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…		…
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	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
257	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		293
260	The following flags are supported:	294	The following flags are supported:
261		295
…		…
282	enabling this flag.	316	enabling this flag.
283		317
284	This works by calling C<getpid ()> on every iteration of the loop,	318	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	319	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	320	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
290		324
291	The big advantage of this flag is that you can forget about fork (and	325	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	326	forget about forgetting to tell libev about forking) when you use this
293	flag.	327	flag.
…		…
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		333
300	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
305		346
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		348
308	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
312		355
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		357
315	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	359	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	360	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
		362	of shortcomings, such as silently dropping events in some hard-to-detect
		363	cases and requiring a syscall per fd change, no fork support and bad
		364	support for dup.
319		365
320	While stopping and starting an I/O watcher in the same iteration will	366	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	367	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	368	(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	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	370	very well if you register events for both fds.
325		371
326	Please note that epoll sometimes generates spurious notifications, so you	372	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	373	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	374	(or space) is available.
329		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		384
332	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
333	was broken on all BSDs except NetBSD (usually it doesn't work with	386	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	387	with anything but sockets and pipes, except on Darwin, where of course
335	completely useless). For this reason its not being "autodetected"	388	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	389	unless you explicitly specify it explicitly in the flags (i.e. using
337	C<EVBACKEND_KQUEUE>).	390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		391	system like NetBSD.
		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
338		396
339	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	398	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	399	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	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	401	two event changes per incident, support for C<fork ()> is very bad and it
		402	drops fds silently in similarly hard-to-detect cases.
		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
344		412
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		414
347	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
348		419
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		421
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	422	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)).	423	it's really slow, but it still scales very well (O(active_fds)).
353		424
354	Please note that solaris ports can result in a lot of spurious	425	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	426	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
357		437
358	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
359		439
360	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		443
		444	It is definitely not recommended to use this flag.
		445
364	=back	446	=back
365		447
366	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		451
371	The most typical usage is like this:	452	The most typical usage is like this:
372		453
373	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
388		469
389	Similar to C<ev_default_loop>, but always creates a new event loop that is	470	Similar to C<ev_default_loop>, but always creates a new event loop that is
390	always distinct from the default loop. Unlike the default loop, it cannot	471	always distinct from the default loop. Unlike the default loop, it cannot
391	handle signal and child watchers, and attempts to do so will be greeted by	472	handle signal and child watchers, and attempts to do so will be greeted by
392	undefined behaviour (or a failed assertion if assertions are enabled).	473	undefined behaviour (or a failed assertion if assertions are enabled).
		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
393		478
394	Example: Try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
395		480
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	482	if (!epoller)
…		…
402	Destroys the default loop again (frees all memory and kernel state	487	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	488	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	489	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>	490	responsibility to either stop all watchers cleanly yoursef I<before>
406	calling this function, or cope with the fact afterwards (which is usually	491	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	492	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	493	for example).
		494
		495	Note that certain global state, such as signal state, will not be freed by
		496	this function, and related watchers (such as signal and child watchers)
		497	would need to be stopped manually.
		498
		499	In general it is not advisable to call this function except in the
		500	rare occasion where you really need to free e.g. the signal handling
		501	pipe fds. If you need dynamically allocated loops it is better to use
		502	C<ev_loop_new> and C<ev_loop_destroy>).
409		503
410	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
411		505
412	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
414		508
415	=item ev_default_fork ()	509	=item ev_default_fork ()
416		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	512	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	513	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	514	the child process (or both child and parent, but that again makes little
420	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
421		517
422	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
425		521
426	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
429		525
430	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
431		527
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)	528	=item ev_loop_fork (loop)
437		529
438	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
441		537
442	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
443		539
444	Returns the count of loop iterations for the loop, which is identical to	540	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	541	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		554
459	Returns the current "event loop time", which is the time the event loop	555	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	556	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	557	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	558	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).	559	event occurring (or more correctly, libev finding out about it).
464		560
465	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
466		562
467	Finally, this is it, the event handler. This function usually is called	563	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	564	after you initialised all your watchers and you want to start handling
…		…
490	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
491		587
492	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
493		589
494	- Before the first iteration, call any pending watchers.	590	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
498	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	596	- Update the "event loop time".
