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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	// a single header file is required
		12	#include <ev.h>
		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
		16	ev_io stdin_watcher;
		17	ev_timer timeout_watcher;
		18
		19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
		21	static void
		22	stdin_cb (EV_P_ struct ev_io *w, int revents)
		23	{
		24	puts ("stdin ready");
		25	// for one-shot events, one must manually stop the watcher
		26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
		31	}
		32
		33	// another callback, this time for a time-out
		34	static void
		35	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		36	{
		37	puts ("timeout");
		38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
		40	}
		41
		42	int
		43	main (void)
		44	{
		45	// use the default event loop unless you have special needs
		46	struct ev_loop *loop = ev_default_loop (0);
		47
		48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
		50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		51	ev_io_start (loop, &stdin_watcher);
		52
		53	// initialise a timer watcher, then start it
		54	// simple non-repeating 5.5 second timeout
		55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		56	ev_timer_start (loop, &timeout_watcher);
		57
		58	// now wait for events to arrive
		59	ev_loop (loop, 0);
		60
		61	// unloop was called, so exit
		62	return 0;
		63	}
		64
9	=head1 DESCRIPTION	65	=head1 DESCRIPTION
10		66
		67	The newest version of this document is also available as an html-formatted
		68	web page you might find easier to navigate when reading it for the first
		69	time: L<http://cvs.schmorp.de/libev/ev.html>.
		70
11	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
13	these event sources and provide your program with events.	73	these event sources and provide your program with events.
14		74
15	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
16	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
17	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
19	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
20	watchers>, which are relatively small C structures you initialise with the	80	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	81	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	82	watcher.
23		83
24	=head1 FEATURES	84	=head2 FEATURES
25		85
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	90	with customised rescheduling (C<ev_periodic>), synchronous signals
		91	(C<ev_signal>), process status change events (C<ev_child>), and event
		92	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		94	file watchers (C<ev_stat>) and even limited support for fork events
		95	(C<ev_fork>).
		96
		97	It also is quite fast (see this
31	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	99	for example).
33		100
34	=head1 CONVENTIONS	101	=head2 CONVENTIONS
35		102
36	Libev is very configurable. In this manual the default configuration	103	Libev is very configurable. In this manual the default (and most common)
37	will be described, which supports multiple event loops. For more info	104	configuration will be described, which supports multiple event loops. For
38	about various configuration options please have a look at the file	105	more info about various configuration options please have a look at
39	F<README.embed> in the libev distribution. If libev was configured without	106	B<EMBED> section in this manual. If libev was configured without support
40	support for multiple event loops, then all functions taking an initial	107	for multiple event loops, then all functions taking an initial argument of
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	108	name C<loop> (which is always of type C<struct ev_loop *>) will not have
42	will not have this argument.	109	this argument.
43		110
44	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
45		112
46	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	118	it, you should treat it as some floatingpoint value. Unlike the name
52		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
53		121
54	=head1 GLOBAL FUNCTIONS	122	=head1 GLOBAL FUNCTIONS
55		123
56	These functions can be called anytime, even before initialising the	124	These functions can be called anytime, even before initialising the
57	library in any way.	125	library in any way.
…		…
62		130
63	Returns the current time as libev would use it. Please note that the	131	Returns the current time as libev would use it. Please note that the
64	C<ev_now> function is usually faster and also often returns the timestamp	132	C<ev_now> function is usually faster and also often returns the timestamp
65	you actually want to know.	133	you actually want to know.
66		134
		135	=item ev_sleep (ev_tstamp interval)
		136
		137	Sleep for the given interval: The current thread will be blocked until
		138	either it is interrupted or the given time interval has passed. Basically
		139	this is a subsecond-resolution C<sleep ()>.
		140
67	=item int ev_version_major ()	141	=item int ev_version_major ()
68		142
69	=item int ev_version_minor ()	143	=item int ev_version_minor ()
70		144
71	You can find out the major and minor version numbers of the library	145	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	146	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	147	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	148	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	149	version of the library your program was compiled against.
76		150
		151	These version numbers refer to the ABI version of the library, not the
		152	release version.
		153
77	Usually, it's a good idea to terminate if the major versions mismatch,	154	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	155	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	156	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	157	not a problem.
81		158
82	Example: make sure we haven't accidentally been linked against the wrong	159	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	160	version.
84		161
85	assert (("libev version mismatch",	162	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	163	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	164	&& ev_version_minor () >= EV_VERSION_MINOR));
88		165
…		…
118		195
119	See the description of C<ev_embed> watchers for more info.	196	See the description of C<ev_embed> watchers for more info.
120		197
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		199
123	Sets the allocation function to use (the prototype is similar to the	200	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	201	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	202	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	203	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	204	potentially destructive action. The default is your system realloc
		205	function.
128		206
129	You could override this function in high-availability programs to, say,	207	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,	208	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.	209	or even to sleep a while and retry until some memory is available.
132		210
133	Example: replace the libev allocator with one that waits a bit and then	211	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	212	retries).
135		213
136	static void *	214	static void *
137	persistent_realloc (void *ptr, long size)	215	persistent_realloc (void *ptr, size_t size)
138	{	216	{
139	for (;;)	217	for (;;)
140	{	218	{
141	void *newptr = realloc (ptr, size);	219	void *newptr = realloc (ptr, size);
142		220
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	236	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	237	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	238	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	239	(such as abort).
162		240
163	Example: do the same thing as libev does internally:	241	Example: This is basically the same thing that libev does internally, too.
164		242
165	static void	243	static void
166	fatal_error (const char *msg)	244	fatal_error (const char *msg)
167	{	245	{
168	perror (msg);	246	perror (msg);
…		…
197	flags. If that is troubling you, check C<ev_backend ()> afterwards).	275	flags. If that is troubling you, check C<ev_backend ()> afterwards).
198		276
199	If you don't know what event loop to use, use the one returned from this	277	If you don't know what event loop to use, use the one returned from this
200	function.	278	function.
201		279
		280	Note that this function is I<not> thread-safe, so if you want to use it
		281	from multiple threads, you have to lock (note also that this is unlikely,
		282	as loops cannot bes hared easily between threads anyway).
		283
		284	The default loop is the only loop that can handle C<ev_signal> and
		285	C<ev_child> watchers, and to do this, it always registers a handler
		286	for C<SIGCHLD>. If this is a problem for your app you can either
		287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		289	C<ev_default_init>.
		290
202	The flags argument can be used to specify special behaviour or specific	291	The flags argument can be used to specify special behaviour or specific
203	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	292	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
204		293
205	The following flags are supported:	294	The following flags are supported:
206		295
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	308	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	309	useful to try out specific backends to test their performance, or to work
221	around bugs.	310	around bugs.
222		311
		312	=item C<EVFLAG_FORKCHECK>
		313
		314	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		315	a fork, you can also make libev check for a fork in each iteration by
		316	enabling this flag.
		317
		318	This works by calling C<getpid ()> on every iteration of the loop,
		319	and thus this might slow down your event loop if you do a lot of loop
		320	iterations and little real work, but is usually not noticeable (on my
		321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
		322	without a syscall and thus I<very> fast, but my GNU/Linux system also has
		323	C<pthread_atfork> which is even faster).
		324
		325	The big advantage of this flag is that you can forget about fork (and
		326	forget about forgetting to tell libev about forking) when you use this
		327	flag.
		328
		329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		330	environment variable.
		331
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		333
225	This is your standard select(2) backend. Not I<completely> standard, as	334	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	335	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	336	but if that fails, expect a fairly low limit on the number of fds when
228	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	337	using this backend. It doesn't scale too well (O(highest_fd)), but its
229	the fastest backend for a low number of fds.	338	usually the fastest backend for a low number of (low-numbered :) fds.
		339
		340	To get good performance out of this backend you need a high amount of
		341	parallelity (most of the file descriptors should be busy). If you are
		342	writing a server, you should C<accept ()> in a loop to accept as many
		343	connections as possible during one iteration. You might also want to have
		344	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		345	readyness notifications you get per iteration.
230		346
231	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
232		348
233	And this is your standard poll(2) backend. It's more complicated than	349	And this is your standard poll(2) backend. It's more complicated
234	select, but handles sparse fds better and has no artificial limit on the	350	than select, but handles sparse fds better and has no artificial
235	number of fds you can use (except it will slow down considerably with a	351	limit on the number of fds you can use (except it will slow down
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	352	considerably with a lot of inactive fds). It scales similarly to select,
		353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		354	performance tips.
237		355
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	356	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		357
240	For few fds, this backend is a bit little slower than poll and select,	358	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	359	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	360	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	361	epoll scales either O(1) or O(active_fds). The epoll design has a number
		362	of shortcomings, such as silently dropping events in some hard-to-detect
		363	cases and rewiring a syscall per fd change, no fork support and bad
		364	support for dup.
244		365
245	While stopping and starting an I/O watcher in the same iteration will	366	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	367	will result in some caching, there is still a syscall per such incident
247	(because the fd could point to a different file description now), so its	368	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	370	very well if you register events for both fds.
250		371
251	Please note that epoll sometimes generates spurious notifications, so you	372	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	373	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	374	(or space) is available.
254		375
		376	Best performance from this backend is achieved by not unregistering all
		377	watchers for a file descriptor until it has been closed, if possible, i.e.
		378	keep at least one watcher active per fd at all times.
		379
		380	While nominally embeddeble in other event loops, this feature is broken in
		381	all kernel versions tested so far.
		382
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		384
257	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
258	was broken on all BSDs except NetBSD (usually it doesn't work with	386	was broken on all BSDs except NetBSD (usually it doesn't work reliably
259	anything but sockets and pipes, except on Darwin, where of course its	387	with anything but sockets and pipes, except on Darwin, where of course
260	completely useless). For this reason its not being "autodetected"	388	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	389	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		391	system like NetBSD.
		392
		393	You still can embed kqueue into a normal poll or select backend and use it
		394	only for sockets (after having made sure that sockets work with kqueue on
		395	the target platform). See C<ev_embed> watchers for more info.
263		396
264	It scales in the same way as the epoll backend, but the interface to the	397	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	398	kernel is more efficient (which says nothing about its actual speed, of
266	course). While starting and stopping an I/O watcher does not cause an	399	course). While stopping, setting and starting an I/O watcher does never
267	extra syscall as with epoll, it still adds up to four event changes per	400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
268	incident, so its best to avoid that.	401	two event changes per incident, support for C<fork ()> is very bad and it
		402	drops fds silently in similarly hard-to-detect cases.
		403
		404	This backend usually performs well under most conditions.
		405
		406	While nominally embeddable in other event loops, this doesn't work
		407	everywhere, so you might need to test for this. And since it is broken
		408	almost everywhere, you should only use it when you have a lot of sockets
		409	(for which it usually works), by embedding it into another event loop
		410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		411	sockets.
269		412
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		414
272	This is not implemented yet (and might never be).	415	This is not implemented yet (and might never be, unless you send me an
		416	implementation). According to reports, C</dev/poll> only supports sockets
		417	and is not embeddable, which would limit the usefulness of this backend
		418	immensely.
273		419
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		421
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	423	it's really slow, but it still scales very well (O(active_fds)).
278		424
279	Please note that solaris ports can result in a lot of spurious	425	Please note that solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	426	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	427	blocking when no data (or space) is available.
		428
		429	While this backend scales well, it requires one system call per active
		430	file descriptor per loop iteration. For small and medium numbers of file
		431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		432	might perform better.
		433
		434	On the positive side, ignoring the spurious readyness notifications, this
		435	backend actually performed to specification in all tests and is fully
		436	embeddable, which is a rare feat among the OS-specific backends.
