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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
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	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	122	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	123	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	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	131	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	132	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	133	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	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	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	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	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,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	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	321	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	322	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	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGNALFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		415
382	For few fds, this backend is a bit little slower than poll and select,	416	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	417	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),	418	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	419	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	420
387	cases and requiring a system call per fd change, no fork support and bad	421	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	422	of the more advanced event mechanisms: mere annoyances include silently
		423	dropping file descriptors, requiring a system call per change per file
		424	descriptor (and unnecessary guessing of parameters), problems with dup and
		425	so on. The biggest issue is fork races, however - if a program forks then
		426	I<both> parent and child process have to recreate the epoll set, which can
		427	take considerable time (one syscall per file descriptor) and is of course
		428	hard to detect.
		429
		430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		431	of course I<doesn't>, and epoll just loves to report events for totally
		432	I<different> file descriptors (even already closed ones, so one cannot
		433	even remove them from the set) than registered in the set (especially
		434	on SMP systems). Libev tries to counter these spurious notifications by
		435	employing an additional generation counter and comparing that against the
		436	events to filter out spurious ones, recreating the set when required.
389		437
390	While stopping, setting and starting an I/O watcher in the same iteration	438	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	439	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	440	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	441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	442	file descriptors might not work very well if you register events for both
395		443	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		444
400	Best performance from this backend is achieved by not unregistering all	445	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	446	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	447	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	448	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	449	extra overhead. A fork can both result in spurious notifications as well
		450	as in libev having to destroy and recreate the epoll object, which can
		451	take considerable time and thus should be avoided.
		452
		453	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		454	faster than epoll for maybe up to a hundred file descriptors, depending on
		455	the usage. So sad.
405		456
406	While nominally embeddable in other event loops, this feature is broken in	457	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	458	all kernel versions tested so far.
408		459
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	461	C<EVBACKEND_POLL>.
411		462
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		464
414	Kqueue deserves special mention, as at the time of this writing, it was	465	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	466	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	467	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	468	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	469	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.	470	without API changes to existing programs. For this reason it's not being
		471	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		472	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		473	system like NetBSD.
420		474
421	You still can embed kqueue into a normal poll or select backend and use it	475	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	476	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.	477	the target platform). See C<ev_embed> watchers for more info.
424		478
425	It scales in the same way as the epoll backend, but the interface to the	479	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	480	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	481	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	482	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	483	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		485	cases
431		486
432	This backend usually performs well under most conditions.	487	This backend usually performs well under most conditions.
433		488
434	While nominally embeddable in other event loops, this doesn't work	489	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	490	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	491	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	492	(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,	493	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	494	also broken on OS X)) and, did I mention it, using it only for sockets.
440		495
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	496	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	497	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	498	C<NOTE_EOF>.
444		499
…		…
464	might perform better.	519	might perform better.
465		520
466	On the positive side, with the exception of the spurious readiness	521	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	522	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	523	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	524	OS-specific backends (I vastly prefer correctness over speed hacks).
470		525
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	527	C<EVBACKEND_POLL>.
473		528
474	=item C<EVBACKEND_ALL>	529	=item C<EVBACKEND_ALL>
…		…
479		534
480	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
481		536
482	=back	537	=back
483		538
484	If one or more of these are or'ed into the flags value, then only these	539	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	540	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
487		543
488	Example: This is the most typical usage.	544	Example: This is the most typical usage.
489		545
490	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	583	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	584	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	585	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	586	for example).
531		587
532	Note that certain global state, such as signal state, will not be freed by	588	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	589	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
535		591
536	In general it is not advisable to call this function except in the	592	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	593	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	594	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
582		638
583	This value can sometimes be useful as a generation counter of sorts (it	639	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	640	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
586		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
		654
587	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
588		656
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	658	use.
591		659
…		…
605		673
606	This function is rarely useful, but when some event callback runs for a	674	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	675	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	676	the current time is a good idea.
609		677
610	See also "The special problem of time updates" in the C<ev_timer> section.	678	See also L<The special problem of time updates> in the C<ev_timer> section.
		679
		680	=item ev_suspend (loop)
		681
		682	=item ev_resume (loop)
		683
		684	These two functions suspend and resume a loop, for use when the loop is
		685	not used for a while and timeouts should not be processed.
		686
		687	A typical use case would be an interactive program such as a game: When
		688	the user presses C<^Z> to suspend the game and resumes it an hour later it
		689	would be best to handle timeouts as if no time had actually passed while
		690	the program was suspended. This can be achieved by calling C<ev_suspend>
		691	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		692	C<ev_resume> directly afterwards to resume timer processing.
		693
		694	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		696	will be rescheduled (that is, they will lose any events that would have
		697	occured while suspended).
		698
		699	After calling C<ev_suspend> you B<must not> call I<any> function on the
		700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		701	without a previous call to C<ev_suspend>.
		702
		703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		704	event loop time (see C<ev_now_update>).
611		705
612	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
613		707
614	Finally, this is it, the event handler. This function usually is called	708	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	709	after you initialised all your watchers and you want to start handling
…		…
631	the loop.	725	the loop.
632		726
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	727	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	728	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	729	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	730	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	731	user-registered callback will be called), and will return after one
638	iteration of the loop.	732	iteration of the loop.
639		733
640	This is useful if you are waiting for some external event in conjunction	734	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	735	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	779	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.	780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		781
688	This "unloop state" will be cleared when entering C<ev_loop> again.	782	This "unloop state" will be cleared when entering C<ev_loop> again.
689		783
		784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		785
690	=item ev_ref (loop)	786	=item ev_ref (loop)
691		787
692	=item ev_unref (loop)	788	=item ev_unref (loop)
693		789
694	Ref/unref can be used to add or remove a reference count on the event	790	Ref/unref can be used to add or remove a reference count on the event
…		…
697		793
698	If you have a watcher you never unregister that should not keep C<ev_loop>	794	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	795	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	796	stopping it.
701		797
702	As an example, libev itself uses this for its internal signal pipe: It is	798	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	799	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	800	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	801	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>	802	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,	803	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	804	before, respectively. Note also that libev might stop watchers itself
		805	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		806	in the callback).
709		807
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	809	running when nothing else is active.
712		810
713	struct ev_signal exitsig;	811	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	812	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	813	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	814	evf_unref (loop);
717		815
718	Example: For some weird reason, unregister the above signal handler again.	816	Example: For some weird reason, unregister the above signal handler again.
…		…
742		840
743	By setting a higher I<io collect interval> you allow libev to spend more	841	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,	842	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	843	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	844	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.	845	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		846	sleep time ensures that libev will not poll for I/O events more often then
		847	once per this interval, on average.
748		848
749	Likewise, by setting a higher I<timeout collect interval> you allow libev	849	Likewise, by setting a higher I<timeout collect interval> you allow libev
750	to spend more time collecting timeouts, at the expense of increased	850	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	851	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	852	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
754		854
755	Many (busy) programs can usually benefit by setting the I/O collect	855	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	856	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	857	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>,	858	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.	859	as this approaches the timing granularity of most systems. Note that if
		860	you do transactions with the outside world and you can't increase the
		861	parallelity, then this setting will limit your transaction rate (if you
		862	need to poll once per transaction and the I/O collect interval is 0.01,
		863	then you can't do more than 100 transations per second).
760		864
761	Setting the I<timeout collect interval> can improve the opportunity for	865	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	866	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	867	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	868	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	869	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
766	they fire on, say, one-second boundaries only.	870	they fire on, say, one-second boundaries only.
767		871
		872	Example: we only need 0.1s timeout granularity, and we wish not to poll
		873	more often than 100 times per second:
		874
		875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
768	=item ev_loop_verify (loop)	943	=item ev_loop_verify (loop)
769		944
770	This function only does something when C<EV_VERIFY> support has been	945	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	946	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	947	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	948	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	949	error and call C<abort ()>.
775		950
776	This can be used to catch bugs inside libev itself: under normal	951	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	955	=back
781		956
782		957
783	=head1 ANATOMY OF A WATCHER	958	=head1 ANATOMY OF A WATCHER
784		959
		960	In the following description, uppercase C<TYPE> in names stands for the
		961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		962	watchers and C<ev_io_start> for I/O watchers.
		963
785	A watcher is a structure that you create and register to record your	964	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	965	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:	966	become readable, you would create an C<ev_io> watcher for that:
788		967
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	969	{
791	ev_io_stop (w);	970	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	971	ev_unloop (loop, EVUNLOOP_ALL);
793	}	972	}
794		973
795	struct ev_loop *loop = ev_default_loop (0);	974	struct ev_loop *loop = ev_default_loop (0);
		975
796	struct ev_io stdin_watcher;	976	ev_io stdin_watcher;
		977
797	ev_init (&stdin_watcher, my_cb);	978	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	980	ev_io_start (loop, &stdin_watcher);
		981
800	ev_loop (loop, 0);	982	ev_loop (loop, 0);
801		983
802	As you can see, you are responsible for allocating the memory for your	984	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,	985	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	986	stack).
		987
		988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		990
806	Each watcher structure must be initialised by a call to C<ev_init	991	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	992	(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	993	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	994	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	995	is readable and/or writable).
811		996
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	997	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	998	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	999	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1000	ev_TYPE_init (watcher *, callback, ...) >>.
816		1001
817	To make the watcher actually watch out for events, you have to start it	1002	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	1003	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	1004	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1006
822	As long as your watcher is active (has been started but not stopped) you	1007	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	1008	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1009	reinitialise it or call its C<ev_TYPE_set> macro.
825		1010
826	Each and every callback receives the event loop pointer as first, the	1011	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	1012	registered watcher structure as second, and a bitset of received events as
828	third argument.	1013	third argument.
829		1014
…		…
887		1072
888	=item C<EV_ASYNC>	1073	=item C<EV_ASYNC>
889		1074
890	The given async watcher has been asynchronously notified (see C<ev_async>).	1075	The given async watcher has been asynchronously notified (see C<ev_async>).
