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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
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
52		106
53	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
54		108
55	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
56	library in any way.	110	library in any way.
…		…
61		115
62	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
63	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
64	you actually want to know.	118	you actually want to know.
65		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
66	=item int ev_version_major ()	126	=item int ev_version_major ()
67		127
68	=item int ev_version_minor ()	128	=item int ev_version_minor ()
69		129
70	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
71	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
72	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
73	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
74	version of the library your program was compiled against.	134	version of the library your program was compiled against.
75		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
76	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,
77	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
78	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
79	not a problem.	142	not a problem.
80		143
81	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
82	version:	145	version.
83		146
84	assert (("libev version mismatch",	147	assert (("libev version mismatch",
85	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
86	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
87		150
…		…
117		180
118	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
119		182
120	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
121		184
122	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
123	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
124	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
125	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
126	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
127		191
128	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
129	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,
130	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.
131		195
132	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
133	retries: better than mine).	197	retries).
134		198
135	static void *	199	static void *
136	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
137	{	201	{
138	for (;;)	202	for (;;)
139	{	203	{
140	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
141		205
…		…
157	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
158	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
159	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
160	(such as abort).	224	(such as abort).
161		225
162	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
163		227
164	static void	228	static void
165	fatal_error (const char *msg)	229	fatal_error (const char *msg)
166	{	230	{
167	perror (msg);	231	perror (msg);
…		…
217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
218	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
219	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
220	around bugs.	284	around bugs.
221		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
222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
223		307
224	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
225	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,
226	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
227	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
228	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.
229		320
230	=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)
231		322
232	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
233	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
234	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
235	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.
236		329
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		331
239	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,
240	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
241	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),
242	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.
243		339
244	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
245	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
246	(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
247	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
248	well if you register events for both fds.	344	very well if you register events for both fds.
249		345
250	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
251	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
252	(or space) is available.	348	(or space) is available.
253		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
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		358
256	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
257	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
258	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
259	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
260	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
261	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.
262		370
263	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
264	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
265	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
266	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
267	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.
268		386
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		388
271	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.
272		393
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		395
275	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,
276	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)).
277		398
278	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
279	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
280	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.
281		407
282	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
283		409
284	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
285	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
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
287		415
288	=back	416	=back
289		417
290	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
291	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
…		…
313	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
314	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
315	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
316	undefined behaviour (or a failed assertion if assertions are enabled).	444	undefined behaviour (or a failed assertion if assertions are enabled).
317		445
318	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.
319		447
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	448	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	449	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	450	fatal ("no epoll found here, maybe it hides under your chair");
323		451
…		…
326	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
327	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
328	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
329	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
330	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
331	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	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>).
333		470
334	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
335		472
336	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
337	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
361		498
362	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
363	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
364	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.
365		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
366	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
367		514
368	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
369	use.	516	use.
370		517
…		…
372		519
373	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
374	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
375	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
376	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
377	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
378		525
379	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
380		527
381	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
382	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
…		…
403	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
404	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
405		552
406	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
407		554
408	* If there are no active watchers (reference count is zero), return.	555	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	556	* If EVFLAG_FORKCHECK was used, check for a fork.
		557	- If a fork was detected, queue and call all fork watchers.
		558	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	559	- If we have been forked, recreate the kernel state.
411	- Update the kernel state with all outstanding changes.	560	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	561	- Update the "event loop time".
413	- Calculate for how long to block.	562	- Calculate for how long to sleep or block, if at all
		563	(active idle watchers, EVLOOP_NONBLOCK or not having
		564	any active watchers at all will result in not sleeping).
		565	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	566	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	567	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	568	- Update the "event loop time" and do time jump handling.
417	- Queue all outstanding timers.	569	- Queue all outstanding timers.
418	- Queue all outstanding periodics.	570	- Queue all outstanding periodics.
419	- If no events are pending now, queue all idle watchers.	571	- If no events are pending now, queue all idle watchers.
420	- Queue all check watchers.	572	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	573	- Call all queued watchers in reverse order (i.e. check watchers first).
422	Signals and child watchers are implemented as I/O watchers, and will	574	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	575	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	576	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	577	were used, or there are no active watchers, return, otherwise
		578	continue with step *.
426		579
427	Example: queue some jobs and then loop until no events are outsanding	580	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	581	anymore.
429		582
430	... queue jobs here, make sure they register event watchers as long	583	... queue jobs here, make sure they register event watchers as long
431	... as they still have work to do (even an idle watcher will do..)	584	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	585	ev_loop (my_loop, 0);
…		…
436		589
437	Can be used to make a call to C<ev_loop> return early (but only after it	590	Can be used to make a call to C<ev_loop> return early (but only after it
438	has processed all outstanding events). The C<how> argument must be either	591	has processed all outstanding events). The C<how> argument must be either
439	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	592	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
440	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	593	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		594
		595	This "unloop state" will be cleared when entering C<ev_loop> again.
441		596
442	=item ev_ref (loop)	597	=item ev_ref (loop)
443		598
444	=item ev_unref (loop)	599	=item ev_unref (loop)
445		600
…		…
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	605	returning, ev_unref() after starting, and ev_ref() before stopping it. For
451	example, libev itself uses this for its internal signal pipe: It is not	606	example, libev itself uses this for its internal signal pipe: It is not
452	visible to the libev user and should not keep C<ev_loop> from exiting if	607	visible to the libev user and should not keep C<ev_loop> from exiting if
453	no event watchers registered by it are active. It is also an excellent	608	no event watchers registered by it are active. It is also an excellent
454	way to do this for generic recurring timers or from within third-party	609	way to do this for generic recurring timers or from within third-party
455	libraries. Just remember to I<unref after start> and I<ref before stop>.	610	libraries. Just remember to I<unref after start> and I<ref before stop>
		611	(but only if the watcher wasn't active before, or was active before,
		612	respectively).
456		613
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	614	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	615	running when nothing else is active.
459		616
460	struct dv_signal exitsig;	617	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	618	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	619	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	620	evf_unref (loop);
464		621
465	Example: for some weird reason, unregister the above signal handler again.	622	Example: For some weird reason, unregister the above signal handler again.
466		623
467	ev_ref (myloop);	624	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	625	ev_signal_stop (loop, &exitsig);
		626
		627	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		628
		629	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		630
		631	These advanced functions influence the time that libev will spend waiting
		632	for events. Both are by default C<0>, meaning that libev will try to
		633	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		634
		635	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		636	allows libev to delay invocation of I/O and timer/periodic callbacks to
		637	increase efficiency of loop iterations.
		638
		639	The background is that sometimes your program runs just fast enough to
		640	handle one (or very few) event(s) per loop iteration. While this makes
		641	the program responsive, it also wastes a lot of CPU time to poll for new
		642	events, especially with backends like C<select ()> which have a high
		643	overhead for the actual polling but can deliver many events at once.
		644
		645	By setting a higher I<io collect interval> you allow libev to spend more
		646	time collecting I/O events, so you can handle more events per iteration,
		647	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		648	C<ev_timer>) will be not affected. Setting this to a non-null value will
		649	introduce an additional C<ev_sleep ()> call into most loop iterations.
		650
		651	Likewise, by setting a higher I<timeout collect interval> you allow libev
		652	to spend more time collecting timeouts, at the expense of increased
		653	latency (the watcher callback will be called later). C<ev_io> watchers
		654	will not be affected. Setting this to a non-null value will not introduce
		655	any overhead in libev.
		656
		657	Many (busy) programs can usually benefit by setting the io collect
		658	interval to a value near C<0.1> or so, which is often enough for
		659	interactive servers (of course not for games), likewise for timeouts. It
		660	usually doesn't make much sense to set it to a lower value than C<0.01>,
		661	as this approsaches the timing granularity of most systems.
469		662
470	=back	663	=back
471		664
472		665
473	=head1 ANATOMY OF A WATCHER	666	=head1 ANATOMY OF A WATCHER
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	846	=item bool ev_is_pending (ev_TYPE *watcher)
654		847
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	848	Returns a true value iff the watcher is pending, (i.e. it has outstanding
656	events but its callback has not yet been invoked). As long as a watcher	849	events but its callback has not yet been invoked). As long as a watcher
657	is pending (but not active) you must not call an init function on it (but	850	is pending (but not active) you must not call an init function on it (but
658	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	851	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	852	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		853	it).
