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…		…
8		8
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
		14	#include <stdio.h> // for puts
13		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;
…		…
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<struct ev_loop *> (the C<struct>	297	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	298	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	299	libev 3 had an C<ev_loop> function colliding with the struct name).
284		300
285	The library knows two types of such loops, the I<default> loop, which	301	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	302	supports signals and child events, and dynamically created event loops
287	not.	303	which do not.
288		304
289	=over 4	305	=over 4
290		306
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	307	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		308
…		…
298	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
299	function.	315	function.
300		316
301	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
302	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,
303	as loops cannot bes hared easily between threads anyway).	319	as loops cannot be shared easily between threads anyway).
304		320
305	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
306	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
307	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
308	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
…		…
330	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
331	around bugs.	347	around bugs.
332		348
333	=item C<EVFLAG_FORKCHECK>	349	=item C<EVFLAG_FORKCHECK>
334		350
335	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
336	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.
337	enabling this flag.
338		353
339	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,
340	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
341	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
342	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
…		…
348	flag.	363	flag.
349		364
350	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>
351	environment variable.	366	environment variable.
352		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
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		389
355	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
356	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,
357	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
…		…
381	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
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		418
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
		423
386	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,
387	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
388	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),
389	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).
390	of shortcomings, such as silently dropping events in some hard-to-detect	428
391	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
392	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...).
393		447
394	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
395	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
396	(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
397	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
398	very well if you register events for both fds.	452	file descriptors might not work very well if you register events for both
399		453	file descriptors.
400	Please note that epoll sometimes generates spurious notifications, so you
401	need to use non-blocking I/O or other means to avoid blocking when no data
402	(or space) is available.
403		454
404	Best performance from this backend is achieved by not unregistering all	455	Best performance from this backend is achieved by not unregistering all
405	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,
406	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
407	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
408	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.
409		466
410	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
411	all kernel versions tested so far.	468	all kernel versions tested so far.
412		469
413	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
414	C<EVBACKEND_POLL>.	471	C<EVBACKEND_POLL>.
415		472
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		474
418	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
419	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
420	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
421	completely useless). For this reason it's not being "auto-detected" unless	478	it's completely useless). Unlike epoll, however, whose brokenness
422	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
423	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.
424		484
425	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
426	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
427	the target platform). See C<ev_embed> watchers for more info.	487	the target platform). See C<ev_embed> watchers for more info.
428		488
429	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
430	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
431	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
432	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
433	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
434	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
435		496
436	This backend usually performs well under most conditions.	497	This backend usually performs well under most conditions.
437		498
438	While nominally embeddable in other event loops, this doesn't work	499	While nominally embeddable in other event loops, this doesn't work
439	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
440	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
441	(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
442	(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
443	using it only for sockets.	504	also broken on OS X)) and, did I mention it, using it only for sockets.
444		505
445	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
446	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
447	C<NOTE_EOF>.	508	C<NOTE_EOF>.
448		509
…		…
468	might perform better.	529	might perform better.
469		530
470	On the positive side, with the exception of the spurious readiness	531	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	532	notifications, this backend actually performed fully to specification
472	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
473	OS-specific backends.	534	OS-specific backends (I vastly prefer correctness over speed hacks).
474		535
475	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
476	C<EVBACKEND_POLL>.	537	C<EVBACKEND_POLL>.
477		538
478	=item C<EVBACKEND_ALL>	539	=item C<EVBACKEND_ALL>
…		…
483		544
484	It is definitely not recommended to use this flag.	545	It is definitely not recommended to use this flag.
485		546
486	=back	547	=back
487		548
488	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,
489	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
490	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.
491		553
492	Example: This is the most typical usage.	554	Example: This is the most typical usage.
493		555
494	if (!ev_default_loop (0))	556	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
508		570
509	=item struct ev_loop *ev_loop_new (unsigned int flags)	571	=item struct ev_loop *ev_loop_new (unsigned int flags)
510		572
511	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
512	always distinct from the default loop. Unlike the default loop, it cannot	574	always distinct from the default loop.
513	handle signal and child watchers, and attempts to do so will be greeted by
514	undefined behaviour (or a failed assertion if assertions are enabled).
515		575
516	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
517	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
518	default loop in the "main" or "initial" thread.	578	default loop in the "main" or "initial" thread.
519		579
520	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.
521		581
…		…
523	if (!epoller)	583	if (!epoller)
524	fatal ("no epoll found here, maybe it hides under your chair");	584	fatal ("no epoll found here, maybe it hides under your chair");
525		585
526	=item ev_default_destroy ()	586	=item ev_default_destroy ()
527		587
528	Destroys the default loop again (frees all memory and kernel state	588	Destroys the default loop (frees all memory and kernel state etc.). None
529	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
530	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
531	responsibility to either stop all watchers cleanly yourself I<before>	591	either stop all watchers cleanly yourself I<before> calling this function,
532	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
533	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).
534	for example).
535		594
536	Note that certain global state, such as signal state (and installed signal	595	Note that certain global state, such as signal state (and installed signal
537	handlers), will not be freed by this function, and related watchers (such	596	handlers), will not be freed by this function, and related watchers (such
538	as signal and child watchers) would need to be stopped manually.	597	as signal and child watchers) would need to be stopped manually.
539		598
540	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
541	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
542	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
543	C<ev_loop_new> and C<ev_loop_destroy>).	602	C<ev_loop_new> and C<ev_loop_destroy>.
544		603
545	=item ev_loop_destroy (loop)	604	=item ev_loop_destroy (loop)
546		605
547	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
548	earlier call to C<ev_loop_new>.	607	earlier call to C<ev_loop_new>.
549		608
550	=item ev_default_fork ()	609	=item ev_default_fork ()
551		610
552	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
553	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
554	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
555	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
556	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
557	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.
558		622
559	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
560	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
561	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).
562		629
563	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
564	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
565	quite nicely into a call to C<pthread_atfork>:	632	quite nicely into a call to C<pthread_atfork>:
566		633
…		…
568		635
569	=item ev_loop_fork (loop)	636	=item ev_loop_fork (loop)
570		637
571	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
572	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
573	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
574	entirely your own problem.	641	them is entirely your own problem.
575		642
576	=item int ev_is_default_loop (loop)	643	=item int ev_is_default_loop (loop)
577		644
578	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
579	otherwise.	646	otherwise.
580		647
581	=item unsigned int ev_loop_count (loop)	648	=item unsigned int ev_iteration (loop)
582		649
583	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
584	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>
585	happily wraps around with enough iterations.	652	and happily wraps around with enough iterations.
586		653
587	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
588	"ticks" the number of loop iterations), as it roughly corresponds with	655	"ticks" the number of loop iterations), as it roughly corresponds with
589	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.
590		671
591	=item unsigned int ev_backend (loop)	672	=item unsigned int ev_backend (loop)
592		673
593	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
594	use.	675	use.
…		…
603		684
604	=item ev_now_update (loop)	685	=item ev_now_update (loop)
605		686
606	Establishes the current time by querying the kernel, updating the time	687	Establishes the current time by querying the kernel, updating the time
607	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
608	is usually done automatically within C<ev_loop ()>.	689	is usually done automatically within C<ev_run ()>.
609		690
610	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
611	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
612	the current time is a good idea.	693	the current time is a good idea.
613		694
614	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.
615		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
616	=item ev_loop (loop, int flags)	723	=item ev_run (loop, int flags)
617		724
618	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
619	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
620	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>.
621		730
622	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
623	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.
624		734
625	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
626	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
627	finished (especially in interactive programs), but having a program	737	finished (especially in interactive programs), but having a program
628	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
629	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
630	beauty.	740	beauty.
631		741
632	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
633	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
634	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
635	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.
636		747
637	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
638	necessary) and will handle those and any already outstanding ones. It	749	necessary) and will handle those and any already outstanding ones. It
639	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
640	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
641	user-registered callback will be called), and will return after one	752	user-registered callback will be called), and will return after one
642	iteration of the loop.	753	iteration of the loop.
643		754
644	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
645	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
646	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
647	usually a better approach for this kind of thing.	758	usually a better approach for this kind of thing.
648		759
649	Here are the gory details of what C<ev_loop> does:	760	Here are the gory details of what C<ev_run> does:
650		761
		762	- Increment loop depth.
		763	- Reset the ev_break status.
651	- Before the first iteration, call any pending watchers.	764	- Before the first iteration, call any pending watchers.
		765	LOOP:
652	* If EVFLAG_FORKCHECK was used, check for a fork.	766	- If EVFLAG_FORKCHECK was used, check for a fork.
653	- 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.
654	- Queue and call all prepare watchers.	768	- Queue and call all prepare watchers.
		769	- If ev_break was called, goto FINISH.
655	- If we have been forked, detach and recreate the kernel state	770	- If we have been forked, detach and recreate the kernel state
656	as to not disturb the other process.	771	as to not disturb the other process.
657	- Update the kernel state with all outstanding changes.	772	- Update the kernel state with all outstanding changes.
658	- Update the "event loop time" (ev_now ()).	773	- Update the "event loop time" (ev_now ()).
659	- Calculate for how long to sleep or block, if at all	774	- Calculate for how long to sleep or block, if at all
660	(active idle watchers, EVLOOP_NONBLOCK or not having	775	(active idle watchers, EVRUN_NOWAIT or not having
661	any active watchers at all will result in not sleeping).	776	any active watchers at all will result in not sleeping).
662	- 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.
663	- Block the process, waiting for any events.	779	- Block the process, waiting for any events.
664	- Queue all outstanding I/O (fd) events.	780	- Queue all outstanding I/O (fd) events.
665	- 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.
666	- Queue all expired timers.	782	- Queue all expired timers.
667	- Queue all expired periodics.	783	- Queue all expired periodics.
668	- Unless any events are pending now, queue all idle watchers.	784	- Queue all idle watchers with priority higher than that of pending events.
669	- Queue all check watchers.	785	- Queue all check watchers.
670	- 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).
671	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
672	be handled here by queueing them when their watcher gets executed.	788	be handled here by queueing them when their watcher gets executed.
673	- 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
674	were used, or there are no active watchers, return, otherwise	790	were used, or there are no active watchers, goto FINISH, otherwise
675	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.
676		796
677	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
678	anymore.	798	anymore.
679		799
680	... queue jobs here, make sure they register event watchers as long	800	... queue jobs here, make sure they register event watchers as long
681	... 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..)
682	ev_loop (my_loop, 0);	802	ev_run (my_loop, 0);
683	... jobs done or somebody called unloop. yeah!	803	... jobs done or somebody called unloop. yeah!
684		804
685	=item ev_unloop (loop, how)	805	=item ev_break (loop, how)
686		806
687	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
688	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
689	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
690	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.
691		811
692	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.
693		813
694	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##
695		815
696	=item ev_ref (loop)	816	=item ev_ref (loop)
697		817
698	=item ev_unref (loop)	818	=item ev_unref (loop)
699		819
700	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
701	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
702	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.
703		823
704	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
705	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>
706	stopping it.	827	before stopping it.
707		828
708	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
709	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
710	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
711	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
712	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
713	(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
714	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).
715		838
716	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>
717	running when nothing else is active.	840	running when nothing else is active.
718		841
719	ev_signal exitsig;	842	ev_signal exitsig;
720	ev_signal_init (&exitsig, sig_cb, SIGINT);	843	ev_signal_init (&exitsig, sig_cb, SIGINT);
721	ev_signal_start (loop, &exitsig);	844	ev_signal_start (loop, &exitsig);
…		…
748		871
749	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
750	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,
751	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
752	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
753	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.
754		879
755	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
756	to spend more time collecting timeouts, at the expense of increased	881	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	882	latency/jitter/inexactness (the watcher callback will be called
758	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
…		…
760		885
761	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
762	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
763	interactive servers (of course not for games), likewise for timeouts. It	888	interactive servers (of course not for games), likewise for timeouts. It
764	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>,
765	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).
766		895
767	Setting the I<timeout collect interval> can improve the opportunity for	896	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	897	saving power, as the program will "bundle" timer callback invocations that
769	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
770	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
771	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
772	they fire on, say, one-second boundaries only.	901	they fire on, say, one-second boundaries only.
773		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. This
		914	function can be invoked from a watcher - this can be useful for example
		915	when you want to do some lengthy calculation and want to pass further
		916	event handling to another thread (you still have to make sure only one
		917	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		918
		919	=item int ev_pending_count (loop)
		920
		921	Returns the number of pending watchers - zero indicates that no watchers
		922	are pending.
		923
		924	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		925
		926	This overrides the invoke pending functionality of the loop: Instead of
		927	invoking all pending watchers when there are any, C<ev_run> will call
		928	this callback instead. This is useful, for example, when you want to
		929	invoke the actual watchers inside another context (another thread etc.).
		930
		931	If you want to reset the callback, use C<ev_invoke_pending> as new
		932	callback.
		933
		934	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		935
		936	Sometimes you want to share the same loop between multiple threads. This
		937	can be done relatively simply by putting mutex_lock/unlock calls around
		938	each call to a libev function.
		939
		940	However, C<ev_run> can run an indefinite time, so it is not feasible
		941	to wait for it to return. One way around this is to wake up the event
		942	loop via C<ev_break> and C<av_async_send>, another way is to set these
		943	I<release> and I<acquire> callbacks on the loop.
		944
		945	When set, then C<release> will be called just before the thread is
		946	suspended waiting for new events, and C<acquire> is called just
		947	afterwards.
		948
		949	Ideally, C<release> will just call your mutex_unlock function, and
		950	C<acquire> will just call the mutex_lock function again.
		951
		952	While event loop modifications are allowed between invocations of
		953	C<release> and C<acquire> (that's their only purpose after all), no
		954	modifications done will affect the event loop, i.e. adding watchers will
		955	have no effect on the set of file descriptors being watched, or the time
		956	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		957	to take note of any changes you made.
		958
		959	In theory, threads executing C<ev_run> will be async-cancel safe between
		960	invocations of C<release> and C<acquire>.
		961
		962	See also the locking example in the C<THREADS> section later in this
		963	document.
		964
		965	=item ev_set_userdata (loop, void *data)
		966
		967	=item ev_userdata (loop)
		968
		969	Set and retrieve a single C<void *> associated with a loop. When
		970	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		971	C<0.>
		972
		973	These two functions can be used to associate arbitrary data with a loop,
		974	and are intended solely for the C<invoke_pending_cb>, C<release> and
		975	C<acquire> callbacks described above, but of course can be (ab-)used for
		976	any other purpose as well.
		977
774	=item ev_loop_verify (loop)	978	=item ev_verify (loop)
775		979
776	This function only does something when C<EV_VERIFY> support has been	980	This function only does something when C<EV_VERIFY> support has been
777	compiled in, which is the default for non-minimal builds. It tries to go	981	compiled in, which is the default for non-minimal builds. It tries to go
778	through all internal structures and checks them for validity. If anything	982	through all internal structures and checks them for validity. If anything
779	is found to be inconsistent, it will print an error message to standard	983	is found to be inconsistent, it will print an error message to standard
…		…
790		994
791	In the following description, uppercase C<TYPE> in names stands for the	995	In the following description, uppercase C<TYPE> in names stands for the
792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	996	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
793	watchers and C<ev_io_start> for I/O watchers.	997	watchers and C<ev_io_start> for I/O watchers.
