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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
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
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<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct 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<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_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	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,	391	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	392	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	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		418
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
382	For few fds, this backend is a bit little slower than poll and select,	424	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	425	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),	426	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	427	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	428
387	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required.
389		445
390	While stopping, setting and starting an I/O watcher in the same iteration	446	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	447	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	448	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	449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	450	file descriptors might not work very well if you register events for both
395		451	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		452
400	Best performance from this backend is achieved by not unregistering all	453	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	454	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	455	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	456	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	457	extra overhead. A fork can both result in spurious notifications as well
		458	as in libev having to destroy and recreate the epoll object, which can
		459	take considerable time and thus should be avoided.
		460
		461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		462	faster than epoll for maybe up to a hundred file descriptors, depending on
		463	the usage. So sad.
405		464
406	While nominally embeddable in other event loops, this feature is broken in	465	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	466	all kernel versions tested so far.
408		467
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	469	C<EVBACKEND_POLL>.
411		470
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		472
414	Kqueue deserves special mention, as at the time of this writing, it was	473	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	474	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	475	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	476	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	477	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.	478	without API changes to existing programs. For this reason it's not being
		479	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		481	system like NetBSD.
420		482
421	You still can embed kqueue into a normal poll or select backend and use it	483	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	484	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.	485	the target platform). See C<ev_embed> watchers for more info.
424		486
425	It scales in the same way as the epoll backend, but the interface to the	487	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	488	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	489	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	490	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	491	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		493	cases
431		494
432	This backend usually performs well under most conditions.	495	This backend usually performs well under most conditions.
433		496
434	While nominally embeddable in other event loops, this doesn't work	497	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	498	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	499	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	500	(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,	501	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	502	also broken on OS X)) and, did I mention it, using it only for sockets.
440		503
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	504	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	505	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	506	C<NOTE_EOF>.
444		507
…		…
464	might perform better.	527	might perform better.
465		528
466	On the positive side, with the exception of the spurious readiness	529	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	530	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	531	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	532	OS-specific backends (I vastly prefer correctness over speed hacks).
470		533
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	535	C<EVBACKEND_POLL>.
473		536
474	=item C<EVBACKEND_ALL>	537	=item C<EVBACKEND_ALL>
…		…
479		542
480	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
481		544
482	=back	545	=back
483		546
484	If one or more of these are or'ed into the flags value, then only these	547	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	548	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.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
487		551
488	Example: This is the most typical usage.	552	Example: This is the most typical usage.
489		553
490	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	591	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	592	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	593	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	594	for example).
531		595
532	Note that certain global state, such as signal state, will not be freed by	596	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	597	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
535		599
536	In general it is not advisable to call this function except in the	600	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	601	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	602	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
540		604
541	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
542		606
543	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
582		646
583	This value can sometimes be useful as a generation counter of sorts (it	647	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	648	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	649	C<ev_prepare> and C<ev_check> calls.
586		650
		651	=item unsigned int ev_loop_depth (loop)
		652
		653	Returns the number of times C<ev_loop> was entered minus the number of
		654	times C<ev_loop> was exited, in other words, the recursion depth.
		655
		656	Outside C<ev_loop>, this number is zero. In a callback, this number is
		657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		658	in which case it is higher.
		659
		660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		661	etc.), doesn't count as exit.
		662
587	=item unsigned int ev_backend (loop)	663	=item unsigned int ev_backend (loop)
588		664
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	666	use.
591		667
…		…
605		681
606	This function is rarely useful, but when some event callback runs for a	682	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	683	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	684	the current time is a good idea.
609		685
610	See also "The special problem of time updates" in the C<ev_timer> section.	686	See also L<The special problem of time updates> in the C<ev_timer> section.
		687
		688	=item ev_suspend (loop)
		689
		690	=item ev_resume (loop)
		691
		692	These two functions suspend and resume a loop, for use when the loop is
		693	not used for a while and timeouts should not be processed.
		694
		695	A typical use case would be an interactive program such as a game: When
		696	the user presses C<^Z> to suspend the game and resumes it an hour later it
		697	would be best to handle timeouts as if no time had actually passed while
		698	the program was suspended. This can be achieved by calling C<ev_suspend>
		699	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		700	C<ev_resume> directly afterwards to resume timer processing.
		701
		702	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		704	will be rescheduled (that is, they will lose any events that would have
		705	occured while suspended).
		706
		707	After calling C<ev_suspend> you B<must not> call I<any> function on the
		708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		709	without a previous call to C<ev_suspend>.
		710
		711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		712	event loop time (see C<ev_now_update>).
611		713
612	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
613		715
614	Finally, this is it, the event handler. This function usually is called	716	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	717	after you have initialised all your watchers and you want to start
616	events.	718	handling events.
617		719
618	If the flags argument is specified as C<0>, it will not return until	720	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.	721	either no event watchers are active anymore or C<ev_unloop> was called.
620		722
621	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	733	the loop.
632		734
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	735	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	736	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	737	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	738	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	739	user-registered callback will be called), and will return after one
638	iteration of the loop.	740	iteration of the loop.
639		741
640	This is useful if you are waiting for some external event in conjunction	742	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	743	with something not expressible using other libev watchers (i.e. "roll your
…		…
695		797
696	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	800	count is nonzero, C<ev_loop> will not return on its own.
699		801
700	If you have a watcher you never unregister that should not keep C<ev_loop>	802	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	805	before stopping it.
703		806
704	As an example, libev itself uses this for its internal signal pipe: It is	807	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	808	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	809	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	810	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>	811	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,	812	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	813	before, respectively. Note also that libev might stop watchers itself
		814	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		815	in the callback).
711		816
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	818	running when nothing else is active.
714		819
715	ev_signal exitsig;	820	ev_signal exitsig;
…		…
744		849
745	By setting a higher I<io collect interval> you allow libev to spend more	850	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,	851	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	852	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	853	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.	854	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		855	sleep time ensures that libev will not poll for I/O events more often then
		856	once per this interval, on average.
750		857
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	858	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	859	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	860	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	861	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		863
757	Many (busy) programs can usually benefit by setting the I/O collect	864	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	865	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	866	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>,	867	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.	868	as this approaches the timing granularity of most systems. Note that if
		869	you do transactions with the outside world and you can't increase the
		870	parallelity, then this setting will limit your transaction rate (if you
		871	need to poll once per transaction and the I/O collect interval is 0.01,
		872	then you can't do more than 100 transations per second).
762		873
763	Setting the I<timeout collect interval> can improve the opportunity for	874	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	875	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	876	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	877	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	878	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	879	they fire on, say, one-second boundaries only.
769		880
		881	Example: we only need 0.1s timeout granularity, and we wish not to poll
		882	more often than 100 times per second:
		883
		884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
		951
770	=item ev_loop_verify (loop)	952	=item ev_loop_verify (loop)
771		953
772	This function only does something when C<EV_VERIFY> support has been	954	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	955	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	956	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	957	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	958	error and call C<abort ()>.
777		959
778	This can be used to catch bugs inside libev itself: under normal	960	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	964	=back
783		965
784		966
785	=head1 ANATOMY OF A WATCHER	967	=head1 ANATOMY OF A WATCHER
786		968
		969	In the following description, uppercase C<TYPE> in names stands for the
		970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		971	watchers and C<ev_io_start> for I/O watchers.
		972
787	A watcher is a structure that you create and register to record your	973	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	974	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:	975	become readable, you would create an C<ev_io> watcher for that:
790		976
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
…		…
793	ev_io_stop (w);	979	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	980	ev_unloop (loop, EVUNLOOP_ALL);
795	}	981	}
796		982
797	struct ev_loop *loop = ev_default_loop (0);	983	struct ev_loop *loop = ev_default_loop (0);
		984
798	ev_io stdin_watcher;	985	ev_io stdin_watcher;
		986
799	ev_init (&stdin_watcher, my_cb);	987	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	989	ev_io_start (loop, &stdin_watcher);
		990
802	ev_loop (loop, 0);	991	ev_loop (loop, 0);
803		992
804	As you can see, you are responsible for allocating the memory for your	993	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,	994	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	995	stack).
