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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;
…		…
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
298	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
299	function.	314	function.
300		315
301	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
303	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
304		319
305	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
306	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
307	for C<SIGCHLD>. If this is a problem for your application you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
330	useful to try out specific backends to test their performance, or to work	345	useful to try out specific backends to test their performance, or to work
331	around bugs.	346	around bugs.
332		347
333	=item C<EVFLAG_FORKCHECK>	348	=item C<EVFLAG_FORKCHECK>
334		349
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	350	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	351	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		352
339	This works by calling C<getpid ()> on every iteration of the loop,	353	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	354	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	355	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	356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	362	flag.
349		363
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	365	environment variable.
352		366
		367	=item C<EVFLAG_NOINOTIFY>
		368
		369	When this flag is specified, then libev will not attempt to use the
		370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		371	testing, this flag can be useful to conserve inotify file descriptors, as
		372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		373
		374	=item C<EVFLAG_SIGNALFD>
		375
		376	When this flag is specified, then libev will attempt to use the
		377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		378	delivers signals synchronously, which makes it both faster and might make
		379	it possible to get the queued signal data. It can also simplify signal
		380	handling with threads, as long as you properly block signals in your
		381	threads that are not interested in handling them.
		382
		383	Signalfd will not be used by default as this changes your signal mask, and
		384	there are a lot of shoddy libraries and programs (glib's threadpool for
		385	example) that can't properly initialise their signal masks.
		386
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	387	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		388
355	This is your standard select(2) backend. Not I<completely> standard, as	389	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,	390	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	391	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	415	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	416	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		417
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	418	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		419
		420	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		421	kernels).
		422
386	For few fds, this backend is a bit little slower than poll and select,	423	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	424	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),	425	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	426	epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect	427
391	cases and requiring a system call per fd change, no fork support and bad	428	The epoll mechanism deserves honorable mention as the most misdesigned
392	support for dup.	429	of the more advanced event mechanisms: mere annoyances include silently
		430	dropping file descriptors, requiring a system call per change per file
		431	descriptor (and unnecessary guessing of parameters), problems with dup and
		432	so on. The biggest issue is fork races, however - if a program forks then
		433	I<both> parent and child process have to recreate the epoll set, which can
		434	take considerable time (one syscall per file descriptor) and is of course
		435	hard to detect.
		436
		437	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		438	of course I<doesn't>, and epoll just loves to report events for totally
		439	I<different> file descriptors (even already closed ones, so one cannot
		440	even remove them from the set) than registered in the set (especially
		441	on SMP systems). Libev tries to counter these spurious notifications by
		442	employing an additional generation counter and comparing that against the
		443	events to filter out spurious ones, recreating the set when required.
393		444
394	While stopping, setting and starting an I/O watcher in the same iteration	445	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	446	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	447	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	448	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
398	very well if you register events for both fds.	449	file descriptors might not work very well if you register events for both
399		450	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		451
404	Best performance from this backend is achieved by not unregistering all	452	Best performance from this backend is achieved by not unregistering all
405	watchers for a file descriptor until it has been closed, if possible,	453	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	454	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	455	starting a watcher (without re-setting it) also usually doesn't cause
408	extra overhead.	456	extra overhead. A fork can both result in spurious notifications as well
		457	as in libev having to destroy and recreate the epoll object, which can
		458	take considerable time and thus should be avoided.
		459
		460	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		461	faster than epoll for maybe up to a hundred file descriptors, depending on
		462	the usage. So sad.
409		463
410	While nominally embeddable in other event loops, this feature is broken in	464	While nominally embeddable in other event loops, this feature is broken in
411	all kernel versions tested so far.	465	all kernel versions tested so far.
412		466
413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	467	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
414	C<EVBACKEND_POLL>.	468	C<EVBACKEND_POLL>.
415		469
416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	470	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
417		471
418	Kqueue deserves special mention, as at the time of this writing, it was	472	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	473	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	474	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	475	it's completely useless). Unlike epoll, however, whose brokenness
422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	476	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.	477	without API changes to existing programs. For this reason it's not being
		478	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		479	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		480	system like NetBSD.
424		481
425	You still can embed kqueue into a normal poll or select backend and use it	482	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	483	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.	484	the target platform). See C<ev_embed> watchers for more info.
428		485
429	It scales in the same way as the epoll backend, but the interface to the	486	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	487	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	488	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	489	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	490	two event changes per incident. Support for C<fork ()> is very bad (but
434	drops fds silently in similarly hard-to-detect cases.	491	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		492	cases
435		493
436	This backend usually performs well under most conditions.	494	This backend usually performs well under most conditions.
437		495
438	While nominally embeddable in other event loops, this doesn't work	496	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	497	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	498	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	499	(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,	500	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
443	using it only for sockets.	501	also broken on OS X)) and, did I mention it, using it only for sockets.
444		502
445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	503	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	504	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
447	C<NOTE_EOF>.	505	C<NOTE_EOF>.
448		506
…		…
468	might perform better.	526	might perform better.
469		527
470	On the positive side, with the exception of the spurious readiness	528	On the positive side, with the exception of the spurious readiness
471	notifications, this backend actually performed fully to specification	529	notifications, this backend actually performed fully to specification
472	in all tests and is fully embeddable, which is a rare feat among the	530	in all tests and is fully embeddable, which is a rare feat among the
473	OS-specific backends.	531	OS-specific backends (I vastly prefer correctness over speed hacks).
474		532
475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	533	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
476	C<EVBACKEND_POLL>.	534	C<EVBACKEND_POLL>.
477		535
478	=item C<EVBACKEND_ALL>	536	=item C<EVBACKEND_ALL>
…		…
483		541
484	It is definitely not recommended to use this flag.	542	It is definitely not recommended to use this flag.
485		543
486	=back	544	=back
487		545
488	If one or more of these are or'ed into the flags value, then only these	546	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	547	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.	548	here). If none are specified, all backends in C<ev_recommended_backends
		549	()> will be tried.
491		550
492	Example: This is the most typical usage.	551	Example: This is the most typical usage.
493		552
494	if (!ev_default_loop (0))	553	if (!ev_default_loop (0))
495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	554	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	566	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
508		567
509	=item struct ev_loop *ev_loop_new (unsigned int flags)	568	=item struct ev_loop *ev_loop_new (unsigned int flags)
510		569
511	Similar to C<ev_default_loop>, but always creates a new event loop that is	570	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	571	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		572
516	Note that this function I<is> thread-safe, and the recommended way to use	573	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	574	libev with threads is indeed to create one loop per thread, and using the
518	default loop in the "main" or "initial" thread.	575	default loop in the "main" or "initial" thread.
519		576
520	Example: Try to create a event loop that uses epoll and nothing else.	577	Example: Try to create a event loop that uses epoll and nothing else.
521		578
…		…
523	if (!epoller)	580	if (!epoller)
524	fatal ("no epoll found here, maybe it hides under your chair");	581	fatal ("no epoll found here, maybe it hides under your chair");
525		582
526	=item ev_default_destroy ()	583	=item ev_default_destroy ()
527		584
528	Destroys the default loop again (frees all memory and kernel state	585	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	586	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	587	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>	588	either stop all watchers cleanly yourself I<before> calling this function,
532	calling this function, or cope with the fact afterwards (which is usually	589	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	590	can just ignore the watchers and/or C<free ()> them for example).
534	for example).
535		591
536	Note that certain global state, such as signal state (and installed signal	592	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	593	handlers), will not be freed by this function, and related watchers (such
538	as signal and child watchers) would need to be stopped manually.	594	as signal and child watchers) would need to be stopped manually.
539		595
540	In general it is not advisable to call this function except in the	596	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	597	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	598	pipe fds. If you need dynamically allocated loops it is better to use
543	C<ev_loop_new> and C<ev_loop_destroy>).	599	C<ev_loop_new> and C<ev_loop_destroy>.
544		600
545	=item ev_loop_destroy (loop)	601	=item ev_loop_destroy (loop)
546		602
547	Like C<ev_default_destroy>, but destroys an event loop created by an	603	Like C<ev_default_destroy>, but destroys an event loop created by an
548	earlier call to C<ev_loop_new>.	604	earlier call to C<ev_loop_new>.
…		…
554	name, you can call it anytime, but it makes most sense after forking, in	610	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	611	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	612	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.	613	functions, and it will only take effect at the next C<ev_loop> iteration.
558		614
		615	Again, you I<have> to call it on I<any> loop that you want to re-use after
		616	a fork, I<even if you do not plan to use the loop in the parent>. This is
		617	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		618	during fork.
		619
559	On the other hand, you only need to call this function in the child	620	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	621	process if and only if you want to use the event loop in the child. If you
561	you just fork+exec, you don't have to call it at all.	622	just fork+exec or create a new loop in the child, you don't have to call
		623	it at all.
562		624
563	The function itself is quite fast and it's usually not a problem to call	625	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	626	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>:	627	quite nicely into a call to C<pthread_atfork>:
566		628
…		…
568		630
569	=item ev_loop_fork (loop)	631	=item ev_loop_fork (loop)
570		632
571	Like C<ev_default_fork>, but acts on an event loop created by	633	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	634	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	635	after fork that you want to re-use in the child, and how you keep track of
574	entirely your own problem.	636	them is entirely your own problem.
575		637
576	=item int ev_is_default_loop (loop)	638	=item int ev_is_default_loop (loop)
577		639
578	Returns true when the given loop is, in fact, the default loop, and false	640	Returns true when the given loop is, in fact, the default loop, and false
579	otherwise.	641	otherwise.
580		642
581	=item unsigned int ev_loop_count (loop)	643	=item unsigned int ev_iteration (loop)
582		644
583	Returns the count of loop iterations for the loop, which is identical to	645	Returns the current iteration count for the loop, which is identical to
584	the number of times libev did poll for new events. It starts at C<0> and	646	the number of times libev did poll for new events. It starts at C<0> and
585	happily wraps around with enough iterations.	647	happily wraps around with enough iterations.
586		648
587	This value can sometimes be useful as a generation counter of sorts (it	649	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	650	"ticks" the number of loop iterations), as it roughly corresponds with
589	C<ev_prepare> and C<ev_check> calls.	651	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		652	prepare and check phases.
		653
		654	=item unsigned int ev_depth (loop)
		655
		656	Returns the number of times C<ev_loop> was entered minus the number of
		657	times C<ev_loop> was exited, in other words, the recursion depth.
		658
		659	Outside C<ev_loop>, this number is zero. In a callback, this number is
		660	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		661	in which case it is higher.
		662
		663	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		664	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		665	ungentleman behaviour unless it's really convenient.
590		666
591	=item unsigned int ev_backend (loop)	667	=item unsigned int ev_backend (loop)
592		668
593	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	669	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
594	use.	670	use.
…		…
609		685
610	This function is rarely useful, but when some event callback runs for a	686	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	687	very long time without entering the event loop, updating libev's idea of
612	the current time is a good idea.	688	the current time is a good idea.
613		689
614	See also "The special problem of time updates" in the C<ev_timer> section.	690	See also L<The special problem of time updates> in the C<ev_timer> section.
		691
		692	=item ev_suspend (loop)
		693
		694	=item ev_resume (loop)
		695
		696	These two functions suspend and resume a loop, for use when the loop is
		697	not used for a while and timeouts should not be processed.
		698
		699	A typical use case would be an interactive program such as a game: When
		700	the user presses C<^Z> to suspend the game and resumes it an hour later it
		701	would be best to handle timeouts as if no time had actually passed while
		702	the program was suspended. This can be achieved by calling C<ev_suspend>
		703	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		704	C<ev_resume> directly afterwards to resume timer processing.
