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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
…		…
115	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
116	recommended ones.	179	recommended ones.
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, size_t size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
121		184
122	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
123	identical to the realloc C function). It is used to allocate and free	186	semantics is identical - to the realloc C function). It is used to
124	memory (no surprises here). If it returns zero when memory needs to be	187	allocate and free memory (no surprises here). If it returns zero when
125	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
126	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, size_t size)	200	persistent_realloc (void *ptr, size_t size)
137	{	201	{
138	for (;;)	202	for (;;)
…		…
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);
…		…
196	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
197		261
198	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
199	function.	263	function.
200		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
201	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
202	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
203		274
204	The following flags are supported:	275	The following flags are supported:
205		276
…		…
217	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
218	override the flags completely if it is found in the environment. This is	289	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	290	useful to try out specific backends to test their performance, or to work
220	around bugs.	291	around bugs.
221		292
		293	=item C<EVFLAG_FORKCHECK>
		294
		295	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		296	a fork, you can also make libev check for a fork in each iteration by
		297	enabling this flag.
		298
		299	This works by calling C<getpid ()> on every iteration of the loop,
		300	and thus this might slow down your event loop if you do a lot of loop
		301	iterations and little real work, but is usually not noticeable (on my
		302	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		303	without a syscall and thus I<very> fast, but my Linux system also has
		304	C<pthread_atfork> which is even faster).
		305
		306	The big advantage of this flag is that you can forget about fork (and
		307	forget about forgetting to tell libev about forking) when you use this
		308	flag.
		309
		310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		311	environment variable.
		312
222	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
223		314
224	This is your standard select(2) backend. Not I<completely> standard, as	315	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,	316	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	317	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	318	using this backend. It doesn't scale too well (O(highest_fd)), but its
228	the fastest backend for a low number of fds.	319	usually the fastest backend for a low number of (low-numbered :) fds.
		320
		321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
229		327
230	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
231		329
232	And this is your standard poll(2) backend. It's more complicated than	330	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	331	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	332	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).	333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
236		336
237	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
238		338
239	For few fds, this backend is a bit little slower than poll and select,	339	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	340	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	341	like O(total_fds) where n is the total number of fds (or the highest fd),
242	either O(1) or O(active_fds).	342	epoll scales either O(1) or O(active_fds). The epoll design has a number
		343	of shortcomings, such as silently dropping events in some hard-to-detect
		344	cases and rewiring a syscall per fd change, no fork support and bad
		345	support for dup.
243		346
244	While stopping and starting an I/O watcher in the same iteration will	347	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	348	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	349	(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	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
248	well if you register events for both fds.	351	very well if you register events for both fds.
249		352
250	Please note that epoll sometimes generates spurious notifications, so you	353	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	354	need to use non-blocking I/O or other means to avoid blocking when no data
252	(or space) is available.	355	(or space) is available.
253		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
254	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
255		365
256	Kqueue deserves special mention, as at the time of this writing, it	366	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	367	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	368	with anything but sockets and pipes, except on Darwin, where of course
259	completely useless). For this reason its not being "autodetected"	369	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	370	unless you explicitly specify it explicitly in the flags (i.e. using
261	C<EVBACKEND_KQUEUE>).	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		372	system like NetBSD.
		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
262		377
263	It scales in the same way as the epoll backend, but the interface to the	378	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	379	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	380	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	381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
267	incident, so its best to avoid that.	382	two event changes per incident, support for C<fork ()> is very bad and it
		383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
268		393
269	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
270		395
271	This is not implemented yet (and might never be).	396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
272		400
273	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
274		402
275	This uses the Solaris 10 port mechanism. As with everything on Solaris,	403	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)).	404	it's really slow, but it still scales very well (O(active_fds)).
277		405
278	Please note that solaris ports can result in a lot of spurious	406	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	407	notifications, so you need to use non-blocking I/O or other means to avoid
280	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
281		418
282	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
283		420
284	Try all backends (even potentially broken ones that wouldn't be tried	421	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	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
286	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
287		424
		425	It is definitely not recommended to use this flag.
		426
288	=back	427	=back
289		428
290	If one or more of these are ored into the flags value, then only these	429	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	430	backends will be tried (in the reverse order as listed here). If none are
292	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
293	order of their flag values :)
294		432
295	The most typical usage is like this:	433	The most typical usage is like this:
296		434
297	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
298	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
313	Similar to C<ev_default_loop>, but always creates a new event loop that is	451	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	452	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	453	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).	454	undefined behaviour (or a failed assertion if assertions are enabled).
317		455
318	Example: try to create a event loop that uses epoll and nothing else.	456	Example: Try to create a event loop that uses epoll and nothing else.
319		457
320	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
321	if (!epoller)	459	if (!epoller)
322	fatal ("no epoll found here, maybe it hides under your chair");	460	fatal ("no epoll found here, maybe it hides under your chair");
323		461
…		…
326	Destroys the default loop again (frees all memory and kernel state	464	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	465	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	466	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>	467	responsibility to either stop all watchers cleanly yoursef I<before>
330	calling this function, or cope with the fact afterwards (which is usually	468	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	469	the easiest thing, you can just ignore the watchers and/or C<free ()> them
332	for example).	470	for example).
		471
		472	Note that certain global state, such as signal state, will not be freed by
		473	this function, and related watchers (such as signal and child watchers)
		474	would need to be stopped manually.
		475
		476	In general it is not advisable to call this function except in the
		477	rare occasion where you really need to free e.g. the signal handling
		478	pipe fds. If you need dynamically allocated loops it is better to use
		479	C<ev_loop_new> and C<ev_loop_destroy>).
333		480
334	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
335		482
336	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
337	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
…		…
361		508
362	Like C<ev_default_fork>, but acts on an event loop created by	509	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	510	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.	511	after fork, and how you do this is entirely your own problem.
365		512
		513	=item unsigned int ev_loop_count (loop)
		514
		515	Returns the count of loop iterations for the loop, which is identical to
		516	the number of times libev did poll for new events. It starts at C<0> and
		517	happily wraps around with enough iterations.
		518
		519	This value can sometimes be useful as a generation counter of sorts (it
		520	"ticks" the number of loop iterations), as it roughly corresponds with
		521	C<ev_prepare> and C<ev_check> calls.
		522
366	=item unsigned int ev_backend (loop)	523	=item unsigned int ev_backend (loop)
367		524
368	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	525	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
369	use.	526	use.
370		527
…		…
372		529
373	Returns the current "event loop time", which is the time the event loop	530	Returns the current "event loop time", which is the time the event loop
374	received events and started processing them. This timestamp does not	531	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	532	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	533	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).	534	event occurring (or more correctly, libev finding out about it).
378		535
379	=item ev_loop (loop, int flags)	536	=item ev_loop (loop, int flags)
380		537
381	Finally, this is it, the event handler. This function usually is called	538	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	539	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	560	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
404	usually a better approach for this kind of thing.	561	usually a better approach for this kind of thing.
405		562
406	Here are the gory details of what C<ev_loop> does:	563	Here are the gory details of what C<ev_loop> does:
407		564
408	* If there are no active watchers (reference count is zero), return.	565	- Before the first iteration, call any pending watchers.
409	- Queue prepare watchers and then call all outstanding watchers.	566	* If EVFLAG_FORKCHECK was used, check for a fork.
		567	- If a fork was detected, queue and call all fork watchers.
		568	- Queue and call all prepare watchers.
410	- If we have been forked, recreate the kernel state.	569	- If we have been forked, recreate the kernel state.
411	- Update the kernel state with all outstanding changes.	570	- Update the kernel state with all outstanding changes.
412	- Update the "event loop time".	571	- Update the "event loop time".
413	- Calculate for how long to block.	572	- Calculate for how long to sleep or block, if at all
		573	(active idle watchers, EVLOOP_NONBLOCK or not having
		574	any active watchers at all will result in not sleeping).
		575	- Sleep if the I/O and timer collect interval say so.
414	- Block the process, waiting for any events.	576	- Block the process, waiting for any events.
415	- Queue all outstanding I/O (fd) events.	577	- Queue all outstanding I/O (fd) events.
416	- Update the "event loop time" and do time jump handling.	578	- Update the "event loop time" and do time jump handling.
417	- Queue all outstanding timers.	579	- Queue all outstanding timers.
418	- Queue all outstanding periodics.	580	- Queue all outstanding periodics.
419	- If no events are pending now, queue all idle watchers.	581	- If no events are pending now, queue all idle watchers.
420	- Queue all check watchers.	582	- Queue all check watchers.
421	- Call all queued watchers in reverse order (i.e. check watchers first).	583	- 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	584	Signals and child watchers are implemented as I/O watchers, and will
423	be handled here by queueing them when their watcher gets executed.	585	be handled here by queueing them when their watcher gets executed.
