[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.100 by root, Sat Dec 22 11:49:17 2007 UTC vs.
Revision 1.140 by root, Wed Apr 2 06:34:51 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 rewiring 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
335	very well if you register events for both fds.	370	very well if you register events for both fds.
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.
		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.
340		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 all BSDs except NetBSD (usually it doesn't work reliably	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
…		…
357	course). While stopping, setting and starting an I/O watcher does never	399	course). While stopping, setting and starting an I/O watcher does never
358	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
359	two event changes per incident, support for C<fork ()> is very bad and it	401	two event changes per incident, support for C<fork ()> is very bad and it
360	drops fds silently in similarly hard-to-detect cases.	402	drops fds silently in similarly hard-to-detect cases.
361		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.
		412
362	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
363		414
364	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.
365		419
366	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
367		421
368	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,
369	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)).
370		424
371	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
372	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
373	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
374		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
375	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
376		439
377	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
378	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
379	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
380		443
		444	It is definitely not recommended to use this flag.
		445
381	=back	446	=back
382		447
383	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
384	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
385	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
386	order of their flag values :)
387		451
388	The most typical usage is like this:	452	The most typical usage is like this:
389		453
390	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
391	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
405		469
406	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
407	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
408	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
409	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.
410		478
411	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.
412		480
413	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
414	if (!epoller)	482	if (!epoller)
…		…
438	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
439	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
440		508
441	=item ev_default_fork ()	509	=item ev_default_fork ()
442		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
443	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
444	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
445	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
446	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.
447		517
448	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
449	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
450	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
451		521
452	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
453	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
454	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
455		525
456	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
457		527
458	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
459	without calling this function, so if you force one of those backends you
460	do not need to care.
461
462	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
463		529
464	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
465	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
466	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.
467		537
468	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
469		539
470	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
471	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
…		…
516	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
517		587
518	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
519		589
520	- Before the first iteration, call any pending watchers.	590	- Before the first iteration, call any pending watchers.
521	* If there are no active watchers (reference count is zero), return.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
522	- 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.
523	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
524	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
525	- Update the "event loop time".	596	- Update the "event loop time".
526	- 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.
527	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
528	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
529	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
530	- Queue all outstanding timers.	604	- Queue all outstanding timers.
531	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
532	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
533	- Queue all check watchers.	607	- Queue all check watchers.
534	- 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).
535	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
536	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
537	- 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
538	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
539		614
540	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
541	anymore.	616	anymore.
542		617
543	... queue jobs here, make sure they register event watchers as long	618	... queue jobs here, make sure they register event watchers as long
544	... 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..)
545	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
549		624
550	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
551	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
552	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
553	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.
554		631
555	=item ev_ref (loop)	632	=item ev_ref (loop)
556		633
557	=item ev_unref (loop)	634	=item ev_unref (loop)
558		635
…		…
563	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
564	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
565	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
566	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
567	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
568	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).
569		648
570	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>
571	running when nothing else is active.	650	running when nothing else is active.
572		651
573	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
599	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.
600		679
601	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
602	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,
603	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
604	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will	683	C<ev_timer>) will be not affected. Setting this to a non-null value will
605	introduce an additional C<ev_sleep ()> call into most loop iterations.	684	introduce an additional C<ev_sleep ()> call into most loop iterations.
606		685
607	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
608	to spend more time collecting timeouts, at the expense of increased	687	to spend more time collecting timeouts, at the expense of increased
609	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
…		…
721		800
722	=item C<EV_FORK>	801	=item C<EV_FORK>
723		802
724	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
725	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>).
726		809
727	=item C<EV_ERROR>	810	=item C<EV_ERROR>
728		811
729	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
730	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
…		…
948	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
949	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
950	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
951	required if you know what you are doing).	1034	required if you know what you are doing).
952		1035
953	You have to be careful with dup'ed file descriptors, though. Some backends
954	(the linux epoll backend is a notable example) cannot handle dup'ed file
955	descriptors correctly if you register interest in two or more fds pointing
956	to the same underlying file/socket/etc. description (that is, they share
957	the same underlying "file open").
958
959	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
960	(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
961	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
962		1039
963	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
…		…
997	optimisations to libev.	1074	optimisations to libev.
998		1075
999	=head3 The special problem of dup'ed file descriptors	1076	=head3 The special problem of dup'ed file descriptors
1000		1077
1001	Some backends (e.g. epoll), cannot register events for file descriptors,	1078	Some backends (e.g. epoll), cannot register events for file descriptors,
1002	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
1003	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
1004	file descriptor might actually receive events.	1081	events for them, only one file descriptor might actually receive events.
