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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.
…		…
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.
117		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
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
122	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	149	version of the library your program was compiled against.
127		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
128	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	157	not a problem.
132		158
133	Example: Make sure we haven't accidentally been linked against the wrong	159	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	160	version.
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		276
251	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
252	function.	278	function.
253		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
254	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
255	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>).
256		293
257	The following flags are supported:	294	The following flags are supported:
258		295
…		…
279	enabling this flag.	316	enabling this flag.
280		317
281	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,
282	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
283	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
284	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
285	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
286	C<pthread_atfork> which is even faster).	323	C<pthread_atfork> which is even faster).
287		324
288	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
289	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
290	flag.	327	flag.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		333
297	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
298	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,
299	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
300	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
301	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.
302		346
303	=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)
304		348
305	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
306	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
307	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
308	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.
309		355
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		357
312	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,
313	but it scales phenomenally better. While poll and select usually scale like	359	but it scales phenomenally better. While poll and select usually scale
314	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),
315	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.
316		365
317	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
318	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
319	(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
320	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
321	well if you register events for both fds.	370	very well if you register events for both fds.
322		371
323	Please note that epoll sometimes generates spurious notifications, so you	372	Please note that epoll sometimes generates spurious notifications, so you
324	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
325	(or space) is available.	374	(or space) is available.
326		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
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		384
329	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
330	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
331	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
332	completely useless). For this reason its not being "autodetected"	388	it's completely useless). For this reason it's not being "autodetected"
333	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
334	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.
335		396
336	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
337	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
338	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
339	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
340	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.
341		412
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		414
344	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.
345		419
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		421
348	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,
349	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)).
350		424
351	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
352	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
353	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.
354		437
355	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
356		439
357	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
358	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
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		443
		444	It is definitely not recommended to use this flag.
		445
361	=back	446	=back
362		447
363	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
364	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
365	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		451
368	The most typical usage is like this:	452	The most typical usage is like this:
369		453
370	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
385		469
386	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
387	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
388	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
389	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.
390		478
391	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.
392		480
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	482	if (!epoller)
…		…
399	Destroys the default loop again (frees all memory and kernel state	487	Destroys the default loop again (frees all memory and kernel state
400	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
401	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
402	responsibility to either stop all watchers cleanly yoursef I<before>	490	responsibility to either stop all watchers cleanly yoursef I<before>
403	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
404	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
405	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>).
406		503
407	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
408		505
409	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
410	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
411		508
412	=item ev_default_fork ()	509	=item ev_default_fork ()
413		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	512	to reinitialise the kernel state for backends that have one. Despite the
415	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
416	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
417	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.
418		517
419	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
420	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
421	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
422		521
423	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
424	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
425	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
426		525
427	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
428		527
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	528	=item ev_loop_fork (loop)
434		529
435	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
436	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
437	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.
438		537
439	=item unsigned int ev_loop_count (loop)	538	=item unsigned int ev_loop_count (loop)
440		539
441	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
442	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
…		…
455		554
456	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
457	received events and started processing them. This timestamp does not	556	received events and started processing them. This timestamp does not
458	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
459	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
460	event occuring (or more correctly, libev finding out about it).	559	event occurring (or more correctly, libev finding out about it).
461		560
462	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
463		562
464	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
465	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
…		…
487	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
488		587
489	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
490		589
491	- Before the first iteration, call any pending watchers.	590	- Before the first iteration, call any pending watchers.
492	* If there are no active watchers (reference count is zero), return.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
493	- 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.
494	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
495	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
496	- Update the "event loop time".	596	- Update the "event loop time".
497	- 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.
498	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
499	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
500	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
501	- Queue all outstanding timers.	604	- Queue all outstanding timers.
502	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
503	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
504	- Queue all check watchers.	607	- Queue all check watchers.
505	- 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).
506	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
507	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
508	- 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
509	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
510		614
511	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
512	anymore.	616	anymore.
513		617
514	... queue jobs here, make sure they register event watchers as long	618	... queue jobs here, make sure they register event watchers as long
515	... 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..)
516	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
520		624
521	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
522	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
523	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
524	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.
525		631
526	=item ev_ref (loop)	632	=item ev_ref (loop)
527		633
528	=item ev_unref (loop)	634	=item ev_unref (loop)
529		635
…		…
534	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
535	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
536	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
537	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
538	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
539	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).
540		648
541	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>
542	running when nothing else is active.	650	running when nothing else is active.
543		651
544	struct ev_signal exitsig;	652	struct ev_signal exitsig;
…		…
548		656
549	Example: For some weird reason, unregister the above signal handler again.	657	Example: For some weird reason, unregister the above signal handler again.
550		658
551	ev_ref (loop);	659	ev_ref (loop);
552	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.
553		697
554	=back	698	=back
555		699
556		700
557	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
…		…
656		800
657	=item C<EV_FORK>	801	=item C<EV_FORK>
658		802
659	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
660	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>).
661		809
662	=item C<EV_ERROR>	810	=item C<EV_ERROR>
663		811
664	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
665	happen because the watcher could not be properly started because libev	813	happen because the watcher could not be properly started because libev
…		…
883	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
884	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
885	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
886	required if you know what you are doing).	1034	required if you know what you are doing).
887		1035
888	You have to be careful with dup'ed file descriptors, though. Some backends
889	(the linux epoll backend is a notable example) cannot handle dup'ed file
890	descriptors correctly if you register interest in two or more fds pointing
891	to the same underlying file/socket/etc. description (that is, they share
892	the same underlying "file open").
893
894	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
895	(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
896	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
897		1039
898	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
…		…
908	play around with an Xlib connection), then you have to seperately re-test	1050	play around with an Xlib connection), then you have to seperately re-test
909	whether a file descriptor is really ready with a known-to-be good interface	1051	whether a file descriptor is really ready with a known-to-be good interface
910	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
911	its own, so its quite safe to use).	1053	its own, so its quite safe to use).
912		1054
		1055	=head3 The special problem of disappearing file descriptors
		1056
		1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1058	descriptor (either by calling C<close> explicitly or by any other means,
		1059	such as C<dup>). The reason is that you register interest in some file
		1060	descriptor, but when it goes away, the operating system will silently drop
		1061	this interest. If another file descriptor with the same number then is
		1062	registered with libev, there is no efficient way to see that this is, in
		1063	fact, a different file descriptor.
		1064
		1065	To avoid having to explicitly tell libev about such cases, libev follows
		1066	the following policy: Each time C<ev_io_set> is being called, libev
		1067	will assume that this is potentially a new file descriptor, otherwise
		1068	it is assumed that the file descriptor stays the same. That means that
		1069	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1070	descriptor even if the file descriptor number itself did not change.
		1071
		1072	This is how one would do it normally anyway, the important point is that
		1073	the libev application should not optimise around libev but should leave
		1074	optimisations to libev.
		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
		1110
		1111	=head3 Watcher-Specific Functions
		1112
913	=over 4	1113	=over 4
914		1114
915	=item ev_io_init (ev_io *, callback, int fd, int events)	1115	=item ev_io_init (ev_io *, callback, int fd, int events)
916		1116
917	=item ev_io_set (ev_io *, int fd, int events)	1117	=item ev_io_set (ev_io *, int fd, int events)
…		…
927	=item int events [read-only]	1127	=item int events [read-only]
928		1128
929	The events being watched.	1129	The events being watched.
930		1130
931	=back	1131	=back
		1132
		1133	=head3 Examples
932		1134
933	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
934	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
935	attempt to read a whole line in the callback.	1137	attempt to read a whole line in the callback.
936		1138
…		…
970		1172
971	The callback is guarenteed to be invoked only when its timeout has passed,	1173	The callback is guarenteed to be invoked only when its timeout has passed,
972	but if multiple timers become ready during the same loop iteration then	1174	but if multiple timers become ready during the same loop iteration then
973	order of execution is undefined.	1175	order of execution is undefined.
974		1176
		1177	=head3 Watcher-Specific Functions and Data Members
		1178
975	=over 4	1179	=over 4
976		1180
977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978		1182
979	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
987	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
988	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
989	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
990	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
991		1195
992	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
993		1197
994	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
995	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
996		1200
997	If the timer is pending, its pending status is cleared.	1201	If the timer is pending, its pending status is cleared.
…		…
1032	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),
1033	which is also when any modifications are taken into account.	1237	which is also when any modifications are taken into account.
1034		1238
1035	=back	1239	=back
1036		1240
		1241	=head3 Examples
		1242
1037	Example: Create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
1038		1244
1039	static void	1245	static void
1040	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)
1041	{	1247	{
…		…
1074	but on wallclock time (absolute time). You can tell a periodic watcher	1280	but on wallclock time (absolute time). You can tell a periodic watcher
1075	to trigger "at" some specific point in time. For example, if you tell a	1281	to trigger "at" some specific point in time. For example, if you tell a
1076	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1077	+ 10.>) and then reset your system clock to the last year, then it will	1283	+ 10.>) and then reset your system clock to the last year, then it will
1078	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1079	roughly 10 seconds later and of course not if you reset your system time	1285	roughly 10 seconds later).
1080	again).
1081		1286
1082	They can also be used to implement vastly more complex timers, such as	1287	They can also be used to implement vastly more complex timers, such as
1083	triggering an event on eahc midnight, local time.	1288	triggering an event on each midnight, local time or other, complicated,
		1289	rules.
1084		1290
1085	As with timers, the callback is guarenteed to be invoked only when the	1291	As with timers, the callback is guarenteed to be invoked only when the
1086	time (C<at>) has been passed, but if multiple periodic timers become ready	1292	time (C<at>) has been passed, but if multiple periodic timers become ready
1087	during the same loop iteration then order of execution is undefined.	1293	during the same loop iteration then order of execution is undefined.
1088		1294
		1295	=head3 Watcher-Specific Functions and Data Members
		1296
1089	=over 4	1297	=over 4
1090		1298
1091	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092		1300
1093	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1095	Lots of arguments, lets sort it out... There are basically three modes of	1303	Lots of arguments, lets sort it out... There are basically three modes of
1096	operation, and we will explain them from simplest to complex:	1304	operation, and we will explain them from simplest to complex:
1097		1305
1098	=over 4	1306	=over 4
1099		1307
1100	=item * absolute timer (interval = reschedule_cb = 0)	1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1101		1309
1102	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
1103	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,
1104	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
1105	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
1106		1314
1107	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1108		1316
1109	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
1110	C<at + N * interval> time (for some integer N) and then repeat, regardless	1318	C<at + N * interval> time (for some integer N, which can also be negative)
1111	of any time jumps.	1319	and then repeat, regardless of any time jumps.
1112		1320
1113	This can be used to create timers that do not drift with respect to system	1321	This can be used to create timers that do not drift with respect to system
1114	time:	1322	time:
1115		1323
1116	ev_periodic_set (&periodic, 0., 3600., 0);	1324	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1122		1330
1123	Another way to think about it (for the mathematically inclined) is that	1331	Another way to think about it (for the mathematically inclined) is that
1124	C<ev_periodic> will try to run the callback in this mode at the next possible	1332	C<ev_periodic> will try to run the callback in this mode at the next possible
1125	time where C<time = at (mod interval)>, regardless of any time jumps.	1333	time where C<time = at (mod interval)>, regardless of any time jumps.
1126		1334
		1335	For numerical stability it is preferable that the C<at> value is near
		1336	C<ev_now ()> (the current time), but there is no range requirement for
		1337	this value.
		1338
1127	=item * manual reschedule mode (reschedule_cb = callback)	1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1128		1340
1129	In this mode the values for C<interval> and C<at> are both being	1341	In this mode the values for C<interval> and C<at> are both being
1130	ignored. Instead, each time the periodic watcher gets scheduled, the	1342	ignored. Instead, each time the periodic watcher gets scheduled, the
1131	reschedule callback will be called with the watcher as first, and the	1343	reschedule callback will be called with the watcher as first, and the
1132	current time as second argument.	1344	current time as second argument.
1133		1345
1134	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1135	ever, or make any event loop modifications>. If you need to stop it,	1347	ever, or make any event loop modifications>. If you need to stop it,
1136	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1137	starting a prepare watcher).	1349	starting an C<ev_prepare> watcher, which is legal).
1138		1350
1139	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1140	ev_tstamp now)>, e.g.:	1352	ev_tstamp now)>, e.g.:
1141		1353
1142	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1165	Simply stops and restarts the periodic watcher again. This is only useful	1377	Simply stops and restarts the periodic watcher again. This is only useful
1166	when you changed some parameters or the reschedule callback would return	1378	when you changed some parameters or the reschedule callback would return
1167	a different time than the last time it was called (e.g. in a crond like	1379	a different time than the last time it was called (e.g. in a crond like
1168	program when the crontabs have changed).	1380	program when the crontabs have changed).
1169		1381
		1382	=item ev_tstamp offset [read-write]
		1383
		1384	When repeating, this contains the offset value, otherwise this is the
		1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1386
		1387	Can be modified any time, but changes only take effect when the periodic
		1388	timer fires or C<ev_periodic_again> is being called.
		1389
1170	=item ev_tstamp interval [read-write]	1390	=item ev_tstamp interval [read-write]
1171		1391
1172	The current interval value. Can be modified any time, but changes only	1392	The current interval value. Can be modified any time, but changes only
1173	take effect when the periodic timer fires or C<ev_periodic_again> is being	1393	take effect when the periodic timer fires or C<ev_periodic_again> is being
1174	called.	1394	called.
…		…
1177		1397
1178	The current reschedule callback, or C<0>, if this functionality is	1398	The current reschedule callback, or C<0>, if this functionality is
1179	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
1180	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.
1181		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
1182	=back	1407	=back
		1408
		1409	=head3 Examples
1183		1410
1184	Example: Call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
1185	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
1186	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
1187		1414
…		…
1227	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
1228	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
1229	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
1230	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1231		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
		1465	=head3 Watcher-Specific Functions and Data Members
		1466
1232	=over 4	1467	=over 4
1233		1468
1234	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
1235		1470
1236	=item ev_signal_set (ev_signal *, int signum)	1471	=item ev_signal_set (ev_signal *, int signum)
…		…
1242		1477
1243	The signal the watcher watches out for.	1478	The signal the watcher watches out for.
1244		1479
1245	=back	1480	=back
1246		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
1247		1496
1248	=head2 C<ev_child> - watch out for process status changes	1497	=head2 C<ev_child> - watch out for process status changes
1249		1498
1250	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
1251	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.
		1526
		1527	=head3 Watcher-Specific Functions and Data Members
1252		1528
1253	=over 4	1529	=over 4
1254		1530
1255	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1256		1532
1257	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1258		1534
1259	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
1260	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
1261	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
1262	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
1263	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
1264	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).
1265		1543
1266	=item int pid [read-only]	1544	=item int pid [read-only]
1267		1545
1268	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.
1269		1547
…		…
1276	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
1277	C<waitpid> and C<sys/wait.h> documentation for details).	1555	C<waitpid> and C<sys/wait.h> documentation for details).
1278		1556
1279	=back	1557	=back
1280		1558
1281	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;
1282		1565
1283	static void	1566	static void
1284	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1285	{	1568	{
1286	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);
1287	}	1571	}
1288		1572
1289	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1290	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1574
1291	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	}
1292		1587
1293		1588
1294	=head2 C<ev_stat> - did the file attributes just change?	1589	=head2 C<ev_stat> - did the file attributes just change?
1295		1590
1296	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
…		…
1325	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
1326	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
1327	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
1328	polling.	1623	polling.
1329		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
		1669	=head3 Watcher-Specific Functions and Data Members
		1670
1330	=over 4	1671	=over 4
1331		1672
1332	=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)
1333		1674
1334	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1675	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1341		1682
1342	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,
1343	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
1344	last change was detected).	1685	last change was detected).
1345		1686
1346	=item ev_stat_stat (ev_stat *)	1687	=item ev_stat_stat (loop, ev_stat *)
1347		1688
1348	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
1349	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
1350	detecting this change (while introducing a race condition). Can also be	1691	detecting this change (while introducing a race condition). Can also be
1351	useful simply to find out the new values.	1692	useful simply to find out the new values.
…		…
1369	=item const char *path [read-only]	1710	=item const char *path [read-only]
1370		1711
1371	The filesystem path that is being watched.	1712	The filesystem path that is being watched.
1372		1713
1373	=back	1714	=back
		1715
		1716	=head3 Examples
1374		1717
1375	Example: Watch C</etc/passwd> for attribute changes.	1718	Example: Watch C</etc/passwd> for attribute changes.
1376		1719
1377	static void	1720	static void
1378	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1391	}	1734	}
1392		1735
1393	...	1736	...
1394	ev_stat passwd;	1737	ev_stat passwd;
1395		1738
1396	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1397	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);
1398		1769
1399		1770
1400	=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...
1401		1772
1402	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
…		…
1416	Apart from keeping your process non-blocking (which is a useful	1787	Apart from keeping your process non-blocking (which is a useful
1417	effect on its own sometimes), idle watchers are a good place to do	1788	effect on its own sometimes), idle watchers are a good place to do
1418	"pseudo-background processing", or delay processing stuff to after the	1789	"pseudo-background processing", or delay processing stuff to after the
1419	event loop has handled all outstanding events.	1790	event loop has handled all outstanding events.
1420		1791
		1792	=head3 Watcher-Specific Functions and Data Members
		1793
1421	=over 4	1794	=over 4
1422		1795
1423	=item ev_idle_init (ev_signal *, callback)	1796	=item ev_idle_init (ev_signal *, callback)
1424		1797
1425	Initialises and configures the idle watcher - it has no parameters of any	1798	Initialises and configures the idle watcher - it has no parameters of any
1426	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,
1427	believe me.	1800	believe me.
1428		1801
1429	=back	1802	=back
		1803
		1804	=head3 Examples
1430		1805
1431	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
1432	callback, free it. Also, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1433		1808
1434	static void	1809	static void
1435	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)
1436	{	1811	{
1437	free (w);	1812	free (w);
1438	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1439	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1440	}	1815	}
1441		1816
1442	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1443	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1444	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
…		…
1486		1861
1487	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>)
1488	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
1489	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,
1490	too) should not activate ("feed") events into libev. While libev fully	1865	too) should not activate ("feed") events into libev. While libev fully
1491	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
1492	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
1493	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
1494	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
1495	others).	1870	coexist peacefully with others).
		1871
		1872	=head3 Watcher-Specific Functions and Data Members
1496		1873
1497	=over 4	1874	=over 4
1498		1875
1499	=item ev_prepare_init (ev_prepare *, callback)	1876	=item ev_prepare_init (ev_prepare *, callback)
1500		1877
…		…
1503	Initialises and configures the prepare or check watcher - they have no	1880	Initialises and configures the prepare or check watcher - they have no
1504	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>
1505	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1506		1883
1507	=back	1884	=back
		1885
		1886	=head3 Examples
1508		1887
1509	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
1510	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
1511	(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
1512	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>
…		…
1681	portable one.	2060	portable one.
1682		2061
1683	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
1684	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
1685	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
1686	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).
1687		2100
1688	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1689	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1690	struct ev_embed embed;	2103	struct ev_embed embed;
1691		2104
…		…
1702	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1703	}	2116	}
1704	else	2117	else
1705	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1706		2119
1707	=over 4	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).
1708		2124
1709	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	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	}
1710		2135
1711	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2136	if (!loop_socket)
		2137	loop_socket = loop;
1712		2138
1713	Configures the watcher to embed the given loop, which must be	2139	// now use loop_socket for all sockets, and loop for everything else
1714	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1715	invoked automatically, otherwise it is the responsibility of the callback
1716	to invoke it (it will continue to be called until the sweep has been done,
1717	if you do not want thta, you need to temporarily stop the embed watcher).
1718
1719	=item ev_embed_sweep (loop, ev_embed *)
1720
1721	Make a single, non-blocking sweep over the embedded loop. This works
1722	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1723	apropriate way for embedded loops.
1724
1725	=item struct ev_loop *loop [read-only]
1726
1727	The embedded event loop.
1728
1729	=back
1730		2140
1731		2141
1732	=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
1733		2143
1734	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
…		…
1737	event loop blocks next and before C<ev_check> watchers are being called,	2147	event loop blocks next and before C<ev_check> watchers are being called,
1738	and only in the child after the fork. If whoever good citizen calling	2148	and only in the child after the fork. If whoever good citizen calling
1739	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1740	handlers will be invoked, too, of course.	2150	handlers will be invoked, too, of course.
1741		2151
		2152	=head3 Watcher-Specific Functions and Data Members
		2153
1742	=over 4	2154	=over 4
1743		2155
1744	=item ev_fork_init (ev_signal *, callback)	2156	=item ev_fork_init (ev_signal *, callback)
1745		2157
1746	Initialises and configures the fork watcher - it has no parameters of any	2158	Initialises and configures the fork watcher - it has no parameters of any
1747	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1748	believe me.	2160	believe me.
		2161
		2162	=back
		2163
		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.
1749		2306
1750	=back	2307	=back
1751		2308
1752		2309
1753	=head1 OTHER FUNCTIONS	2310	=head1 OTHER FUNCTIONS
…		…
1962		2519
1963	=item w->stop ()	2520	=item w->stop ()
1964		2521
1965	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.
1966		2523
1967	=item w->again () C<ev::timer>, C<ev::periodic> only	2524	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1968		2525
1969	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
1970	C<ev_TYPE_again> function.	2527	C<ev_TYPE_again> function.
1971		2528
1972	=item w->sweep () C<ev::embed> only	2529	=item w->sweep () (C<ev::embed> only)
1973		2530
1974	Invokes C<ev_embed_sweep>.	2531	Invokes C<ev_embed_sweep>.
1975		2532
1976	=item w->update () C<ev::stat> only	2533	=item w->update () (C<ev::stat> only)
1977		2534
1978	Invokes C<ev_stat_stat>.	2535	Invokes C<ev_stat_stat>.
1979		2536
1980	=back	2537	=back
1981		2538
…		…
1984	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
1985	the constructor.	2542	the constructor.
1986		2543
1987	class myclass	2544	class myclass
1988	{	2545	{
1989	ev_io io; void io_cb (ev::io &w, int revents);	2546	ev::io io; void io_cb (ev::io &w, int revents);
1990	ev_idle idle void idle_cb (ev::idle &w, int revents);	2547	ev:idle idle void idle_cb (ev::idle &w, int revents);
1991		2548
1992	myclass ();	2549	myclass (int fd)
1993	}
1994
1995	myclass::myclass (int fd)
1996	{	2550	{
1997	io .set <myclass, &myclass::io_cb > (this);	2551	io .set <myclass, &myclass::io_cb > (this);
1998	idle.set <myclass, &myclass::idle_cb> (this);	2552	idle.set <myclass, &myclass::idle_cb> (this);
1999		2553
2000	io.start (fd, ev::READ);	2554	io.start (fd, ev::READ);
		2555	}
2001	}	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
2002		2592
2003		2593
2004	=head1 MACRO MAGIC	2594	=head1 MACRO MAGIC
2005		2595
2006	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
2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2008	callbacks have an initial C<struct ev_loop *> argument.	2598	functions and callbacks have an initial C<struct ev_loop *> argument.
2009		2599
2010	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
2011	following macros are defined:	2601	following macros are defined:
2012		2602
2013	=over 4	2603	=over 4
…		…
2067	Libev can (and often is) directly embedded into host	2657	Libev can (and often is) directly embedded into host
2068	applications. Examples of applications that embed it include the Deliantra	2658	applications. Examples of applications that embed it include the Deliantra
2069	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)
2070	and rxvt-unicode.	2660	and rxvt-unicode.
2071		2661
2072	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
2073	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
2074	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
2075	libev somewhere in your source tree).	2665	libev somewhere in your source tree).
2076		2666
2077	=head2 FILESETS	2667	=head2 FILESETS
…		…
2147		2737
2148	libev.m4	2738	libev.m4
2149		2739
2150	=head2 PREPROCESSOR SYMBOLS/MACROS	2740	=head2 PREPROCESSOR SYMBOLS/MACROS
2151		2741
2152	Libev can be configured via a variety of preprocessor symbols you have to define	2742	Libev can be configured via a variety of preprocessor symbols you have to
2153	before including any of its files. The default is not to build for multiplicity	2743	define before including any of its files. The default in the absense of
2154	and only include the select backend.	2744	autoconf is noted for every option.
2155		2745
2156	=over 4	2746	=over 4
2157		2747
2158	=item EV_STANDALONE	2748	=item EV_STANDALONE
2159		2749
…		…
2167		2757
2168	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
2169	monotonic clock option at both compiletime and runtime. Otherwise no use	2759	monotonic clock option at both compiletime and runtime. Otherwise no use
2170	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
2171	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
2172	the functionality isn't available is safe, though, althoguh you have	2762	the functionality isn't available is safe, though, although you have
2173	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>
2174	function is hiding in (often F<-lrt>).	2764	function is hiding in (often F<-lrt>).
2175		2765
2176	=item EV_USE_REALTIME	2766	=item EV_USE_REALTIME
2177		2767
2178	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
2179	realtime clock option at compiletime (and assume its availability at	2769	realtime clock option at compiletime (and assume its availability at
2180	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
2181	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2182	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2183	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 ()>.
		2779
		2780	=item EV_USE_EVENTFD
		2781
		2782	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2783	available and will probe for kernel support at runtime. This will improve
		2784	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2785	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2786	2.7 or newer, otherwise disabled.
2184		2787
2185	=item EV_USE_SELECT	2788	=item EV_USE_SELECT
2186		2789
2187	If undefined or defined to be C<1>, libev will compile in support for the	2790	If undefined or defined to be C<1>, libev will compile in support for the
2188	C<select>(2) backend. No attempt at autodetection will be done: if no	2791	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2207	be used is the winsock select). This means that it will call	2810	be used is the winsock select). This means that it will call
2208	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2811	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2209	it is assumed that all these functions actually work on fds, even	2812	it is assumed that all these functions actually work on fds, even
2210	on win32. Should not be defined on non-win32 platforms.	2813	on win32. Should not be defined on non-win32 platforms.
2211		2814
		2815	=item EV_FD_TO_WIN32_HANDLE
		2816
		2817	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2818	file descriptors to socket handles. When not defining this symbol (the
		2819	default), then libev will call C<_get_osfhandle>, which is usually
		2820	correct. In some cases, programs use their own file descriptor management,
		2821	in which case they can provide this function to map fds to socket handles.
		2822
2212	=item EV_USE_POLL	2823	=item EV_USE_POLL
2213		2824
2214	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2825	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2215	backend. Otherwise it will be enabled on non-win32 platforms. It	2826	backend. Otherwise it will be enabled on non-win32 platforms. It
2216	takes precedence over select.	2827	takes precedence over select.
2217		2828
2218	=item EV_USE_EPOLL	2829	=item EV_USE_EPOLL
2219		2830
2220	If defined to be C<1>, libev will compile in support for the Linux	2831	If defined to be C<1>, libev will compile in support for the Linux
2221	C<epoll>(7) backend. Its availability will be detected at runtime,	2832	C<epoll>(7) backend. Its availability will be detected at runtime,
2222	otherwise another method will be used as fallback. This is the	2833	otherwise another method will be used as fallback. This is the preferred
2223	preferred backend for GNU/Linux systems.	2834	backend for GNU/Linux systems. If undefined, it will be enabled if the
		2835	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2224		2836
2225	=item EV_USE_KQUEUE	2837	=item EV_USE_KQUEUE
2226		2838
2227	If defined to be C<1>, libev will compile in support for the BSD style	2839	If defined to be C<1>, libev will compile in support for the BSD style
2228	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	2840	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2247		2859
2248	=item EV_USE_INOTIFY	2860	=item EV_USE_INOTIFY
2249		2861
2250	If defined to be C<1>, libev will compile in support for the Linux inotify	2862	If defined to be C<1>, libev will compile in support for the Linux inotify
2251	interface to speed up C<ev_stat> watchers. Its actual availability will	2863	interface to speed up C<ev_stat> watchers. Its actual availability will
2252	be detected at runtime.	2864	be detected at runtime. If undefined, it will be enabled if the headers
		2865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		2866
		2867	=item EV_ATOMIC_T
		2868
		2869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2870	access is atomic with respect to other threads or signal contexts. No such
		2871	type is easily found in the C language, so you can provide your own type
		2872	that you know is safe for your purposes. It is used both for signal handler "locking"
		2873	as well as for signal and thread safety in C<ev_async> watchers.
		2874
		2875	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2876	(from F<signal.h>), which is usually good enough on most platforms.
2253		2877
2254	=item EV_H	2878	=item EV_H
2255		2879
2256	The name of the F<ev.h> header file used to include it. The default if	2880	The name of the F<ev.h> header file used to include it. The default if
2257	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2258	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2882	used to virtually rename the F<ev.h> header file in case of conflicts.
2259		2883
2260	=item EV_CONFIG_H	2884	=item EV_CONFIG_H
2261		2885
2262	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2886	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2263	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2887	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2264	C<EV_H>, above.	2888	C<EV_H>, above.
2265		2889
2266	=item EV_EVENT_H	2890	=item EV_EVENT_H
2267		2891
2268	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2892	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2269	of how the F<event.h> header can be found.	2893	of how the F<event.h> header can be found, the default is C<"event.h">.
2270		2894
2271	=item EV_PROTOTYPES	2895	=item EV_PROTOTYPES
2272		2896
2273	If defined to be C<0>, then F<ev.h> will not define any function	2897	If defined to be C<0>, then F<ev.h> will not define any function
2274	prototypes, but still define all the structs and other symbols. This is	2898	prototypes, but still define all the structs and other symbols. This is
…		…
2325	=item EV_FORK_ENABLE	2949	=item EV_FORK_ENABLE
2326		2950
2327	If undefined or defined to be C<1>, then fork watchers are supported. If	2951	If undefined or defined to be C<1>, then fork watchers are supported. If
2328	defined to be C<0>, then they are not.	2952	defined to be C<0>, then they are not.
2329		2953
		2954	=item EV_ASYNC_ENABLE
		2955
		2956	If undefined or defined to be C<1>, then async watchers are supported. If
		2957	defined to be C<0>, then they are not.
		2958
2330	=item EV_MINIMAL	2959	=item EV_MINIMAL
2331		2960
2332	If you need to shave off some kilobytes of code at the expense of some	2961	If you need to shave off some kilobytes of code at the expense of some
2333	speed, define this symbol to C<1>. Currently only used for gcc to override	2962	speed, define this symbol to C<1>. Currently only used for gcc to override
2334	some inlining decisions, saves roughly 30% codesize of amd64.	2963	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2340	than enough. If you need to manage thousands of children you might want to	2969	than enough. If you need to manage thousands of children you might want to
2341	increase this value (I<must> be a power of two).	2970	increase this value (I<must> be a power of two).
2342		2971
2343	=item EV_INOTIFY_HASHSIZE	2972	=item EV_INOTIFY_HASHSIZE
2344		2973
2345	C<ev_staz> watchers use a small hash table to distribute workload by	2974	C<ev_stat> watchers use a small hash table to distribute workload by
2346	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2975	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2347	usually more than enough. If you need to manage thousands of C<ev_stat>	2976	usually more than enough. If you need to manage thousands of C<ev_stat>
2348	watchers you might want to increase this value (I<must> be a power of	2977	watchers you might want to increase this value (I<must> be a power of
2349	two).	2978	two).
2350		2979
…		…
2367		2996
2368	=item ev_set_cb (ev, cb)	2997	=item ev_set_cb (ev, cb)
2369		2998
2370	Can be used to change the callback member declaration in each watcher,	2999	Can be used to change the callback member declaration in each watcher,
2371	and the way callbacks are invoked and set. Must expand to a struct member	3000	and the way callbacks are invoked and set. Must expand to a struct member
2372	definition and a statement, respectively. See the F<ev.v> header file for	3001	definition and a statement, respectively. See the F<ev.h> header file for
2373	their default definitions. One possible use for overriding these is to	3002	their default definitions. One possible use for overriding these is to
2374	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3003	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2375	method calls instead of plain function calls in C++.	3004	method calls instead of plain function calls in C++.
		3005
		3006	=head2 EXPORTED API SYMBOLS
		3007
		3008	If you need to re-export the API (e.g. via a dll) and you need a list of
		3009	exported symbols, you can use the provided F<Symbol.*> files which list
		3010	all public symbols, one per line:
		3011
		3012	Symbols.ev for libev proper
		3013	Symbols.event for the libevent emulation
		3014
		3015	This can also be used to rename all public symbols to avoid clashes with
		3016	multiple versions of libev linked together (which is obviously bad in
		3017	itself, but sometimes it is inconvinient to avoid this).
		3018
		3019	A sed command like this will create wrapper C<#define>'s that you need to
		3020	include before including F<ev.h>:
		3021
		3022	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3023
		3024	This would create a file F<wrap.h> which essentially looks like this:
		3025
		3026	#define ev_backend myprefix_ev_backend
		3027	#define ev_check_start myprefix_ev_check_start
		3028	#define ev_check_stop myprefix_ev_check_stop
		3029	...
2376		3030
2377	=head2 EXAMPLES	3031	=head2 EXAMPLES
2378		3032
2379	For a real-world example of a program the includes libev	3033	For a real-world example of a program the includes libev
2380	verbatim, you can have a look at the EV perl module	3034	verbatim, you can have a look at the EV perl module
…		…
2421		3075
2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3076	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2423		3077
2424	This means that, when you have a watcher that triggers in one hour and	3078	This means that, when you have a watcher that triggers in one hour and
2425	there are 100 watchers that would trigger before that then inserting will	3079	there are 100 watchers that would trigger before that then inserting will
2426	have to skip those 100 watchers.	3080	have to skip roughly seven (C<ld 100>) of these watchers.
2427		3081
2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3082	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2429		3083
2430	That means that for changing a timer costs less than removing/adding them	3084	That means that changing a timer costs less than removing/adding them
2431	as only the relative motion in the event queue has to be paid for.	3085	as only the relative motion in the event queue has to be paid for.
2432		3086
2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3087	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2434		3088
2435	These just add the watcher into an array or at the head of a list.	3089	These just add the watcher into an array or at the head of a list.
