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Revision 1.97 by root, Sat Dec 22 05:48:02 2007 UTC vs.
Revision 1.142 by root, Sun Apr 6 09:53:18 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
		19	// all watcher callbacks have a similar signature
16	/* called when data readable on stdin */	20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ struct ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	struct ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occurring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
…		…
260	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
261		276
262	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
263	function.	278	function.
264		279
		280	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
265	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
266	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267		293
268	The following flags are supported:	294	The following flags are supported:
269		295
…		…
290	enabling this flag.	316	enabling this flag.
291		317
292	This works by calling C<getpid ()> on every iteration of the loop,	318	This works by calling C<getpid ()> on every iteration of the loop,
293	and thus this might slow down your event loop if you do a lot of loop	319	and thus this might slow down your event loop if you do a lot of loop
294	iterations and little real work, but is usually not noticeable (on my	320	iterations and little real work, but is usually not noticeable (on my
295	Linux system for example, C<getpid> is actually a simple 5-insn sequence	321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
296	without a syscall and thus I<very> fast, but my Linux system also has	322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
297	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
298		324
299	The big advantage of this flag is that you can forget about fork (and	325	The big advantage of this flag is that you can forget about fork (and
300	forget about forgetting to tell libev about forking) when you use this	326	forget about forgetting to tell libev about forking) when you use this
301	flag.	327	flag.
…		…
306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307		333
308	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
309	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
310	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
311	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
312	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
313		346
314	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315		348
316	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
317	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
318	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
320		355
321	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
322		357
323	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
324	but it scales phenomenally better. While poll and select usually scale	359	but it scales phenomenally better. While poll and select usually scale
325	like O(total_fds) where n is the total number of fds (or the highest fd),	360	like O(total_fds) where n is the total number of fds (or the highest fd),
326	epoll scales either O(1) or O(active_fds). The epoll design has a number	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
327	of shortcomings, such as silently dropping events in some hard-to-detect	362	of shortcomings, such as silently dropping events in some hard-to-detect
328	cases and rewiring a syscall per fd change, no fork support and bad	363	cases and requiring a syscall per fd change, no fork support and bad
329	support for dup:	364	support for dup.
330		365
331	While stopping, setting and starting an I/O watcher in the same iteration	366	While stopping, setting and starting an I/O watcher in the same iteration
332	will result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
333	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
336		371
337	Please note that epoll sometimes generates spurious notifications, so you	372	Please note that epoll sometimes generates spurious notifications, so you
338	need to use non-blocking I/O or other means to avoid blocking when no data	373	need to use non-blocking I/O or other means to avoid blocking when no data
339	(or space) is available.	374	(or space) is available.
340		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342		384
343	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
344	was broken on I<all> BSDs (usually it doesn't work with anything but	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
345	sockets and pipes, except on Darwin, where of course it's completely	387	with anything but sockets and pipes, except on Darwin, where of course
346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
347	is used by default there). For this reason it's not being "autodetected"	388	it's completely useless). For this reason it's not being "autodetected"
348	unless you explicitly specify it explicitly in the flags (i.e. using	389	unless you explicitly specify it explicitly in the flags (i.e. using
349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
350	system like NetBSD.	391	system like NetBSD.
351		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
		396
352	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
353	kernel is more efficient (which says nothing about its actual speed,	398	kernel is more efficient (which says nothing about its actual speed, of
354	of course). While stopping, setting and starting an I/O watcher does	399	course). While stopping, setting and starting an I/O watcher does never
355	never cause an extra syscall as with epoll, it still adds up to two event	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
356	changes per incident, support for C<fork ()> is very bad and it drops fds	401	two event changes per incident, support for C<fork ()> is very bad and it
357	silently in similarly hard-to-detetc cases.	402	drops fds silently in similarly hard-to-detect cases.
		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
358		412
359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
360		414
361	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
362		419
363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
364		421
365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
366	it's really slow, but it still scales very well (O(active_fds)).	423	it's really slow, but it still scales very well (O(active_fds)).
