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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head2 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head2 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head2 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
52		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
53		106
54	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
55		108
56	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
57	library in any way.	110	library in any way.
…		…
62		115
63	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	118	you actually want to know.
66		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
67	=item int ev_version_major ()	126	=item int ev_version_major ()
68		127
69	=item int ev_version_minor ()	128	=item int ev_version_minor ()
70		129
71	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	134	version of the library your program was compiled against.
76		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
77	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	142	not a problem.
81		143
82	Example: make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	145	version.
84		146
85	assert (("libev version mismatch",	147	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
88		150
…		…
118		180
119	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
120		182
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		184
123	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
128		191
129	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
132		195
133	Example: replace the libev allocator with one that waits a bit and then	196	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	197	retries).
135		198
136	static void *	199	static void *
137	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
138	{	201	{
139	for (;;)	202	for (;;)
140	{	203	{
141	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
142		205
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	224	(such as abort).
162		225
163	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
164		227
165	static void	228	static void
166	fatal_error (const char *msg)	229	fatal_error (const char *msg)
167	{	230	{
168	perror (msg);	231	perror (msg);
…		…
197	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
198		261
199	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
200	function.	263	function.
201		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
202	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
203	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>).
204		274
205	The following flags are supported:	275	The following flags are supported:
206		276
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	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
220	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
221	around bugs.	291	around bugs.
222		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
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		314
225	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
226	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,
227	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
228	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
229	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.
230		327
231	=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)
232		329
233	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
234	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
235	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
236	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.
237		336
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		338
240	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,
241	but it scales phenomenally better. While poll and select usually scale like	340	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	341	like O(total_fds) where n is the total number of fds (or the highest fd),
243	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.
244		346
245	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
246	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
247	(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
248	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
249	well if you register events for both fds.	351	very well if you register events for both fds.
250		352
251	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	354	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	355	(or space) is available.
254		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
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		365
257	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
258	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
259	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
260	completely useless). For this reason its not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
261	unless you explicitly specify it explicitly in the flags (i.e. using	370	unless you explicitly specify it explicitly in the flags (i.e. using
262	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.
263		377
264	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
265	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
266	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
267	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
268	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.
269		393
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		395
272	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.
273		400
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		402
276	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,
277	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)).
278		405
279	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
280	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
281	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.
282		418
283	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
284		420
285	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
286	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
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288		424
		425	It is definitely not recommended to use this flag.
		426
289	=back	427	=back
290		428
291	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
292	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
293	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
294	order of their flag values :)
295		432
296	The most typical usage is like this:	433	The most typical usage is like this:
297		434
298	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
314	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
315	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
316	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
317	undefined behaviour (or a failed assertion if assertions are enabled).	454	undefined behaviour (or a failed assertion if assertions are enabled).
318		455
319	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.
320		457
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	459	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	460	fatal ("no epoll found here, maybe it hides under your chair");
324		461
…		…
327	Destroys the default loop again (frees all memory and kernel state	464	Destroys the default loop again (frees all memory and kernel state
328	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
329	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
330	responsibility to either stop all watchers cleanly yoursef I<before>	467	responsibility to either stop all watchers cleanly yoursef I<before>
331	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
332	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
333	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>).
334		480
335	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
336		482
337	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
338	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
339		485
340	=item ev_default_fork ()	486	=item ev_default_fork ()
341		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
342	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
343	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
344	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
345	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
346		494
347	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
348	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
349	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
350		498
351	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
352	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
353	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
354		502
355	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
356		504
357	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
358	without calling this function, so if you force one of those backends you
359	do not need to care.
360
361	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
362		506
363	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
		514
		515	=item unsigned int ev_loop_count (loop)
		516
		517	Returns the count of loop iterations for the loop, which is identical to
		518	the number of times libev did poll for new events. It starts at C<0> and
		519	happily wraps around with enough iterations.
		520
		521	This value can sometimes be useful as a generation counter of sorts (it
		522	"ticks" the number of loop iterations), as it roughly corresponds with
		523	C<ev_prepare> and C<ev_check> calls.
366		524
367	=item unsigned int ev_backend (loop)	525	=item unsigned int ev_backend (loop)
368		526
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	527	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	528	use.
…		…
373		531
374	Returns the current "event loop time", which is the time the event loop	532	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	533	received events and started processing them. This timestamp does not
376	change as long as callbacks are being processed, and this is also the base	534	change as long as callbacks are being processed, and this is also the base
377	time used for relative timers. You can treat it as the timestamp of the	535	time used for relative timers. You can treat it as the timestamp of the
378	event occuring (or more correctly, libev finding out about it).	536	event occurring (or more correctly, libev finding out about it).
379		537
380	=item ev_loop (loop, int flags)	538	=item ev_loop (loop, int flags)
381		539
382	Finally, this is it, the event handler. This function usually is called	540	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	541	after you initialised all your watchers and you want to start handling
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	562	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	563	usually a better approach for this kind of thing.
406		564
407	Here are the gory details of what C<ev_loop> does:	565	Here are the gory details of what C<ev_loop> does:
408		566
409	* If there are no active watchers (reference count is zero), return.	567	- Before the first iteration, call any pending watchers.
410	- Queue prepare watchers and then call all outstanding watchers.	568	* If EVFLAG_FORKCHECK was used, check for a fork.
		569	- If a fork was detected, queue and call all fork watchers.
		570	- Queue and call all prepare watchers.
411	- If we have been forked, recreate the kernel state.	571	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	572	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	573	- Update the "event loop time".
414	- Calculate for how long to block.	574	- Calculate for how long to sleep or block, if at all
		575	(active idle watchers, EVLOOP_NONBLOCK or not having
		576	any active watchers at all will result in not sleeping).
		577	- Sleep if the I/O and timer collect interval say so.
415	- Block the process, waiting for any events.	578	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	579	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	580	- Update the "event loop time" and do time jump handling.
418	- Queue all outstanding timers.	581	- Queue all outstanding timers.
419	- Queue all outstanding periodics.	582	- Queue all outstanding periodics.
420	- If no events are pending now, queue all idle watchers.	583	- If no events are pending now, queue all idle watchers.
421	- Queue all check watchers.	584	- Queue all check watchers.
422	- Call all queued watchers in reverse order (i.e. check watchers first).	585	- Call all queued watchers in reverse order (i.e. check watchers first).
423	Signals and child watchers are implemented as I/O watchers, and will	586	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	587	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	589	were used, or there are no active watchers, return, otherwise
		590	continue with step *.
427		591
428	Example: queue some jobs and then loop until no events are outsanding	592	Example: Queue some jobs and then loop until no events are outstanding
429	anymore.	593	anymore.
430		594
431	... queue jobs here, make sure they register event watchers as long	595	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	596	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	597	ev_loop (my_loop, 0);
…		…
437		601
438	Can be used to make a call to C<ev_loop> return early (but only after it	602	Can be used to make a call to C<ev_loop> return early (but only after it
439	has processed all outstanding events). The C<how> argument must be either	603	has processed all outstanding events). The C<how> argument must be either
440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		606
		607	This "unloop state" will be cleared when entering C<ev_loop> again.
442		608
443	=item ev_ref (loop)	609	=item ev_ref (loop)
444		610
445	=item ev_unref (loop)	611	=item ev_unref (loop)
446		612
…		…
451	returning, ev_unref() after starting, and ev_ref() before stopping it. For	617	returning, ev_unref() after starting, and ev_ref() before stopping it. For
452	example, libev itself uses this for its internal signal pipe: It is not	618	example, libev itself uses this for its internal signal pipe: It is not
453	visible to the libev user and should not keep C<ev_loop> from exiting if	619	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	620	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	621	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	622	libraries. Just remember to I<unref after start> and I<ref before stop>
		623	(but only if the watcher wasn't active before, or was active before,
		624	respectively).
457		625
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	627	running when nothing else is active.
460		628
461	struct dv_signal exitsig;	629	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	630	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	631	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	632	evf_unref (loop);
465		633
466	Example: for some weird reason, unregister the above signal handler again.	634	Example: For some weird reason, unregister the above signal handler again.
467		635
468	ev_ref (myloop);	636	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	637	ev_signal_stop (loop, &exitsig);
		638
		639	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		640
		641	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		642
		643	These advanced functions influence the time that libev will spend waiting
		644	for events. Both are by default C<0>, meaning that libev will try to
		645	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		646
		647	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		648	allows libev to delay invocation of I/O and timer/periodic callbacks to
		649	increase efficiency of loop iterations.
		650
		651	The background is that sometimes your program runs just fast enough to
		652	handle one (or very few) event(s) per loop iteration. While this makes
		653	the program responsive, it also wastes a lot of CPU time to poll for new
		654	events, especially with backends like C<select ()> which have a high
		655	overhead for the actual polling but can deliver many events at once.
		656
		657	By setting a higher I<io collect interval> you allow libev to spend more
		658	time collecting I/O events, so you can handle more events per iteration,
		659	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		660	C<ev_timer>) will be not affected. Setting this to a non-null value will
		661	introduce an additional C<ev_sleep ()> call into most loop iterations.
		662
		663	Likewise, by setting a higher I<timeout collect interval> you allow libev
		664	to spend more time collecting timeouts, at the expense of increased
		665	latency (the watcher callback will be called later). C<ev_io> watchers
		666	will not be affected. Setting this to a non-null value will not introduce
		667	any overhead in libev.
		668
		669	Many (busy) programs can usually benefit by setting the io collect
		670	interval to a value near C<0.1> or so, which is often enough for
		671	interactive servers (of course not for games), likewise for timeouts. It
		672	usually doesn't make much sense to set it to a lower value than C<0.01>,
		673	as this approsaches the timing granularity of most systems.
470		674
471	=back	675	=back
		676
472		677
473	=head1 ANATOMY OF A WATCHER	678	=head1 ANATOMY OF A WATCHER
474		679
475	A watcher is a structure that you create and register to record your	680	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	681	interest in some event. For instance, if you want to wait for STDIN to
…		…
543	The signal specified in the C<ev_signal> watcher has been received by a thread.	748	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		749
545	=item C<EV_CHILD>	750	=item C<EV_CHILD>
546		751
547	The pid specified in the C<ev_child> watcher has received a status change.	752	The pid specified in the C<ev_child> watcher has received a status change.
