ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.94 by root, Fri Dec 21 04:38:45 2007 UTC vs.
Revision 1.144 by root, Mon Apr 7 12:33:29 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
…		…
115		130
116	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
117	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
118	you actually want to know.	133	you actually want to know.
119		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
120	=item int ev_version_major ()	141	=item int ev_version_major ()
121		142
122	=item int ev_version_minor ()	143	=item int ev_version_minor ()
123		144
124	You can find out the major and minor ABI version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
…		…
235		256
236	An event loop is described by a C<struct ev_loop *>. The library knows two	257	An event loop is described by a C<struct ev_loop *>. The library knows two
237	types of such loops, the I<default> loop, which supports signals and child	258	types of such loops, the I<default> loop, which supports signals and child
238	events, and dynamically created loops which do not.	259	events, and dynamically created loops which do not.
239		260
240	If you use threads, a common model is to run the default event loop
241	in your main thread (or in a separate thread) and for each thread you
242	create, you also create another event loop. Libev itself does no locking
243	whatsoever, so if you mix calls to the same event loop in different
244	threads, make sure you lock (this is usually a bad idea, though, even if
245	done correctly, because it's hideous and inefficient).
246
247	=over 4	261	=over 4
248		262
249	=item struct ev_loop *ev_default_loop (unsigned int flags)	263	=item struct ev_loop *ev_default_loop (unsigned int flags)
250		264
251	This will initialise the default event loop if it hasn't been initialised	265	This will initialise the default event loop if it hasn't been initialised
…		…
253	false. If it already was initialised it simply returns it (and ignores the	267	false. If it already was initialised it simply returns it (and ignores the
254	flags. If that is troubling you, check C<ev_backend ()> afterwards).	268	flags. If that is troubling you, check C<ev_backend ()> afterwards).
255		269
256	If you don't know what event loop to use, use the one returned from this	270	If you don't know what event loop to use, use the one returned from this
257	function.	271	function.
		272
		273	Note that this function is I<not> thread-safe, so if you want to use it
		274	from multiple threads, you have to lock (note also that this is unlikely,
		275	as loops cannot bes hared easily between threads anyway).
		276
		277	The default loop is the only loop that can handle C<ev_signal> and
		278	C<ev_child> watchers, and to do this, it always registers a handler
		279	for C<SIGCHLD>. If this is a problem for your app you can either
		280	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		281	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		282	C<ev_default_init>.
258		283
259	The flags argument can be used to specify special behaviour or specific	284	The flags argument can be used to specify special behaviour or specific
260	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	285	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
261		286
262	The following flags are supported:	287	The following flags are supported:
…		…
284	enabling this flag.	309	enabling this flag.
285		310
286	This works by calling C<getpid ()> on every iteration of the loop,	311	This works by calling C<getpid ()> on every iteration of the loop,
287	and thus this might slow down your event loop if you do a lot of loop	312	and thus this might slow down your event loop if you do a lot of loop
288	iterations and little real work, but is usually not noticeable (on my	313	iterations and little real work, but is usually not noticeable (on my
289	Linux system for example, C<getpid> is actually a simple 5-insn sequence	314	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
290	without a syscall and thus I<very> fast, but my Linux system also has	315	without a syscall and thus I<very> fast, but my GNU/Linux system also has
291	C<pthread_atfork> which is even faster).	316	C<pthread_atfork> which is even faster).
292		317
293	The big advantage of this flag is that you can forget about fork (and	318	The big advantage of this flag is that you can forget about fork (and
294	forget about forgetting to tell libev about forking) when you use this	319	forget about forgetting to tell libev about forking) when you use this
295	flag.	320	flag.
…		…
300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	325	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301		326
302	This is your standard select(2) backend. Not I<completely> standard, as	327	This is your standard select(2) backend. Not I<completely> standard, as
303	libev tries to roll its own fd_set with no limits on the number of fds,	328	libev tries to roll its own fd_set with no limits on the number of fds,
304	but if that fails, expect a fairly low limit on the number of fds when	329	but if that fails, expect a fairly low limit on the number of fds when
305	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	330	using this backend. It doesn't scale too well (O(highest_fd)), but its
306	the fastest backend for a low number of fds.	331	usually the fastest backend for a low number of (low-numbered :) fds.
		332
		333	To get good performance out of this backend you need a high amount of
		334	parallelity (most of the file descriptors should be busy). If you are
		335	writing a server, you should C<accept ()> in a loop to accept as many
		336	connections as possible during one iteration. You might also want to have
		337	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		338	readyness notifications you get per iteration.
307		339
308	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	340	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309		341
310	And this is your standard poll(2) backend. It's more complicated than	342	And this is your standard poll(2) backend. It's more complicated
311	select, but handles sparse fds better and has no artificial limit on the	343	than select, but handles sparse fds better and has no artificial
312	number of fds you can use (except it will slow down considerably with a	344	limit on the number of fds you can use (except it will slow down
313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	345	considerably with a lot of inactive fds). It scales similarly to select,
		346	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		347	performance tips.
314		348
315	=item C<EVBACKEND_EPOLL> (value 4, Linux)	349	=item C<EVBACKEND_EPOLL> (value 4, Linux)
316		350
317	For few fds, this backend is a bit little slower than poll and select,	351	For few fds, this backend is a bit little slower than poll and select,
318	but it scales phenomenally better. While poll and select usually scale	352	but it scales phenomenally better. While poll and select usually scale
319	like O(total_fds) where n is the total number of fds (or the highest fd),	353	like O(total_fds) where n is the total number of fds (or the highest fd),
320	epoll scales either O(1) or O(active_fds). The epoll design has a number	354	epoll scales either O(1) or O(active_fds). The epoll design has a number
321	of shortcomings, such as silently dropping events in some hard-to-detect	355	of shortcomings, such as silently dropping events in some hard-to-detect
322	cases and rewuiring a syscall per fd change, no fork support and bad	356	cases and requiring a syscall per fd change, no fork support and bad
323	support for dup:	357	support for dup.
324		358
325	While stopping, setting and starting an I/O watcher in the same iteration	359	While stopping, setting and starting an I/O watcher in the same iteration
326	will result in some caching, there is still a syscall per such incident	360	will result in some caching, there is still a syscall per such incident
327	(because the fd could point to a different file description now), so its	361	(because the fd could point to a different file description now), so its
328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	362	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
…		…
330		364
331	Please note that epoll sometimes generates spurious notifications, so you	365	Please note that epoll sometimes generates spurious notifications, so you
332	need to use non-blocking I/O or other means to avoid blocking when no data	366	need to use non-blocking I/O or other means to avoid blocking when no data
333	(or space) is available.	367	(or space) is available.
334		368
		369	Best performance from this backend is achieved by not unregistering all
		370	watchers for a file descriptor until it has been closed, if possible, i.e.
		371	keep at least one watcher active per fd at all times.
		372
		373	While nominally embeddeble in other event loops, this feature is broken in
		374	all kernel versions tested so far.
		375
335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	376	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
336		377
337	Kqueue deserves special mention, as at the time of this writing, it	378	Kqueue deserves special mention, as at the time of this writing, it
338	was broken on I<all> BSDs (usually it doesn't work with anything but	379	was broken on all BSDs except NetBSD (usually it doesn't work reliably
339	sockets and pipes, except on Darwin, where of course it's completely	380	with anything but sockets and pipes, except on Darwin, where of course
340	useless. On NetBSD, it seems to work for all the FD types I tested, so it
341	is used by default there). For this reason it's not being "autodetected"	381	it's completely useless). For this reason it's not being "autodetected"
342	unless you explicitly specify it explicitly in the flags (i.e. using	382	unless you explicitly specify it explicitly in the flags (i.e. using
343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	383	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
344	system like NetBSD.	384	system like NetBSD.
345		385
		386	You still can embed kqueue into a normal poll or select backend and use it
		387	only for sockets (after having made sure that sockets work with kqueue on
		388	the target platform). See C<ev_embed> watchers for more info.
		389
346	It scales in the same way as the epoll backend, but the interface to the	390	It scales in the same way as the epoll backend, but the interface to the
347	kernel is more efficient (which says nothing about its actual speed,	391	kernel is more efficient (which says nothing about its actual speed, of
348	of course). While stopping, setting and starting an I/O watcher does	392	course). While stopping, setting and starting an I/O watcher does never
349	never cause an extra syscall as with epoll, it still adds up to two event	393	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
350	changes per incident, support for C<fork ()> is very bad and it drops fds	394	two event changes per incident, support for C<fork ()> is very bad and it
351	silently in similarly hard-to-detetc cases.	395	drops fds silently in similarly hard-to-detect cases.
		396
		397	This backend usually performs well under most conditions.
		398
		399	While nominally embeddable in other event loops, this doesn't work
		400	everywhere, so you might need to test for this. And since it is broken
		401	almost everywhere, you should only use it when you have a lot of sockets
		402	(for which it usually works), by embedding it into another event loop
		403	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		404	sockets.
