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Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC vs.
Revision 1.190 by root, Tue Sep 30 19:34:14 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
…		…
167	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
168	recommended ones.	215	recommended ones.
169		216
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)) [NOT REENTRANT]
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 (;;)
…		…
200	}	250	}
201		251
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)); [NOT REENTRANT]
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	* If there are no active watchers (reference count is zero), return.	647	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	648	* If EVFLAG_FORKCHECK was used, check for a fork.
		649	- If a fork was detected (by any means), queue and call all fork watchers.
		650	- Queue and call all prepare watchers.
493	- 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.
494	- Update the kernel state with all outstanding changes.	653	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	654	- Update the "event loop time" (ev_now ()).
496	- 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.
497	- Block the process, waiting for any events.	659	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	660	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
500	- Queue all outstanding timers.	662	- Queue all expired timers.
501	- Queue all outstanding periodics.	663	- Queue all expired periodics.
502	- If no events are pending now, queue all idle watchers.	664	- Unless any events are pending now, queue all idle watchers.
503	- Queue all check watchers.	665	- Queue all check watchers.
504	- 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).
505	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
506	be handled here by queueing them when their watcher gets executed.	668	be handled here by queueing them when their watcher gets executed.
507	- 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
508	were used, return, otherwise continue with step *.	670	were used, or there are no active watchers, return, otherwise
		671	continue with step *.
509		672
510	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
511	anymore.	674	anymore.
512		675
513	... queue jobs here, make sure they register event watchers as long	676	... queue jobs here, make sure they register event watchers as long
514	... 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..)
515	ev_loop (my_loop, 0);	678	ev_loop (my_loop, 0);
516	... jobs done. yeah!	679	... jobs done or somebody called unloop. yeah!
517		680
518	=item ev_unloop (loop, how)	681	=item ev_unloop (loop, how)
519		682
520	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
521	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
522	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
523	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.
524		687
		688	This "unloop state" will be cleared when entering C<ev_loop> again.
		689
525	=item ev_ref (loop)	690	=item ev_ref (loop)
526		691
527	=item ev_unref (loop)	692	=item ev_unref (loop)
528		693
529	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
530	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
531	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
532	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>
533	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
534	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
535	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
536	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
537	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
538	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).
539		709
540	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>
541	running when nothing else is active.	711	running when nothing else is active.
542		712
543	struct ev_signal exitsig;	713	struct ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	714	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	715	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	716	evf_unref (loop);
547		717
548	Example: For some weird reason, unregister the above signal handler again.	718	Example: For some weird reason, unregister the above signal handler again.
549		719
550	ev_ref (loop);	720	ev_ref (loop);
551	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.
552		779
553	=back	780	=back
554		781
555		782
556	=head1 ANATOMY OF A WATCHER	783	=head1 ANATOMY OF A WATCHER
557		784
558	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
559	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
560	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:
561		788
562	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)
563	{	790	{
564	ev_io_stop (w);	791	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	792	ev_unloop (loop, EVUNLOOP_ALL);
566	}	793	}
567		794
568	struct ev_loop *loop = ev_default_loop (0);	795	struct ev_loop *loop = ev_default_loop (0);
569	struct ev_io stdin_watcher;	796	struct ev_io stdin_watcher;
570	ev_init (&stdin_watcher, my_cb);	797	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	799	ev_io_start (loop, &stdin_watcher);
573	ev_loop (loop, 0);	800	ev_loop (loop, 0);
574		801
575	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
576	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,
577	although this can sometimes be quite valid).	804	although this can sometimes be quite valid).
578		805
579	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
580	(watcher *, callback)>, which expects a callback to be provided. This	807	(watcher *, callback)>, which expects a callback to be provided. This
581	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
582	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
583	is readable and/or writable).	810	is readable and/or writable).
584		811
585	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
586	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
…		…
656	=item C<EV_FORK>	883	=item C<EV_FORK>
657		884
658	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
659	C<ev_fork>).	886	C<ev_fork>).
660		887
		888	=item C<EV_ASYNC>
		889
		890	The given async watcher has been asynchronously notified (see C<ev_async>).
		891
661	=item C<EV_ERROR>	892	=item C<EV_ERROR>
662		893
663	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
664	happen because the watcher could not be properly started because libev	895	happen because the watcher could not be properly started because libev
665	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
666	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
667	with the watcher being stopped.	898	with the watcher being stopped.
668		899
669	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
670	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
671	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
672	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
673	programs, though, so beware.	904	programs, though, as the fd could already be closed and reused for another
		905	thing, so beware.
674		906
675	=back	907	=back
676		908
677	=head2 GENERIC WATCHER FUNCTIONS	909	=head2 GENERIC WATCHER FUNCTIONS
678		910
…		…
694	(or never started) and there are no pending events outstanding.	926	(or never started) and there are no pending events outstanding.
695		927
696	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,
697	int revents)>.	929	int revents)>.
698		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
699	=item C<ev_TYPE_set> (ev_TYPE *, [args])	937	=item C<ev_TYPE_set> (ev_TYPE *, [args])
700		938
701	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
702	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
703	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
…		…
705	difference to the C<ev_init> macro).	943	difference to the C<ev_init> macro).
706		944
707	Although some watcher types do not have type-specific arguments	945	Although some watcher types do not have type-specific arguments
708	(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.
709		947
		948	See C<ev_init>, above, for an example.
		949
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	950	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		951
712	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
713	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
714	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);
715		959
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		961
718	Starts (activates) the given watcher. Only active watchers will receive	962	Starts (activates) the given watcher. Only active watchers will receive
719	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);
720		969
721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
722		971
723	Stops the given watcher again (if active) and clears the pending	972	Stops the given watcher again (if active) and clears the pending
724	status. It is possible that stopped watchers are pending (for example,	973	status. It is possible that stopped watchers are pending (for example,
…		…
736	=item bool ev_is_pending (ev_TYPE *watcher)	985	=item bool ev_is_pending (ev_TYPE *watcher)
737		986
738	Returns a true value iff the watcher is pending, (i.e. it has outstanding	987	Returns a true value iff the watcher is pending, (i.e. it has outstanding
739	events but its callback has not yet been invoked). As long as a watcher	988	events but its callback has not yet been invoked). As long as a watcher
740	is pending (but not active) you must not call an init function on it (but	989	is pending (but not active) you must not call an init function on it (but
741	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	990	C<ev_TYPE_set> is safe), you must not change its priority, and you must
742	libev (e.g. you cnanot C<free ()> it).	991	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		992	it).
743		993
744	=item callback ev_cb (ev_TYPE *watcher)	994	=item callback ev_cb (ev_TYPE *watcher)
745		995
746	Returns the callback currently set on the watcher.	996	Returns the callback currently set on the watcher.
747		997
…		…
766	watchers on the same event and make sure one is called first.	1016	watchers on the same event and make sure one is called first.
767		1017
768	If you need to suppress invocation when higher priority events are pending	1018	If you need to suppress invocation when higher priority events are pending
769	you need to look at C<ev_idle> watchers, which provide this functionality.	1019	you need to look at C<ev_idle> watchers, which provide this functionality.
770		1020
		1021	You I<must not> change the priority of a watcher as long as it is active or
		1022	pending.
		1023
771	The default priority used by watchers when no priority has been set is	1024	The default priority used by watchers when no priority has been set is
772	always C<0>, which is supposed to not be too high and not be too low :).	1025	always C<0>, which is supposed to not be too high and not be too low :).
773		1026
774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775	fine, as long as you do not mind that the priority value you query might	1028	fine, as long as you do not mind that the priority value you query might
776	or might not have been adjusted to be within valid range.	1029	or might not have been adjusted to be within valid range.
777		1030
		1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1032
		1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1034	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1035	can deal with that fact, as both are simply passed through to the
		1036	callback.
		1037
		1038	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1039
		1040	If the watcher is pending, this function clears its pending status and
		1041	returns its C<revents> bitset (as if its callback was invoked). If the
		1042	watcher isn't pending it does nothing and returns C<0>.
		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
778	=back	1047	=back
779		1048
780		1049
781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
782		1051
783	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
784	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
785	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
786	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
787	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
788	data:	1057	data:
789		1058
790	struct my_io	1059	struct my_io
791	{	1060	{
792	struct ev_io io;	1061	struct ev_io io;
793	int otherfd;	1062	int otherfd;
794	void *somedata;	1063	void *somedata;
795	struct whatever *mostinteresting;	1064	struct whatever *mostinteresting;
796	}	1065	};
		1066
		1067	...
		1068	struct my_io w;
		1069	ev_io_init (&w.io, my_cb, fd, EV_READ);
797		1070
798	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
799	can cast it back to your own type:	1072	can cast it back to your own type:
800		1073
801	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)
802	{	1075	{
803	struct my_io *w = (struct my_io *)w_;	1076	struct my_io *w = (struct my_io *)w_;
804	...	1077	...
805	}	1078	}
806		1079
807	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
808	instead have been omitted.	1081	instead have been omitted.
809		1082
810	Another common scenario is having some data structure with multiple	1083	Another common scenario is to use some data structure with multiple
811	watchers:	1084	embedded watchers:
812		1085
813	struct my_biggy	1086	struct my_biggy
814	{	1087	{
815	int some_data;	1088	int some_data;
816	ev_timer t1;	1089	ev_timer t1;
817	ev_timer t2;	1090	ev_timer t2;
818	}	1091	}
819		1092
820	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
821	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):
822		1098
823	#include <stddef.h>	1099	#include <stddef.h>
824		1100
825	static void	1101	static void
826	t1_cb (EV_P_ struct ev_timer *w, int revents)	1102	t1_cb (EV_P_ struct ev_timer *w, int revents)
827	{	1103	{
828	struct my_biggy big = (struct my_biggy *	1104	struct my_biggy big = (struct my_biggy *
829	(((char *)w) - offsetof (struct my_biggy, t1));	1105	(((char *)w) - offsetof (struct my_biggy, t1));
830	}	1106	}
831		1107
832	static void	1108	static void
833	t2_cb (EV_P_ struct ev_timer *w, int revents)	1109	t2_cb (EV_P_ struct ev_timer *w, int revents)
834	{	1110	{
835	struct my_biggy big = (struct my_biggy *	1111	struct my_biggy big = (struct my_biggy *
836	(((char *)w) - offsetof (struct my_biggy, t2));	1112	(((char *)w) - offsetof (struct my_biggy, t2));
837	}	1113	}
838		1114
839		1115
840	=head1 WATCHER TYPES	1116	=head1 WATCHER TYPES
841		1117
842	This section describes each watcher in detail, but will not repeat	1118	This section describes each watcher in detail, but will not repeat
…		…
866	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
867	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
868	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
869	required if you know what you are doing).	1145	required if you know what you are doing).
870		1146
871	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
872	(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
873	descriptors correctly if you register interest in two or more fds pointing	1149	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
874	to the same underlying file/socket/etc. description (that is, they share
875	the same underlying "file open").
876
877	If you must do this, then force the use of a known-to-be-good backend
878	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
879	C<EVBACKEND_POLL>).
880		1150
881	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
882	receive "spurious" readyness notifications, that is your callback might	1152	receive "spurious" readiness notifications, that is your callback might
883	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
884	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
885	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
886	this situation even with a relatively standard program structure. Thus	1156	this situation even with a relatively standard program structure. Thus
887	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
888	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.
889		1159
890	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
891	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
892	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
893	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
894	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
895		1226
896	=over 4	1227	=over 4
897		1228
898	=item ev_io_init (ev_io *, callback, int fd, int events)	1229	=item ev_io_init (ev_io *, callback, int fd, int events)
899		1230
900	=item ev_io_set (ev_io *, int fd, int events)	1231	=item ev_io_set (ev_io *, int fd, int events)
901		1232
902	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
903	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
904	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.
905		1236
906	=item int fd [read-only]	1237	=item int fd [read-only]
907		1238
908	The file descriptor being watched.	1239	The file descriptor being watched.
909		1240
910	=item int events [read-only]	1241	=item int events [read-only]
911		1242
912	The events being watched.	1243	The events being watched.
913		1244
914	=back	1245	=back
		1246
		1247	=head3 Examples
915		1248
916	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
917	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
918	attempt to read a whole line in the callback.	1251	attempt to read a whole line in the callback.
919		1252
920	static void	1253	static void
921	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)
922	{	1255	{
923	ev_io_stop (loop, w);	1256	ev_io_stop (loop, w);
924	.. 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
925	}	1258	}
926		1259
927	...	1260	...
928	struct ev_loop *loop = ev_default_init (0);	1261	struct ev_loop *loop = ev_default_init (0);
929	struct ev_io stdin_readable;	1262	struct ev_io stdin_readable;
930	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);
931	ev_io_start (loop, &stdin_readable);	1264	ev_io_start (loop, &stdin_readable);
932	ev_loop (loop, 0);	1265	ev_loop (loop, 0);
933		1266
934		1267
935	=head2 C<ev_timer> - relative and optionally repeating timeouts	1268	=head2 C<ev_timer> - relative and optionally repeating timeouts
936		1269
937	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
938	given time, and optionally repeating in regular intervals after that.	1271	given time, and optionally repeating in regular intervals after that.