424	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	586	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
425	were used, return, otherwise continue with step *.	587	were used, or there are no active watchers, return, otherwise
		588	continue with step *.
426		589
427	Example: queue some jobs and then loop until no events are outsanding	590	Example: Queue some jobs and then loop until no events are outstanding
428	anymore.	591	anymore.
429		592
430	... queue jobs here, make sure they register event watchers as long	593	... 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..)	594	... as they still have work to do (even an idle watcher will do..)
432	ev_loop (my_loop, 0);	595	ev_loop (my_loop, 0);
…		…
436		599
437	Can be used to make a call to C<ev_loop> return early (but only after it	600	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	601	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	602	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.	603	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		604
		605	This "unloop state" will be cleared when entering C<ev_loop> again.
441		606
442	=item ev_ref (loop)	607	=item ev_ref (loop)
443		608
444	=item ev_unref (loop)	609	=item ev_unref (loop)
445		610
…		…
450	returning, ev_unref() after starting, and ev_ref() before stopping it. For	615	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	616	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	617	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	618	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	619	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>.	620	libraries. Just remember to I<unref after start> and I<ref before stop>
		621	(but only if the watcher wasn't active before, or was active before,
		622	respectively).
456		623
457	Example: create a signal watcher, but keep it from keeping C<ev_loop>	624	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
458	running when nothing else is active.	625	running when nothing else is active.
459		626
460	struct dv_signal exitsig;	627	struct ev_signal exitsig;
461	ev_signal_init (&exitsig, sig_cb, SIGINT);	628	ev_signal_init (&exitsig, sig_cb, SIGINT);
462	ev_signal_start (myloop, &exitsig);	629	ev_signal_start (loop, &exitsig);
463	evf_unref (myloop);	630	evf_unref (loop);
464		631
465	Example: for some weird reason, unregister the above signal handler again.	632	Example: For some weird reason, unregister the above signal handler again.
466		633
467	ev_ref (myloop);	634	ev_ref (loop);
468	ev_signal_stop (myloop, &exitsig);	635	ev_signal_stop (loop, &exitsig);
		636
		637	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		638
		639	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		640
		641	These advanced functions influence the time that libev will spend waiting
		642	for events. Both are by default C<0>, meaning that libev will try to
		643	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		644
		645	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		646	allows libev to delay invocation of I/O and timer/periodic callbacks to
		647	increase efficiency of loop iterations.
		648
		649	The background is that sometimes your program runs just fast enough to
		650	handle one (or very few) event(s) per loop iteration. While this makes
		651	the program responsive, it also wastes a lot of CPU time to poll for new
		652	events, especially with backends like C<select ()> which have a high
		653	overhead for the actual polling but can deliver many events at once.
		654
		655	By setting a higher I<io collect interval> you allow libev to spend more
		656	time collecting I/O events, so you can handle more events per iteration,
		657	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		658	C<ev_timer>) will be not affected. Setting this to a non-null value will
		659	introduce an additional C<ev_sleep ()> call into most loop iterations.
		660
		661	Likewise, by setting a higher I<timeout collect interval> you allow libev
		662	to spend more time collecting timeouts, at the expense of increased
		663	latency (the watcher callback will be called later). C<ev_io> watchers
		664	will not be affected. Setting this to a non-null value will not introduce
		665	any overhead in libev.
		666
		667	Many (busy) programs can usually benefit by setting the io collect
		668	interval to a value near C<0.1> or so, which is often enough for
		669	interactive servers (of course not for games), likewise for timeouts. It
		670	usually doesn't make much sense to set it to a lower value than C<0.01>,
		671	as this approsaches the timing granularity of most systems.
469		672
470	=back	673	=back
471		674
472		675
473	=head1 ANATOMY OF A WATCHER	676	=head1 ANATOMY OF A WATCHER
…		…
653	=item bool ev_is_pending (ev_TYPE *watcher)	856	=item bool ev_is_pending (ev_TYPE *watcher)
654		857
655	Returns a true value iff the watcher is pending, (i.e. it has outstanding	858	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	859	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	860	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	861	C<ev_TYPE_set> is safe), you must not change its priority, and you must
659	libev (e.g. you cnanot C<free ()> it).	862	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		863	it).
660		864
661	=item callback = ev_cb (ev_TYPE *watcher)	865	=item callback ev_cb (ev_TYPE *watcher)
662		866
663	Returns the callback currently set on the watcher.	867	Returns the callback currently set on the watcher.
664		868
665	=item ev_cb_set (ev_TYPE *watcher, callback)	869	=item ev_cb_set (ev_TYPE *watcher, callback)
666		870
667	Change the callback. You can change the callback at virtually any time	871	Change the callback. You can change the callback at virtually any time
668	(modulo threads).	872	(modulo threads).
		873
		874	=item ev_set_priority (ev_TYPE *watcher, priority)
		875
		876	=item int ev_priority (ev_TYPE *watcher)
		877
		878	Set and query the priority of the watcher. The priority is a small
		879	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		880	(default: C<-2>). Pending watchers with higher priority will be invoked
		881	before watchers with lower priority, but priority will not keep watchers
		882	from being executed (except for C<ev_idle> watchers).
		883
		884	This means that priorities are I<only> used for ordering callback
		885	invocation after new events have been received. This is useful, for
		886	example, to reduce latency after idling, or more often, to bind two
		887	watchers on the same event and make sure one is called first.
		888
		889	If you need to suppress invocation when higher priority events are pending
		890	you need to look at C<ev_idle> watchers, which provide this functionality.
		891
		892	You I<must not> change the priority of a watcher as long as it is active or
		893	pending.
		894
		895	The default priority used by watchers when no priority has been set is
		896	always C<0>, which is supposed to not be too high and not be too low :).
		897
		898	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		899	fine, as long as you do not mind that the priority value you query might
		900	or might not have been adjusted to be within valid range.
		901
		902	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		903
		904	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		905	C<loop> nor C<revents> need to be valid as long as the watcher callback
		906	can deal with that fact.
		907
		908	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		909
		910	If the watcher is pending, this function returns clears its pending status
		911	and returns its C<revents> bitset (as if its callback was invoked). If the
		912	watcher isn't pending it does nothing and returns C<0>.
669		913
670	=back	914	=back
671		915
672		916
673	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	917	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
694	{	938	{
695	struct my_io *w = (struct my_io *)w_;	939	struct my_io *w = (struct my_io *)w_;
696	...	940	...
697	}	941	}
698		942
699	More interesting and less C-conformant ways of catsing your callback type	943	More interesting and less C-conformant ways of casting your callback type
700	have been omitted....	944	instead have been omitted.
		945
		946	Another common scenario is having some data structure with multiple
		947	watchers:
		948
		949	struct my_biggy
		950	{
		951	int some_data;
		952	ev_timer t1;
		953	ev_timer t2;
		954	}
		955
		956	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		957	you need to use C<offsetof>:
		958
		959	#include <stddef.h>
		960
		961	static void
		962	t1_cb (EV_P_ struct ev_timer *w, int revents)
		963	{
		964	struct my_biggy big = (struct my_biggy *
		965	(((char *)w) - offsetof (struct my_biggy, t1));
		966	}
		967
		968	static void
		969	t2_cb (EV_P_ struct ev_timer *w, int revents)
		970	{
		971	struct my_biggy big = (struct my_biggy *
		972	(((char *)w) - offsetof (struct my_biggy, t2));
		973	}
701		974
702		975
703	=head1 WATCHER TYPES	976	=head1 WATCHER TYPES
704		977
705	This section describes each watcher in detail, but will not repeat	978	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	1002	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	1003	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	1004	descriptors to non-blocking mode is also usually a good idea (but not
732	required if you know what you are doing).	1005	required if you know what you are doing).
733		1006
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	1007	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	1008	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
742	C<EVBACKEND_POLL>).	1009	C<EVBACKEND_POLL>).
743		1010
744	Another thing you have to watch out for is that it is quite easy to	1011	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	1017	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.	1018	C<EAGAIN> is far preferable to a program hanging until some data arrives.
752		1019
753	If you cannot run the fd in non-blocking mode (for example you should not	1020	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	1021	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	1022	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	1023	such as poll (fortunately in our Xlib example, Xlib already does this on
757	its own, so its quite safe to use).	1024	its own, so its quite safe to use).
		1025
		1026	=head3 The special problem of disappearing file descriptors
		1027
		1028	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1029	descriptor (either by calling C<close> explicitly or by any other means,
		1030	such as C<dup>). The reason is that you register interest in some file
		1031	descriptor, but when it goes away, the operating system will silently drop
		1032	this interest. If another file descriptor with the same number then is
		1033	registered with libev, there is no efficient way to see that this is, in
		1034	fact, a different file descriptor.