		705
		706	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		707	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		708	will be rescheduled (that is, they will lose any events that would have
		709	occured while suspended).
		710
		711	After calling C<ev_suspend> you B<must not> call I<any> function on the
		712	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		713	without a previous call to C<ev_suspend>.
		714
		715	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		716	event loop time (see C<ev_now_update>).
615		717
616	=item ev_loop (loop, int flags)	718	=item ev_loop (loop, int flags)
617		719
618	Finally, this is it, the event handler. This function usually is called	720	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	721	after you have initialised all your watchers and you want to start
620	events.	722	handling events.
621		723
622	If the flags argument is specified as C<0>, it will not return until	724	If the flags argument is specified as C<0>, it will not return until
623	either no event watchers are active anymore or C<ev_unloop> was called.	725	either no event watchers are active anymore or C<ev_unloop> was called.
624		726
625	Please note that an explicit C<ev_unloop> is usually better than	727	Please note that an explicit C<ev_unloop> is usually better than
…		…
635	the loop.	737	the loop.
636		738
637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	739	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
638	necessary) and will handle those and any already outstanding ones. It	740	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	741	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	742	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	743	user-registered callback will be called), and will return after one
642	iteration of the loop.	744	iteration of the loop.
643		745
644	This is useful if you are waiting for some external event in conjunction	746	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	747	with something not expressible using other libev watchers (i.e. "roll your
…		…
699		801
700	Ref/unref can be used to add or remove a reference count on the event	802	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	803	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.	804	count is nonzero, C<ev_loop> will not return on its own.
703		805
704	If you have a watcher you never unregister that should not keep C<ev_loop>	806	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	807	unregister, but that nevertheless should not keep C<ev_loop> from
		808	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
706	stopping it.	809	before stopping it.
707		810
708	As an example, libev itself uses this for its internal signal pipe: It is	811	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	812	is not visible to the libev user and should not keep C<ev_loop> from
710	if no event watchers registered by it are active. It is also an excellent	813	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	814	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>	815	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,	816	before stop> (but only if the watcher wasn't active before, or was active
714	respectively).	817	before, respectively. Note also that libev might stop watchers itself
		818	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		819	in the callback).
715		820
716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	821	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
717	running when nothing else is active.	822	running when nothing else is active.
718		823
719	ev_signal exitsig;	824	ev_signal exitsig;
…		…
748		853
749	By setting a higher I<io collect interval> you allow libev to spend more	854	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,	855	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	856	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	857	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.	858	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		859	sleep time ensures that libev will not poll for I/O events more often then
		860	once per this interval, on average.
754		861
755	Likewise, by setting a higher I<timeout collect interval> you allow libev	862	Likewise, by setting a higher I<timeout collect interval> you allow libev
756	to spend more time collecting timeouts, at the expense of increased	863	to spend more time collecting timeouts, at the expense of increased
757	latency/jitter/inexactness (the watcher callback will be called	864	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	865	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
760		867
761	Many (busy) programs can usually benefit by setting the I/O collect	868	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	869	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	870	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>,	871	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.	872	as this approaches the timing granularity of most systems. Note that if
		873	you do transactions with the outside world and you can't increase the
		874	parallelity, then this setting will limit your transaction rate (if you
		875	need to poll once per transaction and the I/O collect interval is 0.01,
		876	then you can't do more than 100 transations per second).
766		877
767	Setting the I<timeout collect interval> can improve the opportunity for	878	Setting the I<timeout collect interval> can improve the opportunity for
768	saving power, as the program will "bundle" timer callback invocations that	879	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	880	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	881	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	882	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
772	they fire on, say, one-second boundaries only.	883	they fire on, say, one-second boundaries only.
773		884
		885	Example: we only need 0.1s timeout granularity, and we wish not to poll
		886	more often than 100 times per second:
		887
		888	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		889	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		890
		891	=item ev_invoke_pending (loop)
		892
		893	This call will simply invoke all pending watchers while resetting their
		894	pending state. Normally, C<ev_loop> does this automatically when required,
		895	but when overriding the invoke callback this call comes handy.
		896
		897	=item int ev_pending_count (loop)
		898
		899	Returns the number of pending watchers - zero indicates that no watchers
		900	are pending.
		901
		902	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		903
		904	This overrides the invoke pending functionality of the loop: Instead of
		905	invoking all pending watchers when there are any, C<ev_loop> will call
		906	this callback instead. This is useful, for example, when you want to
		907	invoke the actual watchers inside another context (another thread etc.).
		908
		909	If you want to reset the callback, use C<ev_invoke_pending> as new
		910	callback.
		911
		912	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		913
		914	Sometimes you want to share the same loop between multiple threads. This
		915	can be done relatively simply by putting mutex_lock/unlock calls around
		916	each call to a libev function.
		917
		918	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		919	wait for it to return. One way around this is to wake up the loop via
		920	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		921	and I<acquire> callbacks on the loop.
		922
		923	When set, then C<release> will be called just before the thread is
		924	suspended waiting for new events, and C<acquire> is called just
		925	afterwards.
		926
		927	Ideally, C<release> will just call your mutex_unlock function, and
		928	C<acquire> will just call the mutex_lock function again.
		929
		930	While event loop modifications are allowed between invocations of
		931	C<release> and C<acquire> (that's their only purpose after all), no
		932	modifications done will affect the event loop, i.e. adding watchers will
		933	have no effect on the set of file descriptors being watched, or the time
		934	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		935	to take note of any changes you made.
		936
		937	In theory, threads executing C<ev_loop> will be async-cancel safe between
		938	invocations of C<release> and C<acquire>.
		939
		940	See also the locking example in the C<THREADS> section later in this
		941	document.
		942
		943	=item ev_set_userdata (loop, void *data)
		944
		945	=item ev_userdata (loop)
		946
		947	Set and retrieve a single C<void *> associated with a loop. When
		948	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		949	C<0.>
		950
		951	These two functions can be used to associate arbitrary data with a loop,
		952	and are intended solely for the C<invoke_pending_cb>, C<release> and
		953	C<acquire> callbacks described above, but of course can be (ab-)used for
		954	any other purpose as well.
		955
774	=item ev_loop_verify (loop)	956	=item ev_loop_verify (loop)
775		957
776	This function only does something when C<EV_VERIFY> support has been	958	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	959	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	960	through all internal structures and checks them for validity. If anything
…		…
854	=item C<EV_WRITE>	1036	=item C<EV_WRITE>
855		1037
856	The file descriptor in the C<ev_io> watcher has become readable and/or	1038	The file descriptor in the C<ev_io> watcher has become readable and/or
857	writable.	1039	writable.
858		1040
859	=item C<EV_TIMEOUT>	1041	=item C<EV_TIMER>
860		1042
861	The C<ev_timer> watcher has timed out.	1043	The C<ev_timer> watcher has timed out.
862		1044
863	=item C<EV_PERIODIC>	1045	=item C<EV_PERIODIC>
864		1046
…		…
903		1085
904	=item C<EV_ASYNC>	1086	=item C<EV_ASYNC>
905		1087
906	The given async watcher has been asynchronously notified (see C<ev_async>).	1088	The given async watcher has been asynchronously notified (see C<ev_async>).
907		1089
		1090	=item C<EV_CUSTOM>
		1091
		1092	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1093	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1094
908	=item C<EV_ERROR>	1095	=item C<EV_ERROR>
909		1096
910	An unspecified error has occurred, the watcher has been stopped. This might	1097	An unspecified error has occurred, the watcher has been stopped. This might
911	happen because the watcher could not be properly started because libev	1098	happen because the watcher could not be properly started because libev
912	ran out of memory, a file descriptor was found to be closed or any other	1099	ran out of memory, a file descriptor was found to be closed or any other
…		…
949		1136
950	ev_io w;	1137	ev_io w;
951	ev_init (&w, my_cb);	1138	ev_init (&w, my_cb);
952	ev_io_set (&w, STDIN_FILENO, EV_READ);	1139	ev_io_set (&w, STDIN_FILENO, EV_READ);
953		1140
954	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1141	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
955		1142
956	This macro initialises the type-specific parts of a watcher. You need to	1143	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	1144	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	1145	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	1146	macro on a watcher that is active (it can be pending, however, which is a
…		…
972		1159
973	Example: Initialise and set an C<ev_io> watcher in one step.	1160	Example: Initialise and set an C<ev_io> watcher in one step.
974		1161
975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1162	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
976		1163
977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
978		1165
979	Starts (activates) the given watcher. Only active watchers will receive	1166	Starts (activates) the given watcher. Only active watchers will receive
980	events. If the watcher is already active nothing will happen.	1167	events. If the watcher is already active nothing will happen.
981		1168
982	Example: Start the C<ev_io> watcher that is being abused as example in this	1169	Example: Start the C<ev_io> watcher that is being abused as example in this
983	whole section.	1170	whole section.
984		1171
985	ev_io_start (EV_DEFAULT_UC, &w);	1172	ev_io_start (EV_DEFAULT_UC, &w);
986		1173
987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1174	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
988		1175
989	Stops the given watcher if active, and clears the pending status (whether	1176	Stops the given watcher if active, and clears the pending status (whether
990	the watcher was active or not).	1177	the watcher was active or not).
991		1178
992	It is possible that stopped watchers are pending - for example,	1179	It is possible that stopped watchers are pending - for example,
…		…
1017	=item ev_cb_set (ev_TYPE *watcher, callback)	1204	=item ev_cb_set (ev_TYPE *watcher, callback)
1018		1205
1019	Change the callback. You can change the callback at virtually any time	1206	Change the callback. You can change the callback at virtually any time
1020	(modulo threads).	1207	(modulo threads).
1021		1208
1022	=item ev_set_priority (ev_TYPE *watcher, priority)	1209	=item ev_set_priority (ev_TYPE *watcher, int priority)
1023		1210
1024	=item int ev_priority (ev_TYPE *watcher)	1211	=item int ev_priority (ev_TYPE *watcher)
1025		1212
1026	Set and query the priority of the watcher. The priority is a small	1213	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>	1214	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1028	(default: C<-2>). Pending watchers with higher priority will be invoked	1215	(default: C<-2>). Pending watchers with higher priority will be invoked
1029	before watchers with lower priority, but priority will not keep watchers	1216	before watchers with lower priority, but priority will not keep watchers
1030	from being executed (except for C<ev_idle> watchers).	1217	from being executed (except for C<ev_idle> watchers).
1031		1218
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	1219	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.	1220	you need to look at C<ev_idle> watchers, which provide this functionality.
1039		1221
1040	You I<must not> change the priority of a watcher as long as it is active or	1222	You I<must not> change the priority of a watcher as long as it is active or
1041	pending.	1223	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		1224
1046	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1225	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	1226	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.	1227	or might not have been clamped to the valid range.
		1228
		1229	The default priority used by watchers when no priority has been set is
		1230	always C<0>, which is supposed to not be too high and not be too low :).
		1231
		1232	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1233	priorities.
1049		1234
1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1235	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1051		1236
1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1237	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	1238	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	1245	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>.	1246	watcher isn't pending it does nothing and returns C<0>.
1062		1247
1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1248	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.	1249	callback to be invoked, which can be accomplished with this function.
		1250
		1251	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1252
		1253	Feeds the given event set into the event loop, as if the specified event
		1254	had happened for the specified watcher (which must be a pointer to an
		1255	initialised but not necessarily started event watcher). Obviously you must
		1256	not free the watcher as long as it has pending events.
		1257
		1258	Stopping the watcher, letting libev invoke it, or calling
		1259	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1260	not started in the first place.
		1261
		1262	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1263	functions that do not need a watcher.
