1298	of lower priority watchers, which means as long as higher priority
		1299	watchers receive events, lower priority watchers are not being invoked.
		1300
		1301	The less common only-for-ordering model uses priorities solely to order
		1302	callback invocation within a single event loop iteration: Higher priority
		1303	watchers are invoked before lower priority ones, but they all get invoked
		1304	before polling for new events.
		1305
		1306	Libev uses the second (only-for-ordering) model for all its watchers
		1307	except for idle watchers (which use the lock-out model).
		1308
		1309	The rationale behind this is that implementing the lock-out model for
		1310	watchers is not well supported by most kernel interfaces, and most event
		1311	libraries will just poll for the same events again and again as long as
		1312	their callbacks have not been executed, which is very inefficient in the
		1313	common case of one high-priority watcher locking out a mass of lower
		1314	priority ones.
		1315
		1316	Static (ordering) priorities are most useful when you have two or more
		1317	watchers handling the same resource: a typical usage example is having an
		1318	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1319	timeouts. Under load, data might be received while the program handles
		1320	other jobs, but since timers normally get invoked first, the timeout
		1321	handler will be executed before checking for data. In that case, giving
		1322	the timer a lower priority than the I/O watcher ensures that I/O will be
		1323	handled first even under adverse conditions (which is usually, but not
		1324	always, what you want).
		1325
		1326	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1327	will only be executed when no same or higher priority watchers have
		1328	received events, they can be used to implement the "lock-out" model when
		1329	required.
		1330
		1331	For example, to emulate how many other event libraries handle priorities,
		1332	you can associate an C<ev_idle> watcher to each such watcher, and in
		1333	the normal watcher callback, you just start the idle watcher. The real
		1334	processing is done in the idle watcher callback. This causes libev to
		1335	continously poll and process kernel event data for the watcher, but when
		1336	the lock-out case is known to be rare (which in turn is rare :), this is
		1337	workable.
		1338
		1339	Usually, however, the lock-out model implemented that way will perform
		1340	miserably under the type of load it was designed to handle. In that case,
		1341	it might be preferable to stop the real watcher before starting the
		1342	idle watcher, so the kernel will not have to process the event in case
		1343	the actual processing will be delayed for considerable time.
		1344
		1345	Here is an example of an I/O watcher that should run at a strictly lower
		1346	priority than the default, and which should only process data when no
		1347	other events are pending:
		1348
		1349	ev_idle idle; // actual processing watcher
		1350	ev_io io; // actual event watcher
		1351
		1352	static void
		1353	io_cb (EV_P_ ev_io *w, int revents)
		1354	{
		1355	// stop the I/O watcher, we received the event, but
		1356	// are not yet ready to handle it.
		1357	ev_io_stop (EV_A_ w);
		1358
		1359	// start the idle watcher to ahndle the actual event.
		1360	// it will not be executed as long as other watchers
		1361	// with the default priority are receiving events.
		1362	ev_idle_start (EV_A_ &idle);
		1363	}
		1364
		1365	static void
		1366	idle_cb (EV_P_ ev_idle *w, int revents)
		1367	{
		1368	// actual processing
		1369	read (STDIN_FILENO, ...);
		1370
		1371	// have to start the I/O watcher again, as
		1372	// we have handled the event
		1373	ev_io_start (EV_P_ &io);
		1374	}
		1375
		1376	// initialisation
		1377	ev_idle_init (&idle, idle_cb);
		1378	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1379	ev_io_start (EV_DEFAULT_ &io);
		1380
		1381	In the "real" world, it might also be beneficial to start a timer, so that
		1382	low-priority connections can not be locked out forever under load. This
		1383	enables your program to keep a lower latency for important connections
		1384	during short periods of high load, while not completely locking out less
		1385	important ones.
1114		1386
1115		1387
1116	=head1 WATCHER TYPES	1388	=head1 WATCHER TYPES
1117		1389
1118	This section describes each watcher in detail, but will not repeat	1390	This section describes each watcher in detail, but will not repeat
…		…
1144	descriptors to non-blocking mode is also usually a good idea (but not	1416	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1417	required if you know what you are doing).
1146		1418
1147	If you cannot use non-blocking mode, then force the use of a	1419	If you cannot use non-blocking mode, then force the use of a
1148	known-to-be-good backend (at the time of this writing, this includes only	1420	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1421	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1422	descriptors for which non-blocking operation makes no sense (such as
		1423	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1424
1151	Another thing you have to watch out for is that it is quite easy to	1425	Another thing you have to watch out for is that it is quite easy to
1152	receive "spurious" readiness notifications, that is your callback might	1426	receive "spurious" readiness notifications, that is your callback might
1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1427	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1154	because there is no data. Not only are some backends known to create a	1428	because there is no data. Not only are some backends known to create a
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1523	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1524	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1525	attempt to read a whole line in the callback.
1252		1526
1253	static void	1527	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1528	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1529	{
1256	ev_io_stop (loop, w);	1530	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1531	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1532	}
1259		1533
1260	...	1534	...
1261	struct ev_loop *loop = ev_default_init (0);	1535	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1536	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1537	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1538	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1539	ev_loop (loop, 0);
1266		1540
1267		1541
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1549	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1550	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1551	monotonic clock option helps a lot here).
1278		1552
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1553	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1554	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1555	might introduce a small delay). If multiple timers become ready during the
		1556	same loop iteration then the ones with earlier time-out values are invoked
		1557	before ones of the same priority with later time-out values (but this is
		1558	no longer true when a callback calls C<ev_loop> recursively).
		1559
		1560	=head3 Be smart about timeouts
		1561
		1562	Many real-world problems involve some kind of timeout, usually for error
		1563	recovery. A typical example is an HTTP request - if the other side hangs,
		1564	you want to raise some error after a while.
		1565
		1566	What follows are some ways to handle this problem, from obvious and
		1567	inefficient to smart and efficient.
		1568
		1569	In the following, a 60 second activity timeout is assumed - a timeout that
		1570	gets reset to 60 seconds each time there is activity (e.g. each time some
		1571	data or other life sign was received).
		1572
		1573	=over 4
		1574
		1575	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1576
		1577	This is the most obvious, but not the most simple way: In the beginning,
		1578	start the watcher:
		1579
		1580	ev_timer_init (timer, callback, 60., 0.);
		1581	ev_timer_start (loop, timer);
		1582
		1583	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1584	and start it again:
		1585
		1586	ev_timer_stop (loop, timer);
		1587	ev_timer_set (timer, 60., 0.);
		1588	ev_timer_start (loop, timer);
		1589
		1590	This is relatively simple to implement, but means that each time there is
		1591	some activity, libev will first have to remove the timer from its internal
		1592	data structure and then add it again. Libev tries to be fast, but it's
		1593	still not a constant-time operation.
		1594
		1595	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1596
		1597	This is the easiest way, and involves using C<ev_timer_again> instead of
		1598	C<ev_timer_start>.
		1599
		1600	To implement this, configure an C<ev_timer> with a C<repeat> value
		1601	of C<60> and then call C<ev_timer_again> at start and each time you
		1602	successfully read or write some data. If you go into an idle state where
		1603	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1604	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1605
		1606	That means you can ignore both the C<ev_timer_start> function and the
		1607	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1608	member and C<ev_timer_again>.
		1609
		1610	At start:
		1611
		1612	ev_init (timer, callback);
		1613	timer->repeat = 60.;
		1614	ev_timer_again (loop, timer);
		1615
		1616	Each time there is some activity:
		1617
		1618	ev_timer_again (loop, timer);
		1619
		1620	It is even possible to change the time-out on the fly, regardless of
		1621	whether the watcher is active or not:
		1622
		1623	timer->repeat = 30.;
		1624	ev_timer_again (loop, timer);
		1625
		1626	This is slightly more efficient then stopping/starting the timer each time
		1627	you want to modify its timeout value, as libev does not have to completely
		1628	remove and re-insert the timer from/into its internal data structure.
		1629
		1630	It is, however, even simpler than the "obvious" way to do it.
		1631
		1632	=item 3. Let the timer time out, but then re-arm it as required.
		1633
		1634	This method is more tricky, but usually most efficient: Most timeouts are
		1635	relatively long compared to the intervals between other activity - in
		1636	our example, within 60 seconds, there are usually many I/O events with
		1637	associated activity resets.
