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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_NOSIGFD>
		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
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		413
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
		418
382	For few fds, this backend is a bit little slower than poll and select,	419	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	420	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),	421	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	422	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	423
387	cases and requiring a system call per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
389		440
390	While stopping, setting and starting an I/O watcher in the same iteration	441	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	442	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	443	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	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
395		446	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		447
400	Best performance from this backend is achieved by not unregistering all	448	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	449	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	450	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	451	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
405		459
406	While nominally embeddable in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	461	all kernel versions tested so far.
408		462
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	464	C<EVBACKEND_POLL>.
411		465
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		467
414	Kqueue deserves special mention, as at the time of this writing, it was	468	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	469	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	470	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	471	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	472	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.	473	without API changes to existing programs. For this reason it's not being
		474	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		476	system like NetBSD.
420		477
421	You still can embed kqueue into a normal poll or select backend and use it	478	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	479	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.	480	the target platform). See C<ev_embed> watchers for more info.
424		481
425	It scales in the same way as the epoll backend, but the interface to the	482	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	483	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	484	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	485	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	486	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
431		489
432	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
433		491
434	While nominally embeddable in other event loops, this doesn't work	492	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	493	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	494	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	495	(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,	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
440		498
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	499	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	500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	501	C<NOTE_EOF>.
444		502
…		…
464	might perform better.	522	might perform better.
465		523
466	On the positive side, with the exception of the spurious readiness	524	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	525	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	526	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	527	OS-specific backends (I vastly prefer correctness over speed hacks).
470		528
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	530	C<EVBACKEND_POLL>.
473		531
474	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
…		…
479		537
480	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
481		539
482	=back	540	=back
483		541
484	If one or more of these are or'ed into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
487		546
488	Example: This is the most typical usage.	547	Example: This is the most typical usage.
489		548
490	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	587	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	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	589	for example).
531		590
532	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
535		594
536	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
540		599
541	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
542		601
543	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
582		641
583	This value can sometimes be useful as a generation counter of sorts (it	642	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	643	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
586		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
		657
587	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
588		659
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	661	use.
591		662
…		…
605		676
606	This function is rarely useful, but when some event callback runs for a	677	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	678	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	679	the current time is a good idea.
609		680
610	See also "The special problem of time updates" in the C<ev_timer> section.	681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
611		708
612	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
613		710
614	Finally, this is it, the event handler. This function usually is called	711	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	712	after you have initialised all your watchers and you want to start
616	events.	713	handling events.
617		714
618	If the flags argument is specified as C<0>, it will not return until	715	If the flags argument is specified as C<0>, it will not return until
619	either no event watchers are active anymore or C<ev_unloop> was called.	716	either no event watchers are active anymore or C<ev_unloop> was called.
620		717
621	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	728	the loop.
632		729
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	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	731	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	732	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	733	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	734	user-registered callback will be called), and will return after one
638	iteration of the loop.	735	iteration of the loop.
639		736
640	This is useful if you are waiting for some external event in conjunction	737	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	738	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		796
700	If you have a watcher you never unregister that should not keep C<ev_loop>	797	If you have a watcher you never unregister that should not keep C<ev_loop>
701	from returning, call ev_unref() after starting, and ev_ref() before	798	from returning, call ev_unref() after starting, and ev_ref() before
702	stopping it.	799	stopping it.
703		800
704	As an example, libev itself uses this for its internal signal pipe: It is	801	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	802	is not visible to the libev user and should not keep C<ev_loop> from
706	if no event watchers registered by it are active. It is also an excellent	803	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	804	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	805	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	806	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	807	before, respectively. Note also that libev might stop watchers itself
		808	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		809	in the callback).
711		810
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	812	running when nothing else is active.
714		813
715	struct ev_signal exitsig;	814	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	815	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	816	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	817	evf_unref (loop);
719		818
720	Example: For some weird reason, unregister the above signal handler again.	819	Example: For some weird reason, unregister the above signal handler again.
…		…
744		843
745	By setting a higher I<io collect interval> you allow libev to spend more	844	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	845	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	847	C<ev_timer>) will be not affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
750		851
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	854	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		857
757	Many (busy) programs can usually benefit by setting the I/O collect	858	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	859	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	860	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	861	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
762		867
763	Setting the I<timeout collect interval> can improve the opportunity for	868	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	869	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	870	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	871	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	873	they fire on, say, one-second boundaries only.
769		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
		945
770	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
771		947
772	This function only does something when C<EV_VERIFY> support has been	948	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	949	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	950	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	951	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	952	error and call C<abort ()>.
777		953
778	This can be used to catch bugs inside libev itself: under normal	954	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	958	=back
783		959
784		960
785	=head1 ANATOMY OF A WATCHER	961	=head1 ANATOMY OF A WATCHER
786		962
		963	In the following description, uppercase C<TYPE> in names stands for the
		964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		965	watchers and C<ev_io_start> for I/O watchers.
		966
787	A watcher is a structure that you create and register to record your	967	A watcher is a structure that you create and register to record your
788	interest in some event. For instance, if you want to wait for STDIN to	968	interest in some event. For instance, if you want to wait for STDIN to
789	become readable, you would create an C<ev_io> watcher for that:	969	become readable, you would create an C<ev_io> watcher for that:
790		970
791	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	972	{
793	ev_io_stop (w);	973	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	974	ev_unloop (loop, EVUNLOOP_ALL);
795	}	975	}
796		976
797	struct ev_loop *loop = ev_default_loop (0);	977	struct ev_loop *loop = ev_default_loop (0);
		978
798	struct ev_io stdin_watcher;	979	ev_io stdin_watcher;
		980
799	ev_init (&stdin_watcher, my_cb);	981	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	983	ev_io_start (loop, &stdin_watcher);
		984
802	ev_loop (loop, 0);	985	ev_loop (loop, 0);
803		986
804	As you can see, you are responsible for allocating the memory for your	987	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	988	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	989	stack).
		990
		991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		993
808	Each watcher structure must be initialised by a call to C<ev_init	994	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	995	(watcher *, callback)>, which expects a callback to be provided. This
810	callback gets invoked each time the event occurs (or, in the case of I/O	996	callback gets invoked each time the event occurs (or, in the case of I/O
811	watchers, each time the event loop detects that the file descriptor given	997	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	998	is readable and/or writable).
813		999
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1001	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1002	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1003	ev_TYPE_init (watcher *, callback, ...) >>.
818		1004
819	To make the watcher actually watch out for events, you have to start it	1005	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1006	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1007	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1008	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1009
824	As long as your watcher is active (has been started but not stopped) you	1010	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1011	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1012	reinitialise it or call its C<ev_TYPE_set> macro.
827		1013
828	Each and every callback receives the event loop pointer as first, the	1014	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1015	registered watcher structure as second, and a bitset of received events as
830	third argument.	1016	third argument.
831		1017
…		…
889		1075
890	=item C<EV_ASYNC>	1076	=item C<EV_ASYNC>
891		1077
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1078	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1079
		1080	=item C<EV_CUSTOM>
		1081
		1082	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1083	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1084
894	=item C<EV_ERROR>	1085	=item C<EV_ERROR>
895		1086
896	An unspecified error has occurred, the watcher has been stopped. This might	1087	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1088	happen because the watcher could not be properly started because libev
898	ran out of memory, a file descriptor was found to be closed or any other	1089	ran out of memory, a file descriptor was found to be closed or any other
		1090	problem. Libev considers these application bugs.
		1091
899	problem. You best act on it by reporting the problem and somehow coping	1092	You best act on it by reporting the problem and somehow coping with the
900	with the watcher being stopped.	1093	watcher being stopped. Note that well-written programs should not receive
		1094	an error ever, so when your watcher receives it, this usually indicates a
		1095	bug in your program.
901		1096
902	Libev will usually signal a few "dummy" events together with an error, for	1097	Libev will usually signal a few "dummy" events together with an error, for
903	example it might indicate that a fd is readable or writable, and if your	1098	example it might indicate that a fd is readable or writable, and if your
904	callbacks is well-written it can just attempt the operation and cope with	1099	callbacks is well-written it can just attempt the operation and cope with
905	the error from read() or write(). This will not work in multi-threaded	1100	the error from read() or write(). This will not work in multi-threaded
…		…
908		1103
909	=back	1104	=back
910		1105
911	=head2 GENERIC WATCHER FUNCTIONS	1106	=head2 GENERIC WATCHER FUNCTIONS
912		1107
913	In the following description, C<TYPE> stands for the watcher type,
914	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
915
916	=over 4	1108	=over 4
917		1109
918	=item C<ev_init> (ev_TYPE *watcher, callback)	1110	=item C<ev_init> (ev_TYPE *watcher, callback)
919		1111
920	This macro initialises the generic portion of a watcher. The contents	1112	This macro initialises the generic portion of a watcher. The contents
…		…
925	which rolls both calls into one.	1117	which rolls both calls into one.
926		1118
927	You can reinitialise a watcher at any time as long as it has been stopped	1119	You can reinitialise a watcher at any time as long as it has been stopped
928	(or never started) and there are no pending events outstanding.	1120	(or never started) and there are no pending events outstanding.
929		1121
930	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1122	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
931	int revents)>.	1123	int revents)>.
932		1124
933	Example: Initialise an C<ev_io> watcher in two steps.	1125	Example: Initialise an C<ev_io> watcher in two steps.
934		1126
935	ev_io w;	1127	ev_io w;
…		…
969		1161
970	ev_io_start (EV_DEFAULT_UC, &w);	1162	ev_io_start (EV_DEFAULT_UC, &w);
971		1163
972	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
973		1165
974	Stops the given watcher again (if active) and clears the pending	1166	Stops the given watcher if active, and clears the pending status (whether
		1167	the watcher was active or not).
		1168
975	status. It is possible that stopped watchers are pending (for example,	1169	It is possible that stopped watchers are pending - for example,
976	non-repeating timers are being stopped when they become pending), but	1170	non-repeating timers are being stopped when they become pending - but
977	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1171	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
978	you want to free or reuse the memory used by the watcher it is therefore a	1172	pending. If you want to free or reuse the memory used by the watcher it is
979	good idea to always call its C<ev_TYPE_stop> function.	1173	therefore a good idea to always call its C<ev_TYPE_stop> function.
980		1174
981	=item bool ev_is_active (ev_TYPE *watcher)	1175	=item bool ev_is_active (ev_TYPE *watcher)
982		1176
983	Returns a true value iff the watcher is active (i.e. it has been started	1177	Returns a true value iff the watcher is active (i.e. it has been started
984	and not yet been stopped). As long as a watcher is active you must not modify	1178	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1010	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1011	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
1012	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
1013	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
1014		1208
1015	This means that priorities are I<only> used for ordering callback
1016	invocation after new events have been received. This is useful, for
1017	example, to reduce latency after idling, or more often, to bind two
1018	watchers on the same event and make sure one is called first.
