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Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs.
Revision 1.199 by root, Thu Oct 23 07:18:21 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
		11	// a single header file is required
11	#include <ev.h>	12	#include <ev.h>
12		13
		14	// every watcher type has its own typedef'd struct
		15	// with the name ev_<type>
13	ev_io stdin_watcher;	16	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
15		18
16	/* called when data readable on stdin */	19	// all watcher callbacks have a similar signature
		20	// this callback is called when data is readable on stdin
17	static void	21	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	23	{
20	/* puts ("stdin ready"); */	24	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	25	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	26	// with its corresponding stop function.
		27	ev_io_stop (EV_A_ w);
		28
		29	// this causes all nested ev_loop's to stop iterating
		30	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	31	}
24		32
		33	// another callback, this time for a time-out
25	static void	34	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	36	{
28	/* puts ("timeout"); */	37	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	38	// this causes the innermost ev_loop to stop iterating
		39	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	40	}
31		41
32	int	42	int
33	main (void)	43	main (void)
34	{	44	{
		45	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
36		47
37	/* initialise an io watcher, then start it */	48	// initialise an io watcher, then start it
		49	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
40		52
		53	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	54	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	56	ev_timer_start (loop, &timeout_watcher);
44		57
45	/* loop till timeout or data ready */	58	// now wait for events to arrive
46	ev_loop (loop, 0);	59	ev_loop (loop, 0);
47		60
		61	// unloop was called, so exit
48	return 0;	62	return 0;
49	}	63	}
50		64
51	=head1 DESCRIPTION	65	=head1 DESCRIPTION
52		66
53	The newest version of this document is also available as a html-formatted	67	The newest version of this document is also available as an html-formatted
54	web page you might find easier to navigate when reading it for the first	68	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		70
57	Libev is an event loop: you register interest in certain events (such as a	71	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	72	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	73	these event sources and provide your program with events.
60		74
61	To do this, it must take more or less complete control over your process	75	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	76	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	77	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	79	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	80	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	81	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	82	watcher.
69		83
70	=head1 FEATURES	84	=head2 FEATURES
71		85
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		96
83	It also is quite fast (see this	97	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	99	for example).
86		100
87	=head1 CONVENTIONS	101	=head2 CONVENTIONS
88		102
89	Libev is very configurable. In this manual the default configuration will	103	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	104	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	105	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	106	B<EMBED> section in this manual. If libev was configured without support
93	loops, then all functions taking an initial argument of name C<loop>	107	for multiple event loops, then all functions taking an initial argument of
94	(which is always of type C<struct ev_loop *>) will not have this argument.	108	name C<loop> (which is always of type C<ev_loop *>) will not have
		109	this argument.
95		110
96	=head1 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
97		112
98	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	114	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	115	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	116	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	117	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	118	it, you should treat it as some floating point value. Unlike the name
		119	component C<stamp> might indicate, it is also used for time differences
		120	throughout libev.
		121
		122	=head1 ERROR HANDLING
		123
		124	Libev knows three classes of errors: operating system errors, usage errors
		125	and internal errors (bugs).
		126
		127	When libev catches an operating system error it cannot handle (for example
		128	a system call indicating a condition libev cannot fix), it calls the callback
		129	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		130	abort. The default is to print a diagnostic message and to call C<abort
		131	()>.
		132
		133	When libev detects a usage error such as a negative timer interval, then
		134	it will print a diagnostic message and abort (via the C<assert> mechanism,
		135	so C<NDEBUG> will disable this checking): these are programming errors in
		136	the libev caller and need to be fixed there.
		137
		138	Libev also has a few internal error-checking C<assert>ions, and also has
		139	extensive consistency checking code. These do not trigger under normal
		140	circumstances, as they indicate either a bug in libev or worse.
		141
104		142
105	=head1 GLOBAL FUNCTIONS	143	=head1 GLOBAL FUNCTIONS
106		144
107	These functions can be called anytime, even before initialising the	145	These functions can be called anytime, even before initialising the
108	library in any way.	146	library in any way.
…		…
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.
…		…
226		276
227	=back	277	=back
228		278
229	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
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<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
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		284
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
…		…
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
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
525	=item ev_ref (loop)	692	=item ev_ref (loop)
526		693
527	=item ev_unref (loop)	694	=item ev_unref (loop)
528		695
529	Ref/unref can be used to add or remove a reference count on the event	696	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	697	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	698	count is nonzero, C<ev_loop> will not return on its own.
		699
532	a watcher you never unregister that should not keep C<ev_loop> from	700	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	701	from returning, call ev_unref() after starting, and ev_ref() before
		702	stopping it.
		703
534	example, libev itself uses this for its internal signal pipe: It is not	704	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	705	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	706	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	707	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>.	708	libraries. Just remember to I<unref after start> and I<ref before stop>
		709	(but only if the watcher wasn't active before, or was active before,
		710	respectively).
539		711
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	713	running when nothing else is active.
542		714
543	struct ev_signal exitsig;	715	ev_signal exitsig;
544	ev_signal_init (&exitsig, sig_cb, SIGINT);	716	ev_signal_init (&exitsig, sig_cb, SIGINT);
545	ev_signal_start (loop, &exitsig);	717	ev_signal_start (loop, &exitsig);
546	evf_unref (loop);	718	evf_unref (loop);
547		719
548	Example: For some weird reason, unregister the above signal handler again.	720	Example: For some weird reason, unregister the above signal handler again.
549		721
550	ev_ref (loop);	722	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	723	ev_signal_stop (loop, &exitsig);
		724
		725	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		726
		727	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		728
		729	These advanced functions influence the time that libev will spend waiting
		730	for events. Both time intervals are by default C<0>, meaning that libev
		731	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		732	latency.
		733
		734	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		735	allows libev to delay invocation of I/O and timer/periodic callbacks
		736	to increase efficiency of loop iterations (or to increase power-saving
		737	opportunities).
		738
		739	The idea is that sometimes your program runs just fast enough to handle
		740	one (or very few) event(s) per loop iteration. While this makes the
		741	program responsive, it also wastes a lot of CPU time to poll for new
		742	events, especially with backends like C<select ()> which have a high
		743	overhead for the actual polling but can deliver many events at once.
