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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_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		413
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
		418
382	For few fds, this backend is a bit little slower than poll and select,	419	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	420	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	421	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	422	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	423
387	cases and requiring a system call per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
389		440
390	While stopping, setting and starting an I/O watcher in the same iteration	441	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	442	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	443	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
395		446	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		447
400	Best performance from this backend is achieved by not unregistering all	448	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	449	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	450	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	451	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
405		459
406	While nominally embeddable in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	461	all kernel versions tested so far.
408		462
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	464	C<EVBACKEND_POLL>.
411		465
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		467
414	Kqueue deserves special mention, as at the time of this writing, it was	468	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	469	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	470	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	471	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	472	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	473	without API changes to existing programs. For this reason it's not being
		474	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		476	system like NetBSD.
420		477
421	You still can embed kqueue into a normal poll or select backend and use it	478	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	479	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	480	the target platform). See C<ev_embed> watchers for more info.
424		481
425	It scales in the same way as the epoll backend, but the interface to the	482	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	483	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	484	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	485	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	486	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
431		489
432	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
433		491
434	While nominally embeddable in other event loops, this doesn't work	492	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	493	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	494	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	495	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
440		498
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	499	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	501	C<NOTE_EOF>.
444		502
…		…
464	might perform better.	522	might perform better.
465		523
466	On the positive side, with the exception of the spurious readiness	524	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	525	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	526	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	527	OS-specific backends (I vastly prefer correctness over speed hacks).
470		528
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	530	C<EVBACKEND_POLL>.
473		531
474	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
…		…
479		537
480	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
481		539
482	=back	540	=back
483		541
484	If one or more of these are or'ed into the flags value, then only these	542	If one or more of the backend flags are or'ed into the flags value,
485	backends will be tried (in the reverse order as listed here). If none are	543	then only these backends will be tried (in the reverse order as listed
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
487		546
488	Example: This is the most typical usage.	547	Example: This is the most typical usage.
489		548
490	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	587	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	589	for example).
531		590
532	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
535		594
536	In general it is not advisable to call this function except in the	595	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	596	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	597	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
540		599
541	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
542		601
543	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
582		641
583	This value can sometimes be useful as a generation counter of sorts (it	642	This value can sometimes be useful as a generation counter of sorts (it
584	"ticks" the number of loop iterations), as it roughly corresponds with	643	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
586		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
		657
587	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
588		659
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	661	use.
591		662
…		…
605		676
606	This function is rarely useful, but when some event callback runs for a	677	This function is rarely useful, but when some event callback runs for a
607	very long time without entering the event loop, updating libev's idea of	678	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	679	the current time is a good idea.
609		680
610	See also "The special problem of time updates" in the C<ev_timer> section.	681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
611		708
612	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
613		710
614	Finally, this is it, the event handler. This function usually is called	711	Finally, this is it, the event handler. This function usually is called
615	after you initialised all your watchers and you want to start handling	712	after you have initialised all your watchers and you want to start
616	events.	713	handling events.
617		714
618	If the flags argument is specified as C<0>, it will not return until	715	If the flags argument is specified as C<0>, it will not return until
619	either no event watchers are active anymore or C<ev_unloop> was called.	716	either no event watchers are active anymore or C<ev_unloop> was called.
620		717
621	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
…		…
631	the loop.	728	the loop.
632		729
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	731	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	732	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	733	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	734	user-registered callback will be called), and will return after one
638	iteration of the loop.	735	iteration of the loop.
639		736
640	This is useful if you are waiting for some external event in conjunction	737	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	738	with something not expressible using other libev watchers (i.e. "roll your
…		…
695		792
696	Ref/unref can be used to add or remove a reference count on the event	793	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	794	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.	795	count is nonzero, C<ev_loop> will not return on its own.
699		796
700	If you have a watcher you never unregister that should not keep C<ev_loop>	797	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	798	unregister, but that nevertheless should not keep C<ev_loop> from
		799	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	800	before stopping it.
703		801
704	As an example, libev itself uses this for its internal signal pipe: It is	802	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	803	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	804	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	805	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>	806	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,	807	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	808	before, respectively. Note also that libev might stop watchers itself
		809	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		810	in the callback).
711		811
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	812	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
713	running when nothing else is active.	813	running when nothing else is active.
714		814
715	ev_signal exitsig;	815	ev_signal exitsig;
…		…
744		844
745	By setting a higher I<io collect interval> you allow libev to spend more	845	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,	846	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	847	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	848	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.	849	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		850	sleep time ensures that libev will not poll for I/O events more often then
		851	once per this interval, on average.
750		852
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	853	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	854	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	855	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	856	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		858
757	Many (busy) programs can usually benefit by setting the I/O collect	859	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	860	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	861	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>,	862	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.	863	as this approaches the timing granularity of most systems. Note that if
		864	you do transactions with the outside world and you can't increase the
		865	parallelity, then this setting will limit your transaction rate (if you
		866	need to poll once per transaction and the I/O collect interval is 0.01,
		867	then you can't do more than 100 transations per second).
762		868
763	Setting the I<timeout collect interval> can improve the opportunity for	869	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	870	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	871	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	872	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	873	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	874	they fire on, say, one-second boundaries only.
769		875
		876	Example: we only need 0.1s timeout granularity, and we wish not to poll
		877	more often than 100 times per second:
		878
		879	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		880	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		881
		882	=item ev_invoke_pending (loop)
		883
		884	This call will simply invoke all pending watchers while resetting their
		885	pending state. Normally, C<ev_loop> does this automatically when required,
		886	but when overriding the invoke callback this call comes handy.
		887
		888	=item int ev_pending_count (loop)
		889
		890	Returns the number of pending watchers - zero indicates that no watchers
		891	are pending.
		892
		893	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		894
		895	This overrides the invoke pending functionality of the loop: Instead of
		896	invoking all pending watchers when there are any, C<ev_loop> will call
		897	this callback instead. This is useful, for example, when you want to
		898	invoke the actual watchers inside another context (another thread etc.).
		899
		900	If you want to reset the callback, use C<ev_invoke_pending> as new
		901	callback.
		902
		903	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		904
		905	Sometimes you want to share the same loop between multiple threads. This
		906	can be done relatively simply by putting mutex_lock/unlock calls around
		907	each call to a libev function.
		908
		909	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		910	wait for it to return. One way around this is to wake up the loop via
		911	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		912	and I<acquire> callbacks on the loop.
		913
		914	When set, then C<release> will be called just before the thread is
		915	suspended waiting for new events, and C<acquire> is called just
		916	afterwards.
		917
		918	Ideally, C<release> will just call your mutex_unlock function, and
		919	C<acquire> will just call the mutex_lock function again.
		920
		921	While event loop modifications are allowed between invocations of
		922	C<release> and C<acquire> (that's their only purpose after all), no
		923	modifications done will affect the event loop, i.e. adding watchers will
		924	have no effect on the set of file descriptors being watched, or the time
		925	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		926	to take note of any changes you made.
		927
		928	In theory, threads executing C<ev_loop> will be async-cancel safe between
		929	invocations of C<release> and C<acquire>.
		930
		931	See also the locking example in the C<THREADS> section later in this
		932	document.
		933
		934	=item ev_set_userdata (loop, void *data)
		935
		936	=item ev_userdata (loop)
		937
		938	Set and retrieve a single C<void *> associated with a loop. When
		939	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		940	C<0.>
		941
		942	These two functions can be used to associate arbitrary data with a loop,
		943	and are intended solely for the C<invoke_pending_cb>, C<release> and
		944	C<acquire> callbacks described above, but of course can be (ab-)used for
		945	any other purpose as well.
		946
770	=item ev_loop_verify (loop)	947	=item ev_loop_verify (loop)
771		948
772	This function only does something when C<EV_VERIFY> support has been	949	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	950	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	951	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	952	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	953	error and call C<abort ()>.
777		954
778	This can be used to catch bugs inside libev itself: under normal	955	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	959	=back
783		960
784		961
785	=head1 ANATOMY OF A WATCHER	962	=head1 ANATOMY OF A WATCHER
786		963
		964	In the following description, uppercase C<TYPE> in names stands for the
		965	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		966	watchers and C<ev_io_start> for I/O watchers.
		967
787	A watcher is a structure that you create and register to record your	968	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	969	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:	970	become readable, you would create an C<ev_io> watcher for that:
790		971
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	972	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
…		…
793	ev_io_stop (w);	974	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	975	ev_unloop (loop, EVUNLOOP_ALL);
795	}	976	}
796		977
797	struct ev_loop *loop = ev_default_loop (0);	978	struct ev_loop *loop = ev_default_loop (0);
		979
798	ev_io stdin_watcher;	980	ev_io stdin_watcher;
		981
799	ev_init (&stdin_watcher, my_cb);	982	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	983	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	984	ev_io_start (loop, &stdin_watcher);
		985
802	ev_loop (loop, 0);	986	ev_loop (loop, 0);
803		987
804	As you can see, you are responsible for allocating the memory for your	988	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,	989	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	990	stack).
		991
		992	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		993	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
807		994
808	Each watcher structure must be initialised by a call to C<ev_init	995	Each watcher structure must be initialised by a call to C<ev_init
809	(watcher *, callback)>, which expects a callback to be provided. This	996	(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	997	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	998	watchers, each time the event loop detects that the file descriptor given
812	is readable and/or writable).	999	is readable and/or writable).
813		1000
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1001	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	1002	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	1003	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1004	ev_TYPE_init (watcher *, callback, ...) >>.
818		1005
819	To make the watcher actually watch out for events, you have to start it	1006	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	1007	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	1008	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1009	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1010
824	As long as your watcher is active (has been started but not stopped) you	1011	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	1012	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1013	reinitialise it or call its C<ev_TYPE_set> macro.
827		1014
828	Each and every callback receives the event loop pointer as first, the	1015	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	1016	registered watcher structure as second, and a bitset of received events as
830	third argument.	1017	third argument.
831		1018
…		…
889		1076
890	=item C<EV_ASYNC>	1077	=item C<EV_ASYNC>
891		1078
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1079	The given async watcher has been asynchronously notified (see C<ev_async>).
893		1080
		1081	=item C<EV_CUSTOM>
		1082
		1083	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1084	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1085
894	=item C<EV_ERROR>	1086	=item C<EV_ERROR>
895		1087
896	An unspecified error has occurred, the watcher has been stopped. This might	1088	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1089	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	1090	ran out of memory, a file descriptor was found to be closed or any other
…		…
912		1104
913	=back	1105	=back
914		1106
915	=head2 GENERIC WATCHER FUNCTIONS	1107	=head2 GENERIC WATCHER FUNCTIONS
916		1108
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	1109	=over 4
921		1110
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1111	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1112
924	This macro initialises the generic portion of a watcher. The contents	1113	This macro initialises the generic portion of a watcher. The contents
…		…
938		1127
939	ev_io w;	1128	ev_io w;
940	ev_init (&w, my_cb);	1129	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1130	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1131
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1132	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1133
945	This macro initialises the type-specific parts of a watcher. You need to	1134	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	1135	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	1136	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	1137	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1150
962	Example: Initialise and set an C<ev_io> watcher in one step.	1151	Example: Initialise and set an C<ev_io> watcher in one step.