352		405
353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	406	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
354		407
355	This is not implemented yet (and might never be).	408	This is not implemented yet (and might never be, unless you send me an
		409	implementation). According to reports, C</dev/poll> only supports sockets
		410	and is not embeddable, which would limit the usefulness of this backend
		411	immensely.
356		412
357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	413	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
358		414
359	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	415	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
360	it's really slow, but it still scales very well (O(active_fds)).	416	it's really slow, but it still scales very well (O(active_fds)).
361		417
362	Please note that solaris event ports can deliver a lot of spurious	418	Please note that solaris event ports can deliver a lot of spurious
363	notifications, so you need to use non-blocking I/O or other means to avoid	419	notifications, so you need to use non-blocking I/O or other means to avoid
364	blocking when no data (or space) is available.	420	blocking when no data (or space) is available.
365		421
		422	While this backend scales well, it requires one system call per active
		423	file descriptor per loop iteration. For small and medium numbers of file
		424	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		425	might perform better.
		426
		427	On the positive side, ignoring the spurious readyness notifications, this
		428	backend actually performed to specification in all tests and is fully
		429	embeddable, which is a rare feat among the OS-specific backends.
		430
366	=item C<EVBACKEND_ALL>	431	=item C<EVBACKEND_ALL>
367		432
368	Try all backends (even potentially broken ones that wouldn't be tried	433	Try all backends (even potentially broken ones that wouldn't be tried
369	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	434	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
370	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	435	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
371		436
		437	It is definitely not recommended to use this flag.
		438
372	=back	439	=back
373		440
374	If one or more of these are ored into the flags value, then only these	441	If one or more of these are ored into the flags value, then only these
375	backends will be tried (in the reverse order as given here). If none are	442	backends will be tried (in the reverse order as listed here). If none are
376	specified, most compiled-in backend will be tried, usually in reverse	443	specified, all backends in C<ev_recommended_backends ()> will be tried.
377	order of their flag values :)
378		444
379	The most typical usage is like this:	445	The most typical usage is like this:
380		446
381	if (!ev_default_loop (0))	447	if (!ev_default_loop (0))
382	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	448	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
396		462
397	Similar to C<ev_default_loop>, but always creates a new event loop that is	463	Similar to C<ev_default_loop>, but always creates a new event loop that is
398	always distinct from the default loop. Unlike the default loop, it cannot	464	always distinct from the default loop. Unlike the default loop, it cannot
399	handle signal and child watchers, and attempts to do so will be greeted by	465	handle signal and child watchers, and attempts to do so will be greeted by
400	undefined behaviour (or a failed assertion if assertions are enabled).	466	undefined behaviour (or a failed assertion if assertions are enabled).
		467
		468	Note that this function I<is> thread-safe, and the recommended way to use
		469	libev with threads is indeed to create one loop per thread, and using the
		470	default loop in the "main" or "initial" thread.
401		471
402	Example: Try to create a event loop that uses epoll and nothing else.	472	Example: Try to create a event loop that uses epoll and nothing else.
403		473
404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	474	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
405	if (!epoller)	475	if (!epoller)
…		…
429	Like C<ev_default_destroy>, but destroys an event loop created by an	499	Like C<ev_default_destroy>, but destroys an event loop created by an
430	earlier call to C<ev_loop_new>.	500	earlier call to C<ev_loop_new>.
431		501
432	=item ev_default_fork ()	502	=item ev_default_fork ()
433		503
		504	This function sets a flag that causes subsequent C<ev_loop> iterations
434	This function reinitialises the kernel state for backends that have	505	to reinitialise the kernel state for backends that have one. Despite the
435	one. Despite the name, you can call it anytime, but it makes most sense	506	name, you can call it anytime, but it makes most sense after forking, in
436	after forking, in either the parent or child process (or both, but that	507	the child process (or both child and parent, but that again makes little
437	again makes little sense).	508	sense). You I<must> call it in the child before using any of the libev
		509	functions, and it will only take effect at the next C<ev_loop> iteration.
438		510
439	You I<must> call this function in the child process after forking if and	511	On the other hand, you only need to call this function in the child
440	only if you want to use the event library in both processes. If you just	512	process if and only if you want to use the event library in the child. If
441	fork+exec, you don't have to call it.	513	you just fork+exec, you don't have to call it at all.
442		514
443	The function itself is quite fast and it's usually not a problem to call	515	The function itself is quite fast and it's usually not a problem to call
444	it just in case after a fork. To make this easy, the function will fit in	516	it just in case after a fork. To make this easy, the function will fit in
445	quite nicely into a call to C<pthread_atfork>:	517	quite nicely into a call to C<pthread_atfork>:
446		518
447	pthread_atfork (0, 0, ev_default_fork);	519	pthread_atfork (0, 0, ev_default_fork);
448		520
449	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
450	without calling this function, so if you force one of those backends you
451	do not need to care.
452
453	=item ev_loop_fork (loop)	521	=item ev_loop_fork (loop)
454		522
455	Like C<ev_default_fork>, but acts on an event loop created by	523	Like C<ev_default_fork>, but acts on an event loop created by
456	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	524	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
457	after fork, and how you do this is entirely your own problem.	525	after fork, and how you do this is entirely your own problem.
		526
		527	=item int ev_is_default_loop (loop)
		528
		529	Returns true when the given loop actually is the default loop, false otherwise.
458		530
459	=item unsigned int ev_loop_count (loop)	531	=item unsigned int ev_loop_count (loop)
460		532
461	Returns the count of loop iterations for the loop, which is identical to	533	Returns the count of loop iterations for the loop, which is identical to
462	the number of times libev did poll for new events. It starts at C<0> and	534	the number of times libev did poll for new events. It starts at C<0> and
…		…
507	usually a better approach for this kind of thing.	579	usually a better approach for this kind of thing.
508		580
509	Here are the gory details of what C<ev_loop> does:	581	Here are the gory details of what C<ev_loop> does:
510		582
511	- Before the first iteration, call any pending watchers.	583	- Before the first iteration, call any pending watchers.
512	* If there are no active watchers (reference count is zero), return.	584	* If EVFLAG_FORKCHECK was used, check for a fork.
513	- Queue all prepare watchers and then call all outstanding watchers.	585	- If a fork was detected, queue and call all fork watchers.
		586	- Queue and call all prepare watchers.
514	- If we have been forked, recreate the kernel state.	587	- If we have been forked, recreate the kernel state.
515	- Update the kernel state with all outstanding changes.	588	- Update the kernel state with all outstanding changes.
516	- Update the "event loop time".	589	- Update the "event loop time".
517	- Calculate for how long to block.	590	- Calculate for how long to sleep or block, if at all
		591	(active idle watchers, EVLOOP_NONBLOCK or not having
		592	any active watchers at all will result in not sleeping).
		593	- Sleep if the I/O and timer collect interval say so.
518	- Block the process, waiting for any events.	594	- Block the process, waiting for any events.
519	- Queue all outstanding I/O (fd) events.	595	- Queue all outstanding I/O (fd) events.
520	- Update the "event loop time" and do time jump handling.	596	- Update the "event loop time" and do time jump handling.
521	- Queue all outstanding timers.	597	- Queue all outstanding timers.
522	- Queue all outstanding periodics.	598	- Queue all outstanding periodics.
523	- If no events are pending now, queue all idle watchers.	599	- If no events are pending now, queue all idle watchers.
524	- Queue all check watchers.	600	- Queue all check watchers.
525	- Call all queued watchers in reverse order (i.e. check watchers first).	601	- Call all queued watchers in reverse order (i.e. check watchers first).
526	Signals and child watchers are implemented as I/O watchers, and will	602	Signals and child watchers are implemented as I/O watchers, and will
527	be handled here by queueing them when their watcher gets executed.	603	be handled here by queueing them when their watcher gets executed.
528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	604	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
529	were used, return, otherwise continue with step *.	605	were used, or there are no active watchers, return, otherwise
		606	continue with step *.
530		607
531	Example: Queue some jobs and then loop until no events are outsanding	608	Example: Queue some jobs and then loop until no events are outstanding
532	anymore.	609	anymore.
533		610
534	... queue jobs here, make sure they register event watchers as long	611	... queue jobs here, make sure they register event watchers as long
535	... as they still have work to do (even an idle watcher will do..)	612	... as they still have work to do (even an idle watcher will do..)
536	ev_loop (my_loop, 0);	613	ev_loop (my_loop, 0);
…		…
540		617
541	Can be used to make a call to C<ev_loop> return early (but only after it	618	Can be used to make a call to C<ev_loop> return early (but only after it
542	has processed all outstanding events). The C<how> argument must be either	619	has processed all outstanding events). The C<how> argument must be either
543	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	620	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
544	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	621	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		622
		623	This "unloop state" will be cleared when entering C<ev_loop> again.
545		624
546	=item ev_ref (loop)	625	=item ev_ref (loop)
547		626
548	=item ev_unref (loop)	627	=item ev_unref (loop)
549		628
…		…
554	returning, ev_unref() after starting, and ev_ref() before stopping it. For	633	returning, ev_unref() after starting, and ev_ref() before stopping it. For
555	example, libev itself uses this for its internal signal pipe: It is not	634	example, libev itself uses this for its internal signal pipe: It is not
556	visible to the libev user and should not keep C<ev_loop> from exiting if	635	visible to the libev user and should not keep C<ev_loop> from exiting if
557	no event watchers registered by it are active. It is also an excellent	636	no event watchers registered by it are active. It is also an excellent
558	way to do this for generic recurring timers or from within third-party	637	way to do this for generic recurring timers or from within third-party
559	libraries. Just remember to I<unref after start> and I<ref before stop>.	638	libraries. Just remember to I<unref after start> and I<ref before stop>
		639	(but only if the watcher wasn't active before, or was active before,
		640	respectively).
