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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
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
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);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
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	Familiarity 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 (in practise
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
176	as this indicates an incompatible change. Minor versions are usually	192	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	193	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	194	not a problem.
179		195
180	Example: Make sure we haven't accidentally been linked against the wrong	196	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	197	version (note, however, that this will not detect ABI mismatches :).
182		198
183	assert (("libev version mismatch",	199	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	200	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	201	&& ev_version_minor () >= EV_VERSION_MINOR));
186		202
…		…
276		292
277	=back	293	=back
278		294
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		296
281	An event loop is described by a C<ev_loop *>. The library knows two	297	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	298	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	299	libev 3 had an C<ev_loop> function colliding with the struct name).
		300
		301	The library knows two types of such loops, the I<default> loop, which
		302	supports signals and child events, and dynamically created event loops
		303	which do not.
284		304
285	=over 4	305	=over 4
286		306
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		308
…		…
294	If you don't know what event loop to use, use the one returned from this	314	If you don't know what event loop to use, use the one returned from this
295	function.	315	function.
296		316
297	Note that this function is I<not> thread-safe, so if you want to use it	317	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,	318	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
300		320
301	The default loop is the only loop that can handle C<ev_signal> and	321	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	322	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	323	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	324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
326	useful to try out specific backends to test their performance, or to work	346	useful to try out specific backends to test their performance, or to work
327	around bugs.	347	around bugs.
328		348
329	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
330		350
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	351	Instead of calling C<ev_loop_fork> manually after a fork, you can also
332	a fork, you can also make libev check for a fork in each iteration by	352	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		353
335	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
336	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
337	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		389
351	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		418
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
382	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	427	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	428
387	cases and requiring a system call per fd change, no fork support and bad	429	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	430	of the more advanced event mechanisms: mere annoyances include silently
		431	dropping file descriptors, requiring a system call per change per file
		432	descriptor (and unnecessary guessing of parameters), problems with dup and
		433	so on. The biggest issue is fork races, however - if a program forks then
		434	I<both> parent and child process have to recreate the epoll set, which can
		435	take considerable time (one syscall per file descriptor) and is of course
		436	hard to detect.
		437
		438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		439	of course I<doesn't>, and epoll just loves to report events for totally
		440	I<different> file descriptors (even already closed ones, so one cannot
		441	even remove them from the set) than registered in the set (especially
		442	on SMP systems). Libev tries to counter these spurious notifications by
		443	employing an additional generation counter and comparing that against the
		444	events to filter out spurious ones, recreating the set when required. Last
		445	not least, it also refuses to work with some file descriptors which work
		446	perfectly fine with C<select> (files, many character devices...).
389		447
390	While stopping, setting and starting an I/O watcher in the same iteration	448	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	449	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	450	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	451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	452	file descriptors might not work very well if you register events for both
395		453	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		454
400	Best performance from this backend is achieved by not unregistering all	455	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	456	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	457	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	458	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	459	extra overhead. A fork can both result in spurious notifications as well
		460	as in libev having to destroy and recreate the epoll object, which can
		461	take considerable time and thus should be avoided.
		462
		463	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		464	faster than epoll for maybe up to a hundred file descriptors, depending on
		465	the usage. So sad.
405		466
406	While nominally embeddable in other event loops, this feature is broken in	467	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	468	all kernel versions tested so far.
408		469
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	470	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	471	C<EVBACKEND_POLL>.
411		472
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		474
414	Kqueue deserves special mention, as at the time of this writing, it was	475	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	476	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	477	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	478	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	479	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.	480	without API changes to existing programs. For this reason it's not being
		481	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		482	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		483	system like NetBSD.
420		484
421	You still can embed kqueue into a normal poll or select backend and use it	485	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	486	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.	487	the target platform). See C<ev_embed> watchers for more info.
424		488
425	It scales in the same way as the epoll backend, but the interface to the	489	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	490	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	491	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	492	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	493	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		495	cases
431		496
432	This backend usually performs well under most conditions.	497	This backend usually performs well under most conditions.
433		498
434	While nominally embeddable in other event loops, this doesn't work	499	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	500	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	501	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	502	(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,	503	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	504	also broken on OS X)) and, did I mention it, using it only for sockets.
440		505
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	506	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	507	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	508	C<NOTE_EOF>.
444		509
…		…
464	might perform better.	529	might perform better.
465		530
466	On the positive side, with the exception of the spurious readiness	531	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	532	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	533	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	534	OS-specific backends (I vastly prefer correctness over speed hacks).
470		535
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	537	C<EVBACKEND_POLL>.
473		538
474	=item C<EVBACKEND_ALL>	539	=item C<EVBACKEND_ALL>
…		…
479		544
480	It is definitely not recommended to use this flag.	545	It is definitely not recommended to use this flag.
481		546
482	=back	547	=back
483		548
484	If one or more of these are or'ed into the flags value, then only these	549	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	550	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.	551	here). If none are specified, all backends in C<ev_recommended_backends
		552	()> will be tried.
487		553
488	Example: This is the most typical usage.	554	Example: This is the most typical usage.
489		555
490	if (!ev_default_loop (0))	556	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504		570
505	=item struct ev_loop *ev_loop_new (unsigned int flags)	571	=item struct ev_loop *ev_loop_new (unsigned int flags)
506		572
507	Similar to C<ev_default_loop>, but always creates a new event loop that is	573	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot	574	always distinct from the default loop.
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511		575
512	Note that this function I<is> thread-safe, and the recommended way to use	576	Note that this function I<is> thread-safe, and one common way to use
513	libev with threads is indeed to create one loop per thread, and using the	577	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
515		579
516	Example: Try to create a event loop that uses epoll and nothing else.	580	Example: Try to create a event loop that uses epoll and nothing else.
517		581
…		…
519	if (!epoller)	583	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
521		585
522	=item ev_default_destroy ()	586	=item ev_default_destroy ()
523		587
524	Destroys the default loop again (frees all memory and kernel state	588	Destroys the default loop (frees all memory and kernel state etc.). None
525	etc.). None of the active event watchers will be stopped in the normal	589	of the active event watchers will be stopped in the normal sense, so
526	sense, so e.g. C<ev_is_active> might still return true. It is your	590	e.g. C<ev_is_active> might still return true. It is your responsibility to
527	responsibility to either stop all watchers cleanly yourself I<before>	591	either stop all watchers cleanly yourself I<before> calling this function,
528	calling this function, or cope with the fact afterwards (which is usually	592	or cope with the fact afterwards (which is usually the easiest thing, you
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	593	can just ignore the watchers and/or C<free ()> them for example).
530	for example).
531		594
532	Note that certain global state, such as signal state, will not be freed by	595	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	596	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	597	as signal and child watchers) would need to be stopped manually.
535		598
536	In general it is not advisable to call this function except in the	599	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	600	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	601	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	602	C<ev_loop_new> and C<ev_loop_destroy>.
540		603
541	=item ev_loop_destroy (loop)	604	=item ev_loop_destroy (loop)
542		605
543	Like C<ev_default_destroy>, but destroys an event loop created by an	606	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.	607	earlier call to C<ev_loop_new>.
545		608
546	=item ev_default_fork ()	609	=item ev_default_fork ()
547		610
548	This function sets a flag that causes subsequent C<ev_loop> iterations	611	This function sets a flag that causes subsequent C<ev_run> iterations
549	to reinitialise the kernel state for backends that have one. Despite the	612	to reinitialise the kernel state for backends that have one. Despite the
550	name, you can call it anytime, but it makes most sense after forking, in	613	name, you can call it anytime, but it makes most sense after forking, in
551	the child process (or both child and parent, but that again makes little	614	the child process (or both child and parent, but that again makes little
552	sense). You I<must> call it in the child before using any of the libev	615	sense). You I<must> call it in the child before using any of the libev
553	functions, and it will only take effect at the next C<ev_loop> iteration.	616	functions, and it will only take effect at the next C<ev_run> iteration.
		617
		618	Again, you I<have> to call it on I<any> loop that you want to re-use after
		619	a fork, I<even if you do not plan to use the loop in the parent>. This is
		620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		621	during fork.
554		622
555	On the other hand, you only need to call this function in the child	623	On the other hand, you only need to call this function in the child
556	process if and only if you want to use the event library in the child. If	624	process if and only if you want to use the event loop in the child. If
557	you just fork+exec, you don't have to call it at all.	625	you just fork+exec or create a new loop in the child, you don't have to
		626	call it at all (in fact, C<epoll> is so badly broken that it makes a
		627	difference, but libev will usually detect this case on its own and do a
		628	costly reset of the backend).
558		629
559	The function itself is quite fast and it's usually not a problem to call	630	The function itself is quite fast and it's usually not a problem to call
560	it just in case after a fork. To make this easy, the function will fit in	631	it just in case after a fork. To make this easy, the function will fit in
561	quite nicely into a call to C<pthread_atfork>:	632	quite nicely into a call to C<pthread_atfork>:
562		633
…		…
564		635
565	=item ev_loop_fork (loop)	636	=item ev_loop_fork (loop)
566		637
567	Like C<ev_default_fork>, but acts on an event loop created by	638	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	639	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is	640	after fork that you want to re-use in the child, and how you keep track of
570	entirely your own problem.	641	them is entirely your own problem.
571		642
572	=item int ev_is_default_loop (loop)	643	=item int ev_is_default_loop (loop)
573		644
574	Returns true when the given loop is, in fact, the default loop, and false	645	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	646	otherwise.
576		647
577	=item unsigned int ev_loop_count (loop)	648	=item unsigned int ev_iteration (loop)
578		649
579	Returns the count of loop iterations for the loop, which is identical to	650	Returns the current iteration count for the event loop, which is identical
580	the number of times libev did poll for new events. It starts at C<0> and	651	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	652	and happily wraps around with enough iterations.
582		653
583	This value can sometimes be useful as a generation counter of sorts (it	654	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	655	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	656	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		657	prepare and check phases.
		658
		659	=item unsigned int ev_depth (loop)
		660
		661	Returns the number of times C<ev_run> was entered minus the number of
		662	times C<ev_run> was exited, in other words, the recursion depth.
		663
		664	Outside C<ev_run>, this number is zero. In a callback, this number is
		665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		666	in which case it is higher.
		667
		668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		669	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		670	ungentleman-like behaviour unless it's really convenient.
586		671
587	=item unsigned int ev_backend (loop)	672	=item unsigned int ev_backend (loop)
588		673
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	675	use.
…		…
599		684
600	=item ev_now_update (loop)	685	=item ev_now_update (loop)
601		686
602	Establishes the current time by querying the kernel, updating the time	687	Establishes the current time by querying the kernel, updating the time
603	returned by C<ev_now ()> in the progress. This is a costly operation and	688	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	689	is usually done automatically within C<ev_run ()>.
605		690
606	This function is rarely useful, but when some event callback runs for a	691	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	692	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	693	the current time is a good idea.
609		694
610	See also "The special problem of time updates" in the C<ev_timer> section.	695	See also L<The special problem of time updates> in the C<ev_timer> section.
611		696
		697	=item ev_suspend (loop)
		698
		699	=item ev_resume (loop)
		700
		701	These two functions suspend and resume an event loop, for use when the
		702	loop is not used for a while and timeouts should not be processed.
		703
		704	A typical use case would be an interactive program such as a game: When
		705	the user presses C<^Z> to suspend the game and resumes it an hour later it
		706	would be best to handle timeouts as if no time had actually passed while
		707	the program was suspended. This can be achieved by calling C<ev_suspend>
		708	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		709	C<ev_resume> directly afterwards to resume timer processing.
		710
		711	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		712	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		713	will be rescheduled (that is, they will lose any events that would have
		714	occurred while suspended).
		715
		716	After calling C<ev_suspend> you B<must not> call I<any> function on the
		717	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		718	without a previous call to C<ev_suspend>.
		719
		720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		721	event loop time (see C<ev_now_update>).
		722
612	=item ev_loop (loop, int flags)	723	=item ev_run (loop, int flags)
613		724
614	Finally, this is it, the event handler. This function usually is called	725	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	726	after you have initialised all your watchers and you want to start
616	events.	727	handling events. It will ask the operating system for any new events, call
		728	the watcher callbacks, an then repeat the whole process indefinitely: This
		729	is why event loops are called I<loops>.
617		730
618	If the flags argument is specified as C<0>, it will not return until	731	If the flags argument is specified as C<0>, it will keep handling events
619	either no event watchers are active anymore or C<ev_unloop> was called.	732	until either no event watchers are active anymore or C<ev_break> was
		733	called.
620		734
621	Please note that an explicit C<ev_unloop> is usually better than	735	Please note that an explicit C<ev_break> is usually better than
622	relying on all watchers to be stopped when deciding when a program has	736	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	737	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	738	that automatically loops as long as it has to and no longer by virtue
625	of relying on its watchers stopping correctly, that is truly a thing of	739	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	740	beauty.