		1638
		1639	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1640	but remember the time of last activity, and check for a real timeout only
		1641	within the callback:
		1642
		1643	ev_tstamp last_activity; // time of last activity
		1644
		1645	static void
		1646	callback (EV_P_ ev_timer *w, int revents)
		1647	{
		1648	ev_tstamp now = ev_now (EV_A);
		1649	ev_tstamp timeout = last_activity + 60.;
		1650
		1651	// if last_activity + 60. is older than now, we did time out
		1652	if (timeout < now)
		1653	{
		1654	// timeout occured, take action
		1655	}
		1656	else
		1657	{
		1658	// callback was invoked, but there was some activity, re-arm
		1659	// the watcher to fire in last_activity + 60, which is
		1660	// guaranteed to be in the future, so "again" is positive:
		1661	w->repeat = timeout - now;
		1662	ev_timer_again (EV_A_ w);
		1663	}
		1664	}
		1665
		1666	To summarise the callback: first calculate the real timeout (defined
		1667	as "60 seconds after the last activity"), then check if that time has
		1668	been reached, which means something I<did>, in fact, time out. Otherwise
		1669	the callback was invoked too early (C<timeout> is in the future), so
		1670	re-schedule the timer to fire at that future time, to see if maybe we have
		1671	a timeout then.
		1672
		1673	Note how C<ev_timer_again> is used, taking advantage of the
		1674	C<ev_timer_again> optimisation when the timer is already running.
		1675
		1676	This scheme causes more callback invocations (about one every 60 seconds
		1677	minus half the average time between activity), but virtually no calls to
		1678	libev to change the timeout.
		1679
		1680	To start the timer, simply initialise the watcher and set C<last_activity>
		1681	to the current time (meaning we just have some activity :), then call the
		1682	callback, which will "do the right thing" and start the timer:
		1683
		1684	ev_init (timer, callback);
		1685	last_activity = ev_now (loop);
		1686	callback (loop, timer, EV_TIMEOUT);
		1687
		1688	And when there is some activity, simply store the current time in
		1689	C<last_activity>, no libev calls at all:
		1690
		1691	last_actiivty = ev_now (loop);
		1692
		1693	This technique is slightly more complex, but in most cases where the
		1694	time-out is unlikely to be triggered, much more efficient.
		1695
		1696	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1697	callback :) - just change the timeout and invoke the callback, which will
		1698	fix things for you.
		1699
		1700	=item 4. Wee, just use a double-linked list for your timeouts.
		1701
		1702	If there is not one request, but many thousands (millions...), all
		1703	employing some kind of timeout with the same timeout value, then one can
		1704	do even better:
		1705
		1706	When starting the timeout, calculate the timeout value and put the timeout
		1707	at the I<end> of the list.
		1708
		1709	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1710	the list is expected to fire (for example, using the technique #3).
		1711
		1712	When there is some activity, remove the timer from the list, recalculate
		1713	the timeout, append it to the end of the list again, and make sure to
		1714	update the C<ev_timer> if it was taken from the beginning of the list.
		1715
		1716	This way, one can manage an unlimited number of timeouts in O(1) time for
		1717	starting, stopping and updating the timers, at the expense of a major
		1718	complication, and having to use a constant timeout. The constant timeout
		1719	ensures that the list stays sorted.
		1720
		1721	=back
		1722
		1723	So which method the best?
		1724
		1725	Method #2 is a simple no-brain-required solution that is adequate in most
		1726	situations. Method #3 requires a bit more thinking, but handles many cases
		1727	better, and isn't very complicated either. In most case, choosing either
		1728	one is fine, with #3 being better in typical situations.
		1729
		1730	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1731	rather complicated, but extremely efficient, something that really pays
		1732	off after the first million or so of active timers, i.e. it's usually
		1733	overkill :)
1282		1734
1283	=head3 The special problem of time updates	1735	=head3 The special problem of time updates
1284		1736
1285	Establishing the current time is a costly operation (it usually takes at	1737	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1738	least two system calls): EV therefore updates its idea of the current
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1782	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1783
1332	If the timer is repeating, either start it if necessary (with the	1784	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1785	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1786
1335	This sounds a bit complicated, but here is a useful and typical	1787	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1788	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1789
1366	=item ev_tstamp repeat [read-write]	1790	=item ev_tstamp repeat [read-write]
1367		1791
1368	The current C<repeat> value. Will be used each time the watcher times out	1792	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1793	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1798	=head3 Examples
1375		1799
1376	Example: Create a timer that fires after 60 seconds.	1800	Example: Create a timer that fires after 60 seconds.
1377		1801
1378	static void	1802	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1803	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1804	{
1381	.. one minute over, w is actually stopped right here	1805	.. one minute over, w is actually stopped right here
1382	}	1806	}
1383		1807
1384	struct ev_timer mytimer;	1808	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1809	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1810	ev_timer_start (loop, &mytimer);
1387		1811
1388	Example: Create a timeout timer that times out after 10 seconds of	1812	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1813	inactivity.
1390		1814
1391	static void	1815	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1816	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1817	{
1394	.. ten seconds without any activity	1818	.. ten seconds without any activity
1395	}	1819	}
1396		1820
1397	struct ev_timer mytimer;	1821	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1822	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1823	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1824	ev_loop (loop, 0);
1401		1825
1402	// and in some piece of code that gets executed on any "activity":	1826	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1831	=head2 C<ev_periodic> - to cron or not to cron?
1408		1832
1409	Periodic watchers are also timers of a kind, but they are very versatile	1833	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1834	(and unfortunately a bit complex).
1411		1835
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1836	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1837	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1838	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1839	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1840	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1841	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1842
		1843	You can tell a periodic watcher to trigger after some specific point
		1844	in time: for example, if you tell a periodic watcher to trigger "in 10
		1845	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1846	not a delay) and then reset your system clock to January of the previous
		1847	year, then it will take a year or more to trigger the event (unlike an
		1848	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1849	it, as it uses a relative timeout).
		1850
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1851	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1852	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1853	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1854	those cannot react to time jumps.
1424		1855
1425	As with timers, the callback is guaranteed to be invoked only when the	1856	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1857	point in time where it is supposed to trigger has passed. If multiple
1427	during the same loop iteration, then order of execution is undefined.	1858	timers become ready during the same loop iteration then the ones with
		1859	earlier time-out values are invoked before ones with later time-out values
		1860	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1861
1429	=head3 Watcher-Specific Functions and Data Members	1862	=head3 Watcher-Specific Functions and Data Members
1430		1863
1431	=over 4	1864	=over 4
1432		1865
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1866	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1867
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1868	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1869
1437	Lots of arguments, lets sort it out... There are basically three modes of	1870	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1871	operation, and we will explain them from simplest to most complex:
1439		1872
1440	=over 4	1873	=over 4
1441		1874
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1875	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1876
1444	In this configuration the watcher triggers an event after the wall clock	1877	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1878	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1879	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	1880	will be stopped and invoked when the system clock reaches or surpasses
		1881	this point in time.
1448		1882
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1883	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1884
1451	In this mode the watcher will always be scheduled to time out at the next	1885	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1886	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1887	negative) and then repeat, regardless of any time jumps. The C<offset>
		1888	argument is merely an offset into the C<interval> periods.
1454		1889
1455	This can be used to create timers that do not drift with respect to the	1890	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	1891	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1892	hour, on the hour (with respect to UTC):
1458		1893
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1894	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1895
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1896	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1897	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1898	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1899	by 3600.
1465		1900
1466	Another way to think about it (for the mathematically inclined) is that	1901	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1902	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1903	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1904
1470	For numerical stability it is preferable that the C<at> value is near	1905	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1906	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1907	this value, and in fact is often specified as zero.
1473		1908
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1909	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1910	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1911	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1912	millisecond (if the OS supports it and the machine is fast enough).
1478		1913
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1914	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1915
1481	In this mode the values for C<interval> and C<at> are both being	1916	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	1917	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1918	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1919	current time as second argument.
1485		1920
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1921	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1922	or make ANY other event loop modifications whatsoever, unless explicitly
		1923	allowed by documentation here>.
1488		1924
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1925	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1926	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1927	only event loop modification you are allowed to do).