1019
1020	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
1021	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
1022		1211
1023	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
1024	pending.	1213	pending.
1025		1214
		1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1216	fine, as long as you do not mind that the priority value you query might
		1217	or might not have been clamped to the valid range.
		1218
1026	The default priority used by watchers when no priority has been set is	1219	The default priority used by watchers when no priority has been set is
1027	always C<0>, which is supposed to not be too high and not be too low :).	1220	always C<0>, which is supposed to not be too high and not be too low :).
1028		1221
1029	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1030	fine, as long as you do not mind that the priority value you query might	1223	priorities.
1031	or might not have been adjusted to be within valid range.
1032		1224
1033	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1034		1226
1035	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1036	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1043	returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
1044	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1045		1237
1046	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1047	callback to be invoked, which can be accomplished with this function.	1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
1048		1254
1049	=back	1255	=back
1050		1256
1051		1257
1052	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1058	member, you can also "subclass" the watcher type and provide your own	1264	member, you can also "subclass" the watcher type and provide your own
1059	data:	1265	data:
1060		1266
1061	struct my_io	1267	struct my_io
1062	{	1268	{
1063	struct ev_io io;	1269	ev_io io;
1064	int otherfd;	1270	int otherfd;
1065	void *somedata;	1271	void *somedata;
1066	struct whatever *mostinteresting;	1272	struct whatever *mostinteresting;
1067	};	1273	};
1068		1274
…		…
1071	ev_io_init (&w.io, my_cb, fd, EV_READ);	1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1072		1278
1073	And since your callback will be called with a pointer to the watcher, you	1279	And since your callback will be called with a pointer to the watcher, you
1074	can cast it back to your own type:	1280	can cast it back to your own type:
1075		1281
1076	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1077	{	1283	{
1078	struct my_io *w = (struct my_io *)w_;	1284	struct my_io *w = (struct my_io *)w_;
1079	...	1285	...
1080	}	1286	}
1081		1287
…		…
1099	programmers):	1305	programmers):
1100		1306
1101	#include <stddef.h>	1307	#include <stddef.h>
1102		1308
1103	static void	1309	static void
1104	t1_cb (EV_P_ struct ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
1105	{	1311	{
1106	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1107	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1108	}	1314	}
1109		1315
1110	static void	1316	static void
1111	t2_cb (EV_P_ struct ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1112	{	1318	{
1113	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1114	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1115	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1116		1425
1117		1426
1118	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1119		1428
1120	This section describes each watcher in detail, but will not repeat	1429	This section describes each watcher in detail, but will not repeat
…		…
1146	descriptors to non-blocking mode is also usually a good idea (but not	1455	descriptors to non-blocking mode is also usually a good idea (but not
1147	required if you know what you are doing).	1456	required if you know what you are doing).
1148		1457
1149	If you cannot use non-blocking mode, then force the use of a	1458	If you cannot use non-blocking mode, then force the use of a
1150	known-to-be-good backend (at the time of this writing, this includes only	1459	known-to-be-good backend (at the time of this writing, this includes only
1151	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1152		1463
1153	Another thing you have to watch out for is that it is quite easy to	1464	Another thing you have to watch out for is that it is quite easy to
1154	receive "spurious" readiness notifications, that is your callback might	1465	receive "spurious" readiness notifications, that is your callback might
1155	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1156	because there is no data. Not only are some backends known to create a	1467	because there is no data. Not only are some backends known to create a
…		…
1251	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1562	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1252	readable, but only once. Since it is likely line-buffered, you could	1563	readable, but only once. Since it is likely line-buffered, you could
1253	attempt to read a whole line in the callback.	1564	attempt to read a whole line in the callback.
1254		1565
1255	static void	1566	static void
1256	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1567	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1257	{	1568	{
1258	ev_io_stop (loop, w);	1569	ev_io_stop (loop, w);
1259	.. read from stdin here (or from w->fd) and handle any I/O errors	1570	.. read from stdin here (or from w->fd) and handle any I/O errors
1260	}	1571	}
1261		1572
1262	...	1573	...
1263	struct ev_loop *loop = ev_default_init (0);	1574	struct ev_loop *loop = ev_default_init (0);
1264	struct ev_io stdin_readable;	1575	ev_io stdin_readable;
1265	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1266	ev_io_start (loop, &stdin_readable);	1577	ev_io_start (loop, &stdin_readable);
1267	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1268		1579
1269		1580
…		…
1277	year, it will still time out after (roughly) one hour. "Roughly" because	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1278	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1279	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
1280		1591
1281	The callback is guaranteed to be invoked only I<after> its timeout has	1592	The callback is guaranteed to be invoked only I<after> its timeout has
1282	passed, but if multiple timers become ready during the same loop iteration	1593	passed (not I<at>, so on systems with very low-resolution clocks this
1283	then order of execution is undefined.	1594	might introduce a small delay). If multiple timers become ready during the
		1595	same loop iteration then the ones with earlier time-out values are invoked
		1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
		1598
		1599	=head3 Be smart about timeouts
		1600
		1601	Many real-world problems involve some kind of timeout, usually for error
		1602	recovery. A typical example is an HTTP request - if the other side hangs,
		1603	you want to raise some error after a while.
		1604
		1605	What follows are some ways to handle this problem, from obvious and
		1606	inefficient to smart and efficient.
		1607
		1608	In the following, a 60 second activity timeout is assumed - a timeout that
		1609	gets reset to 60 seconds each time there is activity (e.g. each time some
		1610	data or other life sign was received).
		1611
		1612	=over 4
		1613
		1614	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1615
		1616	This is the most obvious, but not the most simple way: In the beginning,
		1617	start the watcher:
		1618
		1619	ev_timer_init (timer, callback, 60., 0.);
		1620	ev_timer_start (loop, timer);
		1621
		1622	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1623	and start it again:
		1624
		1625	ev_timer_stop (loop, timer);
		1626	ev_timer_set (timer, 60., 0.);
		1627	ev_timer_start (loop, timer);
		1628
		1629	This is relatively simple to implement, but means that each time there is
		1630	some activity, libev will first have to remove the timer from its internal
		1631	data structure and then add it again. Libev tries to be fast, but it's
		1632	still not a constant-time operation.
		1633
		1634	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1635
		1636	This is the easiest way, and involves using C<ev_timer_again> instead of
		1637	C<ev_timer_start>.
		1638
		1639	To implement this, configure an C<ev_timer> with a C<repeat> value
		1640	of C<60> and then call C<ev_timer_again> at start and each time you
		1641	successfully read or write some data. If you go into an idle state where
		1642	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1643	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1644
		1645	That means you can ignore both the C<ev_timer_start> function and the
		1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1647	member and C<ev_timer_again>.
		1648
		1649	At start:
		1650
		1651	ev_init (timer, callback);
		1652	timer->repeat = 60.;
		1653	ev_timer_again (loop, timer);
		1654
		1655	Each time there is some activity:
		1656
		1657	ev_timer_again (loop, timer);
		1658
		1659	It is even possible to change the time-out on the fly, regardless of
		1660	whether the watcher is active or not:
		1661
		1662	timer->repeat = 30.;
		1663	ev_timer_again (loop, timer);
		1664
		1665	This is slightly more efficient then stopping/starting the timer each time
		1666	you want to modify its timeout value, as libev does not have to completely
		1667	remove and re-insert the timer from/into its internal data structure.
		1668
		1669	It is, however, even simpler than the "obvious" way to do it.
		1670
		1671	=item 3. Let the timer time out, but then re-arm it as required.
		1672
		1673	This method is more tricky, but usually most efficient: Most timeouts are
		1674	relatively long compared to the intervals between other activity - in
		1675	our example, within 60 seconds, there are usually many I/O events with
		1676	associated activity resets.
		1677
		1678	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1679	but remember the time of last activity, and check for a real timeout only
		1680	within the callback:
		1681
		1682	ev_tstamp last_activity; // time of last activity
		1683
		1684	static void
		1685	callback (EV_P_ ev_timer *w, int revents)
		1686	{
		1687	ev_tstamp now = ev_now (EV_A);
		1688	ev_tstamp timeout = last_activity + 60.;
		1689
		1690	// if last_activity + 60. is older than now, we did time out
		1691	if (timeout < now)
		1692	{
		1693	// timeout occured, take action
		1694	}
		1695	else
		1696	{
		1697	// callback was invoked, but there was some activity, re-arm
		1698	// the watcher to fire in last_activity + 60, which is
		1699	// guaranteed to be in the future, so "again" is positive:
		1700	w->repeat = timeout - now;
		1701	ev_timer_again (EV_A_ w);
		1702	}
		1703	}
		1704
		1705	To summarise the callback: first calculate the real timeout (defined
		1706	as "60 seconds after the last activity"), then check if that time has
		1707	been reached, which means something I<did>, in fact, time out. Otherwise
		1708	the callback was invoked too early (C<timeout> is in the future), so
		1709	re-schedule the timer to fire at that future time, to see if maybe we have
		1710	a timeout then.
		1711
		1712	Note how C<ev_timer_again> is used, taking advantage of the
		1713	C<ev_timer_again> optimisation when the timer is already running.
		1714
		1715	This scheme causes more callback invocations (about one every 60 seconds
		1716	minus half the average time between activity), but virtually no calls to
		1717	libev to change the timeout.
		1718
		1719	To start the timer, simply initialise the watcher and set C<last_activity>
		1720	to the current time (meaning we just have some activity :), then call the
		1721	callback, which will "do the right thing" and start the timer:
		1722
		1723	ev_init (timer, callback);
		1724	last_activity = ev_now (loop);
		1725	callback (loop, timer, EV_TIMEOUT);
		1726
		1727	And when there is some activity, simply store the current time in
		1728	C<last_activity>, no libev calls at all:
		1729
		1730	last_actiivty = ev_now (loop);
		1731
		1732	This technique is slightly more complex, but in most cases where the
		1733	time-out is unlikely to be triggered, much more efficient.
		1734
		1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1736	callback :) - just change the timeout and invoke the callback, which will
		1737	fix things for you.
		1738
		1739	=item 4. Wee, just use a double-linked list for your timeouts.
		1740
		1741	If there is not one request, but many thousands (millions...), all
		1742	employing some kind of timeout with the same timeout value, then one can
		1743	do even better:
		1744
		1745	When starting the timeout, calculate the timeout value and put the timeout
		1746	at the I<end> of the list.
		1747
		1748	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1749	the list is expected to fire (for example, using the technique #3).