282		437
283	=item C<EVBACKEND_ALL>	438	=item C<EVBACKEND_ALL>
284		439
285	Try all backends (even potentially broken ones that wouldn't be tried	440	Try all backends (even potentially broken ones that wouldn't be tried
286	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
287	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	442	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
288		443
		444	It is definitely not recommended to use this flag.
		445
289	=back	446	=back
290		447
291	If one or more of these are ored into the flags value, then only these	448	If one or more of these are ored into the flags value, then only these
292	backends will be tried (in the reverse order as given here). If none are	449	backends will be tried (in the reverse order as listed here). If none are
293	specified, most compiled-in backend will be tried, usually in reverse	450	specified, all backends in C<ev_recommended_backends ()> will be tried.
294	order of their flag values :)
295		451
296	The most typical usage is like this:	452	The most typical usage is like this:
297		453
298	if (!ev_default_loop (0))	454	if (!ev_default_loop (0))
299	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	455	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	470	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	471	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	472	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).	473	undefined behaviour (or a failed assertion if assertions are enabled).
318		474
		475	Note that this function I<is> thread-safe, and the recommended way to use
		476	libev with threads is indeed to create one loop per thread, and using the
		477	default loop in the "main" or "initial" thread.
		478
319	Example: try to create a event loop that uses epoll and nothing else.	479	Example: Try to create a event loop that uses epoll and nothing else.
320		480
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	482	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	483	fatal ("no epoll found here, maybe it hides under your chair");
324		484
…		…
327	Destroys the default loop again (frees all memory and kernel state	487	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	488	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	489	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>	490	responsibility to either stop all watchers cleanly yoursef I<before>
331	calling this function, or cope with the fact afterwards (which is usually	491	calling this function, or cope with the fact afterwards (which is usually
332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	492	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	493	for example).
		494
		495	Note that certain global state, such as signal state, will not be freed by
		496	this function, and related watchers (such as signal and child watchers)
		497	would need to be stopped manually.
		498
		499	In general it is not advisable to call this function except in the
		500	rare occasion where you really need to free e.g. the signal handling
		501	pipe fds. If you need dynamically allocated loops it is better to use
		502	C<ev_loop_new> and C<ev_loop_destroy>).
334		503
335	=item ev_loop_destroy (loop)	504	=item ev_loop_destroy (loop)
336		505
337	Like C<ev_default_destroy>, but destroys an event loop created by an	506	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	507	earlier call to C<ev_loop_new>.
339		508
340	=item ev_default_fork ()	509	=item ev_default_fork ()
341		510
		511	This function sets a flag that causes subsequent C<ev_loop> iterations
342	This function reinitialises the kernel state for backends that have	512	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	513	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	514	the child process (or both child and parent, but that again makes little
345	again makes little sense).	515	sense). You I<must> call it in the child before using any of the libev
		516	functions, and it will only take effect at the next C<ev_loop> iteration.
346		517
347	You I<must> call this function in the child process after forking if and	518	On the other hand, you only need to call this function in the child
348	only if you want to use the event library in both processes. If you just	519	process if and only if you want to use the event library in the child. If
349	fork+exec, you don't have to call it.	520	you just fork+exec, you don't have to call it at all.
350		521
351	The function itself is quite fast and it's usually not a problem to call	522	The function itself is quite fast and it's usually not a problem to call
352	it just in case after a fork. To make this easy, the function will fit in	523	it just in case after a fork. To make this easy, the function will fit in
353	quite nicely into a call to C<pthread_atfork>:	524	quite nicely into a call to C<pthread_atfork>:
354		525
355	pthread_atfork (0, 0, ev_default_fork);	526	pthread_atfork (0, 0, ev_default_fork);
356		527
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)	528	=item ev_loop_fork (loop)
362		529
363	Like C<ev_default_fork>, but acts on an event loop created by	530	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	532	after fork, and how you do this is entirely your own problem.
		533
		534	=item int ev_is_default_loop (loop)
		535
		536	Returns true when the given loop actually is the default loop, false otherwise.
		537
		538	=item unsigned int ev_loop_count (loop)
		539
		540	Returns the count of loop iterations for the loop, which is identical to
		541	the number of times libev did poll for new events. It starts at C<0> and
		542	happily wraps around with enough iterations.
		543
		544	This value can sometimes be useful as a generation counter of sorts (it
		545	"ticks" the number of loop iterations), as it roughly corresponds with
		546	C<ev_prepare> and C<ev_check> calls.
366		547
367	=item unsigned int ev_backend (loop)	548	=item unsigned int ev_backend (loop)
368		549
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	550	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	551	use.
…		…
373		554
374	Returns the current "event loop time", which is the time the event loop	555	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	556	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	557	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	558	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).	559	event occurring (or more correctly, libev finding out about it).
379		560
380	=item ev_loop (loop, int flags)	561	=item ev_loop (loop, int flags)
381		562
382	Finally, this is it, the event handler. This function usually is called	563	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	564	after you initialised all your watchers and you want to start handling
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	586	usually a better approach for this kind of thing.
406		587
407	Here are the gory details of what C<ev_loop> does:	588	Here are the gory details of what C<ev_loop> does:
408		589
409	* If there are no active watchers (reference count is zero), return.	590	- Before the first iteration, call any pending watchers.
410	- Queue prepare watchers and then call all outstanding watchers.	591	* If EVFLAG_FORKCHECK was used, check for a fork.
		592	- If a fork was detected, queue and call all fork watchers.
		593	- Queue and call all prepare watchers.
411	- If we have been forked, recreate the kernel state.	594	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	595	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	596	- Update the "event loop time".
414	- Calculate for how long to block.	597	- Calculate for how long to sleep or block, if at all
		598	(active idle watchers, EVLOOP_NONBLOCK or not having
		599	any active watchers at all will result in not sleeping).
		600	- Sleep if the I/O and timer collect interval say so.
415	- Block the process, waiting for any events.	601	- Block the process, waiting for any events.
416	- Queue all outstanding I/O (fd) events.	602	- Queue all outstanding I/O (fd) events.
417	- Update the "event loop time" and do time jump handling.	603	- Update the "event loop time" and do time jump handling.
418	- Queue all outstanding timers.	604	- Queue all outstanding timers.
419	- Queue all outstanding periodics.	605	- Queue all outstanding periodics.
420	- If no events are pending now, queue all idle watchers.	606	- If no events are pending now, queue all idle watchers.
421	- Queue all check watchers.	607	- Queue all check watchers.
422	- Call all queued watchers in reverse order (i.e. check watchers first).	608	- Call all queued watchers in reverse order (i.e. check watchers first).
423	Signals and child watchers are implemented as I/O watchers, and will	609	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	610	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	612	were used, or there are no active watchers, return, otherwise
		613	continue with step *.
427		614
428	Example: queue some jobs and then loop until no events are outsanding	615	Example: Queue some jobs and then loop until no events are outstanding
429	anymore.	616	anymore.
430		617
431	... queue jobs here, make sure they register event watchers as long	618	... 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..)	619	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	620	ev_loop (my_loop, 0);
…		…
437		624
438	Can be used to make a call to C<ev_loop> return early (but only after it	625	Can be used to make a call to C<ev_loop> return early (but only after it
439	has processed all outstanding events). The C<how> argument must be either	626	has processed all outstanding events). The C<how> argument must be either
440	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
441	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		629
		630	This "unloop state" will be cleared when entering C<ev_loop> again.
442		631
443	=item ev_ref (loop)	632	=item ev_ref (loop)
444		633
445	=item ev_unref (loop)	634	=item ev_unref (loop)
446		635
…		…
451	returning, ev_unref() after starting, and ev_ref() before stopping it. For	640	returning, ev_unref() after starting, and ev_ref() before stopping it. For
452	example, libev itself uses this for its internal signal pipe: It is not	641	example, libev itself uses this for its internal signal pipe: It is not
453	visible to the libev user and should not keep C<ev_loop> from exiting if	642	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	643	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	644	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	645	libraries. Just remember to I<unref after start> and I<ref before stop>
		646	(but only if the watcher wasn't active before, or was active before,
		647	respectively).
457		648
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	650	running when nothing else is active.
460		651
461	struct dv_signal exitsig;	652	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	653	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	654	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	655	evf_unref (loop);
465		656
466	Example: for some weird reason, unregister the above signal handler again.	657	Example: For some weird reason, unregister the above signal handler again.
467		658
468	ev_ref (myloop);	659	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	660	ev_signal_stop (loop, &exitsig);
		661
		662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		663
		664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		665
		666	These advanced functions influence the time that libev will spend waiting
		667	for events. Both are by default C<0>, meaning that libev will try to
		668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		669
		670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		671	allows libev to delay invocation of I/O and timer/periodic callbacks to
		672	increase efficiency of loop iterations.
		673
		674	The background is that sometimes your program runs just fast enough to
		675	handle one (or very few) event(s) per loop iteration. While this makes
		676	the program responsive, it also wastes a lot of CPU time to poll for new
		677	events, especially with backends like C<select ()> which have a high
		678	overhead for the actual polling but can deliver many events at once.
		679
		680	By setting a higher I<io collect interval> you allow libev to spend more
		681	time collecting I/O events, so you can handle more events per iteration,
		682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		683	C<ev_timer>) will be not affected. Setting this to a non-null value will
		684	introduce an additional C<ev_sleep ()> call into most loop iterations.
		685
		686	Likewise, by setting a higher I<timeout collect interval> you allow libev
		687	to spend more time collecting timeouts, at the expense of increased
		688	latency (the watcher callback will be called later). C<ev_io> watchers
		689	will not be affected. Setting this to a non-null value will not introduce
		690	any overhead in libev.
		691
		692	Many (busy) programs can usually benefit by setting the io collect
		693	interval to a value near C<0.1> or so, which is often enough for
		694	interactive servers (of course not for games), likewise for timeouts. It
		695	usually doesn't make much sense to set it to a lower value than C<0.01>,
		696	as this approsaches the timing granularity of most systems.
470		697
471	=back	698	=back
		699
472		700
473	=head1 ANATOMY OF A WATCHER	701	=head1 ANATOMY OF A WATCHER
474		702
475	A watcher is a structure that you create and register to record your	703	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	704	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.	771	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		772
545	=item C<EV_CHILD>	773	=item C<EV_CHILD>
546		774
547	The pid specified in the C<ev_child> watcher has received a status change.	775	The pid specified in the C<ev_child> watcher has received a status change.
		776
		777	=item C<EV_STAT>
		778
		779	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		780
549	=item C<EV_IDLE>	781	=item C<EV_IDLE>
550		782
551	The C<ev_idle> watcher has determined that you have nothing better to do.	783	The C<ev_idle> watcher has determined that you have nothing better to do.
552		784
…		…
560	received events. Callbacks of both watcher types can start and stop as	792	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	793	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	794	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	795	C<ev_loop> from blocking).
564		796
		797	=item C<EV_EMBED>
		798
		799	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		800
		801	=item C<EV_FORK>
		802
		803	The event loop has been resumed in the child process after fork (see
		804	C<ev_fork>).
		805
		806	=item C<EV_ASYNC>
		807
		808	The given async watcher has been asynchronously notified (see C<ev_async>).
		809
565	=item C<EV_ERROR>	810	=item C<EV_ERROR>
566		811
567	An unspecified error has occured, the watcher has been stopped. This might	812	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	813	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	814	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	821	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	822	programs, though, so beware.
578		823
579	=back	824	=back
580		825
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	826	=head2 GENERIC WATCHER FUNCTIONS
582		827
583	In the following description, C<TYPE> stands for the watcher type,	828	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.	829	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		830
586	=over 4	831	=over 4
…		…
595	which rolls both calls into one.	840	which rolls both calls into one.
596		841
597	You can reinitialise a watcher at any time as long as it has been stopped	842	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.	843	(or never started) and there are no pending events outstanding.
599		844
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	846	int revents)>.
602		847
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	848	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		849
605	This macro initialises the type-specific parts of a watcher. You need to	850	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	885	=item bool ev_is_pending (ev_TYPE *watcher)
641		886
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	887	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	888	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	889	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	890	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	891	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		892	it).