891		1076
		1077	=item C<EV_CUSTOM>
		1078
		1079	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1080	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1081
892	=item C<EV_ERROR>	1082	=item C<EV_ERROR>
893		1083
894	An unspecified error has occurred, the watcher has been stopped. This might	1084	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	1085	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	1086	ran out of memory, a file descriptor was found to be closed or any other
		1087	problem. Libev considers these application bugs.
		1088
897	problem. You best act on it by reporting the problem and somehow coping	1089	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1090	watcher being stopped. Note that well-written programs should not receive
		1091	an error ever, so when your watcher receives it, this usually indicates a
		1092	bug in your program.
899		1093
900	Libev will usually signal a few "dummy" events together with an error, for	1094	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	1095	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	1096	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	1097	the error from read() or write(). This will not work in multi-threaded
…		…
906		1100
907	=back	1101	=back
908		1102
909	=head2 GENERIC WATCHER FUNCTIONS	1103	=head2 GENERIC WATCHER FUNCTIONS
910		1104
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	1105	=over 4
915		1106
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1107	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1108
918	This macro initialises the generic portion of a watcher. The contents	1109	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	1114	which rolls both calls into one.
924		1115
925	You can reinitialise a watcher at any time as long as it has been stopped	1116	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.	1117	(or never started) and there are no pending events outstanding.
927		1118
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1119	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1120	int revents)>.
930		1121
931	Example: Initialise an C<ev_io> watcher in two steps.	1122	Example: Initialise an C<ev_io> watcher in two steps.
932		1123
933	ev_io w;	1124	ev_io w;
…		…
967		1158
968	ev_io_start (EV_DEFAULT_UC, &w);	1159	ev_io_start (EV_DEFAULT_UC, &w);
969		1160
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1162
972	Stops the given watcher again (if active) and clears the pending	1163	Stops the given watcher if active, and clears the pending status (whether
		1164	the watcher was active or not).
		1165
973	status. It is possible that stopped watchers are pending (for example,	1166	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1167	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	1168	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	1169	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.	1170	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1171
979	=item bool ev_is_active (ev_TYPE *watcher)	1172	=item bool ev_is_active (ev_TYPE *watcher)
980		1173
981	Returns a true value iff the watcher is active (i.e. it has been started	1174	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	1175	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>	1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1202	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1203	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1204	from being executed (except for C<ev_idle> watchers).
1012		1205
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	1206	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.	1207	you need to look at C<ev_idle> watchers, which provide this functionality.
1020		1208
1021	You I<must not> change the priority of a watcher as long as it is active or	1209	You I<must not> change the priority of a watcher as long as it is active or
1022	pending.	1210	pending.
1023		1211
		1212	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1213	fine, as long as you do not mind that the priority value you query might
		1214	or might not have been clamped to the valid range.
		1215
1024	The default priority used by watchers when no priority has been set is	1216	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 :).	1217	always C<0>, which is supposed to not be too high and not be too low :).
1026		1218
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1219	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	1220	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1221
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1223
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1224	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	1225	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	1247	member, you can also "subclass" the watcher type and provide your own
1057	data:	1248	data:
1058		1249
1059	struct my_io	1250	struct my_io
1060	{	1251	{
1061	struct ev_io io;	1252	ev_io io;
1062	int otherfd;	1253	int otherfd;
1063	void *somedata;	1254	void *somedata;
1064	struct whatever *mostinteresting;	1255	struct whatever *mostinteresting;
1065	};	1256	};
1066		1257
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1261
1071	And since your callback will be called with a pointer to the watcher, you	1262	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1263	can cast it back to your own type:
1073		1264
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1266	{
1076	struct my_io *w = (struct my_io *)w_;	1267	struct my_io *w = (struct my_io *)w_;
1077	...	1268	...
1078	}	1269	}
1079		1270
…		…
1097	programmers):	1288	programmers):
1098		1289
1099	#include <stddef.h>	1290	#include <stddef.h>
1100		1291
1101	static void	1292	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1293	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1294	{
1104	struct my_biggy big = (struct my_biggy *	1295	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1296	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1297	}
1107		1298
1108	static void	1299	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1300	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1301	{
1111	struct my_biggy big = (struct my_biggy *	1302	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1303	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1304	}
		1305
		1306	=head2 WATCHER PRIORITY MODELS
		1307
		1308	Many event loops support I<watcher priorities>, which are usually small
		1309	integers that influence the ordering of event callback invocation
		1310	between watchers in some way, all else being equal.
		1311
		1312	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1313	description for the more technical details such as the actual priority
		1314	range.
		1315
		1316	There are two common ways how these these priorities are being interpreted
		1317	by event loops:
		1318
		1319	In the more common lock-out model, higher priorities "lock out" invocation
		1320	of lower priority watchers, which means as long as higher priority
		1321	watchers receive events, lower priority watchers are not being invoked.
		1322
		1323	The less common only-for-ordering model uses priorities solely to order
		1324	callback invocation within a single event loop iteration: Higher priority
		1325	watchers are invoked before lower priority ones, but they all get invoked
		1326	before polling for new events.
		1327
		1328	Libev uses the second (only-for-ordering) model for all its watchers
		1329	except for idle watchers (which use the lock-out model).
		1330
		1331	The rationale behind this is that implementing the lock-out model for
		1332	watchers is not well supported by most kernel interfaces, and most event
		1333	libraries will just poll for the same events again and again as long as
		1334	their callbacks have not been executed, which is very inefficient in the
		1335	common case of one high-priority watcher locking out a mass of lower
		1336	priority ones.
		1337
		1338	Static (ordering) priorities are most useful when you have two or more
		1339	watchers handling the same resource: a typical usage example is having an
		1340	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1341	timeouts. Under load, data might be received while the program handles
		1342	other jobs, but since timers normally get invoked first, the timeout
		1343	handler will be executed before checking for data. In that case, giving
		1344	the timer a lower priority than the I/O watcher ensures that I/O will be
		1345	handled first even under adverse conditions (which is usually, but not
		1346	always, what you want).
		1347
		1348	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1349	will only be executed when no same or higher priority watchers have
		1350	received events, they can be used to implement the "lock-out" model when
		1351	required.
		1352
		1353	For example, to emulate how many other event libraries handle priorities,
		1354	you can associate an C<ev_idle> watcher to each such watcher, and in
		1355	the normal watcher callback, you just start the idle watcher. The real
		1356	processing is done in the idle watcher callback. This causes libev to
		1357	continously poll and process kernel event data for the watcher, but when
		1358	the lock-out case is known to be rare (which in turn is rare :), this is
		1359	workable.
		1360
		1361	Usually, however, the lock-out model implemented that way will perform
		1362	miserably under the type of load it was designed to handle. In that case,
		1363	it might be preferable to stop the real watcher before starting the
		1364	idle watcher, so the kernel will not have to process the event in case
		1365	the actual processing will be delayed for considerable time.
		1366
		1367	Here is an example of an I/O watcher that should run at a strictly lower
		1368	priority than the default, and which should only process data when no
		1369	other events are pending:
		1370
		1371	ev_idle idle; // actual processing watcher
		1372	ev_io io; // actual event watcher
		1373
		1374	static void
		1375	io_cb (EV_P_ ev_io *w, int revents)
		1376	{
		1377	// stop the I/O watcher, we received the event, but
		1378	// are not yet ready to handle it.
		1379	ev_io_stop (EV_A_ w);
		1380
		1381	// start the idle watcher to ahndle the actual event.
		1382	// it will not be executed as long as other watchers
		1383	// with the default priority are receiving events.
		1384	ev_idle_start (EV_A_ &idle);
		1385	}
		1386
		1387	static void
		1388	idle_cb (EV_P_ ev_idle *w, int revents)
		1389	{
		1390	// actual processing
		1391	read (STDIN_FILENO, ...);
		1392
		1393	// have to start the I/O watcher again, as
		1394	// we have handled the event
		1395	ev_io_start (EV_P_ &io);
		1396	}
		1397
		1398	// initialisation
		1399	ev_idle_init (&idle, idle_cb);
		1400	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1401	ev_io_start (EV_DEFAULT_ &io);
		1402
		1403	In the "real" world, it might also be beneficial to start a timer, so that
		1404	low-priority connections can not be locked out forever under load. This
		1405	enables your program to keep a lower latency for important connections
		1406	during short periods of high load, while not completely locking out less
		1407	important ones.
1114		1408
1115		1409
1116	=head1 WATCHER TYPES	1410	=head1 WATCHER TYPES
1117		1411
1118	This section describes each watcher in detail, but will not repeat	1412	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	1438	descriptors to non-blocking mode is also usually a good idea (but not
1145	required if you know what you are doing).	1439	required if you know what you are doing).
1146		1440
1147	If you cannot use non-blocking mode, then force the use of a	1441	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	1442	known-to-be-good backend (at the time of this writing, this includes only
1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1444	descriptors for which non-blocking operation makes no sense (such as
		1445	files) - libev doesn't guarentee any specific behaviour in that case.
1150		1446
1151	Another thing you have to watch out for is that it is quite easy to	1447	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	1448	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	1449	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	1450	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	1545	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	1546	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1547	attempt to read a whole line in the callback.
1252		1548
1253	static void	1549	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1550	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1551	{
1256	ev_io_stop (loop, w);	1552	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1553	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1554	}
1259		1555
1260	...	1556	...
1261	struct ev_loop *loop = ev_default_init (0);	1557	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1558	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1560	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1561	ev_loop (loop, 0);
1266		1562
1267		1563
…		…
1275	year, it will still time out after (roughly) one hour. "Roughly" because	1571	year, it will still time out after (roughly) one hour. "Roughly" because
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1573	monotonic clock option helps a lot here).