		1750
		1751	When there is some activity, remove the timer from the list, recalculate
		1752	the timeout, append it to the end of the list again, and make sure to
		1753	update the C<ev_timer> if it was taken from the beginning of the list.
		1754
		1755	This way, one can manage an unlimited number of timeouts in O(1) time for
		1756	starting, stopping and updating the timers, at the expense of a major
		1757	complication, and having to use a constant timeout. The constant timeout
		1758	ensures that the list stays sorted.
		1759
		1760	=back
		1761
		1762	So which method the best?
		1763
		1764	Method #2 is a simple no-brain-required solution that is adequate in most
		1765	situations. Method #3 requires a bit more thinking, but handles many cases
		1766	better, and isn't very complicated either. In most case, choosing either
		1767	one is fine, with #3 being better in typical situations.
		1768
		1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1770	rather complicated, but extremely efficient, something that really pays
		1771	off after the first million or so of active timers, i.e. it's usually
		1772	overkill :)
1284		1773
1285	=head3 The special problem of time updates	1774	=head3 The special problem of time updates
1286		1775
1287	Establishing the current time is a costly operation (it usually takes at	1776	Establishing the current time is a costly operation (it usually takes at
1288	least two system calls): EV therefore updates its idea of the current	1777	least two system calls): EV therefore updates its idea of the current
…		…
1300		1789
1301	If the event loop is suspended for a long time, you can also force an	1790	If the event loop is suspended for a long time, you can also force an
1302	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1303	()>.	1792	()>.
1304		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
		1823
1305	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1306		1825
1307	=over 4	1826	=over 4
1308		1827
1309	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1828	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1332	If the timer is started but non-repeating, stop it (as if it timed out).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1333		1852
1334	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1335	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1336		1855
1337	This sounds a bit complicated, but here is a useful and typical	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1338	example: Imagine you have a TCP connection and you want a so-called idle	1857	usage example.
1339	timeout, that is, you want to be called when there have been, say, 60
1340	seconds of inactivity on the socket. The easiest way to do this is to
1341	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1342	C<ev_timer_again> each time you successfully read or write some data. If
1343	you go into an idle state where you do not expect data to travel on the
1344	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1345	automatically restart it if need be.
1346		1858
1347	That means you can ignore the C<after> value and C<ev_timer_start>	1859	=item ev_timer_remaining (loop, ev_timer *)
1348	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1349		1860
1350	ev_timer_init (timer, callback, 0., 5.);	1861	Returns the remaining time until a timer fires. If the timer is active,
1351	ev_timer_again (loop, timer);	1862	then this time is relative to the current event loop time, otherwise it's
1352	...	1863	the timeout value currently configured.
1353	timer->again = 17.;
1354	ev_timer_again (loop, timer);
1355	...
1356	timer->again = 10.;
1357	ev_timer_again (loop, timer);
1358		1864
1359	This is more slightly efficient then stopping/starting the timer each time	1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1360	you want to modify its timeout value.	1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
1361		1867	will return C<4>. When the timer expires and is restarted, it will return
1362	Note, however, that it is often even more efficient to remember the	1868	roughly C<7> (likely slightly less as callback invocation takes some time,
1363	time of the last activity and let the timer time-out naturally. In the	1869	too), and so on.
1364	callback, you then check whether the time-out is real, or, if there was
1365	some activity, you reschedule the watcher to time-out in "last_activity +
1366	timeout - ev_now ()" seconds.
1367		1870
1368	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1369		1872
1370	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1371	or C<ev_timer_again> is called, and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1376	=head3 Examples	1879	=head3 Examples
1377		1880
1378	Example: Create a timer that fires after 60 seconds.	1881	Example: Create a timer that fires after 60 seconds.
1379		1882
1380	static void	1883	static void
1381	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1884	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1382	{	1885	{
1383	.. one minute over, w is actually stopped right here	1886	.. one minute over, w is actually stopped right here
1384	}	1887	}
1385		1888
1386	struct ev_timer mytimer;	1889	ev_timer mytimer;
1387	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1388	ev_timer_start (loop, &mytimer);	1891	ev_timer_start (loop, &mytimer);
1389		1892
1390	Example: Create a timeout timer that times out after 10 seconds of	1893	Example: Create a timeout timer that times out after 10 seconds of
1391	inactivity.	1894	inactivity.
1392		1895
1393	static void	1896	static void
1394	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1897	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1395	{	1898	{
1396	.. ten seconds without any activity	1899	.. ten seconds without any activity
1397	}	1900	}
1398		1901
1399	struct ev_timer mytimer;	1902	ev_timer mytimer;
1400	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1401	ev_timer_again (&mytimer); /* start timer */	1904	ev_timer_again (&mytimer); /* start timer */
1402	ev_loop (loop, 0);	1905	ev_loop (loop, 0);
1403		1906
1404	// and in some piece of code that gets executed on any "activity":	1907	// and in some piece of code that gets executed on any "activity":
…		…
1409	=head2 C<ev_periodic> - to cron or not to cron?	1912	=head2 C<ev_periodic> - to cron or not to cron?
1410		1913
1411	Periodic watchers are also timers of a kind, but they are very versatile	1914	Periodic watchers are also timers of a kind, but they are very versatile
1412	(and unfortunately a bit complex).	1915	(and unfortunately a bit complex).
1413		1916
1414	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1917	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1415	but on wall clock time (absolute time). You can tell a periodic watcher	1918	relative time, the physical time that passes) but on wall clock time
1416	to trigger after some specific point in time. For example, if you tell a	1919	(absolute time, the thing you can read on your calender or clock). The
1417	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1920	difference is that wall clock time can run faster or slower than real
1418	+ 10.>, that is, an absolute time not a delay) and then reset your system	1921	time, and time jumps are not uncommon (e.g. when you adjust your
1419	clock to January of the previous year, then it will take more than year	1922	wrist-watch).
1420	to trigger the event (unlike an C<ev_timer>, which would still trigger
1421	roughly 10 seconds later as it uses a relative timeout).
1422		1923
		1924	You can tell a periodic watcher to trigger after some specific point
		1925	in time: for example, if you tell a periodic watcher to trigger "in 10
		1926	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1927	not a delay) and then reset your system clock to January of the previous
		1928	year, then it will take a year or more to trigger the event (unlike an
		1929	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1930	it, as it uses a relative timeout).
		1931
1423	C<ev_periodic>s can also be used to implement vastly more complex timers,	1932	C<ev_periodic> watchers can also be used to implement vastly more complex
1424	such as triggering an event on each "midnight, local time", or other	1933	timers, such as triggering an event on each "midnight, local time", or
1425	complicated rules.	1934	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1935	those cannot react to time jumps.
1426		1936
1427	As with timers, the callback is guaranteed to be invoked only when the	1937	As with timers, the callback is guaranteed to be invoked only when the
1428	time (C<at>) has passed, but if multiple periodic timers become ready	1938	point in time where it is supposed to trigger has passed. If multiple
1429	during the same loop iteration, then order of execution is undefined.	1939	timers become ready during the same loop iteration then the ones with
		1940	earlier time-out values are invoked before ones with later time-out values
		1941	(but this is no longer true when a callback calls C<ev_loop> recursively).
1430		1942
1431	=head3 Watcher-Specific Functions and Data Members	1943	=head3 Watcher-Specific Functions and Data Members
1432		1944
1433	=over 4	1945	=over 4
1434		1946
1435	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1947	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1948
1437	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1949	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1438		1950
1439	Lots of arguments, lets sort it out... There are basically three modes of	1951	Lots of arguments, let's sort it out... There are basically three modes of
1440	operation, and we will explain them from simplest to most complex:	1952	operation, and we will explain them from simplest to most complex:
1441		1953
1442	=over 4	1954	=over 4
1443		1955
1444	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1956	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1445		1957
1446	In this configuration the watcher triggers an event after the wall clock	1958	In this configuration the watcher triggers an event after the wall clock
1447	time C<at> has passed. It will not repeat and will not adjust when a time	1959	time C<offset> has passed. It will not repeat and will not adjust when a
1448	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1960	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1449	only run when the system clock reaches or surpasses this time.	1961	will be stopped and invoked when the system clock reaches or surpasses
		1962	this point in time.
1450		1963
1451	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1964	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1452		1965
1453	In this mode the watcher will always be scheduled to time out at the next	1966	In this mode the watcher will always be scheduled to time out at the next
1454	C<at + N * interval> time (for some integer N, which can also be negative)	1967	C<offset + N * interval> time (for some integer N, which can also be
1455	and then repeat, regardless of any time jumps.	1968	negative) and then repeat, regardless of any time jumps. The C<offset>
		1969	argument is merely an offset into the C<interval> periods.
1456		1970
1457	This can be used to create timers that do not drift with respect to the	1971	This can be used to create timers that do not drift with respect to the
1458	system clock, for example, here is a C<ev_periodic> that triggers each	1972	system clock, for example, here is an C<ev_periodic> that triggers each
1459	hour, on the hour:	1973	hour, on the hour (with respect to UTC):
1460		1974
1461	ev_periodic_set (&periodic, 0., 3600., 0);	1975	ev_periodic_set (&periodic, 0., 3600., 0);
1462		1976
1463	This doesn't mean there will always be 3600 seconds in between triggers,	1977	This doesn't mean there will always be 3600 seconds in between triggers,
1464	but only that the callback will be called when the system time shows a	1978	but only that the callback will be called when the system time shows a
1465	full hour (UTC), or more correctly, when the system time is evenly divisible	1979	full hour (UTC), or more correctly, when the system time is evenly divisible
1466	by 3600.	1980	by 3600.
1467		1981
1468	Another way to think about it (for the mathematically inclined) is that	1982	Another way to think about it (for the mathematically inclined) is that
1469	C<ev_periodic> will try to run the callback in this mode at the next possible	1983	C<ev_periodic> will try to run the callback in this mode at the next possible
1470	time where C<time = at (mod interval)>, regardless of any time jumps.	1984	time where C<time = offset (mod interval)>, regardless of any time jumps.
1471		1985
1472	For numerical stability it is preferable that the C<at> value is near	1986	For numerical stability it is preferable that the C<offset> value is near
1473	C<ev_now ()> (the current time), but there is no range requirement for	1987	C<ev_now ()> (the current time), but there is no range requirement for
1474	this value, and in fact is often specified as zero.	1988	this value, and in fact is often specified as zero.
1475		1989
1476	Note also that there is an upper limit to how often a timer can fire (CPU	1990	Note also that there is an upper limit to how often a timer can fire (CPU
1477	speed for example), so if C<interval> is very small then timing stability	1991	speed for example), so if C<interval> is very small then timing stability
1478	will of course deteriorate. Libev itself tries to be exact to be about one	1992	will of course deteriorate. Libev itself tries to be exact to be about one
1479	millisecond (if the OS supports it and the machine is fast enough).	1993	millisecond (if the OS supports it and the machine is fast enough).