		753
		754	=item C<EV_STAT>
		755
		756	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		757
549	=item C<EV_IDLE>	758	=item C<EV_IDLE>
550		759
551	The C<ev_idle> watcher has determined that you have nothing better to do.	760	The C<ev_idle> watcher has determined that you have nothing better to do.
552		761
…		…
560	received events. Callbacks of both watcher types can start and stop as	769	received events. Callbacks of both watcher types can start and stop as
561	many watchers as they want, and all of them will be taken into account	770	many watchers as they want, and all of them will be taken into account
562	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	771	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	772	C<ev_loop> from blocking).
564		773
		774	=item C<EV_EMBED>
		775
		776	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		777
		778	=item C<EV_FORK>
		779
		780	The event loop has been resumed in the child process after fork (see
		781	C<ev_fork>).
		782
		783	=item C<EV_ASYNC>
		784
		785	The given async watcher has been asynchronously notified (see C<ev_async>).
		786
565	=item C<EV_ERROR>	787	=item C<EV_ERROR>
566		788
567	An unspecified error has occured, the watcher has been stopped. This might	789	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	790	happen because the watcher could not be properly started because libev
569	ran out of memory, a file descriptor was found to be closed or any other	791	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	with the error from read() or write(). This will not work in multithreaded	798	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	799	programs, though, so beware.
578		800
579	=back	801	=back
580		802
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	803	=head2 GENERIC WATCHER FUNCTIONS
582		804
583	In the following description, C<TYPE> stands for the watcher type,	805	In the following description, C<TYPE> stands for the watcher type,
584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.	806	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		807
586	=over 4	808	=over 4
…		…
595	which rolls both calls into one.	817	which rolls both calls into one.
596		818
597	You can reinitialise a watcher at any time as long as it has been stopped	819	You can reinitialise a watcher at any time as long as it has been stopped
598	(or never started) and there are no pending events outstanding.	820	(or never started) and there are no pending events outstanding.
599		821
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	822	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	823	int revents)>.
602		824
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	825	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		826
605	This macro initialises the type-specific parts of a watcher. You need to	827	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	862	=item bool ev_is_pending (ev_TYPE *watcher)
641		863
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	864	Returns a true value iff the watcher is pending, (i.e. it has outstanding
643	events but its callback has not yet been invoked). As long as a watcher	865	events but its callback has not yet been invoked). As long as a watcher
644	is pending (but not active) you must not call an init function on it (but	866	is pending (but not active) you must not call an init function on it (but
645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	867	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	868	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		869	it).
647		870
648	=item callback = ev_cb (ev_TYPE *watcher)	871	=item callback ev_cb (ev_TYPE *watcher)
649		872
650	Returns the callback currently set on the watcher.	873	Returns the callback currently set on the watcher.
651		874
652	=item ev_cb_set (ev_TYPE *watcher, callback)	875	=item ev_cb_set (ev_TYPE *watcher, callback)
653		876
654	Change the callback. You can change the callback at virtually any time	877	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	878	(modulo threads).
		879
		880	=item ev_set_priority (ev_TYPE *watcher, priority)
		881
		882	=item int ev_priority (ev_TYPE *watcher)
		883
		884	Set and query the priority of the watcher. The priority is a small
		885	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		886	(default: C<-2>). Pending watchers with higher priority will be invoked
		887	before watchers with lower priority, but priority will not keep watchers
		888	from being executed (except for C<ev_idle> watchers).
		889
		890	This means that priorities are I<only> used for ordering callback
		891	invocation after new events have been received. This is useful, for
		892	example, to reduce latency after idling, or more often, to bind two
		893	watchers on the same event and make sure one is called first.
		894
		895	If you need to suppress invocation when higher priority events are pending
		896	you need to look at C<ev_idle> watchers, which provide this functionality.
		897
		898	You I<must not> change the priority of a watcher as long as it is active or
		899	pending.
		900
		901	The default priority used by watchers when no priority has been set is
		902	always C<0>, which is supposed to not be too high and not be too low :).
		903
		904	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		905	fine, as long as you do not mind that the priority value you query might
		906	or might not have been adjusted to be within valid range.
		907
		908	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		909
		910	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		911	C<loop> nor C<revents> need to be valid as long as the watcher callback
		912	can deal with that fact.
		913
		914	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		915
		916	If the watcher is pending, this function returns clears its pending status
		917	and returns its C<revents> bitset (as if its callback was invoked). If the
		918	watcher isn't pending it does nothing and returns C<0>.
656		919
657	=back	920	=back
658		921
659		922
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	923	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	944	{
682	struct my_io *w = (struct my_io *)w_;	945	struct my_io *w = (struct my_io *)w_;
683	...	946	...
684	}	947	}
685		948
686	More interesting and less C-conformant ways of catsing your callback type	949	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	950	instead have been omitted.
		951
		952	Another common scenario is having some data structure with multiple
		953	watchers:
		954
		955	struct my_biggy
		956	{
		957	int some_data;
		958	ev_timer t1;
		959	ev_timer t2;
		960	}
		961
		962	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		963	you need to use C<offsetof>:
		964
		965	#include <stddef.h>
		966
		967	static void
		968	t1_cb (EV_P_ struct ev_timer *w, int revents)
		969	{
		970	struct my_biggy big = (struct my_biggy *
		971	(((char *)w) - offsetof (struct my_biggy, t1));
		972	}
		973
		974	static void
		975	t2_cb (EV_P_ struct ev_timer *w, int revents)
		976	{
		977	struct my_biggy big = (struct my_biggy *
		978	(((char *)w) - offsetof (struct my_biggy, t2));
		979	}
688		980
689		981
690	=head1 WATCHER TYPES	982	=head1 WATCHER TYPES
691		983
692	This section describes each watcher in detail, but will not repeat	984	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	985	information given in the last section. Any initialisation/set macros,
		986	functions and members specific to the watcher type are explained.
694		987
		988	Members are additionally marked with either I<[read-only]>, meaning that,
		989	while the watcher is active, you can look at the member and expect some
		990	sensible content, but you must not modify it (you can modify it while the
		991	watcher is stopped to your hearts content), or I<[read-write]>, which
		992	means you can expect it to have some sensible content while the watcher
		993	is active, but you can also modify it. Modifying it may not do something
		994	sensible or take immediate effect (or do anything at all), but libev will
		995	not crash or malfunction in any way.
695		996
		997
696	=head2 C<ev_io> - is this file descriptor readable or writable	998	=head2 C<ev_io> - is this file descriptor readable or writable?
697		999
698	I/O watchers check whether a file descriptor is readable or writable	1000	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	1001	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	1002	would not block the process and writing would at least be able to write
701	condition persists. Remember you can stop the watcher if you don't want to	1003	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	1004	receiving events as long as the condition persists. Remember you can stop
		1005	the watcher if you don't want to act on the event and neither want to
		1006	receive future events.
703		1007
704	In general you can register as many read and/or write event watchers per	1008	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	1009	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	1010	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	1011	required if you know what you are doing).
708		1012
709	You have to be careful with dup'ed file descriptors, though. Some backends
710	(the linux epoll backend is a notable example) cannot handle dup'ed file
711	descriptors correctly if you register interest in two or more fds pointing
712	to the same underlying file/socket etc. description (that is, they share
713	the same underlying "file open").
714
715	If you must do this, then force the use of a known-to-be-good backend	1013	If you must do this, then force the use of a known-to-be-good backend
716	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1014	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	1015	C<EVBACKEND_POLL>).
718		1016
		1017	Another thing you have to watch out for is that it is quite easy to
		1018	receive "spurious" readyness notifications, that is your callback might
		1019	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1020	because there is no data. Not only are some backends known to create a
		1021	lot of those (for example solaris ports), it is very easy to get into
		1022	this situation even with a relatively standard program structure. Thus
		1023	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1024	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1025
		1026	If you cannot run the fd in non-blocking mode (for example you should not
		1027	play around with an Xlib connection), then you have to seperately re-test
		1028	whether a file descriptor is really ready with a known-to-be good interface
		1029	such as poll (fortunately in our Xlib example, Xlib already does this on
		1030	its own, so its quite safe to use).
		1031
		1032	=head3 The special problem of disappearing file descriptors
		1033
		1034	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1035	descriptor (either by calling C<close> explicitly or by any other means,
		1036	such as C<dup>). The reason is that you register interest in some file
		1037	descriptor, but when it goes away, the operating system will silently drop
		1038	this interest. If another file descriptor with the same number then is
		1039	registered with libev, there is no efficient way to see that this is, in
		1040	fact, a different file descriptor.
		1041
		1042	To avoid having to explicitly tell libev about such cases, libev follows
		1043	the following policy: Each time C<ev_io_set> is being called, libev
		1044	will assume that this is potentially a new file descriptor, otherwise
		1045	it is assumed that the file descriptor stays the same. That means that
		1046	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1047	descriptor even if the file descriptor number itself did not change.
		1048
		1049	This is how one would do it normally anyway, the important point is that
		1050	the libev application should not optimise around libev but should leave
		1051	optimisations to libev.
		1052
		1053	=head3 The special problem of dup'ed file descriptors
		1054
		1055	Some backends (e.g. epoll), cannot register events for file descriptors,
		1056	but only events for the underlying file descriptions. That means when you
		1057	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1058	events for them, only one file descriptor might actually receive events.
		1059
		1060	There is no workaround possible except not registering events
		1061	for potentially C<dup ()>'ed file descriptors, or to resort to
		1062	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1063
		1064	=head3 The special problem of fork
		1065
		1066	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1067	useless behaviour. Libev fully supports fork, but needs to be told about
		1068	it in the child.
		1069
		1070	To support fork in your programs, you either have to call
		1071	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1072	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1073	C<EVBACKEND_POLL>.
		1074
		1075
		1076	=head3 Watcher-Specific Functions
		1077
719	=over 4	1078	=over 4
720		1079
721	=item ev_io_init (ev_io *, callback, int fd, int events)	1080	=item ev_io_init (ev_io *, callback, int fd, int events)
722		1081
723	=item ev_io_set (ev_io *, int fd, int events)	1082	=item ev_io_set (ev_io *, int fd, int events)
724		1083
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1084	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
726	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1085	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	1086	C<EV_READ | EV_WRITE> to receive the given events.