		996
		997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		999
808	Each watcher structure must be initialised by a call to C<ev_init	1000	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	1001	(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	1002	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	1003	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	1004	is readable and/or writable).
813		1005
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1006	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	1007	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	1008	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1009	ev_TYPE_init (watcher *, callback, ...) >>.
818		1010
819	To make the watcher actually watch out for events, you have to start it	1011	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	1012	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	1013	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1014	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1015
824	As long as your watcher is active (has been started but not stopped) you	1016	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	1017	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1018	reinitialise it or call its C<ev_TYPE_set> macro.
827		1019
828	Each and every callback receives the event loop pointer as first, the	1020	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	1021	registered watcher structure as second, and a bitset of received events as
830	third argument.	1022	third argument.
831		1023
…		…
889		1081
890	=item C<EV_ASYNC>	1082	=item C<EV_ASYNC>
891		1083
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1084	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1085
		1086	=item C<EV_CUSTOM>
		1087
		1088	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1089	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1090
894	=item C<EV_ERROR>	1091	=item C<EV_ERROR>
895		1092
896	An unspecified error has occurred, the watcher has been stopped. This might	1093	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1094	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	1095	ran out of memory, a file descriptor was found to be closed or any other
…		…
912		1109
913	=back	1110	=back
914		1111
915	=head2 GENERIC WATCHER FUNCTIONS	1112	=head2 GENERIC WATCHER FUNCTIONS
916		1113
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1114	=over 4
921		1115
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1116	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1117
924	This macro initialises the generic portion of a watcher. The contents	1118	This macro initialises the generic portion of a watcher. The contents
…		…
938		1132
939	ev_io w;	1133	ev_io w;
940	ev_init (&w, my_cb);	1134	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1136
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1138
945	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1155
962	Example: Initialise and set an C<ev_io> watcher in one step.	1156	Example: Initialise and set an C<ev_io> watcher in one step.
963		1157
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1159
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1161
968	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
970		1164
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1165	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1166	whole section.
973		1167
974	ev_io_start (EV_DEFAULT_UC, &w);	1168	ev_io_start (EV_DEFAULT_UC, &w);
975		1169
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1171
978	Stops the given watcher if active, and clears the pending status (whether	1172	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1173	the watcher was active or not).
980		1174
981	It is possible that stopped watchers are pending - for example,	1175	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1201
1008	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1203	(modulo threads).
1010		1204
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1206
1013	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
1014		1208
1015	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1211	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1212	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1213	from being executed (except for C<ev_idle> watchers).
1020		1214
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1215	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1216	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1217
1029	You I<must not> change the priority of a watcher as long as it is active or	1218	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1219	pending.
1031		1220
		1221	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1222	fine, as long as you do not mind that the priority value you query might
		1223	or might not have been clamped to the valid range.
		1224
1032	The default priority used by watchers when no priority has been set is	1225	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1226	always C<0>, which is supposed to not be too high and not be too low :).
1034		1227
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1229	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1230
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1232
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1234	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1049	returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
1050	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
1051		1243
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
1054		1260
1055	=back	1261	=back
1056		1262
1057		1263
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1107	#include <stddef.h>	1313	#include <stddef.h>
1108		1314
1109	static void	1315	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)	1316	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1317	{
1112	struct my_biggy big = (struct my_biggy *	1318	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1319	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1320	}
1115		1321
1116	static void	1322	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)	1323	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1324	{
1119	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1326	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1327	}
		1328
		1329	=head2 WATCHER PRIORITY MODELS
		1330
		1331	Many event loops support I<watcher priorities>, which are usually small
		1332	integers that influence the ordering of event callback invocation
		1333	between watchers in some way, all else being equal.
		1334
		1335	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1336	description for the more technical details such as the actual priority
		1337	range.
		1338
		1339	There are two common ways how these these priorities are being interpreted
		1340	by event loops:
		1341
		1342	In the more common lock-out model, higher priorities "lock out" invocation
		1343	of lower priority watchers, which means as long as higher priority
		1344	watchers receive events, lower priority watchers are not being invoked.
		1345
		1346	The less common only-for-ordering model uses priorities solely to order
		1347	callback invocation within a single event loop iteration: Higher priority
		1348	watchers are invoked before lower priority ones, but they all get invoked
		1349	before polling for new events.
		1350
		1351	Libev uses the second (only-for-ordering) model for all its watchers
		1352	except for idle watchers (which use the lock-out model).
		1353
		1354	The rationale behind this is that implementing the lock-out model for
		1355	watchers is not well supported by most kernel interfaces, and most event
		1356	libraries will just poll for the same events again and again as long as
		1357	their callbacks have not been executed, which is very inefficient in the
		1358	common case of one high-priority watcher locking out a mass of lower
		1359	priority ones.
		1360
		1361	Static (ordering) priorities are most useful when you have two or more
		1362	watchers handling the same resource: a typical usage example is having an
		1363	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1364	timeouts. Under load, data might be received while the program handles
		1365	other jobs, but since timers normally get invoked first, the timeout
		1366	handler will be executed before checking for data. In that case, giving
		1367	the timer a lower priority than the I/O watcher ensures that I/O will be
		1368	handled first even under adverse conditions (which is usually, but not
		1369	always, what you want).
		1370
		1371	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1372	will only be executed when no same or higher priority watchers have
		1373	received events, they can be used to implement the "lock-out" model when
		1374	required.
		1375
		1376	For example, to emulate how many other event libraries handle priorities,
		1377	you can associate an C<ev_idle> watcher to each such watcher, and in
		1378	the normal watcher callback, you just start the idle watcher. The real
		1379	processing is done in the idle watcher callback. This causes libev to
		1380	continously poll and process kernel event data for the watcher, but when
		1381	the lock-out case is known to be rare (which in turn is rare :), this is
		1382	workable.
		1383
		1384	Usually, however, the lock-out model implemented that way will perform
		1385	miserably under the type of load it was designed to handle. In that case,
		1386	it might be preferable to stop the real watcher before starting the
		1387	idle watcher, so the kernel will not have to process the event in case
		1388	the actual processing will be delayed for considerable time.
		1389
		1390	Here is an example of an I/O watcher that should run at a strictly lower
		1391	priority than the default, and which should only process data when no
		1392	other events are pending:
		1393
		1394	ev_idle idle; // actual processing watcher
		1395	ev_io io; // actual event watcher
		1396
		1397	static void
		1398	io_cb (EV_P_ ev_io *w, int revents)
		1399	{
		1400	// stop the I/O watcher, we received the event, but
		1401	// are not yet ready to handle it.
		1402	ev_io_stop (EV_A_ w);
		1403
		1404	// start the idle watcher to ahndle the actual event.
		1405	// it will not be executed as long as other watchers
		1406	// with the default priority are receiving events.
		1407	ev_idle_start (EV_A_ &idle);
		1408	}
		1409
		1410	static void
		1411	idle_cb (EV_P_ ev_idle *w, int revents)
		1412	{
		1413	// actual processing
		1414	read (STDIN_FILENO, ...);
		1415
		1416	// have to start the I/O watcher again, as
		1417	// we have handled the event
		1418	ev_io_start (EV_P_ &io);
		1419	}
		1420
		1421	// initialisation
		1422	ev_idle_init (&idle, idle_cb);
		1423	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1424	ev_io_start (EV_DEFAULT_ &io);
		1425
		1426	In the "real" world, it might also be beneficial to start a timer, so that
		1427	low-priority connections can not be locked out forever under load. This
		1428	enables your program to keep a lower latency for important connections
		1429	during short periods of high load, while not completely locking out less
		1430	important ones.