1065		1264
1066	=back	1265	=back
1067		1266
1068		1267
1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1268	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1118	#include <stddef.h>	1317	#include <stddef.h>
1119		1318
1120	static void	1319	static void
1121	t1_cb (EV_P_ ev_timer *w, int revents)	1320	t1_cb (EV_P_ ev_timer *w, int revents)
1122	{	1321	{
1123	struct my_biggy big = (struct my_biggy *	1322	struct my_biggy big = (struct my_biggy *)
1124	(((char *)w) - offsetof (struct my_biggy, t1));	1323	(((char *)w) - offsetof (struct my_biggy, t1));
1125	}	1324	}
1126		1325
1127	static void	1326	static void
1128	t2_cb (EV_P_ ev_timer *w, int revents)	1327	t2_cb (EV_P_ ev_timer *w, int revents)
1129	{	1328	{
1130	struct my_biggy big = (struct my_biggy *	1329	struct my_biggy big = (struct my_biggy *)
1131	(((char *)w) - offsetof (struct my_biggy, t2));	1330	(((char *)w) - offsetof (struct my_biggy, t2));
1132	}	1331	}
		1332
		1333	=head2 WATCHER PRIORITY MODELS
		1334
		1335	Many event loops support I<watcher priorities>, which are usually small
		1336	integers that influence the ordering of event callback invocation
		1337	between watchers in some way, all else being equal.
		1338
		1339	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1340	description for the more technical details such as the actual priority
		1341	range.
		1342
		1343	There are two common ways how these these priorities are being interpreted
		1344	by event loops:
		1345
		1346	In the more common lock-out model, higher priorities "lock out" invocation
		1347	of lower priority watchers, which means as long as higher priority
		1348	watchers receive events, lower priority watchers are not being invoked.
		1349
		1350	The less common only-for-ordering model uses priorities solely to order
		1351	callback invocation within a single event loop iteration: Higher priority
		1352	watchers are invoked before lower priority ones, but they all get invoked
		1353	before polling for new events.
		1354
		1355	Libev uses the second (only-for-ordering) model for all its watchers
		1356	except for idle watchers (which use the lock-out model).
		1357
		1358	The rationale behind this is that implementing the lock-out model for
		1359	watchers is not well supported by most kernel interfaces, and most event
		1360	libraries will just poll for the same events again and again as long as
		1361	their callbacks have not been executed, which is very inefficient in the
		1362	common case of one high-priority watcher locking out a mass of lower
		1363	priority ones.
		1364
		1365	Static (ordering) priorities are most useful when you have two or more
		1366	watchers handling the same resource: a typical usage example is having an
		1367	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1368	timeouts. Under load, data might be received while the program handles
		1369	other jobs, but since timers normally get invoked first, the timeout
		1370	handler will be executed before checking for data. In that case, giving
		1371	the timer a lower priority than the I/O watcher ensures that I/O will be
		1372	handled first even under adverse conditions (which is usually, but not
		1373	always, what you want).
		1374
		1375	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1376	will only be executed when no same or higher priority watchers have
		1377	received events, they can be used to implement the "lock-out" model when
		1378	required.
		1379
		1380	For example, to emulate how many other event libraries handle priorities,
		1381	you can associate an C<ev_idle> watcher to each such watcher, and in
		1382	the normal watcher callback, you just start the idle watcher. The real
		1383	processing is done in the idle watcher callback. This causes libev to
		1384	continously poll and process kernel event data for the watcher, but when
		1385	the lock-out case is known to be rare (which in turn is rare :), this is
		1386	workable.
		1387
		1388	Usually, however, the lock-out model implemented that way will perform
		1389	miserably under the type of load it was designed to handle. In that case,
		1390	it might be preferable to stop the real watcher before starting the
		1391	idle watcher, so the kernel will not have to process the event in case
		1392	the actual processing will be delayed for considerable time.
		1393
		1394	Here is an example of an I/O watcher that should run at a strictly lower
		1395	priority than the default, and which should only process data when no
		1396	other events are pending:
		1397
		1398	ev_idle idle; // actual processing watcher
		1399	ev_io io; // actual event watcher
		1400
		1401	static void
		1402	io_cb (EV_P_ ev_io *w, int revents)
		1403	{
		1404	// stop the I/O watcher, we received the event, but
		1405	// are not yet ready to handle it.
		1406	ev_io_stop (EV_A_ w);
		1407
		1408	// start the idle watcher to ahndle the actual event.
		1409	// it will not be executed as long as other watchers
		1410	// with the default priority are receiving events.
		1411	ev_idle_start (EV_A_ &idle);
		1412	}
		1413
		1414	static void
		1415	idle_cb (EV_P_ ev_idle *w, int revents)
		1416	{
		1417	// actual processing
		1418	read (STDIN_FILENO, ...);
		1419
		1420	// have to start the I/O watcher again, as
		1421	// we have handled the event
		1422	ev_io_start (EV_P_ &io);
		1423	}
		1424
		1425	// initialisation
		1426	ev_idle_init (&idle, idle_cb);
		1427	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1428	ev_io_start (EV_DEFAULT_ &io);
		1429
		1430	In the "real" world, it might also be beneficial to start a timer, so that
		1431	low-priority connections can not be locked out forever under load. This
		1432	enables your program to keep a lower latency for important connections
		1433	during short periods of high load, while not completely locking out less
		1434	important ones.
1133		1435
1134		1436
1135	=head1 WATCHER TYPES	1437	=head1 WATCHER TYPES
1136		1438
1137	This section describes each watcher in detail, but will not repeat	1439	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	1465	descriptors to non-blocking mode is also usually a good idea (but not
1164	required if you know what you are doing).	1466	required if you know what you are doing).
1165		1467
1166	If you cannot use non-blocking mode, then force the use of a	1468	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	1469	known-to-be-good backend (at the time of this writing, this includes only
1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1470	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1471	descriptors for which non-blocking operation makes no sense (such as
		1472	files) - libev doesn't guarentee any specific behaviour in that case.
1169		1473
1170	Another thing you have to watch out for is that it is quite easy to	1474	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	1475	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	1476	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	1477	because there is no data. Not only are some backends known to create a
…		…
1238		1542
1239	So when you encounter spurious, unexplained daemon exits, make sure you	1543	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	1544	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).	1545	somewhere, as that would have given you a big clue).
1242		1546
		1547	=head3 The special problem of accept()ing when you can't
		1548
		1549	Many implementations of the POSIX C<accept> function (for example,
		1550	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1551	connection from the pending queue in all error cases.
		1552
		1553	For example, larger servers often run out of file descriptors (because
		1554	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1555	rejecting the connection, leading to libev signalling readiness on
		1556	the next iteration again (the connection still exists after all), and
		1557	typically causing the program to loop at 100% CPU usage.
		1558
		1559	Unfortunately, the set of errors that cause this issue differs between
		1560	operating systems, there is usually little the app can do to remedy the
		1561	situation, and no known thread-safe method of removing the connection to
		1562	cope with overload is known (to me).
		1563
		1564	One of the easiest ways to handle this situation is to just ignore it
		1565	- when the program encounters an overload, it will just loop until the
		1566	situation is over. While this is a form of busy waiting, no OS offers an
		1567	event-based way to handle this situation, so it's the best one can do.
		1568
		1569	A better way to handle the situation is to log any errors other than
		1570	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1571	messages, and continue as usual, which at least gives the user an idea of
		1572	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1573	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1574	usage.
		1575
		1576	If your program is single-threaded, then you could also keep a dummy file
		1577	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1578	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1579	close that fd, and create a new dummy fd. This will gracefully refuse
		1580	clients under typical overload conditions.
		1581
		1582	The last way to handle it is to simply log the error and C<exit>, as
		1583	is often done with C<malloc> failures, but this results in an easy
		1584	opportunity for a DoS attack.
1243		1585
1244	=head3 Watcher-Specific Functions	1586	=head3 Watcher-Specific Functions
1245		1587
1246	=over 4	1588	=over 4
1247		1589
…		…
1294	year, it will still time out after (roughly) one hour. "Roughly" because	1636	year, it will still time out after (roughly) one hour. "Roughly" because
1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1637	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1296	monotonic clock option helps a lot here).	1638	monotonic clock option helps a lot here).
1297		1639
1298	The callback is guaranteed to be invoked only I<after> its timeout has	1640	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	1641	passed (not I<at>, so on systems with very low-resolution clocks this
1300	then order of execution is undefined.	1642	might introduce a small delay). If multiple timers become ready during the
		1643	same loop iteration then the ones with earlier time-out values are invoked
		1644	before ones of the same priority with later time-out values (but this is
		1645	no longer true when a callback calls C<ev_loop> recursively).
1301		1646
1302	=head3 Be smart about timeouts	1647	=head3 Be smart about timeouts
1303		1648
1304	Many real-world problems involve some kind of timeout, usually for error	1649	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,	1650	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>	1694	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1350	member and C<ev_timer_again>.	1695	member and C<ev_timer_again>.
1351		1696
1352	At start:	1697	At start:
1353		1698
1354	ev_timer_init (timer, callback);	1699	ev_init (timer, callback);
1355	timer->repeat = 60.;	1700	timer->repeat = 60.;
1356	ev_timer_again (loop, timer);	1701	ev_timer_again (loop, timer);
1357		1702
1358	Each time there is some activity:	1703	Each time there is some activity:
1359		1704
…		…
1398	else	1743	else
1399	{	1744	{
1400	// callback was invoked, but there was some activity, re-arm	1745	// callback was invoked, but there was some activity, re-arm
1401	// the watcher to fire in last_activity + 60, which is	1746	// the watcher to fire in last_activity + 60, which is
1402	// guaranteed to be in the future, so "again" is positive:	1747	// guaranteed to be in the future, so "again" is positive:
1403	w->again = timeout - now;	1748	w->repeat = timeout - now;
1404	ev_timer_again (EV_A_ w);	1749	ev_timer_again (EV_A_ w);
1405	}	1750	}
1406	}	1751	}
1407		1752
1408	To summarise the callback: first calculate the real timeout (defined	1753	To summarise the callback: first calculate the real timeout (defined
…		…
1421		1766
1422	To start the timer, simply initialise the watcher and set C<last_activity>	1767	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	1768	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:	1769	callback, which will "do the right thing" and start the timer:
1425		1770
1426	ev_timer_init (timer, callback);	1771	ev_init (timer, callback);
1427	last_activity = ev_now (loop);	1772	last_activity = ev_now (loop);
1428	callback (loop, timer, EV_TIMEOUT);	1773	callback (loop, timer, EV_TIMER);
1429		1774
1430	And when there is some activity, simply store the current time in	1775	And when there is some activity, simply store the current time in
1431	C<last_activity>, no libev calls at all:	1776	C<last_activity>, no libev calls at all:
1432		1777
1433	last_actiivty = ev_now (loop);	1778	last_actiivty = ev_now (loop);
…		…
1492		1837
1493	If the event loop is suspended for a long time, you can also force an	1838	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	1839	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1495	()>.	1840	()>.
1496		1841
		1842	=head3 The special problems of suspended animation
		1843
		1844	When you leave the server world it is quite customary to hit machines that
		1845	can suspend/hibernate - what happens to the clocks during such a suspend?
		1846
		1847	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1848	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1849	to run until the system is suspended, but they will not advance while the
		1850	system is suspended. That means, on resume, it will be as if the program
		1851	was frozen for a few seconds, but the suspend time will not be counted
		1852	towards C<ev_timer> when a monotonic clock source is used. The real time
		1853	clock advanced as expected, but if it is used as sole clocksource, then a
		1854	long suspend would be detected as a time jump by libev, and timers would
		1855	be adjusted accordingly.
		1856
		1857	I would not be surprised to see different behaviour in different between
		1858	operating systems, OS versions or even different hardware.