963		1152
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1153	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1154
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1155	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1156
968	Starts (activates) the given watcher. Only active watchers will receive	1157	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1158	events. If the watcher is already active nothing will happen.
970		1159
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1160	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1161	whole section.
973		1162
974	ev_io_start (EV_DEFAULT_UC, &w);	1163	ev_io_start (EV_DEFAULT_UC, &w);
975		1164
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1165	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1166
978	Stops the given watcher if active, and clears the pending status (whether	1167	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1168	the watcher was active or not).
980		1169
981	It is possible that stopped watchers are pending - for example,	1170	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1195	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1196
1008	Change the callback. You can change the callback at virtually any time	1197	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1198	(modulo threads).
1010		1199
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1200	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1201
1013	=item int ev_priority (ev_TYPE *watcher)	1202	=item int ev_priority (ev_TYPE *watcher)
1014		1203
1015	Set and query the priority of the watcher. The priority is a small	1204	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>	1205	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1206	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1207	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1208	from being executed (except for C<ev_idle> watchers).
1020		1209
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	1210	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.	1211	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1212
1029	You I<must not> change the priority of a watcher as long as it is active or	1213	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1214	pending.
1031		1215
		1216	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1217	fine, as long as you do not mind that the priority value you query might
		1218	or might not have been clamped to the valid range.
		1219
1032	The default priority used by watchers when no priority has been set is	1220	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 :).	1221	always C<0>, which is supposed to not be too high and not be too low :).
1034		1222
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1223	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	1224	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1225
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1226	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1227
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1228	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	1229	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	1236	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>.	1237	watcher isn't pending it does nothing and returns C<0>.
1051		1238
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1239	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.	1240	callback to be invoked, which can be accomplished with this function.
		1241
		1242	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1243
		1244	Feeds the given event set into the event loop, as if the specified event
		1245	had happened for the specified watcher (which must be a pointer to an
		1246	initialised but not necessarily started event watcher). Obviously you must
		1247	not free the watcher as long as it has pending events.
		1248
		1249	Stopping the watcher, letting libev invoke it, or calling
		1250	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1251	not started in the first place.
		1252
		1253	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1254	functions that do not need a watcher.
1054		1255
1055	=back	1256	=back
1056		1257
1057		1258
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1259	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1107	#include <stddef.h>	1308	#include <stddef.h>
1108		1309
1109	static void	1310	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)	1311	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1312	{
1112	struct my_biggy big = (struct my_biggy *	1313	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1314	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1315	}
1115		1316
1116	static void	1317	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)	1318	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1319	{
1119	struct my_biggy big = (struct my_biggy *	1320	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1321	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1322	}
		1323
		1324	=head2 WATCHER PRIORITY MODELS
		1325
		1326	Many event loops support I<watcher priorities>, which are usually small
		1327	integers that influence the ordering of event callback invocation
		1328	between watchers in some way, all else being equal.
		1329
		1330	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1331	description for the more technical details such as the actual priority
		1332	range.
		1333
		1334	There are two common ways how these these priorities are being interpreted
		1335	by event loops:
		1336
		1337	In the more common lock-out model, higher priorities "lock out" invocation
		1338	of lower priority watchers, which means as long as higher priority
		1339	watchers receive events, lower priority watchers are not being invoked.
		1340
		1341	The less common only-for-ordering model uses priorities solely to order
		1342	callback invocation within a single event loop iteration: Higher priority
		1343	watchers are invoked before lower priority ones, but they all get invoked
		1344	before polling for new events.
		1345
		1346	Libev uses the second (only-for-ordering) model for all its watchers
		1347	except for idle watchers (which use the lock-out model).
		1348
		1349	The rationale behind this is that implementing the lock-out model for
		1350	watchers is not well supported by most kernel interfaces, and most event
		1351	libraries will just poll for the same events again and again as long as
		1352	their callbacks have not been executed, which is very inefficient in the
		1353	common case of one high-priority watcher locking out a mass of lower
		1354	priority ones.
		1355
		1356	Static (ordering) priorities are most useful when you have two or more
		1357	watchers handling the same resource: a typical usage example is having an
		1358	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1359	timeouts. Under load, data might be received while the program handles
		1360	other jobs, but since timers normally get invoked first, the timeout
		1361	handler will be executed before checking for data. In that case, giving
		1362	the timer a lower priority than the I/O watcher ensures that I/O will be
		1363	handled first even under adverse conditions (which is usually, but not
		1364	always, what you want).
		1365
		1366	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1367	will only be executed when no same or higher priority watchers have
		1368	received events, they can be used to implement the "lock-out" model when
		1369	required.
		1370
		1371	For example, to emulate how many other event libraries handle priorities,
		1372	you can associate an C<ev_idle> watcher to each such watcher, and in
		1373	the normal watcher callback, you just start the idle watcher. The real
		1374	processing is done in the idle watcher callback. This causes libev to
		1375	continously poll and process kernel event data for the watcher, but when
		1376	the lock-out case is known to be rare (which in turn is rare :), this is
		1377	workable.
		1378
		1379	Usually, however, the lock-out model implemented that way will perform
		1380	miserably under the type of load it was designed to handle. In that case,
		1381	it might be preferable to stop the real watcher before starting the
		1382	idle watcher, so the kernel will not have to process the event in case
		1383	the actual processing will be delayed for considerable time.
		1384
		1385	Here is an example of an I/O watcher that should run at a strictly lower
		1386	priority than the default, and which should only process data when no
		1387	other events are pending:
		1388
		1389	ev_idle idle; // actual processing watcher
		1390	ev_io io; // actual event watcher
		1391
		1392	static void
		1393	io_cb (EV_P_ ev_io *w, int revents)
		1394	{
		1395	// stop the I/O watcher, we received the event, but
		1396	// are not yet ready to handle it.
		1397	ev_io_stop (EV_A_ w);
		1398
		1399	// start the idle watcher to ahndle the actual event.
		1400	// it will not be executed as long as other watchers
		1401	// with the default priority are receiving events.
		1402	ev_idle_start (EV_A_ &idle);
		1403	}
		1404
		1405	static void
		1406	idle_cb (EV_P_ ev_idle *w, int revents)
		1407	{
		1408	// actual processing
		1409	read (STDIN_FILENO, ...);
		1410
		1411	// have to start the I/O watcher again, as
		1412	// we have handled the event
		1413	ev_io_start (EV_P_ &io);
		1414	}
		1415
		1416	// initialisation
		1417	ev_idle_init (&idle, idle_cb);
		1418	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1419	ev_io_start (EV_DEFAULT_ &io);
		1420
		1421	In the "real" world, it might also be beneficial to start a timer, so that
		1422	low-priority connections can not be locked out forever under load. This
		1423	enables your program to keep a lower latency for important connections
		1424	during short periods of high load, while not completely locking out less
		1425	important ones.
1122		1426
1123		1427
1124	=head1 WATCHER TYPES	1428	=head1 WATCHER TYPES
1125		1429
1126	This section describes each watcher in detail, but will not repeat	1430	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	1456	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1457	required if you know what you are doing).
1154		1458
1155	If you cannot use non-blocking mode, then force the use of a	1459	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	1460	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1461	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1462	descriptors for which non-blocking operation makes no sense (such as
		1463	files) - libev doesn't guarentee any specific behaviour in that case.
1158		1464
1159	Another thing you have to watch out for is that it is quite easy to	1465	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	1466	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	1467	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	1468	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	1589	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1590	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1591	monotonic clock option helps a lot here).
1286		1592
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1593	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	1594	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1595	might introduce a small delay). If multiple timers become ready during the
		1596	same loop iteration then the ones with earlier time-out values are invoked
		1597	before ones of the same priority with later time-out values (but this is
		1598	no longer true when a callback calls C<ev_loop> recursively).
1290		1599
1291	=head3 Be smart about timeouts	1600	=head3 Be smart about timeouts
1292		1601
1293	Many real-world problems involve some kind of timeout, usually for error	1602	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,	1603	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1338	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1647	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1339	member and C<ev_timer_again>.	1648	member and C<ev_timer_again>.
1340		1649
1341	At start:	1650	At start:
1342		1651
1343	ev_timer_init (timer, callback);	1652	ev_init (timer, callback);
1344	timer->repeat = 60.;	1653	timer->repeat = 60.;
1345	ev_timer_again (loop, timer);	1654	ev_timer_again (loop, timer);
1346		1655
1347	Each time there is some activity:	1656	Each time there is some activity:
1348		1657
…		…
1387	else	1696	else
1388	{	1697	{
1389	// callback was invoked, but there was some activity, re-arm	1698	// callback was invoked, but there was some activity, re-arm
1390	// the watcher to fire in last_activity + 60, which is	1699	// the watcher to fire in last_activity + 60, which is
1391	// guaranteed to be in the future, so "again" is positive:	1700	// guaranteed to be in the future, so "again" is positive:
1392	w->again = timeout - now;	1701	w->repeat = timeout - now;
1393	ev_timer_again (EV_A_ w);	1702	ev_timer_again (EV_A_ w);
1394	}	1703	}
1395	}	1704	}
1396		1705
1397	To summarise the callback: first calculate the real timeout (defined	1706	To summarise the callback: first calculate the real timeout (defined
…		…
1410		1719
1411	To start the timer, simply initialise the watcher and set C<last_activity>	1720	To start the timer, simply initialise the watcher and set C<last_activity>
1412	to the current time (meaning we just have some activity :), then call the	1721	to the current time (meaning we just have some activity :), then call the
1413	callback, which will "do the right thing" and start the timer:	1722	callback, which will "do the right thing" and start the timer:
1414		1723
1415	ev_timer_init (timer, callback);	1724	ev_init (timer, callback);
1416	last_activity = ev_now (loop);	1725	last_activity = ev_now (loop);
1417	callback (loop, timer, EV_TIMEOUT);	1726	callback (loop, timer, EV_TIMEOUT);
1418		1727
1419	And when there is some activity, simply store the current time in	1728	And when there is some activity, simply store the current time in
1420	C<last_activity>, no libev calls at all:	1729	C<last_activity>, no libev calls at all:
…		…
1426		1735
1427	Changing the timeout is trivial as well (if it isn't hard-coded in the	1736	Changing the timeout is trivial as well (if it isn't hard-coded in the
1428	callback :) - just change the timeout and invoke the callback, which will	1737	callback :) - just change the timeout and invoke the callback, which will
1429	fix things for you.	1738	fix things for you.
1430		1739
1431	=item 4. Whee, use a double-linked list for your timeouts.	1740	=item 4. Wee, just use a double-linked list for your timeouts.