1278		1574
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1575	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	1576	passed (not I<at>, so on systems with very low-resolution clocks this
1281	then order of execution is undefined.	1577	might introduce a small delay). If multiple timers become ready during the
		1578	same loop iteration then the ones with earlier time-out values are invoked
		1579	before ones of the same priority with later time-out values (but this is
		1580	no longer true when a callback calls C<ev_loop> recursively).
		1581
		1582	=head3 Be smart about timeouts
		1583
		1584	Many real-world problems involve some kind of timeout, usually for error
		1585	recovery. A typical example is an HTTP request - if the other side hangs,
		1586	you want to raise some error after a while.
		1587
		1588	What follows are some ways to handle this problem, from obvious and
		1589	inefficient to smart and efficient.
		1590
		1591	In the following, a 60 second activity timeout is assumed - a timeout that
		1592	gets reset to 60 seconds each time there is activity (e.g. each time some
		1593	data or other life sign was received).
		1594
		1595	=over 4
		1596
		1597	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1598
		1599	This is the most obvious, but not the most simple way: In the beginning,
		1600	start the watcher:
		1601
		1602	ev_timer_init (timer, callback, 60., 0.);
		1603	ev_timer_start (loop, timer);
		1604
		1605	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1606	and start it again:
		1607
		1608	ev_timer_stop (loop, timer);
		1609	ev_timer_set (timer, 60., 0.);
		1610	ev_timer_start (loop, timer);
		1611
		1612	This is relatively simple to implement, but means that each time there is
		1613	some activity, libev will first have to remove the timer from its internal
		1614	data structure and then add it again. Libev tries to be fast, but it's
		1615	still not a constant-time operation.
		1616
		1617	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1618
		1619	This is the easiest way, and involves using C<ev_timer_again> instead of
		1620	C<ev_timer_start>.
		1621
		1622	To implement this, configure an C<ev_timer> with a C<repeat> value
		1623	of C<60> and then call C<ev_timer_again> at start and each time you
		1624	successfully read or write some data. If you go into an idle state where
		1625	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1626	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1627
		1628	That means you can ignore both the C<ev_timer_start> function and the
		1629	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1630	member and C<ev_timer_again>.
		1631
		1632	At start:
		1633
		1634	ev_init (timer, callback);
		1635	timer->repeat = 60.;
		1636	ev_timer_again (loop, timer);
		1637
		1638	Each time there is some activity:
		1639
		1640	ev_timer_again (loop, timer);
		1641
		1642	It is even possible to change the time-out on the fly, regardless of
		1643	whether the watcher is active or not:
		1644
		1645	timer->repeat = 30.;
		1646	ev_timer_again (loop, timer);
		1647
		1648	This is slightly more efficient then stopping/starting the timer each time
		1649	you want to modify its timeout value, as libev does not have to completely
		1650	remove and re-insert the timer from/into its internal data structure.
		1651
		1652	It is, however, even simpler than the "obvious" way to do it.
		1653
		1654	=item 3. Let the timer time out, but then re-arm it as required.
		1655
		1656	This method is more tricky, but usually most efficient: Most timeouts are
		1657	relatively long compared to the intervals between other activity - in
		1658	our example, within 60 seconds, there are usually many I/O events with
		1659	associated activity resets.
		1660
		1661	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1662	but remember the time of last activity, and check for a real timeout only
		1663	within the callback:
		1664
		1665	ev_tstamp last_activity; // time of last activity
		1666
		1667	static void
		1668	callback (EV_P_ ev_timer *w, int revents)
		1669	{
		1670	ev_tstamp now = ev_now (EV_A);
		1671	ev_tstamp timeout = last_activity + 60.;
		1672
		1673	// if last_activity + 60. is older than now, we did time out
		1674	if (timeout < now)
		1675	{
		1676	// timeout occured, take action
		1677	}
		1678	else
		1679	{
		1680	// callback was invoked, but there was some activity, re-arm
		1681	// the watcher to fire in last_activity + 60, which is
		1682	// guaranteed to be in the future, so "again" is positive:
		1683	w->repeat = timeout - now;
		1684	ev_timer_again (EV_A_ w);
		1685	}
		1686	}
		1687
		1688	To summarise the callback: first calculate the real timeout (defined
		1689	as "60 seconds after the last activity"), then check if that time has
		1690	been reached, which means something I<did>, in fact, time out. Otherwise
		1691	the callback was invoked too early (C<timeout> is in the future), so
		1692	re-schedule the timer to fire at that future time, to see if maybe we have
		1693	a timeout then.
		1694
		1695	Note how C<ev_timer_again> is used, taking advantage of the
		1696	C<ev_timer_again> optimisation when the timer is already running.
		1697
		1698	This scheme causes more callback invocations (about one every 60 seconds
		1699	minus half the average time between activity), but virtually no calls to
		1700	libev to change the timeout.
		1701
		1702	To start the timer, simply initialise the watcher and set C<last_activity>
		1703	to the current time (meaning we just have some activity :), then call the
		1704	callback, which will "do the right thing" and start the timer:
		1705
		1706	ev_init (timer, callback);
		1707	last_activity = ev_now (loop);
		1708	callback (loop, timer, EV_TIMEOUT);
		1709
		1710	And when there is some activity, simply store the current time in
		1711	C<last_activity>, no libev calls at all:
		1712
		1713	last_actiivty = ev_now (loop);
		1714
		1715	This technique is slightly more complex, but in most cases where the
		1716	time-out is unlikely to be triggered, much more efficient.
		1717
		1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1719	callback :) - just change the timeout and invoke the callback, which will
		1720	fix things for you.
		1721
		1722	=item 4. Wee, just use a double-linked list for your timeouts.
		1723
		1724	If there is not one request, but many thousands (millions...), all
		1725	employing some kind of timeout with the same timeout value, then one can
		1726	do even better:
		1727
		1728	When starting the timeout, calculate the timeout value and put the timeout
		1729	at the I<end> of the list.
		1730
		1731	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1732	the list is expected to fire (for example, using the technique #3).
		1733
		1734	When there is some activity, remove the timer from the list, recalculate
		1735	the timeout, append it to the end of the list again, and make sure to
		1736	update the C<ev_timer> if it was taken from the beginning of the list.
		1737
		1738	This way, one can manage an unlimited number of timeouts in O(1) time for
		1739	starting, stopping and updating the timers, at the expense of a major
		1740	complication, and having to use a constant timeout. The constant timeout
		1741	ensures that the list stays sorted.
		1742
		1743	=back
		1744
		1745	So which method the best?
		1746
		1747	Method #2 is a simple no-brain-required solution that is adequate in most
		1748	situations. Method #3 requires a bit more thinking, but handles many cases
		1749	better, and isn't very complicated either. In most case, choosing either
		1750	one is fine, with #3 being better in typical situations.
		1751
		1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1753	rather complicated, but extremely efficient, something that really pays
		1754	off after the first million or so of active timers, i.e. it's usually
		1755	overkill :)
1282		1756
1283	=head3 The special problem of time updates	1757	=head3 The special problem of time updates
1284		1758
1285	Establishing the current time is a costly operation (it usually takes at	1759	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	1760	least two system calls): EV therefore updates its idea of the current
…		…
1298		1772
1299	If the event loop is suspended for a long time, you can also force an	1773	If the event loop is suspended for a long time, you can also force an
1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1301	()>.	1775	()>.
1302		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
		1806
1303	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1304		1808
1305	=over 4	1809	=over 4
1306		1810
1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1834	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1835
1332	If the timer is repeating, either start it if necessary (with the	1836	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.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1838
1335	This sounds a bit complicated, but here is a useful and typical	1839	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	1840	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		1841
1345	That means you can ignore the C<after> value and C<ev_timer_start>	1842	=item ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		1843
1348	ev_timer_init (timer, callback, 0., 5.);	1844	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	1845	then this time is relative to the current event loop time, otherwise it's
1350	...	1846	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		1847
1357	This is more slightly efficient then stopping/starting the timer each time	1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1359		1850	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	1851	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	1852	too), and so on.
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		1853
1366	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1367		1855
1368	The current C<repeat> value. Will be used each time the watcher times out	1856	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),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1862	=head3 Examples
1375		1863
1376	Example: Create a timer that fires after 60 seconds.	1864	Example: Create a timer that fires after 60 seconds.
1377		1865
1378	static void	1866	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1867	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1868	{
1381	.. one minute over, w is actually stopped right here	1869	.. one minute over, w is actually stopped right here
1382	}	1870	}
1383		1871
1384	struct ev_timer mytimer;	1872	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1873	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1874	ev_timer_start (loop, &mytimer);
1387		1875
1388	Example: Create a timeout timer that times out after 10 seconds of	1876	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1877	inactivity.
1390		1878
1391	static void	1879	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1880	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1881	{
1394	.. ten seconds without any activity	1882	.. ten seconds without any activity
1395	}	1883	}
1396		1884
1397	struct ev_timer mytimer;	1885	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1887	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1888	ev_loop (loop, 0);
1401		1889
1402	// and in some piece of code that gets executed on any "activity":	1890	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1895	=head2 C<ev_periodic> - to cron or not to cron?
1408		1896
1409	Periodic watchers are also timers of a kind, but they are very versatile	1897	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1898	(and unfortunately a bit complex).
1411		1899
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1900	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	1901	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	1902	(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 ()	1903	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	1904	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	1905	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		1906
		1907	You can tell a periodic watcher to trigger after some specific point
		1908	in time: for example, if you tell a periodic watcher to trigger "in 10
		1909	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1910	not a delay) and then reset your system clock to January of the previous
		1911	year, then it will take a year or more to trigger the event (unlike an
		1912	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1913	it, as it uses a relative timeout).
		1914
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1915	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	1916	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1917	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1918	those cannot react to time jumps.
