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Revision 1.78 by root, Sun Dec 9 19:42:57 2007 UTC vs.
Revision 1.183 by root, Tue Sep 23 08:37:38 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_ struct 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_ struct 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	struct 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<struct 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.
…		…
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.
117		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 ()>.
		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
122	You can find out the major and minor version numbers of the library	166	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	167	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	168	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	169	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	170	version of the library your program was compiled against.
127		171
		172	These version numbers refer to the ABI version of the library, not the
		173	release version.
		174
128	Usually, it's a good idea to terminate if the major versions mismatch,	175	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	176	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	177	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	178	not a problem.
132		179
133	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
134	version.	181	version.
135		182
136	assert (("libev version mismatch",	183	assert (("libev version mismatch",
137	ev_version_major () == EV_VERSION_MAJOR	184	ev_version_major () == EV_VERSION_MAJOR
138	&& ev_version_minor () >= EV_VERSION_MINOR));	185	&& ev_version_minor () >= EV_VERSION_MINOR));
139		186
140	=item unsigned int ev_supported_backends ()	187	=item unsigned int ev_supported_backends ()
141		188
142	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_*>
143	value) compiled into this binary of libev (independent of their	190	value) compiled into this binary of libev (independent of their
…		…
145	a description of the set values.	192	a description of the set values.
146		193
147	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
148	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
149		196
150	assert (("sorry, no epoll, no sex",	197	assert (("sorry, no epoll, no sex",
151	ev_supported_backends () & EVBACKEND_EPOLL));	198	ev_supported_backends () & EVBACKEND_EPOLL));
152		199
153	=item unsigned int ev_recommended_backends ()	200	=item unsigned int ev_recommended_backends ()
154		201
155	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
156	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
157	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
158	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
159	(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
160	libev will probe for if you specify no backends explicitly.	207	libev will probe for if you specify no backends explicitly.
161		208
162	=item unsigned int ev_embeddable_backends ()	209	=item unsigned int ev_embeddable_backends ()
163		210
…		…
170	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
171		218
172	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
173		220
174	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
175	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
176	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
177	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
178	potentially destructive action. The default is your system realloc	225	or take some potentially destructive action.
179	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.
180		230
181	You could override this function in high-availability programs to, say,	231	You could override this function in high-availability programs to, say,
182	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,
183	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.
184		234
185	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
186	retries).	236	retries (example requires a standards-compliant C<realloc>).
187		237
188	static void *	238	static void *
189	persistent_realloc (void *ptr, size_t size)	239	persistent_realloc (void *ptr, size_t size)
190	{	240	{
191	for (;;)	241	for (;;)
…		…
202	...	252	...
203	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
204		254
205	=item ev_set_syserr_cb (void (*cb)(const char *msg));	255	=item ev_set_syserr_cb (void (*cb)(const char *msg));
206		256
207	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
208	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
209	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
210	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
211	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
212	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
213	(such as abort).	263	(such as abort).
214		264
215	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.
…		…
230		280
231	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 library knows two
232	types of such loops, the I<default> loop, which supports signals and child	282	types of such loops, the I<default> loop, which supports signals and child
233	events, and dynamically created loops which do not.	283	events, and dynamically created loops which do not.
234		284
235	If you use threads, a common model is to run the default event loop
236	in your main thread (or in a separate thread) and for each thread you
237	create, you also create another event loop. Libev itself does no locking
238	whatsoever, so if you mix calls to the same event loop in different
239	threads, make sure you lock (this is usually a bad idea, though, even if
240	done correctly, because it's hideous and inefficient).
241
242	=over 4	285	=over 4
243		286
244	=item struct ev_loop *ev_default_loop (unsigned int flags)	287	=item struct ev_loop *ev_default_loop (unsigned int flags)
245		288
246	This will initialise the default event loop if it hasn't been initialised	289	This will initialise the default event loop if it hasn't been initialised
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	292	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		293
251	If you don't know what event loop to use, use the one returned from this	294	If you don't know what event loop to use, use the one returned from this
252	function.	295	function.
253		296
		297	Note that this function is I<not> thread-safe, so if you want to use it
		298	from multiple threads, you have to lock (note also that this is unlikely,
		299	as loops cannot bes hared easily between threads anyway).
		300
		301	The default loop is the only loop that can handle C<ev_signal> and
		302	C<ev_child> watchers, and to do this, it always registers a handler
		303	for C<SIGCHLD>. If this is a problem for your application you can either
		304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		306	C<ev_default_init>.
		307
254	The flags argument can be used to specify special behaviour or specific	308	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	309	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		310
257	The following flags are supported:	311	The following flags are supported:
258		312
…		…
263	The default flags value. Use this if you have no clue (it's the right	317	The default flags value. Use this if you have no clue (it's the right
264	thing, believe me).	318	thing, believe me).
265		319
266	=item C<EVFLAG_NOENV>	320	=item C<EVFLAG_NOENV>
267		321
268	If this flag bit is ored into the flag value (or the program runs setuid	322	If this flag bit is or'ed into the flag value (or the program runs setuid
269	or setgid) then libev will I<not> look at the environment variable	323	or setgid) then libev will I<not> look at the environment variable
270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
271	override the flags completely if it is found in the environment. This is	325	override the flags completely if it is found in the environment. This is
272	useful to try out specific backends to test their performance, or to work	326	useful to try out specific backends to test their performance, or to work
273	around bugs.	327	around bugs.
…		…
279	enabling this flag.	333	enabling this flag.
280		334
281	This works by calling C<getpid ()> on every iteration of the loop,	335	This works by calling C<getpid ()> on every iteration of the loop,
282	and thus this might slow down your event loop if you do a lot of loop	336	and thus this might slow down your event loop if you do a lot of loop
283	iterations and little real work, but is usually not noticeable (on my	337	iterations and little real work, but is usually not noticeable (on my
284	Linux system for example, C<getpid> is actually a simple 5-insn sequence	338	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
285	without a syscall and thus I<very> fast, but my Linux system also has	339	without a system call and thus I<very> fast, but my GNU/Linux system also has
286	C<pthread_atfork> which is even faster).	340	C<pthread_atfork> which is even faster).
287		341
288	The big advantage of this flag is that you can forget about fork (and	342	The big advantage of this flag is that you can forget about fork (and
289	forget about forgetting to tell libev about forking) when you use this	343	forget about forgetting to tell libev about forking) when you use this
290	flag.	344	flag.
291		345
292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
293	environment variable.	347	environment variable.
294		348
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		350
297	This is your standard select(2) backend. Not I<completely> standard, as	351	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	352	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	353	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	354	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	355	usually the fastest backend for a low number of (low-numbered :) fds.
		356
		357	To get good performance out of this backend you need a high amount of
		358	parallelism (most of the file descriptors should be busy). If you are
		359	writing a server, you should C<accept ()> in a loop to accept as many
		360	connections as possible during one iteration. You might also want to have
		361	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		362	readiness notifications you get per iteration.
		363
		364	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		365	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		366	C<exceptfds> set on that platform).
302		367
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	368	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		369
305	And this is your standard poll(2) backend. It's more complicated than	370	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	371	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	372	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	373	considerably with a lot of inactive fds). It scales similarly to select,
		374	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		375	performance tips.
		376
		377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
309		379
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	380	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		381
312	For few fds, this backend is a bit little slower than poll and select,	382	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	383	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	384	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	385	epoll scales either O(1) or O(active_fds). The epoll design has a number
		386	of shortcomings, such as silently dropping events in some hard-to-detect
		387	cases and requiring a system call per fd change, no fork support and bad
		388	support for dup.
316		389
317	While stopping and starting an I/O watcher in the same iteration will	390	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	391	will result in some caching, there is still a system call per such incident
319	(because the fd could point to a different file description now), so its	392	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	394	very well if you register events for both fds.
322		395
323	Please note that epoll sometimes generates spurious notifications, so you	396	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	397	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	398	(or space) is available.
326		399
		400	Best performance from this backend is achieved by not unregistering all
		401	watchers for a file descriptor until it has been closed, if possible,
		402	i.e. keep at least one watcher active per fd at all times. Stopping and
		403	starting a watcher (without re-setting it) also usually doesn't cause
		404	extra overhead.
		405
		406	While nominally embeddable in other event loops, this feature is broken in
		407	all kernel versions tested so far.
		408
		409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		410	C<EVBACKEND_POLL>.
		411
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		413
329	Kqueue deserves special mention, as at the time of this writing, it	414	Kqueue deserves special mention, as at the time of this writing, it was
330	was broken on all BSDs except NetBSD (usually it doesn't work with	415	broken on all BSDs except NetBSD (usually it doesn't work reliably with
331	anything but sockets and pipes, except on Darwin, where of course its	416	anything but sockets and pipes, except on Darwin, where of course it's
332	completely useless). For this reason its not being "autodetected"	417	completely useless). For this reason it's not being "auto-detected" unless
333	unless you explicitly specify it explicitly in the flags (i.e. using	418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or
334	C<EVBACKEND_KQUEUE>).	419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.
		420
		421	You still can embed kqueue into a normal poll or select backend and use it
		422	only for sockets (after having made sure that sockets work with kqueue on
		423	the target platform). See C<ev_embed> watchers for more info.
335		424
336	It scales in the same way as the epoll backend, but the interface to the	425	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	426	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	427	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	429	two event changes per incident. Support for C<fork ()> is very bad and it
		430	drops fds silently in similarly hard-to-detect cases.
		431
		432	This backend usually performs well under most conditions.
		433
		434	While nominally embeddable in other event loops, this doesn't work
		435	everywhere, so you might need to test for this. And since it is broken
		436	almost everywhere, you should only use it when you have a lot of sockets
		437	(for which it usually works), by embedding it into another event loop
		438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		439	using it only for sockets.
		440
		441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		443	C<NOTE_EOF>.
341		444
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	445	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		446
344	This is not implemented yet (and might never be).	447	This is not implemented yet (and might never be, unless you send me an
		448	implementation). According to reports, C</dev/poll> only supports sockets
		449	and is not embeddable, which would limit the usefulness of this backend
		450	immensely.
345		451
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		453
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	455	it's really slow, but it still scales very well (O(active_fds)).
350		456
351	Please note that solaris ports can result in a lot of spurious	457	Please note that Solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	458	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	459	blocking when no data (or space) is available.
		460
		461	While this backend scales well, it requires one system call per active
		462	file descriptor per loop iteration. For small and medium numbers of file
		463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		464	might perform better.
		465
		466	On the positive side, with the exception of the spurious readiness
		467	notifications, this backend actually performed fully to specification
		468	in all tests and is fully embeddable, which is a rare feat among the
		469	OS-specific backends.
		470
		471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		472	C<EVBACKEND_POLL>.
354		473
355	=item C<EVBACKEND_ALL>	474	=item C<EVBACKEND_ALL>
356		475
357	Try all backends (even potentially broken ones that wouldn't be tried	476	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		479
		480	It is definitely not recommended to use this flag.
		481
361	=back	482	=back
362		483
363	If one or more of these are ored into the flags value, then only these	484	If one or more of these are or'ed into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	485	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	486	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		487
368	The most typical usage is like this:	488	Example: This is the most typical usage.
369		489
370	if (!ev_default_loop (0))	490	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
372		492
373	Restrict libev to the select and poll backends, and do not allow	493	Example: Restrict libev to the select and poll backends, and do not allow
374	environment settings to be taken into account:	494	environment settings to be taken into account:
375		495
376	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
377		497
378	Use whatever libev has to offer, but make sure that kqueue is used if	498	Example: Use whatever libev has to offer, but make sure that kqueue is
379	available (warning, breaks stuff, best use only with your own private	499	used if available (warning, breaks stuff, best use only with your own
380	event loop and only if you know the OS supports your types of fds):	500	private event loop and only if you know the OS supports your types of
		501	fds):
381		502
382	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
383		504
384	=item struct ev_loop *ev_loop_new (unsigned int flags)	505	=item struct ev_loop *ev_loop_new (unsigned int flags)
385		506
386	Similar to C<ev_default_loop>, but always creates a new event loop that is	507	Similar to C<ev_default_loop>, but always creates a new event loop that is
387	always distinct from the default loop. Unlike the default loop, it cannot	508	always distinct from the default loop. Unlike the default loop, it cannot
388	handle signal and child watchers, and attempts to do so will be greeted by	509	handle signal and child watchers, and attempts to do so will be greeted by
389	undefined behaviour (or a failed assertion if assertions are enabled).	510	undefined behaviour (or a failed assertion if assertions are enabled).
390		511
		512	Note that this function I<is> thread-safe, and the recommended way to use
		513	libev with threads is indeed to create one loop per thread, and using the
		514	default loop in the "main" or "initial" thread.
		515
391	Example: Try to create a event loop that uses epoll and nothing else.	516	Example: Try to create a event loop that uses epoll and nothing else.
392		517
393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
394	if (!epoller)	519	if (!epoller)
395	fatal ("no epoll found here, maybe it hides under your chair");	520	fatal ("no epoll found here, maybe it hides under your chair");
396		521
397	=item ev_default_destroy ()	522	=item ev_default_destroy ()
398		523
399	Destroys the default loop again (frees all memory and kernel state	524	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	525	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	526	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	527	responsibility to either stop all watchers cleanly yourself I<before>
403	calling this function, or cope with the fact afterwards (which is usually	528	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	529	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	530	for example).
		531
		532	Note that certain global state, such as signal state, will not be freed by
		533	this function, and related watchers (such as signal and child watchers)
		534	would need to be stopped manually.
		535
		536	In general it is not advisable to call this function except in the
		537	rare occasion where you really need to free e.g. the signal handling
		538	pipe fds. If you need dynamically allocated loops it is better to use
		539	C<ev_loop_new> and C<ev_loop_destroy>).
406		540
407	=item ev_loop_destroy (loop)	541	=item ev_loop_destroy (loop)
408		542
409	Like C<ev_default_destroy>, but destroys an event loop created by an	543	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	544	earlier call to C<ev_loop_new>.
411		545
412	=item ev_default_fork ()	546	=item ev_default_fork ()
413		547
		548	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	549	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	550	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	551	the child process (or both child and parent, but that again makes little
417	again makes little sense).	552	sense). You I<must> call it in the child before using any of the libev
		553	functions, and it will only take effect at the next C<ev_loop> iteration.
418		554
419	You I<must> call this function in the child process after forking if and	555	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	556	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	557	you just fork+exec, you don't have to call it at all.
422		558
423	The function itself is quite fast and it's usually not a problem to call	559	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	560	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	561	quite nicely into a call to C<pthread_atfork>:
426		562
427	pthread_atfork (0, 0, ev_default_fork);	563	pthread_atfork (0, 0, ev_default_fork);
428		564
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	565	=item ev_loop_fork (loop)
434		566
435	Like C<ev_default_fork>, but acts on an event loop created by	567	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	569	after fork that you want to re-use in the child, and how you do this is
		570	entirely your own problem.
		571
		572	=item int ev_is_default_loop (loop)
		573
		574	Returns true when the given loop is, in fact, the default loop, and false
		575	otherwise.
438		576
439	=item unsigned int ev_loop_count (loop)	577	=item unsigned int ev_loop_count (loop)
440		578
441	Returns the count of loop iterations for the loop, which is identical to	579	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	580	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		593
456	Returns the current "event loop time", which is the time the event loop	594	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	595	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	596	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	597	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	598	event occurring (or more correctly, libev finding out about it).
		599
		600	=item ev_now_update (loop)
		601
		602	Establishes the current time by querying the kernel, updating the time
		603	returned by C<ev_now ()> in the progress. This is a costly operation and
		604	is usually done automatically within C<ev_loop ()>.
		605
		606	This function is rarely useful, but when some event callback runs for a
		607	very long time without entering the event loop, updating libev's idea of
		608	the current time is a good idea.
		609
		610	See also "The special problem of time updates" in the C<ev_timer> section.
461		611
462	=item ev_loop (loop, int flags)	612	=item ev_loop (loop, int flags)
463		613
464	Finally, this is it, the event handler. This function usually is called	614	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	615	after you initialised all your watchers and you want to start handling
…		…
468	If the flags argument is specified as C<0>, it will not return until	618	If the flags argument is specified as C<0>, it will not return until
469	either no event watchers are active anymore or C<ev_unloop> was called.	619	either no event watchers are active anymore or C<ev_unloop> was called.
470		620
471	Please note that an explicit C<ev_unloop> is usually better than	621	Please note that an explicit C<ev_unloop> is usually better than
472	relying on all watchers to be stopped when deciding when a program has	622	relying on all watchers to be stopped when deciding when a program has
473	finished (especially in interactive programs), but having a program that	623	finished (especially in interactive programs), but having a program
474	automatically loops as long as it has to and no longer by virtue of	624	that automatically loops as long as it has to and no longer by virtue
475	relying on its watchers stopping correctly is a thing of beauty.	625	of relying on its watchers stopping correctly, that is truly a thing of
		626	beauty.
476		627
477	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
478	those events and any outstanding ones, but will not block your process in	629	those events and any already outstanding ones, but will not block your
479	case there are no events and will return after one iteration of the loop.	630	process in case there are no events and will return after one iteration of
		631	the loop.
