ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.82 by root, Wed Dec 12 17:55:06 2007 UTC vs.
Revision 1.137 by root, Sun Mar 16 16:42:56 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 occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
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
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floatingpoint value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
104		121
105	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
106		123
107	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
108	library in any way.	125	library in any way.
…		…
112	=item ev_tstamp ev_time ()	129	=item ev_tstamp ev_time ()
113		130
114	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
115	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
116	you actually want to know.	133	you actually want to know.
		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 ()>.
117		140
118	=item int ev_version_major ()	141	=item int ev_version_major ()
119		142
120	=item int ev_version_minor ()	143	=item int ev_version_minor ()
121		144
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		276
254	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
255	function.	278	function.
256		279
		280	The default loop is the only loop that can handle C<ev_signal> and
		281	C<ev_child> watchers, and to do this, it always registers a handler
		282	for C<SIGCHLD>. If this is a problem for your app you can either
		283	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		284	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		285	C<ev_default_init>.
		286
257	The flags argument can be used to specify special behaviour or specific	287	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	288	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		289
260	The following flags are supported:	290	The following flags are supported:
261		291
…		…
282	enabling this flag.	312	enabling this flag.
283		313
284	This works by calling C<getpid ()> on every iteration of the loop,	314	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	315	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	316	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	317	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	318	without a syscall and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	319	C<pthread_atfork> which is even faster).
290		320
291	The big advantage of this flag is that you can forget about fork (and	321	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	322	forget about forgetting to tell libev about forking) when you use this
293	flag.	323	flag.
…		…
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	328	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		329
300	This is your standard select(2) backend. Not I<completely> standard, as	330	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	331	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	332	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	333	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	334	usually the fastest backend for a low number of (low-numbered :) fds.
		335
		336	To get good performance out of this backend you need a high amount of
		337	parallelity (most of the file descriptors should be busy). If you are
		338	writing a server, you should C<accept ()> in a loop to accept as many
		339	connections as possible during one iteration. You might also want to have
		340	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		341	readyness notifications you get per iteration.
305		342
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	343	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		344
308	And this is your standard poll(2) backend. It's more complicated than	345	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	346	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	347	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	348	considerably with a lot of inactive fds). It scales similarly to select,
		349	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		350	performance tips.
312		351
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	352	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		353
315	For few fds, this backend is a bit little slower than poll and select,	354	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	355	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	356	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	357	epoll scales either O(1) or O(active_fds). The epoll design has a number
		358	of shortcomings, such as silently dropping events in some hard-to-detect
		359	cases and rewiring a syscall per fd change, no fork support and bad
		360	support for dup.
319		361
320	While stopping and starting an I/O watcher in the same iteration will	362	While stopping, setting and starting an I/O watcher in the same iteration
321	result in some caching, there is still a syscall per such incident	363	will result in some caching, there is still a syscall per such incident
322	(because the fd could point to a different file description now), so its	364	(because the fd could point to a different file description now), so its
323	best to avoid that. Also, dup()ed file descriptors might not work very	365	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	366	very well if you register events for both fds.
325		367
326	Please note that epoll sometimes generates spurious notifications, so you	368	Please note that epoll sometimes generates spurious notifications, so you
327	need to use non-blocking I/O or other means to avoid blocking when no data	369	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	370	(or space) is available.
329		371
		372	Best performance from this backend is achieved by not unregistering all
		373	watchers for a file descriptor until it has been closed, if possible, i.e.
		374	keep at least one watcher active per fd at all times.
		375
		376	While nominally embeddeble in other event loops, this feature is broken in
		377	all kernel versions tested so far.
		378
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	379	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		380
332	Kqueue deserves special mention, as at the time of this writing, it	381	Kqueue deserves special mention, as at the time of this writing, it
333	was broken on all BSDs except NetBSD (usually it doesn't work with	382	was broken on all BSDs except NetBSD (usually it doesn't work reliably
334	anything but sockets and pipes, except on Darwin, where of course its	383	with anything but sockets and pipes, except on Darwin, where of course
335	completely useless). For this reason its not being "autodetected"	384	it's completely useless). For this reason it's not being "autodetected"
336	unless you explicitly specify it explicitly in the flags (i.e. using	385	unless you explicitly specify it explicitly in the flags (i.e. using
337	C<EVBACKEND_KQUEUE>).	386	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		387	system like NetBSD.
		388
		389	You still can embed kqueue into a normal poll or select backend and use it
		390	only for sockets (after having made sure that sockets work with kqueue on
		391	the target platform). See C<ev_embed> watchers for more info.
338		392
339	It scales in the same way as the epoll backend, but the interface to the	393	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	394	kernel is more efficient (which says nothing about its actual speed, of
341	course). While starting and stopping an I/O watcher does not cause an	395	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	396	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	397	two event changes per incident, support for C<fork ()> is very bad and it
		398	drops fds silently in similarly hard-to-detect cases.
		399
		400	This backend usually performs well under most conditions.
		401
		402	While nominally embeddable in other event loops, this doesn't work
		403	everywhere, so you might need to test for this. And since it is broken
		404	almost everywhere, you should only use it when you have a lot of sockets
		405	(for which it usually works), by embedding it into another event loop
		406	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		407	sockets.
344		408
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	409	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		410
347	This is not implemented yet (and might never be).	411	This is not implemented yet (and might never be, unless you send me an
		412	implementation). According to reports, C</dev/poll> only supports sockets
		413	and is not embeddable, which would limit the usefulness of this backend
		414	immensely.
348		415
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	416	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		417
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	418	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	it's really slow, but it still scales very well (O(active_fds)).	419	it's really slow, but it still scales very well (O(active_fds)).
353		420
354	Please note that solaris ports can result in a lot of spurious	421	Please note that solaris event ports can deliver a lot of spurious
355	notifications, so you need to use non-blocking I/O or other means to avoid	422	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	423	blocking when no data (or space) is available.
		424
		425	While this backend scales well, it requires one system call per active
		426	file descriptor per loop iteration. For small and medium numbers of file
		427	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		428	might perform better.
		429
		430	On the positive side, ignoring the spurious readyness notifications, this
		431	backend actually performed to specification in all tests and is fully
		432	embeddable, which is a rare feat among the OS-specific backends.
357		433
358	=item C<EVBACKEND_ALL>	434	=item C<EVBACKEND_ALL>
359		435
360	Try all backends (even potentially broken ones that wouldn't be tried	436	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	437	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	438	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		439
		440	It is definitely not recommended to use this flag.
		441
364	=back	442	=back
365		443
366	If one or more of these are ored into the flags value, then only these	444	If one or more of these are ored into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	445	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	446	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		447
371	The most typical usage is like this:	448	The most typical usage is like this:
372		449
373	if (!ev_default_loop (0))	450	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	451	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
402	Destroys the default loop again (frees all memory and kernel state	479	Destroys the default loop again (frees all memory and kernel state
403	etc.). None of the active event watchers will be stopped in the normal	480	etc.). None of the active event watchers will be stopped in the normal
404	sense, so e.g. C<ev_is_active> might still return true. It is your	481	sense, so e.g. C<ev_is_active> might still return true. It is your
405	responsibility to either stop all watchers cleanly yoursef I<before>	482	responsibility to either stop all watchers cleanly yoursef I<before>
406	calling this function, or cope with the fact afterwards (which is usually	483	calling this function, or cope with the fact afterwards (which is usually
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	484	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	485	for example).