1480		1994
1481	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1995	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1482		1996
1483	In this mode the values for C<interval> and C<at> are both being	1997	In this mode the values for C<interval> and C<offset> are both being
1484	ignored. Instead, each time the periodic watcher gets scheduled, the	1998	ignored. Instead, each time the periodic watcher gets scheduled, the
1485	reschedule callback will be called with the watcher as first, and the	1999	reschedule callback will be called with the watcher as first, and the
1486	current time as second argument.	2000	current time as second argument.
1487		2001
1488	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2002	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1489	ever, or make ANY event loop modifications whatsoever>.	2003	or make ANY other event loop modifications whatsoever, unless explicitly
		2004	allowed by documentation here>.
1490		2005
1491	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2006	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1492	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2007	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1493	only event loop modification you are allowed to do).	2008	only event loop modification you are allowed to do).
1494		2009
1495	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2010	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1496	*w, ev_tstamp now)>, e.g.:	2011	*w, ev_tstamp now)>, e.g.:
1497		2012
		2013	static ev_tstamp
1498	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2014	my_rescheduler (ev_periodic *w, ev_tstamp now)
1499	{	2015	{
1500	return now + 60.;	2016	return now + 60.;
1501	}	2017	}
1502		2018
1503	It must return the next time to trigger, based on the passed time value	2019	It must return the next time to trigger, based on the passed time value
…		…
1523	a different time than the last time it was called (e.g. in a crond like	2039	a different time than the last time it was called (e.g. in a crond like
1524	program when the crontabs have changed).	2040	program when the crontabs have changed).
1525		2041
1526	=item ev_tstamp ev_periodic_at (ev_periodic *)	2042	=item ev_tstamp ev_periodic_at (ev_periodic *)
1527		2043
1528	When active, returns the absolute time that the watcher is supposed to	2044	When active, returns the absolute time that the watcher is supposed
1529	trigger next.	2045	to trigger next. This is not the same as the C<offset> argument to
		2046	C<ev_periodic_set>, but indeed works even in interval and manual
		2047	rescheduling modes.
1530		2048
1531	=item ev_tstamp offset [read-write]	2049	=item ev_tstamp offset [read-write]
1532		2050
1533	When repeating, this contains the offset value, otherwise this is the	2051	When repeating, this contains the offset value, otherwise this is the
1534	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2052	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2053	although libev might modify this value for better numerical stability).
1535		2054
1536	Can be modified any time, but changes only take effect when the periodic	2055	Can be modified any time, but changes only take effect when the periodic
1537	timer fires or C<ev_periodic_again> is being called.	2056	timer fires or C<ev_periodic_again> is being called.
1538		2057
1539	=item ev_tstamp interval [read-write]	2058	=item ev_tstamp interval [read-write]
1540		2059
1541	The current interval value. Can be modified any time, but changes only	2060	The current interval value. Can be modified any time, but changes only
1542	take effect when the periodic timer fires or C<ev_periodic_again> is being	2061	take effect when the periodic timer fires or C<ev_periodic_again> is being
1543	called.	2062	called.
1544		2063
1545	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2064	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1546		2065
1547	The current reschedule callback, or C<0>, if this functionality is	2066	The current reschedule callback, or C<0>, if this functionality is
1548	switched off. Can be changed any time, but changes only take effect when	2067	switched off. Can be changed any time, but changes only take effect when
1549	the periodic timer fires or C<ev_periodic_again> is being called.	2068	the periodic timer fires or C<ev_periodic_again> is being called.
1550		2069
…		…
1555	Example: Call a callback every hour, or, more precisely, whenever the	2074	Example: Call a callback every hour, or, more precisely, whenever the
1556	system time is divisible by 3600. The callback invocation times have	2075	system time is divisible by 3600. The callback invocation times have
1557	potentially a lot of jitter, but good long-term stability.	2076	potentially a lot of jitter, but good long-term stability.
1558		2077
1559	static void	2078	static void
1560	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1561	{	2080	{
1562	... its now a full hour (UTC, or TAI or whatever your clock follows)	2081	... its now a full hour (UTC, or TAI or whatever your clock follows)
1563	}	2082	}
1564		2083
1565	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1566	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2085	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1567	ev_periodic_start (loop, &hourly_tick);	2086	ev_periodic_start (loop, &hourly_tick);
1568		2087
1569	Example: The same as above, but use a reschedule callback to do it:	2088	Example: The same as above, but use a reschedule callback to do it:
1570		2089
1571	#include <math.h>	2090	#include <math.h>
1572		2091
1573	static ev_tstamp	2092	static ev_tstamp
1574	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2093	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1575	{	2094	{
1576	return now + (3600. - fmod (now, 3600.));	2095	return now + (3600. - fmod (now, 3600.));
1577	}	2096	}
1578		2097
1579	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2098	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1580		2099
1581	Example: Call a callback every hour, starting now:	2100	Example: Call a callback every hour, starting now:
1582		2101
1583	struct ev_periodic hourly_tick;	2102	ev_periodic hourly_tick;
1584	ev_periodic_init (&hourly_tick, clock_cb,	2103	ev_periodic_init (&hourly_tick, clock_cb,
1585	fmod (ev_now (loop), 3600.), 3600., 0);	2104	fmod (ev_now (loop), 3600.), 3600., 0);
1586	ev_periodic_start (loop, &hourly_tick);	2105	ev_periodic_start (loop, &hourly_tick);
1587		2106
1588		2107
…		…
1591	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1592	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1593	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1594	normal event processing, like any other event.	2113	normal event processing, like any other event.
1595		2114
1596	If you want signals asynchronously, just use C<sigaction> as you would	2115	If you want signals to be delivered truly asynchronously, just use
1597	do without libev and forget about sharing the signal. You can even use	2116	C<sigaction> as you would do without libev and forget about sharing
1598	C<ev_async> from a signal handler to synchronously wake up an event loop.	2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
1599		2119
1600	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1601	first watcher gets started will libev actually register a signal handler	2126	When the first watcher gets started will libev actually register something
1602	with the kernel (thus it coexists with your own signal handlers as long as	2127	with the kernel (thus it coexists with your own signal handlers as long as
1603	you don't register any with libev for the same signal). Similarly, when	2128	you don't register any with libev for the same signal).
1604	the last signal watcher for a signal is stopped, libev will reset the
1605	signal handler to SIG_DFL (regardless of what it was set to before).
1606		2129
1607	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1608	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1609	interrupted. If you have a problem with system calls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1610	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1611	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1612		2160
1613	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1614		2162
1615	=over 4	2163	=over 4
1616		2164
…		…
1630	=head3 Examples	2178	=head3 Examples
1631		2179
1632	Example: Try to exit cleanly on SIGINT.	2180	Example: Try to exit cleanly on SIGINT.
1633		2181
1634	static void	2182	static void
1635	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1636	{	2184	{
1637	ev_unloop (loop, EVUNLOOP_ALL);	2185	ev_unloop (loop, EVUNLOOP_ALL);
1638	}	2186	}
1639		2187
1640	struct ev_signal signal_watcher;	2188	ev_signal signal_watcher;
1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1642	ev_signal_start (loop, &signal_watcher);	2190	ev_signal_start (loop, &signal_watcher);
1643		2191
1644		2192
1645	=head2 C<ev_child> - watch out for process status changes	2193	=head2 C<ev_child> - watch out for process status changes
…		…
1648	some child status changes (most typically when a child of yours dies or	2196	some child status changes (most typically when a child of yours dies or
1649	exits). It is permissible to install a child watcher I<after> the child	2197	exits). It is permissible to install a child watcher I<after> the child
1650	has been forked (which implies it might have already exited), as long	2198	has been forked (which implies it might have already exited), as long
1651	as the event loop isn't entered (or is continued from a watcher), i.e.,	2199	as the event loop isn't entered (or is continued from a watcher), i.e.,
1652	forking and then immediately registering a watcher for the child is fine,	2200	forking and then immediately registering a watcher for the child is fine,
1653	but forking and registering a watcher a few event loop iterations later is	2201	but forking and registering a watcher a few event loop iterations later or
1654	not.	2202	in the next callback invocation is not.
1655		2203
1656	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1657	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
1658		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
1659	=head3 Process Interaction	2211	=head3 Process Interaction
1660		2212
1661	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1662	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1663	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
1664	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1665	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1666	children, even ones not watched.	2218	children, even ones not watched.
1667		2219
1668	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1678	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
1679		2231
1680	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
1681	child terminates, so normally one needs to stop the watcher in the	2233	child terminates, so normally one needs to stop the watcher in the
1682	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
1683	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1684		2237
1685	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1686		2239
1687	=over 4	2240	=over 4
1688		2241
…		…
1720	its completion.	2273	its completion.
1721		2274
1722	ev_child cw;	2275	ev_child cw;
1723		2276
1724	static void	2277	static void
1725	child_cb (EV_P_ struct ev_child *w, int revents)	2278	child_cb (EV_P_ ev_child *w, int revents)
1726	{	2279	{
1727	ev_child_stop (EV_A_ w);	2280	ev_child_stop (EV_A_ w);
1728	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2281	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1729	}	2282	}
1730		2283
…		…
1745		2298
1746		2299
1747	=head2 C<ev_stat> - did the file attributes just change?	2300	=head2 C<ev_stat> - did the file attributes just change?
1748		2301
1749	This watches a file system path for attribute changes. That is, it calls	2302	This watches a file system path for attribute changes. That is, it calls
1750	C<stat> regularly (or when the OS says it changed) and sees if it changed	2303	C<stat> on that path in regular intervals (or when the OS says it changed)
1751	compared to the last time, invoking the callback if it did.	2304	and sees if it changed compared to the last time, invoking the callback if
		2305	it did.
1752		2306
1753	The path does not need to exist: changing from "path exists" to "path does	2307	The path does not need to exist: changing from "path exists" to "path does
1754	not exist" is a status change like any other. The condition "path does	2308	not exist" is a status change like any other. The condition "path does not
1755	not exist" is signified by the C<st_nlink> field being zero (which is	2309	exist" (or more correctly "path cannot be stat'ed") is signified by the
1756	otherwise always forced to be at least one) and all the other fields of	2310	C<st_nlink> field being zero (which is otherwise always forced to be at
1757	the stat buffer having unspecified contents.	2311	least one) and all the other fields of the stat buffer having unspecified
		2312	contents.
1758		2313
1759	The path I<should> be absolute and I<must not> end in a slash. If it is	2314	The path I<must not> end in a slash or contain special components such as
		2315	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1760	relative and your working directory changes, the behaviour is undefined.	2316	your working directory changes, then the behaviour is undefined.