		744
		745	By setting a higher I<io collect interval> you allow libev to spend more
		746	time collecting I/O events, so you can handle more events per iteration,
		747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		748	C<ev_timer>) will be not affected. Setting this to a non-null value will
		749	introduce an additional C<ev_sleep ()> call into most loop iterations.
		750
		751	Likewise, by setting a higher I<timeout collect interval> you allow libev
		752	to spend more time collecting timeouts, at the expense of increased
		753	latency/jitter/inexactness (the watcher callback will be called
		754	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		755	value will not introduce any overhead in libev.
		756
		757	Many (busy) programs can usually benefit by setting the I/O collect
		758	interval to a value near C<0.1> or so, which is often enough for
		759	interactive servers (of course not for games), likewise for timeouts. It
		760	usually doesn't make much sense to set it to a lower value than C<0.01>,
		761	as this approaches the timing granularity of most systems.
		762
		763	Setting the I<timeout collect interval> can improve the opportunity for
		764	saving power, as the program will "bundle" timer callback invocations that
		765	are "near" in time together, by delaying some, thus reducing the number of
		766	times the process sleeps and wakes up again. Another useful technique to
		767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		768	they fire on, say, one-second boundaries only.
		769
		770	=item ev_loop_verify (loop)
		771
		772	This function only does something when C<EV_VERIFY> support has been
		773	compiled in. which is the default for non-minimal builds. It tries to go
		774	through all internal structures and checks them for validity. If anything
		775	is found to be inconsistent, it will print an error message to standard
		776	error and call C<abort ()>.
		777
		778	This can be used to catch bugs inside libev itself: under normal
		779	circumstances, this function will never abort as of course libev keeps its
		780	data structures consistent.
552		781
553	=back	782	=back
554		783
555		784
556	=head1 ANATOMY OF A WATCHER	785	=head1 ANATOMY OF A WATCHER
557		786
558	A watcher is a structure that you create and register to record your	787	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	788	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:	789	become readable, you would create an C<ev_io> watcher for that:
561		790
562	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
563	{	792	{
564	ev_io_stop (w);	793	ev_io_stop (w);
565	ev_unloop (loop, EVUNLOOP_ALL);	794	ev_unloop (loop, EVUNLOOP_ALL);
566	}	795	}
567		796
568	struct ev_loop *loop = ev_default_loop (0);	797	struct ev_loop *loop = ev_default_loop (0);
569	struct ev_io stdin_watcher;	798	ev_io stdin_watcher;
570	ev_init (&stdin_watcher, my_cb);	799	ev_init (&stdin_watcher, my_cb);
571	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
572	ev_io_start (loop, &stdin_watcher);	801	ev_io_start (loop, &stdin_watcher);
573	ev_loop (loop, 0);	802	ev_loop (loop, 0);
574		803
575	As you can see, you are responsible for allocating the memory for your	804	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,	805	watcher structures (and it is usually a bad idea to do this on the stack,
577	although this can sometimes be quite valid).	806	although this can sometimes be quite valid).
578		807
579	Each watcher structure must be initialised by a call to C<ev_init	808	Each watcher structure must be initialised by a call to C<ev_init
580	(watcher *, callback)>, which expects a callback to be provided. This	809	(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	810	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	811	watchers, each time the event loop detects that the file descriptor given
583	is readable and/or writable).	812	is readable and/or writable).
584		813
585	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	814	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	815	with arguments specific to this watcher type. There is also a macro
…		…
656	=item C<EV_FORK>	885	=item C<EV_FORK>
657		886
658	The event loop has been resumed in the child process after fork (see	887	The event loop has been resumed in the child process after fork (see
659	C<ev_fork>).	888	C<ev_fork>).
660		889
		890	=item C<EV_ASYNC>
		891
		892	The given async watcher has been asynchronously notified (see C<ev_async>).
		893
661	=item C<EV_ERROR>	894	=item C<EV_ERROR>
662		895
663	An unspecified error has occured, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
664	happen because the watcher could not be properly started because libev	897	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	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
666	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
667	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
668		905
669	Libev will usually signal a few "dummy" events together with an error,	906	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	907	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	908	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	909	the error from read() or write(). This will not work in multi-threaded
673	programs, though, so beware.	910	programs, though, as the fd could already be closed and reused for another
		911	thing, so beware.
674		912
675	=back	913	=back
676		914
677	=head2 GENERIC WATCHER FUNCTIONS	915	=head2 GENERIC WATCHER FUNCTIONS
678		916
…		…
691	which rolls both calls into one.	929	which rolls both calls into one.
692		930
693	You can reinitialise a watcher at any time as long as it has been stopped	931	You can reinitialise a watcher at any time as long as it has been stopped
694	(or never started) and there are no pending events outstanding.	932	(or never started) and there are no pending events outstanding.
695		933
696	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	934	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
697	int revents)>.	935	int revents)>.
		936
		937	Example: Initialise an C<ev_io> watcher in two steps.
		938
		939	ev_io w;
		940	ev_init (&w, my_cb);
		941	ev_io_set (&w, STDIN_FILENO, EV_READ);
698		942
699	=item C<ev_TYPE_set> (ev_TYPE *, [args])	943	=item C<ev_TYPE_set> (ev_TYPE *, [args])
700		944
701	This macro initialises the type-specific parts of a watcher. You need to	945	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	946	call C<ev_init> at least once before you call this macro, but you can
…		…
705	difference to the C<ev_init> macro).	949	difference to the C<ev_init> macro).
706		950
707	Although some watcher types do not have type-specific arguments	951	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.	952	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
709		953
		954	See C<ev_init>, above, for an example.
		955
710	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	956	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
711		957
712	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	958	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	959	calls into a single call. This is the most convenient method to initialise
714	a watcher. The same limitations apply, of course.	960	a watcher. The same limitations apply, of course.
		961
		962	Example: Initialise and set an C<ev_io> watcher in one step.
		963
		964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
715		965
716	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
717		967
718	Starts (activates) the given watcher. Only active watchers will receive	968	Starts (activates) the given watcher. Only active watchers will receive
719	events. If the watcher is already active nothing will happen.	969	events. If the watcher is already active nothing will happen.
720		970
		971	Example: Start the C<ev_io> watcher that is being abused as example in this
		972	whole section.