500	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
504	- Queue all outstanding timers.	604	- Queue all outstanding timers.
505	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
506	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
507	- Queue all check watchers.	607	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	609	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
513		614
514	Example: Queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	616	anymore.
516		617
517	... queue jobs here, make sure they register event watchers as long	618	... 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..)	619	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
523		624
524	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
528		631
529	=item ev_ref (loop)	632	=item ev_ref (loop)
530		633
531	=item ev_unref (loop)	634	=item ev_unref (loop)
532		635
…		…
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
538	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
539	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
540	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
543		648
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	650	running when nothing else is active.
546		651
547	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
551		656
552	Example: For some weird reason, unregister the above signal handler again.	657	Example: For some weird reason, unregister the above signal handler again.
553		658
554	ev_ref (loop);	659	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	660	ev_signal_stop (loop, &exitsig);
		661
		662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		663
		664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		665
		666	These advanced functions influence the time that libev will spend waiting
		667	for events. Both are by default C<0>, meaning that libev will try to
		668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		669
		670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		671	allows libev to delay invocation of I/O and timer/periodic callbacks to
		672	increase efficiency of loop iterations.
		673
		674	The background is that sometimes your program runs just fast enough to
		675	handle one (or very few) event(s) per loop iteration. While this makes
		676	the program responsive, it also wastes a lot of CPU time to poll for new
		677	events, especially with backends like C<select ()> which have a high
		678	overhead for the actual polling but can deliver many events at once.
		679
		680	By setting a higher I<io collect interval> you allow libev to spend more
		681	time collecting I/O events, so you can handle more events per iteration,
		682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
		685
		686	Likewise, by setting a higher I<timeout collect interval> you allow libev
		687	to spend more time collecting timeouts, at the expense of increased
		688	latency (the watcher callback will be called later). C<ev_io> watchers
		689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
		691
		692	Many (busy) programs can usually benefit by setting the io collect
		693	interval to a value near C<0.1> or so, which is often enough for
		694	interactive servers (of course not for games), likewise for timeouts. It
		695	usually doesn't make much sense to set it to a lower value than C<0.01>,
		696	as this approsaches the timing granularity of most systems.
556		697
557	=back	698	=back
558		699
559		700
560	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
…		…
659		800
660	=item C<EV_FORK>	801	=item C<EV_FORK>
661		802
662	The event loop has been resumed in the child process after fork (see	803	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
664		809
665	=item C<EV_ERROR>	810	=item C<EV_ERROR>
666		811
667	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	813	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	1031	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	1032	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	1033	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1034	required if you know what you are doing).
890		1035
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	1036	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	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
900		1039
901	Another thing you have to watch out for is that it is quite easy to	1040	Another thing you have to watch out for is that it is quite easy to
…		…
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1052	such as poll (fortunately in our Xlib example, Xlib already does this on
914	its own, so its quite safe to use).	1053	its own, so its quite safe to use).
915		1054
916	=head3 The special problem of disappearing file descriptors	1055	=head3 The special problem of disappearing file descriptors
917		1056
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1057	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,	1058	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	1059	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	1060	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	1061	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	1062	registered with libev, there is no efficient way to see that this is, in
…		…
932		1071
933	This is how one would do it normally anyway, the important point is that	1072	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	1073	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1074	optimisations to libev.
936		1075
		1076	=head3 The special problem of dup'ed file descriptors
		1077
		1078	Some backends (e.g. epoll), cannot register events for file descriptors,
		1079	but only events for the underlying file descriptions. That means when you
		1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1081	events for them, only one file descriptor might actually receive events.
		1082
		1083	There is no workaround possible except not registering events
		1084	for potentially C<dup ()>'ed file descriptors, or to resort to
		1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1086
		1087	=head3 The special problem of fork
		1088
		1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1090	useless behaviour. Libev fully supports fork, but needs to be told about
		1091	it in the child.
		1092
		1093	To support fork in your programs, you either have to call
		1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1096	C<EVBACKEND_POLL>.