1424		1919
1425	As with timers, the callback is guaranteed to be invoked only when the	1920	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	1921	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.	1922	timers become ready during the same loop iteration then the ones with
		1923	earlier time-out values are invoked before ones with later time-out values
		1924	(but this is no longer true when a callback calls C<ev_loop> recursively).
1428		1925
1429	=head3 Watcher-Specific Functions and Data Members	1926	=head3 Watcher-Specific Functions and Data Members
1430		1927
1431	=over 4	1928	=over 4
1432		1929
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1930	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1931
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1932	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1933
1437	Lots of arguments, lets sort it out... There are basically three modes of	1934	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:	1935	operation, and we will explain them from simplest to most complex:
1439		1936
1440	=over 4	1937	=over 4
1441		1938
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1939	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1940
1444	In this configuration the watcher triggers an event after the wall clock	1941	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	1942	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	1943	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.	1944	will be stopped and invoked when the system clock reaches or surpasses
		1945	this point in time.
1448		1946
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1947	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1948
1451	In this mode the watcher will always be scheduled to time out at the next	1949	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)	1950	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1951	negative) and then repeat, regardless of any time jumps. The C<offset>
		1952	argument is merely an offset into the C<interval> periods.
1454		1953
1455	This can be used to create timers that do not drift with respect to the	1954	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	1955	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1956	hour, on the hour (with respect to UTC):
1458		1957
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1958	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1959
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1960	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	1961	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	1962	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1963	by 3600.
1465		1964
1466	Another way to think about it (for the mathematically inclined) is that	1965	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	1966	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.	1967	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1968
1470	For numerical stability it is preferable that the C<at> value is near	1969	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	1970	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1971	this value, and in fact is often specified as zero.
1473		1972
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1973	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	1974	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	1975	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).	1976	millisecond (if the OS supports it and the machine is fast enough).
1478		1977
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1978	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1979
1481	In this mode the values for C<interval> and C<at> are both being	1980	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	1981	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1982	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1983	current time as second argument.
1485		1984
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1985	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1986	or make ANY other event loop modifications whatsoever, unless explicitly
		1987	allowed by documentation here>.
1488		1988
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1989	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	1990	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1991	only event loop modification you are allowed to do).
1492		1992
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1993	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1994	*w, ev_tstamp now)>, e.g.:
1495		1995
		1996	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1997	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1998	{
1498	return now + 60.;	1999	return now + 60.;
1499	}	2000	}
1500		2001
1501	It must return the next time to trigger, based on the passed time value	2002	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	2022	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	2023	program when the crontabs have changed).
1523		2024
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2025	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2026
1526	When active, returns the absolute time that the watcher is supposed to	2027	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	2028	to trigger next. This is not the same as the C<offset> argument to
		2029	C<ev_periodic_set>, but indeed works even in interval and manual
		2030	rescheduling modes.
1528		2031
1529	=item ev_tstamp offset [read-write]	2032	=item ev_tstamp offset [read-write]
1530		2033
1531	When repeating, this contains the offset value, otherwise this is the	2034	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>).	2035	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2036	although libev might modify this value for better numerical stability).
1533		2037
1534	Can be modified any time, but changes only take effect when the periodic	2038	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	2039	timer fires or C<ev_periodic_again> is being called.
1536		2040
1537	=item ev_tstamp interval [read-write]	2041	=item ev_tstamp interval [read-write]
1538		2042
1539	The current interval value. Can be modified any time, but changes only	2043	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	2044	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2045	called.
1542		2046
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2047	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2048
1545	The current reschedule callback, or C<0>, if this functionality is	2049	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	2050	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.	2051	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2052
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2057	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2058	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2059	potentially a lot of jitter, but good long-term stability.
1556		2060
1557	static void	2061	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	2063	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	2064	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	2065	}
1562		2066
1563	struct ev_periodic hourly_tick;	2067	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2068	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2069	ev_periodic_start (loop, &hourly_tick);
1566		2070
1567	Example: The same as above, but use a reschedule callback to do it:	2071	Example: The same as above, but use a reschedule callback to do it:
1568		2072
1569	#include <math.h>	2073	#include <math.h>
1570		2074
1571	static ev_tstamp	2075	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2076	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2077	{
1574	return now + (3600. - fmod (now, 3600.));	2078	return now + (3600. - fmod (now, 3600.));
1575	}	2079	}
1576		2080
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2081	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2082
1579	Example: Call a callback every hour, starting now:	2083	Example: Call a callback every hour, starting now:
1580		2084
1581	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2086	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2087	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2088	ev_periodic_start (loop, &hourly_tick);
1585		2089
1586		2090
…		…
1589	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
1590	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
1591	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1592	normal event processing, like any other event.	2096	normal event processing, like any other event.
1593		2097
1594	If you want signals asynchronously, just use C<sigaction> as you would	2098	If you want signals to be delivered truly asynchronously, just use
1595	do without libev and forget about sharing the signal. You can even use	2099	C<sigaction> as you would do without libev and forget about sharing
1596	C<ev_async> from a signal handler to synchronously wake up an event loop.	2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
1597		2102
1598	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1599	first watcher gets started will libev actually register a signal handler	2109	When the first watcher gets started will libev actually register something
1600	with the kernel (thus it coexists with your own signal handlers as long as	2110	with the kernel (thus it coexists with your own signal handlers as long as
1601	you don't register any with libev for the same signal). Similarly, when	2111	you don't register any with libev for the same signal).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2112
1605	If possible and supported, libev will install its handlers with	2113	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	interrupted. If you have a problem with system calls getting interrupted by	2115	not be unduly interrupted. If you have a problem with system calls getting
1608	signals you can block all signals in an C<ev_check> watcher and unblock	2116	interrupted by signals you can block all signals in an C<ev_check> watcher
1609	them in an C<ev_prepare> watcher.	2117	and unblock them in an C<ev_prepare> watcher.
		2118
		2119	=head3 The special problem of inheritance over execve
		2120
		2121	Both the signal mask (C<sigprocmask>) and the signal disposition
		2122	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2123	stopping it again), that is, libev might or might not block the signal,
		2124	and might or might not set or restore the installed signal handler.
		2125
		2126	While this does not matter for the signal disposition (libev never
		2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2128	C<execve>), this matters for the signal mask: many programs do not expect
		2129	many signals to be blocked.
		2130
		2131	This means that before calling C<exec> (from the child) you should reset
		2132	the signal mask to whatever "default" you expect (all clear is a good
		2133	choice usually).
1610		2134
1611	=head3 Watcher-Specific Functions and Data Members	2135	=head3 Watcher-Specific Functions and Data Members
1612		2136
1613	=over 4	2137	=over 4
1614		2138
…		…
1628	=head3 Examples	2152	=head3 Examples
1629		2153
1630	Example: Try to exit cleanly on SIGINT.	2154	Example: Try to exit cleanly on SIGINT.
1631		2155
1632	static void	2156	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2157	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2158	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2159	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	2160	}
1637		2161
1638	struct ev_signal signal_watcher;	2162	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2163	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &signal_watcher);	2164	ev_signal_start (loop, &signal_watcher);
1641		2165
1642		2166
1643	=head2 C<ev_child> - watch out for process status changes	2167	=head2 C<ev_child> - watch out for process status changes
…		…
1646	some child status changes (most typically when a child of yours dies or	2170	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	2171	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	2172	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.,	2173	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,	2174	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	2175	but forking and registering a watcher a few event loop iterations later or
1652	not.	2176	in the next callback invocation is not.
1653		2177
1654	Only the default event loop is capable of handling signals, and therefore	2178	Only the default event loop is capable of handling signals, and therefore
1655	you can only register child watchers in the default event loop.	2179	you can only register child watchers in the default event loop.
1656		2180
		2181	Due to some design glitches inside libev, child watchers will always be
		2182	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2183	libev)
		2184
1657	=head3 Process Interaction	2185	=head3 Process Interaction
1658		2186
1659	Libev grabs C<SIGCHLD> as soon as the default event loop is	2187	Libev grabs C<SIGCHLD> as soon as the default event loop is
1660	initialised. This is necessary to guarantee proper behaviour even if	2188	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2189	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2190	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	synchronously as part of the event loop processing. Libev always reaps all	2191	synchronously as part of the event loop processing. Libev always reaps all
1664	children, even ones not watched.	2192	children, even ones not watched.
1665		2193
1666	=head3 Overriding the Built-In Processing	2194	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2204	=head3 Stopping the Child Watcher
1677		2205
1678	Currently, the child watcher never gets stopped, even when the	2206	Currently, the child watcher never gets stopped, even when the
1679	child terminates, so normally one needs to stop the watcher in the	2207	child terminates, so normally one needs to stop the watcher in the
1680	callback. Future versions of libev might stop the watcher automatically	2208	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2209	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2210	problem).
1682		2211
1683	=head3 Watcher-Specific Functions and Data Members	2212	=head3 Watcher-Specific Functions and Data Members
1684		2213
1685	=over 4	2214	=over 4
1686		2215
…		…
1718	its completion.	2247	its completion.
1719		2248
1720	ev_child cw;	2249	ev_child cw;
1721		2250
1722	static void	2251	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2252	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2253	{
1725	ev_child_stop (EV_A_ w);	2254	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2255	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2256	}
1728		2257
…		…
1743		2272
1744		2273
1745	=head2 C<ev_stat> - did the file attributes just change?	2274	=head2 C<ev_stat> - did the file attributes just change?
1746		2275
1747	This watches a file system path for attribute changes. That is, it calls	2276	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	2277	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.	2278	and sees if it changed compared to the last time, invoking the callback if
		2279	it did.
1750		2280
1751	The path does not need to exist: changing from "path exists" to "path does	2281	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	2282	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	2283	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	2284	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	2285	least one) and all the other fields of the stat buffer having unspecified
		2286	contents.
1756		2287
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2288	The path I<must not> end in a slash or contain special components such as
		2289	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.	2290	your working directory changes, then the behaviour is undefined.