728		1087
729	Please note that most of the more scalable backend mechanisms (for example	1088	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	1089
731	for file descriptors, so you practically need to use non-blocking I/O (and	1090	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	1091
733	interface before doing I/O (XLib can do this), or force the use of either	1092	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	1093
735	problem. Also note that it is quite easy to have your callback invoked	1094	The events being watched.
736	when the readyness condition is no longer valid even when employing
737	typical ways of handling events, so its a good idea to use non-blocking
738	I/O unconditionally.
739		1095
740	=back	1096	=back
741		1097
		1098	=head3 Examples
		1099
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	1101	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	1102	attempt to read a whole line in the callback.
745		1103
746	static void	1104	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1105	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	1106	{
749	ev_io_stop (loop, w);	1107	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1114	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	1115	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	1116	ev_loop (loop, 0);
759		1117
760		1118
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	1119	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		1120
763	Timer watchers are simple relative timers that generate an event after a	1121	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	1122	given time, and optionally repeating in regular intervals after that.
765		1123
766	The timers are based on real time, that is, if you register an event that	1124	The timers are based on real time, that is, if you register an event that
…		…
779		1137
780	The callback is guarenteed to be invoked only when its timeout has passed,	1138	The callback is guarenteed to be invoked only when its timeout has passed,
781	but if multiple timers become ready during the same loop iteration then	1139	but if multiple timers become ready during the same loop iteration then
782	order of execution is undefined.	1140	order of execution is undefined.
783		1141
		1142	=head3 Watcher-Specific Functions and Data Members
		1143
784	=over 4	1144	=over 4
785		1145
786	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1146	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
787		1147
788	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1148	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
796	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
797	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
798	the timer (because it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
799	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
800		1160
801	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
802		1162
803	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
805		1165
		1166	If the timer is pending, its pending status is cleared.
		1167
806	If the timer is started but nonrepeating, stop it.	1168	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1169
808	If the timer is repeating, either start it if necessary (with the repeat	1170	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1171	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1172
811	This sounds a bit complicated, but here is a useful and typical	1173	This sounds a bit complicated, but here is a useful and typical
812	example: Imagine you have a tcp connection and you want a so-called idle	1174	example: Imagine you have a tcp connection and you want a so-called idle
813	timeout, that is, you want to be called when there have been, say, 60	1175	timeout, that is, you want to be called when there have been, say, 60
814	seconds of inactivity on the socket. The easiest way to do this is to	1176	seconds of inactivity on the socket. The easiest way to do this is to
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1177	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
816	time you successfully read or write some data. If you go into an idle	1178	C<ev_timer_again> each time you successfully read or write some data. If
817	state where you do not expect data to travel on the socket, you can stop	1179	you go into an idle state where you do not expect data to travel on the
818	the timer, and again will automatically restart it if need be.	1180	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1181	automatically restart it if need be.
		1182
		1183	That means you can ignore the C<after> value and C<ev_timer_start>
		1184	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1185
		1186	ev_timer_init (timer, callback, 0., 5.);
		1187	ev_timer_again (loop, timer);
		1188	...
		1189	timer->again = 17.;
		1190	ev_timer_again (loop, timer);
		1191	...
		1192	timer->again = 10.;
		1193	ev_timer_again (loop, timer);
		1194
		1195	This is more slightly efficient then stopping/starting the timer each time
		1196	you want to modify its timeout value.
		1197
		1198	=item ev_tstamp repeat [read-write]
		1199
		1200	The current C<repeat> value. Will be used each time the watcher times out
		1201	or C<ev_timer_again> is called and determines the next timeout (if any),
		1202	which is also when any modifications are taken into account.
819		1203
820	=back	1204	=back
821		1205
		1206	=head3 Examples
		1207
822	Example: create a timer that fires after 60 seconds.	1208	Example: Create a timer that fires after 60 seconds.
823		1209
824	static void	1210	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1211	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1212	{
827	.. one minute over, w is actually stopped right here	1213	.. one minute over, w is actually stopped right here
…		…
829		1215
830	struct ev_timer mytimer;	1216	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1217	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1218	ev_timer_start (loop, &mytimer);
833		1219
834	Example: create a timeout timer that times out after 10 seconds of	1220	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1221	inactivity.
836		1222
837	static void	1223	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1224	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1225	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1234	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1235	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1236	ev_timer_again (&mytimer);
851		1237
852		1238
853	=head2 C<ev_periodic> - to cron or not to cron	1239	=head2 C<ev_periodic> - to cron or not to cron?
854		1240
855	Periodic watchers are also timers of a kind, but they are very versatile	1241	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1242	(and unfortunately a bit complex).
857		1243
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1244	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
859	but on wallclock time (absolute time). You can tell a periodic watcher	1245	but on wallclock time (absolute time). You can tell a periodic watcher
860	to trigger "at" some specific point in time. For example, if you tell a	1246	to trigger "at" some specific point in time. For example, if you tell a
861	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1247	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
862	+ 10.>) and then reset your system clock to the last year, then it will	1248	+ 10.>) and then reset your system clock to the last year, then it will
863	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1249	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
864	roughly 10 seconds later and of course not if you reset your system time	1250	roughly 10 seconds later).
865	again).
866		1251
867	They can also be used to implement vastly more complex timers, such as	1252	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1253	triggering an event on each midnight, local time or other, complicated,
		1254	rules.
869		1255
870	As with timers, the callback is guarenteed to be invoked only when the	1256	As with timers, the callback is guarenteed to be invoked only when the
871	time (C<at>) has been passed, but if multiple periodic timers become ready	1257	time (C<at>) has been passed, but if multiple periodic timers become ready
872	during the same loop iteration then order of execution is undefined.	1258	during the same loop iteration then order of execution is undefined.
873		1259
		1260	=head3 Watcher-Specific Functions and Data Members
		1261
874	=over 4	1262	=over 4
875		1263
876	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1264	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
877		1265
878	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1266	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
880	Lots of arguments, lets sort it out... There are basically three modes of	1268	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1269	operation, and we will explain them from simplest to complex:
882		1270
883	=over 4	1271	=over 4
884		1272
885	=item * absolute timer (interval = reschedule_cb = 0)	1273	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1274
887	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
888	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
889	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
890	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
891		1279
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1281
894	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
895	C<at + N * interval> time (for some integer N) and then repeat, regardless	1283	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1284	and then repeat, regardless of any time jumps.
897		1285
898	This can be used to create timers that do not drift with respect to system	1286	This can be used to create timers that do not drift with respect to system
899	time:	1287	time:
900		1288
901	ev_periodic_set (&periodic, 0., 3600., 0);	1289	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1295
908	Another way to think about it (for the mathematically inclined) is that	1296	Another way to think about it (for the mathematically inclined) is that
909	C<ev_periodic> will try to run the callback in this mode at the next possible	1297	C<ev_periodic> will try to run the callback in this mode at the next possible
910	time where C<time = at (mod interval)>, regardless of any time jumps.	1298	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1299
		1300	For numerical stability it is preferable that the C<at> value is near
		1301	C<ev_now ()> (the current time), but there is no range requirement for
		1302	this value.
		1303
912	=item * manual reschedule mode (reschedule_cb = callback)	1304	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1305
914	In this mode the values for C<interval> and C<at> are both being	1306	In this mode the values for C<interval> and C<at> are both being
915	ignored. Instead, each time the periodic watcher gets scheduled, the	1307	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1308	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1309	current time as second argument.
918		1310
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1311	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
920	ever, or make any event loop modifications>. If you need to stop it,	1312	ever, or make any event loop modifications>. If you need to stop it,
921	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1313	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1314	starting an C<ev_prepare> watcher, which is legal).
923		1315
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1316	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1317	ev_tstamp now)>, e.g.:
926		1318
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1319	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1342	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1343	when you changed some parameters or the reschedule callback would return
952	a different time than the last time it was called (e.g. in a crond like	1344	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1345	program when the crontabs have changed).
954		1346
		1347	=item ev_tstamp offset [read-write]
		1348
		1349	When repeating, this contains the offset value, otherwise this is the
		1350	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1351
		1352	Can be modified any time, but changes only take effect when the periodic
		1353	timer fires or C<ev_periodic_again> is being called.
		1354
		1355	=item ev_tstamp interval [read-write]
		1356
		1357	The current interval value. Can be modified any time, but changes only
		1358	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1359	called.
		1360
		1361	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1362
		1363	The current reschedule callback, or C<0>, if this functionality is
		1364	switched off. Can be changed any time, but changes only take effect when
		1365	the periodic timer fires or C<ev_periodic_again> is being called.
		1366
		1367	=item ev_tstamp at [read-only]
		1368
		1369	When active, contains the absolute time that the watcher is supposed to
		1370	trigger next.
		1371
955	=back	1372	=back
956		1373
		1374	=head3 Examples
		1375
957	Example: call a callback every hour, or, more precisely, whenever the	1376	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1377	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1378	potentially a lot of jittering, but good long-term stability.
960		1379
961	static void	1380	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1381	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1385
967	struct ev_periodic hourly_tick;	1386	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1387	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1388	ev_periodic_start (loop, &hourly_tick);
970		1389
971	Example: the same as above, but use a reschedule callback to do it:	1390	Example: The same as above, but use a reschedule callback to do it:
972		1391
973	#include <math.h>	1392	#include <math.h>
974		1393
975	static ev_tstamp	1394	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1395	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1397	return fmod (now, 3600.) + 3600.;
979	}	1398	}
980		1399
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1400	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1401
983	Example: call a callback every hour, starting now:	1402	Example: Call a callback every hour, starting now:
984		1403
985	struct ev_periodic hourly_tick;	1404	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1405	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1406	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1407	ev_periodic_start (loop, &hourly_tick);
989		1408
990		1409
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1410	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1411
993	Signal watchers will trigger an event when the process receives a specific	1412	Signal watchers will trigger an event when the process receives a specific
994	signal one or more times. Even though signals are very asynchronous, libev	1413	signal one or more times. Even though signals are very asynchronous, libev
995	will try it's best to deliver signals synchronously, i.e. as part of the	1414	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1415	normal event processing, like any other event.