		1035
		1036	To avoid having to explicitly tell libev about such cases, libev follows
		1037	the following policy: Each time C<ev_io_set> is being called, libev
		1038	will assume that this is potentially a new file descriptor, otherwise
		1039	it is assumed that the file descriptor stays the same. That means that
		1040	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1041	descriptor even if the file descriptor number itself did not change.
		1042
		1043	This is how one would do it normally anyway, the important point is that
		1044	the libev application should not optimise around libev but should leave
		1045	optimisations to libev.
		1046
		1047	=head3 The special problem of dup'ed file descriptors
		1048
		1049	Some backends (e.g. epoll), cannot register events for file descriptors,
		1050	but only events for the underlying file descriptions. That means when you
		1051	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1052	events for them, only one file descriptor might actually receive events.
		1053
		1054	There is no workaround possible except not registering events
		1055	for potentially C<dup ()>'ed file descriptors, or to resort to
		1056	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1057
		1058	=head3 The special problem of fork
		1059
		1060	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1061	useless behaviour. Libev fully supports fork, but needs to be told about
		1062	it in the child.
		1063
		1064	To support fork in your programs, you either have to call
		1065	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1066	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1067	C<EVBACKEND_POLL>.
		1068
		1069
		1070	=head3 Watcher-Specific Functions
758		1071
759	=over 4	1072	=over 4
760		1073
761	=item ev_io_init (ev_io *, callback, int fd, int events)	1074	=item ev_io_init (ev_io *, callback, int fd, int events)
762		1075
…		…
774		1087
775	The events being watched.	1088	The events being watched.
776		1089
777	=back	1090	=back
778		1091
		1092	=head3 Examples
		1093
779	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1094	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	1095	readable, but only once. Since it is likely line-buffered, you could
781	attempt to read a whole line in the callback:	1096	attempt to read a whole line in the callback.
782		1097
783	static void	1098	static void
784	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1099	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
785	{	1100	{
786	ev_io_stop (loop, w);	1101	ev_io_stop (loop, w);
…		…
816		1131
817	The callback is guarenteed to be invoked only when its timeout has passed,	1132	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	1133	but if multiple timers become ready during the same loop iteration then
819	order of execution is undefined.	1134	order of execution is undefined.
820		1135
		1136	=head3 Watcher-Specific Functions and Data Members
		1137
821	=over 4	1138	=over 4
822		1139
823	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1140	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
824		1141
825	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1142	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
838	=item ev_timer_again (loop)	1155	=item ev_timer_again (loop)
839		1156
840	This will act as if the timer timed out and restart it again if it is	1157	This will act as if the timer timed out and restart it again if it is
841	repeating. The exact semantics are:	1158	repeating. The exact semantics are:
842		1159
		1160	If the timer is pending, its pending status is cleared.
		1161
843	If the timer is started but nonrepeating, stop it.	1162	If the timer is started but nonrepeating, stop it (as if it timed out).
844		1163
845	If the timer is repeating, either start it if necessary (with the repeat	1164	If the timer is repeating, either start it if necessary (with the
846	value), or reset the running timer to the repeat value.	1165	C<repeat> value), or reset the running timer to the C<repeat> value.
847		1166
848	This sounds a bit complicated, but here is a useful and typical	1167	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	1168	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,	1169	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	1170	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	1171	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	1172	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	1173	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	1174	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
856	need be.	1175	automatically restart it if need be.
857		1176
858	You can also ignore the C<after> value and C<ev_timer_start> altogether	1177	That means you can ignore the C<after> value and C<ev_timer_start>
859	and only ever use the C<repeat> value:	1178	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
860		1179
861	ev_timer_init (timer, callback, 0., 5.);	1180	ev_timer_init (timer, callback, 0., 5.);
862	ev_timer_again (loop, timer);	1181	ev_timer_again (loop, timer);
863	...	1182	...
864	timer->again = 17.;	1183	timer->again = 17.;
865	ev_timer_again (loop, timer);	1184	ev_timer_again (loop, timer);
866	...	1185	...
867	timer->again = 10.;	1186	timer->again = 10.;
868	ev_timer_again (loop, timer);	1187	ev_timer_again (loop, timer);
869		1188
870	This is more efficient then stopping/starting the timer eahc time you want	1189	This is more slightly efficient then stopping/starting the timer each time
871	to modify its timeout value.	1190	you want to modify its timeout value.
872		1191
873	=item ev_tstamp repeat [read-write]	1192	=item ev_tstamp repeat [read-write]
874		1193
875	The current C<repeat> value. Will be used each time the watcher times out	1194	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),	1195	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.	1196	which is also when any modifications are taken into account.
878		1197
879	=back	1198	=back
880		1199
		1200	=head3 Examples
		1201
881	Example: create a timer that fires after 60 seconds.	1202	Example: Create a timer that fires after 60 seconds.
882		1203
883	static void	1204	static void
884	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1205	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
885	{	1206	{
886	.. one minute over, w is actually stopped right here	1207	.. one minute over, w is actually stopped right here
…		…
888		1209
889	struct ev_timer mytimer;	1210	struct ev_timer mytimer;
890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1211	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
891	ev_timer_start (loop, &mytimer);	1212	ev_timer_start (loop, &mytimer);
892		1213
893	Example: create a timeout timer that times out after 10 seconds of	1214	Example: Create a timeout timer that times out after 10 seconds of
894	inactivity.	1215	inactivity.
895		1216
896	static void	1217	static void
897	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1218	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
898	{	1219	{
…		…
918	but on wallclock time (absolute time). You can tell a periodic watcher	1239	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	1240	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 ()	1241	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	1242	+ 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	1243	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	1244	roughly 10 seconds later).
924	again).
925		1245
926	They can also be used to implement vastly more complex timers, such as	1246	They can also be used to implement vastly more complex timers, such as
927	triggering an event on eahc midnight, local time.	1247	triggering an event on each midnight, local time or other, complicated,
		1248	rules.
928		1249
929	As with timers, the callback is guarenteed to be invoked only when the	1250	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	1251	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.	1252	during the same loop iteration then order of execution is undefined.
932		1253
		1254	=head3 Watcher-Specific Functions and Data Members
		1255
933	=over 4	1256	=over 4
934		1257
935	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1258	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
936		1259
937	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1260	=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	1262	Lots of arguments, lets sort it out... There are basically three modes of
940	operation, and we will explain them from simplest to complex:	1263	operation, and we will explain them from simplest to complex:
941		1264
942	=over 4	1265	=over 4
943		1266
944	=item * absolute timer (interval = reschedule_cb = 0)	1267	=item * absolute timer (at = time, interval = reschedule_cb = 0)
945		1268
946	In this configuration the watcher triggers an event at the wallclock time	1269	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,	1270	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	1271	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.	1272	system time reaches or surpasses this time.
950		1273
951	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1274	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
952		1275
953	In this mode the watcher will always be scheduled to time out at the next	1276	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	1277	C<at + N * interval> time (for some integer N, which can also be negative)
955	of any time jumps.	1278	and then repeat, regardless of any time jumps.
956		1279
957	This can be used to create timers that do not drift with respect to system	1280	This can be used to create timers that do not drift with respect to system
958	time:	1281	time:
959		1282
960	ev_periodic_set (&periodic, 0., 3600., 0);	1283	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
966		1289
967	Another way to think about it (for the mathematically inclined) is that	1290	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	1291	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.	1292	time where C<time = at (mod interval)>, regardless of any time jumps.
970		1293
		1294	For numerical stability it is preferable that the C<at> value is near
		1295	C<ev_now ()> (the current time), but there is no range requirement for
		1296	this value.
		1297
971	=item * manual reschedule mode (reschedule_cb = callback)	1298	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
972		1299
973	In this mode the values for C<interval> and C<at> are both being	1300	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	1301	ignored. Instead, each time the periodic watcher gets scheduled, the
975	reschedule callback will be called with the watcher as first, and the	1302	reschedule callback will be called with the watcher as first, and the
976	current time as second argument.	1303	current time as second argument.
977		1304
978	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1305	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,	1306	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	1307	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
981	starting a prepare watcher).	1308	starting an C<ev_prepare> watcher, which is legal).
982		1309
983	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1310	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984	ev_tstamp now)>, e.g.:	1311	ev_tstamp now)>, e.g.:
985		1312
986	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1313	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	1336	Simply stops and restarts the periodic watcher again. This is only useful
1010	when you changed some parameters or the reschedule callback would return	1337	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	1338	a different time than the last time it was called (e.g. in a crond like
1012	program when the crontabs have changed).	1339	program when the crontabs have changed).
1013		1340
		1341	=item ev_tstamp offset [read-write]
		1342
		1343	When repeating, this contains the offset value, otherwise this is the
		1344	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1345
		1346	Can be modified any time, but changes only take effect when the periodic
		1347	timer fires or C<ev_periodic_again> is being called.