1005		1082
1006	There is no workaorund possible except not registering events	1083	There is no workaround possible except not registering events
1007	for potentially C<dup ()>'ed file descriptors or to resort to	1084	for potentially C<dup ()>'ed file descriptors, or to resort to
1008	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1009		1086
1010	=head3 The special problem of fork	1087	=head3 The special problem of fork
1011		1088
1012	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
…		…
1016	To support fork in your programs, you either have to call	1093	To support fork in your programs, you either have to call
1017	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,
1018	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1019	C<EVBACKEND_POLL>.	1096	C<EVBACKEND_POLL>.
1020		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
1021		1110
1022	=head3 Watcher-Specific Functions	1111	=head3 Watcher-Specific Functions
1023		1112
1024	=over 4	1113	=over 4
1025		1114
…		…
1038	=item int events [read-only]	1127	=item int events [read-only]
1039		1128
1040	The events being watched.	1129	The events being watched.
1041		1130
1042	=back	1131	=back
		1132
		1133	=head3 Examples
1043		1134
1044	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
1045	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
1046	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
1047		1138
…		…
1100	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
1101	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
1102	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
1103	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
1104		1195
1105	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
1106		1197
1107	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
1108	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
1109		1200
1110	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1145	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),
1146	which is also when any modifications are taken into account.	1237	which is also when any modifications are taken into account.
1147		1238
1148	=back	1239	=back
1149		1240
		1241	=head3 Examples
		1242
1150	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
1151		1244
1152	static void	1245	static void
1153	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)
1154	{	1247	{
…		…
1217	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
1218	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,
1219	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
1220	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1221		1314
1222	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1223		1316
1224	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
1225	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)
1226	and then repeat, regardless of any time jumps.	1319	and then repeat, regardless of any time jumps.
1227		1320
…		…
1310		1403
1311	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
1312	trigger next.	1405	trigger next.
1313		1406
1314	=back	1407	=back
		1408
		1409	=head3 Examples
1315		1410
1316	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1317	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1318	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1319		1414
…		…
1359	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
1360	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
1361	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
1362	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1363		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
1364	=head3 Watcher-Specific Functions and Data Members	1465	=head3 Watcher-Specific Functions and Data Members
1365		1466
1366	=over 4	1467	=over 4
1367		1468
1368	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1376		1477
1377	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1378		1479
1379	=back	1480	=back
1380		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
1381		1496
1382	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1383		1498
1384	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
1385	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.
1386		1526
1387	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1388		1528
1389	=over 4	1529	=over 4
1390		1530
1391	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1392		1532
1393	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1394		1534
1395	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
1396	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
1397	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
1398	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
1399	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
1400	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).
1401		1543
1402	=item int pid [read-only]	1544	=item int pid [read-only]
1403		1545
1404	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.
1405		1547
…		…
1412	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
1413	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1414		1556
1415	=back	1557	=back
1416		1558
1417	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;
1418		1565
1419	static void	1566	static void
1420	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1421	{	1568	{
1422	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);
1423	}	1571	}
1424		1572
1425	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1426	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1427	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	}
1428		1587
1429		1588
1430	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1431		1590
1432	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
…		…
1461	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
1462	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
1463	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
1464	polling.	1623	polling.
1465		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
1466	=head3 Watcher-Specific Functions and Data Members	1669	=head3 Watcher-Specific Functions and Data Members
1467		1670
1468	=over 4	1671	=over 4
1469		1672
1470	=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)
…		…
1479		1682
1480	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,
1481	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
1482	last change was detected).	1685	last change was detected).
1483		1686
1484	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1485		1688
1486	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
1487	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
1488	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1489	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1507	=item const char *path [read-only]	1710	=item const char *path [read-only]
1508		1711
1509	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1510		1713
1511	=back	1714	=back
		1715
		1716	=head3 Examples
1512		1717
1513	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1514		1719
1515	static void	1720	static void
1516	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1721	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1529	}	1734	}
1530		1735
1531	...	1736	...
1532	ev_stat passwd;	1737	ev_stat passwd;
1533		1738
1534	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1535	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);
1536		1769
1537		1770
1538	=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...
1539		1772
1540	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
…		…
1566	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,
1567	believe me.	1800	believe me.