…		…
1000	with the kernel (thus it coexists with your own signal handlers as long	1419	with the kernel (thus it coexists with your own signal handlers as long
1001	as you don't register any with libev). Similarly, when the last signal	1420	as you don't register any with libev). Similarly, when the last signal
1002	watcher for a signal is stopped libev will reset the signal handler to	1421	watcher for a signal is stopped libev will reset the signal handler to
1003	SIG_DFL (regardless of what it was set to before).	1422	SIG_DFL (regardless of what it was set to before).
1004		1423
		1424	=head3 Watcher-Specific Functions and Data Members
		1425
1005	=over 4	1426	=over 4
1006		1427
1007	=item ev_signal_init (ev_signal *, callback, int signum)	1428	=item ev_signal_init (ev_signal *, callback, int signum)
1008		1429
1009	=item ev_signal_set (ev_signal *, int signum)	1430	=item ev_signal_set (ev_signal *, int signum)
1010		1431
1011	Configures the watcher to trigger on the given signal number (usually one	1432	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1433	of the C<SIGxxx> constants).
1013		1434
		1435	=item int signum [read-only]
		1436
		1437	The signal the watcher watches out for.
		1438
1014	=back	1439	=back
1015		1440
		1441	=head3 Examples
1016		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
		1455
1017	=head2 C<ev_child> - wait for pid status changes	1456	=head2 C<ev_child> - watch out for process status changes
1018		1457
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
		1485
		1486	=head3 Watcher-Specific Functions and Data Members
1021		1487
1022	=over 4	1488	=over 4
1023		1489
1024	=item ev_child_init (ev_child *, callback, int pid)	1490	=item ev_child_init (ev_child *, callback, int pid, int trace)
1025		1491
1026	=item ev_child_set (ev_child *, int pid)	1492	=item ev_child_set (ev_child *, int pid, int trace)
1027		1493
1028	Configures the watcher to wait for status changes of process C<pid> (or	1494	Configures the watcher to wait for status changes of process C<pid> (or
1029	I<any> process if C<pid> is specified as C<0>). The callback can look	1495	I<any> process if C<pid> is specified as C<0>). The callback can look
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1496	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1497	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1498	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1499	process causing the status change. C<trace> must be either C<0> (only
		1500	activate the watcher when the process terminates) or C<1> (additionally
		1501	activate the watcher when the process is stopped or continued).
		1502
		1503	=item int pid [read-only]
		1504
		1505	The process id this watcher watches out for, or C<0>, meaning any process id.
		1506
		1507	=item int rpid [read-write]
		1508
		1509	The process id that detected a status change.
		1510
		1511	=item int rstatus [read-write]
		1512
		1513	The process exit/trace status caused by C<rpid> (see your systems
		1514	C<waitpid> and C<sys/wait.h> documentation for details).
1034		1515
1035	=back	1516	=back
1036		1517
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1518	=head3 Examples
		1519
		1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
1038		1524
1039	static void	1525	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1526	child_cb (EV_P_ struct ev_child *w, int revents)
1041	{	1527	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1043	}	1530	}
1044		1531
1045	struct ev_signal signal_watcher;	1532	pid_t pid = fork ();
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);
1048		1533
		1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
1049		1546
		1547
		1548	=head2 C<ev_stat> - did the file attributes just change?
		1549
		1550	This watches a filesystem path for attribute changes. That is, it calls
		1551	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1552	compared to the last time, invoking the callback if it did.
		1553
		1554	The path does not need to exist: changing from "path exists" to "path does
		1555	not exist" is a status change like any other. The condition "path does
		1556	not exist" is signified by the C<st_nlink> field being zero (which is
		1557	otherwise always forced to be at least one) and all the other fields of
		1558	the stat buffer having unspecified contents.
		1559
		1560	The path I<should> be absolute and I<must not> end in a slash. If it is
		1561	relative and your working directory changes, the behaviour is undefined.
		1562
		1563	Since there is no standard to do this, the portable implementation simply
		1564	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1565	can specify a recommended polling interval for this case. If you specify
		1566	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1567	unspecified default> value will be used (which you can expect to be around
		1568	five seconds, although this might change dynamically). Libev will also
		1569	impose a minimum interval which is currently around C<0.1>, but thats
		1570	usually overkill.
		1571
		1572	This watcher type is not meant for massive numbers of stat watchers,
		1573	as even with OS-supported change notifications, this can be
		1574	resource-intensive.
		1575
		1576	At the time of this writing, only the Linux inotify interface is
		1577	implemented (implementing kqueue support is left as an exercise for the
		1578	reader). Inotify will be used to give hints only and should not change the
		1579	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1580	to fall back to regular polling again even with inotify, but changes are
		1581	usually detected immediately, and if the file exists there will be no
		1582	polling.
		1583
		1584	=head3 Inotify
		1585
		1586	When C<inotify (7)> support has been compiled into libev (generally only
		1587	available on Linux) and present at runtime, it will be used to speed up
		1588	change detection where possible. The inotify descriptor will be created lazily
		1589	when the first C<ev_stat> watcher is being started.
		1590
		1591	Inotify presense does not change the semantics of C<ev_stat> watchers
		1592	except that changes might be detected earlier, and in some cases, to avoid
		1593	making regular C<stat> calls. Even in the presense of inotify support
		1594	there are many cases where libev has to resort to regular C<stat> polling.
		1595
		1596	(There is no support for kqueue, as apparently it cannot be used to
		1597	implement this functionality, due to the requirement of having a file
		1598	descriptor open on the object at all times).
		1599
		1600	=head3 The special problem of stat time resolution
		1601
		1602	The C<stat ()> syscall only supports full-second resolution portably, and
		1603	even on systems where the resolution is higher, many filesystems still
		1604	only support whole seconds.
		1605
		1606	That means that, if the time is the only thing that changes, you might
		1607	miss updates: on the first update, C<ev_stat> detects a change and calls
		1608	your callback, which does something. When there is another update within
		1609	the same second, C<ev_stat> will be unable to detect it.
		1610
		1611	The solution to this is to delay acting on a change for a second (or till
		1612	the next second boundary), using a roughly one-second delay C<ev_timer>
		1613	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1614	is added to work around small timing inconsistencies of some operating
		1615	systems.
		1616
		1617	=head3 Watcher-Specific Functions and Data Members
		1618
		1619	=over 4
		1620
		1621	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1622
		1623	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1624
		1625	Configures the watcher to wait for status changes of the given
		1626	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1627	be detected and should normally be specified as C<0> to let libev choose
		1628	a suitable value. The memory pointed to by C<path> must point to the same
		1629	path for as long as the watcher is active.
		1630
		1631	The callback will be receive C<EV_STAT> when a change was detected,
		1632	relative to the attributes at the time the watcher was started (or the
		1633	last change was detected).
		1634
		1635	=item ev_stat_stat (loop, ev_stat *)
		1636
		1637	Updates the stat buffer immediately with new values. If you change the
		1638	watched path in your callback, you could call this fucntion to avoid
		1639	detecting this change (while introducing a race condition). Can also be
		1640	useful simply to find out the new values.
		1641
		1642	=item ev_statdata attr [read-only]
		1643
		1644	The most-recently detected attributes of the file. Although the type is of
		1645	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1646	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1647	was some error while C<stat>ing the file.
		1648
		1649	=item ev_statdata prev [read-only]
		1650
		1651	The previous attributes of the file. The callback gets invoked whenever
		1652	C<prev> != C<attr>.
		1653
		1654	=item ev_tstamp interval [read-only]
		1655
		1656	The specified interval.
		1657
		1658	=item const char *path [read-only]
		1659
		1660	The filesystem path that is being watched.
		1661
		1662	=back
		1663
		1664	=head3 Examples
		1665
		1666	Example: Watch C</etc/passwd> for attribute changes.
		1667
		1668	static void
		1669	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1670	{
		1671	/* /etc/passwd changed in some way */
		1672	if (w->attr.st_nlink)
		1673	{
		1674	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1675	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1676	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1677	}
		1678	else
		1679	/* you shalt not abuse printf for puts */
		1680	puts ("wow, /etc/passwd is not there, expect problems. "
		1681	"if this is windows, they already arrived\n");
		1682	}
		1683
		1684	...
		1685	ev_stat passwd;
		1686
		1687	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1688	ev_stat_start (loop, &passwd);
		1689
		1690	Example: Like above, but additionally use a one-second delay so we do not
		1691	miss updates (however, frequent updates will delay processing, too, so
		1692	one might do the work both on C<ev_stat> callback invocation I<and> on
		1693	C<ev_timer> callback invocation).
		1694
		1695	static ev_stat passwd;
		1696	static ev_timer timer;
		1697
		1698	static void
		1699	timer_cb (EV_P_ ev_timer *w, int revents)
		1700	{
		1701	ev_timer_stop (EV_A_ w);
		1702
		1703	/* now it's one second after the most recent passwd change */
		1704	}
		1705
		1706	static void
		1707	stat_cb (EV_P_ ev_stat *w, int revents)
		1708	{
		1709	/* reset the one-second timer */
		1710	ev_timer_again (EV_A_ &timer);
		1711	}
		1712
		1713	...
		1714	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1715	ev_stat_start (loop, &passwd);
		1716	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1717
		1718
1050	=head2 C<ev_idle> - when you've got nothing better to do	1719	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1720
1052	Idle watchers trigger events when there are no other events are pending	1721	Idle watchers trigger events when no other events of the same or higher
1053	(prepare, check and other idle watchers do not count). That is, as long	1722	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1723	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1724
1056	watchers are being called again and again, once per event loop iteration -	1725	That is, as long as your process is busy handling sockets or timeouts
		1726	(or even signals, imagine) of the same or higher priority it will not be
		1727	triggered. But when your process is idle (or only lower-priority watchers
		1728	are pending), the idle watchers are being called once per event loop
1057	until stopped, that is, or your process receives more events and becomes	1729	iteration - until stopped, that is, or your process receives more events
1058	busy.	1730	and becomes busy again with higher priority stuff.
1059		1731
1060	The most noteworthy effect is that as long as any idle watchers are	1732	The most noteworthy effect is that as long as any idle watchers are
1061	active, the process will not block when waiting for new events.	1733	active, the process will not block when waiting for new events.