		486
		487	Note that certain global state, such as signal state, will not be freed by
		488	this function, and related watchers (such as signal and child watchers)
		489	would need to be stopped manually.
		490
		491	In general it is not advisable to call this function except in the
		492	rare occasion where you really need to free e.g. the signal handling
		493	pipe fds. If you need dynamically allocated loops it is better to use
		494	C<ev_loop_new> and C<ev_loop_destroy>).
409		495
410	=item ev_loop_destroy (loop)	496	=item ev_loop_destroy (loop)
411		497
412	Like C<ev_default_destroy>, but destroys an event loop created by an	498	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	499	earlier call to C<ev_loop_new>.
414		500
415	=item ev_default_fork ()	501	=item ev_default_fork ()
416		502
		503	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	504	to reinitialise the kernel state for backends that have one. Despite the
418	one. Despite the name, you can call it anytime, but it makes most sense	505	name, you can call it anytime, but it makes most sense after forking, in
419	after forking, in either the parent or child process (or both, but that	506	the child process (or both child and parent, but that again makes little
420	again makes little sense).	507	sense). You I<must> call it in the child before using any of the libev
		508	functions, and it will only take effect at the next C<ev_loop> iteration.
421		509
422	You I<must> call this function in the child process after forking if and	510	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	511	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	512	you just fork+exec, you don't have to call it at all.
425		513
426	The function itself is quite fast and it's usually not a problem to call	514	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	515	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	516	quite nicely into a call to C<pthread_atfork>:
429		517
430	pthread_atfork (0, 0, ev_default_fork);	518	pthread_atfork (0, 0, ev_default_fork);
431		519
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	520	=item ev_loop_fork (loop)
437		521
438	Like C<ev_default_fork>, but acts on an event loop created by	522	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	523	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	524	after fork, and how you do this is entirely your own problem.
		525
		526	=item int ev_is_default_loop (loop)
		527
		528	Returns true when the given loop actually is the default loop, false otherwise.
441		529
442	=item unsigned int ev_loop_count (loop)	530	=item unsigned int ev_loop_count (loop)
443		531
444	Returns the count of loop iterations for the loop, which is identical to	532	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	533	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		546
459	Returns the current "event loop time", which is the time the event loop	547	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	548	received events and started processing them. This timestamp does not
461	change as long as callbacks are being processed, and this is also the base	549	change as long as callbacks are being processed, and this is also the base
462	time used for relative timers. You can treat it as the timestamp of the	550	time used for relative timers. You can treat it as the timestamp of the
463	event occuring (or more correctly, libev finding out about it).	551	event occurring (or more correctly, libev finding out about it).
464		552
465	=item ev_loop (loop, int flags)	553	=item ev_loop (loop, int flags)
466		554
467	Finally, this is it, the event handler. This function usually is called	555	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	556	after you initialised all your watchers and you want to start handling
…		…
490	usually a better approach for this kind of thing.	578	usually a better approach for this kind of thing.
491		579
492	Here are the gory details of what C<ev_loop> does:	580	Here are the gory details of what C<ev_loop> does:
493		581
494	- Before the first iteration, call any pending watchers.	582	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	583	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	584	- If a fork was detected, queue and call all fork watchers.
		585	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	586	- If we have been forked, recreate the kernel state.
498	- Update the kernel state with all outstanding changes.	587	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	588	- Update the "event loop time".
500	- Calculate for how long to block.	589	- Calculate for how long to sleep or block, if at all
		590	(active idle watchers, EVLOOP_NONBLOCK or not having
		591	any active watchers at all will result in not sleeping).
		592	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	593	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	594	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	595	- Update the "event loop time" and do time jump handling.
504	- Queue all outstanding timers.	596	- Queue all outstanding timers.
505	- Queue all outstanding periodics.	597	- Queue all outstanding periodics.
506	- If no events are pending now, queue all idle watchers.	598	- If no events are pending now, queue all idle watchers.
507	- Queue all check watchers.	599	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	600	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	601	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	602	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	603	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	604	were used, or there are no active watchers, return, otherwise
		605	continue with step *.
513		606
514	Example: Queue some jobs and then loop until no events are outsanding	607	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	608	anymore.
516		609
517	... queue jobs here, make sure they register event watchers as long	610	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	611	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	612	ev_loop (my_loop, 0);
…		…
523		616
524	Can be used to make a call to C<ev_loop> return early (but only after it	617	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	618	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	619	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	620	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		621
		622	This "unloop state" will be cleared when entering C<ev_loop> again.
528		623
529	=item ev_ref (loop)	624	=item ev_ref (loop)
530		625
531	=item ev_unref (loop)	626	=item ev_unref (loop)
532		627
…		…
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	632	returning, ev_unref() after starting, and ev_ref() before stopping it. For
538	example, libev itself uses this for its internal signal pipe: It is not	633	example, libev itself uses this for its internal signal pipe: It is not
539	visible to the libev user and should not keep C<ev_loop> from exiting if	634	visible to the libev user and should not keep C<ev_loop> from exiting if
540	no event watchers registered by it are active. It is also an excellent	635	no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	636	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	637	libraries. Just remember to I<unref after start> and I<ref before stop>
		638	(but only if the watcher wasn't active before, or was active before,
		639	respectively).
543		640
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	641	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	642	running when nothing else is active.
546		643
547	struct ev_signal exitsig;	644	struct ev_signal exitsig;
…		…
551		648
552	Example: For some weird reason, unregister the above signal handler again.	649	Example: For some weird reason, unregister the above signal handler again.
553		650
554	ev_ref (loop);	651	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	652	ev_signal_stop (loop, &exitsig);
		653
		654	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		655
		656	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		657
		658	These advanced functions influence the time that libev will spend waiting
		659	for events. Both are by default C<0>, meaning that libev will try to
		660	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		661
		662	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		663	allows libev to delay invocation of I/O and timer/periodic callbacks to
		664	increase efficiency of loop iterations.
		665
		666	The background is that sometimes your program runs just fast enough to
		667	handle one (or very few) event(s) per loop iteration. While this makes
		668	the program responsive, it also wastes a lot of CPU time to poll for new
		669	events, especially with backends like C<select ()> which have a high
		670	overhead for the actual polling but can deliver many events at once.
		671
		672	By setting a higher I<io collect interval> you allow libev to spend more
		673	time collecting I/O events, so you can handle more events per iteration,
		674	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		675	C<ev_timer>) will be not affected. Setting this to a non-null value will
		676	introduce an additional C<ev_sleep ()> call into most loop iterations.
		677
		678	Likewise, by setting a higher I<timeout collect interval> you allow libev
		679	to spend more time collecting timeouts, at the expense of increased
		680	latency (the watcher callback will be called later). C<ev_io> watchers
		681	will not be affected. Setting this to a non-null value will not introduce
		682	any overhead in libev.
		683
		684	Many (busy) programs can usually benefit by setting the io collect
		685	interval to a value near C<0.1> or so, which is often enough for
		686	interactive servers (of course not for games), likewise for timeouts. It
		687	usually doesn't make much sense to set it to a lower value than C<0.01>,
		688	as this approsaches the timing granularity of most systems.
556		689
557	=back	690	=back
558		691
559		692
560	=head1 ANATOMY OF A WATCHER	693	=head1 ANATOMY OF A WATCHER
…		…
659		792
660	=item C<EV_FORK>	793	=item C<EV_FORK>
661		794
662	The event loop has been resumed in the child process after fork (see	795	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	796	C<ev_fork>).