367		424
368	Please note that solaris event ports can deliver a lot of spurious	425	Please note that solaris event ports can deliver a lot of spurious
369	notifications, so you need to use non-blocking I/O or other means to avoid	426	notifications, so you need to use non-blocking I/O or other means to avoid
370	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
371		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
		437
372	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
373		439
374	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
375	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
376	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
377		443
		444	It is definitely not recommended to use this flag.
		445
378	=back	446	=back
379		447
380	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
381	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
382	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
383	order of their flag values :)
384		451
385	The most typical usage is like this:	452	The most typical usage is like this:
386		453
387	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
388	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
402		469
403	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
404	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
405	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
406	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
407		478
408	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
409		480
410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
411	if (!epoller)	482	if (!epoller)
…		…
435	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
436	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
437		508
438	=item ev_default_fork ()	509	=item ev_default_fork ()
439		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
440	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
441	one. Despite the name, you can call it anytime, but it makes most sense	513	name, you can call it anytime, but it makes most sense after forking, in
442	after forking, in either the parent or child process (or both, but that	514	the child process (or both child and parent, but that again makes little
443	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
444		517
445	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
446	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
447	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
448		521
449	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
450	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
451	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
452		525
453	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
454		527
455	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
456	without calling this function, so if you force one of those backends you
457	do not need to care.
458
459	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
460		529
461	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
463	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
464		537
465	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
466		539
467	Returns the count of loop iterations for the loop, which is identical to	540	Returns the count of loop iterations for the loop, which is identical to
468	the number of times libev did poll for new events. It starts at C<0> and	541	the number of times libev did poll for new events. It starts at C<0> and
…		…
513	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
514		587
515	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
516		589
517	- Before the first iteration, call any pending watchers.	590	- Before the first iteration, call any pending watchers.
518	* If there are no active watchers (reference count is zero), return.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
519	- Queue all prepare watchers and then call all outstanding watchers.	592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
520	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
521	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
522	- Update the "event loop time".	596	- Update the "event loop time".
523	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
524	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
525	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
526	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
527	- Queue all outstanding timers.	604	- Queue all outstanding timers.
528	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
529	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
530	- Queue all check watchers.	607	- Queue all check watchers.
531	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
532	Signals and child watchers are implemented as I/O watchers, and will	609	Signals and child watchers are implemented as I/O watchers, and will
533	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
535	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
536		614
537	Example: Queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
538	anymore.	616	anymore.
539		617
540	... queue jobs here, make sure they register event watchers as long	618	... queue jobs here, make sure they register event watchers as long
541	... as they still have work to do (even an idle watcher will do..)	619	... as they still have work to do (even an idle watcher will do..)
542	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
546		624
547	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
548	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
549	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
550	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
551		631
552	=item ev_ref (loop)	632	=item ev_ref (loop)
553		633
554	=item ev_unref (loop)	634	=item ev_unref (loop)
555		635
…		…
560	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
561	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
562	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
563	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
564	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
565	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
566		648
567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
568	running when nothing else is active.	650	running when nothing else is active.
569		651
570	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
596	overhead for the actual polling but can deliver many events at once.	678	overhead for the actual polling but can deliver many events at once.
597		679
598	By setting a higher I<io collect interval> you allow libev to spend more	680	By setting a higher I<io collect interval> you allow libev to spend more
599	time collecting I/O events, so you can handle more events per iteration,	681	time collecting I/O events, so you can handle more events per iteration,
600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
601	C<ev_timer>) will be not affected.	683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
602		685
603	Likewise, by setting a higher I<timeout collect interval> you allow libev	686	Likewise, by setting a higher I<timeout collect interval> you allow libev
604	to spend more time collecting timeouts, at the expense of increased	687	to spend more time collecting timeouts, at the expense of increased
605	latency (the watcher callback will be called later). C<ev_io> watchers	688	latency (the watcher callback will be called later). C<ev_io> watchers
606	will not be affected.	689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
607		691
608	Many programs can usually benefit by setting the io collect interval to	692	Many (busy) programs can usually benefit by setting the io collect
609	a value near C<0.1> or so, which is often enough for interactive servers	693	interval to a value near C<0.1> or so, which is often enough for
610	(of course not for games), likewise for timeouts. It usually doesn't make	694	interactive servers (of course not for games), likewise for timeouts. It
611	much sense to set it to a lower value than C<0.01>, as this approsaches	695	usually doesn't make much sense to set it to a lower value than C<0.01>,
612	the timing granularity of most systems.	696	as this approsaches the timing granularity of most systems.