939		1272
940	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
941	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
942	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
943	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the
944	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.
945		1290
946	The relative timeouts are calculated relative to the C<ev_now ()>	1291	The relative timeouts are calculated relative to the C<ev_now ()>
947	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
948	of the event triggering whatever timeout you are modifying/starting. If	1293	of the event triggering whatever timeout you are modifying/starting. If
949	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
950	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:
951		1296
952	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1297	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953		1298
954	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
955	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
956	order of execution is undefined.	1301	()>.
		1302
		1303	=head3 Watcher-Specific Functions and Data Members
957		1304
958	=over 4	1305	=over 4
959		1306
960	=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)
961		1308
962	=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)
963		1310
964	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>
965	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
966	timer will automatically be configured to trigger again C<repeat> seconds	1313	reached. If it is positive, then the timer will automatically be
967	later, again, and again, until stopped manually.	1314	configured to trigger again C<repeat> seconds later, again, and again,
		1315	until stopped manually.
968		1316
969	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
970	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
971	exactly 10 second intervals. If, however, your program cannot keep up with	1319	trigger at exactly 10 second intervals. If, however, your program cannot
972	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
973	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.
974		1322
975	=item ev_timer_again (loop)	1323	=item ev_timer_again (loop, ev_timer *)
976		1324
977	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
978	repeating. The exact semantics are:	1326	repeating. The exact semantics are:
979		1327
980	If the timer is pending, its pending status is cleared.	1328	If the timer is pending, its pending status is cleared.
981		1329
982	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).
983		1331
984	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
985	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.
986		1334
987	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
988	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
989	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
990	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
991	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
992	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
993	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
…		…
1007	ev_timer_again (loop, timer);	1355	ev_timer_again (loop, timer);
1008		1356
1009	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
1010	you want to modify its timeout value.	1358	you want to modify its timeout value.
1011		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
1012	=item ev_tstamp repeat [read-write]	1366	=item ev_tstamp repeat [read-write]
1013		1367
1014	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
1015	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),
1016	which is also when any modifications are taken into account.	1370	which is also when any modifications are taken into account.
1017		1371
1018	=back	1372	=back
1019		1373
		1374	=head3 Examples
		1375
1020	Example: Create a timer that fires after 60 seconds.	1376	Example: Create a timer that fires after 60 seconds.
1021		1377
1022	static void	1378	static void
1023	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)
1024	{	1380	{
1025	.. one minute over, w is actually stopped right here	1381	.. one minute over, w is actually stopped right here
1026	}	1382	}
1027		1383
1028	struct ev_timer mytimer;	1384	struct ev_timer mytimer;
1029	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1030	ev_timer_start (loop, &mytimer);	1386	ev_timer_start (loop, &mytimer);
1031		1387
1032	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
1033	inactivity.	1389	inactivity.
1034		1390
1035	static void	1391	static void
1036	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)
1037	{	1393	{
1038	.. ten seconds without any activity	1394	.. ten seconds without any activity
1039	}	1395	}
1040		1396
1041	struct ev_timer mytimer;	1397	struct ev_timer mytimer;
1042	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 */
1043	ev_timer_again (&mytimer); /* start timer */	1399	ev_timer_again (&mytimer); /* start timer */
1044	ev_loop (loop, 0);	1400	ev_loop (loop, 0);
1045		1401
1046	// 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":
1047	// reset the timeout to start ticking again at 10 seconds	1403	// reset the timeout to start ticking again at 10 seconds
1048	ev_timer_again (&mytimer);	1404	ev_timer_again (&mytimer);
1049		1405
1050		1406
1051	=head2 C<ev_periodic> - to cron or not to cron?	1407	=head2 C<ev_periodic> - to cron or not to cron?
1052		1408
1053	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
1054	(and unfortunately a bit complex).	1410	(and unfortunately a bit complex).
1055		1411
1056	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)
1057	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
1058	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
1059	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 ()
1060	+ 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
1061	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
1062	roughly 10 seconds later and of course not if you reset your system time	1419	roughly 10 seconds later as it uses a relative timeout).
1063	again).
1064		1420
1065	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,
1066	triggering an event on eahc midnight, local time.	1422	such as triggering an event on each "midnight, local time", or other
		1423	complicated rules.
1067		1424
1068	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
1069	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
1070	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
1071		1430
1072	=over 4	1431	=over 4
1073		1432
1074	=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)
1075		1434
1076	=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)
1077		1436
1078	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
1079	operation, and we will explain them from simplest to complex:	1438	operation, and we will explain them from simplest to most complex:
1080		1439
1081	=over 4	1440	=over 4
1082		1441
1083	=item * absolute timer (interval = reschedule_cb = 0)	1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084		1443
1085	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
1086	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
1087	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
1088	system time reaches or surpasses this time.	1447	only run when the system clock reaches or surpasses this time.
1089		1448
1090	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091		1450
1092	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
1093	C<at + N * interval> time (for some integer N) and then repeat, regardless	1452	C<at + N * interval> time (for some integer N, which can also be negative)
1094	of any time jumps.	1453	and then repeat, regardless of any time jumps.
1095		1454
1096	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
1097	time:	1456	system clock, for example, here is a C<ev_periodic> that triggers each
		1457	hour, on the hour:
1098		1458
1099	ev_periodic_set (&periodic, 0., 3600., 0);	1459	ev_periodic_set (&periodic, 0., 3600., 0);
1100		1460
1101	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,
1102	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
1103	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
1104	by 3600.	1464	by 3600.
1105		1465
1106	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
1107	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
1108	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.
1109		1469
		1470	For numerical stability it is preferable that the C<at> value is near
		1471	C<ev_now ()> (the current time), but there is no range requirement for
		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).
		1478
1110	=item * manual reschedule mode (reschedule_cb = callback)	1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111		1480
1112	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
1113	ignored. Instead, each time the periodic watcher gets scheduled, the	1482	ignored. Instead, each time the periodic watcher gets scheduled, the
1114	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
1115	current time as second argument.	1484	current time as second argument.
1116		1485
1117	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,
1118	ever, or make any event loop modifications>. If you need to stop it,	1487	ever, or make ANY event loop modifications whatsoever>.
1119	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120	starting a prepare watcher).
1121		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
1122	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
1123	ev_tstamp now)>, e.g.:	1494	*w, ev_tstamp now)>, e.g.:
1124		1495
1125	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)
1126	{	1497	{
1127	return now + 60.;	1498	return now + 60.;
1128	}	1499	}
…		…
1130	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
1131	(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
1132	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
1133	might be called at other times, too.	1504	might be called at other times, too.
1134		1505
1135	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
1136	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1507	equal to the passed C<now> value >>.
1137		1508
1138	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
1139	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
1140	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
1141	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
1142	reason I omitted it as an example).	1513	reason I omitted it as an example).
1143		1514
1144	=back	1515	=back
…		…
1148	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
1149	when you changed some parameters or the reschedule callback would return	1520	when you changed some parameters or the reschedule callback would return
1150	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
1151	program when the crontabs have changed).	1522	program when the crontabs have changed).
1152		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
		1529	=item ev_tstamp offset [read-write]
		1530
		1531	When repeating, this contains the offset value, otherwise this is the
		1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1533
		1534	Can be modified any time, but changes only take effect when the periodic
		1535	timer fires or C<ev_periodic_again> is being called.
		1536
1153	=item ev_tstamp interval [read-write]	1537	=item ev_tstamp interval [read-write]
1154		1538
1155	The current interval value. Can be modified any time, but changes only	1539	The current interval value. Can be modified any time, but changes only
1156	take effect when the periodic timer fires or C<ev_periodic_again> is being	1540	take effect when the periodic timer fires or C<ev_periodic_again> is being
1157	called.	1541	called.
…		…
1162	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
1163	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.
1164		1548
1165	=back	1549	=back
1166		1550
		1551	=head3 Examples
		1552
1167	Example: Call a callback every hour, or, more precisely, whenever the	1553	Example: Call a callback every hour, or, more precisely, whenever the
1168	system clock is divisible by 3600. The callback invocation times have	1554	system time is divisible by 3600. The callback invocation times have
1169	potentially a lot of jittering, but good long-term stability.	1555	potentially a lot of jitter, but good long-term stability.
1170		1556
1171	static void	1557	static void
1172	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)
1173	{	1559	{
1174	... 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)
1175	}	1561	}
1176		1562
1177	struct ev_periodic hourly_tick;	1563	struct ev_periodic hourly_tick;
1178	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1179	ev_periodic_start (loop, &hourly_tick);	1565	ev_periodic_start (loop, &hourly_tick);
1180		1566
1181	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:
1182		1568
1183	#include <math.h>	1569	#include <math.h>
1184		1570
1185	static ev_tstamp	1571	static ev_tstamp
1186	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1187	{	1573	{
1188	return fmod (now, 3600.) + 3600.;	1574	return now + (3600. - fmod (now, 3600.));
1189	}	1575	}
1190		1576
1191	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);
1192		1578
1193	Example: Call a callback every hour, starting now:	1579	Example: Call a callback every hour, starting now:
1194		1580
1195	struct ev_periodic hourly_tick;	1581	struct ev_periodic hourly_tick;
1196	ev_periodic_init (&hourly_tick, clock_cb,	1582	ev_periodic_init (&hourly_tick, clock_cb,
1197	fmod (ev_now (loop), 3600.), 3600., 0);	1583	fmod (ev_now (loop), 3600.), 3600., 0);
1198	ev_periodic_start (loop, &hourly_tick);	1584	ev_periodic_start (loop, &hourly_tick);
1199		1585
1200		1586
1201	=head2 C<ev_signal> - signal me when a signal gets signalled!	1587	=head2 C<ev_signal> - signal me when a signal gets signalled!
1202		1588
1203	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
1204	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
1205	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
1206	normal event processing, like any other event.	1592	normal event processing, like any other event.
1207		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
1208	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
1209	first watcher gets started will libev actually register a signal watcher	1599	first watcher gets started will libev actually register a signal handler
1210	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
1211	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
1212	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
1213	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
1214		1612
1215	=over 4	1613	=over 4
1216		1614
1217	=item ev_signal_init (ev_signal *, callback, int signum)	1615	=item ev_signal_init (ev_signal *, callback, int signum)
1218		1616
…		…
1225		1623
1226	The signal the watcher watches out for.	1624	The signal the watcher watches out for.
1227		1625
1228	=back	1626	=back
1229		1627
		1628	=head3 Examples
		1629
		1630	Example: Try to exit cleanly on SIGINT.
		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, &signal_watcher);
		1641
1230		1642
1231	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1232		1644
1233	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
1234	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
1235		1684
1236	=over 4	1685	=over 4
1237		1686
1238	=item ev_child_init (ev_child *, callback, int pid)	1687	=item ev_child_init (ev_child *, callback, int pid, int trace)
1239		1688
1240	=item ev_child_set (ev_child *, int pid)	1689	=item ev_child_set (ev_child *, int pid, int trace)
1241		1690
1242	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
1243	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
1244	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
1245	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
1246	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
1247	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).
1248		1699
1249	=item int pid [read-only]	1700	=item int pid [read-only]
1250		1701
1251	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.
1252		1703
…		…
1259	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
1260	C<waitpid> and C<sys/wait.h> documentation for details).	1711	C<waitpid> and C<sys/wait.h> documentation for details).
1261		1712
1262	=back	1713	=back
1263		1714
1264	Example: Try to exit cleanly on SIGINT and SIGTERM.	1715	=head3 Examples
1265		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
1266	static void	1722	static void
1267	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1723	child_cb (EV_P_ struct ev_child *w, int revents)
1268	{	1724	{
1269	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);
1270	}	1727	}
1271		1728
1272	struct ev_signal signal_watcher;	1729	pid_t pid = fork ();
1273	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1730
1274	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	}
1275		1743
1276		1744
1277	=head2 C<ev_stat> - did the file attributes just change?	1745	=head2 C<ev_stat> - did the file attributes just change?
1278		1746
1279	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
1280	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
1281	compared to the last time, invoking the callback if it did.	1749	compared to the last time, invoking the callback if it did.
1282		1750
1283	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
1284	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
…		…
1287	the stat buffer having unspecified contents.	1755	the stat buffer having unspecified contents.
1288		1756
1289	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
1290	relative and your working directory changes, the behaviour is undefined.	1758	relative and your working directory changes, the behaviour is undefined.
1291		1759
1292	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
1293	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
1294	can specify a recommended polling interval for this case. If you specify	1762	it changed somehow. You can specify a recommended polling interval for
1295	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!)
1296	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
1297	five seconds, although this might change dynamically). Libev will also	1765	you can expect to be around five seconds, although this might change
1298	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
1299	usually overkill.	1767	around C<0.1>, but thats usually overkill.
