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Revision 1.83 by root, Wed Dec 12 17:55:31 2007 UTC vs.
Revision 1.200 by root, Thu Oct 23 07:33:45 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_TYPE
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	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);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	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
58	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
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	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
62	(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
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	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
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	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
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	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
101	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
102	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
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
112	=item ev_tstamp ev_time ()	150	=item ev_tstamp ev_time ()
113		151
114	Returns the current time as libev would use it. Please note that the	152	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	153	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	154	you actually want to know.
		155
		156	=item ev_sleep (ev_tstamp interval)
		157
		158	Sleep for the given interval: The current thread will be blocked until
		159	either it is interrupted or the given time interval has passed. Basically
		160	this is a sub-second-resolution C<sleep ()>.
117		161
118	=item int ev_version_major ()	162	=item int ev_version_major ()
119		163
120	=item int ev_version_minor ()	164	=item int ev_version_minor ()
121		165
…		…
134	not a problem.	178	not a problem.
135		179
136	Example: Make sure we haven't accidentally been linked against the wrong	180	Example: Make sure we haven't accidentally been linked against the wrong
137	version.	181	version.
138		182
139	assert (("libev version mismatch",	183	assert (("libev version mismatch",
140	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
141	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
142		186
143	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
144		188
145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	189	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
146	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
148	a description of the set values.	192	a description of the set values.
149		193
150	Example: make sure we have the epoll method, because yeah this is cool and	194	Example: make sure we have the epoll method, because yeah this is cool and
151	a must have and can we have a torrent of it please!!!11	195	a must have and can we have a torrent of it please!!!11
152		196
153	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
154	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
155		199
156	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
157		201
158	Return the set of all backends compiled into this binary of libev and also	202	Return the set of all backends compiled into this binary of libev and also
159	recommended for this platform. This set is often smaller than the one	203	recommended for this platform. This set is often smaller than the one
160	returned by C<ev_supported_backends>, as for example kqueue is broken on	204	returned by C<ev_supported_backends>, as for example kqueue is broken on
161	most BSDs and will not be autodetected unless you explicitly request it	205	most BSDs and will not be auto-detected unless you explicitly request it
162	(assuming you know what you are doing). This is the set of backends that	206	(assuming you know what you are doing). This is the set of backends that
163	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
164		208
165	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
166		210
…		…
170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
171	recommended ones.	215	recommended ones.
172		216
173	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
174		218
175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
176		220
177	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
178	semantics is identical - to the realloc C function). It is used to	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
179	allocate and free memory (no surprises here). If it returns zero when	223	used to allocate and free memory (no surprises here). If it returns zero
180	memory needs to be allocated, the library might abort or take some	224	when memory needs to be allocated (C<size != 0>), the library might abort
181	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
182	function.	226
		227	Since some systems (at least OpenBSD and Darwin) fail to implement
		228	correct C<realloc> semantics, libev will use a wrapper around the system
		229	C<realloc> and C<free> functions by default.
183		230
184	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
185	free some memory if it cannot allocate memory, to use a special allocator,	232	free some memory if it cannot allocate memory, to use a special allocator,
186	or even to sleep a while and retry until some memory is available.	233	or even to sleep a while and retry until some memory is available.
187		234
188	Example: Replace the libev allocator with one that waits a bit and then	235	Example: Replace the libev allocator with one that waits a bit and then
189	retries).	236	retries (example requires a standards-compliant C<realloc>).
190		237
191	static void *	238	static void *
192	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
193	{	240	{
194	for (;;)	241	for (;;)
…		…
203	}	250	}
204		251
205	...	252	...
206	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
207		254
208	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
209		256
210	Set the callback function to call on a retryable syscall error (such	257	Set the callback function to call on a retryable system call error (such
211	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
212	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
213	callback is set, then libev will expect it to remedy the sitution, no	260	callback is set, then libev will expect it to remedy the situation, no
214	matter what, when it returns. That is, libev will generally retry the	261	matter what, when it returns. That is, libev will generally retry the
215	requested operation, or, if the condition doesn't go away, do bad stuff	262	requested operation, or, if the condition doesn't go away, do bad stuff
216	(such as abort).	263	(such as abort).
217		264
218	Example: This is basically the same thing that libev does internally, too.	265	Example: This is basically the same thing that libev does internally, too.
…		…
229		276
230	=back	277	=back
231		278
232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
233		280
234	An event loop is described by a C<struct ev_loop *>. The library knows two	281	An event loop is described by a C<struct ev_loop *> (the C<struct>
235	types of such loops, the I<default> loop, which supports signals and child	282	is I<not> optional in this case, as there is also an C<ev_loop>
236	events, and dynamically created loops which do not.	283	I<function>).
237		284
238	If you use threads, a common model is to run the default event loop	285	The library knows two types of such loops, the I<default> loop, which
239	in your main thread (or in a separate thread) and for each thread you	286	supports signals and child events, and dynamically created loops which do
240	create, you also create another event loop. Libev itself does no locking	287	not.
241	whatsoever, so if you mix calls to the same event loop in different
242	threads, make sure you lock (this is usually a bad idea, though, even if
243	done correctly, because it's hideous and inefficient).
244		288
245	=over 4	289	=over 4
246		290
247	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
248		292
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	296	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		297
254	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
255	function.	299	function.
256		300
		301	Note that this function is I<not> thread-safe, so if you want to use it
		302	from multiple threads, you have to lock (note also that this is unlikely,
		303	as loops cannot bes hared easily between threads anyway).
		304
		305	The default loop is the only loop that can handle C<ev_signal> and
		306	C<ev_child> watchers, and to do this, it always registers a handler
		307	for C<SIGCHLD>. If this is a problem for your application you can either
		308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		310	C<ev_default_init>.
		311
257	The flags argument can be used to specify special behaviour or specific	312	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		314
260	The following flags are supported:	315	The following flags are supported:
261		316
…		…
266	The default flags value. Use this if you have no clue (it's the right	321	The default flags value. Use this if you have no clue (it's the right
267	thing, believe me).	322	thing, believe me).
268		323
269	=item C<EVFLAG_NOENV>	324	=item C<EVFLAG_NOENV>
270		325
271	If this flag bit is ored into the flag value (or the program runs setuid	326	If this flag bit is or'ed into the flag value (or the program runs setuid
272	or setgid) then libev will I<not> look at the environment variable	327	or setgid) then libev will I<not> look at the environment variable
273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
274	override the flags completely if it is found in the environment. This is	329	override the flags completely if it is found in the environment. This is
275	useful to try out specific backends to test their performance, or to work	330	useful to try out specific backends to test their performance, or to work
276	around bugs.	331	around bugs.
…		…
282	enabling this flag.	337	enabling this flag.
283		338
284	This works by calling C<getpid ()> on every iteration of the loop,	339	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	340	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	341	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	343	without a system call and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	344	C<pthread_atfork> which is even faster).
290		345
291	The big advantage of this flag is that you can forget about fork (and	346	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	347	forget about forgetting to tell libev about forking) when you use this
293	flag.	348	flag.
294		349
295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
296	environment variable.	351	environment variable.
297		352
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		354
300	This is your standard select(2) backend. Not I<completely> standard, as	355	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	356	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	357	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	358	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	359	usually the fastest backend for a low number of (low-numbered :) fds.
		360
		361	To get good performance out of this backend you need a high amount of
		362	parallelism (most of the file descriptors should be busy). If you are
		363	writing a server, you should C<accept ()> in a loop to accept as many
		364	connections as possible during one iteration. You might also want to have
		365	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		366	readiness notifications you get per iteration.
		367
		368	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		369	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		370	C<exceptfds> set on that platform).
305		371
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	372	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		373
308	And this is your standard poll(2) backend. It's more complicated than	374	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	375	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	376	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	377	considerably with a lot of inactive fds). It scales similarly to select,
		378	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		379	performance tips.
		380
		381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
312		383
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		385
315	For few fds, this backend is a bit little slower than poll and select,	386	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	387	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	388	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	389	epoll scales either O(1) or O(active_fds). The epoll design has a number
		390	of shortcomings, such as silently dropping events in some hard-to-detect
		391	cases and requiring a system call per fd change, no fork support and bad
		392	support for dup.
319		393
320	While stopping and starting an I/O watcher in the same iteration will	394	While stopping, setting and starting an I/O watcher in the same iteration
321	result in some caching, there is still a syscall per such incident	395	will result in some caching, there is still a system call per such incident
322	(because the fd could point to a different file description now), so its	396	(because the fd could point to a different file description now), so its
323	best to avoid that. Also, dup()ed file descriptors might not work very	397	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
324	well if you register events for both fds.	398	very well if you register events for both fds.
325		399
326	Please note that epoll sometimes generates spurious notifications, so you	400	Please note that epoll sometimes generates spurious notifications, so you
327	need to use non-blocking I/O or other means to avoid blocking when no data	401	need to use non-blocking I/O or other means to avoid blocking when no data
328	(or space) is available.	402	(or space) is available.
329		403
		404	Best performance from this backend is achieved by not unregistering all
		405	watchers for a file descriptor until it has been closed, if possible,
		406	i.e. keep at least one watcher active per fd at all times. Stopping and
		407	starting a watcher (without re-setting it) also usually doesn't cause
		408	extra overhead.
		409
		410	While nominally embeddable in other event loops, this feature is broken in
		411	all kernel versions tested so far.
		412
		413	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		414	C<EVBACKEND_POLL>.
		415
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	416	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		417
332	Kqueue deserves special mention, as at the time of this writing, it	418	Kqueue deserves special mention, as at the time of this writing, it was
333	was broken on all BSDs except NetBSD (usually it doesn't work with	419	broken on all BSDs except NetBSD (usually it doesn't work reliably with
334	anything but sockets and pipes, except on Darwin, where of course its	420	anything but sockets and pipes, except on Darwin, where of course it's
335	completely useless). For this reason its not being "autodetected"	421	completely useless). For this reason it's not being "auto-detected" unless
336	unless you explicitly specify it explicitly in the flags (i.e. using	422	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
337	C<EVBACKEND_KQUEUE>).	423	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		424
		425	You still can embed kqueue into a normal poll or select backend and use it
		426	only for sockets (after having made sure that sockets work with kqueue on
		427	the target platform). See C<ev_embed> watchers for more info.
338		428
339	It scales in the same way as the epoll backend, but the interface to the	429	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	430	kernel is more efficient (which says nothing about its actual speed, of
341	course). While starting and stopping an I/O watcher does not cause an	431	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	432	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	433	two event changes per incident. Support for C<fork ()> is very bad and it
		434	drops fds silently in similarly hard-to-detect cases.
		435
		436	This backend usually performs well under most conditions.
		437
		438	While nominally embeddable in other event loops, this doesn't work
		439	everywhere, so you might need to test for this. And since it is broken
		440	almost everywhere, you should only use it when you have a lot of sockets
		441	(for which it usually works), by embedding it into another event loop
		442	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		443	using it only for sockets.
		444
		445	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		446	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		447	C<NOTE_EOF>.
344		448
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	449	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		450
347	This is not implemented yet (and might never be).	451	This is not implemented yet (and might never be, unless you send me an
		452	implementation). According to reports, C</dev/poll> only supports sockets
		453	and is not embeddable, which would limit the usefulness of this backend
		454	immensely.
348		455
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	456	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		457
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	458	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	it's really slow, but it still scales very well (O(active_fds)).	459	it's really slow, but it still scales very well (O(active_fds)).
353		460
354	Please note that solaris ports can result in a lot of spurious	461	Please note that Solaris event ports can deliver a lot of spurious
355	notifications, so you need to use non-blocking I/O or other means to avoid	462	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	463	blocking when no data (or space) is available.
		464
		465	While this backend scales well, it requires one system call per active
		466	file descriptor per loop iteration. For small and medium numbers of file
		467	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		468	might perform better.
		469
		470	On the positive side, with the exception of the spurious readiness
		471	notifications, this backend actually performed fully to specification
		472	in all tests and is fully embeddable, which is a rare feat among the
		473	OS-specific backends.
		474
		475	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		476	C<EVBACKEND_POLL>.
357		477
358	=item C<EVBACKEND_ALL>	478	=item C<EVBACKEND_ALL>
359		479
360	Try all backends (even potentially broken ones that wouldn't be tried	480	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	481	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	482	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		483
		484	It is definitely not recommended to use this flag.
		485
364	=back	486	=back
365		487
366	If one or more of these are ored into the flags value, then only these	488	If one or more of these are or'ed into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	489	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	490	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		491
371	The most typical usage is like this:	492	Example: This is the most typical usage.
372		493
373	if (!ev_default_loop (0))	494	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	495	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
375		496
376	Restrict libev to the select and poll backends, and do not allow	497	Example: Restrict libev to the select and poll backends, and do not allow
377	environment settings to be taken into account:	498	environment settings to be taken into account:
378		499
379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	500	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
380		501
381	Use whatever libev has to offer, but make sure that kqueue is used if	502	Example: Use whatever libev has to offer, but make sure that kqueue is
382	available (warning, breaks stuff, best use only with your own private	503	used if available (warning, breaks stuff, best use only with your own
383	event loop and only if you know the OS supports your types of fds):	504	private event loop and only if you know the OS supports your types of
		505	fds):
384		506
385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	507	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
386		508
387	=item struct ev_loop *ev_loop_new (unsigned int flags)	509	=item struct ev_loop *ev_loop_new (unsigned int flags)
388		510
389	Similar to C<ev_default_loop>, but always creates a new event loop that is	511	Similar to C<ev_default_loop>, but always creates a new event loop that is
390	always distinct from the default loop. Unlike the default loop, it cannot	512	always distinct from the default loop. Unlike the default loop, it cannot
391	handle signal and child watchers, and attempts to do so will be greeted by	513	handle signal and child watchers, and attempts to do so will be greeted by
392	undefined behaviour (or a failed assertion if assertions are enabled).	514	undefined behaviour (or a failed assertion if assertions are enabled).
393		515
		516	Note that this function I<is> thread-safe, and the recommended way to use
		517	libev with threads is indeed to create one loop per thread, and using the
		518	default loop in the "main" or "initial" thread.
		519
394	Example: Try to create a event loop that uses epoll and nothing else.	520	Example: Try to create a event loop that uses epoll and nothing else.
395		521
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	522	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	523	if (!epoller)
398	fatal ("no epoll found here, maybe it hides under your chair");	524	fatal ("no epoll found here, maybe it hides under your chair");
399		525
400	=item ev_default_destroy ()	526	=item ev_default_destroy ()
401		527
402	Destroys the default loop again (frees all memory and kernel state	528	Destroys the default loop again (frees all memory and kernel state
403	etc.). None of the active event watchers will be stopped in the normal	529	etc.). None of the active event watchers will be stopped in the normal
404	sense, so e.g. C<ev_is_active> might still return true. It is your	530	sense, so e.g. C<ev_is_active> might still return true. It is your
405	responsibility to either stop all watchers cleanly yoursef I<before>	531	responsibility to either stop all watchers cleanly yourself I<before>
406	calling this function, or cope with the fact afterwards (which is usually	532	calling this function, or cope with the fact afterwards (which is usually
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	533	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	534	for example).
		535
		536	Note that certain global state, such as signal state, will not be freed by
		537	this function, and related watchers (such as signal and child watchers)
		538	would need to be stopped manually.
		539
		540	In general it is not advisable to call this function except in the
		541	rare occasion where you really need to free e.g. the signal handling
		542	pipe fds. If you need dynamically allocated loops it is better to use
		543	C<ev_loop_new> and C<ev_loop_destroy>).
409		544
410	=item ev_loop_destroy (loop)	545	=item ev_loop_destroy (loop)
411		546
412	Like C<ev_default_destroy>, but destroys an event loop created by an	547	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	548	earlier call to C<ev_loop_new>.
414		549
415	=item ev_default_fork ()	550	=item ev_default_fork ()
416		551
		552	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	553	to reinitialise the kernel state for backends that have one. Despite the
418	one. Despite the name, you can call it anytime, but it makes most sense	554	name, you can call it anytime, but it makes most sense after forking, in
419	after forking, in either the parent or child process (or both, but that	555	the child process (or both child and parent, but that again makes little
420	again makes little sense).	556	sense). You I<must> call it in the child before using any of the libev
		557	functions, and it will only take effect at the next C<ev_loop> iteration.
421		558
422	You I<must> call this function in the child process after forking if and	559	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	560	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	561	you just fork+exec, you don't have to call it at all.
425		562
426	The function itself is quite fast and it's usually not a problem to call	563	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	564	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	565	quite nicely into a call to C<pthread_atfork>:
429		566
430	pthread_atfork (0, 0, ev_default_fork);	567	pthread_atfork (0, 0, ev_default_fork);
431		568
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	569	=item ev_loop_fork (loop)
437		570
438	Like C<ev_default_fork>, but acts on an event loop created by	571	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	572	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	573	after fork that you want to re-use in the child, and how you do this is
		574	entirely your own problem.
		575
		576	=item int ev_is_default_loop (loop)
		577
		578	Returns true when the given loop is, in fact, the default loop, and false
		579	otherwise.
441		580
442	=item unsigned int ev_loop_count (loop)	581	=item unsigned int ev_loop_count (loop)
443		582
444	Returns the count of loop iterations for the loop, which is identical to	583	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	584	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		597
459	Returns the current "event loop time", which is the time the event loop	598	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	599	received events and started processing them. This timestamp does not
461	change as long as callbacks are being processed, and this is also the base	600	change as long as callbacks are being processed, and this is also the base
462	time used for relative timers. You can treat it as the timestamp of the	601	time used for relative timers. You can treat it as the timestamp of the
463	event occuring (or more correctly, libev finding out about it).	602	event occurring (or more correctly, libev finding out about it).
		603
		604	=item ev_now_update (loop)
		605
		606	Establishes the current time by querying the kernel, updating the time
		607	returned by C<ev_now ()> in the progress. This is a costly operation and
		608	is usually done automatically within C<ev_loop ()>.
		609
		610	This function is rarely useful, but when some event callback runs for a
		611	very long time without entering the event loop, updating libev's idea of
		612	the current time is a good idea.
		613
		614	See also "The special problem of time updates" in the C<ev_timer> section.
464		615
465	=item ev_loop (loop, int flags)	616	=item ev_loop (loop, int flags)
466		617
467	Finally, this is it, the event handler. This function usually is called	618	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	619	after you initialised all your watchers and you want to start handling
…		…
471	If the flags argument is specified as C<0>, it will not return until	622	If the flags argument is specified as C<0>, it will not return until
472	either no event watchers are active anymore or C<ev_unloop> was called.	623	either no event watchers are active anymore or C<ev_unloop> was called.
473		624
474	Please note that an explicit C<ev_unloop> is usually better than	625	Please note that an explicit C<ev_unloop> is usually better than
475	relying on all watchers to be stopped when deciding when a program has	626	relying on all watchers to be stopped when deciding when a program has
476	finished (especially in interactive programs), but having a program that	627	finished (especially in interactive programs), but having a program
477	automatically loops as long as it has to and no longer by virtue of	628	that automatically loops as long as it has to and no longer by virtue
478	relying on its watchers stopping correctly is a thing of beauty.	629	of relying on its watchers stopping correctly, that is truly a thing of
		630	beauty.
479		631
480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	632	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
481	those events and any outstanding ones, but will not block your process in	633	those events and any already outstanding ones, but will not block your
482	case there are no events and will return after one iteration of the loop.	634	process in case there are no events and will return after one iteration of
		635	the loop.