1432		1741
1433	If there is not one request, but many thousands, all employing some kind	1742	If there is not one request, but many thousands (millions...), all
1434	of timeout with the same timeout value, then one can do even better:	1743	employing some kind of timeout with the same timeout value, then one can
		1744	do even better:
1435		1745
1436	When starting the timeout, calculate the timeout value and put the timeout	1746	When starting the timeout, calculate the timeout value and put the timeout
1437	at the I<end> of the list.	1747	at the I<end> of the list.
1438		1748
1439	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of	1749	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
…		…
1448	complication, and having to use a constant timeout. The constant timeout	1758	complication, and having to use a constant timeout. The constant timeout
1449	ensures that the list stays sorted.	1759	ensures that the list stays sorted.
1450		1760
1451	=back	1761	=back
1452		1762
1453	So what method is the best?	1763	So which method the best?
1454		1764
1455	The method #2 is a simple no-brain-required solution that is adequate in	1765	Method #2 is a simple no-brain-required solution that is adequate in most
1456	most situations. Method #3 requires a bit more thinking, but handles many	1766	situations. Method #3 requires a bit more thinking, but handles many cases
1457	cases better, and isn't very complicated either. In most case, choosing	1767	better, and isn't very complicated either. In most case, choosing either
1458	either one is fine.	1768	one is fine, with #3 being better in typical situations.
1459		1769
1460	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1770	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1461	rather complicated, but extremely efficient, something that really pays	1771	rather complicated, but extremely efficient, something that really pays
1462	off after the first or so million of active timers, i.e. it's usually	1772	off after the first million or so of active timers, i.e. it's usually
1463	overkill :)	1773	overkill :)
1464		1774
1465	=head3 The special problem of time updates	1775	=head3 The special problem of time updates
1466		1776
1467	Establishing the current time is a costly operation (it usually takes at	1777	Establishing the current time is a costly operation (it usually takes at
…		…
1480		1790
1481	If the event loop is suspended for a long time, you can also force an	1791	If the event loop is suspended for a long time, you can also force an
1482	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1792	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1483	()>.	1793	()>.
1484		1794
		1795	=head3 The special problems of suspended animation
		1796
		1797	When you leave the server world it is quite customary to hit machines that
		1798	can suspend/hibernate - what happens to the clocks during such a suspend?
		1799
		1800	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1801	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1802	to run until the system is suspended, but they will not advance while the
		1803	system is suspended. That means, on resume, it will be as if the program
		1804	was frozen for a few seconds, but the suspend time will not be counted
		1805	towards C<ev_timer> when a monotonic clock source is used. The real time
		1806	clock advanced as expected, but if it is used as sole clocksource, then a
		1807	long suspend would be detected as a time jump by libev, and timers would
		1808	be adjusted accordingly.
		1809
		1810	I would not be surprised to see different behaviour in different between
		1811	operating systems, OS versions or even different hardware.
		1812
		1813	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1814	time jump in the monotonic clocks and the realtime clock. If the program
		1815	is suspended for a very long time, and monotonic clock sources are in use,
		1816	then you can expect C<ev_timer>s to expire as the full suspension time
		1817	will be counted towards the timers. When no monotonic clock source is in
		1818	use, then libev will again assume a timejump and adjust accordingly.
		1819
		1820	It might be beneficial for this latter case to call C<ev_suspend>
		1821	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1822	deterministic behaviour in this case (you can do nothing against
		1823	C<SIGSTOP>).
		1824
1485	=head3 Watcher-Specific Functions and Data Members	1825	=head3 Watcher-Specific Functions and Data Members
1486		1826
1487	=over 4	1827	=over 4
1488		1828
1489	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1829	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1512	If the timer is started but non-repeating, stop it (as if it timed out).	1852	If the timer is started but non-repeating, stop it (as if it timed out).
1513		1853
1514	If the timer is repeating, either start it if necessary (with the	1854	If the timer is repeating, either start it if necessary (with the
1515	C<repeat> value), or reset the running timer to the C<repeat> value.	1855	C<repeat> value), or reset the running timer to the C<repeat> value.
1516		1856
1517	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1857	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1518	usage example.	1858	usage example.
		1859
		1860	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1861
		1862	Returns the remaining time until a timer fires. If the timer is active,
		1863	then this time is relative to the current event loop time, otherwise it's
		1864	the timeout value currently configured.
		1865
		1866	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1867	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1868	will return C<4>. When the timer expires and is restarted, it will return
		1869	roughly C<7> (likely slightly less as callback invocation takes some time,
		1870	too), and so on.
1519		1871
1520	=item ev_tstamp repeat [read-write]	1872	=item ev_tstamp repeat [read-write]
1521		1873
1522	The current C<repeat> value. Will be used each time the watcher times out	1874	The current C<repeat> value. Will be used each time the watcher times out
1523	or C<ev_timer_again> is called, and determines the next timeout (if any),	1875	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1561	=head2 C<ev_periodic> - to cron or not to cron?	1913	=head2 C<ev_periodic> - to cron or not to cron?
1562		1914
1563	Periodic watchers are also timers of a kind, but they are very versatile	1915	Periodic watchers are also timers of a kind, but they are very versatile
1564	(and unfortunately a bit complex).	1916	(and unfortunately a bit complex).
1565		1917
1566	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1918	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1567	but on wall clock time (absolute time). You can tell a periodic watcher	1919	relative time, the physical time that passes) but on wall clock time
1568	to trigger after some specific point in time. For example, if you tell a	1920	(absolute time, the thing you can read on your calender or clock). The
1569	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1921	difference is that wall clock time can run faster or slower than real
1570	+ 10.>, that is, an absolute time not a delay) and then reset your system	1922	time, and time jumps are not uncommon (e.g. when you adjust your
1571	clock to January of the previous year, then it will take more than year	1923	wrist-watch).
1572	to trigger the event (unlike an C<ev_timer>, which would still trigger
1573	roughly 10 seconds later as it uses a relative timeout).
1574		1924
		1925	You can tell a periodic watcher to trigger after some specific point
		1926	in time: for example, if you tell a periodic watcher to trigger "in 10
		1927	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1928	not a delay) and then reset your system clock to January of the previous
		1929	year, then it will take a year or more to trigger the event (unlike an
		1930	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1931	it, as it uses a relative timeout).
		1932
1575	C<ev_periodic>s can also be used to implement vastly more complex timers,	1933	C<ev_periodic> watchers can also be used to implement vastly more complex
1576	such as triggering an event on each "midnight, local time", or other	1934	timers, such as triggering an event on each "midnight, local time", or
1577	complicated rules.	1935	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1936	those cannot react to time jumps.
1578		1937
1579	As with timers, the callback is guaranteed to be invoked only when the	1938	As with timers, the callback is guaranteed to be invoked only when the
1580	time (C<at>) has passed, but if multiple periodic timers become ready	1939	point in time where it is supposed to trigger has passed. If multiple
1581	during the same loop iteration, then order of execution is undefined.	1940	timers become ready during the same loop iteration then the ones with
		1941	earlier time-out values are invoked before ones with later time-out values
		1942	(but this is no longer true when a callback calls C<ev_loop> recursively).
1582		1943
1583	=head3 Watcher-Specific Functions and Data Members	1944	=head3 Watcher-Specific Functions and Data Members
1584		1945
1585	=over 4	1946	=over 4
1586		1947
1587	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1948	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1588		1949
1589	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1950	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1590		1951
1591	Lots of arguments, lets sort it out... There are basically three modes of	1952	Lots of arguments, let's sort it out... There are basically three modes of
1592	operation, and we will explain them from simplest to most complex:	1953	operation, and we will explain them from simplest to most complex:
1593		1954
1594	=over 4	1955	=over 4
1595		1956
1596	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1957	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1597		1958
1598	In this configuration the watcher triggers an event after the wall clock	1959	In this configuration the watcher triggers an event after the wall clock
1599	time C<at> has passed. It will not repeat and will not adjust when a time	1960	time C<offset> has passed. It will not repeat and will not adjust when a
1600	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1961	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1601	only run when the system clock reaches or surpasses this time.	1962	will be stopped and invoked when the system clock reaches or surpasses
		1963	this point in time.
1602		1964
1603	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1965	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1604		1966
1605	In this mode the watcher will always be scheduled to time out at the next	1967	In this mode the watcher will always be scheduled to time out at the next
1606	C<at + N * interval> time (for some integer N, which can also be negative)	1968	C<offset + N * interval> time (for some integer N, which can also be
1607	and then repeat, regardless of any time jumps.	1969	negative) and then repeat, regardless of any time jumps. The C<offset>
		1970	argument is merely an offset into the C<interval> periods.
1608		1971
1609	This can be used to create timers that do not drift with respect to the	1972	This can be used to create timers that do not drift with respect to the
1610	system clock, for example, here is a C<ev_periodic> that triggers each	1973	system clock, for example, here is an C<ev_periodic> that triggers each
1611	hour, on the hour:	1974	hour, on the hour (with respect to UTC):
1612		1975
1613	ev_periodic_set (&periodic, 0., 3600., 0);	1976	ev_periodic_set (&periodic, 0., 3600., 0);
1614		1977
1615	This doesn't mean there will always be 3600 seconds in between triggers,	1978	This doesn't mean there will always be 3600 seconds in between triggers,
1616	but only that the callback will be called when the system time shows a	1979	but only that the callback will be called when the system time shows a
1617	full hour (UTC), or more correctly, when the system time is evenly divisible	1980	full hour (UTC), or more correctly, when the system time is evenly divisible
1618	by 3600.	1981	by 3600.
1619		1982
1620	Another way to think about it (for the mathematically inclined) is that	1983	Another way to think about it (for the mathematically inclined) is that
1621	C<ev_periodic> will try to run the callback in this mode at the next possible	1984	C<ev_periodic> will try to run the callback in this mode at the next possible
1622	time where C<time = at (mod interval)>, regardless of any time jumps.	1985	time where C<time = offset (mod interval)>, regardless of any time jumps.
1623		1986
1624	For numerical stability it is preferable that the C<at> value is near	1987	For numerical stability it is preferable that the C<offset> value is near
1625	C<ev_now ()> (the current time), but there is no range requirement for	1988	C<ev_now ()> (the current time), but there is no range requirement for
1626	this value, and in fact is often specified as zero.	1989	this value, and in fact is often specified as zero.
1627		1990
1628	Note also that there is an upper limit to how often a timer can fire (CPU	1991	Note also that there is an upper limit to how often a timer can fire (CPU
1629	speed for example), so if C<interval> is very small then timing stability	1992	speed for example), so if C<interval> is very small then timing stability
1630	will of course deteriorate. Libev itself tries to be exact to be about one	1993	will of course deteriorate. Libev itself tries to be exact to be about one
1631	millisecond (if the OS supports it and the machine is fast enough).	1994	millisecond (if the OS supports it and the machine is fast enough).