1759		2291
1760	Since there is no standard kernel interface to do this, the portable	2292	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2293	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2294	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!)	2295	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	2296	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2297	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2298	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2299	currently around C<0.1>, but that's usually overkill.
1768		2300
1769	This watcher type is not meant for massive numbers of stat watchers,	2301	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	2302	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2303	resource-intensive.
1772		2304
1773	At the time of this writing, the only OS-specific interface implemented	2305	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	2306	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	2307	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	2308	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2309
1778	=head3 ABI Issues (Largefile Support)	2310	=head3 ABI Issues (Largefile Support)
1779		2311
1780	Libev by default (unless the user overrides this) uses the default	2312	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2313	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2314	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	2315	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	2316	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	2317	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	2318	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.	2319	most noticeably displayed with ev_stat and large file support.
1788		2320
1789	The solution for this is to lobby your distribution maker to make large	2321	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	2322	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	2323	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2324	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2325	default compilation environment.
1794		2326
1795	=head3 Inotify and Kqueue	2327	=head3 Inotify and Kqueue
1796		2328
1797	When C<inotify (7)> support has been compiled into libev (generally only	2329	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	2330	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	2331	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2332	watcher is being started.
1801		2333
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2334	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	2335	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	2336	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,	2337	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.	2338	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2339	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2340	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2341	xfs are fully working) libev usually gets away without polling.
1807		2342
1808	There is no support for kqueue, as apparently it cannot be used to	2343	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	2344	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2345	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2346	etc. is difficult.
1812		2347
		2348	=head3 C<stat ()> is a synchronous operation
		2349
		2350	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2351	the process. The exception are C<ev_stat> watchers - those call C<stat
		2352	()>, which is a synchronous operation.
		2353
		2354	For local paths, this usually doesn't matter: unless the system is very
		2355	busy or the intervals between stat's are large, a stat call will be fast,
		2356	as the path data is usually in memory already (except when starting the
		2357	watcher).
		2358
		2359	For networked file systems, calling C<stat ()> can block an indefinite
		2360	time due to network issues, and even under good conditions, a stat call
		2361	often takes multiple milliseconds.
		2362
		2363	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2364	paths, although this is fully supported by libev.
		2365
1813	=head3 The special problem of stat time resolution	2366	=head3 The special problem of stat time resolution
1814		2367
1815	The C<stat ()> system call only supports full-second resolution portably, and	2368	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2369	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2370	still only support whole seconds.
1818		2371
1819	That means that, if the time is the only thing that changes, you can	2372	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	2373	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	2374	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	2375	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2518
1966	=head3 Watcher-Specific Functions and Data Members	2519	=head3 Watcher-Specific Functions and Data Members
1967		2520
1968	=over 4	2521	=over 4
1969		2522
1970	=item ev_idle_init (ev_signal *, callback)	2523	=item ev_idle_init (ev_idle *, callback)
1971		2524
1972	Initialises and configures the idle watcher - it has no parameters of any	2525	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,	2526	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2527	believe me.
1975		2528
…		…
1979		2532
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2533	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2534	callback, free it. Also, use no error checking, as usual.
1982		2535
1983	static void	2536	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2537	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2538	{
1986	free (w);	2539	free (w);
1987	// now do something you wanted to do when the program has	2540	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2541	// no longer anything immediate to do.
1989	}	2542	}
1990		2543
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2544	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2545	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2546	ev_idle_start (loop, idle_watcher);
1994		2547
1995		2548
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2549	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1997		2550
1998	Prepare and check watchers are usually (but not always) used in pairs:	2551	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2077		2630
2078	static ev_io iow [nfd];	2631	static ev_io iow [nfd];
2079	static ev_timer tw;	2632	static ev_timer tw;
2080		2633
2081	static void	2634	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2635	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2636	{
2084	}	2637	}
2085		2638
2086	// create io watchers for each fd and a timer before blocking	2639	// create io watchers for each fd and a timer before blocking
2087	static void	2640	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2641	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2642	{
2090	int timeout = 3600000;	2643	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2644	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2645	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2646	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2647
2095	/* the callback is illegal, but won't be called as we stop during check */	2648	/* the callback is illegal, but won't be called as we stop during check */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2649	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2650	ev_timer_start (loop, &tw);
2098		2651
2099	// create one ev_io per pollfd	2652	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2653	for (int i = 0; i < nfd; ++i)
2101	{	2654	{
…		…
2108	}	2661	}
2109	}	2662	}
2110		2663
2111	// stop all watchers after blocking	2664	// stop all watchers after blocking
2112	static void	2665	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2666	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2667	{
2115	ev_timer_stop (loop, &tw);	2668	ev_timer_stop (loop, &tw);
2116		2669
2117	for (int i = 0; i < nfd; ++i)	2670	for (int i = 0; i < nfd; ++i)
2118	{	2671	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2767	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	2768	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	2769	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.	2770	the rest in a second one, and embed the second one in the first.
2218		2771
2219	As long as the watcher is active, the callback will be invoked every time	2772	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	2773	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	2774	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	2775	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	2776	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	2777	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2778
2227	As long as the watcher is started it will automatically handle events. The	2779	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	2780	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		2781
2232	Also, there have not currently been made special provisions for forking:	2782	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,	2783	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	2784	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,	2785	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2786
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2787	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2788	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2789	portable one.
2241		2790
…		…
2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2835	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287	used).	2836	used).
2288		2837
2289	struct ev_loop *loop_hi = ev_default_init (0);	2838	struct ev_loop *loop_hi = ev_default_init (0);
2290	struct ev_loop *loop_lo = 0;	2839	struct ev_loop *loop_lo = 0;
2291	struct ev_embed embed;	2840	ev_embed embed;
2292		2841
2293	// see if there is a chance of getting one that works	2842	// see if there is a chance of getting one that works
2294	// (remember that a flags value of 0 means autodetection)	2843	// (remember that a flags value of 0 means autodetection)
2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2844	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2845	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2310	kqueue implementation). Store the kqueue/socket-only event loop in	2859	kqueue implementation). Store the kqueue/socket-only event loop in
2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2860	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312		2861
2313	struct ev_loop *loop = ev_default_init (0);	2862	struct ev_loop *loop = ev_default_init (0);
2314	struct ev_loop *loop_socket = 0;	2863	struct ev_loop *loop_socket = 0;
2315	struct ev_embed embed;	2864	ev_embed embed;
2316		2865
2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2866	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2867	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319	{	2868	{
2320	ev_embed_init (&embed, 0, loop_socket);	2869	ev_embed_init (&embed, 0, loop_socket);
…		…
2335	event loop blocks next and before C<ev_check> watchers are being called,	2884	event loop blocks next and before C<ev_check> watchers are being called,
2336	and only in the child after the fork. If whoever good citizen calling	2885	and only in the child after the fork. If whoever good citizen calling
2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2886	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2338	handlers will be invoked, too, of course.	2887	handlers will be invoked, too, of course.
2339		2888
		2889	=head3 The special problem of life after fork - how is it possible?
		2890
		2891	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2892	up/change the process environment, followed by a call to C<exec()>. This
		2893	sequence should be handled by libev without any problems.
		2894
		2895	This changes when the application actually wants to do event handling
		2896	in the child, or both parent in child, in effect "continuing" after the
		2897	fork.
		2898
		2899	The default mode of operation (for libev, with application help to detect
		2900	forks) is to duplicate all the state in the child, as would be expected
		2901	when I<either> the parent I<or> the child process continues.
		2902
		2903	When both processes want to continue using libev, then this is usually the
		2904	wrong result. In that case, usually one process (typically the parent) is
		2905	supposed to continue with all watchers in place as before, while the other
		2906	process typically wants to start fresh, i.e. without any active watchers.
		2907
		2908	The cleanest and most efficient way to achieve that with libev is to
		2909	simply create a new event loop, which of course will be "empty", and
		2910	use that for new watchers. This has the advantage of not touching more
		2911	memory than necessary, and thus avoiding the copy-on-write, and the
		2912	disadvantage of having to use multiple event loops (which do not support
		2913	signal watchers).
		2914
		2915	When this is not possible, or you want to use the default loop for
		2916	other reasons, then in the process that wants to start "fresh", call
		2917	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2918	the default loop will "orphan" (not stop) all registered watchers, so you
		2919	have to be careful not to execute code that modifies those watchers. Note
		2920	also that in that case, you have to re-register any signal watchers.
		2921
2340	=head3 Watcher-Specific Functions and Data Members	2922	=head3 Watcher-Specific Functions and Data Members
2341		2923
2342	=over 4	2924	=over 4
2343		2925
2344	=item ev_fork_init (ev_signal *, callback)	2926	=item ev_fork_init (ev_signal *, callback)
…		…
2461	=over 4	3043	=over 4
2462		3044
2463	=item ev_async_init (ev_async *, callback)	3045	=item ev_async_init (ev_async *, callback)
2464		3046
2465	Initialises and configures the async watcher - it has no parameters of any	3047	Initialises and configures the async watcher - it has no parameters of any
2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3048	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2467	trust me.	3049	trust me.
2468		3050
2469	=item ev_async_send (loop, ev_async *)	3051	=item ev_async_send (loop, ev_async *)
2470		3052
2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3053	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3054	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2473	C<ev_feed_event>, this call is safe to do from other threads, signal or	3055	C<ev_feed_event>, this call is safe to do from other threads, signal or
2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3056	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2475	section below on what exactly this means).	3057	section below on what exactly this means).
2476		3058
		3059	Note that, as with other watchers in libev, multiple events might get
		3060	compressed into a single callback invocation (another way to look at this
		3061	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3062	reset when the event loop detects that).
		3063
2477	This call incurs the overhead of a system call only once per loop iteration,	3064	This call incurs the overhead of a system call only once per event loop
2478	so while the overhead might be noticeable, it doesn't apply to repeated	3065	iteration, so while the overhead might be noticeable, it doesn't apply to
2479	calls to C<ev_async_send>.	3066	repeated calls to C<ev_async_send> for the same event loop.