483		636
484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	637	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
485	neccessary) and will handle those and any outstanding ones. It will block	638	necessary) and will handle those and any already outstanding ones. It
486	your process until at least one new event arrives, and will return after	639	will block your process until at least one new event arrives (which could
487	one iteration of the loop. This is useful if you are waiting for some	640	be an event internal to libev itself, so there is no guarentee that a
488	external event in conjunction with something not expressible using other	641	user-registered callback will be called), and will return after one
		642	iteration of the loop.
		643
		644	This is useful if you are waiting for some external event in conjunction
		645	with something not expressible using other libev watchers (i.e. "roll your
489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	646	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
490	usually a better approach for this kind of thing.	647	usually a better approach for this kind of thing.
491		648
492	Here are the gory details of what C<ev_loop> does:	649	Here are the gory details of what C<ev_loop> does:
493		650
494	- Before the first iteration, call any pending watchers.	651	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	652	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	653	- If a fork was detected (by any means), queue and call all fork watchers.
		654	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	655	- If we have been forked, detach and recreate the kernel state
		656	as to not disturb the other process.
498	- Update the kernel state with all outstanding changes.	657	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	658	- Update the "event loop time" (ev_now ()).
500	- Calculate for how long to block.	659	- Calculate for how long to sleep or block, if at all
		660	(active idle watchers, EVLOOP_NONBLOCK or not having
		661	any active watchers at all will result in not sleeping).
		662	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	663	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	664	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	665	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
504	- Queue all outstanding timers.	666	- Queue all expired timers.
505	- Queue all outstanding periodics.	667	- Queue all expired periodics.
506	- If no events are pending now, queue all idle watchers.	668	- Unless any events are pending now, queue all idle watchers.
507	- Queue all check watchers.	669	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	670	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	671	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	672	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	673	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	674	were used, or there are no active watchers, return, otherwise
		675	continue with step *.
513		676
514	Example: Queue some jobs and then loop until no events are outsanding	677	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	678	anymore.
516		679
517	... queue jobs here, make sure they register event watchers as long	680	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	681	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	682	ev_loop (my_loop, 0);
520	... jobs done. yeah!	683	... jobs done or somebody called unloop. yeah!
521		684
522	=item ev_unloop (loop, how)	685	=item ev_unloop (loop, how)
523		686
524	Can be used to make a call to C<ev_loop> return early (but only after it	687	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	688	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	689	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	690	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
528		691
		692	This "unloop state" will be cleared when entering C<ev_loop> again.
		693
		694	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		695
529	=item ev_ref (loop)	696	=item ev_ref (loop)
530		697
531	=item ev_unref (loop)	698	=item ev_unref (loop)
532		699
533	Ref/unref can be used to add or remove a reference count on the event	700	Ref/unref can be used to add or remove a reference count on the event
534	loop: Every watcher keeps one reference, and as long as the reference	701	loop: Every watcher keeps one reference, and as long as the reference
535	count is nonzero, C<ev_loop> will not return on its own. If you have	702	count is nonzero, C<ev_loop> will not return on its own.
		703
536	a watcher you never unregister that should not keep C<ev_loop> from	704	If you have a watcher you never unregister that should not keep C<ev_loop>
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	705	from returning, call ev_unref() after starting, and ev_ref() before
		706	stopping it.
		707
538	example, libev itself uses this for its internal signal pipe: It is not	708	As an example, libev itself uses this for its internal signal pipe: It is
539	visible to the libev user and should not keep C<ev_loop> from exiting if	709	not visible to the libev user and should not keep C<ev_loop> from exiting
540	no event watchers registered by it are active. It is also an excellent	710	if no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	711	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	712	libraries. Just remember to I<unref after start> and I<ref before stop>
		713	(but only if the watcher wasn't active before, or was active before,
		714	respectively).
543		715
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	716	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	717	running when nothing else is active.
546		718
547	struct ev_signal exitsig;	719	ev_signal exitsig;
548	ev_signal_init (&exitsig, sig_cb, SIGINT);	720	ev_signal_init (&exitsig, sig_cb, SIGINT);
549	ev_signal_start (loop, &exitsig);	721	ev_signal_start (loop, &exitsig);
550	evf_unref (loop);	722	evf_unref (loop);
551		723
552	Example: For some weird reason, unregister the above signal handler again.	724	Example: For some weird reason, unregister the above signal handler again.
553		725
554	ev_ref (loop);	726	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	727	ev_signal_stop (loop, &exitsig);
		728
		729	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		730
		731	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		732
		733	These advanced functions influence the time that libev will spend waiting
		734	for events. Both time intervals are by default C<0>, meaning that libev
		735	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		736	latency.
		737
		738	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		739	allows libev to delay invocation of I/O and timer/periodic callbacks
		740	to increase efficiency of loop iterations (or to increase power-saving
		741	opportunities).
		742
		743	The idea is that sometimes your program runs just fast enough to handle
		744	one (or very few) event(s) per loop iteration. While this makes the
		745	program responsive, it also wastes a lot of CPU time to poll for new
		746	events, especially with backends like C<select ()> which have a high
		747	overhead for the actual polling but can deliver many events at once.
		748
		749	By setting a higher I<io collect interval> you allow libev to spend more
		750	time collecting I/O events, so you can handle more events per iteration,
		751	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		752	C<ev_timer>) will be not affected. Setting this to a non-null value will
		753	introduce an additional C<ev_sleep ()> call into most loop iterations.
		754
		755	Likewise, by setting a higher I<timeout collect interval> you allow libev
		756	to spend more time collecting timeouts, at the expense of increased
		757	latency/jitter/inexactness (the watcher callback will be called
		758	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		759	value will not introduce any overhead in libev.
		760
		761	Many (busy) programs can usually benefit by setting the I/O collect
		762	interval to a value near C<0.1> or so, which is often enough for
		763	interactive servers (of course not for games), likewise for timeouts. It
		764	usually doesn't make much sense to set it to a lower value than C<0.01>,
		765	as this approaches the timing granularity of most systems.
		766
		767	Setting the I<timeout collect interval> can improve the opportunity for
		768	saving power, as the program will "bundle" timer callback invocations that
		769	are "near" in time together, by delaying some, thus reducing the number of
		770	times the process sleeps and wakes up again. Another useful technique to
		771	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		772	they fire on, say, one-second boundaries only.
		773
		774	=item ev_loop_verify (loop)
		775
		776	This function only does something when C<EV_VERIFY> support has been
		777	compiled in, which is the default for non-minimal builds. It tries to go
		778	through all internal structures and checks them for validity. If anything
		779	is found to be inconsistent, it will print an error message to standard
		780	error and call C<abort ()>.
		781
		782	This can be used to catch bugs inside libev itself: under normal
		783	circumstances, this function will never abort as of course libev keeps its
		784	data structures consistent.
556		785
557	=back	786	=back
558		787
559		788
560	=head1 ANATOMY OF A WATCHER	789	=head1 ANATOMY OF A WATCHER
		790
		791	In the following description, uppercase C<TYPE> in names stands for the
		792	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		793	watchers and C<ev_io_start> for I/O watchers.
561		794
562	A watcher is a structure that you create and register to record your	795	A watcher is a structure that you create and register to record your
563	interest in some event. For instance, if you want to wait for STDIN to	796	interest in some event. For instance, if you want to wait for STDIN to
564	become readable, you would create an C<ev_io> watcher for that:	797	become readable, you would create an C<ev_io> watcher for that:
565		798
566	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	799	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
567	{	800	{
568	ev_io_stop (w);	801	ev_io_stop (w);
569	ev_unloop (loop, EVUNLOOP_ALL);	802	ev_unloop (loop, EVUNLOOP_ALL);
570	}	803	}
571		804
572	struct ev_loop *loop = ev_default_loop (0);	805	struct ev_loop *loop = ev_default_loop (0);
		806
573	struct ev_io stdin_watcher;	807	ev_io stdin_watcher;
		808
574	ev_init (&stdin_watcher, my_cb);	809	ev_init (&stdin_watcher, my_cb);
575	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	810	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
576	ev_io_start (loop, &stdin_watcher);	811	ev_io_start (loop, &stdin_watcher);
		812
577	ev_loop (loop, 0);	813	ev_loop (loop, 0);
578		814
579	As you can see, you are responsible for allocating the memory for your	815	As you can see, you are responsible for allocating the memory for your
580	watcher structures (and it is usually a bad idea to do this on the stack,	816	watcher structures (and it is I<usually> a bad idea to do this on the
581	although this can sometimes be quite valid).	817	stack).
		818
		819	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		820	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
582		821
583	Each watcher structure must be initialised by a call to C<ev_init	822	Each watcher structure must be initialised by a call to C<ev_init
584	(watcher *, callback)>, which expects a callback to be provided. This	823	(watcher *, callback)>, which expects a callback to be provided. This
585	callback gets invoked each time the event occurs (or, in the case of io	824	callback gets invoked each time the event occurs (or, in the case of I/O
586	watchers, each time the event loop detects that the file descriptor given	825	watchers, each time the event loop detects that the file descriptor given
587	is readable and/or writable).	826	is readable and/or writable).
588		827
589	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	828	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
590	with arguments specific to this watcher type. There is also a macro	829	macro to configure it, with arguments specific to the watcher type. There
591	to combine initialisation and setting in one call: C<< ev_<type>_init	830	is also a macro to combine initialisation and setting in one call: C<<
592	(watcher *, callback, ...) >>.	831	ev_TYPE_init (watcher *, callback, ...) >>.
593		832
594	To make the watcher actually watch out for events, you have to start it	833	To make the watcher actually watch out for events, you have to start it
595	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	834	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
596	*) >>), and you can stop watching for events at any time by calling the	835	*) >>), and you can stop watching for events at any time by calling the
597	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	836	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
598		837
599	As long as your watcher is active (has been started but not stopped) you	838	As long as your watcher is active (has been started but not stopped) you
600	must not touch the values stored in it. Most specifically you must never	839	must not touch the values stored in it. Most specifically you must never
601	reinitialise it or call its C<set> macro.	840	reinitialise it or call its C<ev_TYPE_set> macro.
602		841
603	Each and every callback receives the event loop pointer as first, the	842	Each and every callback receives the event loop pointer as first, the
604	registered watcher structure as second, and a bitset of received events as	843	registered watcher structure as second, and a bitset of received events as
605	third argument.	844	third argument.
606		845
…		…
660	=item C<EV_FORK>	899	=item C<EV_FORK>
661		900
662	The event loop has been resumed in the child process after fork (see	901	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	902	C<ev_fork>).
664		903
		904	=item C<EV_ASYNC>
		905
		906	The given async watcher has been asynchronously notified (see C<ev_async>).
		907
665	=item C<EV_ERROR>	908	=item C<EV_ERROR>
666		909
667	An unspecified error has occured, the watcher has been stopped. This might	910	An unspecified error has occurred, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	911	happen because the watcher could not be properly started because libev
669	ran out of memory, a file descriptor was found to be closed or any other	912	ran out of memory, a file descriptor was found to be closed or any other
		913	problem. Libev considers these application bugs.
		914
670	problem. You best act on it by reporting the problem and somehow coping	915	You best act on it by reporting the problem and somehow coping with the
671	with the watcher being stopped.	916	watcher being stopped. Note that well-written programs should not receive
		917	an error ever, so when your watcher receives it, this usually indicates a
		918	bug in your program.
672		919
673	Libev will usually signal a few "dummy" events together with an error,	920	Libev will usually signal a few "dummy" events together with an error, for
674	for example it might indicate that a fd is readable or writable, and if	921	example it might indicate that a fd is readable or writable, and if your
675	your callbacks is well-written it can just attempt the operation and cope	922	callbacks is well-written it can just attempt the operation and cope with
676	with the error from read() or write(). This will not work in multithreaded	923	the error from read() or write(). This will not work in multi-threaded
677	programs, though, so beware.	924	programs, though, as the fd could already be closed and reused for another
		925	thing, so beware.
678		926
679	=back	927	=back
680		928
681	=head2 GENERIC WATCHER FUNCTIONS	929	=head2 GENERIC WATCHER FUNCTIONS
682
683	In the following description, C<TYPE> stands for the watcher type,
684	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
685		930
686	=over 4	931	=over 4
687		932
688	=item C<ev_init> (ev_TYPE *watcher, callback)	933	=item C<ev_init> (ev_TYPE *watcher, callback)
689		934
…		…
695	which rolls both calls into one.	940	which rolls both calls into one.
696		941
697	You can reinitialise a watcher at any time as long as it has been stopped	942	You can reinitialise a watcher at any time as long as it has been stopped
698	(or never started) and there are no pending events outstanding.	943	(or never started) and there are no pending events outstanding.
699		944
700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	945	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
701	int revents)>.	946	int revents)>.
		947
		948	Example: Initialise an C<ev_io> watcher in two steps.
		949
		950	ev_io w;
		951	ev_init (&w, my_cb);
		952	ev_io_set (&w, STDIN_FILENO, EV_READ);
702		953
703	=item C<ev_TYPE_set> (ev_TYPE *, [args])	954	=item C<ev_TYPE_set> (ev_TYPE *, [args])
704		955
705	This macro initialises the type-specific parts of a watcher. You need to	956	This macro initialises the type-specific parts of a watcher. You need to
706	call C<ev_init> at least once before you call this macro, but you can	957	call C<ev_init> at least once before you call this macro, but you can
…		…
709	difference to the C<ev_init> macro).	960	difference to the C<ev_init> macro).
710		961
711	Although some watcher types do not have type-specific arguments	962	Although some watcher types do not have type-specific arguments
712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	963	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
713		964
		965	See C<ev_init>, above, for an example.
		966
714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	967	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
715		968
716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	969	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
717	calls into a single call. This is the most convinient method to initialise	970	calls into a single call. This is the most convenient method to initialise
718	a watcher. The same limitations apply, of course.	971	a watcher. The same limitations apply, of course.
		972
		973	Example: Initialise and set an C<ev_io> watcher in one step.
		974
		975	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
719		976
720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	977	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
721		978
722	Starts (activates) the given watcher. Only active watchers will receive	979	Starts (activates) the given watcher. Only active watchers will receive
723	events. If the watcher is already active nothing will happen.	980	events. If the watcher is already active nothing will happen.
724		981
		982	Example: Start the C<ev_io> watcher that is being abused as example in this
		983	whole section.
		984
		985	ev_io_start (EV_DEFAULT_UC, &w);
		986
725	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	987	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
726		988
727	Stops the given watcher again (if active) and clears the pending	989	Stops the given watcher if active, and clears the pending status (whether
		990	the watcher was active or not).
		991
728	status. It is possible that stopped watchers are pending (for example,	992	It is possible that stopped watchers are pending - for example,
729	non-repeating timers are being stopped when they become pending), but	993	non-repeating timers are being stopped when they become pending - but
730	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	994	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
731	you want to free or reuse the memory used by the watcher it is therefore a	995	pending. If you want to free or reuse the memory used by the watcher it is
732	good idea to always call its C<ev_TYPE_stop> function.	996	therefore a good idea to always call its C<ev_TYPE_stop> function.
733		997
734	=item bool ev_is_active (ev_TYPE *watcher)	998	=item bool ev_is_active (ev_TYPE *watcher)
735		999
736	Returns a true value iff the watcher is active (i.e. it has been started	1000	Returns a true value iff the watcher is active (i.e. it has been started
737	and not yet been stopped). As long as a watcher is active you must not modify	1001	and not yet been stopped). As long as a watcher is active you must not modify
…		…
785		1049
786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1050	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
787		1051
788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1052	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
789	C<loop> nor C<revents> need to be valid as long as the watcher callback	1053	C<loop> nor C<revents> need to be valid as long as the watcher callback
790	can deal with that fact.	1054	can deal with that fact, as both are simply passed through to the
		1055	callback.
791		1056
792	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1057	=item int ev_clear_pending (loop, ev_TYPE *watcher)
793		1058
794	If the watcher is pending, this function returns clears its pending status	1059	If the watcher is pending, this function clears its pending status and
795	and returns its C<revents> bitset (as if its callback was invoked). If the	1060	returns its C<revents> bitset (as if its callback was invoked). If the
796	watcher isn't pending it does nothing and returns C<0>.	1061	watcher isn't pending it does nothing and returns C<0>.
797		1062
		1063	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1064	callback to be invoked, which can be accomplished with this function.
		1065
798	=back	1066	=back
799		1067
800		1068
801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1069	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
802		1070
803	Each watcher has, by default, a member C<void *data> that you can change	1071	Each watcher has, by default, a member C<void *data> that you can change
804	and read at any time, libev will completely ignore it. This can be used	1072	and read at any time: libev will completely ignore it. This can be used
805	to associate arbitrary data with your watcher. If you need more data and	1073	to associate arbitrary data with your watcher. If you need more data and
806	don't want to allocate memory and store a pointer to it in that data	1074	don't want to allocate memory and store a pointer to it in that data
807	member, you can also "subclass" the watcher type and provide your own	1075	member, you can also "subclass" the watcher type and provide your own
808	data:	1076	data:
809		1077
810	struct my_io	1078	struct my_io
811	{	1079	{
812	struct ev_io io;	1080	ev_io io;
813	int otherfd;	1081	int otherfd;
814	void *somedata;	1082	void *somedata;
815	struct whatever *mostinteresting;	1083	struct whatever *mostinteresting;
816	}	1084	};
		1085
		1086	...
		1087	struct my_io w;
		1088	ev_io_init (&w.io, my_cb, fd, EV_READ);
817		1089
818	And since your callback will be called with a pointer to the watcher, you	1090	And since your callback will be called with a pointer to the watcher, you
819	can cast it back to your own type:	1091	can cast it back to your own type:
820		1092
821	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
822	{	1094	{
823	struct my_io *w = (struct my_io *)w_;	1095	struct my_io *w = (struct my_io *)w_;
824	...	1096	...
825	}	1097	}
826		1098
827	More interesting and less C-conformant ways of casting your callback type	1099	More interesting and less C-conformant ways of casting your callback type
828	instead have been omitted.	1100	instead have been omitted.
829		1101
830	Another common scenario is having some data structure with multiple	1102	Another common scenario is to use some data structure with multiple
831	watchers:	1103	embedded watchers:
832		1104
833	struct my_biggy	1105	struct my_biggy
834	{	1106	{
835	int some_data;	1107	int some_data;
836	ev_timer t1;	1108	ev_timer t1;
837	ev_timer t2;	1109	ev_timer t2;
838	}	1110	}
839		1111
840	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1112	In this case getting the pointer to C<my_biggy> is a bit more
841	you need to use C<offsetof>:	1113	complicated: Either you store the address of your C<my_biggy> struct
		1114	in the C<data> member of the watcher (for woozies), or you need to use
		1115	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1116	programmers):
842		1117
843	#include <stddef.h>	1118	#include <stddef.h>
844		1119
845	static void	1120	static void
846	t1_cb (EV_P_ struct ev_timer *w, int revents)	1121	t1_cb (EV_P_ ev_timer *w, int revents)
847	{	1122	{
848	struct my_biggy big = (struct my_biggy *	1123	struct my_biggy big = (struct my_biggy *
849	(((char *)w) - offsetof (struct my_biggy, t1));	1124	(((char *)w) - offsetof (struct my_biggy, t1));
850	}	1125	}
851		1126
852	static void	1127	static void
853	t2_cb (EV_P_ struct ev_timer *w, int revents)	1128	t2_cb (EV_P_ ev_timer *w, int revents)
854	{	1129	{
855	struct my_biggy big = (struct my_biggy *	1130	struct my_biggy big = (struct my_biggy *
856	(((char *)w) - offsetof (struct my_biggy, t2));	1131	(((char *)w) - offsetof (struct my_biggy, t2));
857	}	1132	}
858		1133
859		1134
860	=head1 WATCHER TYPES	1135	=head1 WATCHER TYPES
861		1136
862	This section describes each watcher in detail, but will not repeat	1137	This section describes each watcher in detail, but will not repeat
…		…
886	In general you can register as many read and/or write event watchers per	1161	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1162	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1163	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1164	required if you know what you are doing).