660		854
661	=item callback = ev_cb (ev_TYPE *watcher)	855	=item callback ev_cb (ev_TYPE *watcher)
662		856
663	Returns the callback currently set on the watcher.	857	Returns the callback currently set on the watcher.
664		858
665	=item ev_cb_set (ev_TYPE *watcher, callback)	859	=item ev_cb_set (ev_TYPE *watcher, callback)
666		860
667	Change the callback. You can change the callback at virtually any time	861	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	862	(modulo threads).
		863
		864	=item ev_set_priority (ev_TYPE *watcher, priority)
		865
		866	=item int ev_priority (ev_TYPE *watcher)
		867
		868	Set and query the priority of the watcher. The priority is a small
		869	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		870	(default: C<-2>). Pending watchers with higher priority will be invoked
		871	before watchers with lower priority, but priority will not keep watchers
		872	from being executed (except for C<ev_idle> watchers).
		873
		874	This means that priorities are I<only> used for ordering callback
		875	invocation after new events have been received. This is useful, for
		876	example, to reduce latency after idling, or more often, to bind two
		877	watchers on the same event and make sure one is called first.
		878
		879	If you need to suppress invocation when higher priority events are pending
		880	you need to look at C<ev_idle> watchers, which provide this functionality.
		881
		882	You I<must not> change the priority of a watcher as long as it is active or
		883	pending.
		884
		885	The default priority used by watchers when no priority has been set is
		886	always C<0>, which is supposed to not be too high and not be too low :).
		887
		888	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		889	fine, as long as you do not mind that the priority value you query might
		890	or might not have been adjusted to be within valid range.
		891
		892	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		893
		894	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		895	C<loop> nor C<revents> need to be valid as long as the watcher callback
		896	can deal with that fact.
		897
		898	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		899
		900	If the watcher is pending, this function returns clears its pending status
		901	and returns its C<revents> bitset (as if its callback was invoked). If the
		902	watcher isn't pending it does nothing and returns C<0>.
669		903
670	=back	904	=back
671		905
672		906
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	907	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
694	{	928	{
695	struct my_io *w = (struct my_io *)w_;	929	struct my_io *w = (struct my_io *)w_;
696	...	930	...
697	}	931	}
698		932
699	More interesting and less C-conformant ways of catsing your callback type	933	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	934	instead have been omitted.
		935
		936	Another common scenario is having some data structure with multiple
		937	watchers:
		938
		939	struct my_biggy
		940	{
		941	int some_data;
		942	ev_timer t1;
		943	ev_timer t2;
		944	}
		945
		946	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		947	you need to use C<offsetof>:
		948
		949	#include <stddef.h>
		950
		951	static void
		952	t1_cb (EV_P_ struct ev_timer *w, int revents)
		953	{
		954	struct my_biggy big = (struct my_biggy *
		955	(((char *)w) - offsetof (struct my_biggy, t1));
		956	}
		957
		958	static void
		959	t2_cb (EV_P_ struct ev_timer *w, int revents)
		960	{
		961	struct my_biggy big = (struct my_biggy *
		962	(((char *)w) - offsetof (struct my_biggy, t2));
		963	}
701		964
702		965
703	=head1 WATCHER TYPES	966	=head1 WATCHER TYPES
704		967
705	This section describes each watcher in detail, but will not repeat	968	This section describes each watcher in detail, but will not repeat
…		…
729	In general you can register as many read and/or write event watchers per	992	In general you can register as many read and/or write event watchers per
730	fd as you want (as long as you don't confuse yourself). Setting all file	993	fd as you want (as long as you don't confuse yourself). Setting all file
731	descriptors to non-blocking mode is also usually a good idea (but not	994	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	995	required if you know what you are doing).
733		996
734	You have to be careful with dup'ed file descriptors, though. Some backends
735	(the linux epoll backend is a notable example) cannot handle dup'ed file
736	descriptors correctly if you register interest in two or more fds pointing
737	to the same underlying file/socket/etc. description (that is, they share
738	the same underlying "file open").
739
740	If you must do this, then force the use of a known-to-be-good backend	997	If you must do this, then force the use of a known-to-be-good backend
741	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	998	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).	999	C<EVBACKEND_POLL>).
743		1000
744	Another thing you have to watch out for is that it is quite easy to	1001	Another thing you have to watch out for is that it is quite easy to
…		…
750	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1007	it is best to always use non-blocking I/O: An extra C<read>(2) returning
751	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1008	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1009
753	If you cannot run the fd in non-blocking mode (for example you should not	1010	If you cannot run the fd in non-blocking mode (for example you should not
754	play around with an Xlib connection), then you have to seperately re-test	1011	play around with an Xlib connection), then you have to seperately re-test
755	wether a file descriptor is really ready with a known-to-be good interface	1012	whether a file descriptor is really ready with a known-to-be good interface
756	such as poll (fortunately in our Xlib example, Xlib already does this on	1013	such as poll (fortunately in our Xlib example, Xlib already does this on
757	its own, so its quite safe to use).	1014	its own, so its quite safe to use).
		1015
		1016	=head3 The special problem of disappearing file descriptors
		1017
		1018	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1019	descriptor (either by calling C<close> explicitly or by any other means,
		1020	such as C<dup>). The reason is that you register interest in some file
		1021	descriptor, but when it goes away, the operating system will silently drop
		1022	this interest. If another file descriptor with the same number then is
		1023	registered with libev, there is no efficient way to see that this is, in
		1024	fact, a different file descriptor.
		1025
		1026	To avoid having to explicitly tell libev about such cases, libev follows
		1027	the following policy: Each time C<ev_io_set> is being called, libev
		1028	will assume that this is potentially a new file descriptor, otherwise
		1029	it is assumed that the file descriptor stays the same. That means that
		1030	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1031	descriptor even if the file descriptor number itself did not change.
		1032
		1033	This is how one would do it normally anyway, the important point is that
		1034	the libev application should not optimise around libev but should leave
		1035	optimisations to libev.
		1036
		1037	=head3 The special problem of dup'ed file descriptors
		1038
		1039	Some backends (e.g. epoll), cannot register events for file descriptors,
		1040	but only events for the underlying file descriptions. That means when you
		1041	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1042	events for them, only one file descriptor might actually receive events.
		1043
		1044	There is no workaround possible except not registering events
		1045	for potentially C<dup ()>'ed file descriptors, or to resort to
		1046	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1047
		1048	=head3 The special problem of fork
		1049
		1050	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1051	useless behaviour. Libev fully supports fork, but needs to be told about
		1052	it in the child.
		1053
		1054	To support fork in your programs, you either have to call
		1055	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1056	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1057	C<EVBACKEND_POLL>.
		1058
		1059
		1060	=head3 Watcher-Specific Functions
758		1061
759	=over 4	1062	=over 4
760		1063
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1064	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1065
…		…
774		1077
775	The events being watched.	1078	The events being watched.
776		1079
777	=back	1080	=back
778		1081
		1082	=head3 Examples
		1083
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1084	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
780	readable, but only once. Since it is likely line-buffered, you could	1085	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1086	attempt to read a whole line in the callback.
782		1087
783	static void	1088	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1089	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1090	{
786	ev_io_stop (loop, w);	1091	ev_io_stop (loop, w);
…		…
816		1121
817	The callback is guarenteed to be invoked only when its timeout has passed,	1122	The callback is guarenteed to be invoked only when its timeout has passed,
818	but if multiple timers become ready during the same loop iteration then	1123	but if multiple timers become ready during the same loop iteration then
819	order of execution is undefined.	1124	order of execution is undefined.
820		1125
		1126	=head3 Watcher-Specific Functions and Data Members
		1127
821	=over 4	1128	=over 4
822		1129
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1130	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1131
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1132	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
838	=item ev_timer_again (loop)	1145	=item ev_timer_again (loop)
839		1146
840	This will act as if the timer timed out and restart it again if it is	1147	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1148	repeating. The exact semantics are:
842		1149
		1150	If the timer is pending, its pending status is cleared.
		1151
843	If the timer is started but nonrepeating, stop it.	1152	If the timer is started but nonrepeating, stop it (as if it timed out).