1632		1995
1633	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1996	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1634		1997
1635	In this mode the values for C<interval> and C<at> are both being	1998	In this mode the values for C<interval> and C<offset> are both being
1636	ignored. Instead, each time the periodic watcher gets scheduled, the	1999	ignored. Instead, each time the periodic watcher gets scheduled, the
1637	reschedule callback will be called with the watcher as first, and the	2000	reschedule callback will be called with the watcher as first, and the
1638	current time as second argument.	2001	current time as second argument.
1639		2002
1640	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2003	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1641	ever, or make ANY event loop modifications whatsoever>.	2004	or make ANY other event loop modifications whatsoever, unless explicitly
		2005	allowed by documentation here>.
1642		2006
1643	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2007	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1644	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2008	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1645	only event loop modification you are allowed to do).	2009	only event loop modification you are allowed to do).
1646		2010
…		…
1676	a different time than the last time it was called (e.g. in a crond like	2040	a different time than the last time it was called (e.g. in a crond like
1677	program when the crontabs have changed).	2041	program when the crontabs have changed).
1678		2042
1679	=item ev_tstamp ev_periodic_at (ev_periodic *)	2043	=item ev_tstamp ev_periodic_at (ev_periodic *)
1680		2044
1681	When active, returns the absolute time that the watcher is supposed to	2045	When active, returns the absolute time that the watcher is supposed
1682	trigger next.	2046	to trigger next. This is not the same as the C<offset> argument to
		2047	C<ev_periodic_set>, but indeed works even in interval and manual
		2048	rescheduling modes.
1683		2049
1684	=item ev_tstamp offset [read-write]	2050	=item ev_tstamp offset [read-write]
1685		2051
1686	When repeating, this contains the offset value, otherwise this is the	2052	When repeating, this contains the offset value, otherwise this is the
1687	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2053	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2054	although libev might modify this value for better numerical stability).
1688		2055
1689	Can be modified any time, but changes only take effect when the periodic	2056	Can be modified any time, but changes only take effect when the periodic
1690	timer fires or C<ev_periodic_again> is being called.	2057	timer fires or C<ev_periodic_again> is being called.
1691		2058
1692	=item ev_tstamp interval [read-write]	2059	=item ev_tstamp interval [read-write]
…		…
1744	Signal watchers will trigger an event when the process receives a specific	2111	Signal watchers will trigger an event when the process receives a specific
1745	signal one or more times. Even though signals are very asynchronous, libev	2112	signal one or more times. Even though signals are very asynchronous, libev
1746	will try it's best to deliver signals synchronously, i.e. as part of the	2113	will try it's best to deliver signals synchronously, i.e. as part of the
1747	normal event processing, like any other event.	2114	normal event processing, like any other event.
1748		2115
1749	If you want signals asynchronously, just use C<sigaction> as you would	2116	If you want signals to be delivered truly asynchronously, just use
1750	do without libev and forget about sharing the signal. You can even use	2117	C<sigaction> as you would do without libev and forget about sharing
1751	C<ev_async> from a signal handler to synchronously wake up an event loop.	2118	the signal. You can even use C<ev_async> from a signal handler to
		2119	synchronously wake up an event loop.
1752		2120
1753	You can configure as many watchers as you like per signal. Only when the	2121	You can configure as many watchers as you like for the same signal, but
		2122	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2123	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2124	C<SIGINT> in both the default loop and another loop at the same time. At
		2125	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2126
1754	first watcher gets started will libev actually register a signal handler	2127	When the first watcher gets started will libev actually register something
1755	with the kernel (thus it coexists with your own signal handlers as long as	2128	with the kernel (thus it coexists with your own signal handlers as long as
1756	you don't register any with libev for the same signal). Similarly, when	2129	you don't register any with libev for the same signal).
1757	the last signal watcher for a signal is stopped, libev will reset the
1758	signal handler to SIG_DFL (regardless of what it was set to before).
1759		2130
1760	If possible and supported, libev will install its handlers with	2131	If possible and supported, libev will install its handlers with
1761	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2132	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1762	interrupted. If you have a problem with system calls getting interrupted by	2133	not be unduly interrupted. If you have a problem with system calls getting
1763	signals you can block all signals in an C<ev_check> watcher and unblock	2134	interrupted by signals you can block all signals in an C<ev_check> watcher
1764	them in an C<ev_prepare> watcher.	2135	and unblock them in an C<ev_prepare> watcher.
		2136
		2137	=head3 The special problem of inheritance over execve
		2138
		2139	Both the signal mask (C<sigprocmask>) and the signal disposition
		2140	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2141	stopping it again), that is, libev might or might not block the signal,
		2142	and might or might not set or restore the installed signal handler.
		2143
		2144	While this does not matter for the signal disposition (libev never
		2145	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2146	C<execve>), this matters for the signal mask: many programs do not expect
		2147	certain signals to be blocked.
		2148
		2149	This means that before calling C<exec> (from the child) you should reset
		2150	the signal mask to whatever "default" you expect (all clear is a good
		2151	choice usually).
		2152
		2153	The simplest way to ensure that the signal mask is reset in the child is
		2154	to install a fork handler with C<pthread_atfork> that resets it. That will
		2155	catch fork calls done by libraries (such as the libc) as well.
		2156
		2157	In current versions of libev, you can also ensure that the signal mask is
		2158	not blocking any signals (except temporarily, so thread users watch out)
		2159	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2160	is not guaranteed for future versions, however.
1765		2161
1766	=head3 Watcher-Specific Functions and Data Members	2162	=head3 Watcher-Specific Functions and Data Members
1767		2163
1768	=over 4	2164	=over 4
1769		2165
…		…
1801	some child status changes (most typically when a child of yours dies or	2197	some child status changes (most typically when a child of yours dies or
1802	exits). It is permissible to install a child watcher I<after> the child	2198	exits). It is permissible to install a child watcher I<after> the child
1803	has been forked (which implies it might have already exited), as long	2199	has been forked (which implies it might have already exited), as long
1804	as the event loop isn't entered (or is continued from a watcher), i.e.,	2200	as the event loop isn't entered (or is continued from a watcher), i.e.,
1805	forking and then immediately registering a watcher for the child is fine,	2201	forking and then immediately registering a watcher for the child is fine,
1806	but forking and registering a watcher a few event loop iterations later is	2202	but forking and registering a watcher a few event loop iterations later or
1807	not.	2203	in the next callback invocation is not.
1808		2204
1809	Only the default event loop is capable of handling signals, and therefore	2205	Only the default event loop is capable of handling signals, and therefore
1810	you can only register child watchers in the default event loop.	2206	you can only register child watchers in the default event loop.
1811		2207
		2208	Due to some design glitches inside libev, child watchers will always be
		2209	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2210	libev)
		2211
1812	=head3 Process Interaction	2212	=head3 Process Interaction
1813		2213
1814	Libev grabs C<SIGCHLD> as soon as the default event loop is	2214	Libev grabs C<SIGCHLD> as soon as the default event loop is
1815	initialised. This is necessary to guarantee proper behaviour even if	2215	initialised. This is necessary to guarantee proper behaviour even if the
1816	the first child watcher is started after the child exits. The occurrence	2216	first child watcher is started after the child exits. The occurrence
1817	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2217	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1818	synchronously as part of the event loop processing. Libev always reaps all	2218	synchronously as part of the event loop processing. Libev always reaps all
1819	children, even ones not watched.	2219	children, even ones not watched.
1820		2220
1821	=head3 Overriding the Built-In Processing	2221	=head3 Overriding the Built-In Processing
…		…
1831	=head3 Stopping the Child Watcher	2231	=head3 Stopping the Child Watcher
1832		2232
1833	Currently, the child watcher never gets stopped, even when the	2233	Currently, the child watcher never gets stopped, even when the
1834	child terminates, so normally one needs to stop the watcher in the	2234	child terminates, so normally one needs to stop the watcher in the
1835	callback. Future versions of libev might stop the watcher automatically	2235	callback. Future versions of libev might stop the watcher automatically
1836	when a child exit is detected.	2236	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2237	problem).
1837		2238
1838	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1839		2240
1840	=over 4	2241	=over 4
1841		2242
…		…
1898		2299
1899		2300
1900	=head2 C<ev_stat> - did the file attributes just change?	2301	=head2 C<ev_stat> - did the file attributes just change?
1901		2302
1902	This watches a file system path for attribute changes. That is, it calls	2303	This watches a file system path for attribute changes. That is, it calls
1903	C<stat> regularly (or when the OS says it changed) and sees if it changed	2304	C<stat> on that path in regular intervals (or when the OS says it changed)
1904	compared to the last time, invoking the callback if it did.	2305	and sees if it changed compared to the last time, invoking the callback if
		2306	it did.
1905		2307
1906	The path does not need to exist: changing from "path exists" to "path does	2308	The path does not need to exist: changing from "path exists" to "path does
1907	not exist" is a status change like any other. The condition "path does	2309	not exist" is a status change like any other. The condition "path does not
1908	not exist" is signified by the C<st_nlink> field being zero (which is	2310	exist" (or more correctly "path cannot be stat'ed") is signified by the
1909	otherwise always forced to be at least one) and all the other fields of	2311	C<st_nlink> field being zero (which is otherwise always forced to be at
1910	the stat buffer having unspecified contents.	2312	least one) and all the other fields of the stat buffer having unspecified
		2313	contents.
1911		2314
1912	The path I<should> be absolute and I<must not> end in a slash. If it is	2315	The path I<must not> end in a slash or contain special components such as
		2316	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1913	relative and your working directory changes, the behaviour is undefined.	2317	your working directory changes, then the behaviour is undefined.
1914		2318
1915	Since there is no standard kernel interface to do this, the portable	2319	Since there is no portable change notification interface available, the
1916	implementation simply calls C<stat (2)> regularly on the path to see if	2320	portable implementation simply calls C<stat(2)> regularly on the path
1917	it changed somehow. You can specify a recommended polling interval for	2321	to see if it changed somehow. You can specify a recommended polling
1918	this case. If you specify a polling interval of C<0> (highly recommended!)	2322	interval for this case. If you specify a polling interval of C<0> (highly
1919	then a I<suitable, unspecified default> value will be used (which	2323	recommended!) then a I<suitable, unspecified default> value will be used
1920	you can expect to be around five seconds, although this might change	2324	(which you can expect to be around five seconds, although this might
1921	dynamically). Libev will also impose a minimum interval which is currently	2325	change dynamically). Libev will also impose a minimum interval which is
1922	around C<0.1>, but thats usually overkill.	2326	currently around C<0.1>, but that's usually overkill.
1923		2327
1924	This watcher type is not meant for massive numbers of stat watchers,	2328	This watcher type is not meant for massive numbers of stat watchers,
1925	as even with OS-supported change notifications, this can be	2329	as even with OS-supported change notifications, this can be
1926	resource-intensive.	2330	resource-intensive.