		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
937		1110
938	=head3 Watcher-Specific Functions	1111	=head3 Watcher-Specific Functions
939		1112
940	=over 4	1113	=over 4
941		1114
…		…
954	=item int events [read-only]	1127	=item int events [read-only]
955		1128
956	The events being watched.	1129	The events being watched.
957		1130
958	=back	1131	=back
		1132
		1133	=head3 Examples
959		1134
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1136	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
963		1138
…		…
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
1019	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
1020		1195
1021	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
1022		1197
1023	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
1025		1200
1026	If the timer is pending, its pending status is cleared.	1201	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),	1236	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.	1237	which is also when any modifications are taken into account.
1063		1238
1064	=back	1239	=back
1065		1240
		1241	=head3 Examples
		1242
1066	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
1067		1244
1068	static void	1245	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070	{	1247	{
…		…
1133	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
1136	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1137		1314
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1316
1140	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1319	and then repeat, regardless of any time jumps.
1143		1320
…		…
1220		1397
1221	The current reschedule callback, or C<0>, if this functionality is	1398	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	1399	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.	1400	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1401
		1402	=item ev_tstamp at [read-only]
		1403
		1404	When active, contains the absolute time that the watcher is supposed to
		1405	trigger next.
		1406
1225	=back	1407	=back
		1408
		1409	=head3 Examples
1226		1410
1227	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1230		1414
…		…
1270	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1271	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1272	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1273	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1274		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
1275	=head3 Watcher-Specific Functions and Data Members	1465	=head3 Watcher-Specific Functions and Data Members
1276		1466
1277	=over 4	1467	=over 4
1278		1468
1279	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
1287		1477
1288	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1289		1479
1290	=back	1480	=back
1291		1481
		1482	=head3 Examples
		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
1292		1496
1293	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1294		1498
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
1297		1526
1298	=head3 Watcher-Specific Functions and Data Members	1527	=head3 Watcher-Specific Functions and Data Members
1299		1528
1300	=over 4	1529	=over 4
1301		1530
1302	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1532
1304	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1305		1534
1306	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
1312		1543
1313	=item int pid [read-only]	1544	=item int pid [read-only]
1314		1545
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1546	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1547
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1554	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1556
1326	=back	1557	=back
1327		1558
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1329		1565
1330	static void	1566	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1332	{	1568	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1571	}
1335		1572
1336	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1338	ev_signal_start (loop, &sigint_cb);	1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1339		1587
1340		1588
1341	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1342		1590
1343	This watches a filesystem path for attribute changes. That is, it calls	1591	This watches a filesystem path for attribute changes. That is, it calls
…		…
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1373	to fall back to regular polling again even with inotify, but changes are	1621	to fall back to regular polling again even with inotify, but changes are
1374	usually detected immediately, and if the file exists there will be no	1622	usually detected immediately, and if the file exists there will be no
1375	polling.	1623	polling.
1376		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
1377	=head3 Watcher-Specific Functions and Data Members	1669	=head3 Watcher-Specific Functions and Data Members
1378		1670
1379	=over 4	1671	=over 4
1380		1672
1381	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
…		…
1390		1682
1391	The callback will be receive C<EV_STAT> when a change was detected,	1683	The callback will be receive C<EV_STAT> when a change was detected,
1392	relative to the attributes at the time the watcher was started (or the	1684	relative to the attributes at the time the watcher was started (or the
1393	last change was detected).	1685	last change was detected).
1394		1686
1395	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1396		1688
1397	Updates the stat buffer immediately with new values. If you change the	1689	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	1690	watched path in your callback, you could call this fucntion to avoid
1399	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1400	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1418	=item const char *path [read-only]	1710	=item const char *path [read-only]
1419		1711
1420	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1421		1713
1422	=back	1714	=back
		1715
		1716	=head3 Examples
1423		1717
1424	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1425		1719
1426	static void	1720	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1440	}	1734	}
1441		1735
1442	...	1736	...
1443	ev_stat passwd;	1737	ev_stat passwd;
1444		1738
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	1740	ev_stat_start (loop, &passwd);
		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
1447		1769
1448		1770
1449	=head2 C<ev_idle> - when you've got nothing better to do...	1771	=head2 C<ev_idle> - when you've got nothing better to do...
1450		1772
1451	Idle watchers trigger events when no other events of the same or higher	1773	Idle watchers trigger events when no other events of the same or higher
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	1800	believe me.