844		1153
845	If the timer is repeating, either start it if necessary (with the repeat	1154	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1155	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1156
848	This sounds a bit complicated, but here is a useful and typical	1157	This sounds a bit complicated, but here is a useful and typical
849	example: Imagine you have a tcp connection and you want a so-called	1158	example: Imagine you have a tcp connection and you want a so-called idle
850	idle timeout, that is, you want to be called when there have been,	1159	timeout, that is, you want to be called when there have been, say, 60
851	say, 60 seconds of inactivity on the socket. The easiest way to do	1160	seconds of inactivity on the socket. The easiest way to do this is to
852	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1161	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
853	C<ev_timer_again> each time you successfully read or write some data. If	1162	C<ev_timer_again> each time you successfully read or write some data. If
854	you go into an idle state where you do not expect data to travel on the	1163	you go into an idle state where you do not expect data to travel on the
855	socket, you can stop the timer, and again will automatically restart it if	1164	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1165	automatically restart it if need be.
857		1166
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1167	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1168	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1169
861	ev_timer_init (timer, callback, 0., 5.);	1170	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1171	ev_timer_again (loop, timer);
863	...	1172	...
864	timer->again = 17.;	1173	timer->again = 17.;
865	ev_timer_again (loop, timer);	1174	ev_timer_again (loop, timer);
866	...	1175	...
867	timer->again = 10.;	1176	timer->again = 10.;
868	ev_timer_again (loop, timer);	1177	ev_timer_again (loop, timer);
869		1178
870	This is more efficient then stopping/starting the timer eahc time you want	1179	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1180	you want to modify its timeout value.
872		1181
873	=item ev_tstamp repeat [read-write]	1182	=item ev_tstamp repeat [read-write]
874		1183
875	The current C<repeat> value. Will be used each time the watcher times out	1184	The current C<repeat> value. Will be used each time the watcher times out
876	or C<ev_timer_again> is called and determines the next timeout (if any),	1185	or C<ev_timer_again> is called and determines the next timeout (if any),
877	which is also when any modifications are taken into account.	1186	which is also when any modifications are taken into account.
878		1187
879	=back	1188	=back
880		1189
		1190	=head3 Examples
		1191
881	Example: create a timer that fires after 60 seconds.	1192	Example: Create a timer that fires after 60 seconds.
882		1193
883	static void	1194	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1195	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1196	{
886	.. one minute over, w is actually stopped right here	1197	.. one minute over, w is actually stopped right here
…		…
888		1199
889	struct ev_timer mytimer;	1200	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1201	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1202	ev_timer_start (loop, &mytimer);
892		1203
893	Example: create a timeout timer that times out after 10 seconds of	1204	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1205	inactivity.
895		1206
896	static void	1207	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1208	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1209	{
…		…
918	but on wallclock time (absolute time). You can tell a periodic watcher	1229	but on wallclock time (absolute time). You can tell a periodic watcher
919	to trigger "at" some specific point in time. For example, if you tell a	1230	to trigger "at" some specific point in time. For example, if you tell a
920	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1231	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
921	+ 10.>) and then reset your system clock to the last year, then it will	1232	+ 10.>) and then reset your system clock to the last year, then it will
922	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1233	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
923	roughly 10 seconds later and of course not if you reset your system time	1234	roughly 10 seconds later).
924	again).
925		1235
926	They can also be used to implement vastly more complex timers, such as	1236	They can also be used to implement vastly more complex timers, such as
927	triggering an event on eahc midnight, local time.	1237	triggering an event on each midnight, local time or other, complicated,
		1238	rules.
928		1239
929	As with timers, the callback is guarenteed to be invoked only when the	1240	As with timers, the callback is guarenteed to be invoked only when the
930	time (C<at>) has been passed, but if multiple periodic timers become ready	1241	time (C<at>) has been passed, but if multiple periodic timers become ready
931	during the same loop iteration then order of execution is undefined.	1242	during the same loop iteration then order of execution is undefined.
932		1243
		1244	=head3 Watcher-Specific Functions and Data Members
		1245
933	=over 4	1246	=over 4
934		1247
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1248	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1249
937	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1250	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
939	Lots of arguments, lets sort it out... There are basically three modes of	1252	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1253	operation, and we will explain them from simplest to complex:
941		1254
942	=over 4	1255	=over 4
943		1256
944	=item * absolute timer (interval = reschedule_cb = 0)	1257	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1258
946	In this configuration the watcher triggers an event at the wallclock time	1259	In this configuration the watcher triggers an event at the wallclock time
947	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1260	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
948	that is, if it is to be run at January 1st 2011 then it will run when the	1261	that is, if it is to be run at January 1st 2011 then it will run when the
949	system time reaches or surpasses this time.	1262	system time reaches or surpasses this time.
950		1263
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1264	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1265
953	In this mode the watcher will always be scheduled to time out at the next	1266	In this mode the watcher will always be scheduled to time out at the next
954	C<at + N * interval> time (for some integer N) and then repeat, regardless	1267	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1268	and then repeat, regardless of any time jumps.
956		1269
957	This can be used to create timers that do not drift with respect to system	1270	This can be used to create timers that do not drift with respect to system
958	time:	1271	time:
959		1272
960	ev_periodic_set (&periodic, 0., 3600., 0);	1273	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
966		1279
967	Another way to think about it (for the mathematically inclined) is that	1280	Another way to think about it (for the mathematically inclined) is that
968	C<ev_periodic> will try to run the callback in this mode at the next possible	1281	C<ev_periodic> will try to run the callback in this mode at the next possible
969	time where C<time = at (mod interval)>, regardless of any time jumps.	1282	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1283
		1284	For numerical stability it is preferable that the C<at> value is near
		1285	C<ev_now ()> (the current time), but there is no range requirement for
		1286	this value.
		1287
971	=item * manual reschedule mode (reschedule_cb = callback)	1288	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1289
973	In this mode the values for C<interval> and C<at> are both being	1290	In this mode the values for C<interval> and C<at> are both being
974	ignored. Instead, each time the periodic watcher gets scheduled, the	1291	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1292	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1293	current time as second argument.
977		1294
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1295	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
979	ever, or make any event loop modifications>. If you need to stop it,	1296	ever, or make any event loop modifications>. If you need to stop it,
980	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1297	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
981	starting a prepare watcher).	1298	starting an C<ev_prepare> watcher, which is legal).
982		1299
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1300	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984	ev_tstamp now)>, e.g.:	1301	ev_tstamp now)>, e.g.:
985		1302
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1303	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1009	Simply stops and restarts the periodic watcher again. This is only useful	1326	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1327	when you changed some parameters or the reschedule callback would return
1011	a different time than the last time it was called (e.g. in a crond like	1328	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1329	program when the crontabs have changed).
1013		1330
		1331	=item ev_tstamp offset [read-write]
		1332
		1333	When repeating, this contains the offset value, otherwise this is the
		1334	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1335
		1336	Can be modified any time, but changes only take effect when the periodic
		1337	timer fires or C<ev_periodic_again> is being called.
		1338
1014	=item ev_tstamp interval [read-write]	1339	=item ev_tstamp interval [read-write]
1015		1340
1016	The current interval value. Can be modified any time, but changes only	1341	The current interval value. Can be modified any time, but changes only
1017	take effect when the periodic timer fires or C<ev_periodic_again> is being	1342	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1343	called.
…		…
1021		1346
1022	The current reschedule callback, or C<0>, if this functionality is	1347	The current reschedule callback, or C<0>, if this functionality is
1023	switched off. Can be changed any time, but changes only take effect when	1348	switched off. Can be changed any time, but changes only take effect when
1024	the periodic timer fires or C<ev_periodic_again> is being called.	1349	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1350
		1351	=item ev_tstamp at [read-only]
		1352
		1353	When active, contains the absolute time that the watcher is supposed to
		1354	trigger next.
		1355
1026	=back	1356	=back
1027		1357
		1358	=head3 Examples
		1359
1028	Example: call a callback every hour, or, more precisely, whenever the	1360	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1361	system clock is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1362	potentially a lot of jittering, but good long-term stability.