890		1165
891	You have to be careful with dup'ed file descriptors, though. Some backends	1166	If you cannot use non-blocking mode, then force the use of a
892	(the linux epoll backend is a notable example) cannot handle dup'ed file	1167	known-to-be-good backend (at the time of this writing, this includes only
893	descriptors correctly if you register interest in two or more fds pointing	1168	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).
900		1169
901	Another thing you have to watch out for is that it is quite easy to	1170	Another thing you have to watch out for is that it is quite easy to
902	receive "spurious" readyness notifications, that is your callback might	1171	receive "spurious" readiness notifications, that is your callback might
903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1172	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
904	because there is no data. Not only are some backends known to create a	1173	because there is no data. Not only are some backends known to create a
905	lot of those (for example solaris ports), it is very easy to get into	1174	lot of those (for example Solaris ports), it is very easy to get into
906	this situation even with a relatively standard program structure. Thus	1175	this situation even with a relatively standard program structure. Thus
907	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1176	it is best to always use non-blocking I/O: An extra C<read>(2) returning
908	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1177	C<EAGAIN> is far preferable to a program hanging until some data arrives.
909		1178
910	If you cannot run the fd in non-blocking mode (for example you should not	1179	If you cannot run the fd in non-blocking mode (for example you should
911	play around with an Xlib connection), then you have to seperately re-test	1180	not play around with an Xlib connection), then you have to separately
912	whether a file descriptor is really ready with a known-to-be good interface	1181	re-test whether a file descriptor is really ready with a known-to-be good
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1182	interface such as poll (fortunately in our Xlib example, Xlib already
914	its own, so its quite safe to use).	1183	does this on its own, so its quite safe to use). Some people additionally
		1184	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1185	indefinitely.
		1186
		1187	But really, best use non-blocking mode.
915		1188
916	=head3 The special problem of disappearing file descriptors	1189	=head3 The special problem of disappearing file descriptors
917		1190
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1191	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1192	descriptor (either due to calling C<close> explicitly or any other means,
920	such as C<dup>). The reason is that you register interest in some file	1193	such as C<dup2>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1194	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1195	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1196	registered with libev, there is no efficient way to see that this is, in
924	fact, a different file descriptor.	1197	fact, a different file descriptor.
925		1198
…		…
932		1205
933	This is how one would do it normally anyway, the important point is that	1206	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1207	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1208	optimisations to libev.
936		1209
		1210	=head3 The special problem of dup'ed file descriptors
		1211
		1212	Some backends (e.g. epoll), cannot register events for file descriptors,
		1213	but only events for the underlying file descriptions. That means when you
		1214	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1215	events for them, only one file descriptor might actually receive events.
		1216
		1217	There is no workaround possible except not registering events
		1218	for potentially C<dup ()>'ed file descriptors, or to resort to
		1219	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of fork
		1222
		1223	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1224	useless behaviour. Libev fully supports fork, but needs to be told about
		1225	it in the child.
		1226
		1227	To support fork in your programs, you either have to call
		1228	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1229	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1230	C<EVBACKEND_POLL>.
		1231
		1232	=head3 The special problem of SIGPIPE
		1233
		1234	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1235	when writing to a pipe whose other end has been closed, your program gets
		1236	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1237	this is sensible behaviour, for daemons, this is usually undesirable.
		1238
		1239	So when you encounter spurious, unexplained daemon exits, make sure you
		1240	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1241	somewhere, as that would have given you a big clue).
		1242
937		1243
938	=head3 Watcher-Specific Functions	1244	=head3 Watcher-Specific Functions
939		1245
940	=over 4	1246	=over 4
941		1247
942	=item ev_io_init (ev_io *, callback, int fd, int events)	1248	=item ev_io_init (ev_io *, callback, int fd, int events)
943		1249
944	=item ev_io_set (ev_io *, int fd, int events)	1250	=item ev_io_set (ev_io *, int fd, int events)
945		1251
946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1252	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1253	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
948	C<EV_READ | EV_WRITE> to receive the given events.	1254	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
949		1255
950	=item int fd [read-only]	1256	=item int fd [read-only]
951		1257
952	The file descriptor being watched.	1258	The file descriptor being watched.
953		1259
954	=item int events [read-only]	1260	=item int events [read-only]
955		1261
956	The events being watched.	1262	The events being watched.
957		1263
958	=back	1264	=back
		1265
		1266	=head3 Examples
959		1267
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1268	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1269	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1270	attempt to read a whole line in the callback.
963		1271
964	static void	1272	static void
965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1273	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
966	{	1274	{
967	ev_io_stop (loop, w);	1275	ev_io_stop (loop, w);
968	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1276	.. read from stdin here (or from w->fd) and handle any I/O errors
969	}	1277	}
970		1278
971	...	1279	...
972	struct ev_loop *loop = ev_default_init (0);	1280	struct ev_loop *loop = ev_default_init (0);
973	struct ev_io stdin_readable;	1281	ev_io stdin_readable;
974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1282	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
975	ev_io_start (loop, &stdin_readable);	1283	ev_io_start (loop, &stdin_readable);
976	ev_loop (loop, 0);	1284	ev_loop (loop, 0);
977		1285
978		1286
979	=head2 C<ev_timer> - relative and optionally repeating timeouts	1287	=head2 C<ev_timer> - relative and optionally repeating timeouts
980		1288
981	Timer watchers are simple relative timers that generate an event after a	1289	Timer watchers are simple relative timers that generate an event after a
982	given time, and optionally repeating in regular intervals after that.	1290	given time, and optionally repeating in regular intervals after that.
983		1291
984	The timers are based on real time, that is, if you register an event that	1292	The timers are based on real time, that is, if you register an event that
985	times out after an hour and you reset your system clock to last years	1293	times out after an hour and you reset your system clock to January last
986	time, it will still time out after (roughly) and hour. "Roughly" because	1294	year, it will still time out after (roughly) one hour. "Roughly" because
987	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1295	detecting time jumps is hard, and some inaccuracies are unavoidable (the
988	monotonic clock option helps a lot here).	1296	monotonic clock option helps a lot here).
		1297
		1298	The callback is guaranteed to be invoked only I<after> its timeout has
		1299	passed, but if multiple timers become ready during the same loop iteration
		1300	then order of execution is undefined.
		1301
		1302	=head3 Be smart about timeouts
		1303
		1304	Many real-world problems involve some kind of timeout, usually for error
		1305	recovery. A typical example is an HTTP request - if the other side hangs,
		1306	you want to raise some error after a while.
		1307
		1308	What follows are some ways to handle this problem, from obvious and
		1309	inefficient to smart and efficient.
		1310
		1311	In the following, a 60 second activity timeout is assumed - a timeout that
		1312	gets reset to 60 seconds each time there is activity (e.g. each time some
		1313	data or other life sign was received).
		1314
		1315	=over 4
		1316
		1317	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1318
		1319	This is the most obvious, but not the most simple way: In the beginning,
		1320	start the watcher:
		1321
		1322	ev_timer_init (timer, callback, 60., 0.);
		1323	ev_timer_start (loop, timer);
		1324
		1325	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1326	and start it again:
		1327
		1328	ev_timer_stop (loop, timer);
		1329	ev_timer_set (timer, 60., 0.);
		1330	ev_timer_start (loop, timer);
		1331
		1332	This is relatively simple to implement, but means that each time there is
		1333	some activity, libev will first have to remove the timer from its internal
		1334	data structure and then add it again. Libev tries to be fast, but it's
		1335	still not a constant-time operation.
		1336
		1337	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1338
		1339	This is the easiest way, and involves using C<ev_timer_again> instead of
		1340	C<ev_timer_start>.
		1341
		1342	To implement this, configure an C<ev_timer> with a C<repeat> value
		1343	of C<60> and then call C<ev_timer_again> at start and each time you
		1344	successfully read or write some data. If you go into an idle state where
		1345	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1346	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1347
		1348	That means you can ignore both the C<ev_timer_start> function and the
		1349	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1350	member and C<ev_timer_again>.
		1351
		1352	At start:
		1353
		1354	ev_timer_init (timer, callback);
		1355	timer->repeat = 60.;
		1356	ev_timer_again (loop, timer);
		1357
		1358	Each time there is some activity:
		1359
		1360	ev_timer_again (loop, timer);
		1361
		1362	It is even possible to change the time-out on the fly, regardless of
		1363	whether the watcher is active or not:
		1364
		1365	timer->repeat = 30.;
		1366	ev_timer_again (loop, timer);
		1367
		1368	This is slightly more efficient then stopping/starting the timer each time
		1369	you want to modify its timeout value, as libev does not have to completely
		1370	remove and re-insert the timer from/into its internal data structure.
		1371
		1372	It is, however, even simpler than the "obvious" way to do it.
		1373
		1374	=item 3. Let the timer time out, but then re-arm it as required.
		1375
		1376	This method is more tricky, but usually most efficient: Most timeouts are
		1377	relatively long compared to the intervals between other activity - in
		1378	our example, within 60 seconds, there are usually many I/O events with
		1379	associated activity resets.
		1380
		1381	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1382	but remember the time of last activity, and check for a real timeout only
		1383	within the callback:
		1384
		1385	ev_tstamp last_activity; // time of last activity
		1386
		1387	static void
		1388	callback (EV_P_ ev_timer *w, int revents)
		1389	{
		1390	ev_tstamp now = ev_now (EV_A);
		1391	ev_tstamp timeout = last_activity + 60.;
		1392
		1393	// if last_activity + 60. is older than now, we did time out
		1394	if (timeout < now)
		1395	{
		1396	// timeout occured, take action
		1397	}
		1398	else
		1399	{
		1400	// callback was invoked, but there was some activity, re-arm
		1401	// the watcher to fire in last_activity + 60, which is
		1402	// guaranteed to be in the future, so "again" is positive:
		1403	w->again = timeout - now;
		1404	ev_timer_again (EV_A_ w);
		1405	}
		1406	}
		1407
		1408	To summarise the callback: first calculate the real timeout (defined
		1409	as "60 seconds after the last activity"), then check if that time has
		1410	been reached, which means something I<did>, in fact, time out. Otherwise
		1411	the callback was invoked too early (C<timeout> is in the future), so
		1412	re-schedule the timer to fire at that future time, to see if maybe we have
		1413	a timeout then.
		1414
		1415	Note how C<ev_timer_again> is used, taking advantage of the
		1416	C<ev_timer_again> optimisation when the timer is already running.
		1417
		1418	This scheme causes more callback invocations (about one every 60 seconds
		1419	minus half the average time between activity), but virtually no calls to
		1420	libev to change the timeout.
		1421
		1422	To start the timer, simply initialise the watcher and set C<last_activity>
		1423	to the current time (meaning we just have some activity :), then call the
		1424	callback, which will "do the right thing" and start the timer:
		1425
		1426	ev_timer_init (timer, callback);
		1427	last_activity = ev_now (loop);
		1428	callback (loop, timer, EV_TIMEOUT);
		1429
		1430	And when there is some activity, simply store the current time in
		1431	C<last_activity>, no libev calls at all:
		1432
		1433	last_actiivty = ev_now (loop);
		1434
		1435	This technique is slightly more complex, but in most cases where the
		1436	time-out is unlikely to be triggered, much more efficient.
		1437
		1438	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1439	callback :) - just change the timeout and invoke the callback, which will
		1440	fix things for you.
		1441
		1442	=item 4. Wee, just use a double-linked list for your timeouts.
		1443
		1444	If there is not one request, but many thousands (millions...), all
		1445	employing some kind of timeout with the same timeout value, then one can
		1446	do even better:
		1447
		1448	When starting the timeout, calculate the timeout value and put the timeout
		1449	at the I<end> of the list.
		1450
		1451	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1452	the list is expected to fire (for example, using the technique #3).
		1453
		1454	When there is some activity, remove the timer from the list, recalculate
		1455	the timeout, append it to the end of the list again, and make sure to
		1456	update the C<ev_timer> if it was taken from the beginning of the list.
		1457
		1458	This way, one can manage an unlimited number of timeouts in O(1) time for
		1459	starting, stopping and updating the timers, at the expense of a major
		1460	complication, and having to use a constant timeout. The constant timeout
		1461	ensures that the list stays sorted.
		1462
		1463	=back
		1464
		1465	So which method the best?
		1466
		1467	Method #2 is a simple no-brain-required solution that is adequate in most
		1468	situations. Method #3 requires a bit more thinking, but handles many cases
		1469	better, and isn't very complicated either. In most case, choosing either
		1470	one is fine, with #3 being better in typical situations.
		1471
		1472	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1473	rather complicated, but extremely efficient, something that really pays
		1474	off after the first million or so of active timers, i.e. it's usually
		1475	overkill :)
		1476
		1477	=head3 The special problem of time updates
		1478
		1479	Establishing the current time is a costly operation (it usually takes at
		1480	least two system calls): EV therefore updates its idea of the current
		1481	time only before and after C<ev_loop> collects new events, which causes a
		1482	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1483	lots of events in one iteration.
989		1484
990	The relative timeouts are calculated relative to the C<ev_now ()>	1485	The relative timeouts are calculated relative to the C<ev_now ()>
991	time. This is usually the right thing as this timestamp refers to the time	1486	time. This is usually the right thing as this timestamp refers to the time
992	of the event triggering whatever timeout you are modifying/starting. If	1487	of the event triggering whatever timeout you are modifying/starting. If
993	you suspect event processing to be delayed and you I<need> to base the timeout	1488	you suspect event processing to be delayed and you I<need> to base the
994	on the current time, use something like this to adjust for this:	1489	timeout on the current time, use something like this to adjust for this:
995		1490
996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1491	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
997		1492
998	The callback is guarenteed to be invoked only when its timeout has passed,	1493	If the event loop is suspended for a long time, you can also force an
999	but if multiple timers become ready during the same loop iteration then	1494	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1000	order of execution is undefined.	1495	()>.
1001		1496
1002	=head3 Watcher-Specific Functions and Data Members	1497	=head3 Watcher-Specific Functions and Data Members
1003		1498
1004	=over 4	1499	=over 4
1005		1500
1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1501	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1007		1502
1008	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1503	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1009		1504
1010	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1505	Configure the timer to trigger after C<after> seconds. If C<repeat>
1011	C<0.>, then it will automatically be stopped. If it is positive, then the	1506	is C<0.>, then it will automatically be stopped once the timeout is
1012	timer will automatically be configured to trigger again C<repeat> seconds	1507	reached. If it is positive, then the timer will automatically be
1013	later, again, and again, until stopped manually.	1508	configured to trigger again C<repeat> seconds later, again, and again,
		1509	until stopped manually.
1014		1510
1015	The timer itself will do a best-effort at avoiding drift, that is, if you	1511	The timer itself will do a best-effort at avoiding drift, that is, if
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1512	you configure a timer to trigger every 10 seconds, then it will normally
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1513	trigger at exactly 10 second intervals. If, however, your program cannot
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1514	keep up with the timer (because it takes longer than those 10 seconds to
1019	timer will not fire more than once per event loop iteration.	1515	do stuff) the timer will not fire more than once per event loop iteration.
1020		1516
1021	=item ev_timer_again (loop)	1517	=item ev_timer_again (loop, ev_timer *)
1022		1518
1023	This will act as if the timer timed out and restart it again if it is	1519	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1520	repeating. The exact semantics are:
1025		1521
1026	If the timer is pending, its pending status is cleared.	1522	If the timer is pending, its pending status is cleared.
1027		1523
1028	If the timer is started but nonrepeating, stop it (as if it timed out).	1524	If the timer is started but non-repeating, stop it (as if it timed out).
1029		1525
1030	If the timer is repeating, either start it if necessary (with the	1526	If the timer is repeating, either start it if necessary (with the
1031	C<repeat> value), or reset the running timer to the C<repeat> value.	1527	C<repeat> value), or reset the running timer to the C<repeat> value.
1032		1528
1033	This sounds a bit complicated, but here is a useful and typical	1529	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1034	example: Imagine you have a tcp connection and you want a so-called idle	1530	usage example.
1035	timeout, that is, you want to be called when there have been, say, 60
1036	seconds of inactivity on the socket. The easiest way to do this is to
1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1038	C<ev_timer_again> each time you successfully read or write some data. If
1039	you go into an idle state where you do not expect data to travel on the
1040	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1041	automatically restart it if need be.
1042
1043	That means you can ignore the C<after> value and C<ev_timer_start>
1044	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1045
1046	ev_timer_init (timer, callback, 0., 5.);
1047	ev_timer_again (loop, timer);
1048	...
1049	timer->again = 17.;
1050	ev_timer_again (loop, timer);
1051	...
1052	timer->again = 10.;
1053	ev_timer_again (loop, timer);
1054
1055	This is more slightly efficient then stopping/starting the timer each time
1056	you want to modify its timeout value.
1057		1531
1058	=item ev_tstamp repeat [read-write]	1532	=item ev_tstamp repeat [read-write]
1059		1533
1060	The current C<repeat> value. Will be used each time the watcher times out	1534	The current C<repeat> value. Will be used each time the watcher times out
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1535	or C<ev_timer_again> is called, and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1536	which is also when any modifications are taken into account.
1063		1537
1064	=back	1538	=back
1065		1539
		1540	=head3 Examples
		1541
1066	Example: Create a timer that fires after 60 seconds.	1542	Example: Create a timer that fires after 60 seconds.
1067		1543
1068	static void	1544	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1545	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1070	{	1546	{
1071	.. one minute over, w is actually stopped right here	1547	.. one minute over, w is actually stopped right here
1072	}	1548	}
1073		1549
1074	struct ev_timer mytimer;	1550	ev_timer mytimer;
1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1551	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1076	ev_timer_start (loop, &mytimer);	1552	ev_timer_start (loop, &mytimer);
1077		1553
1078	Example: Create a timeout timer that times out after 10 seconds of	1554	Example: Create a timeout timer that times out after 10 seconds of
1079	inactivity.	1555	inactivity.
1080		1556
1081	static void	1557	static void
1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1558	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1083	{	1559	{
1084	.. ten seconds without any activity	1560	.. ten seconds without any activity
1085	}	1561	}
1086		1562
1087	struct ev_timer mytimer;	1563	ev_timer mytimer;
1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1564	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1089	ev_timer_again (&mytimer); /* start timer */	1565	ev_timer_again (&mytimer); /* start timer */
1090	ev_loop (loop, 0);	1566	ev_loop (loop, 0);
1091		1567
1092	// and in some piece of code that gets executed on any "activity":	1568	// and in some piece of code that gets executed on any "activity":
1093	// reset the timeout to start ticking again at 10 seconds	1569	// reset the timeout to start ticking again at 10 seconds
1094	ev_timer_again (&mytimer);	1570	ev_timer_again (&mytimer);
1095		1571
1096		1572
1097	=head2 C<ev_periodic> - to cron or not to cron?	1573	=head2 C<ev_periodic> - to cron or not to cron?
1098		1574
1099	Periodic watchers are also timers of a kind, but they are very versatile	1575	Periodic watchers are also timers of a kind, but they are very versatile
1100	(and unfortunately a bit complex).	1576	(and unfortunately a bit complex).