1927		2331
1928	At the time of this writing, the only OS-specific interface implemented	2332	At the time of this writing, the only OS-specific interface implemented
1929	is the Linux inotify interface (implementing kqueue support is left as	2333	is the Linux inotify interface (implementing kqueue support is left as an
1930	an exercise for the reader. Note, however, that the author sees no way	2334	exercise for the reader. Note, however, that the author sees no way of
1931	of implementing C<ev_stat> semantics with kqueue).	2335	implementing C<ev_stat> semantics with kqueue, except as a hint).
1932		2336
1933	=head3 ABI Issues (Largefile Support)	2337	=head3 ABI Issues (Largefile Support)
1934		2338
1935	Libev by default (unless the user overrides this) uses the default	2339	Libev by default (unless the user overrides this) uses the default
1936	compilation environment, which means that on systems with large file	2340	compilation environment, which means that on systems with large file
1937	support disabled by default, you get the 32 bit version of the stat	2341	support disabled by default, you get the 32 bit version of the stat
1938	structure. When using the library from programs that change the ABI to	2342	structure. When using the library from programs that change the ABI to
1939	use 64 bit file offsets the programs will fail. In that case you have to	2343	use 64 bit file offsets the programs will fail. In that case you have to
1940	compile libev with the same flags to get binary compatibility. This is	2344	compile libev with the same flags to get binary compatibility. This is
1941	obviously the case with any flags that change the ABI, but the problem is	2345	obviously the case with any flags that change the ABI, but the problem is
1942	most noticeably disabled with ev_stat and large file support.	2346	most noticeably displayed with ev_stat and large file support.
1943		2347
1944	The solution for this is to lobby your distribution maker to make large	2348	The solution for this is to lobby your distribution maker to make large
1945	file interfaces available by default (as e.g. FreeBSD does) and not	2349	file interfaces available by default (as e.g. FreeBSD does) and not
1946	optional. Libev cannot simply switch on large file support because it has	2350	optional. Libev cannot simply switch on large file support because it has
1947	to exchange stat structures with application programs compiled using the	2351	to exchange stat structures with application programs compiled using the
1948	default compilation environment.	2352	default compilation environment.
1949		2353
1950	=head3 Inotify and Kqueue	2354	=head3 Inotify and Kqueue
1951		2355
1952	When C<inotify (7)> support has been compiled into libev (generally	2356	When C<inotify (7)> support has been compiled into libev and present at
1953	only available with Linux 2.6.25 or above due to bugs in earlier	2357	runtime, it will be used to speed up change detection where possible. The
1954	implementations) and present at runtime, it will be used to speed up	2358	inotify descriptor will be created lazily when the first C<ev_stat>
1955	change detection where possible. The inotify descriptor will be created	2359	watcher is being started.
1956	lazily when the first C<ev_stat> watcher is being started.
1957		2360
1958	Inotify presence does not change the semantics of C<ev_stat> watchers	2361	Inotify presence does not change the semantics of C<ev_stat> watchers
1959	except that changes might be detected earlier, and in some cases, to avoid	2362	except that changes might be detected earlier, and in some cases, to avoid
1960	making regular C<stat> calls. Even in the presence of inotify support	2363	making regular C<stat> calls. Even in the presence of inotify support
1961	there are many cases where libev has to resort to regular C<stat> polling,	2364	there are many cases where libev has to resort to regular C<stat> polling,
1962	but as long as the path exists, libev usually gets away without polling.	2365	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2366	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2367	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2368	xfs are fully working) libev usually gets away without polling.
1963		2369
1964	There is no support for kqueue, as apparently it cannot be used to	2370	There is no support for kqueue, as apparently it cannot be used to
1965	implement this functionality, due to the requirement of having a file	2371	implement this functionality, due to the requirement of having a file
1966	descriptor open on the object at all times, and detecting renames, unlinks	2372	descriptor open on the object at all times, and detecting renames, unlinks
1967	etc. is difficult.	2373	etc. is difficult.
1968		2374
		2375	=head3 C<stat ()> is a synchronous operation
		2376
		2377	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2378	the process. The exception are C<ev_stat> watchers - those call C<stat
		2379	()>, which is a synchronous operation.
		2380
		2381	For local paths, this usually doesn't matter: unless the system is very
		2382	busy or the intervals between stat's are large, a stat call will be fast,
		2383	as the path data is usually in memory already (except when starting the
		2384	watcher).
		2385
		2386	For networked file systems, calling C<stat ()> can block an indefinite
		2387	time due to network issues, and even under good conditions, a stat call
		2388	often takes multiple milliseconds.
		2389
		2390	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2391	paths, although this is fully supported by libev.
		2392
1969	=head3 The special problem of stat time resolution	2393	=head3 The special problem of stat time resolution
1970		2394
1971	The C<stat ()> system call only supports full-second resolution portably, and	2395	The C<stat ()> system call only supports full-second resolution portably,
1972	even on systems where the resolution is higher, most file systems still	2396	and even on systems where the resolution is higher, most file systems
1973	only support whole seconds.	2397	still only support whole seconds.
1974		2398
1975	That means that, if the time is the only thing that changes, you can	2399	That means that, if the time is the only thing that changes, you can
1976	easily miss updates: on the first update, C<ev_stat> detects a change and	2400	easily miss updates: on the first update, C<ev_stat> detects a change and
1977	calls your callback, which does something. When there is another update	2401	calls your callback, which does something. When there is another update
1978	within the same second, C<ev_stat> will be unable to detect unless the	2402	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2121		2545
2122	=head3 Watcher-Specific Functions and Data Members	2546	=head3 Watcher-Specific Functions and Data Members
2123		2547
2124	=over 4	2548	=over 4
2125		2549
2126	=item ev_idle_init (ev_signal *, callback)	2550	=item ev_idle_init (ev_idle *, callback)
2127		2551
2128	Initialises and configures the idle watcher - it has no parameters of any	2552	Initialises and configures the idle watcher - it has no parameters of any
2129	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2553	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2130	believe me.	2554	believe me.
2131		2555
…		…
2144	// no longer anything immediate to do.	2568	// no longer anything immediate to do.
2145	}	2569	}
2146		2570
2147	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2571	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2148	ev_idle_init (idle_watcher, idle_cb);	2572	ev_idle_init (idle_watcher, idle_cb);
2149	ev_idle_start (loop, idle_cb);	2573	ev_idle_start (loop, idle_watcher);
2150		2574
2151		2575
2152	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2576	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2153		2577
2154	Prepare and check watchers are usually (but not always) used in pairs:	2578	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2247	struct pollfd fds [nfd];	2671	struct pollfd fds [nfd];
2248	// actual code will need to loop here and realloc etc.	2672	// actual code will need to loop here and realloc etc.
2249	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2673	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2250		2674
2251	/* the callback is illegal, but won't be called as we stop during check */	2675	/* the callback is illegal, but won't be called as we stop during check */
2252	ev_timer_init (&tw, 0, timeout * 1e-3);	2676	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2253	ev_timer_start (loop, &tw);	2677	ev_timer_start (loop, &tw);
2254		2678
2255	// create one ev_io per pollfd	2679	// create one ev_io per pollfd
2256	for (int i = 0; i < nfd; ++i)	2680	for (int i = 0; i < nfd; ++i)
2257	{	2681	{
…		…
2370	some fds have to be watched and handled very quickly (with low latency),	2794	some fds have to be watched and handled very quickly (with low latency),
2371	and even priorities and idle watchers might have too much overhead. In	2795	and even priorities and idle watchers might have too much overhead. In
2372	this case you would put all the high priority stuff in one loop and all	2796	this case you would put all the high priority stuff in one loop and all
2373	the rest in a second one, and embed the second one in the first.	2797	the rest in a second one, and embed the second one in the first.
2374		2798
2375	As long as the watcher is active, the callback will be invoked every time	2799	As long as the watcher is active, the callback will be invoked every
2376	there might be events pending in the embedded loop. The callback must then	2800	time there might be events pending in the embedded loop. The callback
2377	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2801	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2378	their callbacks (you could also start an idle watcher to give the embedded	2802	sweep and invoke their callbacks (the callback doesn't need to invoke the
2379	loop strictly lower priority for example). You can also set the callback	2803	C<ev_embed_sweep> function directly, it could also start an idle watcher
2380	to C<0>, in which case the embed watcher will automatically execute the	2804	to give the embedded loop strictly lower priority for example).
2381	embedded loop sweep.
2382		2805
2383	As long as the watcher is started it will automatically handle events. The	2806	You can also set the callback to C<0>, in which case the embed watcher
2384	callback will be invoked whenever some events have been handled. You can	2807	will automatically execute the embedded loop sweep whenever necessary.
2385	set the callback to C<0> to avoid having to specify one if you are not
2386	interested in that.
2387		2808
2388	Also, there have not currently been made special provisions for forking:	2809	Fork detection will be handled transparently while the C<ev_embed> watcher
2389	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2810	is active, i.e., the embedded loop will automatically be forked when the
2390	but you will also have to stop and restart any C<ev_embed> watchers	2811	embedding loop forks. In other cases, the user is responsible for calling
2391	yourself - but you can use a fork watcher to handle this automatically,	2812	C<ev_loop_fork> on the embedded loop.
2392	and future versions of libev might do just that.
2393		2813
2394	Unfortunately, not all backends are embeddable: only the ones returned by	2814	Unfortunately, not all backends are embeddable: only the ones returned by
2395	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2815	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2396	portable one.	2816	portable one.
2397		2817
…		…
2491	event loop blocks next and before C<ev_check> watchers are being called,	2911	event loop blocks next and before C<ev_check> watchers are being called,
2492	and only in the child after the fork. If whoever good citizen calling	2912	and only in the child after the fork. If whoever good citizen calling
2493	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2913	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2494	handlers will be invoked, too, of course.	2914	handlers will be invoked, too, of course.
2495		2915
		2916	=head3 The special problem of life after fork - how is it possible?
		2917
		2918	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2919	up/change the process environment, followed by a call to C<exec()>. This
		2920	sequence should be handled by libev without any problems.
		2921
		2922	This changes when the application actually wants to do event handling
		2923	in the child, or both parent in child, in effect "continuing" after the
		2924	fork.
		2925
		2926	The default mode of operation (for libev, with application help to detect
		2927	forks) is to duplicate all the state in the child, as would be expected
		2928	when I<either> the parent I<or> the child process continues.
		2929
		2930	When both processes want to continue using libev, then this is usually the
		2931	wrong result. In that case, usually one process (typically the parent) is
		2932	supposed to continue with all watchers in place as before, while the other
		2933	process typically wants to start fresh, i.e. without any active watchers.
		2934
		2935	The cleanest and most efficient way to achieve that with libev is to
		2936	simply create a new event loop, which of course will be "empty", and
		2937	use that for new watchers. This has the advantage of not touching more
		2938	memory than necessary, and thus avoiding the copy-on-write, and the
		2939	disadvantage of having to use multiple event loops (which do not support
		2940	signal watchers).