1479		1801
1480	=back	1802	=back
1481		1803
		1804	=head3 Examples
		1805
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1484		1808
1485	static void	1809	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1487	{	1811	{
1488	free (w);	1812	free (w);
1489	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1491	}	1815	}
1492		1816
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1537		1861
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	1863	priority, to ensure that they are being run before any other watchers
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1541	too) should not activate ("feed") events into libev. While libev fully	1865	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	1866	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	1867	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	1868	(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	1869	state until their C<ev_check> watcher ran (always remind yourself to
1546	others).	1870	coexist peacefully with others).
1547		1871
1548	=head3 Watcher-Specific Functions and Data Members	1872	=head3 Watcher-Specific Functions and Data Members
1549		1873
1550	=over 4	1874	=over 4
1551		1875
…		…
1556	Initialises and configures the prepare or check watcher - they have no	1880	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>	1881	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.	1882	macros, but using them is utterly, utterly and completely pointless.
1559		1883
1560	=back	1884	=back
		1885
		1886	=head3 Examples
1561		1887
1562	There are a number of principal ways to embed other event loops or modules	1888	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	1889	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	1891	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1734	portable one.	2060	portable one.
1735		2061
1736	So when you want to use this feature you will always have to be prepared	2062	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2063	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2064	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
1740		2100
1741	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1742	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;	2103	struct ev_embed embed;
1744		2104
…		…
1755	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1756	}	2116	}
1757	else	2117	else
1758	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1759		2119
1760	=head3 Watcher-Specific Functions and Data Members	2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1761		2124
1762	=over 4	2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
1763		2135
1764	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2136	if (!loop_socket)
		2137	loop_socket = loop;
1765		2138
1766	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2139	// now use loop_socket for all sockets, and loop for everything else
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		2140
1786		2141
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2143
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2144	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2160	believe me.
1806		2161
1807	=back	2162	=back
1808		2163
1809		2164
		2165	=head2 C<ev_async> - how to wake up another event loop
		2166
		2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
		2292
		2293	=item bool = ev_async_pending (ev_async *)
		2294
		2295	Returns a non-zero value when C<ev_async_send> has been called on the
		2296	watcher but the event has not yet been processed (or even noted) by the
		2297	event loop.
		2298
		2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2300	the loop iterates next and checks for the watcher to have become active,
		2301	it will reset the flag again. C<ev_async_pending> can be used to very
		2302	quickly check wether invoking the loop might be a good idea.
		2303
		2304	Not that this does I<not> check wether the watcher itself is pending, only
		2305	wether it has been requested to make this watcher pending.
		2306
		2307	=back
		2308
		2309
1810	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
1811		2311
1812	There are some other functions of possible interest. Described. Here. Now.	2312	There are some other functions of possible interest. Described. Here. Now.
1813		2313
1814	=over 4	2314	=over 4
…		…
2019		2519
2020	=item w->stop ()	2520	=item w->stop ()
2021		2521
2022	Stops the watcher if it is active. Again, no C<loop> argument.	2522	Stops the watcher if it is active. Again, no C<loop> argument.
2023		2523
2024	=item w->again () C<ev::timer>, C<ev::periodic> only	2524	=item w->again () (C<ev::timer>, C<ev::periodic> only)
2025		2525
2026	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2526	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
2027	C<ev_TYPE_again> function.	2527	C<ev_TYPE_again> function.
2028		2528
2029	=item w->sweep () C<ev::embed> only	2529	=item w->sweep () (C<ev::embed> only)
2030		2530
2031	Invokes C<ev_embed_sweep>.	2531	Invokes C<ev_embed_sweep>.
2032		2532
2033	=item w->update () C<ev::stat> only	2533	=item w->update () (C<ev::stat> only)
2034		2534
2035	Invokes C<ev_stat_stat>.	2535	Invokes C<ev_stat_stat>.
2036		2536
2037	=back	2537	=back
2038		2538
…		…
2041	Example: Define a class with an IO and idle watcher, start one of them in	2541	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2542	the constructor.
2043		2543
2044	class myclass	2544	class myclass
2045	{	2545	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
2048		2548
2049	myclass ();	2549	myclass (int fd)
2050	}
2051
2052	myclass::myclass (int fd)
2053	{	2550	{
2054	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
2056		2553
2057	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2058	}	2556	};
		2557
		2558
		2559	=head1 OTHER LANGUAGE BINDINGS
		2560
		2561	Libev does not offer other language bindings itself, but bindings for a
		2562	numbe rof languages exist in the form of third-party packages. If you know
		2563	any interesting language binding in addition to the ones listed here, drop
		2564	me a note.