2480		3067
2481	=item bool = ev_async_pending (ev_async *)	3068	=item bool = ev_async_pending (ev_async *)
2482		3069
2483	Returns a non-zero value when C<ev_async_send> has been called on the	3070	Returns a non-zero value when C<ev_async_send> has been called on the
2484	watcher but the event has not yet been processed (or even noted) by the	3071	watcher but the event has not yet been processed (or even noted) by the
…		…
2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3074	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2488	the loop iterates next and checks for the watcher to have become active,	3075	the loop iterates next and checks for the watcher to have become active,
2489	it will reset the flag again. C<ev_async_pending> can be used to very	3076	it will reset the flag again. C<ev_async_pending> can be used to very
2490	quickly check whether invoking the loop might be a good idea.	3077	quickly check whether invoking the loop might be a good idea.
2491		3078
2492	Not that this does I<not> check whether the watcher itself is pending, only	3079	Not that this does I<not> check whether the watcher itself is pending,
2493	whether it has been requested to make this watcher pending.	3080	only whether it has been requested to make this watcher pending: there
		3081	is a time window between the event loop checking and resetting the async
		3082	notification, and the callback being invoked.
2494		3083
2495	=back	3084	=back
2496		3085
2497		3086
2498	=head1 OTHER FUNCTIONS	3087	=head1 OTHER FUNCTIONS
…		…
2513	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for	3102	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	the given C<fd> and C<events> set will be created and started.	3103	the given C<fd> and C<events> set will be created and started.
2515		3104
2516	If C<timeout> is less than 0, then no timeout watcher will be	3105	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3106	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3107	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		3108
2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3109	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2522	passed an C<revents> set like normal event callbacks (a combination of	3110	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3111	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	3112	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3113	a timeout and an io event at the same time - you probably should give io
		3114	events precedence.
		3115
		3116	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		3117
2526	static void stdin_ready (int revents, void *arg)	3118	static void stdin_ready (int revents, void *arg)
2527	{	3119	{
		3120	if (revents & EV_READ)
		3121	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	3122	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	3123	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	3124	}
2533		3125
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3126	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		3127
2536	=item ev_feed_event (ev_loop *, watcher *, int revents)	3128	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2537		3129
2538	Feeds the given event set into the event loop, as if the specified event	3130	Feeds the given event set into the event loop, as if the specified event
2539	had happened for the specified watcher (which must be a pointer to an	3131	had happened for the specified watcher (which must be a pointer to an
2540	initialised but not necessarily started event watcher).	3132	initialised but not necessarily started event watcher).
2541		3133
2542	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3134	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2543		3135
2544	Feed an event on the given fd, as if a file descriptor backend detected	3136	Feed an event on the given fd, as if a file descriptor backend detected
2545	the given events it.	3137	the given events it.
2546		3138
2547	=item ev_feed_signal_event (ev_loop *loop, int signum)	3139	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2548		3140
2549	Feed an event as if the given signal occurred (C<loop> must be the default	3141	Feed an event as if the given signal occurred (C<loop> must be the default
2550	loop!).	3142	loop!).
2551		3143
2552	=back	3144	=back
…		…
2673	}	3265	}
2674		3266
2675	myclass obj;	3267	myclass obj;
2676	ev::io iow;	3268	ev::io iow;
2677	iow.set <myclass, &myclass::io_cb> (&obj);	3269	iow.set <myclass, &myclass::io_cb> (&obj);
		3270
		3271	=item w->set (object *)
		3272
		3273	This is an B<experimental> feature that might go away in a future version.
		3274
		3275	This is a variation of a method callback - leaving out the method to call
		3276	will default the method to C<operator ()>, which makes it possible to use
		3277	functor objects without having to manually specify the C<operator ()> all
		3278	the time. Incidentally, you can then also leave out the template argument
		3279	list.
		3280
		3281	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3282	int revents)>.
		3283
		3284	See the method-C<set> above for more details.
		3285
		3286	Example: use a functor object as callback.
		3287
		3288	struct myfunctor
		3289	{
		3290	void operator() (ev::io &w, int revents)
		3291	{
		3292	...
		3293	}
		3294	}
		3295
		3296	myfunctor f;
		3297
		3298	ev::io w;
		3299	w.set (&f);
2678		3300
2679	=item w->set<function> (void *data = 0)	3301	=item w->set<function> (void *data = 0)
2680		3302
2681	Also sets a callback, but uses a static method or plain function as	3303	Also sets a callback, but uses a static method or plain function as
2682	callback. The optional C<data> argument will be stored in the watcher's	3304	callback. The optional C<data> argument will be stored in the watcher's
…		…
2769	L<http://software.schmorp.de/pkg/EV>.	3391	L<http://software.schmorp.de/pkg/EV>.
2770		3392
2771	=item Python	3393	=item Python
2772		3394
2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3395	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2774	seems to be quite complete and well-documented. Note, however, that the	3396	seems to be quite complete and well-documented.
2775	patch they require for libev is outright dangerous as it breaks the ABI
2776	for everybody else, and therefore, should never be applied in an installed
2777	libev (if python requires an incompatible ABI then it needs to embed
2778	libev).
2779		3397
2780	=item Ruby	3398	=item Ruby
2781		3399
2782	Tony Arcieri has written a ruby extension that offers access to a subset	3400	Tony Arcieri has written a ruby extension that offers access to a subset
2783	of the libev API and adds file handle abstractions, asynchronous DNS and	3401	of the libev API and adds file handle abstractions, asynchronous DNS and
2784	more on top of it. It can be found via gem servers. Its homepage is at	3402	more on top of it. It can be found via gem servers. Its homepage is at
2785	L<http://rev.rubyforge.org/>.	3403	L<http://rev.rubyforge.org/>.
2786		3404
		3405	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3406	makes rev work even on mingw.
		3407
		3408	=item Haskell
		3409
		3410	A haskell binding to libev is available at
		3411	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3412
2787	=item D	3413	=item D
2788		3414
2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3415	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3416	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3417
		3418	=item Ocaml
		3419
		3420	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3421	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3422
		3423	=item Lua
		3424
		3425	Brian Maher has written a partial interface to libev
		3426	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3427	L<http://github.com/brimworks/lua-ev>.
2791		3428
2792	=back	3429	=back
2793		3430
2794		3431
2795	=head1 MACRO MAGIC	3432	=head1 MACRO MAGIC
…		…
2896		3533
2897	#define EV_STANDALONE 1	3534	#define EV_STANDALONE 1
2898	#include "ev.h"	3535	#include "ev.h"
2899		3536
2900	Both header files and implementation files can be compiled with a C++	3537	Both header files and implementation files can be compiled with a C++
2901	compiler (at least, thats a stated goal, and breakage will be treated	3538	compiler (at least, that's a stated goal, and breakage will be treated
2902	as a bug).	3539	as a bug).
2903		3540
2904	You need the following files in your source tree, or in a directory	3541	You need the following files in your source tree, or in a directory
2905	in your include path (e.g. in libev/ when using -Ilibev):	3542	in your include path (e.g. in libev/ when using -Ilibev):
2906		3543
…		…
2962	keeps libev from including F<config.h>, and it also defines dummy	3599	keeps libev from including F<config.h>, and it also defines dummy
2963	implementations for some libevent functions (such as logging, which is not	3600	implementations for some libevent functions (such as logging, which is not
2964	supported). It will also not define any of the structs usually found in	3601	supported). It will also not define any of the structs usually found in
2965	F<event.h> that are not directly supported by the libev core alone.	3602	F<event.h> that are not directly supported by the libev core alone.
2966		3603
		3604	In standalone mode, libev will still try to automatically deduce the
		3605	configuration, but has to be more conservative.
		3606
2967	=item EV_USE_MONOTONIC	3607	=item EV_USE_MONOTONIC
2968		3608
2969	If defined to be C<1>, libev will try to detect the availability of the	3609	If defined to be C<1>, libev will try to detect the availability of the
2970	monotonic clock option at both compile time and runtime. Otherwise no use	3610	monotonic clock option at both compile time and runtime. Otherwise no
2971	of the monotonic clock option will be attempted. If you enable this, you	3611	use of the monotonic clock option will be attempted. If you enable this,
2972	usually have to link against librt or something similar. Enabling it when	3612	you usually have to link against librt or something similar. Enabling it
2973	the functionality isn't available is safe, though, although you have	3613	when the functionality isn't available is safe, though, although you have
2974	to make sure you link against any libraries where the C<clock_gettime>	3614	to make sure you link against any libraries where the C<clock_gettime>
2975	function is hiding in (often F<-lrt>).	3615	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2976		3616
2977	=item EV_USE_REALTIME	3617	=item EV_USE_REALTIME
2978		3618
2979	If defined to be C<1>, libev will try to detect the availability of the	3619	If defined to be C<1>, libev will try to detect the availability of the
2980	real-time clock option at compile time (and assume its availability at	3620	real-time clock option at compile time (and assume its availability
2981	runtime if successful). Otherwise no use of the real-time clock option will	3621	at runtime if successful). Otherwise no use of the real-time clock
2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3622	option will be attempted. This effectively replaces C<gettimeofday>
2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3623	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3624	correctness. See the note about libraries in the description of
		3625	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3626	C<EV_USE_CLOCK_SYSCALL>.
		3627
		3628	=item EV_USE_CLOCK_SYSCALL
		3629
		3630	If defined to be C<1>, libev will try to use a direct syscall instead
		3631	of calling the system-provided C<clock_gettime> function. This option
		3632	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3633	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3634	programs needlessly. Using a direct syscall is slightly slower (in
		3635	theory), because no optimised vdso implementation can be used, but avoids
		3636	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3637	higher, as it simplifies linking (no need for C<-lrt>).
2985		3638
2986	=item EV_USE_NANOSLEEP	3639	=item EV_USE_NANOSLEEP
2987		3640
2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3641	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2989	and will use it for delays. Otherwise it will use C<select ()>.	3642	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3005		3658
3006	=item EV_SELECT_USE_FD_SET	3659	=item EV_SELECT_USE_FD_SET
3007		3660
3008	If defined to C<1>, then the select backend will use the system C<fd_set>	3661	If defined to C<1>, then the select backend will use the system C<fd_set>
3009	structure. This is useful if libev doesn't compile due to a missing	3662	structure. This is useful if libev doesn't compile due to a missing
3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3663	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3011	exotic systems. This usually limits the range of file descriptors to some	3664	on exotic systems. This usually limits the range of file descriptors to
3012	low limit such as 1024 or might have other limitations (winsocket only	3665	some low limit such as 1024 or might have other limitations (winsocket
3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3666	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3014	influence the size of the C<fd_set> used.	3667	configures the maximum size of the C<fd_set>.
3015		3668
3016	=item EV_SELECT_IS_WINSOCKET	3669	=item EV_SELECT_IS_WINSOCKET
3017		3670
3018	When defined to C<1>, the select backend will assume that	3671	When defined to C<1>, the select backend will assume that
3019	select/socket/connect etc. don't understand file descriptors but	3672	select/socket/connect etc. don't understand file descriptors but
…		…
3021	be used is the winsock select). This means that it will call	3674	be used is the winsock select). This means that it will call
3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3675	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3023	it is assumed that all these functions actually work on fds, even	3676	it is assumed that all these functions actually work on fds, even
3024	on win32. Should not be defined on non-win32 platforms.	3677	on win32. Should not be defined on non-win32 platforms.
3025		3678
3026	=item EV_FD_TO_WIN32_HANDLE	3679	=item EV_FD_TO_WIN32_HANDLE(fd)
3027		3680
3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3681	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3029	file descriptors to socket handles. When not defining this symbol (the	3682	file descriptors to socket handles. When not defining this symbol (the
3030	default), then libev will call C<_get_osfhandle>, which is usually	3683	default), then libev will call C<_get_osfhandle>, which is usually
3031	correct. In some cases, programs use their own file descriptor management,	3684	correct. In some cases, programs use their own file descriptor management,
3032	in which case they can provide this function to map fds to socket handles.	3685	in which case they can provide this function to map fds to socket handles.
		3686
		3687	=item EV_WIN32_HANDLE_TO_FD(handle)
		3688
		3689	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3690	using the standard C<_open_osfhandle> function. For programs implementing
		3691	their own fd to handle mapping, overwriting this function makes it easier
		3692	to do so. This can be done by defining this macro to an appropriate value.
		3693
		3694	=item EV_WIN32_CLOSE_FD(fd)
		3695
		3696	If programs implement their own fd to handle mapping on win32, then this
		3697	macro can be used to override the C<close> function, useful to unregister
		3698	file descriptors again. Note that the replacement function has to close
		3699	the underlying OS handle.
3033		3700
3034	=item EV_USE_POLL	3701	=item EV_USE_POLL
3035		3702
3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3703	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3037	backend. Otherwise it will be enabled on non-win32 platforms. It	3704	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3169	defined to be C<0>, then they are not.	3836	defined to be C<0>, then they are not.
3170		3837
3171	=item EV_MINIMAL	3838	=item EV_MINIMAL
3172		3839
3173	If you need to shave off some kilobytes of code at the expense of some	3840	If you need to shave off some kilobytes of code at the expense of some
3174	speed, define this symbol to C<1>. Currently this is used to override some	3841	speed (but with the full API), define this symbol to C<1>. Currently this
3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3842	is used to override some inlining decisions, saves roughly 30% code size
3176	much smaller 2-heap for timer management over the default 4-heap.	3843	on amd64. It also selects a much smaller 2-heap for timer management over
		3844	the default 4-heap.
		3845
		3846	You can save even more by disabling watcher types you do not need
		3847	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3848	(C<-DNDEBUG>) will usually reduce code size a lot.
		3849
		3850	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3851	provide a bare-bones event library. See C<ev.h> for details on what parts
		3852	of the API are still available, and do not complain if this subset changes
		3853	over time.
		3854
		3855	=item EV_NSIG
		3856
		3857	The highest supported signal number, +1 (or, the number of
		3858	signals): Normally, libev tries to deduce the maximum number of signals
		3859	automatically, but sometimes this fails, in which case it can be
		3860	specified. Also, using a lower number than detected (C<32> should be
		3861	good for about any system in existance) can save some memory, as libev
		3862	statically allocates some 12-24 bytes per signal number.
3177		3863
3178	=item EV_PID_HASHSIZE	3864	=item EV_PID_HASHSIZE
3179		3865
3180	C<ev_child> watchers use a small hash table to distribute workload by	3866	C<ev_child> watchers use a small hash table to distribute workload by
3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3867	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3367	default loop and triggering an C<ev_async> watcher from the default loop	4053	default loop and triggering an C<ev_async> watcher from the default loop
3368	watcher callback into the event loop interested in the signal.	4054	watcher callback into the event loop interested in the signal.
3369		4055
3370	=back	4056	=back
3371		4057
		4058	=head4 THREAD LOCKING EXAMPLE
		4059
		4060	Here is a fictitious example of how to run an event loop in a different
		4061	thread than where callbacks are being invoked and watchers are
		4062	created/added/removed.
		4063
		4064	For a real-world example, see the C<EV::Loop::Async> perl module,
		4065	which uses exactly this technique (which is suited for many high-level
		4066	languages).
		4067
		4068	The example uses a pthread mutex to protect the loop data, a condition
		4069	variable to wait for callback invocations, an async watcher to notify the
		4070	event loop thread and an unspecified mechanism to wake up the main thread.
		4071
		4072	First, you need to associate some data with the event loop:
		4073
		4074	typedef struct {
		4075	mutex_t lock; /* global loop lock */
		4076	ev_async async_w;
		4077	thread_t tid;
		4078	cond_t invoke_cv;
		4079	} userdata;
		4080
		4081	void prepare_loop (EV_P)
		4082	{
		4083	// for simplicity, we use a static userdata struct.
		4084	static userdata u;
		4085
		4086	ev_async_init (&u->async_w, async_cb);
		4087	ev_async_start (EV_A_ &u->async_w);
		4088
		4089	pthread_mutex_init (&u->lock, 0);
		4090	pthread_cond_init (&u->invoke_cv, 0);
		4091
		4092	// now associate this with the loop
		4093	ev_set_userdata (EV_A_ u);
		4094	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4095	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4096
		4097	// then create the thread running ev_loop
		4098	pthread_create (&u->tid, 0, l_run, EV_A);
		4099	}
		4100
		4101	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4102	solely to wake up the event loop so it takes notice of any new watchers
		4103	that might have been added:
		4104
		4105	static void
		4106	async_cb (EV_P_ ev_async *w, int revents)
		4107	{
		4108	// just used for the side effects
		4109	}
		4110
		4111	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4112	protecting the loop data, respectively.
		4113
		4114	static void
		4115	l_release (EV_P)
		4116	{
		4117	userdata *u = ev_userdata (EV_A);
		4118	pthread_mutex_unlock (&u->lock);
		4119	}
		4120
		4121	static void
		4122	l_acquire (EV_P)
		4123	{
		4124	userdata *u = ev_userdata (EV_A);
		4125	pthread_mutex_lock (&u->lock);
		4126	}
		4127
		4128	The event loop thread first acquires the mutex, and then jumps straight
		4129	into C<ev_loop>:
		4130
		4131	void *
		4132	l_run (void *thr_arg)
		4133	{
		4134	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4135
		4136	l_acquire (EV_A);
		4137	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4138	ev_loop (EV_A_ 0);
		4139	l_release (EV_A);
		4140
		4141	return 0;
		4142	}
		4143
		4144	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4145	signal the main thread via some unspecified mechanism (signals? pipe
		4146	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4147	have been called (in a while loop because a) spurious wakeups are possible
		4148	and b) skipping inter-thread-communication when there are no pending
		4149	watchers is very beneficial):
		4150
		4151	static void
		4152	l_invoke (EV_P)
		4153	{
		4154	userdata *u = ev_userdata (EV_A);
		4155
		4156	while (ev_pending_count (EV_A))
		4157	{
		4158	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4159	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4160	}
		4161	}
		4162
		4163	Now, whenever the main thread gets told to invoke pending watchers, it
		4164	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4165	thread to continue:
		4166
		4167	static void
		4168	real_invoke_pending (EV_P)
		4169	{
		4170	userdata *u = ev_userdata (EV_A);
		4171
		4172	pthread_mutex_lock (&u->lock);
		4173	ev_invoke_pending (EV_A);
		4174	pthread_cond_signal (&u->invoke_cv);
		4175	pthread_mutex_unlock (&u->lock);
		4176	}
		4177
		4178	Whenever you want to start/stop a watcher or do other modifications to an
		4179	event loop, you will now have to lock:
		4180
		4181	ev_timer timeout_watcher;
		4182	userdata *u = ev_userdata (EV_A);
		4183
		4184	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4185
		4186	pthread_mutex_lock (&u->lock);
		4187	ev_timer_start (EV_A_ &timeout_watcher);
		4188	ev_async_send (EV_A_ &u->async_w);
		4189	pthread_mutex_unlock (&u->lock);
		4190
		4191	Note that sending the C<ev_async> watcher is required because otherwise
		4192	an event loop currently blocking in the kernel will have no knowledge
		4193	about the newly added timer. By waking up the loop it will pick up any new
		4194	watchers in the next event loop iteration.