		1859
		1860	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1861	time jump in the monotonic clocks and the realtime clock. If the program
		1862	is suspended for a very long time, and monotonic clock sources are in use,
		1863	then you can expect C<ev_timer>s to expire as the full suspension time
		1864	will be counted towards the timers. When no monotonic clock source is in
		1865	use, then libev will again assume a timejump and adjust accordingly.
		1866
		1867	It might be beneficial for this latter case to call C<ev_suspend>
		1868	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1869	deterministic behaviour in this case (you can do nothing against
		1870	C<SIGSTOP>).
		1871
1497	=head3 Watcher-Specific Functions and Data Members	1872	=head3 Watcher-Specific Functions and Data Members
1498		1873
1499	=over 4	1874	=over 4
1500		1875
1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1876	=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).	1899	If the timer is started but non-repeating, stop it (as if it timed out).
1525		1900
1526	If the timer is repeating, either start it if necessary (with the	1901	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.	1902	C<repeat> value), or reset the running timer to the C<repeat> value.
1528		1903
1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1904	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1530	usage example.	1905	usage example.
		1906
		1907	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1908
		1909	Returns the remaining time until a timer fires. If the timer is active,
		1910	then this time is relative to the current event loop time, otherwise it's
		1911	the timeout value currently configured.
		1912
		1913	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1914	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1915	will return C<4>. When the timer expires and is restarted, it will return
		1916	roughly C<7> (likely slightly less as callback invocation takes some time,
		1917	too), and so on.
1531		1918
1532	=item ev_tstamp repeat [read-write]	1919	=item ev_tstamp repeat [read-write]
1533		1920
1534	The current C<repeat> value. Will be used each time the watcher times out	1921	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),	1922	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1573	=head2 C<ev_periodic> - to cron or not to cron?	1960	=head2 C<ev_periodic> - to cron or not to cron?
1574		1961
1575	Periodic watchers are also timers of a kind, but they are very versatile	1962	Periodic watchers are also timers of a kind, but they are very versatile
1576	(and unfortunately a bit complex).	1963	(and unfortunately a bit complex).
1577		1964
1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1965	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	1966	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	1967	(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 ()	1968	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	1969	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	1970	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		1971
		1972	You can tell a periodic watcher to trigger after some specific point
		1973	in time: for example, if you tell a periodic watcher to trigger "in 10
		1974	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1975	not a delay) and then reset your system clock to January of the previous
		1976	year, then it will take a year or more to trigger the event (unlike an
		1977	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1978	it, as it uses a relative timeout).
		1979
1587	C<ev_periodic>s can also be used to implement vastly more complex timers,	1980	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	1981	timers, such as triggering an event on each "midnight, local time", or
1589	complicated rules.	1982	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1983	those cannot react to time jumps.
1590		1984
1591	As with timers, the callback is guaranteed to be invoked only when the	1985	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	1986	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.	1987	timers become ready during the same loop iteration then the ones with
		1988	earlier time-out values are invoked before ones with later time-out values
		1989	(but this is no longer true when a callback calls C<ev_loop> recursively).
1594		1990
1595	=head3 Watcher-Specific Functions and Data Members	1991	=head3 Watcher-Specific Functions and Data Members
1596		1992
1597	=over 4	1993	=over 4
1598		1994
1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1995	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1600		1996
1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1997	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1602		1998
1603	Lots of arguments, lets sort it out... There are basically three modes of	1999	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:	2000	operation, and we will explain them from simplest to most complex:
1605		2001
1606	=over 4	2002	=over 4
1607		2003
1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2004	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1609		2005
1610	In this configuration the watcher triggers an event after the wall clock	2006	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	2007	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	2008	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.	2009	will be stopped and invoked when the system clock reaches or surpasses
		2010	this point in time.
1614		2011
1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2012	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1616		2013
1617	In this mode the watcher will always be scheduled to time out at the next	2014	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)	2015	C<offset + N * interval> time (for some integer N, which can also be
1619	and then repeat, regardless of any time jumps.	2016	negative) and then repeat, regardless of any time jumps. The C<offset>
		2017	argument is merely an offset into the C<interval> periods.
1620		2018
1621	This can be used to create timers that do not drift with respect to the	2019	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	2020	system clock, for example, here is an C<ev_periodic> that triggers each
1623	hour, on the hour:	2021	hour, on the hour (with respect to UTC):
1624		2022
1625	ev_periodic_set (&periodic, 0., 3600., 0);	2023	ev_periodic_set (&periodic, 0., 3600., 0);
1626		2024
1627	This doesn't mean there will always be 3600 seconds in between triggers,	2025	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	2026	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	2027	full hour (UTC), or more correctly, when the system time is evenly divisible
1630	by 3600.	2028	by 3600.
1631		2029
1632	Another way to think about it (for the mathematically inclined) is that	2030	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	2031	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.	2032	time where C<time = offset (mod interval)>, regardless of any time jumps.
1635		2033
1636	For numerical stability it is preferable that the C<at> value is near	2034	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	2035	C<ev_now ()> (the current time), but there is no range requirement for
1638	this value, and in fact is often specified as zero.	2036	this value, and in fact is often specified as zero.
1639		2037
1640	Note also that there is an upper limit to how often a timer can fire (CPU	2038	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	2039	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	2040	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).	2041	millisecond (if the OS supports it and the machine is fast enough).
1644		2042
1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2043	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1646		2044
1647	In this mode the values for C<interval> and C<at> are both being	2045	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	2046	ignored. Instead, each time the periodic watcher gets scheduled, the
1649	reschedule callback will be called with the watcher as first, and the	2047	reschedule callback will be called with the watcher as first, and the
1650	current time as second argument.	2048	current time as second argument.
1651		2049
1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2050	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1653	ever, or make ANY event loop modifications whatsoever>.	2051	or make ANY other event loop modifications whatsoever, unless explicitly
		2052	allowed by documentation here>.
1654		2053
1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2054	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	2055	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1657	only event loop modification you are allowed to do).	2056	only event loop modification you are allowed to do).
1658		2057
…		…
1688	a different time than the last time it was called (e.g. in a crond like	2087	a different time than the last time it was called (e.g. in a crond like
1689	program when the crontabs have changed).	2088	program when the crontabs have changed).
1690		2089
1691	=item ev_tstamp ev_periodic_at (ev_periodic *)	2090	=item ev_tstamp ev_periodic_at (ev_periodic *)
1692		2091
1693	When active, returns the absolute time that the watcher is supposed to	2092	When active, returns the absolute time that the watcher is supposed
1694	trigger next.	2093	to trigger next. This is not the same as the C<offset> argument to
		2094	C<ev_periodic_set>, but indeed works even in interval and manual
		2095	rescheduling modes.
1695		2096
1696	=item ev_tstamp offset [read-write]	2097	=item ev_tstamp offset [read-write]
1697		2098
1698	When repeating, this contains the offset value, otherwise this is the	2099	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>).	2100	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2101	although libev might modify this value for better numerical stability).
1700		2102
1701	Can be modified any time, but changes only take effect when the periodic	2103	Can be modified any time, but changes only take effect when the periodic
1702	timer fires or C<ev_periodic_again> is being called.	2104	timer fires or C<ev_periodic_again> is being called.
1703		2105
1704	=item ev_tstamp interval [read-write]	2106	=item ev_tstamp interval [read-write]
…		…
1756	Signal watchers will trigger an event when the process receives a specific	2158	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	2159	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	2160	will try it's best to deliver signals synchronously, i.e. as part of the
1759	normal event processing, like any other event.	2161	normal event processing, like any other event.
1760		2162
1761	If you want signals asynchronously, just use C<sigaction> as you would	2163	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	2164	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.	2165	the signal. You can even use C<ev_async> from a signal handler to
		2166	synchronously wake up an event loop.
1764		2167
1765	You can configure as many watchers as you like per signal. Only when the	2168	You can configure as many watchers as you like for the same signal, but
		2169	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2170	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2171	C<SIGINT> in both the default loop and another loop at the same time. At
		2172	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2173
1766	first watcher gets started will libev actually register a signal handler	2174	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	2175	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	2176	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		2177
1772	If possible and supported, libev will install its handlers with	2178	If possible and supported, libev will install its handlers with
1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2179	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1774	interrupted. If you have a problem with system calls getting interrupted by	2180	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	2181	interrupted by signals you can block all signals in an C<ev_check> watcher
1776	them in an C<ev_prepare> watcher.	2182	and unblock them in an C<ev_prepare> watcher.
		2183
		2184	=head3 The special problem of inheritance over fork/execve/pthread_create
		2185
		2186	Both the signal mask (C<sigprocmask>) and the signal disposition
		2187	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2188	stopping it again), that is, libev might or might not block the signal,
		2189	and might or might not set or restore the installed signal handler.
		2190
		2191	While this does not matter for the signal disposition (libev never
		2192	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2193	C<execve>), this matters for the signal mask: many programs do not expect
		2194	certain signals to be blocked.
		2195
		2196	This means that before calling C<exec> (from the child) you should reset
		2197	the signal mask to whatever "default" you expect (all clear is a good
		2198	choice usually).
		2199
		2200	The simplest way to ensure that the signal mask is reset in the child is
		2201	to install a fork handler with C<pthread_atfork> that resets it. That will
		2202	catch fork calls done by libraries (such as the libc) as well.
		2203
		2204	In current versions of libev, the signal will not be blocked indefinitely
		2205	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2206	the window of opportunity for problems, it will not go away, as libev
		2207	I<has> to modify the signal mask, at least temporarily.
		2208
		2209	So I can't stress this enough: I<If you do not reset your signal mask when
		2210	you expect it to be empty, you have a race condition in your code>. This
		2211	is not a libev-specific thing, this is true for most event libraries.
1777		2212
1778	=head3 Watcher-Specific Functions and Data Members	2213	=head3 Watcher-Specific Functions and Data Members
1779		2214
1780	=over 4	2215	=over 4
1781		2216
…		…
1813	some child status changes (most typically when a child of yours dies or	2248	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	2249	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	2250	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.,	2251	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,	2252	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	2253	but forking and registering a watcher a few event loop iterations later or
1819	not.	2254	in the next callback invocation is not.
1820		2255
1821	Only the default event loop is capable of handling signals, and therefore	2256	Only the default event loop is capable of handling signals, and therefore
1822	you can only register child watchers in the default event loop.	2257	you can only register child watchers in the default event loop.
1823		2258
		2259	Due to some design glitches inside libev, child watchers will always be
		2260	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2261	libev)
		2262
1824	=head3 Process Interaction	2263	=head3 Process Interaction
1825		2264
1826	Libev grabs C<SIGCHLD> as soon as the default event loop is	2265	Libev grabs C<SIGCHLD> as soon as the default event loop is
1827	initialised. This is necessary to guarantee proper behaviour even if	2266	initialised. This is necessary to guarantee proper behaviour even if the
1828	the first child watcher is started after the child exits. The occurrence	2267	first child watcher is started after the child exits. The occurrence
1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2268	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1830	synchronously as part of the event loop processing. Libev always reaps all	2269	synchronously as part of the event loop processing. Libev always reaps all
1831	children, even ones not watched.	2270	children, even ones not watched.
1832		2271
1833	=head3 Overriding the Built-In Processing	2272	=head3 Overriding the Built-In Processing
…		…
1843	=head3 Stopping the Child Watcher	2282	=head3 Stopping the Child Watcher
1844		2283
1845	Currently, the child watcher never gets stopped, even when the	2284	Currently, the child watcher never gets stopped, even when the
1846	child terminates, so normally one needs to stop the watcher in the	2285	child terminates, so normally one needs to stop the watcher in the
1847	callback. Future versions of libev might stop the watcher automatically	2286	callback. Future versions of libev might stop the watcher automatically
1848	when a child exit is detected.	2287	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2288	problem).