647		893
648	=item callback = ev_cb (ev_TYPE *watcher)	894	=item callback ev_cb (ev_TYPE *watcher)
649		895
650	Returns the callback currently set on the watcher.	896	Returns the callback currently set on the watcher.
651		897
652	=item ev_cb_set (ev_TYPE *watcher, callback)	898	=item ev_cb_set (ev_TYPE *watcher, callback)
653		899
654	Change the callback. You can change the callback at virtually any time	900	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	901	(modulo threads).
		902
		903	=item ev_set_priority (ev_TYPE *watcher, priority)
		904
		905	=item int ev_priority (ev_TYPE *watcher)
		906
		907	Set and query the priority of the watcher. The priority is a small
		908	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		909	(default: C<-2>). Pending watchers with higher priority will be invoked
		910	before watchers with lower priority, but priority will not keep watchers
		911	from being executed (except for C<ev_idle> watchers).
		912
		913	This means that priorities are I<only> used for ordering callback
		914	invocation after new events have been received. This is useful, for
		915	example, to reduce latency after idling, or more often, to bind two
		916	watchers on the same event and make sure one is called first.
		917
		918	If you need to suppress invocation when higher priority events are pending
		919	you need to look at C<ev_idle> watchers, which provide this functionality.
		920
		921	You I<must not> change the priority of a watcher as long as it is active or
		922	pending.
		923
		924	The default priority used by watchers when no priority has been set is
		925	always C<0>, which is supposed to not be too high and not be too low :).
		926
		927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		928	fine, as long as you do not mind that the priority value you query might
		929	or might not have been adjusted to be within valid range.
		930
		931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		932
		933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		934	C<loop> nor C<revents> need to be valid as long as the watcher callback
		935	can deal with that fact.
		936
		937	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		938
		939	If the watcher is pending, this function returns clears its pending status
		940	and returns its C<revents> bitset (as if its callback was invoked). If the
		941	watcher isn't pending it does nothing and returns C<0>.
656		942
657	=back	943	=back
658		944
659		945
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	967	{
682	struct my_io *w = (struct my_io *)w_;	968	struct my_io *w = (struct my_io *)w_;
683	...	969	...
684	}	970	}
685		971
686	More interesting and less C-conformant ways of catsing your callback type	972	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	973	instead have been omitted.
		974
		975	Another common scenario is having some data structure with multiple
		976	watchers:
		977
		978	struct my_biggy
		979	{
		980	int some_data;
		981	ev_timer t1;
		982	ev_timer t2;
		983	}
		984
		985	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		986	you need to use C<offsetof>:
		987
		988	#include <stddef.h>
		989
		990	static void
		991	t1_cb (EV_P_ struct ev_timer *w, int revents)
		992	{
		993	struct my_biggy big = (struct my_biggy *
		994	(((char *)w) - offsetof (struct my_biggy, t1));
		995	}
		996
		997	static void
		998	t2_cb (EV_P_ struct ev_timer *w, int revents)
		999	{
		1000	struct my_biggy big = (struct my_biggy *
		1001	(((char *)w) - offsetof (struct my_biggy, t2));
		1002	}
688		1003
689		1004
690	=head1 WATCHER TYPES	1005	=head1 WATCHER TYPES
691		1006
692	This section describes each watcher in detail, but will not repeat	1007	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	1008	information given in the last section. Any initialisation/set macros,
		1009	functions and members specific to the watcher type are explained.
694		1010
		1011	Members are additionally marked with either I<[read-only]>, meaning that,
		1012	while the watcher is active, you can look at the member and expect some
		1013	sensible content, but you must not modify it (you can modify it while the
		1014	watcher is stopped to your hearts content), or I<[read-write]>, which
		1015	means you can expect it to have some sensible content while the watcher
		1016	is active, but you can also modify it. Modifying it may not do something
		1017	sensible or take immediate effect (or do anything at all), but libev will
		1018	not crash or malfunction in any way.
695		1019
		1020
696	=head2 C<ev_io> - is this file descriptor readable or writable	1021	=head2 C<ev_io> - is this file descriptor readable or writable?
697		1022
698	I/O watchers check whether a file descriptor is readable or writable	1023	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	1024	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	1025	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	1026	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	1027	receiving events as long as the condition persists. Remember you can stop
		1028	the watcher if you don't want to act on the event and neither want to
		1029	receive future events.
703		1030
704	In general you can register as many read and/or write event watchers per	1031	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	1032	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	1033	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	1034	required if you know what you are doing).
708		1035
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	1036	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	1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	1038	C<EVBACKEND_POLL>).
718		1039
		1040	Another thing you have to watch out for is that it is quite easy to
		1041	receive "spurious" readyness notifications, that is your callback might
		1042	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		1043	because there is no data. Not only are some backends known to create a
		1044	lot of those (for example solaris ports), it is very easy to get into
		1045	this situation even with a relatively standard program structure. Thus
		1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		1048
		1049	If you cannot run the fd in non-blocking mode (for example you should not
		1050	play around with an Xlib connection), then you have to seperately re-test
		1051	whether a file descriptor is really ready with a known-to-be good interface
		1052	such as poll (fortunately in our Xlib example, Xlib already does this on
		1053	its own, so its quite safe to use).
		1054
		1055	=head3 The special problem of disappearing file descriptors
		1056
		1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1058	descriptor (either by calling C<close> explicitly or by any other means,
		1059	such as C<dup>). The reason is that you register interest in some file
		1060	descriptor, but when it goes away, the operating system will silently drop
		1061	this interest. If another file descriptor with the same number then is
		1062	registered with libev, there is no efficient way to see that this is, in
		1063	fact, a different file descriptor.
		1064
		1065	To avoid having to explicitly tell libev about such cases, libev follows
		1066	the following policy: Each time C<ev_io_set> is being called, libev
		1067	will assume that this is potentially a new file descriptor, otherwise
		1068	it is assumed that the file descriptor stays the same. That means that
		1069	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1070	descriptor even if the file descriptor number itself did not change.
		1071
		1072	This is how one would do it normally anyway, the important point is that
		1073	the libev application should not optimise around libev but should leave
		1074	optimisations to libev.
		1075
		1076	=head3 The special problem of dup'ed file descriptors
		1077
		1078	Some backends (e.g. epoll), cannot register events for file descriptors,
		1079	but only events for the underlying file descriptions. That means when you
		1080	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1081	events for them, only one file descriptor might actually receive events.
		1082
		1083	There is no workaround possible except not registering events
		1084	for potentially C<dup ()>'ed file descriptors, or to resort to
		1085	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1086
		1087	=head3 The special problem of fork
		1088
		1089	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1090	useless behaviour. Libev fully supports fork, but needs to be told about
		1091	it in the child.
		1092
		1093	To support fork in your programs, you either have to call
		1094	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1096	C<EVBACKEND_POLL>.
		1097
		1098	=head3 The special problem of SIGPIPE
		1099
		1100	While not really specific to libev, it is easy to forget about SIGPIPE:
		1101	when reading from a pipe whose other end has been closed, your program
		1102	gets send a SIGPIPE, which, by default, aborts your program. For most
		1103	programs this is sensible behaviour, for daemons, this is usually
		1104	undesirable.
		1105
		1106	So when you encounter spurious, unexplained daemon exits, make sure you
		1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1108	somewhere, as that would have given you a big clue).
		1109
		1110
		1111	=head3 Watcher-Specific Functions
		1112
719	=over 4	1113	=over 4
720		1114
721	=item ev_io_init (ev_io *, callback, int fd, int events)	1115	=item ev_io_init (ev_io *, callback, int fd, int events)
722		1116
723	=item ev_io_set (ev_io *, int fd, int events)	1117	=item ev_io_set (ev_io *, int fd, int events)
724		1118
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1119	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 |	1120	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	1121	C<EV_READ | EV_WRITE> to receive the given events.
728		1122
729	Please note that most of the more scalable backend mechanisms (for example	1123	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	1124
731	for file descriptors, so you practically need to use non-blocking I/O (and	1125	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	1126
733	interface before doing I/O (XLib can do this), or force the use of either	1127	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	1128
735	problem. Also note that it is quite easy to have your callback invoked	1129	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		1130
740	=back	1131	=back
741		1132
		1133	=head3 Examples
		1134
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	1136	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	1137	attempt to read a whole line in the callback.
745		1138
746	static void	1139	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	1141	{
749	ev_io_stop (loop, w);	1142	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	1150	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	1151	ev_loop (loop, 0);
759		1152
760		1153
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	1154	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		1155
763	Timer watchers are simple relative timers that generate an event after a	1156	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	1157	given time, and optionally repeating in regular intervals after that.
765		1158
766	The timers are based on real time, that is, if you register an event that	1159	The timers are based on real time, that is, if you register an event that
…		…
779		1172
780	The callback is guarenteed to be invoked only when its timeout has passed,	1173	The callback is guarenteed to be invoked only when its timeout has passed,
781	but if multiple timers become ready during the same loop iteration then	1174	but if multiple timers become ready during the same loop iteration then
782	order of execution is undefined.	1175	order of execution is undefined.
783		1176
		1177	=head3 Watcher-Specific Functions and Data Members
		1178
784	=over 4	1179	=over 4
785		1180
786	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
787		1182
788	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
796	configure a timer to trigger every 10 seconds, then it will trigger at	1191	configure a timer to trigger every 10 seconds, then it will trigger at
797	exactly 10 second intervals. If, however, your program cannot keep up with	1192	exactly 10 second intervals. If, however, your program cannot keep up with
798	the timer (because it takes longer than those 10 seconds to do stuff) the	1193	the timer (because it takes longer than those 10 seconds to do stuff) the
799	timer will not fire more than once per event loop iteration.	1194	timer will not fire more than once per event loop iteration.
800		1195
801	=item ev_timer_again (loop)	1196	=item ev_timer_again (loop, ev_timer *)
802		1197
803	This will act as if the timer timed out and restart it again if it is	1198	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	1199	repeating. The exact semantics are:
805		1200
		1201	If the timer is pending, its pending status is cleared.
		1202
806	If the timer is started but nonrepeating, stop it.	1203	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1204
808	If the timer is repeating, either start it if necessary (with the repeat	1205	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1206	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1207
811	This sounds a bit complicated, but here is a useful and typical	1208	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	1209	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	1210	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	1211	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	1212	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	1213	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	1214	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.	1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1216	automatically restart it if need be.
		1217
		1218	That means you can ignore the C<after> value and C<ev_timer_start>
		1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1220
		1221	ev_timer_init (timer, callback, 0., 5.);
		1222	ev_timer_again (loop, timer);
		1223	...
		1224	timer->again = 17.;
		1225	ev_timer_again (loop, timer);
		1226	...
		1227	timer->again = 10.;
		1228	ev_timer_again (loop, timer);
		1229
		1230	This is more slightly efficient then stopping/starting the timer each time
		1231	you want to modify its timeout value.
		1232
		1233	=item ev_tstamp repeat [read-write]
		1234
		1235	The current C<repeat> value. Will be used each time the watcher times out
		1236	or C<ev_timer_again> is called and determines the next timeout (if any),
		1237	which is also when any modifications are taken into account.
819		1238
820	=back	1239	=back
821		1240
		1241	=head3 Examples
		1242
822	Example: create a timer that fires after 60 seconds.	1243	Example: Create a timer that fires after 60 seconds.
823		1244
824	static void	1245	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1247	{
827	.. one minute over, w is actually stopped right here	1248	.. one minute over, w is actually stopped right here
…		…
829		1250
830	struct ev_timer mytimer;	1251	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1253	ev_timer_start (loop, &mytimer);
833		1254
834	Example: create a timeout timer that times out after 10 seconds of	1255	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1256	inactivity.
836		1257
837	static void	1258	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1260	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1269	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1270	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1271	ev_timer_again (&mytimer);
851		1272
852		1273
853	=head2 C<ev_periodic> - to cron or not to cron	1274	=head2 C<ev_periodic> - to cron or not to cron?
854		1275
855	Periodic watchers are also timers of a kind, but they are very versatile	1276	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1277	(and unfortunately a bit complex).