1062		1734
1063	Apart from keeping your process non-blocking (which is a useful	1735	Apart from keeping your process non-blocking (which is a useful
1064	effect on its own sometimes), idle watchers are a good place to do	1736	effect on its own sometimes), idle watchers are a good place to do
1065	"pseudo-background processing", or delay processing stuff to after the	1737	"pseudo-background processing", or delay processing stuff to after the
1066	event loop has handled all outstanding events.	1738	event loop has handled all outstanding events.
1067		1739
		1740	=head3 Watcher-Specific Functions and Data Members
		1741
1068	=over 4	1742	=over 4
1069		1743
1070	=item ev_idle_init (ev_signal *, callback)	1744	=item ev_idle_init (ev_signal *, callback)
1071		1745
1072	Initialises and configures the idle watcher - it has no parameters of any	1746	Initialises and configures the idle watcher - it has no parameters of any
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1747	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1748	believe me.
1075		1749
1076	=back	1750	=back
1077		1751
		1752	=head3 Examples
		1753
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1755	callback, free it. Also, use no error checking, as usual.
1080		1756
1081	static void	1757	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1758	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1759	{
1084	free (w);	1760	free (w);
1085	// now do something you wanted to do when the program has	1761	// now do something you wanted to do when the program has
1086	// no longer asnything immediate to do.	1762	// no longer anything immediate to do.
1087	}	1763	}
1088		1764
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1766	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1767	ev_idle_start (loop, idle_cb);
1092		1768
1093		1769
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1770	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1771
1096	Prepare and check watchers are usually (but not always) used in tandem:	1772	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1773	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1774	afterwards.
1099		1775
		1776	You I<must not> call C<ev_loop> or similar functions that enter
		1777	the current event loop from either C<ev_prepare> or C<ev_check>
		1778	watchers. Other loops than the current one are fine, however. The
		1779	rationale behind this is that you do not need to check for recursion in
		1780	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1781	C<ev_check> so if you have one watcher of each kind they will always be
		1782	called in pairs bracketing the blocking call.
		1783
1100	Their main purpose is to integrate other event mechanisms into libev and	1784	Their main purpose is to integrate other event mechanisms into libev and
1101	their use is somewhat advanced. This could be used, for example, to track	1785	their use is somewhat advanced. This could be used, for example, to track
1102	variable changes, implement your own watchers, integrate net-snmp or a	1786	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1787	coroutine library and lots more. They are also occasionally useful if
		1788	you cache some data and want to flush it before blocking (for example,
		1789	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1790	watcher).
1104		1791
1105	This is done by examining in each prepare call which file descriptors need	1792	This is done by examining in each prepare call which file descriptors need
1106	to be watched by the other library, registering C<ev_io> watchers for	1793	to be watched by the other library, registering C<ev_io> watchers for
1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1794	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1108	provide just this functionality). Then, in the check watcher you check for	1795	provide just this functionality). Then, in the check watcher you check for
…		…
1118	with priority higher than or equal to the event loop and one coroutine	1805	with priority higher than or equal to the event loop and one coroutine
1119	of lower priority, but only once, using idle watchers to keep the event	1806	of lower priority, but only once, using idle watchers to keep the event
1120	loop from blocking if lower-priority coroutines are active, thus mapping	1807	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1808	low-priority coroutines to idle/background tasks).
1122		1809
		1810	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1811	priority, to ensure that they are being run before any other watchers
		1812	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1813	too) should not activate ("feed") events into libev. While libev fully
		1814	supports this, they will be called before other C<ev_check> watchers
		1815	did their job. As C<ev_check> watchers are often used to embed other
		1816	(non-libev) event loops those other event loops might be in an unusable
		1817	state until their C<ev_check> watcher ran (always remind yourself to
		1818	coexist peacefully with others).
		1819
		1820	=head3 Watcher-Specific Functions and Data Members
		1821
1123	=over 4	1822	=over 4
1124		1823
1125	=item ev_prepare_init (ev_prepare *, callback)	1824	=item ev_prepare_init (ev_prepare *, callback)
1126		1825
1127	=item ev_check_init (ev_check *, callback)	1826	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1830	macros, but using them is utterly, utterly and completely pointless.
1132		1831
1133	=back	1832	=back
1134		1833
1135	Example: *TODO*.	1834	=head3 Examples
1136		1835
		1836	There are a number of principal ways to embed other event loops or modules
		1837	into libev. Here are some ideas on how to include libadns into libev
		1838	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1839	use for an actually working example. Another Perl module named C<EV::Glib>
		1840	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1841	into the Glib event loop).
1137		1842
		1843	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1844	and in a check watcher, destroy them and call into libadns. What follows
		1845	is pseudo-code only of course. This requires you to either use a low
		1846	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1847	the callbacks for the IO/timeout watchers might not have been called yet.
		1848
		1849	static ev_io iow [nfd];
		1850	static ev_timer tw;
		1851
		1852	static void
		1853	io_cb (ev_loop *loop, ev_io *w, int revents)
		1854	{
		1855	}
		1856
		1857	// create io watchers for each fd and a timer before blocking
		1858	static void
		1859	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1860	{
		1861	int timeout = 3600000;
		1862	struct pollfd fds [nfd];
		1863	// actual code will need to loop here and realloc etc.
		1864	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1865
		1866	/* the callback is illegal, but won't be called as we stop during check */
		1867	ev_timer_init (&tw, 0, timeout * 1e-3);
		1868	ev_timer_start (loop, &tw);
		1869
		1870	// create one ev_io per pollfd
		1871	for (int i = 0; i < nfd; ++i)
		1872	{
		1873	ev_io_init (iow + i, io_cb, fds [i].fd,
		1874	((fds [i].events & POLLIN ? EV_READ : 0)
		1875	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1876
		1877	fds [i].revents = 0;
		1878	ev_io_start (loop, iow + i);
		1879	}
		1880	}
		1881
		1882	// stop all watchers after blocking
		1883	static void
		1884	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1885	{
		1886	ev_timer_stop (loop, &tw);
		1887
		1888	for (int i = 0; i < nfd; ++i)
		1889	{
		1890	// set the relevant poll flags
		1891	// could also call adns_processreadable etc. here
		1892	struct pollfd *fd = fds + i;
		1893	int revents = ev_clear_pending (iow + i);
		1894	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1895	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1896
		1897	// now stop the watcher
		1898	ev_io_stop (loop, iow + i);
		1899	}
		1900
		1901	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1902	}
		1903
		1904	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1905	in the prepare watcher and would dispose of the check watcher.
		1906
		1907	Method 3: If the module to be embedded supports explicit event
		1908	notification (adns does), you can also make use of the actual watcher
		1909	callbacks, and only destroy/create the watchers in the prepare watcher.
		1910
		1911	static void
		1912	timer_cb (EV_P_ ev_timer *w, int revents)
		1913	{
		1914	adns_state ads = (adns_state)w->data;
		1915	update_now (EV_A);
		1916
		1917	adns_processtimeouts (ads, &tv_now);
		1918	}
		1919
		1920	static void
		1921	io_cb (EV_P_ ev_io *w, int revents)
		1922	{
		1923	adns_state ads = (adns_state)w->data;
		1924	update_now (EV_A);
		1925
		1926	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1927	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1928	}
		1929
		1930	// do not ever call adns_afterpoll
		1931
		1932	Method 4: Do not use a prepare or check watcher because the module you
		1933	want to embed is too inflexible to support it. Instead, youc na override
		1934	their poll function. The drawback with this solution is that the main
		1935	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1936	this.
		1937
		1938	static gint
		1939	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1940	{
		1941	int got_events = 0;
		1942
		1943	for (n = 0; n < nfds; ++n)
		1944	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1945
		1946	if (timeout >= 0)
		1947	// create/start timer
		1948
		1949	// poll
		1950	ev_loop (EV_A_ 0);
		1951
		1952	// stop timer again
		1953	if (timeout >= 0)
		1954	ev_timer_stop (EV_A_ &to);
		1955
		1956	// stop io watchers again - their callbacks should have set
		1957	for (n = 0; n < nfds; ++n)
		1958	ev_io_stop (EV_A_ iow [n]);
		1959
		1960	return got_events;
		1961	}
		1962
		1963
1138	=head2 C<ev_embed> - when one backend isn't enough	1964	=head2 C<ev_embed> - when one backend isn't enough...
1139		1965
1140	This is a rather advanced watcher type that lets you embed one event loop	1966	This is a rather advanced watcher type that lets you embed one event loop
1141	into another (currently only C<ev_io> events are supported in the embedded	1967	into another (currently only C<ev_io> events are supported in the embedded
1142	loop, other types of watchers might be handled in a delayed or incorrect	1968	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1969	fashion and must not be used).
…		…
1182	portable one.	2008	portable one.
1183		2009
1184	So when you want to use this feature you will always have to be prepared	2010	So when you want to use this feature you will always have to be prepared
1185	that you cannot get an embeddable loop. The recommended way to get around	2011	that you cannot get an embeddable loop. The recommended way to get around
1186	this is to have a separate variables for your embeddable loop, try to	2012	this is to have a separate variables for your embeddable loop, try to
1187	create it, and if that fails, use the normal loop for everything:	2013	create it, and if that fails, use the normal loop for everything.
		2014
		2015	=head3 Watcher-Specific Functions and Data Members
		2016
		2017	=over 4
		2018
		2019	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2020
		2021	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2022
		2023	Configures the watcher to embed the given loop, which must be
		2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2025	invoked automatically, otherwise it is the responsibility of the callback
		2026	to invoke it (it will continue to be called until the sweep has been done,
		2027	if you do not want thta, you need to temporarily stop the embed watcher).
		2028
		2029	=item ev_embed_sweep (loop, ev_embed *)
		2030
		2031	Make a single, non-blocking sweep over the embedded loop. This works
		2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2033	apropriate way for embedded loops.
		2034
		2035	=item struct ev_loop *other [read-only]
		2036
		2037	The embedded event loop.
		2038
		2039	=back
		2040
		2041	=head3 Examples
		2042
		2043	Example: Try to get an embeddable event loop and embed it into the default
		2044	event loop. If that is not possible, use the default loop. The default
		2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2047	used).
1188		2048
1189	struct ev_loop *loop_hi = ev_default_init (0);	2049	struct ev_loop *loop_hi = ev_default_init (0);
1190	struct ev_loop *loop_lo = 0;	2050	struct ev_loop *loop_lo = 0;
1191	struct ev_embed embed;	2051	struct ev_embed embed;
1192		2052
…		…
1203	ev_embed_start (loop_hi, &embed);	2063	ev_embed_start (loop_hi, &embed);
1204	}	2064	}
1205	else	2065	else
1206	loop_lo = loop_hi;	2066	loop_lo = loop_hi;
1207		2067
		2068	Example: Check if kqueue is available but not recommended and create
		2069	a kqueue backend for use with sockets (which usually work with any
		2070	kqueue implementation). Store the kqueue/socket-only event loop in
		2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2072
		2073	struct ev_loop *loop = ev_default_init (0);
		2074	struct ev_loop *loop_socket = 0;
		2075	struct ev_embed embed;
		2076
		2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2079	{
		2080	ev_embed_init (&embed, 0, loop_socket);
		2081	ev_embed_start (loop, &embed);
		2082	}
		2083
		2084	if (!loop_socket)
		2085	loop_socket = loop;
		2086
		2087	// now use loop_socket for all sockets, and loop for everything else
		2088
		2089
		2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2091
		2092	Fork watchers are called when a C<fork ()> was detected (usually because
		2093	whoever is a good citizen cared to tell libev about it by calling
		2094	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2095	event loop blocks next and before C<ev_check> watchers are being called,
		2096	and only in the child after the fork. If whoever good citizen calling
		2097	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2098	handlers will be invoked, too, of course.
		2099
		2100	=head3 Watcher-Specific Functions and Data Members
		2101
1208	=over 4	2102	=over 4
1209		2103
1210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2104	=item ev_fork_init (ev_signal *, callback)
1211		2105
1212	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2106	Initialises and configures the fork watcher - it has no parameters of any
		2107	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2108	believe me.
1213		2109
1214	Configures the watcher to embed the given loop, which must be	2110	=back
1215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1216	invoked automatically, otherwise it is the responsibility of the callback
1217	to invoke it (it will continue to be called until the sweep has been done,
1218	if you do not want thta, you need to temporarily stop the embed watcher).
1219		2111
1220	=item ev_embed_sweep (loop, ev_embed *)
1221		2112
1222	Make a single, non-blocking sweep over the embedded loop. This works	2113	=head2 C<ev_async> - how to wake up another event loop
1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2114
1224	apropriate way for embedded loops.	2115	In general, you cannot use an C<ev_loop> from multiple threads or other
		2116	asynchronous sources such as signal handlers (as opposed to multiple event
		2117	loops - those are of course safe to use in different threads).
		2118
		2119	Sometimes, however, you need to wake up another event loop you do not
		2120	control, for example because it belongs to another thread. This is what
		2121	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2122	can signal it by calling C<ev_async_send>, which is thread- and signal
		2123	safe.
		2124
		2125	This functionality is very similar to C<ev_signal> watchers, as signals,
		2126	too, are asynchronous in nature, and signals, too, will be compressed
		2127	(i.e. the number of callback invocations may be less than the number of
		2128	C<ev_async_sent> calls).
		2129
		2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2131	just the default loop.
		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
		2221	=over 4
		2222
		2223	=item ev_async_init (ev_async *, callback)
		2224
		2225	Initialises and configures the async watcher - it has no parameters of any
		2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2227	believe me.
		2228
		2229	=item ev_async_send (loop, ev_async *)
		2230
		2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2233	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2235	section below on what exactly this means).
		2236
		2237	This call incurs the overhead of a syscall only once per loop iteration,
		2238	so while the overhead might be noticable, it doesn't apply to repeated
		2239	calls to C<ev_async_send>.
1225		2240
1226	=back	2241	=back
1227		2242
1228		2243
1229	=head1 OTHER FUNCTIONS	2244	=head1 OTHER FUNCTIONS
…		…
1318		2333
1319	To use it,	2334	To use it,
1320		2335
1321	#include <ev++.h>	2336	#include <ev++.h>
1322		2337
1323	(it is not installed by default). This automatically includes F<ev.h>	2338	This automatically includes F<ev.h> and puts all of its definitions (many
1324	and puts all of its definitions (many of them macros) into the global	2339	of them macros) into the global namespace. All C++ specific things are
1325	namespace. All C++ specific things are put into the C<ev> namespace.	2340	put into the C<ev> namespace. It should support all the same embedding
		2341	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		2342
1327	It should support all the same embedding options as F<ev.h>, most notably	2343	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	2344	classes add (compared to plain C-style watchers) is the event loop pointer
		2345	that the watcher is associated with (or no additional members at all if
		2346	you disable C<EV_MULTIPLICITY> when embedding libev).
		2347
		2348	Currently, functions, and static and non-static member functions can be
		2349	used as callbacks. Other types should be easy to add as long as they only
		2350	need one additional pointer for context. If you need support for other
		2351	types of functors please contact the author (preferably after implementing
		2352	it).
1329		2353
1330	Here is a list of things available in the C<ev> namespace:	2354	Here is a list of things available in the C<ev> namespace:
1331		2355
1332	=over 4	2356	=over 4
1333		2357
…		…
1349		2373
1350	All of those classes have these methods:	2374	All of those classes have these methods:
1351		2375
1352	=over 4	2376	=over 4
1353		2377
1354	=item ev::TYPE::TYPE (object *, object::method *)	2378	=item ev::TYPE::TYPE ()
1355		2379
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2380	=item ev::TYPE::TYPE (struct ev_loop *)
1357		2381
1358	=item ev::TYPE::~TYPE	2382	=item ev::TYPE::~TYPE
1359		2383
1360	The constructor takes a pointer to an object and a method pointer to	2384	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	2385	with. If it is omitted, it will use C<EV_DEFAULT>.
1362	C<ev_init> for you, which means you have to call the C<set> method	2386
1363	before starting it. If you do not specify a loop then the constructor	2387	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	2388	C<set> method before starting it.
		2389
		2390	It will not set a callback, however: You have to call the templated C<set>
		2391	method to set a callback before you can start the watcher.
		2392
		2393	(The reason why you have to use a method is a limitation in C++ which does
		2394	not allow explicit template arguments for constructors).
1365		2395
1366	The destructor automatically stops the watcher if it is active.	2396	The destructor automatically stops the watcher if it is active.
		2397
		2398	=item w->set<class, &class::method> (object *)
		2399
		2400	This method sets the callback method to call. The method has to have a
		2401	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2402	first argument and the C<revents> as second. The object must be given as
		2403	parameter and is stored in the C<data> member of the watcher.
		2404
		2405	This method synthesizes efficient thunking code to call your method from
		2406	the C callback that libev requires. If your compiler can inline your
		2407	callback (i.e. it is visible to it at the place of the C<set> call and
		2408	your compiler is good :), then the method will be fully inlined into the
		2409	thunking function, making it as fast as a direct C callback.
		2410
		2411	Example: simple class declaration and watcher initialisation
		2412
		2413	struct myclass
		2414	{
		2415	void io_cb (ev::io &w, int revents) { }
		2416	}
		2417
		2418	myclass obj;
		2419	ev::io iow;
		2420	iow.set <myclass, &myclass::io_cb> (&obj);
		2421
		2422	=item w->set<function> (void *data = 0)
		2423
		2424	Also sets a callback, but uses a static method or plain function as
		2425	callback. The optional C<data> argument will be stored in the watcher's
		2426	C<data> member and is free for you to use.
		2427
		2428	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2429
		2430	See the method-C<set> above for more details.
		2431
		2432	Example:
		2433
		2434	static void io_cb (ev::io &w, int revents) { }
		2435	iow.set <io_cb> ();
1367		2436
1368	=item w->set (struct ev_loop *)	2437	=item w->set (struct ev_loop *)
1369		2438
1370	Associates a different C<struct ev_loop> with this watcher. You can only	2439	Associates a different C<struct ev_loop> with this watcher. You can only
1371	do this when the watcher is inactive (and not pending either).	2440	do this when the watcher is inactive (and not pending either).
1372		2441
1373	=item w->set ([args])	2442	=item w->set ([args])
1374		2443
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2444	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1376	called at least once. Unlike the C counterpart, an active watcher gets	2445	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	2446	automatically stopped and restarted when reconfiguring it with this
		2447	method.
1378		2448
1379	=item w->start ()	2449	=item w->start ()
1380		2450
1381	Starts the watcher. Note that there is no C<loop> argument as the	2451	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	2452	constructor already stores the event loop.
1383		2453
1384	=item w->stop ()	2454	=item w->stop ()
1385		2455
1386	Stops the watcher if it is active. Again, no C<loop> argument.	2456	Stops the watcher if it is active. Again, no C<loop> argument.
1387		2457
1388	=item w->again () C<ev::timer>, C<ev::periodic> only	2458	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1389		2459
1390	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2460	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1391	C<ev_TYPE_again> function.	2461	C<ev_TYPE_again> function.
1392		2462
1393	=item w->sweep () C<ev::embed> only	2463	=item w->sweep () (C<ev::embed> only)
1394		2464
1395	Invokes C<ev_embed_sweep>.	2465	Invokes C<ev_embed_sweep>.
		2466
		2467	=item w->update () (C<ev::stat> only)
		2468
		2469	Invokes C<ev_stat_stat>.
1396		2470
1397	=back	2471	=back
1398		2472
1399	=back	2473	=back
1400		2474
1401	Example: Define a class with an IO and idle watcher, start one of them in	2475	Example: Define a class with an IO and idle watcher, start one of them in
1402	the constructor.	2476	the constructor.
1403		2477
1404	class myclass	2478	class myclass
1405	{	2479	{
1406	ev_io io; void io_cb (ev::io &w, int revents);	2480	ev::io io; void io_cb (ev::io &w, int revents);
1407	ev_idle idle void idle_cb (ev::idle &w, int revents);	2481	ev:idle idle void idle_cb (ev::idle &w, int revents);
1408		2482
1409	myclass ();	2483	myclass (int fd)
		2484	{
		2485	io .set <myclass, &myclass::io_cb > (this);
		2486	idle.set <myclass, &myclass::idle_cb> (this);
		2487
		2488	io.start (fd, ev::READ);
		2489	}
		2490	};
		2491
		2492
		2493	=head1 MACRO MAGIC
		2494
		2495	Libev can be compiled with a variety of options, the most fundamantal
		2496	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2497	functions and callbacks have an initial C<struct ev_loop *> argument.