1031		1363
1032	static void	1364	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1365	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1037		1369
1038	struct ev_periodic hourly_tick;	1370	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1371	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1372	ev_periodic_start (loop, &hourly_tick);
1041		1373
1042	Example: the same as above, but use a reschedule callback to do it:	1374	Example: The same as above, but use a reschedule callback to do it:
1043		1375
1044	#include <math.h>	1376	#include <math.h>
1045		1377
1046	static ev_tstamp	1378	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1379	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1049	return fmod (now, 3600.) + 3600.;	1381	return fmod (now, 3600.) + 3600.;
1050	}	1382	}
1051		1383
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1384	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1385
1054	Example: call a callback every hour, starting now:	1386	Example: Call a callback every hour, starting now:
1055		1387
1056	struct ev_periodic hourly_tick;	1388	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1389	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1390	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1391	ev_periodic_start (loop, &hourly_tick);
…		…
1071	with the kernel (thus it coexists with your own signal handlers as long	1403	with the kernel (thus it coexists with your own signal handlers as long
1072	as you don't register any with libev). Similarly, when the last signal	1404	as you don't register any with libev). Similarly, when the last signal
1073	watcher for a signal is stopped libev will reset the signal handler to	1405	watcher for a signal is stopped libev will reset the signal handler to
1074	SIG_DFL (regardless of what it was set to before).	1406	SIG_DFL (regardless of what it was set to before).
1075		1407
		1408	=head3 Watcher-Specific Functions and Data Members
		1409
1076	=over 4	1410	=over 4
1077		1411
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1412	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1413
1080	=item ev_signal_set (ev_signal *, int signum)	1414	=item ev_signal_set (ev_signal *, int signum)
…		…
1091		1425
1092	=head2 C<ev_child> - watch out for process status changes	1426	=head2 C<ev_child> - watch out for process status changes
1093		1427
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1428	Child watchers trigger when your process receives a SIGCHLD in response to
1095	some child status changes (most typically when a child of yours dies).	1429	some child status changes (most typically when a child of yours dies).
		1430
		1431	=head3 Watcher-Specific Functions and Data Members
1096		1432
1097	=over 4	1433	=over 4
1098		1434
1099	=item ev_child_init (ev_child *, callback, int pid)	1435	=item ev_child_init (ev_child *, callback, int pid)
1100		1436
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1456	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1457	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1458
1123	=back	1459	=back
1124		1460
		1461	=head3 Examples
		1462
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1463	Example: Try to exit cleanly on SIGINT and SIGTERM.
1126		1464
1127	static void	1465	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1466	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1129	{	1467	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1468	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1145	not exist" is a status change like any other. The condition "path does	1483	not exist" is a status change like any other. The condition "path does
1146	not exist" is signified by the C<st_nlink> field being zero (which is	1484	not exist" is signified by the C<st_nlink> field being zero (which is
1147	otherwise always forced to be at least one) and all the other fields of	1485	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1486	the stat buffer having unspecified contents.
1149		1487
		1488	The path I<should> be absolute and I<must not> end in a slash. If it is
		1489	relative and your working directory changes, the behaviour is undefined.
		1490
1150	Since there is no standard to do this, the portable implementation simply	1491	Since there is no standard to do this, the portable implementation simply
1151	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1492	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1152	can specify a recommended polling interval for this case. If you specify	1493	can specify a recommended polling interval for this case. If you specify
1153	a polling interval of C<0> (highly recommended!) then a I<suitable,	1494	a polling interval of C<0> (highly recommended!) then a I<suitable,
1154	unspecified default> value will be used (which you can expect to be around	1495	unspecified default> value will be used (which you can expect to be around
1155	five seconds, although this might change dynamically). Libev will also	1496	five seconds, although this might change dynamically). Libev will also
1156	impose a minimum interval which is currently around C<0.1>, but thats	1497	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1158		1499
1159	This watcher type is not meant for massive numbers of stat watchers,	1500	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1501	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1502	resource-intensive.
1162		1503
1163	At the time of this writing, no specific OS backends are implemented, but	1504	At the time of this writing, only the Linux inotify interface is
1164	if demand increases, at least a kqueue and inotify backend will be added.	1505	implemented (implementing kqueue support is left as an exercise for the
		1506	reader). Inotify will be used to give hints only and should not change the
		1507	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1508	to fall back to regular polling again even with inotify, but changes are
		1509	usually detected immediately, and if the file exists there will be no
		1510	polling.
		1511
		1512	=head3 Inotify
		1513
		1514	When C<inotify (7)> support has been compiled into libev (generally only
		1515	available on Linux) and present at runtime, it will be used to speed up
		1516	change detection where possible. The inotify descriptor will be created lazily
		1517	when the first C<ev_stat> watcher is being started.
		1518
		1519	Inotify presense does not change the semantics of C<ev_stat> watchers
		1520	except that changes might be detected earlier, and in some cases, to avoid
		1521	making regular C<stat> calls. Even in the presense of inotify support
		1522	there are many cases where libev has to resort to regular C<stat> polling.
		1523
		1524	(There is no support for kqueue, as apparently it cannot be used to
		1525	implement this functionality, due to the requirement of having a file
		1526	descriptor open on the object at all times).
		1527
		1528	=head3 The special problem of stat time resolution
		1529
		1530	The C<stat ()> syscall only supports full-second resolution portably, and
		1531	even on systems where the resolution is higher, many filesystems still
		1532	only support whole seconds.
		1533
		1534	That means that, if the time is the only thing that changes, you might
		1535	miss updates: on the first update, C<ev_stat> detects a change and calls
		1536	your callback, which does something. When there is another update within
		1537	the same second, C<ev_stat> will be unable to detect it.
		1538
		1539	The solution to this is to delay acting on a change for a second (or till
		1540	the next second boundary), using a roughly one-second delay C<ev_timer>
		1541	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1542	is added to work around small timing inconsistencies of some operating
		1543	systems.
		1544
		1545	=head3 Watcher-Specific Functions and Data Members
1165		1546
1166	=over 4	1547	=over 4
1167		1548
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1549	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1550
…		…
1205	=item const char *path [read-only]	1586	=item const char *path [read-only]
1206		1587
1207	The filesystem path that is being watched.	1588	The filesystem path that is being watched.
1208		1589
1209	=back	1590	=back
		1591
		1592	=head3 Examples
1210		1593
1211	Example: Watch C</etc/passwd> for attribute changes.	1594	Example: Watch C</etc/passwd> for attribute changes.
1212		1595
1213	static void	1596	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1597	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1227	}	1610	}
1228		1611
1229	...	1612	...
1230	ev_stat passwd;	1613	ev_stat passwd;
1231		1614
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1615	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1616	ev_stat_start (loop, &passwd);
1234		1617
		1618	Example: Like above, but additionally use a one-second delay so we do not
		1619	miss updates (however, frequent updates will delay processing, too, so
		1620	one might do the work both on C<ev_stat> callback invocation I<and> on
		1621	C<ev_timer> callback invocation).
		1622
		1623	static ev_stat passwd;
		1624	static ev_timer timer;
		1625
		1626	static void
		1627	timer_cb (EV_P_ ev_timer *w, int revents)
		1628	{
		1629	ev_timer_stop (EV_A_ w);
		1630
		1631	/* now it's one second after the most recent passwd change */
		1632	}
		1633
		1634	static void
		1635	stat_cb (EV_P_ ev_stat *w, int revents)
		1636	{
		1637	/* reset the one-second timer */
		1638	ev_timer_again (EV_A_ &timer);
		1639	}
		1640
		1641	...
		1642	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1643	ev_stat_start (loop, &passwd);
		1644	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1645
1235		1646
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1647	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1648
1238	Idle watchers trigger events when there are no other events are pending	1649	Idle watchers trigger events when no other events of the same or higher
1239	(prepare, check and other idle watchers do not count). That is, as long	1650	priority are pending (prepare, check and other idle watchers do not
1240	as your process is busy handling sockets or timeouts (or even signals,	1651	count).
1241	imagine) it will not be triggered. But when your process is idle all idle	1652
1242	watchers are being called again and again, once per event loop iteration -	1653	That is, as long as your process is busy handling sockets or timeouts
		1654	(or even signals, imagine) of the same or higher priority it will not be
		1655	triggered. But when your process is idle (or only lower-priority watchers
		1656	are pending), the idle watchers are being called once per event loop
1243	until stopped, that is, or your process receives more events and becomes	1657	iteration - until stopped, that is, or your process receives more events
1244	busy.	1658	and becomes busy again with higher priority stuff.
1245		1659
1246	The most noteworthy effect is that as long as any idle watchers are	1660	The most noteworthy effect is that as long as any idle watchers are
1247	active, the process will not block when waiting for new events.	1661	active, the process will not block when waiting for new events.
1248		1662
1249	Apart from keeping your process non-blocking (which is a useful	1663	Apart from keeping your process non-blocking (which is a useful
1250	effect on its own sometimes), idle watchers are a good place to do	1664	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1665	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1666	event loop has handled all outstanding events.