627		741
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
629	those events and any already outstanding ones, but will not block your	743	those events and any already outstanding ones, but will not wait and
630	process in case there are no events and will return after one iteration of	744	block your process in case there are no events and will return after one
631	the loop.	745	iteration of the loop. This is sometimes useful to poll and handle new
		746	events while doing lengthy calculations, to keep the program responsive.
632		747
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	748	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	749	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	750	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	751	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	752	user-registered callback will be called), and will return after one
638	iteration of the loop.	753	iteration of the loop.
639		754
640	This is useful if you are waiting for some external event in conjunction	755	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	756	with something not expressible using other libev watchers (i.e. "roll your
642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
643	usually a better approach for this kind of thing.	758	usually a better approach for this kind of thing.
644		759
645	Here are the gory details of what C<ev_loop> does:	760	Here are the gory details of what C<ev_run> does:
646		761
		762	- Increment loop depth.
		763	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	764	- Before the first iteration, call any pending watchers.
		765	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	766	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	767	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	768	- Queue and call all prepare watchers.
		769	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	770	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	771	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	772	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	773	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	774	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	775	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	776	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	777	- Sleep if the I/O and timer collect interval say so.
		778	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	779	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	780	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	781	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	782	- Queue all expired timers.
663	- Queue all expired periodics.	783	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	784	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	785	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	786	- Call all queued watchers in reverse order (i.e. check watchers first).
667	Signals and child watchers are implemented as I/O watchers, and will	787	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	788	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	789	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	790	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	791	continue with step LOOP.
		792	FINISH:
		793	- Reset the ev_break status iff it was EVBREAK_ONE.
		794	- Decrement the loop depth.
		795	- Return.
672		796
673	Example: Queue some jobs and then loop until no events are outstanding	797	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	798	anymore.
675		799
676	... queue jobs here, make sure they register event watchers as long	800	... queue jobs here, make sure they register event watchers as long
677	... as they still have work to do (even an idle watcher will do..)	801	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	802	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	803	... jobs done or somebody called unloop. yeah!
680		804
681	=item ev_unloop (loop, how)	805	=item ev_break (loop, how)
682		806
683	Can be used to make a call to C<ev_loop> return early (but only after it	807	Can be used to make a call to C<ev_run> return early (but only after it
684	has processed all outstanding events). The C<how> argument must be either	808	has processed all outstanding events). The C<how> argument must be either
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		811
688	This "unloop state" will be cleared when entering C<ev_loop> again.	812	This "unloop state" will be cleared when entering C<ev_run> again.
689		813
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
691		815
692	=item ev_ref (loop)	816	=item ev_ref (loop)
693		817
694	=item ev_unref (loop)	818	=item ev_unref (loop)
695		819
696	Ref/unref can be used to add or remove a reference count on the event	820	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	821	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.	822	count is nonzero, C<ev_run> will not return on its own.
699		823
700	If you have a watcher you never unregister that should not keep C<ev_loop>	824	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	825	unregister, but that nevertheless should not keep C<ev_run> from
		826	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	827	before stopping it.
703		828
704	As an example, libev itself uses this for its internal signal pipe: It is	829	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	830	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	831	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	832	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>	833	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,	834	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	835	before, respectively. Note also that libev might stop watchers itself
		836	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		837	in the callback).
711		838
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	839	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	840	running when nothing else is active.
714		841
715	ev_signal exitsig;	842	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	843	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	844	ev_signal_start (loop, &exitsig);
…		…
744		871
745	By setting a higher I<io collect interval> you allow libev to spend more	872	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,	873	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	874	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	875	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.	876	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		877	sleep time ensures that libev will not poll for I/O events more often then
		878	once per this interval, on average.
750		879
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	880	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	881	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	882	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	883	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		885
757	Many (busy) programs can usually benefit by setting the I/O collect	886	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	887	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	888	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>,	889	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.	890	as this approaches the timing granularity of most systems. Note that if
		891	you do transactions with the outside world and you can't increase the
		892	parallelity, then this setting will limit your transaction rate (if you
		893	need to poll once per transaction and the I/O collect interval is 0.01,
		894	then you can't do more than 100 transactions per second).
762		895
763	Setting the I<timeout collect interval> can improve the opportunity for	896	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	897	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	898	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	899	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	900	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	901	they fire on, say, one-second boundaries only.
769		902
		903	Example: we only need 0.1s timeout granularity, and we wish not to poll
		904	more often than 100 times per second:
		905
		906	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		907	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		908
		909	=item ev_invoke_pending (loop)
		910
		911	This call will simply invoke all pending watchers while resetting their
		912	pending state. Normally, C<ev_run> does this automatically when required,
		913	but when overriding the invoke callback this call comes handy.
		914
		915	=item int ev_pending_count (loop)
		916
		917	Returns the number of pending watchers - zero indicates that no watchers
		918	are pending.
		919
		920	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		921
		922	This overrides the invoke pending functionality of the loop: Instead of
		923	invoking all pending watchers when there are any, C<ev_run> will call
		924	this callback instead. This is useful, for example, when you want to
		925	invoke the actual watchers inside another context (another thread etc.).
		926
		927	If you want to reset the callback, use C<ev_invoke_pending> as new
		928	callback.
		929
		930	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		931
		932	Sometimes you want to share the same loop between multiple threads. This
		933	can be done relatively simply by putting mutex_lock/unlock calls around
		934	each call to a libev function.
		935
		936	However, C<ev_run> can run an indefinite time, so it is not feasible
		937	to wait for it to return. One way around this is to wake up the event
		938	loop via C<ev_break> and C<av_async_send>, another way is to set these
		939	I<release> and I<acquire> callbacks on the loop.
		940
		941	When set, then C<release> will be called just before the thread is
		942	suspended waiting for new events, and C<acquire> is called just
		943	afterwards.
		944
		945	Ideally, C<release> will just call your mutex_unlock function, and
		946	C<acquire> will just call the mutex_lock function again.
		947
		948	While event loop modifications are allowed between invocations of
		949	C<release> and C<acquire> (that's their only purpose after all), no
		950	modifications done will affect the event loop, i.e. adding watchers will
		951	have no effect on the set of file descriptors being watched, or the time
		952	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		953	to take note of any changes you made.
		954
		955	In theory, threads executing C<ev_run> will be async-cancel safe between
		956	invocations of C<release> and C<acquire>.
		957
		958	See also the locking example in the C<THREADS> section later in this
		959	document.
		960
		961	=item ev_set_userdata (loop, void *data)
		962
		963	=item ev_userdata (loop)
		964
		965	Set and retrieve a single C<void *> associated with a loop. When
		966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		967	C<0.>
		968
		969	These two functions can be used to associate arbitrary data with a loop,
		970	and are intended solely for the C<invoke_pending_cb>, C<release> and
		971	C<acquire> callbacks described above, but of course can be (ab-)used for
		972	any other purpose as well.
		973
770	=item ev_loop_verify (loop)	974	=item ev_verify (loop)
771		975
772	This function only does something when C<EV_VERIFY> support has been	976	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	977	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	978	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	979	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	980	error and call C<abort ()>.
777		981
778	This can be used to catch bugs inside libev itself: under normal	982	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	986	=back
783		987
784		988
785	=head1 ANATOMY OF A WATCHER	989	=head1 ANATOMY OF A WATCHER
786		990
		991	In the following description, uppercase C<TYPE> in names stands for the
		992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		993	watchers and C<ev_io_start> for I/O watchers.
		994
787	A watcher is a structure that you create and register to record your	995	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	996	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	997	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		998	for that:
790		999
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1000	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1001	{
793	ev_io_stop (w);	1002	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1003	ev_break (loop, EVBREAK_ALL);
795	}	1004	}
796		1005
797	struct ev_loop *loop = ev_default_loop (0);	1006	struct ev_loop *loop = ev_default_loop (0);
		1007
798	ev_io stdin_watcher;	1008	ev_io stdin_watcher;
		1009
799	ev_init (&stdin_watcher, my_cb);	1010	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1011	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1012	ev_io_start (loop, &stdin_watcher);
		1013
802	ev_loop (loop, 0);	1014	ev_run (loop, 0);
803		1015
804	As you can see, you are responsible for allocating the memory for your	1016	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,	1017	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1018	stack).
807		1019
		1020	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1021	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1022
808	Each watcher structure must be initialised by a call to C<ev_init	1023	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1024	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1025	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1026	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1027	and/or writable).
813		1028
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1029	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	1030	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	1031	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1032	ev_TYPE_init (watcher *, callback, ...) >>.
818		1033
819	To make the watcher actually watch out for events, you have to start it	1034	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	1035	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	1036	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1037	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1038
824	As long as your watcher is active (has been started but not stopped) you	1039	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	1040	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1041	reinitialise it or call its C<ev_TYPE_set> macro.
827		1042
828	Each and every callback receives the event loop pointer as first, the	1043	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	1044	registered watcher structure as second, and a bitset of received events as
830	third argument.	1045	third argument.
831		1046
…		…
840	=item C<EV_WRITE>	1055	=item C<EV_WRITE>
841		1056
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1057	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1058	writable.
844		1059
845	=item C<EV_TIMEOUT>	1060	=item C<EV_TIMER>
846		1061
847	The C<ev_timer> watcher has timed out.	1062	The C<ev_timer> watcher has timed out.
848		1063
849	=item C<EV_PERIODIC>	1064	=item C<EV_PERIODIC>
850		1065
…		…
868		1083
869	=item C<EV_PREPARE>	1084	=item C<EV_PREPARE>
870		1085
871	=item C<EV_CHECK>	1086	=item C<EV_CHECK>
872		1087
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1088	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
874	to gather new events, and all C<ev_check> watchers are invoked just after	1089	to gather new events, and all C<ev_check> watchers are invoked just after
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1090	C<ev_run> has gathered them, but before it invokes any callbacks for any
876	received events. Callbacks of both watcher types can start and stop as	1091	received events. Callbacks of both watcher types can start and stop as
877	many watchers as they want, and all of them will be taken into account	1092	many watchers as they want, and all of them will be taken into account
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1093	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
879	C<ev_loop> from blocking).	1094	C<ev_run> from blocking).
880		1095
881	=item C<EV_EMBED>	1096	=item C<EV_EMBED>
882		1097
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1098	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1099
…		…
888	C<ev_fork>).	1103	C<ev_fork>).
889		1104
890	=item C<EV_ASYNC>	1105	=item C<EV_ASYNC>
891		1106
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1107	The given async watcher has been asynchronously notified (see C<ev_async>).
		1108
		1109	=item C<EV_CUSTOM>
		1110
		1111	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1112	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1113
894	=item C<EV_ERROR>	1114	=item C<EV_ERROR>
895		1115
896	An unspecified error has occurred, the watcher has been stopped. This might	1116	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1117	happen because the watcher could not be properly started because libev
…		…
910	programs, though, as the fd could already be closed and reused for another	1130	programs, though, as the fd could already be closed and reused for another
911	thing, so beware.	1131	thing, so beware.
912		1132
913	=back	1133	=back
914		1134
		1135	=head2 WATCHER STATES
		1136
		1137	There are various watcher states mentioned throughout this manual -
		1138	active, pending and so on. In this section these states and the rules to
		1139	transition between them will be described in more detail - and while these
		1140	rules might look complicated, they usually do "the right thing".
		1141
		1142	=over 4
		1143
		1144	=item initialiased
		1145
		1146	Before a watcher can be registered with the event looop it has to be
		1147	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1148	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1149
		1150	In this state it is simply some block of memory that is suitable for use
		1151	in an event loop. It can be moved around, freed, reused etc. at will.
		1152
		1153	=item started/running/active
		1154
		1155	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1156	property of the event loop, and is actively waiting for events. While in
		1157	this state it cannot be accessed (except in a few documented ways), moved,
		1158	freed or anything else - the only legal thing is to keep a pointer to it,
		1159	and call libev functions on it that are documented to work on active watchers.
		1160
		1161	=item pending
		1162
		1163	If a watcher is active and libev determines that an event it is interested
		1164	in has occured (such as a timer expiring), it will become pending. It will
		1165	stay in this pending state until either it is stopped or its callback is
		1166	about to be invoked, so it is not normally pending inside the watcher
		1167	callback.
		1168
		1169	The watcher might or might not be active while it is pending (for example,
		1170	an expired non-repeating timer can be pending but no longer active). If it
		1171	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1172	but it is still property of the event loop at this time, so cannot be
		1173	moved, freed or reused. And if it is active the rules described in the
		1174	previous item still apply.
		1175
		1176	It is also possible to feed an event on a watcher that is not active (e.g.
		1177	via C<ev_feed_event>), in which case it becomes pending without being
		1178	active.