1101		1577
1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1578	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1103	but on wallclock time (absolute time). You can tell a periodic watcher	1579	but on wall clock time (absolute time). You can tell a periodic watcher
1104	to trigger "at" some specific point in time. For example, if you tell a	1580	to trigger after some specific point in time. For example, if you tell a
1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1581	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1106	+ 10.>) and then reset your system clock to the last year, then it will	1582	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1583	clock to January of the previous year, then it will take more than year
1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1584	to trigger the event (unlike an C<ev_timer>, which would still trigger
1108	roughly 10 seconds later).	1585	roughly 10 seconds later as it uses a relative timeout).
1109		1586
1110	They can also be used to implement vastly more complex timers, such as	1587	C<ev_periodic>s can also be used to implement vastly more complex timers,
1111	triggering an event on each midnight, local time or other, complicated,	1588	such as triggering an event on each "midnight, local time", or other
1112	rules.	1589	complicated rules.
1113		1590
1114	As with timers, the callback is guarenteed to be invoked only when the	1591	As with timers, the callback is guaranteed to be invoked only when the
1115	time (C<at>) has been passed, but if multiple periodic timers become ready	1592	time (C<at>) has passed, but if multiple periodic timers become ready
1116	during the same loop iteration then order of execution is undefined.	1593	during the same loop iteration, then order of execution is undefined.
1117		1594
1118	=head3 Watcher-Specific Functions and Data Members	1595	=head3 Watcher-Specific Functions and Data Members
1119		1596
1120	=over 4	1597	=over 4
1121		1598
1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1599	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1123		1600
1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1601	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1125		1602
1126	Lots of arguments, lets sort it out... There are basically three modes of	1603	Lots of arguments, lets sort it out... There are basically three modes of
1127	operation, and we will explain them from simplest to complex:	1604	operation, and we will explain them from simplest to most complex:
1128		1605
1129	=over 4	1606	=over 4
1130		1607
1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1608	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1132		1609
1133	In this configuration the watcher triggers an event at the wallclock time	1610	In this configuration the watcher triggers an event after the wall clock
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1611	time C<at> has passed. It will not repeat and will not adjust when a time
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1612	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1136	system time reaches or surpasses this time.	1613	only run when the system clock reaches or surpasses this time.
1137		1614
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1615	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1616
1140	In this mode the watcher will always be scheduled to time out at the next	1617	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1618	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1619	and then repeat, regardless of any time jumps.
1143		1620
1144	This can be used to create timers that do not drift with respect to system	1621	This can be used to create timers that do not drift with respect to the
1145	time:	1622	system clock, for example, here is a C<ev_periodic> that triggers each
		1623	hour, on the hour:
1146		1624
1147	ev_periodic_set (&periodic, 0., 3600., 0);	1625	ev_periodic_set (&periodic, 0., 3600., 0);
1148		1626
1149	This doesn't mean there will always be 3600 seconds in between triggers,	1627	This doesn't mean there will always be 3600 seconds in between triggers,
1150	but only that the the callback will be called when the system time shows a	1628	but only that the callback will be called when the system time shows a
1151	full hour (UTC), or more correctly, when the system time is evenly divisible	1629	full hour (UTC), or more correctly, when the system time is evenly divisible
1152	by 3600.	1630	by 3600.
1153		1631
1154	Another way to think about it (for the mathematically inclined) is that	1632	Another way to think about it (for the mathematically inclined) is that
1155	C<ev_periodic> will try to run the callback in this mode at the next possible	1633	C<ev_periodic> will try to run the callback in this mode at the next possible
1156	time where C<time = at (mod interval)>, regardless of any time jumps.	1634	time where C<time = at (mod interval)>, regardless of any time jumps.
1157		1635
1158	For numerical stability it is preferable that the C<at> value is near	1636	For numerical stability it is preferable that the C<at> value is near
1159	C<ev_now ()> (the current time), but there is no range requirement for	1637	C<ev_now ()> (the current time), but there is no range requirement for
1160	this value.	1638	this value, and in fact is often specified as zero.
		1639
		1640	Note also that there is an upper limit to how often a timer can fire (CPU
		1641	speed for example), so if C<interval> is very small then timing stability
		1642	will of course deteriorate. Libev itself tries to be exact to be about one
		1643	millisecond (if the OS supports it and the machine is fast enough).
1161		1644
1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1645	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1163		1646
1164	In this mode the values for C<interval> and C<at> are both being	1647	In this mode the values for C<interval> and C<at> are both being
1165	ignored. Instead, each time the periodic watcher gets scheduled, the	1648	ignored. Instead, each time the periodic watcher gets scheduled, the
1166	reschedule callback will be called with the watcher as first, and the	1649	reschedule callback will be called with the watcher as first, and the
1167	current time as second argument.	1650	current time as second argument.
1168		1651
1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1652	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1170	ever, or make any event loop modifications>. If you need to stop it,	1653	ever, or make ANY event loop modifications whatsoever>.
1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1172	starting an C<ev_prepare> watcher, which is legal).
1173		1654
		1655	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1656	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1657	only event loop modification you are allowed to do).
		1658
1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1659	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1175	ev_tstamp now)>, e.g.:	1660	*w, ev_tstamp now)>, e.g.:
1176		1661
		1662	static ev_tstamp
1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1663	my_rescheduler (ev_periodic *w, ev_tstamp now)
1178	{	1664	{
1179	return now + 60.;	1665	return now + 60.;
1180	}	1666	}
1181		1667
1182	It must return the next time to trigger, based on the passed time value	1668	It must return the next time to trigger, based on the passed time value
1183	(that is, the lowest time value larger than to the second argument). It	1669	(that is, the lowest time value larger than to the second argument). It
1184	will usually be called just before the callback will be triggered, but	1670	will usually be called just before the callback will be triggered, but
1185	might be called at other times, too.	1671	might be called at other times, too.
1186		1672
1187	NOTE: I<< This callback must always return a time that is later than the	1673	NOTE: I<< This callback must always return a time that is higher than or
1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1674	equal to the passed C<now> value >>.
1189		1675
1190	This can be used to create very complex timers, such as a timer that	1676	This can be used to create very complex timers, such as a timer that
1191	triggers on each midnight, local time. To do this, you would calculate the	1677	triggers on "next midnight, local time". To do this, you would calculate the
1192	next midnight after C<now> and return the timestamp value for this. How	1678	next midnight after C<now> and return the timestamp value for this. How
1193	you do this is, again, up to you (but it is not trivial, which is the main	1679	you do this is, again, up to you (but it is not trivial, which is the main
1194	reason I omitted it as an example).	1680	reason I omitted it as an example).
1195		1681
1196	=back	1682	=back
…		…
1200	Simply stops and restarts the periodic watcher again. This is only useful	1686	Simply stops and restarts the periodic watcher again. This is only useful
1201	when you changed some parameters or the reschedule callback would return	1687	when you changed some parameters or the reschedule callback would return
1202	a different time than the last time it was called (e.g. in a crond like	1688	a different time than the last time it was called (e.g. in a crond like
1203	program when the crontabs have changed).	1689	program when the crontabs have changed).
1204		1690
		1691	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1692
		1693	When active, returns the absolute time that the watcher is supposed to
		1694	trigger next.
		1695
1205	=item ev_tstamp offset [read-write]	1696	=item ev_tstamp offset [read-write]
1206		1697
1207	When repeating, this contains the offset value, otherwise this is the	1698	When repeating, this contains the offset value, otherwise this is the
1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1699	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209		1700
…		…
1214		1705
1215	The current interval value. Can be modified any time, but changes only	1706	The current interval value. Can be modified any time, but changes only
1216	take effect when the periodic timer fires or C<ev_periodic_again> is being	1707	take effect when the periodic timer fires or C<ev_periodic_again> is being
1217	called.	1708	called.
1218		1709
1219	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1710	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1220		1711
1221	The current reschedule callback, or C<0>, if this functionality is	1712	The current reschedule callback, or C<0>, if this functionality is
1222	switched off. Can be changed any time, but changes only take effect when	1713	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1714	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1715
1225	=back	1716	=back
1226		1717
		1718	=head3 Examples
		1719
1227	Example: Call a callback every hour, or, more precisely, whenever the	1720	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1721	system time is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1722	potentially a lot of jitter, but good long-term stability.
1230		1723
1231	static void	1724	static void
1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1725	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1233	{	1726	{
1234	... its now a full hour (UTC, or TAI or whatever your clock follows)	1727	... its now a full hour (UTC, or TAI or whatever your clock follows)
1235	}	1728	}
1236		1729
1237	struct ev_periodic hourly_tick;	1730	ev_periodic hourly_tick;
1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1731	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1239	ev_periodic_start (loop, &hourly_tick);	1732	ev_periodic_start (loop, &hourly_tick);
1240		1733
1241	Example: The same as above, but use a reschedule callback to do it:	1734	Example: The same as above, but use a reschedule callback to do it:
1242		1735
1243	#include <math.h>	1736	#include <math.h>
1244		1737
1245	static ev_tstamp	1738	static ev_tstamp
1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1739	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1247	{	1740	{
1248	return fmod (now, 3600.) + 3600.;	1741	return now + (3600. - fmod (now, 3600.));
1249	}	1742	}
1250		1743
1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1744	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1252		1745
1253	Example: Call a callback every hour, starting now:	1746	Example: Call a callback every hour, starting now:
1254		1747
1255	struct ev_periodic hourly_tick;	1748	ev_periodic hourly_tick;
1256	ev_periodic_init (&hourly_tick, clock_cb,	1749	ev_periodic_init (&hourly_tick, clock_cb,
1257	fmod (ev_now (loop), 3600.), 3600., 0);	1750	fmod (ev_now (loop), 3600.), 3600., 0);
1258	ev_periodic_start (loop, &hourly_tick);	1751	ev_periodic_start (loop, &hourly_tick);
1259		1752
1260		1753
1261	=head2 C<ev_signal> - signal me when a signal gets signalled!	1754	=head2 C<ev_signal> - signal me when a signal gets signalled!
1262		1755
1263	Signal watchers will trigger an event when the process receives a specific	1756	Signal watchers will trigger an event when the process receives a specific
1264	signal one or more times. Even though signals are very asynchronous, libev	1757	signal one or more times. Even though signals are very asynchronous, libev
1265	will try it's best to deliver signals synchronously, i.e. as part of the	1758	will try it's best to deliver signals synchronously, i.e. as part of the
1266	normal event processing, like any other event.	1759	normal event processing, like any other event.
1267		1760
		1761	If you want signals asynchronously, just use C<sigaction> as you would
		1762	do without libev and forget about sharing the signal. You can even use
		1763	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1764
1268	You can configure as many watchers as you like per signal. Only when the	1765	You can configure as many watchers as you like per signal. Only when the
1269	first watcher gets started will libev actually register a signal watcher	1766	first watcher gets started will libev actually register a signal handler
1270	with the kernel (thus it coexists with your own signal handlers as long	1767	with the kernel (thus it coexists with your own signal handlers as long as
1271	as you don't register any with libev). Similarly, when the last signal	1768	you don't register any with libev for the same signal). Similarly, when
1272	watcher for a signal is stopped libev will reset the signal handler to	1769	the last signal watcher for a signal is stopped, libev will reset the
1273	SIG_DFL (regardless of what it was set to before).	1770	signal handler to SIG_DFL (regardless of what it was set to before).
		1771
		1772	If possible and supported, libev will install its handlers with
		1773	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1774	interrupted. If you have a problem with system calls getting interrupted by
		1775	signals you can block all signals in an C<ev_check> watcher and unblock
		1776	them in an C<ev_prepare> watcher.
1274		1777
1275	=head3 Watcher-Specific Functions and Data Members	1778	=head3 Watcher-Specific Functions and Data Members
1276		1779
1277	=over 4	1780	=over 4
1278		1781
…		…
1287		1790
1288	The signal the watcher watches out for.	1791	The signal the watcher watches out for.
1289		1792
1290	=back	1793	=back
1291		1794
		1795	=head3 Examples
		1796
		1797	Example: Try to exit cleanly on SIGINT.
		1798
		1799	static void
		1800	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1801	{
		1802	ev_unloop (loop, EVUNLOOP_ALL);
		1803	}
		1804
		1805	ev_signal signal_watcher;
		1806	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1807	ev_signal_start (loop, &signal_watcher);
		1808
1292		1809
1293	=head2 C<ev_child> - watch out for process status changes	1810	=head2 C<ev_child> - watch out for process status changes
1294		1811
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1812	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1813	some child status changes (most typically when a child of yours dies or
		1814	exits). It is permissible to install a child watcher I<after> the child
		1815	has been forked (which implies it might have already exited), as long
		1816	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1817	forking and then immediately registering a watcher for the child is fine,
		1818	but forking and registering a watcher a few event loop iterations later is
		1819	not.
		1820
		1821	Only the default event loop is capable of handling signals, and therefore
		1822	you can only register child watchers in the default event loop.
		1823
		1824	=head3 Process Interaction
		1825
		1826	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1827	initialised. This is necessary to guarantee proper behaviour even if
		1828	the first child watcher is started after the child exits. The occurrence
		1829	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1830	synchronously as part of the event loop processing. Libev always reaps all
		1831	children, even ones not watched.
		1832
		1833	=head3 Overriding the Built-In Processing
		1834
		1835	Libev offers no special support for overriding the built-in child
		1836	processing, but if your application collides with libev's default child
		1837	handler, you can override it easily by installing your own handler for
		1838	C<SIGCHLD> after initialising the default loop, and making sure the
		1839	default loop never gets destroyed. You are encouraged, however, to use an
		1840	event-based approach to child reaping and thus use libev's support for
		1841	that, so other libev users can use C<ev_child> watchers freely.
		1842
		1843	=head3 Stopping the Child Watcher
		1844
		1845	Currently, the child watcher never gets stopped, even when the
		1846	child terminates, so normally one needs to stop the watcher in the
		1847	callback. Future versions of libev might stop the watcher automatically
		1848	when a child exit is detected.
1297		1849
1298	=head3 Watcher-Specific Functions and Data Members	1850	=head3 Watcher-Specific Functions and Data Members
1299		1851
1300	=over 4	1852	=over 4
1301		1853
1302	=item ev_child_init (ev_child *, callback, int pid)	1854	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1855
1304	=item ev_child_set (ev_child *, int pid)	1856	=item ev_child_set (ev_child *, int pid, int trace)
1305		1857
1306	Configures the watcher to wait for status changes of process C<pid> (or	1858	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1859	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1860	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1861	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1862	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1863	process causing the status change. C<trace> must be either C<0> (only
		1864	activate the watcher when the process terminates) or C<1> (additionally
		1865	activate the watcher when the process is stopped or continued).
1312		1866
1313	=item int pid [read-only]	1867	=item int pid [read-only]
1314		1868
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1869	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1870
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1877	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1878	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1879
1326	=back	1880	=back
1327		1881
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1882	=head3 Examples
1329		1883
		1884	Example: C<fork()> a new process and install a child handler to wait for
		1885	its completion.
		1886
		1887	ev_child cw;
		1888
1330	static void	1889	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1890	child_cb (EV_P_ ev_child *w, int revents)
1332	{	1891	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1892	ev_child_stop (EV_A_ w);
		1893	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1894	}
1335		1895
1336	struct ev_signal signal_watcher;	1896	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1897
1338	ev_signal_start (loop, &sigint_cb);	1898	if (pid < 0)
		1899	// error
		1900	else if (pid == 0)
		1901	{
		1902	// the forked child executes here
		1903	exit (1);
		1904	}
		1905	else
		1906	{
		1907	ev_child_init (&cw, child_cb, pid, 0);
		1908	ev_child_start (EV_DEFAULT_ &cw);
		1909	}
1339		1910
1340		1911
1341	=head2 C<ev_stat> - did the file attributes just change?	1912	=head2 C<ev_stat> - did the file attributes just change?
1342		1913
1343	This watches a filesystem path for attribute changes. That is, it calls	1914	This watches a file system path for attribute changes. That is, it calls
1344	C<stat> regularly (or when the OS says it changed) and sees if it changed	1915	C<stat> regularly (or when the OS says it changed) and sees if it changed
1345	compared to the last time, invoking the callback if it did.	1916	compared to the last time, invoking the callback if it did.
1346		1917
1347	The path does not need to exist: changing from "path exists" to "path does	1918	The path does not need to exist: changing from "path exists" to "path does
1348	not exist" is a status change like any other. The condition "path does	1919	not exist" is a status change like any other. The condition "path does
…		…
1351	the stat buffer having unspecified contents.	1922	the stat buffer having unspecified contents.
1352		1923
1353	The path I<should> be absolute and I<must not> end in a slash. If it is	1924	The path I<should> be absolute and I<must not> end in a slash. If it is
1354	relative and your working directory changes, the behaviour is undefined.	1925	relative and your working directory changes, the behaviour is undefined.
1355		1926
1356	Since there is no standard to do this, the portable implementation simply	1927	Since there is no standard kernel interface to do this, the portable
1357	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1928	implementation simply calls C<stat (2)> regularly on the path to see if
1358	can specify a recommended polling interval for this case. If you specify	1929	it changed somehow. You can specify a recommended polling interval for
1359	a polling interval of C<0> (highly recommended!) then a I<suitable,	1930	this case. If you specify a polling interval of C<0> (highly recommended!)
1360	unspecified default> value will be used (which you can expect to be around	1931	then a I<suitable, unspecified default> value will be used (which
1361	five seconds, although this might change dynamically). Libev will also	1932	you can expect to be around five seconds, although this might change
1362	impose a minimum interval which is currently around C<0.1>, but thats	1933	dynamically). Libev will also impose a minimum interval which is currently
1363	usually overkill.	1934	around C<0.1>, but thats usually overkill.
1364		1935
1365	This watcher type is not meant for massive numbers of stat watchers,	1936	This watcher type is not meant for massive numbers of stat watchers,
1366	as even with OS-supported change notifications, this can be	1937	as even with OS-supported change notifications, this can be
1367	resource-intensive.	1938	resource-intensive.
1368		1939
1369	At the time of this writing, only the Linux inotify interface is	1940	At the time of this writing, the only OS-specific interface implemented
1370	implemented (implementing kqueue support is left as an exercise for the	1941	is the Linux inotify interface (implementing kqueue support is left as
1371	reader). Inotify will be used to give hints only and should not change the	1942	an exercise for the reader. Note, however, that the author sees no way
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1943	of implementing C<ev_stat> semantics with kqueue).
1373	to fall back to regular polling again even with inotify, but changes are	1944
1374	usually detected immediately, and if the file exists there will be no	1945	=head3 ABI Issues (Largefile Support)
1375	polling.	1946
		1947	Libev by default (unless the user overrides this) uses the default
		1948	compilation environment, which means that on systems with large file
		1949	support disabled by default, you get the 32 bit version of the stat
		1950	structure. When using the library from programs that change the ABI to
		1951	use 64 bit file offsets the programs will fail. In that case you have to
		1952	compile libev with the same flags to get binary compatibility. This is
		1953	obviously the case with any flags that change the ABI, but the problem is
		1954	most noticeably disabled with ev_stat and large file support.
		1955
		1956	The solution for this is to lobby your distribution maker to make large
		1957	file interfaces available by default (as e.g. FreeBSD does) and not
		1958	optional. Libev cannot simply switch on large file support because it has
		1959	to exchange stat structures with application programs compiled using the
		1960	default compilation environment.
		1961
		1962	=head3 Inotify and Kqueue
		1963
		1964	When C<inotify (7)> support has been compiled into libev (generally
		1965	only available with Linux 2.6.25 or above due to bugs in earlier
		1966	implementations) and present at runtime, it will be used to speed up
		1967	change detection where possible. The inotify descriptor will be created
		1968	lazily when the first C<ev_stat> watcher is being started.