613		697
614	=back	698	=back
615		699
616		700
617	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
…		…
716		800
717	=item C<EV_FORK>	801	=item C<EV_FORK>
718		802
719	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
720	C<ev_fork>).	804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
721		809
722	=item C<EV_ERROR>	810	=item C<EV_ERROR>
723		811
724	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
725	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
…		…
943	In general you can register as many read and/or write event watchers per	1031	In general you can register as many read and/or write event watchers per
944	fd as you want (as long as you don't confuse yourself). Setting all file	1032	fd as you want (as long as you don't confuse yourself). Setting all file
945	descriptors to non-blocking mode is also usually a good idea (but not	1033	descriptors to non-blocking mode is also usually a good idea (but not
946	required if you know what you are doing).	1034	required if you know what you are doing).
947		1035
948	You have to be careful with dup'ed file descriptors, though. Some backends
949	(the linux epoll backend is a notable example) cannot handle dup'ed file
950	descriptors correctly if you register interest in two or more fds pointing
951	to the same underlying file/socket/etc. description (that is, they share
952	the same underlying "file open").
953
954	If you must do this, then force the use of a known-to-be-good backend	1036	If you must do this, then force the use of a known-to-be-good backend
955	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
956	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
957		1039
958	Another thing you have to watch out for is that it is quite easy to	1040	Another thing you have to watch out for is that it is quite easy to
…		…
992	optimisations to libev.	1074	optimisations to libev.
993		1075
994	=head3 The special problem of dup'ed file descriptors	1076	=head3 The special problem of dup'ed file descriptors
995		1077
996	Some backends (e.g. epoll), cannot register events for file descriptors,	1078	Some backends (e.g. epoll), cannot register events for file descriptors,
997	but only events for the underlying file descriptions. That menas when you	1079	but only events for the underlying file descriptions. That means when you
998	have C<dup ()>'ed file descriptors and register events for them, only one	1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
999	file descriptor might actually receive events.	1081	events for them, only one file descriptor might actually receive events.
1000		1082
1001	There is no workaorund possible except not registering events	1083	There is no workaround possible except not registering events
1002	for potentially C<dup ()>'ed file descriptors or to resort to	1084	for potentially C<dup ()>'ed file descriptors, or to resort to
1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1004		1086
1005	=head3 The special problem of fork	1087	=head3 The special problem of fork
1006		1088
1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
1011	To support fork in your programs, you either have to call	1093	To support fork in your programs, you either have to call
1012	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1013	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1014	C<EVBACKEND_POLL>.	1096	C<EVBACKEND_POLL>.
1015		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
1016		1110
1017	=head3 Watcher-Specific Functions	1111	=head3 Watcher-Specific Functions
1018		1112
1019	=over 4	1113	=over 4
1020		1114
…		…
1033	=item int events [read-only]	1127	=item int events [read-only]
1034		1128
1035	The events being watched.	1129	The events being watched.
1036		1130
1037	=back	1131	=back
		1132
		1133	=head3 Examples
1038		1134
1039	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1040	readable, but only once. Since it is likely line-buffered, you could	1136	readable, but only once. Since it is likely line-buffered, you could
1041	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
1042		1138
…		…
1095	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
1096	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
1097	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
1098	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
1099		1195
1100	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
1101		1197
1102	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
1103	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
1104		1200
1105	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1140	or C<ev_timer_again> is called and determines the next timeout (if any),	1236	or C<ev_timer_again> is called and determines the next timeout (if any),
1141	which is also when any modifications are taken into account.	1237	which is also when any modifications are taken into account.
1142		1238
1143	=back	1239	=back
1144		1240
		1241	=head3 Examples
		1242
1145	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
1146		1244
1147	static void	1245	static void
1148	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1149	{	1247	{
…		…
1212	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1213	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1214	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1215	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1216		1314
1217	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1218		1316
1219	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1220	C<at + N * interval> time (for some integer N, which can also be negative)	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1221	and then repeat, regardless of any time jumps.	1319	and then repeat, regardless of any time jumps.
1222		1320
…		…
1305		1403
1306	When active, contains the absolute time that the watcher is supposed to	1404	When active, contains the absolute time that the watcher is supposed to
1307	trigger next.	1405	trigger next.