1849		2289
1850	=head3 Watcher-Specific Functions and Data Members	2290	=head3 Watcher-Specific Functions and Data Members
1851		2291
1852	=over 4	2292	=over 4
1853		2293
…		…
1910		2350
1911		2351
1912	=head2 C<ev_stat> - did the file attributes just change?	2352	=head2 C<ev_stat> - did the file attributes just change?
1913		2353
1914	This watches a file system path for attribute changes. That is, it calls	2354	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	2355	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.	2356	and sees if it changed compared to the last time, invoking the callback if
		2357	it did.
1917		2358
1918	The path does not need to exist: changing from "path exists" to "path does	2359	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	2360	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	2361	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	2362	C<st_nlink> field being zero (which is otherwise always forced to be at
1922	the stat buffer having unspecified contents.	2363	least one) and all the other fields of the stat buffer having unspecified
		2364	contents.
1923		2365
1924	The path I<should> be absolute and I<must not> end in a slash. If it is	2366	The path I<must not> end in a slash or contain special components such as
		2367	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.	2368	your working directory changes, then the behaviour is undefined.
1926		2369
1927	Since there is no standard kernel interface to do this, the portable	2370	Since there is no portable change notification interface available, the
1928	implementation simply calls C<stat (2)> regularly on the path to see if	2371	portable implementation simply calls C<stat(2)> regularly on the path
1929	it changed somehow. You can specify a recommended polling interval for	2372	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!)	2373	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	2374	recommended!) then a I<suitable, unspecified default> value will be used
1932	you can expect to be around five seconds, although this might change	2375	(which you can expect to be around five seconds, although this might
1933	dynamically). Libev will also impose a minimum interval which is currently	2376	change dynamically). Libev will also impose a minimum interval which is
1934	around C<0.1>, but thats usually overkill.	2377	currently around C<0.1>, but that's usually overkill.
1935		2378
1936	This watcher type is not meant for massive numbers of stat watchers,	2379	This watcher type is not meant for massive numbers of stat watchers,
1937	as even with OS-supported change notifications, this can be	2380	as even with OS-supported change notifications, this can be
1938	resource-intensive.	2381	resource-intensive.
1939		2382
1940	At the time of this writing, the only OS-specific interface implemented	2383	At the time of this writing, the only OS-specific interface implemented
1941	is the Linux inotify interface (implementing kqueue support is left as	2384	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	2385	exercise for the reader. Note, however, that the author sees no way of
1943	of implementing C<ev_stat> semantics with kqueue).	2386	implementing C<ev_stat> semantics with kqueue, except as a hint).
1944		2387
1945	=head3 ABI Issues (Largefile Support)	2388	=head3 ABI Issues (Largefile Support)
1946		2389
1947	Libev by default (unless the user overrides this) uses the default	2390	Libev by default (unless the user overrides this) uses the default
1948	compilation environment, which means that on systems with large file	2391	compilation environment, which means that on systems with large file
1949	support disabled by default, you get the 32 bit version of the stat	2392	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	2393	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	2394	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	2395	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	2396	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.	2397	most noticeably displayed with ev_stat and large file support.
1955		2398
1956	The solution for this is to lobby your distribution maker to make large	2399	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	2400	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	2401	optional. Libev cannot simply switch on large file support because it has
1959	to exchange stat structures with application programs compiled using the	2402	to exchange stat structures with application programs compiled using the
1960	default compilation environment.	2403	default compilation environment.
1961		2404
1962	=head3 Inotify and Kqueue	2405	=head3 Inotify and Kqueue
1963		2406
1964	When C<inotify (7)> support has been compiled into libev (generally	2407	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	2408	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	2409	inotify descriptor will be created lazily when the first C<ev_stat>
1967	change detection where possible. The inotify descriptor will be created	2410	watcher is being started.
1968	lazily when the first C<ev_stat> watcher is being started.
1969		2411
1970	Inotify presence does not change the semantics of C<ev_stat> watchers	2412	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	2413	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	2414	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,	2415	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.	2416	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2417	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2418	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2419	xfs are fully working) libev usually gets away without polling.
1975		2420
1976	There is no support for kqueue, as apparently it cannot be used to	2421	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	2422	implement this functionality, due to the requirement of having a file
1978	descriptor open on the object at all times, and detecting renames, unlinks	2423	descriptor open on the object at all times, and detecting renames, unlinks
1979	etc. is difficult.	2424	etc. is difficult.
1980		2425
		2426	=head3 C<stat ()> is a synchronous operation
		2427
		2428	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2429	the process. The exception are C<ev_stat> watchers - those call C<stat
		2430	()>, which is a synchronous operation.
		2431
		2432	For local paths, this usually doesn't matter: unless the system is very
		2433	busy or the intervals between stat's are large, a stat call will be fast,
		2434	as the path data is usually in memory already (except when starting the
		2435	watcher).
		2436
		2437	For networked file systems, calling C<stat ()> can block an indefinite
		2438	time due to network issues, and even under good conditions, a stat call
		2439	often takes multiple milliseconds.
		2440
		2441	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2442	paths, although this is fully supported by libev.
		2443
1981	=head3 The special problem of stat time resolution	2444	=head3 The special problem of stat time resolution
1982		2445
1983	The C<stat ()> system call only supports full-second resolution portably, and	2446	The C<stat ()> system call only supports full-second resolution portably,
1984	even on systems where the resolution is higher, most file systems still	2447	and even on systems where the resolution is higher, most file systems
1985	only support whole seconds.	2448	still only support whole seconds.
1986		2449
1987	That means that, if the time is the only thing that changes, you can	2450	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	2451	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	2452	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	2453	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2133		2596
2134	=head3 Watcher-Specific Functions and Data Members	2597	=head3 Watcher-Specific Functions and Data Members
2135		2598
2136	=over 4	2599	=over 4
2137		2600
2138	=item ev_idle_init (ev_signal *, callback)	2601	=item ev_idle_init (ev_idle *, callback)
2139		2602
2140	Initialises and configures the idle watcher - it has no parameters of any	2603	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,	2604	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2142	believe me.	2605	believe me.
2143		2606
…		…
2156	// no longer anything immediate to do.	2619	// no longer anything immediate to do.
2157	}	2620	}
2158		2621
2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2622	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2160	ev_idle_init (idle_watcher, idle_cb);	2623	ev_idle_init (idle_watcher, idle_cb);
2161	ev_idle_start (loop, idle_cb);	2624	ev_idle_start (loop, idle_watcher);
2162		2625
2163		2626
2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2627	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2165		2628
2166	Prepare and check watchers are usually (but not always) used in pairs:	2629	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2259	struct pollfd fds [nfd];	2722	struct pollfd fds [nfd];
2260	// actual code will need to loop here and realloc etc.	2723	// actual code will need to loop here and realloc etc.
2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2724	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2262		2725
2263	/* the callback is illegal, but won't be called as we stop during check */	2726	/* the callback is illegal, but won't be called as we stop during check */
2264	ev_timer_init (&tw, 0, timeout * 1e-3);	2727	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2265	ev_timer_start (loop, &tw);	2728	ev_timer_start (loop, &tw);
2266		2729
2267	// create one ev_io per pollfd	2730	// create one ev_io per pollfd
2268	for (int i = 0; i < nfd; ++i)	2731	for (int i = 0; i < nfd; ++i)
2269	{	2732	{
…		…
2382	some fds have to be watched and handled very quickly (with low latency),	2845	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	2846	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	2847	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.	2848	the rest in a second one, and embed the second one in the first.
2386		2849
2387	As long as the watcher is active, the callback will be invoked every time	2850	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	2851	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	2852	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	2853	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	2854	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	2855	to give the embedded loop strictly lower priority for example).
2393	embedded loop sweep.
2394		2856
2395	As long as the watcher is started it will automatically handle events. The	2857	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	2858	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		2859
2400	Also, there have not currently been made special provisions for forking:	2860	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,	2861	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	2862	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,	2863	C<ev_loop_fork> on the embedded loop.
2404	and future versions of libev might do just that.
2405		2864
2406	Unfortunately, not all backends are embeddable: only the ones returned by	2865	Unfortunately, not all backends are embeddable: only the ones returned by
2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2866	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2408	portable one.	2867	portable one.
2409		2868
…		…
2503	event loop blocks next and before C<ev_check> watchers are being called,	2962	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	2963	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	2964	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2506	handlers will be invoked, too, of course.	2965	handlers will be invoked, too, of course.
2507		2966
		2967	=head3 The special problem of life after fork - how is it possible?
		2968
		2969	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2970	up/change the process environment, followed by a call to C<exec()>. This
		2971	sequence should be handled by libev without any problems.
		2972
		2973	This changes when the application actually wants to do event handling
		2974	in the child, or both parent in child, in effect "continuing" after the
		2975	fork.
		2976
		2977	The default mode of operation (for libev, with application help to detect
		2978	forks) is to duplicate all the state in the child, as would be expected
		2979	when I<either> the parent I<or> the child process continues.
		2980
		2981	When both processes want to continue using libev, then this is usually the
		2982	wrong result. In that case, usually one process (typically the parent) is
		2983	supposed to continue with all watchers in place as before, while the other
		2984	process typically wants to start fresh, i.e. without any active watchers.
		2985
		2986	The cleanest and most efficient way to achieve that with libev is to
		2987	simply create a new event loop, which of course will be "empty", and
		2988	use that for new watchers. This has the advantage of not touching more
		2989	memory than necessary, and thus avoiding the copy-on-write, and the
		2990	disadvantage of having to use multiple event loops (which do not support
		2991	signal watchers).
		2992
		2993	When this is not possible, or you want to use the default loop for
		2994	other reasons, then in the process that wants to start "fresh", call
		2995	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2996	the default loop will "orphan" (not stop) all registered watchers, so you
		2997	have to be careful not to execute code that modifies those watchers. Note
		2998	also that in that case, you have to re-register any signal watchers.
		2999
2508	=head3 Watcher-Specific Functions and Data Members	3000	=head3 Watcher-Specific Functions and Data Members
2509		3001
2510	=over 4	3002	=over 4
2511		3003
2512	=item ev_fork_init (ev_signal *, callback)	3004	=item ev_fork_init (ev_signal *, callback)
…		…
2541	=head3 Queueing	3033	=head3 Queueing
2542		3034
2543	C<ev_async> does not support queueing of data in any way. The reason	3035	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	3036	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	3037	multiple-writer-single-reader queue that works in all cases and doesn't
2546	need elaborate support such as pthreads.	3038	need elaborate support such as pthreads or unportable memory access
		3039	semantics.
2547		3040
2548	That means that if you want to queue data, you have to provide your own	3041	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	3042	queue. But at least I can tell you how to implement locking around your
2550	queue:	3043	queue:
2551		3044
…		…
2629	=over 4	3122	=over 4
2630		3123
2631	=item ev_async_init (ev_async *, callback)	3124	=item ev_async_init (ev_async *, callback)
2632		3125
2633	Initialises and configures the async watcher - it has no parameters of any	3126	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,	3127	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2635	trust me.	3128	trust me.
2636		3129
2637	=item ev_async_send (loop, ev_async *)	3130	=item ev_async_send (loop, ev_async *)
2638		3131
2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3132	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	3133	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	3134	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	3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2643	section below on what exactly this means).	3136	section below on what exactly this means).
2644		3137
		3138	Note that, as with other watchers in libev, multiple events might get
		3139	compressed into a single callback invocation (another way to look at this
		3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3141	reset when the event loop detects that).