1253		1667
		1668	=head3 Watcher-Specific Functions and Data Members
		1669
1254	=over 4	1670	=over 4
1255		1671
1256	=item ev_idle_init (ev_signal *, callback)	1672	=item ev_idle_init (ev_signal *, callback)
1257		1673
1258	Initialises and configures the idle watcher - it has no parameters of any	1674	Initialises and configures the idle watcher - it has no parameters of any
1259	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1675	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1676	believe me.
1261		1677
1262	=back	1678	=back
1263		1679
		1680	=head3 Examples
		1681
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1682	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1683	callback, free it. Also, use no error checking, as usual.
1266		1684
1267	static void	1685	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1686	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1687	{
1270	free (w);	1688	free (w);
…		…
1315	with priority higher than or equal to the event loop and one coroutine	1733	with priority higher than or equal to the event loop and one coroutine
1316	of lower priority, but only once, using idle watchers to keep the event	1734	of lower priority, but only once, using idle watchers to keep the event
1317	loop from blocking if lower-priority coroutines are active, thus mapping	1735	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	1736	low-priority coroutines to idle/background tasks).
1319		1737
		1738	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1739	priority, to ensure that they are being run before any other watchers
		1740	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1741	too) should not activate ("feed") events into libev. While libev fully
		1742	supports this, they will be called before other C<ev_check> watchers
		1743	did their job. As C<ev_check> watchers are often used to embed other
		1744	(non-libev) event loops those other event loops might be in an unusable
		1745	state until their C<ev_check> watcher ran (always remind yourself to
		1746	coexist peacefully with others).
		1747
		1748	=head3 Watcher-Specific Functions and Data Members
		1749
1320	=over 4	1750	=over 4
1321		1751
1322	=item ev_prepare_init (ev_prepare *, callback)	1752	=item ev_prepare_init (ev_prepare *, callback)
1323		1753
1324	=item ev_check_init (ev_check *, callback)	1754	=item ev_check_init (ev_check *, callback)
…		…
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1757	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1328	macros, but using them is utterly, utterly and completely pointless.	1758	macros, but using them is utterly, utterly and completely pointless.
1329		1759
1330	=back	1760	=back
1331		1761
1332	Example: To include a library such as adns, you would add IO watchers	1762	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	1763
		1764	There are a number of principal ways to embed other event loops or modules
		1765	into libev. Here are some ideas on how to include libadns into libev
		1766	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1767	use for an actually working example. Another Perl module named C<EV::Glib>
		1768	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1769	into the Glib event loop).
		1770
		1771	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1334	in a check watcher, destroy them and call into libadns. What follows is	1772	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	1773	is pseudo-code only of course. This requires you to either use a low
		1774	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1775	the callbacks for the IO/timeout watchers might not have been called yet.
1336		1776
1337	static ev_io iow [nfd];	1777	static ev_io iow [nfd];
1338	static ev_timer tw;	1778	static ev_timer tw;
1339		1779
1340	static void	1780	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	1781	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	1782	{
1343	// set the relevant poll flags
1344	// could also call adns_processreadable etc. here
1345	struct pollfd *fd = (struct pollfd *)w->data;
1346	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1347	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1348	}	1783	}
1349		1784
1350	// create io watchers for each fd and a timer before blocking	1785	// create io watchers for each fd and a timer before blocking
1351	static void	1786	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1787	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	1788	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	1789	int timeout = 3600000;
		1790	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	1791	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1792	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		1793
1358	/* the callback is illegal, but won't be called as we stop during check */	1794	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	1795	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	1796	ev_timer_start (loop, &tw);
1361		1797
1362	// create on ev_io per pollfd	1798	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	1799	for (int i = 0; i < nfd; ++i)
1364	{	1800	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	1801	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	1802	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1803	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		1804
1369	fds [i].revents = 0;	1805	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	1806	ev_io_start (loop, iow + i);
1372	}	1807	}
1373	}	1808	}
1374		1809
1375	// stop all watchers after blocking	1810	// stop all watchers after blocking
…		…
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1812	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	1813	{
1379	ev_timer_stop (loop, &tw);	1814	ev_timer_stop (loop, &tw);
1380		1815
1381	for (int i = 0; i < nfd; ++i)	1816	for (int i = 0; i < nfd; ++i)
		1817	{
		1818	// set the relevant poll flags
		1819	// could also call adns_processreadable etc. here
		1820	struct pollfd *fd = fds + i;
		1821	int revents = ev_clear_pending (iow + i);
		1822	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1823	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1824
		1825	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	1826	ev_io_stop (loop, iow + i);
		1827	}
1383		1828
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1829	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1830	}
		1831
		1832	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1833	in the prepare watcher and would dispose of the check watcher.
		1834
		1835	Method 3: If the module to be embedded supports explicit event
		1836	notification (adns does), you can also make use of the actual watcher
		1837	callbacks, and only destroy/create the watchers in the prepare watcher.
		1838
		1839	static void
		1840	timer_cb (EV_P_ ev_timer *w, int revents)
		1841	{
		1842	adns_state ads = (adns_state)w->data;
		1843	update_now (EV_A);
		1844
		1845	adns_processtimeouts (ads, &tv_now);
		1846	}
		1847
		1848	static void
		1849	io_cb (EV_P_ ev_io *w, int revents)
		1850	{
		1851	adns_state ads = (adns_state)w->data;
		1852	update_now (EV_A);
		1853
		1854	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1855	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1856	}
		1857
		1858	// do not ever call adns_afterpoll
		1859
		1860	Method 4: Do not use a prepare or check watcher because the module you
		1861	want to embed is too inflexible to support it. Instead, youc na override
		1862	their poll function. The drawback with this solution is that the main
		1863	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1864	this.
		1865
		1866	static gint
		1867	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1868	{
		1869	int got_events = 0;
		1870
		1871	for (n = 0; n < nfds; ++n)
		1872	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1873
		1874	if (timeout >= 0)
		1875	// create/start timer
		1876
		1877	// poll
		1878	ev_loop (EV_A_ 0);
		1879
		1880	// stop timer again
		1881	if (timeout >= 0)
		1882	ev_timer_stop (EV_A_ &to);
		1883
		1884	// stop io watchers again - their callbacks should have set
		1885	for (n = 0; n < nfds; ++n)
		1886	ev_io_stop (EV_A_ iow [n]);
		1887
		1888	return got_events;
1385	}	1889	}
1386		1890
1387		1891
1388	=head2 C<ev_embed> - when one backend isn't enough...	1892	=head2 C<ev_embed> - when one backend isn't enough...
1389		1893
…		…
1432	portable one.	1936	portable one.
1433		1937
1434	So when you want to use this feature you will always have to be prepared	1938	So when you want to use this feature you will always have to be prepared
1435	that you cannot get an embeddable loop. The recommended way to get around	1939	that you cannot get an embeddable loop. The recommended way to get around
1436	this is to have a separate variables for your embeddable loop, try to	1940	this is to have a separate variables for your embeddable loop, try to
1437	create it, and if that fails, use the normal loop for everything:	1941	create it, and if that fails, use the normal loop for everything.
		1942
		1943	=head3 Watcher-Specific Functions and Data Members
		1944
		1945	=over 4
		1946
		1947	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1948
		1949	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1950
		1951	Configures the watcher to embed the given loop, which must be
		1952	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1953	invoked automatically, otherwise it is the responsibility of the callback
		1954	to invoke it (it will continue to be called until the sweep has been done,
		1955	if you do not want thta, you need to temporarily stop the embed watcher).
		1956
		1957	=item ev_embed_sweep (loop, ev_embed *)
		1958
		1959	Make a single, non-blocking sweep over the embedded loop. This works
		1960	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1961	apropriate way for embedded loops.
		1962
		1963	=item struct ev_loop *other [read-only]
		1964
		1965	The embedded event loop.
		1966
		1967	=back
		1968
		1969	=head3 Examples
		1970
		1971	Example: Try to get an embeddable event loop and embed it into the default
		1972	event loop. If that is not possible, use the default loop. The default
		1973	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1974	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1975	used).