857		1278
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1279	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	1280	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	1281	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 ()	1282	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	1283	+ 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	1284	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	1285	roughly 10 seconds later).
865	again).
866		1286
867	They can also be used to implement vastly more complex timers, such as	1287	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1288	triggering an event on each midnight, local time or other, complicated,
		1289	rules.
869		1290
870	As with timers, the callback is guarenteed to be invoked only when the	1291	As with timers, the callback is guarenteed to be invoked only when the
871	time (C<at>) has been passed, but if multiple periodic timers become ready	1292	time (C<at>) has been passed, but if multiple periodic timers become ready
872	during the same loop iteration then order of execution is undefined.	1293	during the same loop iteration then order of execution is undefined.
873		1294
		1295	=head3 Watcher-Specific Functions and Data Members
		1296
874	=over 4	1297	=over 4
875		1298
876	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
877		1300
878	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
880	Lots of arguments, lets sort it out... There are basically three modes of	1303	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1304	operation, and we will explain them from simplest to complex:
882		1305
883	=over 4	1306	=over 4
884		1307
885	=item * absolute timer (interval = reschedule_cb = 0)	1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1309
887	In this configuration the watcher triggers an event at the wallclock time	1310	In this configuration the watcher triggers an event at the wallclock time
888	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
889	that is, if it is to be run at January 1st 2011 then it will run when the	1312	that is, if it is to be run at January 1st 2011 then it will run when the
890	system time reaches or surpasses this time.	1313	system time reaches or surpasses this time.
891		1314
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1316
894	In this mode the watcher will always be scheduled to time out at the next	1317	In this mode the watcher will always be scheduled to time out at the next
895	C<at + N * interval> time (for some integer N) and then repeat, regardless	1318	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1319	and then repeat, regardless of any time jumps.
897		1320
898	This can be used to create timers that do not drift with respect to system	1321	This can be used to create timers that do not drift with respect to system
899	time:	1322	time:
900		1323
901	ev_periodic_set (&periodic, 0., 3600., 0);	1324	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1330
908	Another way to think about it (for the mathematically inclined) is that	1331	Another way to think about it (for the mathematically inclined) is that
909	C<ev_periodic> will try to run the callback in this mode at the next possible	1332	C<ev_periodic> will try to run the callback in this mode at the next possible
910	time where C<time = at (mod interval)>, regardless of any time jumps.	1333	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1334
		1335	For numerical stability it is preferable that the C<at> value is near
		1336	C<ev_now ()> (the current time), but there is no range requirement for
		1337	this value.
		1338
912	=item * manual reschedule mode (reschedule_cb = callback)	1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1340
914	In this mode the values for C<interval> and C<at> are both being	1341	In this mode the values for C<interval> and C<at> are both being
915	ignored. Instead, each time the periodic watcher gets scheduled, the	1342	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1343	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1344	current time as second argument.
918		1345
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
920	ever, or make any event loop modifications>. If you need to stop it,	1347	ever, or make any event loop modifications>. If you need to stop it,
921	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1349	starting an C<ev_prepare> watcher, which is legal).
923		1350
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1352	ev_tstamp now)>, e.g.:
926		1353
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1377	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1378	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	1379	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1380	program when the crontabs have changed).
954		1381
		1382	=item ev_tstamp offset [read-write]
		1383
		1384	When repeating, this contains the offset value, otherwise this is the
		1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1386
		1387	Can be modified any time, but changes only take effect when the periodic
		1388	timer fires or C<ev_periodic_again> is being called.
		1389
		1390	=item ev_tstamp interval [read-write]
		1391
		1392	The current interval value. Can be modified any time, but changes only
		1393	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1394	called.
		1395
		1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1397
		1398	The current reschedule callback, or C<0>, if this functionality is
		1399	switched off. Can be changed any time, but changes only take effect when
		1400	the periodic timer fires or C<ev_periodic_again> is being called.
		1401
		1402	=item ev_tstamp at [read-only]
		1403
		1404	When active, contains the absolute time that the watcher is supposed to
		1405	trigger next.
		1406
955	=back	1407	=back
956		1408
		1409	=head3 Examples
		1410
957	Example: call a callback every hour, or, more precisely, whenever the	1411	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1412	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1413	potentially a lot of jittering, but good long-term stability.
960		1414
961	static void	1415	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1420
967	struct ev_periodic hourly_tick;	1421	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1423	ev_periodic_start (loop, &hourly_tick);
970		1424
971	Example: the same as above, but use a reschedule callback to do it:	1425	Example: The same as above, but use a reschedule callback to do it:
972		1426
973	#include <math.h>	1427	#include <math.h>
974		1428
975	static ev_tstamp	1429	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1432	return fmod (now, 3600.) + 3600.;
979	}	1433	}
980		1434
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1436
983	Example: call a callback every hour, starting now:	1437	Example: Call a callback every hour, starting now:
984		1438
985	struct ev_periodic hourly_tick;	1439	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1440	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1441	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1442	ev_periodic_start (loop, &hourly_tick);
989		1443
990		1444
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1445	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1446
993	Signal watchers will trigger an event when the process receives a specific	1447	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	1448	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	1449	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1450	normal event processing, like any other event.
…		…
1000	with the kernel (thus it coexists with your own signal handlers as long	1454	with the kernel (thus it coexists with your own signal handlers as long
1001	as you don't register any with libev). Similarly, when the last signal	1455	as you don't register any with libev). Similarly, when the last signal
1002	watcher for a signal is stopped libev will reset the signal handler to	1456	watcher for a signal is stopped libev will reset the signal handler to
1003	SIG_DFL (regardless of what it was set to before).	1457	SIG_DFL (regardless of what it was set to before).
1004		1458
		1459	If possible and supported, libev will install its handlers with
		1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly
		1461	interrupted. If you have a problem with syscalls getting interrupted by
		1462	signals you can block all signals in an C<ev_check> watcher and unblock
		1463	them in an C<ev_prepare> watcher.
		1464
		1465	=head3 Watcher-Specific Functions and Data Members
		1466
1005	=over 4	1467	=over 4
1006		1468
1007	=item ev_signal_init (ev_signal *, callback, int signum)	1469	=item ev_signal_init (ev_signal *, callback, int signum)
1008		1470
1009	=item ev_signal_set (ev_signal *, int signum)	1471	=item ev_signal_set (ev_signal *, int signum)
1010		1472
1011	Configures the watcher to trigger on the given signal number (usually one	1473	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1474	of the C<SIGxxx> constants).
1013		1475
		1476	=item int signum [read-only]
		1477
		1478	The signal the watcher watches out for.
		1479
1014	=back	1480	=back
1015		1481
		1482	=head3 Examples
1016		1483
		1484	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1485
		1486	static void
		1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1488	{
		1489	ev_unloop (loop, EVUNLOOP_ALL);
		1490	}
		1491
		1492	struct ev_signal signal_watcher;
		1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1494	ev_signal_start (loop, &sigint_cb);
		1495
		1496
1017	=head2 C<ev_child> - wait for pid status changes	1497	=head2 C<ev_child> - watch out for process status changes
1018		1498
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1499	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1500	some child status changes (most typically when a child of yours dies). It
		1501	is permissible to install a child watcher I<after> the child has been
		1502	forked (which implies it might have already exited), as long as the event
		1503	loop isn't entered (or is continued from a watcher).
		1504
		1505	Only the default event loop is capable of handling signals, and therefore
		1506	you can only rgeister child watchers in the default event loop.
		1507
		1508	=head3 Process Interaction
		1509
		1510	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1511	initialised. This is necessary to guarantee proper behaviour even if
		1512	the first child watcher is started after the child exits. The occurance
		1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1514	synchronously as part of the event loop processing. Libev always reaps all
		1515	children, even ones not watched.
		1516
		1517	=head3 Overriding the Built-In Processing
		1518
		1519	Libev offers no special support for overriding the built-in child
		1520	processing, but if your application collides with libev's default child
		1521	handler, you can override it easily by installing your own handler for
		1522	C<SIGCHLD> after initialising the default loop, and making sure the
		1523	default loop never gets destroyed. You are encouraged, however, to use an
		1524	event-based approach to child reaping and thus use libev's support for
		1525	that, so other libev users can use C<ev_child> watchers freely.
		1526
		1527	=head3 Watcher-Specific Functions and Data Members
1021		1528
1022	=over 4	1529	=over 4
1023		1530
1024	=item ev_child_init (ev_child *, callback, int pid)	1531	=item ev_child_init (ev_child *, callback, int pid, int trace)
1025		1532
1026	=item ev_child_set (ev_child *, int pid)	1533	=item ev_child_set (ev_child *, int pid, int trace)
1027		1534
1028	Configures the watcher to wait for status changes of process C<pid> (or	1535	Configures the watcher to wait for status changes of process C<pid> (or
1029	I<any> process if C<pid> is specified as C<0>). The callback can look	1536	I<any> process if C<pid> is specified as C<0>). The callback can look
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1537	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1538	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1539	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1540	process causing the status change. C<trace> must be either C<0> (only
		1541	activate the watcher when the process terminates) or C<1> (additionally
		1542	activate the watcher when the process is stopped or continued).
		1543
		1544	=item int pid [read-only]
		1545
		1546	The process id this watcher watches out for, or C<0>, meaning any process id.
		1547
		1548	=item int rpid [read-write]
		1549
		1550	The process id that detected a status change.
		1551
		1552	=item int rstatus [read-write]
		1553
		1554	The process exit/trace status caused by C<rpid> (see your systems
		1555	C<waitpid> and C<sys/wait.h> documentation for details).
1034		1556
1035	=back	1557	=back
1036		1558
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1559	=head3 Examples
		1560
		1561	Example: C<fork()> a new process and install a child handler to wait for
		1562	its completion.
		1563
		1564	ev_child cw;
1038		1565
1039	static void	1566	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1567	child_cb (EV_P_ struct ev_child *w, int revents)
1041	{	1568	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1569	ev_child_stop (EV_A_ w);
		1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1043	}	1571	}
1044		1572
1045	struct ev_signal signal_watcher;	1573	pid_t pid = fork ();
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);
1048		1574
		1575	if (pid < 0)
		1576	// error
		1577	else if (pid == 0)
		1578	{
		1579	// the forked child executes here
		1580	exit (1);
		1581	}
		1582	else
		1583	{
		1584	ev_child_init (&cw, child_cb, pid, 0);
		1585	ev_child_start (EV_DEFAULT_ &cw);
		1586	}
1049		1587
		1588
		1589	=head2 C<ev_stat> - did the file attributes just change?
		1590
		1591	This watches a filesystem path for attribute changes. That is, it calls
		1592	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1593	compared to the last time, invoking the callback if it did.
		1594
		1595	The path does not need to exist: changing from "path exists" to "path does
		1596	not exist" is a status change like any other. The condition "path does
		1597	not exist" is signified by the C<st_nlink> field being zero (which is
		1598	otherwise always forced to be at least one) and all the other fields of
		1599	the stat buffer having unspecified contents.
		1600
		1601	The path I<should> be absolute and I<must not> end in a slash. If it is
		1602	relative and your working directory changes, the behaviour is undefined.
		1603
		1604	Since there is no standard to do this, the portable implementation simply
		1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1606	can specify a recommended polling interval for this case. If you specify
		1607	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1608	unspecified default> value will be used (which you can expect to be around
		1609	five seconds, although this might change dynamically). Libev will also
		1610	impose a minimum interval which is currently around C<0.1>, but thats
		1611	usually overkill.
		1612
		1613	This watcher type is not meant for massive numbers of stat watchers,
		1614	as even with OS-supported change notifications, this can be
		1615	resource-intensive.
		1616
		1617	At the time of this writing, only the Linux inotify interface is
		1618	implemented (implementing kqueue support is left as an exercise for the
		1619	reader). Inotify will be used to give hints only and should not change the
		1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1621	to fall back to regular polling again even with inotify, but changes are
		1622	usually detected immediately, and if the file exists there will be no
		1623	polling.