		3142
2645	This call incurs the overhead of a system call only once per loop iteration,	3143	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	3144	iteration, so while the overhead might be noticeable, it doesn't apply to
2647	calls to C<ev_async_send>.	3145	repeated calls to C<ev_async_send> for the same event loop.
2648		3146
2649	=item bool = ev_async_pending (ev_async *)	3147	=item bool = ev_async_pending (ev_async *)
2650		3148
2651	Returns a non-zero value when C<ev_async_send> has been called on the	3149	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	3150	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	3153	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,	3154	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	3155	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.	3156	quickly check whether invoking the loop might be a good idea.
2659		3157
2660	Not that this does I<not> check whether the watcher itself is pending, only	3158	Not that this does I<not> check whether the watcher itself is pending,
2661	whether it has been requested to make this watcher pending.	3159	only whether it has been requested to make this watcher pending: there
		3160	is a time window between the event loop checking and resetting the async
		3161	notification, and the callback being invoked.
2662		3162
2663	=back	3163	=back
2664		3164
2665		3165
2666	=head1 OTHER FUNCTIONS	3166	=head1 OTHER FUNCTIONS
…		…
2683		3183
2684	If C<timeout> is less than 0, then no timeout watcher will be	3184	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	3185	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2686	repeat = 0) will be started. C<0> is a valid timeout.	3186	repeat = 0) will be started. C<0> is a valid timeout.
2687		3187
2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3188	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	3189	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>	3190	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>	3191	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	3192	a timeout and an io event at the same time - you probably should give io
2693	events precedence.	3193	events precedence.
2694		3194
2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3195	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2696		3196
2697	static void stdin_ready (int revents, void *arg)	3197	static void stdin_ready (int revents, void *arg)
2698	{	3198	{
2699	if (revents & EV_READ)	3199	if (revents & EV_READ)
2700	/* stdin might have data for us, joy! */;	3200	/* stdin might have data for us, joy! */;
2701	else if (revents & EV_TIMEOUT)	3201	else if (revents & EV_TIMER)
2702	/* doh, nothing entered */;	3202	/* doh, nothing entered */;
2703	}	3203	}
2704		3204
2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2706		3206
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)	3207	=item ev_feed_fd_event (loop, int fd, int revents)
2714		3208
2715	Feed an event on the given fd, as if a file descriptor backend detected	3209	Feed an event on the given fd, as if a file descriptor backend detected
2716	the given events it.	3210	the given events it.
2717		3211
2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3212	=item ev_feed_signal_event (loop, int signum)
2719		3213
2720	Feed an event as if the given signal occurred (C<loop> must be the default	3214	Feed an event as if the given signal occurred (C<loop> must be the default
2721	loop!).	3215	loop!).
2722		3216
2723	=back	3217	=back
…		…
2803		3297
2804	=over 4	3298	=over 4
2805		3299
2806	=item ev::TYPE::TYPE ()	3300	=item ev::TYPE::TYPE ()
2807		3301
2808	=item ev::TYPE::TYPE (struct ev_loop *)	3302	=item ev::TYPE::TYPE (loop)
2809		3303
2810	=item ev::TYPE::~TYPE	3304	=item ev::TYPE::~TYPE
2811		3305
2812	The constructor (optionally) takes an event loop to associate the watcher	3306	The constructor (optionally) takes an event loop to associate the watcher
2813	with. If it is omitted, it will use C<EV_DEFAULT>.	3307	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2845		3339
2846	myclass obj;	3340	myclass obj;
2847	ev::io iow;	3341	ev::io iow;
2848	iow.set <myclass, &myclass::io_cb> (&obj);	3342	iow.set <myclass, &myclass::io_cb> (&obj);
2849		3343
		3344	=item w->set (object *)
		3345
		3346	This is an B<experimental> feature that might go away in a future version.
		3347
		3348	This is a variation of a method callback - leaving out the method to call
		3349	will default the method to C<operator ()>, which makes it possible to use
		3350	functor objects without having to manually specify the C<operator ()> all
		3351	the time. Incidentally, you can then also leave out the template argument
		3352	list.
		3353
		3354	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3355	int revents)>.
		3356
		3357	See the method-C<set> above for more details.
		3358
		3359	Example: use a functor object as callback.
		3360
		3361	struct myfunctor
		3362	{
		3363	void operator() (ev::io &w, int revents)
		3364	{
		3365	...
		3366	}
		3367	}
		3368
		3369	myfunctor f;
		3370
		3371	ev::io w;
		3372	w.set (&f);
		3373
2850	=item w->set<function> (void *data = 0)	3374	=item w->set<function> (void *data = 0)
2851		3375
2852	Also sets a callback, but uses a static method or plain function as	3376	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	3377	callback. The optional C<data> argument will be stored in the watcher's
2854	C<data> member and is free for you to use.	3378	C<data> member and is free for you to use.
…		…
2860	Example: Use a plain function as callback.	3384	Example: Use a plain function as callback.
2861		3385
2862	static void io_cb (ev::io &w, int revents) { }	3386	static void io_cb (ev::io &w, int revents) { }
2863	iow.set <io_cb> ();	3387	iow.set <io_cb> ();
2864		3388
2865	=item w->set (struct ev_loop *)	3389	=item w->set (loop)
2866		3390
2867	Associates a different C<struct ev_loop> with this watcher. You can only	3391	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).	3392	do this when the watcher is inactive (and not pending either).
2869		3393
2870	=item w->set ([arguments])	3394	=item w->set ([arguments])
…		…
2940	L<http://software.schmorp.de/pkg/EV>.	3464	L<http://software.schmorp.de/pkg/EV>.
2941		3465
2942	=item Python	3466	=item Python
2943		3467
2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3468	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	3469	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		3470
2951	=item Ruby	3471	=item Ruby
2952		3472
2953	Tony Arcieri has written a ruby extension that offers access to a subset	3473	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	3474	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	3475	more on top of it. It can be found via gem servers. Its homepage is at
2956	L<http://rev.rubyforge.org/>.	3476	L<http://rev.rubyforge.org/>.
2957		3477
		3478	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3479	makes rev work even on mingw.
		3480
		3481	=item Haskell
		3482
		3483	A haskell binding to libev is available at
		3484	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3485
2958	=item D	3486	=item D
2959		3487
2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3488	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>.	3489	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2962		3490
2963	=item Ocaml	3491	=item Ocaml
2964		3492
2965	Erkki Seppala has written Ocaml bindings for libev, to be found at	3493	Erkki Seppala has written Ocaml bindings for libev, to be found at
2966	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3494	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3495
		3496	=item Lua
		3497
		3498	Brian Maher has written a partial interface to libev for lua (at the
		3499	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3500	L<http://github.com/brimworks/lua-ev>.
2967		3501
2968	=back	3502	=back
2969		3503
2970		3504
2971	=head1 MACRO MAGIC	3505	=head1 MACRO MAGIC
…		…
3072		3606
3073	#define EV_STANDALONE 1	3607	#define EV_STANDALONE 1
3074	#include "ev.h"	3608	#include "ev.h"
3075		3609
3076	Both header files and implementation files can be compiled with a C++	3610	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	3611	compiler (at least, that's a stated goal, and breakage will be treated
3078	as a bug).	3612	as a bug).
3079		3613
3080	You need the following files in your source tree, or in a directory	3614	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):	3615	in your include path (e.g. in libev/ when using -Ilibev):
3082		3616
…		…
3125	libev.m4	3659	libev.m4
3126		3660
3127	=head2 PREPROCESSOR SYMBOLS/MACROS	3661	=head2 PREPROCESSOR SYMBOLS/MACROS
3128		3662
3129	Libev can be configured via a variety of preprocessor symbols you have to	3663	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	3664	define before including (or compiling) any of its files. The default in
3131	autoconf is documented for every option.	3665	the absence of autoconf is documented for every option.
		3666
		3667	Symbols marked with "(h)" do not change the ABI, and can have different
		3668	values when compiling libev vs. including F<ev.h>, so it is permissible
		3669	to redefine them before including F<ev.h> without breaking compatibility
		3670	to a compiled library. All other symbols change the ABI, which means all
		3671	users of libev and the libev code itself must be compiled with compatible
		3672	settings.
3132		3673
3133	=over 4	3674	=over 4
3134		3675
3135	=item EV_STANDALONE	3676	=item EV_STANDALONE (h)
3136		3677
3137	Must always be C<1> if you do not use autoconf configuration, which	3678	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	3679	keeps libev from including F<config.h>, and it also defines dummy
3139	implementations for some libevent functions (such as logging, which is not	3680	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	3681	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.	3682	F<event.h> that are not directly supported by the libev core alone.
3142		3683
		3684	In standalone mode, libev will still try to automatically deduce the
		3685	configuration, but has to be more conservative.
		3686
3143	=item EV_USE_MONOTONIC	3687	=item EV_USE_MONOTONIC
3144		3688
3145	If defined to be C<1>, libev will try to detect the availability of the	3689	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	3690	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	3691	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	3692	you usually have to link against librt or something similar. Enabling it
3149	the functionality isn't available is safe, though, although you have	3693	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>	3694	to make sure you link against any libraries where the C<clock_gettime>
3151	function is hiding in (often F<-lrt>).	3695	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3152		3696
3153	=item EV_USE_REALTIME	3697	=item EV_USE_REALTIME
3154		3698
3155	If defined to be C<1>, libev will try to detect the availability of the	3699	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	3700	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	3701	at runtime if successful). Otherwise no use of the real-time clock
3158	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3702	option will be attempted. This effectively replaces C<gettimeofday>
3159	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3703	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3160	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3704	correctness. See the note about libraries in the description of
		3705	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3706	C<EV_USE_CLOCK_SYSCALL>.
		3707
		3708	=item EV_USE_CLOCK_SYSCALL
		3709
		3710	If defined to be C<1>, libev will try to use a direct syscall instead
		3711	of calling the system-provided C<clock_gettime> function. This option
		3712	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3713	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3714	programs needlessly. Using a direct syscall is slightly slower (in
		3715	theory), because no optimised vdso implementation can be used, but avoids
		3716	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3717	higher, as it simplifies linking (no need for C<-lrt>).
3161		3718
3162	=item EV_USE_NANOSLEEP	3719	=item EV_USE_NANOSLEEP
3163		3720
3164	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3721	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 ()>.	3722	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3181		3738
3182	=item EV_SELECT_USE_FD_SET	3739	=item EV_SELECT_USE_FD_SET
3183		3740
3184	If defined to C<1>, then the select backend will use the system C<fd_set>	3741	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	3742	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	3743	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	3744	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	3745	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	3746	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3190	influence the size of the C<fd_set> used.	3747	configures the maximum size of the C<fd_set>.
3191		3748
3192	=item EV_SELECT_IS_WINSOCKET	3749	=item EV_SELECT_IS_WINSOCKET
3193		3750
3194	When defined to C<1>, the select backend will assume that	3751	When defined to C<1>, the select backend will assume that
3195	select/socket/connect etc. don't understand file descriptors but	3752	select/socket/connect etc. don't understand file descriptors but
…		…
3197	be used is the winsock select). This means that it will call	3754	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,	3755	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	3756	it is assumed that all these functions actually work on fds, even
3200	on win32. Should not be defined on non-win32 platforms.	3757	on win32. Should not be defined on non-win32 platforms.
3201		3758
3202	=item EV_FD_TO_WIN32_HANDLE	3759	=item EV_FD_TO_WIN32_HANDLE(fd)
3203		3760
3204	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3761	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	3762	file descriptors to socket handles. When not defining this symbol (the
3206	default), then libev will call C<_get_osfhandle>, which is usually	3763	default), then libev will call C<_get_osfhandle>, which is usually
3207	correct. In some cases, programs use their own file descriptor management,	3764	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.	3765	in which case they can provide this function to map fds to socket handles.