1308		1406
1309	=back	1407	=back
		1408
		1409	=head3 Examples
1310		1410
1311	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1312	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1313	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1314		1414
…		…
1354	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1355	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1356	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1357	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1358		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
1359	=head3 Watcher-Specific Functions and Data Members	1465	=head3 Watcher-Specific Functions and Data Members
1360		1466
1361	=over 4	1467	=over 4
1362		1468
1363	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1371		1477
1372	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1373		1479
1374	=back	1480	=back
1375		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1376		1496
1377	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1378		1498
1379	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1380	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
1381		1526
1382	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1383		1528
1384	=over 4	1529	=over 4
1385		1530
1386	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1387		1532
1388	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1389		1534
1390	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1391	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1392	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1393	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1394	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1395	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1396		1543
1397	=item int pid [read-only]	1544	=item int pid [read-only]
1398		1545
1399	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1400		1547
…		…
1407	The process exit/trace status caused by C<rpid> (see your systems	1554	The process exit/trace status caused by C<rpid> (see your systems
1408	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1409		1556
1410	=back	1557	=back
1411		1558
1412	Example: Try to exit cleanly on SIGINT and SIGTERM.	1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1413		1565
1414	static void	1566	static void
1415	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1416	{	1568	{
1417	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1418	}	1571	}
1419		1572
1420	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1421	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1422	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1423		1587
1424		1588
1425	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1426		1590
1427	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1457	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1458	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1459	polling.	1623	polling.
1460		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
1461	=head3 Watcher-Specific Functions and Data Members	1669	=head3 Watcher-Specific Functions and Data Members
1462		1670
1463	=over 4	1671	=over 4
1464		1672
1465	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
…		…
1474		1682
1475	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1476	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1477	last change was detected).	1685	last change was detected).
1478		1686
1479	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1480		1688
1481	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1482	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1483	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1484	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1502	=item const char *path [read-only]	1710	=item const char *path [read-only]
1503		1711
1504	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1505		1713
1506	=back	1714	=back
		1715
		1716	=head3 Examples
1507		1717
1508	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1509		1719
1510	static void	1720	static void
1511	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1524	}	1734	}
1525		1735
1526	...	1736	...
1527	ev_stat passwd;	1737	ev_stat passwd;
1528		1738
1529	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1530	ev_stat_start (loop, &passwd);	1740	ev_stat_start (loop, &passwd);
		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
1531		1769
1532		1770
1533	=head2 C<ev_idle> - when you've got nothing better to do...	1771	=head2 C<ev_idle> - when you've got nothing better to do...
1534		1772
1535	Idle watchers trigger events when no other events of the same or higher	1773	Idle watchers trigger events when no other events of the same or higher
…		…
1561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1562	believe me.	1800	believe me.
1563		1801
1564	=back	1802	=back
1565		1803
		1804	=head3 Examples
		1805
1566	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1567	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1568		1808
1569	static void	1809	static void
1570	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1571	{	1811	{
1572	free (w);	1812	free (w);
1573	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1574	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1575	}	1815	}
1576		1816
1577	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1578	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1579	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1621		1861
1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1623	priority, to ensure that they are being run before any other watchers	1863	priority, to ensure that they are being run before any other watchers
1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1625	too) should not activate ("feed") events into libev. While libev fully	1865	too) should not activate ("feed") events into libev. While libev fully
1626	supports this, they will be called before other C<ev_check> watchers did	1866	supports this, they will be called before other C<ev_check> watchers
1627	their job. As C<ev_check> watchers are often used to embed other event	1867	did their job. As C<ev_check> watchers are often used to embed other
1628	loops those other event loops might be in an unusable state until their	1868	(non-libev) event loops those other event loops might be in an unusable
1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1869	state until their C<ev_check> watcher ran (always remind yourself to
1630	others).	1870	coexist peacefully with others).
1631		1871
1632	=head3 Watcher-Specific Functions and Data Members	1872	=head3 Watcher-Specific Functions and Data Members
1633		1873
1634	=over 4	1874	=over 4
1635		1875
…		…
1640	Initialises and configures the prepare or check watcher - they have no	1880	Initialises and configures the prepare or check watcher - they have no
1641	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1642	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1643		1883
1644	=back	1884	=back
		1885
		1886	=head3 Examples
1645		1887
1646	There are a number of principal ways to embed other event loops or modules	1888	There are a number of principal ways to embed other event loops or modules
1647	into libev. Here are some ideas on how to include libadns into libev	1889	into libev. Here are some ideas on how to include libadns into libev
1648	(there is a Perl module named C<EV::ADNS> that does this, which you could	1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
1649	use for an actually working example. Another Perl module named C<EV::Glib>	1891	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1774	=head2 C<ev_embed> - when one backend isn't enough...	2016	=head2 C<ev_embed> - when one backend isn't enough...