1568		1801
1569	=back	1802	=back
1570		1803
		1804	=head3 Examples
		1805
1571	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
1572	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1573		1808
1574	static void	1809	static void
1575	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)
1576	{	1811	{
1577	free (w);	1812	free (w);
1578	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1579	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1580	}	1815	}
1581		1816
1582	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1583	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1584	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1646	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>
1647	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1648		1883
1649	=back	1884	=back
1650		1885
		1886	=head3 Examples
		1887
1651	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
1652	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
1653	(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
1654	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>
1655	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
…		…
1823	portable one.	2060	portable one.
1824		2061
1825	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
1826	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
1827	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
1828	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).
1829		2100
1830	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1831	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1832	struct ev_embed embed;	2103	struct ev_embed embed;
1833		2104
…		…
1844	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1845	}	2116	}
1846	else	2117	else
1847	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1848		2119
1849	=head3 Watcher-Specific Functions and Data Members	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).
1850		2124
1851	=over 4	2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		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	}
1852		2135
1853	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2136	if (!loop_socket)
		2137	loop_socket = loop;
1854		2138
1855	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	2139	// now use loop_socket for all sockets, and loop for everything else
1856
1857	Configures the watcher to embed the given loop, which must be
1858	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1859	invoked automatically, otherwise it is the responsibility of the callback
1860	to invoke it (it will continue to be called until the sweep has been done,
1861	if you do not want thta, you need to temporarily stop the embed watcher).
1862
1863	=item ev_embed_sweep (loop, ev_embed *)
1864
1865	Make a single, non-blocking sweep over the embedded loop. This works
1866	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1867	apropriate way for embedded loops.
1868
1869	=item struct ev_loop *other [read-only]
1870
1871	The embedded event loop.
1872
1873	=back
1874		2140
1875		2141
1876	=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
1877		2143
1878	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
…		…
1894	believe me.	2160	believe me.
1895		2161
1896	=back	2162	=back
1897		2163
1898		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
1899	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
1900		2311
1901	There are some other functions of possible interest. Described. Here. Now.	2312	There are some other functions of possible interest. Described. Here. Now.
1902		2313
1903	=over 4	2314	=over 4
…		…
2130	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
2131	the constructor.	2542	the constructor.
2132		2543
2133	class myclass	2544	class myclass
2134	{	2545	{
2135	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
2136	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
2137		2548
2138	myclass ();	2549	myclass (int fd)
2139	}
2140
2141	myclass::myclass (int fd)
2142	{	2550	{
2143	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
2144	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
2145		2553
2146	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2147	}	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
2148		2592
2149		2593
2150	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2151		2595
2152	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
…		…
2357	wants osf handles on win32 (this is the case when the select to	2801	wants osf handles on win32 (this is the case when the select to
2358	be used is the winsock select). This means that it will call	2802	be used is the winsock select). This means that it will call
2359	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2803	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2360	it is assumed that all these functions actually work on fds, even	2804	it is assumed that all these functions actually work on fds, even
2361	on win32. Should not be defined on non-win32 platforms.	2805	on win32. Should not be defined on non-win32 platforms.
		2806
		2807	=item EV_FD_TO_WIN32_HANDLE
		2808
		2809	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2810	file descriptors to socket handles. When not defining this symbol (the
		2811	default), then libev will call C<_get_osfhandle>, which is usually
		2812	correct. In some cases, programs use their own file descriptor management,
		2813	in which case they can provide this function to map fds to socket handles.
2362		2814
2363	=item EV_USE_POLL	2815	=item EV_USE_POLL
2364		2816
2365	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2817	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2366	backend. Otherwise it will be enabled on non-win32 platforms. It	2818	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2400		2852
2401	If defined to be C<1>, libev will compile in support for the Linux inotify	2853	If defined to be C<1>, libev will compile in support for the Linux inotify
2402	interface to speed up C<ev_stat> watchers. Its actual availability will	2854	interface to speed up C<ev_stat> watchers. Its actual availability will
2403	be detected at runtime.	2855	be detected at runtime.
2404		2856
		2857	=item EV_ATOMIC_T
		2858
		2859	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2860	access is atomic with respect to other threads or signal contexts. No such
		2861	type is easily found in the C language, so you can provide your own type
		2862	that you know is safe for your purposes. It is used both for signal handler "locking"
		2863	as well as for signal and thread safety in C<ev_async> watchers.
		2864
		2865	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2866	(from F<signal.h>), which is usually good enough on most platforms.
		2867
2405	=item EV_H	2868	=item EV_H
2406		2869
2407	The name of the F<ev.h> header file used to include it. The default if	2870	The name of the F<ev.h> header file used to include it. The default if
2408	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2871	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2409	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2872	used to virtually rename the F<ev.h> header file in case of conflicts.