560		641
561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	642	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
562	running when nothing else is active.	643	running when nothing else is active.
563		644
564	struct ev_signal exitsig;	645	struct ev_signal exitsig;
…		…
568		649
569	Example: For some weird reason, unregister the above signal handler again.	650	Example: For some weird reason, unregister the above signal handler again.
570		651
571	ev_ref (loop);	652	ev_ref (loop);
572	ev_signal_stop (loop, &exitsig);	653	ev_signal_stop (loop, &exitsig);
		654
		655	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		656
		657	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		658
		659	These advanced functions influence the time that libev will spend waiting
		660	for events. Both are by default C<0>, meaning that libev will try to
		661	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		662
		663	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		664	allows libev to delay invocation of I/O and timer/periodic callbacks to
		665	increase efficiency of loop iterations.
		666
		667	The background is that sometimes your program runs just fast enough to
		668	handle one (or very few) event(s) per loop iteration. While this makes
		669	the program responsive, it also wastes a lot of CPU time to poll for new
		670	events, especially with backends like C<select ()> which have a high
		671	overhead for the actual polling but can deliver many events at once.
		672
		673	By setting a higher I<io collect interval> you allow libev to spend more
		674	time collecting I/O events, so you can handle more events per iteration,
		675	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		676	C<ev_timer>) will be not affected. Setting this to a non-null value will
		677	introduce an additional C<ev_sleep ()> call into most loop iterations.
		678
		679	Likewise, by setting a higher I<timeout collect interval> you allow libev
		680	to spend more time collecting timeouts, at the expense of increased
		681	latency (the watcher callback will be called later). C<ev_io> watchers
		682	will not be affected. Setting this to a non-null value will not introduce
		683	any overhead in libev.
		684
		685	Many (busy) programs can usually benefit by setting the io collect
		686	interval to a value near C<0.1> or so, which is often enough for
		687	interactive servers (of course not for games), likewise for timeouts. It
		688	usually doesn't make much sense to set it to a lower value than C<0.01>,
		689	as this approsaches the timing granularity of most systems.
573		690
574	=back	691	=back
575		692
576		693
577	=head1 ANATOMY OF A WATCHER	694	=head1 ANATOMY OF A WATCHER
…		…
676		793
677	=item C<EV_FORK>	794	=item C<EV_FORK>
678		795
679	The event loop has been resumed in the child process after fork (see	796	The event loop has been resumed in the child process after fork (see
680	C<ev_fork>).	797	C<ev_fork>).
		798
		799	=item C<EV_ASYNC>
		800
		801	The given async watcher has been asynchronously notified (see C<ev_async>).
681		802
682	=item C<EV_ERROR>	803	=item C<EV_ERROR>
683		804
684	An unspecified error has occured, the watcher has been stopped. This might	805	An unspecified error has occured, the watcher has been stopped. This might
685	happen because the watcher could not be properly started because libev	806	happen because the watcher could not be properly started because libev
…		…
903	In general you can register as many read and/or write event watchers per	1024	In general you can register as many read and/or write event watchers per
904	fd as you want (as long as you don't confuse yourself). Setting all file	1025	fd as you want (as long as you don't confuse yourself). Setting all file
905	descriptors to non-blocking mode is also usually a good idea (but not	1026	descriptors to non-blocking mode is also usually a good idea (but not
906	required if you know what you are doing).	1027	required if you know what you are doing).
907		1028
908	You have to be careful with dup'ed file descriptors, though. Some backends
909	(the linux epoll backend is a notable example) cannot handle dup'ed file
910	descriptors correctly if you register interest in two or more fds pointing
911	to the same underlying file/socket/etc. description (that is, they share
912	the same underlying "file open").
913
914	If you must do this, then force the use of a known-to-be-good backend	1029	If you must do this, then force the use of a known-to-be-good backend
915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1030	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
916	C<EVBACKEND_POLL>).	1031	C<EVBACKEND_POLL>).
917		1032
918	Another thing you have to watch out for is that it is quite easy to	1033	Another thing you have to watch out for is that it is quite easy to
…		…
949		1064
950	This is how one would do it normally anyway, the important point is that	1065	This is how one would do it normally anyway, the important point is that
951	the libev application should not optimise around libev but should leave	1066	the libev application should not optimise around libev but should leave
952	optimisations to libev.	1067	optimisations to libev.
953		1068
954	=head3 Ths special problem of dup'ed file descriptors	1069	=head3 The special problem of dup'ed file descriptors
955		1070
956	Some backends (e.g. epoll), cannot register events for file descriptors,	1071	Some backends (e.g. epoll), cannot register events for file descriptors,
957	but only events for the underlying file descriptions. That menas when you	1072	but only events for the underlying file descriptions. That means when you
958	have C<dup ()>'ed file descriptors and register events for them, only one	1073	have C<dup ()>'ed file descriptors or weirder constellations, and register
959	file descriptor might actually receive events.	1074	events for them, only one file descriptor might actually receive events.
960		1075
961	There is no workaorund possible except not registering events	1076	There is no workaround possible except not registering events
962	for potentially C<dup ()>'ed file descriptors or to resort to	1077	for potentially C<dup ()>'ed file descriptors, or to resort to
963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1078	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
964		1079
965	=head3 The special problem of fork	1080	=head3 The special problem of fork
966		1081
967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1082	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
…		…
971	To support fork in your programs, you either have to call	1086	To support fork in your programs, you either have to call
972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1087	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1088	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
974	C<EVBACKEND_POLL>.	1089	C<EVBACKEND_POLL>.
975		1090
		1091	=head3 The special problem of SIGPIPE
		1092
		1093	While not really specific to libev, it is easy to forget about SIGPIPE:
		1094	when reading from a pipe whose other end has been closed, your program
		1095	gets send a SIGPIPE, which, by default, aborts your program. For most
		1096	programs this is sensible behaviour, for daemons, this is usually
		1097	undesirable.
		1098
		1099	So when you encounter spurious, unexplained daemon exits, make sure you
		1100	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1101	somewhere, as that would have given you a big clue).
		1102
976		1103
977	=head3 Watcher-Specific Functions	1104	=head3 Watcher-Specific Functions
978		1105
979	=over 4	1106	=over 4
980		1107
…		…
993	=item int events [read-only]	1120	=item int events [read-only]
994		1121
995	The events being watched.	1122	The events being watched.
996		1123
997	=back	1124	=back
		1125
		1126	=head3 Examples
998		1127
999	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1128	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1000	readable, but only once. Since it is likely line-buffered, you could	1129	readable, but only once. Since it is likely line-buffered, you could
1001	attempt to read a whole line in the callback.	1130	attempt to read a whole line in the callback.
1002		1131
…		…
1055	configure a timer to trigger every 10 seconds, then it will trigger at	1184	configure a timer to trigger every 10 seconds, then it will trigger at
1056	exactly 10 second intervals. If, however, your program cannot keep up with	1185	exactly 10 second intervals. If, however, your program cannot keep up with
1057	the timer (because it takes longer than those 10 seconds to do stuff) the	1186	the timer (because it takes longer than those 10 seconds to do stuff) the
1058	timer will not fire more than once per event loop iteration.	1187	timer will not fire more than once per event loop iteration.
1059		1188
1060	=item ev_timer_again (loop)	1189	=item ev_timer_again (loop, ev_timer *)
1061		1190
1062	This will act as if the timer timed out and restart it again if it is	1191	This will act as if the timer timed out and restart it again if it is
1063	repeating. The exact semantics are:	1192	repeating. The exact semantics are:
1064		1193
1065	If the timer is pending, its pending status is cleared.	1194	If the timer is pending, its pending status is cleared.
…		…
1100	or C<ev_timer_again> is called and determines the next timeout (if any),	1229	or C<ev_timer_again> is called and determines the next timeout (if any),
1101	which is also when any modifications are taken into account.	1230	which is also when any modifications are taken into account.
1102		1231
1103	=back	1232	=back
1104		1233
		1234	=head3 Examples
		1235
1105	Example: Create a timer that fires after 60 seconds.	1236	Example: Create a timer that fires after 60 seconds.
1106		1237
1107	static void	1238	static void
1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1239	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1109	{	1240	{
…		…
1172	In this configuration the watcher triggers an event at the wallclock time	1303	In this configuration the watcher triggers an event at the wallclock time
1173	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1304	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1174	that is, if it is to be run at January 1st 2011 then it will run when the	1305	that is, if it is to be run at January 1st 2011 then it will run when the
1175	system time reaches or surpasses this time.	1306	system time reaches or surpasses this time.