1438		1976
1439	struct ev_loop *loop_hi = ev_default_init (0);	1977	struct ev_loop *loop_hi = ev_default_init (0);
1440	struct ev_loop *loop_lo = 0;	1978	struct ev_loop *loop_lo = 0;
1441	struct ev_embed embed;	1979	struct ev_embed embed;
1442		1980
…		…
1453	ev_embed_start (loop_hi, &embed);	1991	ev_embed_start (loop_hi, &embed);
1454	}	1992	}
1455	else	1993	else
1456	loop_lo = loop_hi;	1994	loop_lo = loop_hi;
1457		1995
1458	=over 4	1996	Example: Check if kqueue is available but not recommended and create
		1997	a kqueue backend for use with sockets (which usually work with any
		1998	kqueue implementation). Store the kqueue/socket-only event loop in
		1999	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1459		2000
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2001	struct ev_loop *loop = ev_default_init (0);
		2002	struct ev_loop *loop_socket = 0;
		2003	struct ev_embed embed;
		2004
		2005	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2006	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2007	{
		2008	ev_embed_init (&embed, 0, loop_socket);
		2009	ev_embed_start (loop, &embed);
		2010	}
1461		2011
1462	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2012	if (!loop_socket)
		2013	loop_socket = loop;
1463		2014
1464	Configures the watcher to embed the given loop, which must be	2015	// now use loop_socket for all sockets, and loop for everything else
1465	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1466	invoked automatically, otherwise it is the responsibility of the callback
1467	to invoke it (it will continue to be called until the sweep has been done,
1468	if you do not want thta, you need to temporarily stop the embed watcher).
1469
1470	=item ev_embed_sweep (loop, ev_embed *)
1471
1472	Make a single, non-blocking sweep over the embedded loop. This works
1473	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1474	apropriate way for embedded loops.
1475
1476	=item struct ev_loop *loop [read-only]
1477
1478	The embedded event loop.
1479
1480	=back
1481		2016
1482		2017
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2018	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2019
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2020	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1488	event loop blocks next and before C<ev_check> watchers are being called,	2023	event loop blocks next and before C<ev_check> watchers are being called,
1489	and only in the child after the fork. If whoever good citizen calling	2024	and only in the child after the fork. If whoever good citizen calling
1490	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2025	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2026	handlers will be invoked, too, of course.
1492		2027
		2028	=head3 Watcher-Specific Functions and Data Members
		2029
1493	=over 4	2030	=over 4
1494		2031
1495	=item ev_fork_init (ev_signal *, callback)	2032	=item ev_fork_init (ev_signal *, callback)
1496		2033
1497	Initialises and configures the fork watcher - it has no parameters of any	2034	Initialises and configures the fork watcher - it has no parameters of any
…		…
1593		2130
1594	To use it,	2131	To use it,
1595		2132
1596	#include <ev++.h>	2133	#include <ev++.h>
1597		2134
1598	(it is not installed by default). This automatically includes F<ev.h>	2135	This automatically includes F<ev.h> and puts all of its definitions (many
1599	and puts all of its definitions (many of them macros) into the global	2136	of them macros) into the global namespace. All C++ specific things are
1600	namespace. All C++ specific things are put into the C<ev> namespace.	2137	put into the C<ev> namespace. It should support all the same embedding
		2138	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2139
1602	It should support all the same embedding options as F<ev.h>, most notably	2140	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2141	classes add (compared to plain C-style watchers) is the event loop pointer
		2142	that the watcher is associated with (or no additional members at all if
		2143	you disable C<EV_MULTIPLICITY> when embedding libev).
		2144
		2145	Currently, functions, and static and non-static member functions can be
		2146	used as callbacks. Other types should be easy to add as long as they only
		2147	need one additional pointer for context. If you need support for other
		2148	types of functors please contact the author (preferably after implementing
		2149	it).
1604		2150
1605	Here is a list of things available in the C<ev> namespace:	2151	Here is a list of things available in the C<ev> namespace:
1606		2152
1607	=over 4	2153	=over 4
1608		2154
…		…
1624		2170
1625	All of those classes have these methods:	2171	All of those classes have these methods:
1626		2172
1627	=over 4	2173	=over 4
1628		2174
1629	=item ev::TYPE::TYPE (object *, object::method *)	2175	=item ev::TYPE::TYPE ()
1630		2176
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2177	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2178
1633	=item ev::TYPE::~TYPE	2179	=item ev::TYPE::~TYPE
1634		2180
1635	The constructor takes a pointer to an object and a method pointer to	2181	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2182	with. If it is omitted, it will use C<EV_DEFAULT>.
1637	C<ev_init> for you, which means you have to call the C<set> method	2183
1638	before starting it. If you do not specify a loop then the constructor	2184	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2185	C<set> method before starting it.
		2186
		2187	It will not set a callback, however: You have to call the templated C<set>
		2188	method to set a callback before you can start the watcher.
		2189
		2190	(The reason why you have to use a method is a limitation in C++ which does
		2191	not allow explicit template arguments for constructors).
1640		2192
1641	The destructor automatically stops the watcher if it is active.	2193	The destructor automatically stops the watcher if it is active.
		2194
		2195	=item w->set<class, &class::method> (object *)
		2196
		2197	This method sets the callback method to call. The method has to have a
		2198	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2199	first argument and the C<revents> as second. The object must be given as
		2200	parameter and is stored in the C<data> member of the watcher.
		2201
		2202	This method synthesizes efficient thunking code to call your method from
		2203	the C callback that libev requires. If your compiler can inline your
		2204	callback (i.e. it is visible to it at the place of the C<set> call and
		2205	your compiler is good :), then the method will be fully inlined into the
		2206	thunking function, making it as fast as a direct C callback.
		2207
		2208	Example: simple class declaration and watcher initialisation
		2209
		2210	struct myclass
		2211	{
		2212	void io_cb (ev::io &w, int revents) { }
		2213	}
		2214
		2215	myclass obj;
		2216	ev::io iow;
		2217	iow.set <myclass, &myclass::io_cb> (&obj);
		2218
		2219	=item w->set<function> (void *data = 0)
		2220
		2221	Also sets a callback, but uses a static method or plain function as
		2222	callback. The optional C<data> argument will be stored in the watcher's
		2223	C<data> member and is free for you to use.
		2224
		2225	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2226
		2227	See the method-C<set> above for more details.
		2228
		2229	Example:
		2230
		2231	static void io_cb (ev::io &w, int revents) { }
		2232	iow.set <io_cb> ();
1642		2233
1643	=item w->set (struct ev_loop *)	2234	=item w->set (struct ev_loop *)
1644		2235
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2236	Associates a different C<struct ev_loop> with this watcher. You can only
1646	do this when the watcher is inactive (and not pending either).	2237	do this when the watcher is inactive (and not pending either).
1647		2238
1648	=item w->set ([args])	2239	=item w->set ([args])
1649		2240
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2241	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1651	called at least once. Unlike the C counterpart, an active watcher gets	2242	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2243	automatically stopped and restarted when reconfiguring it with this
		2244	method.
1653		2245
1654	=item w->start ()	2246	=item w->start ()
1655		2247
1656	Starts the watcher. Note that there is no C<loop> argument as the	2248	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2249	constructor already stores the event loop.
1658		2250
1659	=item w->stop ()	2251	=item w->stop ()
1660		2252
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2253	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2254
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2255	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2256
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2257	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2258	C<ev_TYPE_again> function.
1667		2259
1668	=item w->sweep () C<ev::embed> only	2260	=item w->sweep () (C<ev::embed> only)
1669		2261
1670	Invokes C<ev_embed_sweep>.	2262	Invokes C<ev_embed_sweep>.
1671		2263
1672	=item w->update () C<ev::stat> only	2264	=item w->update () (C<ev::stat> only)
1673		2265
1674	Invokes C<ev_stat_stat>.	2266	Invokes C<ev_stat_stat>.
1675		2267
1676	=back	2268	=back
1677		2269
…		…
1687		2279
1688	myclass ();	2280	myclass ();
1689	}	2281	}
1690		2282
1691	myclass::myclass (int fd)	2283	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{	2284	{
		2285	io .set <myclass, &myclass::io_cb > (this);
		2286	idle.set <myclass, &myclass::idle_cb> (this);
		2287
1695	io.start (fd, ev::READ);	2288	io.start (fd, ev::READ);
1696	}	2289	}
1697		2290
1698		2291
1699	=head1 MACRO MAGIC	2292	=head1 MACRO MAGIC
1700		2293
1701	Libev can be compiled with a variety of options, the most fundemantal is	2294	Libev can be compiled with a variety of options, the most fundamantal
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2295	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2296	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2297
1705	To make it easier to write programs that cope with either variant, the	2298	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2299	following macros are defined:
1707		2300
1708	=over 4	2301	=over 4
…		…
1740	Similar to the other two macros, this gives you the value of the default	2333	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2334	loop, if multiple loops are supported ("ev loop default").