794		998
795	A watcher is a structure that you create and register to record your	999	A watcher is an opaque structure that you allocate and register to record
796	interest in some event. For instance, if you want to wait for STDIN to	1000	your interest in some event. To make a concrete example, imagine you want
797	become readable, you would create an C<ev_io> watcher for that:	1001	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1002	for that:
798		1003
799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1004	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
800	{	1005	{
801	ev_io_stop (w);	1006	ev_io_stop (w);
802	ev_unloop (loop, EVUNLOOP_ALL);	1007	ev_break (loop, EVBREAK_ALL);
803	}	1008	}
804		1009
805	struct ev_loop *loop = ev_default_loop (0);	1010	struct ev_loop *loop = ev_default_loop (0);
806		1011
807	ev_io stdin_watcher;	1012	ev_io stdin_watcher;
808		1013
809	ev_init (&stdin_watcher, my_cb);	1014	ev_init (&stdin_watcher, my_cb);
810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1015	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
811	ev_io_start (loop, &stdin_watcher);	1016	ev_io_start (loop, &stdin_watcher);
812		1017
813	ev_loop (loop, 0);	1018	ev_run (loop, 0);
814		1019
815	As you can see, you are responsible for allocating the memory for your	1020	As you can see, you are responsible for allocating the memory for your
816	watcher structures (and it is I<usually> a bad idea to do this on the	1021	watcher structures (and it is I<usually> a bad idea to do this on the
817	stack).	1022	stack).
818		1023
819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1024	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1025	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
821		1026
822	Each watcher structure must be initialised by a call to C<ev_init	1027	Each watcher structure must be initialised by a call to C<ev_init (watcher
823	(watcher *, callback)>, which expects a callback to be provided. This	1028	*, callback)>, which expects a callback to be provided. This callback is
824	callback gets invoked each time the event occurs (or, in the case of I/O	1029	invoked each time the event occurs (or, in the case of I/O watchers, each
825	watchers, each time the event loop detects that the file descriptor given	1030	time the event loop detects that the file descriptor given is readable
826	is readable and/or writable).	1031	and/or writable).
827		1032
828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1033	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
829	macro to configure it, with arguments specific to the watcher type. There	1034	macro to configure it, with arguments specific to the watcher type. There
830	is also a macro to combine initialisation and setting in one call: C<<	1035	is also a macro to combine initialisation and setting in one call: C<<
831	ev_TYPE_init (watcher *, callback, ...) >>.	1036	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
854	=item C<EV_WRITE>	1059	=item C<EV_WRITE>
855		1060
856	The file descriptor in the C<ev_io> watcher has become readable and/or	1061	The file descriptor in the C<ev_io> watcher has become readable and/or
857	writable.	1062	writable.
858		1063
859	=item C<EV_TIMEOUT>	1064	=item C<EV_TIMER>
860		1065
861	The C<ev_timer> watcher has timed out.	1066	The C<ev_timer> watcher has timed out.
862		1067
863	=item C<EV_PERIODIC>	1068	=item C<EV_PERIODIC>
864		1069
…		…
882		1087
883	=item C<EV_PREPARE>	1088	=item C<EV_PREPARE>
884		1089
885	=item C<EV_CHECK>	1090	=item C<EV_CHECK>
886		1091
887	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1092	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
888	to gather new events, and all C<ev_check> watchers are invoked just after	1093	to gather new events, and all C<ev_check> watchers are invoked just after
889	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1094	C<ev_run> has gathered them, but before it invokes any callbacks for any
890	received events. Callbacks of both watcher types can start and stop as	1095	received events. Callbacks of both watcher types can start and stop as
891	many watchers as they want, and all of them will be taken into account	1096	many watchers as they want, and all of them will be taken into account
892	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1097	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
893	C<ev_loop> from blocking).	1098	C<ev_run> from blocking).
894		1099
895	=item C<EV_EMBED>	1100	=item C<EV_EMBED>
896		1101
897	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1102	The embedded event loop specified in the C<ev_embed> watcher needs attention.
898		1103
…		…
902	C<ev_fork>).	1107	C<ev_fork>).
903		1108
904	=item C<EV_ASYNC>	1109	=item C<EV_ASYNC>
905		1110
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1111	The given async watcher has been asynchronously notified (see C<ev_async>).
		1112
		1113	=item C<EV_CUSTOM>
		1114
		1115	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1116	by libev users to signal watchers (e.g. via C<ev_feed_event>).
907		1117
908	=item C<EV_ERROR>	1118	=item C<EV_ERROR>
909		1119
910	An unspecified error has occurred, the watcher has been stopped. This might	1120	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1121	happen because the watcher could not be properly started because libev
…		…
924	programs, though, as the fd could already be closed and reused for another	1134	programs, though, as the fd could already be closed and reused for another
925	thing, so beware.	1135	thing, so beware.
926		1136
927	=back	1137	=back
928		1138
		1139	=head2 WATCHER STATES
		1140
		1141	There are various watcher states mentioned throughout this manual -
		1142	active, pending and so on. In this section these states and the rules to
		1143	transition between them will be described in more detail - and while these
		1144	rules might look complicated, they usually do "the right thing".
		1145
		1146	=over 4
		1147
		1148	=item initialiased
		1149
		1150	Before a watcher can be registered with the event looop it has to be
		1151	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1152	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1153
		1154	In this state it is simply some block of memory that is suitable for use
		1155	in an event loop. It can be moved around, freed, reused etc. at will.
		1156
		1157	=item started/running/active
		1158
		1159	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1160	property of the event loop, and is actively waiting for events. While in
		1161	this state it cannot be accessed (except in a few documented ways), moved,
		1162	freed or anything else - the only legal thing is to keep a pointer to it,
		1163	and call libev functions on it that are documented to work on active watchers.
		1164
		1165	=item pending
		1166
		1167	If a watcher is active and libev determines that an event it is interested
		1168	in has occurred (such as a timer expiring), it will become pending. It will
		1169	stay in this pending state until either it is stopped or its callback is
		1170	about to be invoked, so it is not normally pending inside the watcher
		1171	callback.
		1172
		1173	The watcher might or might not be active while it is pending (for example,
		1174	an expired non-repeating timer can be pending but no longer active). If it
		1175	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1176	but it is still property of the event loop at this time, so cannot be
		1177	moved, freed or reused. And if it is active the rules described in the
		1178	previous item still apply.
		1179
		1180	It is also possible to feed an event on a watcher that is not active (e.g.
		1181	via C<ev_feed_event>), in which case it becomes pending without being
		1182	active.
		1183
		1184	=item stopped
		1185
		1186	A watcher can be stopped implicitly by libev (in which case it might still
		1187	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1188	latter will clear any pending state the watcher might be in, regardless
		1189	of whether it was active or not, so stopping a watcher explicitly before
		1190	freeing it is often a good idea.
		1191
		1192	While stopped (and not pending) the watcher is essentially in the
		1193	initialised state, that is it can be reused, moved, modified in any way
		1194	you wish.
		1195
		1196	=back
		1197
929	=head2 GENERIC WATCHER FUNCTIONS	1198	=head2 GENERIC WATCHER FUNCTIONS
930		1199
931	=over 4	1200	=over 4
932		1201
933	=item C<ev_init> (ev_TYPE *watcher, callback)	1202	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
949		1218
950	ev_io w;	1219	ev_io w;
951	ev_init (&w, my_cb);	1220	ev_init (&w, my_cb);
952	ev_io_set (&w, STDIN_FILENO, EV_READ);	1221	ev_io_set (&w, STDIN_FILENO, EV_READ);
953		1222
954	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1223	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
955		1224
956	This macro initialises the type-specific parts of a watcher. You need to	1225	This macro initialises the type-specific parts of a watcher. You need to
957	call C<ev_init> at least once before you call this macro, but you can	1226	call C<ev_init> at least once before you call this macro, but you can
958	call C<ev_TYPE_set> any number of times. You must not, however, call this	1227	call C<ev_TYPE_set> any number of times. You must not, however, call this
959	macro on a watcher that is active (it can be pending, however, which is a	1228	macro on a watcher that is active (it can be pending, however, which is a
…		…
972		1241
973	Example: Initialise and set an C<ev_io> watcher in one step.	1242	Example: Initialise and set an C<ev_io> watcher in one step.
974		1243
975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1244	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
976		1245
977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1246	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
978		1247
979	Starts (activates) the given watcher. Only active watchers will receive	1248	Starts (activates) the given watcher. Only active watchers will receive
980	events. If the watcher is already active nothing will happen.	1249	events. If the watcher is already active nothing will happen.
981		1250
982	Example: Start the C<ev_io> watcher that is being abused as example in this	1251	Example: Start the C<ev_io> watcher that is being abused as example in this
983	whole section.	1252	whole section.
984		1253
985	ev_io_start (EV_DEFAULT_UC, &w);	1254	ev_io_start (EV_DEFAULT_UC, &w);
986		1255
987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1256	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
988		1257
989	Stops the given watcher if active, and clears the pending status (whether	1258	Stops the given watcher if active, and clears the pending status (whether
990	the watcher was active or not).	1259	the watcher was active or not).
991		1260
992	It is possible that stopped watchers are pending - for example,	1261	It is possible that stopped watchers are pending - for example,
…		…
1017	=item ev_cb_set (ev_TYPE *watcher, callback)	1286	=item ev_cb_set (ev_TYPE *watcher, callback)
1018		1287
1019	Change the callback. You can change the callback at virtually any time	1288	Change the callback. You can change the callback at virtually any time
1020	(modulo threads).	1289	(modulo threads).
1021		1290
1022	=item ev_set_priority (ev_TYPE *watcher, priority)	1291	=item ev_set_priority (ev_TYPE *watcher, int priority)
1023		1292
1024	=item int ev_priority (ev_TYPE *watcher)	1293	=item int ev_priority (ev_TYPE *watcher)
1025		1294
1026	Set and query the priority of the watcher. The priority is a small	1295	Set and query the priority of the watcher. The priority is a small
1027	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1296	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1297	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1298	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1299	from being executed (except for C<ev_idle> watchers).
1031		1300
1032	This means that priorities are I<only> used for ordering callback
1033	invocation after new events have been received. This is useful, for
1034	example, to reduce latency after idling, or more often, to bind two
1035	watchers on the same event and make sure one is called first.
1036
1037	If you need to suppress invocation when higher priority events are pending	1301	If you need to suppress invocation when higher priority events are pending
1038	you need to look at C<ev_idle> watchers, which provide this functionality.	1302	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1303
1040	You I<must not> change the priority of a watcher as long as it is active or	1304	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1305	pending.
1042
1043	The default priority used by watchers when no priority has been set is
1044	always C<0>, which is supposed to not be too high and not be too low :).
1045		1306
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1307	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1047	fine, as long as you do not mind that the priority value you query might	1308	fine, as long as you do not mind that the priority value you query might
1048	or might not have been clamped to the valid range.	1309	or might not have been clamped to the valid range.
		1310
		1311	The default priority used by watchers when no priority has been set is
		1312	always C<0>, which is supposed to not be too high and not be too low :).
		1313
		1314	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1315	priorities.
1049		1316
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1317	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1318
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1319	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1053	C<loop> nor C<revents> need to be valid as long as the watcher callback	1320	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1060	returns its C<revents> bitset (as if its callback was invoked). If the	1327	returns its C<revents> bitset (as if its callback was invoked). If the
1061	watcher isn't pending it does nothing and returns C<0>.	1328	watcher isn't pending it does nothing and returns C<0>.
1062		1329
1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1330	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1064	callback to be invoked, which can be accomplished with this function.	1331	callback to be invoked, which can be accomplished with this function.
		1332
		1333	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1334
		1335	Feeds the given event set into the event loop, as if the specified event
		1336	had happened for the specified watcher (which must be a pointer to an
		1337	initialised but not necessarily started event watcher). Obviously you must
		1338	not free the watcher as long as it has pending events.
		1339
		1340	Stopping the watcher, letting libev invoke it, or calling
		1341	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1342	not started in the first place.
		1343
		1344	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1345	functions that do not need a watcher.
1065		1346
1066	=back	1347	=back
1067		1348
1068		1349
1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1350	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1118	#include <stddef.h>	1399	#include <stddef.h>
1119		1400
1120	static void	1401	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1402	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1403	{
1123	struct my_biggy big = (struct my_biggy *	1404	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1405	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1406	}
1126		1407
1127	static void	1408	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1409	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1410	{
1130	struct my_biggy big = (struct my_biggy *	1411	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1412	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1413	}
		1414
		1415	=head2 WATCHER PRIORITY MODELS
		1416
		1417	Many event loops support I<watcher priorities>, which are usually small
		1418	integers that influence the ordering of event callback invocation
		1419	between watchers in some way, all else being equal.
		1420
		1421	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1422	description for the more technical details such as the actual priority
		1423	range.
		1424
		1425	There are two common ways how these these priorities are being interpreted
		1426	by event loops:
		1427
		1428	In the more common lock-out model, higher priorities "lock out" invocation
		1429	of lower priority watchers, which means as long as higher priority
		1430	watchers receive events, lower priority watchers are not being invoked.
		1431
		1432	The less common only-for-ordering model uses priorities solely to order
		1433	callback invocation within a single event loop iteration: Higher priority
		1434	watchers are invoked before lower priority ones, but they all get invoked
		1435	before polling for new events.
		1436
		1437	Libev uses the second (only-for-ordering) model for all its watchers
		1438	except for idle watchers (which use the lock-out model).
		1439
		1440	The rationale behind this is that implementing the lock-out model for
		1441	watchers is not well supported by most kernel interfaces, and most event
		1442	libraries will just poll for the same events again and again as long as
		1443	their callbacks have not been executed, which is very inefficient in the
		1444	common case of one high-priority watcher locking out a mass of lower
		1445	priority ones.
		1446
		1447	Static (ordering) priorities are most useful when you have two or more
		1448	watchers handling the same resource: a typical usage example is having an
		1449	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1450	timeouts. Under load, data might be received while the program handles
		1451	other jobs, but since timers normally get invoked first, the timeout
		1452	handler will be executed before checking for data. In that case, giving
		1453	the timer a lower priority than the I/O watcher ensures that I/O will be
		1454	handled first even under adverse conditions (which is usually, but not
		1455	always, what you want).
		1456
		1457	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1458	will only be executed when no same or higher priority watchers have
		1459	received events, they can be used to implement the "lock-out" model when
		1460	required.
		1461
		1462	For example, to emulate how many other event libraries handle priorities,
		1463	you can associate an C<ev_idle> watcher to each such watcher, and in
		1464	the normal watcher callback, you just start the idle watcher. The real
		1465	processing is done in the idle watcher callback. This causes libev to
		1466	continuously poll and process kernel event data for the watcher, but when
		1467	the lock-out case is known to be rare (which in turn is rare :), this is
		1468	workable.
		1469
		1470	Usually, however, the lock-out model implemented that way will perform
		1471	miserably under the type of load it was designed to handle. In that case,
		1472	it might be preferable to stop the real watcher before starting the
		1473	idle watcher, so the kernel will not have to process the event in case
		1474	the actual processing will be delayed for considerable time.
		1475
		1476	Here is an example of an I/O watcher that should run at a strictly lower
		1477	priority than the default, and which should only process data when no
		1478	other events are pending:
		1479
		1480	ev_idle idle; // actual processing watcher
		1481	ev_io io; // actual event watcher
		1482
		1483	static void
		1484	io_cb (EV_P_ ev_io *w, int revents)
		1485	{
		1486	// stop the I/O watcher, we received the event, but
		1487	// are not yet ready to handle it.
		1488	ev_io_stop (EV_A_ w);
		1489
		1490	// start the idle watcher to handle the actual event.
		1491	// it will not be executed as long as other watchers
		1492	// with the default priority are receiving events.