1176		1307
1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1308	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1178		1309
1179	In this mode the watcher will always be scheduled to time out at the next	1310	In this mode the watcher will always be scheduled to time out at the next
1180	C<at + N * interval> time (for some integer N, which can also be negative)	1311	C<at + N * interval> time (for some integer N, which can also be negative)
1181	and then repeat, regardless of any time jumps.	1312	and then repeat, regardless of any time jumps.
1182		1313
…		…
1265		1396
1266	When active, contains the absolute time that the watcher is supposed to	1397	When active, contains the absolute time that the watcher is supposed to
1267	trigger next.	1398	trigger next.
1268		1399
1269	=back	1400	=back
		1401
		1402	=head3 Examples
1270		1403
1271	Example: Call a callback every hour, or, more precisely, whenever the	1404	Example: Call a callback every hour, or, more precisely, whenever the
1272	system clock is divisible by 3600. The callback invocation times have	1405	system clock is divisible by 3600. The callback invocation times have
1273	potentially a lot of jittering, but good long-term stability.	1406	potentially a lot of jittering, but good long-term stability.
1274		1407
…		…
1314	with the kernel (thus it coexists with your own signal handlers as long	1447	with the kernel (thus it coexists with your own signal handlers as long
1315	as you don't register any with libev). Similarly, when the last signal	1448	as you don't register any with libev). Similarly, when the last signal
1316	watcher for a signal is stopped libev will reset the signal handler to	1449	watcher for a signal is stopped libev will reset the signal handler to
1317	SIG_DFL (regardless of what it was set to before).	1450	SIG_DFL (regardless of what it was set to before).
1318		1451
		1452	If possible and supported, libev will install its handlers with
		1453	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1454	interrupted. If you have a problem with syscalls getting interrupted by
		1455	signals you can block all signals in an C<ev_check> watcher and unblock
		1456	them in an C<ev_prepare> watcher.
		1457
1319	=head3 Watcher-Specific Functions and Data Members	1458	=head3 Watcher-Specific Functions and Data Members
1320		1459
1321	=over 4	1460	=over 4
1322		1461
1323	=item ev_signal_init (ev_signal *, callback, int signum)	1462	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1331		1470
1332	The signal the watcher watches out for.	1471	The signal the watcher watches out for.
1333		1472
1334	=back	1473	=back
1335		1474
		1475	=head3 Examples
		1476
		1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1478
		1479	static void
		1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1481	{
		1482	ev_unloop (loop, EVUNLOOP_ALL);
		1483	}
		1484
		1485	struct ev_signal signal_watcher;
		1486	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1487	ev_signal_start (loop, &sigint_cb);
		1488
1336		1489
1337	=head2 C<ev_child> - watch out for process status changes	1490	=head2 C<ev_child> - watch out for process status changes
1338		1491
1339	Child watchers trigger when your process receives a SIGCHLD in response to	1492	Child watchers trigger when your process receives a SIGCHLD in response to
1340	some child status changes (most typically when a child of yours dies).	1493	some child status changes (most typically when a child of yours dies). It
		1494	is permissible to install a child watcher I<after> the child has been
		1495	forked (which implies it might have already exited), as long as the event
		1496	loop isn't entered (or is continued from a watcher).
		1497
		1498	Only the default event loop is capable of handling signals, and therefore
		1499	you can only rgeister child watchers in the default event loop.
		1500
		1501	=head3 Process Interaction
		1502
		1503	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1504	initialised. This is necessary to guarantee proper behaviour even if
		1505	the first child watcher is started after the child exits. The occurance
		1506	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1507	synchronously as part of the event loop processing. Libev always reaps all
		1508	children, even ones not watched.
		1509
		1510	=head3 Overriding the Built-In Processing
		1511
		1512	Libev offers no special support for overriding the built-in child
		1513	processing, but if your application collides with libev's default child
		1514	handler, you can override it easily by installing your own handler for
		1515	C<SIGCHLD> after initialising the default loop, and making sure the
		1516	default loop never gets destroyed. You are encouraged, however, to use an
		1517	event-based approach to child reaping and thus use libev's support for
		1518	that, so other libev users can use C<ev_child> watchers freely.
1341		1519
1342	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1343		1521
1344	=over 4	1522	=over 4
1345		1523
1346	=item ev_child_init (ev_child *, callback, int pid)	1524	=item ev_child_init (ev_child *, callback, int pid, int trace)
1347		1525
1348	=item ev_child_set (ev_child *, int pid)	1526	=item ev_child_set (ev_child *, int pid, int trace)
1349		1527
1350	Configures the watcher to wait for status changes of process C<pid> (or	1528	Configures the watcher to wait for status changes of process C<pid> (or
1351	I<any> process if C<pid> is specified as C<0>). The callback can look	1529	I<any> process if C<pid> is specified as C<0>). The callback can look
1352	at the C<rstatus> member of the C<ev_child> watcher structure to see	1530	at the C<rstatus> member of the C<ev_child> watcher structure to see
1353	the status word (use the macros from C<sys/wait.h> and see your systems	1531	the status word (use the macros from C<sys/wait.h> and see your systems
1354	C<waitpid> documentation). The C<rpid> member contains the pid of the	1532	C<waitpid> documentation). The C<rpid> member contains the pid of the
1355	process causing the status change.	1533	process causing the status change. C<trace> must be either C<0> (only
		1534	activate the watcher when the process terminates) or C<1> (additionally
		1535	activate the watcher when the process is stopped or continued).
1356		1536
1357	=item int pid [read-only]	1537	=item int pid [read-only]
1358		1538
1359	The process id this watcher watches out for, or C<0>, meaning any process id.	1539	The process id this watcher watches out for, or C<0>, meaning any process id.
1360		1540
…		…
1367	The process exit/trace status caused by C<rpid> (see your systems	1547	The process exit/trace status caused by C<rpid> (see your systems
1368	C<waitpid> and C<sys/wait.h> documentation for details).	1548	C<waitpid> and C<sys/wait.h> documentation for details).
1369		1549
1370	=back	1550	=back
1371		1551
1372	Example: Try to exit cleanly on SIGINT and SIGTERM.	1552	=head3 Examples
		1553
		1554	Example: C<fork()> a new process and install a child handler to wait for
		1555	its completion.
		1556
		1557	ev_child cw;
1373		1558
1374	static void	1559	static void
1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1560	child_cb (EV_P_ struct ev_child *w, int revents)
1376	{	1561	{
1377	ev_unloop (loop, EVUNLOOP_ALL);	1562	ev_child_stop (EV_A_ w);
		1563	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1378	}	1564	}
1379		1565
1380	struct ev_signal signal_watcher;	1566	pid_t pid = fork ();
1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1567
1382	ev_signal_start (loop, &sigint_cb);	1568	if (pid < 0)
		1569	// error
		1570	else if (pid == 0)
		1571	{
		1572	// the forked child executes here
		1573	exit (1);
		1574	}
		1575	else
		1576	{
		1577	ev_child_init (&cw, child_cb, pid, 0);
		1578	ev_child_start (EV_DEFAULT_ &cw);
		1579	}
1383		1580
1384		1581
1385	=head2 C<ev_stat> - did the file attributes just change?	1582	=head2 C<ev_stat> - did the file attributes just change?
1386		1583
1387	This watches a filesystem path for attribute changes. That is, it calls	1584	This watches a filesystem path for attribute changes. That is, it calls
…		…
1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1613	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1417	to fall back to regular polling again even with inotify, but changes are	1614	to fall back to regular polling again even with inotify, but changes are
1418	usually detected immediately, and if the file exists there will be no	1615	usually detected immediately, and if the file exists there will be no
1419	polling.	1616	polling.
1420		1617
		1618	=head3 ABI Issues (Largefile Support)
		1619
		1620	Libev by default (unless the user overrides this) uses the default
		1621	compilation environment, which means that on systems with optionally
		1622	disabled large file support, you get the 32 bit version of the stat
		1623	structure. When using the library from programs that change the ABI to
		1624	use 64 bit file offsets the programs will fail. In that case you have to
		1625	compile libev with the same flags to get binary compatibility. This is
		1626	obviously the case with any flags that change the ABI, but the problem is
		1627	most noticably with ev_stat and largefile support.
		1628
		1629	=head3 Inotify
		1630
		1631	When C<inotify (7)> support has been compiled into libev (generally only
		1632	available on Linux) and present at runtime, it will be used to speed up
		1633	change detection where possible. The inotify descriptor will be created lazily
		1634	when the first C<ev_stat> watcher is being started.
		1635
		1636	Inotify presense does not change the semantics of C<ev_stat> watchers
		1637	except that changes might be detected earlier, and in some cases, to avoid
		1638	making regular C<stat> calls. Even in the presense of inotify support
		1639	there are many cases where libev has to resort to regular C<stat> polling.