		2498
		2499	To make it easier to write programs that cope with either variant, the
		2500	following macros are defined:
		2501
		2502	=over 4
		2503
		2504	=item C<EV_A>, C<EV_A_>
		2505
		2506	This provides the loop I<argument> for functions, if one is required ("ev
		2507	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2508	C<EV_A_> is used when other arguments are following. Example:
		2509
		2510	ev_unref (EV_A);
		2511	ev_timer_add (EV_A_ watcher);
		2512	ev_loop (EV_A_ 0);
		2513
		2514	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2515	which is often provided by the following macro.
		2516
		2517	=item C<EV_P>, C<EV_P_>
		2518
		2519	This provides the loop I<parameter> for functions, if one is required ("ev
		2520	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2521	C<EV_P_> is used when other parameters are following. Example:
		2522
		2523	// this is how ev_unref is being declared
		2524	static void ev_unref (EV_P);
		2525
		2526	// this is how you can declare your typical callback
		2527	static void cb (EV_P_ ev_timer *w, int revents)
		2528
		2529	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2530	suitable for use with C<EV_A>.
		2531
		2532	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2533
		2534	Similar to the other two macros, this gives you the value of the default
		2535	loop, if multiple loops are supported ("ev loop default").
		2536
		2537	=back
		2538
		2539	Example: Declare and initialise a check watcher, utilising the above
		2540	macros so it will work regardless of whether multiple loops are supported
		2541	or not.
		2542
		2543	static void
		2544	check_cb (EV_P_ ev_timer *w, int revents)
		2545	{
		2546	ev_check_stop (EV_A_ w);
1410	}	2547	}
1411		2548
1412	myclass::myclass (int fd)	2549	ev_check check;
1413	: io (this, &myclass::io_cb),	2550	ev_check_init (&check, check_cb);
1414	idle (this, &myclass::idle_cb)	2551	ev_check_start (EV_DEFAULT_ &check);
1415	{	2552	ev_loop (EV_DEFAULT_ 0);
1416	io.start (fd, ev::READ);
1417	}
1418		2553
1419	=head1 EMBEDDING	2554	=head1 EMBEDDING
1420		2555
1421	Libev can (and often is) directly embedded into host	2556	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	2557	applications. Examples of applications that embed it include the Deliantra
1423	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2558	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1424	and rxvt-unicode.	2559	and rxvt-unicode.
1425		2560
1426	The goal is to enable you to just copy the neecssary files into your	2561	The goal is to enable you to just copy the necessary files into your
1427	source directory without having to change even a single line in them, so	2562	source directory without having to change even a single line in them, so
1428	you can easily upgrade by simply copying (or having a checked-out copy of	2563	you can easily upgrade by simply copying (or having a checked-out copy of
1429	libev somewhere in your source tree).	2564	libev somewhere in your source tree).
1430		2565
1431	=head2 FILESETS	2566	=head2 FILESETS
…		…
1462	ev_vars.h	2597	ev_vars.h
1463	ev_wrap.h	2598	ev_wrap.h
1464		2599
1465	ev_win32.c required on win32 platforms only	2600	ev_win32.c required on win32 platforms only
1466		2601
1467	ev_select.c only when select backend is enabled (which is is by default)	2602	ev_select.c only when select backend is enabled (which is enabled by default)
1468	ev_poll.c only when poll backend is enabled (disabled by default)	2603	ev_poll.c only when poll backend is enabled (disabled by default)
1469	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2604	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1470	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2605	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1471	ev_port.c only when the solaris port backend is enabled (disabled by default)	2606	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		2607
1473	F<ev.c> includes the backend files directly when enabled, so you only need	2608	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	2609	to compile this single file.
1475		2610
1476	=head3 LIBEVENT COMPATIBILITY API	2611	=head3 LIBEVENT COMPATIBILITY API
1477		2612
1478	To include the libevent compatibility API, also include:	2613	To include the libevent compatibility API, also include:
1479		2614
…		…
1492		2627
1493	=head3 AUTOCONF SUPPORT	2628	=head3 AUTOCONF SUPPORT
1494		2629
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	2630	Instead of using C<EV_STANDALONE=1> and providing your config in
1496	whatever way you want, you can also C<m4_include([libev.m4])> in your	2631	whatever way you want, you can also C<m4_include([libev.m4])> in your
1497	F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include	2632	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	2633	include F<config.h> and configure itself accordingly.
1499		2634
1500	For this of course you need the m4 file:	2635	For this of course you need the m4 file:
1501		2636
1502	libev.m4	2637	libev.m4
1503		2638
…		…
1521		2656
1522	If defined to be C<1>, libev will try to detect the availability of the	2657	If defined to be C<1>, libev will try to detect the availability of the
1523	monotonic clock option at both compiletime and runtime. Otherwise no use	2658	monotonic clock option at both compiletime and runtime. Otherwise no use
1524	of the monotonic clock option will be attempted. If you enable this, you	2659	of the monotonic clock option will be attempted. If you enable this, you
1525	usually have to link against librt or something similar. Enabling it when	2660	usually have to link against librt or something similar. Enabling it when
1526	the functionality isn't available is safe, though, althoguh you have	2661	the functionality isn't available is safe, though, although you have
1527	to make sure you link against any libraries where the C<clock_gettime>	2662	to make sure you link against any libraries where the C<clock_gettime>
1528	function is hiding in (often F<-lrt>).	2663	function is hiding in (often F<-lrt>).
1529		2664
1530	=item EV_USE_REALTIME	2665	=item EV_USE_REALTIME
1531		2666
1532	If defined to be C<1>, libev will try to detect the availability of the	2667	If defined to be C<1>, libev will try to detect the availability of the
1533	realtime clock option at compiletime (and assume its availability at	2668	realtime clock option at compiletime (and assume its availability at
1534	runtime if successful). Otherwise no use of the realtime clock option will	2669	runtime if successful). Otherwise no use of the realtime clock option will
1535	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2670	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1536	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2671	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1537	in the description of C<EV_USE_MONOTONIC>, though.	2672	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2673
		2674	=item EV_USE_NANOSLEEP
		2675
		2676	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2677	and will use it for delays. Otherwise it will use C<select ()>.
1538		2678
1539	=item EV_USE_SELECT	2679	=item EV_USE_SELECT
1540		2680
1541	If undefined or defined to be C<1>, libev will compile in support for the	2681	If undefined or defined to be C<1>, libev will compile in support for the
1542	C<select>(2) backend. No attempt at autodetection will be done: if no	2682	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1560	wants osf handles on win32 (this is the case when the select to	2700	wants osf handles on win32 (this is the case when the select to
1561	be used is the winsock select). This means that it will call	2701	be used is the winsock select). This means that it will call
1562	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1563	it is assumed that all these functions actually work on fds, even	2703	it is assumed that all these functions actually work on fds, even
1564	on win32. Should not be defined on non-win32 platforms.	2704	on win32. Should not be defined on non-win32 platforms.
		2705
		2706	=item EV_FD_TO_WIN32_HANDLE
		2707
		2708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2709	file descriptors to socket handles. When not defining this symbol (the
		2710	default), then libev will call C<_get_osfhandle>, which is usually
		2711	correct. In some cases, programs use their own file descriptor management,
		2712	in which case they can provide this function to map fds to socket handles.
1565		2713
1566	=item EV_USE_POLL	2714	=item EV_USE_POLL
1567		2715
1568	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2716	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1569	backend. Otherwise it will be enabled on non-win32 platforms. It	2717	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1597		2745
1598	=item EV_USE_DEVPOLL	2746	=item EV_USE_DEVPOLL
1599		2747
1600	reserved for future expansion, works like the USE symbols above.	2748	reserved for future expansion, works like the USE symbols above.
1601		2749
		2750	=item EV_USE_INOTIFY
		2751
		2752	If defined to be C<1>, libev will compile in support for the Linux inotify
		2753	interface to speed up C<ev_stat> watchers. Its actual availability will
		2754	be detected at runtime.
		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
1602	=item EV_H	2767	=item EV_H
1603		2768
1604	The name of the F<ev.h> header file used to include it. The default if	2769	The name of the F<ev.h> header file used to include it. The default if
1605	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1606	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2771	used to virtually rename the F<ev.h> header file in case of conflicts.
1607		2772
1608	=item EV_CONFIG_H	2773	=item EV_CONFIG_H
1609		2774
1610	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2775	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1611	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2776	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1612	C<EV_H>, above.	2777	C<EV_H>, above.
1613		2778
1614	=item EV_EVENT_H	2779	=item EV_EVENT_H
1615		2780
1616	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2781	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1617	of how the F<event.h> header can be found.	2782	of how the F<event.h> header can be found, the default is C<"event.h">.
1618		2783
1619	=item EV_PROTOTYPES	2784	=item EV_PROTOTYPES
1620		2785
1621	If defined to be C<0>, then F<ev.h> will not define any function	2786	If defined to be C<0>, then F<ev.h> will not define any function
1622	prototypes, but still define all the structs and other symbols. This is	2787	prototypes, but still define all the structs and other symbols. This is
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2794	will have the C<struct ev_loop *> as first argument, and you can create
1630	additional independent event loops. Otherwise there will be no support	2795	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2796	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2797	argument. Instead, all functions act on the single default loop.
1633		2798
		2799	=item EV_MINPRI
		2800
		2801	=item EV_MAXPRI
		2802
		2803	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2804	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2805	provide for more priorities by overriding those symbols (usually defined
		2806	to be C<-2> and C<2>, respectively).
		2807
		2808	When doing priority-based operations, libev usually has to linearly search
		2809	all the priorities, so having many of them (hundreds) uses a lot of space
		2810	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2811	fine.
		2812
		2813	If your embedding app does not need any priorities, defining these both to
		2814	C<0> will save some memory and cpu.
		2815
1634	=item EV_PERIODICS	2816	=item EV_PERIODIC_ENABLE
1635		2817
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2818	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2819	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2820	code.