		1179
		1180	=item stopped
		1181
		1182	A watcher can be stopped implicitly by libev (in which case it might still
		1183	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1184	latter will clear any pending state the watcher might be in, regardless
		1185	of whether it was active or not, so stopping a watcher explicitly before
		1186	freeing it is often a good idea.
		1187
		1188	While stopped (and not pending) the watcher is essentially in the
		1189	initialised state, that is it can be reused, moved, modified in any way
		1190	you wish.
		1191
		1192	=back
		1193
915	=head2 GENERIC WATCHER FUNCTIONS	1194	=head2 GENERIC WATCHER FUNCTIONS
916
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		1195
920	=over 4	1196	=over 4
921		1197
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1198	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1199
…		…
938		1214
939	ev_io w;	1215	ev_io w;
940	ev_init (&w, my_cb);	1216	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1217	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1218
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1219	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1220
945	This macro initialises the type-specific parts of a watcher. You need to	1221	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	1222	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	1223	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	1224	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1237
962	Example: Initialise and set an C<ev_io> watcher in one step.	1238	Example: Initialise and set an C<ev_io> watcher in one step.
963		1239
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1240	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1241
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1242	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1243
968	Starts (activates) the given watcher. Only active watchers will receive	1244	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1245	events. If the watcher is already active nothing will happen.
970		1246
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1247	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1248	whole section.
973		1249
974	ev_io_start (EV_DEFAULT_UC, &w);	1250	ev_io_start (EV_DEFAULT_UC, &w);
975		1251
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1252	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1253
978	Stops the given watcher if active, and clears the pending status (whether	1254	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1255	the watcher was active or not).
980		1256
981	It is possible that stopped watchers are pending - for example,	1257	It is possible that stopped watchers are pending - for example,
…		…
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1282	=item ev_cb_set (ev_TYPE *watcher, callback)
1007		1283
1008	Change the callback. You can change the callback at virtually any time	1284	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1285	(modulo threads).
1010		1286
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1287	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1288
1013	=item int ev_priority (ev_TYPE *watcher)	1289	=item int ev_priority (ev_TYPE *watcher)
1014		1290
1015	Set and query the priority of the watcher. The priority is a small	1291	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>	1292	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1293	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1294	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1295	from being executed (except for C<ev_idle> watchers).
1020		1296
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	1297	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.	1298	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1299
1029	You I<must not> change the priority of a watcher as long as it is active or	1300	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1301	pending.
1031		1302
		1303	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1304	fine, as long as you do not mind that the priority value you query might
		1305	or might not have been clamped to the valid range.
		1306
1032	The default priority used by watchers when no priority has been set is	1307	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 :).	1308	always C<0>, which is supposed to not be too high and not be too low :).
1034		1309
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1310	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	1311	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1312
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1313	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1314
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1315	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	1316	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	1323	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>.	1324	watcher isn't pending it does nothing and returns C<0>.
1051		1325
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1326	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.	1327	callback to be invoked, which can be accomplished with this function.
		1328
		1329	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1330
		1331	Feeds the given event set into the event loop, as if the specified event
		1332	had happened for the specified watcher (which must be a pointer to an
		1333	initialised but not necessarily started event watcher). Obviously you must
		1334	not free the watcher as long as it has pending events.
		1335
		1336	Stopping the watcher, letting libev invoke it, or calling
		1337	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1338	not started in the first place.
		1339
		1340	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1341	functions that do not need a watcher.
1054		1342
1055	=back	1343	=back
1056		1344
1057		1345
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1346	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1107	#include <stddef.h>	1395	#include <stddef.h>
1108		1396
1109	static void	1397	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)	1398	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{	1399	{
1112	struct my_biggy big = (struct my_biggy *	1400	struct my_biggy big = (struct my_biggy *)
1113	(((char *)w) - offsetof (struct my_biggy, t1));	1401	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}	1402	}
1115		1403
1116	static void	1404	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)	1405	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{	1406	{
1119	struct my_biggy big = (struct my_biggy *	1407	struct my_biggy big = (struct my_biggy *)
1120	(((char *)w) - offsetof (struct my_biggy, t2));	1408	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}	1409	}
		1410
		1411	=head2 WATCHER PRIORITY MODELS
		1412
		1413	Many event loops support I<watcher priorities>, which are usually small
		1414	integers that influence the ordering of event callback invocation
		1415	between watchers in some way, all else being equal.
		1416
		1417	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1418	description for the more technical details such as the actual priority
		1419	range.
		1420
		1421	There are two common ways how these these priorities are being interpreted
		1422	by event loops:
		1423
		1424	In the more common lock-out model, higher priorities "lock out" invocation
		1425	of lower priority watchers, which means as long as higher priority
		1426	watchers receive events, lower priority watchers are not being invoked.
		1427
		1428	The less common only-for-ordering model uses priorities solely to order
		1429	callback invocation within a single event loop iteration: Higher priority
		1430	watchers are invoked before lower priority ones, but they all get invoked
		1431	before polling for new events.
		1432
		1433	Libev uses the second (only-for-ordering) model for all its watchers
		1434	except for idle watchers (which use the lock-out model).
		1435
		1436	The rationale behind this is that implementing the lock-out model for
		1437	watchers is not well supported by most kernel interfaces, and most event
		1438	libraries will just poll for the same events again and again as long as
		1439	their callbacks have not been executed, which is very inefficient in the
		1440	common case of one high-priority watcher locking out a mass of lower
		1441	priority ones.
		1442
		1443	Static (ordering) priorities are most useful when you have two or more
		1444	watchers handling the same resource: a typical usage example is having an
		1445	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1446	timeouts. Under load, data might be received while the program handles
		1447	other jobs, but since timers normally get invoked first, the timeout
		1448	handler will be executed before checking for data. In that case, giving
		1449	the timer a lower priority than the I/O watcher ensures that I/O will be
		1450	handled first even under adverse conditions (which is usually, but not
		1451	always, what you want).
		1452
		1453	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1454	will only be executed when no same or higher priority watchers have
		1455	received events, they can be used to implement the "lock-out" model when
		1456	required.
		1457
		1458	For example, to emulate how many other event libraries handle priorities,
		1459	you can associate an C<ev_idle> watcher to each such watcher, and in
		1460	the normal watcher callback, you just start the idle watcher. The real
		1461	processing is done in the idle watcher callback. This causes libev to
		1462	continuously poll and process kernel event data for the watcher, but when
		1463	the lock-out case is known to be rare (which in turn is rare :), this is
		1464	workable.
		1465
		1466	Usually, however, the lock-out model implemented that way will perform
		1467	miserably under the type of load it was designed to handle. In that case,
		1468	it might be preferable to stop the real watcher before starting the
		1469	idle watcher, so the kernel will not have to process the event in case
		1470	the actual processing will be delayed for considerable time.
		1471
		1472	Here is an example of an I/O watcher that should run at a strictly lower
		1473	priority than the default, and which should only process data when no
		1474	other events are pending:
		1475
		1476	ev_idle idle; // actual processing watcher
		1477	ev_io io; // actual event watcher
		1478
		1479	static void
		1480	io_cb (EV_P_ ev_io *w, int revents)
		1481	{
		1482	// stop the I/O watcher, we received the event, but
		1483	// are not yet ready to handle it.
		1484	ev_io_stop (EV_A_ w);
		1485
		1486	// start the idle watcher to handle the actual event.
		1487	// it will not be executed as long as other watchers
		1488	// with the default priority are receiving events.
		1489	ev_idle_start (EV_A_ &idle);
		1490	}
		1491
		1492	static void
		1493	idle_cb (EV_P_ ev_idle *w, int revents)
		1494	{
		1495	// actual processing
		1496	read (STDIN_FILENO, ...);
		1497
		1498	// have to start the I/O watcher again, as
		1499	// we have handled the event
		1500	ev_io_start (EV_P_ &io);
		1501	}
		1502
		1503	// initialisation
		1504	ev_idle_init (&idle, idle_cb);
		1505	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1506	ev_io_start (EV_DEFAULT_ &io);
		1507
		1508	In the "real" world, it might also be beneficial to start a timer, so that
		1509	low-priority connections can not be locked out forever under load. This
		1510	enables your program to keep a lower latency for important connections
		1511	during short periods of high load, while not completely locking out less
		1512	important ones.
1122		1513
1123		1514
1124	=head1 WATCHER TYPES	1515	=head1 WATCHER TYPES
1125		1516
1126	This section describes each watcher in detail, but will not repeat	1517	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	1543	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1544	required if you know what you are doing).
1154		1545
1155	If you cannot use non-blocking mode, then force the use of a	1546	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	1547	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1548	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1549	descriptors for which non-blocking operation makes no sense (such as
		1550	files) - libev doesn't guarantee any specific behaviour in that case.
1158		1551
1159	Another thing you have to watch out for is that it is quite easy to	1552	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	1553	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	1554	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	1555	because there is no data. Not only are some backends known to create a
…		…
1227		1620
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1621	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1622	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1623	somewhere, as that would have given you a big clue).
1231		1624
		1625	=head3 The special problem of accept()ing when you can't
		1626
		1627	Many implementations of the POSIX C<accept> function (for example,
		1628	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1629	connection from the pending queue in all error cases.
		1630
		1631	For example, larger servers often run out of file descriptors (because
		1632	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1633	rejecting the connection, leading to libev signalling readiness on
		1634	the next iteration again (the connection still exists after all), and
		1635	typically causing the program to loop at 100% CPU usage.
		1636
		1637	Unfortunately, the set of errors that cause this issue differs between
		1638	operating systems, there is usually little the app can do to remedy the
		1639	situation, and no known thread-safe method of removing the connection to
		1640	cope with overload is known (to me).
		1641
		1642	One of the easiest ways to handle this situation is to just ignore it
		1643	- when the program encounters an overload, it will just loop until the
		1644	situation is over. While this is a form of busy waiting, no OS offers an
		1645	event-based way to handle this situation, so it's the best one can do.
		1646
		1647	A better way to handle the situation is to log any errors other than
		1648	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1649	messages, and continue as usual, which at least gives the user an idea of
		1650	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1651	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1652	usage.
		1653
		1654	If your program is single-threaded, then you could also keep a dummy file
		1655	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1656	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1657	close that fd, and create a new dummy fd. This will gracefully refuse
		1658	clients under typical overload conditions.
		1659
		1660	The last way to handle it is to simply log the error and C<exit>, as
		1661	is often done with C<malloc> failures, but this results in an easy
		1662	opportunity for a DoS attack.
1232		1663
1233	=head3 Watcher-Specific Functions	1664	=head3 Watcher-Specific Functions
1234		1665
1235	=over 4	1666	=over 4
1236		1667
…		…
1268	...	1699	...
1269	struct ev_loop *loop = ev_default_init (0);	1700	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1701	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1702	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1703	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1704	ev_run (loop, 0);
1274		1705
1275		1706
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1707	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1708
1278	Timer watchers are simple relative timers that generate an event after a	1709	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1714	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1715	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1716	monotonic clock option helps a lot here).
1286		1717
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1718	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	1719	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1720	might introduce a small delay). If multiple timers become ready during the
		1721	same loop iteration then the ones with earlier time-out values are invoked
		1722	before ones of the same priority with later time-out values (but this is
		1723	no longer true when a callback calls C<ev_run> recursively).
1290		1724
1291	=head3 Be smart about timeouts	1725	=head3 Be smart about timeouts
1292		1726
1293	Many real-world problems invole some kind of time-out, usually for error	1727	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,	1728	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1729	you want to raise some error after a while.
1296		1730
1297	Here are some ways on how to handle this problem, from simple and	1731	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1732	inefficient to smart and efficient.
1299		1733
1300	In the following examples a 60 second activity timeout is assumed - a	1734	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1735	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1736	data or other life sign was received).
1303		1737
1304	=over 4	1738	=over 4
1305		1739
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1740	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1741
1308	This is the most obvious, but not the most simple way: In the beginning,	1742	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1743	start the watcher:
1310		1744
1311	ev_timer_init (timer, callback, 60., 0.);	1745	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1746	ev_timer_start (loop, timer);
1313		1747
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1748	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1749	and start it again:
1316		1750
1317	ev_timer_stop (loop, timer);	1751	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1752	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1753	ev_timer_start (loop, timer);
1320		1754
1321	This is relatively simple to implement, but means that each time there	1755	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1756	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1757	data structure and then add it again. Libev tries to be fast, but it's
		1758	still not a constant-time operation.
1324		1759
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1760	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1761
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1762	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1763	C<ev_timer_start>.
1329		1764
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1765	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1766	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1767	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1768	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1769	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1770
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1771	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1772	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1773	member and C<ev_timer_again>.