		797
		798	=item C<EV_ASYNC>
		799
		800	The given async watcher has been asynchronously notified (see C<ev_async>).
664		801
665	=item C<EV_ERROR>	802	=item C<EV_ERROR>
666		803
667	An unspecified error has occured, the watcher has been stopped. This might	804	An unspecified error has occured, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	805	happen because the watcher could not be properly started because libev
…		…
886	In general you can register as many read and/or write event watchers per	1023	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1024	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1025	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1026	required if you know what you are doing).
890		1027
891	You have to be careful with dup'ed file descriptors, though. Some backends
892	(the linux epoll backend is a notable example) cannot handle dup'ed file
893	descriptors correctly if you register interest in two or more fds pointing
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend	1028	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1029	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).	1030	C<EVBACKEND_POLL>).
900		1031
901	Another thing you have to watch out for is that it is quite easy to	1032	Another thing you have to watch out for is that it is quite easy to
…		…
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1044	such as poll (fortunately in our Xlib example, Xlib already does this on
914	its own, so its quite safe to use).	1045	its own, so its quite safe to use).
915		1046
916	=head3 The special problem of disappearing file descriptors	1047	=head3 The special problem of disappearing file descriptors
917		1048
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1049	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1050	descriptor (either by calling C<close> explicitly or by any other means,
920	such as C<dup>). The reason is that you register interest in some file	1051	such as C<dup>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1052	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1053	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1054	registered with libev, there is no efficient way to see that this is, in
…		…
932		1063
933	This is how one would do it normally anyway, the important point is that	1064	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1065	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1066	optimisations to libev.
936		1067
		1068	=head3 The special problem of dup'ed file descriptors
		1069
		1070	Some backends (e.g. epoll), cannot register events for file descriptors,
		1071	but only events for the underlying file descriptions. That means when you
		1072	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1073	events for them, only one file descriptor might actually receive events.
		1074
		1075	There is no workaround possible except not registering events
		1076	for potentially C<dup ()>'ed file descriptors, or to resort to
		1077	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1078
		1079	=head3 The special problem of fork
		1080
		1081	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1082	useless behaviour. Libev fully supports fork, but needs to be told about
		1083	it in the child.
		1084
		1085	To support fork in your programs, you either have to call
		1086	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1087	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1088	C<EVBACKEND_POLL>.
		1089
937		1090
938	=head3 Watcher-Specific Functions	1091	=head3 Watcher-Specific Functions
939		1092
940	=over 4	1093	=over 4
941		1094
…		…
954	=item int events [read-only]	1107	=item int events [read-only]
955		1108
956	The events being watched.	1109	The events being watched.
957		1110
958	=back	1111	=back
		1112
		1113	=head3 Examples
959		1114
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1115	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1116	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1117	attempt to read a whole line in the callback.
963		1118
…		…
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1171	configure a timer to trigger every 10 seconds, then it will trigger at
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1172	exactly 10 second intervals. If, however, your program cannot keep up with
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1173	the timer (because it takes longer than those 10 seconds to do stuff) the
1019	timer will not fire more than once per event loop iteration.	1174	timer will not fire more than once per event loop iteration.
1020		1175
1021	=item ev_timer_again (loop)	1176	=item ev_timer_again (loop, ev_timer *)
1022		1177
1023	This will act as if the timer timed out and restart it again if it is	1178	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1179	repeating. The exact semantics are:
1025		1180
1026	If the timer is pending, its pending status is cleared.	1181	If the timer is pending, its pending status is cleared.
…		…
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1216	or C<ev_timer_again> is called and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1217	which is also when any modifications are taken into account.
1063		1218
1064	=back	1219	=back
1065		1220
		1221	=head3 Examples
		1222
1066	Example: Create a timer that fires after 60 seconds.	1223	Example: Create a timer that fires after 60 seconds.
1067		1224
1068	static void	1225	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1226	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070	{	1227	{
…		…
1133	In this configuration the watcher triggers an event at the wallclock time	1290	In this configuration the watcher triggers an event at the wallclock time
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1291	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1292	that is, if it is to be run at January 1st 2011 then it will run when the
1136	system time reaches or surpasses this time.	1293	system time reaches or surpasses this time.
1137		1294
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1295	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1296
1140	In this mode the watcher will always be scheduled to time out at the next	1297	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1298	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1299	and then repeat, regardless of any time jumps.
1143		1300
…		…
1220		1377
1221	The current reschedule callback, or C<0>, if this functionality is	1378	The current reschedule callback, or C<0>, if this functionality is
1222	switched off. Can be changed any time, but changes only take effect when	1379	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1380	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1381
		1382	=item ev_tstamp at [read-only]
		1383
		1384	When active, contains the absolute time that the watcher is supposed to
		1385	trigger next.
		1386
1225	=back	1387	=back
		1388
		1389	=head3 Examples
1226		1390
1227	Example: Call a callback every hour, or, more precisely, whenever the	1391	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1392	system clock is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1393	potentially a lot of jittering, but good long-term stability.
1230		1394
…		…
1270	with the kernel (thus it coexists with your own signal handlers as long	1434	with the kernel (thus it coexists with your own signal handlers as long
1271	as you don't register any with libev). Similarly, when the last signal	1435	as you don't register any with libev). Similarly, when the last signal
1272	watcher for a signal is stopped libev will reset the signal handler to	1436	watcher for a signal is stopped libev will reset the signal handler to
1273	SIG_DFL (regardless of what it was set to before).	1437	SIG_DFL (regardless of what it was set to before).
1274		1438
		1439	If possible and supported, libev will install its handlers with
		1440	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1441	interrupted. If you have a problem with syscalls getting interrupted by
		1442	signals you can block all signals in an C<ev_check> watcher and unblock
		1443	them in an C<ev_prepare> watcher.
		1444
1275	=head3 Watcher-Specific Functions and Data Members	1445	=head3 Watcher-Specific Functions and Data Members
1276		1446
1277	=over 4	1447	=over 4
1278		1448
1279	=item ev_signal_init (ev_signal *, callback, int signum)	1449	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1287		1457
1288	The signal the watcher watches out for.	1458	The signal the watcher watches out for.
1289		1459
1290	=back	1460	=back
1291		1461
		1462	=head3 Examples
		1463
		1464	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1465
		1466	static void
		1467	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1468	{
		1469	ev_unloop (loop, EVUNLOOP_ALL);
		1470	}
		1471
		1472	struct ev_signal signal_watcher;
		1473	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1474	ev_signal_start (loop, &sigint_cb);
		1475
1292		1476
1293	=head2 C<ev_child> - watch out for process status changes	1477	=head2 C<ev_child> - watch out for process status changes
1294		1478
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1479	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1480	some child status changes (most typically when a child of yours dies). It
		1481	is permissible to install a child watcher I<after> the child has been
		1482	forked (which implies it might have already exited), as long as the event
		1483	loop isn't entered (or is continued from a watcher).
		1484
		1485	Only the default event loop is capable of handling signals, and therefore
		1486	you can only rgeister child watchers in the default event loop.
		1487
		1488	=head3 Process Interaction
		1489
		1490	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1491	initialised. This is necessary to guarantee proper behaviour even if
		1492	the first child watcher is started after the child exits. The occurance
		1493	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1494	synchronously as part of the event loop processing. Libev always reaps all
		1495	children, even ones not watched.