		2565
		2566	=over 4
		2567
		2568	=item Perl
		2569
		2570	The EV module implements the full libev API and is actually used to test
		2571	libev. EV is developed together with libev. Apart from the EV core module,
		2572	there are additional modules that implement libev-compatible interfaces
		2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2575
		2576	It can be found and installed via CPAN, its homepage is found at
		2577	L<http://software.schmorp.de/pkg/EV>.
		2578
		2579	=item Ruby
		2580
		2581	Tony Arcieri has written a ruby extension that offers access to a subset
		2582	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2583	more on top of it. It can be found via gem servers. Its homepage is at
		2584	L<http://rev.rubyforge.org/>.
		2585
		2586	=item D
		2587
		2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2590
		2591	=back
2059		2592
2060		2593
2061	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2062		2595
2063	Libev can be compiled with a variety of options, the most fundemantal is	2596	Libev can be compiled with a variety of options, the most fundamantal
2064	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	callbacks have an initial C<struct ev_loop *> argument.	2598	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		2599
2067	To make it easier to write programs that cope with either variant, the	2600	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	2601	following macros are defined:
2069		2602
2070	=over 4	2603	=over 4
…		…
2124	Libev can (and often is) directly embedded into host	2657	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	2658	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2659	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	2660	and rxvt-unicode.
2128		2661
2129	The goal is to enable you to just copy the neecssary files into your	2662	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	2663	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	2664	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	2665	libev somewhere in your source tree).
2133		2666
2134	=head2 FILESETS	2667	=head2 FILESETS
…		…
2224		2757
2225	If defined to be C<1>, libev will try to detect the availability of the	2758	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	2759	monotonic clock option at both compiletime and runtime. Otherwise no use
2227	of the monotonic clock option will be attempted. If you enable this, you	2760	of the monotonic clock option will be attempted. If you enable this, you
2228	usually have to link against librt or something similar. Enabling it when	2761	usually have to link against librt or something similar. Enabling it when
2229	the functionality isn't available is safe, though, althoguh you have	2762	the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	2763	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	2764	function is hiding in (often F<-lrt>).
2232		2765
2233	=item EV_USE_REALTIME	2766	=item EV_USE_REALTIME
2234		2767
2235	If defined to be C<1>, libev will try to detect the availability of the	2768	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	2769	realtime clock option at compiletime (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	2770	runtime if successful). Otherwise no use of the realtime clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	2773	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2774
		2775	=item EV_USE_NANOSLEEP
		2776
		2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2778	and will use it for delays. Otherwise it will use C<select ()>.
2241		2779
2242	=item EV_USE_SELECT	2780	=item EV_USE_SELECT
2243		2781
2244	If undefined or defined to be C<1>, libev will compile in support for the	2782	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	2783	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2263	wants osf handles on win32 (this is the case when the select to	2801	wants osf handles on win32 (this is the case when the select to
2264	be used is the winsock select). This means that it will call	2802	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2803	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	2804	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	2805	on win32. Should not be defined on non-win32 platforms.
		2806
		2807	=item EV_FD_TO_WIN32_HANDLE
		2808
		2809	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2810	file descriptors to socket handles. When not defining this symbol (the
		2811	default), then libev will call C<_get_osfhandle>, which is usually
		2812	correct. In some cases, programs use their own file descriptor management,
		2813	in which case they can provide this function to map fds to socket handles.
2268		2814
2269	=item EV_USE_POLL	2815	=item EV_USE_POLL
2270		2816
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2817	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	2818	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2306		2852
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	2853	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	2854	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	2855	be detected at runtime.
2310		2856
		2857	=item EV_ATOMIC_T
		2858
		2859	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2860	access is atomic with respect to other threads or signal contexts. No such
		2861	type is easily found in the C language, so you can provide your own type
		2862	that you know is safe for your purposes. It is used both for signal handler "locking"
		2863	as well as for signal and thread safety in C<ev_async> watchers.
		2864
		2865	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2866	(from F<signal.h>), which is usually good enough on most platforms.