		1493	ev_idle_start (EV_A_ &idle);
		1494	}
		1495
		1496	static void
		1497	idle_cb (EV_P_ ev_idle *w, int revents)
		1498	{
		1499	// actual processing
		1500	read (STDIN_FILENO, ...);
		1501
		1502	// have to start the I/O watcher again, as
		1503	// we have handled the event
		1504	ev_io_start (EV_P_ &io);
		1505	}
		1506
		1507	// initialisation
		1508	ev_idle_init (&idle, idle_cb);
		1509	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1510	ev_io_start (EV_DEFAULT_ &io);
		1511
		1512	In the "real" world, it might also be beneficial to start a timer, so that
		1513	low-priority connections can not be locked out forever under load. This
		1514	enables your program to keep a lower latency for important connections
		1515	during short periods of high load, while not completely locking out less
		1516	important ones.
1133		1517
1134		1518
1135	=head1 WATCHER TYPES	1519	=head1 WATCHER TYPES
1136		1520
1137	This section describes each watcher in detail, but will not repeat	1521	This section describes each watcher in detail, but will not repeat
…		…
1163	descriptors to non-blocking mode is also usually a good idea (but not	1547	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1548	required if you know what you are doing).
1165		1549
1166	If you cannot use non-blocking mode, then force the use of a	1550	If you cannot use non-blocking mode, then force the use of a
1167	known-to-be-good backend (at the time of this writing, this includes only	1551	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1552	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1553	descriptors for which non-blocking operation makes no sense (such as
		1554	files) - libev doesn't guarantee any specific behaviour in that case.
1169		1555
1170	Another thing you have to watch out for is that it is quite easy to	1556	Another thing you have to watch out for is that it is quite easy to
1171	receive "spurious" readiness notifications, that is your callback might	1557	receive "spurious" readiness notifications, that is your callback might
1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1558	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1173	because there is no data. Not only are some backends known to create a	1559	because there is no data. Not only are some backends known to create a
…		…
1238		1624
1239	So when you encounter spurious, unexplained daemon exits, make sure you	1625	So when you encounter spurious, unexplained daemon exits, make sure you
1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1626	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1241	somewhere, as that would have given you a big clue).	1627	somewhere, as that would have given you a big clue).
1242		1628
		1629	=head3 The special problem of accept()ing when you can't
		1630
		1631	Many implementations of the POSIX C<accept> function (for example,
		1632	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1633	connection from the pending queue in all error cases.
		1634
		1635	For example, larger servers often run out of file descriptors (because
		1636	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1637	rejecting the connection, leading to libev signalling readiness on
		1638	the next iteration again (the connection still exists after all), and
		1639	typically causing the program to loop at 100% CPU usage.
		1640
		1641	Unfortunately, the set of errors that cause this issue differs between
		1642	operating systems, there is usually little the app can do to remedy the
		1643	situation, and no known thread-safe method of removing the connection to
		1644	cope with overload is known (to me).
		1645
		1646	One of the easiest ways to handle this situation is to just ignore it
		1647	- when the program encounters an overload, it will just loop until the
		1648	situation is over. While this is a form of busy waiting, no OS offers an
		1649	event-based way to handle this situation, so it's the best one can do.
		1650
		1651	A better way to handle the situation is to log any errors other than
		1652	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1653	messages, and continue as usual, which at least gives the user an idea of
		1654	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1655	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1656	usage.
		1657
		1658	If your program is single-threaded, then you could also keep a dummy file
		1659	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1660	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1661	close that fd, and create a new dummy fd. This will gracefully refuse
		1662	clients under typical overload conditions.
		1663
		1664	The last way to handle it is to simply log the error and C<exit>, as
		1665	is often done with C<malloc> failures, but this results in an easy
		1666	opportunity for a DoS attack.
1243		1667
1244	=head3 Watcher-Specific Functions	1668	=head3 Watcher-Specific Functions
1245		1669
1246	=over 4	1670	=over 4
1247		1671
…		…
1279	...	1703	...
1280	struct ev_loop *loop = ev_default_init (0);	1704	struct ev_loop *loop = ev_default_init (0);
1281	ev_io stdin_readable;	1705	ev_io stdin_readable;
1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1706	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1283	ev_io_start (loop, &stdin_readable);	1707	ev_io_start (loop, &stdin_readable);
1284	ev_loop (loop, 0);	1708	ev_run (loop, 0);
1285		1709
1286		1710
1287	=head2 C<ev_timer> - relative and optionally repeating timeouts	1711	=head2 C<ev_timer> - relative and optionally repeating timeouts
1288		1712
1289	Timer watchers are simple relative timers that generate an event after a	1713	Timer watchers are simple relative timers that generate an event after a
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1718	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1719	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1720	monotonic clock option helps a lot here).
1297		1721
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1722	The callback is guaranteed to be invoked only I<after> its timeout has
1299	passed, but if multiple timers become ready during the same loop iteration	1723	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1724	might introduce a small delay). If multiple timers become ready during the
		1725	same loop iteration then the ones with earlier time-out values are invoked
		1726	before ones of the same priority with later time-out values (but this is
		1727	no longer true when a callback calls C<ev_run> recursively).
1301		1728
1302	=head3 Be smart about timeouts	1729	=head3 Be smart about timeouts
1303		1730
1304	Many real-world problems involve some kind of timeout, usually for error	1731	Many real-world problems involve some kind of timeout, usually for error
1305	recovery. A typical example is an HTTP request - if the other side hangs,	1732	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1776	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1777	member and C<ev_timer_again>.
1351		1778
1352	At start:	1779	At start:
1353		1780
1354	ev_timer_init (timer, callback);	1781	ev_init (timer, callback);
1355	timer->repeat = 60.;	1782	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1783	ev_timer_again (loop, timer);
1357		1784
1358	Each time there is some activity:	1785	Each time there is some activity:
1359		1786
…		…
1391	ev_tstamp timeout = last_activity + 60.;	1818	ev_tstamp timeout = last_activity + 60.;
1392		1819
1393	// if last_activity + 60. is older than now, we did time out	1820	// if last_activity + 60. is older than now, we did time out
1394	if (timeout < now)	1821	if (timeout < now)
1395	{	1822	{
1396	// timeout occured, take action	1823	// timeout occurred, take action
1397	}	1824	}
1398	else	1825	else
1399	{	1826	{
1400	// callback was invoked, but there was some activity, re-arm	1827	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1828	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1829	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1830	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1831	ev_timer_again (EV_A_ w);
1405	}	1832	}
1406	}	1833	}
1407		1834
1408	To summarise the callback: first calculate the real timeout (defined	1835	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1848
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1849	To start the timer, simply initialise the watcher and set C<last_activity>
1423	to the current time (meaning we just have some activity :), then call the	1850	to the current time (meaning we just have some activity :), then call the
1424	callback, which will "do the right thing" and start the timer:	1851	callback, which will "do the right thing" and start the timer:
1425		1852
1426	ev_timer_init (timer, callback);	1853	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1854	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1855	callback (loop, timer, EV_TIMER);
1429		1856
1430	And when there is some activity, simply store the current time in	1857	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1858	C<last_activity>, no libev calls at all:
1432		1859
1433	last_actiivty = ev_now (loop);	1860	last_activity = ev_now (loop);
1434		1861
1435	This technique is slightly more complex, but in most cases where the	1862	This technique is slightly more complex, but in most cases where the
1436	time-out is unlikely to be triggered, much more efficient.	1863	time-out is unlikely to be triggered, much more efficient.
1437		1864
1438	Changing the timeout is trivial as well (if it isn't hard-coded in the	1865	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1476		1903
1477	=head3 The special problem of time updates	1904	=head3 The special problem of time updates
1478		1905
1479	Establishing the current time is a costly operation (it usually takes at	1906	Establishing the current time is a costly operation (it usually takes at
1480	least two system calls): EV therefore updates its idea of the current	1907	least two system calls): EV therefore updates its idea of the current
1481	time only before and after C<ev_loop> collects new events, which causes a	1908	time only before and after C<ev_run> collects new events, which causes a
1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1909	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1483	lots of events in one iteration.	1910	lots of events in one iteration.
1484		1911
1485	The relative timeouts are calculated relative to the C<ev_now ()>	1912	The relative timeouts are calculated relative to the C<ev_now ()>
1486	time. This is usually the right thing as this timestamp refers to the time	1913	time. This is usually the right thing as this timestamp refers to the time
…		…
1492		1919
1493	If the event loop is suspended for a long time, you can also force an	1920	If the event loop is suspended for a long time, you can also force an
1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1921	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1495	()>.	1922	()>.
1496		1923
		1924	=head3 The special problems of suspended animation
		1925
		1926	When you leave the server world it is quite customary to hit machines that
		1927	can suspend/hibernate - what happens to the clocks during such a suspend?
		1928
		1929	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1930	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1931	to run until the system is suspended, but they will not advance while the
		1932	system is suspended. That means, on resume, it will be as if the program
		1933	was frozen for a few seconds, but the suspend time will not be counted
		1934	towards C<ev_timer> when a monotonic clock source is used. The real time
		1935	clock advanced as expected, but if it is used as sole clocksource, then a
		1936	long suspend would be detected as a time jump by libev, and timers would
		1937	be adjusted accordingly.
		1938
		1939	I would not be surprised to see different behaviour in different between
		1940	operating systems, OS versions or even different hardware.
		1941
		1942	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1943	time jump in the monotonic clocks and the realtime clock. If the program
		1944	is suspended for a very long time, and monotonic clock sources are in use,
		1945	then you can expect C<ev_timer>s to expire as the full suspension time
		1946	will be counted towards the timers. When no monotonic clock source is in
		1947	use, then libev will again assume a timejump and adjust accordingly.
		1948
		1949	It might be beneficial for this latter case to call C<ev_suspend>
		1950	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1951	deterministic behaviour in this case (you can do nothing against
		1952	C<SIGSTOP>).
		1953
1497	=head3 Watcher-Specific Functions and Data Members	1954	=head3 Watcher-Specific Functions and Data Members
1498		1955
1499	=over 4	1956	=over 4
1500		1957
1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1958	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1524	If the timer is started but non-repeating, stop it (as if it timed out).	1981	If the timer is started but non-repeating, stop it (as if it timed out).
1525		1982
1526	If the timer is repeating, either start it if necessary (with the	1983	If the timer is repeating, either start it if necessary (with the
1527	C<repeat> value), or reset the running timer to the C<repeat> value.	1984	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		1985
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1986	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1987	usage example.
		1988
		1989	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1990
		1991	Returns the remaining time until a timer fires. If the timer is active,
		1992	then this time is relative to the current event loop time, otherwise it's
		1993	the timeout value currently configured.
		1994
		1995	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1996	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1997	will return C<4>. When the timer expires and is restarted, it will return
		1998	roughly C<7> (likely slightly less as callback invocation takes some time,
		1999	too), and so on.
1531		2000
1532	=item ev_tstamp repeat [read-write]	2001	=item ev_tstamp repeat [read-write]
1533		2002
1534	The current C<repeat> value. Will be used each time the watcher times out	2003	The current C<repeat> value. Will be used each time the watcher times out
1535	or C<ev_timer_again> is called, and determines the next timeout (if any),	2004	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1561	}	2030	}
1562		2031
1563	ev_timer mytimer;	2032	ev_timer mytimer;
1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2033	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1565	ev_timer_again (&mytimer); /* start timer */	2034	ev_timer_again (&mytimer); /* start timer */
1566	ev_loop (loop, 0);	2035	ev_run (loop, 0);
1567		2036
1568	// and in some piece of code that gets executed on any "activity":	2037	// and in some piece of code that gets executed on any "activity":
1569	// reset the timeout to start ticking again at 10 seconds	2038	// reset the timeout to start ticking again at 10 seconds
1570	ev_timer_again (&mytimer);	2039	ev_timer_again (&mytimer);
1571		2040
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	2042	=head2 C<ev_periodic> - to cron or not to cron?
1574		2043
1575	Periodic watchers are also timers of a kind, but they are very versatile	2044	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	2045	(and unfortunately a bit complex).
1577		2046
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2047	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1579	but on wall clock time (absolute time). You can tell a periodic watcher	2048	relative time, the physical time that passes) but on wall clock time
1580	to trigger after some specific point in time. For example, if you tell a	2049	(absolute time, the thing you can read on your calender or clock). The
1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2050	difference is that wall clock time can run faster or slower than real
1582	+ 10.>, that is, an absolute time not a delay) and then reset your system	2051	time, and time jumps are not uncommon (e.g. when you adjust your
1583	clock to January of the previous year, then it will take more than year	2052	wrist-watch).
1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1585	roughly 10 seconds later as it uses a relative timeout).
1586		2053
		2054	You can tell a periodic watcher to trigger after some specific point
		2055	in time: for example, if you tell a periodic watcher to trigger "in 10
		2056	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2057	not a delay) and then reset your system clock to January of the previous
		2058	year, then it will take a year or more to trigger the event (unlike an
		2059	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2060	it, as it uses a relative timeout).
		2061
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	2062	C<ev_periodic> watchers can also be used to implement vastly more complex
1588	such as triggering an event on each "midnight, local time", or other	2063	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	2064	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2065	those cannot react to time jumps.
1590		2066
1591	As with timers, the callback is guaranteed to be invoked only when the	2067	As with timers, the callback is guaranteed to be invoked only when the
1592	time (C<at>) has passed, but if multiple periodic timers become ready	2068	point in time where it is supposed to trigger has passed. If multiple
1593	during the same loop iteration, then order of execution is undefined.	2069	timers become ready during the same loop iteration then the ones with
		2070	earlier time-out values are invoked before ones with later time-out values
		2071	(but this is no longer true when a callback calls C<ev_run> recursively).
1594		2072
1595	=head3 Watcher-Specific Functions and Data Members	2073	=head3 Watcher-Specific Functions and Data Members
1596		2074
1597	=over 4	2075	=over 4
1598		2076
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2077	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		2078
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2079	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		2080
1603	Lots of arguments, lets sort it out... There are basically three modes of	2081	Lots of arguments, let's sort it out... There are basically three modes of
1604	operation, and we will explain them from simplest to most complex:	2082	operation, and we will explain them from simplest to most complex:
1605		2083
1606	=over 4	2084	=over 4
1607		2085
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2086	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		2087
1610	In this configuration the watcher triggers an event after the wall clock	2088	In this configuration the watcher triggers an event after the wall clock
1611	time C<at> has passed. It will not repeat and will not adjust when a time	2089	time C<offset> has passed. It will not repeat and will not adjust when a
1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2090	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1613	only run when the system clock reaches or surpasses this time.	2091	will be stopped and invoked when the system clock reaches or surpasses
		2092	this point in time.
1614		2093
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2094	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		2095
1617	In this mode the watcher will always be scheduled to time out at the next	2096	In this mode the watcher will always be scheduled to time out at the next
1618	C<at + N * interval> time (for some integer N, which can also be negative)	2097	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	2098	negative) and then repeat, regardless of any time jumps. The C<offset>
		2099	argument is merely an offset into the C<interval> periods.
1620		2100
1621	This can be used to create timers that do not drift with respect to the	2101	This can be used to create timers that do not drift with respect to the
1622	system clock, for example, here is a C<ev_periodic> that triggers each	2102	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	2103	hour, on the hour (with respect to UTC):
1624		2104
1625	ev_periodic_set (&periodic, 0., 3600., 0);	2105	ev_periodic_set (&periodic, 0., 3600., 0);
1626		2106
1627	This doesn't mean there will always be 3600 seconds in between triggers,	2107	This doesn't mean there will always be 3600 seconds in between triggers,
1628	but only that the callback will be called when the system time shows a	2108	but only that the callback will be called when the system time shows a
1629	full hour (UTC), or more correctly, when the system time is evenly divisible	2109	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	2110	by 3600.