1300		1768
1301	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,
1302	as even with OS-supported change notifications, this can be	1770	as even with OS-supported change notifications, this can be
1303	resource-intensive.	1771	resource-intensive.
1304		1772
1305	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
1306	implemented (implementing kqueue support is left as an exercise for the	1774	is the Linux inotify interface (implementing kqueue support is left as
1307	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
1308	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1776	of implementing C<ev_stat> semantics with kqueue).
1309	to fall back to regular polling again even with inotify, but changes are	1777
1310	usually detected immediately, and if the file exists there will be no	1778	=head3 ABI Issues (Largefile Support)
1311	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
1312		1840
1313	=over 4	1841	=over 4
1314		1842
1315	=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)
1316		1844
…		…
1320	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
1321	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
1322	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
1323	path for as long as the watcher is active.	1851	path for as long as the watcher is active.
1324		1852
1325	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,
1326	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
1327	last change was detected).	1855	last change was detected).
1328		1856
1329	=item ev_stat_stat (ev_stat *)	1857	=item ev_stat_stat (loop, ev_stat *)
1330		1858
1331	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
1332	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
1333	detecting this change (while introducing a race condition). Can also be	1861	detecting this change (while introducing a race condition if you are not
1334	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.
1335		1864
1336	=item ev_statdata attr [read-only]	1865	=item ev_statdata attr [read-only]
1337		1866
1338	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
1339	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
1340	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
1341	was some error while C<stat>ing the file.	1871	some error while C<stat>ing the file.
1342		1872
1343	=item ev_statdata prev [read-only]	1873	=item ev_statdata prev [read-only]
1344		1874
1345	The previous attributes of the file. The callback gets invoked whenever	1875	The previous attributes of the file. The callback gets invoked whenever
1346	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>.
1347		1879
1348	=item ev_tstamp interval [read-only]	1880	=item ev_tstamp interval [read-only]
1349		1881
1350	The specified interval.	1882	The specified interval.
1351		1883
1352	=item const char *path [read-only]	1884	=item const char *path [read-only]
1353		1885
1354	The filesystem path that is being watched.	1886	The file system path that is being watched.
1355		1887
1356	=back	1888	=back
1357		1889
		1890	=head3 Examples
		1891
1358	Example: Watch C</etc/passwd> for attribute changes.	1892	Example: Watch C</etc/passwd> for attribute changes.
1359		1893
1360	static void	1894	static void
1361	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1895	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1362	{	1896	{
1363	/* /etc/passwd changed in some way */	1897	/* /etc/passwd changed in some way */
1364	if (w->attr.st_nlink)	1898	if (w->attr.st_nlink)
1365	{	1899	{
1366	printf ("passwd current size %ld\n", (long)w->attr.st_size);	1900	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1367	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	1901	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1368	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	1902	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1369	}	1903	}
1370	else	1904	else
1371	/* you shalt not abuse printf for puts */	1905	/* you shalt not abuse printf for puts */
1372	puts ("wow, /etc/passwd is not there, expect problems. "	1906	puts ("wow, /etc/passwd is not there, expect problems. "
1373	"if this is windows, they already arrived\n");	1907	"if this is windows, they already arrived\n");
1374	}	1908	}
1375		1909
1376	...	1910	...
1377	ev_stat passwd;	1911	ev_stat passwd;
1378		1912
1379	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1913	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1380	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);
1381		1943
1382		1944
1383	=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...
1384		1946
1385	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
1386	priority are pending (prepare, check and other idle watchers do not	1948	priority are pending (prepare, check and other idle watchers do not count
1387	count).	1949	as receiving "events").
1388		1950
1389	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
1390	(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
1391	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
1392	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
…		…
1399	Apart from keeping your process non-blocking (which is a useful	1961	Apart from keeping your process non-blocking (which is a useful
1400	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
1401	"pseudo-background processing", or delay processing stuff to after the	1963	"pseudo-background processing", or delay processing stuff to after the
1402	event loop has handled all outstanding events.	1964	event loop has handled all outstanding events.
1403		1965
		1966	=head3 Watcher-Specific Functions and Data Members
		1967
1404	=over 4	1968	=over 4
1405		1969
1406	=item ev_idle_init (ev_signal *, callback)	1970	=item ev_idle_init (ev_signal *, callback)
1407		1971
1408	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
1409	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,
1410	believe me.	1974	believe me.
1411		1975
1412	=back	1976	=back
1413		1977
		1978	=head3 Examples
		1979
1414	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
1415	callback, free it. Also, use no error checking, as usual.	1981	callback, free it. Also, use no error checking, as usual.
1416		1982
1417	static void	1983	static void
1418	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)
1419	{	1985	{
1420	free (w);	1986	free (w);
1421	// now do something you wanted to do when the program has	1987	// now do something you wanted to do when the program has
1422	// no longer asnything immediate to do.	1988	// no longer anything immediate to do.
1423	}	1989	}
1424		1990
1425	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1426	ev_idle_init (idle_watcher, idle_cb);	1992	ev_idle_init (idle_watcher, idle_cb);
1427	ev_idle_start (loop, idle_cb);	1993	ev_idle_start (loop, idle_cb);
1428		1994
1429		1995
1430	=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!
1431		1997
1432	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:
1433	prepare watchers get invoked before the process blocks and check watchers	1999	prepare watchers get invoked before the process blocks and check watchers
1434	afterwards.	2000	afterwards.
1435		2001
1436	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
1437	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>
…		…
1440	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,
1441	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
1442	called in pairs bracketing the blocking call.	2008	called in pairs bracketing the blocking call.
1443		2009
1444	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
1445	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
1446	variable changes, implement your own watchers, integrate net-snmp or a	2012	variable changes, implement your own watchers, integrate net-snmp or a
1447	coroutine library and lots more. They are also occasionally useful if	2013	coroutine library and lots more. They are also occasionally useful if
1448	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,
1449	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>
1450	watcher).	2016	watcher).
1451		2017
1452	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
1453	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
1454	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
1455	provide just this functionality). Then, in the check watcher you check for	2021	libraries provide exactly this functionality). Then, in the check watcher,
1456	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
1457	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
1458	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
1459	because you never know, you know?).	2025	nevertheless, because you never know, you know?).
1460		2026
1461	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
1462	coroutines into libev programs, by yielding to other active coroutines	2028	coroutines into libev programs, by yielding to other active coroutines
1463	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
1464	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
1465	with priority higher than or equal to the event loop and one coroutine	2031	with priority higher than or equal to the event loop and one coroutine
1466	of lower priority, but only once, using idle watchers to keep the event	2032	of lower priority, but only once, using idle watchers to keep the event
1467	loop from blocking if lower-priority coroutines are active, thus mapping	2033	loop from blocking if lower-priority coroutines are active, thus mapping
1468	low-priority coroutines to idle/background tasks).	2034	low-priority coroutines to idle/background tasks).
1469		2035
		2036	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		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
		2040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2041	activate ("feed") events into libev. While libev fully supports this, they
		2042	might get executed before other C<ev_check> watchers did their job. As
		2043	C<ev_check> watchers are often used to embed other (non-libev) event
		2044	loops those other event loops might be in an unusable state until their
		2045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2046	others).
		2047
		2048	=head3 Watcher-Specific Functions and Data Members
		2049
1470	=over 4	2050	=over 4
1471		2051
1472	=item ev_prepare_init (ev_prepare *, callback)	2052	=item ev_prepare_init (ev_prepare *, callback)
1473		2053
1474	=item ev_check_init (ev_check *, callback)	2054	=item ev_check_init (ev_check *, callback)
1475		2055
1476	Initialises and configures the prepare or check watcher - they have no	2056	Initialises and configures the prepare or check watcher - they have no
1477	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>
1478	macros, but using them is utterly, utterly and completely pointless.	2058	macros, but using them is utterly, utterly, utterly and completely
		2059	pointless.
1479		2060
1480	=back	2061	=back
1481		2062
1482	Example: To include a library such as adns, you would add IO watchers	2063	=head3 Examples
1483	and a timeout watcher in a prepare handler, as required by libadns, and	2064
		2065	There are a number of principal ways to embed other event loops or modules
		2066	into libev. Here are some ideas on how to include libadns into libev
		2067	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2068	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2069	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2070	Glib event loop).
		2071
		2072	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484	in a check watcher, destroy them and call into libadns. What follows is	2073	and in a check watcher, destroy them and call into libadns. What follows
1485	pseudo-code only of course:	2074	is pseudo-code only of course. This requires you to either use a low
		2075	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2076	the callbacks for the IO/timeout watchers might not have been called yet.
1486		2077
1487	static ev_io iow [nfd];	2078	static ev_io iow [nfd];
1488	static ev_timer tw;	2079	static ev_timer tw;
1489		2080
1490	static void	2081	static void
1491	io_cb (ev_loop *loop, ev_io *w, int revents)	2082	io_cb (ev_loop *loop, ev_io *w, int revents)
1492	{	2083	{
1493	// set the relevant poll flags
1494	// could also call adns_processreadable etc. here
1495	struct pollfd *fd = (struct pollfd *)w->data;
1496	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498	}	2084	}
1499		2085
1500	// create io watchers for each fd and a timer before blocking	2086	// create io watchers for each fd and a timer before blocking
1501	static void	2087	static void
1502	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1503	{	2089	{
1504	int timeout = 3600000;	2090	int timeout = 3600000;
1505	struct pollfd fds [nfd];	2091	struct pollfd fds [nfd];
1506	// actual code will need to loop here and realloc etc.	2092	// actual code will need to loop here and realloc etc.
1507	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1508		2094
1509	/* 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 */
1510	ev_timer_init (&tw, 0, timeout * 1e-3);	2096	ev_timer_init (&tw, 0, timeout * 1e-3);
1511	ev_timer_start (loop, &tw);	2097	ev_timer_start (loop, &tw);
1512		2098
1513	// create on ev_io per pollfd	2099	// create one ev_io per pollfd
1514	for (int i = 0; i < nfd; ++i)	2100	for (int i = 0; i < nfd; ++i)
1515	{	2101	{
1516	ev_io_init (iow + i, io_cb, fds [i].fd,	2102	ev_io_init (iow + i, io_cb, fds [i].fd,
1517	((fds [i].events & POLLIN ? EV_READ : 0)	2103	((fds [i].events & POLLIN ? EV_READ : 0)
1518	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2104	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519		2105
1520	fds [i].revents = 0;	2106	fds [i].revents = 0;
1521	iow [i].data = fds + i;
1522	ev_io_start (loop, iow + i);	2107	ev_io_start (loop, iow + i);
1523	}	2108	}
1524	}	2109	}
1525		2110
1526	// stop all watchers after blocking	2111	// stop all watchers after blocking
1527	static void	2112	static void
1528	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1529	{	2114	{
1530	ev_timer_stop (loop, &tw);	2115	ev_timer_stop (loop, &tw);
1531		2116
1532	for (int i = 0; i < nfd; ++i)	2117	for (int i = 0; i < nfd; ++i)
		2118	{
		2119	// set the relevant poll flags
		2120	// could also call adns_processreadable etc. here
		2121	struct pollfd *fd = fds + i;
		2122	int revents = ev_clear_pending (iow + i);
		2123	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2124	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2125
		2126	// now stop the watcher
1533	ev_io_stop (loop, iow + i);	2127	ev_io_stop (loop, iow + i);
		2128	}
1534		2129
1535	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2130	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1536	}	2131	}
		2132
		2133	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2134	in the prepare watcher and would dispose of the check watcher.
		2135
		2136	Method 3: If the module to be embedded supports explicit event
		2137	notification (libadns does), you can also make use of the actual watcher
		2138	callbacks, and only destroy/create the watchers in the prepare watcher.
		2139
		2140	static void
		2141	timer_cb (EV_P_ ev_timer *w, int revents)
		2142	{
		2143	adns_state ads = (adns_state)w->data;
		2144	update_now (EV_A);
		2145
		2146	adns_processtimeouts (ads, &tv_now);
		2147	}
		2148
		2149	static void
		2150	io_cb (EV_P_ ev_io *w, int revents)
		2151	{
		2152	adns_state ads = (adns_state)w->data;
		2153	update_now (EV_A);
		2154
		2155	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2156	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2157	}
		2158
		2159	// do not ever call adns_afterpoll
		2160
		2161	Method 4: Do not use a prepare or check watcher because the module you
		2162	want to embed is not flexible enough to support it. Instead, you can
		2163	override their poll function. The drawback with this solution is that the
		2164	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2165	this approach, effectively embedding EV as a client into the horrible
		2166	libglib event loop.