1761		2317
1762	Since there is no standard kernel interface to do this, the portable	2318	Since there is no portable change notification interface available, the
1763	implementation simply calls C<stat (2)> regularly on the path to see if	2319	portable implementation simply calls C<stat(2)> regularly on the path
1764	it changed somehow. You can specify a recommended polling interval for	2320	to see if it changed somehow. You can specify a recommended polling
1765	this case. If you specify a polling interval of C<0> (highly recommended!)	2321	interval for this case. If you specify a polling interval of C<0> (highly
1766	then a I<suitable, unspecified default> value will be used (which	2322	recommended!) then a I<suitable, unspecified default> value will be used
1767	you can expect to be around five seconds, although this might change	2323	(which you can expect to be around five seconds, although this might
1768	dynamically). Libev will also impose a minimum interval which is currently	2324	change dynamically). Libev will also impose a minimum interval which is
1769	around C<0.1>, but thats usually overkill.	2325	currently around C<0.1>, but that's usually overkill.
1770		2326
1771	This watcher type is not meant for massive numbers of stat watchers,	2327	This watcher type is not meant for massive numbers of stat watchers,
1772	as even with OS-supported change notifications, this can be	2328	as even with OS-supported change notifications, this can be
1773	resource-intensive.	2329	resource-intensive.
1774		2330
1775	At the time of this writing, the only OS-specific interface implemented	2331	At the time of this writing, the only OS-specific interface implemented
1776	is the Linux inotify interface (implementing kqueue support is left as	2332	is the Linux inotify interface (implementing kqueue support is left as an
1777	an exercise for the reader. Note, however, that the author sees no way	2333	exercise for the reader. Note, however, that the author sees no way of
1778	of implementing C<ev_stat> semantics with kqueue).	2334	implementing C<ev_stat> semantics with kqueue, except as a hint).
1779		2335
1780	=head3 ABI Issues (Largefile Support)	2336	=head3 ABI Issues (Largefile Support)
1781		2337
1782	Libev by default (unless the user overrides this) uses the default	2338	Libev by default (unless the user overrides this) uses the default
1783	compilation environment, which means that on systems with large file	2339	compilation environment, which means that on systems with large file
1784	support disabled by default, you get the 32 bit version of the stat	2340	support disabled by default, you get the 32 bit version of the stat
1785	structure. When using the library from programs that change the ABI to	2341	structure. When using the library from programs that change the ABI to
1786	use 64 bit file offsets the programs will fail. In that case you have to	2342	use 64 bit file offsets the programs will fail. In that case you have to
1787	compile libev with the same flags to get binary compatibility. This is	2343	compile libev with the same flags to get binary compatibility. This is
1788	obviously the case with any flags that change the ABI, but the problem is	2344	obviously the case with any flags that change the ABI, but the problem is
1789	most noticeably disabled with ev_stat and large file support.	2345	most noticeably displayed with ev_stat and large file support.
1790		2346
1791	The solution for this is to lobby your distribution maker to make large	2347	The solution for this is to lobby your distribution maker to make large
1792	file interfaces available by default (as e.g. FreeBSD does) and not	2348	file interfaces available by default (as e.g. FreeBSD does) and not
1793	optional. Libev cannot simply switch on large file support because it has	2349	optional. Libev cannot simply switch on large file support because it has
1794	to exchange stat structures with application programs compiled using the	2350	to exchange stat structures with application programs compiled using the
1795	default compilation environment.	2351	default compilation environment.
1796		2352
1797	=head3 Inotify and Kqueue	2353	=head3 Inotify and Kqueue
1798		2354
1799	When C<inotify (7)> support has been compiled into libev (generally only	2355	When C<inotify (7)> support has been compiled into libev and present at
1800	available with Linux) and present at runtime, it will be used to speed up	2356	runtime, it will be used to speed up change detection where possible. The
1801	change detection where possible. The inotify descriptor will be created lazily	2357	inotify descriptor will be created lazily when the first C<ev_stat>
1802	when the first C<ev_stat> watcher is being started.	2358	watcher is being started.
1803		2359
1804	Inotify presence does not change the semantics of C<ev_stat> watchers	2360	Inotify presence does not change the semantics of C<ev_stat> watchers
1805	except that changes might be detected earlier, and in some cases, to avoid	2361	except that changes might be detected earlier, and in some cases, to avoid
1806	making regular C<stat> calls. Even in the presence of inotify support	2362	making regular C<stat> calls. Even in the presence of inotify support
1807	there are many cases where libev has to resort to regular C<stat> polling,	2363	there are many cases where libev has to resort to regular C<stat> polling,
1808	but as long as the path exists, libev usually gets away without polling.	2364	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2365	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2366	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2367	xfs are fully working) libev usually gets away without polling.
1809		2368
1810	There is no support for kqueue, as apparently it cannot be used to	2369	There is no support for kqueue, as apparently it cannot be used to
1811	implement this functionality, due to the requirement of having a file	2370	implement this functionality, due to the requirement of having a file
1812	descriptor open on the object at all times, and detecting renames, unlinks	2371	descriptor open on the object at all times, and detecting renames, unlinks
1813	etc. is difficult.	2372	etc. is difficult.
1814		2373
		2374	=head3 C<stat ()> is a synchronous operation
		2375
		2376	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2377	the process. The exception are C<ev_stat> watchers - those call C<stat
		2378	()>, which is a synchronous operation.
		2379
		2380	For local paths, this usually doesn't matter: unless the system is very
		2381	busy or the intervals between stat's are large, a stat call will be fast,
		2382	as the path data is usually in memory already (except when starting the
		2383	watcher).
		2384
		2385	For networked file systems, calling C<stat ()> can block an indefinite
		2386	time due to network issues, and even under good conditions, a stat call
		2387	often takes multiple milliseconds.
		2388
		2389	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2390	paths, although this is fully supported by libev.
		2391
1815	=head3 The special problem of stat time resolution	2392	=head3 The special problem of stat time resolution
1816		2393
1817	The C<stat ()> system call only supports full-second resolution portably, and	2394	The C<stat ()> system call only supports full-second resolution portably,
1818	even on systems where the resolution is higher, most file systems still	2395	and even on systems where the resolution is higher, most file systems
1819	only support whole seconds.	2396	still only support whole seconds.
1820		2397
1821	That means that, if the time is the only thing that changes, you can	2398	That means that, if the time is the only thing that changes, you can
1822	easily miss updates: on the first update, C<ev_stat> detects a change and	2399	easily miss updates: on the first update, C<ev_stat> detects a change and
1823	calls your callback, which does something. When there is another update	2400	calls your callback, which does something. When there is another update
1824	within the same second, C<ev_stat> will be unable to detect unless the	2401	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1967		2544
1968	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1969		2546
1970	=over 4	2547	=over 4
1971		2548
1972	=item ev_idle_init (ev_signal *, callback)	2549	=item ev_idle_init (ev_idle *, callback)
1973		2550
1974	Initialises and configures the idle watcher - it has no parameters of any	2551	Initialises and configures the idle watcher - it has no parameters of any
1975	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2552	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1976	believe me.	2553	believe me.
1977		2554
…		…
1981		2558
1982	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2559	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1983	callback, free it. Also, use no error checking, as usual.	2560	callback, free it. Also, use no error checking, as usual.
1984		2561
1985	static void	2562	static void
1986	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1987	{	2564	{
1988	free (w);	2565	free (w);
1989	// now do something you wanted to do when the program has	2566	// now do something you wanted to do when the program has
1990	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
1991	}	2568	}
1992		2569
1993	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1994	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
1995	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
1996		2573
1997		2574
1998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1999		2576
2000	Prepare and check watchers are usually (but not always) used in pairs:	2577	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2079		2656
2080	static ev_io iow [nfd];	2657	static ev_io iow [nfd];
2081	static ev_timer tw;	2658	static ev_timer tw;
2082		2659
2083	static void	2660	static void
2084	io_cb (ev_loop *loop, ev_io *w, int revents)	2661	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2085	{	2662	{
2086	}	2663	}
2087		2664
2088	// create io watchers for each fd and a timer before blocking	2665	// create io watchers for each fd and a timer before blocking
2089	static void	2666	static void
2090	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2667	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2091	{	2668	{
2092	int timeout = 3600000;	2669	int timeout = 3600000;
2093	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
2094	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
2095	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2096		2673
2097	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
2098	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2099	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
2100		2677
2101	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
2102	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
2103	{	2680	{
…		…
2110	}	2687	}
2111	}	2688	}
2112		2689
2113	// stop all watchers after blocking	2690	// stop all watchers after blocking
2114	static void	2691	static void
2115	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2692	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2116	{	2693	{
2117	ev_timer_stop (loop, &tw);	2694	ev_timer_stop (loop, &tw);
2118		2695
2119	for (int i = 0; i < nfd; ++i)	2696	for (int i = 0; i < nfd; ++i)
2120	{	2697	{
…		…
2216	some fds have to be watched and handled very quickly (with low latency),	2793	some fds have to be watched and handled very quickly (with low latency),
2217	and even priorities and idle watchers might have too much overhead. In	2794	and even priorities and idle watchers might have too much overhead. In
2218	this case you would put all the high priority stuff in one loop and all	2795	this case you would put all the high priority stuff in one loop and all
2219	the rest in a second one, and embed the second one in the first.	2796	the rest in a second one, and embed the second one in the first.
2220		2797
2221	As long as the watcher is active, the callback will be invoked every time	2798	As long as the watcher is active, the callback will be invoked every
2222	there might be events pending in the embedded loop. The callback must then	2799	time there might be events pending in the embedded loop. The callback
2223	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2800	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2224	their callbacks (you could also start an idle watcher to give the embedded	2801	sweep and invoke their callbacks (the callback doesn't need to invoke the
2225	loop strictly lower priority for example). You can also set the callback	2802	C<ev_embed_sweep> function directly, it could also start an idle watcher
2226	to C<0>, in which case the embed watcher will automatically execute the	2803	to give the embedded loop strictly lower priority for example).
2227	embedded loop sweep.
2228		2804
2229	As long as the watcher is started it will automatically handle events. The	2805	You can also set the callback to C<0>, in which case the embed watcher
2230	callback will be invoked whenever some events have been handled. You can	2806	will automatically execute the embedded loop sweep whenever necessary.
2231	set the callback to C<0> to avoid having to specify one if you are not
2232	interested in that.