		1969
		1970	Inotify presence does not change the semantics of C<ev_stat> watchers
		1971	except that changes might be detected earlier, and in some cases, to avoid
		1972	making regular C<stat> calls. Even in the presence of inotify support
		1973	there are many cases where libev has to resort to regular C<stat> polling,
		1974	but as long as the path exists, libev usually gets away without polling.
		1975
		1976	There is no support for kqueue, as apparently it cannot be used to
		1977	implement this functionality, due to the requirement of having a file
		1978	descriptor open on the object at all times, and detecting renames, unlinks
		1979	etc. is difficult.
		1980
		1981	=head3 The special problem of stat time resolution
		1982
		1983	The C<stat ()> system call only supports full-second resolution portably, and
		1984	even on systems where the resolution is higher, most file systems still
		1985	only support whole seconds.
		1986
		1987	That means that, if the time is the only thing that changes, you can
		1988	easily miss updates: on the first update, C<ev_stat> detects a change and
		1989	calls your callback, which does something. When there is another update
		1990	within the same second, C<ev_stat> will be unable to detect unless the
		1991	stat data does change in other ways (e.g. file size).
		1992
		1993	The solution to this is to delay acting on a change for slightly more
		1994	than a second (or till slightly after the next full second boundary), using
		1995	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1996	ev_timer_again (loop, w)>).
		1997
		1998	The C<.02> offset is added to work around small timing inconsistencies
		1999	of some operating systems (where the second counter of the current time
		2000	might be be delayed. One such system is the Linux kernel, where a call to
		2001	C<gettimeofday> might return a timestamp with a full second later than
		2002	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2003	update file times then there will be a small window where the kernel uses
		2004	the previous second to update file times but libev might already execute
		2005	the timer callback).
1376		2006
1377	=head3 Watcher-Specific Functions and Data Members	2007	=head3 Watcher-Specific Functions and Data Members
1378		2008
1379	=over 4	2009	=over 4
1380		2010
…		…
1386	C<path>. The C<interval> is a hint on how quickly a change is expected to	2016	C<path>. The C<interval> is a hint on how quickly a change is expected to
1387	be detected and should normally be specified as C<0> to let libev choose	2017	be detected and should normally be specified as C<0> to let libev choose
1388	a suitable value. The memory pointed to by C<path> must point to the same	2018	a suitable value. The memory pointed to by C<path> must point to the same
1389	path for as long as the watcher is active.	2019	path for as long as the watcher is active.
1390		2020
1391	The callback will be receive C<EV_STAT> when a change was detected,	2021	The callback will receive an C<EV_STAT> event when a change was detected,
1392	relative to the attributes at the time the watcher was started (or the	2022	relative to the attributes at the time the watcher was started (or the
1393	last change was detected).	2023	last change was detected).
1394		2024
1395	=item ev_stat_stat (ev_stat *)	2025	=item ev_stat_stat (loop, ev_stat *)
1396		2026
1397	Updates the stat buffer immediately with new values. If you change the	2027	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	2028	watched path in your callback, you could call this function to avoid
1399	detecting this change (while introducing a race condition). Can also be	2029	detecting this change (while introducing a race condition if you are not
1400	useful simply to find out the new values.	2030	the only one changing the path). Can also be useful simply to find out the
		2031	new values.
1401		2032
1402	=item ev_statdata attr [read-only]	2033	=item ev_statdata attr [read-only]
1403		2034
1404	The most-recently detected attributes of the file. Although the type is of	2035	The most-recently detected attributes of the file. Although the type is
1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2036	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1406	suitable for your system. If the C<st_nlink> member is C<0>, then there	2037	suitable for your system, but you can only rely on the POSIX-standardised
		2038	members to be present. If the C<st_nlink> member is C<0>, then there was
1407	was some error while C<stat>ing the file.	2039	some error while C<stat>ing the file.
1408		2040
1409	=item ev_statdata prev [read-only]	2041	=item ev_statdata prev [read-only]
1410		2042
1411	The previous attributes of the file. The callback gets invoked whenever	2043	The previous attributes of the file. The callback gets invoked whenever
1412	C<prev> != C<attr>.	2044	C<prev> != C<attr>, or, more precisely, one or more of these members
		2045	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2046	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1413		2047
1414	=item ev_tstamp interval [read-only]	2048	=item ev_tstamp interval [read-only]
1415		2049
1416	The specified interval.	2050	The specified interval.
1417		2051
1418	=item const char *path [read-only]	2052	=item const char *path [read-only]
1419		2053
1420	The filesystem path that is being watched.	2054	The file system path that is being watched.
1421		2055
1422	=back	2056	=back
1423		2057
		2058	=head3 Examples
		2059
1424	Example: Watch C</etc/passwd> for attribute changes.	2060	Example: Watch C</etc/passwd> for attribute changes.
1425		2061
1426	static void	2062	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2063	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1428	{	2064	{
1429	/* /etc/passwd changed in some way */	2065	/* /etc/passwd changed in some way */
1430	if (w->attr.st_nlink)	2066	if (w->attr.st_nlink)
1431	{	2067	{
1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2068	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2069	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2070	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1435	}	2071	}
1436	else	2072	else
1437	/* you shalt not abuse printf for puts */	2073	/* you shalt not abuse printf for puts */
1438	puts ("wow, /etc/passwd is not there, expect problems. "	2074	puts ("wow, /etc/passwd is not there, expect problems. "
1439	"if this is windows, they already arrived\n");	2075	"if this is windows, they already arrived\n");
1440	}	2076	}
1441		2077
1442	...	2078	...
1443	ev_stat passwd;	2079	ev_stat passwd;
1444		2080
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2081	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	2082	ev_stat_start (loop, &passwd);
		2083
		2084	Example: Like above, but additionally use a one-second delay so we do not
		2085	miss updates (however, frequent updates will delay processing, too, so
		2086	one might do the work both on C<ev_stat> callback invocation I<and> on
		2087	C<ev_timer> callback invocation).
		2088
		2089	static ev_stat passwd;
		2090	static ev_timer timer;
		2091
		2092	static void
		2093	timer_cb (EV_P_ ev_timer *w, int revents)
		2094	{
		2095	ev_timer_stop (EV_A_ w);
		2096
		2097	/* now it's one second after the most recent passwd change */
		2098	}
		2099
		2100	static void
		2101	stat_cb (EV_P_ ev_stat *w, int revents)
		2102	{
		2103	/* reset the one-second timer */
		2104	ev_timer_again (EV_A_ &timer);
		2105	}
		2106
		2107	...
		2108	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2109	ev_stat_start (loop, &passwd);
		2110	ev_timer_init (&timer, timer_cb, 0., 1.02);
1447		2111
1448		2112
1449	=head2 C<ev_idle> - when you've got nothing better to do...	2113	=head2 C<ev_idle> - when you've got nothing better to do...
1450		2114
1451	Idle watchers trigger events when no other events of the same or higher	2115	Idle watchers trigger events when no other events of the same or higher
1452	priority are pending (prepare, check and other idle watchers do not	2116	priority are pending (prepare, check and other idle watchers do not count
1453	count).	2117	as receiving "events").
1454		2118
1455	That is, as long as your process is busy handling sockets or timeouts	2119	That is, as long as your process is busy handling sockets or timeouts
1456	(or even signals, imagine) of the same or higher priority it will not be	2120	(or even signals, imagine) of the same or higher priority it will not be
1457	triggered. But when your process is idle (or only lower-priority watchers	2121	triggered. But when your process is idle (or only lower-priority watchers
1458	are pending), the idle watchers are being called once per event loop	2122	are pending), the idle watchers are being called once per event loop
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2141	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	2142	believe me.
1479		2143
1480	=back	2144	=back
1481		2145
		2146	=head3 Examples
		2147
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2148	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	2149	callback, free it. Also, use no error checking, as usual.
1484		2150
1485	static void	2151	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2152	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1487	{	2153	{
1488	free (w);	2154	free (w);
1489	// now do something you wanted to do when the program has	2155	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	2156	// no longer anything immediate to do.
1491	}	2157	}
1492		2158
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2159	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	2160	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	2161	ev_idle_start (loop, idle_cb);
1496		2162
1497		2163
1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2164	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1499		2165
1500	Prepare and check watchers are usually (but not always) used in tandem:	2166	Prepare and check watchers are usually (but not always) used in pairs:
1501	prepare watchers get invoked before the process blocks and check watchers	2167	prepare watchers get invoked before the process blocks and check watchers
1502	afterwards.	2168	afterwards.
1503		2169
1504	You I<must not> call C<ev_loop> or similar functions that enter	2170	You I<must not> call C<ev_loop> or similar functions that enter
1505	the current event loop from either C<ev_prepare> or C<ev_check>	2171	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1508	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2174	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1509	C<ev_check> so if you have one watcher of each kind they will always be	2175	C<ev_check> so if you have one watcher of each kind they will always be
1510	called in pairs bracketing the blocking call.	2176	called in pairs bracketing the blocking call.
1511		2177
1512	Their main purpose is to integrate other event mechanisms into libev and	2178	Their main purpose is to integrate other event mechanisms into libev and
1513	their use is somewhat advanced. This could be used, for example, to track	2179	their use is somewhat advanced. They could be used, for example, to track
1514	variable changes, implement your own watchers, integrate net-snmp or a	2180	variable changes, implement your own watchers, integrate net-snmp or a
1515	coroutine library and lots more. They are also occasionally useful if	2181	coroutine library and lots more. They are also occasionally useful if
1516	you cache some data and want to flush it before blocking (for example,	2182	you cache some data and want to flush it before blocking (for example,
1517	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2183	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1518	watcher).	2184	watcher).
1519		2185
1520	This is done by examining in each prepare call which file descriptors need	2186	This is done by examining in each prepare call which file descriptors
1521	to be watched by the other library, registering C<ev_io> watchers for	2187	need to be watched by the other library, registering C<ev_io> watchers
1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2188	for them and starting an C<ev_timer> watcher for any timeouts (many
1523	provide just this functionality). Then, in the check watcher you check for	2189	libraries provide exactly this functionality). Then, in the check watcher,
1524	any events that occured (by checking the pending status of all watchers	2190	you check for any events that occurred (by checking the pending status
1525	and stopping them) and call back into the library. The I/O and timer	2191	of all watchers and stopping them) and call back into the library. The
1526	callbacks will never actually be called (but must be valid nevertheless,	2192	I/O and timer callbacks will never actually be called (but must be valid
1527	because you never know, you know?).	2193	nevertheless, because you never know, you know?).
1528		2194
1529	As another example, the Perl Coro module uses these hooks to integrate	2195	As another example, the Perl Coro module uses these hooks to integrate
1530	coroutines into libev programs, by yielding to other active coroutines	2196	coroutines into libev programs, by yielding to other active coroutines
1531	during each prepare and only letting the process block if no coroutines	2197	during each prepare and only letting the process block if no coroutines
1532	are ready to run (it's actually more complicated: it only runs coroutines	2198	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1535	loop from blocking if lower-priority coroutines are active, thus mapping	2201	loop from blocking if lower-priority coroutines are active, thus mapping
1536	low-priority coroutines to idle/background tasks).	2202	low-priority coroutines to idle/background tasks).
1537		2203
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2204	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	2205	priority, to ensure that they are being run before any other watchers
		2206	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2207
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2208	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1541	too) should not activate ("feed") events into libev. While libev fully	2209	activate ("feed") events into libev. While libev fully supports this, they
1542	supports this, they will be called before other C<ev_check> watchers did	2210	might get executed before other C<ev_check> watchers did their job. As
1543	their job. As C<ev_check> watchers are often used to embed other event	2211	C<ev_check> watchers are often used to embed other (non-libev) event
1544	loops those other event loops might be in an unusable state until their	2212	loops those other event loops might be in an unusable state until their
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2213	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1546	others).	2214	others).
1547		2215
1548	=head3 Watcher-Specific Functions and Data Members	2216	=head3 Watcher-Specific Functions and Data Members
…		…
1553		2221
1554	=item ev_check_init (ev_check *, callback)	2222	=item ev_check_init (ev_check *, callback)
1555		2223
1556	Initialises and configures the prepare or check watcher - they have no	2224	Initialises and configures the prepare or check watcher - they have no
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2225	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	2226	macros, but using them is utterly, utterly, utterly and completely
		2227	pointless.
1559		2228
1560	=back	2229	=back
		2230
		2231	=head3 Examples
1561		2232
1562	There are a number of principal ways to embed other event loops or modules	2233	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	2234	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	2235	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	2236	use as a working example. Another Perl module named C<EV::Glib> embeds a
1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2237	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1567	into the Glib event loop).	2238	Glib event loop).
1568		2239
1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2240	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1570	and in a check watcher, destroy them and call into libadns. What follows	2241	and in a check watcher, destroy them and call into libadns. What follows
1571	is pseudo-code only of course. This requires you to either use a low	2242	is pseudo-code only of course. This requires you to either use a low
1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2243	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573	the callbacks for the IO/timeout watchers might not have been called yet.	2244	the callbacks for the IO/timeout watchers might not have been called yet.
1574		2245
1575	static ev_io iow [nfd];	2246	static ev_io iow [nfd];
1576	static ev_timer tw;	2247	static ev_timer tw;
1577		2248
1578	static void	2249	static void
1579	io_cb (ev_loop *loop, ev_io *w, int revents)	2250	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1580	{	2251	{
1581	}	2252	}
1582		2253
1583	// create io watchers for each fd and a timer before blocking	2254	// create io watchers for each fd and a timer before blocking
1584	static void	2255	static void
1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2256	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1586	{	2257	{
1587	int timeout = 3600000;	2258	int timeout = 3600000;
1588	struct pollfd fds [nfd];	2259	struct pollfd fds [nfd];
1589	// actual code will need to loop here and realloc etc.	2260	// actual code will need to loop here and realloc etc.
1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2261	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1591		2262
1592	/* the callback is illegal, but won't be called as we stop during check */	2263	/* the callback is illegal, but won't be called as we stop during check */
1593	ev_timer_init (&tw, 0, timeout * 1e-3);	2264	ev_timer_init (&tw, 0, timeout * 1e-3);
1594	ev_timer_start (loop, &tw);	2265	ev_timer_start (loop, &tw);
1595		2266
1596	// create one ev_io per pollfd	2267	// create one ev_io per pollfd
1597	for (int i = 0; i < nfd; ++i)	2268	for (int i = 0; i < nfd; ++i)
1598	{	2269	{
1599	ev_io_init (iow + i, io_cb, fds [i].fd,	2270	ev_io_init (iow + i, io_cb, fds [i].fd,
1600	((fds [i].events & POLLIN ? EV_READ : 0)	2271	((fds [i].events & POLLIN ? EV_READ : 0)
1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2272	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1602		2273
1603	fds [i].revents = 0;	2274	fds [i].revents = 0;
1604	ev_io_start (loop, iow + i);	2275	ev_io_start (loop, iow + i);
1605	}	2276	}
1606	}	2277	}
1607		2278
1608	// stop all watchers after blocking	2279	// stop all watchers after blocking
1609	static void	2280	static void
1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2281	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1611	{	2282	{
1612	ev_timer_stop (loop, &tw);	2283	ev_timer_stop (loop, &tw);
1613		2284
1614	for (int i = 0; i < nfd; ++i)	2285	for (int i = 0; i < nfd; ++i)
1615	{	2286	{
1616	// set the relevant poll flags	2287	// set the relevant poll flags
1617	// could also call adns_processreadable etc. here	2288	// could also call adns_processreadable etc. here
1618	struct pollfd *fd = fds + i;	2289	struct pollfd *fd = fds + i;
1619	int revents = ev_clear_pending (iow + i);	2290	int revents = ev_clear_pending (iow + i);
1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2291	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2292	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622		2293
1623	// now stop the watcher	2294	// now stop the watcher
1624	ev_io_stop (loop, iow + i);	2295	ev_io_stop (loop, iow + i);
1625	}	2296	}
1626		2297
1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2298	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628	}	2299	}
1629		2300
1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2301	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631	in the prepare watcher and would dispose of the check watcher.	2302	in the prepare watcher and would dispose of the check watcher.
1632		2303
1633	Method 3: If the module to be embedded supports explicit event	2304	Method 3: If the module to be embedded supports explicit event
1634	notification (adns does), you can also make use of the actual watcher	2305	notification (libadns does), you can also make use of the actual watcher
1635	callbacks, and only destroy/create the watchers in the prepare watcher.	2306	callbacks, and only destroy/create the watchers in the prepare watcher.
1636		2307
1637	static void	2308	static void
1638	timer_cb (EV_P_ ev_timer *w, int revents)	2309	timer_cb (EV_P_ ev_timer *w, int revents)
1639	{	2310	{
1640	adns_state ads = (adns_state)w->data;	2311	adns_state ads = (adns_state)w->data;
1641	update_now (EV_A);	2312	update_now (EV_A);
1642		2313
1643	adns_processtimeouts (ads, &tv_now);	2314	adns_processtimeouts (ads, &tv_now);
1644	}	2315	}
1645		2316
1646	static void	2317	static void
1647	io_cb (EV_P_ ev_io *w, int revents)	2318	io_cb (EV_P_ ev_io *w, int revents)
1648	{	2319	{
1649	adns_state ads = (adns_state)w->data;	2320	adns_state ads = (adns_state)w->data;
1650	update_now (EV_A);	2321	update_now (EV_A);
1651		2322
1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2323	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2324	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654	}	2325	}
1655		2326
1656	// do not ever call adns_afterpoll	2327	// do not ever call adns_afterpoll
1657		2328
1658	Method 4: Do not use a prepare or check watcher because the module you	2329	Method 4: Do not use a prepare or check watcher because the module you
1659	want to embed is too inflexible to support it. Instead, youc na override	2330	want to embed is not flexible enough to support it. Instead, you can
1660	their poll function. The drawback with this solution is that the main	2331	override their poll function. The drawback with this solution is that the
1661	loop is now no longer controllable by EV. The C<Glib::EV> module does	2332	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1662	this.	2333	this approach, effectively embedding EV as a client into the horrible
		2334	libglib event loop.
1663		2335
1664	static gint	2336	static gint
1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2337	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666	{	2338	{
1667	int got_events = 0;	2339	int got_events = 0;
1668		2340
1669	for (n = 0; n < nfds; ++n)	2341	for (n = 0; n < nfds; ++n)
1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2342	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671		2343
1672	if (timeout >= 0)	2344	if (timeout >= 0)
1673	// create/start timer	2345	// create/start timer
1674		2346
1675	// poll	2347	// poll
1676	ev_loop (EV_A_ 0);	2348	ev_loop (EV_A_ 0);
1677		2349
1678	// stop timer again	2350	// stop timer again
1679	if (timeout >= 0)	2351	if (timeout >= 0)
1680	ev_timer_stop (EV_A_ &to);	2352	ev_timer_stop (EV_A_ &to);
1681		2353
1682	// stop io watchers again - their callbacks should have set	2354	// stop io watchers again - their callbacks should have set
1683	for (n = 0; n < nfds; ++n)	2355	for (n = 0; n < nfds; ++n)
1684	ev_io_stop (EV_A_ iow [n]);	2356	ev_io_stop (EV_A_ iow [n]);
1685		2357
1686	return got_events;	2358	return got_events;
1687	}	2359	}
1688		2360
1689		2361
1690	=head2 C<ev_embed> - when one backend isn't enough...	2362	=head2 C<ev_embed> - when one backend isn't enough...
1691		2363
1692	This is a rather advanced watcher type that lets you embed one event loop	2364	This is a rather advanced watcher type that lets you embed one event loop
…		…
1698	prioritise I/O.	2370	prioritise I/O.