		1624
		1625	=head3 ABI Issues (Largefile Support)
		1626
		1627	Libev by default (unless the user overrides this) uses the default
		1628	compilation environment, which means that on systems with optionally
		1629	disabled large file support, you get the 32 bit version of the stat
		1630	structure. When using the library from programs that change the ABI to
		1631	use 64 bit file offsets the programs will fail. In that case you have to
		1632	compile libev with the same flags to get binary compatibility. This is
		1633	obviously the case with any flags that change the ABI, but the problem is
		1634	most noticably with ev_stat and largefile support.
		1635
		1636	=head3 Inotify
		1637
		1638	When C<inotify (7)> support has been compiled into libev (generally only
		1639	available on Linux) and present at runtime, it will be used to speed up
		1640	change detection where possible. The inotify descriptor will be created lazily
		1641	when the first C<ev_stat> watcher is being started.
		1642
		1643	Inotify presense does not change the semantics of C<ev_stat> watchers
		1644	except that changes might be detected earlier, and in some cases, to avoid
		1645	making regular C<stat> calls. Even in the presense of inotify support
		1646	there are many cases where libev has to resort to regular C<stat> polling.
		1647
		1648	(There is no support for kqueue, as apparently it cannot be used to
		1649	implement this functionality, due to the requirement of having a file
		1650	descriptor open on the object at all times).
		1651
		1652	=head3 The special problem of stat time resolution
		1653
		1654	The C<stat ()> syscall only supports full-second resolution portably, and
		1655	even on systems where the resolution is higher, many filesystems still
		1656	only support whole seconds.
		1657
		1658	That means that, if the time is the only thing that changes, you might
		1659	miss updates: on the first update, C<ev_stat> detects a change and calls
		1660	your callback, which does something. When there is another update within
		1661	the same second, C<ev_stat> will be unable to detect it.
		1662
		1663	The solution to this is to delay acting on a change for a second (or till
		1664	the next second boundary), using a roughly one-second delay C<ev_timer>
		1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1666	is added to work around small timing inconsistencies of some operating
		1667	systems.
		1668
		1669	=head3 Watcher-Specific Functions and Data Members
		1670
		1671	=over 4
		1672
		1673	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1674
		1675	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1676
		1677	Configures the watcher to wait for status changes of the given
		1678	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1679	be detected and should normally be specified as C<0> to let libev choose
		1680	a suitable value. The memory pointed to by C<path> must point to the same
		1681	path for as long as the watcher is active.
		1682
		1683	The callback will be receive C<EV_STAT> when a change was detected,
		1684	relative to the attributes at the time the watcher was started (or the
		1685	last change was detected).
		1686
		1687	=item ev_stat_stat (loop, ev_stat *)
		1688
		1689	Updates the stat buffer immediately with new values. If you change the
		1690	watched path in your callback, you could call this fucntion to avoid
		1691	detecting this change (while introducing a race condition). Can also be
		1692	useful simply to find out the new values.
		1693
		1694	=item ev_statdata attr [read-only]
		1695
		1696	The most-recently detected attributes of the file. Although the type is of
		1697	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1698	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1699	was some error while C<stat>ing the file.
		1700
		1701	=item ev_statdata prev [read-only]
		1702
		1703	The previous attributes of the file. The callback gets invoked whenever
		1704	C<prev> != C<attr>.
		1705
		1706	=item ev_tstamp interval [read-only]
		1707
		1708	The specified interval.
		1709
		1710	=item const char *path [read-only]
		1711
		1712	The filesystem path that is being watched.
		1713
		1714	=back
		1715
		1716	=head3 Examples
		1717
		1718	Example: Watch C</etc/passwd> for attribute changes.
		1719
		1720	static void
		1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1722	{
		1723	/* /etc/passwd changed in some way */
		1724	if (w->attr.st_nlink)
		1725	{
		1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1729	}
		1730	else
		1731	/* you shalt not abuse printf for puts */
		1732	puts ("wow, /etc/passwd is not there, expect problems. "
		1733	"if this is windows, they already arrived\n");
		1734	}
		1735
		1736	...
		1737	ev_stat passwd;
		1738
		1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
		1740	ev_stat_start (loop, &passwd);
		1741
		1742	Example: Like above, but additionally use a one-second delay so we do not
		1743	miss updates (however, frequent updates will delay processing, too, so
		1744	one might do the work both on C<ev_stat> callback invocation I<and> on
		1745	C<ev_timer> callback invocation).
		1746
		1747	static ev_stat passwd;
		1748	static ev_timer timer;
		1749
		1750	static void
		1751	timer_cb (EV_P_ ev_timer *w, int revents)
		1752	{
		1753	ev_timer_stop (EV_A_ w);
		1754
		1755	/* now it's one second after the most recent passwd change */
		1756	}
		1757
		1758	static void
		1759	stat_cb (EV_P_ ev_stat *w, int revents)
		1760	{
		1761	/* reset the one-second timer */
		1762	ev_timer_again (EV_A_ &timer);
		1763	}
		1764
		1765	...
		1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1767	ev_stat_start (loop, &passwd);
		1768	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1769
		1770
1050	=head2 C<ev_idle> - when you've got nothing better to do	1771	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1772
1052	Idle watchers trigger events when there are no other events are pending	1773	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	1774	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1775	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1776
1056	watchers are being called again and again, once per event loop iteration -	1777	That is, as long as your process is busy handling sockets or timeouts
		1778	(or even signals, imagine) of the same or higher priority it will not be
		1779	triggered. But when your process is idle (or only lower-priority watchers
		1780	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	1781	iteration - until stopped, that is, or your process receives more events
1058	busy.	1782	and becomes busy again with higher priority stuff.
1059		1783
1060	The most noteworthy effect is that as long as any idle watchers are	1784	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.	1785	active, the process will not block when waiting for new events.
1062		1786
1063	Apart from keeping your process non-blocking (which is a useful	1787	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	1788	effect on its own sometimes), idle watchers are a good place to do
1065	"pseudo-background processing", or delay processing stuff to after the	1789	"pseudo-background processing", or delay processing stuff to after the
1066	event loop has handled all outstanding events.	1790	event loop has handled all outstanding events.
1067		1791
		1792	=head3 Watcher-Specific Functions and Data Members
		1793
1068	=over 4	1794	=over 4
1069		1795
1070	=item ev_idle_init (ev_signal *, callback)	1796	=item ev_idle_init (ev_signal *, callback)
1071		1797
1072	Initialises and configures the idle watcher - it has no parameters of any	1798	Initialises and configures the idle watcher - it has no parameters of any
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1800	believe me.
1075		1801
1076	=back	1802	=back
1077		1803
		1804	=head3 Examples
		1805
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1807	callback, free it. Also, use no error checking, as usual.
1080		1808
1081	static void	1809	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1811	{
1084	free (w);	1812	free (w);
1085	// now do something you wanted to do when the program has	1813	// now do something you wanted to do when the program has
1086	// no longer asnything immediate to do.	1814	// no longer anything immediate to do.
1087	}	1815	}
1088		1816
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1818	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1819	ev_idle_start (loop, idle_cb);
1092		1820
1093		1821
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1823
1096	Prepare and check watchers are usually (but not always) used in tandem:	1824	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1825	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1826	afterwards.
1099		1827
		1828	You I<must not> call C<ev_loop> or similar functions that enter
		1829	the current event loop from either C<ev_prepare> or C<ev_check>
		1830	watchers. Other loops than the current one are fine, however. The
		1831	rationale behind this is that you do not need to check for recursion in
		1832	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1833	C<ev_check> so if you have one watcher of each kind they will always be
		1834	called in pairs bracketing the blocking call.
		1835
1100	Their main purpose is to integrate other event mechanisms into libev and	1836	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	1837	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	1838	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1839	coroutine library and lots more. They are also occasionally useful if
		1840	you cache some data and want to flush it before blocking (for example,
		1841	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1842	watcher).
1104		1843
1105	This is done by examining in each prepare call which file descriptors need	1844	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	1845	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	1846	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	1847	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	1857	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	1858	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	1859	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1860	low-priority coroutines to idle/background tasks).
1122		1861
		1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1863	priority, to ensure that they are being run before any other watchers
		1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1865	too) should not activate ("feed") events into libev. While libev fully
		1866	supports this, they will be called before other C<ev_check> watchers
		1867	did their job. As C<ev_check> watchers are often used to embed other
		1868	(non-libev) event loops those other event loops might be in an unusable
		1869	state until their C<ev_check> watcher ran (always remind yourself to
		1870	coexist peacefully with others).
		1871
		1872	=head3 Watcher-Specific Functions and Data Members
		1873
1123	=over 4	1874	=over 4
1124		1875
1125	=item ev_prepare_init (ev_prepare *, callback)	1876	=item ev_prepare_init (ev_prepare *, callback)
1126		1877
1127	=item ev_check_init (ev_check *, callback)	1878	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1882	macros, but using them is utterly, utterly and completely pointless.
1132		1883
1133	=back	1884	=back
1134		1885
1135	Example: *TODO*.	1886	=head3 Examples
1136		1887
		1888	There are a number of principal ways to embed other event loops or modules
		1889	into libev. Here are some ideas on how to include libadns into libev
		1890	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1891	use for an actually working example. Another Perl module named C<EV::Glib>
		1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1893	into the Glib event loop).
1137		1894
		1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1896	and in a check watcher, destroy them and call into libadns. What follows
		1897	is pseudo-code only of course. This requires you to either use a low
		1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1899	the callbacks for the IO/timeout watchers might not have been called yet.
		1900
		1901	static ev_io iow [nfd];
		1902	static ev_timer tw;
		1903
		1904	static void
		1905	io_cb (ev_loop *loop, ev_io *w, int revents)
		1906	{
		1907	}
		1908
		1909	// create io watchers for each fd and a timer before blocking
		1910	static void
		1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1912	{
		1913	int timeout = 3600000;
		1914	struct pollfd fds [nfd];
		1915	// actual code will need to loop here and realloc etc.
		1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1917
		1918	/* the callback is illegal, but won't be called as we stop during check */
		1919	ev_timer_init (&tw, 0, timeout * 1e-3);
		1920	ev_timer_start (loop, &tw);
		1921
		1922	// create one ev_io per pollfd
		1923	for (int i = 0; i < nfd; ++i)
		1924	{
		1925	ev_io_init (iow + i, io_cb, fds [i].fd,
		1926	((fds [i].events & POLLIN ? EV_READ : 0)
		1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1928
		1929	fds [i].revents = 0;
		1930	ev_io_start (loop, iow + i);
		1931	}
		1932	}
		1933
		1934	// stop all watchers after blocking
		1935	static void
		1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1937	{
		1938	ev_timer_stop (loop, &tw);
		1939
		1940	for (int i = 0; i < nfd; ++i)
		1941	{
		1942	// set the relevant poll flags
		1943	// could also call adns_processreadable etc. here
		1944	struct pollfd *fd = fds + i;
		1945	int revents = ev_clear_pending (iow + i);
		1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1948
		1949	// now stop the watcher
		1950	ev_io_stop (loop, iow + i);
		1951	}
		1952
		1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1954	}
		1955
		1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1957	in the prepare watcher and would dispose of the check watcher.
		1958
		1959	Method 3: If the module to be embedded supports explicit event
		1960	notification (adns does), you can also make use of the actual watcher
		1961	callbacks, and only destroy/create the watchers in the prepare watcher.
		1962
		1963	static void
		1964	timer_cb (EV_P_ ev_timer *w, int revents)
		1965	{
		1966	adns_state ads = (adns_state)w->data;
		1967	update_now (EV_A);
		1968
		1969	adns_processtimeouts (ads, &tv_now);
		1970	}
		1971
		1972	static void
		1973	io_cb (EV_P_ ev_io *w, int revents)
		1974	{
		1975	adns_state ads = (adns_state)w->data;
		1976	update_now (EV_A);
		1977
		1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1980	}
		1981
		1982	// do not ever call adns_afterpoll
		1983
		1984	Method 4: Do not use a prepare or check watcher because the module you
		1985	want to embed is too inflexible to support it. Instead, youc na override
		1986	their poll function. The drawback with this solution is that the main
		1987	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1988	this.