		2167
		2168	static gint
		2169	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2170	{
		2171	int got_events = 0;
		2172
		2173	for (n = 0; n < nfds; ++n)
		2174	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2175
		2176	if (timeout >= 0)
		2177	// create/start timer
		2178
		2179	// poll
		2180	ev_loop (EV_A_ 0);
		2181
		2182	// stop timer again
		2183	if (timeout >= 0)
		2184	ev_timer_stop (EV_A_ &to);
		2185
		2186	// stop io watchers again - their callbacks should have set
		2187	for (n = 0; n < nfds; ++n)
		2188	ev_io_stop (EV_A_ iow [n]);
		2189
		2190	return got_events;
		2191	}
1537		2192
1538		2193
1539	=head2 C<ev_embed> - when one backend isn't enough...	2194	=head2 C<ev_embed> - when one backend isn't enough...
1540		2195
1541	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
…		…
1547	prioritise I/O.	2202	prioritise I/O.
1548		2203
1549	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
1550	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
1551	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
1552	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
1553	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
1554	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
1555	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 :)
1556		2212
1557	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
1558	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),
1559	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
1560	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
1561	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.
1562		2218
1563	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
1564	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
1565	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
1566	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
…		…
1574	interested in that.	2230	interested in that.
1575		2231
1576	Also, there have not currently been made special provisions for forking:	2232	Also, there have not currently been made special provisions for forking:
1577	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,
1578	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
1579	yourself.	2235	yourself - but you can use a fork watcher to handle this automatically,
		2236	and future versions of libev might do just that.
1580		2237
1581	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
1582	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1583	portable one.	2240	portable one.
1584		2241
1585	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
1586	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
1587	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
1588	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.
1589		2246
1590	struct ev_loop *loop_hi = ev_default_init (0);	2247	=head3 C<ev_embed> and fork
1591	struct ev_loop *loop_lo = 0;
1592	struct ev_embed embed;
1593
1594	// see if there is a chance of getting one that works
1595	// (remember that a flags value of 0 means autodetection)
1596	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1597	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1598	: 0;
1599		2248
1600	// if we got one, then embed it, otherwise default to loop_hi	2249	While the C<ev_embed> watcher is running, forks in the embedding loop will
1601	if (loop_lo)	2250	automatically be applied to the embedded loop as well, so no special
1602	{	2251	fork handling is required in that case. When the watcher is not running,
1603	ev_embed_init (&embed, 0, loop_lo);	2252	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1604	ev_embed_start (loop_hi, &embed);	2253	as applicable.
1605	}	2254
1606	else	2255	=head3 Watcher-Specific Functions and Data Members
1607	loop_lo = loop_hi;
1608		2256
1609	=over 4	2257	=over 4
1610		2258
1611	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2259	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1612		2260
…		…
1614		2262
1615	Configures the watcher to embed the given loop, which must be	2263	Configures the watcher to embed the given loop, which must be
1616	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2264	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1617	invoked automatically, otherwise it is the responsibility of the callback	2265	invoked automatically, otherwise it is the responsibility of the callback
1618	to invoke it (it will continue to be called until the sweep has been done,	2266	to invoke it (it will continue to be called until the sweep has been done,
1619	if you do not want thta, you need to temporarily stop the embed watcher).	2267	if you do not want that, you need to temporarily stop the embed watcher).
1620		2268
1621	=item ev_embed_sweep (loop, ev_embed *)	2269	=item ev_embed_sweep (loop, ev_embed *)
1622		2270
1623	Make a single, non-blocking sweep over the embedded loop. This works	2271	Make a single, non-blocking sweep over the embedded loop. This works
1624	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2272	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1625	apropriate way for embedded loops.	2273	appropriate way for embedded loops.
1626		2274
1627	=item struct ev_loop *loop [read-only]	2275	=item struct ev_loop *other [read-only]
1628		2276
1629	The embedded event loop.	2277	The embedded event loop.
1630		2278
1631	=back	2279	=back
		2280
		2281	=head3 Examples
		2282
		2283	Example: Try to get an embeddable event loop and embed it into the default
		2284	event loop. If that is not possible, use the default loop. The default
		2285	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2286	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2287	used).
		2288
		2289	struct ev_loop *loop_hi = ev_default_init (0);
		2290	struct ev_loop *loop_lo = 0;
		2291	struct ev_embed embed;
		2292
		2293	// see if there is a chance of getting one that works
		2294	// (remember that a flags value of 0 means autodetection)
		2295	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2296	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2297	: 0;
		2298
		2299	// if we got one, then embed it, otherwise default to loop_hi
		2300	if (loop_lo)
		2301	{
		2302	ev_embed_init (&embed, 0, loop_lo);
		2303	ev_embed_start (loop_hi, &embed);
		2304	}
		2305	else
		2306	loop_lo = loop_hi;
		2307
		2308	Example: Check if kqueue is available but not recommended and create
		2309	a kqueue backend for use with sockets (which usually work with any
		2310	kqueue implementation). Store the kqueue/socket-only event loop in
		2311	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2312
		2313	struct ev_loop *loop = ev_default_init (0);
		2314	struct ev_loop *loop_socket = 0;
		2315	struct ev_embed embed;
		2316
		2317	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2318	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2319	{
		2320	ev_embed_init (&embed, 0, loop_socket);
		2321	ev_embed_start (loop, &embed);
		2322	}
		2323
		2324	if (!loop_socket)
		2325	loop_socket = loop;
		2326
		2327	// now use loop_socket for all sockets, and loop for everything else
1632		2328
1633		2329
1634	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2330	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1635		2331
1636	Fork watchers are called when a C<fork ()> was detected (usually because	2332	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1639	event loop blocks next and before C<ev_check> watchers are being called,	2335	event loop blocks next and before C<ev_check> watchers are being called,
1640	and only in the child after the fork. If whoever good citizen calling	2336	and only in the child after the fork. If whoever good citizen calling
1641	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2337	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642	handlers will be invoked, too, of course.	2338	handlers will be invoked, too, of course.
1643		2339
		2340	=head3 Watcher-Specific Functions and Data Members
		2341
1644	=over 4	2342	=over 4
1645		2343
1646	=item ev_fork_init (ev_signal *, callback)	2344	=item ev_fork_init (ev_signal *, callback)
1647		2345
1648	Initialises and configures the fork watcher - it has no parameters of any	2346	Initialises and configures the fork watcher - it has no parameters of any
1649	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2347	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1650	believe me.	2348	believe me.
		2349
		2350	=back
		2351
		2352
		2353	=head2 C<ev_async> - how to wake up another event loop
		2354
		2355	In general, you cannot use an C<ev_loop> from multiple threads or other
		2356	asynchronous sources such as signal handlers (as opposed to multiple event
		2357	loops - those are of course safe to use in different threads).
		2358
		2359	Sometimes, however, you need to wake up another event loop you do not
		2360	control, for example because it belongs to another thread. This is what
		2361	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2362	can signal it by calling C<ev_async_send>, which is thread- and signal
		2363	safe.
		2364
		2365	This functionality is very similar to C<ev_signal> watchers, as signals,
		2366	too, are asynchronous in nature, and signals, too, will be compressed
		2367	(i.e. the number of callback invocations may be less than the number of
		2368	C<ev_async_sent> calls).
		2369
		2370	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2371	just the default loop.
		2372
		2373	=head3 Queueing
		2374
		2375	C<ev_async> does not support queueing of data in any way. The reason
		2376	is that the author does not know of a simple (or any) algorithm for a
		2377	multiple-writer-single-reader queue that works in all cases and doesn't
		2378	need elaborate support such as pthreads.
		2379
		2380	That means that if you want to queue data, you have to provide your own
		2381	queue. But at least I can tell you how to implement locking around your
		2382	queue:
		2383
		2384	=over 4
		2385
		2386	=item queueing from a signal handler context
		2387
		2388	To implement race-free queueing, you simply add to the queue in the signal
		2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2390	some fictitious SIGUSR1 handler:
		2391
		2392	static ev_async mysig;
		2393
		2394	static void
		2395	sigusr1_handler (void)
		2396	{
		2397	sometype data;
		2398
		2399	// no locking etc.
		2400	queue_put (data);
		2401	ev_async_send (EV_DEFAULT_ &mysig);
		2402	}
		2403
		2404	static void
		2405	mysig_cb (EV_P_ ev_async *w, int revents)
		2406	{
		2407	sometype data;
		2408	sigset_t block, prev;
		2409
		2410	sigemptyset (&block);
		2411	sigaddset (&block, SIGUSR1);
		2412	sigprocmask (SIG_BLOCK, &block, &prev);
		2413
		2414	while (queue_get (&data))
		2415	process (data);
		2416
		2417	if (sigismember (&prev, SIGUSR1)
		2418	sigprocmask (SIG_UNBLOCK, &block, 0);
		2419	}
		2420
		2421	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2422	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2423	either...).
		2424
		2425	=item queueing from a thread context
		2426
		2427	The strategy for threads is different, as you cannot (easily) block
		2428	threads but you can easily preempt them, so to queue safely you need to
		2429	employ a traditional mutex lock, such as in this pthread example:
		2430
		2431	static ev_async mysig;
		2432	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2433
		2434	static void
		2435	otherthread (void)
		2436	{
		2437	// only need to lock the actual queueing operation
		2438	pthread_mutex_lock (&mymutex);
		2439	queue_put (data);
		2440	pthread_mutex_unlock (&mymutex);
		2441
		2442	ev_async_send (EV_DEFAULT_ &mysig);
		2443	}
		2444
		2445	static void
		2446	mysig_cb (EV_P_ ev_async *w, int revents)
		2447	{
		2448	pthread_mutex_lock (&mymutex);
		2449
		2450	while (queue_get (&data))
		2451	process (data);
		2452
		2453	pthread_mutex_unlock (&mymutex);
		2454	}
		2455
		2456	=back
		2457
		2458
		2459	=head3 Watcher-Specific Functions and Data Members
		2460
		2461	=over 4
		2462
		2463	=item ev_async_init (ev_async *, callback)
		2464
		2465	Initialises and configures the async watcher - it has no parameters of any
		2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2467	trust me.
		2468
		2469	=item ev_async_send (loop, ev_async *)
		2470
		2471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2472	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2473	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2475	section below on what exactly this means).
		2476
		2477	This call incurs the overhead of a system call only once per loop iteration,
		2478	so while the overhead might be noticeable, it doesn't apply to repeated
		2479	calls to C<ev_async_send>.
		2480
		2481	=item bool = ev_async_pending (ev_async *)
		2482
		2483	Returns a non-zero value when C<ev_async_send> has been called on the
		2484	watcher but the event has not yet been processed (or even noted) by the
		2485	event loop.
		2486
		2487	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2488	the loop iterates next and checks for the watcher to have become active,
		2489	it will reset the flag again. C<ev_async_pending> can be used to very
		2490	quickly check whether invoking the loop might be a good idea.
		2491
		2492	Not that this does I<not> check whether the watcher itself is pending, only
		2493	whether it has been requested to make this watcher pending.
1651		2494
1652	=back	2495	=back
1653		2496
1654		2497
1655	=head1 OTHER FUNCTIONS	2498	=head1 OTHER FUNCTIONS
…		…
1666	or timeout without having to allocate/configure/start/stop/free one or	2509	or timeout without having to allocate/configure/start/stop/free one or
1667	more watchers yourself.	2510	more watchers yourself.
1668		2511
1669	If C<fd> is less than 0, then no I/O watcher will be started and events	2512	If C<fd> is less than 0, then no I/O watcher will be started and events
1670	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
1671	C<events> set will be craeted and started.	2514	C<events> set will be created and started.
1672		2515
1673	If C<timeout> is less than 0, then no timeout watcher will be	2516	If C<timeout> is less than 0, then no timeout watcher will be
1674	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1675	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of
1676	dubious value.	2519	dubious value.
…		…
1678	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2521	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1679	passed an C<revents> set like normal event callbacks (a combination of	2522	passed an C<revents> set like normal event callbacks (a combination of
1680	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1681	value passed to C<ev_once>:	2524	value passed to C<ev_once>:
1682		2525
1683	static void stdin_ready (int revents, void *arg)	2526	static void stdin_ready (int revents, void *arg)
1684	{	2527	{
1685	if (revents & EV_TIMEOUT)	2528	if (revents & EV_TIMEOUT)
1686	/* doh, nothing entered */;	2529	/* doh, nothing entered */;
1687	else if (revents & EV_READ)	2530	else if (revents & EV_READ)
1688	/* stdin might have data for us, joy! */;	2531	/* stdin might have data for us, joy! */;
1689	}	2532	}
1690		2533
1691	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1692		2535
1693	=item ev_feed_event (ev_loop *, watcher *, int revents)	2536	=item ev_feed_event (ev_loop *, watcher *, int revents)
1694		2537
1695	Feeds the given event set into the event loop, as if the specified event	2538	Feeds the given event set into the event loop, as if the specified event
1696	had happened for the specified watcher (which must be a pointer to an	2539	had happened for the specified watcher (which must be a pointer to an
…		…
1701	Feed an event on the given fd, as if a file descriptor backend detected	2544	Feed an event on the given fd, as if a file descriptor backend detected
1702	the given events it.	2545	the given events it.