1631		2111
1632	Another way to think about it (for the mathematically inclined) is that	2112	Another way to think about it (for the mathematically inclined) is that
1633	C<ev_periodic> will try to run the callback in this mode at the next possible	2113	C<ev_periodic> will try to run the callback in this mode at the next possible
1634	time where C<time = at (mod interval)>, regardless of any time jumps.	2114	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		2115
1636	For numerical stability it is preferable that the C<at> value is near	2116	For numerical stability it is preferable that the C<offset> value is near
1637	C<ev_now ()> (the current time), but there is no range requirement for	2117	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	2118	this value, and in fact is often specified as zero.
1639		2119
1640	Note also that there is an upper limit to how often a timer can fire (CPU	2120	Note also that there is an upper limit to how often a timer can fire (CPU
1641	speed for example), so if C<interval> is very small then timing stability	2121	speed for example), so if C<interval> is very small then timing stability
1642	will of course deteriorate. Libev itself tries to be exact to be about one	2122	will of course deteriorate. Libev itself tries to be exact to be about one
1643	millisecond (if the OS supports it and the machine is fast enough).	2123	millisecond (if the OS supports it and the machine is fast enough).
1644		2124
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2125	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		2126
1647	In this mode the values for C<interval> and C<at> are both being	2127	In this mode the values for C<interval> and C<offset> are both being
1648	ignored. Instead, each time the periodic watcher gets scheduled, the	2128	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	2129	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	2130	current time as second argument.
1651		2131
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2132	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	2133	or make ANY other event loop modifications whatsoever, unless explicitly
		2134	allowed by documentation here>.
1654		2135
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2136	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2137	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	2138	only event loop modification you are allowed to do).
1658		2139
…		…
1688	a different time than the last time it was called (e.g. in a crond like	2169	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	2170	program when the crontabs have changed).
1690		2171
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2172	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2173
1693	When active, returns the absolute time that the watcher is supposed to	2174	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	2175	to trigger next. This is not the same as the C<offset> argument to
		2176	C<ev_periodic_set>, but indeed works even in interval and manual
		2177	rescheduling modes.
1695		2178
1696	=item ev_tstamp offset [read-write]	2179	=item ev_tstamp offset [read-write]
1697		2180
1698	When repeating, this contains the offset value, otherwise this is the	2181	When repeating, this contains the offset value, otherwise this is the
1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2182	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2183	although libev might modify this value for better numerical stability).
1700		2184
1701	Can be modified any time, but changes only take effect when the periodic	2185	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	2186	timer fires or C<ev_periodic_again> is being called.
1703		2187
1704	=item ev_tstamp interval [read-write]	2188	=item ev_tstamp interval [read-write]
…		…
1720	Example: Call a callback every hour, or, more precisely, whenever the	2204	Example: Call a callback every hour, or, more precisely, whenever the
1721	system time is divisible by 3600. The callback invocation times have	2205	system time is divisible by 3600. The callback invocation times have
1722	potentially a lot of jitter, but good long-term stability.	2206	potentially a lot of jitter, but good long-term stability.
1723		2207
1724	static void	2208	static void
1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2209	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1726	{	2210	{
1727	... its now a full hour (UTC, or TAI or whatever your clock follows)	2211	... its now a full hour (UTC, or TAI or whatever your clock follows)
1728	}	2212	}
1729		2213
1730	ev_periodic hourly_tick;	2214	ev_periodic hourly_tick;
…		…
1756	Signal watchers will trigger an event when the process receives a specific	2240	Signal watchers will trigger an event when the process receives a specific
1757	signal one or more times. Even though signals are very asynchronous, libev	2241	signal one or more times. Even though signals are very asynchronous, libev
1758	will try it's best to deliver signals synchronously, i.e. as part of the	2242	will try it's best to deliver signals synchronously, i.e. as part of the
1759	normal event processing, like any other event.	2243	normal event processing, like any other event.
1760		2244
1761	If you want signals asynchronously, just use C<sigaction> as you would	2245	If you want signals to be delivered truly asynchronously, just use
1762	do without libev and forget about sharing the signal. You can even use	2246	C<sigaction> as you would do without libev and forget about sharing
1763	C<ev_async> from a signal handler to synchronously wake up an event loop.	2247	the signal. You can even use C<ev_async> from a signal handler to
		2248	synchronously wake up an event loop.
1764		2249
1765	You can configure as many watchers as you like per signal. Only when the	2250	You can configure as many watchers as you like for the same signal, but
		2251	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2252	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2253	C<SIGINT> in both the default loop and another loop at the same time. At
		2254	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2255
1766	first watcher gets started will libev actually register a signal handler	2256	When the first watcher gets started will libev actually register something
1767	with the kernel (thus it coexists with your own signal handlers as long as	2257	with the kernel (thus it coexists with your own signal handlers as long as
1768	you don't register any with libev for the same signal). Similarly, when	2258	you don't register any with libev for the same signal).
1769	the last signal watcher for a signal is stopped, libev will reset the
1770	signal handler to SIG_DFL (regardless of what it was set to before).
1771		2259
1772	If possible and supported, libev will install its handlers with	2260	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2261	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	interrupted. If you have a problem with system calls getting interrupted by	2262	not be unduly interrupted. If you have a problem with system calls getting
1775	signals you can block all signals in an C<ev_check> watcher and unblock	2263	interrupted by signals you can block all signals in an C<ev_check> watcher
1776	them in an C<ev_prepare> watcher.	2264	and unblock them in an C<ev_prepare> watcher.
		2265
		2266	=head3 The special problem of inheritance over fork/execve/pthread_create
		2267
		2268	Both the signal mask (C<sigprocmask>) and the signal disposition
		2269	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2270	stopping it again), that is, libev might or might not block the signal,
		2271	and might or might not set or restore the installed signal handler.
		2272
		2273	While this does not matter for the signal disposition (libev never
		2274	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2275	C<execve>), this matters for the signal mask: many programs do not expect
		2276	certain signals to be blocked.
		2277
		2278	This means that before calling C<exec> (from the child) you should reset
		2279	the signal mask to whatever "default" you expect (all clear is a good
		2280	choice usually).
		2281
		2282	The simplest way to ensure that the signal mask is reset in the child is
		2283	to install a fork handler with C<pthread_atfork> that resets it. That will
		2284	catch fork calls done by libraries (such as the libc) as well.
		2285
		2286	In current versions of libev, the signal will not be blocked indefinitely
		2287	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2288	the window of opportunity for problems, it will not go away, as libev
		2289	I<has> to modify the signal mask, at least temporarily.
		2290
		2291	So I can't stress this enough: I<If you do not reset your signal mask when
		2292	you expect it to be empty, you have a race condition in your code>. This
		2293	is not a libev-specific thing, this is true for most event libraries.
1777		2294
1778	=head3 Watcher-Specific Functions and Data Members	2295	=head3 Watcher-Specific Functions and Data Members
1779		2296
1780	=over 4	2297	=over 4
1781		2298
…		…
1797	Example: Try to exit cleanly on SIGINT.	2314	Example: Try to exit cleanly on SIGINT.
1798		2315
1799	static void	2316	static void
1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2317	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1801	{	2318	{
1802	ev_unloop (loop, EVUNLOOP_ALL);	2319	ev_break (loop, EVBREAK_ALL);
1803	}	2320	}
1804		2321
1805	ev_signal signal_watcher;	2322	ev_signal signal_watcher;
1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2323	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1807	ev_signal_start (loop, &signal_watcher);	2324	ev_signal_start (loop, &signal_watcher);
…		…
1813	some child status changes (most typically when a child of yours dies or	2330	some child status changes (most typically when a child of yours dies or
1814	exits). It is permissible to install a child watcher I<after> the child	2331	exits). It is permissible to install a child watcher I<after> the child
1815	has been forked (which implies it might have already exited), as long	2332	has been forked (which implies it might have already exited), as long
1816	as the event loop isn't entered (or is continued from a watcher), i.e.,	2333	as the event loop isn't entered (or is continued from a watcher), i.e.,
1817	forking and then immediately registering a watcher for the child is fine,	2334	forking and then immediately registering a watcher for the child is fine,
1818	but forking and registering a watcher a few event loop iterations later is	2335	but forking and registering a watcher a few event loop iterations later or
1819	not.	2336	in the next callback invocation is not.
1820		2337
1821	Only the default event loop is capable of handling signals, and therefore	2338	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2339	you can only register child watchers in the default event loop.
1823		2340
		2341	Due to some design glitches inside libev, child watchers will always be
		2342	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2343	libev)
		2344
1824	=head3 Process Interaction	2345	=head3 Process Interaction
1825		2346
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2347	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2348	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2349	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2350	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	synchronously as part of the event loop processing. Libev always reaps all	2351	synchronously as part of the event loop processing. Libev always reaps all
1831	children, even ones not watched.	2352	children, even ones not watched.
1832		2353
1833	=head3 Overriding the Built-In Processing	2354	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2364	=head3 Stopping the Child Watcher
1844		2365
1845	Currently, the child watcher never gets stopped, even when the	2366	Currently, the child watcher never gets stopped, even when the
1846	child terminates, so normally one needs to stop the watcher in the	2367	child terminates, so normally one needs to stop the watcher in the
1847	callback. Future versions of libev might stop the watcher automatically	2368	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2369	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2370	problem).
1849		2371
1850	=head3 Watcher-Specific Functions and Data Members	2372	=head3 Watcher-Specific Functions and Data Members
1851		2373
1852	=over 4	2374	=over 4
1853		2375
…		…
1910		2432
1911		2433
1912	=head2 C<ev_stat> - did the file attributes just change?	2434	=head2 C<ev_stat> - did the file attributes just change?
1913		2435
1914	This watches a file system path for attribute changes. That is, it calls	2436	This watches a file system path for attribute changes. That is, it calls
1915	C<stat> regularly (or when the OS says it changed) and sees if it changed	2437	C<stat> on that path in regular intervals (or when the OS says it changed)
1916	compared to the last time, invoking the callback if it did.	2438	and sees if it changed compared to the last time, invoking the callback if
		2439	it did.
1917		2440
1918	The path does not need to exist: changing from "path exists" to "path does	2441	The path does not need to exist: changing from "path exists" to "path does
1919	not exist" is a status change like any other. The condition "path does	2442	not exist" is a status change like any other. The condition "path does not
1920	not exist" is signified by the C<st_nlink> field being zero (which is	2443	exist" (or more correctly "path cannot be stat'ed") is signified by the
1921	otherwise always forced to be at least one) and all the other fields of	2444	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2445	least one) and all the other fields of the stat buffer having unspecified
		2446	contents.
1923		2447
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2448	The path I<must not> end in a slash or contain special components such as
		2449	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1925	relative and your working directory changes, the behaviour is undefined.	2450	your working directory changes, then the behaviour is undefined.
1926		2451
1927	Since there is no standard kernel interface to do this, the portable	2452	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2453	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2454	to see if it changed somehow. You can specify a recommended polling
1930	this case. If you specify a polling interval of C<0> (highly recommended!)	2455	interval for this case. If you specify a polling interval of C<0> (highly
1931	then a I<suitable, unspecified default> value will be used (which	2456	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2457	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2458	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2459	currently around C<0.1>, but that's usually overkill.
1935		2460
1936	This watcher type is not meant for massive numbers of stat watchers,	2461	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2462	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2463	resource-intensive.
1939		2464
1940	At the time of this writing, the only OS-specific interface implemented	2465	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2466	is the Linux inotify interface (implementing kqueue support is left as an
1942	an exercise for the reader. Note, however, that the author sees no way	2467	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2468	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2469
1945	=head3 ABI Issues (Largefile Support)	2470	=head3 ABI Issues (Largefile Support)
1946		2471
1947	Libev by default (unless the user overrides this) uses the default	2472	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2473	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2474	support disabled by default, you get the 32 bit version of the stat
1950	structure. When using the library from programs that change the ABI to	2475	structure. When using the library from programs that change the ABI to
1951	use 64 bit file offsets the programs will fail. In that case you have to	2476	use 64 bit file offsets the programs will fail. In that case you have to
1952	compile libev with the same flags to get binary compatibility. This is	2477	compile libev with the same flags to get binary compatibility. This is
1953	obviously the case with any flags that change the ABI, but the problem is	2478	obviously the case with any flags that change the ABI, but the problem is
1954	most noticeably disabled with ev_stat and large file support.	2479	most noticeably displayed with ev_stat and large file support.
1955		2480
1956	The solution for this is to lobby your distribution maker to make large	2481	The solution for this is to lobby your distribution maker to make large
1957	file interfaces available by default (as e.g. FreeBSD does) and not	2482	file interfaces available by default (as e.g. FreeBSD does) and not
1958	optional. Libev cannot simply switch on large file support because it has	2483	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2484	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2485	default compilation environment.
1961		2486
1962	=head3 Inotify and Kqueue	2487	=head3 Inotify and Kqueue
1963		2488
1964	When C<inotify (7)> support has been compiled into libev (generally	2489	When C<inotify (7)> support has been compiled into libev and present at
1965	only available with Linux 2.6.25 or above due to bugs in earlier	2490	runtime, it will be used to speed up change detection where possible. The
1966	implementations) and present at runtime, it will be used to speed up	2491	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2492	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2493
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2494	Inotify presence does not change the semantics of C<ev_stat> watchers
1971	except that changes might be detected earlier, and in some cases, to avoid	2495	except that changes might be detected earlier, and in some cases, to avoid
1972	making regular C<stat> calls. Even in the presence of inotify support	2496	making regular C<stat> calls. Even in the presence of inotify support
1973	there are many cases where libev has to resort to regular C<stat> polling,	2497	there are many cases where libev has to resort to regular C<stat> polling,
1974	but as long as the path exists, libev usually gets away without polling.	2498	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2499	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2500	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2501	xfs are fully working) libev usually gets away without polling.
1975		2502
1976	There is no support for kqueue, as apparently it cannot be used to	2503	There is no support for kqueue, as apparently it cannot be used to
1977	implement this functionality, due to the requirement of having a file	2504	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2505	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2506	etc. is difficult.
1980		2507
		2508	=head3 C<stat ()> is a synchronous operation
		2509
		2510	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2511	the process. The exception are C<ev_stat> watchers - those call C<stat
		2512	()>, which is a synchronous operation.
		2513
		2514	For local paths, this usually doesn't matter: unless the system is very
		2515	busy or the intervals between stat's are large, a stat call will be fast,
		2516	as the path data is usually in memory already (except when starting the
		2517	watcher).
		2518
		2519	For networked file systems, calling C<stat ()> can block an indefinite
		2520	time due to network issues, and even under good conditions, a stat call
		2521	often takes multiple milliseconds.
		2522
		2523	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2524	paths, although this is fully supported by libev.
		2525
1981	=head3 The special problem of stat time resolution	2526	=head3 The special problem of stat time resolution
1982		2527
1983	The C<stat ()> system call only supports full-second resolution portably, and	2528	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2529	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2530	still only support whole seconds.
1986		2531
1987	That means that, if the time is the only thing that changes, you can	2532	That means that, if the time is the only thing that changes, you can
1988	easily miss updates: on the first update, C<ev_stat> detects a change and	2533	easily miss updates: on the first update, C<ev_stat> detects a change and
1989	calls your callback, which does something. When there is another update	2534	calls your callback, which does something. When there is another update
1990	within the same second, C<ev_stat> will be unable to detect unless the	2535	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2678
2134	=head3 Watcher-Specific Functions and Data Members	2679	=head3 Watcher-Specific Functions and Data Members
2135		2680
2136	=over 4	2681	=over 4
2137		2682
2138	=item ev_idle_init (ev_signal *, callback)	2683	=item ev_idle_init (ev_idle *, callback)
2139		2684
2140	Initialises and configures the idle watcher - it has no parameters of any	2685	Initialises and configures the idle watcher - it has no parameters of any
2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2686	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2687	believe me.