		1348
1014	=item ev_tstamp interval [read-write]	1349	=item ev_tstamp interval [read-write]
1015		1350
1016	The current interval value. Can be modified any time, but changes only	1351	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	1352	take effect when the periodic timer fires or C<ev_periodic_again> is being
1018	called.	1353	called.
…		…
1021		1356
1022	The current reschedule callback, or C<0>, if this functionality is	1357	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	1358	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.	1359	the periodic timer fires or C<ev_periodic_again> is being called.
1025		1360
		1361	=item ev_tstamp at [read-only]
		1362
		1363	When active, contains the absolute time that the watcher is supposed to
		1364	trigger next.
		1365
1026	=back	1366	=back
1027		1367
		1368	=head3 Examples
		1369
1028	Example: call a callback every hour, or, more precisely, whenever the	1370	Example: Call a callback every hour, or, more precisely, whenever the
1029	system clock is divisible by 3600. The callback invocation times have	1371	system clock is divisible by 3600. The callback invocation times have
1030	potentially a lot of jittering, but good long-term stability.	1372	potentially a lot of jittering, but good long-term stability.
1031		1373
1032	static void	1374	static void
1033	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1375	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1037		1379
1038	struct ev_periodic hourly_tick;	1380	struct ev_periodic hourly_tick;
1039	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1381	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040	ev_periodic_start (loop, &hourly_tick);	1382	ev_periodic_start (loop, &hourly_tick);
1041		1383
1042	Example: the same as above, but use a reschedule callback to do it:	1384	Example: The same as above, but use a reschedule callback to do it:
1043		1385
1044	#include <math.h>	1386	#include <math.h>
1045		1387
1046	static ev_tstamp	1388	static ev_tstamp
1047	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1389	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1049	return fmod (now, 3600.) + 3600.;	1391	return fmod (now, 3600.) + 3600.;
1050	}	1392	}
1051		1393
1052	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1394	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1053		1395
1054	Example: call a callback every hour, starting now:	1396	Example: Call a callback every hour, starting now:
1055		1397
1056	struct ev_periodic hourly_tick;	1398	struct ev_periodic hourly_tick;
1057	ev_periodic_init (&hourly_tick, clock_cb,	1399	ev_periodic_init (&hourly_tick, clock_cb,
1058	fmod (ev_now (loop), 3600.), 3600., 0);	1400	fmod (ev_now (loop), 3600.), 3600., 0);
1059	ev_periodic_start (loop, &hourly_tick);	1401	ev_periodic_start (loop, &hourly_tick);
…		…
1071	with the kernel (thus it coexists with your own signal handlers as long	1413	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	1414	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	1415	watcher for a signal is stopped libev will reset the signal handler to
1074	SIG_DFL (regardless of what it was set to before).	1416	SIG_DFL (regardless of what it was set to before).
1075		1417
		1418	=head3 Watcher-Specific Functions and Data Members
		1419
1076	=over 4	1420	=over 4
1077		1421
1078	=item ev_signal_init (ev_signal *, callback, int signum)	1422	=item ev_signal_init (ev_signal *, callback, int signum)
1079		1423
1080	=item ev_signal_set (ev_signal *, int signum)	1424	=item ev_signal_set (ev_signal *, int signum)
…		…
1091		1435
1092	=head2 C<ev_child> - watch out for process status changes	1436	=head2 C<ev_child> - watch out for process status changes
1093		1437
1094	Child watchers trigger when your process receives a SIGCHLD in response to	1438	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).	1439	some child status changes (most typically when a child of yours dies).
		1440
		1441	=head3 Watcher-Specific Functions and Data Members
1096		1442
1097	=over 4	1443	=over 4
1098		1444
1099	=item ev_child_init (ev_child *, callback, int pid)	1445	=item ev_child_init (ev_child *, callback, int pid)
1100		1446
…		…
1120	The process exit/trace status caused by C<rpid> (see your systems	1466	The process exit/trace status caused by C<rpid> (see your systems
1121	C<waitpid> and C<sys/wait.h> documentation for details).	1467	C<waitpid> and C<sys/wait.h> documentation for details).
1122		1468
1123	=back	1469	=back
1124		1470
		1471	=head3 Examples
		1472
1125	Example: try to exit cleanly on SIGINT and SIGTERM.	1473	Example: Try to exit cleanly on SIGINT and SIGTERM.
1126		1474
1127	static void	1475	static void
1128	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1476	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1129	{	1477	{
1130	ev_unloop (loop, EVUNLOOP_ALL);	1478	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1145	not exist" is a status change like any other. The condition "path does	1493	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	1494	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	1495	otherwise always forced to be at least one) and all the other fields of
1148	the stat buffer having unspecified contents.	1496	the stat buffer having unspecified contents.
1149		1497
		1498	The path I<should> be absolute and I<must not> end in a slash. If it is
		1499	relative and your working directory changes, the behaviour is undefined.
		1500
1150	Since there is no standard to do this, the portable implementation simply	1501	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	1502	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	1503	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,	1504	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	1505	unspecified default> value will be used (which you can expect to be around
1155	five seconds, although this might change dynamically). Libev will also	1506	five seconds, although this might change dynamically). Libev will also
1156	impose a minimum interval which is currently around C<0.1>, but thats	1507	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1158		1509
1159	This watcher type is not meant for massive numbers of stat watchers,	1510	This watcher type is not meant for massive numbers of stat watchers,
1160	as even with OS-supported change notifications, this can be	1511	as even with OS-supported change notifications, this can be
1161	resource-intensive.	1512	resource-intensive.
1162		1513
1163	At the time of this writing, no specific OS backends are implemented, but	1514	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.	1515	implemented (implementing kqueue support is left as an exercise for the
		1516	reader). Inotify will be used to give hints only and should not change the
		1517	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1518	to fall back to regular polling again even with inotify, but changes are
		1519	usually detected immediately, and if the file exists there will be no
		1520	polling.
		1521
		1522	=head3 Inotify
		1523
		1524	When C<inotify (7)> support has been compiled into libev (generally only
		1525	available on Linux) and present at runtime, it will be used to speed up
		1526	change detection where possible. The inotify descriptor will be created lazily
		1527	when the first C<ev_stat> watcher is being started.
		1528
		1529	Inotify presense does not change the semantics of C<ev_stat> watchers
		1530	except that changes might be detected earlier, and in some cases, to avoid
		1531	making regular C<stat> calls. Even in the presense of inotify support
		1532	there are many cases where libev has to resort to regular C<stat> polling.
		1533
		1534	(There is no support for kqueue, as apparently it cannot be used to
		1535	implement this functionality, due to the requirement of having a file
		1536	descriptor open on the object at all times).
		1537
		1538	=head3 The special problem of stat time resolution
		1539
		1540	The C<stat ()> syscall only supports full-second resolution portably, and
		1541	even on systems where the resolution is higher, many filesystems still
		1542	only support whole seconds.
		1543
		1544	That means that, if the time is the only thing that changes, you might
		1545	miss updates: on the first update, C<ev_stat> detects a change and calls
		1546	your callback, which does something. When there is another update within
		1547	the same second, C<ev_stat> will be unable to detect it.
		1548
		1549	The solution to this is to delay acting on a change for a second (or till
		1550	the next second boundary), using a roughly one-second delay C<ev_timer>
		1551	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1552	is added to work around small timing inconsistencies of some operating
		1553	systems.
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
1165		1556
1166	=over 4	1557	=over 4
1167		1558
1168	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1559	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1169		1560
…		…
1205	=item const char *path [read-only]	1596	=item const char *path [read-only]
1206		1597
1207	The filesystem path that is being watched.	1598	The filesystem path that is being watched.
1208		1599
1209	=back	1600	=back
		1601
		1602	=head3 Examples
1210		1603
1211	Example: Watch C</etc/passwd> for attribute changes.	1604	Example: Watch C</etc/passwd> for attribute changes.
1212		1605
1213	static void	1606	static void
1214	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1607	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1227	}	1620	}
1228		1621
1229	...	1622	...
1230	ev_stat passwd;	1623	ev_stat passwd;
1231		1624
1232	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1233	ev_stat_start (loop, &passwd);	1626	ev_stat_start (loop, &passwd);
1234		1627
		1628	Example: Like above, but additionally use a one-second delay so we do not
		1629	miss updates (however, frequent updates will delay processing, too, so
		1630	one might do the work both on C<ev_stat> callback invocation I<and> on
		1631	C<ev_timer> callback invocation).
		1632
		1633	static ev_stat passwd;
		1634	static ev_timer timer;
		1635
		1636	static void
		1637	timer_cb (EV_P_ ev_timer *w, int revents)
		1638	{
		1639	ev_timer_stop (EV_A_ w);
		1640
		1641	/* now it's one second after the most recent passwd change */
		1642	}
		1643
		1644	static void
		1645	stat_cb (EV_P_ ev_stat *w, int revents)
		1646	{
		1647	/* reset the one-second timer */
		1648	ev_timer_again (EV_A_ &timer);
		1649	}
		1650
		1651	...