		2821
		2822	=item EV_IDLE_ENABLE
		2823
		2824	If undefined or defined to be C<1>, then idle watchers are supported. If
		2825	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2826	code.
		2827
		2828	=item EV_EMBED_ENABLE
		2829
		2830	If undefined or defined to be C<1>, then embed watchers are supported. If
		2831	defined to be C<0>, then they are not.
		2832
		2833	=item EV_STAT_ENABLE
		2834
		2835	If undefined or defined to be C<1>, then stat watchers are supported. If
		2836	defined to be C<0>, then they are not.
		2837
		2838	=item EV_FORK_ENABLE
		2839
		2840	If undefined or defined to be C<1>, then fork watchers are supported. If
		2841	defined to be C<0>, then they are not.
		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
		2846	defined to be C<0>, then they are not.
		2847
		2848	=item EV_MINIMAL
		2849
		2850	If you need to shave off some kilobytes of code at the expense of some
		2851	speed, define this symbol to C<1>. Currently only used for gcc to override
		2852	some inlining decisions, saves roughly 30% codesize of amd64.
		2853
		2854	=item EV_PID_HASHSIZE
		2855
		2856	C<ev_child> watchers use a small hash table to distribute workload by
		2857	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2858	than enough. If you need to manage thousands of children you might want to
		2859	increase this value (I<must> be a power of two).
		2860
		2861	=item EV_INOTIFY_HASHSIZE
		2862
		2863	C<ev_stat> watchers use a small hash table to distribute workload by
		2864	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2865	usually more than enough. If you need to manage thousands of C<ev_stat>
		2866	watchers you might want to increase this value (I<must> be a power of
		2867	two).
1638		2868
1639	=item EV_COMMON	2869	=item EV_COMMON
1640		2870
1641	By default, all watchers have a C<void *data> member. By redefining	2871	By default, all watchers have a C<void *data> member. By redefining
1642	this macro to a something else you can include more and other types of	2872	this macro to a something else you can include more and other types of
…		…
1647		2877
1648	#define EV_COMMON \	2878	#define EV_COMMON \
1649	SV *self; /* contains this struct */ \	2879	SV *self; /* contains this struct */ \
1650	SV *cb_sv, *fh /* note no trailing ";" */	2880	SV *cb_sv, *fh /* note no trailing ";" */
1651		2881
1652	=item EV_CB_DECLARE(type)	2882	=item EV_CB_DECLARE (type)
1653		2883
1654	=item EV_CB_INVOKE(watcher,revents)	2884	=item EV_CB_INVOKE (watcher, revents)
1655		2885
1656	=item ev_set_cb(ev,cb)	2886	=item ev_set_cb (ev, cb)
1657		2887
1658	Can be used to change the callback member declaration in each watcher,	2888	Can be used to change the callback member declaration in each watcher,
1659	and the way callbacks are invoked and set. Must expand to a struct member	2889	and the way callbacks are invoked and set. Must expand to a struct member
1660	definition and a statement, respectively. See the F<ev.v> header file for	2890	definition and a statement, respectively. See the F<ev.h> header file for
1661	their default definitions. One possible use for overriding these is to	2891	their default definitions. One possible use for overriding these is to
1662	avoid the ev_loop pointer as first argument in all cases, or to use method	2892	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2893	method calls instead of plain function calls in C++.
		2894
		2895	=head2 EXPORTED API SYMBOLS
		2896
		2897	If you need to re-export the API (e.g. via a dll) and you need a list of
		2898	exported symbols, you can use the provided F<Symbol.*> files which list
		2899	all public symbols, one per line:
		2900
		2901	Symbols.ev for libev proper
		2902	Symbols.event for the libevent emulation
		2903
		2904	This can also be used to rename all public symbols to avoid clashes with
		2905	multiple versions of libev linked together (which is obviously bad in
		2906	itself, but sometimes it is inconvinient to avoid this).
		2907
		2908	A sed command like this will create wrapper C<#define>'s that you need to
		2909	include before including F<ev.h>:
		2910
		2911	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2912
		2913	This would create a file F<wrap.h> which essentially looks like this:
		2914
		2915	#define ev_backend myprefix_ev_backend
		2916	#define ev_check_start myprefix_ev_check_start
		2917	#define ev_check_stop myprefix_ev_check_stop
		2918	...
1664		2919
1665	=head2 EXAMPLES	2920	=head2 EXAMPLES
1666		2921
1667	For a real-world example of a program the includes libev	2922	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2923	verbatim, you can have a look at the EV perl module
…		…
1671	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2926	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1672	will be compiled. It is pretty complex because it provides its own header	2927	will be compiled. It is pretty complex because it provides its own header
1673	file.	2928	file.
1674		2929
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2930	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1676	that everybody includes and which overrides some autoconf choices:	2931	that everybody includes and which overrides some configure choices:
1677		2932
		2933	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	2934	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	2935	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	2936	#define EV_PERIODIC_ENABLE 0
		2937	#define EV_STAT_ENABLE 0
		2938	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	2939	#define EV_CONFIG_H <config.h>
		2940	#define EV_MINPRI 0
		2941	#define EV_MAXPRI 0
1682		2942
1683	#include "ev++.h"	2943	#include "ev++.h"
1684		2944
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2945	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2946
1687	#include "ev_cpp.h"	2947	#include "ev_cpp.h"
1688	#include "ev.c"	2948	#include "ev.c"
1689		2949
		2950
		2951	=head1 COMPLEXITIES
		2952
		2953	In this section the complexities of (many of) the algorithms used inside
		2954	libev will be explained. For complexity discussions about backends see the
		2955	documentation for C<ev_default_init>.
		2956
		2957	All of the following are about amortised time: If an array needs to be
		2958	extended, libev needs to realloc and move the whole array, but this
		2959	happens asymptotically never with higher number of elements, so O(1) might
		2960	mean it might do a lengthy realloc operation in rare cases, but on average
		2961	it is much faster and asymptotically approaches constant time.
		2962
		2963	=over 4
		2964
		2965	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2966
		2967	This means that, when you have a watcher that triggers in one hour and
		2968	there are 100 watchers that would trigger before that then inserting will
		2969	have to skip roughly seven (C<ld 100>) of these watchers.
		2970
		2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2972
		2973	That means that changing a timer costs less than removing/adding them
		2974	as only the relative motion in the event queue has to be paid for.
		2975
		2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		2977
		2978	These just add the watcher into an array or at the head of a list.
		2979
		2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		2981
		2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2983
		2984	These watchers are stored in lists then need to be walked to find the
		2985	correct watcher to remove. The lists are usually short (you don't usually
		2986	have many watchers waiting for the same fd or signal).
		2987
		2988	=item Finding the next timer in each loop iteration: O(1)
		2989
		2990	By virtue of using a binary heap, the next timer is always found at the
		2991	beginning of the storage array.
		2992
		2993	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2994
		2995	A change means an I/O watcher gets started or stopped, which requires
		2996	libev to recalculate its status (and possibly tell the kernel, depending
		2997	on backend and wether C<ev_io_set> was used).
		2998
		2999	=item Activating one watcher (putting it into the pending state): O(1)
		3000
		3001	=item Priority handling: O(number_of_priorities)
		3002
		3003	Priorities are implemented by allocating some space for each
		3004	priority. When doing priority-based operations, libev usually has to
		3005	linearly search all the priorities, but starting/stopping and activating
		3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
		3017
		3018	=back
		3019
		3020
		3021	=head1 Win32 platform limitations and workarounds
		3022
		3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3024	requires, and its I/O model is fundamentally incompatible with the POSIX
		3025	model. Libev still offers limited functionality on this platform in
		3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3027	descriptors. This only applies when using Win32 natively, not when using
		3028	e.g. cygwin.
		3029
		3030	There is no supported compilation method available on windows except
		3031	embedding it into other applications.
		3032
		3033	Due to the many, low, and arbitrary limits on the win32 platform and the
		3034	abysmal performance of winsockets, using a large number of sockets is not
		3035	recommended (and not reasonable). If your program needs to use more than
		3036	a hundred or so sockets, then likely it needs to use a totally different
		3037	implementation for windows, as libev offers the POSIX model, which cannot
		3038	be implemented efficiently on windows (microsoft monopoly games).
		3039
		3040	=over 4
		3041
		3042	=item The winsocket select function
		3043
		3044	The winsocket C<select> function doesn't follow POSIX in that it requires
		3045	socket I<handles> and not socket I<file descriptors>. This makes select
		3046	very inefficient, and also requires a mapping from file descriptors
		3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3049	symbols for more info.
		3050
		3051	The configuration for a "naked" win32 using the microsoft runtime
		3052	libraries and raw winsocket select is:
		3053
		3054	#define EV_USE_SELECT 1
		3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3056
		3057	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3058	complexity in the O(n²) range when using win32.
		3059
		3060	=item Limited number of file descriptors
		3061
		3062	Windows has numerous arbitrary (and low) limits on things. Early versions
		3063	of winsocket's select only supported waiting for a max. of C<64> handles
		3064	(probably owning to the fact that all windows kernels can only wait for
		3065	C<64> things at the same time internally; microsoft recommends spawning a
		3066	chain of threads and wait for 63 handles and the previous thread in each).
		3067
		3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3069	to some high number (e.g. C<2048>) before compiling the winsocket select
		3070	call (which might be in libev or elsewhere, for example, perl does its own
		3071	select emulation on windows).
		3072
		3073	Another limit is the number of file descriptors in the microsoft runtime
		3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3075	or something like this inside microsoft). You can increase this by calling
		3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3077	arbitrary limit), but is broken in many versions of the microsoft runtime
		3078	libraries.
		3079
		3080	This might get you to about C<512> or C<2048> sockets (depending on
		3081	windows version and/or the phase of the moon). To get more, you need to
		3082	wrap all I/O functions and provide your own fd management, but the cost of
		3083	calling select (O(n²)) will likely make this unworkable.
		3084
		3085	=back
		3086
		3087
1690	=head1 AUTHOR	3088	=head1 AUTHOR
1691		3089
1692	Marc Lehmann <libev@schmorp.de>.	3090	Marc Lehmann <libev@schmorp.de>.
1693		3091

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