		1989
		1990	static gint
		1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1992	{
		1993	int got_events = 0;
		1994
		1995	for (n = 0; n < nfds; ++n)
		1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1997
		1998	if (timeout >= 0)
		1999	// create/start timer
		2000
		2001	// poll
		2002	ev_loop (EV_A_ 0);
		2003
		2004	// stop timer again
		2005	if (timeout >= 0)
		2006	ev_timer_stop (EV_A_ &to);
		2007
		2008	// stop io watchers again - their callbacks should have set
		2009	for (n = 0; n < nfds; ++n)
		2010	ev_io_stop (EV_A_ iow [n]);
		2011
		2012	return got_events;
		2013	}
		2014
		2015
1138	=head2 C<ev_embed> - when one backend isn't enough	2016	=head2 C<ev_embed> - when one backend isn't enough...
1139		2017
1140	This is a rather advanced watcher type that lets you embed one event loop	2018	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	2019	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	2020	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	2021	fashion and must not be used).
…		…
1182	portable one.	2060	portable one.
1183		2061
1184	So when you want to use this feature you will always have to be prepared	2062	So when you want to use this feature you will always have to be prepared
1185	that you cannot get an embeddable loop. The recommended way to get around	2063	that you cannot get an embeddable loop. The recommended way to get around
1186	this is to have a separate variables for your embeddable loop, try to	2064	this is to have a separate variables for your embeddable loop, try to
1187	create it, and if that fails, use the normal loop for everything:	2065	create it, and if that fails, use the normal loop for everything.
		2066
		2067	=head3 Watcher-Specific Functions and Data Members
		2068
		2069	=over 4
		2070
		2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2072
		2073	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2074
		2075	Configures the watcher to embed the given loop, which must be
		2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2077	invoked automatically, otherwise it is the responsibility of the callback
		2078	to invoke it (it will continue to be called until the sweep has been done,
		2079	if you do not want thta, you need to temporarily stop the embed watcher).
		2080
		2081	=item ev_embed_sweep (loop, ev_embed *)
		2082
		2083	Make a single, non-blocking sweep over the embedded loop. This works
		2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2085	apropriate way for embedded loops.
		2086
		2087	=item struct ev_loop *other [read-only]
		2088
		2089	The embedded event loop.
		2090
		2091	=back
		2092
		2093	=head3 Examples
		2094
		2095	Example: Try to get an embeddable event loop and embed it into the default
		2096	event loop. If that is not possible, use the default loop. The default
		2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2099	used).
1188		2100
1189	struct ev_loop *loop_hi = ev_default_init (0);	2101	struct ev_loop *loop_hi = ev_default_init (0);
1190	struct ev_loop *loop_lo = 0;	2102	struct ev_loop *loop_lo = 0;
1191	struct ev_embed embed;	2103	struct ev_embed embed;
1192		2104
…		…
1203	ev_embed_start (loop_hi, &embed);	2115	ev_embed_start (loop_hi, &embed);
1204	}	2116	}
1205	else	2117	else
1206	loop_lo = loop_hi;	2118	loop_lo = loop_hi;
1207		2119
		2120	Example: Check if kqueue is available but not recommended and create
		2121	a kqueue backend for use with sockets (which usually work with any
		2122	kqueue implementation). Store the kqueue/socket-only event loop in
		2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2124
		2125	struct ev_loop *loop = ev_default_init (0);
		2126	struct ev_loop *loop_socket = 0;
		2127	struct ev_embed embed;
		2128
		2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2131	{
		2132	ev_embed_init (&embed, 0, loop_socket);
		2133	ev_embed_start (loop, &embed);
		2134	}
		2135
		2136	if (!loop_socket)
		2137	loop_socket = loop;
		2138
		2139	// now use loop_socket for all sockets, and loop for everything else
		2140
		2141
		2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		2143
		2144	Fork watchers are called when a C<fork ()> was detected (usually because
		2145	whoever is a good citizen cared to tell libev about it by calling
		2146	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		2147	event loop blocks next and before C<ev_check> watchers are being called,
		2148	and only in the child after the fork. If whoever good citizen calling
		2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		2150	handlers will be invoked, too, of course.
		2151
		2152	=head3 Watcher-Specific Functions and Data Members
		2153
1208	=over 4	2154	=over 4
1209		2155
1210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2156	=item ev_fork_init (ev_signal *, callback)
1211		2157
1212	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2158	Initialises and configures the fork watcher - it has no parameters of any
		2159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		2160	believe me.
1213		2161
1214	Configures the watcher to embed the given loop, which must be	2162	=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		2163
1220	=item ev_embed_sweep (loop, ev_embed *)
1221		2164
1222	Make a single, non-blocking sweep over the embedded loop. This works	2165	=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	2166
1224	apropriate way for embedded loops.	2167	In general, you cannot use an C<ev_loop> from multiple threads or other
		2168	asynchronous sources such as signal handlers (as opposed to multiple event
		2169	loops - those are of course safe to use in different threads).
		2170
		2171	Sometimes, however, you need to wake up another event loop you do not
		2172	control, for example because it belongs to another thread. This is what
		2173	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2174	can signal it by calling C<ev_async_send>, which is thread- and signal
		2175	safe.
		2176
		2177	This functionality is very similar to C<ev_signal> watchers, as signals,
		2178	too, are asynchronous in nature, and signals, too, will be compressed
		2179	(i.e. the number of callback invocations may be less than the number of
		2180	C<ev_async_sent> calls).
		2181
		2182	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2183	just the default loop.
		2184
		2185	=head3 Queueing
		2186
		2187	C<ev_async> does not support queueing of data in any way. The reason
		2188	is that the author does not know of a simple (or any) algorithm for a
		2189	multiple-writer-single-reader queue that works in all cases and doesn't
		2190	need elaborate support such as pthreads.
		2191
		2192	That means that if you want to queue data, you have to provide your own
		2193	queue. But at least I can tell you would implement locking around your
		2194	queue:
		2195
		2196	=over 4
		2197
		2198	=item queueing from a signal handler context
		2199
		2200	To implement race-free queueing, you simply add to the queue in the signal
		2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2202	some fictitiuous SIGUSR1 handler:
		2203
		2204	static ev_async mysig;
		2205
		2206	static void
		2207	sigusr1_handler (void)
		2208	{
		2209	sometype data;
		2210
		2211	// no locking etc.
		2212	queue_put (data);
		2213	ev_async_send (EV_DEFAULT_ &mysig);
		2214	}
		2215
		2216	static void
		2217	mysig_cb (EV_P_ ev_async *w, int revents)
		2218	{
		2219	sometype data;
		2220	sigset_t block, prev;
		2221
		2222	sigemptyset (&block);
		2223	sigaddset (&block, SIGUSR1);
		2224	sigprocmask (SIG_BLOCK, &block, &prev);
		2225
		2226	while (queue_get (&data))
		2227	process (data);
		2228
		2229	if (sigismember (&prev, SIGUSR1)
		2230	sigprocmask (SIG_UNBLOCK, &block, 0);
		2231	}
		2232
		2233	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2234	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2235	either...).
		2236
		2237	=item queueing from a thread context
		2238
		2239	The strategy for threads is different, as you cannot (easily) block
		2240	threads but you can easily preempt them, so to queue safely you need to
		2241	employ a traditional mutex lock, such as in this pthread example:
		2242
		2243	static ev_async mysig;
		2244	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2245
		2246	static void
		2247	otherthread (void)
		2248	{
		2249	// only need to lock the actual queueing operation
		2250	pthread_mutex_lock (&mymutex);
		2251	queue_put (data);
		2252	pthread_mutex_unlock (&mymutex);
		2253
		2254	ev_async_send (EV_DEFAULT_ &mysig);
		2255	}
		2256
		2257	static void
		2258	mysig_cb (EV_P_ ev_async *w, int revents)
		2259	{
		2260	pthread_mutex_lock (&mymutex);
		2261
		2262	while (queue_get (&data))
		2263	process (data);
		2264
		2265	pthread_mutex_unlock (&mymutex);
		2266	}
		2267
		2268	=back
		2269
		2270
		2271	=head3 Watcher-Specific Functions and Data Members
		2272
		2273	=over 4
		2274
		2275	=item ev_async_init (ev_async *, callback)
		2276
		2277	Initialises and configures the async watcher - it has no parameters of any
		2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2279	believe me.
		2280
		2281	=item ev_async_send (loop, ev_async *)
		2282
		2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2285	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2287	section below on what exactly this means).
		2288
		2289	This call incurs the overhead of a syscall only once per loop iteration,
		2290	so while the overhead might be noticable, it doesn't apply to repeated
		2291	calls to C<ev_async_send>.
1225		2292
1226	=back	2293	=back
1227		2294
1228		2295
1229	=head1 OTHER FUNCTIONS	2296	=head1 OTHER FUNCTIONS
…		…
1318		2385
1319	To use it,	2386	To use it,
1320		2387
1321	#include <ev++.h>	2388	#include <ev++.h>
1322		2389
1323	(it is not installed by default). This automatically includes F<ev.h>	2390	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	2391	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.	2392	put into the C<ev> namespace. It should support all the same embedding
		2393	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		2394
1327	It should support all the same embedding options as F<ev.h>, most notably	2395	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	2396	classes add (compared to plain C-style watchers) is the event loop pointer
		2397	that the watcher is associated with (or no additional members at all if
		2398	you disable C<EV_MULTIPLICITY> when embedding libev).
		2399
		2400	Currently, functions, and static and non-static member functions can be
		2401	used as callbacks. Other types should be easy to add as long as they only
		2402	need one additional pointer for context. If you need support for other
		2403	types of functors please contact the author (preferably after implementing
		2404	it).
1329		2405
1330	Here is a list of things available in the C<ev> namespace:	2406	Here is a list of things available in the C<ev> namespace:
1331		2407
1332	=over 4	2408	=over 4
1333		2409
…		…
1349		2425
1350	All of those classes have these methods:	2426	All of those classes have these methods:
1351		2427
1352	=over 4	2428	=over 4
1353		2429
1354	=item ev::TYPE::TYPE (object *, object::method *)	2430	=item ev::TYPE::TYPE ()
1355		2431
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2432	=item ev::TYPE::TYPE (struct ev_loop *)
1357		2433
1358	=item ev::TYPE::~TYPE	2434	=item ev::TYPE::~TYPE
1359		2435
1360	The constructor takes a pointer to an object and a method pointer to	2436	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	2437	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	2438
1363	before starting it. If you do not specify a loop then the constructor	2439	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	2440	C<set> method before starting it.
		2441
		2442	It will not set a callback, however: You have to call the templated C<set>
		2443	method to set a callback before you can start the watcher.
		2444
		2445	(The reason why you have to use a method is a limitation in C++ which does
		2446	not allow explicit template arguments for constructors).
1365		2447
1366	The destructor automatically stops the watcher if it is active.	2448	The destructor automatically stops the watcher if it is active.
		2449
		2450	=item w->set<class, &class::method> (object *)
		2451
		2452	This method sets the callback method to call. The method has to have a
		2453	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2454	first argument and the C<revents> as second. The object must be given as
		2455	parameter and is stored in the C<data> member of the watcher.
		2456
		2457	This method synthesizes efficient thunking code to call your method from
		2458	the C callback that libev requires. If your compiler can inline your
		2459	callback (i.e. it is visible to it at the place of the C<set> call and
		2460	your compiler is good :), then the method will be fully inlined into the
		2461	thunking function, making it as fast as a direct C callback.