1699		2371
1700	As an example for a bug workaround, the kqueue backend might only support	2372	As an example for a bug workaround, the kqueue backend might only support
1701	sockets on some platform, so it is unusable as generic backend, but you	2373	sockets on some platform, so it is unusable as generic backend, but you
1702	still want to make use of it because you have many sockets and it scales	2374	still want to make use of it because you have many sockets and it scales
1703	so nicely. In this case, you would create a kqueue-based loop and embed it	2375	so nicely. In this case, you would create a kqueue-based loop and embed
1704	into your default loop (which might use e.g. poll). Overall operation will	2376	it into your default loop (which might use e.g. poll). Overall operation
1705	be a bit slower because first libev has to poll and then call kevent, but	2377	will be a bit slower because first libev has to call C<poll> and then
1706	at least you can use both at what they are best.	2378	C<kevent>, but at least you can use both mechanisms for what they are
		2379	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1707		2380
1708	As for prioritising I/O: rarely you have the case where some fds have	2381	As for prioritising I/O: under rare circumstances you have the case where
1709	to be watched and handled very quickly (with low latency), and even	2382	some fds have to be watched and handled very quickly (with low latency),
1710	priorities and idle watchers might have too much overhead. In this case	2383	and even priorities and idle watchers might have too much overhead. In
1711	you would put all the high priority stuff in one loop and all the rest in	2384	this case you would put all the high priority stuff in one loop and all
1712	a second one, and embed the second one in the first.	2385	the rest in a second one, and embed the second one in the first.
1713		2386
1714	As long as the watcher is active, the callback will be invoked every time	2387	As long as the watcher is active, the callback will be invoked every time
1715	there might be events pending in the embedded loop. The callback must then	2388	there might be events pending in the embedded loop. The callback must then
1716	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2389	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1717	their callbacks (you could also start an idle watcher to give the embedded	2390	their callbacks (you could also start an idle watcher to give the embedded
…		…
1725	interested in that.	2398	interested in that.
1726		2399
1727	Also, there have not currently been made special provisions for forking:	2400	Also, there have not currently been made special provisions for forking:
1728	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2401	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1729	but you will also have to stop and restart any C<ev_embed> watchers	2402	but you will also have to stop and restart any C<ev_embed> watchers
1730	yourself.	2403	yourself - but you can use a fork watcher to handle this automatically,
		2404	and future versions of libev might do just that.
1731		2405
1732	Unfortunately, not all backends are embeddable, only the ones returned by	2406	Unfortunately, not all backends are embeddable: only the ones returned by
1733	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2407	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1734	portable one.	2408	portable one.
1735		2409
1736	So when you want to use this feature you will always have to be prepared	2410	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2411	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2412	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2413	create it, and if that fails, use the normal loop for everything.
1740		2414
1741	struct ev_loop *loop_hi = ev_default_init (0);	2415	=head3 C<ev_embed> and fork
1742	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;
1744
1745	// see if there is a chance of getting one that works
1746	// (remember that a flags value of 0 means autodetection)
1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1749	: 0;
1750		2416
1751	// if we got one, then embed it, otherwise default to loop_hi	2417	While the C<ev_embed> watcher is running, forks in the embedding loop will
1752	if (loop_lo)	2418	automatically be applied to the embedded loop as well, so no special
1753	{	2419	fork handling is required in that case. When the watcher is not running,
1754	ev_embed_init (&embed, 0, loop_lo);	2420	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1755	ev_embed_start (loop_hi, &embed);	2421	as applicable.
1756	}
1757	else
1758	loop_lo = loop_hi;
1759		2422
1760	=head3 Watcher-Specific Functions and Data Members	2423	=head3 Watcher-Specific Functions and Data Members
1761		2424
1762	=over 4	2425	=over 4
1763		2426
…		…
1767		2430
1768	Configures the watcher to embed the given loop, which must be	2431	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2432	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback	2433	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,	2434	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).	2435	if you do not want that, you need to temporarily stop the embed watcher).
1773		2436
1774	=item ev_embed_sweep (loop, ev_embed *)	2437	=item ev_embed_sweep (loop, ev_embed *)
1775		2438
1776	Make a single, non-blocking sweep over the embedded loop. This works	2439	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2440	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.	2441	appropriate way for embedded loops.
1779		2442
1780	=item struct ev_loop *loop [read-only]	2443	=item struct ev_loop *other [read-only]
1781		2444
1782	The embedded event loop.	2445	The embedded event loop.
1783		2446
1784	=back	2447	=back
		2448
		2449	=head3 Examples
		2450
		2451	Example: Try to get an embeddable event loop and embed it into the default
		2452	event loop. If that is not possible, use the default loop. The default
		2453	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2454	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2455	used).
		2456
		2457	struct ev_loop *loop_hi = ev_default_init (0);
		2458	struct ev_loop *loop_lo = 0;
		2459	ev_embed embed;
		2460
		2461	// see if there is a chance of getting one that works
		2462	// (remember that a flags value of 0 means autodetection)
		2463	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2464	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2465	: 0;
		2466
		2467	// if we got one, then embed it, otherwise default to loop_hi
		2468	if (loop_lo)
		2469	{
		2470	ev_embed_init (&embed, 0, loop_lo);
		2471	ev_embed_start (loop_hi, &embed);
		2472	}
		2473	else
		2474	loop_lo = loop_hi;
		2475
		2476	Example: Check if kqueue is available but not recommended and create
		2477	a kqueue backend for use with sockets (which usually work with any
		2478	kqueue implementation). Store the kqueue/socket-only event loop in
		2479	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2480
		2481	struct ev_loop *loop = ev_default_init (0);
		2482	struct ev_loop *loop_socket = 0;
		2483	ev_embed embed;
		2484
		2485	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2486	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2487	{
		2488	ev_embed_init (&embed, 0, loop_socket);
		2489	ev_embed_start (loop, &embed);
		2490	}
		2491
		2492	if (!loop_socket)
		2493	loop_socket = loop;
		2494
		2495	// now use loop_socket for all sockets, and loop for everything else
1785		2496
1786		2497
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2498	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2499
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2500	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2516	believe me.
1806		2517
1807	=back	2518	=back
1808		2519
1809		2520
		2521	=head2 C<ev_async> - how to wake up another event loop
		2522
		2523	In general, you cannot use an C<ev_loop> from multiple threads or other
		2524	asynchronous sources such as signal handlers (as opposed to multiple event
		2525	loops - those are of course safe to use in different threads).
		2526
		2527	Sometimes, however, you need to wake up another event loop you do not
		2528	control, for example because it belongs to another thread. This is what
		2529	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2530	can signal it by calling C<ev_async_send>, which is thread- and signal
		2531	safe.
		2532
		2533	This functionality is very similar to C<ev_signal> watchers, as signals,
		2534	too, are asynchronous in nature, and signals, too, will be compressed
		2535	(i.e. the number of callback invocations may be less than the number of
		2536	C<ev_async_sent> calls).
		2537
		2538	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2539	just the default loop.
		2540
		2541	=head3 Queueing
		2542
		2543	C<ev_async> does not support queueing of data in any way. The reason
		2544	is that the author does not know of a simple (or any) algorithm for a
		2545	multiple-writer-single-reader queue that works in all cases and doesn't
		2546	need elaborate support such as pthreads.
		2547
		2548	That means that if you want to queue data, you have to provide your own
		2549	queue. But at least I can tell you how to implement locking around your
		2550	queue:
		2551
		2552	=over 4
		2553
		2554	=item queueing from a signal handler context
		2555
		2556	To implement race-free queueing, you simply add to the queue in the signal
		2557	handler but you block the signal handler in the watcher callback. Here is
		2558	an example that does that for some fictitious SIGUSR1 handler:
		2559
		2560	static ev_async mysig;
		2561
		2562	static void
		2563	sigusr1_handler (void)
		2564	{
		2565	sometype data;
		2566
		2567	// no locking etc.
		2568	queue_put (data);
		2569	ev_async_send (EV_DEFAULT_ &mysig);
		2570	}
		2571
		2572	static void
		2573	mysig_cb (EV_P_ ev_async *w, int revents)
		2574	{
		2575	sometype data;
		2576	sigset_t block, prev;
		2577
		2578	sigemptyset (&block);
		2579	sigaddset (&block, SIGUSR1);
		2580	sigprocmask (SIG_BLOCK, &block, &prev);
		2581
		2582	while (queue_get (&data))
		2583	process (data);
		2584
		2585	if (sigismember (&prev, SIGUSR1)
		2586	sigprocmask (SIG_UNBLOCK, &block, 0);
		2587	}
		2588
		2589	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2590	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2591	either...).
		2592
		2593	=item queueing from a thread context
		2594
		2595	The strategy for threads is different, as you cannot (easily) block
		2596	threads but you can easily preempt them, so to queue safely you need to
		2597	employ a traditional mutex lock, such as in this pthread example:
		2598
		2599	static ev_async mysig;
		2600	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2601
		2602	static void
		2603	otherthread (void)
		2604	{
		2605	// only need to lock the actual queueing operation
		2606	pthread_mutex_lock (&mymutex);
		2607	queue_put (data);
		2608	pthread_mutex_unlock (&mymutex);
		2609
		2610	ev_async_send (EV_DEFAULT_ &mysig);
		2611	}
		2612
		2613	static void
		2614	mysig_cb (EV_P_ ev_async *w, int revents)
		2615	{
		2616	pthread_mutex_lock (&mymutex);
		2617
		2618	while (queue_get (&data))
		2619	process (data);
		2620
		2621	pthread_mutex_unlock (&mymutex);
		2622	}
		2623
		2624	=back
		2625
		2626
		2627	=head3 Watcher-Specific Functions and Data Members
		2628
		2629	=over 4
		2630
		2631	=item ev_async_init (ev_async *, callback)
		2632
		2633	Initialises and configures the async watcher - it has no parameters of any
		2634	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2635	trust me.
		2636
		2637	=item ev_async_send (loop, ev_async *)
		2638
		2639	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2640	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2641	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2642	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2643	section below on what exactly this means).
		2644
		2645	This call incurs the overhead of a system call only once per loop iteration,
		2646	so while the overhead might be noticeable, it doesn't apply to repeated
		2647	calls to C<ev_async_send>.
		2648
		2649	=item bool = ev_async_pending (ev_async *)
		2650
		2651	Returns a non-zero value when C<ev_async_send> has been called on the
		2652	watcher but the event has not yet been processed (or even noted) by the
		2653	event loop.
		2654
		2655	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2656	the loop iterates next and checks for the watcher to have become active,
		2657	it will reset the flag again. C<ev_async_pending> can be used to very
		2658	quickly check whether invoking the loop might be a good idea.
		2659
		2660	Not that this does I<not> check whether the watcher itself is pending, only
		2661	whether it has been requested to make this watcher pending.
		2662
		2663	=back
		2664
		2665
1810	=head1 OTHER FUNCTIONS	2666	=head1 OTHER FUNCTIONS
1811		2667
1812	There are some other functions of possible interest. Described. Here. Now.	2668	There are some other functions of possible interest. Described. Here. Now.
1813		2669
1814	=over 4	2670	=over 4
1815		2671
1816	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2672	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1817		2673
1818	This function combines a simple timer and an I/O watcher, calls your	2674	This function combines a simple timer and an I/O watcher, calls your
1819	callback on whichever event happens first and automatically stop both	2675	callback on whichever event happens first and automatically stops both
1820	watchers. This is useful if you want to wait for a single event on an fd	2676	watchers. This is useful if you want to wait for a single event on an fd
1821	or timeout without having to allocate/configure/start/stop/free one or	2677	or timeout without having to allocate/configure/start/stop/free one or
1822	more watchers yourself.	2678	more watchers yourself.
1823		2679
1824	If C<fd> is less than 0, then no I/O watcher will be started and events	2680	If C<fd> is less than 0, then no I/O watcher will be started and the
1825	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2681	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1826	C<events> set will be craeted and started.	2682	the given C<fd> and C<events> set will be created and started.
1827		2683
1828	If C<timeout> is less than 0, then no timeout watcher will be	2684	If C<timeout> is less than 0, then no timeout watcher will be
1829	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2685	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1830	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2686	repeat = 0) will be started. C<0> is a valid timeout.
1831	dubious value.
1832		2687
1833	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2688	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1834	passed an C<revents> set like normal event callbacks (a combination of	2689	passed an C<revents> set like normal event callbacks (a combination of
1835	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2690	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1836	value passed to C<ev_once>:	2691	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2692	a timeout and an io event at the same time - you probably should give io
		2693	events precedence.
1837		2694
		2695	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2696
1838	static void stdin_ready (int revents, void *arg)	2697	static void stdin_ready (int revents, void *arg)
1839	{	2698	{
1840	if (revents & EV_TIMEOUT)
1841	/* doh, nothing entered */;
1842	else if (revents & EV_READ)	2699	if (revents & EV_READ)
1843	/* stdin might have data for us, joy! */;	2700	/* stdin might have data for us, joy! */;
		2701	else if (revents & EV_TIMEOUT)
		2702	/* doh, nothing entered */;
1844	}	2703	}
1845		2704
1846	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2705	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1847		2706
1848	=item ev_feed_event (ev_loop *, watcher *, int revents)	2707	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1849		2708
1850	Feeds the given event set into the event loop, as if the specified event	2709	Feeds the given event set into the event loop, as if the specified event
1851	had happened for the specified watcher (which must be a pointer to an	2710	had happened for the specified watcher (which must be a pointer to an
1852	initialised but not necessarily started event watcher).	2711	initialised but not necessarily started event watcher).
1853		2712
1854	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2713	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1855		2714
1856	Feed an event on the given fd, as if a file descriptor backend detected	2715	Feed an event on the given fd, as if a file descriptor backend detected
1857	the given events it.	2716	the given events it.
1858		2717
1859	=item ev_feed_signal_event (ev_loop *loop, int signum)	2718	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1860		2719
1861	Feed an event as if the given signal occured (C<loop> must be the default	2720	Feed an event as if the given signal occurred (C<loop> must be the default
1862	loop!).	2721	loop!).
1863		2722
1864	=back	2723	=back
1865		2724
1866		2725
…		…
1882		2741
1883	=item * Priorities are not currently supported. Initialising priorities	2742	=item * Priorities are not currently supported. Initialising priorities
1884	will fail and all watchers will have the same priority, even though there	2743	will fail and all watchers will have the same priority, even though there
1885	is an ev_pri field.	2744	is an ev_pri field.
1886		2745
		2746	=item * In libevent, the last base created gets the signals, in libev, the
		2747	first base created (== the default loop) gets the signals.
		2748
1887	=item * Other members are not supported.	2749	=item * Other members are not supported.
1888		2750
1889	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2751	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1890	to use the libev header file and library.	2752	to use the libev header file and library.
1891		2753
1892	=back	2754	=back
1893		2755
1894	=head1 C++ SUPPORT	2756	=head1 C++ SUPPORT
1895		2757
1896	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2758	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1897	you to use some convinience methods to start/stop watchers and also change	2759	you to use some convenience methods to start/stop watchers and also change
1898	the callback model to a model using method callbacks on objects.	2760	the callback model to a model using method callbacks on objects.
1899		2761
1900	To use it,	2762	To use it,
1901		2763
1902	#include <ev++.h>	2764	#include <ev++.h>
1903		2765
1904	This automatically includes F<ev.h> and puts all of its definitions (many	2766	This automatically includes F<ev.h> and puts all of its definitions (many
1905	of them macros) into the global namespace. All C++ specific things are	2767	of them macros) into the global namespace. All C++ specific things are
1906	put into the C<ev> namespace. It should support all the same embedding	2768	put into the C<ev> namespace. It should support all the same embedding
1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2769	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1974	your compiler is good :), then the method will be fully inlined into the	2836	your compiler is good :), then the method will be fully inlined into the
1975	thunking function, making it as fast as a direct C callback.	2837	thunking function, making it as fast as a direct C callback.
1976		2838
1977	Example: simple class declaration and watcher initialisation	2839	Example: simple class declaration and watcher initialisation
1978		2840
1979	struct myclass	2841	struct myclass
1980	{	2842	{
1981	void io_cb (ev::io &w, int revents) { }	2843	void io_cb (ev::io &w, int revents) { }
1982	}	2844	}
1983		2845
1984	myclass obj;	2846	myclass obj;
1985	ev::io iow;	2847	ev::io iow;
1986	iow.set <myclass, &myclass::io_cb> (&obj);	2848	iow.set <myclass, &myclass::io_cb> (&obj);
1987		2849
1988	=item w->set<function> (void *data = 0)	2850	=item w->set<function> (void *data = 0)
1989		2851
1990	Also sets a callback, but uses a static method or plain function as	2852	Also sets a callback, but uses a static method or plain function as
1991	callback. The optional C<data> argument will be stored in the watcher's	2853	callback. The optional C<data> argument will be stored in the watcher's
…		…
1993		2855
1994	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2856	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
1995		2857
1996	See the method-C<set> above for more details.	2858	See the method-C<set> above for more details.
1997		2859
1998	Example:	2860	Example: Use a plain function as callback.
1999		2861
2000	static void io_cb (ev::io &w, int revents) { }	2862	static void io_cb (ev::io &w, int revents) { }
2001	iow.set <io_cb> ();	2863	iow.set <io_cb> ();
2002		2864
2003	=item w->set (struct ev_loop *)	2865	=item w->set (struct ev_loop *)
2004		2866
2005	Associates a different C<struct ev_loop> with this watcher. You can only	2867	Associates a different C<struct ev_loop> with this watcher. You can only
2006	do this when the watcher is inactive (and not pending either).	2868	do this when the watcher is inactive (and not pending either).
2007		2869
2008	=item w->set ([args])	2870	=item w->set ([arguments])
2009		2871
2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2872	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2011	called at least once. Unlike the C counterpart, an active watcher gets	2873	called at least once. Unlike the C counterpart, an active watcher gets
2012	automatically stopped and restarted when reconfiguring it with this	2874	automatically stopped and restarted when reconfiguring it with this
2013	method.	2875	method.
2014		2876
2015	=item w->start ()	2877	=item w->start ()
…		…
2019		2881
2020	=item w->stop ()	2882	=item w->stop ()
2021		2883
2022	Stops the watcher if it is active. Again, no C<loop> argument.	2884	Stops the watcher if it is active. Again, no C<loop> argument.
2023		2885
2024	=item w->again () C<ev::timer>, C<ev::periodic> only	2886	=item w->again () (C<ev::timer>, C<ev::periodic> only)
2025		2887
2026	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2888	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
2027	C<ev_TYPE_again> function.	2889	C<ev_TYPE_again> function.
2028		2890
2029	=item w->sweep () C<ev::embed> only	2891	=item w->sweep () (C<ev::embed> only)
2030		2892
2031	Invokes C<ev_embed_sweep>.	2893	Invokes C<ev_embed_sweep>.
2032		2894
2033	=item w->update () C<ev::stat> only	2895	=item w->update () (C<ev::stat> only)
2034		2896
2035	Invokes C<ev_stat_stat>.	2897	Invokes C<ev_stat_stat>.
2036		2898
2037	=back	2899	=back
2038		2900
2039	=back	2901	=back
2040		2902
2041	Example: Define a class with an IO and idle watcher, start one of them in	2903	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2904	the constructor.
2043		2905
2044	class myclass	2906	class myclass
2045	{	2907	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2908	ev::io io ; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2909	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2048		2910
2049	myclass ();	2911	myclass (int fd)
2050	}	2912	{
2051
2052	myclass::myclass (int fd)
2053	{
2054	io .set <myclass, &myclass::io_cb > (this);	2913	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2914	idle.set <myclass, &myclass::idle_cb> (this);
2056		2915
2057	io.start (fd, ev::READ);	2916	io.start (fd, ev::READ);
		2917	}
2058	}	2918	};
		2919
		2920
		2921	=head1 OTHER LANGUAGE BINDINGS
		2922
		2923	Libev does not offer other language bindings itself, but bindings for a
		2924	number of languages exist in the form of third-party packages. If you know
		2925	any interesting language binding in addition to the ones listed here, drop
		2926	me a note.