		1496
		1497	=head3 Overriding the Built-In Processing
		1498
		1499	Libev offers no special support for overriding the built-in child
		1500	processing, but if your application collides with libev's default child
		1501	handler, you can override it easily by installing your own handler for
		1502	C<SIGCHLD> after initialising the default loop, and making sure the
		1503	default loop never gets destroyed. You are encouraged, however, to use an
		1504	event-based approach to child reaping and thus use libev's support for
		1505	that, so other libev users can use C<ev_child> watchers freely.
1297		1506
1298	=head3 Watcher-Specific Functions and Data Members	1507	=head3 Watcher-Specific Functions and Data Members
1299		1508
1300	=over 4	1509	=over 4
1301		1510
1302	=item ev_child_init (ev_child *, callback, int pid)	1511	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1512
1304	=item ev_child_set (ev_child *, int pid)	1513	=item ev_child_set (ev_child *, int pid, int trace)
1305		1514
1306	Configures the watcher to wait for status changes of process C<pid> (or	1515	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1516	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1517	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1518	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1519	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1520	process causing the status change. C<trace> must be either C<0> (only
		1521	activate the watcher when the process terminates) or C<1> (additionally
		1522	activate the watcher when the process is stopped or continued).
1312		1523
1313	=item int pid [read-only]	1524	=item int pid [read-only]
1314		1525
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1526	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1527
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1534	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1535	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1536
1326	=back	1537	=back
1327		1538
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1539	=head3 Examples
		1540
		1541	Example: C<fork()> a new process and install a child handler to wait for
		1542	its completion.
		1543
		1544	ev_child cw;
1329		1545
1330	static void	1546	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1547	child_cb (EV_P_ struct ev_child *w, int revents)
1332	{	1548	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1549	ev_child_stop (EV_A_ w);
		1550	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1551	}
1335		1552
1336	struct ev_signal signal_watcher;	1553	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1554
1338	ev_signal_start (loop, &sigint_cb);	1555	if (pid < 0)
		1556	// error
		1557	else if (pid == 0)
		1558	{
		1559	// the forked child executes here
		1560	exit (1);
		1561	}
		1562	else
		1563	{
		1564	ev_child_init (&cw, child_cb, pid, 0);
		1565	ev_child_start (EV_DEFAULT_ &cw);
		1566	}
1339		1567
1340		1568
1341	=head2 C<ev_stat> - did the file attributes just change?	1569	=head2 C<ev_stat> - did the file attributes just change?
1342		1570
1343	This watches a filesystem path for attribute changes. That is, it calls	1571	This watches a filesystem path for attribute changes. That is, it calls
…		…
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1600	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1373	to fall back to regular polling again even with inotify, but changes are	1601	to fall back to regular polling again even with inotify, but changes are
1374	usually detected immediately, and if the file exists there will be no	1602	usually detected immediately, and if the file exists there will be no
1375	polling.	1603	polling.
1376		1604
		1605	=head3 ABI Issues (Largefile Support)
		1606
		1607	Libev by default (unless the user overrides this) uses the default
		1608	compilation environment, which means that on systems with optionally
		1609	disabled large file support, you get the 32 bit version of the stat
		1610	structure. When using the library from programs that change the ABI to
		1611	use 64 bit file offsets the programs will fail. In that case you have to
		1612	compile libev with the same flags to get binary compatibility. This is
		1613	obviously the case with any flags that change the ABI, but the problem is
		1614	most noticably with ev_stat and largefile support.
		1615
		1616	=head3 Inotify
		1617
		1618	When C<inotify (7)> support has been compiled into libev (generally only
		1619	available on Linux) and present at runtime, it will be used to speed up
		1620	change detection where possible. The inotify descriptor will be created lazily
		1621	when the first C<ev_stat> watcher is being started.
		1622
		1623	Inotify presense does not change the semantics of C<ev_stat> watchers
		1624	except that changes might be detected earlier, and in some cases, to avoid
		1625	making regular C<stat> calls. Even in the presense of inotify support
		1626	there are many cases where libev has to resort to regular C<stat> polling.
		1627
		1628	(There is no support for kqueue, as apparently it cannot be used to
		1629	implement this functionality, due to the requirement of having a file
		1630	descriptor open on the object at all times).
		1631
		1632	=head3 The special problem of stat time resolution
		1633
		1634	The C<stat ()> syscall only supports full-second resolution portably, and
		1635	even on systems where the resolution is higher, many filesystems still
		1636	only support whole seconds.
		1637
		1638	That means that, if the time is the only thing that changes, you might
		1639	miss updates: on the first update, C<ev_stat> detects a change and calls
		1640	your callback, which does something. When there is another update within
		1641	the same second, C<ev_stat> will be unable to detect it.
		1642
		1643	The solution to this is to delay acting on a change for a second (or till
		1644	the next second boundary), using a roughly one-second delay C<ev_timer>
		1645	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1646	is added to work around small timing inconsistencies of some operating
		1647	systems.
		1648
1377	=head3 Watcher-Specific Functions and Data Members	1649	=head3 Watcher-Specific Functions and Data Members
1378		1650
1379	=over 4	1651	=over 4
1380		1652
1381	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1653	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
…		…
1390		1662
1391	The callback will be receive C<EV_STAT> when a change was detected,	1663	The callback will be receive C<EV_STAT> when a change was detected,
1392	relative to the attributes at the time the watcher was started (or the	1664	relative to the attributes at the time the watcher was started (or the
1393	last change was detected).	1665	last change was detected).
1394		1666
1395	=item ev_stat_stat (ev_stat *)	1667	=item ev_stat_stat (loop, ev_stat *)
1396		1668
1397	Updates the stat buffer immediately with new values. If you change the	1669	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	1670	watched path in your callback, you could call this fucntion to avoid
1399	detecting this change (while introducing a race condition). Can also be	1671	detecting this change (while introducing a race condition). Can also be
1400	useful simply to find out the new values.	1672	useful simply to find out the new values.
…		…
1418	=item const char *path [read-only]	1690	=item const char *path [read-only]
1419		1691
1420	The filesystem path that is being watched.	1692	The filesystem path that is being watched.
1421		1693
1422	=back	1694	=back
		1695
		1696	=head3 Examples
1423		1697
1424	Example: Watch C</etc/passwd> for attribute changes.	1698	Example: Watch C</etc/passwd> for attribute changes.
1425		1699
1426	static void	1700	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1701	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1440	}	1714	}
1441		1715
1442	...	1716	...
1443	ev_stat passwd;	1717	ev_stat passwd;
1444		1718
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1719	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	1720	ev_stat_start (loop, &passwd);
		1721
		1722	Example: Like above, but additionally use a one-second delay so we do not
		1723	miss updates (however, frequent updates will delay processing, too, so
		1724	one might do the work both on C<ev_stat> callback invocation I<and> on
		1725	C<ev_timer> callback invocation).
		1726
		1727	static ev_stat passwd;
		1728	static ev_timer timer;
		1729
		1730	static void
		1731	timer_cb (EV_P_ ev_timer *w, int revents)
		1732	{
		1733	ev_timer_stop (EV_A_ w);
		1734
		1735	/* now it's one second after the most recent passwd change */
		1736	}
		1737
		1738	static void
		1739	stat_cb (EV_P_ ev_stat *w, int revents)
		1740	{
		1741	/* reset the one-second timer */
		1742	ev_timer_again (EV_A_ &timer);
		1743	}
		1744
		1745	...