		2941
		2942	When this is not possible, or you want to use the default loop for
		2943	other reasons, then in the process that wants to start "fresh", call
		2944	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2945	the default loop will "orphan" (not stop) all registered watchers, so you
		2946	have to be careful not to execute code that modifies those watchers. Note
		2947	also that in that case, you have to re-register any signal watchers.
		2948
2496	=head3 Watcher-Specific Functions and Data Members	2949	=head3 Watcher-Specific Functions and Data Members
2497		2950
2498	=over 4	2951	=over 4
2499		2952
2500	=item ev_fork_init (ev_signal *, callback)	2953	=item ev_fork_init (ev_signal *, callback)
…		…
2529	=head3 Queueing	2982	=head3 Queueing
2530		2983
2531	C<ev_async> does not support queueing of data in any way. The reason	2984	C<ev_async> does not support queueing of data in any way. The reason
2532	is that the author does not know of a simple (or any) algorithm for a	2985	is that the author does not know of a simple (or any) algorithm for a
2533	multiple-writer-single-reader queue that works in all cases and doesn't	2986	multiple-writer-single-reader queue that works in all cases and doesn't
2534	need elaborate support such as pthreads.	2987	need elaborate support such as pthreads or unportable memory access
		2988	semantics.
2535		2989
2536	That means that if you want to queue data, you have to provide your own	2990	That means that if you want to queue data, you have to provide your own
2537	queue. But at least I can tell you how to implement locking around your	2991	queue. But at least I can tell you how to implement locking around your
2538	queue:	2992	queue:
2539		2993
…		…
2617	=over 4	3071	=over 4
2618		3072
2619	=item ev_async_init (ev_async *, callback)	3073	=item ev_async_init (ev_async *, callback)
2620		3074
2621	Initialises and configures the async watcher - it has no parameters of any	3075	Initialises and configures the async watcher - it has no parameters of any
2622	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3076	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2623	trust me.	3077	trust me.
2624		3078
2625	=item ev_async_send (loop, ev_async *)	3079	=item ev_async_send (loop, ev_async *)
2626		3080
2627	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3081	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2628	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3082	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2629	C<ev_feed_event>, this call is safe to do from other threads, signal or	3083	C<ev_feed_event>, this call is safe to do from other threads, signal or
2630	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3084	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2631	section below on what exactly this means).	3085	section below on what exactly this means).
2632		3086
		3087	Note that, as with other watchers in libev, multiple events might get
		3088	compressed into a single callback invocation (another way to look at this
		3089	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3090	reset when the event loop detects that).
		3091
2633	This call incurs the overhead of a system call only once per loop iteration,	3092	This call incurs the overhead of a system call only once per event loop
2634	so while the overhead might be noticeable, it doesn't apply to repeated	3093	iteration, so while the overhead might be noticeable, it doesn't apply to
2635	calls to C<ev_async_send>.	3094	repeated calls to C<ev_async_send> for the same event loop.
2636		3095
2637	=item bool = ev_async_pending (ev_async *)	3096	=item bool = ev_async_pending (ev_async *)
2638		3097
2639	Returns a non-zero value when C<ev_async_send> has been called on the	3098	Returns a non-zero value when C<ev_async_send> has been called on the
2640	watcher but the event has not yet been processed (or even noted) by the	3099	watcher but the event has not yet been processed (or even noted) by the
…		…
2643	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3102	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2644	the loop iterates next and checks for the watcher to have become active,	3103	the loop iterates next and checks for the watcher to have become active,
2645	it will reset the flag again. C<ev_async_pending> can be used to very	3104	it will reset the flag again. C<ev_async_pending> can be used to very
2646	quickly check whether invoking the loop might be a good idea.	3105	quickly check whether invoking the loop might be a good idea.
2647		3106
2648	Not that this does I<not> check whether the watcher itself is pending, only	3107	Not that this does I<not> check whether the watcher itself is pending,
2649	whether it has been requested to make this watcher pending.	3108	only whether it has been requested to make this watcher pending: there
		3109	is a time window between the event loop checking and resetting the async
		3110	notification, and the callback being invoked.
2650		3111
2651	=back	3112	=back
2652		3113
2653		3114
2654	=head1 OTHER FUNCTIONS	3115	=head1 OTHER FUNCTIONS
…		…
2690	/* doh, nothing entered */;	3151	/* doh, nothing entered */;
2691	}	3152	}
2692		3153
2693	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3154	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2694		3155
2695	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2696
2697	Feeds the given event set into the event loop, as if the specified event
2698	had happened for the specified watcher (which must be a pointer to an
2699	initialised but not necessarily started event watcher).
2700
2701	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3156	=item ev_feed_fd_event (loop, int fd, int revents)
2702		3157
2703	Feed an event on the given fd, as if a file descriptor backend detected	3158	Feed an event on the given fd, as if a file descriptor backend detected
2704	the given events it.	3159	the given events it.
2705		3160
2706	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3161	=item ev_feed_signal_event (loop, int signum)
2707		3162
2708	Feed an event as if the given signal occurred (C<loop> must be the default	3163	Feed an event as if the given signal occurred (C<loop> must be the default
2709	loop!).	3164	loop!).
2710		3165
2711	=back	3166	=back
…		…
2791		3246
2792	=over 4	3247	=over 4
2793		3248
2794	=item ev::TYPE::TYPE ()	3249	=item ev::TYPE::TYPE ()
2795		3250
2796	=item ev::TYPE::TYPE (struct ev_loop *)	3251	=item ev::TYPE::TYPE (loop)
2797		3252
2798	=item ev::TYPE::~TYPE	3253	=item ev::TYPE::~TYPE
2799		3254
2800	The constructor (optionally) takes an event loop to associate the watcher	3255	The constructor (optionally) takes an event loop to associate the watcher
2801	with. If it is omitted, it will use C<EV_DEFAULT>.	3256	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2833		3288
2834	myclass obj;	3289	myclass obj;
2835	ev::io iow;	3290	ev::io iow;
2836	iow.set <myclass, &myclass::io_cb> (&obj);	3291	iow.set <myclass, &myclass::io_cb> (&obj);
2837		3292
		3293	=item w->set (object *)
		3294
		3295	This is an B<experimental> feature that might go away in a future version.
		3296
		3297	This is a variation of a method callback - leaving out the method to call
		3298	will default the method to C<operator ()>, which makes it possible to use
		3299	functor objects without having to manually specify the C<operator ()> all
		3300	the time. Incidentally, you can then also leave out the template argument
		3301	list.
		3302
		3303	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3304	int revents)>.
		3305
		3306	See the method-C<set> above for more details.
		3307
		3308	Example: use a functor object as callback.
		3309
		3310	struct myfunctor
		3311	{
		3312	void operator() (ev::io &w, int revents)
		3313	{
		3314	...
		3315	}
		3316	}
		3317
		3318	myfunctor f;
		3319
		3320	ev::io w;
		3321	w.set (&f);
		3322
2838	=item w->set<function> (void *data = 0)	3323	=item w->set<function> (void *data = 0)
2839		3324
2840	Also sets a callback, but uses a static method or plain function as	3325	Also sets a callback, but uses a static method or plain function as
2841	callback. The optional C<data> argument will be stored in the watcher's	3326	callback. The optional C<data> argument will be stored in the watcher's
2842	C<data> member and is free for you to use.	3327	C<data> member and is free for you to use.
…		…
2848	Example: Use a plain function as callback.	3333	Example: Use a plain function as callback.
2849		3334
2850	static void io_cb (ev::io &w, int revents) { }	3335	static void io_cb (ev::io &w, int revents) { }
2851	iow.set <io_cb> ();	3336	iow.set <io_cb> ();
2852		3337
2853	=item w->set (struct ev_loop *)	3338	=item w->set (loop)
2854		3339
2855	Associates a different C<struct ev_loop> with this watcher. You can only	3340	Associates a different C<struct ev_loop> with this watcher. You can only
2856	do this when the watcher is inactive (and not pending either).	3341	do this when the watcher is inactive (and not pending either).
2857		3342
2858	=item w->set ([arguments])	3343	=item w->set ([arguments])
…		…
2928	L<http://software.schmorp.de/pkg/EV>.	3413	L<http://software.schmorp.de/pkg/EV>.
2929		3414
2930	=item Python	3415	=item Python
2931		3416
2932	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3417	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2933	seems to be quite complete and well-documented. Note, however, that the	3418	seems to be quite complete and well-documented.
2934	patch they require for libev is outright dangerous as it breaks the ABI
2935	for everybody else, and therefore, should never be applied in an installed
2936	libev (if python requires an incompatible ABI then it needs to embed
2937	libev).
2938		3419
2939	=item Ruby	3420	=item Ruby
2940		3421
2941	Tony Arcieri has written a ruby extension that offers access to a subset	3422	Tony Arcieri has written a ruby extension that offers access to a subset
2942	of the libev API and adds file handle abstractions, asynchronous DNS and	3423	of the libev API and adds file handle abstractions, asynchronous DNS and
2943	more on top of it. It can be found via gem servers. Its homepage is at	3424	more on top of it. It can be found via gem servers. Its homepage is at
2944	L<http://rev.rubyforge.org/>.	3425	L<http://rev.rubyforge.org/>.
2945		3426
		3427	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3428	makes rev work even on mingw.
		3429
		3430	=item Haskell
		3431
		3432	A haskell binding to libev is available at
		3433	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3434
2946	=item D	3435	=item D
2947		3436
2948	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3437	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2949	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3438	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3439
		3440	=item Ocaml
		3441
		3442	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3443	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3444
		3445	=item Lua
		3446
		3447	Brian Maher has written a partial interface to libev
		3448	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3449	L<http://github.com/brimworks/lua-ev>.
2950		3450
2951	=back	3451	=back
2952		3452
2953		3453
2954	=head1 MACRO MAGIC	3454	=head1 MACRO MAGIC
…		…
3055		3555
3056	#define EV_STANDALONE 1	3556	#define EV_STANDALONE 1
3057	#include "ev.h"	3557	#include "ev.h"
3058		3558
3059	Both header files and implementation files can be compiled with a C++	3559	Both header files and implementation files can be compiled with a C++
3060	compiler (at least, thats a stated goal, and breakage will be treated	3560	compiler (at least, that's a stated goal, and breakage will be treated
3061	as a bug).	3561	as a bug).
3062		3562
3063	You need the following files in your source tree, or in a directory	3563	You need the following files in your source tree, or in a directory
3064	in your include path (e.g. in libev/ when using -Ilibev):	3564	in your include path (e.g. in libev/ when using -Ilibev):
3065		3565
…		…
3121	keeps libev from including F<config.h>, and it also defines dummy	3621	keeps libev from including F<config.h>, and it also defines dummy
3122	implementations for some libevent functions (such as logging, which is not	3622	implementations for some libevent functions (such as logging, which is not
3123	supported). It will also not define any of the structs usually found in	3623	supported). It will also not define any of the structs usually found in
3124	F<event.h> that are not directly supported by the libev core alone.	3624	F<event.h> that are not directly supported by the libev core alone.