1742		2335
1743	=back	2336	=back
1744		2337
1745	Example: Declare and initialise a check watcher, working regardless of	2338	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2339	macros so it will work regardless of whether multiple loops are supported
		2340	or not.
1747		2341
1748	static void	2342	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2343	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2344	{
1751	ev_check_stop (EV_A_ w);	2345	ev_check_stop (EV_A_ w);
…		…
1754	ev_check check;	2348	ev_check check;
1755	ev_check_init (&check, check_cb);	2349	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2350	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2351	ev_loop (EV_DEFAULT_ 0);
1758		2352
1759
1760	=head1 EMBEDDING	2353	=head1 EMBEDDING
1761		2354
1762	Libev can (and often is) directly embedded into host	2355	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2356	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2357	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2358	and rxvt-unicode.
1766		2359
1767	The goal is to enable you to just copy the neecssary files into your	2360	The goal is to enable you to just copy the necessary files into your
1768	source directory without having to change even a single line in them, so	2361	source directory without having to change even a single line in them, so
1769	you can easily upgrade by simply copying (or having a checked-out copy of	2362	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2363	libev somewhere in your source tree).
1771		2364
1772	=head2 FILESETS	2365	=head2 FILESETS
…		…
1803	ev_vars.h	2396	ev_vars.h
1804	ev_wrap.h	2397	ev_wrap.h
1805		2398
1806	ev_win32.c required on win32 platforms only	2399	ev_win32.c required on win32 platforms only
1807		2400
1808	ev_select.c only when select backend is enabled (which is by default)	2401	ev_select.c only when select backend is enabled (which is enabled by default)
1809	ev_poll.c only when poll backend is enabled (disabled by default)	2402	ev_poll.c only when poll backend is enabled (disabled by default)
1810	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2403	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1811	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2404	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1812	ev_port.c only when the solaris port backend is enabled (disabled by default)	2405	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2406
…		…
1862		2455
1863	If defined to be C<1>, libev will try to detect the availability of the	2456	If defined to be C<1>, libev will try to detect the availability of the
1864	monotonic clock option at both compiletime and runtime. Otherwise no use	2457	monotonic clock option at both compiletime and runtime. Otherwise no use
1865	of the monotonic clock option will be attempted. If you enable this, you	2458	of the monotonic clock option will be attempted. If you enable this, you
1866	usually have to link against librt or something similar. Enabling it when	2459	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2460	the functionality isn't available is safe, though, although you have
1868	to make sure you link against any libraries where the C<clock_gettime>	2461	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2462	function is hiding in (often F<-lrt>).
1870		2463
1871	=item EV_USE_REALTIME	2464	=item EV_USE_REALTIME
1872		2465
1873	If defined to be C<1>, libev will try to detect the availability of the	2466	If defined to be C<1>, libev will try to detect the availability of the
1874	realtime clock option at compiletime (and assume its availability at	2467	realtime clock option at compiletime (and assume its availability at
1875	runtime if successful). Otherwise no use of the realtime clock option will	2468	runtime if successful). Otherwise no use of the realtime clock option will
1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2469	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1877	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2470	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2471	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2472
		2473	=item EV_USE_NANOSLEEP
		2474
		2475	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2476	and will use it for delays. Otherwise it will use C<select ()>.
1879		2477
1880	=item EV_USE_SELECT	2478	=item EV_USE_SELECT
1881		2479
1882	If undefined or defined to be C<1>, libev will compile in support for the	2480	If undefined or defined to be C<1>, libev will compile in support for the
1883	C<select>(2) backend. No attempt at autodetection will be done: if no	2481	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1901	wants osf handles on win32 (this is the case when the select to	2499	wants osf handles on win32 (this is the case when the select to
1902	be used is the winsock select). This means that it will call	2500	be used is the winsock select). This means that it will call
1903	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2501	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1904	it is assumed that all these functions actually work on fds, even	2502	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	2503	on win32. Should not be defined on non-win32 platforms.
		2504
		2505	=item EV_FD_TO_WIN32_HANDLE
		2506
		2507	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2508	file descriptors to socket handles. When not defining this symbol (the
		2509	default), then libev will call C<_get_osfhandle>, which is usually
		2510	correct. In some cases, programs use their own file descriptor management,
		2511	in which case they can provide this function to map fds to socket handles.
1906		2512
1907	=item EV_USE_POLL	2513	=item EV_USE_POLL
1908		2514
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2515	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1910	backend. Otherwise it will be enabled on non-win32 platforms. It	2516	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1938		2544
1939	=item EV_USE_DEVPOLL	2545	=item EV_USE_DEVPOLL
1940		2546
1941	reserved for future expansion, works like the USE symbols above.	2547	reserved for future expansion, works like the USE symbols above.
1942		2548
		2549	=item EV_USE_INOTIFY
		2550
		2551	If defined to be C<1>, libev will compile in support for the Linux inotify
		2552	interface to speed up C<ev_stat> watchers. Its actual availability will
		2553	be detected at runtime.
		2554
1943	=item EV_H	2555	=item EV_H
1944		2556
1945	The name of the F<ev.h> header file used to include it. The default if	2557	The name of the F<ev.h> header file used to include it. The default if
1946	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2558	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2559	virtually rename the F<ev.h> header file in case of conflicts.
1948		2560
1949	=item EV_CONFIG_H	2561	=item EV_CONFIG_H
1950		2562
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2563	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2564	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	2565	C<EV_H>, above.
1954		2566
1955	=item EV_EVENT_H	2567	=item EV_EVENT_H
1956		2568
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2569	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1958	of how the F<event.h> header can be found.	2570	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
1959		2571
1960	=item EV_PROTOTYPES	2572	=item EV_PROTOTYPES
1961		2573
1962	If defined to be C<0>, then F<ev.h> will not define any function	2574	If defined to be C<0>, then F<ev.h> will not define any function
1963	prototypes, but still define all the structs and other symbols. This is	2575	prototypes, but still define all the structs and other symbols. This is
…		…
1970	will have the C<struct ev_loop *> as first argument, and you can create	2582	will have the C<struct ev_loop *> as first argument, and you can create
1971	additional independent event loops. Otherwise there will be no support	2583	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	2584	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	2585	argument. Instead, all functions act on the single default loop.
1974		2586
		2587	=item EV_MINPRI
		2588
		2589	=item EV_MAXPRI
		2590
		2591	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2592	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2593	provide for more priorities by overriding those symbols (usually defined
		2594	to be C<-2> and C<2>, respectively).
		2595
		2596	When doing priority-based operations, libev usually has to linearly search
		2597	all the priorities, so having many of them (hundreds) uses a lot of space
		2598	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2599	fine.
		2600
		2601	If your embedding app does not need any priorities, defining these both to
		2602	C<0> will save some memory and cpu.
		2603
1975	=item EV_PERIODIC_ENABLE	2604	=item EV_PERIODIC_ENABLE
1976		2605
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	2606	If undefined or defined to be C<1>, then periodic timers are supported. If
1978	defined to be C<0>, then they are not. Disabling them saves a few kB of	2607	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	2608	code.
1980		2609
		2610	=item EV_IDLE_ENABLE
		2611
		2612	If undefined or defined to be C<1>, then idle watchers are supported. If
		2613	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2614	code.
		2615
1981	=item EV_EMBED_ENABLE	2616	=item EV_EMBED_ENABLE
1982		2617
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	2618	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	2619	defined to be C<0>, then they are not.
1985		2620
…		…
2002	=item EV_PID_HASHSIZE	2637	=item EV_PID_HASHSIZE
2003		2638
2004	C<ev_child> watchers use a small hash table to distribute workload by	2639	C<ev_child> watchers use a small hash table to distribute workload by
2005	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2640	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2006	than enough. If you need to manage thousands of children you might want to	2641	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	2642	increase this value (I<must> be a power of two).
		2643
		2644	=item EV_INOTIFY_HASHSIZE
		2645
		2646	C<ev_stat> watchers use a small hash table to distribute workload by
		2647	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2648	usually more than enough. If you need to manage thousands of C<ev_stat>
		2649	watchers you might want to increase this value (I<must> be a power of
		2650	two).