		1746	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1747	ev_stat_start (loop, &passwd);
		1748	ev_timer_init (&timer, timer_cb, 0., 1.01);
1447		1749
1448		1750
1449	=head2 C<ev_idle> - when you've got nothing better to do...	1751	=head2 C<ev_idle> - when you've got nothing better to do...
1450		1752
1451	Idle watchers trigger events when no other events of the same or higher	1753	Idle watchers trigger events when no other events of the same or higher
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1779	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	1780	believe me.
1479		1781
1480	=back	1782	=back
1481		1783
		1784	=head3 Examples
		1785
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1786	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	1787	callback, free it. Also, use no error checking, as usual.
1484		1788
1485	static void	1789	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1790	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1487	{	1791	{
1488	free (w);	1792	free (w);
1489	// now do something you wanted to do when the program has	1793	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	1794	// no longer anything immediate to do.
1491	}	1795	}
1492		1796
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1797	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	1798	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	1799	ev_idle_start (loop, idle_cb);
…		…
1537		1841
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1842	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	1843	priority, to ensure that they are being run before any other watchers
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1844	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1541	too) should not activate ("feed") events into libev. While libev fully	1845	too) should not activate ("feed") events into libev. While libev fully
1542	supports this, they will be called before other C<ev_check> watchers did	1846	supports this, they will be called before other C<ev_check> watchers
1543	their job. As C<ev_check> watchers are often used to embed other event	1847	did their job. As C<ev_check> watchers are often used to embed other
1544	loops those other event loops might be in an unusable state until their	1848	(non-libev) event loops those other event loops might be in an unusable
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1849	state until their C<ev_check> watcher ran (always remind yourself to
1546	others).	1850	coexist peacefully with others).
1547		1851
1548	=head3 Watcher-Specific Functions and Data Members	1852	=head3 Watcher-Specific Functions and Data Members
1549		1853
1550	=over 4	1854	=over 4
1551		1855
…		…
1556	Initialises and configures the prepare or check watcher - they have no	1860	Initialises and configures the prepare or check watcher - they have no
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1861	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	1862	macros, but using them is utterly, utterly and completely pointless.
1559		1863
1560	=back	1864	=back
		1865
		1866	=head3 Examples
1561		1867
1562	There are a number of principal ways to embed other event loops or modules	1868	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	1869	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	1870	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	1871	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	portable one.	2040	portable one.
1735		2041
1736	So when you want to use this feature you will always have to be prepared	2042	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2043	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2044	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2045	create it, and if that fails, use the normal loop for everything.
		2046
		2047	=head3 Watcher-Specific Functions and Data Members
		2048
		2049	=over 4
		2050
		2051	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2052
		2053	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2054
		2055	Configures the watcher to embed the given loop, which must be
		2056	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2057	invoked automatically, otherwise it is the responsibility of the callback
		2058	to invoke it (it will continue to be called until the sweep has been done,
		2059	if you do not want thta, you need to temporarily stop the embed watcher).
		2060
		2061	=item ev_embed_sweep (loop, ev_embed *)
		2062
		2063	Make a single, non-blocking sweep over the embedded loop. This works
		2064	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2065	apropriate way for embedded loops.
		2066
		2067	=item struct ev_loop *other [read-only]
		2068
		2069	The embedded event loop.
		2070
		2071	=back
		2072
		2073	=head3 Examples
		2074
		2075	Example: Try to get an embeddable event loop and embed it into the default
		2076	event loop. If that is not possible, use the default loop. The default
		2077	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2078	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2079	used).
1740		2080
1741	struct ev_loop *loop_hi = ev_default_init (0);	2081	struct ev_loop *loop_hi = ev_default_init (0);
1742	struct ev_loop *loop_lo = 0;	2082	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;	2083	struct ev_embed embed;
1744		2084
…		…
1755	ev_embed_start (loop_hi, &embed);	2095	ev_embed_start (loop_hi, &embed);
1756	}	2096	}
1757	else	2097	else
1758	loop_lo = loop_hi;	2098	loop_lo = loop_hi;
1759		2099
1760	=head3 Watcher-Specific Functions and Data Members	2100	Example: Check if kqueue is available but not recommended and create
		2101	a kqueue backend for use with sockets (which usually work with any
		2102	kqueue implementation). Store the kqueue/socket-only event loop in
		2103	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1761		2104
1762	=over 4	2105	struct ev_loop *loop = ev_default_init (0);
		2106	struct ev_loop *loop_socket = 0;
		2107	struct ev_embed embed;
		2108
		2109	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2110	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2111	{
		2112	ev_embed_init (&embed, 0, loop_socket);
		2113	ev_embed_start (loop, &embed);
		2114	}
1763		2115
1764	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2116	if (!loop_socket)
		2117	loop_socket = loop;
1765		2118
1766	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2119	// now use loop_socket for all sockets, and loop for everything else
1767
1768	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).
1773
1774	=item ev_embed_sweep (loop, ev_embed *)
1775
1776	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.
1779
1780	=item struct ev_loop *loop [read-only]
1781
1782	The embedded event loop.
1783
1784	=back
1785		2120
1786		2121
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2122	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2123
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2124	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1792	event loop blocks next and before C<ev_check> watchers are being called,	2127	event loop blocks next and before C<ev_check> watchers are being called,
1793	and only in the child after the fork. If whoever good citizen calling	2128	and only in the child after the fork. If whoever good citizen calling
1794	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2129	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1795	handlers will be invoked, too, of course.	2130	handlers will be invoked, too, of course.
1796		2131
		2132	=head3 Watcher-Specific Functions and Data Members
		2133
1797	=over 4	2134	=over 4
1798		2135
1799	=item ev_fork_init (ev_signal *, callback)	2136	=item ev_fork_init (ev_signal *, callback)
1800		2137
1801	Initialises and configures the fork watcher - it has no parameters of any	2138	Initialises and configures the fork watcher - it has no parameters of any
1802	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2139	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1803	believe me.	2140	believe me.
		2141
		2142	=back
		2143
		2144
		2145	=head2 C<ev_async> - how to wake up another event loop
		2146
		2147	In general, you cannot use an C<ev_loop> from multiple threads or other
		2148	asynchronous sources such as signal handlers (as opposed to multiple event
		2149	loops - those are of course safe to use in different threads).
		2150
		2151	Sometimes, however, you need to wake up another event loop you do not
		2152	control, for example because it belongs to another thread. This is what
		2153	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2154	can signal it by calling C<ev_async_send>, which is thread- and signal
		2155	safe.
		2156
		2157	This functionality is very similar to C<ev_signal> watchers, as signals,
		2158	too, are asynchronous in nature, and signals, too, will be compressed
		2159	(i.e. the number of callback invocations may be less than the number of
		2160	C<ev_async_sent> calls).
		2161
		2162	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2163	just the default loop.
		2164
		2165	=head3 Queueing
		2166
		2167	C<ev_async> does not support queueing of data in any way. The reason
		2168	is that the author does not know of a simple (or any) algorithm for a
		2169	multiple-writer-single-reader queue that works in all cases and doesn't
		2170	need elaborate support such as pthreads.