		973
		974	ev_io_start (EV_DEFAULT_UC, &w);
		975
721	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
722		977
723	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
724	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
725	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
726	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
727	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
728	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
729		986
730	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
731		988
732	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
733	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
781		1038
782	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
783		1040
784	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
785	C<loop> nor C<revents> need to be valid as long as the watcher callback	1042	C<loop> nor C<revents> need to be valid as long as the watcher callback
786	can deal with that fact.	1043	can deal with that fact, as both are simply passed through to the
		1044	callback.
787		1045
788	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1046	=item int ev_clear_pending (loop, ev_TYPE *watcher)
789		1047
790	If the watcher is pending, this function returns clears its pending status	1048	If the watcher is pending, this function clears its pending status and
791	and returns its C<revents> bitset (as if its callback was invoked). If the	1049	returns its C<revents> bitset (as if its callback was invoked). If the
792	watcher isn't pending it does nothing and returns C<0>.	1050	watcher isn't pending it does nothing and returns C<0>.
793		1051
		1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1053	callback to be invoked, which can be accomplished with this function.
		1054
794	=back	1055	=back
795		1056
796		1057
797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
798		1059
799	Each watcher has, by default, a member C<void *data> that you can change	1060	Each watcher has, by default, a member C<void *data> that you can change
800	and read at any time, libev will completely ignore it. This can be used	1061	and read at any time: libev will completely ignore it. This can be used
801	to associate arbitrary data with your watcher. If you need more data and	1062	to associate arbitrary data with your watcher. If you need more data and
802	don't want to allocate memory and store a pointer to it in that data	1063	don't want to allocate memory and store a pointer to it in that data
803	member, you can also "subclass" the watcher type and provide your own	1064	member, you can also "subclass" the watcher type and provide your own
804	data:	1065	data:
805		1066
806	struct my_io	1067	struct my_io
807	{	1068	{
808	struct ev_io io;	1069	ev_io io;
809	int otherfd;	1070	int otherfd;
810	void *somedata;	1071	void *somedata;
811	struct whatever *mostinteresting;	1072	struct whatever *mostinteresting;
812	}	1073	};
		1074
		1075	...
		1076	struct my_io w;
		1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
813		1078
814	And since your callback will be called with a pointer to the watcher, you	1079	And since your callback will be called with a pointer to the watcher, you
815	can cast it back to your own type:	1080	can cast it back to your own type:
816		1081
817	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
818	{	1083	{
819	struct my_io *w = (struct my_io *)w_;	1084	struct my_io *w = (struct my_io *)w_;
820	...	1085	...
821	}	1086	}
822		1087
823	More interesting and less C-conformant ways of casting your callback type	1088	More interesting and less C-conformant ways of casting your callback type
824	instead have been omitted.	1089	instead have been omitted.
825		1090
826	Another common scenario is having some data structure with multiple	1091	Another common scenario is to use some data structure with multiple
827	watchers:	1092	embedded watchers:
828		1093
829	struct my_biggy	1094	struct my_biggy
830	{	1095	{
831	int some_data;	1096	int some_data;
832	ev_timer t1;	1097	ev_timer t1;
833	ev_timer t2;	1098	ev_timer t2;
834	}	1099	}
835		1100
836	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1101	In this case getting the pointer to C<my_biggy> is a bit more
837	you need to use C<offsetof>:	1102	complicated: Either you store the address of your C<my_biggy> struct
		1103	in the C<data> member of the watcher (for woozies), or you need to use
		1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1105	programmers):
838		1106
839	#include <stddef.h>	1107	#include <stddef.h>
840		1108
841	static void	1109	static void
842	t1_cb (EV_P_ struct ev_timer *w, int revents)	1110	t1_cb (EV_P_ ev_timer *w, int revents)
843	{	1111	{
844	struct my_biggy big = (struct my_biggy *	1112	struct my_biggy big = (struct my_biggy *
845	(((char *)w) - offsetof (struct my_biggy, t1));	1113	(((char *)w) - offsetof (struct my_biggy, t1));
846	}	1114	}
847		1115
848	static void	1116	static void
849	t2_cb (EV_P_ struct ev_timer *w, int revents)	1117	t2_cb (EV_P_ ev_timer *w, int revents)
850	{	1118	{
851	struct my_biggy big = (struct my_biggy *	1119	struct my_biggy big = (struct my_biggy *
852	(((char *)w) - offsetof (struct my_biggy, t2));	1120	(((char *)w) - offsetof (struct my_biggy, t2));
853	}	1121	}
854		1122
855		1123
856	=head1 WATCHER TYPES	1124	=head1 WATCHER TYPES
857		1125
858	This section describes each watcher in detail, but will not repeat	1126	This section describes each watcher in detail, but will not repeat
…		…
882	In general you can register as many read and/or write event watchers per	1150	In general you can register as many read and/or write event watchers per
883	fd as you want (as long as you don't confuse yourself). Setting all file	1151	fd as you want (as long as you don't confuse yourself). Setting all file
884	descriptors to non-blocking mode is also usually a good idea (but not	1152	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	1153	required if you know what you are doing).
886		1154
887	You have to be careful with dup'ed file descriptors, though. Some backends	1155	If you cannot use non-blocking mode, then force the use of a
888	(the linux epoll backend is a notable example) cannot handle dup'ed file	1156	known-to-be-good backend (at the time of this writing, this includes only
889	descriptors correctly if you register interest in two or more fds pointing	1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
890	to the same underlying file/socket/etc. description (that is, they share
891	the same underlying "file open").
892
893	If you must do this, then force the use of a known-to-be-good backend
894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).
896		1158
897	Another thing you have to watch out for is that it is quite easy to	1159	Another thing you have to watch out for is that it is quite easy to
898	receive "spurious" readyness notifications, that is your callback might	1160	receive "spurious" readiness notifications, that is your callback might
899	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
900	because there is no data. Not only are some backends known to create a	1162	because there is no data. Not only are some backends known to create a
901	lot of those (for example solaris ports), it is very easy to get into	1163	lot of those (for example Solaris ports), it is very easy to get into
902	this situation even with a relatively standard program structure. Thus	1164	this situation even with a relatively standard program structure. Thus
903	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
904	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.