2233		2807
2234	Also, there have not currently been made special provisions for forking:	2808	Fork detection will be handled transparently while the C<ev_embed> watcher
2235	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2809	is active, i.e., the embedded loop will automatically be forked when the
2236	but you will also have to stop and restart any C<ev_embed> watchers	2810	embedding loop forks. In other cases, the user is responsible for calling
2237	yourself - but you can use a fork watcher to handle this automatically,	2811	C<ev_loop_fork> on the embedded loop.
2238	and future versions of libev might do just that.
2239		2812
2240	Unfortunately, not all backends are embeddable: only the ones returned by	2813	Unfortunately, not all backends are embeddable: only the ones returned by
2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2814	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2242	portable one.	2815	portable one.
2243		2816
…		…
2288	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2861	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2289	used).	2862	used).
2290		2863
2291	struct ev_loop *loop_hi = ev_default_init (0);	2864	struct ev_loop *loop_hi = ev_default_init (0);
2292	struct ev_loop *loop_lo = 0;	2865	struct ev_loop *loop_lo = 0;
2293	struct ev_embed embed;	2866	ev_embed embed;
2294		2867
2295	// see if there is a chance of getting one that works	2868	// see if there is a chance of getting one that works
2296	// (remember that a flags value of 0 means autodetection)	2869	// (remember that a flags value of 0 means autodetection)
2297	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2870	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2298	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2871	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2312	kqueue implementation). Store the kqueue/socket-only event loop in	2885	kqueue implementation). Store the kqueue/socket-only event loop in
2313	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2886	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2314		2887
2315	struct ev_loop *loop = ev_default_init (0);	2888	struct ev_loop *loop = ev_default_init (0);
2316	struct ev_loop *loop_socket = 0;	2889	struct ev_loop *loop_socket = 0;
2317	struct ev_embed embed;	2890	ev_embed embed;
2318		2891
2319	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2892	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2320	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2893	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2321	{	2894	{
2322	ev_embed_init (&embed, 0, loop_socket);	2895	ev_embed_init (&embed, 0, loop_socket);
…		…
2337	event loop blocks next and before C<ev_check> watchers are being called,	2910	event loop blocks next and before C<ev_check> watchers are being called,
2338	and only in the child after the fork. If whoever good citizen calling	2911	and only in the child after the fork. If whoever good citizen calling
2339	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2340	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2341		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2342	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2343		2949
2344	=over 4	2950	=over 4
2345		2951
2346	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2463	=over 4	3069	=over 4
2464		3070
2465	=item ev_async_init (ev_async *, callback)	3071	=item ev_async_init (ev_async *, callback)
2466		3072
2467	Initialises and configures the async watcher - it has no parameters of any	3073	Initialises and configures the async watcher - it has no parameters of any
2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3074	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2469	trust me.	3075	trust me.
2470		3076
2471	=item ev_async_send (loop, ev_async *)	3077	=item ev_async_send (loop, ev_async *)
2472		3078
2473	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3079	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2474	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3080	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2475	C<ev_feed_event>, this call is safe to do from other threads, signal or	3081	C<ev_feed_event>, this call is safe to do from other threads, signal or
2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3082	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2477	section below on what exactly this means).	3083	section below on what exactly this means).
2478		3084
		3085	Note that, as with other watchers in libev, multiple events might get
		3086	compressed into a single callback invocation (another way to look at this
		3087	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3088	reset when the event loop detects that).
		3089
2479	This call incurs the overhead of a system call only once per loop iteration,	3090	This call incurs the overhead of a system call only once per event loop
2480	so while the overhead might be noticeable, it doesn't apply to repeated	3091	iteration, so while the overhead might be noticeable, it doesn't apply to
2481	calls to C<ev_async_send>.	3092	repeated calls to C<ev_async_send> for the same event loop.
2482		3093
2483	=item bool = ev_async_pending (ev_async *)	3094	=item bool = ev_async_pending (ev_async *)
2484		3095
2485	Returns a non-zero value when C<ev_async_send> has been called on the	3096	Returns a non-zero value when C<ev_async_send> has been called on the
2486	watcher but the event has not yet been processed (or even noted) by the	3097	watcher but the event has not yet been processed (or even noted) by the
…		…
2489	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3100	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2490	the loop iterates next and checks for the watcher to have become active,	3101	the loop iterates next and checks for the watcher to have become active,
2491	it will reset the flag again. C<ev_async_pending> can be used to very	3102	it will reset the flag again. C<ev_async_pending> can be used to very
2492	quickly check whether invoking the loop might be a good idea.	3103	quickly check whether invoking the loop might be a good idea.
2493		3104
2494	Not that this does I<not> check whether the watcher itself is pending, only	3105	Not that this does I<not> check whether the watcher itself is pending,
2495	whether it has been requested to make this watcher pending.	3106	only whether it has been requested to make this watcher pending: there
		3107	is a time window between the event loop checking and resetting the async
		3108	notification, and the callback being invoked.
2496		3109
2497	=back	3110	=back
2498		3111
2499		3112
2500	=head1 OTHER FUNCTIONS	3113	=head1 OTHER FUNCTIONS
…		…
2536	/* doh, nothing entered */;	3149	/* doh, nothing entered */;
2537	}	3150	}
2538		3151
2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2540		3153
2541	=item ev_feed_event (ev_loop *, watcher *, int revents)
2542
2543	Feeds the given event set into the event loop, as if the specified event
2544	had happened for the specified watcher (which must be a pointer to an
2545	initialised but not necessarily started event watcher).
2546
2547	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2548		3155
2549	Feed an event on the given fd, as if a file descriptor backend detected	3156	Feed an event on the given fd, as if a file descriptor backend detected
2550	the given events it.	3157	the given events it.
2551		3158
2552	=item ev_feed_signal_event (ev_loop *loop, int signum)	3159	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2553		3160
2554	Feed an event as if the given signal occurred (C<loop> must be the default	3161	Feed an event as if the given signal occurred (C<loop> must be the default
2555	loop!).	3162	loop!).
2556		3163
2557	=back	3164	=back
…		…
2678	}	3285	}
2679		3286
2680	myclass obj;	3287	myclass obj;
2681	ev::io iow;	3288	ev::io iow;
2682	iow.set <myclass, &myclass::io_cb> (&obj);	3289	iow.set <myclass, &myclass::io_cb> (&obj);
		3290
		3291	=item w->set (object *)
		3292
		3293	This is an B<experimental> feature that might go away in a future version.
		3294
		3295	This is a variation of a method callback - leaving out the method to call
		3296	will default the method to C<operator ()>, which makes it possible to use
		3297	functor objects without having to manually specify the C<operator ()> all
		3298	the time. Incidentally, you can then also leave out the template argument
		3299	list.
		3300
		3301	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3302	int revents)>.
		3303
		3304	See the method-C<set> above for more details.
		3305
		3306	Example: use a functor object as callback.
		3307
		3308	struct myfunctor
		3309	{
		3310	void operator() (ev::io &w, int revents)
		3311	{
		3312	...
		3313	}
		3314	}
		3315
		3316	myfunctor f;
		3317
		3318	ev::io w;
		3319	w.set (&f);
2683		3320
2684	=item w->set<function> (void *data = 0)	3321	=item w->set<function> (void *data = 0)
2685		3322
2686	Also sets a callback, but uses a static method or plain function as	3323	Also sets a callback, but uses a static method or plain function as
2687	callback. The optional C<data> argument will be stored in the watcher's	3324	callback. The optional C<data> argument will be stored in the watcher's
…		…
2774	L<http://software.schmorp.de/pkg/EV>.	3411	L<http://software.schmorp.de/pkg/EV>.
2775		3412
2776	=item Python	3413	=item Python
2777		3414
2778	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3415	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2779	seems to be quite complete and well-documented. Note, however, that the	3416	seems to be quite complete and well-documented.
2780	patch they require for libev is outright dangerous as it breaks the ABI
2781	for everybody else, and therefore, should never be applied in an installed
2782	libev (if python requires an incompatible ABI then it needs to embed
2783	libev).
2784		3417
2785	=item Ruby	3418	=item Ruby
2786		3419
2787	Tony Arcieri has written a ruby extension that offers access to a subset	3420	Tony Arcieri has written a ruby extension that offers access to a subset
2788	of the libev API and adds file handle abstractions, asynchronous DNS and	3421	of the libev API and adds file handle abstractions, asynchronous DNS and
2789	more on top of it. It can be found via gem servers. Its homepage is at	3422	more on top of it. It can be found via gem servers. Its homepage is at
2790	L<http://rev.rubyforge.org/>.	3423	L<http://rev.rubyforge.org/>.
2791		3424
		3425	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3426	makes rev work even on mingw.
		3427
		3428	=item Haskell
		3429
		3430	A haskell binding to libev is available at
		3431	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3432
2792	=item D	3433	=item D
2793		3434
2794	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3435	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2795	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3436	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3437
		3438	=item Ocaml
		3439
		3440	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3442
		3443	=item Lua
		3444
		3445	Brian Maher has written a partial interface to libev
		3446	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3447	L<http://github.com/brimworks/lua-ev>.
2796		3448
2797	=back	3449	=back
2798		3450
2799		3451
2800	=head1 MACRO MAGIC	3452	=head1 MACRO MAGIC
…		…
2901		3553
2902	#define EV_STANDALONE 1	3554	#define EV_STANDALONE 1
2903	#include "ev.h"	3555	#include "ev.h"
2904		3556
2905	Both header files and implementation files can be compiled with a C++	3557	Both header files and implementation files can be compiled with a C++
2906	compiler (at least, thats a stated goal, and breakage will be treated	3558	compiler (at least, that's a stated goal, and breakage will be treated
2907	as a bug).	3559	as a bug).
2908		3560
2909	You need the following files in your source tree, or in a directory	3561	You need the following files in your source tree, or in a directory
2910	in your include path (e.g. in libev/ when using -Ilibev):	3562	in your include path (e.g. in libev/ when using -Ilibev):
2911		3563
…		…
2967	keeps libev from including F<config.h>, and it also defines dummy	3619	keeps libev from including F<config.h>, and it also defines dummy
2968	implementations for some libevent functions (such as logging, which is not	3620	implementations for some libevent functions (such as logging, which is not
2969	supported). It will also not define any of the structs usually found in	3621	supported). It will also not define any of the structs usually found in
2970	F<event.h> that are not directly supported by the libev core alone.	3622	F<event.h> that are not directly supported by the libev core alone.
2971		3623
		3624	In standalone mode, libev will still try to automatically deduce the
		3625	configuration, but has to be more conservative.