		3766
		3767	=item EV_WIN32_HANDLE_TO_FD(handle)
		3768
		3769	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3770	using the standard C<_open_osfhandle> function. For programs implementing
		3771	their own fd to handle mapping, overwriting this function makes it easier
		3772	to do so. This can be done by defining this macro to an appropriate value.
		3773
		3774	=item EV_WIN32_CLOSE_FD(fd)
		3775
		3776	If programs implement their own fd to handle mapping on win32, then this
		3777	macro can be used to override the C<close> function, useful to unregister
		3778	file descriptors again. Note that the replacement function has to close
		3779	the underlying OS handle.
3209		3780
3210	=item EV_USE_POLL	3781	=item EV_USE_POLL
3211		3782
3212	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3783	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	3784	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.	3831	as well as for signal and thread safety in C<ev_async> watchers.
3261		3832
3262	In the absence of this define, libev will use C<sig_atomic_t volatile>	3833	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.	3834	(from F<signal.h>), which is usually good enough on most platforms.
3264		3835
3265	=item EV_H	3836	=item EV_H (h)
3266		3837
3267	The name of the F<ev.h> header file used to include it. The default if	3838	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	3839	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.	3840	used to virtually rename the F<ev.h> header file in case of conflicts.
3270		3841
3271	=item EV_CONFIG_H	3842	=item EV_CONFIG_H (h)
3272		3843
3273	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3844	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	3845	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3275	C<EV_H>, above.	3846	C<EV_H>, above.
3276		3847
3277	=item EV_EVENT_H	3848	=item EV_EVENT_H (h)
3278		3849
3279	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3850	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">.	3851	of how the F<event.h> header can be found, the default is C<"event.h">.
3281		3852
3282	=item EV_PROTOTYPES	3853	=item EV_PROTOTYPES (h)
3283		3854
3284	If defined to be C<0>, then F<ev.h> will not define any function	3855	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	3856	prototypes, but still define all the structs and other symbols. This is
3286	occasionally useful if you want to provide your own wrapper functions	3857	occasionally useful if you want to provide your own wrapper functions
3287	around libev functions.	3858	around libev functions.
…		…
3309	fine.	3880	fine.
3310		3881
3311	If your embedding application does not need any priorities, defining these	3882	If your embedding application does not need any priorities, defining these
3312	both to C<0> will save some memory and CPU.	3883	both to C<0> will save some memory and CPU.
3313		3884
3314	=item EV_PERIODIC_ENABLE	3885	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3886	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3887	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3315		3888
3316	If undefined or defined to be C<1>, then periodic timers are supported. If	3889	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	3890	the respective watcher type is supported. If defined to be C<0>, then it
3318	code.	3891	is not. Disabling watcher types mainly saves codesize.
3319		3892
3320	=item EV_IDLE_ENABLE	3893	=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		3894
3349	If you need to shave off some kilobytes of code at the expense of some	3895	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	3896	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	3897	certain subsets of functionality. The default is to enable all features
3352	much smaller 2-heap for timer management over the default 4-heap.	3898	that can be enabled on the platform.
		3899
		3900	A typical way to use this symbol is to define it to C<0> (or to a bitset
		3901	with some broad features you want) and then selectively re-enable
		3902	additional parts you want, for example if you want everything minimal,
		3903	but multiple event loop support, async and child watchers and the poll
		3904	backend, use this:
		3905
		3906	#define EV_FEATURES 0
		3907	#define EV_MULTIPLICITY 1
		3908	#define EV_USE_POLL 1
		3909	#define EV_CHILD_ENABLE 1
		3910	#define EV_ASYNC_ENABLE 1
		3911
		3912	The actual value is a bitset, it can be a combination of the following
		3913	values:
		3914
		3915	=over 4
		3916
		3917	=item C<1> - faster/larger code
		3918
		3919	Use larger code to speed up some operations.
		3920
		3921	Currently this is used to override some inlining decisions (enlarging the roughly
		3922	30% code size on amd64.
		3923
		3924	When optimising for size, use of compiler flags such as C<-Os> with
		3925	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
		3926	assertions.
		3927
		3928	=item C<2> - faster/larger data structures
		3929
		3930	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		3931	hash table sizes and so on. This will usually further increase codesize
		3932	and can additionally have an effect on the size of data structures at
		3933	runtime.
		3934
		3935	=item C<4> - full API configuration
		3936
		3937	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		3938	enables multiplicity (C<EV_MULTIPLICITY>=1).
		3939
		3940	=item C<8> - full API
		3941
		3942	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		3943	details on which parts of the API are still available without this
		3944	feature, and do not complain if this subset changes over time.
		3945
		3946	=item C<16> - enable all optional watcher types
		3947
		3948	Enables all optional watcher types. If you want to selectively enable
		3949	only some watcher types other than I/O and timers (e.g. prepare,
		3950	embed, async, child...) you can enable them manually by defining
		3951	C<EV_watchertype_ENABLE> to C<1> instead.
		3952
		3953	=item C<32> - enable all backends
		3954
		3955	This enables all backends - without this feature, you need to enable at
		3956	least one backend manually (C<EV_USE_SELECT> is a good choice).
		3957
		3958	=item C<64> - enable OS-specific "helper" APIs
		3959
		3960	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		3961	default.
		3962
		3963	=back
		3964
		3965	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		3966	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		3967	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		3968	watchers, timers and monotonic clock support.
		3969
		3970	With an intelligent-enough linker (gcc+binutils are intelligent enough
		3971	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		3972	your program might be left out as well - a binary starting a timer and an
		3973	I/O watcher then might come out at only 5Kb.
		3974
		3975	=item EV_AVOID_STDIO
		3976
		3977	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3978	functions (printf, scanf, perror etc.). This will increase the codesize
		3979	somewhat, but if your program doesn't otherwise depend on stdio and your
		3980	libc allows it, this avoids linking in the stdio library which is quite
		3981	big.
		3982
		3983	Note that error messages might become less precise when this option is
		3984	enabled.
		3985
		3986	=item EV_NSIG
		3987
		3988	The highest supported signal number, +1 (or, the number of
		3989	signals): Normally, libev tries to deduce the maximum number of signals
		3990	automatically, but sometimes this fails, in which case it can be
		3991	specified. Also, using a lower number than detected (C<32> should be
		3992	good for about any system in existance) can save some memory, as libev
		3993	statically allocates some 12-24 bytes per signal number.
3353		3994
3354	=item EV_PID_HASHSIZE	3995	=item EV_PID_HASHSIZE
3355		3996
3356	C<ev_child> watchers use a small hash table to distribute workload by	3997	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	3998	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	3999	usually more than enough. If you need to manage thousands of children you
3359	increase this value (I<must> be a power of two).	4000	might want to increase this value (I<must> be a power of two).
3360		4001
3361	=item EV_INOTIFY_HASHSIZE	4002	=item EV_INOTIFY_HASHSIZE
3362		4003
3363	C<ev_stat> watchers use a small hash table to distribute workload by	4004	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>),	4005	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>	4006	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	4007	C<ev_stat> watchers you might want to increase this value (I<must> be a
3367	two).	4008	power of two).
3368		4009
3369	=item EV_USE_4HEAP	4010	=item EV_USE_4HEAP
3370		4011
3371	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4012	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	4013	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	4014	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3374	faster performance with many (thousands) of watchers.	4015	faster performance with many (thousands) of watchers.
3375		4016
3376	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4017	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3377	(disabled).	4018	will be C<0>.
3378		4019
3379	=item EV_HEAP_CACHE_AT	4020	=item EV_HEAP_CACHE_AT
3380		4021
3381	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4022	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	4023	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>),	4024	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,	4025	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	4026	but avoids random read accesses on heap changes. This improves performance
3386	noticeably with many (hundreds) of watchers.	4027	noticeably with many (hundreds) of watchers.
3387		4028
3388	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3389	(disabled).	4030	will be C<0>.
3390		4031
3391	=item EV_VERIFY	4032	=item EV_VERIFY
3392		4033
3393	Controls how much internal verification (see C<ev_loop_verify ()>) will	4034	Controls how much internal verification (see C<ev_loop_verify ()>) will
3394	be done: If set to C<0>, no internal verification code will be compiled	4035	be done: If set to C<0>, no internal verification code will be compiled
…		…
3396	called. If set to C<2>, then the internal verification code will be	4037	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	4038	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	4039	verification code will be called very frequently, which will slow down
3399	libev considerably.	4040	libev considerably.
3400		4041
3401	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4042	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3402	C<0>.	4043	will be C<0>.
3403		4044
3404	=item EV_COMMON	4045	=item EV_COMMON
3405		4046
3406	By default, all watchers have a C<void *data> member. By redefining	4047	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	4048	this macro to a something else you can include more and other types of
…		…
3465	file.	4106	file.
3466		4107
3467	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4108	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:	4109	that everybody includes and which overrides some configure choices:
3469		4110
3470	#define EV_MINIMAL 1	4111	#define EV_FEATURES 8
3471	#define EV_USE_POLL 0	4112	#define EV_USE_SELECT 1
3472	#define EV_MULTIPLICITY 0
3473	#define EV_PERIODIC_ENABLE 0	4113	#define EV_PREPARE_ENABLE 1
		4114	#define EV_IDLE_ENABLE 1
3474	#define EV_STAT_ENABLE 0	4115	#define EV_SIGNAL_ENABLE 1
3475	#define EV_FORK_ENABLE 0	4116	#define EV_CHILD_ENABLE 1
		4117	#define EV_USE_STDEXCEPT 0
3476	#define EV_CONFIG_H <config.h>	4118	#define EV_CONFIG_H <config.h>
3477	#define EV_MINPRI 0
3478	#define EV_MAXPRI 0
3479		4119
3480	#include "ev++.h"	4120	#include "ev++.h"
3481		4121
3482	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3483		4123
…		…
3543	default loop and triggering an C<ev_async> watcher from the default loop	4183	default loop and triggering an C<ev_async> watcher from the default loop
3544	watcher callback into the event loop interested in the signal.	4184	watcher callback into the event loop interested in the signal.
3545		4185
3546	=back	4186	=back
3547		4187
		4188	=head4 THREAD LOCKING EXAMPLE
		4189
		4190	Here is a fictitious example of how to run an event loop in a different
		4191	thread than where callbacks are being invoked and watchers are
		4192	created/added/removed.
		4193
		4194	For a real-world example, see the C<EV::Loop::Async> perl module,
		4195	which uses exactly this technique (which is suited for many high-level
		4196	languages).
		4197
		4198	The example uses a pthread mutex to protect the loop data, a condition
		4199	variable to wait for callback invocations, an async watcher to notify the
		4200	event loop thread and an unspecified mechanism to wake up the main thread.
		4201
		4202	First, you need to associate some data with the event loop:
		4203
		4204	typedef struct {
		4205	mutex_t lock; /* global loop lock */
		4206	ev_async async_w;
		4207	thread_t tid;
		4208	cond_t invoke_cv;
		4209	} userdata;
		4210
		4211	void prepare_loop (EV_P)
		4212	{
		4213	// for simplicity, we use a static userdata struct.
		4214	static userdata u;
		4215
		4216	ev_async_init (&u->async_w, async_cb);
		4217	ev_async_start (EV_A_ &u->async_w);
		4218
		4219	pthread_mutex_init (&u->lock, 0);
		4220	pthread_cond_init (&u->invoke_cv, 0);
		4221
		4222	// now associate this with the loop
		4223	ev_set_userdata (EV_A_ u);
		4224	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4225	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4226
		4227	// then create the thread running ev_loop
		4228	pthread_create (&u->tid, 0, l_run, EV_A);
		4229	}
		4230
		4231	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4232	solely to wake up the event loop so it takes notice of any new watchers
		4233	that might have been added:
		4234
		4235	static void
		4236	async_cb (EV_P_ ev_async *w, int revents)
		4237	{
		4238	// just used for the side effects
		4239	}
		4240
		4241	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4242	protecting the loop data, respectively.