1338		1774
1339	At start:	1775	At start:
1340		1776
1341	ev_timer_init (timer, callback, 0., 60.);	1777	ev_init (timer, callback);
		1778	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1779	ev_timer_again (loop, timer);
1343		1780
1344	Each time you receive some data:	1781	Each time there is some activity:
1345		1782
1346	ev_timer_again (loop, timer);	1783	ev_timer_again (loop, timer);
1347		1784
1348	It is even possible to change the time-out on the fly:	1785	It is even possible to change the time-out on the fly, regardless of
		1786	whether the watcher is active or not:
1349		1787
1350	timer->repeat = 30.;	1788	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1789	ev_timer_again (loop, timer);
1352		1790
1353	This is slightly more efficient then stopping/starting the timer each time	1791	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1792	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1793	remove and re-insert the timer from/into its internal data structure.
		1794
		1795	It is, however, even simpler than the "obvious" way to do it.
1356		1796
1357	=item 3. Let the timer time out, but then re-arm it as required.	1797	=item 3. Let the timer time out, but then re-arm it as required.
1358		1798
1359	This method is more tricky, but usually most efficient: Most timeouts are	1799	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1800	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1801	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1802	associated activity resets.
1363		1803
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1804	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1805	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1806	within the callback:
1367		1807
1368	ev_tstamp last_activity; // time of last activity	1808	ev_tstamp last_activity; // time of last activity
1369		1809
1370	static void	1810	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1811	callback (EV_P_ ev_timer *w, int revents)
1372	{	1812	{
1373	ev_tstamp now = ev_now (EV_A);	1813	ev_tstamp now = ev_now (EV_A);
1374	ev_tstamp timeout = last_activity + 60.;	1814	ev_tstamp timeout = last_activity + 60.;
1375		1815
1376	// if last_activity is older than now - timeout, we did time out	1816	// if last_activity + 60. is older than now, we did time out
1377	if (timeout < now)	1817	if (timeout < now)
1378	{	1818	{
1379	// timeout occured, take action	1819	// timeout occurred, take action
1380	}	1820	}
1381	else	1821	else
1382	{	1822	{
1383	// callback was invoked, but there was some activity, re-arm	1823	// callback was invoked, but there was some activity, re-arm
1384	// to fire in last_activity + 60.	1824	// the watcher to fire in last_activity + 60, which is
		1825	// guaranteed to be in the future, so "again" is positive:
1385	w->again = timeout - now;	1826	w->repeat = timeout - now;
1386	ev_timer_again (EV_A_ w);	1827	ev_timer_again (EV_A_ w);
1387	}	1828	}
1388	}	1829	}
1389		1830
1390	To summarise the callback: first calculate the real time-out (defined as	1831	To summarise the callback: first calculate the real timeout (defined
1391	"60 seconds after the last activity"), then check if that time has been	1832	as "60 seconds after the last activity"), then check if that time has
1392	reached, which means there was a real timeout. Otherwise the callback was	1833	been reached, which means something I<did>, in fact, time out. Otherwise
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1834	the callback was invoked too early (C<timeout> is in the future), so
1394	fire at that future time.	1835	re-schedule the timer to fire at that future time, to see if maybe we have
		1836	a timeout then.
1395		1837
1396	Note how C<ev_timer_again> is used, taking advantage of the	1838	Note how C<ev_timer_again> is used, taking advantage of the
1397	C<ev_timer_again> optimisation when the timer is already running.	1839	C<ev_timer_again> optimisation when the timer is already running.
1398		1840
1399	This scheme causes more callback invocations (about one every 60 seconds),	1841	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1842	minus half the average time between activity), but virtually no calls to
		1843	libev to change the timeout.
1401		1844
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1845	To start the timer, simply initialise the watcher and set C<last_activity>
1403	then call the callback:	1846	to the current time (meaning we just have some activity :), then call the
		1847	callback, which will "do the right thing" and start the timer:
1404		1848
1405	ev_timer_init (timer, callback);	1849	ev_init (timer, callback);
1406	last_activity = ev_now (loop);	1850	last_activity = ev_now (loop);
1407	callback (loop, timer, EV_TIMEOUT);	1851	callback (loop, timer, EV_TIMER);
1408		1852
1409	And when there is some activity, simply remember the time in	1853	And when there is some activity, simply store the current time in
1410	C<last_activity>:	1854	C<last_activity>, no libev calls at all:
1411		1855
1412	last_actiivty = ev_now (loop);	1856	last_activity = ev_now (loop);
1413		1857
1414	This technique is slightly more complex, but in most cases where the	1858	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	1859	time-out is unlikely to be triggered, much more efficient.
1416		1860
		1861	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1862	callback :) - just change the timeout and invoke the callback, which will
		1863	fix things for you.
		1864
		1865	=item 4. Wee, just use a double-linked list for your timeouts.
		1866
		1867	If there is not one request, but many thousands (millions...), all
		1868	employing some kind of timeout with the same timeout value, then one can
		1869	do even better:
		1870
		1871	When starting the timeout, calculate the timeout value and put the timeout
		1872	at the I<end> of the list.
		1873
		1874	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1875	the list is expected to fire (for example, using the technique #3).
		1876
		1877	When there is some activity, remove the timer from the list, recalculate
		1878	the timeout, append it to the end of the list again, and make sure to
		1879	update the C<ev_timer> if it was taken from the beginning of the list.
		1880
		1881	This way, one can manage an unlimited number of timeouts in O(1) time for
		1882	starting, stopping and updating the timers, at the expense of a major
		1883	complication, and having to use a constant timeout. The constant timeout
		1884	ensures that the list stays sorted.
		1885
1417	=back	1886	=back
		1887
		1888	So which method the best?
		1889
		1890	Method #2 is a simple no-brain-required solution that is adequate in most
		1891	situations. Method #3 requires a bit more thinking, but handles many cases
		1892	better, and isn't very complicated either. In most case, choosing either
		1893	one is fine, with #3 being better in typical situations.
		1894
		1895	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1896	rather complicated, but extremely efficient, something that really pays
		1897	off after the first million or so of active timers, i.e. it's usually
		1898	overkill :)
1418		1899
1419	=head3 The special problem of time updates	1900	=head3 The special problem of time updates
1420		1901
1421	Establishing the current time is a costly operation (it usually takes at	1902	Establishing the current time is a costly operation (it usually takes at
1422	least two system calls): EV therefore updates its idea of the current	1903	least two system calls): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	1904	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1905	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	1906	lots of events in one iteration.
1426		1907
1427	The relative timeouts are calculated relative to the C<ev_now ()>	1908	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	1909	time. This is usually the right thing as this timestamp refers to the time
…		…
1434		1915
1435	If the event loop is suspended for a long time, you can also force an	1916	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1917	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	1918	()>.
1438		1919
		1920	=head3 The special problems of suspended animation
		1921
		1922	When you leave the server world it is quite customary to hit machines that
		1923	can suspend/hibernate - what happens to the clocks during such a suspend?
		1924
		1925	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1926	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1927	to run until the system is suspended, but they will not advance while the
		1928	system is suspended. That means, on resume, it will be as if the program
		1929	was frozen for a few seconds, but the suspend time will not be counted
		1930	towards C<ev_timer> when a monotonic clock source is used. The real time
		1931	clock advanced as expected, but if it is used as sole clocksource, then a
		1932	long suspend would be detected as a time jump by libev, and timers would
		1933	be adjusted accordingly.
		1934
		1935	I would not be surprised to see different behaviour in different between
		1936	operating systems, OS versions or even different hardware.
		1937
		1938	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1939	time jump in the monotonic clocks and the realtime clock. If the program
		1940	is suspended for a very long time, and monotonic clock sources are in use,
		1941	then you can expect C<ev_timer>s to expire as the full suspension time
		1942	will be counted towards the timers. When no monotonic clock source is in
		1943	use, then libev will again assume a timejump and adjust accordingly.
		1944
		1945	It might be beneficial for this latter case to call C<ev_suspend>
		1946	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1947	deterministic behaviour in this case (you can do nothing against
		1948	C<SIGSTOP>).
		1949
1439	=head3 Watcher-Specific Functions and Data Members	1950	=head3 Watcher-Specific Functions and Data Members
1440		1951
1441	=over 4	1952	=over 4
1442		1953
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1954	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1466	If the timer is started but non-repeating, stop it (as if it timed out).	1977	If the timer is started but non-repeating, stop it (as if it timed out).
1467		1978
1468	If the timer is repeating, either start it if necessary (with the	1979	If the timer is repeating, either start it if necessary (with the
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	1980	C<repeat> value), or reset the running timer to the C<repeat> value.
1470		1981
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1982	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1472	usage example.	1983	usage example.
		1984
		1985	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1986
		1987	Returns the remaining time until a timer fires. If the timer is active,
		1988	then this time is relative to the current event loop time, otherwise it's
		1989	the timeout value currently configured.
		1990
		1991	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1992	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1993	will return C<4>. When the timer expires and is restarted, it will return
		1994	roughly C<7> (likely slightly less as callback invocation takes some time,
		1995	too), and so on.
1473		1996
1474	=item ev_tstamp repeat [read-write]	1997	=item ev_tstamp repeat [read-write]
1475		1998
1476	The current C<repeat> value. Will be used each time the watcher times out	1999	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2000	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2026	}
1504		2027
1505	ev_timer mytimer;	2028	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2029	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2030	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2031	ev_run (loop, 0);
1509		2032
1510	// and in some piece of code that gets executed on any "activity":	2033	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2034	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2035	ev_timer_again (&mytimer);
1513		2036
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2038	=head2 C<ev_periodic> - to cron or not to cron?
1516		2039
1517	Periodic watchers are also timers of a kind, but they are very versatile	2040	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2041	(and unfortunately a bit complex).
1519		2042
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2043	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2044	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2045	(absolute time, the thing you can read on your calender or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2046	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2047	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2048	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2049
		2050	You can tell a periodic watcher to trigger after some specific point
		2051	in time: for example, if you tell a periodic watcher to trigger "in 10
		2052	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2053	not a delay) and then reset your system clock to January of the previous
		2054	year, then it will take a year or more to trigger the event (unlike an
		2055	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2056	it, as it uses a relative timeout).
		2057
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2058	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2059	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2060	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2061	those cannot react to time jumps.
1532		2062
1533	As with timers, the callback is guaranteed to be invoked only when the	2063	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2064	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2065	timers become ready during the same loop iteration then the ones with
		2066	earlier time-out values are invoked before ones with later time-out values
		2067	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2068
1537	=head3 Watcher-Specific Functions and Data Members	2069	=head3 Watcher-Specific Functions and Data Members
1538		2070
1539	=over 4	2071	=over 4
1540		2072
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2073	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2074
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2075	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2076
1545	Lots of arguments, lets sort it out... There are basically three modes of	2077	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2078	operation, and we will explain them from simplest to most complex:
1547		2079
1548	=over 4	2080	=over 4
1549		2081
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2082	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2083
1552	In this configuration the watcher triggers an event after the wall clock	2084	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2085	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2086	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2087	will be stopped and invoked when the system clock reaches or surpasses
		2088	this point in time.
1556		2089
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2090	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2091
1559	In this mode the watcher will always be scheduled to time out at the next	2092	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2093	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2094	negative) and then repeat, regardless of any time jumps. The C<offset>
		2095	argument is merely an offset into the C<interval> periods.
1562		2096
1563	This can be used to create timers that do not drift with respect to the	2097	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2098	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2099	hour, on the hour (with respect to UTC):
1566		2100
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2101	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2102
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2103	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2104	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2105	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2106	by 3600.
1573		2107
1574	Another way to think about it (for the mathematically inclined) is that	2108	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2109	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2110	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2111
1578	For numerical stability it is preferable that the C<at> value is near	2112	For numerical stability it is preferable that the C<offset> value is near
1579	C<ev_now ()> (the current time), but there is no range requirement for	2113	C<ev_now ()> (the current time), but there is no range requirement for
1580	this value, and in fact is often specified as zero.	2114	this value, and in fact is often specified as zero.
1581		2115
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2116	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2117	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2118	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2119	millisecond (if the OS supports it and the machine is fast enough).
1586		2120
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2121	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2122
1589	In this mode the values for C<interval> and C<at> are both being	2123	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2124	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2125	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2126	current time as second argument.
1593		2127
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2128	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2129	or make ANY other event loop modifications whatsoever, unless explicitly
		2130	allowed by documentation here>.
1596		2131
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2132	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2133	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2134	only event loop modification you are allowed to do).
1600		2135
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2165	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2166	program when the crontabs have changed).
1632		2167
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2168	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2169
1635	When active, returns the absolute time that the watcher is supposed to	2170	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2171	to trigger next. This is not the same as the C<offset> argument to
		2172	C<ev_periodic_set>, but indeed works even in interval and manual
		2173	rescheduling modes.