1775		2017
1776	This is a rather advanced watcher type that lets you embed one event loop	2018	This is a rather advanced watcher type that lets you embed one event loop
1777	into another (currently only C<ev_io> events are supported in the embedded	2019	into another (currently only C<ev_io> events are supported in the embedded
1778	loop, other types of watchers might be handled in a delayed or incorrect	2020	loop, other types of watchers might be handled in a delayed or incorrect
1779	fashion and must not be used). (See portability notes, below).	2021	fashion and must not be used).
1780		2022
1781	There are primarily two reasons you would want that: work around bugs and	2023	There are primarily two reasons you would want that: work around bugs and
1782	prioritise I/O.	2024	prioritise I/O.
1783		2025
1784	As an example for a bug workaround, the kqueue backend might only support	2026	As an example for a bug workaround, the kqueue backend might only support
…		…
1818	portable one.	2060	portable one.
1819		2061
1820	So when you want to use this feature you will always have to be prepared	2062	So when you want to use this feature you will always have to be prepared
1821	that you cannot get an embeddable loop. The recommended way to get around	2063	that you cannot get an embeddable loop. The recommended way to get around
1822	this is to have a separate variables for your embeddable loop, try to	2064	this is to have a separate variables for your embeddable loop, try to
1823	create it, and if that fails, use the normal loop for everything:	2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
1824		2100
1825	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1826	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1827	struct ev_embed embed;	2103	struct ev_embed embed;
1828		2104
…		…
1839	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1840	}	2116	}
1841	else	2117	else
1842	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1843		2119
1844	=head2 Portability notes	2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1845		2124
1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2125	struct ev_loop *loop = ev_default_init (0);
1847	tried, in various ways. Usually the embedded event loop will simply never	2126	struct ev_loop *loop_socket = 0;
1848	receive events, sometimes it will only trigger a few times, sometimes in a	2127	struct ev_embed embed;
1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2128
1850	will always eport the epoll fd as ready, even when no events are pending.	2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
1851		2135
1852	While libev allows embedding these backends (they are contained in	2136	if (!loop_socket)
1853	C<ev_embeddable_backends ()>), take extreme care that it will actually	2137	loop_socket = loop;
1854	work.
1855		2138
1856	When in doubt, create a dynamic event loop forced to use sockets (this	2139	// now use loop_socket for all sockets, and loop for everything else
1857	usually works) and possibly another thread and a pipe or so to report to
1858	your main event loop.
1859
1860	=head3 Watcher-Specific Functions and Data Members
1861
1862	=over 4
1863
1864	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1865
1866	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1867
1868	Configures the watcher to embed the given loop, which must be
1869	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1870	invoked automatically, otherwise it is the responsibility of the callback
1871	to invoke it (it will continue to be called until the sweep has been done,
1872	if you do not want thta, you need to temporarily stop the embed watcher).
1873
1874	=item ev_embed_sweep (loop, ev_embed *)
1875
1876	Make a single, non-blocking sweep over the embedded loop. This works
1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1878	apropriate way for embedded loops.
1879
1880	=item struct ev_loop *other [read-only]
1881
1882	The embedded event loop.
1883
1884	=back
1885		2140
1886		2141
1887	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1888		2143
1889	Fork watchers are called when a C<fork ()> was detected (usually because	2144	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1905	believe me.	2160	believe me.
1906		2161
1907	=back	2162	=back
1908		2163
1909		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
		2306
		2307	=back
		2308
		2309
1910	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
1911		2311
1912	There are some other functions of possible interest. Described. Here. Now.	2312	There are some other functions of possible interest. Described. Here. Now.
1913		2313
1914	=over 4	2314	=over 4
…		…
2141	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
2142	the constructor.	2542	the constructor.
2143		2543
2144	class myclass	2544	class myclass
2145	{	2545	{
2146	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
2147	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
2148		2548
2149	myclass ();	2549	myclass (int fd)
2150	}
2151
2152	myclass::myclass (int fd)
2153	{	2550	{
2154	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
2155	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
2156		2553
2157	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2158	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
2159		2592
2160		2593
2161	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2162		2595
2163	Libev can be compiled with a variety of options, the most fundamantal	2596	Libev can be compiled with a variety of options, the most fundamantal
…		…
2304		2737
2305	libev.m4	2738	libev.m4
2306		2739
2307	=head2 PREPROCESSOR SYMBOLS/MACROS	2740	=head2 PREPROCESSOR SYMBOLS/MACROS
2308		2741
2309	Libev can be configured via a variety of preprocessor symbols you have to define	2742	Libev can be configured via a variety of preprocessor symbols you have to
2310	before including any of its files. The default is not to build for multiplicity	2743	define before including any of its files. The default in the absense of
2311	and only include the select backend.	2744	autoconf is noted for every option.