1703		2546
1704	=item ev_feed_signal_event (ev_loop *loop, int signum)	2547	=item ev_feed_signal_event (ev_loop *loop, int signum)
1705		2548
1706	Feed an event as if the given signal occured (C<loop> must be the default	2549	Feed an event as if the given signal occurred (C<loop> must be the default
1707	loop!).	2550	loop!).
1708		2551
1709	=back	2552	=back
1710		2553
1711		2554
…		…
1727		2570
1728	=item * Priorities are not currently supported. Initialising priorities	2571	=item * Priorities are not currently supported. Initialising priorities
1729	will fail and all watchers will have the same priority, even though there	2572	will fail and all watchers will have the same priority, even though there
1730	is an ev_pri field.	2573	is an ev_pri field.
1731		2574
		2575	=item * In libevent, the last base created gets the signals, in libev, the
		2576	first base created (== the default loop) gets the signals.
		2577
1732	=item * Other members are not supported.	2578	=item * Other members are not supported.
1733		2579
1734	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2580	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1735	to use the libev header file and library.	2581	to use the libev header file and library.
1736		2582
1737	=back	2583	=back
1738		2584
1739	=head1 C++ SUPPORT	2585	=head1 C++ SUPPORT
1740		2586
1741	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2587	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1742	you to use some convinience methods to start/stop watchers and also change	2588	you to use some convenience methods to start/stop watchers and also change
1743	the callback model to a model using method callbacks on objects.	2589	the callback model to a model using method callbacks on objects.
1744		2590
1745	To use it,	2591	To use it,
1746		2592
1747	#include <ev++.h>	2593	#include <ev++.h>
1748		2594
1749	(it is not installed by default). This automatically includes F<ev.h>	2595	This automatically includes F<ev.h> and puts all of its definitions (many
1750	and puts all of its definitions (many of them macros) into the global	2596	of them macros) into the global namespace. All C++ specific things are
1751	namespace. All C++ specific things are put into the C<ev> namespace.	2597	put into the C<ev> namespace. It should support all the same embedding
		2598	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1752		2599
1753	It should support all the same embedding options as F<ev.h>, most notably	2600	Care has been taken to keep the overhead low. The only data member the C++
1754	C<EV_MULTIPLICITY>.	2601	classes add (compared to plain C-style watchers) is the event loop pointer
		2602	that the watcher is associated with (or no additional members at all if
		2603	you disable C<EV_MULTIPLICITY> when embedding libev).
		2604
		2605	Currently, functions, and static and non-static member functions can be
		2606	used as callbacks. Other types should be easy to add as long as they only
		2607	need one additional pointer for context. If you need support for other
		2608	types of functors please contact the author (preferably after implementing
		2609	it).
1755		2610
1756	Here is a list of things available in the C<ev> namespace:	2611	Here is a list of things available in the C<ev> namespace:
1757		2612
1758	=over 4	2613	=over 4
1759		2614
…		…
1775		2630
1776	All of those classes have these methods:	2631	All of those classes have these methods:
1777		2632
1778	=over 4	2633	=over 4
1779		2634
1780	=item ev::TYPE::TYPE (object *, object::method *)	2635	=item ev::TYPE::TYPE ()
1781		2636
1782	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2637	=item ev::TYPE::TYPE (struct ev_loop *)
1783		2638
1784	=item ev::TYPE::~TYPE	2639	=item ev::TYPE::~TYPE
1785		2640
1786	The constructor takes a pointer to an object and a method pointer to	2641	The constructor (optionally) takes an event loop to associate the watcher
1787	the event handler callback to call in this class. The constructor calls	2642	with. If it is omitted, it will use C<EV_DEFAULT>.
1788	C<ev_init> for you, which means you have to call the C<set> method	2643
1789	before starting it. If you do not specify a loop then the constructor	2644	The constructor calls C<ev_init> for you, which means you have to call the
1790	automatically associates the default loop with this watcher.	2645	C<set> method before starting it.
		2646
		2647	It will not set a callback, however: You have to call the templated C<set>
		2648	method to set a callback before you can start the watcher.
		2649
		2650	(The reason why you have to use a method is a limitation in C++ which does
		2651	not allow explicit template arguments for constructors).
1791		2652
1792	The destructor automatically stops the watcher if it is active.	2653	The destructor automatically stops the watcher if it is active.
		2654
		2655	=item w->set<class, &class::method> (object *)
		2656
		2657	This method sets the callback method to call. The method has to have a
		2658	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2659	first argument and the C<revents> as second. The object must be given as
		2660	parameter and is stored in the C<data> member of the watcher.
		2661
		2662	This method synthesizes efficient thunking code to call your method from
		2663	the C callback that libev requires. If your compiler can inline your
		2664	callback (i.e. it is visible to it at the place of the C<set> call and
		2665	your compiler is good :), then the method will be fully inlined into the
		2666	thunking function, making it as fast as a direct C callback.
		2667
		2668	Example: simple class declaration and watcher initialisation
		2669
		2670	struct myclass
		2671	{
		2672	void io_cb (ev::io &w, int revents) { }
		2673	}
		2674
		2675	myclass obj;
		2676	ev::io iow;
		2677	iow.set <myclass, &myclass::io_cb> (&obj);
		2678
		2679	=item w->set<function> (void *data = 0)
		2680
		2681	Also sets a callback, but uses a static method or plain function as
		2682	callback. The optional C<data> argument will be stored in the watcher's
		2683	C<data> member and is free for you to use.
		2684
		2685	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2686
		2687	See the method-C<set> above for more details.
		2688
		2689	Example: Use a plain function as callback.
		2690
		2691	static void io_cb (ev::io &w, int revents) { }
		2692	iow.set <io_cb> ();
1793		2693
1794	=item w->set (struct ev_loop *)	2694	=item w->set (struct ev_loop *)
1795		2695
1796	Associates a different C<struct ev_loop> with this watcher. You can only	2696	Associates a different C<struct ev_loop> with this watcher. You can only
1797	do this when the watcher is inactive (and not pending either).	2697	do this when the watcher is inactive (and not pending either).
1798		2698
1799	=item w->set ([args])	2699	=item w->set ([arguments])
1800		2700
1801	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2701	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1802	called at least once. Unlike the C counterpart, an active watcher gets	2702	called at least once. Unlike the C counterpart, an active watcher gets
1803	automatically stopped and restarted.	2703	automatically stopped and restarted when reconfiguring it with this
		2704	method.
1804		2705
1805	=item w->start ()	2706	=item w->start ()
1806		2707
1807	Starts the watcher. Note that there is no C<loop> argument as the	2708	Starts the watcher. Note that there is no C<loop> argument, as the
1808	constructor already takes the loop.	2709	constructor already stores the event loop.
1809		2710
1810	=item w->stop ()	2711	=item w->stop ()
1811		2712
1812	Stops the watcher if it is active. Again, no C<loop> argument.	2713	Stops the watcher if it is active. Again, no C<loop> argument.
1813		2714
1814	=item w->again () C<ev::timer>, C<ev::periodic> only	2715	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1815		2716
1816	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2717	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1817	C<ev_TYPE_again> function.	2718	C<ev_TYPE_again> function.
1818		2719
1819	=item w->sweep () C<ev::embed> only	2720	=item w->sweep () (C<ev::embed> only)
1820		2721
1821	Invokes C<ev_embed_sweep>.	2722	Invokes C<ev_embed_sweep>.
1822		2723
1823	=item w->update () C<ev::stat> only	2724	=item w->update () (C<ev::stat> only)
1824		2725
1825	Invokes C<ev_stat_stat>.	2726	Invokes C<ev_stat_stat>.
1826		2727
1827	=back	2728	=back
1828		2729
1829	=back	2730	=back
1830		2731
1831	Example: Define a class with an IO and idle watcher, start one of them in	2732	Example: Define a class with an IO and idle watcher, start one of them in
1832	the constructor.	2733	the constructor.
1833		2734
1834	class myclass	2735	class myclass
1835	{	2736	{
1836	ev_io io; void io_cb (ev::io &w, int revents);	2737	ev::io io ; void io_cb (ev::io &w, int revents);
1837	ev_idle idle void idle_cb (ev::idle &w, int revents);	2738	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1838		2739
1839	myclass ();	2740	myclass (int fd)
1840	}	2741	{
		2742	io .set <myclass, &myclass::io_cb > (this);
		2743	idle.set <myclass, &myclass::idle_cb> (this);
1841		2744
1842	myclass::myclass (int fd)
1843	: io (this, &myclass::io_cb),
1844	idle (this, &myclass::idle_cb)
1845	{
1846	io.start (fd, ev::READ);	2745	io.start (fd, ev::READ);
		2746	}
1847	}	2747	};
		2748
		2749
		2750	=head1 OTHER LANGUAGE BINDINGS
		2751
		2752	Libev does not offer other language bindings itself, but bindings for a
		2753	number of languages exist in the form of third-party packages. If you know
		2754	any interesting language binding in addition to the ones listed here, drop
		2755	me a note.
		2756
		2757	=over 4
		2758
		2759	=item Perl
		2760
		2761	The EV module implements the full libev API and is actually used to test
		2762	libev. EV is developed together with libev. Apart from the EV core module,
		2763	there are additional modules that implement libev-compatible interfaces
		2764	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2765	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2766	and C<EV::Glib>).
		2767
		2768	It can be found and installed via CPAN, its homepage is at
		2769	L<http://software.schmorp.de/pkg/EV>.
		2770
		2771	=item Python
		2772
		2773	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2774	seems to be quite complete and well-documented. Note, however, that the
		2775	patch they require for libev is outright dangerous as it breaks the ABI
		2776	for everybody else, and therefore, should never be applied in an installed
		2777	libev (if python requires an incompatible ABI then it needs to embed
		2778	libev).
		2779
		2780	=item Ruby
		2781
		2782	Tony Arcieri has written a ruby extension that offers access to a subset
		2783	of the libev API and adds file handle abstractions, asynchronous DNS and
		2784	more on top of it. It can be found via gem servers. Its homepage is at
		2785	L<http://rev.rubyforge.org/>.
		2786
		2787	=item D
		2788
		2789	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2790	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2791
		2792	=back
1848		2793
1849		2794
1850	=head1 MACRO MAGIC	2795	=head1 MACRO MAGIC
1851		2796
1852	Libev can be compiled with a variety of options, the most fundemantal is	2797	Libev can be compiled with a variety of options, the most fundamental
1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2798	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1854	callbacks have an initial C<struct ev_loop *> argument.	2799	functions and callbacks have an initial C<struct ev_loop *> argument.
1855		2800
1856	To make it easier to write programs that cope with either variant, the	2801	To make it easier to write programs that cope with either variant, the
1857	following macros are defined:	2802	following macros are defined:
1858		2803
1859	=over 4	2804	=over 4
…		…
1862		2807
1863	This provides the loop I<argument> for functions, if one is required ("ev	2808	This provides the loop I<argument> for functions, if one is required ("ev
1864	loop argument"). The C<EV_A> form is used when this is the sole argument,	2809	loop argument"). The C<EV_A> form is used when this is the sole argument,
1865	C<EV_A_> is used when other arguments are following. Example:	2810	C<EV_A_> is used when other arguments are following. Example:
1866		2811
1867	ev_unref (EV_A);	2812	ev_unref (EV_A);
1868	ev_timer_add (EV_A_ watcher);	2813	ev_timer_add (EV_A_ watcher);
1869	ev_loop (EV_A_ 0);	2814	ev_loop (EV_A_ 0);
1870		2815
1871	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2816	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1872	which is often provided by the following macro.	2817	which is often provided by the following macro.
1873		2818
1874	=item C<EV_P>, C<EV_P_>	2819	=item C<EV_P>, C<EV_P_>
1875		2820
1876	This provides the loop I<parameter> for functions, if one is required ("ev	2821	This provides the loop I<parameter> for functions, if one is required ("ev
1877	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2822	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1878	C<EV_P_> is used when other parameters are following. Example:	2823	C<EV_P_> is used when other parameters are following. Example:
1879		2824
1880	// this is how ev_unref is being declared	2825	// this is how ev_unref is being declared
1881	static void ev_unref (EV_P);	2826	static void ev_unref (EV_P);
1882		2827
1883	// this is how you can declare your typical callback	2828	// this is how you can declare your typical callback
1884	static void cb (EV_P_ ev_timer *w, int revents)	2829	static void cb (EV_P_ ev_timer *w, int revents)
1885		2830
1886	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2831	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1887	suitable for use with C<EV_A>.	2832	suitable for use with C<EV_A>.
1888		2833
1889	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2834	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1890		2835
1891	Similar to the other two macros, this gives you the value of the default	2836	Similar to the other two macros, this gives you the value of the default
1892	loop, if multiple loops are supported ("ev loop default").	2837	loop, if multiple loops are supported ("ev loop default").