		2171
		2172	That means that if you want to queue data, you have to provide your own
		2173	queue. But at least I can tell you would implement locking around your
		2174	queue:
		2175
		2176	=over 4
		2177
		2178	=item queueing from a signal handler context
		2179
		2180	To implement race-free queueing, you simply add to the queue in the signal
		2181	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2182	some fictitiuous SIGUSR1 handler:
		2183
		2184	static ev_async mysig;
		2185
		2186	static void
		2187	sigusr1_handler (void)
		2188	{
		2189	sometype data;
		2190
		2191	// no locking etc.
		2192	queue_put (data);
		2193	ev_async_send (EV_DEFAULT_ &mysig);
		2194	}
		2195
		2196	static void
		2197	mysig_cb (EV_P_ ev_async *w, int revents)
		2198	{
		2199	sometype data;
		2200	sigset_t block, prev;
		2201
		2202	sigemptyset (&block);
		2203	sigaddset (&block, SIGUSR1);
		2204	sigprocmask (SIG_BLOCK, &block, &prev);
		2205
		2206	while (queue_get (&data))
		2207	process (data);
		2208
		2209	if (sigismember (&prev, SIGUSR1)
		2210	sigprocmask (SIG_UNBLOCK, &block, 0);
		2211	}
		2212
		2213	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2214	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2215	either...).
		2216
		2217	=item queueing from a thread context
		2218
		2219	The strategy for threads is different, as you cannot (easily) block
		2220	threads but you can easily preempt them, so to queue safely you need to
		2221	employ a traditional mutex lock, such as in this pthread example:
		2222
		2223	static ev_async mysig;
		2224	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2225
		2226	static void
		2227	otherthread (void)
		2228	{
		2229	// only need to lock the actual queueing operation
		2230	pthread_mutex_lock (&mymutex);
		2231	queue_put (data);
		2232	pthread_mutex_unlock (&mymutex);
		2233
		2234	ev_async_send (EV_DEFAULT_ &mysig);
		2235	}
		2236
		2237	static void
		2238	mysig_cb (EV_P_ ev_async *w, int revents)
		2239	{
		2240	pthread_mutex_lock (&mymutex);
		2241
		2242	while (queue_get (&data))
		2243	process (data);
		2244
		2245	pthread_mutex_unlock (&mymutex);
		2246	}
		2247
		2248	=back
		2249
		2250
		2251	=head3 Watcher-Specific Functions and Data Members
		2252
		2253	=over 4
		2254
		2255	=item ev_async_init (ev_async *, callback)
		2256
		2257	Initialises and configures the async watcher - it has no parameters of any
		2258	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2259	believe me.
		2260
		2261	=item ev_async_send (loop, ev_async *)
		2262
		2263	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2264	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2265	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2266	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2267	section below on what exactly this means).
		2268
		2269	This call incurs the overhead of a syscall only once per loop iteration,
		2270	so while the overhead might be noticable, it doesn't apply to repeated
		2271	calls to C<ev_async_send>.
1804		2272
1805	=back	2273	=back
1806		2274
1807		2275
1808	=head1 OTHER FUNCTIONS	2276	=head1 OTHER FUNCTIONS
…		…
2017		2485
2018	=item w->stop ()	2486	=item w->stop ()
2019		2487
2020	Stops the watcher if it is active. Again, no C<loop> argument.	2488	Stops the watcher if it is active. Again, no C<loop> argument.
2021		2489
2022	=item w->again () C<ev::timer>, C<ev::periodic> only	2490	=item w->again () (C<ev::timer>, C<ev::periodic> only)
2023		2491
2024	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2492	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
2025	C<ev_TYPE_again> function.	2493	C<ev_TYPE_again> function.
2026		2494
2027	=item w->sweep () C<ev::embed> only	2495	=item w->sweep () (C<ev::embed> only)
2028		2496
2029	Invokes C<ev_embed_sweep>.	2497	Invokes C<ev_embed_sweep>.
2030		2498
2031	=item w->update () C<ev::stat> only	2499	=item w->update () (C<ev::stat> only)
2032		2500
2033	Invokes C<ev_stat_stat>.	2501	Invokes C<ev_stat_stat>.
2034		2502
2035	=back	2503	=back
2036		2504
…		…
2039	Example: Define a class with an IO and idle watcher, start one of them in	2507	Example: Define a class with an IO and idle watcher, start one of them in
2040	the constructor.	2508	the constructor.
2041		2509
2042	class myclass	2510	class myclass
2043	{	2511	{
2044	ev_io io; void io_cb (ev::io &w, int revents);	2512	ev::io io; void io_cb (ev::io &w, int revents);
2045	ev_idle idle void idle_cb (ev::idle &w, int revents);	2513	ev:idle idle void idle_cb (ev::idle &w, int revents);
2046		2514
2047	myclass ();	2515	myclass (int fd)
2048	}
2049
2050	myclass::myclass (int fd)
2051	{	2516	{
2052	io .set <myclass, &myclass::io_cb > (this);	2517	io .set <myclass, &myclass::io_cb > (this);
2053	idle.set <myclass, &myclass::idle_cb> (this);	2518	idle.set <myclass, &myclass::idle_cb> (this);
2054		2519
2055	io.start (fd, ev::READ);	2520	io.start (fd, ev::READ);
		2521	}
2056	}	2522	};
		2523
		2524
		2525	=head1 OTHER LANGUAGE BINDINGS
		2526
		2527	Libev does not offer other language bindings itself, but bindings for a
		2528	numbe rof languages exist in the form of third-party packages. If you know
		2529	any interesting language binding in addition to the ones listed here, drop
		2530	me a note.
		2531
		2532	=over 4
		2533
		2534	=item Perl
		2535
		2536	The EV module implements the full libev API and is actually used to test
		2537	libev. EV is developed together with libev. Apart from the EV core module,
		2538	there are additional modules that implement libev-compatible interfaces
		2539	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2540	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2541
		2542	It can be found and installed via CPAN, its homepage is found at
		2543	L<http://software.schmorp.de/pkg/EV>.
		2544
		2545	=item Ruby
		2546
		2547	Tony Arcieri has written a ruby extension that offers access to a subset
		2548	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2549	more on top of it. It can be found via gem servers. Its homepage is at
		2550	L<http://rev.rubyforge.org/>.
		2551
		2552	=item D
		2553
		2554	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2555	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2556
		2557	=back
2057		2558
2058		2559
2059	=head1 MACRO MAGIC	2560	=head1 MACRO MAGIC
2060		2561
2061	Libev can be compiled with a variety of options, the most fundemantal is	2562	Libev can be compiled with a variety of options, the most fundamantal
2062	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2563	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2063	callbacks have an initial C<struct ev_loop *> argument.	2564	functions and callbacks have an initial C<struct ev_loop *> argument.
2064		2565
2065	To make it easier to write programs that cope with either variant, the	2566	To make it easier to write programs that cope with either variant, the
2066	following macros are defined:	2567	following macros are defined:
2067		2568
2068	=over 4	2569	=over 4
…		…
2122	Libev can (and often is) directly embedded into host	2623	Libev can (and often is) directly embedded into host
2123	applications. Examples of applications that embed it include the Deliantra	2624	applications. Examples of applications that embed it include the Deliantra
2124	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2625	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2125	and rxvt-unicode.	2626	and rxvt-unicode.
2126		2627
2127	The goal is to enable you to just copy the neecssary files into your	2628	The goal is to enable you to just copy the necessary files into your
2128	source directory without having to change even a single line in them, so	2629	source directory without having to change even a single line in them, so
2129	you can easily upgrade by simply copying (or having a checked-out copy of	2630	you can easily upgrade by simply copying (or having a checked-out copy of
2130	libev somewhere in your source tree).	2631	libev somewhere in your source tree).