1122		1431
1123		1432
1124	=head1 WATCHER TYPES	1433	=head1 WATCHER TYPES
1125		1434
1126	This section describes each watcher in detail, but will not repeat	1435	This section describes each watcher in detail, but will not repeat
…		…
1152	descriptors to non-blocking mode is also usually a good idea (but not	1461	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1462	required if you know what you are doing).
1154		1463
1155	If you cannot use non-blocking mode, then force the use of a	1464	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only	1465	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1467	descriptors for which non-blocking operation makes no sense (such as
		1468	files) - libev doesn't guarentee any specific behaviour in that case.
1158		1469
1159	Another thing you have to watch out for is that it is quite easy to	1470	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1471	receive "spurious" readiness notifications, that is your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1473	because there is no data. Not only are some backends known to create a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1594	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1595	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1596	monotonic clock option helps a lot here).
1286		1597
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1598	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1599	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1600	might introduce a small delay). If multiple timers become ready during the
		1601	same loop iteration then the ones with earlier time-out values are invoked
		1602	before ones of the same priority with later time-out values (but this is
		1603	no longer true when a callback calls C<ev_loop> recursively).
1290		1604
1291	=head3 Be smart about timeouts	1605	=head3 Be smart about timeouts
1292		1606
1293	Many real-world problems invole some kind of time-out, usually for error	1607	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1608	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1609	you want to raise some error after a while.
1296		1610
1297	Here are some ways on how to handle this problem, from simple and	1611	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1612	inefficient to smart and efficient.
1299		1613
1300	In the following examples a 60 second activity timeout is assumed - a	1614	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1615	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1616	data or other life sign was received).
1303		1617
1304	=over 4	1618	=over 4
1305		1619
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1620	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1621
1308	This is the most obvious, but not the most simple way: In the beginning,	1622	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1623	start the watcher:
1310		1624
1311	ev_timer_init (timer, callback, 60., 0.);	1625	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1626	ev_timer_start (loop, timer);
1313		1627
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1628	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1629	and start it again:
1316		1630
1317	ev_timer_stop (loop, timer);	1631	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1632	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1633	ev_timer_start (loop, timer);
1320		1634
1321	This is relatively simple to implement, but means that each time there	1635	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1636	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1637	data structure and then add it again. Libev tries to be fast, but it's
		1638	still not a constant-time operation.
1324		1639
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1640	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1641
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1642	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1643	C<ev_timer_start>.
1329		1644
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1645	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1646	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1647	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1648	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1649	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1650
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1651	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1652	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1653	member and C<ev_timer_again>.
1338		1654
1339	At start:	1655	At start:
1340		1656
1341	ev_timer_init (timer, callback, 0., 60.);	1657	ev_init (timer, callback);
		1658	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1659	ev_timer_again (loop, timer);
1343		1660
1344	Each time you receive some data:	1661	Each time there is some activity:
1345		1662
1346	ev_timer_again (loop, timer);	1663	ev_timer_again (loop, timer);
1347		1664
1348	It is even possible to change the time-out on the fly:	1665	It is even possible to change the time-out on the fly, regardless of
		1666	whether the watcher is active or not:
1349		1667
1350	timer->repeat = 30.;	1668	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1669	ev_timer_again (loop, timer);
1352		1670
1353	This is slightly more efficient then stopping/starting the timer each time	1671	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1672	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1673	remove and re-insert the timer from/into its internal data structure.
		1674
		1675	It is, however, even simpler than the "obvious" way to do it.
1356		1676
1357	=item 3. Let the timer time out, but then re-arm it as required.	1677	=item 3. Let the timer time out, but then re-arm it as required.
1358		1678
1359	This method is more tricky, but usually most efficient: Most timeouts are	1679	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1680	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1681	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1682	associated activity resets.
1363		1683
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1684	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1685	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1686	within the callback:
1367		1687
1368	ev_tstamp last_activity; // time of last activity	1688	ev_tstamp last_activity; // time of last activity
1369		1689
1370	static void	1690	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1691	callback (EV_P_ ev_timer *w, int revents)
1372	{	1692	{
1373	ev_tstamp now = ev_now (EV_A);	1693	ev_tstamp now = ev_now (EV_A);
1374	ev_tstamp timeout = last_activity + 60.;	1694	ev_tstamp timeout = last_activity + 60.;
1375		1695
1376	// if last_activity is older than now - timeout, we did time out	1696	// if last_activity + 60. is older than now, we did time out
1377	if (timeout < now)	1697	if (timeout < now)
1378	{	1698	{
1379	// timeout occured, take action	1699	// timeout occured, take action
1380	}	1700	}
1381	else	1701	else
1382	{	1702	{
1383	// callback was invoked, but there was some activity, re-arm	1703	// callback was invoked, but there was some activity, re-arm
1384	// to fire in last_activity + 60.	1704	// the watcher to fire in last_activity + 60, which is
		1705	// guaranteed to be in the future, so "again" is positive:
1385	w->again = timeout - now;	1706	w->repeat = timeout - now;
1386	ev_timer_again (EV_A_ w);	1707	ev_timer_again (EV_A_ w);
1387	}	1708	}
1388	}	1709	}
1389		1710
1390	To summarise the callback: first calculate the real time-out (defined as	1711	To summarise the callback: first calculate the real timeout (defined
1391	"60 seconds after the last activity"), then check if that time has been	1712	as "60 seconds after the last activity"), then check if that time has
1392	reached, which means there was a real timeout. Otherwise the callback was	1713	been reached, which means something I<did>, in fact, time out. Otherwise
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1714	the callback was invoked too early (C<timeout> is in the future), so
1394	fire at that future time.	1715	re-schedule the timer to fire at that future time, to see if maybe we have
		1716	a timeout then.
1395		1717
1396	Note how C<ev_timer_again> is used, taking advantage of the	1718	Note how C<ev_timer_again> is used, taking advantage of the
1397	C<ev_timer_again> optimisation when the timer is already running.	1719	C<ev_timer_again> optimisation when the timer is already running.
1398		1720
1399	This scheme causes more callback invocations (about one every 60 seconds),	1721	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1722	minus half the average time between activity), but virtually no calls to
		1723	libev to change the timeout.
1401		1724
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1725	To start the timer, simply initialise the watcher and set C<last_activity>
1403	then call the callback:	1726	to the current time (meaning we just have some activity :), then call the
		1727	callback, which will "do the right thing" and start the timer:
1404		1728
1405	ev_timer_init (timer, callback);	1729	ev_init (timer, callback);
1406	last_activity = ev_now (loop);	1730	last_activity = ev_now (loop);
1407	callback (loop, timer, EV_TIMEOUT);	1731	callback (loop, timer, EV_TIMEOUT);
1408		1732
1409	And when there is some activity, simply remember the time in	1733	And when there is some activity, simply store the current time in
1410	C<last_activity>:	1734	C<last_activity>, no libev calls at all:
1411		1735
1412	last_actiivty = ev_now (loop);	1736	last_actiivty = ev_now (loop);
1413		1737
1414	This technique is slightly more complex, but in most cases where the	1738	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1739	time-out is unlikely to be triggered, much more efficient.
1416		1740
		1741	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1742	callback :) - just change the timeout and invoke the callback, which will
		1743	fix things for you.
		1744
		1745	=item 4. Wee, just use a double-linked list for your timeouts.
		1746
		1747	If there is not one request, but many thousands (millions...), all
		1748	employing some kind of timeout with the same timeout value, then one can
		1749	do even better:
		1750
		1751	When starting the timeout, calculate the timeout value and put the timeout
		1752	at the I<end> of the list.
		1753
		1754	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1755	the list is expected to fire (for example, using the technique #3).
		1756
		1757	When there is some activity, remove the timer from the list, recalculate
		1758	the timeout, append it to the end of the list again, and make sure to
		1759	update the C<ev_timer> if it was taken from the beginning of the list.