		1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1653	ev_stat_start (loop, &passwd);
		1654	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1655
1235		1656
1236	=head2 C<ev_idle> - when you've got nothing better to do...	1657	=head2 C<ev_idle> - when you've got nothing better to do...
1237		1658
1238	Idle watchers trigger events when there are no other events are pending	1659	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	1660	priority are pending (prepare, check and other idle watchers do not
1240	as your process is busy handling sockets or timeouts (or even signals,	1661	count).
1241	imagine) it will not be triggered. But when your process is idle all idle	1662
1242	watchers are being called again and again, once per event loop iteration -	1663	That is, as long as your process is busy handling sockets or timeouts
		1664	(or even signals, imagine) of the same or higher priority it will not be
		1665	triggered. But when your process is idle (or only lower-priority watchers
		1666	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	1667	iteration - until stopped, that is, or your process receives more events
1244	busy.	1668	and becomes busy again with higher priority stuff.
1245		1669
1246	The most noteworthy effect is that as long as any idle watchers are	1670	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.	1671	active, the process will not block when waiting for new events.
1248		1672
1249	Apart from keeping your process non-blocking (which is a useful	1673	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	1674	effect on its own sometimes), idle watchers are a good place to do
1251	"pseudo-background processing", or delay processing stuff to after the	1675	"pseudo-background processing", or delay processing stuff to after the
1252	event loop has handled all outstanding events.	1676	event loop has handled all outstanding events.
1253		1677
		1678	=head3 Watcher-Specific Functions and Data Members
		1679
1254	=over 4	1680	=over 4
1255		1681
1256	=item ev_idle_init (ev_signal *, callback)	1682	=item ev_idle_init (ev_signal *, callback)
1257		1683
1258	Initialises and configures the idle watcher - it has no parameters of any	1684	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,	1685	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1260	believe me.	1686	believe me.
1261		1687
1262	=back	1688	=back
1263		1689
		1690	=head3 Examples
		1691
1264	Example: dynamically allocate an C<ev_idle>, start it, and in the	1692	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1265	callback, free it. Alos, use no error checking, as usual.	1693	callback, free it. Also, use no error checking, as usual.
1266		1694
1267	static void	1695	static void
1268	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1696	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1269	{	1697	{
1270	free (w);	1698	free (w);
…		…
1315	with priority higher than or equal to the event loop and one coroutine	1743	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	1744	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	1745	loop from blocking if lower-priority coroutines are active, thus mapping
1318	low-priority coroutines to idle/background tasks).	1746	low-priority coroutines to idle/background tasks).
1319		1747
		1748	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1749	priority, to ensure that they are being run before any other watchers
		1750	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1751	too) should not activate ("feed") events into libev. While libev fully
		1752	supports this, they will be called before other C<ev_check> watchers
		1753	did their job. As C<ev_check> watchers are often used to embed other
		1754	(non-libev) event loops those other event loops might be in an unusable
		1755	state until their C<ev_check> watcher ran (always remind yourself to
		1756	coexist peacefully with others).
		1757
		1758	=head3 Watcher-Specific Functions and Data Members
		1759
1320	=over 4	1760	=over 4
1321		1761
1322	=item ev_prepare_init (ev_prepare *, callback)	1762	=item ev_prepare_init (ev_prepare *, callback)
1323		1763
1324	=item ev_check_init (ev_check *, callback)	1764	=item ev_check_init (ev_check *, callback)
…		…
1327	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1767	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.	1768	macros, but using them is utterly, utterly and completely pointless.
1329		1769
1330	=back	1770	=back
1331		1771
1332	Example: To include a library such as adns, you would add IO watchers	1772	=head3 Examples
1333	and a timeout watcher in a prepare handler, as required by libadns, and	1773
		1774	There are a number of principal ways to embed other event loops or modules
		1775	into libev. Here are some ideas on how to include libadns into libev
		1776	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1777	use for an actually working example. Another Perl module named C<EV::Glib>
		1778	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1779	into the Glib event loop).
		1780
		1781	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	1782	and in a check watcher, destroy them and call into libadns. What follows
1335	pseudo-code only of course:	1783	is pseudo-code only of course. This requires you to either use a low
		1784	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1785	the callbacks for the IO/timeout watchers might not have been called yet.
1336		1786
1337	static ev_io iow [nfd];	1787	static ev_io iow [nfd];
1338	static ev_timer tw;	1788	static ev_timer tw;
1339		1789
1340	static void	1790	static void
1341	io_cb (ev_loop *loop, ev_io *w, int revents)	1791	io_cb (ev_loop *loop, ev_io *w, int revents)
1342	{	1792	{
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	}	1793	}
1349		1794
1350	// create io watchers for each fd and a timer before blocking	1795	// create io watchers for each fd and a timer before blocking
1351	static void	1796	static void
1352	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1797	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1353	{	1798	{
1354	int timeout = 3600000;truct pollfd fds [nfd];	1799	int timeout = 3600000;
		1800	struct pollfd fds [nfd];
1355	// actual code will need to loop here and realloc etc.	1801	// actual code will need to loop here and realloc etc.
1356	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1357		1803
1358	/* the callback is illegal, but won't be called as we stop during check */	1804	/* the callback is illegal, but won't be called as we stop during check */
1359	ev_timer_init (&tw, 0, timeout * 1e-3);	1805	ev_timer_init (&tw, 0, timeout * 1e-3);
1360	ev_timer_start (loop, &tw);	1806	ev_timer_start (loop, &tw);
1361		1807
1362	// create on ev_io per pollfd	1808	// create one ev_io per pollfd
1363	for (int i = 0; i < nfd; ++i)	1809	for (int i = 0; i < nfd; ++i)
1364	{	1810	{
1365	ev_io_init (iow + i, io_cb, fds [i].fd,	1811	ev_io_init (iow + i, io_cb, fds [i].fd,
1366	((fds [i].events & POLLIN ? EV_READ : 0)	1812	((fds [i].events & POLLIN ? EV_READ : 0)
1367	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1813	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1368		1814
1369	fds [i].revents = 0;	1815	fds [i].revents = 0;
1370	iow [i].data = fds + i;
1371	ev_io_start (loop, iow + i);	1816	ev_io_start (loop, iow + i);
1372	}	1817	}
1373	}	1818	}
1374		1819
1375	// stop all watchers after blocking	1820	// stop all watchers after blocking
…		…
1377	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1822	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1378	{	1823	{
1379	ev_timer_stop (loop, &tw);	1824	ev_timer_stop (loop, &tw);
1380		1825
1381	for (int i = 0; i < nfd; ++i)	1826	for (int i = 0; i < nfd; ++i)
		1827	{
		1828	// set the relevant poll flags
		1829	// could also call adns_processreadable etc. here
		1830	struct pollfd *fd = fds + i;
		1831	int revents = ev_clear_pending (iow + i);
		1832	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1833	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1834
		1835	// now stop the watcher
1382	ev_io_stop (loop, iow + i);	1836	ev_io_stop (loop, iow + i);
		1837	}
1383		1838
1384	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1839	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1840	}
		1841
		1842	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1843	in the prepare watcher and would dispose of the check watcher.
		1844
		1845	Method 3: If the module to be embedded supports explicit event
		1846	notification (adns does), you can also make use of the actual watcher
		1847	callbacks, and only destroy/create the watchers in the prepare watcher.
		1848
		1849	static void
		1850	timer_cb (EV_P_ ev_timer *w, int revents)
		1851	{
		1852	adns_state ads = (adns_state)w->data;
		1853	update_now (EV_A);
		1854
		1855	adns_processtimeouts (ads, &tv_now);
		1856	}
		1857
		1858	static void
		1859	io_cb (EV_P_ ev_io *w, int revents)
		1860	{
		1861	adns_state ads = (adns_state)w->data;
		1862	update_now (EV_A);
		1863
		1864	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1865	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1866	}
		1867
		1868	// do not ever call adns_afterpoll
		1869
		1870	Method 4: Do not use a prepare or check watcher because the module you
		1871	want to embed is too inflexible to support it. Instead, youc na override
		1872	their poll function. The drawback with this solution is that the main
		1873	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1874	this.
		1875
		1876	static gint
		1877	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1878	{
		1879	int got_events = 0;
		1880
		1881	for (n = 0; n < nfds; ++n)
		1882	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1883
		1884	if (timeout >= 0)
		1885	// create/start timer
		1886
		1887	// poll
		1888	ev_loop (EV_A_ 0);
		1889
		1890	// stop timer again
		1891	if (timeout >= 0)
		1892	ev_timer_stop (EV_A_ &to);
		1893
		1894	// stop io watchers again - their callbacks should have set
		1895	for (n = 0; n < nfds; ++n)
		1896	ev_io_stop (EV_A_ iow [n]);
		1897
		1898	return got_events;
1385	}	1899	}
1386		1900
1387		1901
1388	=head2 C<ev_embed> - when one backend isn't enough...	1902	=head2 C<ev_embed> - when one backend isn't enough...