3125		3625
		3626	In standalone mode, libev will still try to automatically deduce the
		3627	configuration, but has to be more conservative.
		3628
3126	=item EV_USE_MONOTONIC	3629	=item EV_USE_MONOTONIC
3127		3630
3128	If defined to be C<1>, libev will try to detect the availability of the	3631	If defined to be C<1>, libev will try to detect the availability of the
3129	monotonic clock option at both compile time and runtime. Otherwise no use	3632	monotonic clock option at both compile time and runtime. Otherwise no
3130	of the monotonic clock option will be attempted. If you enable this, you	3633	use of the monotonic clock option will be attempted. If you enable this,
3131	usually have to link against librt or something similar. Enabling it when	3634	you usually have to link against librt or something similar. Enabling it
3132	the functionality isn't available is safe, though, although you have	3635	when the functionality isn't available is safe, though, although you have
3133	to make sure you link against any libraries where the C<clock_gettime>	3636	to make sure you link against any libraries where the C<clock_gettime>
3134	function is hiding in (often F<-lrt>).	3637	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3135		3638
3136	=item EV_USE_REALTIME	3639	=item EV_USE_REALTIME
3137		3640
3138	If defined to be C<1>, libev will try to detect the availability of the	3641	If defined to be C<1>, libev will try to detect the availability of the
3139	real-time clock option at compile time (and assume its availability at	3642	real-time clock option at compile time (and assume its availability
3140	runtime if successful). Otherwise no use of the real-time clock option will	3643	at runtime if successful). Otherwise no use of the real-time clock
3141	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3644	option will be attempted. This effectively replaces C<gettimeofday>
3142	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3645	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3143	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3646	correctness. See the note about libraries in the description of
		3647	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3648	C<EV_USE_CLOCK_SYSCALL>.
		3649
		3650	=item EV_USE_CLOCK_SYSCALL
		3651
		3652	If defined to be C<1>, libev will try to use a direct syscall instead
		3653	of calling the system-provided C<clock_gettime> function. This option
		3654	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3655	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3656	programs needlessly. Using a direct syscall is slightly slower (in
		3657	theory), because no optimised vdso implementation can be used, but avoids
		3658	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3659	higher, as it simplifies linking (no need for C<-lrt>).
3144		3660
3145	=item EV_USE_NANOSLEEP	3661	=item EV_USE_NANOSLEEP
3146		3662
3147	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3663	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3148	and will use it for delays. Otherwise it will use C<select ()>.	3664	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3164		3680
3165	=item EV_SELECT_USE_FD_SET	3681	=item EV_SELECT_USE_FD_SET
3166		3682
3167	If defined to C<1>, then the select backend will use the system C<fd_set>	3683	If defined to C<1>, then the select backend will use the system C<fd_set>
3168	structure. This is useful if libev doesn't compile due to a missing	3684	structure. This is useful if libev doesn't compile due to a missing
3169	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3685	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3170	exotic systems. This usually limits the range of file descriptors to some	3686	on exotic systems. This usually limits the range of file descriptors to
3171	low limit such as 1024 or might have other limitations (winsocket only	3687	some low limit such as 1024 or might have other limitations (winsocket
3172	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3688	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3173	influence the size of the C<fd_set> used.	3689	configures the maximum size of the C<fd_set>.
3174		3690
3175	=item EV_SELECT_IS_WINSOCKET	3691	=item EV_SELECT_IS_WINSOCKET
3176		3692
3177	When defined to C<1>, the select backend will assume that	3693	When defined to C<1>, the select backend will assume that
3178	select/socket/connect etc. don't understand file descriptors but	3694	select/socket/connect etc. don't understand file descriptors but
…		…
3180	be used is the winsock select). This means that it will call	3696	be used is the winsock select). This means that it will call
3181	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3697	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3182	it is assumed that all these functions actually work on fds, even	3698	it is assumed that all these functions actually work on fds, even
3183	on win32. Should not be defined on non-win32 platforms.	3699	on win32. Should not be defined on non-win32 platforms.
3184		3700
3185	=item EV_FD_TO_WIN32_HANDLE	3701	=item EV_FD_TO_WIN32_HANDLE(fd)
3186		3702
3187	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3703	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3188	file descriptors to socket handles. When not defining this symbol (the	3704	file descriptors to socket handles. When not defining this symbol (the
3189	default), then libev will call C<_get_osfhandle>, which is usually	3705	default), then libev will call C<_get_osfhandle>, which is usually
3190	correct. In some cases, programs use their own file descriptor management,	3706	correct. In some cases, programs use their own file descriptor management,
3191	in which case they can provide this function to map fds to socket handles.	3707	in which case they can provide this function to map fds to socket handles.
		3708
		3709	=item EV_WIN32_HANDLE_TO_FD(handle)
		3710
		3711	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3712	using the standard C<_open_osfhandle> function. For programs implementing
		3713	their own fd to handle mapping, overwriting this function makes it easier
		3714	to do so. This can be done by defining this macro to an appropriate value.
		3715
		3716	=item EV_WIN32_CLOSE_FD(fd)
		3717
		3718	If programs implement their own fd to handle mapping on win32, then this
		3719	macro can be used to override the C<close> function, useful to unregister
		3720	file descriptors again. Note that the replacement function has to close
		3721	the underlying OS handle.
3192		3722
3193	=item EV_USE_POLL	3723	=item EV_USE_POLL
3194		3724
3195	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3725	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3196	backend. Otherwise it will be enabled on non-win32 platforms. It	3726	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3328	defined to be C<0>, then they are not.	3858	defined to be C<0>, then they are not.
3329		3859
3330	=item EV_MINIMAL	3860	=item EV_MINIMAL
3331		3861
3332	If you need to shave off some kilobytes of code at the expense of some	3862	If you need to shave off some kilobytes of code at the expense of some
3333	speed, define this symbol to C<1>. Currently this is used to override some	3863	speed (but with the full API), define this symbol to C<1>. Currently this
3334	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3864	is used to override some inlining decisions, saves roughly 30% code size
3335	much smaller 2-heap for timer management over the default 4-heap.	3865	on amd64. It also selects a much smaller 2-heap for timer management over
		3866	the default 4-heap.
		3867
		3868	You can save even more by disabling watcher types you do not need
		3869	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3870	(C<-DNDEBUG>) will usually reduce code size a lot.
		3871
		3872	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3873	provide a bare-bones event library. See C<ev.h> for details on what parts
		3874	of the API are still available, and do not complain if this subset changes
		3875	over time.
		3876
		3877	=item EV_NSIG
		3878
		3879	The highest supported signal number, +1 (or, the number of
		3880	signals): Normally, libev tries to deduce the maximum number of signals
		3881	automatically, but sometimes this fails, in which case it can be
		3882	specified. Also, using a lower number than detected (C<32> should be
		3883	good for about any system in existance) can save some memory, as libev
		3884	statically allocates some 12-24 bytes per signal number.
3336		3885
3337	=item EV_PID_HASHSIZE	3886	=item EV_PID_HASHSIZE
3338		3887
3339	C<ev_child> watchers use a small hash table to distribute workload by	3888	C<ev_child> watchers use a small hash table to distribute workload by
3340	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3889	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3526	default loop and triggering an C<ev_async> watcher from the default loop	4075	default loop and triggering an C<ev_async> watcher from the default loop
3527	watcher callback into the event loop interested in the signal.	4076	watcher callback into the event loop interested in the signal.
3528		4077
3529	=back	4078	=back
3530		4079
		4080	=head4 THREAD LOCKING EXAMPLE
		4081
		4082	Here is a fictitious example of how to run an event loop in a different
		4083	thread than where callbacks are being invoked and watchers are
		4084	created/added/removed.
		4085
		4086	For a real-world example, see the C<EV::Loop::Async> perl module,
		4087	which uses exactly this technique (which is suited for many high-level
		4088	languages).
		4089
		4090	The example uses a pthread mutex to protect the loop data, a condition
		4091	variable to wait for callback invocations, an async watcher to notify the
		4092	event loop thread and an unspecified mechanism to wake up the main thread.
		4093
		4094	First, you need to associate some data with the event loop:
		4095
		4096	typedef struct {
		4097	mutex_t lock; /* global loop lock */
		4098	ev_async async_w;
		4099	thread_t tid;
		4100	cond_t invoke_cv;
		4101	} userdata;
		4102
		4103	void prepare_loop (EV_P)
		4104	{
		4105	// for simplicity, we use a static userdata struct.
		4106	static userdata u;
		4107
		4108	ev_async_init (&u->async_w, async_cb);
		4109	ev_async_start (EV_A_ &u->async_w);
		4110
		4111	pthread_mutex_init (&u->lock, 0);
		4112	pthread_cond_init (&u->invoke_cv, 0);
		4113
		4114	// now associate this with the loop
		4115	ev_set_userdata (EV_A_ u);
		4116	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4117	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4118
		4119	// then create the thread running ev_loop
		4120	pthread_create (&u->tid, 0, l_run, EV_A);
		4121	}
		4122
		4123	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4124	solely to wake up the event loop so it takes notice of any new watchers
		4125	that might have been added:
		4126
		4127	static void
		4128	async_cb (EV_P_ ev_async *w, int revents)
		4129	{
		4130	// just used for the side effects
		4131	}
		4132
		4133	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4134	protecting the loop data, respectively.
		4135
		4136	static void
		4137	l_release (EV_P)
		4138	{
		4139	userdata *u = ev_userdata (EV_A);
		4140	pthread_mutex_unlock (&u->lock);
		4141	}
		4142
		4143	static void
		4144	l_acquire (EV_P)
		4145	{
		4146	userdata *u = ev_userdata (EV_A);
		4147	pthread_mutex_lock (&u->lock);
		4148	}
		4149
		4150	The event loop thread first acquires the mutex, and then jumps straight
		4151	into C<ev_loop>:
		4152
		4153	void *
		4154	l_run (void *thr_arg)
		4155	{
		4156	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4157
		4158	l_acquire (EV_A);
		4159	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4160	ev_loop (EV_A_ 0);
		4161	l_release (EV_A);
		4162
		4163	return 0;
		4164	}
		4165
		4166	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4167	signal the main thread via some unspecified mechanism (signals? pipe
		4168	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4169	have been called (in a while loop because a) spurious wakeups are possible
		4170	and b) skipping inter-thread-communication when there are no pending
		4171	watchers is very beneficial):
		4172
		4173	static void
		4174	l_invoke (EV_P)
		4175	{
		4176	userdata *u = ev_userdata (EV_A);
		4177
		4178	while (ev_pending_count (EV_A))
		4179	{
		4180	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4181	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4182	}
		4183	}
		4184
		4185	Now, whenever the main thread gets told to invoke pending watchers, it
		4186	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4187	thread to continue:
		4188
		4189	static void
		4190	real_invoke_pending (EV_P)
		4191	{
		4192	userdata *u = ev_userdata (EV_A);
		4193
		4194	pthread_mutex_lock (&u->lock);
		4195	ev_invoke_pending (EV_A);
		4196	pthread_cond_signal (&u->invoke_cv);
		4197	pthread_mutex_unlock (&u->lock);
		4198	}
		4199
		4200	Whenever you want to start/stop a watcher or do other modifications to an
		4201	event loop, you will now have to lock:
		4202
		4203	ev_timer timeout_watcher;
		4204	userdata *u = ev_userdata (EV_A);
		4205
		4206	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4207
		4208	pthread_mutex_lock (&u->lock);
		4209	ev_timer_start (EV_A_ &timeout_watcher);
		4210	ev_async_send (EV_A_ &u->async_w);
		4211	pthread_mutex_unlock (&u->lock);
		4212
		4213	Note that sending the C<ev_async> watcher is required because otherwise
		4214	an event loop currently blocking in the kernel will have no knowledge
		4215	about the newly added timer. By waking up the loop it will pick up any new
		4216	watchers in the next event loop iteration.