1492		1928
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1929	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1930	*w, ev_tstamp now)>, e.g.:
1495		1931
		1932	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1933	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1934	{
1498	return now + 60.;	1935	return now + 60.;
1499	}	1936	}
1500		1937
1501	It must return the next time to trigger, based on the passed time value	1938	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	1958	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1959	program when the crontabs have changed).
1523		1960
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1961	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1962
1526	When active, returns the absolute time that the watcher is supposed to	1963	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1964	to trigger next. This is not the same as the C<offset> argument to
		1965	C<ev_periodic_set>, but indeed works even in interval and manual
		1966	rescheduling modes.
1528		1967
1529	=item ev_tstamp offset [read-write]	1968	=item ev_tstamp offset [read-write]
1530		1969
1531	When repeating, this contains the offset value, otherwise this is the	1970	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1971	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1972	although libev might modify this value for better numerical stability).
1533		1973
1534	Can be modified any time, but changes only take effect when the periodic	1974	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1975	timer fires or C<ev_periodic_again> is being called.
1536		1976
1537	=item ev_tstamp interval [read-write]	1977	=item ev_tstamp interval [read-write]
1538		1978
1539	The current interval value. Can be modified any time, but changes only	1979	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1980	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1981	called.
1542		1982
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1983	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1984
1545	The current reschedule callback, or C<0>, if this functionality is	1985	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1986	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1987	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1988
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1993	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1994	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1995	potentially a lot of jitter, but good long-term stability.
1556		1996
1557	static void	1997	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1998	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1999	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2000	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2001	}
1562		2002
1563	struct ev_periodic hourly_tick;	2003	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2004	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2005	ev_periodic_start (loop, &hourly_tick);
1566		2006
1567	Example: The same as above, but use a reschedule callback to do it:	2007	Example: The same as above, but use a reschedule callback to do it:
1568		2008
1569	#include <math.h>	2009	#include <math.h>
1570		2010
1571	static ev_tstamp	2011	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2012	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2013	{
1574	return now + (3600. - fmod (now, 3600.));	2014	return now + (3600. - fmod (now, 3600.));
1575	}	2015	}
1576		2016
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2017	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2018
1579	Example: Call a callback every hour, starting now:	2019	Example: Call a callback every hour, starting now:
1580		2020
1581	struct ev_periodic hourly_tick;	2021	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2022	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2023	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2024	ev_periodic_start (loop, &hourly_tick);
1585		2025
1586		2026
…		…
1625		2065
1626	=back	2066	=back
1627		2067
1628	=head3 Examples	2068	=head3 Examples
1629		2069
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2070	Example: Try to exit cleanly on SIGINT.
1631		2071
1632	static void	2072	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2073	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2074	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2075	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2076	}
1637		2077
1638	struct ev_signal signal_watcher;	2078	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2079	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2080	ev_signal_start (loop, &signal_watcher);
1641		2081
1642		2082
1643	=head2 C<ev_child> - watch out for process status changes	2083	=head2 C<ev_child> - watch out for process status changes
1644		2084
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2085	Child watchers trigger when your process receives a SIGCHLD in response to
1646	some child status changes (most typically when a child of yours dies or	2086	some child status changes (most typically when a child of yours dies or
1647	exits). It is permissible to install a child watcher I<after> the child	2087	exits). It is permissible to install a child watcher I<after> the child
1648	has been forked (which implies it might have already exited), as long	2088	has been forked (which implies it might have already exited), as long
1649	as the event loop isn't entered (or is continued from a watcher), i.e.,	2089	as the event loop isn't entered (or is continued from a watcher), i.e.,
1650	forking and then immediately registering a watcher for the child is fine,	2090	forking and then immediately registering a watcher for the child is fine,
1651	but forking and registering a watcher a few event loop iterations later is	2091	but forking and registering a watcher a few event loop iterations later or
1652	not.	2092	in the next callback invocation is not.
1653		2093
1654	Only the default event loop is capable of handling signals, and therefore	2094	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2095	you can only register child watchers in the default event loop.
		2096
		2097	Due to some design glitches inside libev, child watchers will always be
		2098	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2099	libev)
1656		2100
1657	=head3 Process Interaction	2101	=head3 Process Interaction
1658		2102
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2103	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2104	initialised. This is necessary to guarantee proper behaviour even if
…		…
1718	its completion.	2162	its completion.
1719		2163
1720	ev_child cw;	2164	ev_child cw;
1721		2165
1722	static void	2166	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2167	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2168	{
1725	ev_child_stop (EV_A_ w);	2169	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2170	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2171	}
1728		2172
…		…
1743		2187
1744		2188
1745	=head2 C<ev_stat> - did the file attributes just change?	2189	=head2 C<ev_stat> - did the file attributes just change?
1746		2190
1747	This watches a file system path for attribute changes. That is, it calls	2191	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2192	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2193	and sees if it changed compared to the last time, invoking the callback if
		2194	it did.
1750		2195
1751	The path does not need to exist: changing from "path exists" to "path does	2196	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	2197	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	2198	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	2199	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2200	least one) and all the other fields of the stat buffer having unspecified
		2201	contents.
1756		2202
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2203	The path I<must not> end in a slash or contain special components such as
		2204	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2205	your working directory changes, then the behaviour is undefined.
1759		2206
1760	Since there is no standard kernel interface to do this, the portable	2207	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2208	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2209	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2210	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2211	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2212	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2213	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2214	currently around C<0.1>, but that's usually overkill.
1768		2215
1769	This watcher type is not meant for massive numbers of stat watchers,	2216	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2217	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2218	resource-intensive.
1772		2219
1773	At the time of this writing, the only OS-specific interface implemented	2220	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2221	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	2222	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2223	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2224
1778	=head3 ABI Issues (Largefile Support)	2225	=head3 ABI Issues (Largefile Support)
1779		2226
1780	Libev by default (unless the user overrides this) uses the default	2227	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2228	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2229	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2230	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2231	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2232	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2233	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2234	most noticeably displayed with ev_stat and large file support.
1788		2235
1789	The solution for this is to lobby your distribution maker to make large	2236	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2237	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2238	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2239	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2240	default compilation environment.
1794		2241
1795	=head3 Inotify and Kqueue	2242	=head3 Inotify and Kqueue
1796		2243
1797	When C<inotify (7)> support has been compiled into libev (generally only	2244	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2245	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2246	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2247	watcher is being started.
1801		2248
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2249	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2250	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2251	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2252	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2253	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2254	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2255	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2256	xfs are fully working) libev usually gets away without polling.
1807		2257
1808	There is no support for kqueue, as apparently it cannot be used to	2258	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2259	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2260	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2261	etc. is difficult.
1812		2262
		2263	=head3 C<stat ()> is a synchronous operation
		2264
		2265	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2266	the process. The exception are C<ev_stat> watchers - those call C<stat
		2267	()>, which is a synchronous operation.
		2268
		2269	For local paths, this usually doesn't matter: unless the system is very
		2270	busy or the intervals between stat's are large, a stat call will be fast,
		2271	as the path data is usually in memory already (except when starting the
		2272	watcher).
		2273
		2274	For networked file systems, calling C<stat ()> can block an indefinite
		2275	time due to network issues, and even under good conditions, a stat call
		2276	often takes multiple milliseconds.
		2277
		2278	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2279	paths, although this is fully supported by libev.
		2280
1813	=head3 The special problem of stat time resolution	2281	=head3 The special problem of stat time resolution
1814		2282
1815	The C<stat ()> system call only supports full-second resolution portably, and	2283	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2284	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2285	still only support whole seconds.
1818		2286
1819	That means that, if the time is the only thing that changes, you can	2287	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2288	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2289	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2290	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2433
1966	=head3 Watcher-Specific Functions and Data Members	2434	=head3 Watcher-Specific Functions and Data Members
1967		2435
1968	=over 4	2436	=over 4
1969		2437
1970	=item ev_idle_init (ev_signal *, callback)	2438	=item ev_idle_init (ev_idle *, callback)
1971		2439
1972	Initialises and configures the idle watcher - it has no parameters of any	2440	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2441	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2442	believe me.
1975		2443
…		…
1979		2447
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2448	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2449	callback, free it. Also, use no error checking, as usual.