2312		2745
2313	=over 4	2746	=over 4
2314		2747
2315	=item EV_STANDALONE	2748	=item EV_STANDALONE
2316		2749
…		…
2342	=item EV_USE_NANOSLEEP	2775	=item EV_USE_NANOSLEEP
2343		2776
2344	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2345	and will use it for delays. Otherwise it will use C<select ()>.	2778	and will use it for delays. Otherwise it will use C<select ()>.
2346		2779
		2780	=item EV_USE_EVENTFD
		2781
		2782	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2783	available and will probe for kernel support at runtime. This will improve
		2784	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2785	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2786	2.7 or newer, otherwise disabled.
		2787
2347	=item EV_USE_SELECT	2788	=item EV_USE_SELECT
2348		2789
2349	If undefined or defined to be C<1>, libev will compile in support for the	2790	If undefined or defined to be C<1>, libev will compile in support for the
2350	C<select>(2) backend. No attempt at autodetection will be done: if no	2791	C<select>(2) backend. No attempt at autodetection will be done: if no
2351	other method takes over, select will be it. Otherwise the select backend	2792	other method takes over, select will be it. Otherwise the select backend
…		…
2369	be used is the winsock select). This means that it will call	2810	be used is the winsock select). This means that it will call
2370	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2811	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2371	it is assumed that all these functions actually work on fds, even	2812	it is assumed that all these functions actually work on fds, even
2372	on win32. Should not be defined on non-win32 platforms.	2813	on win32. Should not be defined on non-win32 platforms.
2373		2814
		2815	=item EV_FD_TO_WIN32_HANDLE
		2816
		2817	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2818	file descriptors to socket handles. When not defining this symbol (the
		2819	default), then libev will call C<_get_osfhandle>, which is usually
		2820	correct. In some cases, programs use their own file descriptor management,
		2821	in which case they can provide this function to map fds to socket handles.
		2822
2374	=item EV_USE_POLL	2823	=item EV_USE_POLL
2375		2824
2376	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2825	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2377	backend. Otherwise it will be enabled on non-win32 platforms. It	2826	backend. Otherwise it will be enabled on non-win32 platforms. It
2378	takes precedence over select.	2827	takes precedence over select.
2379		2828
2380	=item EV_USE_EPOLL	2829	=item EV_USE_EPOLL
2381		2830
2382	If defined to be C<1>, libev will compile in support for the Linux	2831	If defined to be C<1>, libev will compile in support for the Linux
2383	C<epoll>(7) backend. Its availability will be detected at runtime,	2832	C<epoll>(7) backend. Its availability will be detected at runtime,
2384	otherwise another method will be used as fallback. This is the	2833	otherwise another method will be used as fallback. This is the preferred
2385	preferred backend for GNU/Linux systems.	2834	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2835	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2386		2836
2387	=item EV_USE_KQUEUE	2837	=item EV_USE_KQUEUE
2388		2838
2389	If defined to be C<1>, libev will compile in support for the BSD style	2839	If defined to be C<1>, libev will compile in support for the BSD style
2390	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2840	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2409		2859
2410	=item EV_USE_INOTIFY	2860	=item EV_USE_INOTIFY
2411		2861
2412	If defined to be C<1>, libev will compile in support for the Linux inotify	2862	If defined to be C<1>, libev will compile in support for the Linux inotify
2413	interface to speed up C<ev_stat> watchers. Its actual availability will	2863	interface to speed up C<ev_stat> watchers. Its actual availability will
2414	be detected at runtime.	2864	be detected at runtime. If undefined, it will be enabled if the headers
		2865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2866
		2867	=item EV_ATOMIC_T
		2868
		2869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2870	access is atomic with respect to other threads or signal contexts. No such
		2871	type is easily found in the C language, so you can provide your own type
		2872	that you know is safe for your purposes. It is used both for signal handler "locking"
		2873	as well as for signal and thread safety in C<ev_async> watchers.
		2874
		2875	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2876	(from F<signal.h>), which is usually good enough on most platforms.