		4217
3531	=head3 COROUTINES	4218	=head3 COROUTINES
3532		4219
3533	Libev is very accommodating to coroutines ("cooperative threads"):	4220	Libev is very accommodating to coroutines ("cooperative threads"):
3534	libev fully supports nesting calls to its functions from different	4221	libev fully supports nesting calls to its functions from different
3535	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4222	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3536	different coroutines, and switch freely between both coroutines running the	4223	different coroutines, and switch freely between both coroutines running
3537	loop, as long as you don't confuse yourself). The only exception is that	4224	the loop, as long as you don't confuse yourself). The only exception is
3538	you must not do this from C<ev_periodic> reschedule callbacks.	4225	that you must not do this from C<ev_periodic> reschedule callbacks.
3539		4226
3540	Care has been taken to ensure that libev does not keep local state inside	4227	Care has been taken to ensure that libev does not keep local state inside
3541	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4228	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3542	they do not clal any callbacks.	4229	they do not call any callbacks.
3543		4230
3544	=head2 COMPILER WARNINGS	4231	=head2 COMPILER WARNINGS
3545		4232
3546	Depending on your compiler and compiler settings, you might get no or a	4233	Depending on your compiler and compiler settings, you might get no or a
3547	lot of warnings when compiling libev code. Some people are apparently	4234	lot of warnings when compiling libev code. Some people are apparently
…		…
3581	==2274== definitely lost: 0 bytes in 0 blocks.	4268	==2274== definitely lost: 0 bytes in 0 blocks.
3582	==2274== possibly lost: 0 bytes in 0 blocks.	4269	==2274== possibly lost: 0 bytes in 0 blocks.
3583	==2274== still reachable: 256 bytes in 1 blocks.	4270	==2274== still reachable: 256 bytes in 1 blocks.
3584		4271
3585	Then there is no memory leak, just as memory accounted to global variables	4272	Then there is no memory leak, just as memory accounted to global variables
3586	is not a memleak - the memory is still being refernced, and didn't leak.	4273	is not a memleak - the memory is still being referenced, and didn't leak.
3587		4274
3588	Similarly, under some circumstances, valgrind might report kernel bugs	4275	Similarly, under some circumstances, valgrind might report kernel bugs
3589	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4276	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3590	although an acceptable workaround has been found here), or it might be	4277	although an acceptable workaround has been found here), or it might be
3591	confused.	4278	confused.
…		…
3620	way (note also that glib is the slowest event library known to man).	4307	way (note also that glib is the slowest event library known to man).
3621		4308
3622	There is no supported compilation method available on windows except	4309	There is no supported compilation method available on windows except
3623	embedding it into other applications.	4310	embedding it into other applications.
3624		4311
		4312	Sensible signal handling is officially unsupported by Microsoft - libev
		4313	tries its best, but under most conditions, signals will simply not work.
		4314
3625	Not a libev limitation but worth mentioning: windows apparently doesn't	4315	Not a libev limitation but worth mentioning: windows apparently doesn't
3626	accept large writes: instead of resulting in a partial write, windows will	4316	accept large writes: instead of resulting in a partial write, windows will
3627	either accept everything or return C<ENOBUFS> if the buffer is too large,	4317	either accept everything or return C<ENOBUFS> if the buffer is too large,
3628	so make sure you only write small amounts into your sockets (less than a	4318	so make sure you only write small amounts into your sockets (less than a
3629	megabyte seems safe, but this apparently depends on the amount of memory	4319	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3633	the abysmal performance of winsockets, using a large number of sockets	4323	the abysmal performance of winsockets, using a large number of sockets
3634	is not recommended (and not reasonable). If your program needs to use	4324	is not recommended (and not reasonable). If your program needs to use
3635	more than a hundred or so sockets, then likely it needs to use a totally	4325	more than a hundred or so sockets, then likely it needs to use a totally
3636	different implementation for windows, as libev offers the POSIX readiness	4326	different implementation for windows, as libev offers the POSIX readiness
3637	notification model, which cannot be implemented efficiently on windows	4327	notification model, which cannot be implemented efficiently on windows
3638	(Microsoft monopoly games).	4328	(due to Microsoft monopoly games).
3639		4329
3640	A typical way to use libev under windows is to embed it (see the embedding	4330	A typical way to use libev under windows is to embed it (see the embedding
3641	section for details) and use the following F<evwrap.h> header file instead	4331	section for details) and use the following F<evwrap.h> header file instead
3642	of F<ev.h>:	4332	of F<ev.h>:
3643		4333
…		…
3679		4369
3680	Early versions of winsocket's select only supported waiting for a maximum	4370	Early versions of winsocket's select only supported waiting for a maximum
3681	of C<64> handles (probably owning to the fact that all windows kernels	4371	of C<64> handles (probably owning to the fact that all windows kernels
3682	can only wait for C<64> things at the same time internally; Microsoft	4372	can only wait for C<64> things at the same time internally; Microsoft
3683	recommends spawning a chain of threads and wait for 63 handles and the	4373	recommends spawning a chain of threads and wait for 63 handles and the
3684	previous thread in each. Great).	4374	previous thread in each. Sounds great!).
3685		4375
3686	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4376	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3687	to some high number (e.g. C<2048>) before compiling the winsocket select	4377	to some high number (e.g. C<2048>) before compiling the winsocket select
3688	call (which might be in libev or elsewhere, for example, perl does its own	4378	call (which might be in libev or elsewhere, for example, perl and many
3689	select emulation on windows).	4379	other interpreters do their own select emulation on windows).
3690		4380
3691	Another limit is the number of file descriptors in the Microsoft runtime	4381	Another limit is the number of file descriptors in the Microsoft runtime
3692	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4382	libraries, which by default is C<64> (there must be a hidden I<64>
3693	or something like this inside Microsoft). You can increase this by calling	4383	fetish or something like this inside Microsoft). You can increase this
3694	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4384	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3695	arbitrary limit), but is broken in many versions of the Microsoft runtime	4385	(another arbitrary limit), but is broken in many versions of the Microsoft
3696	libraries.
3697
3698	This might get you to about C<512> or C<2048> sockets (depending on	4386	runtime libraries. This might get you to about C<512> or C<2048> sockets
3699	windows version and/or the phase of the moon). To get more, you need to	4387	(depending on windows version and/or the phase of the moon). To get more,
3700	wrap all I/O functions and provide your own fd management, but the cost of	4388	you need to wrap all I/O functions and provide your own fd management, but
3701	calling select (O(n²)) will likely make this unworkable.	4389	the cost of calling select (O(n²)) will likely make this unworkable.
3702		4390
3703	=back	4391	=back
3704		4392
3705	=head2 PORTABILITY REQUIREMENTS	4393	=head2 PORTABILITY REQUIREMENTS
3706		4394
…		…
3749	=item C<double> must hold a time value in seconds with enough accuracy	4437	=item C<double> must hold a time value in seconds with enough accuracy
3750		4438
3751	The type C<double> is used to represent timestamps. It is required to	4439	The type C<double> is used to represent timestamps. It is required to
3752	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4440	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3753	enough for at least into the year 4000. This requirement is fulfilled by	4441	enough for at least into the year 4000. This requirement is fulfilled by
3754	implementations implementing IEEE 754 (basically all existing ones).	4442	implementations implementing IEEE 754, which is basically all existing
		4443	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4444	2200.
3755		4445
3756	=back	4446	=back
3757		4447
3758	If you know of other additional requirements drop me a note.	4448	If you know of other additional requirements drop me a note.
3759		4449
…		…
3827	involves iterating over all running async watchers or all signal numbers.	4517	involves iterating over all running async watchers or all signal numbers.
3828		4518
3829	=back	4519	=back
3830		4520
3831		4521
		4522	=head1 GLOSSARY
		4523
		4524	=over 4
		4525
		4526	=item active
		4527
		4528	A watcher is active as long as it has been started (has been attached to
		4529	an event loop) but not yet stopped (disassociated from the event loop).
		4530
		4531	=item application
		4532
		4533	In this document, an application is whatever is using libev.
		4534
		4535	=item callback
		4536
		4537	The address of a function that is called when some event has been
		4538	detected. Callbacks are being passed the event loop, the watcher that
		4539	received the event, and the actual event bitset.
		4540
		4541	=item callback invocation
		4542
		4543	The act of calling the callback associated with a watcher.
		4544
		4545	=item event
		4546
		4547	A change of state of some external event, such as data now being available
		4548	for reading on a file descriptor, time having passed or simply not having
		4549	any other events happening anymore.
		4550
		4551	In libev, events are represented as single bits (such as C<EV_READ> or
		4552	C<EV_TIMEOUT>).
		4553
		4554	=item event library
		4555
		4556	A software package implementing an event model and loop.
		4557
		4558	=item event loop
		4559
		4560	An entity that handles and processes external events and converts them
		4561	into callback invocations.
		4562
		4563	=item event model
		4564
		4565	The model used to describe how an event loop handles and processes
		4566	watchers and events.
		4567
		4568	=item pending
		4569
		4570	A watcher is pending as soon as the corresponding event has been detected,
		4571	and stops being pending as soon as the watcher will be invoked or its
		4572	pending status is explicitly cleared by the application.
		4573
		4574	A watcher can be pending, but not active. Stopping a watcher also clears
		4575	its pending status.
		4576
		4577	=item real time
		4578
		4579	The physical time that is observed. It is apparently strictly monotonic :)
		4580
		4581	=item wall-clock time
		4582
		4583	The time and date as shown on clocks. Unlike real time, it can actually
		4584	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4585	clock.
		4586
		4587	=item watcher
		4588
		4589	A data structure that describes interest in certain events. Watchers need
		4590	to be started (attached to an event loop) before they can receive events.
		4591
		4592	=item watcher invocation
		4593
		4594	The act of calling the callback associated with a watcher.
		4595
		4596	=back
		4597
3832	=head1 AUTHOR	4598	=head1 AUTHOR
3833		4599
3834	Marc Lehmann <libev@schmorp.de>.	4600	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3835		4601

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