2143		2688
…		…
2156	// no longer anything immediate to do.	2701	// no longer anything immediate to do.
2157	}	2702	}
2158		2703
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2704	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2705	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2706	ev_idle_start (loop, idle_watcher);
2162		2707
2163		2708
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2709	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2710
2166	Prepare and check watchers are usually (but not always) used in pairs:	2711	Prepare and check watchers are usually (but not always) used in pairs:
2167	prepare watchers get invoked before the process blocks and check watchers	2712	prepare watchers get invoked before the process blocks and check watchers
2168	afterwards.	2713	afterwards.
2169		2714
2170	You I<must not> call C<ev_loop> or similar functions that enter	2715	You I<must not> call C<ev_run> or similar functions that enter
2171	the current event loop from either C<ev_prepare> or C<ev_check>	2716	the current event loop from either C<ev_prepare> or C<ev_check>
2172	watchers. Other loops than the current one are fine, however. The	2717	watchers. Other loops than the current one are fine, however. The
2173	rationale behind this is that you do not need to check for recursion in	2718	rationale behind this is that you do not need to check for recursion in
2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2719	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2175	C<ev_check> so if you have one watcher of each kind they will always be	2720	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2259	struct pollfd fds [nfd];	2804	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2805	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2807
2263	/* the callback is illegal, but won't be called as we stop during check */	2808	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2809	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2810	ev_timer_start (loop, &tw);
2266		2811
2267	// create one ev_io per pollfd	2812	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2813	for (int i = 0; i < nfd; ++i)
2269	{	2814	{
…		…
2343		2888
2344	if (timeout >= 0)	2889	if (timeout >= 0)
2345	// create/start timer	2890	// create/start timer
2346		2891
2347	// poll	2892	// poll
2348	ev_loop (EV_A_ 0);	2893	ev_run (EV_A_ 0);
2349		2894
2350	// stop timer again	2895	// stop timer again
2351	if (timeout >= 0)	2896	if (timeout >= 0)
2352	ev_timer_stop (EV_A_ &to);	2897	ev_timer_stop (EV_A_ &to);
2353		2898
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2927	some fds have to be watched and handled very quickly (with low latency),
2383	and even priorities and idle watchers might have too much overhead. In	2928	and even priorities and idle watchers might have too much overhead. In
2384	this case you would put all the high priority stuff in one loop and all	2929	this case you would put all the high priority stuff in one loop and all
2385	the rest in a second one, and embed the second one in the first.	2930	the rest in a second one, and embed the second one in the first.
2386		2931
2387	As long as the watcher is active, the callback will be invoked every time	2932	As long as the watcher is active, the callback will be invoked every
2388	there might be events pending in the embedded loop. The callback must then	2933	time there might be events pending in the embedded loop. The callback
2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2934	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2390	their callbacks (you could also start an idle watcher to give the embedded	2935	sweep and invoke their callbacks (the callback doesn't need to invoke the
2391	loop strictly lower priority for example). You can also set the callback	2936	C<ev_embed_sweep> function directly, it could also start an idle watcher
2392	to C<0>, in which case the embed watcher will automatically execute the	2937	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2938
2395	As long as the watcher is started it will automatically handle events. The	2939	You can also set the callback to C<0>, in which case the embed watcher
2396	callback will be invoked whenever some events have been handled. You can	2940	will automatically execute the embedded loop sweep whenever necessary.
2397	set the callback to C<0> to avoid having to specify one if you are not
2398	interested in that.
2399		2941
2400	Also, there have not currently been made special provisions for forking:	2942	Fork detection will be handled transparently while the C<ev_embed> watcher
2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2943	is active, i.e., the embedded loop will automatically be forked when the
2402	but you will also have to stop and restart any C<ev_embed> watchers	2944	embedding loop forks. In other cases, the user is responsible for calling
2403	yourself - but you can use a fork watcher to handle this automatically,	2945	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2946
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2947	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2948	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2949	portable one.
2409		2950
…		…
2435	if you do not want that, you need to temporarily stop the embed watcher).	2976	if you do not want that, you need to temporarily stop the embed watcher).
2436		2977
2437	=item ev_embed_sweep (loop, ev_embed *)	2978	=item ev_embed_sweep (loop, ev_embed *)
2438		2979
2439	Make a single, non-blocking sweep over the embedded loop. This works	2980	Make a single, non-blocking sweep over the embedded loop. This works
2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2981	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2441	appropriate way for embedded loops.	2982	appropriate way for embedded loops.
2442		2983
2443	=item struct ev_loop *other [read-only]	2984	=item struct ev_loop *other [read-only]
2444		2985
2445	The embedded event loop.	2986	The embedded event loop.
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	3044	event loop blocks next and before C<ev_check> watchers are being called,
2504	and only in the child after the fork. If whoever good citizen calling	3045	and only in the child after the fork. If whoever good citizen calling
2505	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3046	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	3047	handlers will be invoked, too, of course.
2507		3048
		3049	=head3 The special problem of life after fork - how is it possible?
		3050
		3051	Most uses of C<fork()> consist of forking, then some simple calls to set
		3052	up/change the process environment, followed by a call to C<exec()>. This
		3053	sequence should be handled by libev without any problems.
		3054
		3055	This changes when the application actually wants to do event handling
		3056	in the child, or both parent in child, in effect "continuing" after the
		3057	fork.
		3058
		3059	The default mode of operation (for libev, with application help to detect
		3060	forks) is to duplicate all the state in the child, as would be expected
		3061	when I<either> the parent I<or> the child process continues.
		3062
		3063	When both processes want to continue using libev, then this is usually the
		3064	wrong result. In that case, usually one process (typically the parent) is
		3065	supposed to continue with all watchers in place as before, while the other
		3066	process typically wants to start fresh, i.e. without any active watchers.
		3067
		3068	The cleanest and most efficient way to achieve that with libev is to
		3069	simply create a new event loop, which of course will be "empty", and
		3070	use that for new watchers. This has the advantage of not touching more
		3071	memory than necessary, and thus avoiding the copy-on-write, and the
		3072	disadvantage of having to use multiple event loops (which do not support
		3073	signal watchers).
		3074
		3075	When this is not possible, or you want to use the default loop for
		3076	other reasons, then in the process that wants to start "fresh", call
		3077	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		3078	the default loop will "orphan" (not stop) all registered watchers, so you
		3079	have to be careful not to execute code that modifies those watchers. Note
		3080	also that in that case, you have to re-register any signal watchers.
		3081
2508	=head3 Watcher-Specific Functions and Data Members	3082	=head3 Watcher-Specific Functions and Data Members
2509		3083
2510	=over 4	3084	=over 4
2511		3085
2512	=item ev_fork_init (ev_signal *, callback)	3086	=item ev_fork_init (ev_signal *, callback)
…		…
2516	believe me.	3090	believe me.
2517		3091
2518	=back	3092	=back
2519		3093
2520		3094
2521	=head2 C<ev_async> - how to wake up another event loop	3095	=head2 C<ev_async> - how to wake up an event loop
2522		3096
2523	In general, you cannot use an C<ev_loop> from multiple threads or other	3097	In general, you cannot use an C<ev_run> from multiple threads or other
2524	asynchronous sources such as signal handlers (as opposed to multiple event	3098	asynchronous sources such as signal handlers (as opposed to multiple event
2525	loops - those are of course safe to use in different threads).	3099	loops - those are of course safe to use in different threads).
2526		3100
2527	Sometimes, however, you need to wake up another event loop you do not	3101	Sometimes, however, you need to wake up an event loop you do not control,
2528	control, for example because it belongs to another thread. This is what	3102	for example because it belongs to another thread. This is what C<ev_async>
2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3103	watchers do: as long as the C<ev_async> watcher is active, you can signal
2530	can signal it by calling C<ev_async_send>, which is thread- and signal	3104	it by calling C<ev_async_send>, which is thread- and signal safe.
2531	safe.
2532		3105
2533	This functionality is very similar to C<ev_signal> watchers, as signals,	3106	This functionality is very similar to C<ev_signal> watchers, as signals,
2534	too, are asynchronous in nature, and signals, too, will be compressed	3107	too, are asynchronous in nature, and signals, too, will be compressed
2535	(i.e. the number of callback invocations may be less than the number of	3108	(i.e. the number of callback invocations may be less than the number of
2536	C<ev_async_sent> calls).	3109	C<ev_async_sent> calls).
…		…
2541	=head3 Queueing	3114	=head3 Queueing
2542		3115
2543	C<ev_async> does not support queueing of data in any way. The reason	3116	C<ev_async> does not support queueing of data in any way. The reason
2544	is that the author does not know of a simple (or any) algorithm for a	3117	is that the author does not know of a simple (or any) algorithm for a
2545	multiple-writer-single-reader queue that works in all cases and doesn't	3118	multiple-writer-single-reader queue that works in all cases and doesn't
2546	need elaborate support such as pthreads.	3119	need elaborate support such as pthreads or unportable memory access
		3120	semantics.
2547		3121
2548	That means that if you want to queue data, you have to provide your own	3122	That means that if you want to queue data, you have to provide your own
2549	queue. But at least I can tell you how to implement locking around your	3123	queue. But at least I can tell you how to implement locking around your
2550	queue:	3124	queue:
2551		3125
…		…
2629	=over 4	3203	=over 4
2630		3204
2631	=item ev_async_init (ev_async *, callback)	3205	=item ev_async_init (ev_async *, callback)
2632		3206
2633	Initialises and configures the async watcher - it has no parameters of any	3207	Initialises and configures the async watcher - it has no parameters of any
2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3208	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	3209	trust me.
2636		3210
2637	=item ev_async_send (loop, ev_async *)	3211	=item ev_async_send (loop, ev_async *)
2638		3212
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3213	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3214	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2641	C<ev_feed_event>, this call is safe to do from other threads, signal or	3215	C<ev_feed_event>, this call is safe to do from other threads, signal or
2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3216	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	3217	section below on what exactly this means).
2644		3218
		3219	Note that, as with other watchers in libev, multiple events might get
		3220	compressed into a single callback invocation (another way to look at this
		3221	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3222	reset when the event loop detects that).
		3223
2645	This call incurs the overhead of a system call only once per loop iteration,	3224	This call incurs the overhead of a system call only once per event loop
2646	so while the overhead might be noticeable, it doesn't apply to repeated	3225	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	3226	repeated calls to C<ev_async_send> for the same event loop.
2648		3227
2649	=item bool = ev_async_pending (ev_async *)	3228	=item bool = ev_async_pending (ev_async *)
2650		3229
2651	Returns a non-zero value when C<ev_async_send> has been called on the	3230	Returns a non-zero value when C<ev_async_send> has been called on the
2652	watcher but the event has not yet been processed (or even noted) by the	3231	watcher but the event has not yet been processed (or even noted) by the
…		…
2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3234	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2656	the loop iterates next and checks for the watcher to have become active,	3235	the loop iterates next and checks for the watcher to have become active,
2657	it will reset the flag again. C<ev_async_pending> can be used to very	3236	it will reset the flag again. C<ev_async_pending> can be used to very
2658	quickly check whether invoking the loop might be a good idea.	3237	quickly check whether invoking the loop might be a good idea.
2659		3238
2660	Not that this does I<not> check whether the watcher itself is pending, only	3239	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	3240	only whether it has been requested to make this watcher pending: there
		3241	is a time window between the event loop checking and resetting the async
		3242	notification, and the callback being invoked.
2662		3243
2663	=back	3244	=back
2664		3245
2665		3246
2666	=head1 OTHER FUNCTIONS	3247	=head1 OTHER FUNCTIONS
…		…
2683		3264
2684	If C<timeout> is less than 0, then no timeout watcher will be	3265	If C<timeout> is less than 0, then no timeout watcher will be
2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3266	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2686	repeat = 0) will be started. C<0> is a valid timeout.	3267	repeat = 0) will be started. C<0> is a valid timeout.
2687		3268
2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3269	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2689	passed an C<revents> set like normal event callbacks (a combination of	3270	passed an C<revents> set like normal event callbacks (a combination of
2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3271	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2691	value passed to C<ev_once>. Note that it is possible to receive I<both>	3272	value passed to C<ev_once>. Note that it is possible to receive I<both>
2692	a timeout and an io event at the same time - you probably should give io	3273	a timeout and an io event at the same time - you probably should give io
2693	events precedence.	3274	events precedence.
2694		3275
2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3276	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2696		3277
2697	static void stdin_ready (int revents, void *arg)	3278	static void stdin_ready (int revents, void *arg)
2698	{	3279	{
2699	if (revents & EV_READ)	3280	if (revents & EV_READ)
2700	/* stdin might have data for us, joy! */;	3281	/* stdin might have data for us, joy! */;
2701	else if (revents & EV_TIMEOUT)	3282	else if (revents & EV_TIMER)
2702	/* doh, nothing entered */;	3283	/* doh, nothing entered */;
2703	}	3284	}
2704		3285
2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3286	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2706		3287
2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2708
2709	Feeds the given event set into the event loop, as if the specified event
2710	had happened for the specified watcher (which must be a pointer to an
2711	initialised but not necessarily started event watcher).
2712
2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3288	=item ev_feed_fd_event (loop, int fd, int revents)
2714		3289
2715	Feed an event on the given fd, as if a file descriptor backend detected	3290	Feed an event on the given fd, as if a file descriptor backend detected
2716	the given events it.	3291	the given events it.
2717		3292
2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3293	=item ev_feed_signal_event (loop, int signum)
2719		3294
2720	Feed an event as if the given signal occurred (C<loop> must be the default	3295	Feed an event as if the given signal occurred (C<loop> must be the default
2721	loop!).	3296	loop!).
2722		3297
2723	=back	3298	=back
…		…
2803		3378
2804	=over 4	3379	=over 4
2805		3380
2806	=item ev::TYPE::TYPE ()	3381	=item ev::TYPE::TYPE ()
2807		3382
2808	=item ev::TYPE::TYPE (struct ev_loop *)	3383	=item ev::TYPE::TYPE (loop)
2809		3384
2810	=item ev::TYPE::~TYPE	3385	=item ev::TYPE::~TYPE
2811		3386
2812	The constructor (optionally) takes an event loop to associate the watcher	3387	The constructor (optionally) takes an event loop to associate the watcher
2813	with. If it is omitted, it will use C<EV_DEFAULT>.	3388	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2845		3420
2846	myclass obj;	3421	myclass obj;
2847	ev::io iow;	3422	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3423	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3424
		3425	=item w->set (object *)
		3426
		3427	This is a variation of a method callback - leaving out the method to call
		3428	will default the method to C<operator ()>, which makes it possible to use
		3429	functor objects without having to manually specify the C<operator ()> all
		3430	the time. Incidentally, you can then also leave out the template argument
		3431	list.
		3432
		3433	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3434	int revents)>.
		3435
		3436	See the method-C<set> above for more details.
		3437
		3438	Example: use a functor object as callback.
		3439
		3440	struct myfunctor
		3441	{
		3442	void operator() (ev::io &w, int revents)
		3443	{
		3444	...
		3445	}
		3446	}
		3447
		3448	myfunctor f;
		3449
		3450	ev::io w;
		3451	w.set (&f);
		3452
2850	=item w->set<function> (void *data = 0)	3453	=item w->set<function> (void *data = 0)
2851		3454
2852	Also sets a callback, but uses a static method or plain function as	3455	Also sets a callback, but uses a static method or plain function as
2853	callback. The optional C<data> argument will be stored in the watcher's	3456	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3457	C<data> member and is free for you to use.