		1760
		1761	This way, one can manage an unlimited number of timeouts in O(1) time for
		1762	starting, stopping and updating the timers, at the expense of a major
		1763	complication, and having to use a constant timeout. The constant timeout
		1764	ensures that the list stays sorted.
		1765
1417	=back	1766	=back
		1767
		1768	So which method the best?
		1769
		1770	Method #2 is a simple no-brain-required solution that is adequate in most
		1771	situations. Method #3 requires a bit more thinking, but handles many cases
		1772	better, and isn't very complicated either. In most case, choosing either
		1773	one is fine, with #3 being better in typical situations.
		1774
		1775	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1776	rather complicated, but extremely efficient, something that really pays
		1777	off after the first million or so of active timers, i.e. it's usually
		1778	overkill :)
1418		1779
1419	=head3 The special problem of time updates	1780	=head3 The special problem of time updates
1420		1781
1421	Establishing the current time is a costly operation (it usually takes at	1782	Establishing the current time is a costly operation (it usually takes at
1422	least two system calls): EV therefore updates its idea of the current	1783	least two system calls): EV therefore updates its idea of the current
…		…
1434		1795
1435	If the event loop is suspended for a long time, you can also force an	1796	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1797	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	1798	()>.
1438		1799
		1800	=head3 The special problems of suspended animation
		1801
		1802	When you leave the server world it is quite customary to hit machines that
		1803	can suspend/hibernate - what happens to the clocks during such a suspend?
		1804
		1805	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1806	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1807	to run until the system is suspended, but they will not advance while the
		1808	system is suspended. That means, on resume, it will be as if the program
		1809	was frozen for a few seconds, but the suspend time will not be counted
		1810	towards C<ev_timer> when a monotonic clock source is used. The real time
		1811	clock advanced as expected, but if it is used as sole clocksource, then a
		1812	long suspend would be detected as a time jump by libev, and timers would
		1813	be adjusted accordingly.
		1814
		1815	I would not be surprised to see different behaviour in different between
		1816	operating systems, OS versions or even different hardware.
		1817
		1818	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1819	time jump in the monotonic clocks and the realtime clock. If the program
		1820	is suspended for a very long time, and monotonic clock sources are in use,
		1821	then you can expect C<ev_timer>s to expire as the full suspension time
		1822	will be counted towards the timers. When no monotonic clock source is in
		1823	use, then libev will again assume a timejump and adjust accordingly.
		1824
		1825	It might be beneficial for this latter case to call C<ev_suspend>
		1826	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1827	deterministic behaviour in this case (you can do nothing against
		1828	C<SIGSTOP>).
		1829
1439	=head3 Watcher-Specific Functions and Data Members	1830	=head3 Watcher-Specific Functions and Data Members
1440		1831
1441	=over 4	1832	=over 4
1442		1833
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1834	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1466	If the timer is started but non-repeating, stop it (as if it timed out).	1857	If the timer is started but non-repeating, stop it (as if it timed out).
1467		1858
1468	If the timer is repeating, either start it if necessary (with the	1859	If the timer is repeating, either start it if necessary (with the
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	1860	C<repeat> value), or reset the running timer to the C<repeat> value.
1470		1861
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1862	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	1863	usage example.
		1864
		1865	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1866
		1867	Returns the remaining time until a timer fires. If the timer is active,
		1868	then this time is relative to the current event loop time, otherwise it's
		1869	the timeout value currently configured.
		1870
		1871	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1872	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1873	will return C<4>. When the timer expires and is restarted, it will return
		1874	roughly C<7> (likely slightly less as callback invocation takes some time,
		1875	too), and so on.
1473		1876
1474	=item ev_tstamp repeat [read-write]	1877	=item ev_tstamp repeat [read-write]
1475		1878
1476	The current C<repeat> value. Will be used each time the watcher times out	1879	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	1880	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	1918	=head2 C<ev_periodic> - to cron or not to cron?
1516		1919
1517	Periodic watchers are also timers of a kind, but they are very versatile	1920	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	1921	(and unfortunately a bit complex).
1519		1922
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1923	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	1924	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	1925	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1926	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	1927	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	1928	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		1929
		1930	You can tell a periodic watcher to trigger after some specific point
		1931	in time: for example, if you tell a periodic watcher to trigger "in 10
		1932	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1933	not a delay) and then reset your system clock to January of the previous
		1934	year, then it will take a year or more to trigger the event (unlike an
		1935	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1936	it, as it uses a relative timeout).
		1937
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	1938	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	1939	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	1940	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1941	those cannot react to time jumps.
1532		1942
1533	As with timers, the callback is guaranteed to be invoked only when the	1943	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	1944	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	1945	timers become ready during the same loop iteration then the ones with
		1946	earlier time-out values are invoked before ones with later time-out values
		1947	(but this is no longer true when a callback calls C<ev_loop> recursively).
1536		1948
1537	=head3 Watcher-Specific Functions and Data Members	1949	=head3 Watcher-Specific Functions and Data Members
1538		1950
1539	=over 4	1951	=over 4
1540		1952
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1953	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		1954
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1955	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		1956
1545	Lots of arguments, lets sort it out... There are basically three modes of	1957	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	1958	operation, and we will explain them from simplest to most complex:
1547		1959
1548	=over 4	1960	=over 4
1549		1961
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1962	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		1963
1552	In this configuration the watcher triggers an event after the wall clock	1964	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	1965	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1966	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	1967	will be stopped and invoked when the system clock reaches or surpasses
		1968	this point in time.
1556		1969
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1970	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		1971
1559	In this mode the watcher will always be scheduled to time out at the next	1972	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	1973	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	1974	negative) and then repeat, regardless of any time jumps. The C<offset>
		1975	argument is merely an offset into the C<interval> periods.
1562		1976
1563	This can be used to create timers that do not drift with respect to the	1977	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	1978	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	1979	hour, on the hour (with respect to UTC):
1566		1980
1567	ev_periodic_set (&periodic, 0., 3600., 0);	1981	ev_periodic_set (&periodic, 0., 3600., 0);
1568		1982
1569	This doesn't mean there will always be 3600 seconds in between triggers,	1983	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	1984	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	1985	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	1986	by 3600.
1573		1987
1574	Another way to think about it (for the mathematically inclined) is that	1988	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	1989	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	1990	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		1991
1578	For numerical stability it is preferable that the C<at> value is near	1992	For numerical stability it is preferable that the C<offset> value is near
1579	C<ev_now ()> (the current time), but there is no range requirement for	1993	C<ev_now ()> (the current time), but there is no range requirement for
1580	this value, and in fact is often specified as zero.	1994	this value, and in fact is often specified as zero.
1581		1995
1582	Note also that there is an upper limit to how often a timer can fire (CPU	1996	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	1997	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	1998	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	1999	millisecond (if the OS supports it and the machine is fast enough).
1586		2000
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2001	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2002
1589	In this mode the values for C<interval> and C<at> are both being	2003	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2004	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2005	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2006	current time as second argument.
1593		2007
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2008	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2009	or make ANY other event loop modifications whatsoever, unless explicitly
		2010	allowed by documentation here>.
1596		2011
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2012	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2013	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2014	only event loop modification you are allowed to do).
1600		2015
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2045	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2046	program when the crontabs have changed).
1632		2047
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2048	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2049
1635	When active, returns the absolute time that the watcher is supposed to	2050	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2051	to trigger next. This is not the same as the C<offset> argument to
		2052	C<ev_periodic_set>, but indeed works even in interval and manual
		2053	rescheduling modes.
1637		2054
1638	=item ev_tstamp offset [read-write]	2055	=item ev_tstamp offset [read-write]
1639		2056
1640	When repeating, this contains the offset value, otherwise this is the	2057	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2058	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2059	although libev might modify this value for better numerical stability).