		4243
		4244	static void
		4245	l_release (EV_P)
		4246	{
		4247	userdata *u = ev_userdata (EV_A);
		4248	pthread_mutex_unlock (&u->lock);
		4249	}
		4250
		4251	static void
		4252	l_acquire (EV_P)
		4253	{
		4254	userdata *u = ev_userdata (EV_A);
		4255	pthread_mutex_lock (&u->lock);
		4256	}
		4257
		4258	The event loop thread first acquires the mutex, and then jumps straight
		4259	into C<ev_loop>:
		4260
		4261	void *
		4262	l_run (void *thr_arg)
		4263	{
		4264	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4265
		4266	l_acquire (EV_A);
		4267	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4268	ev_loop (EV_A_ 0);
		4269	l_release (EV_A);
		4270
		4271	return 0;
		4272	}
		4273
		4274	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4275	signal the main thread via some unspecified mechanism (signals? pipe
		4276	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4277	have been called (in a while loop because a) spurious wakeups are possible
		4278	and b) skipping inter-thread-communication when there are no pending
		4279	watchers is very beneficial):
		4280
		4281	static void
		4282	l_invoke (EV_P)
		4283	{
		4284	userdata *u = ev_userdata (EV_A);
		4285
		4286	while (ev_pending_count (EV_A))
		4287	{
		4288	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4289	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4290	}
		4291	}
		4292
		4293	Now, whenever the main thread gets told to invoke pending watchers, it
		4294	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4295	thread to continue:
		4296
		4297	static void
		4298	real_invoke_pending (EV_P)
		4299	{
		4300	userdata *u = ev_userdata (EV_A);
		4301
		4302	pthread_mutex_lock (&u->lock);
		4303	ev_invoke_pending (EV_A);
		4304	pthread_cond_signal (&u->invoke_cv);
		4305	pthread_mutex_unlock (&u->lock);
		4306	}
		4307
		4308	Whenever you want to start/stop a watcher or do other modifications to an
		4309	event loop, you will now have to lock:
		4310
		4311	ev_timer timeout_watcher;
		4312	userdata *u = ev_userdata (EV_A);
		4313
		4314	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4315
		4316	pthread_mutex_lock (&u->lock);
		4317	ev_timer_start (EV_A_ &timeout_watcher);
		4318	ev_async_send (EV_A_ &u->async_w);
		4319	pthread_mutex_unlock (&u->lock);
		4320
		4321	Note that sending the C<ev_async> watcher is required because otherwise
		4322	an event loop currently blocking in the kernel will have no knowledge
		4323	about the newly added timer. By waking up the loop it will pick up any new
		4324	watchers in the next event loop iteration.
		4325
3548	=head3 COROUTINES	4326	=head3 COROUTINES
3549		4327
3550	Libev is very accommodating to coroutines ("cooperative threads"):	4328	Libev is very accommodating to coroutines ("cooperative threads"):
3551	libev fully supports nesting calls to its functions from different	4329	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	4330	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3553	different coroutines, and switch freely between both coroutines running the	4331	different coroutines, and switch freely between both coroutines running
3554	loop, as long as you don't confuse yourself). The only exception is that	4332	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.	4333	that you must not do this from C<ev_periodic> reschedule callbacks.
3556		4334
3557	Care has been taken to ensure that libev does not keep local state inside	4335	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	4336	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3559	they do not clal any callbacks.	4337	they do not call any callbacks.
3560		4338
3561	=head2 COMPILER WARNINGS	4339	=head2 COMPILER WARNINGS
3562		4340
3563	Depending on your compiler and compiler settings, you might get no or a	4341	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	4342	lot of warnings when compiling libev code. Some people are apparently
…		…
3598	==2274== definitely lost: 0 bytes in 0 blocks.	4376	==2274== definitely lost: 0 bytes in 0 blocks.
3599	==2274== possibly lost: 0 bytes in 0 blocks.	4377	==2274== possibly lost: 0 bytes in 0 blocks.
3600	==2274== still reachable: 256 bytes in 1 blocks.	4378	==2274== still reachable: 256 bytes in 1 blocks.
3601		4379
3602	Then there is no memory leak, just as memory accounted to global variables	4380	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.	4381	is not a memleak - the memory is still being referenced, and didn't leak.
3604		4382
3605	Similarly, under some circumstances, valgrind might report kernel bugs	4383	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,	4384	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	4385	although an acceptable workaround has been found here), or it might be
3608	confused.	4386	confused.
…		…
3637	way (note also that glib is the slowest event library known to man).	4415	way (note also that glib is the slowest event library known to man).
3638		4416
3639	There is no supported compilation method available on windows except	4417	There is no supported compilation method available on windows except
3640	embedding it into other applications.	4418	embedding it into other applications.
3641		4419
		4420	Sensible signal handling is officially unsupported by Microsoft - libev
		4421	tries its best, but under most conditions, signals will simply not work.
		4422
3642	Not a libev limitation but worth mentioning: windows apparently doesn't	4423	Not a libev limitation but worth mentioning: windows apparently doesn't
3643	accept large writes: instead of resulting in a partial write, windows will	4424	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,	4425	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	4426	so make sure you only write small amounts into your sockets (less than a
3646	megabyte seems safe, but this apparently depends on the amount of memory	4427	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3650	the abysmal performance of winsockets, using a large number of sockets	4431	the abysmal performance of winsockets, using a large number of sockets
3651	is not recommended (and not reasonable). If your program needs to use	4432	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	4433	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	4434	different implementation for windows, as libev offers the POSIX readiness
3654	notification model, which cannot be implemented efficiently on windows	4435	notification model, which cannot be implemented efficiently on windows
3655	(Microsoft monopoly games).	4436	(due to Microsoft monopoly games).
3656		4437
3657	A typical way to use libev under windows is to embed it (see the embedding	4438	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	4439	section for details) and use the following F<evwrap.h> header file instead
3659	of F<ev.h>:	4440	of F<ev.h>:
3660		4441
…		…
3696		4477
3697	Early versions of winsocket's select only supported waiting for a maximum	4478	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	4479	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	4480	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	4481	recommends spawning a chain of threads and wait for 63 handles and the
3701	previous thread in each. Great).	4482	previous thread in each. Sounds great!).
3702		4483
3703	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4484	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	4485	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	4486	call (which might be in libev or elsewhere, for example, perl and many
3706	select emulation on windows).	4487	other interpreters do their own select emulation on windows).
3707		4488
3708	Another limit is the number of file descriptors in the Microsoft runtime	4489	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	4490	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	4491	fetish or something like this inside Microsoft). You can increase this
3711	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4492	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	4493	(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	4494	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	4495	(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	4496	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.	4497	the cost of calling select (O(n²)) will likely make this unworkable.
3719		4498
3720	=back	4499	=back
3721		4500
3722	=head2 PORTABILITY REQUIREMENTS	4501	=head2 PORTABILITY REQUIREMENTS
3723		4502
…		…
3766	=item C<double> must hold a time value in seconds with enough accuracy	4545	=item C<double> must hold a time value in seconds with enough accuracy
3767		4546
3768	The type C<double> is used to represent timestamps. It is required to	4547	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	4548	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3770	enough for at least into the year 4000. This requirement is fulfilled by	4549	enough for at least into the year 4000. This requirement is fulfilled by
3771	implementations implementing IEEE 754 (basically all existing ones).	4550	implementations implementing IEEE 754, which is basically all existing
		4551	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4552	2200.
3772		4553
3773	=back	4554	=back
3774		4555
3775	If you know of other additional requirements drop me a note.	4556	If you know of other additional requirements drop me a note.
3776		4557
…		…
3844	involves iterating over all running async watchers or all signal numbers.	4625	involves iterating over all running async watchers or all signal numbers.
3845		4626
3846	=back	4627	=back
3847		4628
3848		4629
		4630	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4631
		4632	The major version 4 introduced some minor incompatible changes to the API.
		4633
		4634	At the moment, the C<ev.h> header file tries to implement superficial
		4635	compatibility, so most programs should still compile. Those might be
		4636	removed in later versions of libev, so better update early than late.
		4637
		4638	=over 4
		4639
		4640	=item C<ev_loop_count> renamed to C<ev_iteration>
		4641
		4642	=item C<ev_loop_depth> renamed to C<ev_depth>
		4643
		4644	=item C<ev_loop_verify> renamed to C<ev_verify>
		4645
		4646	Most functions working on C<struct ev_loop> objects don't have an
		4647	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
		4648	still called C<ev_loop_fork> because it would otherwise clash with the
		4649	C<ev_fork> typedef.
		4650
		4651	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
		4652
		4653	This is a simple rename - all other watcher types use their name
		4654	as revents flag, and now C<ev_timer> does, too.
		4655
		4656	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
		4657	and continue to be present for the forseeable future, so this is mostly a
		4658	documentation change.
		4659
		4660	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4661
		4662	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4663	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4664	and work, but the library code will of course be larger.
		4665
		4666	=back
		4667
		4668
		4669	=head1 GLOSSARY
		4670
		4671	=over 4
		4672
		4673	=item active
		4674
		4675	A watcher is active as long as it has been started (has been attached to
		4676	an event loop) but not yet stopped (disassociated from the event loop).
		4677
		4678	=item application
		4679
		4680	In this document, an application is whatever is using libev.
		4681
		4682	=item callback
		4683
		4684	The address of a function that is called when some event has been
		4685	detected. Callbacks are being passed the event loop, the watcher that
		4686	received the event, and the actual event bitset.
		4687
		4688	=item callback invocation
		4689
		4690	The act of calling the callback associated with a watcher.
		4691
		4692	=item event
		4693
		4694	A change of state of some external event, such as data now being available
		4695	for reading on a file descriptor, time having passed or simply not having
		4696	any other events happening anymore.
		4697
		4698	In libev, events are represented as single bits (such as C<EV_READ> or
		4699	C<EV_TIMER>).
		4700
		4701	=item event library
		4702
		4703	A software package implementing an event model and loop.
		4704
		4705	=item event loop
		4706
		4707	An entity that handles and processes external events and converts them
		4708	into callback invocations.
		4709
		4710	=item event model
		4711
		4712	The model used to describe how an event loop handles and processes
		4713	watchers and events.
		4714
		4715	=item pending
		4716
		4717	A watcher is pending as soon as the corresponding event has been detected,
		4718	and stops being pending as soon as the watcher will be invoked or its
		4719	pending status is explicitly cleared by the application.
		4720
		4721	A watcher can be pending, but not active. Stopping a watcher also clears
		4722	its pending status.
		4723
		4724	=item real time
		4725
		4726	The physical time that is observed. It is apparently strictly monotonic :)
		4727
		4728	=item wall-clock time
		4729
		4730	The time and date as shown on clocks. Unlike real time, it can actually
		4731	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4732	clock.
		4733
		4734	=item watcher
		4735
		4736	A data structure that describes interest in certain events. Watchers need
		4737	to be started (attached to an event loop) before they can receive events.
		4738
		4739	=item watcher invocation
		4740
		4741	The act of calling the callback associated with a watcher.
		4742
		4743	=back
		4744
3849	=head1 AUTHOR	4745	=head1 AUTHOR
3850		4746
3851	Marc Lehmann <libev@schmorp.de>.	4747	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3852		4748

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