		2838
		2839	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2840
		2841	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		2842	default loop has been initialised (C<UC> == unchecked). Their behaviour
		2843	is undefined when the default loop has not been initialised by a previous
		2844	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		2845
		2846	It is often prudent to use C<EV_DEFAULT> when initialising the first
		2847	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1893		2848
1894	=back	2849	=back
1895		2850
1896	Example: Declare and initialise a check watcher, utilising the above	2851	Example: Declare and initialise a check watcher, utilising the above
1897	macros so it will work regardless of whether multiple loops are supported	2852	macros so it will work regardless of whether multiple loops are supported
1898	or not.	2853	or not.
1899		2854
1900	static void	2855	static void
1901	check_cb (EV_P_ ev_timer *w, int revents)	2856	check_cb (EV_P_ ev_timer *w, int revents)
1902	{	2857	{
1903	ev_check_stop (EV_A_ w);	2858	ev_check_stop (EV_A_ w);
1904	}	2859	}
1905		2860
1906	ev_check check;	2861	ev_check check;
1907	ev_check_init (&check, check_cb);	2862	ev_check_init (&check, check_cb);
1908	ev_check_start (EV_DEFAULT_ &check);	2863	ev_check_start (EV_DEFAULT_ &check);
1909	ev_loop (EV_DEFAULT_ 0);	2864	ev_loop (EV_DEFAULT_ 0);
1910		2865
1911	=head1 EMBEDDING	2866	=head1 EMBEDDING
1912		2867
1913	Libev can (and often is) directly embedded into host	2868	Libev can (and often is) directly embedded into host
1914	applications. Examples of applications that embed it include the Deliantra	2869	applications. Examples of applications that embed it include the Deliantra
1915	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2870	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1916	and rxvt-unicode.	2871	and rxvt-unicode.
1917		2872
1918	The goal is to enable you to just copy the neecssary files into your	2873	The goal is to enable you to just copy the necessary files into your
1919	source directory without having to change even a single line in them, so	2874	source directory without having to change even a single line in them, so
1920	you can easily upgrade by simply copying (or having a checked-out copy of	2875	you can easily upgrade by simply copying (or having a checked-out copy of
1921	libev somewhere in your source tree).	2876	libev somewhere in your source tree).
1922		2877
1923	=head2 FILESETS	2878	=head2 FILESETS
1924		2879
1925	Depending on what features you need you need to include one or more sets of files	2880	Depending on what features you need you need to include one or more sets of files
1926	in your app.	2881	in your application.
1927		2882
1928	=head3 CORE EVENT LOOP	2883	=head3 CORE EVENT LOOP
1929		2884
1930	To include only the libev core (all the C<ev_*> functions), with manual	2885	To include only the libev core (all the C<ev_*> functions), with manual
1931	configuration (no autoconf):	2886	configuration (no autoconf):
1932		2887
1933	#define EV_STANDALONE 1	2888	#define EV_STANDALONE 1
1934	#include "ev.c"	2889	#include "ev.c"
1935		2890
1936	This will automatically include F<ev.h>, too, and should be done in a	2891	This will automatically include F<ev.h>, too, and should be done in a
1937	single C source file only to provide the function implementations. To use	2892	single C source file only to provide the function implementations. To use
1938	it, do the same for F<ev.h> in all files wishing to use this API (best	2893	it, do the same for F<ev.h> in all files wishing to use this API (best
1939	done by writing a wrapper around F<ev.h> that you can include instead and	2894	done by writing a wrapper around F<ev.h> that you can include instead and
1940	where you can put other configuration options):	2895	where you can put other configuration options):
1941		2896
1942	#define EV_STANDALONE 1	2897	#define EV_STANDALONE 1
1943	#include "ev.h"	2898	#include "ev.h"
1944		2899
1945	Both header files and implementation files can be compiled with a C++	2900	Both header files and implementation files can be compiled with a C++
1946	compiler (at least, thats a stated goal, and breakage will be treated	2901	compiler (at least, thats a stated goal, and breakage will be treated
1947	as a bug).	2902	as a bug).
1948		2903
1949	You need the following files in your source tree, or in a directory	2904	You need the following files in your source tree, or in a directory
1950	in your include path (e.g. in libev/ when using -Ilibev):	2905	in your include path (e.g. in libev/ when using -Ilibev):
1951		2906
1952	ev.h	2907	ev.h
1953	ev.c	2908	ev.c
1954	ev_vars.h	2909	ev_vars.h
1955	ev_wrap.h	2910	ev_wrap.h
1956		2911
1957	ev_win32.c required on win32 platforms only	2912	ev_win32.c required on win32 platforms only
1958		2913
1959	ev_select.c only when select backend is enabled (which is enabled by default)	2914	ev_select.c only when select backend is enabled (which is enabled by default)
1960	ev_poll.c only when poll backend is enabled (disabled by default)	2915	ev_poll.c only when poll backend is enabled (disabled by default)
1961	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2916	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1962	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2917	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1963	ev_port.c only when the solaris port backend is enabled (disabled by default)	2918	ev_port.c only when the solaris port backend is enabled (disabled by default)
1964		2919
1965	F<ev.c> includes the backend files directly when enabled, so you only need	2920	F<ev.c> includes the backend files directly when enabled, so you only need
1966	to compile this single file.	2921	to compile this single file.
1967		2922
1968	=head3 LIBEVENT COMPATIBILITY API	2923	=head3 LIBEVENT COMPATIBILITY API
1969		2924
1970	To include the libevent compatibility API, also include:	2925	To include the libevent compatibility API, also include:
1971		2926
1972	#include "event.c"	2927	#include "event.c"
1973		2928
1974	in the file including F<ev.c>, and:	2929	in the file including F<ev.c>, and:
1975		2930
1976	#include "event.h"	2931	#include "event.h"
1977		2932
1978	in the files that want to use the libevent API. This also includes F<ev.h>.	2933	in the files that want to use the libevent API. This also includes F<ev.h>.
1979		2934
1980	You need the following additional files for this:	2935	You need the following additional files for this:
1981		2936
1982	event.h	2937	event.h
1983	event.c	2938	event.c
1984		2939
1985	=head3 AUTOCONF SUPPORT	2940	=head3 AUTOCONF SUPPORT
1986		2941
1987	Instead of using C<EV_STANDALONE=1> and providing your config in	2942	Instead of using C<EV_STANDALONE=1> and providing your configuration in
1988	whatever way you want, you can also C<m4_include([libev.m4])> in your	2943	whatever way you want, you can also C<m4_include([libev.m4])> in your
1989	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	2944	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1990	include F<config.h> and configure itself accordingly.	2945	include F<config.h> and configure itself accordingly.
1991		2946
1992	For this of course you need the m4 file:	2947	For this of course you need the m4 file:
1993		2948
1994	libev.m4	2949	libev.m4
1995		2950
1996	=head2 PREPROCESSOR SYMBOLS/MACROS	2951	=head2 PREPROCESSOR SYMBOLS/MACROS
1997		2952
1998	Libev can be configured via a variety of preprocessor symbols you have to define	2953	Libev can be configured via a variety of preprocessor symbols you have to
1999	before including any of its files. The default is not to build for multiplicity	2954	define before including any of its files. The default in the absence of
2000	and only include the select backend.	2955	autoconf is documented for every option.
2001		2956
2002	=over 4	2957	=over 4
2003		2958
2004	=item EV_STANDALONE	2959	=item EV_STANDALONE
2005		2960
…		…
2010	F<event.h> that are not directly supported by the libev core alone.	2965	F<event.h> that are not directly supported by the libev core alone.
2011		2966
2012	=item EV_USE_MONOTONIC	2967	=item EV_USE_MONOTONIC
2013		2968
2014	If defined to be C<1>, libev will try to detect the availability of the	2969	If defined to be C<1>, libev will try to detect the availability of the
2015	monotonic clock option at both compiletime and runtime. Otherwise no use	2970	monotonic clock option at both compile time and runtime. Otherwise no use
2016	of the monotonic clock option will be attempted. If you enable this, you	2971	of the monotonic clock option will be attempted. If you enable this, you
2017	usually have to link against librt or something similar. Enabling it when	2972	usually have to link against librt or something similar. Enabling it when
2018	the functionality isn't available is safe, though, althoguh you have	2973	the functionality isn't available is safe, though, although you have
2019	to make sure you link against any libraries where the C<clock_gettime>	2974	to make sure you link against any libraries where the C<clock_gettime>
2020	function is hiding in (often F<-lrt>).	2975	function is hiding in (often F<-lrt>).
2021		2976
2022	=item EV_USE_REALTIME	2977	=item EV_USE_REALTIME
2023		2978
2024	If defined to be C<1>, libev will try to detect the availability of the	2979	If defined to be C<1>, libev will try to detect the availability of the
2025	realtime clock option at compiletime (and assume its availability at	2980	real-time clock option at compile time (and assume its availability at
2026	runtime if successful). Otherwise no use of the realtime clock option will	2981	runtime if successful). Otherwise no use of the real-time clock option will
2027	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2982	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2028	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2983	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2029	in the description of C<EV_USE_MONOTONIC>, though.	2984	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2985
		2986	=item EV_USE_NANOSLEEP
		2987
		2988	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2989	and will use it for delays. Otherwise it will use C<select ()>.
		2990
		2991	=item EV_USE_EVENTFD
		2992
		2993	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		2994	available and will probe for kernel support at runtime. This will improve
		2995	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		2996	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		2997	2.7 or newer, otherwise disabled.
2030		2998
2031	=item EV_USE_SELECT	2999	=item EV_USE_SELECT
2032		3000
2033	If undefined or defined to be C<1>, libev will compile in support for the	3001	If undefined or defined to be C<1>, libev will compile in support for the
2034	C<select>(2) backend. No attempt at autodetection will be done: if no	3002	C<select>(2) backend. No attempt at auto-detection will be done: if no
2035	other method takes over, select will be it. Otherwise the select backend	3003	other method takes over, select will be it. Otherwise the select backend
2036	will not be compiled in.	3004	will not be compiled in.
2037		3005
2038	=item EV_SELECT_USE_FD_SET	3006	=item EV_SELECT_USE_FD_SET
2039		3007
2040	If defined to C<1>, then the select backend will use the system C<fd_set>	3008	If defined to C<1>, then the select backend will use the system C<fd_set>
2041	structure. This is useful if libev doesn't compile due to a missing	3009	structure. This is useful if libev doesn't compile due to a missing
2042	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3010	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2043	exotic systems. This usually limits the range of file descriptors to some	3011	exotic systems. This usually limits the range of file descriptors to some
2044	low limit such as 1024 or might have other limitations (winsocket only	3012	low limit such as 1024 or might have other limitations (winsocket only
2045	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3013	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2046	influence the size of the C<fd_set> used.	3014	influence the size of the C<fd_set> used.
2047		3015
…		…
2053	be used is the winsock select). This means that it will call	3021	be used is the winsock select). This means that it will call
2054	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3022	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2055	it is assumed that all these functions actually work on fds, even	3023	it is assumed that all these functions actually work on fds, even
2056	on win32. Should not be defined on non-win32 platforms.	3024	on win32. Should not be defined on non-win32 platforms.
2057		3025
		3026	=item EV_FD_TO_WIN32_HANDLE
		3027
		3028	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3029	file descriptors to socket handles. When not defining this symbol (the
		3030	default), then libev will call C<_get_osfhandle>, which is usually
		3031	correct. In some cases, programs use their own file descriptor management,
		3032	in which case they can provide this function to map fds to socket handles.
		3033
2058	=item EV_USE_POLL	3034	=item EV_USE_POLL
2059		3035
2060	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3036	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2061	backend. Otherwise it will be enabled on non-win32 platforms. It	3037	backend. Otherwise it will be enabled on non-win32 platforms. It
2062	takes precedence over select.	3038	takes precedence over select.
2063		3039
2064	=item EV_USE_EPOLL	3040	=item EV_USE_EPOLL
2065		3041
2066	If defined to be C<1>, libev will compile in support for the Linux	3042	If defined to be C<1>, libev will compile in support for the Linux
2067	C<epoll>(7) backend. Its availability will be detected at runtime,	3043	C<epoll>(7) backend. Its availability will be detected at runtime,
2068	otherwise another method will be used as fallback. This is the	3044	otherwise another method will be used as fallback. This is the preferred
2069	preferred backend for GNU/Linux systems.	3045	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3046	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2070		3047
2071	=item EV_USE_KQUEUE	3048	=item EV_USE_KQUEUE
2072		3049
2073	If defined to be C<1>, libev will compile in support for the BSD style	3050	If defined to be C<1>, libev will compile in support for the BSD style
2074	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3051	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2087	otherwise another method will be used as fallback. This is the preferred	3064	otherwise another method will be used as fallback. This is the preferred
2088	backend for Solaris 10 systems.	3065	backend for Solaris 10 systems.
2089		3066
2090	=item EV_USE_DEVPOLL	3067	=item EV_USE_DEVPOLL
2091		3068
2092	reserved for future expansion, works like the USE symbols above.	3069	Reserved for future expansion, works like the USE symbols above.