…		…
2860	Example: Use a plain function as callback.	3463	Example: Use a plain function as callback.
2861		3464
2862	static void io_cb (ev::io &w, int revents) { }	3465	static void io_cb (ev::io &w, int revents) { }
2863	iow.set <io_cb> ();	3466	iow.set <io_cb> ();
2864		3467
2865	=item w->set (struct ev_loop *)	3468	=item w->set (loop)
2866		3469
2867	Associates a different C<struct ev_loop> with this watcher. You can only	3470	Associates a different C<struct ev_loop> with this watcher. You can only
2868	do this when the watcher is inactive (and not pending either).	3471	do this when the watcher is inactive (and not pending either).
2869		3472
2870	=item w->set ([arguments])	3473	=item w->set ([arguments])
2871		3474
2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3475	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2873	called at least once. Unlike the C counterpart, an active watcher gets	3476	method or a suitable start method must be called at least once. Unlike the
2874	automatically stopped and restarted when reconfiguring it with this	3477	C counterpart, an active watcher gets automatically stopped and restarted
2875	method.	3478	when reconfiguring it with this method.
2876		3479
2877	=item w->start ()	3480	=item w->start ()
2878		3481
2879	Starts the watcher. Note that there is no C<loop> argument, as the	3482	Starts the watcher. Note that there is no C<loop> argument, as the
2880	constructor already stores the event loop.	3483	constructor already stores the event loop.
2881		3484
		3485	=item w->start ([arguments])
		3486
		3487	Instead of calling C<set> and C<start> methods separately, it is often
		3488	convenient to wrap them in one call. Uses the same type of arguments as
		3489	the configure C<set> method of the watcher.
		3490
2882	=item w->stop ()	3491	=item w->stop ()
2883		3492
2884	Stops the watcher if it is active. Again, no C<loop> argument.	3493	Stops the watcher if it is active. Again, no C<loop> argument.
2885		3494
2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3495	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2898		3507
2899	=back	3508	=back
2900		3509
2901	=back	3510	=back
2902		3511
2903	Example: Define a class with an IO and idle watcher, start one of them in	3512	Example: Define a class with two I/O and idle watchers, start the I/O
2904	the constructor.	3513	watchers in the constructor.
2905		3514
2906	class myclass	3515	class myclass
2907	{	3516	{
2908	ev::io io ; void io_cb (ev::io &w, int revents);	3517	ev::io io ; void io_cb (ev::io &w, int revents);
		3518	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3519	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2910		3520
2911	myclass (int fd)	3521	myclass (int fd)
2912	{	3522	{
2913	io .set <myclass, &myclass::io_cb > (this);	3523	io .set <myclass, &myclass::io_cb > (this);
		3524	io2 .set <myclass, &myclass::io2_cb > (this);
2914	idle.set <myclass, &myclass::idle_cb> (this);	3525	idle.set <myclass, &myclass::idle_cb> (this);
2915		3526
2916	io.start (fd, ev::READ);	3527	io.set (fd, ev::WRITE); // configure the watcher
		3528	io.start (); // start it whenever convenient
		3529
		3530	io2.start (fd, ev::READ); // set + start in one call
2917	}	3531	}
2918	};	3532	};
2919		3533
2920		3534
2921	=head1 OTHER LANGUAGE BINDINGS	3535	=head1 OTHER LANGUAGE BINDINGS
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3554	L<http://software.schmorp.de/pkg/EV>.
2941		3555
2942	=item Python	3556	=item Python
2943		3557
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3558	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2945	seems to be quite complete and well-documented. Note, however, that the	3559	seems to be quite complete and well-documented.
2946	patch they require for libev is outright dangerous as it breaks the ABI
2947	for everybody else, and therefore, should never be applied in an installed
2948	libev (if python requires an incompatible ABI then it needs to embed
2949	libev).
2950		3560
2951	=item Ruby	3561	=item Ruby
2952		3562
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3563	Tony Arcieri has written a ruby extension that offers access to a subset
2954	of the libev API and adds file handle abstractions, asynchronous DNS and	3564	of the libev API and adds file handle abstractions, asynchronous DNS and
2955	more on top of it. It can be found via gem servers. Its homepage is at	3565	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3566	L<http://rev.rubyforge.org/>.
2957		3567
		3568	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3569	makes rev work even on mingw.
		3570
		3571	=item Haskell
		3572
		3573	A haskell binding to libev is available at
		3574	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3575
2958	=item D	3576	=item D
2959		3577
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3578	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3579	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2962		3580
2963	=item Ocaml	3581	=item Ocaml
2964		3582
2965	Erkki Seppala has written Ocaml bindings for libev, to be found at	3583	Erkki Seppala has written Ocaml bindings for libev, to be found at
2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3584	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3585
		3586	=item Lua
		3587
		3588	Brian Maher has written a partial interface to libev for lua (at the
		3589	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3590	L<http://github.com/brimworks/lua-ev>.
2967		3591
2968	=back	3592	=back
2969		3593
2970		3594
2971	=head1 MACRO MAGIC	3595	=head1 MACRO MAGIC
…		…
2985	loop argument"). The C<EV_A> form is used when this is the sole argument,	3609	loop argument"). The C<EV_A> form is used when this is the sole argument,
2986	C<EV_A_> is used when other arguments are following. Example:	3610	C<EV_A_> is used when other arguments are following. Example:
2987		3611
2988	ev_unref (EV_A);	3612	ev_unref (EV_A);
2989	ev_timer_add (EV_A_ watcher);	3613	ev_timer_add (EV_A_ watcher);
2990	ev_loop (EV_A_ 0);	3614	ev_run (EV_A_ 0);
2991		3615
2992	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3616	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2993	which is often provided by the following macro.	3617	which is often provided by the following macro.
2994		3618
2995	=item C<EV_P>, C<EV_P_>	3619	=item C<EV_P>, C<EV_P_>
…		…
3035	}	3659	}
3036		3660
3037	ev_check check;	3661	ev_check check;
3038	ev_check_init (&check, check_cb);	3662	ev_check_init (&check, check_cb);
3039	ev_check_start (EV_DEFAULT_ &check);	3663	ev_check_start (EV_DEFAULT_ &check);
3040	ev_loop (EV_DEFAULT_ 0);	3664	ev_run (EV_DEFAULT_ 0);
3041		3665
3042	=head1 EMBEDDING	3666	=head1 EMBEDDING
3043		3667
3044	Libev can (and often is) directly embedded into host	3668	Libev can (and often is) directly embedded into host
3045	applications. Examples of applications that embed it include the Deliantra	3669	applications. Examples of applications that embed it include the Deliantra
…		…
3072		3696
3073	#define EV_STANDALONE 1	3697	#define EV_STANDALONE 1
3074	#include "ev.h"	3698	#include "ev.h"
3075		3699
3076	Both header files and implementation files can be compiled with a C++	3700	Both header files and implementation files can be compiled with a C++
3077	compiler (at least, thats a stated goal, and breakage will be treated	3701	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3702	as a bug).
3079		3703
3080	You need the following files in your source tree, or in a directory	3704	You need the following files in your source tree, or in a directory
3081	in your include path (e.g. in libev/ when using -Ilibev):	3705	in your include path (e.g. in libev/ when using -Ilibev):
3082		3706
…		…
3125	libev.m4	3749	libev.m4
3126		3750
3127	=head2 PREPROCESSOR SYMBOLS/MACROS	3751	=head2 PREPROCESSOR SYMBOLS/MACROS
3128		3752
3129	Libev can be configured via a variety of preprocessor symbols you have to	3753	Libev can be configured via a variety of preprocessor symbols you have to
3130	define before including any of its files. The default in the absence of	3754	define before including (or compiling) any of its files. The default in
3131	autoconf is documented for every option.	3755	the absence of autoconf is documented for every option.
		3756
		3757	Symbols marked with "(h)" do not change the ABI, and can have different
		3758	values when compiling libev vs. including F<ev.h>, so it is permissible
		3759	to redefine them before including F<ev.h> without breaking compatibility
		3760	to a compiled library. All other symbols change the ABI, which means all
		3761	users of libev and the libev code itself must be compiled with compatible
		3762	settings.
3132		3763
3133	=over 4	3764	=over 4
3134		3765
		3766	=item EV_COMPAT3 (h)
		3767
		3768	Backwards compatibility is a major concern for libev. This is why this
		3769	release of libev comes with wrappers for the functions and symbols that
		3770	have been renamed between libev version 3 and 4.
		3771
		3772	You can disable these wrappers (to test compatibility with future
		3773	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3774	sources. This has the additional advantage that you can drop the C<struct>
		3775	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3776	typedef in that case.
		3777
		3778	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3779	and in some even more future version the compatibility code will be
		3780	removed completely.
		3781
3135	=item EV_STANDALONE	3782	=item EV_STANDALONE (h)
3136		3783
3137	Must always be C<1> if you do not use autoconf configuration, which	3784	Must always be C<1> if you do not use autoconf configuration, which
3138	keeps libev from including F<config.h>, and it also defines dummy	3785	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3786	implementations for some libevent functions (such as logging, which is not
3140	supported). It will also not define any of the structs usually found in	3787	supported). It will also not define any of the structs usually found in
3141	F<event.h> that are not directly supported by the libev core alone.	3788	F<event.h> that are not directly supported by the libev core alone.
3142		3789
		3790	In standalone mode, libev will still try to automatically deduce the
		3791	configuration, but has to be more conservative.
		3792
3143	=item EV_USE_MONOTONIC	3793	=item EV_USE_MONOTONIC
3144		3794
3145	If defined to be C<1>, libev will try to detect the availability of the	3795	If defined to be C<1>, libev will try to detect the availability of the
3146	monotonic clock option at both compile time and runtime. Otherwise no use	3796	monotonic clock option at both compile time and runtime. Otherwise no
3147	of the monotonic clock option will be attempted. If you enable this, you	3797	use of the monotonic clock option will be attempted. If you enable this,
3148	usually have to link against librt or something similar. Enabling it when	3798	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3799	when the functionality isn't available is safe, though, although you have
3150	to make sure you link against any libraries where the C<clock_gettime>	3800	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3801	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3802
3153	=item EV_USE_REALTIME	3803	=item EV_USE_REALTIME
3154		3804
3155	If defined to be C<1>, libev will try to detect the availability of the	3805	If defined to be C<1>, libev will try to detect the availability of the
3156	real-time clock option at compile time (and assume its availability at	3806	real-time clock option at compile time (and assume its availability
3157	runtime if successful). Otherwise no use of the real-time clock option will	3807	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3808	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3809	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3810	correctness. See the note about libraries in the description of
		3811	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3812	C<EV_USE_CLOCK_SYSCALL>.
		3813
		3814	=item EV_USE_CLOCK_SYSCALL
		3815
		3816	If defined to be C<1>, libev will try to use a direct syscall instead
		3817	of calling the system-provided C<clock_gettime> function. This option
		3818	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3819	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3820	programs needlessly. Using a direct syscall is slightly slower (in
		3821	theory), because no optimised vdso implementation can be used, but avoids
		3822	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3823	higher, as it simplifies linking (no need for C<-lrt>).
3161		3824
3162	=item EV_USE_NANOSLEEP	3825	=item EV_USE_NANOSLEEP
3163		3826
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3827	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3165	and will use it for delays. Otherwise it will use C<select ()>.	3828	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		3844
3182	=item EV_SELECT_USE_FD_SET	3845	=item EV_SELECT_USE_FD_SET
3183		3846
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	3847	If defined to C<1>, then the select backend will use the system C<fd_set>
3185	structure. This is useful if libev doesn't compile due to a missing	3848	structure. This is useful if libev doesn't compile due to a missing
3186	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3849	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3187	exotic systems. This usually limits the range of file descriptors to some	3850	on exotic systems. This usually limits the range of file descriptors to
3188	low limit such as 1024 or might have other limitations (winsocket only	3851	some low limit such as 1024 or might have other limitations (winsocket
3189	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3852	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	3853	configures the maximum size of the C<fd_set>.
3191		3854
3192	=item EV_SELECT_IS_WINSOCKET	3855	=item EV_SELECT_IS_WINSOCKET
3193		3856
3194	When defined to C<1>, the select backend will assume that	3857	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3858	select/socket/connect etc. don't understand file descriptors but
…		…
3197	be used is the winsock select). This means that it will call	3860	be used is the winsock select). This means that it will call
3198	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3861	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3199	it is assumed that all these functions actually work on fds, even	3862	it is assumed that all these functions actually work on fds, even
3200	on win32. Should not be defined on non-win32 platforms.	3863	on win32. Should not be defined on non-win32 platforms.
3201		3864
3202	=item EV_FD_TO_WIN32_HANDLE	3865	=item EV_FD_TO_WIN32_HANDLE(fd)
3203		3866
3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3867	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3205	file descriptors to socket handles. When not defining this symbol (the	3868	file descriptors to socket handles. When not defining this symbol (the
3206	default), then libev will call C<_get_osfhandle>, which is usually	3869	default), then libev will call C<_get_osfhandle>, which is usually
3207	correct. In some cases, programs use their own file descriptor management,	3870	correct. In some cases, programs use their own file descriptor management,
3208	in which case they can provide this function to map fds to socket handles.	3871	in which case they can provide this function to map fds to socket handles.
		3872
		3873	=item EV_WIN32_HANDLE_TO_FD(handle)
		3874
		3875	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3876	using the standard C<_open_osfhandle> function. For programs implementing
		3877	their own fd to handle mapping, overwriting this function makes it easier
		3878	to do so. This can be done by defining this macro to an appropriate value.
		3879
		3880	=item EV_WIN32_CLOSE_FD(fd)
		3881
		3882	If programs implement their own fd to handle mapping on win32, then this
		3883	macro can be used to override the C<close> function, useful to unregister
		3884	file descriptors again. Note that the replacement function has to close
		3885	the underlying OS handle.
3209		3886
3210	=item EV_USE_POLL	3887	=item EV_USE_POLL
3211		3888
3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3889	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3213	backend. Otherwise it will be enabled on non-win32 platforms. It	3890	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3260	as well as for signal and thread safety in C<ev_async> watchers.	3937	as well as for signal and thread safety in C<ev_async> watchers.
3261		3938
3262	In the absence of this define, libev will use C<sig_atomic_t volatile>	3939	In the absence of this define, libev will use C<sig_atomic_t volatile>
3263	(from F<signal.h>), which is usually good enough on most platforms.	3940	(from F<signal.h>), which is usually good enough on most platforms.
3264		3941
3265	=item EV_H	3942	=item EV_H (h)
3266		3943
3267	The name of the F<ev.h> header file used to include it. The default if	3944	The name of the F<ev.h> header file used to include it. The default if
3268	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3945	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3269	used to virtually rename the F<ev.h> header file in case of conflicts.	3946	used to virtually rename the F<ev.h> header file in case of conflicts.
3270		3947
3271	=item EV_CONFIG_H	3948	=item EV_CONFIG_H (h)
3272		3949
3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3950	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3274	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3951	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3275	C<EV_H>, above.	3952	C<EV_H>, above.
3276		3953
3277	=item EV_EVENT_H	3954	=item EV_EVENT_H (h)
3278		3955
3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3956	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3280	of how the F<event.h> header can be found, the default is C<"event.h">.	3957	of how the F<event.h> header can be found, the default is C<"event.h">.