1637		2174
1638	=item ev_tstamp offset [read-write]	2175	=item ev_tstamp offset [read-write]
1639		2176
1640	When repeating, this contains the offset value, otherwise this is the	2177	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2178	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2179	although libev might modify this value for better numerical stability).
1642		2180
1643	Can be modified any time, but changes only take effect when the periodic	2181	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2182	timer fires or C<ev_periodic_again> is being called.
1645		2183
1646	=item ev_tstamp interval [read-write]	2184	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2200	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2201	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2202	potentially a lot of jitter, but good long-term stability.
1665		2203
1666	static void	2204	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2205	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2206	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2207	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2208	}
1671		2209
1672	ev_periodic hourly_tick;	2210	ev_periodic hourly_tick;
…		…
1698	Signal watchers will trigger an event when the process receives a specific	2236	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2237	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2238	will try it's best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2239	normal event processing, like any other event.
1702		2240
1703	If you want signals asynchronously, just use C<sigaction> as you would	2241	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2242	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2243	the signal. You can even use C<ev_async> from a signal handler to
		2244	synchronously wake up an event loop.
1706		2245
1707	You can configure as many watchers as you like per signal. Only when the	2246	You can configure as many watchers as you like for the same signal, but
		2247	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2248	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2249	C<SIGINT> in both the default loop and another loop at the same time. At
		2250	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2251
1708	first watcher gets started will libev actually register a signal handler	2252	When the first watcher gets started will libev actually register something
1709	with the kernel (thus it coexists with your own signal handlers as long as	2253	with the kernel (thus it coexists with your own signal handlers as long as
1710	you don't register any with libev for the same signal). Similarly, when	2254	you don't register any with libev for the same signal).
1711	the last signal watcher for a signal is stopped, libev will reset the
1712	signal handler to SIG_DFL (regardless of what it was set to before).
1713		2255
1714	If possible and supported, libev will install its handlers with	2256	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2257	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2258	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2259	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2260	and unblock them in an C<ev_prepare> watcher.
		2261
		2262	=head3 The special problem of inheritance over fork/execve/pthread_create
		2263
		2264	Both the signal mask (C<sigprocmask>) and the signal disposition
		2265	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2266	stopping it again), that is, libev might or might not block the signal,
		2267	and might or might not set or restore the installed signal handler.
		2268
		2269	While this does not matter for the signal disposition (libev never
		2270	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2271	C<execve>), this matters for the signal mask: many programs do not expect
		2272	certain signals to be blocked.
		2273
		2274	This means that before calling C<exec> (from the child) you should reset
		2275	the signal mask to whatever "default" you expect (all clear is a good
		2276	choice usually).
		2277
		2278	The simplest way to ensure that the signal mask is reset in the child is
		2279	to install a fork handler with C<pthread_atfork> that resets it. That will
		2280	catch fork calls done by libraries (such as the libc) as well.
		2281
		2282	In current versions of libev, the signal will not be blocked indefinitely
		2283	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2284	the window of opportunity for problems, it will not go away, as libev
		2285	I<has> to modify the signal mask, at least temporarily.
		2286
		2287	So I can't stress this enough: I<If you do not reset your signal mask when
		2288	you expect it to be empty, you have a race condition in your code>. This
		2289	is not a libev-specific thing, this is true for most event libraries.
1719		2290
1720	=head3 Watcher-Specific Functions and Data Members	2291	=head3 Watcher-Specific Functions and Data Members
1721		2292
1722	=over 4	2293	=over 4
1723		2294
…		…
1739	Example: Try to exit cleanly on SIGINT.	2310	Example: Try to exit cleanly on SIGINT.
1740		2311
1741	static void	2312	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2313	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2314	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2315	ev_break (loop, EVBREAK_ALL);
1745	}	2316	}
1746		2317
1747	ev_signal signal_watcher;	2318	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2319	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2320	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2326	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2327	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2328	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2329	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2330	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2331	but forking and registering a watcher a few event loop iterations later or
1761	not.	2332	in the next callback invocation is not.
1762		2333
1763	Only the default event loop is capable of handling signals, and therefore	2334	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2335	you can only register child watchers in the default event loop.
1765		2336
		2337	Due to some design glitches inside libev, child watchers will always be
		2338	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2339	libev)
		2340
1766	=head3 Process Interaction	2341	=head3 Process Interaction
1767		2342
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2343	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2344	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2345	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2346	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2347	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2348	children, even ones not watched.
1774		2349
1775	=head3 Overriding the Built-In Processing	2350	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2360	=head3 Stopping the Child Watcher
1786		2361
1787	Currently, the child watcher never gets stopped, even when the	2362	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2363	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2364	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2365	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2366	problem).
1791		2367
1792	=head3 Watcher-Specific Functions and Data Members	2368	=head3 Watcher-Specific Functions and Data Members
1793		2369
1794	=over 4	2370	=over 4
1795		2371
…		…
1852		2428
1853		2429
1854	=head2 C<ev_stat> - did the file attributes just change?	2430	=head2 C<ev_stat> - did the file attributes just change?
1855		2431
1856	This watches a file system path for attribute changes. That is, it calls	2432	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2433	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2434	and sees if it changed compared to the last time, invoking the callback if
		2435	it did.
1859		2436
1860	The path does not need to exist: changing from "path exists" to "path does	2437	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2438	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2439	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2440	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2441	least one) and all the other fields of the stat buffer having unspecified
		2442	contents.
1865		2443
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2444	The path I<must not> end in a slash or contain special components such as
		2445	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2446	your working directory changes, then the behaviour is undefined.
1868		2447
1869	Since there is no standard kernel interface to do this, the portable	2448	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2449	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2450	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2451	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2452	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2453	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2454	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2455	currently around C<0.1>, but that's usually overkill.
1877		2456
1878	This watcher type is not meant for massive numbers of stat watchers,	2457	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2458	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2459	resource-intensive.
1881		2460
1882	At the time of this writing, the only OS-specific interface implemented	2461	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2462	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2463	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2464	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2465
1887	=head3 ABI Issues (Largefile Support)	2466	=head3 ABI Issues (Largefile Support)
1888		2467
1889	Libev by default (unless the user overrides this) uses the default	2468	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2469	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2470	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2471	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2472	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2473	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2474	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2475	most noticeably displayed with ev_stat and large file support.
1897		2476
1898	The solution for this is to lobby your distribution maker to make large	2477	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2478	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2479	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2480	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2481	default compilation environment.
1903		2482
1904	=head3 Inotify and Kqueue	2483	=head3 Inotify and Kqueue
1905		2484
1906	When C<inotify (7)> support has been compiled into libev (generally	2485	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2486	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2487	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2488	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2489
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2490	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2491	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2492	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2493	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2494	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2495	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2496	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2497	xfs are fully working) libev usually gets away without polling.
1917		2498
1918	There is no support for kqueue, as apparently it cannot be used to	2499	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2500	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2501	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2502	etc. is difficult.
1922		2503
		2504	=head3 C<stat ()> is a synchronous operation
		2505
		2506	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2507	the process. The exception are C<ev_stat> watchers - those call C<stat
		2508	()>, which is a synchronous operation.
		2509
		2510	For local paths, this usually doesn't matter: unless the system is very
		2511	busy or the intervals between stat's are large, a stat call will be fast,
		2512	as the path data is usually in memory already (except when starting the
		2513	watcher).
		2514
		2515	For networked file systems, calling C<stat ()> can block an indefinite
		2516	time due to network issues, and even under good conditions, a stat call
		2517	often takes multiple milliseconds.
		2518
		2519	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2520	paths, although this is fully supported by libev.
		2521
1923	=head3 The special problem of stat time resolution	2522	=head3 The special problem of stat time resolution
1924		2523
1925	The C<stat ()> system call only supports full-second resolution portably, and	2524	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2525	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2526	still only support whole seconds.
1928		2527
1929	That means that, if the time is the only thing that changes, you can	2528	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2529	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2530	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2531	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2075		2674
2076	=head3 Watcher-Specific Functions and Data Members	2675	=head3 Watcher-Specific Functions and Data Members
2077		2676
2078	=over 4	2677	=over 4
2079		2678
2080	=item ev_idle_init (ev_signal *, callback)	2679	=item ev_idle_init (ev_idle *, callback)
2081		2680
2082	Initialises and configures the idle watcher - it has no parameters of any	2681	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2682	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2683	believe me.
2085		2684
…		…
2098	// no longer anything immediate to do.	2697	// no longer anything immediate to do.
2099	}	2698	}
2100		2699
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2700	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2701	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2702	ev_idle_start (loop, idle_watcher);
2104		2703
2105		2704
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2705	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2706
2108	Prepare and check watchers are usually (but not always) used in pairs:	2707	Prepare and check watchers are usually (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2708	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2709	afterwards.
2111		2710
2112	You I<must not> call C<ev_loop> or similar functions that enter	2711	You I<must not> call C<ev_run> or similar functions that enter
2113	the current event loop from either C<ev_prepare> or C<ev_check>	2712	the current event loop from either C<ev_prepare> or C<ev_check>
2114	watchers. Other loops than the current one are fine, however. The	2713	watchers. Other loops than the current one are fine, however. The
2115	rationale behind this is that you do not need to check for recursion in	2714	rationale behind this is that you do not need to check for recursion in
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2715	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2117	C<ev_check> so if you have one watcher of each kind they will always be	2716	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2201	struct pollfd fds [nfd];	2800	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	2801	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		2803
2205	/* the callback is illegal, but won't be called as we stop during check */	2804	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	2805	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	2806	ev_timer_start (loop, &tw);
2208		2807
2209	// create one ev_io per pollfd	2808	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	2809	for (int i = 0; i < nfd; ++i)
2211	{	2810	{
…		…
2285		2884
2286	if (timeout >= 0)	2885	if (timeout >= 0)
2287	// create/start timer	2886	// create/start timer
2288		2887
2289	// poll	2888	// poll
2290	ev_loop (EV_A_ 0);	2889	ev_run (EV_A_ 0);
2291		2890
2292	// stop timer again	2891	// stop timer again
2293	if (timeout >= 0)	2892	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	2893	ev_timer_stop (EV_A_ &to);
2295		2894
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	2923	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	2924	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	2925	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	2926	the rest in a second one, and embed the second one in the first.
2328		2927
2329	As long as the watcher is active, the callback will be invoked every time	2928	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	2929	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2930	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	2931	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	2932	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	2933	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		2934
2337	As long as the watcher is started it will automatically handle events. The	2935	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	2936	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		2937
2342	Also, there have not currently been made special provisions for forking:	2938	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2939	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	2940	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	2941	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		2942
2348	Unfortunately, not all backends are embeddable: only the ones returned by	2943	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2944	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	2945	portable one.
2351		2946
…		…
2377	if you do not want that, you need to temporarily stop the embed watcher).	2972	if you do not want that, you need to temporarily stop the embed watcher).
2378		2973
2379	=item ev_embed_sweep (loop, ev_embed *)	2974	=item ev_embed_sweep (loop, ev_embed *)
2380		2975
2381	Make a single, non-blocking sweep over the embedded loop. This works	2976	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2977	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	2978	appropriate way for embedded loops.
2384		2979
2385	=item struct ev_loop *other [read-only]	2980	=item struct ev_loop *other [read-only]
2386		2981
2387	The embedded event loop.	2982	The embedded event loop.
…		…
2445	event loop blocks next and before C<ev_check> watchers are being called,	3040	event loop blocks next and before C<ev_check> watchers are being called,
2446	and only in the child after the fork. If whoever good citizen calling	3041	and only in the child after the fork. If whoever good citizen calling
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3042	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2448	handlers will be invoked, too, of course.	3043	handlers will be invoked, too, of course.
2449		3044
		3045	=head3 The special problem of life after fork - how is it possible?
		3046
		3047	Most uses of C<fork()> consist of forking, then some simple calls to set
		3048	up/change the process environment, followed by a call to C<exec()>. This
		3049	sequence should be handled by libev without any problems.
		3050
		3051	This changes when the application actually wants to do event handling
		3052	in the child, or both parent in child, in effect "continuing" after the
		3053	fork.
		3054
		3055	The default mode of operation (for libev, with application help to detect
		3056	forks) is to duplicate all the state in the child, as would be expected
		3057	when I<either> the parent I<or> the child process continues.
		3058
		3059	When both processes want to continue using libev, then this is usually the
		3060	wrong result. In that case, usually one process (typically the parent) is
		3061	supposed to continue with all watchers in place as before, while the other
		3062	process typically wants to start fresh, i.e. without any active watchers.