905		1167
906	If you cannot run the fd in non-blocking mode (for example you should not	1168	If you cannot run the fd in non-blocking mode (for example you should
907	play around with an Xlib connection), then you have to seperately re-test	1169	not play around with an Xlib connection), then you have to separately
908	whether a file descriptor is really ready with a known-to-be good interface	1170	re-test whether a file descriptor is really ready with a known-to-be good
909	such as poll (fortunately in our Xlib example, Xlib already does this on	1171	interface such as poll (fortunately in our Xlib example, Xlib already
910	its own, so its quite safe to use).	1172	does this on its own, so its quite safe to use). Some people additionally
		1173	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1174	indefinitely.
		1175
		1176	But really, best use non-blocking mode.
		1177
		1178	=head3 The special problem of disappearing file descriptors
		1179
		1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1181	descriptor (either due to calling C<close> explicitly or any other means,
		1182	such as C<dup2>). The reason is that you register interest in some file
		1183	descriptor, but when it goes away, the operating system will silently drop
		1184	this interest. If another file descriptor with the same number then is
		1185	registered with libev, there is no efficient way to see that this is, in
		1186	fact, a different file descriptor.
		1187
		1188	To avoid having to explicitly tell libev about such cases, libev follows
		1189	the following policy: Each time C<ev_io_set> is being called, libev
		1190	will assume that this is potentially a new file descriptor, otherwise
		1191	it is assumed that the file descriptor stays the same. That means that
		1192	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1193	descriptor even if the file descriptor number itself did not change.
		1194
		1195	This is how one would do it normally anyway, the important point is that
		1196	the libev application should not optimise around libev but should leave
		1197	optimisations to libev.
		1198
		1199	=head3 The special problem of dup'ed file descriptors
		1200
		1201	Some backends (e.g. epoll), cannot register events for file descriptors,
		1202	but only events for the underlying file descriptions. That means when you
		1203	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1204	events for them, only one file descriptor might actually receive events.
		1205
		1206	There is no workaround possible except not registering events
		1207	for potentially C<dup ()>'ed file descriptors, or to resort to
		1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1209
		1210	=head3 The special problem of fork
		1211
		1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1213	useless behaviour. Libev fully supports fork, but needs to be told about
		1214	it in the child.
		1215
		1216	To support fork in your programs, you either have to call
		1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1219	C<EVBACKEND_POLL>.
		1220
		1221	=head3 The special problem of SIGPIPE
		1222
		1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1224	when writing to a pipe whose other end has been closed, your program gets
		1225	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1226	this is sensible behaviour, for daemons, this is usually undesirable.
		1227
		1228	So when you encounter spurious, unexplained daemon exits, make sure you
		1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1230	somewhere, as that would have given you a big clue).
		1231
		1232
		1233	=head3 Watcher-Specific Functions
911		1234
912	=over 4	1235	=over 4
913		1236
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1237	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1238
916	=item ev_io_set (ev_io *, int fd, int events)	1239	=item ev_io_set (ev_io *, int fd, int events)
917		1240
918	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1241	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
919	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1242	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
920	C<EV_READ | EV_WRITE> to receive the given events.	1243	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
921		1244
922	=item int fd [read-only]	1245	=item int fd [read-only]
923		1246
924	The file descriptor being watched.	1247	The file descriptor being watched.
925		1248
926	=item int events [read-only]	1249	=item int events [read-only]
927		1250
928	The events being watched.	1251	The events being watched.
929		1252
930	=back	1253	=back
		1254
		1255	=head3 Examples
931		1256
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1257	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
933	readable, but only once. Since it is likely line-buffered, you could	1258	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1259	attempt to read a whole line in the callback.
935		1260
936	static void	1261	static void
937	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1262	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
938	{	1263	{
939	ev_io_stop (loop, w);	1264	ev_io_stop (loop, w);
940	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1265	.. read from stdin here (or from w->fd) and handle any I/O errors
941	}	1266	}
942		1267
943	...	1268	...
944	struct ev_loop *loop = ev_default_init (0);	1269	struct ev_loop *loop = ev_default_init (0);
945	struct ev_io stdin_readable;	1270	ev_io stdin_readable;
946	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
947	ev_io_start (loop, &stdin_readable);	1272	ev_io_start (loop, &stdin_readable);
948	ev_loop (loop, 0);	1273	ev_loop (loop, 0);
949		1274
950		1275
951	=head2 C<ev_timer> - relative and optionally repeating timeouts	1276	=head2 C<ev_timer> - relative and optionally repeating timeouts
952		1277
953	Timer watchers are simple relative timers that generate an event after a	1278	Timer watchers are simple relative timers that generate an event after a
954	given time, and optionally repeating in regular intervals after that.	1279	given time, and optionally repeating in regular intervals after that.
955		1280
956	The timers are based on real time, that is, if you register an event that	1281	The timers are based on real time, that is, if you register an event that
957	times out after an hour and you reset your system clock to last years	1282	times out after an hour and you reset your system clock to January last
958	time, it will still time out after (roughly) and hour. "Roughly" because	1283	year, it will still time out after (roughly) one hour. "Roughly" because
959	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the
960	monotonic clock option helps a lot here).	1285	monotonic clock option helps a lot here).
		1286
		1287	The callback is guaranteed to be invoked only I<after> its timeout has
		1288	passed, but if multiple timers become ready during the same loop iteration
		1289	then order of execution is undefined.
		1290
		1291	=head3 Be smart about timeouts
		1292
		1293	Many real-world problems involve some kind of timeout, usually for error
		1294	recovery. A typical example is an HTTP request - if the other side hangs,
		1295	you want to raise some error after a while.
		1296
		1297	What follows are some ways to handle this problem, from obvious and
		1298	inefficient to smart and efficient.
		1299
		1300	In the following, a 60 second activity timeout is assumed - a timeout that
		1301	gets reset to 60 seconds each time there is activity (e.g. each time some
		1302	data or other life sign was received).
		1303
		1304	=over 4
		1305
		1306	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1307
		1308	This is the most obvious, but not the most simple way: In the beginning,
		1309	start the watcher:
		1310
		1311	ev_timer_init (timer, callback, 60., 0.);
		1312	ev_timer_start (loop, timer);
		1313
		1314	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1315	and start it again:
		1316
		1317	ev_timer_stop (loop, timer);
		1318	ev_timer_set (timer, 60., 0.);
		1319	ev_timer_start (loop, timer);
		1320
		1321	This is relatively simple to implement, but means that each time there is
		1322	some activity, libev will first have to remove the timer from its internal
		1323	data structure and then add it again. Libev tries to be fast, but it's
		1324	still not a constant-time operation.