		2927
		2928	=over 4
		2929
		2930	=item Perl
		2931
		2932	The EV module implements the full libev API and is actually used to test
		2933	libev. EV is developed together with libev. Apart from the EV core module,
		2934	there are additional modules that implement libev-compatible interfaces
		2935	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2936	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2937	and C<EV::Glib>).
		2938
		2939	It can be found and installed via CPAN, its homepage is at
		2940	L<http://software.schmorp.de/pkg/EV>.
		2941
		2942	=item Python
		2943
		2944	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2945	seems to be quite complete and well-documented. Note, however, that the
		2946	patch they require for libev is outright dangerous as it breaks the ABI
		2947	for everybody else, and therefore, should never be applied in an installed
		2948	libev (if python requires an incompatible ABI then it needs to embed
		2949	libev).
		2950
		2951	=item Ruby
		2952
		2953	Tony Arcieri has written a ruby extension that offers access to a subset
		2954	of the libev API and adds file handle abstractions, asynchronous DNS and
		2955	more on top of it. It can be found via gem servers. Its homepage is at
		2956	L<http://rev.rubyforge.org/>.
		2957
		2958	=item D
		2959
		2960	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2961	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2962
		2963	=back
2059		2964
2060		2965
2061	=head1 MACRO MAGIC	2966	=head1 MACRO MAGIC
2062		2967
2063	Libev can be compiled with a variety of options, the most fundemantal is	2968	Libev can be compiled with a variety of options, the most fundamental
2064	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2969	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	callbacks have an initial C<struct ev_loop *> argument.	2970	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		2971
2067	To make it easier to write programs that cope with either variant, the	2972	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	2973	following macros are defined:
2069		2974
2070	=over 4	2975	=over 4
…		…
2073		2978
2074	This provides the loop I<argument> for functions, if one is required ("ev	2979	This provides the loop I<argument> for functions, if one is required ("ev
2075	loop argument"). The C<EV_A> form is used when this is the sole argument,	2980	loop argument"). The C<EV_A> form is used when this is the sole argument,
2076	C<EV_A_> is used when other arguments are following. Example:	2981	C<EV_A_> is used when other arguments are following. Example:
2077		2982
2078	ev_unref (EV_A);	2983	ev_unref (EV_A);
2079	ev_timer_add (EV_A_ watcher);	2984	ev_timer_add (EV_A_ watcher);
2080	ev_loop (EV_A_ 0);	2985	ev_loop (EV_A_ 0);
2081		2986
2082	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2987	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2083	which is often provided by the following macro.	2988	which is often provided by the following macro.
2084		2989
2085	=item C<EV_P>, C<EV_P_>	2990	=item C<EV_P>, C<EV_P_>
2086		2991
2087	This provides the loop I<parameter> for functions, if one is required ("ev	2992	This provides the loop I<parameter> for functions, if one is required ("ev
2088	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2993	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2089	C<EV_P_> is used when other parameters are following. Example:	2994	C<EV_P_> is used when other parameters are following. Example:
2090		2995
2091	// this is how ev_unref is being declared	2996	// this is how ev_unref is being declared
2092	static void ev_unref (EV_P);	2997	static void ev_unref (EV_P);
2093		2998
2094	// this is how you can declare your typical callback	2999	// this is how you can declare your typical callback
2095	static void cb (EV_P_ ev_timer *w, int revents)	3000	static void cb (EV_P_ ev_timer *w, int revents)
2096		3001
2097	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3002	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2098	suitable for use with C<EV_A>.	3003	suitable for use with C<EV_A>.
2099		3004
2100	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3005	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2101		3006
2102	Similar to the other two macros, this gives you the value of the default	3007	Similar to the other two macros, this gives you the value of the default
2103	loop, if multiple loops are supported ("ev loop default").	3008	loop, if multiple loops are supported ("ev loop default").
		3009
		3010	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3011
		3012	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3013	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3014	is undefined when the default loop has not been initialised by a previous
		3015	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3016
		3017	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3018	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2104		3019
2105	=back	3020	=back
2106		3021
2107	Example: Declare and initialise a check watcher, utilising the above	3022	Example: Declare and initialise a check watcher, utilising the above
2108	macros so it will work regardless of whether multiple loops are supported	3023	macros so it will work regardless of whether multiple loops are supported
2109	or not.	3024	or not.
2110		3025
2111	static void	3026	static void
2112	check_cb (EV_P_ ev_timer *w, int revents)	3027	check_cb (EV_P_ ev_timer *w, int revents)
2113	{	3028	{
2114	ev_check_stop (EV_A_ w);	3029	ev_check_stop (EV_A_ w);
2115	}	3030	}
2116		3031
2117	ev_check check;	3032	ev_check check;
2118	ev_check_init (&check, check_cb);	3033	ev_check_init (&check, check_cb);
2119	ev_check_start (EV_DEFAULT_ &check);	3034	ev_check_start (EV_DEFAULT_ &check);
2120	ev_loop (EV_DEFAULT_ 0);	3035	ev_loop (EV_DEFAULT_ 0);
2121		3036
2122	=head1 EMBEDDING	3037	=head1 EMBEDDING
2123		3038
2124	Libev can (and often is) directly embedded into host	3039	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	3040	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3041	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	3042	and rxvt-unicode.
2128		3043
2129	The goal is to enable you to just copy the neecssary files into your	3044	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	3045	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	3046	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	3047	libev somewhere in your source tree).
2133		3048
2134	=head2 FILESETS	3049	=head2 FILESETS
2135		3050
2136	Depending on what features you need you need to include one or more sets of files	3051	Depending on what features you need you need to include one or more sets of files
2137	in your app.	3052	in your application.
2138		3053
2139	=head3 CORE EVENT LOOP	3054	=head3 CORE EVENT LOOP
2140		3055
2141	To include only the libev core (all the C<ev_*> functions), with manual	3056	To include only the libev core (all the C<ev_*> functions), with manual
2142	configuration (no autoconf):	3057	configuration (no autoconf):
2143		3058
2144	#define EV_STANDALONE 1	3059	#define EV_STANDALONE 1
2145	#include "ev.c"	3060	#include "ev.c"
2146		3061
2147	This will automatically include F<ev.h>, too, and should be done in a	3062	This will automatically include F<ev.h>, too, and should be done in a
2148	single C source file only to provide the function implementations. To use	3063	single C source file only to provide the function implementations. To use
2149	it, do the same for F<ev.h> in all files wishing to use this API (best	3064	it, do the same for F<ev.h> in all files wishing to use this API (best
2150	done by writing a wrapper around F<ev.h> that you can include instead and	3065	done by writing a wrapper around F<ev.h> that you can include instead and
2151	where you can put other configuration options):	3066	where you can put other configuration options):
2152		3067
2153	#define EV_STANDALONE 1	3068	#define EV_STANDALONE 1
2154	#include "ev.h"	3069	#include "ev.h"
2155		3070
2156	Both header files and implementation files can be compiled with a C++	3071	Both header files and implementation files can be compiled with a C++
2157	compiler (at least, thats a stated goal, and breakage will be treated	3072	compiler (at least, thats a stated goal, and breakage will be treated
2158	as a bug).	3073	as a bug).
2159		3074
2160	You need the following files in your source tree, or in a directory	3075	You need the following files in your source tree, or in a directory
2161	in your include path (e.g. in libev/ when using -Ilibev):	3076	in your include path (e.g. in libev/ when using -Ilibev):
2162		3077
2163	ev.h	3078	ev.h
2164	ev.c	3079	ev.c
2165	ev_vars.h	3080	ev_vars.h
2166	ev_wrap.h	3081	ev_wrap.h
2167		3082
2168	ev_win32.c required on win32 platforms only	3083	ev_win32.c required on win32 platforms only
2169		3084
2170	ev_select.c only when select backend is enabled (which is enabled by default)	3085	ev_select.c only when select backend is enabled (which is enabled by default)
2171	ev_poll.c only when poll backend is enabled (disabled by default)	3086	ev_poll.c only when poll backend is enabled (disabled by default)
2172	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3087	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2173	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3088	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2174	ev_port.c only when the solaris port backend is enabled (disabled by default)	3089	ev_port.c only when the solaris port backend is enabled (disabled by default)
2175		3090
2176	F<ev.c> includes the backend files directly when enabled, so you only need	3091	F<ev.c> includes the backend files directly when enabled, so you only need
2177	to compile this single file.	3092	to compile this single file.
2178		3093
2179	=head3 LIBEVENT COMPATIBILITY API	3094	=head3 LIBEVENT COMPATIBILITY API
2180		3095
2181	To include the libevent compatibility API, also include:	3096	To include the libevent compatibility API, also include:
2182		3097
2183	#include "event.c"	3098	#include "event.c"
2184		3099
2185	in the file including F<ev.c>, and:	3100	in the file including F<ev.c>, and:
2186		3101
2187	#include "event.h"	3102	#include "event.h"
2188		3103
2189	in the files that want to use the libevent API. This also includes F<ev.h>.	3104	in the files that want to use the libevent API. This also includes F<ev.h>.
2190		3105
2191	You need the following additional files for this:	3106	You need the following additional files for this:
2192		3107
2193	event.h	3108	event.h
2194	event.c	3109	event.c
2195		3110
2196	=head3 AUTOCONF SUPPORT	3111	=head3 AUTOCONF SUPPORT
2197		3112
2198	Instead of using C<EV_STANDALONE=1> and providing your config in	3113	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2199	whatever way you want, you can also C<m4_include([libev.m4])> in your	3114	whatever way you want, you can also C<m4_include([libev.m4])> in your
2200	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3115	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2201	include F<config.h> and configure itself accordingly.	3116	include F<config.h> and configure itself accordingly.
2202		3117
2203	For this of course you need the m4 file:	3118	For this of course you need the m4 file:
2204		3119
2205	libev.m4	3120	libev.m4
2206		3121
2207	=head2 PREPROCESSOR SYMBOLS/MACROS	3122	=head2 PREPROCESSOR SYMBOLS/MACROS
2208		3123
2209	Libev can be configured via a variety of preprocessor symbols you have to define	3124	Libev can be configured via a variety of preprocessor symbols you have to
2210	before including any of its files. The default is not to build for multiplicity	3125	define before including any of its files. The default in the absence of
2211	and only include the select backend.	3126	autoconf is documented for every option.
2212		3127
2213	=over 4	3128	=over 4
2214		3129
2215	=item EV_STANDALONE	3130	=item EV_STANDALONE
2216		3131
…		…
2221	F<event.h> that are not directly supported by the libev core alone.	3136	F<event.h> that are not directly supported by the libev core alone.
2222		3137
2223	=item EV_USE_MONOTONIC	3138	=item EV_USE_MONOTONIC
2224		3139
2225	If defined to be C<1>, libev will try to detect the availability of the	3140	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	3141	monotonic clock option at both compile time and runtime. Otherwise no use
2227	of the monotonic clock option will be attempted. If you enable this, you	3142	of the monotonic clock option will be attempted. If you enable this, you
2228	usually have to link against librt or something similar. Enabling it when	3143	usually have to link against librt or something similar. Enabling it when
2229	the functionality isn't available is safe, though, althoguh you have	3144	the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	3145	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	3146	function is hiding in (often F<-lrt>).
2232		3147
2233	=item EV_USE_REALTIME	3148	=item EV_USE_REALTIME
2234		3149
2235	If defined to be C<1>, libev will try to detect the availability of the	3150	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	3151	real-time clock option at compile time (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	3152	runtime if successful). Otherwise no use of the real-time clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3153	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3154	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	3155	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3156
		3157	=item EV_USE_NANOSLEEP
		3158
		3159	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3160	and will use it for delays. Otherwise it will use C<select ()>.
		3161
		3162	=item EV_USE_EVENTFD
		3163
		3164	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3165	available and will probe for kernel support at runtime. This will improve
		3166	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3167	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3168	2.7 or newer, otherwise disabled.
2241		3169
2242	=item EV_USE_SELECT	3170	=item EV_USE_SELECT
2243		3171
2244	If undefined or defined to be C<1>, libev will compile in support for the	3172	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	3173	C<select>(2) backend. No attempt at auto-detection will be done: if no
2246	other method takes over, select will be it. Otherwise the select backend	3174	other method takes over, select will be it. Otherwise the select backend
2247	will not be compiled in.	3175	will not be compiled in.
2248		3176
2249	=item EV_SELECT_USE_FD_SET	3177	=item EV_SELECT_USE_FD_SET
2250		3178
2251	If defined to C<1>, then the select backend will use the system C<fd_set>	3179	If defined to C<1>, then the select backend will use the system C<fd_set>
2252	structure. This is useful if libev doesn't compile due to a missing	3180	structure. This is useful if libev doesn't compile due to a missing
2253	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3181	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2254	exotic systems. This usually limits the range of file descriptors to some	3182	exotic systems. This usually limits the range of file descriptors to some
2255	low limit such as 1024 or might have other limitations (winsocket only	3183	low limit such as 1024 or might have other limitations (winsocket only
2256	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3184	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2257	influence the size of the C<fd_set> used.	3185	influence the size of the C<fd_set> used.
2258		3186
…		…
2264	be used is the winsock select). This means that it will call	3192	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3193	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	3194	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	3195	on win32. Should not be defined on non-win32 platforms.
2268		3196
		3197	=item EV_FD_TO_WIN32_HANDLE
		3198
		3199	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3200	file descriptors to socket handles. When not defining this symbol (the
		3201	default), then libev will call C<_get_osfhandle>, which is usually
		3202	correct. In some cases, programs use their own file descriptor management,
		3203	in which case they can provide this function to map fds to socket handles.
		3204
2269	=item EV_USE_POLL	3205	=item EV_USE_POLL
2270		3206
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3207	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	3208	backend. Otherwise it will be enabled on non-win32 platforms. It
2273	takes precedence over select.	3209	takes precedence over select.
2274		3210
2275	=item EV_USE_EPOLL	3211	=item EV_USE_EPOLL
2276		3212
2277	If defined to be C<1>, libev will compile in support for the Linux	3213	If defined to be C<1>, libev will compile in support for the Linux
2278	C<epoll>(7) backend. Its availability will be detected at runtime,	3214	C<epoll>(7) backend. Its availability will be detected at runtime,
2279	otherwise another method will be used as fallback. This is the	3215	otherwise another method will be used as fallback. This is the preferred
2280	preferred backend for GNU/Linux systems.	3216	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3217	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2281		3218
2282	=item EV_USE_KQUEUE	3219	=item EV_USE_KQUEUE
2283		3220
2284	If defined to be C<1>, libev will compile in support for the BSD style	3221	If defined to be C<1>, libev will compile in support for the BSD style
2285	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3222	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2298	otherwise another method will be used as fallback. This is the preferred	3235	otherwise another method will be used as fallback. This is the preferred
2299	backend for Solaris 10 systems.	3236	backend for Solaris 10 systems.
2300		3237
2301	=item EV_USE_DEVPOLL	3238	=item EV_USE_DEVPOLL
2302		3239
2303	reserved for future expansion, works like the USE symbols above.	3240	Reserved for future expansion, works like the USE symbols above.
2304		3241
2305	=item EV_USE_INOTIFY	3242	=item EV_USE_INOTIFY
2306		3243
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	3244	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	3245	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	3246	be detected at runtime. If undefined, it will be enabled if the headers
		3247	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3248
		3249	=item EV_ATOMIC_T
		3250
		3251	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3252	access is atomic with respect to other threads or signal contexts. No such
		3253	type is easily found in the C language, so you can provide your own type
		3254	that you know is safe for your purposes. It is used both for signal handler "locking"
		3255	as well as for signal and thread safety in C<ev_async> watchers.
		3256
		3257	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3258	(from F<signal.h>), which is usually good enough on most platforms.
2310		3259
2311	=item EV_H	3260	=item EV_H
2312		3261
2313	The name of the F<ev.h> header file used to include it. The default if	3262	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3263	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3264	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		3265
2317	=item EV_CONFIG_H	3266	=item EV_CONFIG_H
2318		3267
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3268	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3269	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	3270	C<EV_H>, above.
2322		3271
2323	=item EV_EVENT_H	3272	=item EV_EVENT_H
2324		3273
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3274	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	3275	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		3276
2328	=item EV_PROTOTYPES	3277	=item EV_PROTOTYPES
2329		3278
2330	If defined to be C<0>, then F<ev.h> will not define any function	3279	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	3280	prototypes, but still define all the structs and other symbols. This is
…		…
2352	When doing priority-based operations, libev usually has to linearly search	3301	When doing priority-based operations, libev usually has to linearly search
2353	all the priorities, so having many of them (hundreds) uses a lot of space	3302	all the priorities, so having many of them (hundreds) uses a lot of space
2354	and time, so using the defaults of five priorities (-2 .. +2) is usually	3303	and time, so using the defaults of five priorities (-2 .. +2) is usually
2355	fine.	3304	fine.
2356		3305
2357	If your embedding app does not need any priorities, defining these both to	3306	If your embedding application does not need any priorities, defining these
2358	C<0> will save some memory and cpu.	3307	both to C<0> will save some memory and CPU.
2359		3308
2360	=item EV_PERIODIC_ENABLE	3309	=item EV_PERIODIC_ENABLE
2361		3310
2362	If undefined or defined to be C<1>, then periodic timers are supported. If	3311	If undefined or defined to be C<1>, then periodic timers are supported. If
2363	defined to be C<0>, then they are not. Disabling them saves a few kB of	3312	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2370	code.	3319	code.
2371		3320
2372	=item EV_EMBED_ENABLE	3321	=item EV_EMBED_ENABLE
2373		3322
2374	If undefined or defined to be C<1>, then embed watchers are supported. If	3323	If undefined or defined to be C<1>, then embed watchers are supported. If
2375	defined to be C<0>, then they are not.	3324	defined to be C<0>, then they are not. Embed watchers rely on most other
		3325	watcher types, which therefore must not be disabled.
2376		3326
2377	=item EV_STAT_ENABLE	3327	=item EV_STAT_ENABLE
2378		3328
2379	If undefined or defined to be C<1>, then stat watchers are supported. If	3329	If undefined or defined to be C<1>, then stat watchers are supported. If
2380	defined to be C<0>, then they are not.	3330	defined to be C<0>, then they are not.
…		…
2382	=item EV_FORK_ENABLE	3332	=item EV_FORK_ENABLE
2383		3333
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	3334	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	3335	defined to be C<0>, then they are not.
2386		3336
		3337	=item EV_ASYNC_ENABLE
		3338
		3339	If undefined or defined to be C<1>, then async watchers are supported. If
		3340	defined to be C<0>, then they are not.
		3341
2387	=item EV_MINIMAL	3342	=item EV_MINIMAL
2388		3343
2389	If you need to shave off some kilobytes of code at the expense of some	3344	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	3345	speed, define this symbol to C<1>. Currently this is used to override some
2391	some inlining decisions, saves roughly 30% codesize of amd64.	3346	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3347	much smaller 2-heap for timer management over the default 4-heap.
2392		3348
2393	=item EV_PID_HASHSIZE	3349	=item EV_PID_HASHSIZE
2394		3350
2395	C<ev_child> watchers use a small hash table to distribute workload by	3351	C<ev_child> watchers use a small hash table to distribute workload by
2396	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3352	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2397	than enough. If you need to manage thousands of children you might want to	3353	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	3354	increase this value (I<must> be a power of two).