		1640
		1641	(There is no support for kqueue, as apparently it cannot be used to
		1642	implement this functionality, due to the requirement of having a file
		1643	descriptor open on the object at all times).
		1644
		1645	=head3 The special problem of stat time resolution
		1646
		1647	The C<stat ()> syscall only supports full-second resolution portably, and
		1648	even on systems where the resolution is higher, many filesystems still
		1649	only support whole seconds.
		1650
		1651	That means that, if the time is the only thing that changes, you might
		1652	miss updates: on the first update, C<ev_stat> detects a change and calls
		1653	your callback, which does something. When there is another update within
		1654	the same second, C<ev_stat> will be unable to detect it.
		1655
		1656	The solution to this is to delay acting on a change for a second (or till
		1657	the next second boundary), using a roughly one-second delay C<ev_timer>
		1658	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1659	is added to work around small timing inconsistencies of some operating
		1660	systems.
		1661
1421	=head3 Watcher-Specific Functions and Data Members	1662	=head3 Watcher-Specific Functions and Data Members
1422		1663
1423	=over 4	1664	=over 4
1424		1665
1425	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1666	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
…		…
1434		1675
1435	The callback will be receive C<EV_STAT> when a change was detected,	1676	The callback will be receive C<EV_STAT> when a change was detected,
1436	relative to the attributes at the time the watcher was started (or the	1677	relative to the attributes at the time the watcher was started (or the
1437	last change was detected).	1678	last change was detected).
1438		1679
1439	=item ev_stat_stat (ev_stat *)	1680	=item ev_stat_stat (loop, ev_stat *)
1440		1681
1441	Updates the stat buffer immediately with new values. If you change the	1682	Updates the stat buffer immediately with new values. If you change the
1442	watched path in your callback, you could call this fucntion to avoid	1683	watched path in your callback, you could call this fucntion to avoid
1443	detecting this change (while introducing a race condition). Can also be	1684	detecting this change (while introducing a race condition). Can also be
1444	useful simply to find out the new values.	1685	useful simply to find out the new values.
…		…
1462	=item const char *path [read-only]	1703	=item const char *path [read-only]
1463		1704
1464	The filesystem path that is being watched.	1705	The filesystem path that is being watched.
1465		1706
1466	=back	1707	=back
		1708
		1709	=head3 Examples
1467		1710
1468	Example: Watch C</etc/passwd> for attribute changes.	1711	Example: Watch C</etc/passwd> for attribute changes.
1469		1712
1470	static void	1713	static void
1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1714	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1484	}	1727	}
1485		1728
1486	...	1729	...
1487	ev_stat passwd;	1730	ev_stat passwd;
1488		1731
1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1732	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1490	ev_stat_start (loop, &passwd);	1733	ev_stat_start (loop, &passwd);
		1734
		1735	Example: Like above, but additionally use a one-second delay so we do not
		1736	miss updates (however, frequent updates will delay processing, too, so
		1737	one might do the work both on C<ev_stat> callback invocation I<and> on
		1738	C<ev_timer> callback invocation).
		1739
		1740	static ev_stat passwd;
		1741	static ev_timer timer;
		1742
		1743	static void
		1744	timer_cb (EV_P_ ev_timer *w, int revents)
		1745	{
		1746	ev_timer_stop (EV_A_ w);
		1747
		1748	/* now it's one second after the most recent passwd change */
		1749	}
		1750
		1751	static void
		1752	stat_cb (EV_P_ ev_stat *w, int revents)
		1753	{
		1754	/* reset the one-second timer */
		1755	ev_timer_again (EV_A_ &timer);
		1756	}
		1757
		1758	...
		1759	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1760	ev_stat_start (loop, &passwd);
		1761	ev_timer_init (&timer, timer_cb, 0., 1.01);
1491		1762
1492		1763
1493	=head2 C<ev_idle> - when you've got nothing better to do...	1764	=head2 C<ev_idle> - when you've got nothing better to do...
1494		1765
1495	Idle watchers trigger events when no other events of the same or higher	1766	Idle watchers trigger events when no other events of the same or higher
…		…
1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1792	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1522	believe me.	1793	believe me.
1523		1794
1524	=back	1795	=back
1525		1796
		1797	=head3 Examples
		1798
1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1799	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1527	callback, free it. Also, use no error checking, as usual.	1800	callback, free it. Also, use no error checking, as usual.
1528		1801
1529	static void	1802	static void
1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1803	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1531	{	1804	{
1532	free (w);	1805	free (w);
1533	// now do something you wanted to do when the program has	1806	// now do something you wanted to do when the program has
1534	// no longer asnything immediate to do.	1807	// no longer anything immediate to do.
1535	}	1808	}
1536		1809
1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1810	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1538	ev_idle_init (idle_watcher, idle_cb);	1811	ev_idle_init (idle_watcher, idle_cb);
1539	ev_idle_start (loop, idle_cb);	1812	ev_idle_start (loop, idle_cb);
…		…
1581		1854
1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1855	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1583	priority, to ensure that they are being run before any other watchers	1856	priority, to ensure that they are being run before any other watchers
1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1857	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1585	too) should not activate ("feed") events into libev. While libev fully	1858	too) should not activate ("feed") events into libev. While libev fully
1586	supports this, they will be called before other C<ev_check> watchers did	1859	supports this, they will be called before other C<ev_check> watchers
1587	their job. As C<ev_check> watchers are often used to embed other event	1860	did their job. As C<ev_check> watchers are often used to embed other
1588	loops those other event loops might be in an unusable state until their	1861	(non-libev) event loops those other event loops might be in an unusable
1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1862	state until their C<ev_check> watcher ran (always remind yourself to
1590	others).	1863	coexist peacefully with others).
1591		1864
1592	=head3 Watcher-Specific Functions and Data Members	1865	=head3 Watcher-Specific Functions and Data Members
1593		1866
1594	=over 4	1867	=over 4
1595		1868
…		…
1600	Initialises and configures the prepare or check watcher - they have no	1873	Initialises and configures the prepare or check watcher - they have no
1601	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1874	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1602	macros, but using them is utterly, utterly and completely pointless.	1875	macros, but using them is utterly, utterly and completely pointless.
1603		1876
1604	=back	1877	=back
		1878
		1879	=head3 Examples
1605		1880
1606	There are a number of principal ways to embed other event loops or modules	1881	There are a number of principal ways to embed other event loops or modules
1607	into libev. Here are some ideas on how to include libadns into libev	1882	into libev. Here are some ideas on how to include libadns into libev
1608	(there is a Perl module named C<EV::ADNS> that does this, which you could	1883	(there is a Perl module named C<EV::ADNS> that does this, which you could
1609	use for an actually working example. Another Perl module named C<EV::Glib>	1884	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	=head2 C<ev_embed> - when one backend isn't enough...	2009	=head2 C<ev_embed> - when one backend isn't enough...
1735		2010
1736	This is a rather advanced watcher type that lets you embed one event loop	2011	This is a rather advanced watcher type that lets you embed one event loop
1737	into another (currently only C<ev_io> events are supported in the embedded	2012	into another (currently only C<ev_io> events are supported in the embedded
1738	loop, other types of watchers might be handled in a delayed or incorrect	2013	loop, other types of watchers might be handled in a delayed or incorrect
1739	fashion and must not be used). (See portability notes, below).	2014	fashion and must not be used).
1740		2015
1741	There are primarily two reasons you would want that: work around bugs and	2016	There are primarily two reasons you would want that: work around bugs and
1742	prioritise I/O.	2017	prioritise I/O.
1743		2018
1744	As an example for a bug workaround, the kqueue backend might only support	2019	As an example for a bug workaround, the kqueue backend might only support
…		…
1778	portable one.	2053	portable one.
1779		2054
1780	So when you want to use this feature you will always have to be prepared	2055	So when you want to use this feature you will always have to be prepared
1781	that you cannot get an embeddable loop. The recommended way to get around	2056	that you cannot get an embeddable loop. The recommended way to get around
1782	this is to have a separate variables for your embeddable loop, try to	2057	this is to have a separate variables for your embeddable loop, try to
1783	create it, and if that fails, use the normal loop for everything:	2058	create it, and if that fails, use the normal loop for everything.
		2059
		2060	=head3 Watcher-Specific Functions and Data Members
		2061
		2062	=over 4
		2063
		2064	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2065
		2066	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2067
		2068	Configures the watcher to embed the given loop, which must be
		2069	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2070	invoked automatically, otherwise it is the responsibility of the callback
		2071	to invoke it (it will continue to be called until the sweep has been done,
		2072	if you do not want thta, you need to temporarily stop the embed watcher).
		2073
		2074	=item ev_embed_sweep (loop, ev_embed *)
		2075
		2076	Make a single, non-blocking sweep over the embedded loop. This works
		2077	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2078	apropriate way for embedded loops.
		2079
		2080	=item struct ev_loop *other [read-only]
		2081
		2082	The embedded event loop.
		2083
		2084	=back
		2085
		2086	=head3 Examples
		2087
		2088	Example: Try to get an embeddable event loop and embed it into the default
		2089	event loop. If that is not possible, use the default loop. The default
		2090	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2091	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2092	used).