1389		1903
…		…
1432	portable one.	1946	portable one.
1433		1947
1434	So when you want to use this feature you will always have to be prepared	1948	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	1949	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	1950	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:	1951	create it, and if that fails, use the normal loop for everything.
		1952
		1953	=head3 Watcher-Specific Functions and Data Members
		1954
		1955	=over 4
		1956
		1957	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1958
		1959	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1960
		1961	Configures the watcher to embed the given loop, which must be
		1962	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1963	invoked automatically, otherwise it is the responsibility of the callback
		1964	to invoke it (it will continue to be called until the sweep has been done,
		1965	if you do not want thta, you need to temporarily stop the embed watcher).
		1966
		1967	=item ev_embed_sweep (loop, ev_embed *)
		1968
		1969	Make a single, non-blocking sweep over the embedded loop. This works
		1970	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1971	apropriate way for embedded loops.
		1972
		1973	=item struct ev_loop *other [read-only]
		1974
		1975	The embedded event loop.
		1976
		1977	=back
		1978
		1979	=head3 Examples
		1980
		1981	Example: Try to get an embeddable event loop and embed it into the default
		1982	event loop. If that is not possible, use the default loop. The default
		1983	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1984	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1985	used).
1438		1986
1439	struct ev_loop *loop_hi = ev_default_init (0);	1987	struct ev_loop *loop_hi = ev_default_init (0);
1440	struct ev_loop *loop_lo = 0;	1988	struct ev_loop *loop_lo = 0;
1441	struct ev_embed embed;	1989	struct ev_embed embed;
1442		1990
…		…
1453	ev_embed_start (loop_hi, &embed);	2001	ev_embed_start (loop_hi, &embed);
1454	}	2002	}
1455	else	2003	else
1456	loop_lo = loop_hi;	2004	loop_lo = loop_hi;
1457		2005
1458	=over 4	2006	Example: Check if kqueue is available but not recommended and create
		2007	a kqueue backend for use with sockets (which usually work with any
		2008	kqueue implementation). Store the kqueue/socket-only event loop in
		2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1459		2010
1460	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2011	struct ev_loop *loop = ev_default_init (0);
		2012	struct ev_loop *loop_socket = 0;
		2013	struct ev_embed embed;
		2014
		2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2017	{
		2018	ev_embed_init (&embed, 0, loop_socket);
		2019	ev_embed_start (loop, &embed);
		2020	}
1461		2021
1462	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2022	if (!loop_socket)
		2023	loop_socket = loop;
1463		2024
1464	Configures the watcher to embed the given loop, which must be	2025	// 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		2026
1482		2027
1483	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2028	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1484		2029
1485	Fork watchers are called when a C<fork ()> was detected (usually because	2030	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,	2033	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	2034	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	2035	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1491	handlers will be invoked, too, of course.	2036	handlers will be invoked, too, of course.
1492		2037
		2038	=head3 Watcher-Specific Functions and Data Members
		2039
1493	=over 4	2040	=over 4
1494		2041
1495	=item ev_fork_init (ev_signal *, callback)	2042	=item ev_fork_init (ev_signal *, callback)
1496		2043
1497	Initialises and configures the fork watcher - it has no parameters of any	2044	Initialises and configures the fork watcher - it has no parameters of any
…		…
1593		2140
1594	To use it,	2141	To use it,
1595		2142
1596	#include <ev++.h>	2143	#include <ev++.h>
1597		2144
1598	(it is not installed by default). This automatically includes F<ev.h>	2145	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	2146	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.	2147	put into the C<ev> namespace. It should support all the same embedding
		2148	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1601		2149
1602	It should support all the same embedding options as F<ev.h>, most notably	2150	Care has been taken to keep the overhead low. The only data member the C++
1603	C<EV_MULTIPLICITY>.	2151	classes add (compared to plain C-style watchers) is the event loop pointer
		2152	that the watcher is associated with (or no additional members at all if
		2153	you disable C<EV_MULTIPLICITY> when embedding libev).
		2154
		2155	Currently, functions, and static and non-static member functions can be
		2156	used as callbacks. Other types should be easy to add as long as they only
		2157	need one additional pointer for context. If you need support for other
		2158	types of functors please contact the author (preferably after implementing
		2159	it).
1604		2160
1605	Here is a list of things available in the C<ev> namespace:	2161	Here is a list of things available in the C<ev> namespace:
1606		2162
1607	=over 4	2163	=over 4
1608		2164
…		…
1624		2180
1625	All of those classes have these methods:	2181	All of those classes have these methods:
1626		2182
1627	=over 4	2183	=over 4
1628		2184
1629	=item ev::TYPE::TYPE (object *, object::method *)	2185	=item ev::TYPE::TYPE ()
1630		2186
1631	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2187	=item ev::TYPE::TYPE (struct ev_loop *)
1632		2188
1633	=item ev::TYPE::~TYPE	2189	=item ev::TYPE::~TYPE
1634		2190
1635	The constructor takes a pointer to an object and a method pointer to	2191	The constructor (optionally) takes an event loop to associate the watcher
1636	the event handler callback to call in this class. The constructor calls	2192	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	2193
1638	before starting it. If you do not specify a loop then the constructor	2194	The constructor calls C<ev_init> for you, which means you have to call the
1639	automatically associates the default loop with this watcher.	2195	C<set> method before starting it.
		2196
		2197	It will not set a callback, however: You have to call the templated C<set>
		2198	method to set a callback before you can start the watcher.
		2199
		2200	(The reason why you have to use a method is a limitation in C++ which does
		2201	not allow explicit template arguments for constructors).
1640		2202
1641	The destructor automatically stops the watcher if it is active.	2203	The destructor automatically stops the watcher if it is active.
		2204
		2205	=item w->set<class, &class::method> (object *)
		2206
		2207	This method sets the callback method to call. The method has to have a
		2208	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2209	first argument and the C<revents> as second. The object must be given as
		2210	parameter and is stored in the C<data> member of the watcher.
		2211
		2212	This method synthesizes efficient thunking code to call your method from
		2213	the C callback that libev requires. If your compiler can inline your
		2214	callback (i.e. it is visible to it at the place of the C<set> call and
		2215	your compiler is good :), then the method will be fully inlined into the
		2216	thunking function, making it as fast as a direct C callback.
		2217
		2218	Example: simple class declaration and watcher initialisation
		2219
		2220	struct myclass
		2221	{
		2222	void io_cb (ev::io &w, int revents) { }
		2223	}
		2224
		2225	myclass obj;
		2226	ev::io iow;
		2227	iow.set <myclass, &myclass::io_cb> (&obj);
		2228
		2229	=item w->set<function> (void *data = 0)
		2230
		2231	Also sets a callback, but uses a static method or plain function as
		2232	callback. The optional C<data> argument will be stored in the watcher's
		2233	C<data> member and is free for you to use.
		2234
		2235	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2236
		2237	See the method-C<set> above for more details.
		2238
		2239	Example:
		2240
		2241	static void io_cb (ev::io &w, int revents) { }
		2242	iow.set <io_cb> ();
1642		2243
1643	=item w->set (struct ev_loop *)	2244	=item w->set (struct ev_loop *)
1644		2245
1645	Associates a different C<struct ev_loop> with this watcher. You can only	2246	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).	2247	do this when the watcher is inactive (and not pending either).
1647		2248
1648	=item w->set ([args])	2249	=item w->set ([args])
1649		2250
1650	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2251	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	2252	called at least once. Unlike the C counterpart, an active watcher gets
1652	automatically stopped and restarted.	2253	automatically stopped and restarted when reconfiguring it with this
		2254	method.
1653		2255
1654	=item w->start ()	2256	=item w->start ()
1655		2257
1656	Starts the watcher. Note that there is no C<loop> argument as the	2258	Starts the watcher. Note that there is no C<loop> argument, as the
1657	constructor already takes the loop.	2259	constructor already stores the event loop.
1658		2260
1659	=item w->stop ()	2261	=item w->stop ()
1660		2262
1661	Stops the watcher if it is active. Again, no C<loop> argument.	2263	Stops the watcher if it is active. Again, no C<loop> argument.
1662		2264
1663	=item w->again () C<ev::timer>, C<ev::periodic> only	2265	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1664		2266
1665	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2267	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1666	C<ev_TYPE_again> function.	2268	C<ev_TYPE_again> function.