		3063
		3064	The cleanest and most efficient way to achieve that with libev is to
		3065	simply create a new event loop, which of course will be "empty", and
		3066	use that for new watchers. This has the advantage of not touching more
		3067	memory than necessary, and thus avoiding the copy-on-write, and the
		3068	disadvantage of having to use multiple event loops (which do not support
		3069	signal watchers).
		3070
		3071	When this is not possible, or you want to use the default loop for
		3072	other reasons, then in the process that wants to start "fresh", call
		3073	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		3074	the default loop will "orphan" (not stop) all registered watchers, so you
		3075	have to be careful not to execute code that modifies those watchers. Note
		3076	also that in that case, you have to re-register any signal watchers.
		3077
2450	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2451		3079
2452	=over 4	3080	=over 4
2453		3081
2454	=item ev_fork_init (ev_signal *, callback)	3082	=item ev_fork_init (ev_signal *, callback)
…		…
2458	believe me.	3086	believe me.
2459		3087
2460	=back	3088	=back
2461		3089
2462		3090
2463	=head2 C<ev_async> - how to wake up another event loop	3091	=head2 C<ev_async> - how to wake up an event loop
2464		3092
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3093	In general, you cannot use an C<ev_run> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3094	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3095	loops - those are of course safe to use in different threads).
2468		3096
2469	Sometimes, however, you need to wake up another event loop you do not	3097	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3098	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3099	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3100	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3101
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3102	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3103	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3104	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3105	C<ev_async_sent> calls).
…		…
2483	=head3 Queueing	3110	=head3 Queueing
2484		3111
2485	C<ev_async> does not support queueing of data in any way. The reason	3112	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3113	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3114	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3115	need elaborate support such as pthreads or unportable memory access
		3116	semantics.
2489		3117
2490	That means that if you want to queue data, you have to provide your own	3118	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3119	queue. But at least I can tell you how to implement locking around your
2492	queue:	3120	queue:
2493		3121
…		…
2571	=over 4	3199	=over 4
2572		3200
2573	=item ev_async_init (ev_async *, callback)	3201	=item ev_async_init (ev_async *, callback)
2574		3202
2575	Initialises and configures the async watcher - it has no parameters of any	3203	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3204	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3205	trust me.
2578		3206
2579	=item ev_async_send (loop, ev_async *)	3207	=item ev_async_send (loop, ev_async *)
2580		3208
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3209	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3210	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3211	C<ev_feed_event>, this call is safe to do from other threads, signal or
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3212	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2585	section below on what exactly this means).	3213	section below on what exactly this means).
2586		3214
		3215	Note that, as with other watchers in libev, multiple events might get
		3216	compressed into a single callback invocation (another way to look at this
		3217	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3218	reset when the event loop detects that).
		3219
2587	This call incurs the overhead of a system call only once per loop iteration,	3220	This call incurs the overhead of a system call only once per event loop
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3221	iteration, so while the overhead might be noticeable, it doesn't apply to
2589	calls to C<ev_async_send>.	3222	repeated calls to C<ev_async_send> for the same event loop.
2590		3223
2591	=item bool = ev_async_pending (ev_async *)	3224	=item bool = ev_async_pending (ev_async *)
2592		3225
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3226	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3227	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3230	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3231	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3232	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3233	quickly check whether invoking the loop might be a good idea.
2601		3234
2602	Not that this does I<not> check whether the watcher itself is pending, only	3235	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3236	only whether it has been requested to make this watcher pending: there
		3237	is a time window between the event loop checking and resetting the async
		3238	notification, and the callback being invoked.
2604		3239
2605	=back	3240	=back
2606		3241
2607		3242
2608	=head1 OTHER FUNCTIONS	3243	=head1 OTHER FUNCTIONS
…		…
2625		3260
2626	If C<timeout> is less than 0, then no timeout watcher will be	3261	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3262	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3263	repeat = 0) will be started. C<0> is a valid timeout.
2629		3264
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3265	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3266	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3267	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3268	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3269	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3270	events precedence.
2636		3271
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3272	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3273
2639	static void stdin_ready (int revents, void *arg)	3274	static void stdin_ready (int revents, void *arg)
2640	{	3275	{
2641	if (revents & EV_READ)	3276	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3277	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3278	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3279	/* doh, nothing entered */;
2645	}	3280	}
2646		3281
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3282	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3283
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3284	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3285
2657	Feed an event on the given fd, as if a file descriptor backend detected	3286	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3287	the given events it.
2659		3288
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3289	=item ev_feed_signal_event (loop, int signum)
2661		3290
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3291	Feed an event as if the given signal occurred (C<loop> must be the default
2663	loop!).	3292	loop!).
2664		3293
2665	=back	3294	=back
…		…
2745		3374
2746	=over 4	3375	=over 4
2747		3376
2748	=item ev::TYPE::TYPE ()	3377	=item ev::TYPE::TYPE ()
2749		3378
2750	=item ev::TYPE::TYPE (struct ev_loop *)	3379	=item ev::TYPE::TYPE (loop)
2751		3380
2752	=item ev::TYPE::~TYPE	3381	=item ev::TYPE::~TYPE
2753		3382
2754	The constructor (optionally) takes an event loop to associate the watcher	3383	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	3384	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		3416
2788	myclass obj;	3417	myclass obj;
2789	ev::io iow;	3418	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	3419	iow.set <myclass, &myclass::io_cb> (&obj);
2791		3420
		3421	=item w->set (object *)
		3422
		3423	This is a variation of a method callback - leaving out the method to call
		3424	will default the method to C<operator ()>, which makes it possible to use
		3425	functor objects without having to manually specify the C<operator ()> all
		3426	the time. Incidentally, you can then also leave out the template argument
		3427	list.
		3428
		3429	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3430	int revents)>.
		3431
		3432	See the method-C<set> above for more details.
		3433
		3434	Example: use a functor object as callback.
		3435
		3436	struct myfunctor
		3437	{
		3438	void operator() (ev::io &w, int revents)
		3439	{
		3440	...
		3441	}
		3442	}
		3443
		3444	myfunctor f;
		3445
		3446	ev::io w;
		3447	w.set (&f);
		3448
2792	=item w->set<function> (void *data = 0)	3449	=item w->set<function> (void *data = 0)
2793		3450
2794	Also sets a callback, but uses a static method or plain function as	3451	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	3452	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	3453	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	3459	Example: Use a plain function as callback.
2803		3460
2804	static void io_cb (ev::io &w, int revents) { }	3461	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	3462	iow.set <io_cb> ();
2806		3463
2807	=item w->set (struct ev_loop *)	3464	=item w->set (loop)
2808		3465
2809	Associates a different C<struct ev_loop> with this watcher. You can only	3466	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	3467	do this when the watcher is inactive (and not pending either).
2811		3468
2812	=item w->set ([arguments])	3469	=item w->set ([arguments])
2813		3470
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3471	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2815	called at least once. Unlike the C counterpart, an active watcher gets	3472	method or a suitable start method must be called at least once. Unlike the
2816	automatically stopped and restarted when reconfiguring it with this	3473	C counterpart, an active watcher gets automatically stopped and restarted
2817	method.	3474	when reconfiguring it with this method.
2818		3475
2819	=item w->start ()	3476	=item w->start ()
2820		3477
2821	Starts the watcher. Note that there is no C<loop> argument, as the	3478	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	3479	constructor already stores the event loop.
2823		3480
		3481	=item w->start ([arguments])
		3482
		3483	Instead of calling C<set> and C<start> methods separately, it is often
		3484	convenient to wrap them in one call. Uses the same type of arguments as
		3485	the configure C<set> method of the watcher.
		3486
2824	=item w->stop ()	3487	=item w->stop ()
2825		3488
2826	Stops the watcher if it is active. Again, no C<loop> argument.	3489	Stops the watcher if it is active. Again, no C<loop> argument.
2827		3490
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3491	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		3503
2841	=back	3504	=back
2842		3505
2843	=back	3506	=back
2844		3507
2845	Example: Define a class with an IO and idle watcher, start one of them in	3508	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	3509	watchers in the constructor.
2847		3510
2848	class myclass	3511	class myclass
2849	{	3512	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	3513	ev::io io ; void io_cb (ev::io &w, int revents);
		3514	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3515	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		3516
2853	myclass (int fd)	3517	myclass (int fd)
2854	{	3518	{
2855	io .set <myclass, &myclass::io_cb > (this);	3519	io .set <myclass, &myclass::io_cb > (this);
		3520	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	3521	idle.set <myclass, &myclass::idle_cb> (this);
2857		3522
2858	io.start (fd, ev::READ);	3523	io.set (fd, ev::WRITE); // configure the watcher
		3524	io.start (); // start it whenever convenient
		3525
		3526	io2.start (fd, ev::READ); // set + start in one call
2859	}	3527	}
2860	};	3528	};
2861		3529
2862		3530
2863	=head1 OTHER LANGUAGE BINDINGS	3531	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	3550	L<http://software.schmorp.de/pkg/EV>.
2883		3551
2884	=item Python	3552	=item Python
2885		3553
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3554	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	3555	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		3556
2893	=item Ruby	3557	=item Ruby
2894		3558
2895	Tony Arcieri has written a ruby extension that offers access to a subset	3559	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	3560	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	3561	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	3562	L<http://rev.rubyforge.org/>.
2899		3563
		3564	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3565	makes rev work even on mingw.
		3566
		3567	=item Haskell
		3568
		3569	A haskell binding to libev is available at
		3570	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3571
2900	=item D	3572	=item D
2901		3573
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3575	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3576
		3577	=item Ocaml
		3578
		3579	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3580	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3581
		3582	=item Lua
		3583
		3584	Brian Maher has written a partial interface to libev for lua (at the
		3585	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3586	L<http://github.com/brimworks/lua-ev>.
2904		3587
2905	=back	3588	=back
2906		3589
2907		3590
2908	=head1 MACRO MAGIC	3591	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	3605	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	3606	C<EV_A_> is used when other arguments are following. Example:
2924		3607
2925	ev_unref (EV_A);	3608	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	3609	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	3610	ev_run (EV_A_ 0);
2928		3611
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3612	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	3613	which is often provided by the following macro.
2931		3614
2932	=item C<EV_P>, C<EV_P_>	3615	=item C<EV_P>, C<EV_P_>
…		…
2972	}	3655	}
2973		3656
2974	ev_check check;	3657	ev_check check;
2975	ev_check_init (&check, check_cb);	3658	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	3659	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	3660	ev_run (EV_DEFAULT_ 0);
2978		3661
2979	=head1 EMBEDDING	3662	=head1 EMBEDDING
2980		3663
2981	Libev can (and often is) directly embedded into host	3664	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	3665	applications. Examples of applications that embed it include the Deliantra
…		…
3009		3692
3010	#define EV_STANDALONE 1	3693	#define EV_STANDALONE 1
3011	#include "ev.h"	3694	#include "ev.h"
3012		3695
3013	Both header files and implementation files can be compiled with a C++	3696	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	3697	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	3698	as a bug).
3016		3699
3017	You need the following files in your source tree, or in a directory	3700	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	3701	in your include path (e.g. in libev/ when using -Ilibev):
3019		3702
…		…
3062	libev.m4	3745	libev.m4
3063		3746
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	3747	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		3748
3066	Libev can be configured via a variety of preprocessor symbols you have to	3749	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	3750	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	3751	the absence of autoconf is documented for every option.
		3752
		3753	Symbols marked with "(h)" do not change the ABI, and can have different
		3754	values when compiling libev vs. including F<ev.h>, so it is permissible
		3755	to redefine them before including F<ev.h> without breaking compatibility
		3756	to a compiled library. All other symbols change the ABI, which means all
		3757	users of libev and the libev code itself must be compiled with compatible
		3758	settings.
3069		3759
3070	=over 4	3760	=over 4
3071		3761
		3762	=item EV_COMPAT3 (h)
		3763
		3764	Backwards compatibility is a major concern for libev. This is why this
		3765	release of libev comes with wrappers for the functions and symbols that
		3766	have been renamed between libev version 3 and 4.
		3767
		3768	You can disable these wrappers (to test compatibility with future
		3769	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3770	sources. This has the additional advantage that you can drop the C<struct>
		3771	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3772	typedef in that case.
		3773
		3774	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3775	and in some even more future version the compatibility code will be
		3776	removed completely.
		3777
3072	=item EV_STANDALONE	3778	=item EV_STANDALONE (h)
3073		3779
3074	Must always be C<1> if you do not use autoconf configuration, which	3780	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	3781	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	3782	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	3783	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	3784	F<event.h> that are not directly supported by the libev core alone.
3079		3785
		3786	In standalone mode, libev will still try to automatically deduce the
		3787	configuration, but has to be more conservative.