1982		2450
1983	static void	2451	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2452	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2453	{
1986	free (w);	2454	free (w);
1987	// now do something you wanted to do when the program has	2455	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2456	// no longer anything immediate to do.
1989	}	2457	}
1990		2458
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2459	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2460	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2461	ev_idle_start (loop, idle_watcher);
1994		2462
1995		2463
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2464	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2465
1998	Prepare and check watchers are usually (but not always) used in pairs:	2466	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2545
2078	static ev_io iow [nfd];	2546	static ev_io iow [nfd];
2079	static ev_timer tw;	2547	static ev_timer tw;
2080		2548
2081	static void	2549	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2550	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2551	{
2084	}	2552	}
2085		2553
2086	// create io watchers for each fd and a timer before blocking	2554	// create io watchers for each fd and a timer before blocking
2087	static void	2555	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2556	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2557	{
2090	int timeout = 3600000;	2558	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2559	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2560	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2561	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2562
2095	/* the callback is illegal, but won't be called as we stop during check */	2563	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2564	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2565	ev_timer_start (loop, &tw);
2098		2566
2099	// create one ev_io per pollfd	2567	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2568	for (int i = 0; i < nfd; ++i)
2101	{	2569	{
…		…
2108	}	2576	}
2109	}	2577	}
2110		2578
2111	// stop all watchers after blocking	2579	// stop all watchers after blocking
2112	static void	2580	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2581	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2582	{
2115	ev_timer_stop (loop, &tw);	2583	ev_timer_stop (loop, &tw);
2116		2584
2117	for (int i = 0; i < nfd; ++i)	2585	for (int i = 0; i < nfd; ++i)
2118	{	2586	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2682	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2683	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2684	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2685	the rest in a second one, and embed the second one in the first.
2218		2686
2219	As long as the watcher is active, the callback will be invoked every time	2687	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2688	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2689	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2690	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2691	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2692	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2693
2227	As long as the watcher is started it will automatically handle events. The	2694	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2695	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2696
2232	Also, there have not currently been made special provisions for forking:	2697	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2698	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2699	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2700	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2701
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2702	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2703	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2704	portable one.
2241		2705
2242	So when you want to use this feature you will always have to be prepared	2706	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2707	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2708	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2709	create it, and if that fails, use the normal loop for everything.
		2710
		2711	=head3 C<ev_embed> and fork
		2712
		2713	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2714	automatically be applied to the embedded loop as well, so no special
		2715	fork handling is required in that case. When the watcher is not running,
		2716	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2717	as applicable.
2246		2718
2247	=head3 Watcher-Specific Functions and Data Members	2719	=head3 Watcher-Specific Functions and Data Members
2248		2720
2249	=over 4	2721	=over 4
2250		2722
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2750	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2751	used).
2280		2752
2281	struct ev_loop *loop_hi = ev_default_init (0);	2753	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2754	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2755	ev_embed embed;
2284		2756
2285	// see if there is a chance of getting one that works	2757	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2758	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2759	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2760	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2774	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2775	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2776
2305	struct ev_loop *loop = ev_default_init (0);	2777	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2778	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2779	ev_embed embed;
2308		2780
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2781	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2782	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2783	{
2312	ev_embed_init (&embed, 0, loop_socket);	2784	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	event loop blocks next and before C<ev_check> watchers are being called,	2799	event loop blocks next and before C<ev_check> watchers are being called,
2328	and only in the child after the fork. If whoever good citizen calling	2800	and only in the child after the fork. If whoever good citizen calling
2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2330	handlers will be invoked, too, of course.	2802	handlers will be invoked, too, of course.
2331		2803
		2804	=head3 The special problem of life after fork - how is it possible?
		2805
		2806	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2807	up/change the process environment, followed by a call to C<exec()>. This
		2808	sequence should be handled by libev without any problems.
		2809
		2810	This changes when the application actually wants to do event handling
		2811	in the child, or both parent in child, in effect "continuing" after the
		2812	fork.
		2813
		2814	The default mode of operation (for libev, with application help to detect
		2815	forks) is to duplicate all the state in the child, as would be expected
		2816	when I<either> the parent I<or> the child process continues.
		2817
		2818	When both processes want to continue using libev, then this is usually the
		2819	wrong result. In that case, usually one process (typically the parent) is
		2820	supposed to continue with all watchers in place as before, while the other
		2821	process typically wants to start fresh, i.e. without any active watchers.
		2822
		2823	The cleanest and most efficient way to achieve that with libev is to
		2824	simply create a new event loop, which of course will be "empty", and
		2825	use that for new watchers. This has the advantage of not touching more
		2826	memory than necessary, and thus avoiding the copy-on-write, and the
		2827	disadvantage of having to use multiple event loops (which do not support
		2828	signal watchers).
		2829
		2830	When this is not possible, or you want to use the default loop for
		2831	other reasons, then in the process that wants to start "fresh", call
		2832	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2833	the default loop will "orphan" (not stop) all registered watchers, so you
		2834	have to be careful not to execute code that modifies those watchers. Note
		2835	also that in that case, you have to re-register any signal watchers.
		2836
2332	=head3 Watcher-Specific Functions and Data Members	2837	=head3 Watcher-Specific Functions and Data Members
2333		2838
2334	=over 4	2839	=over 4
2335		2840
2336	=item ev_fork_init (ev_signal *, callback)	2841	=item ev_fork_init (ev_signal *, callback)
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2873	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2874	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2875	need elaborate support such as pthreads.
2371		2876
2372	That means that if you want to queue data, you have to provide your own	2877	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2878	queue. But at least I can tell you how to implement locking around your
2374	queue:	2879	queue:
2375		2880
2376	=over 4	2881	=over 4
2377		2882
2378	=item queueing from a signal handler context	2883	=item queueing from a signal handler context
2379		2884
2380	To implement race-free queueing, you simply add to the queue in the signal	2885	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2886	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2887	an example that does that for some fictitious SIGUSR1 handler:
2383		2888
2384	static ev_async mysig;	2889	static ev_async mysig;
2385		2890
2386	static void	2891	static void
2387	sigusr1_handler (void)	2892	sigusr1_handler (void)
…		…
2453	=over 4	2958	=over 4
2454		2959
2455	=item ev_async_init (ev_async *, callback)	2960	=item ev_async_init (ev_async *, callback)
2456		2961
2457	Initialises and configures the async watcher - it has no parameters of any	2962	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2963	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	believe me.	2964	trust me.
2460		2965
2461	=item ev_async_send (loop, ev_async *)	2966	=item ev_async_send (loop, ev_async *)
2462		2967
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2968	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2969	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2970	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2971	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2972	section below on what exactly this means).
2468		2973
		2974	Note that, as with other watchers in libev, multiple events might get
		2975	compressed into a single callback invocation (another way to look at this
		2976	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2977	reset when the event loop detects that).
		2978
2469	This call incurs the overhead of a system call only once per loop iteration,	2979	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2980	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	2981	repeated calls to C<ev_async_send> for the same event loop.
2472		2982
2473	=item bool = ev_async_pending (ev_async *)	2983	=item bool = ev_async_pending (ev_async *)
2474		2984
2475	Returns a non-zero value when C<ev_async_send> has been called on the	2985	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	2986	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2989	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	2990	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	2991	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	2992	quickly check whether invoking the loop might be a good idea.
2483		2993
2484	Not that this does I<not> check whether the watcher itself is pending, only	2994	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	2995	only whether it has been requested to make this watcher pending: there
		2996	is a time window between the event loop checking and resetting the async
		2997	notification, and the callback being invoked.
2486		2998
2487	=back	2999	=back
2488		3000
2489		3001
2490	=head1 OTHER FUNCTIONS	3002	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3006	=over 4
2495		3007
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3008	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3009
2498	This function combines a simple timer and an I/O watcher, calls your	3010	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3011	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3012	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3013	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3014	more watchers yourself.
2503		3015
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3016	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3017	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3018	the given C<fd> and C<events> set will be created and started.
2507		3019
2508	If C<timeout> is less than 0, then no timeout watcher will be	3020	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3021	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3022	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3023
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3024	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	3025	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3026	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	3027	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3028	a timeout and an io event at the same time - you probably should give io
		3029	events precedence.