3281		3958
3282	=item EV_PROTOTYPES	3959	=item EV_PROTOTYPES (h)
3283		3960
3284	If defined to be C<0>, then F<ev.h> will not define any function	3961	If defined to be C<0>, then F<ev.h> will not define any function
3285	prototypes, but still define all the structs and other symbols. This is	3962	prototypes, but still define all the structs and other symbols. This is
3286	occasionally useful if you want to provide your own wrapper functions	3963	occasionally useful if you want to provide your own wrapper functions
3287	around libev functions.	3964	around libev functions.
…		…
3309	fine.	3986	fine.
3310		3987
3311	If your embedding application does not need any priorities, defining these	3988	If your embedding application does not need any priorities, defining these
3312	both to C<0> will save some memory and CPU.	3989	both to C<0> will save some memory and CPU.
3313		3990
3314	=item EV_PERIODIC_ENABLE	3991	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3992	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3993	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3315		3994
3316	If undefined or defined to be C<1>, then periodic timers are supported. If	3995	If undefined or defined to be C<1> (and the platform supports it), then
3317	defined to be C<0>, then they are not. Disabling them saves a few kB of	3996	the respective watcher type is supported. If defined to be C<0>, then it
3318	code.	3997	is not. Disabling watcher types mainly saves code size.
3319		3998
3320	=item EV_IDLE_ENABLE	3999	=item EV_FEATURES
3321
3322	If undefined or defined to be C<1>, then idle watchers are supported. If
3323	defined to be C<0>, then they are not. Disabling them saves a few kB of
3324	code.
3325
3326	=item EV_EMBED_ENABLE
3327
3328	If undefined or defined to be C<1>, then embed watchers are supported. If
3329	defined to be C<0>, then they are not. Embed watchers rely on most other
3330	watcher types, which therefore must not be disabled.
3331
3332	=item EV_STAT_ENABLE
3333
3334	If undefined or defined to be C<1>, then stat watchers are supported. If
3335	defined to be C<0>, then they are not.
3336
3337	=item EV_FORK_ENABLE
3338
3339	If undefined or defined to be C<1>, then fork watchers are supported. If
3340	defined to be C<0>, then they are not.
3341
3342	=item EV_ASYNC_ENABLE
3343
3344	If undefined or defined to be C<1>, then async watchers are supported. If
3345	defined to be C<0>, then they are not.
3346
3347	=item EV_MINIMAL
3348		4000
3349	If you need to shave off some kilobytes of code at the expense of some	4001	If you need to shave off some kilobytes of code at the expense of some
3350	speed, define this symbol to C<1>. Currently this is used to override some	4002	speed (but with the full API), you can define this symbol to request
3351	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4003	certain subsets of functionality. The default is to enable all features
3352	much smaller 2-heap for timer management over the default 4-heap.	4004	that can be enabled on the platform.
		4005
		4006	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4007	with some broad features you want) and then selectively re-enable
		4008	additional parts you want, for example if you want everything minimal,
		4009	but multiple event loop support, async and child watchers and the poll
		4010	backend, use this:
		4011
		4012	#define EV_FEATURES 0
		4013	#define EV_MULTIPLICITY 1
		4014	#define EV_USE_POLL 1
		4015	#define EV_CHILD_ENABLE 1
		4016	#define EV_ASYNC_ENABLE 1
		4017
		4018	The actual value is a bitset, it can be a combination of the following
		4019	values:
		4020
		4021	=over 4
		4022
		4023	=item C<1> - faster/larger code
		4024
		4025	Use larger code to speed up some operations.
		4026
		4027	Currently this is used to override some inlining decisions (enlarging the
		4028	code size by roughly 30% on amd64).
		4029
		4030	When optimising for size, use of compiler flags such as C<-Os> with
		4031	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4032	assertions.
		4033
		4034	=item C<2> - faster/larger data structures
		4035
		4036	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4037	hash table sizes and so on. This will usually further increase code size
		4038	and can additionally have an effect on the size of data structures at
		4039	runtime.
		4040
		4041	=item C<4> - full API configuration
		4042
		4043	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4044	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4045
		4046	=item C<8> - full API
		4047
		4048	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4049	details on which parts of the API are still available without this
		4050	feature, and do not complain if this subset changes over time.
		4051
		4052	=item C<16> - enable all optional watcher types
		4053
		4054	Enables all optional watcher types. If you want to selectively enable
		4055	only some watcher types other than I/O and timers (e.g. prepare,
		4056	embed, async, child...) you can enable them manually by defining
		4057	C<EV_watchertype_ENABLE> to C<1> instead.
		4058
		4059	=item C<32> - enable all backends
		4060
		4061	This enables all backends - without this feature, you need to enable at
		4062	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4063
		4064	=item C<64> - enable OS-specific "helper" APIs
		4065
		4066	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4067	default.
		4068
		4069	=back
		4070
		4071	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4072	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4073	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4074	watchers, timers and monotonic clock support.
		4075
		4076	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4077	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4078	your program might be left out as well - a binary starting a timer and an
		4079	I/O watcher then might come out at only 5Kb.
		4080
		4081	=item EV_AVOID_STDIO
		4082
		4083	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4084	functions (printf, scanf, perror etc.). This will increase the code size
		4085	somewhat, but if your program doesn't otherwise depend on stdio and your
		4086	libc allows it, this avoids linking in the stdio library which is quite
		4087	big.
		4088
		4089	Note that error messages might become less precise when this option is
		4090	enabled.
		4091
		4092	=item EV_NSIG
		4093
		4094	The highest supported signal number, +1 (or, the number of
		4095	signals): Normally, libev tries to deduce the maximum number of signals
		4096	automatically, but sometimes this fails, in which case it can be
		4097	specified. Also, using a lower number than detected (C<32> should be
		4098	good for about any system in existence) can save some memory, as libev
		4099	statically allocates some 12-24 bytes per signal number.
3353		4100
3354	=item EV_PID_HASHSIZE	4101	=item EV_PID_HASHSIZE
3355		4102
3356	C<ev_child> watchers use a small hash table to distribute workload by	4103	C<ev_child> watchers use a small hash table to distribute workload by
3357	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4104	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3358	than enough. If you need to manage thousands of children you might want to	4105	usually more than enough. If you need to manage thousands of children you
3359	increase this value (I<must> be a power of two).	4106	might want to increase this value (I<must> be a power of two).
3360		4107
3361	=item EV_INOTIFY_HASHSIZE	4108	=item EV_INOTIFY_HASHSIZE
3362		4109
3363	C<ev_stat> watchers use a small hash table to distribute workload by	4110	C<ev_stat> watchers use a small hash table to distribute workload by
3364	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4111	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3365	usually more than enough. If you need to manage thousands of C<ev_stat>	4112	disabled), usually more than enough. If you need to manage thousands of
3366	watchers you might want to increase this value (I<must> be a power of	4113	C<ev_stat> watchers you might want to increase this value (I<must> be a
3367	two).	4114	power of two).
3368		4115
3369	=item EV_USE_4HEAP	4116	=item EV_USE_4HEAP
3370		4117
3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4118	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3372	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4119	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3373	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4120	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3374	faster performance with many (thousands) of watchers.	4121	faster performance with many (thousands) of watchers.
3375		4122
3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4123	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3377	(disabled).	4124	will be C<0>.
3378		4125
3379	=item EV_HEAP_CACHE_AT	4126	=item EV_HEAP_CACHE_AT
3380		4127
3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4128	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3382	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4129	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3383	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4130	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3384	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4131	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3385	but avoids random read accesses on heap changes. This improves performance	4132	but avoids random read accesses on heap changes. This improves performance
3386	noticeably with many (hundreds) of watchers.	4133	noticeably with many (hundreds) of watchers.
3387		4134
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4135	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4136	will be C<0>.
3390		4137
3391	=item EV_VERIFY	4138	=item EV_VERIFY
3392		4139
3393	Controls how much internal verification (see C<ev_loop_verify ()>) will	4140	Controls how much internal verification (see C<ev_verify ()>) will
3394	be done: If set to C<0>, no internal verification code will be compiled	4141	be done: If set to C<0>, no internal verification code will be compiled
3395	in. If set to C<1>, then verification code will be compiled in, but not	4142	in. If set to C<1>, then verification code will be compiled in, but not
3396	called. If set to C<2>, then the internal verification code will be	4143	called. If set to C<2>, then the internal verification code will be
3397	called once per loop, which can slow down libev. If set to C<3>, then the	4144	called once per loop, which can slow down libev. If set to C<3>, then the
3398	verification code will be called very frequently, which will slow down	4145	verification code will be called very frequently, which will slow down
3399	libev considerably.	4146	libev considerably.
3400		4147
3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4148	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3402	C<0>.	4149	will be C<0>.
3403		4150
3404	=item EV_COMMON	4151	=item EV_COMMON
3405		4152
3406	By default, all watchers have a C<void *data> member. By redefining	4153	By default, all watchers have a C<void *data> member. By redefining
3407	this macro to a something else you can include more and other types of	4154	this macro to something else you can include more and other types of
3408	members. You have to define it each time you include one of the files,	4155	members. You have to define it each time you include one of the files,
3409	though, and it must be identical each time.	4156	though, and it must be identical each time.
3410		4157
3411	For example, the perl EV module uses something like this:	4158	For example, the perl EV module uses something like this:
3412		4159
…		…
3465	file.	4212	file.
3466		4213
3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4214	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3468	that everybody includes and which overrides some configure choices:	4215	that everybody includes and which overrides some configure choices:
3469		4216
3470	#define EV_MINIMAL 1	4217	#define EV_FEATURES 8
3471	#define EV_USE_POLL 0	4218	#define EV_USE_SELECT 1
3472	#define EV_MULTIPLICITY 0
3473	#define EV_PERIODIC_ENABLE 0	4219	#define EV_PREPARE_ENABLE 1
		4220	#define EV_IDLE_ENABLE 1
3474	#define EV_STAT_ENABLE 0	4221	#define EV_SIGNAL_ENABLE 1
3475	#define EV_FORK_ENABLE 0	4222	#define EV_CHILD_ENABLE 1
		4223	#define EV_USE_STDEXCEPT 0
3476	#define EV_CONFIG_H <config.h>	4224	#define EV_CONFIG_H <config.h>
3477	#define EV_MINPRI 0
3478	#define EV_MAXPRI 0
3479		4225
3480	#include "ev++.h"	4226	#include "ev++.h"
3481		4227
3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4228	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3483		4229
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	4289	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	4290	watcher callback into the event loop interested in the signal.
3545		4291
3546	=back	4292	=back
3547		4293
		4294	=head4 THREAD LOCKING EXAMPLE
		4295
		4296	Here is a fictitious example of how to run an event loop in a different
		4297	thread than where callbacks are being invoked and watchers are
		4298	created/added/removed.
		4299
		4300	For a real-world example, see the C<EV::Loop::Async> perl module,
		4301	which uses exactly this technique (which is suited for many high-level
		4302	languages).
		4303
		4304	The example uses a pthread mutex to protect the loop data, a condition
		4305	variable to wait for callback invocations, an async watcher to notify the
		4306	event loop thread and an unspecified mechanism to wake up the main thread.
		4307
		4308	First, you need to associate some data with the event loop:
		4309
		4310	typedef struct {
		4311	mutex_t lock; /* global loop lock */
		4312	ev_async async_w;
		4313	thread_t tid;
		4314	cond_t invoke_cv;
		4315	} userdata;
		4316
		4317	void prepare_loop (EV_P)
		4318	{
		4319	// for simplicity, we use a static userdata struct.
		4320	static userdata u;
		4321
		4322	ev_async_init (&u->async_w, async_cb);
		4323	ev_async_start (EV_A_ &u->async_w);
		4324
		4325	pthread_mutex_init (&u->lock, 0);
		4326	pthread_cond_init (&u->invoke_cv, 0);
		4327
		4328	// now associate this with the loop
		4329	ev_set_userdata (EV_A_ u);
		4330	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4331	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4332
		4333	// then create the thread running ev_loop
		4334	pthread_create (&u->tid, 0, l_run, EV_A);
		4335	}
		4336
		4337	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4338	solely to wake up the event loop so it takes notice of any new watchers
		4339	that might have been added:
		4340
		4341	static void
		4342	async_cb (EV_P_ ev_async *w, int revents)
		4343	{
		4344	// just used for the side effects
		4345	}
		4346
		4347	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4348	protecting the loop data, respectively.
		4349
		4350	static void
		4351	l_release (EV_P)
		4352	{
		4353	userdata *u = ev_userdata (EV_A);
		4354	pthread_mutex_unlock (&u->lock);
		4355	}
		4356
		4357	static void
		4358	l_acquire (EV_P)
		4359	{
		4360	userdata *u = ev_userdata (EV_A);
		4361	pthread_mutex_lock (&u->lock);
		4362	}
		4363
		4364	The event loop thread first acquires the mutex, and then jumps straight
		4365	into C<ev_run>:
		4366
		4367	void *
		4368	l_run (void *thr_arg)
		4369	{
		4370	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4371
		4372	l_acquire (EV_A);
		4373	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4374	ev_run (EV_A_ 0);
		4375	l_release (EV_A);
		4376
		4377	return 0;
		4378	}
		4379
		4380	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4381	signal the main thread via some unspecified mechanism (signals? pipe
		4382	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4383	have been called (in a while loop because a) spurious wakeups are possible
		4384	and b) skipping inter-thread-communication when there are no pending
		4385	watchers is very beneficial):
		4386
		4387	static void
		4388	l_invoke (EV_P)
		4389	{
		4390	userdata *u = ev_userdata (EV_A);
		4391
		4392	while (ev_pending_count (EV_A))
		4393	{
		4394	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4395	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4396	}
		4397	}
		4398
		4399	Now, whenever the main thread gets told to invoke pending watchers, it
		4400	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4401	thread to continue:
		4402
		4403	static void
		4404	real_invoke_pending (EV_P)
		4405	{
		4406	userdata *u = ev_userdata (EV_A);
		4407
		4408	pthread_mutex_lock (&u->lock);
		4409	ev_invoke_pending (EV_A);
		4410	pthread_cond_signal (&u->invoke_cv);
		4411	pthread_mutex_unlock (&u->lock);
		4412	}
		4413
		4414	Whenever you want to start/stop a watcher or do other modifications to an
		4415	event loop, you will now have to lock:
		4416
		4417	ev_timer timeout_watcher;
		4418	userdata *u = ev_userdata (EV_A);
		4419
		4420	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4421
		4422	pthread_mutex_lock (&u->lock);
		4423	ev_timer_start (EV_A_ &timeout_watcher);
		4424	ev_async_send (EV_A_ &u->async_w);
		4425	pthread_mutex_unlock (&u->lock);
		4426
		4427	Note that sending the C<ev_async> watcher is required because otherwise
		4428	an event loop currently blocking in the kernel will have no knowledge
		4429	about the newly added timer. By waking up the loop it will pick up any new
		4430	watchers in the next event loop iteration.
		4431
3548	=head3 COROUTINES	4432	=head3 COROUTINES
3549		4433
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4434	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4435	libev fully supports nesting calls to its functions from different
3552	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4436	coroutines (e.g. you can call C<ev_run> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4437	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4438	the loop, as long as you don't confuse yourself). The only exception is
3555	you must not do this from C<ev_periodic> reschedule callbacks.	4439	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4440
3557	Care has been taken to ensure that libev does not keep local state inside	4441	Care has been taken to ensure that libev does not keep local state inside
3558	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4442	C<ev_run>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4443	they do not call any callbacks.