		3788
3080	=item EV_USE_MONOTONIC	3789	=item EV_USE_MONOTONIC
3081		3790
3082	If defined to be C<1>, libev will try to detect the availability of the	3791	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	3792	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	3793	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	3794	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	3795	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	3796	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	3797	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		3798
3090	=item EV_USE_REALTIME	3799	=item EV_USE_REALTIME
3091		3800
3092	If defined to be C<1>, libev will try to detect the availability of the	3801	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	3802	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	3803	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3804	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3805	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3806	correctness. See the note about libraries in the description of
		3807	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3808	C<EV_USE_CLOCK_SYSCALL>.
		3809
		3810	=item EV_USE_CLOCK_SYSCALL
		3811
		3812	If defined to be C<1>, libev will try to use a direct syscall instead
		3813	of calling the system-provided C<clock_gettime> function. This option
		3814	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3815	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3816	programs needlessly. Using a direct syscall is slightly slower (in
		3817	theory), because no optimised vdso implementation can be used, but avoids
		3818	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3819	higher, as it simplifies linking (no need for C<-lrt>).
3098		3820
3099	=item EV_USE_NANOSLEEP	3821	=item EV_USE_NANOSLEEP
3100		3822
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3823	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	3824	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		3840
3119	=item EV_SELECT_USE_FD_SET	3841	=item EV_SELECT_USE_FD_SET
3120		3842
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	3843	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	3844	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3845	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	3846	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	3847	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3848	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	3849	configures the maximum size of the C<fd_set>.
3128		3850
3129	=item EV_SELECT_IS_WINSOCKET	3851	=item EV_SELECT_IS_WINSOCKET
3130		3852
3131	When defined to C<1>, the select backend will assume that	3853	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	3854	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	3856	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3857	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	3858	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	3859	on win32. Should not be defined on non-win32 platforms.
3138		3860
3139	=item EV_FD_TO_WIN32_HANDLE	3861	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		3862
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3863	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	3864	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	3865	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	3866	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	3867	in which case they can provide this function to map fds to socket handles.
		3868
		3869	=item EV_WIN32_HANDLE_TO_FD(handle)
		3870
		3871	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3872	using the standard C<_open_osfhandle> function. For programs implementing
		3873	their own fd to handle mapping, overwriting this function makes it easier
		3874	to do so. This can be done by defining this macro to an appropriate value.
		3875
		3876	=item EV_WIN32_CLOSE_FD(fd)
		3877
		3878	If programs implement their own fd to handle mapping on win32, then this
		3879	macro can be used to override the C<close> function, useful to unregister
		3880	file descriptors again. Note that the replacement function has to close
		3881	the underlying OS handle.
3146		3882
3147	=item EV_USE_POLL	3883	=item EV_USE_POLL
3148		3884
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3885	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	3886	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3197	as well as for signal and thread safety in C<ev_async> watchers.	3933	as well as for signal and thread safety in C<ev_async> watchers.
3198		3934
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	3935	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	3936	(from F<signal.h>), which is usually good enough on most platforms.
3201		3937
3202	=item EV_H	3938	=item EV_H (h)
3203		3939
3204	The name of the F<ev.h> header file used to include it. The default if	3940	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3941	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	3942	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		3943
3208	=item EV_CONFIG_H	3944	=item EV_CONFIG_H (h)
3209		3945
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3946	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3947	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	3948	C<EV_H>, above.
3213		3949
3214	=item EV_EVENT_H	3950	=item EV_EVENT_H (h)
3215		3951
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3952	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	3953	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		3954
3219	=item EV_PROTOTYPES	3955	=item EV_PROTOTYPES (h)
3220		3956
3221	If defined to be C<0>, then F<ev.h> will not define any function	3957	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	3958	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	3959	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	3960	around libev functions.
…		…
3246	fine.	3982	fine.
3247		3983
3248	If your embedding application does not need any priorities, defining these	3984	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	3985	both to C<0> will save some memory and CPU.
3250		3986
3251	=item EV_PERIODIC_ENABLE	3987	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3988	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3989	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		3990
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	3991	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	3992	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	3993	is not. Disabling watcher types mainly saves code size.
3256		3994
3257	=item EV_IDLE_ENABLE	3995	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		3996
3286	If you need to shave off some kilobytes of code at the expense of some	3997	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	3998	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3999	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4000	that can be enabled on the platform.
		4001
		4002	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4003	with some broad features you want) and then selectively re-enable
		4004	additional parts you want, for example if you want everything minimal,
		4005	but multiple event loop support, async and child watchers and the poll
		4006	backend, use this:
		4007
		4008	#define EV_FEATURES 0
		4009	#define EV_MULTIPLICITY 1
		4010	#define EV_USE_POLL 1
		4011	#define EV_CHILD_ENABLE 1
		4012	#define EV_ASYNC_ENABLE 1
		4013
		4014	The actual value is a bitset, it can be a combination of the following
		4015	values:
		4016
		4017	=over 4
		4018
		4019	=item C<1> - faster/larger code
		4020
		4021	Use larger code to speed up some operations.
		4022
		4023	Currently this is used to override some inlining decisions (enlarging the
		4024	code size by roughly 30% on amd64).
		4025
		4026	When optimising for size, use of compiler flags such as C<-Os> with
		4027	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4028	assertions.
		4029
		4030	=item C<2> - faster/larger data structures
		4031
		4032	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4033	hash table sizes and so on. This will usually further increase code size
		4034	and can additionally have an effect on the size of data structures at
		4035	runtime.
		4036
		4037	=item C<4> - full API configuration
		4038
		4039	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4040	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4041
		4042	=item C<8> - full API
		4043
		4044	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4045	details on which parts of the API are still available without this
		4046	feature, and do not complain if this subset changes over time.
		4047
		4048	=item C<16> - enable all optional watcher types
		4049
		4050	Enables all optional watcher types. If you want to selectively enable
		4051	only some watcher types other than I/O and timers (e.g. prepare,
		4052	embed, async, child...) you can enable them manually by defining
		4053	C<EV_watchertype_ENABLE> to C<1> instead.
		4054
		4055	=item C<32> - enable all backends
		4056
		4057	This enables all backends - without this feature, you need to enable at
		4058	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4059
		4060	=item C<64> - enable OS-specific "helper" APIs
		4061
		4062	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4063	default.
		4064
		4065	=back
		4066
		4067	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4068	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4069	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4070	watchers, timers and monotonic clock support.
		4071
		4072	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4073	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4074	your program might be left out as well - a binary starting a timer and an
		4075	I/O watcher then might come out at only 5Kb.
		4076
		4077	=item EV_AVOID_STDIO
		4078
		4079	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4080	functions (printf, scanf, perror etc.). This will increase the code size
		4081	somewhat, but if your program doesn't otherwise depend on stdio and your
		4082	libc allows it, this avoids linking in the stdio library which is quite
		4083	big.
		4084
		4085	Note that error messages might become less precise when this option is
		4086	enabled.
		4087
		4088	=item EV_NSIG
		4089
		4090	The highest supported signal number, +1 (or, the number of
		4091	signals): Normally, libev tries to deduce the maximum number of signals
		4092	automatically, but sometimes this fails, in which case it can be
		4093	specified. Also, using a lower number than detected (C<32> should be
		4094	good for about any system in existence) can save some memory, as libev
		4095	statically allocates some 12-24 bytes per signal number.
3290		4096
3291	=item EV_PID_HASHSIZE	4097	=item EV_PID_HASHSIZE
3292		4098
3293	C<ev_child> watchers use a small hash table to distribute workload by	4099	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4100	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4101	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4102	might want to increase this value (I<must> be a power of two).
3297		4103
3298	=item EV_INOTIFY_HASHSIZE	4104	=item EV_INOTIFY_HASHSIZE
3299		4105
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4106	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4107	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4108	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4109	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4110	power of two).
3305		4111
3306	=item EV_USE_4HEAP	4112	=item EV_USE_4HEAP
3307		4113
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4114	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4115	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4116	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4117	faster performance with many (thousands) of watchers.
3312		4118
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4119	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4120	will be C<0>.
3315		4121
3316	=item EV_HEAP_CACHE_AT	4122	=item EV_HEAP_CACHE_AT
3317		4123
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4124	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4125	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4126	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4127	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4128	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4129	noticeably with many (hundreds) of watchers.
3324		4130
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4131	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4132	will be C<0>.
3327		4133
3328	=item EV_VERIFY	4134	=item EV_VERIFY
3329		4135
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4136	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4137	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4138	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4139	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4140	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4141	verification code will be called very frequently, which will slow down
3336	libev considerably.	4142	libev considerably.
3337		4143
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4144	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4145	will be C<0>.
3340		4146
3341	=item EV_COMMON	4147	=item EV_COMMON
3342		4148
3343	By default, all watchers have a C<void *data> member. By redefining	4149	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4150	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4151	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4152	though, and it must be identical each time.
3347		4153
3348	For example, the perl EV module uses something like this:	4154	For example, the perl EV module uses something like this:
3349		4155
…		…
3402	file.	4208	file.
3403		4209
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4210	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	4211	that everybody includes and which overrides some configure choices:
3406		4212
3407	#define EV_MINIMAL 1	4213	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	4214	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	4215	#define EV_PREPARE_ENABLE 1
		4216	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	4217	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	4218	#define EV_CHILD_ENABLE 1
		4219	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	4220	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		4221
3417	#include "ev++.h"	4222	#include "ev++.h"
3418		4223
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4224	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		4225
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	4285	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	4286	watcher callback into the event loop interested in the signal.
3482		4287
3483	=back	4288	=back
3484		4289
		4290	=head4 THREAD LOCKING EXAMPLE
		4291
		4292	Here is a fictitious example of how to run an event loop in a different
		4293	thread than where callbacks are being invoked and watchers are
		4294	created/added/removed.
		4295
		4296	For a real-world example, see the C<EV::Loop::Async> perl module,
		4297	which uses exactly this technique (which is suited for many high-level
		4298	languages).
		4299
		4300	The example uses a pthread mutex to protect the loop data, a condition
		4301	variable to wait for callback invocations, an async watcher to notify the
		4302	event loop thread and an unspecified mechanism to wake up the main thread.
		4303
		4304	First, you need to associate some data with the event loop:
		4305
		4306	typedef struct {
		4307	mutex_t lock; /* global loop lock */
		4308	ev_async async_w;
		4309	thread_t tid;
		4310	cond_t invoke_cv;
		4311	} userdata;
		4312
		4313	void prepare_loop (EV_P)
		4314	{
		4315	// for simplicity, we use a static userdata struct.
		4316	static userdata u;
		4317
		4318	ev_async_init (&u->async_w, async_cb);
		4319	ev_async_start (EV_A_ &u->async_w);
		4320
		4321	pthread_mutex_init (&u->lock, 0);
		4322	pthread_cond_init (&u->invoke_cv, 0);
		4323
		4324	// now associate this with the loop
		4325	ev_set_userdata (EV_A_ u);
		4326	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4327	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4328
		4329	// then create the thread running ev_loop
		4330	pthread_create (&u->tid, 0, l_run, EV_A);
		4331	}
		4332
		4333	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4334	solely to wake up the event loop so it takes notice of any new watchers
		4335	that might have been added:
		4336
		4337	static void
		4338	async_cb (EV_P_ ev_async *w, int revents)
		4339	{
		4340	// just used for the side effects
		4341	}
		4342
		4343	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4344	protecting the loop data, respectively.
		4345
		4346	static void
		4347	l_release (EV_P)
		4348	{
		4349	userdata *u = ev_userdata (EV_A);
		4350	pthread_mutex_unlock (&u->lock);
		4351	}
		4352
		4353	static void
		4354	l_acquire (EV_P)
		4355	{
		4356	userdata *u = ev_userdata (EV_A);
		4357	pthread_mutex_lock (&u->lock);
		4358	}
		4359
		4360	The event loop thread first acquires the mutex, and then jumps straight
		4361	into C<ev_run>:
		4362
		4363	void *
		4364	l_run (void *thr_arg)
		4365	{
		4366	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4367
		4368	l_acquire (EV_A);
		4369	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4370	ev_run (EV_A_ 0);
		4371	l_release (EV_A);
		4372
		4373	return 0;
		4374	}
		4375
		4376	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4377	signal the main thread via some unspecified mechanism (signals? pipe
		4378	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4379	have been called (in a while loop because a) spurious wakeups are possible
		4380	and b) skipping inter-thread-communication when there are no pending
		4381	watchers is very beneficial):
		4382
		4383	static void
		4384	l_invoke (EV_P)
		4385	{
		4386	userdata *u = ev_userdata (EV_A);
		4387
		4388	while (ev_pending_count (EV_A))
		4389	{
		4390	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4391	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4392	}
		4393	}
		4394
		4395	Now, whenever the main thread gets told to invoke pending watchers, it
		4396	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4397	thread to continue:
		4398
		4399	static void
		4400	real_invoke_pending (EV_P)
		4401	{
		4402	userdata *u = ev_userdata (EV_A);
		4403
		4404	pthread_mutex_lock (&u->lock);
		4405	ev_invoke_pending (EV_A);
		4406	pthread_cond_signal (&u->invoke_cv);
		4407	pthread_mutex_unlock (&u->lock);
		4408	}
		4409
		4410	Whenever you want to start/stop a watcher or do other modifications to an
		4411	event loop, you will now have to lock:
		4412
		4413	ev_timer timeout_watcher;
		4414	userdata *u = ev_userdata (EV_A);
		4415
		4416	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4417
		4418	pthread_mutex_lock (&u->lock);
		4419	ev_timer_start (EV_A_ &timeout_watcher);
		4420	ev_async_send (EV_A_ &u->async_w);
		4421	pthread_mutex_unlock (&u->lock);
		4422
		4423	Note that sending the C<ev_async> watcher is required because otherwise
		4424	an event loop currently blocking in the kernel will have no knowledge
		4425	about the newly added timer. By waking up the loop it will pick up any new
		4426	watchers in the next event loop iteration.