		3030
		3031	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3032
2518	static void stdin_ready (int revents, void *arg)	3033	static void stdin_ready (int revents, void *arg)
2519	{	3034	{
		3035	if (revents & EV_READ)
		3036	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3037	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	3038	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3039	}
2525		3040
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3041	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3042
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)	3043	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2529		3044
2530	Feeds the given event set into the event loop, as if the specified event	3045	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an	3046	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	3047	initialised but not necessarily started event watcher).
2533		3048
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3049	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		3050
2536	Feed an event on the given fd, as if a file descriptor backend detected	3051	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	3052	the given events it.
2538		3053
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3054	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		3055
2541	Feed an event as if the given signal occurred (C<loop> must be the default	3056	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	3057	loop!).
2543		3058
2544	=back	3059	=back
…		…
2666		3181
2667	myclass obj;	3182	myclass obj;
2668	ev::io iow;	3183	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3184	iow.set <myclass, &myclass::io_cb> (&obj);
2670		3185
		3186	=item w->set (object *)
		3187
		3188	This is an B<experimental> feature that might go away in a future version.
		3189
		3190	This is a variation of a method callback - leaving out the method to call
		3191	will default the method to C<operator ()>, which makes it possible to use
		3192	functor objects without having to manually specify the C<operator ()> all
		3193	the time. Incidentally, you can then also leave out the template argument
		3194	list.
		3195
		3196	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3197	int revents)>.
		3198
		3199	See the method-C<set> above for more details.
		3200
		3201	Example: use a functor object as callback.
		3202
		3203	struct myfunctor
		3204	{
		3205	void operator() (ev::io &w, int revents)
		3206	{
		3207	...
		3208	}
		3209	}
		3210
		3211	myfunctor f;
		3212
		3213	ev::io w;
		3214	w.set (&f);
		3215
2671	=item w->set<function> (void *data = 0)	3216	=item w->set<function> (void *data = 0)
2672		3217
2673	Also sets a callback, but uses a static method or plain function as	3218	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	3219	callback. The optional C<data> argument will be stored in the watcher's
2675	C<data> member and is free for you to use.	3220	C<data> member and is free for you to use.
2676		3221
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3222	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		3223
2679	See the method-C<set> above for more details.	3224	See the method-C<set> above for more details.
2680		3225
2681	Example:	3226	Example: Use a plain function as callback.
2682		3227
2683	static void io_cb (ev::io &w, int revents) { }	3228	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3229	iow.set <io_cb> ();
2685		3230
2686	=item w->set (struct ev_loop *)	3231	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	3269	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	3270	the constructor.
2726		3271
2727	class myclass	3272	class myclass
2728	{	3273	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	3274	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	3275	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		3276
2732	myclass (int fd)	3277	myclass (int fd)
2733	{	3278	{
2734	io .set <myclass, &myclass::io_cb > (this);	3279	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	3280	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	3296	=item Perl
2752		3297
2753	The EV module implements the full libev API and is actually used to test	3298	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	3299	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	3300	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3301	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3302	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3303	and C<EV::Glib>).
2758		3304
2759	It can be found and installed via CPAN, its homepage is at	3305	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	3306	L<http://software.schmorp.de/pkg/EV>.
2761		3307
2762	=item Python	3308	=item Python
2763		3309
2764	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3310	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2765	seems to be quite complete and well-documented. Note, however, that the	3311	seems to be quite complete and well-documented.
2766	patch they require for libev is outright dangerous as it breaks the ABI
2767	for everybody else, and therefore, should never be applied in an installed
2768	libev (if python requires an incompatible ABI then it needs to embed
2769	libev).
2770		3312
2771	=item Ruby	3313	=item Ruby
2772		3314
2773	Tony Arcieri has written a ruby extension that offers access to a subset	3315	Tony Arcieri has written a ruby extension that offers access to a subset
2774	of the libev API and adds file handle abstractions, asynchronous DNS and	3316	of the libev API and adds file handle abstractions, asynchronous DNS and
2775	more on top of it. It can be found via gem servers. Its homepage is at	3317	more on top of it. It can be found via gem servers. Its homepage is at
2776	L<http://rev.rubyforge.org/>.	3318	L<http://rev.rubyforge.org/>.
2777		3319
		3320	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3321	makes rev work even on mingw.
		3322
		3323	=item Haskell
		3324
		3325	A haskell binding to libev is available at
		3326	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3327
2778	=item D	3328	=item D
2779		3329
2780	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3330	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3331	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3332
		3333	=item Ocaml
		3334
		3335	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3336	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2782		3337
2783	=back	3338	=back
2784		3339
2785		3340
2786	=head1 MACRO MAGIC	3341	=head1 MACRO MAGIC
…		…
2887		3442
2888	#define EV_STANDALONE 1	3443	#define EV_STANDALONE 1
2889	#include "ev.h"	3444	#include "ev.h"
2890		3445
2891	Both header files and implementation files can be compiled with a C++	3446	Both header files and implementation files can be compiled with a C++
2892	compiler (at least, thats a stated goal, and breakage will be treated	3447	compiler (at least, that's a stated goal, and breakage will be treated
2893	as a bug).	3448	as a bug).
2894		3449
2895	You need the following files in your source tree, or in a directory	3450	You need the following files in your source tree, or in a directory
2896	in your include path (e.g. in libev/ when using -Ilibev):	3451	in your include path (e.g. in libev/ when using -Ilibev):
2897		3452
…		…
2941		3496
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3497	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3498
2944	Libev can be configured via a variety of preprocessor symbols you have to	3499	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3500	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3501	autoconf is documented for every option.
2947		3502
2948	=over 4	3503	=over 4
2949		3504
2950	=item EV_STANDALONE	3505	=item EV_STANDALONE
2951		3506
…		…
2953	keeps libev from including F<config.h>, and it also defines dummy	3508	keeps libev from including F<config.h>, and it also defines dummy
2954	implementations for some libevent functions (such as logging, which is not	3509	implementations for some libevent functions (such as logging, which is not
2955	supported). It will also not define any of the structs usually found in	3510	supported). It will also not define any of the structs usually found in
2956	F<event.h> that are not directly supported by the libev core alone.	3511	F<event.h> that are not directly supported by the libev core alone.
2957		3512
		3513	In stanbdalone mode, libev will still try to automatically deduce the
		3514	configuration, but has to be more conservative.
		3515
2958	=item EV_USE_MONOTONIC	3516	=item EV_USE_MONOTONIC
2959		3517
2960	If defined to be C<1>, libev will try to detect the availability of the	3518	If defined to be C<1>, libev will try to detect the availability of the
2961	monotonic clock option at both compile time and runtime. Otherwise no use	3519	monotonic clock option at both compile time and runtime. Otherwise no
2962	of the monotonic clock option will be attempted. If you enable this, you	3520	use of the monotonic clock option will be attempted. If you enable this,
2963	usually have to link against librt or something similar. Enabling it when	3521	you usually have to link against librt or something similar. Enabling it
2964	the functionality isn't available is safe, though, although you have	3522	when the functionality isn't available is safe, though, although you have
2965	to make sure you link against any libraries where the C<clock_gettime>	3523	to make sure you link against any libraries where the C<clock_gettime>
2966	function is hiding in (often F<-lrt>).	3524	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2967		3525
2968	=item EV_USE_REALTIME	3526	=item EV_USE_REALTIME
2969		3527
2970	If defined to be C<1>, libev will try to detect the availability of the	3528	If defined to be C<1>, libev will try to detect the availability of the
2971	real-time clock option at compile time (and assume its availability at	3529	real-time clock option at compile time (and assume its availability
2972	runtime if successful). Otherwise no use of the real-time clock option will	3530	at runtime if successful). Otherwise no use of the real-time clock
2973	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3531	option will be attempted. This effectively replaces C<gettimeofday>
2974	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3532	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2975	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3533	correctness. See the note about libraries in the description of
		3534	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3535	C<EV_USE_CLOCK_SYSCALL>.
		3536
		3537	=item EV_USE_CLOCK_SYSCALL
		3538
		3539	If defined to be C<1>, libev will try to use a direct syscall instead
		3540	of calling the system-provided C<clock_gettime> function. This option
		3541	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3542	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3543	programs needlessly. Using a direct syscall is slightly slower (in
		3544	theory), because no optimised vdso implementation can be used, but avoids
		3545	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3546	higher, as it simplifies linking (no need for C<-lrt>).