		2462
		2463	Example: simple class declaration and watcher initialisation
		2464
		2465	struct myclass
		2466	{
		2467	void io_cb (ev::io &w, int revents) { }
		2468	}
		2469
		2470	myclass obj;
		2471	ev::io iow;
		2472	iow.set <myclass, &myclass::io_cb> (&obj);
		2473
		2474	=item w->set<function> (void *data = 0)
		2475
		2476	Also sets a callback, but uses a static method or plain function as
		2477	callback. The optional C<data> argument will be stored in the watcher's
		2478	C<data> member and is free for you to use.
		2479
		2480	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2481
		2482	See the method-C<set> above for more details.
		2483
		2484	Example:
		2485
		2486	static void io_cb (ev::io &w, int revents) { }
		2487	iow.set <io_cb> ();
1367		2488
1368	=item w->set (struct ev_loop *)	2489	=item w->set (struct ev_loop *)
1369		2490
1370	Associates a different C<struct ev_loop> with this watcher. You can only	2491	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).	2492	do this when the watcher is inactive (and not pending either).
1372		2493
1373	=item w->set ([args])	2494	=item w->set ([args])
1374		2495
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2496	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	2497	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	2498	automatically stopped and restarted when reconfiguring it with this
		2499	method.
1378		2500
1379	=item w->start ()	2501	=item w->start ()
1380		2502
1381	Starts the watcher. Note that there is no C<loop> argument as the	2503	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	2504	constructor already stores the event loop.
1383		2505
1384	=item w->stop ()	2506	=item w->stop ()
1385		2507
1386	Stops the watcher if it is active. Again, no C<loop> argument.	2508	Stops the watcher if it is active. Again, no C<loop> argument.
1387		2509
1388	=item w->again () C<ev::timer>, C<ev::periodic> only	2510	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1389		2511
1390	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2512	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1391	C<ev_TYPE_again> function.	2513	C<ev_TYPE_again> function.
1392		2514
1393	=item w->sweep () C<ev::embed> only	2515	=item w->sweep () (C<ev::embed> only)
1394		2516
1395	Invokes C<ev_embed_sweep>.	2517	Invokes C<ev_embed_sweep>.
		2518
		2519	=item w->update () (C<ev::stat> only)
		2520
		2521	Invokes C<ev_stat_stat>.
1396		2522
1397	=back	2523	=back
1398		2524
1399	=back	2525	=back
1400		2526
1401	Example: Define a class with an IO and idle watcher, start one of them in	2527	Example: Define a class with an IO and idle watcher, start one of them in
1402	the constructor.	2528	the constructor.
1403		2529
1404	class myclass	2530	class myclass
1405	{	2531	{
1406	ev_io io; void io_cb (ev::io &w, int revents);	2532	ev::io io; void io_cb (ev::io &w, int revents);
1407	ev_idle idle void idle_cb (ev::idle &w, int revents);	2533	ev:idle idle void idle_cb (ev::idle &w, int revents);
1408		2534
1409	myclass ();	2535	myclass (int fd)
		2536	{
		2537	io .set <myclass, &myclass::io_cb > (this);
		2538	idle.set <myclass, &myclass::idle_cb> (this);
		2539
		2540	io.start (fd, ev::READ);
		2541	}
		2542	};
		2543
		2544
		2545	=head1 OTHER LANGUAGE BINDINGS
		2546
		2547	Libev does not offer other language bindings itself, but bindings for a
		2548	numbe rof languages exist in the form of third-party packages. If you know
		2549	any interesting language binding in addition to the ones listed here, drop
		2550	me a note.
		2551
		2552	=over 4
		2553
		2554	=item Perl
		2555
		2556	The EV module implements the full libev API and is actually used to test
		2557	libev. EV is developed together with libev. Apart from the EV core module,
		2558	there are additional modules that implement libev-compatible interfaces
		2559	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2560	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2561
		2562	It can be found and installed via CPAN, its homepage is found at
		2563	L<http://software.schmorp.de/pkg/EV>.
		2564
		2565	=item Ruby
		2566
		2567	Tony Arcieri has written a ruby extension that offers access to a subset
		2568	of the libev API and adds filehandle abstractions, asynchronous DNS and
		2569	more on top of it. It can be found via gem servers. Its homepage is at
		2570	L<http://rev.rubyforge.org/>.
		2571
		2572	=item D
		2573
		2574	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2575	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.
		2576
		2577	=back
		2578
		2579
		2580	=head1 MACRO MAGIC
		2581
		2582	Libev can be compiled with a variety of options, the most fundamantal
		2583	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2584	functions and callbacks have an initial C<struct ev_loop *> argument.
		2585
		2586	To make it easier to write programs that cope with either variant, the
		2587	following macros are defined:
		2588
		2589	=over 4
		2590
		2591	=item C<EV_A>, C<EV_A_>
		2592
		2593	This provides the loop I<argument> for functions, if one is required ("ev
		2594	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2595	C<EV_A_> is used when other arguments are following. Example:
		2596
		2597	ev_unref (EV_A);
		2598	ev_timer_add (EV_A_ watcher);
		2599	ev_loop (EV_A_ 0);
		2600
		2601	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2602	which is often provided by the following macro.
		2603
		2604	=item C<EV_P>, C<EV_P_>
		2605
		2606	This provides the loop I<parameter> for functions, if one is required ("ev
		2607	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2608	C<EV_P_> is used when other parameters are following. Example:
		2609
		2610	// this is how ev_unref is being declared
		2611	static void ev_unref (EV_P);
		2612
		2613	// this is how you can declare your typical callback
		2614	static void cb (EV_P_ ev_timer *w, int revents)
		2615
		2616	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2617	suitable for use with C<EV_A>.
		2618
		2619	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2620
		2621	Similar to the other two macros, this gives you the value of the default
		2622	loop, if multiple loops are supported ("ev loop default").
		2623
		2624	=back
		2625
		2626	Example: Declare and initialise a check watcher, utilising the above
		2627	macros so it will work regardless of whether multiple loops are supported
		2628	or not.
		2629
		2630	static void
		2631	check_cb (EV_P_ ev_timer *w, int revents)
		2632	{
		2633	ev_check_stop (EV_A_ w);
1410	}	2634	}
1411		2635
1412	myclass::myclass (int fd)	2636	ev_check check;
1413	: io (this, &myclass::io_cb),	2637	ev_check_init (&check, check_cb);
1414	idle (this, &myclass::idle_cb)	2638	ev_check_start (EV_DEFAULT_ &check);
1415	{	2639	ev_loop (EV_DEFAULT_ 0);
1416	io.start (fd, ev::READ);
1417	}
1418		2640
1419	=head1 EMBEDDING	2641	=head1 EMBEDDING
1420		2642
1421	Libev can (and often is) directly embedded into host	2643	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	2644	applications. Examples of applications that embed it include the Deliantra
1423	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2645	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1424	and rxvt-unicode.	2646	and rxvt-unicode.
1425		2647
1426	The goal is to enable you to just copy the neecssary files into your	2648	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	2649	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	2650	you can easily upgrade by simply copying (or having a checked-out copy of
1429	libev somewhere in your source tree).	2651	libev somewhere in your source tree).
1430		2652
1431	=head2 FILESETS	2653	=head2 FILESETS
…		…
1462	ev_vars.h	2684	ev_vars.h
1463	ev_wrap.h	2685	ev_wrap.h
1464		2686
1465	ev_win32.c required on win32 platforms only	2687	ev_win32.c required on win32 platforms only
1466		2688
1467	ev_select.c only when select backend is enabled (which is is by default)	2689	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)	2690	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)	2691	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)	2692	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)	2693	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		2694
1473	F<ev.c> includes the backend files directly when enabled, so you only need	2695	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	2696	to compile this single file.
1475		2697
1476	=head3 LIBEVENT COMPATIBILITY API	2698	=head3 LIBEVENT COMPATIBILITY API
1477		2699
1478	To include the libevent compatibility API, also include:	2700	To include the libevent compatibility API, also include:
1479		2701
…		…
1492		2714
1493	=head3 AUTOCONF SUPPORT	2715	=head3 AUTOCONF SUPPORT
1494		2716
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	2717	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	2718	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	2719	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	2720	include F<config.h> and configure itself accordingly.
1499		2721
1500	For this of course you need the m4 file:	2722	For this of course you need the m4 file:
1501		2723
1502	libev.m4	2724	libev.m4
1503		2725
…		…
1521		2743
1522	If defined to be C<1>, libev will try to detect the availability of the	2744	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	2745	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	2746	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	2747	usually have to link against librt or something similar. Enabling it when
1526	the functionality isn't available is safe, though, althoguh you have	2748	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>	2749	to make sure you link against any libraries where the C<clock_gettime>
1528	function is hiding in (often F<-lrt>).	2750	function is hiding in (often F<-lrt>).
1529		2751
1530	=item EV_USE_REALTIME	2752	=item EV_USE_REALTIME
1531		2753
1532	If defined to be C<1>, libev will try to detect the availability of the	2754	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	2755	realtime clock option at compiletime (and assume its availability at
1534	runtime if successful). Otherwise no use of the realtime clock option will	2756	runtime if successful). Otherwise no use of the realtime clock option will
1535	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2757	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	2758	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1537	in the description of C<EV_USE_MONOTONIC>, though.	2759	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2760
		2761	=item EV_USE_NANOSLEEP
		2762
		2763	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2764	and will use it for delays. Otherwise it will use C<select ()>.
1538		2765
1539	=item EV_USE_SELECT	2766	=item EV_USE_SELECT
1540		2767
1541	If undefined or defined to be C<1>, libev will compile in support for the	2768	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	2769	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1561	be used is the winsock select). This means that it will call	2788	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,	2789	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	2790	it is assumed that all these functions actually work on fds, even
1564	on win32. Should not be defined on non-win32 platforms.	2791	on win32. Should not be defined on non-win32 platforms.
1565		2792
		2793	=item EV_FD_TO_WIN32_HANDLE
		2794
		2795	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2796	file descriptors to socket handles. When not defining this symbol (the
		2797	default), then libev will call C<_get_osfhandle>, which is usually
		2798	correct. In some cases, programs use their own file descriptor management,
		2799	in which case they can provide this function to map fds to socket handles.
		2800
1566	=item EV_USE_POLL	2801	=item EV_USE_POLL
1567		2802
1568	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2803	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	2804	backend. Otherwise it will be enabled on non-win32 platforms. It
1570	takes precedence over select.	2805	takes precedence over select.
…		…
1583	otherwise another method will be used as fallback. This is the preferred	2818	otherwise another method will be used as fallback. This is the preferred
1584	backend for BSD and BSD-like systems, although on most BSDs kqueue only	2819	backend for BSD and BSD-like systems, although on most BSDs kqueue only
1585	supports some types of fds correctly (the only platform we found that	2820	supports some types of fds correctly (the only platform we found that
1586	supports ptys for example was NetBSD), so kqueue might be compiled in, but	2821	supports ptys for example was NetBSD), so kqueue might be compiled in, but
1587	not be used unless explicitly requested. The best way to use it is to find	2822	not be used unless explicitly requested. The best way to use it is to find
1588	out wether kqueue supports your type of fd properly and use an embedded	2823	out whether kqueue supports your type of fd properly and use an embedded
1589	kqueue loop.	2824	kqueue loop.
1590		2825
1591	=item EV_USE_PORT	2826	=item EV_USE_PORT
1592		2827
1593	If defined to be C<1>, libev will compile in support for the Solaris	2828	If defined to be C<1>, libev will compile in support for the Solaris
…		…
1597		2832
1598	=item EV_USE_DEVPOLL	2833	=item EV_USE_DEVPOLL
1599		2834
1600	reserved for future expansion, works like the USE symbols above.	2835	reserved for future expansion, works like the USE symbols above.
1601		2836
		2837	=item EV_USE_INOTIFY
		2838
		2839	If defined to be C<1>, libev will compile in support for the Linux inotify
		2840	interface to speed up C<ev_stat> watchers. Its actual availability will
		2841	be detected at runtime.