1784		2093
1785	struct ev_loop *loop_hi = ev_default_init (0);	2094	struct ev_loop *loop_hi = ev_default_init (0);
1786	struct ev_loop *loop_lo = 0;	2095	struct ev_loop *loop_lo = 0;
1787	struct ev_embed embed;	2096	struct ev_embed embed;
1788		2097
…		…
1799	ev_embed_start (loop_hi, &embed);	2108	ev_embed_start (loop_hi, &embed);
1800	}	2109	}
1801	else	2110	else
1802	loop_lo = loop_hi;	2111	loop_lo = loop_hi;
1803		2112
1804	=head2 Portability notes	2113	Example: Check if kqueue is available but not recommended and create
		2114	a kqueue backend for use with sockets (which usually work with any
		2115	kqueue implementation). Store the kqueue/socket-only event loop in
		2116	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1805		2117
1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I	2118	struct ev_loop *loop = ev_default_init (0);
1807	tried, in various ways. Usually the embedded event loop will simply never	2119	struct ev_loop *loop_socket = 0;
1808	receive events, sometimes it will only trigger a few times, sometimes in a	2120	struct ev_embed embed;
1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions	2121
1810	will always eport the epoll fd as ready, even when no events are pending.	2122	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2123	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2124	{
		2125	ev_embed_init (&embed, 0, loop_socket);
		2126	ev_embed_start (loop, &embed);
		2127	}
1811		2128
1812	While libev allows embedding these backends (they are contained in	2129	if (!loop_socket)
1813	C<ev_embeddable_backends ()>), take extreme care that it will actually	2130	loop_socket = loop;
1814	work.
1815		2131
1816	When in doubt, create a dynamic event loop forced to use sockets (this	2132	// now use loop_socket for all sockets, and loop for everything else
1817	usually works) and possibly another thread and a pipe or so to report to
1818	your main event loop.
1819
1820	=head3 Watcher-Specific Functions and Data Members
1821
1822	=over 4
1823
1824	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1825
1826	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1827
1828	Configures the watcher to embed the given loop, which must be
1829	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1830	invoked automatically, otherwise it is the responsibility of the callback
1831	to invoke it (it will continue to be called until the sweep has been done,
1832	if you do not want thta, you need to temporarily stop the embed watcher).
1833
1834	=item ev_embed_sweep (loop, ev_embed *)
1835
1836	Make a single, non-blocking sweep over the embedded loop. This works
1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1838	apropriate way for embedded loops.
1839
1840	=item struct ev_loop *other [read-only]
1841
1842	The embedded event loop.
1843
1844	=back
1845		2133
1846		2134
1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2135	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1848		2136
1849	Fork watchers are called when a C<fork ()> was detected (usually because	2137	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1865	believe me.	2153	believe me.
1866		2154
1867	=back	2155	=back
1868		2156
1869		2157
		2158	=head2 C<ev_async> - how to wake up another event loop
		2159
		2160	In general, you cannot use an C<ev_loop> from multiple threads or other
		2161	asynchronous sources such as signal handlers (as opposed to multiple event
		2162	loops - those are of course safe to use in different threads).
		2163
		2164	Sometimes, however, you need to wake up another event loop you do not
		2165	control, for example because it belongs to another thread. This is what
		2166	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2167	can signal it by calling C<ev_async_send>, which is thread- and signal
		2168	safe.
		2169
		2170	This functionality is very similar to C<ev_signal> watchers, as signals,
		2171	too, are asynchronous in nature, and signals, too, will be compressed
		2172	(i.e. the number of callback invocations may be less than the number of
		2173	C<ev_async_sent> calls).
		2174
		2175	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2176	just the default loop.
		2177
		2178	=head3 Queueing
		2179
		2180	C<ev_async> does not support queueing of data in any way. The reason
		2181	is that the author does not know of a simple (or any) algorithm for a
		2182	multiple-writer-single-reader queue that works in all cases and doesn't
		2183	need elaborate support such as pthreads.
		2184
		2185	That means that if you want to queue data, you have to provide your own
		2186	queue. But at least I can tell you would implement locking around your
		2187	queue:
		2188
		2189	=over 4
		2190
		2191	=item queueing from a signal handler context
		2192
		2193	To implement race-free queueing, you simply add to the queue in the signal
		2194	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2195	some fictitiuous SIGUSR1 handler:
		2196
		2197	static ev_async mysig;
		2198
		2199	static void
		2200	sigusr1_handler (void)
		2201	{
		2202	sometype data;
		2203
		2204	// no locking etc.
		2205	queue_put (data);
		2206	ev_async_send (EV_DEFAULT_ &mysig);
		2207	}
		2208
		2209	static void
		2210	mysig_cb (EV_P_ ev_async *w, int revents)
		2211	{
		2212	sometype data;
		2213	sigset_t block, prev;
		2214
		2215	sigemptyset (&block);
		2216	sigaddset (&block, SIGUSR1);
		2217	sigprocmask (SIG_BLOCK, &block, &prev);
		2218
		2219	while (queue_get (&data))
		2220	process (data);
		2221
		2222	if (sigismember (&prev, SIGUSR1)
		2223	sigprocmask (SIG_UNBLOCK, &block, 0);
		2224	}
		2225
		2226	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2227	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2228	either...).
		2229
		2230	=item queueing from a thread context
		2231
		2232	The strategy for threads is different, as you cannot (easily) block
		2233	threads but you can easily preempt them, so to queue safely you need to
		2234	employ a traditional mutex lock, such as in this pthread example:
		2235
		2236	static ev_async mysig;
		2237	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2238
		2239	static void
		2240	otherthread (void)
		2241	{
		2242	// only need to lock the actual queueing operation
		2243	pthread_mutex_lock (&mymutex);
		2244	queue_put (data);
		2245	pthread_mutex_unlock (&mymutex);
		2246
		2247	ev_async_send (EV_DEFAULT_ &mysig);
		2248	}
		2249
		2250	static void
		2251	mysig_cb (EV_P_ ev_async *w, int revents)
		2252	{
		2253	pthread_mutex_lock (&mymutex);
		2254
		2255	while (queue_get (&data))
		2256	process (data);
		2257
		2258	pthread_mutex_unlock (&mymutex);
		2259	}
		2260
		2261	=back
		2262
		2263
		2264	=head3 Watcher-Specific Functions and Data Members
		2265
		2266	=over 4
		2267
		2268	=item ev_async_init (ev_async *, callback)
		2269
		2270	Initialises and configures the async watcher - it has no parameters of any
		2271	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2272	believe me.
		2273
		2274	=item ev_async_send (loop, ev_async *)
		2275
		2276	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2277	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2278	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2279	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2280	section below on what exactly this means).
		2281
		2282	This call incurs the overhead of a syscall only once per loop iteration,
		2283	so while the overhead might be noticable, it doesn't apply to repeated
		2284	calls to C<ev_async_send>.
		2285
		2286	=item bool = ev_async_pending (ev_async *)
		2287
		2288	Returns a non-zero value when C<ev_async_send> has been called on the
		2289	watcher but the event has not yet been processed (or even noted) by the
		2290	event loop.
		2291
		2292	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2293	the loop iterates next and checks for the watcher to have become active,
		2294	it will reset the flag again. C<ev_async_pending> can be used to very
		2295	quickly check wether invoking the loop might be a good idea.
		2296
		2297	Not that this does I<not> check wether the watcher itself is pending, only
		2298	wether it has been requested to make this watcher pending.
		2299
		2300	=back
		2301
		2302
1870	=head1 OTHER FUNCTIONS	2303	=head1 OTHER FUNCTIONS
1871		2304
1872	There are some other functions of possible interest. Described. Here. Now.	2305	There are some other functions of possible interest. Described. Here. Now.
1873		2306
1874	=over 4	2307	=over 4
…		…
2101	Example: Define a class with an IO and idle watcher, start one of them in	2534	Example: Define a class with an IO and idle watcher, start one of them in
2102	the constructor.	2535	the constructor.
2103		2536
2104	class myclass	2537	class myclass
2105	{	2538	{
2106	ev_io io; void io_cb (ev::io &w, int revents);	2539	ev::io io; void io_cb (ev::io &w, int revents);
2107	ev_idle idle void idle_cb (ev::idle &w, int revents);	2540	ev:idle idle void idle_cb (ev::idle &w, int revents);
2108		2541
2109	myclass ();	2542	myclass (int fd)
2110	}
2111
2112	myclass::myclass (int fd)
2113	{	2543	{
2114	io .set <myclass, &myclass::io_cb > (this);	2544	io .set <myclass, &myclass::io_cb > (this);
2115	idle.set <myclass, &myclass::idle_cb> (this);	2545	idle.set <myclass, &myclass::idle_cb> (this);
2116		2546
2117	io.start (fd, ev::READ);	2547	io.start (fd, ev::READ);
		2548	}
2118	}	2549	};
		2550
		2551
		2552	=head1 OTHER LANGUAGE BINDINGS
		2553
		2554	Libev does not offer other language bindings itself, but bindings for a
		2555	numbe rof languages exist in the form of third-party packages. If you know
		2556	any interesting language binding in addition to the ones listed here, drop
		2557	me a note.