2976		3547
2977	=item EV_USE_NANOSLEEP	3548	=item EV_USE_NANOSLEEP
2978		3549
2979	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3550	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2980	and will use it for delays. Otherwise it will use C<select ()>.	3551	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2996		3567
2997	=item EV_SELECT_USE_FD_SET	3568	=item EV_SELECT_USE_FD_SET
2998		3569
2999	If defined to C<1>, then the select backend will use the system C<fd_set>	3570	If defined to C<1>, then the select backend will use the system C<fd_set>
3000	structure. This is useful if libev doesn't compile due to a missing	3571	structure. This is useful if libev doesn't compile due to a missing
3001	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3572	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3002	exotic systems. This usually limits the range of file descriptors to some	3573	on exotic systems. This usually limits the range of file descriptors to
3003	low limit such as 1024 or might have other limitations (winsocket only	3574	some low limit such as 1024 or might have other limitations (winsocket
3004	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3575	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3005	influence the size of the C<fd_set> used.	3576	configures the maximum size of the C<fd_set>.
3006		3577
3007	=item EV_SELECT_IS_WINSOCKET	3578	=item EV_SELECT_IS_WINSOCKET
3008		3579
3009	When defined to C<1>, the select backend will assume that	3580	When defined to C<1>, the select backend will assume that
3010	select/socket/connect etc. don't understand file descriptors but	3581	select/socket/connect etc. don't understand file descriptors but
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3692	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3693	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3694	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3695	fine.
3125		3696
3126	If your embedding application does not need any priorities, defining these both to	3697	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3698	both to C<0> will save some memory and CPU.
3128		3699
3129	=item EV_PERIODIC_ENABLE	3700	=item EV_PERIODIC_ENABLE
3130		3701
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3702	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3703	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3710	code.
3140		3711
3141	=item EV_EMBED_ENABLE	3712	=item EV_EMBED_ENABLE
3142		3713
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3714	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3715	defined to be C<0>, then they are not. Embed watchers rely on most other
		3716	watcher types, which therefore must not be disabled.
3145		3717
3146	=item EV_STAT_ENABLE	3718	=item EV_STAT_ENABLE
3147		3719
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3720	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3721	defined to be C<0>, then they are not.
…		…
3159	defined to be C<0>, then they are not.	3731	defined to be C<0>, then they are not.
3160		3732
3161	=item EV_MINIMAL	3733	=item EV_MINIMAL
3162		3734
3163	If you need to shave off some kilobytes of code at the expense of some	3735	If you need to shave off some kilobytes of code at the expense of some
3164	speed, define this symbol to C<1>. Currently this is used to override some	3736	speed (but with the full API), define this symbol to C<1>. Currently this
3165	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3737	is used to override some inlining decisions, saves roughly 30% code size
3166	much smaller 2-heap for timer management over the default 4-heap.	3738	on amd64. It also selects a much smaller 2-heap for timer management over
		3739	the default 4-heap.
		3740
		3741	You can save even more by disabling watcher types you do not need
		3742	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3743	(C<-DNDEBUG>) will usually reduce code size a lot.
		3744
		3745	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3746	provide a bare-bones event library. See C<ev.h> for details on what parts
		3747	of the API are still available, and do not complain if this subset changes
		3748	over time.
3167		3749
3168	=item EV_PID_HASHSIZE	3750	=item EV_PID_HASHSIZE
3169		3751
3170	C<ev_child> watchers use a small hash table to distribute workload by	3752	C<ev_child> watchers use a small hash table to distribute workload by
3171	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3753	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3181	two).	3763	two).
3182		3764
3183	=item EV_USE_4HEAP	3765	=item EV_USE_4HEAP
3184		3766
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3767	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3768	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3769	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3770	faster performance with many (thousands) of watchers.
3189		3771
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3772	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3773	(disabled).
3192		3774
3193	=item EV_HEAP_CACHE_AT	3775	=item EV_HEAP_CACHE_AT
3194		3776
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3777	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3778	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3779	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3780	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3781	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3782	noticeably with many (hundreds) of watchers.
3201		3783
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3784	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3785	(disabled).
3204		3786
3205	=item EV_VERIFY	3787	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3793	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3794	verification code will be called very frequently, which will slow down
3213	libev considerably.	3795	libev considerably.
3214		3796
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3797	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3798	C<0>.
3217		3799
3218	=item EV_COMMON	3800	=item EV_COMMON
3219		3801
3220	By default, all watchers have a C<void *data> member. By redefining	3802	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3803	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3820	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3821	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3822	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3823	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3824	method calls instead of plain function calls in C++.
		3825
		3826	=back
3243		3827
3244	=head2 EXPORTED API SYMBOLS	3828	=head2 EXPORTED API SYMBOLS
3245		3829
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3830	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3831	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3878	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3879
3296	#include "ev_cpp.h"	3880	#include "ev_cpp.h"
3297	#include "ev.c"	3881	#include "ev.c"
3298		3882
		3883	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3884
3300	=head1 THREADS AND COROUTINES	3885	=head2 THREADS AND COROUTINES
3301		3886
3302	=head2 THREADS	3887	=head3 THREADS
3303		3888
3304	Libev itself is thread-safe (unless the opposite is specifically	3889	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3890	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3891	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3892	are no concurrent calls into any libev function with the same loop
		3893	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3894	of course): libev guarantees that different event loops share no data
3309	need locking.	3895	structures that need any locking.
3310		3896
3311	Or to put it differently: calls with different loop parameters can be done	3897	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3898	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3899	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3900	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3901	a mutex per loop).
3316		3902
3317	Specifically to support threads (and signal handlers), libev implements	3903	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3904	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3905	concurrency on the same event loop, namely waking it up "from the
		3906	outside".
3320		3907
3321	If you want to know which design (one loop, locking, or multiple loops	3908	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3909	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3910	help you, but here is some generic advice:
3324		3911
3325	=over 4	3912	=over 4
3326		3913
3327	=item * most applications have a main thread: use the default libev loop	3914	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3915	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3939	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3940	watcher callback into the event loop interested in the signal.
3354		3941
3355	=back	3942	=back
3356		3943
		3944	=head4 THREAD LOCKING EXAMPLE
		3945
		3946	Here is a fictitious example of how to run an event loop in a different
		3947	thread than where callbacks are being invoked and watchers are
		3948	created/added/removed.
		3949
		3950	For a real-world example, see the C<EV::Loop::Async> perl module,
		3951	which uses exactly this technique (which is suited for many high-level
		3952	languages).
		3953
		3954	The example uses a pthread mutex to protect the loop data, a condition
		3955	variable to wait for callback invocations, an async watcher to notify the
		3956	event loop thread and an unspecified mechanism to wake up the main thread.
		3957
		3958	First, you need to associate some data with the event loop:
		3959
		3960	typedef struct {
		3961	mutex_t lock; /* global loop lock */
		3962	ev_async async_w;
		3963	thread_t tid;
		3964	cond_t invoke_cv;
		3965	} userdata;
		3966
		3967	void prepare_loop (EV_P)
		3968	{
		3969	// for simplicity, we use a static userdata struct.
		3970	static userdata u;
		3971
		3972	ev_async_init (&u->async_w, async_cb);
		3973	ev_async_start (EV_A_ &u->async_w);
		3974
		3975	pthread_mutex_init (&u->lock, 0);
		3976	pthread_cond_init (&u->invoke_cv, 0);
		3977
		3978	// now associate this with the loop
		3979	ev_set_userdata (EV_A_ u);
		3980	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3981	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3982
		3983	// then create the thread running ev_loop
		3984	pthread_create (&u->tid, 0, l_run, EV_A);
		3985	}
		3986
		3987	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3988	solely to wake up the event loop so it takes notice of any new watchers
		3989	that might have been added:
		3990
		3991	static void
		3992	async_cb (EV_P_ ev_async *w, int revents)
		3993	{
		3994	// just used for the side effects
		3995	}
		3996
		3997	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3998	protecting the loop data, respectively.