		1325
		1326	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1327
		1328	This is the easiest way, and involves using C<ev_timer_again> instead of
		1329	C<ev_timer_start>.
		1330
		1331	To implement this, configure an C<ev_timer> with a C<repeat> value
		1332	of C<60> and then call C<ev_timer_again> at start and each time you
		1333	successfully read or write some data. If you go into an idle state where
		1334	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1335	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1336
		1337	That means you can ignore both the C<ev_timer_start> function and the
		1338	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1339	member and C<ev_timer_again>.
		1340
		1341	At start:
		1342
		1343	ev_timer_init (timer, callback);
		1344	timer->repeat = 60.;
		1345	ev_timer_again (loop, timer);
		1346
		1347	Each time there is some activity:
		1348
		1349	ev_timer_again (loop, timer);
		1350
		1351	It is even possible to change the time-out on the fly, regardless of
		1352	whether the watcher is active or not:
		1353
		1354	timer->repeat = 30.;
		1355	ev_timer_again (loop, timer);
		1356
		1357	This is slightly more efficient then stopping/starting the timer each time
		1358	you want to modify its timeout value, as libev does not have to completely
		1359	remove and re-insert the timer from/into its internal data structure.
		1360
		1361	It is, however, even simpler than the "obvious" way to do it.
		1362
		1363	=item 3. Let the timer time out, but then re-arm it as required.
		1364
		1365	This method is more tricky, but usually most efficient: Most timeouts are
		1366	relatively long compared to the intervals between other activity - in
		1367	our example, within 60 seconds, there are usually many I/O events with
		1368	associated activity resets.
		1369
		1370	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1371	but remember the time of last activity, and check for a real timeout only
		1372	within the callback:
		1373
		1374	ev_tstamp last_activity; // time of last activity
		1375
		1376	static void
		1377	callback (EV_P_ ev_timer *w, int revents)
		1378	{
		1379	ev_tstamp now = ev_now (EV_A);
		1380	ev_tstamp timeout = last_activity + 60.;
		1381
		1382	// if last_activity + 60. is older than now, we did time out
		1383	if (timeout < now)
		1384	{
		1385	// timeout occured, take action
		1386	}
		1387	else
		1388	{
		1389	// callback was invoked, but there was some activity, re-arm
		1390	// the watcher to fire in last_activity + 60, which is
		1391	// guaranteed to be in the future, so "again" is positive:
		1392	w->again = timeout - now;
		1393	ev_timer_again (EV_A_ w);
		1394	}
		1395	}
		1396
		1397	To summarise the callback: first calculate the real timeout (defined
		1398	as "60 seconds after the last activity"), then check if that time has
		1399	been reached, which means something I<did>, in fact, time out. Otherwise
		1400	the callback was invoked too early (C<timeout> is in the future), so
		1401	re-schedule the timer to fire at that future time, to see if maybe we have
		1402	a timeout then.
		1403
		1404	Note how C<ev_timer_again> is used, taking advantage of the
		1405	C<ev_timer_again> optimisation when the timer is already running.
		1406
		1407	This scheme causes more callback invocations (about one every 60 seconds
		1408	minus half the average time between activity), but virtually no calls to
		1409	libev to change the timeout.
		1410
		1411	To start the timer, simply initialise the watcher and set C<last_activity>
		1412	to the current time (meaning we just have some activity :), then call the
		1413	callback, which will "do the right thing" and start the timer:
		1414
		1415	ev_timer_init (timer, callback);
		1416	last_activity = ev_now (loop);
		1417	callback (loop, timer, EV_TIMEOUT);
		1418
		1419	And when there is some activity, simply store the current time in
		1420	C<last_activity>, no libev calls at all:
		1421
		1422	last_actiivty = ev_now (loop);
		1423
		1424	This technique is slightly more complex, but in most cases where the
		1425	time-out is unlikely to be triggered, much more efficient.
		1426
		1427	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1428	callback :) - just change the timeout and invoke the callback, which will
		1429	fix things for you.
		1430
		1431	=item 4. Whee, use a double-linked list for your timeouts.
		1432
		1433	If there is not one request, but many thousands, all employing some kind
		1434	of timeout with the same timeout value, then one can do even better:
		1435
		1436	When starting the timeout, calculate the timeout value and put the timeout
		1437	at the I<end> of the list.
		1438
		1439	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1440	the list is expected to fire (for example, using the technique #3).
		1441
		1442	When there is some activity, remove the timer from the list, recalculate
		1443	the timeout, append it to the end of the list again, and make sure to
		1444	update the C<ev_timer> if it was taken from the beginning of the list.
		1445
		1446	This way, one can manage an unlimited number of timeouts in O(1) time for
		1447	starting, stopping and updating the timers, at the expense of a major
		1448	complication, and having to use a constant timeout. The constant timeout
		1449	ensures that the list stays sorted.
		1450
		1451	=back
		1452
		1453	So what method is the best?
		1454
		1455	The method #2 is a simple no-brain-required solution that is adequate in
		1456	most situations. Method #3 requires a bit more thinking, but handles many
		1457	cases better, and isn't very complicated either. In most case, choosing
		1458	either one is fine.
		1459
		1460	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1461	rather complicated, but extremely efficient, something that really pays
		1462	off after the first or so million of active timers, i.e. it's usually
		1463	overkill :)
		1464
		1465	=head3 The special problem of time updates
		1466
		1467	Establishing the current time is a costly operation (it usually takes at
		1468	least two system calls): EV therefore updates its idea of the current
		1469	time only before and after C<ev_loop> collects new events, which causes a
		1470	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1471	lots of events in one iteration.
961		1472
962	The relative timeouts are calculated relative to the C<ev_now ()>	1473	The relative timeouts are calculated relative to the C<ev_now ()>
963	time. This is usually the right thing as this timestamp refers to the time	1474	time. This is usually the right thing as this timestamp refers to the time
964	of the event triggering whatever timeout you are modifying/starting. If	1475	of the event triggering whatever timeout you are modifying/starting. If
965	you suspect event processing to be delayed and you I<need> to base the timeout	1476	you suspect event processing to be delayed and you I<need> to base the
966	on the current time, use something like this to adjust for this:	1477	timeout on the current time, use something like this to adjust for this:
967		1478
968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1479	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
969		1480
970	The callback is guarenteed to be invoked only when its timeout has passed,	1481	If the event loop is suspended for a long time, you can also force an
971	but if multiple timers become ready during the same loop iteration then	1482	update of the time returned by C<ev_now ()> by calling C<ev_now_update
972	order of execution is undefined.	1483	()>.