		2558
		2559	=over 4
		2560
		2561	=item Perl
		2562
		2563	The EV module implements the full libev API and is actually used to test
		2564	libev. EV is developed together with libev. Apart from the EV core module,
		2565	there are additional modules that implement libev-compatible interfaces
		2566	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2567	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2568
		2569	It can be found and installed via CPAN, its homepage is found at
		2570	L<http://software.schmorp.de/pkg/EV>.
		2571
		2572	=item Ruby
		2573
		2574	Tony Arcieri has written a ruby extension that offers access to a subset
		2575	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2576	more on top of it. It can be found via gem servers. Its homepage is at
		2577	L<http://rev.rubyforge.org/>.
		2578
		2579	=item D
		2580
		2581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2582	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2583
		2584	=back
2119		2585
2120		2586
2121	=head1 MACRO MAGIC	2587	=head1 MACRO MAGIC
2122		2588
2123	Libev can be compiled with a variety of options, the most fundamantal	2589	Libev can be compiled with a variety of options, the most fundamantal
…		…
2159		2625
2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2626	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2161		2627
2162	Similar to the other two macros, this gives you the value of the default	2628	Similar to the other two macros, this gives you the value of the default
2163	loop, if multiple loops are supported ("ev loop default").	2629	loop, if multiple loops are supported ("ev loop default").
		2630
		2631	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2632
		2633	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2634	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2635	is undefined when the default loop has not been initialised by a previous
		2636	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2637
		2638	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2639	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2164		2640
2165	=back	2641	=back
2166		2642
2167	Example: Declare and initialise a check watcher, utilising the above	2643	Example: Declare and initialise a check watcher, utilising the above
2168	macros so it will work regardless of whether multiple loops are supported	2644	macros so it will work regardless of whether multiple loops are supported
…		…
2264		2740
2265	libev.m4	2741	libev.m4
2266		2742
2267	=head2 PREPROCESSOR SYMBOLS/MACROS	2743	=head2 PREPROCESSOR SYMBOLS/MACROS
2268		2744
2269	Libev can be configured via a variety of preprocessor symbols you have to define	2745	Libev can be configured via a variety of preprocessor symbols you have to
2270	before including any of its files. The default is not to build for multiplicity	2746	define before including any of its files. The default in the absense of
2271	and only include the select backend.	2747	autoconf is noted for every option.
2272		2748
2273	=over 4	2749	=over 4
2274		2750
2275	=item EV_STANDALONE	2751	=item EV_STANDALONE
2276		2752
…		…
2297	runtime if successful). Otherwise no use of the realtime clock option will	2773	runtime if successful). Otherwise no use of the realtime clock option will
2298	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2774	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	2775	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	2776	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2301		2777
		2778	=item EV_USE_NANOSLEEP
		2779
		2780	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2781	and will use it for delays. Otherwise it will use C<select ()>.
		2782
		2783	=item EV_USE_EVENTFD
		2784
		2785	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2786	available and will probe for kernel support at runtime. This will improve
		2787	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2788	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2789	2.7 or newer, otherwise disabled.
		2790
2302	=item EV_USE_SELECT	2791	=item EV_USE_SELECT
2303		2792
2304	If undefined or defined to be C<1>, libev will compile in support for the	2793	If undefined or defined to be C<1>, libev will compile in support for the
2305	C<select>(2) backend. No attempt at autodetection will be done: if no	2794	C<select>(2) backend. No attempt at autodetection will be done: if no
2306	other method takes over, select will be it. Otherwise the select backend	2795	other method takes over, select will be it. Otherwise the select backend
…		…
2324	be used is the winsock select). This means that it will call	2813	be used is the winsock select). This means that it will call
2325	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2814	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2326	it is assumed that all these functions actually work on fds, even	2815	it is assumed that all these functions actually work on fds, even
2327	on win32. Should not be defined on non-win32 platforms.	2816	on win32. Should not be defined on non-win32 platforms.
2328		2817
		2818	=item EV_FD_TO_WIN32_HANDLE
		2819
		2820	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2821	file descriptors to socket handles. When not defining this symbol (the
		2822	default), then libev will call C<_get_osfhandle>, which is usually
		2823	correct. In some cases, programs use their own file descriptor management,
		2824	in which case they can provide this function to map fds to socket handles.
		2825
2329	=item EV_USE_POLL	2826	=item EV_USE_POLL
2330		2827
2331	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2828	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2332	backend. Otherwise it will be enabled on non-win32 platforms. It	2829	backend. Otherwise it will be enabled on non-win32 platforms. It
2333	takes precedence over select.	2830	takes precedence over select.
2334		2831
2335	=item EV_USE_EPOLL	2832	=item EV_USE_EPOLL
2336		2833
2337	If defined to be C<1>, libev will compile in support for the Linux	2834	If defined to be C<1>, libev will compile in support for the Linux
2338	C<epoll>(7) backend. Its availability will be detected at runtime,	2835	C<epoll>(7) backend. Its availability will be detected at runtime,
2339	otherwise another method will be used as fallback. This is the	2836	otherwise another method will be used as fallback. This is the preferred
2340	preferred backend for GNU/Linux systems.	2837	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2838	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2341		2839
2342	=item EV_USE_KQUEUE	2840	=item EV_USE_KQUEUE
2343		2841
2344	If defined to be C<1>, libev will compile in support for the BSD style	2842	If defined to be C<1>, libev will compile in support for the BSD style
2345	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2843	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2364		2862
2365	=item EV_USE_INOTIFY	2863	=item EV_USE_INOTIFY
2366		2864
2367	If defined to be C<1>, libev will compile in support for the Linux inotify	2865	If defined to be C<1>, libev will compile in support for the Linux inotify
2368	interface to speed up C<ev_stat> watchers. Its actual availability will	2866	interface to speed up C<ev_stat> watchers. Its actual availability will
2369	be detected at runtime.	2867	be detected at runtime. If undefined, it will be enabled if the headers
		2868	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2869
		2870	=item EV_ATOMIC_T
		2871
		2872	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2873	access is atomic with respect to other threads or signal contexts. No such
		2874	type is easily found in the C language, so you can provide your own type
		2875	that you know is safe for your purposes. It is used both for signal handler "locking"
		2876	as well as for signal and thread safety in C<ev_async> watchers.
		2877
		2878	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2879	(from F<signal.h>), which is usually good enough on most platforms.
2370		2880
2371	=item EV_H	2881	=item EV_H
2372		2882
2373	The name of the F<ev.h> header file used to include it. The default if	2883	The name of the F<ev.h> header file used to include it. The default if
2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2884	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2375	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2885	used to virtually rename the F<ev.h> header file in case of conflicts.
2376		2886
2377	=item EV_CONFIG_H	2887	=item EV_CONFIG_H
2378		2888
2379	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2889	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2380	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2890	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2381	C<EV_H>, above.	2891	C<EV_H>, above.
2382		2892
2383	=item EV_EVENT_H	2893	=item EV_EVENT_H
2384		2894
2385	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2895	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2386	of how the F<event.h> header can be found.	2896	of how the F<event.h> header can be found, the default is C<"event.h">.
2387		2897
2388	=item EV_PROTOTYPES	2898	=item EV_PROTOTYPES
2389		2899
2390	If defined to be C<0>, then F<ev.h> will not define any function	2900	If defined to be C<0>, then F<ev.h> will not define any function
2391	prototypes, but still define all the structs and other symbols. This is	2901	prototypes, but still define all the structs and other symbols. This is
…		…
2442	=item EV_FORK_ENABLE	2952	=item EV_FORK_ENABLE
2443		2953
2444	If undefined or defined to be C<1>, then fork watchers are supported. If	2954	If undefined or defined to be C<1>, then fork watchers are supported. If
2445	defined to be C<0>, then they are not.	2955	defined to be C<0>, then they are not.
2446		2956
		2957	=item EV_ASYNC_ENABLE
		2958
		2959	If undefined or defined to be C<1>, then async watchers are supported. If
		2960	defined to be C<0>, then they are not.
		2961
2447	=item EV_MINIMAL	2962	=item EV_MINIMAL
2448		2963
2449	If you need to shave off some kilobytes of code at the expense of some	2964	If you need to shave off some kilobytes of code at the expense of some
2450	speed, define this symbol to C<1>. Currently only used for gcc to override	2965	speed, define this symbol to C<1>. Currently only used for gcc to override
2451	some inlining decisions, saves roughly 30% codesize of amd64.	2966	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2457	than enough. If you need to manage thousands of children you might want to	2972	than enough. If you need to manage thousands of children you might want to
2458	increase this value (I<must> be a power of two).	2973	increase this value (I<must> be a power of two).