1667		2269
1668	=item w->sweep () C<ev::embed> only	2270	=item w->sweep () (C<ev::embed> only)
1669		2271
1670	Invokes C<ev_embed_sweep>.	2272	Invokes C<ev_embed_sweep>.
1671		2273
1672	=item w->update () C<ev::stat> only	2274	=item w->update () (C<ev::stat> only)
1673		2275
1674	Invokes C<ev_stat_stat>.	2276	Invokes C<ev_stat_stat>.
1675		2277
1676	=back	2278	=back
1677		2279
…		…
1687		2289
1688	myclass ();	2290	myclass ();
1689	}	2291	}
1690		2292
1691	myclass::myclass (int fd)	2293	myclass::myclass (int fd)
1692	: io (this, &myclass::io_cb),
1693	idle (this, &myclass::idle_cb)
1694	{	2294	{
		2295	io .set <myclass, &myclass::io_cb > (this);
		2296	idle.set <myclass, &myclass::idle_cb> (this);
		2297
1695	io.start (fd, ev::READ);	2298	io.start (fd, ev::READ);
1696	}	2299	}
1697		2300
1698		2301
1699	=head1 MACRO MAGIC	2302	=head1 MACRO MAGIC
1700		2303
1701	Libev can be compiled with a variety of options, the most fundemantal is	2304	Libev can be compiled with a variety of options, the most fundamantal
1702	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2305	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1703	callbacks have an initial C<struct ev_loop *> argument.	2306	functions and callbacks have an initial C<struct ev_loop *> argument.
1704		2307
1705	To make it easier to write programs that cope with either variant, the	2308	To make it easier to write programs that cope with either variant, the
1706	following macros are defined:	2309	following macros are defined:
1707		2310
1708	=over 4	2311	=over 4
…		…
1740	Similar to the other two macros, this gives you the value of the default	2343	Similar to the other two macros, this gives you the value of the default
1741	loop, if multiple loops are supported ("ev loop default").	2344	loop, if multiple loops are supported ("ev loop default").
1742		2345
1743	=back	2346	=back
1744		2347
1745	Example: Declare and initialise a check watcher, working regardless of	2348	Example: Declare and initialise a check watcher, utilising the above
1746	wether multiple loops are supported or not.	2349	macros so it will work regardless of whether multiple loops are supported
		2350	or not.
1747		2351
1748	static void	2352	static void
1749	check_cb (EV_P_ ev_timer *w, int revents)	2353	check_cb (EV_P_ ev_timer *w, int revents)
1750	{	2354	{
1751	ev_check_stop (EV_A_ w);	2355	ev_check_stop (EV_A_ w);
…		…
1754	ev_check check;	2358	ev_check check;
1755	ev_check_init (&check, check_cb);	2359	ev_check_init (&check, check_cb);
1756	ev_check_start (EV_DEFAULT_ &check);	2360	ev_check_start (EV_DEFAULT_ &check);
1757	ev_loop (EV_DEFAULT_ 0);	2361	ev_loop (EV_DEFAULT_ 0);
1758		2362
1759
1760	=head1 EMBEDDING	2363	=head1 EMBEDDING
1761		2364
1762	Libev can (and often is) directly embedded into host	2365	Libev can (and often is) directly embedded into host
1763	applications. Examples of applications that embed it include the Deliantra	2366	applications. Examples of applications that embed it include the Deliantra
1764	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2367	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1765	and rxvt-unicode.	2368	and rxvt-unicode.
1766		2369
1767	The goal is to enable you to just copy the neecssary files into your	2370	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	2371	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	2372	you can easily upgrade by simply copying (or having a checked-out copy of
1770	libev somewhere in your source tree).	2373	libev somewhere in your source tree).
1771		2374
1772	=head2 FILESETS	2375	=head2 FILESETS
…		…
1803	ev_vars.h	2406	ev_vars.h
1804	ev_wrap.h	2407	ev_wrap.h
1805		2408
1806	ev_win32.c required on win32 platforms only	2409	ev_win32.c required on win32 platforms only
1807		2410
1808	ev_select.c only when select backend is enabled (which is by default)	2411	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)	2412	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)	2413	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)	2414	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)	2415	ev_port.c only when the solaris port backend is enabled (disabled by default)
1813		2416
…		…
1862		2465
1863	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
1864	monotonic clock option at both compiletime and runtime. Otherwise no use	2467	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	2468	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	2469	usually have to link against librt or something similar. Enabling it when
1867	the functionality isn't available is safe, though, althoguh you have	2470	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>	2471	to make sure you link against any libraries where the C<clock_gettime>
1869	function is hiding in (often F<-lrt>).	2472	function is hiding in (often F<-lrt>).
1870		2473
1871	=item EV_USE_REALTIME	2474	=item EV_USE_REALTIME
1872		2475
1873	If defined to be C<1>, libev will try to detect the availability of the	2476	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	2477	realtime clock option at compiletime (and assume its availability at
1875	runtime if successful). Otherwise no use of the realtime clock option will	2478	runtime if successful). Otherwise no use of the realtime clock option will
1876	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2479	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	2480	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1878	in the description of C<EV_USE_MONOTONIC>, though.	2481	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2482
		2483	=item EV_USE_NANOSLEEP
		2484
		2485	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2486	and will use it for delays. Otherwise it will use C<select ()>.
1879		2487
1880	=item EV_USE_SELECT	2488	=item EV_USE_SELECT
1881		2489
1882	If undefined or defined to be C<1>, libev will compile in support for the	2490	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	2491	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	2509	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	2510	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,	2511	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	2512	it is assumed that all these functions actually work on fds, even
1905	on win32. Should not be defined on non-win32 platforms.	2513	on win32. Should not be defined on non-win32 platforms.
		2514
		2515	=item EV_FD_TO_WIN32_HANDLE
		2516
		2517	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2518	file descriptors to socket handles. When not defining this symbol (the
		2519	default), then libev will call C<_get_osfhandle>, which is usually
		2520	correct. In some cases, programs use their own file descriptor management,
		2521	in which case they can provide this function to map fds to socket handles.
1906		2522
1907	=item EV_USE_POLL	2523	=item EV_USE_POLL
1908		2524
1909	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2525	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	2526	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1938		2554
1939	=item EV_USE_DEVPOLL	2555	=item EV_USE_DEVPOLL
1940		2556
1941	reserved for future expansion, works like the USE symbols above.	2557	reserved for future expansion, works like the USE symbols above.
1942		2558
		2559	=item EV_USE_INOTIFY
		2560
		2561	If defined to be C<1>, libev will compile in support for the Linux inotify
		2562	interface to speed up C<ev_stat> watchers. Its actual availability will
		2563	be detected at runtime.
		2564
1943	=item EV_H	2565	=item EV_H
1944		2566
1945	The name of the F<ev.h> header file used to include it. The default if	2567	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	2568	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1947	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2569	used to virtually rename the F<ev.h> header file in case of conflicts.
1948		2570
1949	=item EV_CONFIG_H	2571	=item EV_CONFIG_H
1950		2572
1951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2573	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	2574	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1953	C<EV_H>, above.	2575	C<EV_H>, above.
1954		2576
1955	=item EV_EVENT_H	2577	=item EV_EVENT_H
1956		2578
1957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2579	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.	2580	of how the F<event.h> header can be found, the default is C<"event.h">.
1959		2581
1960	=item EV_PROTOTYPES	2582	=item EV_PROTOTYPES
1961		2583
1962	If defined to be C<0>, then F<ev.h> will not define any function	2584	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	2585	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	2592	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	2593	additional independent event loops. Otherwise there will be no support
1972	for multiple event loops and there is no first event loop pointer	2594	for multiple event loops and there is no first event loop pointer
1973	argument. Instead, all functions act on the single default loop.	2595	argument. Instead, all functions act on the single default loop.
1974		2596
		2597	=item EV_MINPRI
		2598
		2599	=item EV_MAXPRI
		2600
		2601	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2602	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2603	provide for more priorities by overriding those symbols (usually defined
		2604	to be C<-2> and C<2>, respectively).
		2605
		2606	When doing priority-based operations, libev usually has to linearly search
		2607	all the priorities, so having many of them (hundreds) uses a lot of space
		2608	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2609	fine.
		2610
		2611	If your embedding app does not need any priorities, defining these both to
		2612	C<0> will save some memory and cpu.
		2613
1975	=item EV_PERIODIC_ENABLE	2614	=item EV_PERIODIC_ENABLE
1976		2615
1977	If undefined or defined to be C<1>, then periodic timers are supported. If	2616	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	2617	defined to be C<0>, then they are not. Disabling them saves a few kB of
1979	code.	2618	code.
1980		2619
		2620	=item EV_IDLE_ENABLE
		2621
		2622	If undefined or defined to be C<1>, then idle watchers are supported. If
		2623	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2624	code.
		2625
1981	=item EV_EMBED_ENABLE	2626	=item EV_EMBED_ENABLE
1982		2627
1983	If undefined or defined to be C<1>, then embed watchers are supported. If	2628	If undefined or defined to be C<1>, then embed watchers are supported. If
1984	defined to be C<0>, then they are not.	2629	defined to be C<0>, then they are not.