480		632
481	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
482	neccessary) and will handle those and any outstanding ones. It will block	634	necessary) and will handle those and any already outstanding ones. It
483	your process until at least one new event arrives, and will return after	635	will block your process until at least one new event arrives (which could
484	one iteration of the loop. This is useful if you are waiting for some	636	be an event internal to libev itself, so there is no guarentee that a
485	external event in conjunction with something not expressible using other	637	user-registered callback will be called), and will return after one
		638	iteration of the loop.
		639
		640	This is useful if you are waiting for some external event in conjunction
		641	with something not expressible using other libev watchers (i.e. "roll your
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	642	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	643	usually a better approach for this kind of thing.
488		644
489	Here are the gory details of what C<ev_loop> does:	645	Here are the gory details of what C<ev_loop> does:
490		646
491	- Before the first iteration, call any pending watchers.	647	- Before the first iteration, call any pending watchers.
492	* If there are no active watchers (reference count is zero), return.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
493	- Queue all prepare watchers and then call all outstanding watchers.	649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
494	- If we have been forked, recreate the kernel state.	651	- If we have been forked, detach and recreate the kernel state
		652	as to not disturb the other process.
495	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
496	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
497	- Calculate for how long to block.	655	- Calculate for how long to sleep or block, if at all
		656	(active idle watchers, EVLOOP_NONBLOCK or not having
		657	any active watchers at all will result in not sleeping).
		658	- Sleep if the I/O and timer collect interval say so.
498	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
499	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
500	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
501	- Queue all outstanding timers.	662	- Queue all expired timers.
502	- Queue all outstanding periodics.	663	- Queue all expired periodics.
503	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
504	- Queue all check watchers.	665	- Queue all check watchers.
505	- Call all queued watchers in reverse order (i.e. check watchers first).	666	- Call all queued watchers in reverse order (i.e. check watchers first).
506	Signals and child watchers are implemented as I/O watchers, and will	667	Signals and child watchers are implemented as I/O watchers, and will
507	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
508	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
509	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
510		672
511	Example: Queue some jobs and then loop until no events are outsanding	673	Example: Queue some jobs and then loop until no events are outstanding
512	anymore.	674	anymore.
513		675
514	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
515	... as they still have work to do (even an idle watcher will do..)	677	... as they still have work to do (even an idle watcher will do..)
516	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
517	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
518		680
519	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
520		682
521	Can be used to make a call to C<ev_loop> return early (but only after it	683	Can be used to make a call to C<ev_loop> return early (but only after it
522	has processed all outstanding events). The C<how> argument must be either	684	has processed all outstanding events). The C<how> argument must be either
523	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
524	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
525		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
526	=item ev_ref (loop)	690	=item ev_ref (loop)
527		691
528	=item ev_unref (loop)	692	=item ev_unref (loop)
529		693
530	Ref/unref can be used to add or remove a reference count on the event	694	Ref/unref can be used to add or remove a reference count on the event
531	loop: Every watcher keeps one reference, and as long as the reference	695	loop: Every watcher keeps one reference, and as long as the reference
532	count is nonzero, C<ev_loop> will not return on its own. If you have	696	count is nonzero, C<ev_loop> will not return on its own.
		697
533	a watcher you never unregister that should not keep C<ev_loop> from	698	If you have a watcher you never unregister that should not keep C<ev_loop>
534	returning, ev_unref() after starting, and ev_ref() before stopping it. For	699	from returning, call ev_unref() after starting, and ev_ref() before
		700	stopping it.
		701
535	example, libev itself uses this for its internal signal pipe: It is not	702	As an example, libev itself uses this for its internal signal pipe: It is
536	visible to the libev user and should not keep C<ev_loop> from exiting if	703	not visible to the libev user and should not keep C<ev_loop> from exiting
537	no event watchers registered by it are active. It is also an excellent	704	if no event watchers registered by it are active. It is also an excellent
538	way to do this for generic recurring timers or from within third-party	705	way to do this for generic recurring timers or from within third-party
539	libraries. Just remember to I<unref after start> and I<ref before stop>.	706	libraries. Just remember to I<unref after start> and I<ref before stop>
		707	(but only if the watcher wasn't active before, or was active before,
		708	respectively).
540		709
541	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
542	running when nothing else is active.	711	running when nothing else is active.
543		712
544	struct ev_signal exitsig;	713	struct ev_signal exitsig;
545	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
546	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
547	evf_unref (loop);	716	evf_unref (loop);
548		717
549	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
550		719
551	ev_ref (loop);	720	ev_ref (loop);
552	ev_signal_stop (loop, &exitsig);	721	ev_signal_stop (loop, &exitsig);
		722
		723	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		724
		725	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		726
		727	These advanced functions influence the time that libev will spend waiting
		728	for events. Both time intervals are by default C<0>, meaning that libev
		729	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		730	latency.
		731
		732	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		733	allows libev to delay invocation of I/O and timer/periodic callbacks
		734	to increase efficiency of loop iterations (or to increase power-saving
		735	opportunities).
		736
		737	The idea is that sometimes your program runs just fast enough to handle
		738	one (or very few) event(s) per loop iteration. While this makes the
		739	program responsive, it also wastes a lot of CPU time to poll for new
		740	events, especially with backends like C<select ()> which have a high
		741	overhead for the actual polling but can deliver many events at once.
		742
		743	By setting a higher I<io collect interval> you allow libev to spend more
		744	time collecting I/O events, so you can handle more events per iteration,
		745	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		746	C<ev_timer>) will be not affected. Setting this to a non-null value will
		747	introduce an additional C<ev_sleep ()> call into most loop iterations.
		748
		749	Likewise, by setting a higher I<timeout collect interval> you allow libev
		750	to spend more time collecting timeouts, at the expense of increased
		751	latency/jitter/inexactness (the watcher callback will be called
		752	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		753	value will not introduce any overhead in libev.
		754
		755	Many (busy) programs can usually benefit by setting the I/O collect
		756	interval to a value near C<0.1> or so, which is often enough for
		757	interactive servers (of course not for games), likewise for timeouts. It
		758	usually doesn't make much sense to set it to a lower value than C<0.01>,
		759	as this approaches the timing granularity of most systems.
		760
		761	Setting the I<timeout collect interval> can improve the opportunity for
		762	saving power, as the program will "bundle" timer callback invocations that
		763	are "near" in time together, by delaying some, thus reducing the number of
		764	times the process sleeps and wakes up again. Another useful technique to
		765	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		766	they fire on, say, one-second boundaries only.
		767
		768	=item ev_loop_verify (loop)
		769
		770	This function only does something when C<EV_VERIFY> support has been
		771	compiled in. which is the default for non-minimal builds. It tries to go
		772	through all internal structures and checks them for validity. If anything
		773	is found to be inconsistent, it will print an error message to standard
		774	error and call C<abort ()>.
		775
		776	This can be used to catch bugs inside libev itself: under normal
		777	circumstances, this function will never abort as of course libev keeps its
		778	data structures consistent.
553		779
554	=back	780	=back
555		781
556		782
557	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
558		784
559	A watcher is a structure that you create and register to record your	785	A watcher is a structure that you create and register to record your
560	interest in some event. For instance, if you want to wait for STDIN to	786	interest in some event. For instance, if you want to wait for STDIN to
561	become readable, you would create an C<ev_io> watcher for that:	787	become readable, you would create an C<ev_io> watcher for that:
562		788
563	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
564	{	790	{
565	ev_io_stop (w);	791	ev_io_stop (w);
566	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
567	}	793	}
568		794
569	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
570	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
571	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
572	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
573	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
574	ev_loop (loop, 0);	800	ev_loop (loop, 0);
575		801
576	As you can see, you are responsible for allocating the memory for your	802	As you can see, you are responsible for allocating the memory for your
577	watcher structures (and it is usually a bad idea to do this on the stack,	803	watcher structures (and it is usually a bad idea to do this on the stack,
578	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
579		805
580	Each watcher structure must be initialised by a call to C<ev_init	806	Each watcher structure must be initialised by a call to C<ev_init
581	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
582	callback gets invoked each time the event occurs (or, in the case of io	808	callback gets invoked each time the event occurs (or, in the case of I/O
583	watchers, each time the event loop detects that the file descriptor given	809	watchers, each time the event loop detects that the file descriptor given
584	is readable and/or writable).	810	is readable and/or writable).
585		811
586	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro
587	with arguments specific to this watcher type. There is also a macro	813	with arguments specific to this watcher type. There is also a macro
…		…
657	=item C<EV_FORK>	883	=item C<EV_FORK>
658		884
659	The event loop has been resumed in the child process after fork (see	885	The event loop has been resumed in the child process after fork (see
660	C<ev_fork>).	886	C<ev_fork>).
661		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
662	=item C<EV_ERROR>	892	=item C<EV_ERROR>
663		893
664	An unspecified error has occured, the watcher has been stopped. This might	894	An unspecified error has occurred, the watcher has been stopped. This might
665	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
666	ran out of memory, a file descriptor was found to be closed or any other	896	ran out of memory, a file descriptor was found to be closed or any other
667	problem. You best act on it by reporting the problem and somehow coping	897	problem. You best act on it by reporting the problem and somehow coping
668	with the watcher being stopped.	898	with the watcher being stopped.
669		899
670	Libev will usually signal a few "dummy" events together with an error,	900	Libev will usually signal a few "dummy" events together with an error, for
671	for example it might indicate that a fd is readable or writable, and if	901	example it might indicate that a fd is readable or writable, and if your
672	your callbacks is well-written it can just attempt the operation and cope	902	callbacks is well-written it can just attempt the operation and cope with
673	with the error from read() or write(). This will not work in multithreaded	903	the error from read() or write(). This will not work in multi-threaded
674	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
675		906
676	=back	907	=back
677		908
678	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
679		910
…		…
695	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
696		927
697	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
698	int revents)>.	929	int revents)>.
699		930
		931	Example: Initialise an C<ev_io> watcher in two steps.
		932
		933	ev_io w;
		934	ev_init (&w, my_cb);
		935	ev_io_set (&w, STDIN_FILENO, EV_READ);
		936
700	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
701		938
702	This macro initialises the type-specific parts of a watcher. You need to	939	This macro initialises the type-specific parts of a watcher. You need to
703	call C<ev_init> at least once before you call this macro, but you can	940	call C<ev_init> at least once before you call this macro, but you can
704	call C<ev_TYPE_set> any number of times. You must not, however, call this	941	call C<ev_TYPE_set> any number of times. You must not, however, call this
…		…
706	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
707		944
708	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
709	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	946	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
710		947
		948	See C<ev_init>, above, for an example.
		949
711	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
712		951
713	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	952	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
714	calls into a single call. This is the most convinient method to initialise	953	calls into a single call. This is the most convenient method to initialise
715	a watcher. The same limitations apply, of course.	954	a watcher. The same limitations apply, of course.
		955
		956	Example: Initialise and set an C<ev_io> watcher in one step.
		957
		958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
716		959
717	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
718		961
719	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
720	events. If the watcher is already active nothing will happen.	963	events. If the watcher is already active nothing will happen.
		964
		965	Example: Start the C<ev_io> watcher that is being abused as example in this
		966	whole section.
		967
		968	ev_io_start (EV_DEFAULT_UC, &w);
721		969
722	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
723		971
724	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
725	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
782		1030
783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
784		1032
785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
786	C<loop> nor C<revents> need to be valid as long as the watcher callback	1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
787	can deal with that fact.	1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
788		1037
789	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
790		1039
791	If the watcher is pending, this function returns clears its pending status	1040	If the watcher is pending, this function clears its pending status and
792	and returns its C<revents> bitset (as if its callback was invoked). If the	1041	returns its C<revents> bitset (as if its callback was invoked). If the
793	watcher isn't pending it does nothing and returns C<0>.	1042	watcher isn't pending it does nothing and returns C<0>.
794		1043
		1044	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1045	callback to be invoked, which can be accomplished with this function.
		1046
795	=back	1047	=back
796		1048
797		1049
798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
799		1051
800	Each watcher has, by default, a member C<void *data> that you can change	1052	Each watcher has, by default, a member C<void *data> that you can change
801	and read at any time, libev will completely ignore it. This can be used	1053	and read at any time: libev will completely ignore it. This can be used
802	to associate arbitrary data with your watcher. If you need more data and	1054	to associate arbitrary data with your watcher. If you need more data and
803	don't want to allocate memory and store a pointer to it in that data	1055	don't want to allocate memory and store a pointer to it in that data
804	member, you can also "subclass" the watcher type and provide your own	1056	member, you can also "subclass" the watcher type and provide your own
805	data:	1057	data:
806		1058
807	struct my_io	1059	struct my_io
808	{	1060	{
809	struct ev_io io;	1061	struct ev_io io;
810	int otherfd;	1062	int otherfd;
811	void *somedata;	1063	void *somedata;
812	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
813	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
814		1070
815	And since your callback will be called with a pointer to the watcher, you	1071	And since your callback will be called with a pointer to the watcher, you
816	can cast it back to your own type:	1072	can cast it back to your own type:
817		1073
818	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
819	{	1075	{
820	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
821	...	1077	...
822	}	1078	}
823		1079
824	More interesting and less C-conformant ways of casting your callback type	1080	More interesting and less C-conformant ways of casting your callback type
825	instead have been omitted.	1081	instead have been omitted.
826		1082
827	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
828	watchers:	1084	embedded watchers:
829		1085
830	struct my_biggy	1086	struct my_biggy
831	{	1087	{
832	int some_data;	1088	int some_data;
833	ev_timer t1;	1089	ev_timer t1;
834	ev_timer t2;	1090	ev_timer t2;
835	}	1091	}
836		1092
837	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1093	In this case getting the pointer to C<my_biggy> is a bit more
838	you need to use C<offsetof>:	1094	complicated: Either you store the address of your C<my_biggy> struct
		1095	in the C<data> member of the watcher (for woozies), or you need to use
		1096	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1097	programmers):
839		1098
840	#include <stddef.h>	1099	#include <stddef.h>
841		1100
842	static void	1101	static void
843	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
844	{	1103	{
845	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
846	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
847	}	1106	}
848		1107
849	static void	1108	static void
850	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
851	{	1110	{
852	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
853	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
854	}	1113	}
855		1114
856		1115
857	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
858		1117
859	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
883	In general you can register as many read and/or write event watchers per	1142	In general you can register as many read and/or write event watchers per
884	fd as you want (as long as you don't confuse yourself). Setting all file	1143	fd as you want (as long as you don't confuse yourself). Setting all file
885	descriptors to non-blocking mode is also usually a good idea (but not	1144	descriptors to non-blocking mode is also usually a good idea (but not
886	required if you know what you are doing).	1145	required if you know what you are doing).
887		1146
888	You have to be careful with dup'ed file descriptors, though. Some backends	1147	If you cannot use non-blocking mode, then force the use of a
889	(the linux epoll backend is a notable example) cannot handle dup'ed file	1148	known-to-be-good backend (at the time of this writing, this includes only
890	descriptors correctly if you register interest in two or more fds pointing	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
891	to the same underlying file/socket/etc. description (that is, they share
892	the same underlying "file open").
893
894	If you must do this, then force the use of a known-to-be-good backend
895	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
896	C<EVBACKEND_POLL>).
897		1150
898	Another thing you have to watch out for is that it is quite easy to	1151	Another thing you have to watch out for is that it is quite easy to
899	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
900	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1153	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
901	because there is no data. Not only are some backends known to create a	1154	because there is no data. Not only are some backends known to create a
902	lot of those (for example solaris ports), it is very easy to get into	1155	lot of those (for example Solaris ports), it is very easy to get into
903	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
904	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1157	it is best to always use non-blocking I/O: An extra C<read>(2) returning
905	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1158	C<EAGAIN> is far preferable to a program hanging until some data arrives.
906		1159
907	If you cannot run the fd in non-blocking mode (for example you should not	1160	If you cannot run the fd in non-blocking mode (for example you should
908	play around with an Xlib connection), then you have to seperately re-test	1161	not play around with an Xlib connection), then you have to separately
909	whether a file descriptor is really ready with a known-to-be good interface	1162	re-test whether a file descriptor is really ready with a known-to-be good
910	such as poll (fortunately in our Xlib example, Xlib already does this on	1163	interface such as poll (fortunately in our Xlib example, Xlib already
911	its own, so its quite safe to use).	1164	does this on its own, so its quite safe to use). Some people additionally
		1165	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1166	indefinitely.
		1167
		1168	But really, best use non-blocking mode.
		1169
		1170	=head3 The special problem of disappearing file descriptors
		1171
		1172	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1173	descriptor (either due to calling C<close> explicitly or any other means,
		1174	such as C<dup2>). The reason is that you register interest in some file
		1175	descriptor, but when it goes away, the operating system will silently drop
		1176	this interest. If another file descriptor with the same number then is
		1177	registered with libev, there is no efficient way to see that this is, in
		1178	fact, a different file descriptor.
		1179
		1180	To avoid having to explicitly tell libev about such cases, libev follows
		1181	the following policy: Each time C<ev_io_set> is being called, libev
		1182	will assume that this is potentially a new file descriptor, otherwise
		1183	it is assumed that the file descriptor stays the same. That means that
		1184	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1185	descriptor even if the file descriptor number itself did not change.
		1186
		1187	This is how one would do it normally anyway, the important point is that
		1188	the libev application should not optimise around libev but should leave
		1189	optimisations to libev.
		1190
		1191	=head3 The special problem of dup'ed file descriptors
		1192
		1193	Some backends (e.g. epoll), cannot register events for file descriptors,
		1194	but only events for the underlying file descriptions. That means when you
		1195	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1196	events for them, only one file descriptor might actually receive events.
		1197
		1198	There is no workaround possible except not registering events
		1199	for potentially C<dup ()>'ed file descriptors, or to resort to
		1200	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1201
		1202	=head3 The special problem of fork
		1203
		1204	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1205	useless behaviour. Libev fully supports fork, but needs to be told about
		1206	it in the child.
		1207
		1208	To support fork in your programs, you either have to call
		1209	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1210	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1211	C<EVBACKEND_POLL>.
		1212
		1213	=head3 The special problem of SIGPIPE
		1214
		1215	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1216	when writing to a pipe whose other end has been closed, your program gets
		1217	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1218	this is sensible behaviour, for daemons, this is usually undesirable.
		1219
		1220	So when you encounter spurious, unexplained daemon exits, make sure you
		1221	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1222	somewhere, as that would have given you a big clue).
		1223
		1224
		1225	=head3 Watcher-Specific Functions
912		1226
913	=over 4	1227	=over 4
914		1228
915	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
916		1230
917	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
918		1232
919	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1233	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
920	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1234	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
921	C<EV_READ | EV_WRITE> to receive the given events.	1235	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
922		1236
923	=item int fd [read-only]	1237	=item int fd [read-only]
924		1238
925	The file descriptor being watched.	1239	The file descriptor being watched.
926		1240
927	=item int events [read-only]	1241	=item int events [read-only]
928		1242
929	The events being watched.	1243	The events being watched.
930		1244
931	=back	1245	=back
		1246
		1247	=head3 Examples
932		1248
933	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
934	readable, but only once. Since it is likely line-buffered, you could	1250	readable, but only once. Since it is likely line-buffered, you could
935	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
936		1252
937	static void	1253	static void
938	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
939	{	1255	{
940	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
941	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1257	.. read from stdin here (or from w->fd) and handle any I/O errors
942	}	1258	}
943		1259
944	...	1260	...
945	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
946	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
947	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
948	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
949	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
950		1266
951		1267
952	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
953		1269
954	Timer watchers are simple relative timers that generate an event after a	1270	Timer watchers are simple relative timers that generate an event after a
955	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
956		1272
957	The timers are based on real time, that is, if you register an event that	1273	The timers are based on real time, that is, if you register an event that
958	times out after an hour and you reset your system clock to last years	1274	times out after an hour and you reset your system clock to January last
959	time, it will still time out after (roughly) and hour. "Roughly" because	1275	year, it will still time out after (roughly) one hour. "Roughly" because
960	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
961	monotonic clock option helps a lot here).	1277	monotonic clock option helps a lot here).
		1278
		1279	The callback is guaranteed to be invoked only I<after> its timeout has
		1280	passed, but if multiple timers become ready during the same loop iteration
		1281	then order of execution is undefined.
		1282
		1283	=head3 The special problem of time updates
		1284
		1285	Establishing the current time is a costly operation (it usually takes at
		1286	least two system calls): EV therefore updates its idea of the current
		1287	time only before and after C<ev_loop> collects new events, which causes a
		1288	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1289	lots of events in one iteration.
962		1290
963	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
964	time. This is usually the right thing as this timestamp refers to the time	1292	time. This is usually the right thing as this timestamp refers to the time
965	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
966	you suspect event processing to be delayed and you I<need> to base the timeout	1294	you suspect event processing to be delayed and you I<need> to base the
967	on the current time, use something like this to adjust for this:	1295	timeout on the current time, use something like this to adjust for this:
968		1296
969	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
970		1298
971	The callback is guarenteed to be invoked only when its timeout has passed,	1299	If the event loop is suspended for a long time, you can also force an
972	but if multiple timers become ready during the same loop iteration then	1300	update of the time returned by C<ev_now ()> by calling C<ev_now_update
973	order of execution is undefined.	1301	()>.
		1302
		1303	=head3 Watcher-Specific Functions and Data Members
974		1304
975	=over 4	1305	=over 4
976		1306
977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1307	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978		1308
979	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1309	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
980		1310
981	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1311	Configure the timer to trigger after C<after> seconds. If C<repeat>
982	C<0.>, then it will automatically be stopped. If it is positive, then the	1312	is C<0.>, then it will automatically be stopped once the timeout is
983	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
984	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
985		1316
986	The timer itself will do a best-effort at avoiding drift, that is, if you	1317	The timer itself will do a best-effort at avoiding drift, that is, if
987	configure a timer to trigger every 10 seconds, then it will trigger at	1318	you configure a timer to trigger every 10 seconds, then it will normally
988	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
989	the timer (because it takes longer than those 10 seconds to do stuff) the	1320	keep up with the timer (because it takes longer than those 10 seconds to
990	timer will not fire more than once per event loop iteration.	1321	do stuff) the timer will not fire more than once per event loop iteration.
991		1322
992	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
993		1324
994	This will act as if the timer timed out and restart it again if it is	1325	This will act as if the timer timed out and restart it again if it is
995	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
996		1327
997	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
998		1329
999	If the timer is started but nonrepeating, stop it (as if it timed out).	1330	If the timer is started but non-repeating, stop it (as if it timed out).
1000		1331
1001	If the timer is repeating, either start it if necessary (with the	1332	If the timer is repeating, either start it if necessary (with the
1002	C<repeat> value), or reset the running timer to the C<repeat> value.	1333	C<repeat> value), or reset the running timer to the C<repeat> value.
1003		1334
1004	This sounds a bit complicated, but here is a useful and typical	1335	This sounds a bit complicated, but here is a useful and typical
1005	example: Imagine you have a tcp connection and you want a so-called idle	1336	example: Imagine you have a TCP connection and you want a so-called idle
1006	timeout, that is, you want to be called when there have been, say, 60	1337	timeout, that is, you want to be called when there have been, say, 60
1007	seconds of inactivity on the socket. The easiest way to do this is to	1338	seconds of inactivity on the socket. The easiest way to do this is to
1008	configure an C<ev_timer> with a C<repeat> value of C<60> and then call	1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1009	C<ev_timer_again> each time you successfully read or write some data. If	1340	C<ev_timer_again> each time you successfully read or write some data. If
1010	you go into an idle state where you do not expect data to travel on the	1341	you go into an idle state where you do not expect data to travel on the
…		…
1024	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1025		1356
1026	This is more slightly efficient then stopping/starting the timer each time	1357	This is more slightly efficient then stopping/starting the timer each time
1027	you want to modify its timeout value.	1358	you want to modify its timeout value.
1028		1359
		1360	Note, however, that it is often even more efficient to remember the
		1361	time of the last activity and let the timer time-out naturally. In the
		1362	callback, you then check whether the time-out is real, or, if there was
		1363	some activity, you reschedule the watcher to time-out in "last_activity +
		1364	timeout - ev_now ()" seconds.
		1365
1029	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1030		1367
1031	The current C<repeat> value. Will be used each time the watcher times out	1368	The current C<repeat> value. Will be used each time the watcher times out
1032	or C<ev_timer_again> is called and determines the next timeout (if any),	1369	or C<ev_timer_again> is called, and determines the next timeout (if any),
1033	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1034		1371
1035	=back	1372	=back
1036		1373
		1374	=head3 Examples
		1375
1037	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1038		1377
1039	static void	1378	static void
1040	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1041	{	1380	{
1042	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1043	}	1382	}
1044		1383
1045	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1046	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1047	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1048		1387
1049	Example: Create a timeout timer that times out after 10 seconds of	1388	Example: Create a timeout timer that times out after 10 seconds of
1050	inactivity.	1389	inactivity.
1051		1390
1052	static void	1391	static void
1053	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1054	{	1393	{
1055	.. ten seconds without any activity	1394	.. ten seconds without any activity
1056	}	1395	}
1057		1396
1058	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1059	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1060	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1061	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1062		1401
1063	// and in some piece of code that gets executed on any "activity":	1402	// and in some piece of code that gets executed on any "activity":
1064	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1065	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1066		1405
1067		1406
1068	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1069		1408
1070	Periodic watchers are also timers of a kind, but they are very versatile	1409	Periodic watchers are also timers of a kind, but they are very versatile
1071	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1072		1411
1073	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1074	but on wallclock time (absolute time). You can tell a periodic watcher	1413	but on wall clock time (absolute time). You can tell a periodic watcher
1075	to trigger "at" some specific point in time. For example, if you tell a	1414	to trigger after some specific point in time. For example, if you tell a
1076	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1077	+ 10.>) and then reset your system clock to the last year, then it will	1416	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1417	clock to January of the previous year, then it will take more than year
1078	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1079	roughly 10 seconds later).	1419	roughly 10 seconds later as it uses a relative timeout).
1080		1420
1081	They can also be used to implement vastly more complex timers, such as	1421	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on each midnight, local time or other, complicated,	1422	such as triggering an event on each "midnight, local time", or other
1083	rules.	1423	complicated rules.
1084		1424
1085	As with timers, the callback is guarenteed to be invoked only when the	1425	As with timers, the callback is guaranteed to be invoked only when the
1086	time (C<at>) has been passed, but if multiple periodic timers become ready	1426	time (C<at>) has passed, but if multiple periodic timers become ready
1087	during the same loop iteration then order of execution is undefined.	1427	during the same loop iteration, then order of execution is undefined.
		1428
		1429	=head3 Watcher-Specific Functions and Data Members
1088		1430
1089	=over 4	1431	=over 4
1090		1432
1091	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092		1434
1093	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1094		1436
1095	Lots of arguments, lets sort it out... There are basically three modes of	1437	Lots of arguments, lets sort it out... There are basically three modes of
1096	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1097		1439
1098	=over 4	1440	=over 4
1099		1441
1100	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1101		1443
1102	In this configuration the watcher triggers an event at the wallclock time	1444	In this configuration the watcher triggers an event after the wall clock
1103	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1445	time C<at> has passed. It will not repeat and will not adjust when a time
1104	that is, if it is to be run at January 1st 2011 then it will run when the	1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1105	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1106		1448
1107	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1108		1450
1109	In this mode the watcher will always be scheduled to time out at the next	1451	In this mode the watcher will always be scheduled to time out at the next
1110	C<at + N * interval> time (for some integer N, which can also be negative)	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1111	and then repeat, regardless of any time jumps.	1453	and then repeat, regardless of any time jumps.
1112		1454
1113	This can be used to create timers that do not drift with respect to system	1455	This can be used to create timers that do not drift with respect to the
1114	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1115		1458
1116	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1117		1460
1118	This doesn't mean there will always be 3600 seconds in between triggers,	1461	This doesn't mean there will always be 3600 seconds in between triggers,
1119	but only that the the callback will be called when the system time shows a	1462	but only that the callback will be called when the system time shows a
1120	full hour (UTC), or more correctly, when the system time is evenly divisible	1463	full hour (UTC), or more correctly, when the system time is evenly divisible
1121	by 3600.	1464	by 3600.
1122		1465
1123	Another way to think about it (for the mathematically inclined) is that	1466	Another way to think about it (for the mathematically inclined) is that
1124	C<ev_periodic> will try to run the callback in this mode at the next possible	1467	C<ev_periodic> will try to run the callback in this mode at the next possible
1125	time where C<time = at (mod interval)>, regardless of any time jumps.	1468	time where C<time = at (mod interval)>, regardless of any time jumps.
1126		1469
1127	For numerical stability it is preferable that the C<at> value is near	1470	For numerical stability it is preferable that the C<at> value is near
1128	C<ev_now ()> (the current time), but there is no range requirement for	1471	C<ev_now ()> (the current time), but there is no range requirement for
1129	this value.	1472	this value, and in fact is often specified as zero.
		1473
		1474	Note also that there is an upper limit to how often a timer can fire (CPU
		1475	speed for example), so if C<interval> is very small then timing stability
		1476	will of course deteriorate. Libev itself tries to be exact to be about one
		1477	millisecond (if the OS supports it and the machine is fast enough).
1130		1478
1131	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1132		1480
1133	In this mode the values for C<interval> and C<at> are both being	1481	In this mode the values for C<interval> and C<at> are both being
1134	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1135	reschedule callback will be called with the watcher as first, and the	1483	reschedule callback will be called with the watcher as first, and the
1136	current time as second argument.	1484	current time as second argument.
1137		1485
1138	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1139	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1140	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1141	starting an C<ev_prepare> watcher, which is legal).
1142		1488
		1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1491	only event loop modification you are allowed to do).
		1492
1143	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic
1144	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1145		1495
1146	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1147	{	1497	{
1148	return now + 60.;	1498	return now + 60.;
1149	}	1499	}
…		…
1151	It must return the next time to trigger, based on the passed time value	1501	It must return the next time to trigger, based on the passed time value
1152	(that is, the lowest time value larger than to the second argument). It	1502	(that is, the lowest time value larger than to the second argument). It
1153	will usually be called just before the callback will be triggered, but	1503	will usually be called just before the callback will be triggered, but
1154	might be called at other times, too.	1504	might be called at other times, too.
1155		1505
1156	NOTE: I<< This callback must always return a time that is later than the	1506	NOTE: I<< This callback must always return a time that is higher than or
1157	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1158		1508
1159	This can be used to create very complex timers, such as a timer that	1509	This can be used to create very complex timers, such as a timer that
1160	triggers on each midnight, local time. To do this, you would calculate the	1510	triggers on "next midnight, local time". To do this, you would calculate the
1161	next midnight after C<now> and return the timestamp value for this. How	1511	next midnight after C<now> and return the timestamp value for this. How
1162	you do this is, again, up to you (but it is not trivial, which is the main	1512	you do this is, again, up to you (but it is not trivial, which is the main
1163	reason I omitted it as an example).	1513	reason I omitted it as an example).
1164		1514
1165	=back	1515	=back
…		…
1169	Simply stops and restarts the periodic watcher again. This is only useful	1519	Simply stops and restarts the periodic watcher again. This is only useful
1170	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1171	a different time than the last time it was called (e.g. in a crond like	1521	a different time than the last time it was called (e.g. in a crond like
1172	program when the crontabs have changed).	1522	program when the crontabs have changed).
1173		1523
		1524	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1525
		1526	When active, returns the absolute time that the watcher is supposed to
		1527	trigger next.
		1528
1174	=item ev_tstamp offset [read-write]	1529	=item ev_tstamp offset [read-write]
1175		1530
1176	When repeating, this contains the offset value, otherwise this is the	1531	When repeating, this contains the offset value, otherwise this is the
1177	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1178		1533
…		…
1191	switched off. Can be changed any time, but changes only take effect when	1546	switched off. Can be changed any time, but changes only take effect when
1192	the periodic timer fires or C<ev_periodic_again> is being called.	1547	the periodic timer fires or C<ev_periodic_again> is being called.
1193		1548
1194	=back	1549	=back
1195		1550
		1551	=head3 Examples
		1552
1196	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1197	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1198	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1199		1556
1200	static void	1557	static void
1201	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1202	{	1559	{
1203	... its now a full hour (UTC, or TAI or whatever your clock follows)	1560	... its now a full hour (UTC, or TAI or whatever your clock follows)
1204	}	1561	}
1205		1562
1206	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1208	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1209		1566
1210	Example: The same as above, but use a reschedule callback to do it:	1567	Example: The same as above, but use a reschedule callback to do it:
1211		1568
1212	#include <math.h>	1569	#include <math.h>
1213		1570
1214	static ev_tstamp	1571	static ev_tstamp
1215	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1216	{	1573	{
1217	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1218	}	1575	}
1219		1576
1220	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1221		1578
1222	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1223		1580
1224	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1225	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1226	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1227	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1228		1585
1229		1586
1230	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1231		1588
1232	Signal watchers will trigger an event when the process receives a specific	1589	Signal watchers will trigger an event when the process receives a specific
1233	signal one or more times. Even though signals are very asynchronous, libev	1590	signal one or more times. Even though signals are very asynchronous, libev
1234	will try it's best to deliver signals synchronously, i.e. as part of the	1591	will try it's best to deliver signals synchronously, i.e. as part of the
1235	normal event processing, like any other event.	1592	normal event processing, like any other event.
1236		1593
		1594	If you want signals asynchronously, just use C<sigaction> as you would
		1595	do without libev and forget about sharing the signal. You can even use
		1596	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1597
1237	You can configure as many watchers as you like per signal. Only when the	1598	You can configure as many watchers as you like per signal. Only when the
1238	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1239	with the kernel (thus it coexists with your own signal handlers as long	1600	with the kernel (thus it coexists with your own signal handlers as long as
1240	as you don't register any with libev). Similarly, when the last signal	1601	you don't register any with libev for the same signal). Similarly, when
1241	watcher for a signal is stopped libev will reset the signal handler to	1602	the last signal watcher for a signal is stopped, libev will reset the
1242	SIG_DFL (regardless of what it was set to before).	1603	signal handler to SIG_DFL (regardless of what it was set to before).
		1604
		1605	If possible and supported, libev will install its handlers with
		1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1607	interrupted. If you have a problem with system calls getting interrupted by
		1608	signals you can block all signals in an C<ev_check> watcher and unblock
		1609	them in an C<ev_prepare> watcher.
		1610
		1611	=head3 Watcher-Specific Functions and Data Members
1243		1612
1244	=over 4	1613	=over 4
1245		1614
1246	=item ev_signal_init (ev_signal *, callback, int signum)	1615	=item ev_signal_init (ev_signal *, callback, int signum)
1247		1616
…		…
1254		1623
1255	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1256		1625
1257	=back	1626	=back
1258		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1631
		1632	static void
		1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1634	{
		1635	ev_unloop (loop, EVUNLOOP_ALL);
		1636	}
		1637
		1638	struct ev_signal signal_watcher;
		1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1640	ev_signal_start (loop, &sigint_cb);
		1641
1259		1642
1260	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1261		1644
1262	Child watchers trigger when your process receives a SIGCHLD in response to	1645	Child watchers trigger when your process receives a SIGCHLD in response to
1263	some child status changes (most typically when a child of yours dies).	1646	some child status changes (most typically when a child of yours dies or
		1647	exits). It is permissible to install a child watcher I<after> the child
		1648	has been forked (which implies it might have already exited), as long
		1649	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1650	forking and then immediately registering a watcher for the child is fine,
		1651	but forking and registering a watcher a few event loop iterations later is
		1652	not.
		1653
		1654	Only the default event loop is capable of handling signals, and therefore
		1655	you can only register child watchers in the default event loop.
		1656
		1657	=head3 Process Interaction
		1658
		1659	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1660	initialised. This is necessary to guarantee proper behaviour even if
		1661	the first child watcher is started after the child exits. The occurrence
		1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1663	synchronously as part of the event loop processing. Libev always reaps all
		1664	children, even ones not watched.
		1665
		1666	=head3 Overriding the Built-In Processing
		1667
		1668	Libev offers no special support for overriding the built-in child
		1669	processing, but if your application collides with libev's default child
		1670	handler, you can override it easily by installing your own handler for
		1671	C<SIGCHLD> after initialising the default loop, and making sure the
		1672	default loop never gets destroyed. You are encouraged, however, to use an
		1673	event-based approach to child reaping and thus use libev's support for
		1674	that, so other libev users can use C<ev_child> watchers freely.
		1675
		1676	=head3 Stopping the Child Watcher
		1677
		1678	Currently, the child watcher never gets stopped, even when the
		1679	child terminates, so normally one needs to stop the watcher in the
		1680	callback. Future versions of libev might stop the watcher automatically
		1681	when a child exit is detected.
		1682
		1683	=head3 Watcher-Specific Functions and Data Members
1264		1684
1265	=over 4	1685	=over 4
1266		1686
1267	=item ev_child_init (ev_child *, callback, int pid)	1687	=item ev_child_init (ev_child *, callback, int pid, int trace)
1268		1688
1269	=item ev_child_set (ev_child *, int pid)	1689	=item ev_child_set (ev_child *, int pid, int trace)
1270		1690
1271	Configures the watcher to wait for status changes of process C<pid> (or	1691	Configures the watcher to wait for status changes of process C<pid> (or
1272	I<any> process if C<pid> is specified as C<0>). The callback can look	1692	I<any> process if C<pid> is specified as C<0>). The callback can look
1273	at the C<rstatus> member of the C<ev_child> watcher structure to see	1693	at the C<rstatus> member of the C<ev_child> watcher structure to see
1274	the status word (use the macros from C<sys/wait.h> and see your systems	1694	the status word (use the macros from C<sys/wait.h> and see your systems
1275	C<waitpid> documentation). The C<rpid> member contains the pid of the	1695	C<waitpid> documentation). The C<rpid> member contains the pid of the
1276	process causing the status change.	1696	process causing the status change. C<trace> must be either C<0> (only
		1697	activate the watcher when the process terminates) or C<1> (additionally
		1698	activate the watcher when the process is stopped or continued).
1277		1699
1278	=item int pid [read-only]	1700	=item int pid [read-only]
1279		1701
1280	The process id this watcher watches out for, or C<0>, meaning any process id.	1702	The process id this watcher watches out for, or C<0>, meaning any process id.
1281		1703
…		…
1288	The process exit/trace status caused by C<rpid> (see your systems	1710	The process exit/trace status caused by C<rpid> (see your systems
1289	C<waitpid> and C<sys/wait.h> documentation for details).	1711	C<waitpid> and C<sys/wait.h> documentation for details).
1290		1712
1291	=back	1713	=back
1292		1714
1293	Example: Try to exit cleanly on SIGINT and SIGTERM.	1715	=head3 Examples
1294		1716
		1717	Example: C<fork()> a new process and install a child handler to wait for
		1718	its completion.
		1719
		1720	ev_child cw;
		1721
1295	static void	1722	static void
1296	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1297	{	1724	{
1298	ev_unloop (loop, EVUNLOOP_ALL);	1725	ev_child_stop (EV_A_ w);
		1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1299	}	1727	}
1300		1728
1301	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1302	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1303	ev_signal_start (loop, &sigint_cb);	1731	if (pid < 0)
		1732	// error
		1733	else if (pid == 0)
		1734	{
		1735	// the forked child executes here
		1736	exit (1);
		1737	}
		1738	else
		1739	{
		1740	ev_child_init (&cw, child_cb, pid, 0);
		1741	ev_child_start (EV_DEFAULT_ &cw);
		1742	}
1304		1743
1305		1744
1306	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1307		1746
1308	This watches a filesystem path for attribute changes. That is, it calls	1747	This watches a file system path for attribute changes. That is, it calls
1309	C<stat> regularly (or when the OS says it changed) and sees if it changed	1748	C<stat> regularly (or when the OS says it changed) and sees if it changed
1310	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1311		1750
1312	The path does not need to exist: changing from "path exists" to "path does	1751	The path does not need to exist: changing from "path exists" to "path does
1313	not exist" is a status change like any other. The condition "path does	1752	not exist" is a status change like any other. The condition "path does
…		…
1316	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1317		1756
1318	The path I<should> be absolute and I<must not> end in a slash. If it is	1757	The path I<should> be absolute and I<must not> end in a slash. If it is
1319	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1320		1759
1321	Since there is no standard to do this, the portable implementation simply	1760	Since there is no standard kernel interface to do this, the portable
1322	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1761	implementation simply calls C<stat (2)> regularly on the path to see if
1323	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1324	a polling interval of C<0> (highly recommended!) then a I<suitable,	1763	this case. If you specify a polling interval of C<0> (highly recommended!)
1325	unspecified default> value will be used (which you can expect to be around	1764	then a I<suitable, unspecified default> value will be used (which
1326	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1327	impose a minimum interval which is currently around C<0.1>, but thats	1766	dynamically). Libev will also impose a minimum interval which is currently
1328	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1329		1768
1330	This watcher type is not meant for massive numbers of stat watchers,	1769	This watcher type is not meant for massive numbers of stat watchers,
1331	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1332	resource-intensive.	1771	resource-intensive.
1333		1772
1334	At the time of this writing, only the Linux inotify interface is	1773	At the time of this writing, the only OS-specific interface implemented
1335	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1336	reader). Inotify will be used to give hints only and should not change the	1775	an exercise for the reader. Note, however, that the author sees no way
1337	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1338	to fall back to regular polling again even with inotify, but changes are	1777
1339	usually detected immediately, and if the file exists there will be no	1778	=head3 ABI Issues (Largefile Support)
1340	polling.	1779
		1780	Libev by default (unless the user overrides this) uses the default
		1781	compilation environment, which means that on systems with large file
		1782	support disabled by default, you get the 32 bit version of the stat
		1783	structure. When using the library from programs that change the ABI to
		1784	use 64 bit file offsets the programs will fail. In that case you have to
		1785	compile libev with the same flags to get binary compatibility. This is
		1786	obviously the case with any flags that change the ABI, but the problem is
		1787	most noticeably disabled with ev_stat and large file support.
		1788
		1789	The solution for this is to lobby your distribution maker to make large
		1790	file interfaces available by default (as e.g. FreeBSD does) and not
		1791	optional. Libev cannot simply switch on large file support because it has
		1792	to exchange stat structures with application programs compiled using the
		1793	default compilation environment.
		1794
		1795	=head3 Inotify and Kqueue
		1796
		1797	When C<inotify (7)> support has been compiled into libev (generally only
		1798	available with Linux) and present at runtime, it will be used to speed up
		1799	change detection where possible. The inotify descriptor will be created lazily
		1800	when the first C<ev_stat> watcher is being started.
		1801
		1802	Inotify presence does not change the semantics of C<ev_stat> watchers
		1803	except that changes might be detected earlier, and in some cases, to avoid
		1804	making regular C<stat> calls. Even in the presence of inotify support
		1805	there are many cases where libev has to resort to regular C<stat> polling,
		1806	but as long as the path exists, libev usually gets away without polling.
		1807
		1808	There is no support for kqueue, as apparently it cannot be used to
		1809	implement this functionality, due to the requirement of having a file
		1810	descriptor open on the object at all times, and detecting renames, unlinks
		1811	etc. is difficult.
		1812
		1813	=head3 The special problem of stat time resolution
		1814
		1815	The C<stat ()> system call only supports full-second resolution portably, and
		1816	even on systems where the resolution is higher, most file systems still
		1817	only support whole seconds.
		1818
		1819	That means that, if the time is the only thing that changes, you can
		1820	easily miss updates: on the first update, C<ev_stat> detects a change and
		1821	calls your callback, which does something. When there is another update
		1822	within the same second, C<ev_stat> will be unable to detect unless the
		1823	stat data does change in other ways (e.g. file size).
		1824
		1825	The solution to this is to delay acting on a change for slightly more
		1826	than a second (or till slightly after the next full second boundary), using
		1827	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1828	ev_timer_again (loop, w)>).
		1829
		1830	The C<.02> offset is added to work around small timing inconsistencies
		1831	of some operating systems (where the second counter of the current time
		1832	might be be delayed. One such system is the Linux kernel, where a call to
		1833	C<gettimeofday> might return a timestamp with a full second later than
		1834	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1835	update file times then there will be a small window where the kernel uses
		1836	the previous second to update file times but libev might already execute
		1837	the timer callback).
		1838
		1839	=head3 Watcher-Specific Functions and Data Members
1341		1840
1342	=over 4	1841	=over 4
1343		1842
1344	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1843	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1345		1844
…		…
1349	C<path>. The C<interval> is a hint on how quickly a change is expected to	1848	C<path>. The C<interval> is a hint on how quickly a change is expected to
1350	be detected and should normally be specified as C<0> to let libev choose	1849	be detected and should normally be specified as C<0> to let libev choose
1351	a suitable value. The memory pointed to by C<path> must point to the same	1850	a suitable value. The memory pointed to by C<path> must point to the same
1352	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1353		1852
1354	The callback will be receive C<EV_STAT> when a change was detected,	1853	The callback will receive an C<EV_STAT> event when a change was detected,
1355	relative to the attributes at the time the watcher was started (or the	1854	relative to the attributes at the time the watcher was started (or the
1356	last change was detected).	1855	last change was detected).
1357		1856
1358	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1359		1858
1360	Updates the stat buffer immediately with new values. If you change the	1859	Updates the stat buffer immediately with new values. If you change the
1361	watched path in your callback, you could call this fucntion to avoid	1860	watched path in your callback, you could call this function to avoid
1362	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1363	useful simply to find out the new values.	1862	the only one changing the path). Can also be useful simply to find out the
		1863	new values.
1364		1864
1365	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1366		1866
1367	The most-recently detected attributes of the file. Although the type is of	1867	The most-recently detected attributes of the file. Although the type is
1368	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	1868	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1369	suitable for your system. If the C<st_nlink> member is C<0>, then there	1869	suitable for your system, but you can only rely on the POSIX-standardised
		1870	members to be present. If the C<st_nlink> member is C<0>, then there was
1370	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1371		1872
1372	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1373		1874
1374	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1375	C<prev> != C<attr>.	1876	C<prev> != C<attr>, or, more precisely, one or more of these members
		1877	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		1878	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1376		1879
1377	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1378		1881
1379	The specified interval.	1882	The specified interval.
1380		1883
1381	=item const char *path [read-only]	1884	=item const char *path [read-only]
1382		1885
1383	The filesystem path that is being watched.	1886	The file system path that is being watched.
1384		1887
1385	=back	1888	=back
1386		1889
		1890	=head3 Examples
		1891
1387	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1388		1893
1389	static void	1894	static void
1390	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1391	{	1896	{
1392	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1393	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1394	{	1899	{
1395	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1396	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1397	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1398	}	1903	}
1399	else	1904	else
1400	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1401	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1402	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1403	}	1908	}
1404		1909
1405	...	1910	...
1406	ev_stat passwd;	1911	ev_stat passwd;
1407		1912
1408	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1409	ev_stat_start (loop, &passwd);	1914	ev_stat_start (loop, &passwd);
		1915
		1916	Example: Like above, but additionally use a one-second delay so we do not
		1917	miss updates (however, frequent updates will delay processing, too, so
		1918	one might do the work both on C<ev_stat> callback invocation I<and> on
		1919	C<ev_timer> callback invocation).
		1920
		1921	static ev_stat passwd;
		1922	static ev_timer timer;
		1923
		1924	static void
		1925	timer_cb (EV_P_ ev_timer *w, int revents)
		1926	{
		1927	ev_timer_stop (EV_A_ w);
		1928
		1929	/* now it's one second after the most recent passwd change */
		1930	}
		1931
		1932	static void
		1933	stat_cb (EV_P_ ev_stat *w, int revents)
		1934	{
		1935	/* reset the one-second timer */
		1936	ev_timer_again (EV_A_ &timer);
		1937	}
		1938
		1939	...
		1940	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1941	ev_stat_start (loop, &passwd);
		1942	ev_timer_init (&timer, timer_cb, 0., 1.02);
1410		1943
1411		1944
1412	=head2 C<ev_idle> - when you've got nothing better to do...	1945	=head2 C<ev_idle> - when you've got nothing better to do...
1413		1946
1414	Idle watchers trigger events when no other events of the same or higher	1947	Idle watchers trigger events when no other events of the same or higher
1415	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1416	count).	1949	as receiving "events").
1417		1950
1418	That is, as long as your process is busy handling sockets or timeouts	1951	That is, as long as your process is busy handling sockets or timeouts
1419	(or even signals, imagine) of the same or higher priority it will not be	1952	(or even signals, imagine) of the same or higher priority it will not be
1420	triggered. But when your process is idle (or only lower-priority watchers	1953	triggered. But when your process is idle (or only lower-priority watchers
1421	are pending), the idle watchers are being called once per event loop	1954	are pending), the idle watchers are being called once per event loop
…		…
1428	Apart from keeping your process non-blocking (which is a useful	1961	Apart from keeping your process non-blocking (which is a useful
1429	effect on its own sometimes), idle watchers are a good place to do	1962	effect on its own sometimes), idle watchers are a good place to do
1430	"pseudo-background processing", or delay processing stuff to after the	1963	"pseudo-background processing", or delay processing stuff to after the
1431	event loop has handled all outstanding events.	1964	event loop has handled all outstanding events.
1432		1965
		1966	=head3 Watcher-Specific Functions and Data Members
		1967
1433	=over 4	1968	=over 4
1434		1969
1435	=item ev_idle_init (ev_signal *, callback)	1970	=item ev_idle_init (ev_signal *, callback)
1436		1971
1437	Initialises and configures the idle watcher - it has no parameters of any	1972	Initialises and configures the idle watcher - it has no parameters of any
1438	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1439	believe me.	1974	believe me.
1440		1975
1441	=back	1976	=back
1442		1977
		1978	=head3 Examples
		1979
1443	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1444	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1445		1982
1446	static void	1983	static void
1447	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1448	{	1985	{
1449	free (w);	1986	free (w);
1450	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1451	// no longer asnything immediate to do.	1988	// no longer anything immediate to do.
1452	}	1989	}
1453		1990
1454	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1455	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1456	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1457		1994
1458		1995
1459	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1460		1997
1461	Prepare and check watchers are usually (but not always) used in tandem:	1998	Prepare and check watchers are usually (but not always) used in pairs:
1462	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1463	afterwards.	2000	afterwards.
1464		2001
1465	You I<must not> call C<ev_loop> or similar functions that enter	2002	You I<must not> call C<ev_loop> or similar functions that enter
1466	the current event loop from either C<ev_prepare> or C<ev_check>	2003	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1469	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2006	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1470	C<ev_check> so if you have one watcher of each kind they will always be	2007	C<ev_check> so if you have one watcher of each kind they will always be
1471	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1472		2009
1473	Their main purpose is to integrate other event mechanisms into libev and	2010	Their main purpose is to integrate other event mechanisms into libev and
1474	their use is somewhat advanced. This could be used, for example, to track	2011	their use is somewhat advanced. They could be used, for example, to track
1475	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1476	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1477	you cache some data and want to flush it before blocking (for example,	2014	you cache some data and want to flush it before blocking (for example,
1478	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2015	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1479	watcher).	2016	watcher).
1480		2017
1481	This is done by examining in each prepare call which file descriptors need	2018	This is done by examining in each prepare call which file descriptors
1482	to be watched by the other library, registering C<ev_io> watchers for	2019	need to be watched by the other library, registering C<ev_io> watchers
1483	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2020	for them and starting an C<ev_timer> watcher for any timeouts (many
1484	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1485	any events that occured (by checking the pending status of all watchers	2022	you check for any events that occurred (by checking the pending status
1486	and stopping them) and call back into the library. The I/O and timer	2023	of all watchers and stopping them) and call back into the library. The
1487	callbacks will never actually be called (but must be valid nevertheless,	2024	I/O and timer callbacks will never actually be called (but must be valid
1488	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1489		2026
1490	As another example, the Perl Coro module uses these hooks to integrate	2027	As another example, the Perl Coro module uses these hooks to integrate
1491	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1492	during each prepare and only letting the process block if no coroutines	2029	during each prepare and only letting the process block if no coroutines
1493	are ready to run (it's actually more complicated: it only runs coroutines	2030	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1496	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1497	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1498		2035
1499	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1500	priority, to ensure that they are being run before any other watchers	2037	priority, to ensure that they are being run before any other watchers
		2038	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2039
1501	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1502	too) should not activate ("feed") events into libev. While libev fully	2041	activate ("feed") events into libev. While libev fully supports this, they
1503	supports this, they will be called before other C<ev_check> watchers did	2042	might get executed before other C<ev_check> watchers did their job. As
1504	their job. As C<ev_check> watchers are often used to embed other event	2043	C<ev_check> watchers are often used to embed other (non-libev) event
1505	loops those other event loops might be in an unusable state until their	2044	loops those other event loops might be in an unusable state until their
1506	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1507	others).	2046	others).
1508		2047
		2048	=head3 Watcher-Specific Functions and Data Members
		2049
1509	=over 4	2050	=over 4
1510		2051
1511	=item ev_prepare_init (ev_prepare *, callback)	2052	=item ev_prepare_init (ev_prepare *, callback)
1512		2053
1513	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1514		2055
1515	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1516	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2057	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1517	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1518		2060
1519	=back	2061	=back
		2062
		2063	=head3 Examples
1520		2064
1521	There are a number of principal ways to embed other event loops or modules	2065	There are a number of principal ways to embed other event loops or modules
1522	into libev. Here are some ideas on how to include libadns into libev	2066	into libev. Here are some ideas on how to include libadns into libev
1523	(there is a Perl module named C<EV::ADNS> that does this, which you could	2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
1524	use for an actually working example. Another Perl module named C<EV::Glib>	2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
1525	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1526	into the Glib event loop).	2070	Glib event loop).
1527		2071
1528	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1529	and in a check watcher, destroy them and call into libadns. What follows	2073	and in a check watcher, destroy them and call into libadns. What follows
1530	is pseudo-code only of course. This requires you to either use a low	2074	is pseudo-code only of course. This requires you to either use a low
1531	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1532	the callbacks for the IO/timeout watchers might not have been called yet.	2076	the callbacks for the IO/timeout watchers might not have been called yet.
1533		2077
1534	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1535	static ev_timer tw;	2079	static ev_timer tw;
1536		2080
1537	static void	2081	static void
1538	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1539	{	2083	{
1540	}	2084	}
1541		2085
1542	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1543	static void	2087	static void
1544	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1545	{	2089	{
1546	int timeout = 3600000;	2090	int timeout = 3600000;
1547	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1548	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1549	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1550		2094
1551	/* the callback is illegal, but won't be called as we stop during check */	2095	/* the callback is illegal, but won't be called as we stop during check */
1552	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1553	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1554		2098
1555	// create one ev_io per pollfd	2099	// create one ev_io per pollfd
1556	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1557	{	2101	{
1558	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1559	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1560	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1561		2105
1562	fds [i].revents = 0;	2106	fds [i].revents = 0;
1563	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1564	}	2108	}
1565	}	2109	}
1566		2110
1567	// stop all watchers after blocking	2111	// stop all watchers after blocking
1568	static void	2112	static void
1569	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1570	{	2114	{
1571	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1572		2116
1573	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
1574	{	2118	{
1575	// set the relevant poll flags	2119	// set the relevant poll flags
1576	// could also call adns_processreadable etc. here	2120	// could also call adns_processreadable etc. here
1577	struct pollfd *fd = fds + i;	2121	struct pollfd *fd = fds + i;
1578	int revents = ev_clear_pending (iow + i);	2122	int revents = ev_clear_pending (iow + i);
1579	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1580	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1581		2125
1582	// now stop the watcher	2126	// now stop the watcher
1583	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
1584	}	2128	}
1585		2129
1586	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1587	}	2131	}
1588		2132
1589	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1590	in the prepare watcher and would dispose of the check watcher.	2134	in the prepare watcher and would dispose of the check watcher.
1591		2135
1592	Method 3: If the module to be embedded supports explicit event	2136	Method 3: If the module to be embedded supports explicit event
1593	notification (adns does), you can also make use of the actual watcher	2137	notification (libadns does), you can also make use of the actual watcher
1594	callbacks, and only destroy/create the watchers in the prepare watcher.	2138	callbacks, and only destroy/create the watchers in the prepare watcher.
1595		2139
1596	static void	2140	static void
1597	timer_cb (EV_P_ ev_timer *w, int revents)	2141	timer_cb (EV_P_ ev_timer *w, int revents)
1598	{	2142	{
1599	adns_state ads = (adns_state)w->data;	2143	adns_state ads = (adns_state)w->data;
1600	update_now (EV_A);	2144	update_now (EV_A);
1601		2145
1602	adns_processtimeouts (ads, &tv_now);	2146	adns_processtimeouts (ads, &tv_now);
1603	}	2147	}
1604		2148
1605	static void	2149	static void
1606	io_cb (EV_P_ ev_io *w, int revents)	2150	io_cb (EV_P_ ev_io *w, int revents)
1607	{	2151	{
1608	adns_state ads = (adns_state)w->data;	2152	adns_state ads = (adns_state)w->data;
1609	update_now (EV_A);	2153	update_now (EV_A);
1610		2154
1611	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1612	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1613	}	2157	}
1614		2158
1615	// do not ever call adns_afterpoll	2159	// do not ever call adns_afterpoll
1616		2160
1617	Method 4: Do not use a prepare or check watcher because the module you	2161	Method 4: Do not use a prepare or check watcher because the module you
1618	want to embed is too inflexible to support it. Instead, youc na override	2162	want to embed is not flexible enough to support it. Instead, you can
1619	their poll function. The drawback with this solution is that the main	2163	override their poll function. The drawback with this solution is that the
1620	loop is now no longer controllable by EV. The C<Glib::EV> module does	2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1621	this.	2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
1622		2167
1623	static gint	2168	static gint
1624	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1625	{	2170	{
1626	int got_events = 0;	2171	int got_events = 0;
1627		2172
1628	for (n = 0; n < nfds; ++n)	2173	for (n = 0; n < nfds; ++n)
1629	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1630		2175
1631	if (timeout >= 0)	2176	if (timeout >= 0)
1632	// create/start timer	2177	// create/start timer
1633		2178
1634	// poll	2179	// poll
1635	ev_loop (EV_A_ 0);	2180	ev_loop (EV_A_ 0);
1636		2181
1637	// stop timer again	2182	// stop timer again
1638	if (timeout >= 0)	2183	if (timeout >= 0)
1639	ev_timer_stop (EV_A_ &to);	2184	ev_timer_stop (EV_A_ &to);
1640		2185
1641	// stop io watchers again - their callbacks should have set	2186	// stop io watchers again - their callbacks should have set
1642	for (n = 0; n < nfds; ++n)	2187	for (n = 0; n < nfds; ++n)
1643	ev_io_stop (EV_A_ iow [n]);	2188	ev_io_stop (EV_A_ iow [n]);
1644		2189
1645	return got_events;	2190	return got_events;
1646	}	2191	}
1647		2192
1648		2193
1649	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1650		2195
1651	This is a rather advanced watcher type that lets you embed one event loop	2196	This is a rather advanced watcher type that lets you embed one event loop
…		…
1657	prioritise I/O.	2202	prioritise I/O.
1658		2203
1659	As an example for a bug workaround, the kqueue backend might only support	2204	As an example for a bug workaround, the kqueue backend might only support
1660	sockets on some platform, so it is unusable as generic backend, but you	2205	sockets on some platform, so it is unusable as generic backend, but you
1661	still want to make use of it because you have many sockets and it scales	2206	still want to make use of it because you have many sockets and it scales
1662	so nicely. In this case, you would create a kqueue-based loop and embed it	2207	so nicely. In this case, you would create a kqueue-based loop and embed
1663	into your default loop (which might use e.g. poll). Overall operation will	2208	it into your default loop (which might use e.g. poll). Overall operation
1664	be a bit slower because first libev has to poll and then call kevent, but	2209	will be a bit slower because first libev has to call C<poll> and then
1665	at least you can use both at what they are best.	2210	C<kevent>, but at least you can use both mechanisms for what they are
		2211	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1666		2212
1667	As for prioritising I/O: rarely you have the case where some fds have	2213	As for prioritising I/O: under rare circumstances you have the case where
1668	to be watched and handled very quickly (with low latency), and even	2214	some fds have to be watched and handled very quickly (with low latency),
1669	priorities and idle watchers might have too much overhead. In this case	2215	and even priorities and idle watchers might have too much overhead. In
1670	you would put all the high priority stuff in one loop and all the rest in	2216	this case you would put all the high priority stuff in one loop and all
1671	a second one, and embed the second one in the first.	2217	the rest in a second one, and embed the second one in the first.
1672		2218
1673	As long as the watcher is active, the callback will be invoked every time	2219	As long as the watcher is active, the callback will be invoked every time
1674	there might be events pending in the embedded loop. The callback must then	2220	there might be events pending in the embedded loop. The callback must then
1675	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1676	their callbacks (you could also start an idle watcher to give the embedded	2222	their callbacks (you could also start an idle watcher to give the embedded
…		…
1684	interested in that.	2230	interested in that.
1685		2231
1686	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1687	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1688	but you will also have to stop and restart any C<ev_embed> watchers	2234	but you will also have to stop and restart any C<ev_embed> watchers
1689	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1690		2237
1691	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable, only the ones returned by
1692	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1693	portable one.	2240	portable one.
1694		2241
1695	So when you want to use this feature you will always have to be prepared	2242	So when you want to use this feature you will always have to be prepared
1696	that you cannot get an embeddable loop. The recommended way to get around	2243	that you cannot get an embeddable loop. The recommended way to get around
1697	this is to have a separate variables for your embeddable loop, try to	2244	this is to have a separate variables for your embeddable loop, try to
1698	create it, and if that fails, use the normal loop for everything:	2245	create it, and if that fails, use the normal loop for everything.
1699		2246
1700	struct ev_loop *loop_hi = ev_default_init (0);	2247	=head3 Watcher-Specific Functions and Data Members
1701	struct ev_loop *loop_lo = 0;
1702	struct ev_embed embed;
1703
1704	// see if there is a chance of getting one that works
1705	// (remember that a flags value of 0 means autodetection)
1706	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1707	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1708	: 0;
1709
1710	// if we got one, then embed it, otherwise default to loop_hi
1711	if (loop_lo)
1712	{
1713	ev_embed_init (&embed, 0, loop_lo);
1714	ev_embed_start (loop_hi, &embed);
1715	}
1716	else
1717	loop_lo = loop_hi;
1718		2248
1719	=over 4	2249	=over 4
1720		2250
1721	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2251	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1722		2252
…		…
1724		2254
1725	Configures the watcher to embed the given loop, which must be	2255	Configures the watcher to embed the given loop, which must be
1726	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2256	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1727	invoked automatically, otherwise it is the responsibility of the callback	2257	invoked automatically, otherwise it is the responsibility of the callback
1728	to invoke it (it will continue to be called until the sweep has been done,	2258	to invoke it (it will continue to be called until the sweep has been done,
1729	if you do not want thta, you need to temporarily stop the embed watcher).	2259	if you do not want that, you need to temporarily stop the embed watcher).
1730		2260
1731	=item ev_embed_sweep (loop, ev_embed *)	2261	=item ev_embed_sweep (loop, ev_embed *)
1732		2262
1733	Make a single, non-blocking sweep over the embedded loop. This works	2263	Make a single, non-blocking sweep over the embedded loop. This works
1734	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2264	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1735	apropriate way for embedded loops.	2265	appropriate way for embedded loops.
1736		2266
1737	=item struct ev_loop *loop [read-only]	2267	=item struct ev_loop *other [read-only]
1738		2268
1739	The embedded event loop.	2269	The embedded event loop.
1740		2270
1741	=back	2271	=back
		2272
		2273	=head3 Examples
		2274
		2275	Example: Try to get an embeddable event loop and embed it into the default
		2276	event loop. If that is not possible, use the default loop. The default
		2277	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2279	used).
		2280
		2281	struct ev_loop *loop_hi = ev_default_init (0);
		2282	struct ev_loop *loop_lo = 0;
		2283	struct ev_embed embed;
		2284
		2285	// see if there is a chance of getting one that works
		2286	// (remember that a flags value of 0 means autodetection)
		2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2289	: 0;
		2290
		2291	// if we got one, then embed it, otherwise default to loop_hi
		2292	if (loop_lo)
		2293	{
		2294	ev_embed_init (&embed, 0, loop_lo);
		2295	ev_embed_start (loop_hi, &embed);
		2296	}
		2297	else
		2298	loop_lo = loop_hi;
		2299
		2300	Example: Check if kqueue is available but not recommended and create
		2301	a kqueue backend for use with sockets (which usually work with any
		2302	kqueue implementation). Store the kqueue/socket-only event loop in
		2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2304
		2305	struct ev_loop *loop = ev_default_init (0);
		2306	struct ev_loop *loop_socket = 0;
		2307	struct ev_embed embed;
		2308
		2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2311	{
		2312	ev_embed_init (&embed, 0, loop_socket);
		2313	ev_embed_start (loop, &embed);
		2314	}
		2315
		2316	if (!loop_socket)
		2317	loop_socket = loop;
		2318
		2319	// now use loop_socket for all sockets, and loop for everything else
1742		2320
1743		2321
1744	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2322	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1745		2323
1746	Fork watchers are called when a C<fork ()> was detected (usually because	2324	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1749	event loop blocks next and before C<ev_check> watchers are being called,	2327	event loop blocks next and before C<ev_check> watchers are being called,
1750	and only in the child after the fork. If whoever good citizen calling	2328	and only in the child after the fork. If whoever good citizen calling
1751	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2329	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1752	handlers will be invoked, too, of course.	2330	handlers will be invoked, too, of course.
1753		2331
		2332	=head3 Watcher-Specific Functions and Data Members
		2333
1754	=over 4	2334	=over 4
1755		2335
1756	=item ev_fork_init (ev_signal *, callback)	2336	=item ev_fork_init (ev_signal *, callback)
1757		2337
1758	Initialises and configures the fork watcher - it has no parameters of any	2338	Initialises and configures the fork watcher - it has no parameters of any
1759	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2339	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1760	believe me.	2340	believe me.
		2341
		2342	=back
		2343
		2344
		2345	=head2 C<ev_async> - how to wake up another event loop
		2346
		2347	In general, you cannot use an C<ev_loop> from multiple threads or other
		2348	asynchronous sources such as signal handlers (as opposed to multiple event
		2349	loops - those are of course safe to use in different threads).
		2350
		2351	Sometimes, however, you need to wake up another event loop you do not
		2352	control, for example because it belongs to another thread. This is what
		2353	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2354	can signal it by calling C<ev_async_send>, which is thread- and signal
		2355	safe.
		2356
		2357	This functionality is very similar to C<ev_signal> watchers, as signals,
		2358	too, are asynchronous in nature, and signals, too, will be compressed
		2359	(i.e. the number of callback invocations may be less than the number of
		2360	C<ev_async_sent> calls).
		2361
		2362	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2363	just the default loop.
		2364
		2365	=head3 Queueing
		2366
		2367	C<ev_async> does not support queueing of data in any way. The reason
		2368	is that the author does not know of a simple (or any) algorithm for a
		2369	multiple-writer-single-reader queue that works in all cases and doesn't
		2370	need elaborate support such as pthreads.
		2371
		2372	That means that if you want to queue data, you have to provide your own
		2373	queue. But at least I can tell you would implement locking around your
		2374	queue:
		2375
		2376	=over 4
		2377
		2378	=item queueing from a signal handler context
		2379
		2380	To implement race-free queueing, you simply add to the queue in the signal
		2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2382	some fictitious SIGUSR1 handler:
		2383
		2384	static ev_async mysig;
		2385
		2386	static void
		2387	sigusr1_handler (void)
		2388	{
		2389	sometype data;
		2390
		2391	// no locking etc.
		2392	queue_put (data);
		2393	ev_async_send (EV_DEFAULT_ &mysig);
		2394	}
		2395
		2396	static void
		2397	mysig_cb (EV_P_ ev_async *w, int revents)
		2398	{
		2399	sometype data;
		2400	sigset_t block, prev;
		2401
		2402	sigemptyset (&block);
		2403	sigaddset (&block, SIGUSR1);
		2404	sigprocmask (SIG_BLOCK, &block, &prev);
		2405
		2406	while (queue_get (&data))
		2407	process (data);
		2408
		2409	if (sigismember (&prev, SIGUSR1)
		2410	sigprocmask (SIG_UNBLOCK, &block, 0);
		2411	}
		2412
		2413	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2414	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2415	either...).
		2416
		2417	=item queueing from a thread context
		2418
		2419	The strategy for threads is different, as you cannot (easily) block
		2420	threads but you can easily preempt them, so to queue safely you need to
		2421	employ a traditional mutex lock, such as in this pthread example:
		2422
		2423	static ev_async mysig;
		2424	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2425
		2426	static void
		2427	otherthread (void)
		2428	{
		2429	// only need to lock the actual queueing operation
		2430	pthread_mutex_lock (&mymutex);
		2431	queue_put (data);
		2432	pthread_mutex_unlock (&mymutex);
		2433
		2434	ev_async_send (EV_DEFAULT_ &mysig);
		2435	}
		2436
		2437	static void
		2438	mysig_cb (EV_P_ ev_async *w, int revents)
		2439	{
		2440	pthread_mutex_lock (&mymutex);
		2441
		2442	while (queue_get (&data))
		2443	process (data);
		2444
		2445	pthread_mutex_unlock (&mymutex);
		2446	}
		2447
		2448	=back
		2449
		2450
		2451	=head3 Watcher-Specific Functions and Data Members
		2452
		2453	=over 4
		2454
		2455	=item ev_async_init (ev_async *, callback)
		2456
		2457	Initialises and configures the async watcher - it has no parameters of any
		2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2459	believe me.
		2460
		2461	=item ev_async_send (loop, ev_async *)
		2462
		2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2465	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2467	section below on what exactly this means).
		2468
		2469	This call incurs the overhead of a system call only once per loop iteration,
		2470	so while the overhead might be noticeable, it doesn't apply to repeated
		2471	calls to C<ev_async_send>.
		2472
		2473	=item bool = ev_async_pending (ev_async *)
		2474
		2475	Returns a non-zero value when C<ev_async_send> has been called on the
		2476	watcher but the event has not yet been processed (or even noted) by the
		2477	event loop.
		2478
		2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2480	the loop iterates next and checks for the watcher to have become active,
		2481	it will reset the flag again. C<ev_async_pending> can be used to very
		2482	quickly check whether invoking the loop might be a good idea.
		2483
		2484	Not that this does I<not> check whether the watcher itself is pending, only
		2485	whether it has been requested to make this watcher pending.
1761		2486
1762	=back	2487	=back
1763		2488
1764		2489
1765	=head1 OTHER FUNCTIONS	2490	=head1 OTHER FUNCTIONS
…		…
1776	or timeout without having to allocate/configure/start/stop/free one or	2501	or timeout without having to allocate/configure/start/stop/free one or
1777	more watchers yourself.	2502	more watchers yourself.
1778		2503
1779	If C<fd> is less than 0, then no I/O watcher will be started and events	2504	If C<fd> is less than 0, then no I/O watcher will be started and events
1780	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1781	C<events> set will be craeted and started.	2506	C<events> set will be created and started.
1782		2507
1783	If C<timeout> is less than 0, then no timeout watcher will be	2508	If C<timeout> is less than 0, then no timeout watcher will be
1784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1785	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1786	dubious value.	2511	dubious value.
…		…
1788	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1789	passed an C<revents> set like normal event callbacks (a combination of	2514	passed an C<revents> set like normal event callbacks (a combination of
1790	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1791	value passed to C<ev_once>:	2516	value passed to C<ev_once>:
1792		2517
1793	static void stdin_ready (int revents, void *arg)	2518	static void stdin_ready (int revents, void *arg)
1794	{	2519	{
1795	if (revents & EV_TIMEOUT)	2520	if (revents & EV_TIMEOUT)
1796	/* doh, nothing entered */;	2521	/* doh, nothing entered */;
1797	else if (revents & EV_READ)	2522	else if (revents & EV_READ)
1798	/* stdin might have data for us, joy! */;	2523	/* stdin might have data for us, joy! */;
1799	}	2524	}
1800		2525
1801	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1802		2527
1803	=item ev_feed_event (ev_loop *, watcher *, int revents)	2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
1804		2529
1805	Feeds the given event set into the event loop, as if the specified event	2530	Feeds the given event set into the event loop, as if the specified event
1806	had happened for the specified watcher (which must be a pointer to an	2531	had happened for the specified watcher (which must be a pointer to an
…		…
1811	Feed an event on the given fd, as if a file descriptor backend detected	2536	Feed an event on the given fd, as if a file descriptor backend detected
1812	the given events it.	2537	the given events it.
1813		2538
1814	=item ev_feed_signal_event (ev_loop *loop, int signum)	2539	=item ev_feed_signal_event (ev_loop *loop, int signum)
1815		2540
1816	Feed an event as if the given signal occured (C<loop> must be the default	2541	Feed an event as if the given signal occurred (C<loop> must be the default
1817	loop!).	2542	loop!).
1818		2543
1819	=back	2544	=back
1820		2545
1821		2546
…		…
1837		2562
1838	=item * Priorities are not currently supported. Initialising priorities	2563	=item * Priorities are not currently supported. Initialising priorities
1839	will fail and all watchers will have the same priority, even though there	2564	will fail and all watchers will have the same priority, even though there
1840	is an ev_pri field.	2565	is an ev_pri field.
1841		2566
		2567	=item * In libevent, the last base created gets the signals, in libev, the
		2568	first base created (== the default loop) gets the signals.
		2569
1842	=item * Other members are not supported.	2570	=item * Other members are not supported.
1843		2571
1844	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2572	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1845	to use the libev header file and library.	2573	to use the libev header file and library.
1846		2574
1847	=back	2575	=back
1848		2576
1849	=head1 C++ SUPPORT	2577	=head1 C++ SUPPORT
1850		2578
1851	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2579	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1852	you to use some convinience methods to start/stop watchers and also change	2580	you to use some convenience methods to start/stop watchers and also change
1853	the callback model to a model using method callbacks on objects.	2581	the callback model to a model using method callbacks on objects.
1854		2582
1855	To use it,	2583	To use it,
1856		2584
1857	#include <ev++.h>	2585	#include <ev++.h>
1858		2586
1859	This automatically includes F<ev.h> and puts all of its definitions (many	2587	This automatically includes F<ev.h> and puts all of its definitions (many
1860	of them macros) into the global namespace. All C++ specific things are	2588	of them macros) into the global namespace. All C++ specific things are
1861	put into the C<ev> namespace. It should support all the same embedding	2589	put into the C<ev> namespace. It should support all the same embedding
1862	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2590	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1929	your compiler is good :), then the method will be fully inlined into the	2657	your compiler is good :), then the method will be fully inlined into the
1930	thunking function, making it as fast as a direct C callback.	2658	thunking function, making it as fast as a direct C callback.
1931		2659
1932	Example: simple class declaration and watcher initialisation	2660	Example: simple class declaration and watcher initialisation
1933		2661
1934	struct myclass	2662	struct myclass
1935	{	2663	{
1936	void io_cb (ev::io &w, int revents) { }	2664	void io_cb (ev::io &w, int revents) { }
1937	}	2665	}
1938		2666
1939	myclass obj;	2667	myclass obj;
1940	ev::io iow;	2668	ev::io iow;
1941	iow.set <myclass, &myclass::io_cb> (&obj);	2669	iow.set <myclass, &myclass::io_cb> (&obj);
1942		2670
1943	=item w->set<function> (void *data = 0)	2671	=item w->set<function> (void *data = 0)
1944		2672
1945	Also sets a callback, but uses a static method or plain function as	2673	Also sets a callback, but uses a static method or plain function as
1946	callback. The optional C<data> argument will be stored in the watcher's	2674	callback. The optional C<data> argument will be stored in the watcher's
…		…
1950		2678
1951	See the method-C<set> above for more details.	2679	See the method-C<set> above for more details.
1952		2680
1953	Example:	2681	Example:
1954		2682
1955	static void io_cb (ev::io &w, int revents) { }	2683	static void io_cb (ev::io &w, int revents) { }
1956	iow.set <io_cb> ();	2684	iow.set <io_cb> ();
1957		2685
1958	=item w->set (struct ev_loop *)	2686	=item w->set (struct ev_loop *)
1959		2687
1960	Associates a different C<struct ev_loop> with this watcher. You can only	2688	Associates a different C<struct ev_loop> with this watcher. You can only
1961	do this when the watcher is inactive (and not pending either).	2689	do this when the watcher is inactive (and not pending either).
1962		2690
1963	=item w->set ([args])	2691	=item w->set ([arguments])
1964		2692
1965	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2693	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1966	called at least once. Unlike the C counterpart, an active watcher gets	2694	called at least once. Unlike the C counterpart, an active watcher gets
1967	automatically stopped and restarted when reconfiguring it with this	2695	automatically stopped and restarted when reconfiguring it with this
1968	method.	2696	method.
1969		2697
1970	=item w->start ()	2698	=item w->start ()
…		…
1974		2702
1975	=item w->stop ()	2703	=item w->stop ()
1976		2704
1977	Stops the watcher if it is active. Again, no C<loop> argument.	2705	Stops the watcher if it is active. Again, no C<loop> argument.
1978		2706
1979	=item w->again () C<ev::timer>, C<ev::periodic> only	2707	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1980		2708
1981	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2709	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1982	C<ev_TYPE_again> function.	2710	C<ev_TYPE_again> function.
1983		2711
1984	=item w->sweep () C<ev::embed> only	2712	=item w->sweep () (C<ev::embed> only)
1985		2713
1986	Invokes C<ev_embed_sweep>.	2714	Invokes C<ev_embed_sweep>.
1987		2715
1988	=item w->update () C<ev::stat> only	2716	=item w->update () (C<ev::stat> only)
1989		2717
1990	Invokes C<ev_stat_stat>.	2718	Invokes C<ev_stat_stat>.
1991		2719
1992	=back	2720	=back
1993		2721
1994	=back	2722	=back
1995		2723
1996	Example: Define a class with an IO and idle watcher, start one of them in	2724	Example: Define a class with an IO and idle watcher, start one of them in
1997	the constructor.	2725	the constructor.
1998		2726
1999	class myclass	2727	class myclass
2000	{	2728	{
2001	ev_io io; void io_cb (ev::io &w, int revents);	2729	ev::io io; void io_cb (ev::io &w, int revents);
2002	ev_idle idle void idle_cb (ev::idle &w, int revents);	2730	ev:idle idle void idle_cb (ev::idle &w, int revents);
2003		2731
2004	myclass ();	2732	myclass (int fd)
2005	}	2733	{
2006
2007	myclass::myclass (int fd)
2008	{
2009	io .set <myclass, &myclass::io_cb > (this);	2734	io .set <myclass, &myclass::io_cb > (this);
2010	idle.set <myclass, &myclass::idle_cb> (this);	2735	idle.set <myclass, &myclass::idle_cb> (this);
2011		2736
2012	io.start (fd, ev::READ);	2737	io.start (fd, ev::READ);
		2738	}
2013	}	2739	};
		2740
		2741
		2742	=head1 OTHER LANGUAGE BINDINGS
		2743
		2744	Libev does not offer other language bindings itself, but bindings for a
		2745	number of languages exist in the form of third-party packages. If you know
		2746	any interesting language binding in addition to the ones listed here, drop
		2747	me a note.
		2748
		2749	=over 4
		2750
		2751	=item Perl
		2752
		2753	The EV module implements the full libev API and is actually used to test
		2754	libev. EV is developed together with libev. Apart from the EV core module,
		2755	there are additional modules that implement libev-compatible interfaces
		2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the
		2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).
		2758
		2759	It can be found and installed via CPAN, its homepage is at
		2760	L<http://software.schmorp.de/pkg/EV>.
		2761
		2762	=item Python
		2763
		2764	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2765	seems to be quite complete and well-documented. Note, however, that the
		2766	patch they require for libev is outright dangerous as it breaks the ABI
		2767	for everybody else, and therefore, should never be applied in an installed
		2768	libev (if python requires an incompatible ABI then it needs to embed
		2769	libev).
		2770
		2771	=item Ruby
		2772
		2773	Tony Arcieri has written a ruby extension that offers access to a subset
		2774	of the libev API and adds file handle abstractions, asynchronous DNS and
		2775	more on top of it. It can be found via gem servers. Its homepage is at
		2776	L<http://rev.rubyforge.org/>.
		2777
		2778	=item D
		2779
		2780	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2782
		2783	=back
2014		2784
2015		2785
2016	=head1 MACRO MAGIC	2786	=head1 MACRO MAGIC
2017		2787
2018	Libev can be compiled with a variety of options, the most fundemantal is	2788	Libev can be compiled with a variety of options, the most fundamental
2019	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2789	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2020	callbacks have an initial C<struct ev_loop *> argument.	2790	functions and callbacks have an initial C<struct ev_loop *> argument.
2021		2791
2022	To make it easier to write programs that cope with either variant, the	2792	To make it easier to write programs that cope with either variant, the
2023	following macros are defined:	2793	following macros are defined:
2024		2794
2025	=over 4	2795	=over 4
…		…
2028		2798
2029	This provides the loop I<argument> for functions, if one is required ("ev	2799	This provides the loop I<argument> for functions, if one is required ("ev
2030	loop argument"). The C<EV_A> form is used when this is the sole argument,	2800	loop argument"). The C<EV_A> form is used when this is the sole argument,
2031	C<EV_A_> is used when other arguments are following. Example:	2801	C<EV_A_> is used when other arguments are following. Example:
2032		2802
2033	ev_unref (EV_A);	2803	ev_unref (EV_A);
2034	ev_timer_add (EV_A_ watcher);	2804	ev_timer_add (EV_A_ watcher);
2035	ev_loop (EV_A_ 0);	2805	ev_loop (EV_A_ 0);
2036		2806
2037	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2807	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2038	which is often provided by the following macro.	2808	which is often provided by the following macro.
2039		2809
2040	=item C<EV_P>, C<EV_P_>	2810	=item C<EV_P>, C<EV_P_>
2041		2811
2042	This provides the loop I<parameter> for functions, if one is required ("ev	2812	This provides the loop I<parameter> for functions, if one is required ("ev
2043	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2813	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2044	C<EV_P_> is used when other parameters are following. Example:	2814	C<EV_P_> is used when other parameters are following. Example:
2045		2815
2046	// this is how ev_unref is being declared	2816	// this is how ev_unref is being declared
2047	static void ev_unref (EV_P);	2817	static void ev_unref (EV_P);
2048		2818
2049	// this is how you can declare your typical callback	2819	// this is how you can declare your typical callback
2050	static void cb (EV_P_ ev_timer *w, int revents)	2820	static void cb (EV_P_ ev_timer *w, int revents)
2051		2821
2052	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2822	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2053	suitable for use with C<EV_A>.	2823	suitable for use with C<EV_A>.
2054		2824
2055	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2825	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2056		2826
2057	Similar to the other two macros, this gives you the value of the default	2827	Similar to the other two macros, this gives you the value of the default
2058	loop, if multiple loops are supported ("ev loop default").	2828	loop, if multiple loops are supported ("ev loop default").
		2829
		2830	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2831
		2832	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2833	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2834	is undefined when the default loop has not been initialised by a previous
		2835	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2836
		2837	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2838	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2059		2839
2060	=back	2840	=back
2061		2841
2062	Example: Declare and initialise a check watcher, utilising the above	2842	Example: Declare and initialise a check watcher, utilising the above
2063	macros so it will work regardless of whether multiple loops are supported	2843	macros so it will work regardless of whether multiple loops are supported
2064	or not.	2844	or not.
2065		2845
2066	static void	2846	static void
2067	check_cb (EV_P_ ev_timer *w, int revents)	2847	check_cb (EV_P_ ev_timer *w, int revents)
2068	{	2848	{
2069	ev_check_stop (EV_A_ w);	2849	ev_check_stop (EV_A_ w);
2070	}	2850	}
2071		2851
2072	ev_check check;	2852	ev_check check;
2073	ev_check_init (&check, check_cb);	2853	ev_check_init (&check, check_cb);
2074	ev_check_start (EV_DEFAULT_ &check);	2854	ev_check_start (EV_DEFAULT_ &check);
2075	ev_loop (EV_DEFAULT_ 0);	2855	ev_loop (EV_DEFAULT_ 0);
2076		2856
2077	=head1 EMBEDDING	2857	=head1 EMBEDDING
2078		2858
2079	Libev can (and often is) directly embedded into host	2859	Libev can (and often is) directly embedded into host
2080	applications. Examples of applications that embed it include the Deliantra	2860	applications. Examples of applications that embed it include the Deliantra
2081	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2861	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2082	and rxvt-unicode.	2862	and rxvt-unicode.
2083		2863
2084	The goal is to enable you to just copy the neecssary files into your	2864	The goal is to enable you to just copy the necessary files into your
2085	source directory without having to change even a single line in them, so	2865	source directory without having to change even a single line in them, so
2086	you can easily upgrade by simply copying (or having a checked-out copy of	2866	you can easily upgrade by simply copying (or having a checked-out copy of
2087	libev somewhere in your source tree).	2867	libev somewhere in your source tree).
2088		2868
2089	=head2 FILESETS	2869	=head2 FILESETS
2090		2870
2091	Depending on what features you need you need to include one or more sets of files	2871	Depending on what features you need you need to include one or more sets of files
2092	in your app.	2872	in your application.
2093		2873
2094	=head3 CORE EVENT LOOP	2874	=head3 CORE EVENT LOOP
2095		2875
2096	To include only the libev core (all the C<ev_*> functions), with manual	2876	To include only the libev core (all the C<ev_*> functions), with manual
2097	configuration (no autoconf):	2877	configuration (no autoconf):
2098		2878
2099	#define EV_STANDALONE 1	2879	#define EV_STANDALONE 1
2100	#include "ev.c"	2880	#include "ev.c"
2101		2881
2102	This will automatically include F<ev.h>, too, and should be done in a	2882	This will automatically include F<ev.h>, too, and should be done in a
2103	single C source file only to provide the function implementations. To use	2883	single C source file only to provide the function implementations. To use
2104	it, do the same for F<ev.h> in all files wishing to use this API (best	2884	it, do the same for F<ev.h> in all files wishing to use this API (best
2105	done by writing a wrapper around F<ev.h> that you can include instead and	2885	done by writing a wrapper around F<ev.h> that you can include instead and
2106	where you can put other configuration options):	2886	where you can put other configuration options):
2107		2887
2108	#define EV_STANDALONE 1	2888	#define EV_STANDALONE 1
2109	#include "ev.h"	2889	#include "ev.h"
2110		2890
2111	Both header files and implementation files can be compiled with a C++	2891	Both header files and implementation files can be compiled with a C++
2112	compiler (at least, thats a stated goal, and breakage will be treated	2892	compiler (at least, thats a stated goal, and breakage will be treated
2113	as a bug).	2893	as a bug).
2114		2894
2115	You need the following files in your source tree, or in a directory	2895	You need the following files in your source tree, or in a directory
2116	in your include path (e.g. in libev/ when using -Ilibev):	2896	in your include path (e.g. in libev/ when using -Ilibev):
2117		2897
2118	ev.h	2898	ev.h
2119	ev.c	2899	ev.c
2120	ev_vars.h	2900	ev_vars.h
2121	ev_wrap.h	2901	ev_wrap.h
2122		2902
2123	ev_win32.c required on win32 platforms only	2903	ev_win32.c required on win32 platforms only
2124		2904
2125	ev_select.c only when select backend is enabled (which is enabled by default)	2905	ev_select.c only when select backend is enabled (which is enabled by default)
2126	ev_poll.c only when poll backend is enabled (disabled by default)	2906	ev_poll.c only when poll backend is enabled (disabled by default)
2127	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2907	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2128	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2908	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2129	ev_port.c only when the solaris port backend is enabled (disabled by default)	2909	ev_port.c only when the solaris port backend is enabled (disabled by default)
2130		2910
2131	F<ev.c> includes the backend files directly when enabled, so you only need	2911	F<ev.c> includes the backend files directly when enabled, so you only need
2132	to compile this single file.	2912	to compile this single file.
2133		2913
2134	=head3 LIBEVENT COMPATIBILITY API	2914	=head3 LIBEVENT COMPATIBILITY API
2135		2915
2136	To include the libevent compatibility API, also include:	2916	To include the libevent compatibility API, also include:
2137		2917
2138	#include "event.c"	2918	#include "event.c"
2139		2919
2140	in the file including F<ev.c>, and:	2920	in the file including F<ev.c>, and:
2141		2921
2142	#include "event.h"	2922	#include "event.h"
2143		2923
2144	in the files that want to use the libevent API. This also includes F<ev.h>.	2924	in the files that want to use the libevent API. This also includes F<ev.h>.
2145		2925
2146	You need the following additional files for this:	2926	You need the following additional files for this:
2147		2927
2148	event.h	2928	event.h
2149	event.c	2929	event.c
2150		2930
2151	=head3 AUTOCONF SUPPORT	2931	=head3 AUTOCONF SUPPORT
2152		2932
2153	Instead of using C<EV_STANDALONE=1> and providing your config in	2933	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2154	whatever way you want, you can also C<m4_include([libev.m4])> in your	2934	whatever way you want, you can also C<m4_include([libev.m4])> in your
2155	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2935	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2156	include F<config.h> and configure itself accordingly.	2936	include F<config.h> and configure itself accordingly.
2157		2937
2158	For this of course you need the m4 file:	2938	For this of course you need the m4 file:
2159		2939
2160	libev.m4	2940	libev.m4
2161		2941
2162	=head2 PREPROCESSOR SYMBOLS/MACROS	2942	=head2 PREPROCESSOR SYMBOLS/MACROS
2163		2943
2164	Libev can be configured via a variety of preprocessor symbols you have to define	2944	Libev can be configured via a variety of preprocessor symbols you have to
2165	before including any of its files. The default is not to build for multiplicity	2945	define before including any of its files. The default in the absence of
2166	and only include the select backend.	2946	autoconf is noted for every option.
2167		2947
2168	=over 4	2948	=over 4
2169		2949
2170	=item EV_STANDALONE	2950	=item EV_STANDALONE
2171		2951
…		…
2176	F<event.h> that are not directly supported by the libev core alone.	2956	F<event.h> that are not directly supported by the libev core alone.
2177		2957
2178	=item EV_USE_MONOTONIC	2958	=item EV_USE_MONOTONIC
2179		2959
2180	If defined to be C<1>, libev will try to detect the availability of the	2960	If defined to be C<1>, libev will try to detect the availability of the
2181	monotonic clock option at both compiletime and runtime. Otherwise no use	2961	monotonic clock option at both compile time and runtime. Otherwise no use
2182	of the monotonic clock option will be attempted. If you enable this, you	2962	of the monotonic clock option will be attempted. If you enable this, you
2183	usually have to link against librt or something similar. Enabling it when	2963	usually have to link against librt or something similar. Enabling it when
2184	the functionality isn't available is safe, though, althoguh you have	2964	the functionality isn't available is safe, though, although you have
2185	to make sure you link against any libraries where the C<clock_gettime>	2965	to make sure you link against any libraries where the C<clock_gettime>
2186	function is hiding in (often F<-lrt>).	2966	function is hiding in (often F<-lrt>).
2187		2967
2188	=item EV_USE_REALTIME	2968	=item EV_USE_REALTIME
2189		2969
2190	If defined to be C<1>, libev will try to detect the availability of the	2970	If defined to be C<1>, libev will try to detect the availability of the
2191	realtime clock option at compiletime (and assume its availability at	2971	real-time clock option at compile time (and assume its availability at
2192	runtime if successful). Otherwise no use of the realtime clock option will	2972	runtime if successful). Otherwise no use of the real-time clock option will
2193	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2973	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2194	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2974	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2195	in the description of C<EV_USE_MONOTONIC>, though.	2975	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2976
		2977	=item EV_USE_NANOSLEEP
		2978
		2979	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2980	and will use it for delays. Otherwise it will use C<select ()>.
		2981
		2982	=item EV_USE_EVENTFD
		2983
		2984	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2985	available and will probe for kernel support at runtime. This will improve
		2986	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2987	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2988	2.7 or newer, otherwise disabled.
2196		2989
2197	=item EV_USE_SELECT	2990	=item EV_USE_SELECT
2198		2991
2199	If undefined or defined to be C<1>, libev will compile in support for the	2992	If undefined or defined to be C<1>, libev will compile in support for the
2200	C<select>(2) backend. No attempt at autodetection will be done: if no	2993	C<select>(2) backend. No attempt at auto-detection will be done: if no
2201	other method takes over, select will be it. Otherwise the select backend	2994	other method takes over, select will be it. Otherwise the select backend
2202	will not be compiled in.	2995	will not be compiled in.
2203		2996
2204	=item EV_SELECT_USE_FD_SET	2997	=item EV_SELECT_USE_FD_SET
2205		2998
2206	If defined to C<1>, then the select backend will use the system C<fd_set>	2999	If defined to C<1>, then the select backend will use the system C<fd_set>
2207	structure. This is useful if libev doesn't compile due to a missing	3000	structure. This is useful if libev doesn't compile due to a missing
2208	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3001	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2209	exotic systems. This usually limits the range of file descriptors to some	3002	exotic systems. This usually limits the range of file descriptors to some
2210	low limit such as 1024 or might have other limitations (winsocket only	3003	low limit such as 1024 or might have other limitations (winsocket only
2211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3004	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2212	influence the size of the C<fd_set> used.	3005	influence the size of the C<fd_set> used.
2213		3006
…		…
2219	be used is the winsock select). This means that it will call	3012	be used is the winsock select). This means that it will call
2220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3013	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2221	it is assumed that all these functions actually work on fds, even	3014	it is assumed that all these functions actually work on fds, even
2222	on win32. Should not be defined on non-win32 platforms.	3015	on win32. Should not be defined on non-win32 platforms.
2223		3016
		3017	=item EV_FD_TO_WIN32_HANDLE
		3018
		3019	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3020	file descriptors to socket handles. When not defining this symbol (the
		3021	default), then libev will call C<_get_osfhandle>, which is usually
		3022	correct. In some cases, programs use their own file descriptor management,
		3023	in which case they can provide this function to map fds to socket handles.
		3024
2224	=item EV_USE_POLL	3025	=item EV_USE_POLL
2225		3026
2226	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3027	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2227	backend. Otherwise it will be enabled on non-win32 platforms. It	3028	backend. Otherwise it will be enabled on non-win32 platforms. It
2228	takes precedence over select.	3029	takes precedence over select.
2229		3030
2230	=item EV_USE_EPOLL	3031	=item EV_USE_EPOLL
2231		3032
2232	If defined to be C<1>, libev will compile in support for the Linux	3033	If defined to be C<1>, libev will compile in support for the Linux
2233	C<epoll>(7) backend. Its availability will be detected at runtime,	3034	C<epoll>(7) backend. Its availability will be detected at runtime,
2234	otherwise another method will be used as fallback. This is the	3035	otherwise another method will be used as fallback. This is the preferred
2235	preferred backend for GNU/Linux systems.	3036	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3037	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2236		3038
2237	=item EV_USE_KQUEUE	3039	=item EV_USE_KQUEUE
2238		3040
2239	If defined to be C<1>, libev will compile in support for the BSD style	3041	If defined to be C<1>, libev will compile in support for the BSD style
2240	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3042	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2253	otherwise another method will be used as fallback. This is the preferred	3055	otherwise another method will be used as fallback. This is the preferred
2254	backend for Solaris 10 systems.	3056	backend for Solaris 10 systems.
2255		3057
2256	=item EV_USE_DEVPOLL	3058	=item EV_USE_DEVPOLL
2257		3059
2258	reserved for future expansion, works like the USE symbols above.	3060	Reserved for future expansion, works like the USE symbols above.
2259		3061
2260	=item EV_USE_INOTIFY	3062	=item EV_USE_INOTIFY
2261		3063
2262	If defined to be C<1>, libev will compile in support for the Linux inotify	3064	If defined to be C<1>, libev will compile in support for the Linux inotify
2263	interface to speed up C<ev_stat> watchers. Its actual availability will	3065	interface to speed up C<ev_stat> watchers. Its actual availability will
2264	be detected at runtime.	3066	be detected at runtime. If undefined, it will be enabled if the headers
		3067	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3068
		3069	=item EV_ATOMIC_T
		3070
		3071	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3072	access is atomic with respect to other threads or signal contexts. No such
		3073	type is easily found in the C language, so you can provide your own type
		3074	that you know is safe for your purposes. It is used both for signal handler "locking"
		3075	as well as for signal and thread safety in C<ev_async> watchers.
		3076
		3077	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3078	(from F<signal.h>), which is usually good enough on most platforms.
2265		3079
2266	=item EV_H	3080	=item EV_H
2267		3081
2268	The name of the F<ev.h> header file used to include it. The default if	3082	The name of the F<ev.h> header file used to include it. The default if
2269	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3083	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2270	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3084	used to virtually rename the F<ev.h> header file in case of conflicts.
2271		3085
2272	=item EV_CONFIG_H	3086	=item EV_CONFIG_H
2273		3087
2274	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3088	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2275	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3089	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2276	C<EV_H>, above.	3090	C<EV_H>, above.
2277		3091
2278	=item EV_EVENT_H	3092	=item EV_EVENT_H
2279		3093
2280	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3094	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2281	of how the F<event.h> header can be found.	3095	of how the F<event.h> header can be found, the default is C<"event.h">.
2282		3096
2283	=item EV_PROTOTYPES	3097	=item EV_PROTOTYPES
2284		3098
2285	If defined to be C<0>, then F<ev.h> will not define any function	3099	If defined to be C<0>, then F<ev.h> will not define any function
2286	prototypes, but still define all the structs and other symbols. This is	3100	prototypes, but still define all the structs and other symbols. This is
…		…
2307	When doing priority-based operations, libev usually has to linearly search	3121	When doing priority-based operations, libev usually has to linearly search
2308	all the priorities, so having many of them (hundreds) uses a lot of space	3122	all the priorities, so having many of them (hundreds) uses a lot of space
2309	and time, so using the defaults of five priorities (-2 .. +2) is usually	3123	and time, so using the defaults of five priorities (-2 .. +2) is usually
2310	fine.	3124	fine.
2311		3125
2312	If your embedding app does not need any priorities, defining these both to	3126	If your embedding application does not need any priorities, defining these both to
2313	C<0> will save some memory and cpu.	3127	C<0> will save some memory and CPU.
2314		3128
2315	=item EV_PERIODIC_ENABLE	3129	=item EV_PERIODIC_ENABLE
2316		3130
2317	If undefined or defined to be C<1>, then periodic timers are supported. If	3131	If undefined or defined to be C<1>, then periodic timers are supported. If
2318	defined to be C<0>, then they are not. Disabling them saves a few kB of	3132	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2337	=item EV_FORK_ENABLE	3151	=item EV_FORK_ENABLE
2338		3152
2339	If undefined or defined to be C<1>, then fork watchers are supported. If	3153	If undefined or defined to be C<1>, then fork watchers are supported. If
2340	defined to be C<0>, then they are not.	3154	defined to be C<0>, then they are not.
2341		3155
		3156	=item EV_ASYNC_ENABLE
		3157
		3158	If undefined or defined to be C<1>, then async watchers are supported. If
		3159	defined to be C<0>, then they are not.
		3160
2342	=item EV_MINIMAL	3161	=item EV_MINIMAL
2343		3162
2344	If you need to shave off some kilobytes of code at the expense of some	3163	If you need to shave off some kilobytes of code at the expense of some
2345	speed, define this symbol to C<1>. Currently only used for gcc to override	3164	speed, define this symbol to C<1>. Currently this is used to override some
2346	some inlining decisions, saves roughly 30% codesize of amd64.	3165	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3166	much smaller 2-heap for timer management over the default 4-heap.
2347		3167
2348	=item EV_PID_HASHSIZE	3168	=item EV_PID_HASHSIZE
2349		3169
2350	C<ev_child> watchers use a small hash table to distribute workload by	3170	C<ev_child> watchers use a small hash table to distribute workload by
2351	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3171	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2352	than enough. If you need to manage thousands of children you might want to	3172	than enough. If you need to manage thousands of children you might want to
2353	increase this value (I<must> be a power of two).	3173	increase this value (I<must> be a power of two).
2354		3174
2355	=item EV_INOTIFY_HASHSIZE	3175	=item EV_INOTIFY_HASHSIZE
2356		3176
2357	C<ev_staz> watchers use a small hash table to distribute workload by	3177	C<ev_stat> watchers use a small hash table to distribute workload by
2358	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3178	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2359	usually more than enough. If you need to manage thousands of C<ev_stat>	3179	usually more than enough. If you need to manage thousands of C<ev_stat>
2360	watchers you might want to increase this value (I<must> be a power of	3180	watchers you might want to increase this value (I<must> be a power of
2361	two).	3181	two).
2362		3182
		3183	=item EV_USE_4HEAP
		3184
		3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined
		3187	to C<1>. The 4-heap uses more complicated (longer) code but has
		3188	noticeably faster performance with many (thousands) of watchers.
		3189
		3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3191	(disabled).
		3192
		3193	=item EV_HEAP_CACHE_AT
		3194
		3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3196	timer and periodics heap, libev can cache the timestamp (I<at>) within
		3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3199	but avoids random read accesses on heap changes. This improves performance
		3200	noticeably with with many (hundreds) of watchers.
		3201
		3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3203	(disabled).
		3204
		3205	=item EV_VERIFY
		3206
		3207	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3208	be done: If set to C<0>, no internal verification code will be compiled
		3209	in. If set to C<1>, then verification code will be compiled in, but not
		3210	called. If set to C<2>, then the internal verification code will be
		3211	called once per loop, which can slow down libev. If set to C<3>, then the
		3212	verification code will be called very frequently, which will slow down
		3213	libev considerably.
		3214
		3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3216	C<0.>
		3217
2363	=item EV_COMMON	3218	=item EV_COMMON
2364		3219
2365	By default, all watchers have a C<void *data> member. By redefining	3220	By default, all watchers have a C<void *data> member. By redefining
2366	this macro to a something else you can include more and other types of	3221	this macro to a something else you can include more and other types of
2367	members. You have to define it each time you include one of the files,	3222	members. You have to define it each time you include one of the files,
2368	though, and it must be identical each time.	3223	though, and it must be identical each time.