		3999
		4000	static void
		4001	l_release (EV_P)
		4002	{
		4003	userdata *u = ev_userdata (EV_A);
		4004	pthread_mutex_unlock (&u->lock);
		4005	}
		4006
		4007	static void
		4008	l_acquire (EV_P)
		4009	{
		4010	userdata *u = ev_userdata (EV_A);
		4011	pthread_mutex_lock (&u->lock);
		4012	}
		4013
		4014	The event loop thread first acquires the mutex, and then jumps straight
		4015	into C<ev_loop>:
		4016
		4017	void *
		4018	l_run (void *thr_arg)
		4019	{
		4020	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4021
		4022	l_acquire (EV_A);
		4023	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4024	ev_loop (EV_A_ 0);
		4025	l_release (EV_A);
		4026
		4027	return 0;
		4028	}
		4029
		4030	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4031	signal the main thread via some unspecified mechanism (signals? pipe
		4032	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4033	have been called:
		4034
		4035	static void
		4036	l_invoke (EV_P)
		4037	{
		4038	userdata *u = ev_userdata (EV_A);
		4039
		4040	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4041
		4042	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4043	}
		4044
		4045	Now, whenever the main thread gets told to invoke pending watchers, it
		4046	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4047	thread to continue:
		4048
		4049	static void
		4050	real_invoke_pending (EV_P)
		4051	{
		4052	userdata *u = ev_userdata (EV_A);
		4053
		4054	pthread_mutex_lock (&u->lock);
		4055	ev_invoke_pending (EV_A);
		4056	pthread_cond_signal (&u->invoke_cv);
		4057	pthread_mutex_unlock (&u->lock);
		4058	}
		4059
		4060	Whenever you want to start/stop a watcher or do other modifications to an
		4061	event loop, you will now have to lock:
		4062
		4063	ev_timer timeout_watcher;
		4064	userdata *u = ev_userdata (EV_A);
		4065
		4066	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4067
		4068	pthread_mutex_lock (&u->lock);
		4069	ev_timer_start (EV_A_ &timeout_watcher);
		4070	ev_async_send (EV_A_ &u->async_w);
		4071	pthread_mutex_unlock (&u->lock);
		4072
		4073	Note that sending the C<ev_async> watcher is required because otherwise
		4074	an event loop currently blocking in the kernel will have no knowledge
		4075	about the newly added timer. By waking up the loop it will pick up any new
		4076	watchers in the next event loop iteration.
		4077
3357	=head2 COROUTINES	4078	=head3 COROUTINES
3358		4079
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	4080	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	4081	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4082	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	4083	different coroutines, and switch freely between both coroutines running
3363	loop, as long as you don't confuse yourself). The only exception is that	4084	the loop, as long as you don't confuse yourself). The only exception is
3364	you must not do this from C<ev_periodic> reschedule callbacks.	4085	that you must not do this from C<ev_periodic> reschedule callbacks.
3365		4086
3366	Care has been taken to ensure that libev does not keep local state inside	4087	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	4088	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4089	they do not call any callbacks.
3368		4090
		4091	=head2 COMPILER WARNINGS
3369		4092
3370	=head1 COMPLEXITIES	4093	Depending on your compiler and compiler settings, you might get no or a
		4094	lot of warnings when compiling libev code. Some people are apparently
		4095	scared by this.
3371		4096
3372	In this section the complexities of (many of) the algorithms used inside	4097	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	4098	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	4099	warning options. "Warn-free" code therefore cannot be a goal except when
		4100	targeting a specific compiler and compiler-version.
3375		4101
3376	All of the following are about amortised time: If an array needs to be	4102	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	4103	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	4104	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		4105
3382	=over 4	4106	And of course, some compiler warnings are just plain stupid, or simply
		4107	wrong (because they don't actually warn about the condition their message
		4108	seems to warn about). For example, certain older gcc versions had some
		4109	warnings that resulted an extreme number of false positives. These have
		4110	been fixed, but some people still insist on making code warn-free with
		4111	such buggy versions.
3383		4112
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4113	While libev is written to generate as few warnings as possible,
		4114	"warn-free" code is not a goal, and it is recommended not to build libev
		4115	with any compiler warnings enabled unless you are prepared to cope with
		4116	them (e.g. by ignoring them). Remember that warnings are just that:
		4117	warnings, not errors, or proof of bugs.
3385		4118
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		4119
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4120	=head2 VALGRIND
3391		4121
3392	That means that changing a timer costs less than removing/adding them	4122	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	4123	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		4124
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4125	If you think you found a bug (memory leak, uninitialised data access etc.)
		4126	in libev, then check twice: If valgrind reports something like:
3396		4127
3397	These just add the watcher into an array or at the head of a list.	4128	==2274== definitely lost: 0 bytes in 0 blocks.
		4129	==2274== possibly lost: 0 bytes in 0 blocks.
		4130	==2274== still reachable: 256 bytes in 1 blocks.
3398		4131
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4132	Then there is no memory leak, just as memory accounted to global variables
		4133	is not a memleak - the memory is still being referenced, and didn't leak.
3400		4134
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4135	Similarly, under some circumstances, valgrind might report kernel bugs
		4136	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4137	although an acceptable workaround has been found here), or it might be
		4138	confused.
3402		4139
3403	These watchers are stored in lists then need to be walked to find the	4140	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	4141	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		4142
3407	=item Finding the next timer in each loop iteration: O(1)	4143	If you are unsure about something, feel free to contact the mailing list
		4144	with the full valgrind report and an explanation on why you think this
		4145	is a bug in libev (best check the archives, too :). However, don't be
		4146	annoyed when you get a brisk "this is no bug" answer and take the chance
		4147	of learning how to interpret valgrind properly.
3408		4148
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	4149	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	4150	I suggest using suppression lists.
3411		4151
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		4152
3414	A change means an I/O watcher gets started or stopped, which requires	4153	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		4154
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4155	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		4156
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4157	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	4158	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	4159	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4160	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3452	way (note also that glib is the slowest event library known to man).	4167	way (note also that glib is the slowest event library known to man).
3453		4168
3454	There is no supported compilation method available on windows except	4169	There is no supported compilation method available on windows except
3455	embedding it into other applications.	4170	embedding it into other applications.
3456		4171
		4172	Sensible signal handling is officially unsupported by Microsoft - libev
		4173	tries its best, but under most conditions, signals will simply not work.
		4174
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	4175	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	4176	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	4177	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	4178	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	4179	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	4180	available).
3463		4181
3464	Due to the many, low, and arbitrary limits on the win32 platform and	4182	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	4183	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	4184	is not recommended (and not reasonable). If your program needs to use
3467	more than a hundred or so sockets, then likely it needs to use a totally	4185	more than a hundred or so sockets, then likely it needs to use a totally
3468	different implementation for windows, as libev offers the POSIX readiness	4186	different implementation for windows, as libev offers the POSIX readiness
3469	notification model, which cannot be implemented efficiently on windows	4187	notification model, which cannot be implemented efficiently on windows
3470	(Microsoft monopoly games).	4188	(due to Microsoft monopoly games).
3471		4189
3472	A typical way to use libev under windows is to embed it (see the embedding	4190	A typical way to use libev under windows is to embed it (see the embedding
3473	section for details) and use the following F<evwrap.h> header file instead	4191	section for details) and use the following F<evwrap.h> header file instead
3474	of F<ev.h>:	4192	of F<ev.h>:
3475		4193
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4195	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		4196
3479	#include "ev.h"	4197	#include "ev.h"
3480		4198
3481	And compile the following F<evwrap.c> file into your project (make sure	4199	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4200	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		4201
3484	#include "evwrap.h"	4202	#include "evwrap.h"
3485	#include "ev.c"	4203	#include "ev.c"
3486		4204
3487	=over 4	4205	=over 4
…		…
3511		4229
3512	Early versions of winsocket's select only supported waiting for a maximum	4230	Early versions of winsocket's select only supported waiting for a maximum
3513	of C<64> handles (probably owning to the fact that all windows kernels	4231	of C<64> handles (probably owning to the fact that all windows kernels
3514	can only wait for C<64> things at the same time internally; Microsoft	4232	can only wait for C<64> things at the same time internally; Microsoft
3515	recommends spawning a chain of threads and wait for 63 handles and the	4233	recommends spawning a chain of threads and wait for 63 handles and the
3516	previous thread in each. Great).	4234	previous thread in each. Sounds great!).