		2867
2311	=item EV_H	2868	=item EV_H
2312		2869
2313	The name of the F<ev.h> header file used to include it. The default if	2870	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2871	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2872	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		2873
2317	=item EV_CONFIG_H	2874	=item EV_CONFIG_H
2318		2875
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2876	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2877	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	2878	C<EV_H>, above.
2322		2879
2323	=item EV_EVENT_H	2880	=item EV_EVENT_H
2324		2881
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2882	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	2883	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		2884
2328	=item EV_PROTOTYPES	2885	=item EV_PROTOTYPES
2329		2886
2330	If defined to be C<0>, then F<ev.h> will not define any function	2887	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	2888	prototypes, but still define all the structs and other symbols. This is
…		…
2382	=item EV_FORK_ENABLE	2939	=item EV_FORK_ENABLE
2383		2940
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	2941	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	2942	defined to be C<0>, then they are not.
2386		2943
		2944	=item EV_ASYNC_ENABLE
		2945
		2946	If undefined or defined to be C<1>, then async watchers are supported. If
		2947	defined to be C<0>, then they are not.
		2948
2387	=item EV_MINIMAL	2949	=item EV_MINIMAL
2388		2950
2389	If you need to shave off some kilobytes of code at the expense of some	2951	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	2952	speed, define this symbol to C<1>. Currently only used for gcc to override
2391	some inlining decisions, saves roughly 30% codesize of amd64.	2953	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2397	than enough. If you need to manage thousands of children you might want to	2959	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	2960	increase this value (I<must> be a power of two).
2399		2961
2400	=item EV_INOTIFY_HASHSIZE	2962	=item EV_INOTIFY_HASHSIZE
2401		2963
2402	C<ev_staz> watchers use a small hash table to distribute workload by	2964	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2965	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	2966	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	2967	watchers you might want to increase this value (I<must> be a power of
2406	two).	2968	two).
2407		2969
…		…
2424		2986
2425	=item ev_set_cb (ev, cb)	2987	=item ev_set_cb (ev, cb)
2426		2988
2427	Can be used to change the callback member declaration in each watcher,	2989	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	2990	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	2991	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	2992	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2993	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	2994	method calls instead of plain function calls in C++.
		2995
		2996	=head2 EXPORTED API SYMBOLS
		2997
		2998	If you need to re-export the API (e.g. via a dll) and you need a list of
		2999	exported symbols, you can use the provided F<Symbol.*> files which list
		3000	all public symbols, one per line:
		3001
		3002	Symbols.ev for libev proper
		3003	Symbols.event for the libevent emulation
		3004
		3005	This can also be used to rename all public symbols to avoid clashes with
		3006	multiple versions of libev linked together (which is obviously bad in
		3007	itself, but sometimes it is inconvinient to avoid this).
		3008
		3009	A sed command like this will create wrapper C<#define>'s that you need to
		3010	include before including F<ev.h>:
		3011
		3012	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3013
		3014	This would create a file F<wrap.h> which essentially looks like this:
		3015
		3016	#define ev_backend myprefix_ev_backend
		3017	#define ev_check_start myprefix_ev_check_start
		3018	#define ev_check_stop myprefix_ev_check_stop
		3019	...
2433		3020
2434	=head2 EXAMPLES	3021	=head2 EXAMPLES
2435		3022
2436	For a real-world example of a program the includes libev	3023	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3024	verbatim, you can have a look at the EV perl module
…		…
2478		3065
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3066	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3067
2481	This means that, when you have a watcher that triggers in one hour and	3068	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3069	there are 100 watchers that would trigger before that then inserting will
2483	have to skip those 100 watchers.	3070	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3071
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3072	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3073
2487	That means that for changing a timer costs less than removing/adding them	3074	That means that changing a timer costs less than removing/adding them
2488	as only the relative motion in the event queue has to be paid for.	3075	as only the relative motion in the event queue has to be paid for.
2489		3076
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3077	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3078
2492	These just add the watcher into an array or at the head of a list.	3079	These just add the watcher into an array or at the head of a list.
		3080
2493	=item Stopping check/prepare/idle watchers: O(1)	3081	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3082
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3083	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3084
2497	These watchers are stored in lists then need to be walked to find the	3085	These watchers are stored in lists then need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3086	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3087	have many watchers waiting for the same fd or signal).