2093		3070
2094	=item EV_USE_INOTIFY	3071	=item EV_USE_INOTIFY
2095		3072
2096	If defined to be C<1>, libev will compile in support for the Linux inotify	3073	If defined to be C<1>, libev will compile in support for the Linux inotify
2097	interface to speed up C<ev_stat> watchers. Its actual availability will	3074	interface to speed up C<ev_stat> watchers. Its actual availability will
2098	be detected at runtime.	3075	be detected at runtime. If undefined, it will be enabled if the headers
		3076	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3077
		3078	=item EV_ATOMIC_T
		3079
		3080	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3081	access is atomic with respect to other threads or signal contexts. No such
		3082	type is easily found in the C language, so you can provide your own type
		3083	that you know is safe for your purposes. It is used both for signal handler "locking"
		3084	as well as for signal and thread safety in C<ev_async> watchers.
		3085
		3086	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3087	(from F<signal.h>), which is usually good enough on most platforms.
2099		3088
2100	=item EV_H	3089	=item EV_H
2101		3090
2102	The name of the F<ev.h> header file used to include it. The default if	3091	The name of the F<ev.h> header file used to include it. The default if
2103	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3092	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2104	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3093	used to virtually rename the F<ev.h> header file in case of conflicts.
2105		3094
2106	=item EV_CONFIG_H	3095	=item EV_CONFIG_H
2107		3096
2108	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3097	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2109	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3098	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2110	C<EV_H>, above.	3099	C<EV_H>, above.
2111		3100
2112	=item EV_EVENT_H	3101	=item EV_EVENT_H
2113		3102
2114	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3103	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2115	of how the F<event.h> header can be found.	3104	of how the F<event.h> header can be found, the default is C<"event.h">.
2116		3105
2117	=item EV_PROTOTYPES	3106	=item EV_PROTOTYPES
2118		3107
2119	If defined to be C<0>, then F<ev.h> will not define any function	3108	If defined to be C<0>, then F<ev.h> will not define any function
2120	prototypes, but still define all the structs and other symbols. This is	3109	prototypes, but still define all the structs and other symbols. This is
…		…
2141	When doing priority-based operations, libev usually has to linearly search	3130	When doing priority-based operations, libev usually has to linearly search
2142	all the priorities, so having many of them (hundreds) uses a lot of space	3131	all the priorities, so having many of them (hundreds) uses a lot of space
2143	and time, so using the defaults of five priorities (-2 .. +2) is usually	3132	and time, so using the defaults of five priorities (-2 .. +2) is usually
2144	fine.	3133	fine.
2145		3134
2146	If your embedding app does not need any priorities, defining these both to	3135	If your embedding application does not need any priorities, defining these
2147	C<0> will save some memory and cpu.	3136	both to C<0> will save some memory and CPU.
2148		3137
2149	=item EV_PERIODIC_ENABLE	3138	=item EV_PERIODIC_ENABLE
2150		3139
2151	If undefined or defined to be C<1>, then periodic timers are supported. If	3140	If undefined or defined to be C<1>, then periodic timers are supported. If
2152	defined to be C<0>, then they are not. Disabling them saves a few kB of	3141	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2159	code.	3148	code.
2160		3149
2161	=item EV_EMBED_ENABLE	3150	=item EV_EMBED_ENABLE
2162		3151
2163	If undefined or defined to be C<1>, then embed watchers are supported. If	3152	If undefined or defined to be C<1>, then embed watchers are supported. If
2164	defined to be C<0>, then they are not.	3153	defined to be C<0>, then they are not. Embed watchers rely on most other
		3154	watcher types, which therefore must not be disabled.
2165		3155
2166	=item EV_STAT_ENABLE	3156	=item EV_STAT_ENABLE
2167		3157
2168	If undefined or defined to be C<1>, then stat watchers are supported. If	3158	If undefined or defined to be C<1>, then stat watchers are supported. If
2169	defined to be C<0>, then they are not.	3159	defined to be C<0>, then they are not.
…		…
2171	=item EV_FORK_ENABLE	3161	=item EV_FORK_ENABLE
2172		3162
2173	If undefined or defined to be C<1>, then fork watchers are supported. If	3163	If undefined or defined to be C<1>, then fork watchers are supported. If
2174	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
2175		3165
		3166	=item EV_ASYNC_ENABLE
		3167
		3168	If undefined or defined to be C<1>, then async watchers are supported. If
		3169	defined to be C<0>, then they are not.
		3170
2176	=item EV_MINIMAL	3171	=item EV_MINIMAL
2177		3172
2178	If you need to shave off some kilobytes of code at the expense of some	3173	If you need to shave off some kilobytes of code at the expense of some
2179	speed, define this symbol to C<1>. Currently only used for gcc to override	3174	speed, define this symbol to C<1>. Currently this is used to override some
2180	some inlining decisions, saves roughly 30% codesize of amd64.	3175	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3176	much smaller 2-heap for timer management over the default 4-heap.
2181		3177
2182	=item EV_PID_HASHSIZE	3178	=item EV_PID_HASHSIZE
2183		3179
2184	C<ev_child> watchers use a small hash table to distribute workload by	3180	C<ev_child> watchers use a small hash table to distribute workload by
2185	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3181	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2186	than enough. If you need to manage thousands of children you might want to	3182	than enough. If you need to manage thousands of children you might want to
2187	increase this value (I<must> be a power of two).	3183	increase this value (I<must> be a power of two).
2188		3184
2189	=item EV_INOTIFY_HASHSIZE	3185	=item EV_INOTIFY_HASHSIZE
2190		3186
2191	C<ev_staz> watchers use a small hash table to distribute workload by	3187	C<ev_stat> watchers use a small hash table to distribute workload by
2192	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3188	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2193	usually more than enough. If you need to manage thousands of C<ev_stat>	3189	usually more than enough. If you need to manage thousands of C<ev_stat>
2194	watchers you might want to increase this value (I<must> be a power of	3190	watchers you might want to increase this value (I<must> be a power of
2195	two).	3191	two).
2196		3192
		3193	=item EV_USE_4HEAP
		3194
		3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3196	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3197	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3198	faster performance with many (thousands) of watchers.
		3199
		3200	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3201	(disabled).
		3202
		3203	=item EV_HEAP_CACHE_AT
		3204
		3205	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3206	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3207	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3208	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3209	but avoids random read accesses on heap changes. This improves performance
		3210	noticeably with many (hundreds) of watchers.
		3211
		3212	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3213	(disabled).
		3214
		3215	=item EV_VERIFY
		3216
		3217	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3218	be done: If set to C<0>, no internal verification code will be compiled
		3219	in. If set to C<1>, then verification code will be compiled in, but not
		3220	called. If set to C<2>, then the internal verification code will be
		3221	called once per loop, which can slow down libev. If set to C<3>, then the
		3222	verification code will be called very frequently, which will slow down
		3223	libev considerably.
		3224
		3225	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3226	C<0>.
		3227
2197	=item EV_COMMON	3228	=item EV_COMMON
2198		3229
2199	By default, all watchers have a C<void *data> member. By redefining	3230	By default, all watchers have a C<void *data> member. By redefining
2200	this macro to a something else you can include more and other types of	3231	this macro to a something else you can include more and other types of
2201	members. You have to define it each time you include one of the files,	3232	members. You have to define it each time you include one of the files,
2202	though, and it must be identical each time.	3233	though, and it must be identical each time.
2203		3234
2204	For example, the perl EV module uses something like this:	3235	For example, the perl EV module uses something like this:
2205		3236
2206	#define EV_COMMON \	3237	#define EV_COMMON \
2207	SV *self; /* contains this struct */ \	3238	SV *self; /* contains this struct */ \
2208	SV *cb_sv, *fh /* note no trailing ";" */	3239	SV *cb_sv, *fh /* note no trailing ";" */
2209		3240
2210	=item EV_CB_DECLARE (type)	3241	=item EV_CB_DECLARE (type)
2211		3242
2212	=item EV_CB_INVOKE (watcher, revents)	3243	=item EV_CB_INVOKE (watcher, revents)
2213		3244
2214	=item ev_set_cb (ev, cb)	3245	=item ev_set_cb (ev, cb)
2215		3246
2216	Can be used to change the callback member declaration in each watcher,	3247	Can be used to change the callback member declaration in each watcher,
2217	and the way callbacks are invoked and set. Must expand to a struct member	3248	and the way callbacks are invoked and set. Must expand to a struct member
2218	definition and a statement, respectively. See the F<ev.v> header file for	3249	definition and a statement, respectively. See the F<ev.h> header file for
2219	their default definitions. One possible use for overriding these is to	3250	their default definitions. One possible use for overriding these is to
2220	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3251	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2221	method calls instead of plain function calls in C++.	3252	method calls instead of plain function calls in C++.
		3253
		3254	=back
		3255
		3256	=head2 EXPORTED API SYMBOLS
		3257
		3258	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3259	exported symbols, you can use the provided F<Symbol.*> files which list
		3260	all public symbols, one per line:
		3261
		3262	Symbols.ev for libev proper
		3263	Symbols.event for the libevent emulation
		3264
		3265	This can also be used to rename all public symbols to avoid clashes with
		3266	multiple versions of libev linked together (which is obviously bad in
		3267	itself, but sometimes it is inconvenient to avoid this).
		3268
		3269	A sed command like this will create wrapper C<#define>'s that you need to
		3270	include before including F<ev.h>:
		3271
		3272	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3273
		3274	This would create a file F<wrap.h> which essentially looks like this:
		3275
		3276	#define ev_backend myprefix_ev_backend
		3277	#define ev_check_start myprefix_ev_check_start
		3278	#define ev_check_stop myprefix_ev_check_stop
		3279	...
2222		3280
2223	=head2 EXAMPLES	3281	=head2 EXAMPLES
2224		3282
2225	For a real-world example of a program the includes libev	3283	For a real-world example of a program the includes libev
2226	verbatim, you can have a look at the EV perl module	3284	verbatim, you can have a look at the EV perl module
…		…
2231	file.	3289	file.
2232		3290
2233	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3291	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2234	that everybody includes and which overrides some configure choices:	3292	that everybody includes and which overrides some configure choices:
2235		3293
2236	#define EV_MINIMAL 1	3294	#define EV_MINIMAL 1
2237	#define EV_USE_POLL 0	3295	#define EV_USE_POLL 0
2238	#define EV_MULTIPLICITY 0	3296	#define EV_MULTIPLICITY 0
2239	#define EV_PERIODIC_ENABLE 0	3297	#define EV_PERIODIC_ENABLE 0
2240	#define EV_STAT_ENABLE 0	3298	#define EV_STAT_ENABLE 0
2241	#define EV_FORK_ENABLE 0	3299	#define EV_FORK_ENABLE 0
2242	#define EV_CONFIG_H <config.h>	3300	#define EV_CONFIG_H <config.h>
2243	#define EV_MINPRI 0	3301	#define EV_MINPRI 0
2244	#define EV_MAXPRI 0	3302	#define EV_MAXPRI 0
2245		3303
2246	#include "ev++.h"	3304	#include "ev++.h"
2247		3305
2248	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2249		3307
2250	#include "ev_cpp.h"	3308	#include "ev_cpp.h"
2251	#include "ev.c"	3309	#include "ev.c"
		3310
		3311	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
		3312
		3313	=head2 THREADS AND COROUTINES
		3314
		3315	=head3 THREADS
		3316
		3317	All libev functions are reentrant and thread-safe unless explicitly
		3318	documented otherwise, but it uses no locking itself. This means that you
		3319	can use as many loops as you want in parallel, as long as there are no
		3320	concurrent calls into any libev function with the same loop parameter
		3321	(C<ev_default_*> calls have an implicit default loop parameter, of
		3322	course): libev guarantees that different event loops share no data
		3323	structures that need any locking.
		3324
		3325	Or to put it differently: calls with different loop parameters can be done
		3326	concurrently from multiple threads, calls with the same loop parameter
		3327	must be done serially (but can be done from different threads, as long as
		3328	only one thread ever is inside a call at any point in time, e.g. by using
		3329	a mutex per loop).
		3330
		3331	Specifically to support threads (and signal handlers), libev implements
		3332	so-called C<ev_async> watchers, which allow some limited form of
		3333	concurrency on the same event loop, namely waking it up "from the
		3334	outside".
		3335
		3336	If you want to know which design (one loop, locking, or multiple loops
		3337	without or something else still) is best for your problem, then I cannot
		3338	help you, but here is some generic advice:
		3339
		3340	=over 4
		3341
		3342	=item * most applications have a main thread: use the default libev loop
		3343	in that thread, or create a separate thread running only the default loop.
		3344
		3345	This helps integrating other libraries or software modules that use libev
		3346	themselves and don't care/know about threading.
		3347
		3348	=item * one loop per thread is usually a good model.
		3349
		3350	Doing this is almost never wrong, sometimes a better-performance model
		3351	exists, but it is always a good start.