2415		2877
2416	=item EV_H	2878	=item EV_H
2417		2879
2418	The name of the F<ev.h> header file used to include it. The default if	2880	The name of the F<ev.h> header file used to include it. The default if
2419	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2420	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2882	used to virtually rename the F<ev.h> header file in case of conflicts.
2421		2883
2422	=item EV_CONFIG_H	2884	=item EV_CONFIG_H
2423		2885
2424	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2886	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2425	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2887	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2426	C<EV_H>, above.	2888	C<EV_H>, above.
2427		2889
2428	=item EV_EVENT_H	2890	=item EV_EVENT_H
2429		2891
2430	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2892	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2431	of how the F<event.h> header can be found.	2893	of how the F<event.h> header can be found, the default is C<"event.h">.
2432		2894
2433	=item EV_PROTOTYPES	2895	=item EV_PROTOTYPES
2434		2896
2435	If defined to be C<0>, then F<ev.h> will not define any function	2897	If defined to be C<0>, then F<ev.h> will not define any function
2436	prototypes, but still define all the structs and other symbols. This is	2898	prototypes, but still define all the structs and other symbols. This is
…		…
2487	=item EV_FORK_ENABLE	2949	=item EV_FORK_ENABLE
2488		2950
2489	If undefined or defined to be C<1>, then fork watchers are supported. If	2951	If undefined or defined to be C<1>, then fork watchers are supported. If
2490	defined to be C<0>, then they are not.	2952	defined to be C<0>, then they are not.
2491		2953
		2954	=item EV_ASYNC_ENABLE
		2955
		2956	If undefined or defined to be C<1>, then async watchers are supported. If
		2957	defined to be C<0>, then they are not.
		2958
2492	=item EV_MINIMAL	2959	=item EV_MINIMAL
2493		2960
2494	If you need to shave off some kilobytes of code at the expense of some	2961	If you need to shave off some kilobytes of code at the expense of some
2495	speed, define this symbol to C<1>. Currently only used for gcc to override	2962	speed, define this symbol to C<1>. Currently only used for gcc to override
2496	some inlining decisions, saves roughly 30% codesize of amd64.	2963	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2502	than enough. If you need to manage thousands of children you might want to	2969	than enough. If you need to manage thousands of children you might want to
2503	increase this value (I<must> be a power of two).	2970	increase this value (I<must> be a power of two).
2504		2971
2505	=item EV_INOTIFY_HASHSIZE	2972	=item EV_INOTIFY_HASHSIZE
2506		2973
2507	C<ev_staz> watchers use a small hash table to distribute workload by	2974	C<ev_stat> watchers use a small hash table to distribute workload by
2508	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2975	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2509	usually more than enough. If you need to manage thousands of C<ev_stat>	2976	usually more than enough. If you need to manage thousands of C<ev_stat>
2510	watchers you might want to increase this value (I<must> be a power of	2977	watchers you might want to increase this value (I<must> be a power of
2511	two).	2978	two).
2512		2979
…		…
2608		3075
2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3076	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2610		3077
2611	This means that, when you have a watcher that triggers in one hour and	3078	This means that, when you have a watcher that triggers in one hour and
2612	there are 100 watchers that would trigger before that then inserting will	3079	there are 100 watchers that would trigger before that then inserting will
2613	have to skip those 100 watchers.	3080	have to skip roughly seven (C<ld 100>) of these watchers.
2614		3081
2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3082	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2616		3083
2617	That means that for changing a timer costs less than removing/adding them	3084	That means that changing a timer costs less than removing/adding them
2618	as only the relative motion in the event queue has to be paid for.	3085	as only the relative motion in the event queue has to be paid for.
2619		3086
2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3087	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2621		3088
2622	These just add the watcher into an array or at the head of a list.	3089	These just add the watcher into an array or at the head of a list.
		3090
2623	=item Stopping check/prepare/idle watchers: O(1)	3091	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2624		3092
2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3093	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2626		3094
2627	These watchers are stored in lists then need to be walked to find the	3095	These watchers are stored in lists then need to be walked to find the
2628	correct watcher to remove. The lists are usually short (you don't usually	3096	correct watcher to remove. The lists are usually short (you don't usually
2629	have many watchers waiting for the same fd or signal).	3097	have many watchers waiting for the same fd or signal).
2630		3098
2631	=item Finding the next timer per loop iteration: O(1)	3099	=item Finding the next timer in each loop iteration: O(1)
		3100
		3101	By virtue of using a binary heap, the next timer is always found at the
		3102	beginning of the storage array.