1985		2630
…		…
2002	=item EV_PID_HASHSIZE	2647	=item EV_PID_HASHSIZE
2003		2648
2004	C<ev_child> watchers use a small hash table to distribute workload by	2649	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	2650	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	2651	than enough. If you need to manage thousands of children you might want to
2007	increase this value.	2652	increase this value (I<must> be a power of two).
		2653
		2654	=item EV_INOTIFY_HASHSIZE
		2655
		2656	C<ev_stat> watchers use a small hash table to distribute workload by
		2657	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2658	usually more than enough. If you need to manage thousands of C<ev_stat>
		2659	watchers you might want to increase this value (I<must> be a power of
		2660	two).
2008		2661
2009	=item EV_COMMON	2662	=item EV_COMMON
2010		2663
2011	By default, all watchers have a C<void *data> member. By redefining	2664	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	2665	this macro to a something else you can include more and other types of
…		…
2025		2678
2026	=item ev_set_cb (ev, cb)	2679	=item ev_set_cb (ev, cb)
2027		2680
2028	Can be used to change the callback member declaration in each watcher,	2681	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	2682	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	2683	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	2684	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	2685	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++.	2686	method calls instead of plain function calls in C++.
		2687
		2688	=head2 EXPORTED API SYMBOLS
		2689
		2690	If you need to re-export the API (e.g. via a dll) and you need a list of
		2691	exported symbols, you can use the provided F<Symbol.*> files which list
		2692	all public symbols, one per line:
		2693
		2694	Symbols.ev for libev proper
		2695	Symbols.event for the libevent emulation
		2696
		2697	This can also be used to rename all public symbols to avoid clashes with
		2698	multiple versions of libev linked together (which is obviously bad in
		2699	itself, but sometimes it is inconvinient to avoid this).
		2700
		2701	A sed command like this will create wrapper C<#define>'s that you need to
		2702	include before including F<ev.h>:
		2703
		2704	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2705
		2706	This would create a file F<wrap.h> which essentially looks like this:
		2707
		2708	#define ev_backend myprefix_ev_backend
		2709	#define ev_check_start myprefix_ev_check_start
		2710	#define ev_check_stop myprefix_ev_check_stop
		2711	...
2034		2712
2035	=head2 EXAMPLES	2713	=head2 EXAMPLES
2036		2714
2037	For a real-world example of a program the includes libev	2715	For a real-world example of a program the includes libev
2038	verbatim, you can have a look at the EV perl module	2716	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	2719	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	2720	will be compiled. It is pretty complex because it provides its own header
2043	file.	2721	file.
2044		2722
2045	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2723	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:	2724	that everybody includes and which overrides some configure choices:
2047		2725
		2726	#define EV_MINIMAL 1
2048	#define EV_USE_POLL 0	2727	#define EV_USE_POLL 0
2049	#define EV_MULTIPLICITY 0	2728	#define EV_MULTIPLICITY 0
2050	#define EV_PERIODICS 0	2729	#define EV_PERIODIC_ENABLE 0
		2730	#define EV_STAT_ENABLE 0
		2731	#define EV_FORK_ENABLE 0
2051	#define EV_CONFIG_H <config.h>	2732	#define EV_CONFIG_H <config.h>
		2733	#define EV_MINPRI 0
		2734	#define EV_MAXPRI 0
2052		2735
2053	#include "ev++.h"	2736	#include "ev++.h"
2054		2737
2055	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2738	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2056		2739
…		…
2062		2745
2063	In this section the complexities of (many of) the algorithms used inside	2746	In this section the complexities of (many of) the algorithms used inside
2064	libev will be explained. For complexity discussions about backends see the	2747	libev will be explained. For complexity discussions about backends see the
2065	documentation for C<ev_default_init>.	2748	documentation for C<ev_default_init>.
2066		2749
		2750	All of the following are about amortised time: If an array needs to be
		2751	extended, libev needs to realloc and move the whole array, but this
		2752	happens asymptotically never with higher number of elements, so O(1) might
		2753	mean it might do a lengthy realloc operation in rare cases, but on average
		2754	it is much faster and asymptotically approaches constant time.
		2755
2067	=over 4	2756	=over 4
2068		2757
2069	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2758	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2070		2759
		2760	This means that, when you have a watcher that triggers in one hour and
		2761	there are 100 watchers that would trigger before that then inserting will
		2762	have to skip roughly seven (C<ld 100>) of these watchers.
		2763
2071	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2764	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2765
		2766	That means that changing a timer costs less than removing/adding them
		2767	as only the relative motion in the event queue has to be paid for.
2072		2768
2073	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2769	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2074		2770
		2771	These just add the watcher into an array or at the head of a list.
		2772
2075	=item Stopping check/prepare/idle watchers: O(1)	2773	=item Stopping check/prepare/idle watchers: O(1)
2076		2774
2077	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2775	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2078		2776
		2777	These watchers are stored in lists then need to be walked to find the
		2778	correct watcher to remove. The lists are usually short (you don't usually
		2779	have many watchers waiting for the same fd or signal).
		2780
2079	=item Finding the next timer per loop iteration: O(1)	2781	=item Finding the next timer in each loop iteration: O(1)
		2782
		2783	By virtue of using a binary heap, the next timer is always found at the
		2784	beginning of the storage array.
2080		2785
2081	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2786	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2082		2787
2083	=item Activating one watcher: O(1)	2788	A change means an I/O watcher gets started or stopped, which requires
		2789	libev to recalculate its status (and possibly tell the kernel, depending
		2790	on backend and wether C<ev_io_set> was used).
		2791
		2792	=item Activating one watcher (putting it into the pending state): O(1)
		2793
		2794	=item Priority handling: O(number_of_priorities)
		2795
		2796	Priorities are implemented by allocating some space for each
		2797	priority. When doing priority-based operations, libev usually has to
		2798	linearly search all the priorities, but starting/stopping and activating
		2799	watchers becomes O(1) w.r.t. prioritiy handling.
2084		2800
2085	=back	2801	=back
2086		2802
2087		2803
		2804	=head1 Win32 platform limitations and workarounds
		2805
		2806	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2807	requires, and its I/O model is fundamentally incompatible with the POSIX
		2808	model. Libev still offers limited functionality on this platform in
		2809	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2810	descriptors. This only applies when using Win32 natively, not when using
		2811	e.g. cygwin.
		2812
		2813	There is no supported compilation method available on windows except
		2814	embedding it into other applications.
		2815
		2816	Due to the many, low, and arbitrary limits on the win32 platform and the
		2817	abysmal performance of winsockets, using a large number of sockets is not
		2818	recommended (and not reasonable). If your program needs to use more than
		2819	a hundred or so sockets, then likely it needs to use a totally different
		2820	implementation for windows, as libev offers the POSIX model, which cannot
		2821	be implemented efficiently on windows (microsoft monopoly games).
		2822
		2823	=over 4
		2824
		2825	=item The winsocket select function
		2826
		2827	The winsocket C<select> function doesn't follow POSIX in that it requires
		2828	socket I<handles> and not socket I<file descriptors>. This makes select
		2829	very inefficient, and also requires a mapping from file descriptors
		2830	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2831	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2832	symbols for more info.
		2833
		2834	The configuration for a "naked" win32 using the microsoft runtime
		2835	libraries and raw winsocket select is:
		2836
		2837	#define EV_USE_SELECT 1
		2838	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2839
		2840	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2841	complexity in the O(n²) range when using win32.
		2842
		2843	=item Limited number of file descriptors
		2844
		2845	Windows has numerous arbitrary (and low) limits on things. Early versions
		2846	of winsocket's select only supported waiting for a max. of C<64> handles
		2847	(probably owning to the fact that all windows kernels can only wait for
		2848	C<64> things at the same time internally; microsoft recommends spawning a
		2849	chain of threads and wait for 63 handles and the previous thread in each).
		2850
		2851	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2852	to some high number (e.g. C<2048>) before compiling the winsocket select
		2853	call (which might be in libev or elsewhere, for example, perl does its own
		2854	select emulation on windows).
		2855
		2856	Another limit is the number of file descriptors in the microsoft runtime
		2857	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2858	or something like this inside microsoft). You can increase this by calling
		2859	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2860	arbitrary limit), but is broken in many versions of the microsoft runtime
		2861	libraries.
		2862
		2863	This might get you to about C<512> or C<2048> sockets (depending on
		2864	windows version and/or the phase of the moon). To get more, you need to
		2865	wrap all I/O functions and provide your own fd management, but the cost of
		2866	calling select (O(n²)) will likely make this unworkable.
		2867
		2868	=back
		2869
		2870
2088	=head1 AUTHOR	2871	=head1 AUTHOR
2089		2872
2090	Marc Lehmann <libev@schmorp.de>.	2873	Marc Lehmann <libev@schmorp.de>.
2091		2874

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