		2842
		2843	=item EV_ATOMIC_T
		2844
		2845	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2846	access is atomic with respect to other threads or signal contexts. No such
		2847	type is easily found in the C language, so you can provide your own type
		2848	that you know is safe for your purposes. It is used both for signal handler "locking"
		2849	as well as for signal and thread safety in C<ev_async> watchers.
		2850
		2851	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2852	(from F<signal.h>), which is usually good enough on most platforms.
		2853
1602	=item EV_H	2854	=item EV_H
1603		2855
1604	The name of the F<ev.h> header file used to include it. The default if	2856	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	2857	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.	2858	used to virtually rename the F<ev.h> header file in case of conflicts.
1607		2859
1608	=item EV_CONFIG_H	2860	=item EV_CONFIG_H
1609		2861
1610	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2862	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	2863	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1612	C<EV_H>, above.	2864	C<EV_H>, above.
1613		2865
1614	=item EV_EVENT_H	2866	=item EV_EVENT_H
1615		2867
1616	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2868	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.	2869	of how the F<event.h> header can be found, the default is C<"event.h">.
1618		2870
1619	=item EV_PROTOTYPES	2871	=item EV_PROTOTYPES
1620		2872
1621	If defined to be C<0>, then F<ev.h> will not define any function	2873	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	2874	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	2881	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	2882	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2883	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2884	argument. Instead, all functions act on the single default loop.
1633		2885
		2886	=item EV_MINPRI
		2887
		2888	=item EV_MAXPRI
		2889
		2890	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2891	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2892	provide for more priorities by overriding those symbols (usually defined
		2893	to be C<-2> and C<2>, respectively).
		2894
		2895	When doing priority-based operations, libev usually has to linearly search
		2896	all the priorities, so having many of them (hundreds) uses a lot of space
		2897	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2898	fine.
		2899
		2900	If your embedding app does not need any priorities, defining these both to
		2901	C<0> will save some memory and cpu.
		2902
1634	=item EV_PERIODICS	2903	=item EV_PERIODIC_ENABLE
1635		2904
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2905	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2906	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2907	code.
		2908
		2909	=item EV_IDLE_ENABLE
		2910
		2911	If undefined or defined to be C<1>, then idle watchers are supported. If
		2912	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2913	code.
		2914
		2915	=item EV_EMBED_ENABLE
		2916
		2917	If undefined or defined to be C<1>, then embed watchers are supported. If
		2918	defined to be C<0>, then they are not.
		2919
		2920	=item EV_STAT_ENABLE
		2921
		2922	If undefined or defined to be C<1>, then stat watchers are supported. If
		2923	defined to be C<0>, then they are not.
		2924
		2925	=item EV_FORK_ENABLE
		2926
		2927	If undefined or defined to be C<1>, then fork watchers are supported. If
		2928	defined to be C<0>, then they are not.
		2929
		2930	=item EV_ASYNC_ENABLE
		2931
		2932	If undefined or defined to be C<1>, then async watchers are supported. If
		2933	defined to be C<0>, then they are not.
		2934
		2935	=item EV_MINIMAL
		2936
		2937	If you need to shave off some kilobytes of code at the expense of some
		2938	speed, define this symbol to C<1>. Currently only used for gcc to override
		2939	some inlining decisions, saves roughly 30% codesize of amd64.
		2940
		2941	=item EV_PID_HASHSIZE
		2942
		2943	C<ev_child> watchers use a small hash table to distribute workload by
		2944	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2945	than enough. If you need to manage thousands of children you might want to
		2946	increase this value (I<must> be a power of two).
		2947
		2948	=item EV_INOTIFY_HASHSIZE
		2949
		2950	C<ev_stat> watchers use a small hash table to distribute workload by
		2951	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2952	usually more than enough. If you need to manage thousands of C<ev_stat>
		2953	watchers you might want to increase this value (I<must> be a power of
		2954	two).
1638		2955
1639	=item EV_COMMON	2956	=item EV_COMMON
1640		2957
1641	By default, all watchers have a C<void *data> member. By redefining	2958	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	2959	this macro to a something else you can include more and other types of
…		…
1647		2964
1648	#define EV_COMMON \	2965	#define EV_COMMON \
1649	SV *self; /* contains this struct */ \	2966	SV *self; /* contains this struct */ \
1650	SV *cb_sv, *fh /* note no trailing ";" */	2967	SV *cb_sv, *fh /* note no trailing ";" */
1651		2968
1652	=item EV_CB_DECLARE(type)	2969	=item EV_CB_DECLARE (type)
1653		2970
1654	=item EV_CB_INVOKE(watcher,revents)	2971	=item EV_CB_INVOKE (watcher, revents)
1655		2972
1656	=item ev_set_cb(ev,cb)	2973	=item ev_set_cb (ev, cb)
1657		2974
1658	Can be used to change the callback member declaration in each watcher,	2975	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	2976	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	2977	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	2978	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	2979	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2980	method calls instead of plain function calls in C++.
		2981
		2982	=head2 EXPORTED API SYMBOLS
		2983
		2984	If you need to re-export the API (e.g. via a dll) and you need a list of
		2985	exported symbols, you can use the provided F<Symbol.*> files which list
		2986	all public symbols, one per line:
		2987
		2988	Symbols.ev for libev proper
		2989	Symbols.event for the libevent emulation
		2990
		2991	This can also be used to rename all public symbols to avoid clashes with
		2992	multiple versions of libev linked together (which is obviously bad in
		2993	itself, but sometimes it is inconvinient to avoid this).
		2994
		2995	A sed command like this will create wrapper C<#define>'s that you need to
		2996	include before including F<ev.h>:
		2997
		2998	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2999
		3000	This would create a file F<wrap.h> which essentially looks like this:
		3001
		3002	#define ev_backend myprefix_ev_backend
		3003	#define ev_check_start myprefix_ev_check_start
		3004	#define ev_check_stop myprefix_ev_check_stop
		3005	...
1664		3006
1665	=head2 EXAMPLES	3007	=head2 EXAMPLES
1666		3008
1667	For a real-world example of a program the includes libev	3009	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	3010	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	3013	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	3014	will be compiled. It is pretty complex because it provides its own header
1673	file.	3015	file.
1674		3016
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3017	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:	3018	that everybody includes and which overrides some configure choices:
1677		3019
		3020	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	3021	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	3022	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	3023	#define EV_PERIODIC_ENABLE 0
		3024	#define EV_STAT_ENABLE 0
		3025	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	3026	#define EV_CONFIG_H <config.h>
		3027	#define EV_MINPRI 0
		3028	#define EV_MAXPRI 0
1682		3029
1683	#include "ev++.h"	3030	#include "ev++.h"
1684		3031
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3032	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		3033
1687	#include "ev_cpp.h"	3034	#include "ev_cpp.h"
1688	#include "ev.c"	3035	#include "ev.c"
1689		3036
		3037
		3038	=head1 COMPLEXITIES
		3039
		3040	In this section the complexities of (many of) the algorithms used inside
		3041	libev will be explained. For complexity discussions about backends see the
		3042	documentation for C<ev_default_init>.
		3043
		3044	All of the following are about amortised time: If an array needs to be
		3045	extended, libev needs to realloc and move the whole array, but this
		3046	happens asymptotically never with higher number of elements, so O(1) might
		3047	mean it might do a lengthy realloc operation in rare cases, but on average
		3048	it is much faster and asymptotically approaches constant time.
		3049
		3050	=over 4
		3051
		3052	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		3053
		3054	This means that, when you have a watcher that triggers in one hour and
		3055	there are 100 watchers that would trigger before that then inserting will
		3056	have to skip roughly seven (C<ld 100>) of these watchers.
		3057
		3058	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		3059
		3060	That means that changing a timer costs less than removing/adding them
		3061	as only the relative motion in the event queue has to be paid for.
		3062
		3063	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		3064
		3065	These just add the watcher into an array or at the head of a list.
		3066
		3067	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		3068
		3069	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		3070
		3071	These watchers are stored in lists then need to be walked to find the
		3072	correct watcher to remove. The lists are usually short (you don't usually
		3073	have many watchers waiting for the same fd or signal).
		3074
		3075	=item Finding the next timer in each loop iteration: O(1)
		3076
		3077	By virtue of using a binary heap, the next timer is always found at the
		3078	beginning of the storage array.
		3079
		3080	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3081
		3082	A change means an I/O watcher gets started or stopped, which requires
		3083	libev to recalculate its status (and possibly tell the kernel, depending
		3084	on backend and wether C<ev_io_set> was used).
		3085
		3086	=item Activating one watcher (putting it into the pending state): O(1)
		3087
		3088	=item Priority handling: O(number_of_priorities)
		3089
		3090	Priorities are implemented by allocating some space for each
		3091	priority. When doing priority-based operations, libev usually has to
		3092	linearly search all the priorities, but starting/stopping and activating
		3093	watchers becomes O(1) w.r.t. priority handling.
		3094
		3095	=item Sending an ev_async: O(1)
		3096
		3097	=item Processing ev_async_send: O(number_of_async_watchers)
		3098
		3099	=item Processing signals: O(max_signal_number)
		3100
		3101	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3102	calls in the current loop iteration. Checking for async and signal events
		3103	involves iterating over all running async watchers or all signal numbers.
		3104
		3105	=back
		3106
		3107
		3108	=head1 Win32 platform limitations and workarounds
		3109
		3110	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3111	requires, and its I/O model is fundamentally incompatible with the POSIX
		3112	model. Libev still offers limited functionality on this platform in
		3113	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3114	descriptors. This only applies when using Win32 natively, not when using
		3115	e.g. cygwin.
		3116
		3117	There is no supported compilation method available on windows except
		3118	embedding it into other applications.
		3119
		3120	Due to the many, low, and arbitrary limits on the win32 platform and the
		3121	abysmal performance of winsockets, using a large number of sockets is not
		3122	recommended (and not reasonable). If your program needs to use more than
		3123	a hundred or so sockets, then likely it needs to use a totally different
		3124	implementation for windows, as libev offers the POSIX model, which cannot
		3125	be implemented efficiently on windows (microsoft monopoly games).
		3126
		3127	=over 4
		3128
		3129	=item The winsocket select function
		3130
		3131	The winsocket C<select> function doesn't follow POSIX in that it requires
		3132	socket I<handles> and not socket I<file descriptors>. This makes select
		3133	very inefficient, and also requires a mapping from file descriptors
		3134	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3135	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3136	symbols for more info.
		3137
		3138	The configuration for a "naked" win32 using the microsoft runtime
		3139	libraries and raw winsocket select is:
		3140
		3141	#define EV_USE_SELECT 1
		3142	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3143
		3144	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3145	complexity in the O(n²) range when using win32.
		3146
		3147	=item Limited number of file descriptors
		3148
		3149	Windows has numerous arbitrary (and low) limits on things. Early versions
		3150	of winsocket's select only supported waiting for a max. of C<64> handles
		3151	(probably owning to the fact that all windows kernels can only wait for
		3152	C<64> things at the same time internally; microsoft recommends spawning a
		3153	chain of threads and wait for 63 handles and the previous thread in each).
		3154
		3155	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3156	to some high number (e.g. C<2048>) before compiling the winsocket select
		3157	call (which might be in libev or elsewhere, for example, perl does its own
		3158	select emulation on windows).
		3159
		3160	Another limit is the number of file descriptors in the microsoft runtime
		3161	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3162	or something like this inside microsoft). You can increase this by calling
		3163	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3164	arbitrary limit), but is broken in many versions of the microsoft runtime
		3165	libraries.
		3166
		3167	This might get you to about C<512> or C<2048> sockets (depending on
		3168	windows version and/or the phase of the moon). To get more, you need to
		3169	wrap all I/O functions and provide your own fd management, but the cost of
		3170	calling select (O(n²)) will likely make this unworkable.
		3171
		3172	=back
		3173
		3174
1690	=head1 AUTHOR	3175	=head1 AUTHOR
1691		3176
1692	Marc Lehmann <libev@schmorp.de>.	3177	Marc Lehmann <libev@schmorp.de>.
1693		3178

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