		1484
		1485	=head3 Watcher-Specific Functions and Data Members
973		1486
974	=over 4	1487	=over 4
975		1488
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1489	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1490
978	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1491	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
979		1492
980	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1493	Configure the timer to trigger after C<after> seconds. If C<repeat>
981	C<0.>, then it will automatically be stopped. If it is positive, then the	1494	is C<0.>, then it will automatically be stopped once the timeout is
982	timer will automatically be configured to trigger again C<repeat> seconds	1495	reached. If it is positive, then the timer will automatically be
983	later, again, and again, until stopped manually.	1496	configured to trigger again C<repeat> seconds later, again, and again,
		1497	until stopped manually.
984		1498
985	The timer itself will do a best-effort at avoiding drift, that is, if you	1499	The timer itself will do a best-effort at avoiding drift, that is, if
986	configure a timer to trigger every 10 seconds, then it will trigger at	1500	you configure a timer to trigger every 10 seconds, then it will normally
987	exactly 10 second intervals. If, however, your program cannot keep up with	1501	trigger at exactly 10 second intervals. If, however, your program cannot
988	the timer (because it takes longer than those 10 seconds to do stuff) the	1502	keep up with the timer (because it takes longer than those 10 seconds to
989	timer will not fire more than once per event loop iteration.	1503	do stuff) the timer will not fire more than once per event loop iteration.
990		1504
991	=item ev_timer_again (loop)	1505	=item ev_timer_again (loop, ev_timer *)
992		1506
993	This will act as if the timer timed out and restart it again if it is	1507	This will act as if the timer timed out and restart it again if it is
994	repeating. The exact semantics are:	1508	repeating. The exact semantics are:
995		1509
996	If the timer is pending, its pending status is cleared.	1510	If the timer is pending, its pending status is cleared.
997		1511
998	If the timer is started but nonrepeating, stop it (as if it timed out).	1512	If the timer is started but non-repeating, stop it (as if it timed out).
999		1513
1000	If the timer is repeating, either start it if necessary (with the	1514	If the timer is repeating, either start it if necessary (with the
1001	C<repeat> value), or reset the running timer to the C<repeat> value.	1515	C<repeat> value), or reset the running timer to the C<repeat> value.
1002		1516
1003	This sounds a bit complicated, but here is a useful and typical	1517	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1004	example: Imagine you have a tcp connection and you want a so-called idle	1518	usage example.
1005	timeout, that is, you want to be called when there have been, say, 60
1006	seconds of inactivity on the socket. The easiest way to do this is to
1007	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1008	C<ev_timer_again> each time you successfully read or write some data. If
1009	you go into an idle state where you do not expect data to travel on the
1010	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1011	automatically restart it if need be.
1012
1013	That means you can ignore the C<after> value and C<ev_timer_start>
1014	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1015
1016	ev_timer_init (timer, callback, 0., 5.);
1017	ev_timer_again (loop, timer);
1018	...
1019	timer->again = 17.;
1020	ev_timer_again (loop, timer);
1021	...
1022	timer->again = 10.;
1023	ev_timer_again (loop, timer);
1024
1025	This is more slightly efficient then stopping/starting the timer each time
1026	you want to modify its timeout value.
1027		1519
1028	=item ev_tstamp repeat [read-write]	1520	=item ev_tstamp repeat [read-write]
1029		1521
1030	The current C<repeat> value. Will be used each time the watcher times out	1522	The current C<repeat> value. Will be used each time the watcher times out
1031	or C<ev_timer_again> is called and determines the next timeout (if any),	1523	or C<ev_timer_again> is called, and determines the next timeout (if any),
1032	which is also when any modifications are taken into account.	1524	which is also when any modifications are taken into account.
1033		1525
1034	=back	1526	=back
1035		1527
		1528	=head3 Examples
		1529
1036	Example: Create a timer that fires after 60 seconds.	1530	Example: Create a timer that fires after 60 seconds.
1037		1531
1038	static void	1532	static void
1039	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1533	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1040	{	1534	{
1041	.. one minute over, w is actually stopped right here	1535	.. one minute over, w is actually stopped right here
1042	}	1536	}
1043		1537
1044	struct ev_timer mytimer;	1538	ev_timer mytimer;
1045	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1539	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1046	ev_timer_start (loop, &mytimer);	1540	ev_timer_start (loop, &mytimer);
1047		1541
1048	Example: Create a timeout timer that times out after 10 seconds of	1542	Example: Create a timeout timer that times out after 10 seconds of
1049	inactivity.	1543	inactivity.
1050		1544
1051	static void	1545	static void
1052	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1546	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1053	{	1547	{
1054	.. ten seconds without any activity	1548	.. ten seconds without any activity
1055	}	1549	}
1056		1550
1057	struct ev_timer mytimer;	1551	ev_timer mytimer;
1058	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1552	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1059	ev_timer_again (&mytimer); /* start timer */	1553	ev_timer_again (&mytimer); /* start timer */
1060	ev_loop (loop, 0);	1554	ev_loop (loop, 0);
1061		1555
1062	// and in some piece of code that gets executed on any "activity":	1556	// and in some piece of code that gets executed on any "activity":
1063	// reset the timeout to start ticking again at 10 seconds	1557	// reset the timeout to start ticking again at 10 seconds
1064	ev_timer_again (&mytimer);	1558	ev_timer_again (&mytimer);
1065		1559
1066		1560
1067	=head2 C<ev_periodic> - to cron or not to cron?	1561	=head2 C<ev_periodic> - to cron or not to cron?
1068		1562
1069	Periodic watchers are also timers of a kind, but they are very versatile	1563	Periodic watchers are also timers of a kind, but they are very versatile
1070	(and unfortunately a bit complex).	1564	(and unfortunately a bit complex).
1071		1565
1072	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1566	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1073	but on wallclock time (absolute time). You can tell a periodic watcher	1567	but on wall clock time (absolute time). You can tell a periodic watcher
1074	to trigger "at" some specific point in time. For example, if you tell a	1568	to trigger after some specific point in time. For example, if you tell a
1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1569	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1076	+ 10.>) and then reset your system clock to the last year, then it will	1570	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1571	clock to January of the previous year, then it will take more than year
1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1572	to trigger the event (unlike an C<ev_timer>, which would still trigger
1078	roughly 10 seconds later and of course not if you reset your system time	1573	roughly 10 seconds later as it uses a relative timeout).
1079	again).
1080		1574
1081	They can also be used to implement vastly more complex timers, such as	1575	C<ev_periodic>s can also be used to implement vastly more complex timers,
1082	triggering an event on eahc midnight, local time.	1576	such as triggering an event on each "midnight, local time", or other
		1577	complicated rules.
1083		1578
1084	As with timers, the callback is guarenteed to be invoked only when the	1579	As with timers, the callback is guaranteed to be invoked only when the
1085	time (C<at>) has been passed, but if multiple periodic timers become ready	1580	time (C<at>) has passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1581	during the same loop iteration, then order of execution is undefined.
		1582
		1583	=head3 Watcher-Specific Functions and Data Members
1087		1584
1088	=over 4	1585	=over 4
1089		1586
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1587	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1588
1092	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1589	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1093		1590
1094	Lots of arguments, lets sort it out... There are basically three modes of	1591	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1592	operation, and we will explain them from simplest to most complex:
1096		1593
1097	=over 4	1594	=over 4
1098		1595
1099	=item * absolute timer (interval = reschedule_cb = 0)	1596	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1597
1101	In this configuration the watcher triggers an event at the wallclock time	1598	In this configuration the watcher triggers an event after the wall clock
1102	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1599	time C<at> has passed. It will not repeat and will not adjust when a time
1103	that is, if it is to be run at January 1st 2011 then it will run when the	1600	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1104	system time reaches or surpasses this time.	1601	only run when the system clock reaches or surpasses this time.
1105		1602
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1603	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1604
1108	In this mode the watcher will always be scheduled to time out at the next	1605	In this mode the watcher will always be scheduled to time out at the next
1109	C<at + N * interval> time (for some integer N) and then repeat, regardless	1606	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1607	and then repeat, regardless of any time jumps.
1111		1608
1112	This can be used to create timers that do not drift with respect to system	1609	This can be used to create timers that do not drift with respect to the
1113	time:	1610	system clock, for example, here is a C<ev_periodic> that triggers each
		1611	hour, on the hour:
1114		1612
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1613	ev_periodic_set (&periodic, 0., 3600., 0);
1116		1614
1117	This doesn't mean there will always be 3600 seconds in between triggers,	1615	This doesn't mean there will always be 3600 seconds in between triggers,
1118	but only that the the callback will be called when the system time shows a	1616	but only that the callback will be called when the system time shows a
1119	full hour (UTC), or more correctly, when the system time is evenly divisible	1617	full hour (UTC), or more correctly, when the system time is evenly divisible
1120	by 3600.	1618	by 3600.
1121		1619
1122	Another way to think about it (for the mathematically inclined) is that	1620	Another way to think about it (for the mathematically inclined) is that
1123	C<ev_periodic> will try to run the callback in this mode at the next possible	1621	C<ev_periodic> will try to run the callback in this mode at the next possible
1124	time where C<time = at (mod interval)>, regardless of any time jumps.	1622	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1623
		1624	For numerical stability it is preferable that the C<at> value is near
		1625	C<ev_now ()> (the current time), but there is no range requirement for
		1626	this value, and in fact is often specified as zero.
		1627
		1628	Note also that there is an upper limit to how often a timer can fire (CPU
		1629	speed for example), so if C<interval> is very small then timing stability
		1630	will of course deteriorate. Libev itself tries to be exact to be about one
		1631	millisecond (if the OS supports it and the machine is fast enough).
		1632
1126	=item * manual reschedule mode (reschedule_cb = callback)	1633	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1634
1128	In this mode the values for C<interval> and C<at> are both being	1635	In this mode the values for C<interval> and C<at> are both being
1129	ignored. Instead, each time the periodic watcher gets scheduled, the	1636	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1637	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1638	current time as second argument.
1132		1639
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1640	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1134	ever, or make any event loop modifications>. If you need to stop it,	1641	ever, or make ANY event loop modifications whatsoever>.
1135	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1136	starting a prepare watcher).
1137		1642
		1643	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1644	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1645	only event loop modification you are allowed to do).
		1646
1138	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1647	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1139	ev_tstamp now)>, e.g.:	1648	*w, ev_tstamp now)>, e.g.:
1140		1649
		1650	static ev_tstamp
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1651	my_rescheduler (ev_periodic *w, ev_tstamp now)
1142	{	1652	{
1143	return now + 60.;	1653	return now + 60.;
1144	}	1654	}
1145		1655
1146	It must return the next time to trigger, based on the passed time value	1656	It must return the next time to trigger, based on the passed time value
1147	(that is, the lowest time value larger than to the second argument). It	1657	(that is, the lowest time value larger than to the second argument). It
1148	will usually be called just before the callback will be triggered, but	1658	will usually be called just before the callback will be triggered, but
1149	might be called at other times, too.	1659	might be called at other times, too.
1150		1660
1151	NOTE: I<< This callback must always return a time that is later than the	1661	NOTE: I<< This callback must always return a time that is higher than or
1152	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1662	equal to the passed C<now> value >>.
1153		1663
1154	This can be used to create very complex timers, such as a timer that	1664	This can be used to create very complex timers, such as a timer that
1155	triggers on each midnight, local time. To do this, you would calculate the	1665	triggers on "next midnight, local time". To do this, you would calculate the
1156	next midnight after C<now> and return the timestamp value for this. How	1666	next midnight after C<now> and return the timestamp value for this. How
1157	you do this is, again, up to you (but it is not trivial, which is the main	1667	you do this is, again, up to you (but it is not trivial, which is the main
1158	reason I omitted it as an example).	1668	reason I omitted it as an example).
1159		1669
1160	=back	1670	=back
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1674	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1675	when you changed some parameters or the reschedule callback would return
1166	a different time than the last time it was called (e.g. in a crond like	1676	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1677	program when the crontabs have changed).
1168		1678
		1679	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1680
		1681	When active, returns the absolute time that the watcher is supposed to
		1682	trigger next.