1642		2060
1643	Can be modified any time, but changes only take effect when the periodic	2061	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2062	timer fires or C<ev_periodic_again> is being called.
1645		2063
1646	=item ev_tstamp interval [read-write]	2064	=item ev_tstamp interval [read-write]
…		…
1698	Signal watchers will trigger an event when the process receives a specific	2116	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2117	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2118	will try it's best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2119	normal event processing, like any other event.
1702		2120
1703	If you want signals asynchronously, just use C<sigaction> as you would	2121	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2122	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2123	the signal. You can even use C<ev_async> from a signal handler to
		2124	synchronously wake up an event loop.
1706		2125
1707	You can configure as many watchers as you like per signal. Only when the	2126	You can configure as many watchers as you like for the same signal, but
		2127	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2128	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2129	C<SIGINT> in both the default loop and another loop at the same time. At
		2130	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2131
1708	first watcher gets started will libev actually register a signal handler	2132	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2133	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2134	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2135
1714	If possible and supported, libev will install its handlers with	2136	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2137	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2138	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2139	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2140	and unblock them in an C<ev_prepare> watcher.
		2141
		2142	=head3 The special problem of inheritance over fork/execve/pthread_create
		2143
		2144	Both the signal mask (C<sigprocmask>) and the signal disposition
		2145	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2146	stopping it again), that is, libev might or might not block the signal,
		2147	and might or might not set or restore the installed signal handler.
		2148
		2149	While this does not matter for the signal disposition (libev never
		2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2151	C<execve>), this matters for the signal mask: many programs do not expect
		2152	certain signals to be blocked.
		2153
		2154	This means that before calling C<exec> (from the child) you should reset
		2155	the signal mask to whatever "default" you expect (all clear is a good
		2156	choice usually).
		2157
		2158	The simplest way to ensure that the signal mask is reset in the child is
		2159	to install a fork handler with C<pthread_atfork> that resets it. That will
		2160	catch fork calls done by libraries (such as the libc) as well.
		2161
		2162	In current versions of libev, the signal will not be blocked indefinitely
		2163	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2164	the window of opportunity for problems, it will not go away, as libev
		2165	I<has> to modify the signal mask, at least temporarily.
		2166
		2167	So I can't stress this enough: I<If you do not reset your signal mask when
		2168	you expect it to be empty, you have a race condition in your code>. This
		2169	is not a libev-specific thing, this is true for most event libraries.
1719		2170
1720	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1721		2172
1722	=over 4	2173	=over 4
1723		2174
…		…
1755	some child status changes (most typically when a child of yours dies or	2206	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2207	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2208	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2209	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2210	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2211	but forking and registering a watcher a few event loop iterations later or
1761	not.	2212	in the next callback invocation is not.
1762		2213
1763	Only the default event loop is capable of handling signals, and therefore	2214	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2215	you can only register child watchers in the default event loop.
1765		2216
		2217	Due to some design glitches inside libev, child watchers will always be
		2218	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2219	libev)
		2220
1766	=head3 Process Interaction	2221	=head3 Process Interaction
1767		2222
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2223	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2224	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2225	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2226	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2227	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2228	children, even ones not watched.
1774		2229
1775	=head3 Overriding the Built-In Processing	2230	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2240	=head3 Stopping the Child Watcher
1786		2241
1787	Currently, the child watcher never gets stopped, even when the	2242	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2243	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2244	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2245	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2246	problem).
1791		2247
1792	=head3 Watcher-Specific Functions and Data Members	2248	=head3 Watcher-Specific Functions and Data Members
1793		2249
1794	=over 4	2250	=over 4
1795		2251
…		…
1852		2308
1853		2309
1854	=head2 C<ev_stat> - did the file attributes just change?	2310	=head2 C<ev_stat> - did the file attributes just change?
1855		2311
1856	This watches a file system path for attribute changes. That is, it calls	2312	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2313	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2314	and sees if it changed compared to the last time, invoking the callback if
		2315	it did.
1859		2316
1860	The path does not need to exist: changing from "path exists" to "path does	2317	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2318	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2319	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2320	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2321	least one) and all the other fields of the stat buffer having unspecified
		2322	contents.
1865		2323
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2324	The path I<must not> end in a slash or contain special components such as
		2325	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2326	your working directory changes, then the behaviour is undefined.
1868		2327
1869	Since there is no standard kernel interface to do this, the portable	2328	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2329	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2330	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2331	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2332	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2333	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2334	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2335	currently around C<0.1>, but that's usually overkill.
1877		2336
1878	This watcher type is not meant for massive numbers of stat watchers,	2337	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2338	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2339	resource-intensive.
1881		2340
1882	At the time of this writing, the only OS-specific interface implemented	2341	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2342	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2343	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2344	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2345
1887	=head3 ABI Issues (Largefile Support)	2346	=head3 ABI Issues (Largefile Support)
1888		2347
1889	Libev by default (unless the user overrides this) uses the default	2348	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2349	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2350	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2351	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2352	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2353	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2354	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2355	most noticeably displayed with ev_stat and large file support.
1897		2356
1898	The solution for this is to lobby your distribution maker to make large	2357	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2358	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2359	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2360	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2361	default compilation environment.
1903		2362
1904	=head3 Inotify and Kqueue	2363	=head3 Inotify and Kqueue
1905		2364
1906	When C<inotify (7)> support has been compiled into libev (generally	2365	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2366	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2367	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2368	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2369
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2370	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2371	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2372	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2373	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2374	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2375	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2376	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2377	xfs are fully working) libev usually gets away without polling.
1917		2378
1918	There is no support for kqueue, as apparently it cannot be used to	2379	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2380	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2381	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2382	etc. is difficult.
1922		2383
		2384	=head3 C<stat ()> is a synchronous operation
		2385
		2386	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2387	the process. The exception are C<ev_stat> watchers - those call C<stat
		2388	()>, which is a synchronous operation.
		2389
		2390	For local paths, this usually doesn't matter: unless the system is very
		2391	busy or the intervals between stat's are large, a stat call will be fast,
		2392	as the path data is usually in memory already (except when starting the
		2393	watcher).
		2394
		2395	For networked file systems, calling C<stat ()> can block an indefinite
		2396	time due to network issues, and even under good conditions, a stat call
		2397	often takes multiple milliseconds.
		2398
		2399	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2400	paths, although this is fully supported by libev.
		2401
1923	=head3 The special problem of stat time resolution	2402	=head3 The special problem of stat time resolution
1924		2403
1925	The C<stat ()> system call only supports full-second resolution portably, and	2404	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2405	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2406	still only support whole seconds.
1928		2407
1929	That means that, if the time is the only thing that changes, you can	2408	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2409	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2410	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2411	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2554
2076	=head3 Watcher-Specific Functions and Data Members	2555	=head3 Watcher-Specific Functions and Data Members
2077		2556
2078	=over 4	2557	=over 4
2079		2558
2080	=item ev_idle_init (ev_signal *, callback)	2559	=item ev_idle_init (ev_idle *, callback)
2081		2560
2082	Initialises and configures the idle watcher - it has no parameters of any	2561	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2562	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2563	believe me.
2085		2564
…		…
2098	// no longer anything immediate to do.	2577	// no longer anything immediate to do.
2099	}	2578	}
2100		2579
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2580	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2581	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2582	ev_idle_start (loop, idle_watcher);
2104		2583
2105		2584
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2585	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2586
2108	Prepare and check watchers are usually (but not always) used in pairs:	2587	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2201	struct pollfd fds [nfd];	2680	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2681	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2682	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2683
2205	/* the callback is illegal, but won't be called as we stop during check */	2684	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2685	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2686	ev_timer_start (loop, &tw);
2208		2687
2209	// create one ev_io per pollfd	2688	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2689	for (int i = 0; i < nfd; ++i)
2211	{	2690	{
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	2803	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	2804	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	2805	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	2806	the rest in a second one, and embed the second one in the first.