3560		4444
3561	=head2 COMPILER WARNINGS	4445	=head2 COMPILER WARNINGS
3562		4446
3563	Depending on your compiler and compiler settings, you might get no or a	4447	Depending on your compiler and compiler settings, you might get no or a
3564	lot of warnings when compiling libev code. Some people are apparently	4448	lot of warnings when compiling libev code. Some people are apparently
…		…
3574	maintainable.	4458	maintainable.
3575		4459
3576	And of course, some compiler warnings are just plain stupid, or simply	4460	And of course, some compiler warnings are just plain stupid, or simply
3577	wrong (because they don't actually warn about the condition their message	4461	wrong (because they don't actually warn about the condition their message
3578	seems to warn about). For example, certain older gcc versions had some	4462	seems to warn about). For example, certain older gcc versions had some
3579	warnings that resulted an extreme number of false positives. These have	4463	warnings that resulted in an extreme number of false positives. These have
3580	been fixed, but some people still insist on making code warn-free with	4464	been fixed, but some people still insist on making code warn-free with
3581	such buggy versions.	4465	such buggy versions.
3582		4466
3583	While libev is written to generate as few warnings as possible,	4467	While libev is written to generate as few warnings as possible,
3584	"warn-free" code is not a goal, and it is recommended not to build libev	4468	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4482	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4483	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4484	==2274== still reachable: 256 bytes in 1 blocks.
3601		4485
3602	Then there is no memory leak, just as memory accounted to global variables	4486	Then there is no memory leak, just as memory accounted to global variables
3603	is not a memleak - the memory is still being refernced, and didn't leak.	4487	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4488
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4489	Similarly, under some circumstances, valgrind might report kernel bugs
3606	as if it were a bug in libev (e.g. in realloc or in the poll backend,	4490	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3607	although an acceptable workaround has been found here), or it might be	4491	although an acceptable workaround has been found here), or it might be
3608	confused.	4492	confused.
…		…
3620	I suggest using suppression lists.	4504	I suggest using suppression lists.
3621		4505
3622		4506
3623	=head1 PORTABILITY NOTES	4507	=head1 PORTABILITY NOTES
3624		4508
		4509	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4510
		4511	GNU/Linux is the only common platform that supports 64 bit file/large file
		4512	interfaces but I<disables> them by default.
		4513
		4514	That means that libev compiled in the default environment doesn't support
		4515	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4516
		4517	Unfortunately, many programs try to work around this GNU/Linux issue
		4518	by enabling the large file API, which makes them incompatible with the
		4519	standard libev compiled for their system.
		4520
		4521	Likewise, libev cannot enable the large file API itself as this would
		4522	suddenly make it incompatible to the default compile time environment,
		4523	i.e. all programs not using special compile switches.
		4524
		4525	=head2 OS/X AND DARWIN BUGS
		4526
		4527	The whole thing is a bug if you ask me - basically any system interface
		4528	you touch is broken, whether it is locales, poll, kqueue or even the
		4529	OpenGL drivers.
		4530
		4531	=head3 C<kqueue> is buggy
		4532
		4533	The kqueue syscall is broken in all known versions - most versions support
		4534	only sockets, many support pipes.
		4535
		4536	Libev tries to work around this by not using C<kqueue> by default on this
		4537	rotten platform, but of course you can still ask for it when creating a
		4538	loop - embedding a socket-only kqueue loop into a select-based one is
		4539	probably going to work well.
		4540
		4541	=head3 C<poll> is buggy
		4542
		4543	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4544	implementation by something calling C<kqueue> internally around the 10.5.6
		4545	release, so now C<kqueue> I<and> C<poll> are broken.
		4546
		4547	Libev tries to work around this by not using C<poll> by default on
		4548	this rotten platform, but of course you can still ask for it when creating
		4549	a loop.
		4550
		4551	=head3 C<select> is buggy
		4552
		4553	All that's left is C<select>, and of course Apple found a way to fuck this
		4554	one up as well: On OS/X, C<select> actively limits the number of file
		4555	descriptors you can pass in to 1024 - your program suddenly crashes when
		4556	you use more.
		4557
		4558	There is an undocumented "workaround" for this - defining
		4559	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4560	work on OS/X.
		4561
		4562	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4563
		4564	=head3 C<errno> reentrancy
		4565
		4566	The default compile environment on Solaris is unfortunately so
		4567	thread-unsafe that you can't even use components/libraries compiled
		4568	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4569	defined by default. A valid, if stupid, implementation choice.
		4570
		4571	If you want to use libev in threaded environments you have to make sure
		4572	it's compiled with C<_REENTRANT> defined.
		4573
		4574	=head3 Event port backend
		4575
		4576	The scalable event interface for Solaris is called "event
		4577	ports". Unfortunately, this mechanism is very buggy in all major
		4578	releases. If you run into high CPU usage, your program freezes or you get
		4579	a large number of spurious wakeups, make sure you have all the relevant
		4580	and latest kernel patches applied. No, I don't know which ones, but there
		4581	are multiple ones to apply, and afterwards, event ports actually work
		4582	great.
		4583
		4584	If you can't get it to work, you can try running the program by setting
		4585	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4586	C<select> backends.
		4587
		4588	=head2 AIX POLL BUG
		4589
		4590	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4591	this by trying to avoid the poll backend altogether (i.e. it's not even
		4592	compiled in), which normally isn't a big problem as C<select> works fine
		4593	with large bitsets on AIX, and AIX is dead anyway.
		4594
3625	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4595	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4596
		4597	=head3 General issues
3626		4598
3627	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4599	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3628	requires, and its I/O model is fundamentally incompatible with the POSIX	4600	requires, and its I/O model is fundamentally incompatible with the POSIX
3629	model. Libev still offers limited functionality on this platform in	4601	model. Libev still offers limited functionality on this platform in
3630	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4602	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3631	descriptors. This only applies when using Win32 natively, not when using	4603	descriptors. This only applies when using Win32 natively, not when using
3632	e.g. cygwin.	4604	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4605	as every compielr comes with a slightly differently broken/incompatible
		4606	environment.
3633		4607
3634	Lifting these limitations would basically require the full	4608	Lifting these limitations would basically require the full
3635	re-implementation of the I/O system. If you are into these kinds of	4609	re-implementation of the I/O system. If you are into this kind of thing,
3636	things, then note that glib does exactly that for you in a very portable	4610	then note that glib does exactly that for you in a very portable way (note
3637	way (note also that glib is the slowest event library known to man).	4611	also that glib is the slowest event library known to man).
3638		4612
3639	There is no supported compilation method available on windows except	4613	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4614	embedding it into other applications.
		4615
		4616	Sensible signal handling is officially unsupported by Microsoft - libev
		4617	tries its best, but under most conditions, signals will simply not work.
3641		4618
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4619	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4620	accept large writes: instead of resulting in a partial write, windows will
3644	either accept everything or return C<ENOBUFS> if the buffer is too large,	4621	either accept everything or return C<ENOBUFS> if the buffer is too large,
3645	so make sure you only write small amounts into your sockets (less than a	4622	so make sure you only write small amounts into your sockets (less than a
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4627	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4628	is not recommended (and not reasonable). If your program needs to use
3652	more than a hundred or so sockets, then likely it needs to use a totally	4629	more than a hundred or so sockets, then likely it needs to use a totally
3653	different implementation for windows, as libev offers the POSIX readiness	4630	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4631	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4632	(due to Microsoft monopoly games).
3656		4633
3657	A typical way to use libev under windows is to embed it (see the embedding	4634	A typical way to use libev under windows is to embed it (see the embedding
3658	section for details) and use the following F<evwrap.h> header file instead	4635	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4636	of F<ev.h>:
3660		4637
…		…
3667	you do I<not> compile the F<ev.c> or any other embedded source files!):	4644	you do I<not> compile the F<ev.c> or any other embedded source files!):
3668		4645
3669	#include "evwrap.h"	4646	#include "evwrap.h"
3670	#include "ev.c"	4647	#include "ev.c"
3671		4648
3672	=over 4
3673
3674	=item The winsocket select function	4649	=head3 The winsocket C<select> function
3675		4650
3676	The winsocket C<select> function doesn't follow POSIX in that it	4651	The winsocket C<select> function doesn't follow POSIX in that it
3677	requires socket I<handles> and not socket I<file descriptors> (it is	4652	requires socket I<handles> and not socket I<file descriptors> (it is
3678	also extremely buggy). This makes select very inefficient, and also	4653	also extremely buggy). This makes select very inefficient, and also
3679	requires a mapping from file descriptors to socket handles (the Microsoft	4654	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3688	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4663	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3689		4664
3690	Note that winsockets handling of fd sets is O(n), so you can easily get a	4665	Note that winsockets handling of fd sets is O(n), so you can easily get a
3691	complexity in the O(n²) range when using win32.	4666	complexity in the O(n²) range when using win32.
3692		4667
3693	=item Limited number of file descriptors	4668	=head3 Limited number of file descriptors
3694		4669
3695	Windows has numerous arbitrary (and low) limits on things.	4670	Windows has numerous arbitrary (and low) limits on things.
3696		4671
3697	Early versions of winsocket's select only supported waiting for a maximum	4672	Early versions of winsocket's select only supported waiting for a maximum
3698	of C<64> handles (probably owning to the fact that all windows kernels	4673	of C<64> handles (probably owning to the fact that all windows kernels
3699	can only wait for C<64> things at the same time internally; Microsoft	4674	can only wait for C<64> things at the same time internally; Microsoft
3700	recommends spawning a chain of threads and wait for 63 handles and the	4675	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4676	previous thread in each. Sounds great!).
3702		4677
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4678	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3704	to some high number (e.g. C<2048>) before compiling the winsocket select	4679	to some high number (e.g. C<2048>) before compiling the winsocket select
3705	call (which might be in libev or elsewhere, for example, perl does its own	4680	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4681	other interpreters do their own select emulation on windows).
3707		4682
3708	Another limit is the number of file descriptors in the Microsoft runtime	4683	Another limit is the number of file descriptors in the Microsoft runtime
3709	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4684	libraries, which by default is C<64> (there must be a hidden I<64>
3710	or something like this inside Microsoft). You can increase this by calling	4685	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4686	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3712	arbitrary limit), but is broken in many versions of the Microsoft runtime	4687	(another arbitrary limit), but is broken in many versions of the Microsoft
3713	libraries.
3714
3715	This might get you to about C<512> or C<2048> sockets (depending on	4688	runtime libraries. This might get you to about C<512> or C<2048> sockets
3716	windows version and/or the phase of the moon). To get more, you need to	4689	(depending on windows version and/or the phase of the moon). To get more,
3717	wrap all I/O functions and provide your own fd management, but the cost of	4690	you need to wrap all I/O functions and provide your own fd management, but
3718	calling select (O(n²)) will likely make this unworkable.	4691	the cost of calling select (O(n²)) will likely make this unworkable.
3719
3720	=back
3721		4692
3722	=head2 PORTABILITY REQUIREMENTS	4693	=head2 PORTABILITY REQUIREMENTS
3723		4694
3724	In addition to a working ISO-C implementation and of course the	4695	In addition to a working ISO-C implementation and of course the
3725	backend-specific APIs, libev relies on a few additional extensions:	4696	backend-specific APIs, libev relies on a few additional extensions:
…		…
3764	watchers.	4735	watchers.
3765		4736
3766	=item C<double> must hold a time value in seconds with enough accuracy	4737	=item C<double> must hold a time value in seconds with enough accuracy
3767		4738
3768	The type C<double> is used to represent timestamps. It is required to	4739	The type C<double> is used to represent timestamps. It is required to
3769	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4740	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3770	enough for at least into the year 4000. This requirement is fulfilled by	4741	good enough for at least into the year 4000 with millisecond accuracy
		4742	(the design goal for libev). This requirement is overfulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	4743	implementations using IEEE 754, which is basically all existing ones. With
		4744	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3772		4745
3773	=back	4746	=back
3774		4747
3775	If you know of other additional requirements drop me a note.	4748	If you know of other additional requirements drop me a note.
3776		4749
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4817	involves iterating over all running async watchers or all signal numbers.
3845		4818
3846	=back	4819	=back
3847		4820
3848		4821
		4822	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4823
		4824	The major version 4 introduced some minor incompatible changes to the API.
		4825
		4826	At the moment, the C<ev.h> header file tries to implement superficial
		4827	compatibility, so most programs should still compile. Those might be
		4828	removed in later versions of libev, so better update early than late.
		4829
		4830	=over 4
		4831
		4832	=item function/symbol renames
		4833
		4834	A number of functions and symbols have been renamed:
		4835
		4836	ev_loop => ev_run
		4837	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4838	EVLOOP_ONESHOT => EVRUN_ONCE
		4839
		4840	ev_unloop => ev_break
		4841	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4842	EVUNLOOP_ONE => EVBREAK_ONE
		4843	EVUNLOOP_ALL => EVBREAK_ALL
		4844
		4845	EV_TIMEOUT => EV_TIMER
		4846
		4847	ev_loop_count => ev_iteration
		4848	ev_loop_depth => ev_depth
		4849	ev_loop_verify => ev_verify
		4850
		4851	Most functions working on C<struct ev_loop> objects don't have an
		4852	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4853	associated constants have been renamed to not collide with the C<struct
		4854	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4855	as all other watcher types. Note that C<ev_loop_fork> is still called
		4856	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4857	typedef.
		4858
		4859	=item C<EV_COMPAT3> backwards compatibility mechanism
		4860
		4861	The backward compatibility mechanism can be controlled by
		4862	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4863	section.
		4864
		4865	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4866
		4867	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4868	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4869	and work, but the library code will of course be larger.
		4870
		4871	=back
		4872
		4873
		4874	=head1 GLOSSARY
		4875
		4876	=over 4
		4877
		4878	=item active
		4879
		4880	A watcher is active as long as it has been started and not yet stopped.
		4881	See L<WATCHER STATES> for details.
		4882
		4883	=item application
		4884
		4885	In this document, an application is whatever is using libev.
		4886
		4887	=item backend
		4888
		4889	The part of the code dealing with the operating system interfaces.
		4890
		4891	=item callback
		4892
		4893	The address of a function that is called when some event has been
		4894	detected. Callbacks are being passed the event loop, the watcher that
		4895	received the event, and the actual event bitset.
		4896
		4897	=item callback/watcher invocation
		4898
		4899	The act of calling the callback associated with a watcher.
		4900
		4901	=item event
		4902
		4903	A change of state of some external event, such as data now being available
		4904	for reading on a file descriptor, time having passed or simply not having
		4905	any other events happening anymore.
		4906
		4907	In libev, events are represented as single bits (such as C<EV_READ> or
		4908	C<EV_TIMER>).
		4909
		4910	=item event library
		4911
		4912	A software package implementing an event model and loop.
		4913
		4914	=item event loop
		4915
		4916	An entity that handles and processes external events and converts them
		4917	into callback invocations.
		4918
		4919	=item event model
		4920
		4921	The model used to describe how an event loop handles and processes
		4922	watchers and events.
		4923
		4924	=item pending
		4925
		4926	A watcher is pending as soon as the corresponding event has been
		4927	detected. See L<WATCHER STATES> for details.
		4928
		4929	=item real time
		4930
		4931	The physical time that is observed. It is apparently strictly monotonic :)
		4932
		4933	=item wall-clock time
		4934
		4935	The time and date as shown on clocks. Unlike real time, it can actually
		4936	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4937	clock.
		4938
		4939	=item watcher
		4940
		4941	A data structure that describes interest in certain events. Watchers need
		4942	to be started (attached to an event loop) before they can receive events.
		4943
		4944	=back
		4945
3849	=head1 AUTHOR	4946	=head1 AUTHOR
3850		4947
3851	Marc Lehmann <libev@schmorp.de>.	4948	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4949

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