3517		4235
3518	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4236	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3519	to some high number (e.g. C<2048>) before compiling the winsocket select	4237	to some high number (e.g. C<2048>) before compiling the winsocket select
3520	call (which might be in libev or elsewhere, for example, perl does its own	4238	call (which might be in libev or elsewhere, for example, perl and many
3521	select emulation on windows).	4239	other interpreters do their own select emulation on windows).
3522		4240
3523	Another limit is the number of file descriptors in the Microsoft runtime	4241	Another limit is the number of file descriptors in the Microsoft runtime
3524	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4242	libraries, which by default is C<64> (there must be a hidden I<64>
3525	or something like this inside Microsoft). You can increase this by calling	4243	fetish or something like this inside Microsoft). You can increase this
3526	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4244	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3527	arbitrary limit), but is broken in many versions of the Microsoft runtime	4245	(another arbitrary limit), but is broken in many versions of the Microsoft
3528	libraries.
3529
3530	This might get you to about C<512> or C<2048> sockets (depending on	4246	runtime libraries. This might get you to about C<512> or C<2048> sockets
3531	windows version and/or the phase of the moon). To get more, you need to	4247	(depending on windows version and/or the phase of the moon). To get more,
3532	wrap all I/O functions and provide your own fd management, but the cost of	4248	you need to wrap all I/O functions and provide your own fd management, but
3533	calling select (O(n²)) will likely make this unworkable.	4249	the cost of calling select (O(n²)) will likely make this unworkable.
3534		4250
3535	=back	4251	=back
3536		4252
3537
3538	=head1 PORTABILITY REQUIREMENTS	4253	=head2 PORTABILITY REQUIREMENTS
3539		4254
3540	In addition to a working ISO-C implementation, libev relies on a few	4255	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	4256	backend-specific APIs, libev relies on a few additional extensions:
3542		4257
3543	=over 4	4258	=over 4
3544		4259
3545	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4260	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	4261	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	4267	calls them using an C<ev_watcher *> internally.
3553		4268
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	4269	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		4270
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	4271	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4272	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	4273	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	4274	believed to be sufficiently portable.
3560		4275
3561	=item C<sigprocmask> must work in a threaded environment	4276	=item C<sigprocmask> must work in a threaded environment
3562		4277
…		…
3571	except the initial one, and run the default loop in the initial thread as	4286	except the initial one, and run the default loop in the initial thread as
3572	well.	4287	well.
3573		4288
3574	=item C<long> must be large enough for common memory allocation sizes	4289	=item C<long> must be large enough for common memory allocation sizes
3575		4290
3576	To improve portability and simplify using libev, libev uses C<long>	4291	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	4292	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4293	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	4294	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	4295	watchers.
3581		4296
3582	=item C<double> must hold a time value in seconds with enough accuracy	4297	=item C<double> must hold a time value in seconds with enough accuracy
3583		4298
3584	The type C<double> is used to represent timestamps. It is required to	4299	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4300	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3586	enough for at least into the year 4000. This requirement is fulfilled by	4301	enough for at least into the year 4000. This requirement is fulfilled by
3587	implementations implementing IEEE 754 (basically all existing ones).	4302	implementations implementing IEEE 754, which is basically all existing
		4303	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4304	2200.
3588		4305
3589	=back	4306	=back
3590		4307
3591	If you know of other additional requirements drop me a note.	4308	If you know of other additional requirements drop me a note.
3592		4309
3593		4310
3594	=head1 COMPILER WARNINGS	4311	=head1 ALGORITHMIC COMPLEXITIES
3595		4312
3596	Depending on your compiler and compiler settings, you might get no or a	4313	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	4314	libev will be documented. For complexity discussions about backends see
3598	scared by this.	4315	the documentation for C<ev_default_init>.
3599		4316
3600	However, these are unavoidable for many reasons. For one, each compiler	4317	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	4318	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	4319	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	4320	mean that libev does a lengthy realloc operation in rare cases, but on
		4321	average it is much faster and asymptotically approaches constant time.
3604		4322
3605	Another reason is that some compiler warnings require elaborate	4323	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		4324
3609	And of course, some compiler warnings are just plain stupid, or simply	4325	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		4326
3613	While libev is written to generate as few warnings as possible,	4327	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	4328	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	4329	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		4330
		4331	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		4332
3620	=head1 VALGRIND	4333	That means that changing a timer costs less than removing/adding them,
		4334	as only the relative motion in the event queue has to be paid for.
3621		4335
3622	Valgrind has a special section here because it is a popular tool that is	4336	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		4337
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	4338	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		4339
3628	==2274== definitely lost: 0 bytes in 0 blocks.	4340	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		4341
3632	Then there is no memory leak. Similarly, under some circumstances,	4342	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		4343
3636	If you are unsure about something, feel free to contact the mailing list	4344	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	4345	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	4346	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	4347	is rare).
3640	properly.
3641		4348
3642	If you need, for some reason, empty reports from valgrind for your project	4349	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.
3644		4350
		4351	By virtue of using a binary or 4-heap, the next timer is always found at a
		4352	fixed position in the storage array.
		4353
		4354	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4355
		4356	A change means an I/O watcher gets started or stopped, which requires
		4357	libev to recalculate its status (and possibly tell the kernel, depending
		4358	on backend and whether C<ev_io_set> was used).
		4359
		4360	=item Activating one watcher (putting it into the pending state): O(1)
		4361
		4362	=item Priority handling: O(number_of_priorities)
		4363
		4364	Priorities are implemented by allocating some space for each
		4365	priority. When doing priority-based operations, libev usually has to
		4366	linearly search all the priorities, but starting/stopping and activating
		4367	watchers becomes O(1) with respect to priority handling.
		4368
		4369	=item Sending an ev_async: O(1)
		4370
		4371	=item Processing ev_async_send: O(number_of_async_watchers)
		4372
		4373	=item Processing signals: O(max_signal_number)
		4374
		4375	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4376	calls in the current loop iteration. Checking for async and signal events
		4377	involves iterating over all running async watchers or all signal numbers.
		4378
		4379	=back
		4380
		4381
		4382	=head1 GLOSSARY
		4383
		4384	=over 4
		4385
		4386	=item active
		4387
		4388	A watcher is active as long as it has been started (has been attached to
		4389	an event loop) but not yet stopped (disassociated from the event loop).
		4390
		4391	=item application
		4392
		4393	In this document, an application is whatever is using libev.
		4394
		4395	=item callback
		4396
		4397	The address of a function that is called when some event has been
		4398	detected. Callbacks are being passed the event loop, the watcher that
		4399	received the event, and the actual event bitset.
		4400
		4401	=item callback invocation
		4402
		4403	The act of calling the callback associated with a watcher.
		4404
		4405	=item event
		4406
		4407	A change of state of some external event, such as data now being available
		4408	for reading on a file descriptor, time having passed or simply not having
		4409	any other events happening anymore.
		4410
		4411	In libev, events are represented as single bits (such as C<EV_READ> or
		4412	C<EV_TIMEOUT>).
		4413
		4414	=item event library
		4415
		4416	A software package implementing an event model and loop.
		4417
		4418	=item event loop
		4419
		4420	An entity that handles and processes external events and converts them
		4421	into callback invocations.
		4422
		4423	=item event model
		4424
		4425	The model used to describe how an event loop handles and processes
		4426	watchers and events.
		4427
		4428	=item pending
		4429
		4430	A watcher is pending as soon as the corresponding event has been detected,
		4431	and stops being pending as soon as the watcher will be invoked or its
		4432	pending status is explicitly cleared by the application.
		4433
		4434	A watcher can be pending, but not active. Stopping a watcher also clears
		4435	its pending status.
		4436
		4437	=item real time
		4438
		4439	The physical time that is observed. It is apparently strictly monotonic :)
		4440
		4441	=item wall-clock time
		4442
		4443	The time and date as shown on clocks. Unlike real time, it can actually
		4444	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4445	clock.
		4446
		4447	=item watcher
		4448
		4449	A data structure that describes interest in certain events. Watchers need
		4450	to be started (attached to an event loop) before they can receive events.
		4451
		4452	=item watcher invocation
		4453
		4454	The act of calling the callback associated with a watcher.
		4455
		4456	=back
3645		4457
3646	=head1 AUTHOR	4458	=head1 AUTHOR
3647		4459
3648	Marc Lehmann <libev@schmorp.de>.	4460	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3649		4461

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