2410		2873
2411	=item EV_CONFIG_H	2874	=item EV_CONFIG_H
2412		2875
2413	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2876	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2414	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2877	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2415	C<EV_H>, above.	2878	C<EV_H>, above.
2416		2879
2417	=item EV_EVENT_H	2880	=item EV_EVENT_H
2418		2881
2419	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2882	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2420	of how the F<event.h> header can be found.	2883	of how the F<event.h> header can be found, the default is C<"event.h">.
2421		2884
2422	=item EV_PROTOTYPES	2885	=item EV_PROTOTYPES
2423		2886
2424	If defined to be C<0>, then F<ev.h> will not define any function	2887	If defined to be C<0>, then F<ev.h> will not define any function
2425	prototypes, but still define all the structs and other symbols. This is	2888	prototypes, but still define all the structs and other symbols. This is
…		…
2476	=item EV_FORK_ENABLE	2939	=item EV_FORK_ENABLE
2477		2940
2478	If undefined or defined to be C<1>, then fork watchers are supported. If	2941	If undefined or defined to be C<1>, then fork watchers are supported. If
2479	defined to be C<0>, then they are not.	2942	defined to be C<0>, then they are not.
2480		2943
		2944	=item EV_ASYNC_ENABLE
		2945
		2946	If undefined or defined to be C<1>, then async watchers are supported. If
		2947	defined to be C<0>, then they are not.
		2948
2481	=item EV_MINIMAL	2949	=item EV_MINIMAL
2482		2950
2483	If you need to shave off some kilobytes of code at the expense of some	2951	If you need to shave off some kilobytes of code at the expense of some
2484	speed, define this symbol to C<1>. Currently only used for gcc to override	2952	speed, define this symbol to C<1>. Currently only used for gcc to override
2485	some inlining decisions, saves roughly 30% codesize of amd64.	2953	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2491	than enough. If you need to manage thousands of children you might want to	2959	than enough. If you need to manage thousands of children you might want to
2492	increase this value (I<must> be a power of two).	2960	increase this value (I<must> be a power of two).
2493		2961
2494	=item EV_INOTIFY_HASHSIZE	2962	=item EV_INOTIFY_HASHSIZE
2495		2963
2496	C<ev_staz> watchers use a small hash table to distribute workload by	2964	C<ev_stat> watchers use a small hash table to distribute workload by
2497	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2965	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2498	usually more than enough. If you need to manage thousands of C<ev_stat>	2966	usually more than enough. If you need to manage thousands of C<ev_stat>
2499	watchers you might want to increase this value (I<must> be a power of	2967	watchers you might want to increase this value (I<must> be a power of
2500	two).	2968	two).
2501		2969
…		…
2597		3065
2598	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3066	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2599		3067
2600	This means that, when you have a watcher that triggers in one hour and	3068	This means that, when you have a watcher that triggers in one hour and
2601	there are 100 watchers that would trigger before that then inserting will	3069	there are 100 watchers that would trigger before that then inserting will
2602	have to skip those 100 watchers.	3070	have to skip roughly seven (C<ld 100>) of these watchers.
2603		3071
2604	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3072	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2605		3073
2606	That means that for changing a timer costs less than removing/adding them	3074	That means that changing a timer costs less than removing/adding them
2607	as only the relative motion in the event queue has to be paid for.	3075	as only the relative motion in the event queue has to be paid for.
2608		3076
2609	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3077	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2610		3078
2611	These just add the watcher into an array or at the head of a list.	3079	These just add the watcher into an array or at the head of a list.
		3080
2612	=item Stopping check/prepare/idle watchers: O(1)	3081	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2613		3082
2614	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3083	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2615		3084
2616	These watchers are stored in lists then need to be walked to find the	3085	These watchers are stored in lists then need to be walked to find the
2617	correct watcher to remove. The lists are usually short (you don't usually	3086	correct watcher to remove. The lists are usually short (you don't usually
2618	have many watchers waiting for the same fd or signal).	3087	have many watchers waiting for the same fd or signal).
2619		3088
2620	=item Finding the next timer per loop iteration: O(1)	3089	=item Finding the next timer in each loop iteration: O(1)
		3090
		3091	By virtue of using a binary heap, the next timer is always found at the
		3092	beginning of the storage array.