2131		2632
2132	=head2 FILESETS	2633	=head2 FILESETS
…		…
2222		2723
2223	If defined to be C<1>, libev will try to detect the availability of the	2724	If defined to be C<1>, libev will try to detect the availability of the
2224	monotonic clock option at both compiletime and runtime. Otherwise no use	2725	monotonic clock option at both compiletime and runtime. Otherwise no use
2225	of the monotonic clock option will be attempted. If you enable this, you	2726	of the monotonic clock option will be attempted. If you enable this, you
2226	usually have to link against librt or something similar. Enabling it when	2727	usually have to link against librt or something similar. Enabling it when
2227	the functionality isn't available is safe, though, althoguh you have	2728	the functionality isn't available is safe, though, although you have
2228	to make sure you link against any libraries where the C<clock_gettime>	2729	to make sure you link against any libraries where the C<clock_gettime>
2229	function is hiding in (often F<-lrt>).	2730	function is hiding in (often F<-lrt>).
2230		2731
2231	=item EV_USE_REALTIME	2732	=item EV_USE_REALTIME
2232		2733
2233	If defined to be C<1>, libev will try to detect the availability of the	2734	If defined to be C<1>, libev will try to detect the availability of the
2234	realtime clock option at compiletime (and assume its availability at	2735	realtime clock option at compiletime (and assume its availability at
2235	runtime if successful). Otherwise no use of the realtime clock option will	2736	runtime if successful). Otherwise no use of the realtime clock option will
2236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2737	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2738	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2238	in the description of C<EV_USE_MONOTONIC>, though.	2739	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2740
		2741	=item EV_USE_NANOSLEEP
		2742
		2743	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2744	and will use it for delays. Otherwise it will use C<select ()>.
2239		2745
2240	=item EV_USE_SELECT	2746	=item EV_USE_SELECT
2241		2747
2242	If undefined or defined to be C<1>, libev will compile in support for the	2748	If undefined or defined to be C<1>, libev will compile in support for the
2243	C<select>(2) backend. No attempt at autodetection will be done: if no	2749	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2261	wants osf handles on win32 (this is the case when the select to	2767	wants osf handles on win32 (this is the case when the select to
2262	be used is the winsock select). This means that it will call	2768	be used is the winsock select). This means that it will call
2263	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2769	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2264	it is assumed that all these functions actually work on fds, even	2770	it is assumed that all these functions actually work on fds, even
2265	on win32. Should not be defined on non-win32 platforms.	2771	on win32. Should not be defined on non-win32 platforms.
		2772
		2773	=item EV_FD_TO_WIN32_HANDLE
		2774
		2775	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2776	file descriptors to socket handles. When not defining this symbol (the
		2777	default), then libev will call C<_get_osfhandle>, which is usually
		2778	correct. In some cases, programs use their own file descriptor management,
		2779	in which case they can provide this function to map fds to socket handles.
2266		2780
2267	=item EV_USE_POLL	2781	=item EV_USE_POLL
2268		2782
2269	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2783	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2270	backend. Otherwise it will be enabled on non-win32 platforms. It	2784	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2304		2818
2305	If defined to be C<1>, libev will compile in support for the Linux inotify	2819	If defined to be C<1>, libev will compile in support for the Linux inotify
2306	interface to speed up C<ev_stat> watchers. Its actual availability will	2820	interface to speed up C<ev_stat> watchers. Its actual availability will
2307	be detected at runtime.	2821	be detected at runtime.
2308		2822
		2823	=item EV_ATOMIC_T
		2824
		2825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2826	access is atomic with respect to other threads or signal contexts. No such
		2827	type is easily found in the C language, so you can provide your own type
		2828	that you know is safe for your purposes. It is used both for signal handler "locking"
		2829	as well as for signal and thread safety in C<ev_async> watchers.
		2830
		2831	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2832	(from F<signal.h>), which is usually good enough on most platforms.
		2833
2309	=item EV_H	2834	=item EV_H
2310		2835
2311	The name of the F<ev.h> header file used to include it. The default if	2836	The name of the F<ev.h> header file used to include it. The default if
2312	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2837	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2313	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2838	used to virtually rename the F<ev.h> header file in case of conflicts.
2314		2839
2315	=item EV_CONFIG_H	2840	=item EV_CONFIG_H
2316		2841
2317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2842	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2843	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2319	C<EV_H>, above.	2844	C<EV_H>, above.
2320		2845
2321	=item EV_EVENT_H	2846	=item EV_EVENT_H
2322		2847
2323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2848	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2324	of how the F<event.h> header can be found.	2849	of how the F<event.h> header can be found, the default is C<"event.h">.
2325		2850
2326	=item EV_PROTOTYPES	2851	=item EV_PROTOTYPES
2327		2852
2328	If defined to be C<0>, then F<ev.h> will not define any function	2853	If defined to be C<0>, then F<ev.h> will not define any function
2329	prototypes, but still define all the structs and other symbols. This is	2854	prototypes, but still define all the structs and other symbols. This is
…		…
2380	=item EV_FORK_ENABLE	2905	=item EV_FORK_ENABLE
2381		2906
2382	If undefined or defined to be C<1>, then fork watchers are supported. If	2907	If undefined or defined to be C<1>, then fork watchers are supported. If
2383	defined to be C<0>, then they are not.	2908	defined to be C<0>, then they are not.
2384		2909
		2910	=item EV_ASYNC_ENABLE
		2911
		2912	If undefined or defined to be C<1>, then async watchers are supported. If
		2913	defined to be C<0>, then they are not.
		2914
2385	=item EV_MINIMAL	2915	=item EV_MINIMAL
2386		2916
2387	If you need to shave off some kilobytes of code at the expense of some	2917	If you need to shave off some kilobytes of code at the expense of some
2388	speed, define this symbol to C<1>. Currently only used for gcc to override	2918	speed, define this symbol to C<1>. Currently only used for gcc to override
2389	some inlining decisions, saves roughly 30% codesize of amd64.	2919	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2395	than enough. If you need to manage thousands of children you might want to	2925	than enough. If you need to manage thousands of children you might want to
2396	increase this value (I<must> be a power of two).	2926	increase this value (I<must> be a power of two).
2397		2927
2398	=item EV_INOTIFY_HASHSIZE	2928	=item EV_INOTIFY_HASHSIZE
2399		2929
2400	C<ev_staz> watchers use a small hash table to distribute workload by	2930	C<ev_stat> watchers use a small hash table to distribute workload by
2401	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2931	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2402	usually more than enough. If you need to manage thousands of C<ev_stat>	2932	usually more than enough. If you need to manage thousands of C<ev_stat>
2403	watchers you might want to increase this value (I<must> be a power of	2933	watchers you might want to increase this value (I<must> be a power of
2404	two).	2934	two).
2405		2935
…		…
2422		2952
2423	=item ev_set_cb (ev, cb)	2953	=item ev_set_cb (ev, cb)
2424		2954
2425	Can be used to change the callback member declaration in each watcher,	2955	Can be used to change the callback member declaration in each watcher,
2426	and the way callbacks are invoked and set. Must expand to a struct member	2956	and the way callbacks are invoked and set. Must expand to a struct member
2427	definition and a statement, respectively. See the F<ev.v> header file for	2957	definition and a statement, respectively. See the F<ev.h> header file for
2428	their default definitions. One possible use for overriding these is to	2958	their default definitions. One possible use for overriding these is to
2429	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2959	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2430	method calls instead of plain function calls in C++.	2960	method calls instead of plain function calls in C++.