2328		2807
2329	As long as the watcher is active, the callback will be invoked every time	2808	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	2809	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2810	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	2811	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	2812	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	2813	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		2814
2337	As long as the watcher is started it will automatically handle events. The	2815	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	2816	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		2817
2342	Also, there have not currently been made special provisions for forking:	2818	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2819	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	2820	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	2821	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		2822
2348	Unfortunately, not all backends are embeddable: only the ones returned by	2823	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2824	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	2825	portable one.
2351		2826
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	2920	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	2921	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2922	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	2923	handlers will be invoked, too, of course.
2449		2924
		2925	=head3 The special problem of life after fork - how is it possible?
		2926
		2927	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2928	up/change the process environment, followed by a call to C<exec()>. This
		2929	sequence should be handled by libev without any problems.
		2930
		2931	This changes when the application actually wants to do event handling
		2932	in the child, or both parent in child, in effect "continuing" after the
		2933	fork.
		2934
		2935	The default mode of operation (for libev, with application help to detect
		2936	forks) is to duplicate all the state in the child, as would be expected
		2937	when I<either> the parent I<or> the child process continues.
		2938
		2939	When both processes want to continue using libev, then this is usually the
		2940	wrong result. In that case, usually one process (typically the parent) is
		2941	supposed to continue with all watchers in place as before, while the other
		2942	process typically wants to start fresh, i.e. without any active watchers.
		2943
		2944	The cleanest and most efficient way to achieve that with libev is to
		2945	simply create a new event loop, which of course will be "empty", and
		2946	use that for new watchers. This has the advantage of not touching more
		2947	memory than necessary, and thus avoiding the copy-on-write, and the
		2948	disadvantage of having to use multiple event loops (which do not support
		2949	signal watchers).
		2950
		2951	When this is not possible, or you want to use the default loop for
		2952	other reasons, then in the process that wants to start "fresh", call
		2953	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2954	the default loop will "orphan" (not stop) all registered watchers, so you
		2955	have to be careful not to execute code that modifies those watchers. Note
		2956	also that in that case, you have to re-register any signal watchers.
		2957
2450	=head3 Watcher-Specific Functions and Data Members	2958	=head3 Watcher-Specific Functions and Data Members
2451		2959
2452	=over 4	2960	=over 4
2453		2961
2454	=item ev_fork_init (ev_signal *, callback)	2962	=item ev_fork_init (ev_signal *, callback)
…		…
2483	=head3 Queueing	2991	=head3 Queueing
2484		2992
2485	C<ev_async> does not support queueing of data in any way. The reason	2993	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	2994	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	2995	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	2996	need elaborate support such as pthreads or unportable memory access
		2997	semantics.
2489		2998
2490	That means that if you want to queue data, you have to provide your own	2999	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3000	queue. But at least I can tell you how to implement locking around your
2492	queue:	3001	queue:
2493		3002
…		…
2571	=over 4	3080	=over 4
2572		3081
2573	=item ev_async_init (ev_async *, callback)	3082	=item ev_async_init (ev_async *, callback)
2574		3083
2575	Initialises and configures the async watcher - it has no parameters of any	3084	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3085	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3086	trust me.
2578		3087
2579	=item ev_async_send (loop, ev_async *)	3088	=item ev_async_send (loop, ev_async *)
2580		3089
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3090	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3091	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3092	C<ev_feed_event>, this call is safe to do from other threads, signal or
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3093	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2585	section below on what exactly this means).	3094	section below on what exactly this means).
2586		3095
		3096	Note that, as with other watchers in libev, multiple events might get
		3097	compressed into a single callback invocation (another way to look at this
		3098	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3099	reset when the event loop detects that).
		3100
2587	This call incurs the overhead of a system call only once per loop iteration,	3101	This call incurs the overhead of a system call only once per event loop
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3102	iteration, so while the overhead might be noticeable, it doesn't apply to
2589	calls to C<ev_async_send>.	3103	repeated calls to C<ev_async_send> for the same event loop.
2590		3104
2591	=item bool = ev_async_pending (ev_async *)	3105	=item bool = ev_async_pending (ev_async *)
2592		3106
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3107	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3108	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3111	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3112	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3113	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3114	quickly check whether invoking the loop might be a good idea.
2601		3115
2602	Not that this does I<not> check whether the watcher itself is pending, only	3116	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3117	only whether it has been requested to make this watcher pending: there
		3118	is a time window between the event loop checking and resetting the async
		3119	notification, and the callback being invoked.
2604		3120
2605	=back	3121	=back
2606		3122
2607		3123
2608	=head1 OTHER FUNCTIONS	3124	=head1 OTHER FUNCTIONS
…		…
2644	/* doh, nothing entered */;	3160	/* doh, nothing entered */;
2645	}	3161	}
2646		3162
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3164
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3165	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3166
2657	Feed an event on the given fd, as if a file descriptor backend detected	3167	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3168	the given events it.
2659		3169
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3170	=item ev_feed_signal_event (loop, int signum)
2661		3171
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3172	Feed an event as if the given signal occurred (C<loop> must be the default
2663	loop!).	3173	loop!).
2664		3174
2665	=back	3175	=back
…		…
2745		3255
2746	=over 4	3256	=over 4
2747		3257
2748	=item ev::TYPE::TYPE ()	3258	=item ev::TYPE::TYPE ()
2749		3259
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3260	=item ev::TYPE::TYPE (loop)
2751		3261
2752	=item ev::TYPE::~TYPE	3262	=item ev::TYPE::~TYPE
2753		3263
2754	The constructor (optionally) takes an event loop to associate the watcher	3264	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3265	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3297
2788	myclass obj;	3298	myclass obj;
2789	ev::io iow;	3299	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3300	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3301
		3302	=item w->set (object *)
		3303
		3304	This is an B<experimental> feature that might go away in a future version.
		3305
		3306	This is a variation of a method callback - leaving out the method to call
		3307	will default the method to C<operator ()>, which makes it possible to use
		3308	functor objects without having to manually specify the C<operator ()> all
		3309	the time. Incidentally, you can then also leave out the template argument
		3310	list.
		3311
		3312	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3313	int revents)>.
		3314
		3315	See the method-C<set> above for more details.
		3316
		3317	Example: use a functor object as callback.
		3318
		3319	struct myfunctor
		3320	{
		3321	void operator() (ev::io &w, int revents)
		3322	{
		3323	...
		3324	}
		3325	}
		3326
		3327	myfunctor f;
		3328
		3329	ev::io w;
		3330	w.set (&f);
		3331
2792	=item w->set<function> (void *data = 0)	3332	=item w->set<function> (void *data = 0)
2793		3333
2794	Also sets a callback, but uses a static method or plain function as	3334	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	3335	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	3336	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	3342	Example: Use a plain function as callback.
2803		3343
2804	static void io_cb (ev::io &w, int revents) { }	3344	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	3345	iow.set <io_cb> ();
2806		3346
2807	=item w->set (struct ev_loop *)	3347	=item w->set (loop)
2808		3348
2809	Associates a different C<struct ev_loop> with this watcher. You can only	3349	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	3350	do this when the watcher is inactive (and not pending either).
2811		3351
2812	=item w->set ([arguments])	3352	=item w->set ([arguments])
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	3422	L<http://software.schmorp.de/pkg/EV>.
2883		3423
2884	=item Python	3424	=item Python
2885		3425
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3426	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	3427	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		3428
2893	=item Ruby	3429	=item Ruby
2894		3430
2895	Tony Arcieri has written a ruby extension that offers access to a subset	3431	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	3432	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	3433	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	3434	L<http://rev.rubyforge.org/>.
2899		3435
		3436	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3437	makes rev work even on mingw.
		3438
		3439	=item Haskell
		3440
		3441	A haskell binding to libev is available at
		3442	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3443
2900	=item D	3444	=item D
2901		3445
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3446	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3447	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3448
		3449	=item Ocaml
		3450
		3451	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3453
		3454	=item Lua
		3455
		3456	Brian Maher has written a partial interface to libev
		3457	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3458	L<http://github.com/brimworks/lua-ev>.
2904		3459
2905	=back	3460	=back
2906		3461
2907		3462
2908	=head1 MACRO MAGIC	3463	=head1 MACRO MAGIC
…		…
3009		3564
3010	#define EV_STANDALONE 1	3565	#define EV_STANDALONE 1
3011	#include "ev.h"	3566	#include "ev.h"
3012		3567
3013	Both header files and implementation files can be compiled with a C++	3568	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	3569	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	3570	as a bug).
3016		3571
3017	You need the following files in your source tree, or in a directory	3572	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	3573	in your include path (e.g. in libev/ when using -Ilibev):
3019		3574
…		…
3075	keeps libev from including F<config.h>, and it also defines dummy	3630	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	3631	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	3632	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	3633	F<event.h> that are not directly supported by the libev core alone.
3079		3634
		3635	In standalone mode, libev will still try to automatically deduce the
		3636	configuration, but has to be more conservative.
		3637
3080	=item EV_USE_MONOTONIC	3638	=item EV_USE_MONOTONIC
3081		3639
3082	If defined to be C<1>, libev will try to detect the availability of the	3640	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	3641	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	3642	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	3643	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	3644	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	3645	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	3646	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		3647
3090	=item EV_USE_REALTIME	3648	=item EV_USE_REALTIME
3091		3649
3092	If defined to be C<1>, libev will try to detect the availability of the	3650	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	3651	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	3652	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3653	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3654	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3655	correctness. See the note about libraries in the description of
		3656	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3657	C<EV_USE_CLOCK_SYSCALL>.
		3658
		3659	=item EV_USE_CLOCK_SYSCALL
		3660
		3661	If defined to be C<1>, libev will try to use a direct syscall instead
		3662	of calling the system-provided C<clock_gettime> function. This option
		3663	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3664	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3665	programs needlessly. Using a direct syscall is slightly slower (in
		3666	theory), because no optimised vdso implementation can be used, but avoids
		3667	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3668	higher, as it simplifies linking (no need for C<-lrt>).
3098		3669
3099	=item EV_USE_NANOSLEEP	3670	=item EV_USE_NANOSLEEP
3100		3671
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3672	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	3673	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		3689
3119	=item EV_SELECT_USE_FD_SET	3690	=item EV_SELECT_USE_FD_SET
3120		3691
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	3692	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	3693	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3694	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	3695	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	3696	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3697	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	3698	configures the maximum size of the C<fd_set>.
3128		3699
3129	=item EV_SELECT_IS_WINSOCKET	3700	=item EV_SELECT_IS_WINSOCKET
3130		3701
3131	When defined to C<1>, the select backend will assume that	3702	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	3703	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	3705	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3706	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	3707	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	3708	on win32. Should not be defined on non-win32 platforms.
3138		3709
3139	=item EV_FD_TO_WIN32_HANDLE	3710	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		3711
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3712	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	3713	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	3714	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	3715	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	3716	in which case they can provide this function to map fds to socket handles.
		3717
		3718	=item EV_WIN32_HANDLE_TO_FD(handle)
		3719
		3720	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3721	using the standard C<_open_osfhandle> function. For programs implementing
		3722	their own fd to handle mapping, overwriting this function makes it easier
		3723	to do so. This can be done by defining this macro to an appropriate value.
		3724
		3725	=item EV_WIN32_CLOSE_FD(fd)
		3726
		3727	If programs implement their own fd to handle mapping on win32, then this
		3728	macro can be used to override the C<close> function, useful to unregister
		3729	file descriptors again. Note that the replacement function has to close
		3730	the underlying OS handle.
3146		3731
3147	=item EV_USE_POLL	3732	=item EV_USE_POLL
3148		3733
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3734	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	3735	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3282	defined to be C<0>, then they are not.	3867	defined to be C<0>, then they are not.
3283		3868
3284	=item EV_MINIMAL	3869	=item EV_MINIMAL
3285		3870
3286	If you need to shave off some kilobytes of code at the expense of some	3871	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	3872	speed (but with the full API), define this symbol to C<1>. Currently this
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3873	is used to override some inlining decisions, saves roughly 30% code size
3289	much smaller 2-heap for timer management over the default 4-heap.	3874	on amd64. It also selects a much smaller 2-heap for timer management over
		3875	the default 4-heap.
		3876
		3877	You can save even more by disabling watcher types you do not need
		3878	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3879	(C<-DNDEBUG>) will usually reduce code size a lot.
		3880
		3881	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3882	provide a bare-bones event library. See C<ev.h> for details on what parts
		3883	of the API are still available, and do not complain if this subset changes
		3884	over time.
		3885
		3886	=item EV_NSIG
		3887
		3888	The highest supported signal number, +1 (or, the number of
		3889	signals): Normally, libev tries to deduce the maximum number of signals
		3890	automatically, but sometimes this fails, in which case it can be
		3891	specified. Also, using a lower number than detected (C<32> should be
		3892	good for about any system in existance) can save some memory, as libev
		3893	statically allocates some 12-24 bytes per signal number.
3290		3894
3291	=item EV_PID_HASHSIZE	3895	=item EV_PID_HASHSIZE
3292		3896
3293	C<ev_child> watchers use a small hash table to distribute workload by	3897	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3898	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4084	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4085	watcher callback into the event loop interested in the signal.
3482		4086
3483	=back	4087	=back
3484		4088
		4089	=head4 THREAD LOCKING EXAMPLE
		4090
		4091	Here is a fictitious example of how to run an event loop in a different
		4092	thread than where callbacks are being invoked and watchers are
		4093	created/added/removed.
		4094
		4095	For a real-world example, see the C<EV::Loop::Async> perl module,
		4096	which uses exactly this technique (which is suited for many high-level
		4097	languages).
		4098
		4099	The example uses a pthread mutex to protect the loop data, a condition
		4100	variable to wait for callback invocations, an async watcher to notify the
		4101	event loop thread and an unspecified mechanism to wake up the main thread.
		4102
		4103	First, you need to associate some data with the event loop:
		4104
		4105	typedef struct {
		4106	mutex_t lock; /* global loop lock */
		4107	ev_async async_w;
		4108	thread_t tid;
		4109	cond_t invoke_cv;
		4110	} userdata;
		4111
		4112	void prepare_loop (EV_P)
		4113	{
		4114	// for simplicity, we use a static userdata struct.
		4115	static userdata u;
		4116
		4117	ev_async_init (&u->async_w, async_cb);
		4118	ev_async_start (EV_A_ &u->async_w);
		4119
		4120	pthread_mutex_init (&u->lock, 0);
		4121	pthread_cond_init (&u->invoke_cv, 0);
		4122
		4123	// now associate this with the loop
		4124	ev_set_userdata (EV_A_ u);
		4125	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4126	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4127
		4128	// then create the thread running ev_loop
		4129	pthread_create (&u->tid, 0, l_run, EV_A);
		4130	}
		4131
		4132	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4133	solely to wake up the event loop so it takes notice of any new watchers
		4134	that might have been added:
		4135
		4136	static void
		4137	async_cb (EV_P_ ev_async *w, int revents)
		4138	{
		4139	// just used for the side effects
		4140	}
		4141
		4142	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4143	protecting the loop data, respectively.