2399		3355
2400	=item EV_INOTIFY_HASHSIZE	3356	=item EV_INOTIFY_HASHSIZE
2401		3357
2402	C<ev_staz> watchers use a small hash table to distribute workload by	3358	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3359	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	3360	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	3361	watchers you might want to increase this value (I<must> be a power of
2406	two).	3362	two).
2407		3363
		3364	=item EV_USE_4HEAP
		3365
		3366	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3367	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3368	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3369	faster performance with many (thousands) of watchers.
		3370
		3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3372	(disabled).
		3373
		3374	=item EV_HEAP_CACHE_AT
		3375
		3376	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3377	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3378	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3379	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3380	but avoids random read accesses on heap changes. This improves performance
		3381	noticeably with many (hundreds) of watchers.
		3382
		3383	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3384	(disabled).
		3385
		3386	=item EV_VERIFY
		3387
		3388	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3389	be done: If set to C<0>, no internal verification code will be compiled
		3390	in. If set to C<1>, then verification code will be compiled in, but not
		3391	called. If set to C<2>, then the internal verification code will be
		3392	called once per loop, which can slow down libev. If set to C<3>, then the
		3393	verification code will be called very frequently, which will slow down
		3394	libev considerably.
		3395
		3396	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3397	C<0>.
		3398
2408	=item EV_COMMON	3399	=item EV_COMMON
2409		3400
2410	By default, all watchers have a C<void *data> member. By redefining	3401	By default, all watchers have a C<void *data> member. By redefining
2411	this macro to a something else you can include more and other types of	3402	this macro to a something else you can include more and other types of
2412	members. You have to define it each time you include one of the files,	3403	members. You have to define it each time you include one of the files,
2413	though, and it must be identical each time.	3404	though, and it must be identical each time.
2414		3405
2415	For example, the perl EV module uses something like this:	3406	For example, the perl EV module uses something like this:
2416		3407
2417	#define EV_COMMON \	3408	#define EV_COMMON \
2418	SV *self; /* contains this struct */ \	3409	SV *self; /* contains this struct */ \
2419	SV *cb_sv, *fh /* note no trailing ";" */	3410	SV *cb_sv, *fh /* note no trailing ";" */
2420		3411
2421	=item EV_CB_DECLARE (type)	3412	=item EV_CB_DECLARE (type)
2422		3413
2423	=item EV_CB_INVOKE (watcher, revents)	3414	=item EV_CB_INVOKE (watcher, revents)
2424		3415
2425	=item ev_set_cb (ev, cb)	3416	=item ev_set_cb (ev, cb)
2426		3417
2427	Can be used to change the callback member declaration in each watcher,	3418	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	3419	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	3420	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	3421	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3422	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	3423	method calls instead of plain function calls in C++.
		3424
		3425	=back
		3426
		3427	=head2 EXPORTED API SYMBOLS
		3428
		3429	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3430	exported symbols, you can use the provided F<Symbol.*> files which list
		3431	all public symbols, one per line:
		3432
		3433	Symbols.ev for libev proper
		3434	Symbols.event for the libevent emulation
		3435
		3436	This can also be used to rename all public symbols to avoid clashes with
		3437	multiple versions of libev linked together (which is obviously bad in
		3438	itself, but sometimes it is inconvenient to avoid this).
		3439
		3440	A sed command like this will create wrapper C<#define>'s that you need to
		3441	include before including F<ev.h>:
		3442
		3443	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3444
		3445	This would create a file F<wrap.h> which essentially looks like this:
		3446
		3447	#define ev_backend myprefix_ev_backend
		3448	#define ev_check_start myprefix_ev_check_start
		3449	#define ev_check_stop myprefix_ev_check_stop
		3450	...
2433		3451
2434	=head2 EXAMPLES	3452	=head2 EXAMPLES
2435		3453
2436	For a real-world example of a program the includes libev	3454	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3455	verbatim, you can have a look at the EV perl module
…		…
2442	file.	3460	file.
2443		3461
2444	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3462	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2445	that everybody includes and which overrides some configure choices:	3463	that everybody includes and which overrides some configure choices:
2446		3464
2447	#define EV_MINIMAL 1	3465	#define EV_MINIMAL 1
2448	#define EV_USE_POLL 0	3466	#define EV_USE_POLL 0
2449	#define EV_MULTIPLICITY 0	3467	#define EV_MULTIPLICITY 0
2450	#define EV_PERIODIC_ENABLE 0	3468	#define EV_PERIODIC_ENABLE 0
2451	#define EV_STAT_ENABLE 0	3469	#define EV_STAT_ENABLE 0
2452	#define EV_FORK_ENABLE 0	3470	#define EV_FORK_ENABLE 0
2453	#define EV_CONFIG_H <config.h>	3471	#define EV_CONFIG_H <config.h>
2454	#define EV_MINPRI 0	3472	#define EV_MINPRI 0
2455	#define EV_MAXPRI 0	3473	#define EV_MAXPRI 0
2456		3474
2457	#include "ev++.h"	3475	#include "ev++.h"
2458		3476
2459	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3477	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2460		3478
2461	#include "ev_cpp.h"	3479	#include "ev_cpp.h"
2462	#include "ev.c"	3480	#include "ev.c"
2463		3481
		3482	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2464		3483
		3484	=head2 THREADS AND COROUTINES
		3485
		3486	=head3 THREADS
		3487
		3488	All libev functions are reentrant and thread-safe unless explicitly
		3489	documented otherwise, but libev implements no locking itself. This means
		3490	that you can use as many loops as you want in parallel, as long as there
		3491	are no concurrent calls into any libev function with the same loop
		3492	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3493	of course): libev guarantees that different event loops share no data
		3494	structures that need any locking.
		3495
		3496	Or to put it differently: calls with different loop parameters can be done
		3497	concurrently from multiple threads, calls with the same loop parameter
		3498	must be done serially (but can be done from different threads, as long as
		3499	only one thread ever is inside a call at any point in time, e.g. by using
		3500	a mutex per loop).
		3501
		3502	Specifically to support threads (and signal handlers), libev implements
		3503	so-called C<ev_async> watchers, which allow some limited form of
		3504	concurrency on the same event loop, namely waking it up "from the
		3505	outside".
		3506
		3507	If you want to know which design (one loop, locking, or multiple loops
		3508	without or something else still) is best for your problem, then I cannot
		3509	help you, but here is some generic advice:
		3510
		3511	=over 4
		3512
		3513	=item * most applications have a main thread: use the default libev loop
		3514	in that thread, or create a separate thread running only the default loop.
		3515
		3516	This helps integrating other libraries or software modules that use libev
		3517	themselves and don't care/know about threading.
		3518
		3519	=item * one loop per thread is usually a good model.
		3520
		3521	Doing this is almost never wrong, sometimes a better-performance model
		3522	exists, but it is always a good start.
		3523
		3524	=item * other models exist, such as the leader/follower pattern, where one
		3525	loop is handed through multiple threads in a kind of round-robin fashion.
		3526
		3527	Choosing a model is hard - look around, learn, know that usually you can do
		3528	better than you currently do :-)
		3529
		3530	=item * often you need to talk to some other thread which blocks in the
		3531	event loop.
		3532
		3533	C<ev_async> watchers can be used to wake them up from other threads safely
		3534	(or from signal contexts...).
		3535
		3536	An example use would be to communicate signals or other events that only
		3537	work in the default loop by registering the signal watcher with the
		3538	default loop and triggering an C<ev_async> watcher from the default loop
		3539	watcher callback into the event loop interested in the signal.
		3540
		3541	=back
		3542
		3543	=head3 COROUTINES
		3544
		3545	Libev is very accommodating to coroutines ("cooperative threads"):
		3546	libev fully supports nesting calls to its functions from different
		3547	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3548	different coroutines, and switch freely between both coroutines running the
		3549	loop, as long as you don't confuse yourself). The only exception is that
		3550	you must not do this from C<ev_periodic> reschedule callbacks.
		3551
		3552	Care has been taken to ensure that libev does not keep local state inside
		3553	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3554	they do not clal any callbacks.
		3555
		3556	=head2 COMPILER WARNINGS
		3557
		3558	Depending on your compiler and compiler settings, you might get no or a
		3559	lot of warnings when compiling libev code. Some people are apparently
		3560	scared by this.
		3561
		3562	However, these are unavoidable for many reasons. For one, each compiler
		3563	has different warnings, and each user has different tastes regarding
		3564	warning options. "Warn-free" code therefore cannot be a goal except when
		3565	targeting a specific compiler and compiler-version.
		3566
		3567	Another reason is that some compiler warnings require elaborate
		3568	workarounds, or other changes to the code that make it less clear and less
		3569	maintainable.
		3570
		3571	And of course, some compiler warnings are just plain stupid, or simply
		3572	wrong (because they don't actually warn about the condition their message
		3573	seems to warn about). For example, certain older gcc versions had some
		3574	warnings that resulted an extreme number of false positives. These have
		3575	been fixed, but some people still insist on making code warn-free with
		3576	such buggy versions.
		3577
		3578	While libev is written to generate as few warnings as possible,
		3579	"warn-free" code is not a goal, and it is recommended not to build libev
		3580	with any compiler warnings enabled unless you are prepared to cope with
		3581	them (e.g. by ignoring them). Remember that warnings are just that:
		3582	warnings, not errors, or proof of bugs.
		3583
		3584
		3585	=head2 VALGRIND
		3586
		3587	Valgrind has a special section here because it is a popular tool that is
		3588	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3589
		3590	If you think you found a bug (memory leak, uninitialised data access etc.)
		3591	in libev, then check twice: If valgrind reports something like:
		3592
		3593	==2274== definitely lost: 0 bytes in 0 blocks.
		3594	==2274== possibly lost: 0 bytes in 0 blocks.
		3595	==2274== still reachable: 256 bytes in 1 blocks.
		3596
		3597	Then there is no memory leak, just as memory accounted to global variables
		3598	is not a memleak - the memory is still being refernced, and didn't leak.
		3599
		3600	Similarly, under some circumstances, valgrind might report kernel bugs
		3601	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3602	although an acceptable workaround has been found here), or it might be
		3603	confused.
		3604
		3605	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3606	make it into some kind of religion.
		3607
		3608	If you are unsure about something, feel free to contact the mailing list
		3609	with the full valgrind report and an explanation on why you think this
		3610	is a bug in libev (best check the archives, too :). However, don't be
		3611	annoyed when you get a brisk "this is no bug" answer and take the chance
		3612	of learning how to interpret valgrind properly.
		3613
		3614	If you need, for some reason, empty reports from valgrind for your project
		3615	I suggest using suppression lists.
		3616
		3617
		3618	=head1 PORTABILITY NOTES
		3619
		3620	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3621
		3622	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3623	requires, and its I/O model is fundamentally incompatible with the POSIX
		3624	model. Libev still offers limited functionality on this platform in
		3625	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3626	descriptors. This only applies when using Win32 natively, not when using
		3627	e.g. cygwin.
		3628
		3629	Lifting these limitations would basically require the full
		3630	re-implementation of the I/O system. If you are into these kinds of
		3631	things, then note that glib does exactly that for you in a very portable
		3632	way (note also that glib is the slowest event library known to man).
		3633
		3634	There is no supported compilation method available on windows except
		3635	embedding it into other applications.
		3636
		3637	Not a libev limitation but worth mentioning: windows apparently doesn't
		3638	accept large writes: instead of resulting in a partial write, windows will
		3639	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3640	so make sure you only write small amounts into your sockets (less than a
		3641	megabyte seems safe, but this apparently depends on the amount of memory
		3642	available).
		3643
		3644	Due to the many, low, and arbitrary limits on the win32 platform and
		3645	the abysmal performance of winsockets, using a large number of sockets
		3646	is not recommended (and not reasonable). If your program needs to use
		3647	more than a hundred or so sockets, then likely it needs to use a totally
		3648	different implementation for windows, as libev offers the POSIX readiness
		3649	notification model, which cannot be implemented efficiently on windows
		3650	(Microsoft monopoly games).
		3651
		3652	A typical way to use libev under windows is to embed it (see the embedding
		3653	section for details) and use the following F<evwrap.h> header file instead
		3654	of F<ev.h>:
		3655
		3656	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3657	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3658
		3659	#include "ev.h"
		3660
		3661	And compile the following F<evwrap.c> file into your project (make sure
		3662	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3663
		3664	#include "evwrap.h"
		3665	#include "ev.c"
		3666
		3667	=over 4
		3668
		3669	=item The winsocket select function
		3670
		3671	The winsocket C<select> function doesn't follow POSIX in that it
		3672	requires socket I<handles> and not socket I<file descriptors> (it is
		3673	also extremely buggy). This makes select very inefficient, and also
		3674	requires a mapping from file descriptors to socket handles (the Microsoft
		3675	C runtime provides the function C<_open_osfhandle> for this). See the
		3676	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3677	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3678
		3679	The configuration for a "naked" win32 using the Microsoft runtime
		3680	libraries and raw winsocket select is:
		3681
		3682	#define EV_USE_SELECT 1
		3683	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3684
		3685	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3686	complexity in the O(n²) range when using win32.
		3687
		3688	=item Limited number of file descriptors
		3689
		3690	Windows has numerous arbitrary (and low) limits on things.
		3691
		3692	Early versions of winsocket's select only supported waiting for a maximum
		3693	of C<64> handles (probably owning to the fact that all windows kernels
		3694	can only wait for C<64> things at the same time internally; Microsoft
		3695	recommends spawning a chain of threads and wait for 63 handles and the
		3696	previous thread in each. Great).
		3697
		3698	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3699	to some high number (e.g. C<2048>) before compiling the winsocket select
		3700	call (which might be in libev or elsewhere, for example, perl does its own
		3701	select emulation on windows).
		3702
		3703	Another limit is the number of file descriptors in the Microsoft runtime
		3704	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3705	or something like this inside Microsoft). You can increase this by calling
		3706	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3707	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3708	libraries.
		3709
		3710	This might get you to about C<512> or C<2048> sockets (depending on
		3711	windows version and/or the phase of the moon). To get more, you need to
		3712	wrap all I/O functions and provide your own fd management, but the cost of
		3713	calling select (O(n²)) will likely make this unworkable.
		3714
		3715	=back
		3716
		3717	=head2 PORTABILITY REQUIREMENTS
		3718
		3719	In addition to a working ISO-C implementation and of course the
		3720	backend-specific APIs, libev relies on a few additional extensions:
		3721
		3722	=over 4
		3723
		3724	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3725	calling conventions regardless of C<ev_watcher_type *>.
		3726
		3727	Libev assumes not only that all watcher pointers have the same internal
		3728	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3729	assumes that the same (machine) code can be used to call any watcher
		3730	callback: The watcher callbacks have different type signatures, but libev
		3731	calls them using an C<ev_watcher *> internally.
		3732
		3733	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3734
		3735	The type C<sig_atomic_t volatile> (or whatever is defined as
		3736	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3737	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3738	believed to be sufficiently portable.
		3739
		3740	=item C<sigprocmask> must work in a threaded environment
		3741
		3742	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3743	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3744	pthread implementations will either allow C<sigprocmask> in the "main
		3745	thread" or will block signals process-wide, both behaviours would
		3746	be compatible with libev. Interaction between C<sigprocmask> and
		3747	C<pthread_sigmask> could complicate things, however.
		3748
		3749	The most portable way to handle signals is to block signals in all threads
		3750	except the initial one, and run the default loop in the initial thread as
		3751	well.
		3752
		3753	=item C<long> must be large enough for common memory allocation sizes
		3754
		3755	To improve portability and simplify its API, libev uses C<long> internally
		3756	instead of C<size_t> when allocating its data structures. On non-POSIX
		3757	systems (Microsoft...) this might be unexpectedly low, but is still at
		3758	least 31 bits everywhere, which is enough for hundreds of millions of
		3759	watchers.
		3760
		3761	=item C<double> must hold a time value in seconds with enough accuracy
		3762
		3763	The type C<double> is used to represent timestamps. It is required to
		3764	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3765	enough for at least into the year 4000. This requirement is fulfilled by
		3766	implementations implementing IEEE 754 (basically all existing ones).
		3767
		3768	=back
		3769
		3770	If you know of other additional requirements drop me a note.
		3771
		3772
2465	=head1 COMPLEXITIES	3773	=head1 ALGORITHMIC COMPLEXITIES
2466		3774
2467	In this section the complexities of (many of) the algorithms used inside	3775	In this section the complexities of (many of) the algorithms used inside
2468	libev will be explained. For complexity discussions about backends see the	3776	libev will be documented. For complexity discussions about backends see
2469	documentation for C<ev_default_init>.	3777	the documentation for C<ev_default_init>.
2470		3778
2471	All of the following are about amortised time: If an array needs to be	3779	All of the following are about amortised time: If an array needs to be
2472	extended, libev needs to realloc and move the whole array, but this	3780	extended, libev needs to realloc and move the whole array, but this
2473	happens asymptotically never with higher number of elements, so O(1) might	3781	happens asymptotically rarer with higher number of elements, so O(1) might
2474	mean it might do a lengthy realloc operation in rare cases, but on average	3782	mean that libev does a lengthy realloc operation in rare cases, but on
2475	it is much faster and asymptotically approaches constant time.	3783	average it is much faster and asymptotically approaches constant time.
2476		3784
2477	=over 4	3785	=over 4
2478		3786
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3787	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3788
2481	This means that, when you have a watcher that triggers in one hour and	3789	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3790	there are 100 watchers that would trigger before that, then inserting will
2483	have to skip those 100 watchers.	3791	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3792
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3793	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3794
2487	That means that for changing a timer costs less than removing/adding them	3795	That means that changing a timer costs less than removing/adding them,
2488	as only the relative motion in the event queue has to be paid for.	3796	as only the relative motion in the event queue has to be paid for.
2489		3797
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3798	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3799
2492	These just add the watcher into an array or at the head of a list.	3800	These just add the watcher into an array or at the head of a list.
		3801
2493	=item Stopping check/prepare/idle watchers: O(1)	3802	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3803
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3804	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3805
2497	These watchers are stored in lists then need to be walked to find the	3806	These watchers are stored in lists, so they need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3807	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3808	have many watchers waiting for the same fd or signal: one is typical, two
		3809	is rare).
2500		3810
2501	=item Finding the next timer per loop iteration: O(1)	3811	=item Finding the next timer in each loop iteration: O(1)
		3812
		3813	By virtue of using a binary or 4-heap, the next timer is always found at a
		3814	fixed position in the storage array.
2502		3815
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3816	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3817
2505	A change means an I/O watcher gets started or stopped, which requires	3818	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3819	libev to recalculate its status (and possibly tell the kernel, depending
		3820	on backend and whether C<ev_io_set> was used).
2507		3821
2508	=item Activating one watcher: O(1)	3822	=item Activating one watcher (putting it into the pending state): O(1)
2509		3823
2510	=item Priority handling: O(number_of_priorities)	3824	=item Priority handling: O(number_of_priorities)
2511		3825
2512	Priorities are implemented by allocating some space for each	3826	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3827	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3828	linearly search all the priorities, but starting/stopping and activating
		3829	watchers becomes O(1) with respect to priority handling.
		3830
		3831	=item Sending an ev_async: O(1)
		3832
		3833	=item Processing ev_async_send: O(number_of_async_watchers)
		3834
		3835	=item Processing signals: O(max_signal_number)
		3836
		3837	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3838	calls in the current loop iteration. Checking for async and signal events
		3839	involves iterating over all running async watchers or all signal numbers.
2515		3840
2516	=back	3841	=back
2517		3842
2518		3843
2519	=head1 AUTHOR	3844	=head1 AUTHOR

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