		3626
2972	=item EV_USE_MONOTONIC	3627	=item EV_USE_MONOTONIC
2973		3628
2974	If defined to be C<1>, libev will try to detect the availability of the	3629	If defined to be C<1>, libev will try to detect the availability of the
2975	monotonic clock option at both compile time and runtime. Otherwise no use	3630	monotonic clock option at both compile time and runtime. Otherwise no
2976	of the monotonic clock option will be attempted. If you enable this, you	3631	use of the monotonic clock option will be attempted. If you enable this,
2977	usually have to link against librt or something similar. Enabling it when	3632	you usually have to link against librt or something similar. Enabling it
2978	the functionality isn't available is safe, though, although you have	3633	when the functionality isn't available is safe, though, although you have
2979	to make sure you link against any libraries where the C<clock_gettime>	3634	to make sure you link against any libraries where the C<clock_gettime>
2980	function is hiding in (often F<-lrt>).	3635	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2981		3636
2982	=item EV_USE_REALTIME	3637	=item EV_USE_REALTIME
2983		3638
2984	If defined to be C<1>, libev will try to detect the availability of the	3639	If defined to be C<1>, libev will try to detect the availability of the
2985	real-time clock option at compile time (and assume its availability at	3640	real-time clock option at compile time (and assume its availability
2986	runtime if successful). Otherwise no use of the real-time clock option will	3641	at runtime if successful). Otherwise no use of the real-time clock
2987	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3642	option will be attempted. This effectively replaces C<gettimeofday>
2988	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3643	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2989	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3644	correctness. See the note about libraries in the description of
		3645	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3646	C<EV_USE_CLOCK_SYSCALL>.
		3647
		3648	=item EV_USE_CLOCK_SYSCALL
		3649
		3650	If defined to be C<1>, libev will try to use a direct syscall instead
		3651	of calling the system-provided C<clock_gettime> function. This option
		3652	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3653	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3654	programs needlessly. Using a direct syscall is slightly slower (in
		3655	theory), because no optimised vdso implementation can be used, but avoids
		3656	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3657	higher, as it simplifies linking (no need for C<-lrt>).
2990		3658
2991	=item EV_USE_NANOSLEEP	3659	=item EV_USE_NANOSLEEP
2992		3660
2993	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3661	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2994	and will use it for delays. Otherwise it will use C<select ()>.	3662	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3010		3678
3011	=item EV_SELECT_USE_FD_SET	3679	=item EV_SELECT_USE_FD_SET
3012		3680
3013	If defined to C<1>, then the select backend will use the system C<fd_set>	3681	If defined to C<1>, then the select backend will use the system C<fd_set>
3014	structure. This is useful if libev doesn't compile due to a missing	3682	structure. This is useful if libev doesn't compile due to a missing
3015	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3683	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3016	exotic systems. This usually limits the range of file descriptors to some	3684	on exotic systems. This usually limits the range of file descriptors to
3017	low limit such as 1024 or might have other limitations (winsocket only	3685	some low limit such as 1024 or might have other limitations (winsocket
3018	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3686	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3019	influence the size of the C<fd_set> used.	3687	configures the maximum size of the C<fd_set>.
3020		3688
3021	=item EV_SELECT_IS_WINSOCKET	3689	=item EV_SELECT_IS_WINSOCKET
3022		3690
3023	When defined to C<1>, the select backend will assume that	3691	When defined to C<1>, the select backend will assume that
3024	select/socket/connect etc. don't understand file descriptors but	3692	select/socket/connect etc. don't understand file descriptors but
…		…
3026	be used is the winsock select). This means that it will call	3694	be used is the winsock select). This means that it will call
3027	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3695	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3028	it is assumed that all these functions actually work on fds, even	3696	it is assumed that all these functions actually work on fds, even
3029	on win32. Should not be defined on non-win32 platforms.	3697	on win32. Should not be defined on non-win32 platforms.
3030		3698
3031	=item EV_FD_TO_WIN32_HANDLE	3699	=item EV_FD_TO_WIN32_HANDLE(fd)
3032		3700
3033	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3701	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3034	file descriptors to socket handles. When not defining this symbol (the	3702	file descriptors to socket handles. When not defining this symbol (the
3035	default), then libev will call C<_get_osfhandle>, which is usually	3703	default), then libev will call C<_get_osfhandle>, which is usually
3036	correct. In some cases, programs use their own file descriptor management,	3704	correct. In some cases, programs use their own file descriptor management,
3037	in which case they can provide this function to map fds to socket handles.	3705	in which case they can provide this function to map fds to socket handles.
		3706
		3707	=item EV_WIN32_HANDLE_TO_FD(handle)
		3708
		3709	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3710	using the standard C<_open_osfhandle> function. For programs implementing
		3711	their own fd to handle mapping, overwriting this function makes it easier
		3712	to do so. This can be done by defining this macro to an appropriate value.
		3713
		3714	=item EV_WIN32_CLOSE_FD(fd)
		3715
		3716	If programs implement their own fd to handle mapping on win32, then this
		3717	macro can be used to override the C<close> function, useful to unregister
		3718	file descriptors again. Note that the replacement function has to close
		3719	the underlying OS handle.
3038		3720
3039	=item EV_USE_POLL	3721	=item EV_USE_POLL
3040		3722
3041	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3723	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3042	backend. Otherwise it will be enabled on non-win32 platforms. It	3724	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3174	defined to be C<0>, then they are not.	3856	defined to be C<0>, then they are not.
3175		3857
3176	=item EV_MINIMAL	3858	=item EV_MINIMAL
3177		3859
3178	If you need to shave off some kilobytes of code at the expense of some	3860	If you need to shave off some kilobytes of code at the expense of some
3179	speed, define this symbol to C<1>. Currently this is used to override some	3861	speed (but with the full API), define this symbol to C<1>. Currently this
3180	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3862	is used to override some inlining decisions, saves roughly 30% code size
3181	much smaller 2-heap for timer management over the default 4-heap.	3863	on amd64. It also selects a much smaller 2-heap for timer management over
		3864	the default 4-heap.
		3865
		3866	You can save even more by disabling watcher types you do not need
		3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3868	(C<-DNDEBUG>) will usually reduce code size a lot.
		3869
		3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3871	provide a bare-bones event library. See C<ev.h> for details on what parts
		3872	of the API are still available, and do not complain if this subset changes
		3873	over time.
		3874
		3875	=item EV_NSIG
		3876
		3877	The highest supported signal number, +1 (or, the number of
		3878	signals): Normally, libev tries to deduce the maximum number of signals
		3879	automatically, but sometimes this fails, in which case it can be
		3880	specified. Also, using a lower number than detected (C<32> should be
		3881	good for about any system in existance) can save some memory, as libev
		3882	statically allocates some 12-24 bytes per signal number.
3182		3883
3183	=item EV_PID_HASHSIZE	3884	=item EV_PID_HASHSIZE
3184		3885
3185	C<ev_child> watchers use a small hash table to distribute workload by	3886	C<ev_child> watchers use a small hash table to distribute workload by
3186	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3887	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3372	default loop and triggering an C<ev_async> watcher from the default loop	4073	default loop and triggering an C<ev_async> watcher from the default loop
3373	watcher callback into the event loop interested in the signal.	4074	watcher callback into the event loop interested in the signal.
3374		4075
3375	=back	4076	=back
3376		4077
		4078	=head4 THREAD LOCKING EXAMPLE
		4079
		4080	Here is a fictitious example of how to run an event loop in a different
		4081	thread than where callbacks are being invoked and watchers are
		4082	created/added/removed.
		4083
		4084	For a real-world example, see the C<EV::Loop::Async> perl module,
		4085	which uses exactly this technique (which is suited for many high-level
		4086	languages).
		4087
		4088	The example uses a pthread mutex to protect the loop data, a condition
		4089	variable to wait for callback invocations, an async watcher to notify the
		4090	event loop thread and an unspecified mechanism to wake up the main thread.
		4091
		4092	First, you need to associate some data with the event loop:
		4093
		4094	typedef struct {
		4095	mutex_t lock; /* global loop lock */
		4096	ev_async async_w;
		4097	thread_t tid;
		4098	cond_t invoke_cv;
		4099	} userdata;
		4100
		4101	void prepare_loop (EV_P)
		4102	{
		4103	// for simplicity, we use a static userdata struct.
		4104	static userdata u;
		4105
		4106	ev_async_init (&u->async_w, async_cb);
		4107	ev_async_start (EV_A_ &u->async_w);
		4108
		4109	pthread_mutex_init (&u->lock, 0);
		4110	pthread_cond_init (&u->invoke_cv, 0);
		4111
		4112	// now associate this with the loop
		4113	ev_set_userdata (EV_A_ u);
		4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4116
		4117	// then create the thread running ev_loop
		4118	pthread_create (&u->tid, 0, l_run, EV_A);
		4119	}
		4120
		4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4122	solely to wake up the event loop so it takes notice of any new watchers
		4123	that might have been added:
		4124
		4125	static void
		4126	async_cb (EV_P_ ev_async *w, int revents)
		4127	{
		4128	// just used for the side effects
		4129	}
		4130
		4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4132	protecting the loop data, respectively.
		4133
		4134	static void
		4135	l_release (EV_P)
		4136	{
		4137	userdata *u = ev_userdata (EV_A);
		4138	pthread_mutex_unlock (&u->lock);
		4139	}
		4140
		4141	static void
		4142	l_acquire (EV_P)
		4143	{
		4144	userdata *u = ev_userdata (EV_A);
		4145	pthread_mutex_lock (&u->lock);
		4146	}
		4147
		4148	The event loop thread first acquires the mutex, and then jumps straight
		4149	into C<ev_loop>:
		4150
		4151	void *
		4152	l_run (void *thr_arg)
		4153	{
		4154	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4155
		4156	l_acquire (EV_A);
		4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4158	ev_loop (EV_A_ 0);
		4159	l_release (EV_A);
		4160
		4161	return 0;
		4162	}
		4163
		4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4165	signal the main thread via some unspecified mechanism (signals? pipe
		4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4167	have been called (in a while loop because a) spurious wakeups are possible
		4168	and b) skipping inter-thread-communication when there are no pending
		4169	watchers is very beneficial):
		4170
		4171	static void
		4172	l_invoke (EV_P)
		4173	{
		4174	userdata *u = ev_userdata (EV_A);
		4175
		4176	while (ev_pending_count (EV_A))
		4177	{
		4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4180	}
		4181	}
		4182
		4183	Now, whenever the main thread gets told to invoke pending watchers, it
		4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4185	thread to continue:
		4186
		4187	static void
		4188	real_invoke_pending (EV_P)
		4189	{
		4190	userdata *u = ev_userdata (EV_A);
		4191
		4192	pthread_mutex_lock (&u->lock);
		4193	ev_invoke_pending (EV_A);
		4194	pthread_cond_signal (&u->invoke_cv);
		4195	pthread_mutex_unlock (&u->lock);
		4196	}
		4197
		4198	Whenever you want to start/stop a watcher or do other modifications to an
		4199	event loop, you will now have to lock:
		4200
		4201	ev_timer timeout_watcher;
		4202	userdata *u = ev_userdata (EV_A);
		4203
		4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4205
		4206	pthread_mutex_lock (&u->lock);
		4207	ev_timer_start (EV_A_ &timeout_watcher);
		4208	ev_async_send (EV_A_ &u->async_w);
		4209	pthread_mutex_unlock (&u->lock);
		4210
		4211	Note that sending the C<ev_async> watcher is required because otherwise
		4212	an event loop currently blocking in the kernel will have no knowledge
		4213	about the newly added timer. By waking up the loop it will pick up any new
		4214	watchers in the next event loop iteration.