2500		3088
2501	=item Finding the next timer per loop iteration: O(1)	3089	=item Finding the next timer in each loop iteration: O(1)
		3090
		3091	By virtue of using a binary heap, the next timer is always found at the
		3092	beginning of the storage array.
2502		3093
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3094	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3095
2505	A change means an I/O watcher gets started or stopped, which requires	3096	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3097	libev to recalculate its status (and possibly tell the kernel, depending
		3098	on backend and wether C<ev_io_set> was used).
2507		3099
2508	=item Activating one watcher: O(1)	3100	=item Activating one watcher (putting it into the pending state): O(1)
2509		3101
2510	=item Priority handling: O(number_of_priorities)	3102	=item Priority handling: O(number_of_priorities)
2511		3103
2512	Priorities are implemented by allocating some space for each	3104	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3105	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3106	linearly search all the priorities, but starting/stopping and activating
		3107	watchers becomes O(1) w.r.t. priority handling.
		3108
		3109	=item Sending an ev_async: O(1)
		3110
		3111	=item Processing ev_async_send: O(number_of_async_watchers)
		3112
		3113	=item Processing signals: O(max_signal_number)
		3114
		3115	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3116	calls in the current loop iteration. Checking for async and signal events
		3117	involves iterating over all running async watchers or all signal numbers.
2515		3118
2516	=back	3119	=back
2517		3120
2518		3121
		3122	=head1 Win32 platform limitations and workarounds
		3123
		3124	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3125	requires, and its I/O model is fundamentally incompatible with the POSIX
		3126	model. Libev still offers limited functionality on this platform in
		3127	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3128	descriptors. This only applies when using Win32 natively, not when using
		3129	e.g. cygwin.
		3130
		3131	There is no supported compilation method available on windows except
		3132	embedding it into other applications.
		3133
		3134	Due to the many, low, and arbitrary limits on the win32 platform and the
		3135	abysmal performance of winsockets, using a large number of sockets is not
		3136	recommended (and not reasonable). If your program needs to use more than
		3137	a hundred or so sockets, then likely it needs to use a totally different
		3138	implementation for windows, as libev offers the POSIX model, which cannot
		3139	be implemented efficiently on windows (microsoft monopoly games).
		3140
		3141	=over 4
		3142
		3143	=item The winsocket select function
		3144
		3145	The winsocket C<select> function doesn't follow POSIX in that it requires
		3146	socket I<handles> and not socket I<file descriptors>. This makes select
		3147	very inefficient, and also requires a mapping from file descriptors
		3148	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3149	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3150	symbols for more info.
		3151
		3152	The configuration for a "naked" win32 using the microsoft runtime
		3153	libraries and raw winsocket select is:
		3154
		3155	#define EV_USE_SELECT 1
		3156	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3157
		3158	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3159	complexity in the O(n²) range when using win32.
		3160
		3161	=item Limited number of file descriptors
		3162
		3163	Windows has numerous arbitrary (and low) limits on things. Early versions
		3164	of winsocket's select only supported waiting for a max. of C<64> handles
		3165	(probably owning to the fact that all windows kernels can only wait for
		3166	C<64> things at the same time internally; microsoft recommends spawning a
		3167	chain of threads and wait for 63 handles and the previous thread in each).
		3168
		3169	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3170	to some high number (e.g. C<2048>) before compiling the winsocket select
		3171	call (which might be in libev or elsewhere, for example, perl does its own
		3172	select emulation on windows).
		3173
		3174	Another limit is the number of file descriptors in the microsoft runtime
		3175	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3176	or something like this inside microsoft). You can increase this by calling
		3177	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3178	arbitrary limit), but is broken in many versions of the microsoft runtime
		3179	libraries.
		3180
		3181	This might get you to about C<512> or C<2048> sockets (depending on
		3182	windows version and/or the phase of the moon). To get more, you need to
		3183	wrap all I/O functions and provide your own fd management, but the cost of
		3184	calling select (O(n²)) will likely make this unworkable.
		3185
		3186	=back
		3187
		3188
2519	=head1 AUTHOR	3189	=head1 AUTHOR
2520		3190
2521	Marc Lehmann <libev@schmorp.de>.	3191	Marc Lehmann <libev@schmorp.de>.
2522		3192

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