2459		2974
2460	=item EV_INOTIFY_HASHSIZE	2975	=item EV_INOTIFY_HASHSIZE
2461		2976
2462	C<ev_staz> watchers use a small hash table to distribute workload by	2977	C<ev_stat> watchers use a small hash table to distribute workload by
2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2464	usually more than enough. If you need to manage thousands of C<ev_stat>	2979	usually more than enough. If you need to manage thousands of C<ev_stat>
2465	watchers you might want to increase this value (I<must> be a power of	2980	watchers you might want to increase this value (I<must> be a power of
2466	two).	2981	two).
2467		2982
…		…
2545		3060
2546	#include "ev_cpp.h"	3061	#include "ev_cpp.h"
2547	#include "ev.c"	3062	#include "ev.c"
2548		3063
2549		3064
		3065	=head1 THREADS AND COROUTINES
		3066
		3067	=head2 THREADS
		3068
		3069	Libev itself is completely threadsafe, but it uses no locking. This
		3070	means that you can use as many loops as you want in parallel, as long as
		3071	only one thread ever calls into one libev function with the same loop
		3072	parameter.
		3073
		3074	Or put differently: calls with different loop parameters can be done in
		3075	parallel from multiple threads, calls with the same loop parameter must be
		3076	done serially (but can be done from different threads, as long as only one
		3077	thread ever is inside a call at any point in time, e.g. by using a mutex
		3078	per loop).
		3079
		3080	If you want to know which design is best for your problem, then I cannot
		3081	help you but by giving some generic advice:
		3082
		3083	=over 4
		3084
		3085	=item * most applications have a main thread: use the default libev loop
		3086	in that thread, or create a seperate thread running only the default loop.
		3087
		3088	This helps integrating other libraries or software modules that use libev
		3089	themselves and don't care/know about threading.
		3090
		3091	=item * one loop per thread is usually a good model.
		3092
		3093	Doing this is almost never wrong, sometimes a better-performance model
		3094	exists, but it is always a good start.
		3095
		3096	=item * other models exist, such as the leader/follower pattern, where one
		3097	loop is handed through multiple threads in a kind of round-robbin fashion.
		3098
		3099	Chosing a model is hard - look around, learn, know that usually you cna do
		3100	better than you currently do :-)
		3101
		3102	=item * often you need to talk to some other thread which blocks in the
		3103	event loop - C<ev_async> watchers can be used to wake them up from other
		3104	threads safely (or from signal contexts...).
		3105
		3106	=back
		3107
		3108	=head2 COROUTINES
		3109
		3110	Libev is much more accomodating to coroutines ("cooperative threads"):
		3111	libev fully supports nesting calls to it's functions from different
		3112	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3113	different coroutines and switch freely between both coroutines running the
		3114	loop, as long as you don't confuse yourself). The only exception is that
		3115	you must not do this from C<ev_periodic> reschedule callbacks.
		3116
		3117	Care has been invested into making sure that libev does not keep local
		3118	state inside C<ev_loop>, and other calls do not usually allow coroutine
		3119	switches.
		3120
		3121
2550	=head1 COMPLEXITIES	3122	=head1 COMPLEXITIES
2551		3123
2552	In this section the complexities of (many of) the algorithms used inside	3124	In this section the complexities of (many of) the algorithms used inside
2553	libev will be explained. For complexity discussions about backends see the	3125	libev will be explained. For complexity discussions about backends see the
2554	documentation for C<ev_default_init>.	3126	documentation for C<ev_default_init>.
…		…
2563		3135
2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3136	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2565		3137
2566	This means that, when you have a watcher that triggers in one hour and	3138	This means that, when you have a watcher that triggers in one hour and
2567	there are 100 watchers that would trigger before that then inserting will	3139	there are 100 watchers that would trigger before that then inserting will
2568	have to skip those 100 watchers.	3140	have to skip roughly seven (C<ld 100>) of these watchers.
2569		3141
2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3142	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2571		3143
2572	That means that for changing a timer costs less than removing/adding them	3144	That means that changing a timer costs less than removing/adding them
2573	as only the relative motion in the event queue has to be paid for.	3145	as only the relative motion in the event queue has to be paid for.
2574		3146
2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3147	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2576		3148
2577	These just add the watcher into an array or at the head of a list.	3149	These just add the watcher into an array or at the head of a list.
		3150
2578	=item Stopping check/prepare/idle watchers: O(1)	3151	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2579		3152
2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3153	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2581		3154
2582	These watchers are stored in lists then need to be walked to find the	3155	These watchers are stored in lists then need to be walked to find the
2583	correct watcher to remove. The lists are usually short (you don't usually	3156	correct watcher to remove. The lists are usually short (you don't usually
2584	have many watchers waiting for the same fd or signal).	3157	have many watchers waiting for the same fd or signal).
2585		3158
2586	=item Finding the next timer per loop iteration: O(1)	3159	=item Finding the next timer in each loop iteration: O(1)
		3160
		3161	By virtue of using a binary heap, the next timer is always found at the
		3162	beginning of the storage array.
2587		3163
2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3164	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2589		3165
2590	A change means an I/O watcher gets started or stopped, which requires	3166	A change means an I/O watcher gets started or stopped, which requires
2591	libev to recalculate its status (and possibly tell the kernel).	3167	libev to recalculate its status (and possibly tell the kernel, depending
		3168	on backend and wether C<ev_io_set> was used).
2592		3169
2593	=item Activating one watcher: O(1)	3170	=item Activating one watcher (putting it into the pending state): O(1)
2594		3171
2595	=item Priority handling: O(number_of_priorities)	3172	=item Priority handling: O(number_of_priorities)
2596		3173
2597	Priorities are implemented by allocating some space for each	3174	Priorities are implemented by allocating some space for each
2598	priority. When doing priority-based operations, libev usually has to	3175	priority. When doing priority-based operations, libev usually has to
2599	linearly search all the priorities.	3176	linearly search all the priorities, but starting/stopping and activating
		3177	watchers becomes O(1) w.r.t. priority handling.
		3178
		3179	=item Sending an ev_async: O(1)
		3180
		3181	=item Processing ev_async_send: O(number_of_async_watchers)
		3182
		3183	=item Processing signals: O(max_signal_number)
		3184
		3185	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3186	calls in the current loop iteration. Checking for async and signal events
		3187	involves iterating over all running async watchers or all signal numbers.
2600		3188
2601	=back	3189	=back
2602		3190
2603		3191
		3192	=head1 Win32 platform limitations and workarounds
		3193
		3194	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3195	requires, and its I/O model is fundamentally incompatible with the POSIX
		3196	model. Libev still offers limited functionality on this platform in
		3197	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3198	descriptors. This only applies when using Win32 natively, not when using
		3199	e.g. cygwin.
		3200
		3201	There is no supported compilation method available on windows except
		3202	embedding it into other applications.
		3203
		3204	Due to the many, low, and arbitrary limits on the win32 platform and the
		3205	abysmal performance of winsockets, using a large number of sockets is not
		3206	recommended (and not reasonable). If your program needs to use more than
		3207	a hundred or so sockets, then likely it needs to use a totally different
		3208	implementation for windows, as libev offers the POSIX model, which cannot
		3209	be implemented efficiently on windows (microsoft monopoly games).
		3210
		3211	=over 4
		3212
		3213	=item The winsocket select function
		3214
		3215	The winsocket C<select> function doesn't follow POSIX in that it requires
		3216	socket I<handles> and not socket I<file descriptors>. This makes select
		3217	very inefficient, and also requires a mapping from file descriptors
		3218	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3219	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3220	symbols for more info.
		3221
		3222	The configuration for a "naked" win32 using the microsoft runtime
		3223	libraries and raw winsocket select is:
		3224
		3225	#define EV_USE_SELECT 1
		3226	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3227
		3228	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3229	complexity in the O(n²) range when using win32.
		3230
		3231	=item Limited number of file descriptors
		3232
		3233	Windows has numerous arbitrary (and low) limits on things. Early versions
		3234	of winsocket's select only supported waiting for a max. of C<64> handles
		3235	(probably owning to the fact that all windows kernels can only wait for
		3236	C<64> things at the same time internally; microsoft recommends spawning a
		3237	chain of threads and wait for 63 handles and the previous thread in each).
		3238
		3239	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3240	to some high number (e.g. C<2048>) before compiling the winsocket select
		3241	call (which might be in libev or elsewhere, for example, perl does its own
		3242	select emulation on windows).
		3243
		3244	Another limit is the number of file descriptors in the microsoft runtime
		3245	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3246	or something like this inside microsoft). You can increase this by calling
		3247	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3248	arbitrary limit), but is broken in many versions of the microsoft runtime
		3249	libraries.
		3250
		3251	This might get you to about C<512> or C<2048> sockets (depending on
		3252	windows version and/or the phase of the moon). To get more, you need to
		3253	wrap all I/O functions and provide your own fd management, but the cost of
		3254	calling select (O(n²)) will likely make this unworkable.
		3255
		3256	=back
		3257
		3258
2604	=head1 AUTHOR	3259	=head1 AUTHOR
2605		3260
2606	Marc Lehmann <libev@schmorp.de>.	3261	Marc Lehmann <libev@schmorp.de>.
2607		3262

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines