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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	=head2 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head2 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head2 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
52		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
53		106
54	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
55		108
56	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
57	library in any way.	110	library in any way.
…		…
62		115
63	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	118	you actually want to know.
66		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
67	=item int ev_version_major ()	126	=item int ev_version_major ()
68		127
69	=item int ev_version_minor ()	128	=item int ev_version_minor ()
70		129
71	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	134	version of the library your program was compiled against.
76		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
77	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	142	not a problem.
81		143
82	Example: make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	145	version.
84		146
85	assert (("libev version mismatch",	147	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
88		150
…		…
118		180
119	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
120		182
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		184
123	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
128		191
129	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
132		195
133	Example: replace the libev allocator with one that waits a bit and then	196	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	197	retries).
135		198
136	static void *	199	static void *
137	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
138	{	201	{
139	for (;;)	202	for (;;)
140	{	203	{
141	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
142		205
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	224	(such as abort).
162		225
163	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
164		227
165	static void	228	static void
166	fatal_error (const char *msg)	229	fatal_error (const char *msg)
167	{	230	{
168	perror (msg);	231	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
221	around bugs.	284	around bugs.
222		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		307
225	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
229	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
230		320
231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
232		322
233	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
234	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
235	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
237		329
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		331
240	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
244		339
245	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
247	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	344	very well if you register events for both fds.
250		345
251	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	348	(or space) is available.
254		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		358
257	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
258	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
259	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
260	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
261	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
263		370
264	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
266	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
267	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
268	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
269		386
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		388
272	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
273		393
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		395
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
278		398
279	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
282		407
283	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
284		409
285	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
288		415
289	=back	416	=back
290		417
291	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
292	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	441	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	442	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	443	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	444	undefined behaviour (or a failed assertion if assertions are enabled).
318		445
319	Example: try to create a event loop that uses epoll and nothing else.	446	Example: Try to create a event loop that uses epoll and nothing else.
320		447
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	449	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	450	fatal ("no epoll found here, maybe it hides under your chair");
324		451
325	=item ev_default_destroy ()	452	=item ev_default_destroy ()
326		453
327	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
328	etc.). This stops all registered event watchers (by not touching them in	455	etc.). None of the active event watchers will be stopped in the normal
329	any way whatsoever, although you cannot rely on this :).	456	sense, so e.g. C<ev_is_active> might still return true. It is your
		457	responsibility to either stop all watchers cleanly yoursef I<before>
		458	calling this function, or cope with the fact afterwards (which is usually
		459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
330		470
331	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
332		472
333	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
334	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
358		498
359	Like C<ev_default_fork>, but acts on an event loop created by	499	Like C<ev_default_fork>, but acts on an event loop created by
360	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
361	after fork, and how you do this is entirely your own problem.	501	after fork, and how you do this is entirely your own problem.
362		502
		503	=item unsigned int ev_loop_count (loop)
		504
		505	Returns the count of loop iterations for the loop, which is identical to
		506	the number of times libev did poll for new events. It starts at C<0> and
		507	happily wraps around with enough iterations.
		508
		509	This value can sometimes be useful as a generation counter of sorts (it
		510	"ticks" the number of loop iterations), as it roughly corresponds with
		511	C<ev_prepare> and C<ev_check> calls.
		512
363	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
364		514
365	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
366	use.	516	use.
367		517
…		…
369		519
370	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
371	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
372	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
373	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
374	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
375		525
376	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
377		527
378	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
379	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
400	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
401	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
402		552
403	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
404		554
		555	- Before the first iteration, call any pending watchers.
405	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
406	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
407	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
408	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
409	- Update the "event loop time".	560	- Update the "event loop time".
410	- Calculate for how long to block.	561	- Calculate for how long to block.
411	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
419	Signals and child watchers are implemented as I/O watchers, and will	570	Signals and child watchers are implemented as I/O watchers, and will
420	be handled here by queueing them when their watcher gets executed.	571	be handled here by queueing them when their watcher gets executed.
421	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	572	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
422	were used, return, otherwise continue with step *.	573	were used, return, otherwise continue with step *.
423		574
424	Example: queue some jobs and then loop until no events are outsanding	575	Example: Queue some jobs and then loop until no events are outsanding
425	anymore.	576	anymore.
426		577
427	... queue jobs here, make sure they register event watchers as long	578	... queue jobs here, make sure they register event watchers as long
428	... as they still have work to do (even an idle watcher will do..)	579	... as they still have work to do (even an idle watcher will do..)
429	ev_loop (my_loop, 0);	580	ev_loop (my_loop, 0);
…		…
449	visible to the libev user and should not keep C<ev_loop> from exiting if	600	visible to the libev user and should not keep C<ev_loop> from exiting if
450	no event watchers registered by it are active. It is also an excellent	601	no event watchers registered by it are active. It is also an excellent
451	way to do this for generic recurring timers or from within third-party	602	way to do this for generic recurring timers or from within third-party
452	libraries. Just remember to I<unref after start> and I<ref before stop>.	603	libraries. Just remember to I<unref after start> and I<ref before stop>.
453		604
454	Example: create a signal watcher, but keep it from keeping C<ev_loop>	605	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
455	running when nothing else is active.	606	running when nothing else is active.
456		607
457	struct dv_signal exitsig;	608	struct ev_signal exitsig;
458	ev_signal_init (&exitsig, sig_cb, SIGINT);	609	ev_signal_init (&exitsig, sig_cb, SIGINT);
459	ev_signal_start (myloop, &exitsig);	610	ev_signal_start (loop, &exitsig);
460	evf_unref (myloop);	611	evf_unref (loop);
461		612
462	Example: for some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
463		614
464	ev_ref (myloop);	615	ev_ref (loop);
465	ev_signal_stop (myloop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
		617
		618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		619
		620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		621
		622	These advanced functions influence the time that libev will spend waiting
		623	for events. Both are by default C<0>, meaning that libev will try to
		624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		625
		626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		627	allows libev to delay invocation of I/O and timer/periodic callbacks to
		628	increase efficiency of loop iterations.
		629
		630	The background is that sometimes your program runs just fast enough to
		631	handle one (or very few) event(s) per loop iteration. While this makes
		632	the program responsive, it also wastes a lot of CPU time to poll for new
		633	events, especially with backends like C<select ()> which have a high
		634	overhead for the actual polling but can deliver many events at once.
		635
		636	By setting a higher I<io collect interval> you allow libev to spend more
		637	time collecting I/O events, so you can handle more events per iteration,
		638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		639	C<ev_timer>) will be not affected. Setting this to a non-null value will
		640	introduce an additional C<ev_sleep ()> call into most loop iterations.
		641
		642	Likewise, by setting a higher I<timeout collect interval> you allow libev
		643	to spend more time collecting timeouts, at the expense of increased
		644	latency (the watcher callback will be called later). C<ev_io> watchers
		645	will not be affected. Setting this to a non-null value will not introduce
		646	any overhead in libev.
		647
		648	Many (busy) programs can usually benefit by setting the io collect
		649	interval to a value near C<0.1> or so, which is often enough for
		650	interactive servers (of course not for games), likewise for timeouts. It
		651	usually doesn't make much sense to set it to a lower value than C<0.01>,
		652	as this approsaches the timing granularity of most systems.
466		653
467	=back	654	=back
		655
468		656
469	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
470		658
471	A watcher is a structure that you create and register to record your	659	A watcher is a structure that you create and register to record your
472	interest in some event. For instance, if you want to wait for STDIN to	660	interest in some event. For instance, if you want to wait for STDIN to
…		…
505	*) >>), and you can stop watching for events at any time by calling the	693	*) >>), and you can stop watching for events at any time by calling the
506	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	694	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
507		695
508	As long as your watcher is active (has been started but not stopped) you	696	As long as your watcher is active (has been started but not stopped) you
509	must not touch the values stored in it. Most specifically you must never	697	must not touch the values stored in it. Most specifically you must never
510	reinitialise it or call its set macro.	698	reinitialise it or call its C<set> macro.
511
512	You can check whether an event is active by calling the C<ev_is_active
513	(watcher *)> macro. To see whether an event is outstanding (but the
514	callback for it has not been called yet) you can use the C<ev_is_pending
515	(watcher *)> macro.
516		699
517	Each and every callback receives the event loop pointer as first, the	700	Each and every callback receives the event loop pointer as first, the
518	registered watcher structure as second, and a bitset of received events as	701	registered watcher structure as second, and a bitset of received events as
519	third argument.	702	third argument.
520		703
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	727	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		728
546	=item C<EV_CHILD>	729	=item C<EV_CHILD>
547		730
548	The pid specified in the C<ev_child> watcher has received a status change.	731	The pid specified in the C<ev_child> watcher has received a status change.
		732
		733	=item C<EV_STAT>
		734
		735	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		736
550	=item C<EV_IDLE>	737	=item C<EV_IDLE>
551		738
552	The C<ev_idle> watcher has determined that you have nothing better to do.	739	The C<ev_idle> watcher has determined that you have nothing better to do.
553		740
…		…
561	received events. Callbacks of both watcher types can start and stop as	748	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	749	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	750	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	751	C<ev_loop> from blocking).
565		752
		753	=item C<EV_EMBED>
		754
		755	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		756
		757	=item C<EV_FORK>
		758
		759	The event loop has been resumed in the child process after fork (see
		760	C<ev_fork>).
		761
566	=item C<EV_ERROR>	762	=item C<EV_ERROR>
567		763
568	An unspecified error has occured, the watcher has been stopped. This might	764	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	765	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	766	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	your callbacks is well-written it can just attempt the operation and cope	772	your callbacks is well-written it can just attempt the operation and cope
577	with the error from read() or write(). This will not work in multithreaded	773	with the error from read() or write(). This will not work in multithreaded
578	programs, though, so beware.	774	programs, though, so beware.
579		775
580	=back	776	=back
		777
		778	=head2 GENERIC WATCHER FUNCTIONS
		779
		780	In the following description, C<TYPE> stands for the watcher type,
		781	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		782
		783	=over 4
		784
		785	=item C<ev_init> (ev_TYPE *watcher, callback)
		786
		787	This macro initialises the generic portion of a watcher. The contents
		788	of the watcher object can be arbitrary (so C<malloc> will do). Only
		789	the generic parts of the watcher are initialised, you I<need> to call
		790	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		791	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		792	which rolls both calls into one.
		793
		794	You can reinitialise a watcher at any time as long as it has been stopped
		795	(or never started) and there are no pending events outstanding.
		796
		797	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
		798	int revents)>.
		799
		800	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		801
		802	This macro initialises the type-specific parts of a watcher. You need to
		803	call C<ev_init> at least once before you call this macro, but you can
		804	call C<ev_TYPE_set> any number of times. You must not, however, call this
		805	macro on a watcher that is active (it can be pending, however, which is a
		806	difference to the C<ev_init> macro).
		807
		808	Although some watcher types do not have type-specific arguments
		809	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		810
		811	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		812
		813	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		814	calls into a single call. This is the most convinient method to initialise
		815	a watcher. The same limitations apply, of course.
		816
		817	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
		818
		819	Starts (activates) the given watcher. Only active watchers will receive
		820	events. If the watcher is already active nothing will happen.
		821
		822	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
		823
		824	Stops the given watcher again (if active) and clears the pending
		825	status. It is possible that stopped watchers are pending (for example,
		826	non-repeating timers are being stopped when they become pending), but
		827	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		828	you want to free or reuse the memory used by the watcher it is therefore a
		829	good idea to always call its C<ev_TYPE_stop> function.
		830
		831	=item bool ev_is_active (ev_TYPE *watcher)
		832
		833	Returns a true value iff the watcher is active (i.e. it has been started
		834	and not yet been stopped). As long as a watcher is active you must not modify
		835	it.
		836
		837	=item bool ev_is_pending (ev_TYPE *watcher)
		838
		839	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		840	events but its callback has not yet been invoked). As long as a watcher
		841	is pending (but not active) you must not call an init function on it (but
		842	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		843	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		844	it).
		845
		846	=item callback ev_cb (ev_TYPE *watcher)
		847
		848	Returns the callback currently set on the watcher.
		849
		850	=item ev_cb_set (ev_TYPE *watcher, callback)
		851
		852	Change the callback. You can change the callback at virtually any time
		853	(modulo threads).
		854
		855	=item ev_set_priority (ev_TYPE *watcher, priority)
		856
		857	=item int ev_priority (ev_TYPE *watcher)
		858
		859	Set and query the priority of the watcher. The priority is a small
		860	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		861	(default: C<-2>). Pending watchers with higher priority will be invoked
		862	before watchers with lower priority, but priority will not keep watchers
		863	from being executed (except for C<ev_idle> watchers).
		864
		865	This means that priorities are I<only> used for ordering callback
		866	invocation after new events have been received. This is useful, for
		867	example, to reduce latency after idling, or more often, to bind two
		868	watchers on the same event and make sure one is called first.
		869
		870	If you need to suppress invocation when higher priority events are pending
		871	you need to look at C<ev_idle> watchers, which provide this functionality.
		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
		876	The default priority used by watchers when no priority has been set is
		877	always C<0>, which is supposed to not be too high and not be too low :).
		878
		879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		880	fine, as long as you do not mind that the priority value you query might
		881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
		894
		895	=back
		896
581		897
582	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
583		899
584	Each watcher has, by default, a member C<void *data> that you can change	900	Each watcher has, by default, a member C<void *data> that you can change
585	and read at any time, libev will completely ignore it. This can be used	901	and read at any time, libev will completely ignore it. This can be used
…		…
603	{	919	{
604	struct my_io *w = (struct my_io *)w_;	920	struct my_io *w = (struct my_io *)w_;
605	...	921	...
606	}	922	}
607		923
608	More interesting and less C-conformant ways of catsing your callback type	924	More interesting and less C-conformant ways of casting your callback type
609	have been omitted....	925	instead have been omitted.
		926
		927	Another common scenario is having some data structure with multiple
		928	watchers:
		929
		930	struct my_biggy
		931	{
		932	int some_data;
		933	ev_timer t1;
		934	ev_timer t2;
		935	}
		936
		937	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		938	you need to use C<offsetof>:
		939
		940	#include <stddef.h>
		941
		942	static void
		943	t1_cb (EV_P_ struct ev_timer *w, int revents)
		944	{
		945	struct my_biggy big = (struct my_biggy *
		946	(((char *)w) - offsetof (struct my_biggy, t1));
		947	}
		948
		949	static void
		950	t2_cb (EV_P_ struct ev_timer *w, int revents)
		951	{
		952	struct my_biggy big = (struct my_biggy *
		953	(((char *)w) - offsetof (struct my_biggy, t2));
		954	}
610		955
611		956
612	=head1 WATCHER TYPES	957	=head1 WATCHER TYPES
613		958
614	This section describes each watcher in detail, but will not repeat	959	This section describes each watcher in detail, but will not repeat
615	information given in the last section.	960	information given in the last section. Any initialisation/set macros,
		961	functions and members specific to the watcher type are explained.
616		962
		963	Members are additionally marked with either I<[read-only]>, meaning that,
		964	while the watcher is active, you can look at the member and expect some
		965	sensible content, but you must not modify it (you can modify it while the
		966	watcher is stopped to your hearts content), or I<[read-write]>, which
		967	means you can expect it to have some sensible content while the watcher
		968	is active, but you can also modify it. Modifying it may not do something
		969	sensible or take immediate effect (or do anything at all), but libev will
		970	not crash or malfunction in any way.
617		971
		972
618	=head2 C<ev_io> - is this file descriptor readable or writable	973	=head2 C<ev_io> - is this file descriptor readable or writable?
619		974
620	I/O watchers check whether a file descriptor is readable or writable	975	I/O watchers check whether a file descriptor is readable or writable
621	in each iteration of the event loop (This behaviour is called	976	in each iteration of the event loop, or, more precisely, when reading
622	level-triggering because you keep receiving events as long as the	977	would not block the process and writing would at least be able to write
623	condition persists. Remember you can stop the watcher if you don't want to	978	some data. This behaviour is called level-triggering because you keep
624	act on the event and neither want to receive future events).	979	receiving events as long as the condition persists. Remember you can stop
		980	the watcher if you don't want to act on the event and neither want to
		981	receive future events.
625		982
626	In general you can register as many read and/or write event watchers per	983	In general you can register as many read and/or write event watchers per
627	fd as you want (as long as you don't confuse yourself). Setting all file	984	fd as you want (as long as you don't confuse yourself). Setting all file
628	descriptors to non-blocking mode is also usually a good idea (but not	985	descriptors to non-blocking mode is also usually a good idea (but not
629	required if you know what you are doing).	986	required if you know what you are doing).
630		987
631	You have to be careful with dup'ed file descriptors, though. Some backends
632	(the linux epoll backend is a notable example) cannot handle dup'ed file
633	descriptors correctly if you register interest in two or more fds pointing
634	to the same underlying file/socket etc. description (that is, they share
635	the same underlying "file open").
636
637	If you must do this, then force the use of a known-to-be-good backend	988	If you must do this, then force the use of a known-to-be-good backend
638	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	989	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
639	C<EVBACKEND_POLL>).	990	C<EVBACKEND_POLL>).
640		991
		992	Another thing you have to watch out for is that it is quite easy to
		993	receive "spurious" readyness notifications, that is your callback might
		994	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		995	because there is no data. Not only are some backends known to create a
		996	lot of those (for example solaris ports), it is very easy to get into
		997	this situation even with a relatively standard program structure. Thus
		998	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		999	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1000
		1001	If you cannot run the fd in non-blocking mode (for example you should not
		1002	play around with an Xlib connection), then you have to seperately re-test
		1003	whether a file descriptor is really ready with a known-to-be good interface
		1004	such as poll (fortunately in our Xlib example, Xlib already does this on
		1005	its own, so its quite safe to use).
		1006
		1007	=head3 The special problem of disappearing file descriptors
		1008
		1009	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1010	descriptor (either by calling C<close> explicitly or by any other means,
		1011	such as C<dup>). The reason is that you register interest in some file
		1012	descriptor, but when it goes away, the operating system will silently drop
		1013	this interest. If another file descriptor with the same number then is
		1014	registered with libev, there is no efficient way to see that this is, in
		1015	fact, a different file descriptor.
		1016
		1017	To avoid having to explicitly tell libev about such cases, libev follows
		1018	the following policy: Each time C<ev_io_set> is being called, libev
		1019	will assume that this is potentially a new file descriptor, otherwise
		1020	it is assumed that the file descriptor stays the same. That means that
		1021	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1022	descriptor even if the file descriptor number itself did not change.
		1023
		1024	This is how one would do it normally anyway, the important point is that
		1025	the libev application should not optimise around libev but should leave
		1026	optimisations to libev.
		1027
		1028	=head3 The special problem of dup'ed file descriptors
		1029
		1030	Some backends (e.g. epoll), cannot register events for file descriptors,
		1031	but only events for the underlying file descriptions. That means when you
		1032	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1033	events for them, only one file descriptor might actually receive events.
		1034
		1035	There is no workaround possible except not registering events
		1036	for potentially C<dup ()>'ed file descriptors, or to resort to
		1037	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1038
		1039	=head3 The special problem of fork
		1040
		1041	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1042	useless behaviour. Libev fully supports fork, but needs to be told about
		1043	it in the child.
		1044
		1045	To support fork in your programs, you either have to call
		1046	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1047	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1048	C<EVBACKEND_POLL>.
		1049
		1050
		1051	=head3 Watcher-Specific Functions
		1052
641	=over 4	1053	=over 4
642		1054
643	=item ev_io_init (ev_io *, callback, int fd, int events)	1055	=item ev_io_init (ev_io *, callback, int fd, int events)
644		1056
645	=item ev_io_set (ev_io *, int fd, int events)	1057	=item ev_io_set (ev_io *, int fd, int events)
646		1058
647	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1059	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
648	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1060	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
649	EV_WRITE> to receive the given events.	1061	C<EV_READ | EV_WRITE> to receive the given events.
650		1062
651	Please note that most of the more scalable backend mechanisms (for example	1063	=item int fd [read-only]
652	epoll and solaris ports) can result in spurious readyness notifications	1064
653	for file descriptors, so you practically need to use non-blocking I/O (and	1065	The file descriptor being watched.
654	treat callback invocation as hint only), or retest separately with a safe	1066
655	interface before doing I/O (XLib can do this), or force the use of either	1067	=item int events [read-only]
656	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	1068
657	problem. Also note that it is quite easy to have your callback invoked	1069	The events being watched.
658	when the readyness condition is no longer valid even when employing
659	typical ways of handling events, so its a good idea to use non-blocking
660	I/O unconditionally.
661		1070
662	=back	1071	=back
663		1072
		1073	=head3 Examples
		1074
664	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1075	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
665	readable, but only once. Since it is likely line-buffered, you could	1076	readable, but only once. Since it is likely line-buffered, you could
666	attempt to read a whole line in the callback:	1077	attempt to read a whole line in the callback.
667		1078
668	static void	1079	static void
669	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1080	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
670	{	1081	{
671	ev_io_stop (loop, w);	1082	ev_io_stop (loop, w);
…		…
678	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1089	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
679	ev_io_start (loop, &stdin_readable);	1090	ev_io_start (loop, &stdin_readable);
680	ev_loop (loop, 0);	1091	ev_loop (loop, 0);
681		1092
682		1093
683	=head2 C<ev_timer> - relative and optionally recurring timeouts	1094	=head2 C<ev_timer> - relative and optionally repeating timeouts
684		1095
685	Timer watchers are simple relative timers that generate an event after a	1096	Timer watchers are simple relative timers that generate an event after a
686	given time, and optionally repeating in regular intervals after that.	1097	given time, and optionally repeating in regular intervals after that.
687		1098
688	The timers are based on real time, that is, if you register an event that	1099	The timers are based on real time, that is, if you register an event that
…		…
701		1112
702	The callback is guarenteed to be invoked only when its timeout has passed,	1113	The callback is guarenteed to be invoked only when its timeout has passed,
703	but if multiple timers become ready during the same loop iteration then	1114	but if multiple timers become ready during the same loop iteration then
704	order of execution is undefined.	1115	order of execution is undefined.
705		1116
		1117	=head3 Watcher-Specific Functions and Data Members
		1118
706	=over 4	1119	=over 4
707		1120
708	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1121	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
709		1122
710	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1123	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
723	=item ev_timer_again (loop)	1136	=item ev_timer_again (loop)
724		1137
725	This will act as if the timer timed out and restart it again if it is	1138	This will act as if the timer timed out and restart it again if it is
726	repeating. The exact semantics are:	1139	repeating. The exact semantics are:
727		1140
		1141	If the timer is pending, its pending status is cleared.
		1142
728	If the timer is started but nonrepeating, stop it.	1143	If the timer is started but nonrepeating, stop it (as if it timed out).
729		1144
730	If the timer is repeating, either start it if necessary (with the repeat	1145	If the timer is repeating, either start it if necessary (with the
731	value), or reset the running timer to the repeat value.	1146	C<repeat> value), or reset the running timer to the C<repeat> value.
732		1147
733	This sounds a bit complicated, but here is a useful and typical	1148	This sounds a bit complicated, but here is a useful and typical
734	example: Imagine you have a tcp connection and you want a so-called idle	1149	example: Imagine you have a tcp connection and you want a so-called idle
735	timeout, that is, you want to be called when there have been, say, 60	1150	timeout, that is, you want to be called when there have been, say, 60
736	seconds of inactivity on the socket. The easiest way to do this is to	1151	seconds of inactivity on the socket. The easiest way to do this is to
737	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1152	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
738	time you successfully read or write some data. If you go into an idle	1153	C<ev_timer_again> each time you successfully read or write some data. If
739	state where you do not expect data to travel on the socket, you can stop	1154	you go into an idle state where you do not expect data to travel on the
740	the timer, and again will automatically restart it if need be.	1155	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1156	automatically restart it if need be.
		1157
		1158	That means you can ignore the C<after> value and C<ev_timer_start>
		1159	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1160
		1161	ev_timer_init (timer, callback, 0., 5.);
		1162	ev_timer_again (loop, timer);
		1163	...
		1164	timer->again = 17.;
		1165	ev_timer_again (loop, timer);
		1166	...
		1167	timer->again = 10.;
		1168	ev_timer_again (loop, timer);
		1169
		1170	This is more slightly efficient then stopping/starting the timer each time
		1171	you want to modify its timeout value.
		1172
		1173	=item ev_tstamp repeat [read-write]
		1174
		1175	The current C<repeat> value. Will be used each time the watcher times out
		1176	or C<ev_timer_again> is called and determines the next timeout (if any),
		1177	which is also when any modifications are taken into account.
741		1178
742	=back	1179	=back
743		1180
		1181	=head3 Examples
		1182
744	Example: create a timer that fires after 60 seconds.	1183	Example: Create a timer that fires after 60 seconds.
745		1184
746	static void	1185	static void
747	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1186	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
748	{	1187	{
749	.. one minute over, w is actually stopped right here	1188	.. one minute over, w is actually stopped right here
…		…
751		1190
752	struct ev_timer mytimer;	1191	struct ev_timer mytimer;
753	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1192	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
754	ev_timer_start (loop, &mytimer);	1193	ev_timer_start (loop, &mytimer);
755		1194
756	Example: create a timeout timer that times out after 10 seconds of	1195	Example: Create a timeout timer that times out after 10 seconds of
757	inactivity.	1196	inactivity.
758		1197
759	static void	1198	static void
760	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1199	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
761	{	1200	{
…		…
770	// and in some piece of code that gets executed on any "activity":	1209	// and in some piece of code that gets executed on any "activity":
771	// reset the timeout to start ticking again at 10 seconds	1210	// reset the timeout to start ticking again at 10 seconds
772	ev_timer_again (&mytimer);	1211	ev_timer_again (&mytimer);
773		1212
774		1213
775	=head2 C<ev_periodic> - to cron or not to cron	1214	=head2 C<ev_periodic> - to cron or not to cron?
776		1215
777	Periodic watchers are also timers of a kind, but they are very versatile	1216	Periodic watchers are also timers of a kind, but they are very versatile
778	(and unfortunately a bit complex).	1217	(and unfortunately a bit complex).
779		1218
780	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1219	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
781	but on wallclock time (absolute time). You can tell a periodic watcher	1220	but on wallclock time (absolute time). You can tell a periodic watcher
782	to trigger "at" some specific point in time. For example, if you tell a	1221	to trigger "at" some specific point in time. For example, if you tell a
783	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1222	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
784	+ 10.>) and then reset your system clock to the last year, then it will	1223	+ 10.>) and then reset your system clock to the last year, then it will
785	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1224	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
786	roughly 10 seconds later and of course not if you reset your system time	1225	roughly 10 seconds later).
787	again).
788		1226
789	They can also be used to implement vastly more complex timers, such as	1227	They can also be used to implement vastly more complex timers, such as
790	triggering an event on eahc midnight, local time.	1228	triggering an event on each midnight, local time or other, complicated,
		1229	rules.
791		1230
792	As with timers, the callback is guarenteed to be invoked only when the	1231	As with timers, the callback is guarenteed to be invoked only when the
793	time (C<at>) has been passed, but if multiple periodic timers become ready	1232	time (C<at>) has been passed, but if multiple periodic timers become ready
794	during the same loop iteration then order of execution is undefined.	1233	during the same loop iteration then order of execution is undefined.
795		1234
		1235	=head3 Watcher-Specific Functions and Data Members
		1236
796	=over 4	1237	=over 4
797		1238
798	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1239	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
799		1240
800	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1241	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
802	Lots of arguments, lets sort it out... There are basically three modes of	1243	Lots of arguments, lets sort it out... There are basically three modes of
803	operation, and we will explain them from simplest to complex:	1244	operation, and we will explain them from simplest to complex:
804		1245
805	=over 4	1246	=over 4
806		1247
807	=item * absolute timer (interval = reschedule_cb = 0)	1248	=item * absolute timer (at = time, interval = reschedule_cb = 0)
808		1249
809	In this configuration the watcher triggers an event at the wallclock time	1250	In this configuration the watcher triggers an event at the wallclock time
810	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1251	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
811	that is, if it is to be run at January 1st 2011 then it will run when the	1252	that is, if it is to be run at January 1st 2011 then it will run when the
812	system time reaches or surpasses this time.	1253	system time reaches or surpasses this time.
813		1254
814	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1255	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
815		1256
816	In this mode the watcher will always be scheduled to time out at the next	1257	In this mode the watcher will always be scheduled to time out at the next
817	C<at + N * interval> time (for some integer N) and then repeat, regardless	1258	C<at + N * interval> time (for some integer N, which can also be negative)
818	of any time jumps.	1259	and then repeat, regardless of any time jumps.
819		1260
820	This can be used to create timers that do not drift with respect to system	1261	This can be used to create timers that do not drift with respect to system
821	time:	1262	time:
822		1263
823	ev_periodic_set (&periodic, 0., 3600., 0);	1264	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
829		1270
830	Another way to think about it (for the mathematically inclined) is that	1271	Another way to think about it (for the mathematically inclined) is that
831	C<ev_periodic> will try to run the callback in this mode at the next possible	1272	C<ev_periodic> will try to run the callback in this mode at the next possible
832	time where C<time = at (mod interval)>, regardless of any time jumps.	1273	time where C<time = at (mod interval)>, regardless of any time jumps.
833		1274
		1275	For numerical stability it is preferable that the C<at> value is near
		1276	C<ev_now ()> (the current time), but there is no range requirement for
		1277	this value.
		1278
834	=item * manual reschedule mode (reschedule_cb = callback)	1279	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
835		1280
836	In this mode the values for C<interval> and C<at> are both being	1281	In this mode the values for C<interval> and C<at> are both being
837	ignored. Instead, each time the periodic watcher gets scheduled, the	1282	ignored. Instead, each time the periodic watcher gets scheduled, the
838	reschedule callback will be called with the watcher as first, and the	1283	reschedule callback will be called with the watcher as first, and the
839	current time as second argument.	1284	current time as second argument.
840		1285
841	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1286	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
842	ever, or make any event loop modifications>. If you need to stop it,	1287	ever, or make any event loop modifications>. If you need to stop it,
843	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1288	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
844	starting a prepare watcher).	1289	starting an C<ev_prepare> watcher, which is legal).
845		1290
846	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1291	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
847	ev_tstamp now)>, e.g.:	1292	ev_tstamp now)>, e.g.:
848		1293
849	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1294	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
872	Simply stops and restarts the periodic watcher again. This is only useful	1317	Simply stops and restarts the periodic watcher again. This is only useful
873	when you changed some parameters or the reschedule callback would return	1318	when you changed some parameters or the reschedule callback would return
874	a different time than the last time it was called (e.g. in a crond like	1319	a different time than the last time it was called (e.g. in a crond like
875	program when the crontabs have changed).	1320	program when the crontabs have changed).
876		1321
		1322	=item ev_tstamp offset [read-write]
		1323
		1324	When repeating, this contains the offset value, otherwise this is the
		1325	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1326
		1327	Can be modified any time, but changes only take effect when the periodic
		1328	timer fires or C<ev_periodic_again> is being called.
		1329
		1330	=item ev_tstamp interval [read-write]
		1331
		1332	The current interval value. Can be modified any time, but changes only
		1333	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1334	called.
		1335
		1336	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1337
		1338	The current reschedule callback, or C<0>, if this functionality is
		1339	switched off. Can be changed any time, but changes only take effect when
		1340	the periodic timer fires or C<ev_periodic_again> is being called.
		1341
		1342	=item ev_tstamp at [read-only]
		1343
		1344	When active, contains the absolute time that the watcher is supposed to
		1345	trigger next.
		1346
877	=back	1347	=back
878		1348
		1349	=head3 Examples
		1350
879	Example: call a callback every hour, or, more precisely, whenever the	1351	Example: Call a callback every hour, or, more precisely, whenever the
880	system clock is divisible by 3600. The callback invocation times have	1352	system clock is divisible by 3600. The callback invocation times have
881	potentially a lot of jittering, but good long-term stability.	1353	potentially a lot of jittering, but good long-term stability.
882		1354
883	static void	1355	static void
884	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1356	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
888		1360
889	struct ev_periodic hourly_tick;	1361	struct ev_periodic hourly_tick;
890	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1362	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
891	ev_periodic_start (loop, &hourly_tick);	1363	ev_periodic_start (loop, &hourly_tick);
892		1364
893	Example: the same as above, but use a reschedule callback to do it:	1365	Example: The same as above, but use a reschedule callback to do it:
894		1366
895	#include <math.h>	1367	#include <math.h>
896		1368
897	static ev_tstamp	1369	static ev_tstamp
898	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1370	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
900	return fmod (now, 3600.) + 3600.;	1372	return fmod (now, 3600.) + 3600.;
901	}	1373	}
902		1374
903	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1375	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
904		1376
905	Example: call a callback every hour, starting now:	1377	Example: Call a callback every hour, starting now:
906		1378
907	struct ev_periodic hourly_tick;	1379	struct ev_periodic hourly_tick;
908	ev_periodic_init (&hourly_tick, clock_cb,	1380	ev_periodic_init (&hourly_tick, clock_cb,
909	fmod (ev_now (loop), 3600.), 3600., 0);	1381	fmod (ev_now (loop), 3600.), 3600., 0);
910	ev_periodic_start (loop, &hourly_tick);	1382	ev_periodic_start (loop, &hourly_tick);
911		1383
912		1384
913	=head2 C<ev_signal> - signal me when a signal gets signalled	1385	=head2 C<ev_signal> - signal me when a signal gets signalled!
914		1386
915	Signal watchers will trigger an event when the process receives a specific	1387	Signal watchers will trigger an event when the process receives a specific
916	signal one or more times. Even though signals are very asynchronous, libev	1388	signal one or more times. Even though signals are very asynchronous, libev
917	will try it's best to deliver signals synchronously, i.e. as part of the	1389	will try it's best to deliver signals synchronously, i.e. as part of the
918	normal event processing, like any other event.	1390	normal event processing, like any other event.
…		…
922	with the kernel (thus it coexists with your own signal handlers as long	1394	with the kernel (thus it coexists with your own signal handlers as long
923	as you don't register any with libev). Similarly, when the last signal	1395	as you don't register any with libev). Similarly, when the last signal
924	watcher for a signal is stopped libev will reset the signal handler to	1396	watcher for a signal is stopped libev will reset the signal handler to
925	SIG_DFL (regardless of what it was set to before).	1397	SIG_DFL (regardless of what it was set to before).
926		1398
		1399	=head3 Watcher-Specific Functions and Data Members
		1400
927	=over 4	1401	=over 4
928		1402
929	=item ev_signal_init (ev_signal *, callback, int signum)	1403	=item ev_signal_init (ev_signal *, callback, int signum)
930		1404
931	=item ev_signal_set (ev_signal *, int signum)	1405	=item ev_signal_set (ev_signal *, int signum)
932		1406
933	Configures the watcher to trigger on the given signal number (usually one	1407	Configures the watcher to trigger on the given signal number (usually one
934	of the C<SIGxxx> constants).	1408	of the C<SIGxxx> constants).
935		1409
		1410	=item int signum [read-only]
		1411
		1412	The signal the watcher watches out for.
		1413
936	=back	1414	=back
937		1415
938		1416
939	=head2 C<ev_child> - wait for pid status changes	1417	=head2 C<ev_child> - watch out for process status changes
940		1418
941	Child watchers trigger when your process receives a SIGCHLD in response to	1419	Child watchers trigger when your process receives a SIGCHLD in response to
942	some child status changes (most typically when a child of yours dies).	1420	some child status changes (most typically when a child of yours dies).
		1421
		1422	=head3 Watcher-Specific Functions and Data Members
943		1423
944	=over 4	1424	=over 4
945		1425
946	=item ev_child_init (ev_child *, callback, int pid)	1426	=item ev_child_init (ev_child *, callback, int pid)
947		1427
…		…
952	at the C<rstatus> member of the C<ev_child> watcher structure to see	1432	at the C<rstatus> member of the C<ev_child> watcher structure to see
953	the status word (use the macros from C<sys/wait.h> and see your systems	1433	the status word (use the macros from C<sys/wait.h> and see your systems
954	C<waitpid> documentation). The C<rpid> member contains the pid of the	1434	C<waitpid> documentation). The C<rpid> member contains the pid of the
955	process causing the status change.	1435	process causing the status change.
956		1436
		1437	=item int pid [read-only]
		1438
		1439	The process id this watcher watches out for, or C<0>, meaning any process id.
		1440
		1441	=item int rpid [read-write]
		1442
		1443	The process id that detected a status change.
		1444
		1445	=item int rstatus [read-write]
		1446
		1447	The process exit/trace status caused by C<rpid> (see your systems
		1448	C<waitpid> and C<sys/wait.h> documentation for details).
		1449
957	=back	1450	=back
958		1451
		1452	=head3 Examples
		1453
959	Example: try to exit cleanly on SIGINT and SIGTERM.	1454	Example: Try to exit cleanly on SIGINT and SIGTERM.
960		1455
961	static void	1456	static void
962	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1457	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
963	{	1458	{
964	ev_unloop (loop, EVUNLOOP_ALL);	1459	ev_unloop (loop, EVUNLOOP_ALL);
…		…
967	struct ev_signal signal_watcher;	1462	struct ev_signal signal_watcher;
968	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1463	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
969	ev_signal_start (loop, &sigint_cb);	1464	ev_signal_start (loop, &sigint_cb);
970		1465
971		1466
		1467	=head2 C<ev_stat> - did the file attributes just change?
		1468
		1469	This watches a filesystem path for attribute changes. That is, it calls
		1470	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1471	compared to the last time, invoking the callback if it did.
		1472
		1473	The path does not need to exist: changing from "path exists" to "path does
		1474	not exist" is a status change like any other. The condition "path does
		1475	not exist" is signified by the C<st_nlink> field being zero (which is
		1476	otherwise always forced to be at least one) and all the other fields of
		1477	the stat buffer having unspecified contents.
		1478
		1479	The path I<should> be absolute and I<must not> end in a slash. If it is
		1480	relative and your working directory changes, the behaviour is undefined.
		1481
		1482	Since there is no standard to do this, the portable implementation simply
		1483	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1484	can specify a recommended polling interval for this case. If you specify
		1485	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1486	unspecified default> value will be used (which you can expect to be around
		1487	five seconds, although this might change dynamically). Libev will also
		1488	impose a minimum interval which is currently around C<0.1>, but thats
		1489	usually overkill.
		1490
		1491	This watcher type is not meant for massive numbers of stat watchers,
		1492	as even with OS-supported change notifications, this can be
		1493	resource-intensive.
		1494
		1495	At the time of this writing, only the Linux inotify interface is
		1496	implemented (implementing kqueue support is left as an exercise for the
		1497	reader). Inotify will be used to give hints only and should not change the
		1498	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1499	to fall back to regular polling again even with inotify, but changes are
		1500	usually detected immediately, and if the file exists there will be no
		1501	polling.
		1502
		1503	=head3 Inotify
		1504
		1505	When C<inotify (7)> support has been compiled into libev (generally only
		1506	available on Linux) and present at runtime, it will be used to speed up
		1507	change detection where possible. The inotify descriptor will be created lazily
		1508	when the first C<ev_stat> watcher is being started.
		1509
		1510	Inotify presense does not change the semantics of C<ev_stat> watchers
		1511	except that changes might be detected earlier, and in some cases, to avoid
		1512	making regular C<stat> calls. Even in the presense of inotify support
		1513	there are many cases where libev has to resort to regular C<stat> polling.
		1514
		1515	(There is no support for kqueue, as apparently it cannot be used to
		1516	implement this functionality, due to the requirement of having a file
		1517	descriptor open on the object at all times).
		1518
		1519	=head3 The special problem of stat time resolution
		1520
		1521	The C<stat ()> syscall only supports full-second resolution portably, and
		1522	even on systems where the resolution is higher, many filesystems still
		1523	only support whole seconds.
		1524
		1525	That means that, if the time is the only thing that changes, you might
		1526	miss updates: on the first update, C<ev_stat> detects a change and calls
		1527	your callback, which does something. When there is another update within
		1528	the same second, C<ev_stat> will be unable to detect it.
		1529
		1530	The solution to this is to delay acting on a change for a second (or till
		1531	the next second boundary), using a roughly one-second delay C<ev_timer>
		1532	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1533	is added to work around small timing inconsistencies of some operating
		1534	systems.
		1535
		1536	=head3 Watcher-Specific Functions and Data Members
		1537
		1538	=over 4
		1539
		1540	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1541
		1542	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1543
		1544	Configures the watcher to wait for status changes of the given
		1545	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1546	be detected and should normally be specified as C<0> to let libev choose
		1547	a suitable value. The memory pointed to by C<path> must point to the same
		1548	path for as long as the watcher is active.
		1549
		1550	The callback will be receive C<EV_STAT> when a change was detected,
		1551	relative to the attributes at the time the watcher was started (or the
		1552	last change was detected).
		1553
		1554	=item ev_stat_stat (ev_stat *)
		1555
		1556	Updates the stat buffer immediately with new values. If you change the
		1557	watched path in your callback, you could call this fucntion to avoid
		1558	detecting this change (while introducing a race condition). Can also be
		1559	useful simply to find out the new values.
		1560
		1561	=item ev_statdata attr [read-only]
		1562
		1563	The most-recently detected attributes of the file. Although the type is of
		1564	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1565	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1566	was some error while C<stat>ing the file.
		1567
		1568	=item ev_statdata prev [read-only]
		1569
		1570	The previous attributes of the file. The callback gets invoked whenever
		1571	C<prev> != C<attr>.
		1572
		1573	=item ev_tstamp interval [read-only]
		1574
		1575	The specified interval.
		1576
		1577	=item const char *path [read-only]
		1578
		1579	The filesystem path that is being watched.
		1580
		1581	=back
		1582
		1583	=head3 Examples
		1584
		1585	Example: Watch C</etc/passwd> for attribute changes.
		1586
		1587	static void
		1588	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1589	{
		1590	/* /etc/passwd changed in some way */
		1591	if (w->attr.st_nlink)
		1592	{
		1593	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1594	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1595	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1596	}
		1597	else
		1598	/* you shalt not abuse printf for puts */
		1599	puts ("wow, /etc/passwd is not there, expect problems. "
		1600	"if this is windows, they already arrived\n");
		1601	}
		1602
		1603	...
		1604	ev_stat passwd;
		1605
		1606	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1607	ev_stat_start (loop, &passwd);
		1608
		1609	Example: Like above, but additionally use a one-second delay so we do not
		1610	miss updates (however, frequent updates will delay processing, too, so
		1611	one might do the work both on C<ev_stat> callback invocation I<and> on
		1612	C<ev_timer> callback invocation).
		1613
		1614	static ev_stat passwd;
		1615	static ev_timer timer;
		1616
		1617	static void
		1618	timer_cb (EV_P_ ev_timer *w, int revents)
		1619	{
		1620	ev_timer_stop (EV_A_ w);
		1621
		1622	/* now it's one second after the most recent passwd change */
		1623	}
		1624
		1625	static void
		1626	stat_cb (EV_P_ ev_stat *w, int revents)
		1627	{
		1628	/* reset the one-second timer */
		1629	ev_timer_again (EV_A_ &timer);
		1630	}
		1631
		1632	...
		1633	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1634	ev_stat_start (loop, &passwd);
		1635	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1636
		1637
972	=head2 C<ev_idle> - when you've got nothing better to do	1638	=head2 C<ev_idle> - when you've got nothing better to do...
973		1639
974	Idle watchers trigger events when there are no other events are pending	1640	Idle watchers trigger events when no other events of the same or higher
975	(prepare, check and other idle watchers do not count). That is, as long	1641	priority are pending (prepare, check and other idle watchers do not
976	as your process is busy handling sockets or timeouts (or even signals,	1642	count).
977	imagine) it will not be triggered. But when your process is idle all idle	1643
978	watchers are being called again and again, once per event loop iteration -	1644	That is, as long as your process is busy handling sockets or timeouts
		1645	(or even signals, imagine) of the same or higher priority it will not be
		1646	triggered. But when your process is idle (or only lower-priority watchers
		1647	are pending), the idle watchers are being called once per event loop
979	until stopped, that is, or your process receives more events and becomes	1648	iteration - until stopped, that is, or your process receives more events
980	busy.	1649	and becomes busy again with higher priority stuff.
981		1650
982	The most noteworthy effect is that as long as any idle watchers are	1651	The most noteworthy effect is that as long as any idle watchers are
983	active, the process will not block when waiting for new events.	1652	active, the process will not block when waiting for new events.
984		1653
985	Apart from keeping your process non-blocking (which is a useful	1654	Apart from keeping your process non-blocking (which is a useful
986	effect on its own sometimes), idle watchers are a good place to do	1655	effect on its own sometimes), idle watchers are a good place to do
987	"pseudo-background processing", or delay processing stuff to after the	1656	"pseudo-background processing", or delay processing stuff to after the
988	event loop has handled all outstanding events.	1657	event loop has handled all outstanding events.
989		1658
		1659	=head3 Watcher-Specific Functions and Data Members
		1660
990	=over 4	1661	=over 4
991		1662
992	=item ev_idle_init (ev_signal *, callback)	1663	=item ev_idle_init (ev_signal *, callback)
993		1664
994	Initialises and configures the idle watcher - it has no parameters of any	1665	Initialises and configures the idle watcher - it has no parameters of any
995	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1666	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
996	believe me.	1667	believe me.
997		1668
998	=back	1669	=back
999		1670
		1671	=head3 Examples
		1672
1000	Example: dynamically allocate an C<ev_idle>, start it, and in the	1673	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1001	callback, free it. Alos, use no error checking, as usual.	1674	callback, free it. Also, use no error checking, as usual.
1002		1675
1003	static void	1676	static void
1004	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1677	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1005	{	1678	{
1006	free (w);	1679	free (w);
…		…
1011	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1684	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1012	ev_idle_init (idle_watcher, idle_cb);	1685	ev_idle_init (idle_watcher, idle_cb);
1013	ev_idle_start (loop, idle_cb);	1686	ev_idle_start (loop, idle_cb);
1014		1687
1015		1688
1016	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1689	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1017		1690
1018	Prepare and check watchers are usually (but not always) used in tandem:	1691	Prepare and check watchers are usually (but not always) used in tandem:
1019	prepare watchers get invoked before the process blocks and check watchers	1692	prepare watchers get invoked before the process blocks and check watchers
1020	afterwards.	1693	afterwards.
1021		1694
		1695	You I<must not> call C<ev_loop> or similar functions that enter
		1696	the current event loop from either C<ev_prepare> or C<ev_check>
		1697	watchers. Other loops than the current one are fine, however. The
		1698	rationale behind this is that you do not need to check for recursion in
		1699	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1700	C<ev_check> so if you have one watcher of each kind they will always be
		1701	called in pairs bracketing the blocking call.
		1702
1022	Their main purpose is to integrate other event mechanisms into libev and	1703	Their main purpose is to integrate other event mechanisms into libev and
1023	their use is somewhat advanced. This could be used, for example, to track	1704	their use is somewhat advanced. This could be used, for example, to track
1024	variable changes, implement your own watchers, integrate net-snmp or a	1705	variable changes, implement your own watchers, integrate net-snmp or a
1025	coroutine library and lots more.	1706	coroutine library and lots more. They are also occasionally useful if
		1707	you cache some data and want to flush it before blocking (for example,
		1708	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1709	watcher).
1026		1710
1027	This is done by examining in each prepare call which file descriptors need	1711	This is done by examining in each prepare call which file descriptors need
1028	to be watched by the other library, registering C<ev_io> watchers for	1712	to be watched by the other library, registering C<ev_io> watchers for
1029	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1713	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1030	provide just this functionality). Then, in the check watcher you check for	1714	provide just this functionality). Then, in the check watcher you check for
…		…
1040	with priority higher than or equal to the event loop and one coroutine	1724	with priority higher than or equal to the event loop and one coroutine
1041	of lower priority, but only once, using idle watchers to keep the event	1725	of lower priority, but only once, using idle watchers to keep the event
1042	loop from blocking if lower-priority coroutines are active, thus mapping	1726	loop from blocking if lower-priority coroutines are active, thus mapping
1043	low-priority coroutines to idle/background tasks).	1727	low-priority coroutines to idle/background tasks).
1044		1728
		1729	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1730	priority, to ensure that they are being run before any other watchers
		1731	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1732	too) should not activate ("feed") events into libev. While libev fully
		1733	supports this, they will be called before other C<ev_check> watchers
		1734	did their job. As C<ev_check> watchers are often used to embed other
		1735	(non-libev) event loops those other event loops might be in an unusable
		1736	state until their C<ev_check> watcher ran (always remind yourself to
		1737	coexist peacefully with others).
		1738
		1739	=head3 Watcher-Specific Functions and Data Members
		1740
1045	=over 4	1741	=over 4
1046		1742
1047	=item ev_prepare_init (ev_prepare *, callback)	1743	=item ev_prepare_init (ev_prepare *, callback)
1048		1744
1049	=item ev_check_init (ev_check *, callback)	1745	=item ev_check_init (ev_check *, callback)
…		…
1052	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1748	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1053	macros, but using them is utterly, utterly and completely pointless.	1749	macros, but using them is utterly, utterly and completely pointless.
1054		1750
1055	=back	1751	=back
1056		1752
1057	Example: *TODO*.	1753	=head3 Examples
1058		1754
		1755	There are a number of principal ways to embed other event loops or modules
		1756	into libev. Here are some ideas on how to include libadns into libev
		1757	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1758	use for an actually working example. Another Perl module named C<EV::Glib>
		1759	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1760	into the Glib event loop).
1059		1761
		1762	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1763	and in a check watcher, destroy them and call into libadns. What follows
		1764	is pseudo-code only of course. This requires you to either use a low
		1765	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1766	the callbacks for the IO/timeout watchers might not have been called yet.
		1767
		1768	static ev_io iow [nfd];
		1769	static ev_timer tw;
		1770
		1771	static void
		1772	io_cb (ev_loop *loop, ev_io *w, int revents)
		1773	{
		1774	}
		1775
		1776	// create io watchers for each fd and a timer before blocking
		1777	static void
		1778	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1779	{
		1780	int timeout = 3600000;
		1781	struct pollfd fds [nfd];
		1782	// actual code will need to loop here and realloc etc.
		1783	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1784
		1785	/* the callback is illegal, but won't be called as we stop during check */
		1786	ev_timer_init (&tw, 0, timeout * 1e-3);
		1787	ev_timer_start (loop, &tw);
		1788
		1789	// create one ev_io per pollfd
		1790	for (int i = 0; i < nfd; ++i)
		1791	{
		1792	ev_io_init (iow + i, io_cb, fds [i].fd,
		1793	((fds [i].events & POLLIN ? EV_READ : 0)
		1794	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1795
		1796	fds [i].revents = 0;
		1797	ev_io_start (loop, iow + i);
		1798	}
		1799	}
		1800
		1801	// stop all watchers after blocking
		1802	static void
		1803	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1804	{
		1805	ev_timer_stop (loop, &tw);
		1806
		1807	for (int i = 0; i < nfd; ++i)
		1808	{
		1809	// set the relevant poll flags
		1810	// could also call adns_processreadable etc. here
		1811	struct pollfd *fd = fds + i;
		1812	int revents = ev_clear_pending (iow + i);
		1813	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1814	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1815
		1816	// now stop the watcher
		1817	ev_io_stop (loop, iow + i);
		1818	}
		1819
		1820	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1821	}
		1822
		1823	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1824	in the prepare watcher and would dispose of the check watcher.
		1825
		1826	Method 3: If the module to be embedded supports explicit event
		1827	notification (adns does), you can also make use of the actual watcher
		1828	callbacks, and only destroy/create the watchers in the prepare watcher.
		1829
		1830	static void
		1831	timer_cb (EV_P_ ev_timer *w, int revents)
		1832	{
		1833	adns_state ads = (adns_state)w->data;
		1834	update_now (EV_A);
		1835
		1836	adns_processtimeouts (ads, &tv_now);
		1837	}
		1838
		1839	static void
		1840	io_cb (EV_P_ ev_io *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1846	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1847	}
		1848
		1849	// do not ever call adns_afterpoll
		1850
		1851	Method 4: Do not use a prepare or check watcher because the module you
		1852	want to embed is too inflexible to support it. Instead, youc na override
		1853	their poll function. The drawback with this solution is that the main
		1854	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1855	this.
		1856
		1857	static gint
		1858	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1859	{
		1860	int got_events = 0;
		1861
		1862	for (n = 0; n < nfds; ++n)
		1863	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1864
		1865	if (timeout >= 0)
		1866	// create/start timer
		1867
		1868	// poll
		1869	ev_loop (EV_A_ 0);
		1870
		1871	// stop timer again
		1872	if (timeout >= 0)
		1873	ev_timer_stop (EV_A_ &to);
		1874
		1875	// stop io watchers again - their callbacks should have set
		1876	for (n = 0; n < nfds; ++n)
		1877	ev_io_stop (EV_A_ iow [n]);
		1878
		1879	return got_events;
		1880	}
		1881
		1882
1060	=head2 C<ev_embed> - when one backend isn't enough	1883	=head2 C<ev_embed> - when one backend isn't enough...
1061		1884
1062	This is a rather advanced watcher type that lets you embed one event loop	1885	This is a rather advanced watcher type that lets you embed one event loop
1063	into another.	1886	into another (currently only C<ev_io> events are supported in the embedded
		1887	loop, other types of watchers might be handled in a delayed or incorrect
		1888	fashion and must not be used).
1064		1889
1065	There are primarily two reasons you would want that: work around bugs and	1890	There are primarily two reasons you would want that: work around bugs and
1066	prioritise I/O.	1891	prioritise I/O.
1067		1892
1068	As an example for a bug workaround, the kqueue backend might only support	1893	As an example for a bug workaround, the kqueue backend might only support
…		…
1077	to be watched and handled very quickly (with low latency), and even	1902	to be watched and handled very quickly (with low latency), and even
1078	priorities and idle watchers might have too much overhead. In this case	1903	priorities and idle watchers might have too much overhead. In this case
1079	you would put all the high priority stuff in one loop and all the rest in	1904	you would put all the high priority stuff in one loop and all the rest in
1080	a second one, and embed the second one in the first.	1905	a second one, and embed the second one in the first.
1081		1906
		1907	As long as the watcher is active, the callback will be invoked every time
		1908	there might be events pending in the embedded loop. The callback must then
		1909	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1910	their callbacks (you could also start an idle watcher to give the embedded
		1911	loop strictly lower priority for example). You can also set the callback
		1912	to C<0>, in which case the embed watcher will automatically execute the
		1913	embedded loop sweep.
		1914
1082	As long as the watcher is started it will automatically handle events. The	1915	As long as the watcher is started it will automatically handle events. The
1083	callback will be invoked whenever some events have been handled. You can	1916	callback will be invoked whenever some events have been handled. You can
1084	set the callback to C<0> to avoid having to specify one if you are not	1917	set the callback to C<0> to avoid having to specify one if you are not
1085	interested in that.	1918	interested in that.
1086		1919
…		…
1094	portable one.	1927	portable one.
1095		1928
1096	So when you want to use this feature you will always have to be prepared	1929	So when you want to use this feature you will always have to be prepared
1097	that you cannot get an embeddable loop. The recommended way to get around	1930	that you cannot get an embeddable loop. The recommended way to get around
1098	this is to have a separate variables for your embeddable loop, try to	1931	this is to have a separate variables for your embeddable loop, try to
1099	create it, and if that fails, use the normal loop for everything:	1932	create it, and if that fails, use the normal loop for everything.
		1933
		1934	=head3 Watcher-Specific Functions and Data Members
		1935
		1936	=over 4
		1937
		1938	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1939
		1940	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1941
		1942	Configures the watcher to embed the given loop, which must be
		1943	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1944	invoked automatically, otherwise it is the responsibility of the callback
		1945	to invoke it (it will continue to be called until the sweep has been done,
		1946	if you do not want thta, you need to temporarily stop the embed watcher).
		1947
		1948	=item ev_embed_sweep (loop, ev_embed *)
		1949
		1950	Make a single, non-blocking sweep over the embedded loop. This works
		1951	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1952	apropriate way for embedded loops.
		1953
		1954	=item struct ev_loop *other [read-only]
		1955
		1956	The embedded event loop.
		1957
		1958	=back
		1959
		1960	=head3 Examples
		1961
		1962	Example: Try to get an embeddable event loop and embed it into the default
		1963	event loop. If that is not possible, use the default loop. The default
		1964	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1965	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1966	used).
1100		1967
1101	struct ev_loop *loop_hi = ev_default_init (0);	1968	struct ev_loop *loop_hi = ev_default_init (0);
1102	struct ev_loop *loop_lo = 0;	1969	struct ev_loop *loop_lo = 0;
1103	struct ev_embed embed;	1970	struct ev_embed embed;
1104		1971
…		…
1115	ev_embed_start (loop_hi, &embed);	1982	ev_embed_start (loop_hi, &embed);
1116	}	1983	}
1117	else	1984	else
1118	loop_lo = loop_hi;	1985	loop_lo = loop_hi;
1119		1986
		1987	Example: Check if kqueue is available but not recommended and create
		1988	a kqueue backend for use with sockets (which usually work with any
		1989	kqueue implementation). Store the kqueue/socket-only event loop in
		1990	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		1991
		1992	struct ev_loop *loop = ev_default_init (0);
		1993	struct ev_loop *loop_socket = 0;
		1994	struct ev_embed embed;
		1995
		1996	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		1997	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		1998	{
		1999	ev_embed_init (&embed, 0, loop_socket);
		2000	ev_embed_start (loop, &embed);
		2001	}
		2002
		2003	if (!loop_socket)
		2004	loop_socket = loop;
		2005
		2006	// now use loop_socket for all sockets, and loop for everything else
		2007
		2008
		2009	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2010
		2011	Fork watchers are called when a C<fork ()> was detected (usually because
		2012	whoever is a good citizen cared to tell libev about it by calling
		2013	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2014	event loop blocks next and before C<ev_check> watchers are being called,
		2015	and only in the child after the fork. If whoever good citizen calling
		2016	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2017	handlers will be invoked, too, of course.
		2018
		2019	=head3 Watcher-Specific Functions and Data Members
		2020
1120	=over 4	2021	=over 4
1121		2022
1122	=item ev_embed_init (ev_embed *, callback, struct ev_loop *loop)	2023	=item ev_fork_init (ev_signal *, callback)
1123		2024
1124	=item ev_embed_set (ev_embed *, callback, struct ev_loop *loop)	2025	Initialises and configures the fork watcher - it has no parameters of any
1125		2026	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1126	Configures the watcher to embed the given loop, which must be embeddable.	2027	believe me.
1127		2028
1128	=back	2029	=back
1129		2030
1130		2031
1131	=head1 OTHER FUNCTIONS	2032	=head1 OTHER FUNCTIONS
…		…
1164	/* stdin might have data for us, joy! */;	2065	/* stdin might have data for us, joy! */;
1165	}	2066	}
1166		2067
1167	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2068	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1168		2069
1169	=item ev_feed_event (loop, watcher, int events)	2070	=item ev_feed_event (ev_loop *, watcher *, int revents)
1170		2071
1171	Feeds the given event set into the event loop, as if the specified event	2072	Feeds the given event set into the event loop, as if the specified event
1172	had happened for the specified watcher (which must be a pointer to an	2073	had happened for the specified watcher (which must be a pointer to an
1173	initialised but not necessarily started event watcher).	2074	initialised but not necessarily started event watcher).
1174		2075
1175	=item ev_feed_fd_event (loop, int fd, int revents)	2076	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
1176		2077
1177	Feed an event on the given fd, as if a file descriptor backend detected	2078	Feed an event on the given fd, as if a file descriptor backend detected
1178	the given events it.	2079	the given events it.
1179		2080
1180	=item ev_feed_signal_event (loop, int signum)	2081	=item ev_feed_signal_event (ev_loop *loop, int signum)
1181		2082
1182	Feed an event as if the given signal occured (loop must be the default loop!).	2083	Feed an event as if the given signal occured (C<loop> must be the default
		2084	loop!).
1183		2085
1184	=back	2086	=back
1185		2087
1186		2088
1187	=head1 LIBEVENT EMULATION	2089	=head1 LIBEVENT EMULATION
…		…
1211		2113
1212	=back	2114	=back
1213		2115
1214	=head1 C++ SUPPORT	2116	=head1 C++ SUPPORT
1215		2117
1216	TBD.	2118	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		2119	you to use some convinience methods to start/stop watchers and also change
		2120	the callback model to a model using method callbacks on objects.
		2121
		2122	To use it,
		2123
		2124	#include <ev++.h>
		2125
		2126	This automatically includes F<ev.h> and puts all of its definitions (many
		2127	of them macros) into the global namespace. All C++ specific things are
		2128	put into the C<ev> namespace. It should support all the same embedding
		2129	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2130
		2131	Care has been taken to keep the overhead low. The only data member the C++
		2132	classes add (compared to plain C-style watchers) is the event loop pointer
		2133	that the watcher is associated with (or no additional members at all if
		2134	you disable C<EV_MULTIPLICITY> when embedding libev).
		2135
		2136	Currently, functions, and static and non-static member functions can be
		2137	used as callbacks. Other types should be easy to add as long as they only
		2138	need one additional pointer for context. If you need support for other
		2139	types of functors please contact the author (preferably after implementing
		2140	it).
		2141
		2142	Here is a list of things available in the C<ev> namespace:
		2143
		2144	=over 4
		2145
		2146	=item C<ev::READ>, C<ev::WRITE> etc.
		2147
		2148	These are just enum values with the same values as the C<EV_READ> etc.
		2149	macros from F<ev.h>.
		2150
		2151	=item C<ev::tstamp>, C<ev::now>
		2152
		2153	Aliases to the same types/functions as with the C<ev_> prefix.
		2154
		2155	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2156
		2157	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2158	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2159	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2160	defines by many implementations.
		2161
		2162	All of those classes have these methods:
		2163
		2164	=over 4
		2165
		2166	=item ev::TYPE::TYPE ()
		2167
		2168	=item ev::TYPE::TYPE (struct ev_loop *)
		2169
		2170	=item ev::TYPE::~TYPE
		2171
		2172	The constructor (optionally) takes an event loop to associate the watcher
		2173	with. If it is omitted, it will use C<EV_DEFAULT>.
		2174
		2175	The constructor calls C<ev_init> for you, which means you have to call the
		2176	C<set> method before starting it.
		2177
		2178	It will not set a callback, however: You have to call the templated C<set>
		2179	method to set a callback before you can start the watcher.
		2180
		2181	(The reason why you have to use a method is a limitation in C++ which does
		2182	not allow explicit template arguments for constructors).
		2183
		2184	The destructor automatically stops the watcher if it is active.
		2185
		2186	=item w->set<class, &class::method> (object *)
		2187
		2188	This method sets the callback method to call. The method has to have a
		2189	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2190	first argument and the C<revents> as second. The object must be given as
		2191	parameter and is stored in the C<data> member of the watcher.
		2192
		2193	This method synthesizes efficient thunking code to call your method from
		2194	the C callback that libev requires. If your compiler can inline your
		2195	callback (i.e. it is visible to it at the place of the C<set> call and
		2196	your compiler is good :), then the method will be fully inlined into the
		2197	thunking function, making it as fast as a direct C callback.
		2198
		2199	Example: simple class declaration and watcher initialisation
		2200
		2201	struct myclass
		2202	{
		2203	void io_cb (ev::io &w, int revents) { }
		2204	}
		2205
		2206	myclass obj;
		2207	ev::io iow;
		2208	iow.set <myclass, &myclass::io_cb> (&obj);
		2209
		2210	=item w->set<function> (void *data = 0)
		2211
		2212	Also sets a callback, but uses a static method or plain function as
		2213	callback. The optional C<data> argument will be stored in the watcher's
		2214	C<data> member and is free for you to use.
		2215
		2216	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2217
		2218	See the method-C<set> above for more details.
		2219
		2220	Example:
		2221
		2222	static void io_cb (ev::io &w, int revents) { }
		2223	iow.set <io_cb> ();
		2224
		2225	=item w->set (struct ev_loop *)
		2226
		2227	Associates a different C<struct ev_loop> with this watcher. You can only
		2228	do this when the watcher is inactive (and not pending either).
		2229
		2230	=item w->set ([args])
		2231
		2232	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2233	called at least once. Unlike the C counterpart, an active watcher gets
		2234	automatically stopped and restarted when reconfiguring it with this
		2235	method.
		2236
		2237	=item w->start ()
		2238
		2239	Starts the watcher. Note that there is no C<loop> argument, as the
		2240	constructor already stores the event loop.
		2241
		2242	=item w->stop ()
		2243
		2244	Stops the watcher if it is active. Again, no C<loop> argument.
		2245
		2246	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2247
		2248	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2249	C<ev_TYPE_again> function.
		2250
		2251	=item w->sweep () (C<ev::embed> only)
		2252
		2253	Invokes C<ev_embed_sweep>.
		2254
		2255	=item w->update () (C<ev::stat> only)
		2256
		2257	Invokes C<ev_stat_stat>.
		2258
		2259	=back
		2260
		2261	=back
		2262
		2263	Example: Define a class with an IO and idle watcher, start one of them in
		2264	the constructor.
		2265
		2266	class myclass
		2267	{
		2268	ev_io io; void io_cb (ev::io &w, int revents);
		2269	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2270
		2271	myclass ();
		2272	}
		2273
		2274	myclass::myclass (int fd)
		2275	{
		2276	io .set <myclass, &myclass::io_cb > (this);
		2277	idle.set <myclass, &myclass::idle_cb> (this);
		2278
		2279	io.start (fd, ev::READ);
		2280	}
		2281
		2282
		2283	=head1 MACRO MAGIC
		2284
		2285	Libev can be compiled with a variety of options, the most fundamantal
		2286	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2287	functions and callbacks have an initial C<struct ev_loop *> argument.
		2288
		2289	To make it easier to write programs that cope with either variant, the
		2290	following macros are defined:
		2291
		2292	=over 4
		2293
		2294	=item C<EV_A>, C<EV_A_>
		2295
		2296	This provides the loop I<argument> for functions, if one is required ("ev
		2297	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2298	C<EV_A_> is used when other arguments are following. Example:
		2299
		2300	ev_unref (EV_A);
		2301	ev_timer_add (EV_A_ watcher);
		2302	ev_loop (EV_A_ 0);
		2303
		2304	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2305	which is often provided by the following macro.
		2306
		2307	=item C<EV_P>, C<EV_P_>
		2308
		2309	This provides the loop I<parameter> for functions, if one is required ("ev
		2310	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2311	C<EV_P_> is used when other parameters are following. Example:
		2312
		2313	// this is how ev_unref is being declared
		2314	static void ev_unref (EV_P);
		2315
		2316	// this is how you can declare your typical callback
		2317	static void cb (EV_P_ ev_timer *w, int revents)
		2318
		2319	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2320	suitable for use with C<EV_A>.
		2321
		2322	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2323
		2324	Similar to the other two macros, this gives you the value of the default
		2325	loop, if multiple loops are supported ("ev loop default").
		2326
		2327	=back
		2328
		2329	Example: Declare and initialise a check watcher, utilising the above
		2330	macros so it will work regardless of whether multiple loops are supported
		2331	or not.
		2332
		2333	static void
		2334	check_cb (EV_P_ ev_timer *w, int revents)
		2335	{
		2336	ev_check_stop (EV_A_ w);
		2337	}
		2338
		2339	ev_check check;
		2340	ev_check_init (&check, check_cb);
		2341	ev_check_start (EV_DEFAULT_ &check);
		2342	ev_loop (EV_DEFAULT_ 0);
		2343
		2344	=head1 EMBEDDING
		2345
		2346	Libev can (and often is) directly embedded into host
		2347	applications. Examples of applications that embed it include the Deliantra
		2348	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2349	and rxvt-unicode.
		2350
		2351	The goal is to enable you to just copy the necessary files into your
		2352	source directory without having to change even a single line in them, so
		2353	you can easily upgrade by simply copying (or having a checked-out copy of
		2354	libev somewhere in your source tree).
		2355
		2356	=head2 FILESETS
		2357
		2358	Depending on what features you need you need to include one or more sets of files
		2359	in your app.
		2360
		2361	=head3 CORE EVENT LOOP
		2362
		2363	To include only the libev core (all the C<ev_*> functions), with manual
		2364	configuration (no autoconf):
		2365
		2366	#define EV_STANDALONE 1
		2367	#include "ev.c"
		2368
		2369	This will automatically include F<ev.h>, too, and should be done in a
		2370	single C source file only to provide the function implementations. To use
		2371	it, do the same for F<ev.h> in all files wishing to use this API (best
		2372	done by writing a wrapper around F<ev.h> that you can include instead and
		2373	where you can put other configuration options):
		2374
		2375	#define EV_STANDALONE 1
		2376	#include "ev.h"
		2377
		2378	Both header files and implementation files can be compiled with a C++
		2379	compiler (at least, thats a stated goal, and breakage will be treated
		2380	as a bug).
		2381
		2382	You need the following files in your source tree, or in a directory
		2383	in your include path (e.g. in libev/ when using -Ilibev):
		2384
		2385	ev.h
		2386	ev.c
		2387	ev_vars.h
		2388	ev_wrap.h
		2389
		2390	ev_win32.c required on win32 platforms only
		2391
		2392	ev_select.c only when select backend is enabled (which is enabled by default)
		2393	ev_poll.c only when poll backend is enabled (disabled by default)
		2394	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2395	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2396	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2397
		2398	F<ev.c> includes the backend files directly when enabled, so you only need
		2399	to compile this single file.
		2400
		2401	=head3 LIBEVENT COMPATIBILITY API
		2402
		2403	To include the libevent compatibility API, also include:
		2404
		2405	#include "event.c"
		2406
		2407	in the file including F<ev.c>, and:
		2408
		2409	#include "event.h"
		2410
		2411	in the files that want to use the libevent API. This also includes F<ev.h>.
		2412
		2413	You need the following additional files for this:
		2414
		2415	event.h
		2416	event.c
		2417
		2418	=head3 AUTOCONF SUPPORT
		2419
		2420	Instead of using C<EV_STANDALONE=1> and providing your config in
		2421	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2422	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2423	include F<config.h> and configure itself accordingly.
		2424
		2425	For this of course you need the m4 file:
		2426
		2427	libev.m4
		2428
		2429	=head2 PREPROCESSOR SYMBOLS/MACROS
		2430
		2431	Libev can be configured via a variety of preprocessor symbols you have to define
		2432	before including any of its files. The default is not to build for multiplicity
		2433	and only include the select backend.
		2434
		2435	=over 4
		2436
		2437	=item EV_STANDALONE
		2438
		2439	Must always be C<1> if you do not use autoconf configuration, which
		2440	keeps libev from including F<config.h>, and it also defines dummy
		2441	implementations for some libevent functions (such as logging, which is not
		2442	supported). It will also not define any of the structs usually found in
		2443	F<event.h> that are not directly supported by the libev core alone.
		2444
		2445	=item EV_USE_MONOTONIC
		2446
		2447	If defined to be C<1>, libev will try to detect the availability of the
		2448	monotonic clock option at both compiletime and runtime. Otherwise no use
		2449	of the monotonic clock option will be attempted. If you enable this, you
		2450	usually have to link against librt or something similar. Enabling it when
		2451	the functionality isn't available is safe, though, although you have
		2452	to make sure you link against any libraries where the C<clock_gettime>
		2453	function is hiding in (often F<-lrt>).
		2454
		2455	=item EV_USE_REALTIME
		2456
		2457	If defined to be C<1>, libev will try to detect the availability of the
		2458	realtime clock option at compiletime (and assume its availability at
		2459	runtime if successful). Otherwise no use of the realtime clock option will
		2460	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2461	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2462	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2463
		2464	=item EV_USE_NANOSLEEP
		2465
		2466	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2467	and will use it for delays. Otherwise it will use C<select ()>.
		2468
		2469	=item EV_USE_SELECT
		2470
		2471	If undefined or defined to be C<1>, libev will compile in support for the
		2472	C<select>(2) backend. No attempt at autodetection will be done: if no
		2473	other method takes over, select will be it. Otherwise the select backend
		2474	will not be compiled in.
		2475
		2476	=item EV_SELECT_USE_FD_SET
		2477
		2478	If defined to C<1>, then the select backend will use the system C<fd_set>
		2479	structure. This is useful if libev doesn't compile due to a missing
		2480	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2481	exotic systems. This usually limits the range of file descriptors to some
		2482	low limit such as 1024 or might have other limitations (winsocket only
		2483	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2484	influence the size of the C<fd_set> used.
		2485
		2486	=item EV_SELECT_IS_WINSOCKET
		2487
		2488	When defined to C<1>, the select backend will assume that
		2489	select/socket/connect etc. don't understand file descriptors but
		2490	wants osf handles on win32 (this is the case when the select to
		2491	be used is the winsock select). This means that it will call
		2492	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2493	it is assumed that all these functions actually work on fds, even
		2494	on win32. Should not be defined on non-win32 platforms.
		2495
		2496	=item EV_USE_POLL
		2497
		2498	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2499	backend. Otherwise it will be enabled on non-win32 platforms. It
		2500	takes precedence over select.
		2501
		2502	=item EV_USE_EPOLL
		2503
		2504	If defined to be C<1>, libev will compile in support for the Linux
		2505	C<epoll>(7) backend. Its availability will be detected at runtime,
		2506	otherwise another method will be used as fallback. This is the
		2507	preferred backend for GNU/Linux systems.
		2508
		2509	=item EV_USE_KQUEUE
		2510
		2511	If defined to be C<1>, libev will compile in support for the BSD style
		2512	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2513	otherwise another method will be used as fallback. This is the preferred
		2514	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2515	supports some types of fds correctly (the only platform we found that
		2516	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2517	not be used unless explicitly requested. The best way to use it is to find
		2518	out whether kqueue supports your type of fd properly and use an embedded
		2519	kqueue loop.
		2520
		2521	=item EV_USE_PORT
		2522
		2523	If defined to be C<1>, libev will compile in support for the Solaris
		2524	10 port style backend. Its availability will be detected at runtime,
		2525	otherwise another method will be used as fallback. This is the preferred
		2526	backend for Solaris 10 systems.
		2527
		2528	=item EV_USE_DEVPOLL
		2529
		2530	reserved for future expansion, works like the USE symbols above.
		2531
		2532	=item EV_USE_INOTIFY
		2533
		2534	If defined to be C<1>, libev will compile in support for the Linux inotify
		2535	interface to speed up C<ev_stat> watchers. Its actual availability will
		2536	be detected at runtime.
		2537
		2538	=item EV_H
		2539
		2540	The name of the F<ev.h> header file used to include it. The default if
		2541	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
		2542	virtually rename the F<ev.h> header file in case of conflicts.
		2543
		2544	=item EV_CONFIG_H
		2545
		2546	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2547	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2548	C<EV_H>, above.
		2549
		2550	=item EV_EVENT_H
		2551
		2552	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2553	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
		2554
		2555	=item EV_PROTOTYPES
		2556
		2557	If defined to be C<0>, then F<ev.h> will not define any function
		2558	prototypes, but still define all the structs and other symbols. This is
		2559	occasionally useful if you want to provide your own wrapper functions
		2560	around libev functions.
		2561
		2562	=item EV_MULTIPLICITY
		2563
		2564	If undefined or defined to C<1>, then all event-loop-specific functions
		2565	will have the C<struct ev_loop *> as first argument, and you can create
		2566	additional independent event loops. Otherwise there will be no support
		2567	for multiple event loops and there is no first event loop pointer
		2568	argument. Instead, all functions act on the single default loop.
		2569
		2570	=item EV_MINPRI
		2571
		2572	=item EV_MAXPRI
		2573
		2574	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2575	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2576	provide for more priorities by overriding those symbols (usually defined
		2577	to be C<-2> and C<2>, respectively).
		2578
		2579	When doing priority-based operations, libev usually has to linearly search
		2580	all the priorities, so having many of them (hundreds) uses a lot of space
		2581	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2582	fine.
		2583
		2584	If your embedding app does not need any priorities, defining these both to
		2585	C<0> will save some memory and cpu.
		2586
		2587	=item EV_PERIODIC_ENABLE
		2588
		2589	If undefined or defined to be C<1>, then periodic timers are supported. If
		2590	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2591	code.
		2592
		2593	=item EV_IDLE_ENABLE
		2594
		2595	If undefined or defined to be C<1>, then idle watchers are supported. If
		2596	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2597	code.
		2598
		2599	=item EV_EMBED_ENABLE
		2600
		2601	If undefined or defined to be C<1>, then embed watchers are supported. If
		2602	defined to be C<0>, then they are not.
		2603
		2604	=item EV_STAT_ENABLE
		2605
		2606	If undefined or defined to be C<1>, then stat watchers are supported. If
		2607	defined to be C<0>, then they are not.
		2608
		2609	=item EV_FORK_ENABLE
		2610
		2611	If undefined or defined to be C<1>, then fork watchers are supported. If
		2612	defined to be C<0>, then they are not.
		2613
		2614	=item EV_MINIMAL
		2615
		2616	If you need to shave off some kilobytes of code at the expense of some
		2617	speed, define this symbol to C<1>. Currently only used for gcc to override
		2618	some inlining decisions, saves roughly 30% codesize of amd64.
		2619
		2620	=item EV_PID_HASHSIZE
		2621
		2622	C<ev_child> watchers use a small hash table to distribute workload by
		2623	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2624	than enough. If you need to manage thousands of children you might want to
		2625	increase this value (I<must> be a power of two).
		2626
		2627	=item EV_INOTIFY_HASHSIZE
		2628
		2629	C<ev_stat> watchers use a small hash table to distribute workload by
		2630	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2631	usually more than enough. If you need to manage thousands of C<ev_stat>
		2632	watchers you might want to increase this value (I<must> be a power of
		2633	two).
		2634
		2635	=item EV_COMMON
		2636
		2637	By default, all watchers have a C<void *data> member. By redefining
		2638	this macro to a something else you can include more and other types of
		2639	members. You have to define it each time you include one of the files,
		2640	though, and it must be identical each time.
		2641
		2642	For example, the perl EV module uses something like this:
		2643
		2644	#define EV_COMMON \
		2645	SV *self; /* contains this struct */ \
		2646	SV *cb_sv, *fh /* note no trailing ";" */
		2647
		2648	=item EV_CB_DECLARE (type)
		2649
		2650	=item EV_CB_INVOKE (watcher, revents)
		2651
		2652	=item ev_set_cb (ev, cb)
		2653
		2654	Can be used to change the callback member declaration in each watcher,
		2655	and the way callbacks are invoked and set. Must expand to a struct member
		2656	definition and a statement, respectively. See the F<ev.h> header file for
		2657	their default definitions. One possible use for overriding these is to
		2658	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2659	method calls instead of plain function calls in C++.
		2660
		2661	=head2 EXPORTED API SYMBOLS
		2662
		2663	If you need to re-export the API (e.g. via a dll) and you need a list of
		2664	exported symbols, you can use the provided F<Symbol.*> files which list
		2665	all public symbols, one per line:
		2666
		2667	Symbols.ev for libev proper
		2668	Symbols.event for the libevent emulation
		2669
		2670	This can also be used to rename all public symbols to avoid clashes with
		2671	multiple versions of libev linked together (which is obviously bad in
		2672	itself, but sometimes it is inconvinient to avoid this).
		2673
		2674	A sed command like this will create wrapper C<#define>'s that you need to
		2675	include before including F<ev.h>:
		2676
		2677	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2678
		2679	This would create a file F<wrap.h> which essentially looks like this:
		2680
		2681	#define ev_backend myprefix_ev_backend
		2682	#define ev_check_start myprefix_ev_check_start
		2683	#define ev_check_stop myprefix_ev_check_stop
		2684	...
		2685
		2686	=head2 EXAMPLES
		2687
		2688	For a real-world example of a program the includes libev
		2689	verbatim, you can have a look at the EV perl module
		2690	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2691	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2692	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2693	will be compiled. It is pretty complex because it provides its own header
		2694	file.
		2695
		2696	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2697	that everybody includes and which overrides some configure choices:
		2698
		2699	#define EV_MINIMAL 1
		2700	#define EV_USE_POLL 0
		2701	#define EV_MULTIPLICITY 0
		2702	#define EV_PERIODIC_ENABLE 0
		2703	#define EV_STAT_ENABLE 0
		2704	#define EV_FORK_ENABLE 0
		2705	#define EV_CONFIG_H <config.h>
		2706	#define EV_MINPRI 0
		2707	#define EV_MAXPRI 0
		2708
		2709	#include "ev++.h"
		2710
		2711	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2712
		2713	#include "ev_cpp.h"
		2714	#include "ev.c"
		2715
		2716
		2717	=head1 COMPLEXITIES
		2718
		2719	In this section the complexities of (many of) the algorithms used inside
		2720	libev will be explained. For complexity discussions about backends see the
		2721	documentation for C<ev_default_init>.
		2722
		2723	All of the following are about amortised time: If an array needs to be
		2724	extended, libev needs to realloc and move the whole array, but this
		2725	happens asymptotically never with higher number of elements, so O(1) might
		2726	mean it might do a lengthy realloc operation in rare cases, but on average
		2727	it is much faster and asymptotically approaches constant time.
		2728
		2729	=over 4
		2730
		2731	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2732
		2733	This means that, when you have a watcher that triggers in one hour and
		2734	there are 100 watchers that would trigger before that then inserting will
		2735	have to skip roughly seven (C<ld 100>) of these watchers.
		2736
		2737	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2738
		2739	That means that changing a timer costs less than removing/adding them
		2740	as only the relative motion in the event queue has to be paid for.
		2741
		2742	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2743
		2744	These just add the watcher into an array or at the head of a list.
		2745
		2746	=item Stopping check/prepare/idle watchers: O(1)
		2747
		2748	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2749
		2750	These watchers are stored in lists then need to be walked to find the
		2751	correct watcher to remove. The lists are usually short (you don't usually
		2752	have many watchers waiting for the same fd or signal).
		2753
		2754	=item Finding the next timer in each loop iteration: O(1)
		2755
		2756	By virtue of using a binary heap, the next timer is always found at the
		2757	beginning of the storage array.
		2758
		2759	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2760
		2761	A change means an I/O watcher gets started or stopped, which requires
		2762	libev to recalculate its status (and possibly tell the kernel, depending
		2763	on backend and wether C<ev_io_set> was used).
		2764
		2765	=item Activating one watcher (putting it into the pending state): O(1)
		2766
		2767	=item Priority handling: O(number_of_priorities)
		2768
		2769	Priorities are implemented by allocating some space for each
		2770	priority. When doing priority-based operations, libev usually has to
		2771	linearly search all the priorities, but starting/stopping and activating
		2772	watchers becomes O(1) w.r.t. prioritiy handling.
		2773
		2774	=back
		2775
1217		2776
1218	=head1 AUTHOR	2777	=head1 AUTHOR
1219		2778
1220	Marc Lehmann <libev@schmorp.de>.	2779	Marc Lehmann <libev@schmorp.de>.
1221		2780

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