2008		2651
2009	=item EV_COMMON	2652	=item EV_COMMON
2010		2653
2011	By default, all watchers have a C<void *data> member. By redefining	2654	By default, all watchers have a C<void *data> member. By redefining
2012	this macro to a something else you can include more and other types of	2655	this macro to a something else you can include more and other types of
…		…
2025		2668
2026	=item ev_set_cb (ev, cb)	2669	=item ev_set_cb (ev, cb)
2027		2670
2028	Can be used to change the callback member declaration in each watcher,	2671	Can be used to change the callback member declaration in each watcher,
2029	and the way callbacks are invoked and set. Must expand to a struct member	2672	and the way callbacks are invoked and set. Must expand to a struct member
2030	definition and a statement, respectively. See the F<ev.v> header file for	2673	definition and a statement, respectively. See the F<ev.h> header file for
2031	their default definitions. One possible use for overriding these is to	2674	their default definitions. One possible use for overriding these is to
2032	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2675	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2033	method calls instead of plain function calls in C++.	2676	method calls instead of plain function calls in C++.
		2677
		2678	=head2 EXPORTED API SYMBOLS
		2679
		2680	If you need to re-export the API (e.g. via a dll) and you need a list of
		2681	exported symbols, you can use the provided F<Symbol.*> files which list
		2682	all public symbols, one per line:
		2683
		2684	Symbols.ev for libev proper
		2685	Symbols.event for the libevent emulation
		2686
		2687	This can also be used to rename all public symbols to avoid clashes with
		2688	multiple versions of libev linked together (which is obviously bad in
		2689	itself, but sometimes it is inconvinient to avoid this).
		2690
		2691	A sed command like this will create wrapper C<#define>'s that you need to
		2692	include before including F<ev.h>:
		2693
		2694	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2695
		2696	This would create a file F<wrap.h> which essentially looks like this:
		2697
		2698	#define ev_backend myprefix_ev_backend
		2699	#define ev_check_start myprefix_ev_check_start
		2700	#define ev_check_stop myprefix_ev_check_stop
		2701	...
2034		2702
2035	=head2 EXAMPLES	2703	=head2 EXAMPLES
2036		2704
2037	For a real-world example of a program the includes libev	2705	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	2706	verbatim, you can have a look at the EV perl module
…		…
2041	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2709	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2042	will be compiled. It is pretty complex because it provides its own header	2710	will be compiled. It is pretty complex because it provides its own header
2043	file.	2711	file.
2044		2712
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2713	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2046	that everybody includes and which overrides some autoconf choices:	2714	that everybody includes and which overrides some configure choices:
2047		2715
		2716	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	2717	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	2718	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	2719	#define EV_PERIODIC_ENABLE 0
		2720	#define EV_STAT_ENABLE 0
		2721	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	2722	#define EV_CONFIG_H <config.h>
		2723	#define EV_MINPRI 0
		2724	#define EV_MAXPRI 0
2052		2725
2053	#include "ev++.h"	2726	#include "ev++.h"
2054		2727
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2728	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		2729
…		…
2062		2735
2063	In this section the complexities of (many of) the algorithms used inside	2736	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	2737	libev will be explained. For complexity discussions about backends see the
2065	documentation for C<ev_default_init>.	2738	documentation for C<ev_default_init>.
2066		2739
		2740	All of the following are about amortised time: If an array needs to be
		2741	extended, libev needs to realloc and move the whole array, but this
		2742	happens asymptotically never with higher number of elements, so O(1) might
		2743	mean it might do a lengthy realloc operation in rare cases, but on average
		2744	it is much faster and asymptotically approaches constant time.
		2745
2067	=over 4	2746	=over 4
2068		2747
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2748	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		2749
		2750	This means that, when you have a watcher that triggers in one hour and
		2751	there are 100 watchers that would trigger before that then inserting will
		2752	have to skip roughly seven (C<ld 100>) of these watchers.
		2753
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2754	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2755
		2756	That means that changing a timer costs less than removing/adding them
		2757	as only the relative motion in the event queue has to be paid for.
2072		2758
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2759	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2074		2760
		2761	These just add the watcher into an array or at the head of a list.
		2762
2075	=item Stopping check/prepare/idle watchers: O(1)	2763	=item Stopping check/prepare/idle watchers: O(1)
2076		2764
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2765	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		2766
		2767	These watchers are stored in lists then need to be walked to find the
		2768	correct watcher to remove. The lists are usually short (you don't usually
		2769	have many watchers waiting for the same fd or signal).
		2770
2079	=item Finding the next timer per loop iteration: O(1)	2771	=item Finding the next timer in each loop iteration: O(1)
		2772
		2773	By virtue of using a binary heap, the next timer is always found at the
		2774	beginning of the storage array.
2080		2775
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2776	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		2777
2083	=item Activating one watcher: O(1)	2778	A change means an I/O watcher gets started or stopped, which requires
		2779	libev to recalculate its status (and possibly tell the kernel, depending
		2780	on backend and wether C<ev_io_set> was used).
		2781
		2782	=item Activating one watcher (putting it into the pending state): O(1)
		2783
		2784	=item Priority handling: O(number_of_priorities)
		2785
		2786	Priorities are implemented by allocating some space for each
		2787	priority. When doing priority-based operations, libev usually has to
		2788	linearly search all the priorities, but starting/stopping and activating
		2789	watchers becomes O(1) w.r.t. prioritiy handling.
2084		2790
2085	=back	2791	=back
2086		2792
2087		2793
		2794	=head1 Win32 platform limitations and workarounds
		2795
		2796	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2797	requires, and its I/O model is fundamentally incompatible with the POSIX
		2798	model. Libev still offers limited functionality on this platform in
		2799	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2800	descriptors. This only applies when using Win32 natively, not when using
		2801	e.g. cygwin.
		2802
		2803	There is no supported compilation method available on windows except
		2804	embedding it into other applications.
		2805
		2806	Due to the many, low, and arbitrary limits on the win32 platform and the
		2807	abysmal performance of winsockets, using a large number of sockets is not
		2808	recommended (and not reasonable). If your program needs to use more than
		2809	a hundred or so sockets, then likely it needs to use a totally different
		2810	implementation for windows, as libev offers the POSIX model, which cannot
		2811	be implemented efficiently on windows (microsoft monopoly games).
		2812
		2813	=over 4
		2814
		2815	=item The winsocket select function
		2816
		2817	The winsocket C<select> function doesn't follow POSIX in that it requires
		2818	socket I<handles> and not socket I<file descriptors>. This makes select
		2819	very inefficient, and also requires a mapping from file descriptors
		2820	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2821	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2822	symbols for more info.
		2823
		2824	The configuration for a "naked" win32 using the microsoft runtime
		2825	libraries and raw winsocket select is:
		2826
		2827	#define EV_USE_SELECT 1
		2828	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2829
		2830	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2831	complexity in the O(n²) range when using win32.
		2832
		2833	=item Limited number of file descriptors
		2834
		2835	Windows has numerous arbitrary (and low) limits on things. Early versions
		2836	of winsocket's select only supported waiting for a max. of C<64> handles
		2837	(probably owning to the fact that all windows kernels can only wait for
		2838	C<64> things at the same time internally; microsoft recommends spawning a
		2839	chain of threads and wait for 63 handles and the previous thread in each).
		2840
		2841	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2842	to some high number (e.g. C<2048>) before compiling the winsocket select
		2843	call (which might be in libev or elsewhere, for example, perl does its own
		2844	select emulation on windows).
		2845
		2846	Another limit is the number of file descriptors in the microsoft runtime
		2847	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2848	or something like this inside microsoft). You can increase this by calling
		2849	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2850	arbitrary limit), but is broken in many versions of the microsoft runtime
		2851	libraries.
		2852
		2853	This might get you to about C<512> or C<2048> sockets (depending on
		2854	windows version and/or the phase of the moon). To get more, you need to
		2855	wrap all I/O functions and provide your own fd management, but the cost of
		2856	calling select (O(n²)) will likely make this unworkable.
		2857
		2858	=back
		2859
		2860
2088	=head1 AUTHOR	2861	=head1 AUTHOR
2089		2862
2090	Marc Lehmann <libev@schmorp.de>.	2863	Marc Lehmann <libev@schmorp.de>.
2091		2864

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