		4215
3377	=head3 COROUTINES	4216	=head3 COROUTINES
3378		4217
3379	Libev is very accommodating to coroutines ("cooperative threads"):	4218	Libev is very accommodating to coroutines ("cooperative threads"):
3380	libev fully supports nesting calls to its functions from different	4219	libev fully supports nesting calls to its functions from different
3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4220	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3382	different coroutines, and switch freely between both coroutines running the	4221	different coroutines, and switch freely between both coroutines running
3383	loop, as long as you don't confuse yourself). The only exception is that	4222	the loop, as long as you don't confuse yourself). The only exception is
3384	you must not do this from C<ev_periodic> reschedule callbacks.	4223	that you must not do this from C<ev_periodic> reschedule callbacks.
3385		4224
3386	Care has been taken to ensure that libev does not keep local state inside	4225	Care has been taken to ensure that libev does not keep local state inside
3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3388	they do not clal any callbacks.	4227	they do not call any callbacks.
3389		4228
3390	=head2 COMPILER WARNINGS	4229	=head2 COMPILER WARNINGS
3391		4230
3392	Depending on your compiler and compiler settings, you might get no or a	4231	Depending on your compiler and compiler settings, you might get no or a
3393	lot of warnings when compiling libev code. Some people are apparently	4232	lot of warnings when compiling libev code. Some people are apparently
…		…
3427	==2274== definitely lost: 0 bytes in 0 blocks.	4266	==2274== definitely lost: 0 bytes in 0 blocks.
3428	==2274== possibly lost: 0 bytes in 0 blocks.	4267	==2274== possibly lost: 0 bytes in 0 blocks.
3429	==2274== still reachable: 256 bytes in 1 blocks.	4268	==2274== still reachable: 256 bytes in 1 blocks.
3430		4269
3431	Then there is no memory leak, just as memory accounted to global variables	4270	Then there is no memory leak, just as memory accounted to global variables
3432	is not a memleak - the memory is still being refernced, and didn't leak.	4271	is not a memleak - the memory is still being referenced, and didn't leak.
3433		4272
3434	Similarly, under some circumstances, valgrind might report kernel bugs	4273	Similarly, under some circumstances, valgrind might report kernel bugs
3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4274	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3436	although an acceptable workaround has been found here), or it might be	4275	although an acceptable workaround has been found here), or it might be
3437	confused.	4276	confused.
…		…
3466	way (note also that glib is the slowest event library known to man).	4305	way (note also that glib is the slowest event library known to man).
3467		4306
3468	There is no supported compilation method available on windows except	4307	There is no supported compilation method available on windows except
3469	embedding it into other applications.	4308	embedding it into other applications.
3470		4309
		4310	Sensible signal handling is officially unsupported by Microsoft - libev
		4311	tries its best, but under most conditions, signals will simply not work.
		4312
3471	Not a libev limitation but worth mentioning: windows apparently doesn't	4313	Not a libev limitation but worth mentioning: windows apparently doesn't
3472	accept large writes: instead of resulting in a partial write, windows will	4314	accept large writes: instead of resulting in a partial write, windows will
3473	either accept everything or return C<ENOBUFS> if the buffer is too large,	4315	either accept everything or return C<ENOBUFS> if the buffer is too large,
3474	so make sure you only write small amounts into your sockets (less than a	4316	so make sure you only write small amounts into your sockets (less than a
3475	megabyte seems safe, but this apparently depends on the amount of memory	4317	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3479	the abysmal performance of winsockets, using a large number of sockets	4321	the abysmal performance of winsockets, using a large number of sockets
3480	is not recommended (and not reasonable). If your program needs to use	4322	is not recommended (and not reasonable). If your program needs to use
3481	more than a hundred or so sockets, then likely it needs to use a totally	4323	more than a hundred or so sockets, then likely it needs to use a totally
3482	different implementation for windows, as libev offers the POSIX readiness	4324	different implementation for windows, as libev offers the POSIX readiness
3483	notification model, which cannot be implemented efficiently on windows	4325	notification model, which cannot be implemented efficiently on windows
3484	(Microsoft monopoly games).	4326	(due to Microsoft monopoly games).
3485		4327
3486	A typical way to use libev under windows is to embed it (see the embedding	4328	A typical way to use libev under windows is to embed it (see the embedding
3487	section for details) and use the following F<evwrap.h> header file instead	4329	section for details) and use the following F<evwrap.h> header file instead
3488	of F<ev.h>:	4330	of F<ev.h>:
3489		4331
…		…
3525		4367
3526	Early versions of winsocket's select only supported waiting for a maximum	4368	Early versions of winsocket's select only supported waiting for a maximum
3527	of C<64> handles (probably owning to the fact that all windows kernels	4369	of C<64> handles (probably owning to the fact that all windows kernels
3528	can only wait for C<64> things at the same time internally; Microsoft	4370	can only wait for C<64> things at the same time internally; Microsoft
3529	recommends spawning a chain of threads and wait for 63 handles and the	4371	recommends spawning a chain of threads and wait for 63 handles and the
3530	previous thread in each. Great).	4372	previous thread in each. Sounds great!).
3531		4373
3532	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4374	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3533	to some high number (e.g. C<2048>) before compiling the winsocket select	4375	to some high number (e.g. C<2048>) before compiling the winsocket select
3534	call (which might be in libev or elsewhere, for example, perl does its own	4376	call (which might be in libev or elsewhere, for example, perl and many
3535	select emulation on windows).	4377	other interpreters do their own select emulation on windows).
3536		4378
3537	Another limit is the number of file descriptors in the Microsoft runtime	4379	Another limit is the number of file descriptors in the Microsoft runtime
3538	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4380	libraries, which by default is C<64> (there must be a hidden I<64>
3539	or something like this inside Microsoft). You can increase this by calling	4381	fetish or something like this inside Microsoft). You can increase this
3540	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4382	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3541	arbitrary limit), but is broken in many versions of the Microsoft runtime	4383	(another arbitrary limit), but is broken in many versions of the Microsoft
3542	libraries.
3543
3544	This might get you to about C<512> or C<2048> sockets (depending on	4384	runtime libraries. This might get you to about C<512> or C<2048> sockets
3545	windows version and/or the phase of the moon). To get more, you need to	4385	(depending on windows version and/or the phase of the moon). To get more,
3546	wrap all I/O functions and provide your own fd management, but the cost of	4386	you need to wrap all I/O functions and provide your own fd management, but
3547	calling select (O(n²)) will likely make this unworkable.	4387	the cost of calling select (O(n²)) will likely make this unworkable.
3548		4388
3549	=back	4389	=back
3550		4390
3551	=head2 PORTABILITY REQUIREMENTS	4391	=head2 PORTABILITY REQUIREMENTS
3552		4392
…		…
3595	=item C<double> must hold a time value in seconds with enough accuracy	4435	=item C<double> must hold a time value in seconds with enough accuracy
3596		4436
3597	The type C<double> is used to represent timestamps. It is required to	4437	The type C<double> is used to represent timestamps. It is required to
3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4438	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3599	enough for at least into the year 4000. This requirement is fulfilled by	4439	enough for at least into the year 4000. This requirement is fulfilled by
3600	implementations implementing IEEE 754 (basically all existing ones).	4440	implementations implementing IEEE 754, which is basically all existing
		4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4442	2200.
3601		4443
3602	=back	4444	=back
3603		4445
3604	If you know of other additional requirements drop me a note.	4446	If you know of other additional requirements drop me a note.
3605		4447
…		…
3673	involves iterating over all running async watchers or all signal numbers.	4515	involves iterating over all running async watchers or all signal numbers.
3674		4516
3675	=back	4517	=back
3676		4518
3677		4519
		4520	=head1 GLOSSARY
		4521
		4522	=over 4
		4523
		4524	=item active
		4525
		4526	A watcher is active as long as it has been started (has been attached to
		4527	an event loop) but not yet stopped (disassociated from the event loop).
		4528
		4529	=item application
		4530
		4531	In this document, an application is whatever is using libev.
		4532
		4533	=item callback
		4534
		4535	The address of a function that is called when some event has been
		4536	detected. Callbacks are being passed the event loop, the watcher that
		4537	received the event, and the actual event bitset.
		4538
		4539	=item callback invocation
		4540
		4541	The act of calling the callback associated with a watcher.
		4542
		4543	=item event
		4544
		4545	A change of state of some external event, such as data now being available
		4546	for reading on a file descriptor, time having passed or simply not having
		4547	any other events happening anymore.
		4548
		4549	In libev, events are represented as single bits (such as C<EV_READ> or
		4550	C<EV_TIMEOUT>).
		4551
		4552	=item event library
		4553
		4554	A software package implementing an event model and loop.
		4555
		4556	=item event loop
		4557
		4558	An entity that handles and processes external events and converts them
		4559	into callback invocations.
		4560
		4561	=item event model
		4562
		4563	The model used to describe how an event loop handles and processes
		4564	watchers and events.
		4565
		4566	=item pending
		4567
		4568	A watcher is pending as soon as the corresponding event has been detected,
		4569	and stops being pending as soon as the watcher will be invoked or its
		4570	pending status is explicitly cleared by the application.
		4571
		4572	A watcher can be pending, but not active. Stopping a watcher also clears
		4573	its pending status.
		4574
		4575	=item real time
		4576
		4577	The physical time that is observed. It is apparently strictly monotonic :)
		4578
		4579	=item wall-clock time
		4580
		4581	The time and date as shown on clocks. Unlike real time, it can actually
		4582	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4583	clock.
		4584
		4585	=item watcher
		4586
		4587	A data structure that describes interest in certain events. Watchers need
		4588	to be started (attached to an event loop) before they can receive events.
		4589
		4590	=item watcher invocation
		4591
		4592	The act of calling the callback associated with a watcher.
		4593
		4594	=back
		4595
3678	=head1 AUTHOR	4596	=head1 AUTHOR
3679		4597
3680	Marc Lehmann <libev@schmorp.de>.	4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3681		4599

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