		3090
2436	=item Stopping check/prepare/idle watchers: O(1)	3091	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2437		3092
2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3093	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2439		3094
2440	These watchers are stored in lists then need to be walked to find the	3095	These watchers are stored in lists then need to be walked to find the
2441	correct watcher to remove. The lists are usually short (you don't usually	3096	correct watcher to remove. The lists are usually short (you don't usually
2442	have many watchers waiting for the same fd or signal).	3097	have many watchers waiting for the same fd or signal).
2443		3098
2444	=item Finding the next timer per loop iteration: O(1)	3099	=item Finding the next timer in each loop iteration: O(1)
		3100
		3101	By virtue of using a binary heap, the next timer is always found at the
		3102	beginning of the storage array.
2445		3103
2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3104	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2447		3105
2448	A change means an I/O watcher gets started or stopped, which requires	3106	A change means an I/O watcher gets started or stopped, which requires
2449	libev to recalculate its status (and possibly tell the kernel).	3107	libev to recalculate its status (and possibly tell the kernel, depending
		3108	on backend and wether C<ev_io_set> was used).
2450		3109
2451	=item Activating one watcher: O(1)	3110	=item Activating one watcher (putting it into the pending state): O(1)
2452		3111
2453	=item Priority handling: O(number_of_priorities)	3112	=item Priority handling: O(number_of_priorities)
2454		3113
2455	Priorities are implemented by allocating some space for each	3114	Priorities are implemented by allocating some space for each
2456	priority. When doing priority-based operations, libev usually has to	3115	priority. When doing priority-based operations, libev usually has to
2457	linearly search all the priorities.	3116	linearly search all the priorities, but starting/stopping and activating
		3117	watchers becomes O(1) w.r.t. priority handling.
		3118
		3119	=item Sending an ev_async: O(1)
		3120
		3121	=item Processing ev_async_send: O(number_of_async_watchers)
		3122
		3123	=item Processing signals: O(max_signal_number)
		3124
		3125	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3126	calls in the current loop iteration. Checking for async and signal events
		3127	involves iterating over all running async watchers or all signal numbers.
2458		3128
2459	=back	3129	=back
2460		3130
2461		3131
		3132	=head1 Win32 platform limitations and workarounds
		3133
		3134	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3135	requires, and its I/O model is fundamentally incompatible with the POSIX
		3136	model. Libev still offers limited functionality on this platform in
		3137	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3138	descriptors. This only applies when using Win32 natively, not when using
		3139	e.g. cygwin.
		3140
		3141	There is no supported compilation method available on windows except
		3142	embedding it into other applications.
		3143
		3144	Due to the many, low, and arbitrary limits on the win32 platform and the
		3145	abysmal performance of winsockets, using a large number of sockets is not
		3146	recommended (and not reasonable). If your program needs to use more than
		3147	a hundred or so sockets, then likely it needs to use a totally different
		3148	implementation for windows, as libev offers the POSIX model, which cannot
		3149	be implemented efficiently on windows (microsoft monopoly games).
		3150
		3151	=over 4
		3152
		3153	=item The winsocket select function
		3154
		3155	The winsocket C<select> function doesn't follow POSIX in that it requires
		3156	socket I<handles> and not socket I<file descriptors>. This makes select
		3157	very inefficient, and also requires a mapping from file descriptors
		3158	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3159	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3160	symbols for more info.
		3161
		3162	The configuration for a "naked" win32 using the microsoft runtime
		3163	libraries and raw winsocket select is:
		3164
		3165	#define EV_USE_SELECT 1
		3166	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3167
		3168	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3169	complexity in the O(n²) range when using win32.
		3170
		3171	=item Limited number of file descriptors
		3172
		3173	Windows has numerous arbitrary (and low) limits on things. Early versions
		3174	of winsocket's select only supported waiting for a max. of C<64> handles
		3175	(probably owning to the fact that all windows kernels can only wait for
		3176	C<64> things at the same time internally; microsoft recommends spawning a
		3177	chain of threads and wait for 63 handles and the previous thread in each).
		3178
		3179	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3180	to some high number (e.g. C<2048>) before compiling the winsocket select
		3181	call (which might be in libev or elsewhere, for example, perl does its own
		3182	select emulation on windows).
		3183
		3184	Another limit is the number of file descriptors in the microsoft runtime
		3185	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3186	or something like this inside microsoft). You can increase this by calling
		3187	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3188	arbitrary limit), but is broken in many versions of the microsoft runtime
		3189	libraries.
		3190
		3191	This might get you to about C<512> or C<2048> sockets (depending on
		3192	windows version and/or the phase of the moon). To get more, you need to
		3193	wrap all I/O functions and provide your own fd management, but the cost of
		3194	calling select (O(n²)) will likely make this unworkable.
		3195
		3196	=back
		3197
		3198
2462	=head1 AUTHOR	3199	=head1 AUTHOR
2463		3200
2464	Marc Lehmann <libev@schmorp.de>.	3201	Marc Lehmann <libev@schmorp.de>.
2465		3202

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