2621		3093
2622	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3094	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2623		3095
2624	A change means an I/O watcher gets started or stopped, which requires	3096	A change means an I/O watcher gets started or stopped, which requires
2625	libev to recalculate its status (and possibly tell the kernel).	3097	libev to recalculate its status (and possibly tell the kernel, depending
		3098	on backend and wether C<ev_io_set> was used).
2626		3099
2627	=item Activating one watcher: O(1)	3100	=item Activating one watcher (putting it into the pending state): O(1)
2628		3101
2629	=item Priority handling: O(number_of_priorities)	3102	=item Priority handling: O(number_of_priorities)
2630		3103
2631	Priorities are implemented by allocating some space for each	3104	Priorities are implemented by allocating some space for each
2632	priority. When doing priority-based operations, libev usually has to	3105	priority. When doing priority-based operations, libev usually has to
2633	linearly search all the priorities.	3106	linearly search all the priorities, but starting/stopping and activating
		3107	watchers becomes O(1) w.r.t. priority handling.
		3108
		3109	=item Sending an ev_async: O(1)
		3110
		3111	=item Processing ev_async_send: O(number_of_async_watchers)
		3112
		3113	=item Processing signals: O(max_signal_number)
		3114
		3115	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3116	calls in the current loop iteration. Checking for async and signal events
		3117	involves iterating over all running async watchers or all signal numbers.
2634		3118
2635	=back	3119	=back
2636		3120
2637		3121
		3122	=head1 Win32 platform limitations and workarounds
		3123
		3124	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3125	requires, and its I/O model is fundamentally incompatible with the POSIX
		3126	model. Libev still offers limited functionality on this platform in
		3127	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3128	descriptors. This only applies when using Win32 natively, not when using
		3129	e.g. cygwin.
		3130
		3131	There is no supported compilation method available on windows except
		3132	embedding it into other applications.
		3133
		3134	Due to the many, low, and arbitrary limits on the win32 platform and the
		3135	abysmal performance of winsockets, using a large number of sockets is not
		3136	recommended (and not reasonable). If your program needs to use more than
		3137	a hundred or so sockets, then likely it needs to use a totally different
		3138	implementation for windows, as libev offers the POSIX model, which cannot
		3139	be implemented efficiently on windows (microsoft monopoly games).
		3140
		3141	=over 4
		3142
		3143	=item The winsocket select function
		3144
		3145	The winsocket C<select> function doesn't follow POSIX in that it requires
		3146	socket I<handles> and not socket I<file descriptors>. This makes select
		3147	very inefficient, and also requires a mapping from file descriptors
		3148	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3149	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3150	symbols for more info.
		3151
		3152	The configuration for a "naked" win32 using the microsoft runtime
		3153	libraries and raw winsocket select is:
		3154
		3155	#define EV_USE_SELECT 1
		3156	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3157
		3158	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3159	complexity in the O(n²) range when using win32.
		3160
		3161	=item Limited number of file descriptors
		3162
		3163	Windows has numerous arbitrary (and low) limits on things. Early versions
		3164	of winsocket's select only supported waiting for a max. of C<64> handles
		3165	(probably owning to the fact that all windows kernels can only wait for
		3166	C<64> things at the same time internally; microsoft recommends spawning a
		3167	chain of threads and wait for 63 handles and the previous thread in each).
		3168
		3169	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3170	to some high number (e.g. C<2048>) before compiling the winsocket select
		3171	call (which might be in libev or elsewhere, for example, perl does its own
		3172	select emulation on windows).
		3173
		3174	Another limit is the number of file descriptors in the microsoft runtime
		3175	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3176	or something like this inside microsoft). You can increase this by calling
		3177	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3178	arbitrary limit), but is broken in many versions of the microsoft runtime
		3179	libraries.
		3180
		3181	This might get you to about C<512> or C<2048> sockets (depending on
		3182	windows version and/or the phase of the moon). To get more, you need to
		3183	wrap all I/O functions and provide your own fd management, but the cost of
		3184	calling select (O(n²)) will likely make this unworkable.
		3185
		3186	=back
		3187
		3188
2638	=head1 AUTHOR	3189	=head1 AUTHOR
2639		3190
2640	Marc Lehmann <libev@schmorp.de>.	3191	Marc Lehmann <libev@schmorp.de>.
2641		3192

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Comparing libev/ev.pod (file contents): Revision 1.100 by root, Sat Dec 22 11:49:17 2007 UTC vs. Revision 1.140 by root, Wed Apr 2 06:34:51 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.100 by root, Sat Dec 22 11:49:17 2007 UTC vs.
Revision 1.140 by root, Wed Apr 2 06:34:51 2008 UTC