		4144
		4145	static void
		4146	l_release (EV_P)
		4147	{
		4148	userdata *u = ev_userdata (EV_A);
		4149	pthread_mutex_unlock (&u->lock);
		4150	}
		4151
		4152	static void
		4153	l_acquire (EV_P)
		4154	{
		4155	userdata *u = ev_userdata (EV_A);
		4156	pthread_mutex_lock (&u->lock);
		4157	}
		4158
		4159	The event loop thread first acquires the mutex, and then jumps straight
		4160	into C<ev_loop>:
		4161
		4162	void *
		4163	l_run (void *thr_arg)
		4164	{
		4165	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4166
		4167	l_acquire (EV_A);
		4168	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4169	ev_loop (EV_A_ 0);
		4170	l_release (EV_A);
		4171
		4172	return 0;
		4173	}
		4174
		4175	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4176	signal the main thread via some unspecified mechanism (signals? pipe
		4177	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4178	have been called (in a while loop because a) spurious wakeups are possible
		4179	and b) skipping inter-thread-communication when there are no pending
		4180	watchers is very beneficial):
		4181
		4182	static void
		4183	l_invoke (EV_P)
		4184	{
		4185	userdata *u = ev_userdata (EV_A);
		4186
		4187	while (ev_pending_count (EV_A))
		4188	{
		4189	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4190	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4191	}
		4192	}
		4193
		4194	Now, whenever the main thread gets told to invoke pending watchers, it
		4195	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4196	thread to continue:
		4197
		4198	static void
		4199	real_invoke_pending (EV_P)
		4200	{
		4201	userdata *u = ev_userdata (EV_A);
		4202
		4203	pthread_mutex_lock (&u->lock);
		4204	ev_invoke_pending (EV_A);
		4205	pthread_cond_signal (&u->invoke_cv);
		4206	pthread_mutex_unlock (&u->lock);
		4207	}
		4208
		4209	Whenever you want to start/stop a watcher or do other modifications to an
		4210	event loop, you will now have to lock:
		4211
		4212	ev_timer timeout_watcher;
		4213	userdata *u = ev_userdata (EV_A);
		4214
		4215	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4216
		4217	pthread_mutex_lock (&u->lock);
		4218	ev_timer_start (EV_A_ &timeout_watcher);
		4219	ev_async_send (EV_A_ &u->async_w);
		4220	pthread_mutex_unlock (&u->lock);
		4221
		4222	Note that sending the C<ev_async> watcher is required because otherwise
		4223	an event loop currently blocking in the kernel will have no knowledge
		4224	about the newly added timer. By waking up the loop it will pick up any new
		4225	watchers in the next event loop iteration.
		4226
3485	=head3 COROUTINES	4227	=head3 COROUTINES
3486		4228
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4229	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4230	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4231	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4232	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4233	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4234	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4235
3494	Care has been taken to ensure that libev does not keep local state inside	4236	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4237	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4238	they do not call any callbacks.
3497		4239
3498	=head2 COMPILER WARNINGS	4240	=head2 COMPILER WARNINGS
3499		4241
3500	Depending on your compiler and compiler settings, you might get no or a	4242	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4243	lot of warnings when compiling libev code. Some people are apparently
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4277	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4278	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4279	==2274== still reachable: 256 bytes in 1 blocks.
3538		4280
3539	Then there is no memory leak, just as memory accounted to global variables	4281	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	4282	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4283
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4284	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4285	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	4286	although an acceptable workaround has been found here), or it might be
3545	confused.	4287	confused.
…		…
3574	way (note also that glib is the slowest event library known to man).	4316	way (note also that glib is the slowest event library known to man).
3575		4317
3576	There is no supported compilation method available on windows except	4318	There is no supported compilation method available on windows except
3577	embedding it into other applications.	4319	embedding it into other applications.
3578		4320
		4321	Sensible signal handling is officially unsupported by Microsoft - libev
		4322	tries its best, but under most conditions, signals will simply not work.
		4323
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	4324	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	4325	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	4326	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	4327	so make sure you only write small amounts into your sockets (less than a
3583	megabyte seems safe, but this apparently depends on the amount of memory	4328	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	4332	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	4333	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	4334	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	4335	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	4336	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	4337	(due to Microsoft monopoly games).
3593		4338
3594	A typical way to use libev under windows is to embed it (see the embedding	4339	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	4340	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	4341	of F<ev.h>:
3597		4342
…		…
3633		4378
3634	Early versions of winsocket's select only supported waiting for a maximum	4379	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	4380	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	4381	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	4382	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	4383	previous thread in each. Sounds great!).
3639		4384
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4385	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	4386	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	4387	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	4388	other interpreters do their own select emulation on windows).
3644		4389
3645	Another limit is the number of file descriptors in the Microsoft runtime	4390	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4391	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	4392	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4393	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	4394	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	4395	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	4396	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	4397	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	4398	the cost of calling select (O(n²)) will likely make this unworkable.
3656		4399
3657	=back	4400	=back
3658		4401
3659	=head2 PORTABILITY REQUIREMENTS	4402	=head2 PORTABILITY REQUIREMENTS
3660		4403
…		…
3703	=item C<double> must hold a time value in seconds with enough accuracy	4446	=item C<double> must hold a time value in seconds with enough accuracy
3704		4447
3705	The type C<double> is used to represent timestamps. It is required to	4448	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4449	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3707	enough for at least into the year 4000. This requirement is fulfilled by	4450	enough for at least into the year 4000. This requirement is fulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	4451	implementations implementing IEEE 754, which is basically all existing
		4452	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4453	2200.
3709		4454
3710	=back	4455	=back
3711		4456
3712	If you know of other additional requirements drop me a note.	4457	If you know of other additional requirements drop me a note.
3713		4458
…		…
3781	involves iterating over all running async watchers or all signal numbers.	4526	involves iterating over all running async watchers or all signal numbers.
3782		4527
3783	=back	4528	=back
3784		4529
3785		4530
		4531	=head1 GLOSSARY
		4532
		4533	=over 4
		4534
		4535	=item active
		4536
		4537	A watcher is active as long as it has been started (has been attached to
		4538	an event loop) but not yet stopped (disassociated from the event loop).
		4539
		4540	=item application
		4541
		4542	In this document, an application is whatever is using libev.
		4543
		4544	=item callback
		4545
		4546	The address of a function that is called when some event has been
		4547	detected. Callbacks are being passed the event loop, the watcher that
		4548	received the event, and the actual event bitset.
		4549
		4550	=item callback invocation
		4551
		4552	The act of calling the callback associated with a watcher.
		4553
		4554	=item event
		4555
		4556	A change of state of some external event, such as data now being available
		4557	for reading on a file descriptor, time having passed or simply not having
		4558	any other events happening anymore.
		4559
		4560	In libev, events are represented as single bits (such as C<EV_READ> or
		4561	C<EV_TIMEOUT>).
		4562
		4563	=item event library
		4564
		4565	A software package implementing an event model and loop.
		4566
		4567	=item event loop
		4568
		4569	An entity that handles and processes external events and converts them
		4570	into callback invocations.
		4571
		4572	=item event model
		4573
		4574	The model used to describe how an event loop handles and processes
		4575	watchers and events.
		4576
		4577	=item pending
		4578
		4579	A watcher is pending as soon as the corresponding event has been detected,
		4580	and stops being pending as soon as the watcher will be invoked or its
		4581	pending status is explicitly cleared by the application.
		4582
		4583	A watcher can be pending, but not active. Stopping a watcher also clears
		4584	its pending status.
		4585
		4586	=item real time
		4587
		4588	The physical time that is observed. It is apparently strictly monotonic :)
		4589
		4590	=item wall-clock time
		4591
		4592	The time and date as shown on clocks. Unlike real time, it can actually
		4593	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4594	clock.
		4595
		4596	=item watcher
		4597
		4598	A data structure that describes interest in certain events. Watchers need
		4599	to be started (attached to an event loop) before they can receive events.
		4600
		4601	=item watcher invocation
		4602
		4603	The act of calling the callback associated with a watcher.
		4604
		4605	=back
		4606
3786	=head1 AUTHOR	4607	=head1 AUTHOR
3787		4608
3788	Marc Lehmann <libev@schmorp.de>.	4609	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3789		4610

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