		3352
		3353	=item * other models exist, such as the leader/follower pattern, where one
		3354	loop is handed through multiple threads in a kind of round-robin fashion.
		3355
		3356	Choosing a model is hard - look around, learn, know that usually you can do
		3357	better than you currently do :-)
		3358
		3359	=item * often you need to talk to some other thread which blocks in the
		3360	event loop.
		3361
		3362	C<ev_async> watchers can be used to wake them up from other threads safely
		3363	(or from signal contexts...).
		3364
		3365	An example use would be to communicate signals or other events that only
		3366	work in the default loop by registering the signal watcher with the
		3367	default loop and triggering an C<ev_async> watcher from the default loop
		3368	watcher callback into the event loop interested in the signal.
		3369
		3370	=back
		3371
		3372	=head3 COROUTINES
		3373
		3374	Libev is much more accommodating to coroutines ("cooperative threads"):
		3375	libev fully supports nesting calls to it's functions from different
		3376	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3377	different coroutines and switch freely between both coroutines running the
		3378	loop, as long as you don't confuse yourself). The only exception is that
		3379	you must not do this from C<ev_periodic> reschedule callbacks.
		3380
		3381	Care has been taken to ensure that libev does not keep local state inside
		3382	C<ev_loop>, and other calls do not usually allow coroutine switches.
		3383
		3384	=head2 COMPILER WARNINGS
		3385
		3386	Depending on your compiler and compiler settings, you might get no or a
		3387	lot of warnings when compiling libev code. Some people are apparently
		3388	scared by this.
		3389
		3390	However, these are unavoidable for many reasons. For one, each compiler
		3391	has different warnings, and each user has different tastes regarding
		3392	warning options. "Warn-free" code therefore cannot be a goal except when
		3393	targeting a specific compiler and compiler-version.
		3394
		3395	Another reason is that some compiler warnings require elaborate
		3396	workarounds, or other changes to the code that make it less clear and less
		3397	maintainable.
		3398
		3399	And of course, some compiler warnings are just plain stupid, or simply
		3400	wrong (because they don't actually warn about the condition their message
		3401	seems to warn about). For example, certain older gcc versions had some
		3402	warnings that resulted an extreme number of false positives. These have
		3403	been fixed, but some people still insist on making code warn-free with
		3404	such buggy versions.
		3405
		3406	While libev is written to generate as few warnings as possible,
		3407	"warn-free" code is not a goal, and it is recommended not to build libev
		3408	with any compiler warnings enabled unless you are prepared to cope with
		3409	them (e.g. by ignoring them). Remember that warnings are just that:
		3410	warnings, not errors, or proof of bugs.
		3411
		3412
		3413	=head2 VALGRIND
		3414
		3415	Valgrind has a special section here because it is a popular tool that is
		3416	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3417
		3418	If you think you found a bug (memory leak, uninitialised data access etc.)
		3419	in libev, then check twice: If valgrind reports something like:
		3420
		3421	==2274== definitely lost: 0 bytes in 0 blocks.
		3422	==2274== possibly lost: 0 bytes in 0 blocks.
		3423	==2274== still reachable: 256 bytes in 1 blocks.
		3424
		3425	Then there is no memory leak, just as memory accounted to global variables
		3426	is not a memleak - the memory is still being refernced, and didn't leak.
		3427
		3428	Similarly, under some circumstances, valgrind might report kernel bugs
		3429	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3430	although an acceptable workaround has been found here), or it might be
		3431	confused.
		3432
		3433	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3434	make it into some kind of religion.
		3435
		3436	If you are unsure about something, feel free to contact the mailing list
		3437	with the full valgrind report and an explanation on why you think this
		3438	is a bug in libev (best check the archives, too :). However, don't be
		3439	annoyed when you get a brisk "this is no bug" answer and take the chance
		3440	of learning how to interpret valgrind properly.
		3441
		3442	If you need, for some reason, empty reports from valgrind for your project
		3443	I suggest using suppression lists.
		3444
2252		3445
2253		3446
2254	=head1 COMPLEXITIES	3447	=head1 COMPLEXITIES
2255		3448
2256	In this section the complexities of (many of) the algorithms used inside	3449	In this section the complexities of (many of) the algorithms used inside
…		…
2267		3460
2268	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3461	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2269		3462
2270	This means that, when you have a watcher that triggers in one hour and	3463	This means that, when you have a watcher that triggers in one hour and
2271	there are 100 watchers that would trigger before that then inserting will	3464	there are 100 watchers that would trigger before that then inserting will
2272	have to skip those 100 watchers.	3465	have to skip roughly seven (C<ld 100>) of these watchers.
2273		3466
2274	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3467	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2275		3468
2276	That means that for changing a timer costs less than removing/adding them	3469	That means that changing a timer costs less than removing/adding them
2277	as only the relative motion in the event queue has to be paid for.	3470	as only the relative motion in the event queue has to be paid for.
2278		3471
2279	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3472	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2280		3473
2281	These just add the watcher into an array or at the head of a list.	3474	These just add the watcher into an array or at the head of a list.
		3475
2282	=item Stopping check/prepare/idle watchers: O(1)	3476	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2283		3477
2284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3478	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2285		3479
2286	These watchers are stored in lists then need to be walked to find the	3480	These watchers are stored in lists then need to be walked to find the
2287	correct watcher to remove. The lists are usually short (you don't usually	3481	correct watcher to remove. The lists are usually short (you don't usually
2288	have many watchers waiting for the same fd or signal).	3482	have many watchers waiting for the same fd or signal).
2289		3483
2290	=item Finding the next timer per loop iteration: O(1)	3484	=item Finding the next timer in each loop iteration: O(1)
		3485
		3486	By virtue of using a binary or 4-heap, the next timer is always found at a
		3487	fixed position in the storage array.
2291		3488
2292	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3489	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2293		3490
2294	A change means an I/O watcher gets started or stopped, which requires	3491	A change means an I/O watcher gets started or stopped, which requires
2295	libev to recalculate its status (and possibly tell the kernel).	3492	libev to recalculate its status (and possibly tell the kernel, depending
		3493	on backend and whether C<ev_io_set> was used).
2296		3494
2297	=item Activating one watcher: O(1)	3495	=item Activating one watcher (putting it into the pending state): O(1)
2298		3496
2299	=item Priority handling: O(number_of_priorities)	3497	=item Priority handling: O(number_of_priorities)
2300		3498
2301	Priorities are implemented by allocating some space for each	3499	Priorities are implemented by allocating some space for each
2302	priority. When doing priority-based operations, libev usually has to	3500	priority. When doing priority-based operations, libev usually has to
2303	linearly search all the priorities.	3501	linearly search all the priorities, but starting/stopping and activating
		3502	watchers becomes O(1) with respect to priority handling.
		3503
		3504	=item Sending an ev_async: O(1)
		3505
		3506	=item Processing ev_async_send: O(number_of_async_watchers)
		3507
		3508	=item Processing signals: O(max_signal_number)
		3509
		3510	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3511	calls in the current loop iteration. Checking for async and signal events
		3512	involves iterating over all running async watchers or all signal numbers.
2304		3513
2305	=back	3514	=back
2306		3515
2307		3516
		3517	=head1 PORTABILITY NOTES
		3518
		3519	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3520
		3521	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3522	requires, and its I/O model is fundamentally incompatible with the POSIX
		3523	model. Libev still offers limited functionality on this platform in
		3524	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3525	descriptors. This only applies when using Win32 natively, not when using
		3526	e.g. cygwin.
		3527
		3528	Lifting these limitations would basically require the full
		3529	re-implementation of the I/O system. If you are into these kinds of
		3530	things, then note that glib does exactly that for you in a very portable
		3531	way (note also that glib is the slowest event library known to man).
		3532
		3533	There is no supported compilation method available on windows except
		3534	embedding it into other applications.
		3535
		3536	Not a libev limitation but worth mentioning: windows apparently doesn't
		3537	accept large writes: instead of resulting in a partial write, windows will
		3538	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3539	so make sure you only write small amounts into your sockets (less than a
		3540	megabyte seems safe, but this apparently depends on the amount of memory
		3541	available).
		3542
		3543	Due to the many, low, and arbitrary limits on the win32 platform and
		3544	the abysmal performance of winsockets, using a large number of sockets
		3545	is not recommended (and not reasonable). If your program needs to use
		3546	more than a hundred or so sockets, then likely it needs to use a totally
		3547	different implementation for windows, as libev offers the POSIX readiness
		3548	notification model, which cannot be implemented efficiently on windows
		3549	(Microsoft monopoly games).
		3550
		3551	A typical way to use libev under windows is to embed it (see the embedding
		3552	section for details) and use the following F<evwrap.h> header file instead
		3553	of F<ev.h>:
		3554
		3555	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3556	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3557
		3558	#include "ev.h"
		3559
		3560	And compile the following F<evwrap.c> file into your project (make sure
		3561	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3562
		3563	#include "evwrap.h"
		3564	#include "ev.c"
		3565
		3566	=over 4
		3567
		3568	=item The winsocket select function
		3569
		3570	The winsocket C<select> function doesn't follow POSIX in that it
		3571	requires socket I<handles> and not socket I<file descriptors> (it is
		3572	also extremely buggy). This makes select very inefficient, and also
		3573	requires a mapping from file descriptors to socket handles (the Microsoft
		3574	C runtime provides the function C<_open_osfhandle> for this). See the
		3575	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3576	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3577
		3578	The configuration for a "naked" win32 using the Microsoft runtime
		3579	libraries and raw winsocket select is:
		3580
		3581	#define EV_USE_SELECT 1
		3582	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3583
		3584	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3585	complexity in the O(n²) range when using win32.
		3586
		3587	=item Limited number of file descriptors
		3588
		3589	Windows has numerous arbitrary (and low) limits on things.
		3590
		3591	Early versions of winsocket's select only supported waiting for a maximum
		3592	of C<64> handles (probably owning to the fact that all windows kernels
		3593	can only wait for C<64> things at the same time internally; Microsoft
		3594	recommends spawning a chain of threads and wait for 63 handles and the
		3595	previous thread in each. Great).
		3596
		3597	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3598	to some high number (e.g. C<2048>) before compiling the winsocket select
		3599	call (which might be in libev or elsewhere, for example, perl does its own
		3600	select emulation on windows).
		3601
		3602	Another limit is the number of file descriptors in the Microsoft runtime
		3603	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3604	or something like this inside Microsoft). You can increase this by calling
		3605	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3606	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3607	libraries.
		3608
		3609	This might get you to about C<512> or C<2048> sockets (depending on
		3610	windows version and/or the phase of the moon). To get more, you need to
		3611	wrap all I/O functions and provide your own fd management, but the cost of
		3612	calling select (O(n²)) will likely make this unworkable.
		3613
		3614	=back
		3615
		3616	=head2 PORTABILITY REQUIREMENTS
		3617
		3618	In addition to a working ISO-C implementation and of course the
		3619	backend-specific APIs, libev relies on a few additional extensions:
		3620
		3621	=over 4
		3622
		3623	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3624	calling conventions regardless of C<ev_watcher_type *>.
		3625
		3626	Libev assumes not only that all watcher pointers have the same internal
		3627	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3628	assumes that the same (machine) code can be used to call any watcher
		3629	callback: The watcher callbacks have different type signatures, but libev
		3630	calls them using an C<ev_watcher *> internally.
		3631
		3632	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3633
		3634	The type C<sig_atomic_t volatile> (or whatever is defined as
		3635	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3636	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3637	believed to be sufficiently portable.
		3638
		3639	=item C<sigprocmask> must work in a threaded environment
		3640
		3641	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3642	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3643	pthread implementations will either allow C<sigprocmask> in the "main
		3644	thread" or will block signals process-wide, both behaviours would
		3645	be compatible with libev. Interaction between C<sigprocmask> and
		3646	C<pthread_sigmask> could complicate things, however.
		3647
		3648	The most portable way to handle signals is to block signals in all threads
		3649	except the initial one, and run the default loop in the initial thread as
		3650	well.
		3651
		3652	=item C<long> must be large enough for common memory allocation sizes
		3653
		3654	To improve portability and simplify its API, libev uses C<long> internally
		3655	instead of C<size_t> when allocating its data structures. On non-POSIX
		3656	systems (Microsoft...) this might be unexpectedly low, but is still at
		3657	least 31 bits everywhere, which is enough for hundreds of millions of
		3658	watchers.
		3659
		3660	=item C<double> must hold a time value in seconds with enough accuracy
		3661
		3662	The type C<double> is used to represent timestamps. It is required to
		3663	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3664	enough for at least into the year 4000. This requirement is fulfilled by
		3665	implementations implementing IEEE 754 (basically all existing ones).
		3666
		3667	=back
		3668
		3669	If you know of other additional requirements drop me a note.
		3670
		3671
2308	=head1 AUTHOR	3672	=head1 AUTHOR
2309		3673
2310	Marc Lehmann <libev@schmorp.de>.	3674	Marc Lehmann <libev@schmorp.de>.
2311		3675

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