		4195
3372	=head3 COROUTINES	4196	=head3 COROUTINES
3373		4197
3374	Libev is very accommodating to coroutines ("cooperative threads"):	4198	Libev is very accommodating to coroutines ("cooperative threads"):
3375	libev fully supports nesting calls to its functions from different	4199	libev fully supports nesting calls to its functions from different
3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4200	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3377	different coroutines, and switch freely between both coroutines running the	4201	different coroutines, and switch freely between both coroutines running
3378	loop, as long as you don't confuse yourself). The only exception is that	4202	the loop, as long as you don't confuse yourself). The only exception is
3379	you must not do this from C<ev_periodic> reschedule callbacks.	4203	that you must not do this from C<ev_periodic> reschedule callbacks.
3380		4204
3381	Care has been taken to ensure that libev does not keep local state inside	4205	Care has been taken to ensure that libev does not keep local state inside
3382	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4206	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3383	they do not clal any callbacks.	4207	they do not call any callbacks.
3384		4208
3385	=head2 COMPILER WARNINGS	4209	=head2 COMPILER WARNINGS
3386		4210
3387	Depending on your compiler and compiler settings, you might get no or a	4211	Depending on your compiler and compiler settings, you might get no or a
3388	lot of warnings when compiling libev code. Some people are apparently	4212	lot of warnings when compiling libev code. Some people are apparently
…		…
3422	==2274== definitely lost: 0 bytes in 0 blocks.	4246	==2274== definitely lost: 0 bytes in 0 blocks.
3423	==2274== possibly lost: 0 bytes in 0 blocks.	4247	==2274== possibly lost: 0 bytes in 0 blocks.
3424	==2274== still reachable: 256 bytes in 1 blocks.	4248	==2274== still reachable: 256 bytes in 1 blocks.
3425		4249
3426	Then there is no memory leak, just as memory accounted to global variables	4250	Then there is no memory leak, just as memory accounted to global variables
3427	is not a memleak - the memory is still being refernced, and didn't leak.	4251	is not a memleak - the memory is still being referenced, and didn't leak.
3428		4252
3429	Similarly, under some circumstances, valgrind might report kernel bugs	4253	Similarly, under some circumstances, valgrind might report kernel bugs
3430	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4254	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3431	although an acceptable workaround has been found here), or it might be	4255	although an acceptable workaround has been found here), or it might be
3432	confused.	4256	confused.
…		…
3461	way (note also that glib is the slowest event library known to man).	4285	way (note also that glib is the slowest event library known to man).
3462		4286
3463	There is no supported compilation method available on windows except	4287	There is no supported compilation method available on windows except
3464	embedding it into other applications.	4288	embedding it into other applications.
3465		4289
		4290	Sensible signal handling is officially unsupported by Microsoft - libev
		4291	tries its best, but under most conditions, signals will simply not work.
		4292
3466	Not a libev limitation but worth mentioning: windows apparently doesn't	4293	Not a libev limitation but worth mentioning: windows apparently doesn't
3467	accept large writes: instead of resulting in a partial write, windows will	4294	accept large writes: instead of resulting in a partial write, windows will
3468	either accept everything or return C<ENOBUFS> if the buffer is too large,	4295	either accept everything or return C<ENOBUFS> if the buffer is too large,
3469	so make sure you only write small amounts into your sockets (less than a	4296	so make sure you only write small amounts into your sockets (less than a
3470	megabyte seems safe, but this apparently depends on the amount of memory	4297	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3474	the abysmal performance of winsockets, using a large number of sockets	4301	the abysmal performance of winsockets, using a large number of sockets
3475	is not recommended (and not reasonable). If your program needs to use	4302	is not recommended (and not reasonable). If your program needs to use
3476	more than a hundred or so sockets, then likely it needs to use a totally	4303	more than a hundred or so sockets, then likely it needs to use a totally
3477	different implementation for windows, as libev offers the POSIX readiness	4304	different implementation for windows, as libev offers the POSIX readiness
3478	notification model, which cannot be implemented efficiently on windows	4305	notification model, which cannot be implemented efficiently on windows
3479	(Microsoft monopoly games).	4306	(due to Microsoft monopoly games).
3480		4307
3481	A typical way to use libev under windows is to embed it (see the embedding	4308	A typical way to use libev under windows is to embed it (see the embedding
3482	section for details) and use the following F<evwrap.h> header file instead	4309	section for details) and use the following F<evwrap.h> header file instead
3483	of F<ev.h>:	4310	of F<ev.h>:
3484		4311
…		…
3520		4347
3521	Early versions of winsocket's select only supported waiting for a maximum	4348	Early versions of winsocket's select only supported waiting for a maximum
3522	of C<64> handles (probably owning to the fact that all windows kernels	4349	of C<64> handles (probably owning to the fact that all windows kernels
3523	can only wait for C<64> things at the same time internally; Microsoft	4350	can only wait for C<64> things at the same time internally; Microsoft
3524	recommends spawning a chain of threads and wait for 63 handles and the	4351	recommends spawning a chain of threads and wait for 63 handles and the
3525	previous thread in each. Great).	4352	previous thread in each. Sounds great!).
3526		4353
3527	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4354	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3528	to some high number (e.g. C<2048>) before compiling the winsocket select	4355	to some high number (e.g. C<2048>) before compiling the winsocket select
3529	call (which might be in libev or elsewhere, for example, perl does its own	4356	call (which might be in libev or elsewhere, for example, perl and many
3530	select emulation on windows).	4357	other interpreters do their own select emulation on windows).
3531		4358
3532	Another limit is the number of file descriptors in the Microsoft runtime	4359	Another limit is the number of file descriptors in the Microsoft runtime
3533	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4360	libraries, which by default is C<64> (there must be a hidden I<64>
3534	or something like this inside Microsoft). You can increase this by calling	4361	fetish or something like this inside Microsoft). You can increase this
3535	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4362	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3536	arbitrary limit), but is broken in many versions of the Microsoft runtime	4363	(another arbitrary limit), but is broken in many versions of the Microsoft
3537	libraries.
3538
3539	This might get you to about C<512> or C<2048> sockets (depending on	4364	runtime libraries. This might get you to about C<512> or C<2048> sockets
3540	windows version and/or the phase of the moon). To get more, you need to	4365	(depending on windows version and/or the phase of the moon). To get more,
3541	wrap all I/O functions and provide your own fd management, but the cost of	4366	you need to wrap all I/O functions and provide your own fd management, but
3542	calling select (O(n²)) will likely make this unworkable.	4367	the cost of calling select (O(n²)) will likely make this unworkable.
3543		4368
3544	=back	4369	=back
3545		4370
3546	=head2 PORTABILITY REQUIREMENTS	4371	=head2 PORTABILITY REQUIREMENTS
3547		4372
…		…
3590	=item C<double> must hold a time value in seconds with enough accuracy	4415	=item C<double> must hold a time value in seconds with enough accuracy
3591		4416
3592	The type C<double> is used to represent timestamps. It is required to	4417	The type C<double> is used to represent timestamps. It is required to
3593	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4418	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3594	enough for at least into the year 4000. This requirement is fulfilled by	4419	enough for at least into the year 4000. This requirement is fulfilled by
3595	implementations implementing IEEE 754 (basically all existing ones).	4420	implementations implementing IEEE 754, which is basically all existing
		4421	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4422	2200.
3596		4423
3597	=back	4424	=back
3598		4425
3599	If you know of other additional requirements drop me a note.	4426	If you know of other additional requirements drop me a note.
3600		4427
…		…
3668	involves iterating over all running async watchers or all signal numbers.	4495	involves iterating over all running async watchers or all signal numbers.
3669		4496
3670	=back	4497	=back
3671		4498
3672		4499
		4500	=head1 GLOSSARY
		4501
		4502	=over 4
		4503
		4504	=item active
		4505
		4506	A watcher is active as long as it has been started (has been attached to
		4507	an event loop) but not yet stopped (disassociated from the event loop).
		4508
		4509	=item application
		4510
		4511	In this document, an application is whatever is using libev.
		4512
		4513	=item callback
		4514
		4515	The address of a function that is called when some event has been
		4516	detected. Callbacks are being passed the event loop, the watcher that
		4517	received the event, and the actual event bitset.
		4518
		4519	=item callback invocation
		4520
		4521	The act of calling the callback associated with a watcher.
		4522
		4523	=item event
		4524
		4525	A change of state of some external event, such as data now being available
		4526	for reading on a file descriptor, time having passed or simply not having
		4527	any other events happening anymore.
		4528
		4529	In libev, events are represented as single bits (such as C<EV_READ> or
		4530	C<EV_TIMEOUT>).
		4531
		4532	=item event library
		4533
		4534	A software package implementing an event model and loop.
		4535
		4536	=item event loop
		4537
		4538	An entity that handles and processes external events and converts them
		4539	into callback invocations.
		4540
		4541	=item event model
		4542
		4543	The model used to describe how an event loop handles and processes
		4544	watchers and events.
		4545
		4546	=item pending
		4547
		4548	A watcher is pending as soon as the corresponding event has been detected,
		4549	and stops being pending as soon as the watcher will be invoked or its
		4550	pending status is explicitly cleared by the application.
		4551
		4552	A watcher can be pending, but not active. Stopping a watcher also clears
		4553	its pending status.
		4554
		4555	=item real time
		4556
		4557	The physical time that is observed. It is apparently strictly monotonic :)
		4558
		4559	=item wall-clock time
		4560
		4561	The time and date as shown on clocks. Unlike real time, it can actually
		4562	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4563	clock.
		4564
		4565	=item watcher
		4566
		4567	A data structure that describes interest in certain events. Watchers need
		4568	to be started (attached to an event loop) before they can receive events.
		4569
		4570	=item watcher invocation
		4571
		4572	The act of calling the callback associated with a watcher.
		4573
		4574	=back
		4575
3673	=head1 AUTHOR	4576	=head1 AUTHOR
3674		4577
3675	Marc Lehmann <libev@schmorp.de>.	4578	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3676		4579

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