2369		3224
2370	For example, the perl EV module uses something like this:	3225	For example, the perl EV module uses something like this:
2371		3226
2372	#define EV_COMMON \	3227	#define EV_COMMON \
2373	SV *self; /* contains this struct */ \	3228	SV *self; /* contains this struct */ \
2374	SV *cb_sv, *fh /* note no trailing ";" */	3229	SV *cb_sv, *fh /* note no trailing ";" */
2375		3230
2376	=item EV_CB_DECLARE (type)	3231	=item EV_CB_DECLARE (type)
2377		3232
2378	=item EV_CB_INVOKE (watcher, revents)	3233	=item EV_CB_INVOKE (watcher, revents)
2379		3234
2380	=item ev_set_cb (ev, cb)	3235	=item ev_set_cb (ev, cb)
2381		3236
2382	Can be used to change the callback member declaration in each watcher,	3237	Can be used to change the callback member declaration in each watcher,
2383	and the way callbacks are invoked and set. Must expand to a struct member	3238	and the way callbacks are invoked and set. Must expand to a struct member
2384	definition and a statement, respectively. See the F<ev.v> header file for	3239	definition and a statement, respectively. See the F<ev.h> header file for
2385	their default definitions. One possible use for overriding these is to	3240	their default definitions. One possible use for overriding these is to
2386	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2387	method calls instead of plain function calls in C++.	3242	method calls instead of plain function calls in C++.
		3243
		3244	=head2 EXPORTED API SYMBOLS
		3245
		3246	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3247	exported symbols, you can use the provided F<Symbol.*> files which list
		3248	all public symbols, one per line:
		3249
		3250	Symbols.ev for libev proper
		3251	Symbols.event for the libevent emulation
		3252
		3253	This can also be used to rename all public symbols to avoid clashes with
		3254	multiple versions of libev linked together (which is obviously bad in
		3255	itself, but sometimes it is inconvenient to avoid this).
		3256
		3257	A sed command like this will create wrapper C<#define>'s that you need to
		3258	include before including F<ev.h>:
		3259
		3260	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3261
		3262	This would create a file F<wrap.h> which essentially looks like this:
		3263
		3264	#define ev_backend myprefix_ev_backend
		3265	#define ev_check_start myprefix_ev_check_start
		3266	#define ev_check_stop myprefix_ev_check_stop
		3267	...
2388		3268
2389	=head2 EXAMPLES	3269	=head2 EXAMPLES
2390		3270
2391	For a real-world example of a program the includes libev	3271	For a real-world example of a program the includes libev
2392	verbatim, you can have a look at the EV perl module	3272	verbatim, you can have a look at the EV perl module
…		…
2397	file.	3277	file.
2398		3278
2399	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3279	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2400	that everybody includes and which overrides some configure choices:	3280	that everybody includes and which overrides some configure choices:
2401		3281
2402	#define EV_MINIMAL 1	3282	#define EV_MINIMAL 1
2403	#define EV_USE_POLL 0	3283	#define EV_USE_POLL 0
2404	#define EV_MULTIPLICITY 0	3284	#define EV_MULTIPLICITY 0
2405	#define EV_PERIODIC_ENABLE 0	3285	#define EV_PERIODIC_ENABLE 0
2406	#define EV_STAT_ENABLE 0	3286	#define EV_STAT_ENABLE 0
2407	#define EV_FORK_ENABLE 0	3287	#define EV_FORK_ENABLE 0
2408	#define EV_CONFIG_H <config.h>	3288	#define EV_CONFIG_H <config.h>
2409	#define EV_MINPRI 0	3289	#define EV_MINPRI 0
2410	#define EV_MAXPRI 0	3290	#define EV_MAXPRI 0
2411		3291
2412	#include "ev++.h"	3292	#include "ev++.h"
2413		3293
2414	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2415		3295
2416	#include "ev_cpp.h"	3296	#include "ev_cpp.h"
2417	#include "ev.c"	3297	#include "ev.c"
		3298
		3299
		3300	=head1 THREADS AND COROUTINES
		3301
		3302	=head2 THREADS
		3303
		3304	Libev itself is thread-safe (unless the opposite is specifically
		3305	documented for a function), but it uses no locking itself. This means that
		3306	you can use as many loops as you want in parallel, as long as only one
		3307	thread ever calls into one libev function with the same loop parameter:
		3308	libev guarentees that different event loops share no data structures that
		3309	need locking.
		3310
		3311	Or to put it differently: calls with different loop parameters can be done
		3312	concurrently from multiple threads, calls with the same loop parameter
		3313	must be done serially (but can be done from different threads, as long as
		3314	only one thread ever is inside a call at any point in time, e.g. by using
		3315	a mutex per loop).
		3316
		3317	Specifically to support threads (and signal handlers), libev implements
		3318	so-called C<ev_async> watchers, which allow some limited form of
		3319	concurrency on the same event loop.
		3320
		3321	If you want to know which design (one loop, locking, or multiple loops
		3322	without or something else still) is best for your problem, then I cannot
		3323	help you. I can give some generic advice however:
		3324
		3325	=over 4
		3326
		3327	=item * most applications have a main thread: use the default libev loop
		3328	in that thread, or create a separate thread running only the default loop.
		3329
		3330	This helps integrating other libraries or software modules that use libev
		3331	themselves and don't care/know about threading.
		3332
		3333	=item * one loop per thread is usually a good model.
		3334
		3335	Doing this is almost never wrong, sometimes a better-performance model
		3336	exists, but it is always a good start.
		3337
		3338	=item * other models exist, such as the leader/follower pattern, where one
		3339	loop is handed through multiple threads in a kind of round-robin fashion.
		3340
		3341	Choosing a model is hard - look around, learn, know that usually you can do
		3342	better than you currently do :-)
		3343
		3344	=item * often you need to talk to some other thread which blocks in the
		3345	event loop.
		3346
		3347	C<ev_async> watchers can be used to wake them up from other threads safely
		3348	(or from signal contexts...).
		3349
		3350	An example use would be to communicate signals or other events that only
		3351	work in the default loop by registering the signal watcher with the
		3352	default loop and triggering an C<ev_async> watcher from the default loop
		3353	watcher callback into the event loop interested in the signal.
		3354
		3355	=back
		3356
		3357	=head2 COROUTINES
		3358
		3359	Libev is much more accommodating to coroutines ("cooperative threads"):
		3360	libev fully supports nesting calls to it's functions from different
		3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3362	different coroutines and switch freely between both coroutines running the
		3363	loop, as long as you don't confuse yourself). The only exception is that
		3364	you must not do this from C<ev_periodic> reschedule callbacks.
		3365
		3366	Care has been taken to ensure that libev does not keep local state inside
		3367	C<ev_loop>, and other calls do not usually allow coroutine switches.
2418		3368
2419		3369
2420	=head1 COMPLEXITIES	3370	=head1 COMPLEXITIES
2421		3371
2422	In this section the complexities of (many of) the algorithms used inside	3372	In this section the complexities of (many of) the algorithms used inside
…		…
2433		3383
2434	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2435		3385
2436	This means that, when you have a watcher that triggers in one hour and	3386	This means that, when you have a watcher that triggers in one hour and
2437	there are 100 watchers that would trigger before that then inserting will	3387	there are 100 watchers that would trigger before that then inserting will
2438	have to skip those 100 watchers.	3388	have to skip roughly seven (C<ld 100>) of these watchers.
2439		3389
2440	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2441		3391
2442	That means that for changing a timer costs less than removing/adding them	3392	That means that changing a timer costs less than removing/adding them
2443	as only the relative motion in the event queue has to be paid for.	3393	as only the relative motion in the event queue has to be paid for.
2444		3394
2445	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2446		3396
2447	These just add the watcher into an array or at the head of a list.	3397	These just add the watcher into an array or at the head of a list.
		3398
2448	=item Stopping check/prepare/idle watchers: O(1)	3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2449		3400
2450	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2451		3402
2452	These watchers are stored in lists then need to be walked to find the	3403	These watchers are stored in lists then need to be walked to find the
2453	correct watcher to remove. The lists are usually short (you don't usually	3404	correct watcher to remove. The lists are usually short (you don't usually
2454	have many watchers waiting for the same fd or signal).	3405	have many watchers waiting for the same fd or signal).
2455		3406
2456	=item Finding the next timer per loop iteration: O(1)	3407	=item Finding the next timer in each loop iteration: O(1)
		3408
		3409	By virtue of using a binary or 4-heap, the next timer is always found at a
		3410	fixed position in the storage array.
2457		3411
2458	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2459		3413
2460	A change means an I/O watcher gets started or stopped, which requires	3414	A change means an I/O watcher gets started or stopped, which requires
2461	libev to recalculate its status (and possibly tell the kernel).	3415	libev to recalculate its status (and possibly tell the kernel, depending
		3416	on backend and whether C<ev_io_set> was used).
2462		3417
2463	=item Activating one watcher: O(1)	3418	=item Activating one watcher (putting it into the pending state): O(1)
2464		3419
2465	=item Priority handling: O(number_of_priorities)	3420	=item Priority handling: O(number_of_priorities)
2466		3421
2467	Priorities are implemented by allocating some space for each	3422	Priorities are implemented by allocating some space for each
2468	priority. When doing priority-based operations, libev usually has to	3423	priority. When doing priority-based operations, libev usually has to
2469	linearly search all the priorities.	3424	linearly search all the priorities, but starting/stopping and activating
		3425	watchers becomes O(1) w.r.t. priority handling.
		3426
		3427	=item Sending an ev_async: O(1)
		3428
		3429	=item Processing ev_async_send: O(number_of_async_watchers)
		3430
		3431	=item Processing signals: O(max_signal_number)
		3432
		3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3434	calls in the current loop iteration. Checking for async and signal events
		3435	involves iterating over all running async watchers or all signal numbers.
2470		3436
2471	=back	3437	=back
2472		3438
2473		3439
		3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3441
		3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3443	requires, and its I/O model is fundamentally incompatible with the POSIX
		3444	model. Libev still offers limited functionality on this platform in
		3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3446	descriptors. This only applies when using Win32 natively, not when using
		3447	e.g. cygwin.
		3448
		3449	Lifting these limitations would basically require the full
		3450	re-implementation of the I/O system. If you are into these kinds of
		3451	things, then note that glib does exactly that for you in a very portable
		3452	way (note also that glib is the slowest event library known to man).
		3453
		3454	There is no supported compilation method available on windows except
		3455	embedding it into other applications.
		3456
		3457	Not a libev limitation but worth mentioning: windows apparently doesn't
		3458	accept large writes: instead of resulting in a partial write, windows will
		3459	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3460	so make sure you only write small amounts into your sockets (less than a
		3461	megabyte seems safe, but thsi apparently depends on the amount of memory
		3462	available).
		3463
		3464	Due to the many, low, and arbitrary limits on the win32 platform and
		3465	the abysmal performance of winsockets, using a large number of sockets
		3466	is not recommended (and not reasonable). If your program needs to use
		3467	more than a hundred or so sockets, then likely it needs to use a totally
		3468	different implementation for windows, as libev offers the POSIX readiness
		3469	notification model, which cannot be implemented efficiently on windows
		3470	(Microsoft monopoly games).
		3471
		3472	A typical way to use libev under windows is to embed it (see the embedding
		3473	section for details) and use the following F<evwrap.h> header file instead
		3474	of F<ev.h>:
		3475
		3476	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3478
		3479	#include "ev.h"
		3480
		3481	And compile the following F<evwrap.c> file into your project (make sure
		3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):
		3483
		3484	#include "evwrap.h"
		3485	#include "ev.c"
		3486
		3487	=over 4
		3488
		3489	=item The winsocket select function
		3490
		3491	The winsocket C<select> function doesn't follow POSIX in that it
		3492	requires socket I<handles> and not socket I<file descriptors> (it is
		3493	also extremely buggy). This makes select very inefficient, and also
		3494	requires a mapping from file descriptors to socket handles (the Microsoft
		3495	C runtime provides the function C<_open_osfhandle> for this). See the
		3496	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3497	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3498
		3499	The configuration for a "naked" win32 using the Microsoft runtime
		3500	libraries and raw winsocket select is:
		3501
		3502	#define EV_USE_SELECT 1
		3503	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3504
		3505	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3506	complexity in the O(n²) range when using win32.
		3507
		3508	=item Limited number of file descriptors
		3509
		3510	Windows has numerous arbitrary (and low) limits on things.
		3511
		3512	Early versions of winsocket's select only supported waiting for a maximum
		3513	of C<64> handles (probably owning to the fact that all windows kernels
		3514	can only wait for C<64> things at the same time internally; Microsoft
		3515	recommends spawning a chain of threads and wait for 63 handles and the
		3516	previous thread in each. Great).
		3517
		3518	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3519	to some high number (e.g. C<2048>) before compiling the winsocket select
		3520	call (which might be in libev or elsewhere, for example, perl does its own
		3521	select emulation on windows).
		3522
		3523	Another limit is the number of file descriptors in the Microsoft runtime
		3524	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3525	or something like this inside Microsoft). You can increase this by calling
		3526	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3527	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3528	libraries.
		3529
		3530	This might get you to about C<512> or C<2048> sockets (depending on
		3531	windows version and/or the phase of the moon). To get more, you need to
		3532	wrap all I/O functions and provide your own fd management, but the cost of
		3533	calling select (O(n²)) will likely make this unworkable.
		3534
		3535	=back
		3536
		3537
		3538	=head1 PORTABILITY REQUIREMENTS
		3539
		3540	In addition to a working ISO-C implementation, libev relies on a few
		3541	additional extensions:
		3542
		3543	=over 4
		3544
		3545	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3546	calling conventions regardless of C<ev_watcher_type *>.
		3547
		3548	Libev assumes not only that all watcher pointers have the same internal
		3549	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3550	assumes that the same (machine) code can be used to call any watcher
		3551	callback: The watcher callbacks have different type signatures, but libev
		3552	calls them using an C<ev_watcher *> internally.
		3553
		3554	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3555
		3556	The type C<sig_atomic_t volatile> (or whatever is defined as
		3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different
		3558	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3559	believed to be sufficiently portable.
		3560
		3561	=item C<sigprocmask> must work in a threaded environment
		3562
		3563	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3564	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3565	pthread implementations will either allow C<sigprocmask> in the "main
		3566	thread" or will block signals process-wide, both behaviours would
		3567	be compatible with libev. Interaction between C<sigprocmask> and
		3568	C<pthread_sigmask> could complicate things, however.
		3569
		3570	The most portable way to handle signals is to block signals in all threads
		3571	except the initial one, and run the default loop in the initial thread as
		3572	well.
		3573
		3574	=item C<long> must be large enough for common memory allocation sizes
		3575
		3576	To improve portability and simplify using libev, libev uses C<long>
		3577	internally instead of C<size_t> when allocating its data structures. On
		3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but
		3579	is still at least 31 bits everywhere, which is enough for hundreds of
		3580	millions of watchers.
		3581
		3582	=item C<double> must hold a time value in seconds with enough accuracy
		3583
		3584	The type C<double> is used to represent timestamps. It is required to
		3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3586	enough for at least into the year 4000. This requirement is fulfilled by
		3587	implementations implementing IEEE 754 (basically all existing ones).
		3588
		3589	=back
		3590
		3591	If you know of other additional requirements drop me a note.
		3592
		3593
		3594	=head1 COMPILER WARNINGS
		3595
		3596	Depending on your compiler and compiler settings, you might get no or a
		3597	lot of warnings when compiling libev code. Some people are apparently
		3598	scared by this.
		3599
		3600	However, these are unavoidable for many reasons. For one, each compiler
		3601	has different warnings, and each user has different tastes regarding
		3602	warning options. "Warn-free" code therefore cannot be a goal except when
		3603	targeting a specific compiler and compiler-version.
		3604
		3605	Another reason is that some compiler warnings require elaborate
		3606	workarounds, or other changes to the code that make it less clear and less
		3607	maintainable.
		3608
		3609	And of course, some compiler warnings are just plain stupid, or simply
		3610	wrong (because they don't actually warn about the condition their message
		3611	seems to warn about).
		3612
		3613	While libev is written to generate as few warnings as possible,
		3614	"warn-free" code is not a goal, and it is recommended not to build libev
		3615	with any compiler warnings enabled unless you are prepared to cope with
		3616	them (e.g. by ignoring them). Remember that warnings are just that:
		3617	warnings, not errors, or proof of bugs.
		3618
		3619
		3620	=head1 VALGRIND
		3621
		3622	Valgrind has a special section here because it is a popular tool that is
		3623	highly useful, but valgrind reports are very hard to interpret.
		3624
		3625	If you think you found a bug (memory leak, uninitialised data access etc.)
		3626	in libev, then check twice: If valgrind reports something like:
		3627
		3628	==2274== definitely lost: 0 bytes in 0 blocks.
		3629	==2274== possibly lost: 0 bytes in 0 blocks.
		3630	==2274== still reachable: 256 bytes in 1 blocks.
		3631
		3632	Then there is no memory leak. Similarly, under some circumstances,
		3633	valgrind might report kernel bugs as if it were a bug in libev, or it
		3634	might be confused (it is a very good tool, but only a tool).
		3635
		3636	If you are unsure about something, feel free to contact the mailing list
		3637	with the full valgrind report and an explanation on why you think this is
		3638	a bug in libev. However, don't be annoyed when you get a brisk "this is
		3639	no bug" answer and take the chance of learning how to interpret valgrind
		3640	properly.
		3641
		3642	If you need, for some reason, empty reports from valgrind for your project
		3643	I suggest using suppression lists.
		3644
		3645
2474	=head1 AUTHOR	3646	=head1 AUTHOR
2475		3647
2476	Marc Lehmann <libev@schmorp.de>.	3648	Marc Lehmann <libev@schmorp.de>.
2477		3649

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