		2961
		2962	=head2 EXPORTED API SYMBOLS
		2963
		2964	If you need to re-export the API (e.g. via a dll) and you need a list of
		2965	exported symbols, you can use the provided F<Symbol.*> files which list
		2966	all public symbols, one per line:
		2967
		2968	Symbols.ev for libev proper
		2969	Symbols.event for the libevent emulation
		2970
		2971	This can also be used to rename all public symbols to avoid clashes with
		2972	multiple versions of libev linked together (which is obviously bad in
		2973	itself, but sometimes it is inconvinient to avoid this).
		2974
		2975	A sed command like this will create wrapper C<#define>'s that you need to
		2976	include before including F<ev.h>:
		2977
		2978	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2979
		2980	This would create a file F<wrap.h> which essentially looks like this:
		2981
		2982	#define ev_backend myprefix_ev_backend
		2983	#define ev_check_start myprefix_ev_check_start
		2984	#define ev_check_stop myprefix_ev_check_stop
		2985	...
2431		2986
2432	=head2 EXAMPLES	2987	=head2 EXAMPLES
2433		2988
2434	For a real-world example of a program the includes libev	2989	For a real-world example of a program the includes libev
2435	verbatim, you can have a look at the EV perl module	2990	verbatim, you can have a look at the EV perl module
…		…
2476		3031
2477	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3032	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2478		3033
2479	This means that, when you have a watcher that triggers in one hour and	3034	This means that, when you have a watcher that triggers in one hour and
2480	there are 100 watchers that would trigger before that then inserting will	3035	there are 100 watchers that would trigger before that then inserting will
2481	have to skip those 100 watchers.	3036	have to skip roughly seven (C<ld 100>) of these watchers.
2482		3037
2483	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3038	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2484		3039
2485	That means that for changing a timer costs less than removing/adding them	3040	That means that changing a timer costs less than removing/adding them
2486	as only the relative motion in the event queue has to be paid for.	3041	as only the relative motion in the event queue has to be paid for.
2487		3042
2488	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3043	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2489		3044
2490	These just add the watcher into an array or at the head of a list.	3045	These just add the watcher into an array or at the head of a list.
		3046
2491	=item Stopping check/prepare/idle watchers: O(1)	3047	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2492		3048
2493	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3049	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2494		3050
2495	These watchers are stored in lists then need to be walked to find the	3051	These watchers are stored in lists then need to be walked to find the
2496	correct watcher to remove. The lists are usually short (you don't usually	3052	correct watcher to remove. The lists are usually short (you don't usually
2497	have many watchers waiting for the same fd or signal).	3053	have many watchers waiting for the same fd or signal).
2498		3054
2499	=item Finding the next timer per loop iteration: O(1)	3055	=item Finding the next timer in each loop iteration: O(1)
		3056
		3057	By virtue of using a binary heap, the next timer is always found at the
		3058	beginning of the storage array.
2500		3059
2501	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3060	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2502		3061
2503	A change means an I/O watcher gets started or stopped, which requires	3062	A change means an I/O watcher gets started or stopped, which requires
2504	libev to recalculate its status (and possibly tell the kernel).	3063	libev to recalculate its status (and possibly tell the kernel, depending
		3064	on backend and wether C<ev_io_set> was used).
2505		3065
2506	=item Activating one watcher: O(1)	3066	=item Activating one watcher (putting it into the pending state): O(1)
2507		3067
2508	=item Priority handling: O(number_of_priorities)	3068	=item Priority handling: O(number_of_priorities)
2509		3069
2510	Priorities are implemented by allocating some space for each	3070	Priorities are implemented by allocating some space for each
2511	priority. When doing priority-based operations, libev usually has to	3071	priority. When doing priority-based operations, libev usually has to
2512	linearly search all the priorities.	3072	linearly search all the priorities, but starting/stopping and activating
		3073	watchers becomes O(1) w.r.t. priority handling.
		3074
		3075	=item Sending an ev_async: O(1)
		3076
		3077	=item Processing ev_async_send: O(number_of_async_watchers)
		3078
		3079	=item Processing signals: O(max_signal_number)
		3080
		3081	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3082	calls in the current loop iteration. Checking for async and signal events
		3083	involves iterating over all running async watchers or all signal numbers.
2513		3084
2514	=back	3085	=back
2515		3086
2516		3087
		3088	=head1 Win32 platform limitations and workarounds
		3089
		3090	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3091	requires, and its I/O model is fundamentally incompatible with the POSIX
		3092	model. Libev still offers limited functionality on this platform in
		3093	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3094	descriptors. This only applies when using Win32 natively, not when using
		3095	e.g. cygwin.
		3096
		3097	There is no supported compilation method available on windows except
		3098	embedding it into other applications.
		3099
		3100	Due to the many, low, and arbitrary limits on the win32 platform and the
		3101	abysmal performance of winsockets, using a large number of sockets is not
		3102	recommended (and not reasonable). If your program needs to use more than
		3103	a hundred or so sockets, then likely it needs to use a totally different
		3104	implementation for windows, as libev offers the POSIX model, which cannot
		3105	be implemented efficiently on windows (microsoft monopoly games).
		3106
		3107	=over 4
		3108
		3109	=item The winsocket select function
		3110
		3111	The winsocket C<select> function doesn't follow POSIX in that it requires
		3112	socket I<handles> and not socket I<file descriptors>. This makes select
		3113	very inefficient, and also requires a mapping from file descriptors
		3114	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3115	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3116	symbols for more info.
		3117
		3118	The configuration for a "naked" win32 using the microsoft runtime
		3119	libraries and raw winsocket select is:
		3120
		3121	#define EV_USE_SELECT 1
		3122	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3123
		3124	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3125	complexity in the O(n²) range when using win32.
		3126
		3127	=item Limited number of file descriptors
		3128
		3129	Windows has numerous arbitrary (and low) limits on things. Early versions
		3130	of winsocket's select only supported waiting for a max. of C<64> handles
		3131	(probably owning to the fact that all windows kernels can only wait for
		3132	C<64> things at the same time internally; microsoft recommends spawning a
		3133	chain of threads and wait for 63 handles and the previous thread in each).
		3134
		3135	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3136	to some high number (e.g. C<2048>) before compiling the winsocket select
		3137	call (which might be in libev or elsewhere, for example, perl does its own
		3138	select emulation on windows).
		3139
		3140	Another limit is the number of file descriptors in the microsoft runtime
		3141	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3142	or something like this inside microsoft). You can increase this by calling
		3143	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3144	arbitrary limit), but is broken in many versions of the microsoft runtime
		3145	libraries.
		3146
		3147	This might get you to about C<512> or C<2048> sockets (depending on
		3148	windows version and/or the phase of the moon). To get more, you need to
		3149	wrap all I/O functions and provide your own fd management, but the cost of
		3150	calling select (O(n²)) will likely make this unworkable.
		3151
		3152	=back
		3153
		3154
2517	=head1 AUTHOR	3155	=head1 AUTHOR
2518		3156
2519	Marc Lehmann <libev@schmorp.de>.	3157	Marc Lehmann <libev@schmorp.de>.
2520		3158

Diff Legend

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