		4427
3485	=head3 COROUTINES	4428	=head3 COROUTINES
3486		4429
3487	Libev is very accommodating to coroutines ("cooperative threads"):	4430	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	4431	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4432	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	4433	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	4434	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	4435	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		4436
3494	Care has been taken to ensure that libev does not keep local state inside	4437	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4438	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	4439	they do not call any callbacks.
3497		4440
3498	=head2 COMPILER WARNINGS	4441	=head2 COMPILER WARNINGS
3499		4442
3500	Depending on your compiler and compiler settings, you might get no or a	4443	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	4444	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	4454	maintainable.
3512		4455
3513	And of course, some compiler warnings are just plain stupid, or simply	4456	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	4457	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	4458	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	4459	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	4460	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	4461	such buggy versions.
3519		4462
3520	While libev is written to generate as few warnings as possible,	4463	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	4464	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	4478	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	4479	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	4480	==2274== still reachable: 256 bytes in 1 blocks.
3538		4481
3539	Then there is no memory leak, just as memory accounted to global variables	4482	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	4483	is not a memleak - the memory is still being referenced, and didn't leak.
3541		4484
3542	Similarly, under some circumstances, valgrind might report kernel bugs	4485	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4486	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	4487	although an acceptable workaround has been found here), or it might be
3545	confused.	4488	confused.
…		…
3557	I suggest using suppression lists.	4500	I suggest using suppression lists.
3558		4501
3559		4502
3560	=head1 PORTABILITY NOTES	4503	=head1 PORTABILITY NOTES
3561		4504
		4505	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4506
		4507	GNU/Linux is the only common platform that supports 64 bit file/large file
		4508	interfaces but I<disables> them by default.
		4509
		4510	That means that libev compiled in the default environment doesn't support
		4511	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4512
		4513	Unfortunately, many programs try to work around this GNU/Linux issue
		4514	by enabling the large file API, which makes them incompatible with the
		4515	standard libev compiled for their system.
		4516
		4517	Likewise, libev cannot enable the large file API itself as this would
		4518	suddenly make it incompatible to the default compile time environment,
		4519	i.e. all programs not using special compile switches.
		4520
		4521	=head2 OS/X AND DARWIN BUGS
		4522
		4523	The whole thing is a bug if you ask me - basically any system interface
		4524	you touch is broken, whether it is locales, poll, kqueue or even the
		4525	OpenGL drivers.
		4526
		4527	=head3 C<kqueue> is buggy
		4528
		4529	The kqueue syscall is broken in all known versions - most versions support
		4530	only sockets, many support pipes.
		4531
		4532	Libev tries to work around this by not using C<kqueue> by default on
		4533	this rotten platform, but of course you can still ask for it when creating
		4534	a loop.
		4535
		4536	=head3 C<poll> is buggy
		4537
		4538	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4539	implementation by something calling C<kqueue> internally around the 10.5.6
		4540	release, so now C<kqueue> I<and> C<poll> are broken.
		4541
		4542	Libev tries to work around this by not using C<poll> by default on
		4543	this rotten platform, but of course you can still ask for it when creating
		4544	a loop.
		4545
		4546	=head3 C<select> is buggy
		4547
		4548	All that's left is C<select>, and of course Apple found a way to fuck this
		4549	one up as well: On OS/X, C<select> actively limits the number of file
		4550	descriptors you can pass in to 1024 - your program suddenly crashes when
		4551	you use more.
		4552
		4553	There is an undocumented "workaround" for this - defining
		4554	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4555	work on OS/X.
		4556
		4557	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4558
		4559	=head3 C<errno> reentrancy
		4560
		4561	The default compile environment on Solaris is unfortunately so
		4562	thread-unsafe that you can't even use components/libraries compiled
		4563	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
		4564	isn't defined by default.
		4565
		4566	If you want to use libev in threaded environments you have to make sure
		4567	it's compiled with C<_REENTRANT> defined.
		4568
		4569	=head3 Event port backend
		4570
		4571	The scalable event interface for Solaris is called "event ports". Unfortunately,
		4572	this mechanism is very buggy. If you run into high CPU usage, your program
		4573	freezes or you get a large number of spurious wakeups, make sure you have
		4574	all the relevant and latest kernel patches applied. No, I don't know which
		4575	ones, but there are multiple ones.
		4576
		4577	If you can't get it to work, you can try running the program by setting
		4578	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4579	C<select> backends.
		4580
		4581	=head2 AIX POLL BUG
		4582
		4583	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4584	this by trying to avoid the poll backend altogether (i.e. it's not even
		4585	compiled in), which normally isn't a big problem as C<select> works fine
		4586	with large bitsets, and AIX is dead anyway.
		4587
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4588	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4589
		4590	=head3 General issues
3563		4591
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4592	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	4593	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	4594	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4595	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	4596	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	4597	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4598	as every compielr comes with a slightly differently broken/incompatible
		4599	environment.
3570		4600
3571	Lifting these limitations would basically require the full	4601	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	4602	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	4603	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	4604	also that glib is the slowest event library known to man).
3575		4605
3576	There is no supported compilation method available on windows except	4606	There is no supported compilation method available on windows except
3577	embedding it into other applications.	4607	embedding it into other applications.
		4608
		4609	Sensible signal handling is officially unsupported by Microsoft - libev
		4610	tries its best, but under most conditions, signals will simply not work.
3578		4611
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	4612	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	4613	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	4614	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	4615	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	4620	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	4621	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	4622	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	4623	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	4624	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	4625	(due to Microsoft monopoly games).
3593		4626
3594	A typical way to use libev under windows is to embed it (see the embedding	4627	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	4628	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	4629	of F<ev.h>:
3597		4630
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	4637	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		4638
3606	#include "evwrap.h"	4639	#include "evwrap.h"
3607	#include "ev.c"	4640	#include "ev.c"
3608		4641
3609	=over 4
3610
3611	=item The winsocket select function	4642	=head3 The winsocket C<select> function
3612		4643
3613	The winsocket C<select> function doesn't follow POSIX in that it	4644	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	4645	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	4646	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	4647	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4656	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		4657
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	4658	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	4659	complexity in the O(n²) range when using win32.
3629		4660
3630	=item Limited number of file descriptors	4661	=head3 Limited number of file descriptors
3631		4662
3632	Windows has numerous arbitrary (and low) limits on things.	4663	Windows has numerous arbitrary (and low) limits on things.
3633		4664
3634	Early versions of winsocket's select only supported waiting for a maximum	4665	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	4666	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	4667	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	4668	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	4669	previous thread in each. Sounds great!).
3639		4670
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4671	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	4672	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	4673	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	4674	other interpreters do their own select emulation on windows).
3644		4675
3645	Another limit is the number of file descriptors in the Microsoft runtime	4676	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4677	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	4678	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4679	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	4680	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	4681	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	4682	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	4683	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	4684	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		4685
3659	=head2 PORTABILITY REQUIREMENTS	4686	=head2 PORTABILITY REQUIREMENTS
3660		4687
3661	In addition to a working ISO-C implementation and of course the	4688	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	4689	backend-specific APIs, libev relies on a few additional extensions:
…		…
3701	watchers.	4728	watchers.
3702		4729
3703	=item C<double> must hold a time value in seconds with enough accuracy	4730	=item C<double> must hold a time value in seconds with enough accuracy
3704		4731
3705	The type C<double> is used to represent timestamps. It is required to	4732	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4733	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	4734	good enough for at least into the year 4000 with millisecond accuracy
		4735	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	4736	implementations using IEEE 754, which is basically all existing ones. With
		4737	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3709		4738
3710	=back	4739	=back
3711		4740
3712	If you know of other additional requirements drop me a note.	4741	If you know of other additional requirements drop me a note.
3713		4742
…		…
3781	involves iterating over all running async watchers or all signal numbers.	4810	involves iterating over all running async watchers or all signal numbers.
3782		4811
3783	=back	4812	=back
3784		4813
3785		4814
		4815	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4816
		4817	The major version 4 introduced some minor incompatible changes to the API.
		4818
		4819	At the moment, the C<ev.h> header file tries to implement superficial
		4820	compatibility, so most programs should still compile. Those might be
		4821	removed in later versions of libev, so better update early than late.
		4822
		4823	=over 4
		4824
		4825	=item function/symbol renames
		4826
		4827	A number of functions and symbols have been renamed:
		4828
		4829	ev_loop => ev_run
		4830	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4831	EVLOOP_ONESHOT => EVRUN_ONCE
		4832
		4833	ev_unloop => ev_break
		4834	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4835	EVUNLOOP_ONE => EVBREAK_ONE
		4836	EVUNLOOP_ALL => EVBREAK_ALL
		4837
		4838	EV_TIMEOUT => EV_TIMER
		4839
		4840	ev_loop_count => ev_iteration
		4841	ev_loop_depth => ev_depth
		4842	ev_loop_verify => ev_verify
		4843
		4844	Most functions working on C<struct ev_loop> objects don't have an
		4845	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4846	associated constants have been renamed to not collide with the C<struct
		4847	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4848	as all other watcher types. Note that C<ev_loop_fork> is still called
		4849	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4850	typedef.
		4851
		4852	=item C<EV_COMPAT3> backwards compatibility mechanism
		4853
		4854	The backward compatibility mechanism can be controlled by
		4855	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4856	section.
		4857
		4858	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4859
		4860	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4861	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4862	and work, but the library code will of course be larger.
		4863
		4864	=back
		4865
		4866
		4867	=head1 GLOSSARY
		4868
		4869	=over 4
		4870
		4871	=item active
		4872
		4873	A watcher is active as long as it has been started (has been attached to
		4874	an event loop) but not yet stopped (disassociated from the event loop).
		4875
		4876	=item application
		4877
		4878	In this document, an application is whatever is using libev.
		4879
		4880	=item callback
		4881
		4882	The address of a function that is called when some event has been
		4883	detected. Callbacks are being passed the event loop, the watcher that
		4884	received the event, and the actual event bitset.
		4885
		4886	=item callback invocation
		4887
		4888	The act of calling the callback associated with a watcher.
		4889
		4890	=item event
		4891
		4892	A change of state of some external event, such as data now being available
		4893	for reading on a file descriptor, time having passed or simply not having
		4894	any other events happening anymore.
		4895
		4896	In libev, events are represented as single bits (such as C<EV_READ> or
		4897	C<EV_TIMER>).
		4898
		4899	=item event library
		4900
		4901	A software package implementing an event model and loop.
		4902
		4903	=item event loop
		4904
		4905	An entity that handles and processes external events and converts them
		4906	into callback invocations.
		4907
		4908	=item event model
		4909
		4910	The model used to describe how an event loop handles and processes
		4911	watchers and events.
		4912
		4913	=item pending
		4914
		4915	A watcher is pending as soon as the corresponding event has been detected,
		4916	and stops being pending as soon as the watcher will be invoked or its
		4917	pending status is explicitly cleared by the application.
		4918
		4919	A watcher can be pending, but not active. Stopping a watcher also clears
		4920	its pending status.
		4921
		4922	=item real time
		4923
		4924	The physical time that is observed. It is apparently strictly monotonic :)
		4925
		4926	=item wall-clock time
		4927
		4928	The time and date as shown on clocks. Unlike real time, it can actually
		4929	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4930	clock.
		4931
		4932	=item watcher
		4933
		4934	A data structure that describes interest in certain events. Watchers need
		4935	to be started (attached to an event loop) before they can receive events.
		4936
		4937	=item watcher invocation
		4938
		4939	The act of calling the callback associated with a watcher.
		4940
		4941	=back
		4942
3786	=head1 AUTHOR	4943	=head1 AUTHOR
3787		4944
3788	Marc Lehmann <libev@schmorp.de>.	4945	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3789		4946

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