2632		3103
2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3104	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2634		3105
2635	A change means an I/O watcher gets started or stopped, which requires	3106	A change means an I/O watcher gets started or stopped, which requires
2636	libev to recalculate its status (and possibly tell the kernel).	3107	libev to recalculate its status (and possibly tell the kernel, depending
		3108	on backend and wether C<ev_io_set> was used).
2637		3109
2638	=item Activating one watcher: O(1)	3110	=item Activating one watcher (putting it into the pending state): O(1)
2639		3111
2640	=item Priority handling: O(number_of_priorities)	3112	=item Priority handling: O(number_of_priorities)
2641		3113
2642	Priorities are implemented by allocating some space for each	3114	Priorities are implemented by allocating some space for each
2643	priority. When doing priority-based operations, libev usually has to	3115	priority. When doing priority-based operations, libev usually has to
2644	linearly search all the priorities.	3116	linearly search all the priorities, but starting/stopping and activating
		3117	watchers becomes O(1) w.r.t. priority handling.
		3118
		3119	=item Sending an ev_async: O(1)
		3120
		3121	=item Processing ev_async_send: O(number_of_async_watchers)
		3122
		3123	=item Processing signals: O(max_signal_number)
		3124
		3125	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3126	calls in the current loop iteration. Checking for async and signal events
		3127	involves iterating over all running async watchers or all signal numbers.
2645		3128
2646	=back	3129	=back
2647		3130
2648		3131
		3132	=head1 Win32 platform limitations and workarounds
		3133
		3134	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3135	requires, and its I/O model is fundamentally incompatible with the POSIX
		3136	model. Libev still offers limited functionality on this platform in
		3137	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3138	descriptors. This only applies when using Win32 natively, not when using
		3139	e.g. cygwin.
		3140
		3141	There is no supported compilation method available on windows except
		3142	embedding it into other applications.
		3143
		3144	Due to the many, low, and arbitrary limits on the win32 platform and the
		3145	abysmal performance of winsockets, using a large number of sockets is not
		3146	recommended (and not reasonable). If your program needs to use more than
		3147	a hundred or so sockets, then likely it needs to use a totally different
		3148	implementation for windows, as libev offers the POSIX model, which cannot
		3149	be implemented efficiently on windows (microsoft monopoly games).
		3150
		3151	=over 4
		3152
		3153	=item The winsocket select function
		3154
		3155	The winsocket C<select> function doesn't follow POSIX in that it requires
		3156	socket I<handles> and not socket I<file descriptors>. This makes select
		3157	very inefficient, and also requires a mapping from file descriptors
		3158	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3159	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3160	symbols for more info.
		3161
		3162	The configuration for a "naked" win32 using the microsoft runtime
		3163	libraries and raw winsocket select is:
		3164
		3165	#define EV_USE_SELECT 1
		3166	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3167
		3168	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3169	complexity in the O(n²) range when using win32.
		3170
		3171	=item Limited number of file descriptors
		3172
		3173	Windows has numerous arbitrary (and low) limits on things. Early versions
		3174	of winsocket's select only supported waiting for a max. of C<64> handles
		3175	(probably owning to the fact that all windows kernels can only wait for
		3176	C<64> things at the same time internally; microsoft recommends spawning a
		3177	chain of threads and wait for 63 handles and the previous thread in each).
		3178
		3179	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3180	to some high number (e.g. C<2048>) before compiling the winsocket select
		3181	call (which might be in libev or elsewhere, for example, perl does its own
		3182	select emulation on windows).
		3183
		3184	Another limit is the number of file descriptors in the microsoft runtime
		3185	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3186	or something like this inside microsoft). You can increase this by calling
		3187	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3188	arbitrary limit), but is broken in many versions of the microsoft runtime
		3189	libraries.
		3190
		3191	This might get you to about C<512> or C<2048> sockets (depending on
		3192	windows version and/or the phase of the moon). To get more, you need to
		3193	wrap all I/O functions and provide your own fd management, but the cost of
		3194	calling select (O(n²)) will likely make this unworkable.
		3195
		3196	=back
		3197
		3198
2649	=head1 AUTHOR	3199	=head1 AUTHOR
2650		3200
2651	Marc Lehmann <libev@schmorp.de>.	3201	Marc Lehmann <libev@schmorp.de>.
2652		3202

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