		1683
		1684	=item ev_tstamp offset [read-write]
		1685
		1686	When repeating, this contains the offset value, otherwise this is the
		1687	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1688
		1689	Can be modified any time, but changes only take effect when the periodic
		1690	timer fires or C<ev_periodic_again> is being called.
		1691
1169	=item ev_tstamp interval [read-write]	1692	=item ev_tstamp interval [read-write]
1170		1693
1171	The current interval value. Can be modified any time, but changes only	1694	The current interval value. Can be modified any time, but changes only
1172	take effect when the periodic timer fires or C<ev_periodic_again> is being	1695	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1696	called.
1174		1697
1175	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1698	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1176		1699
1177	The current reschedule callback, or C<0>, if this functionality is	1700	The current reschedule callback, or C<0>, if this functionality is
1178	switched off. Can be changed any time, but changes only take effect when	1701	switched off. Can be changed any time, but changes only take effect when
1179	the periodic timer fires or C<ev_periodic_again> is being called.	1702	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1703
1181	=back	1704	=back
1182		1705
		1706	=head3 Examples
		1707
1183	Example: Call a callback every hour, or, more precisely, whenever the	1708	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1709	system time is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1710	potentially a lot of jitter, but good long-term stability.
1186		1711
1187	static void	1712	static void
1188	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1713	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1189	{	1714	{
1190	... its now a full hour (UTC, or TAI or whatever your clock follows)	1715	... its now a full hour (UTC, or TAI or whatever your clock follows)
1191	}	1716	}
1192		1717
1193	struct ev_periodic hourly_tick;	1718	ev_periodic hourly_tick;
1194	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1719	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1195	ev_periodic_start (loop, &hourly_tick);	1720	ev_periodic_start (loop, &hourly_tick);
1196		1721
1197	Example: The same as above, but use a reschedule callback to do it:	1722	Example: The same as above, but use a reschedule callback to do it:
1198		1723
1199	#include <math.h>	1724	#include <math.h>
1200		1725
1201	static ev_tstamp	1726	static ev_tstamp
1202	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1727	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1203	{	1728	{
1204	return fmod (now, 3600.) + 3600.;	1729	return now + (3600. - fmod (now, 3600.));
1205	}	1730	}
1206		1731
1207	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1732	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1208		1733
1209	Example: Call a callback every hour, starting now:	1734	Example: Call a callback every hour, starting now:
1210		1735
1211	struct ev_periodic hourly_tick;	1736	ev_periodic hourly_tick;
1212	ev_periodic_init (&hourly_tick, clock_cb,	1737	ev_periodic_init (&hourly_tick, clock_cb,
1213	fmod (ev_now (loop), 3600.), 3600., 0);	1738	fmod (ev_now (loop), 3600.), 3600., 0);
1214	ev_periodic_start (loop, &hourly_tick);	1739	ev_periodic_start (loop, &hourly_tick);
1215		1740
1216		1741
1217	=head2 C<ev_signal> - signal me when a signal gets signalled!	1742	=head2 C<ev_signal> - signal me when a signal gets signalled!
1218		1743
1219	Signal watchers will trigger an event when the process receives a specific	1744	Signal watchers will trigger an event when the process receives a specific
1220	signal one or more times. Even though signals are very asynchronous, libev	1745	signal one or more times. Even though signals are very asynchronous, libev
1221	will try it's best to deliver signals synchronously, i.e. as part of the	1746	will try it's best to deliver signals synchronously, i.e. as part of the
1222	normal event processing, like any other event.	1747	normal event processing, like any other event.
1223		1748
		1749	If you want signals asynchronously, just use C<sigaction> as you would
		1750	do without libev and forget about sharing the signal. You can even use
		1751	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1752
1224	You can configure as many watchers as you like per signal. Only when the	1753	You can configure as many watchers as you like per signal. Only when the
1225	first watcher gets started will libev actually register a signal watcher	1754	first watcher gets started will libev actually register a signal handler
1226	with the kernel (thus it coexists with your own signal handlers as long	1755	with the kernel (thus it coexists with your own signal handlers as long as
1227	as you don't register any with libev). Similarly, when the last signal	1756	you don't register any with libev for the same signal). Similarly, when
1228	watcher for a signal is stopped libev will reset the signal handler to	1757	the last signal watcher for a signal is stopped, libev will reset the
1229	SIG_DFL (regardless of what it was set to before).	1758	signal handler to SIG_DFL (regardless of what it was set to before).
		1759
		1760	If possible and supported, libev will install its handlers with
		1761	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1762	interrupted. If you have a problem with system calls getting interrupted by
		1763	signals you can block all signals in an C<ev_check> watcher and unblock
		1764	them in an C<ev_prepare> watcher.
		1765
		1766	=head3 Watcher-Specific Functions and Data Members
1230		1767
1231	=over 4	1768	=over 4
1232		1769
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1770	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1771
…		…
1241		1778
1242	The signal the watcher watches out for.	1779	The signal the watcher watches out for.
1243		1780
1244	=back	1781	=back
1245		1782
		1783	=head3 Examples
		1784
		1785	Example: Try to exit cleanly on SIGINT.
		1786
		1787	static void
		1788	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1789	{
		1790	ev_unloop (loop, EVUNLOOP_ALL);
		1791	}
		1792
		1793	ev_signal signal_watcher;
		1794	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1795	ev_signal_start (loop, &signal_watcher);
		1796
1246		1797
1247	=head2 C<ev_child> - watch out for process status changes	1798	=head2 C<ev_child> - watch out for process status changes
1248		1799
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1800	Child watchers trigger when your process receives a SIGCHLD in response to
1250	some child status changes (most typically when a child of yours dies).	1801	some child status changes (most typically when a child of yours dies or
		1802	exits). It is permissible to install a child watcher I<after> the child
		1803	has been forked (which implies it might have already exited), as long
		1804	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1805	forking and then immediately registering a watcher for the child is fine,
		1806	but forking and registering a watcher a few event loop iterations later is
		1807	not.
		1808
		1809	Only the default event loop is capable of handling signals, and therefore
		1810	you can only register child watchers in the default event loop.
		1811
		1812	=head3 Process Interaction
		1813
		1814	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1815	initialised. This is necessary to guarantee proper behaviour even if
		1816	the first child watcher is started after the child exits. The occurrence
		1817	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1818	synchronously as part of the event loop processing. Libev always reaps all
		1819	children, even ones not watched.
		1820
		1821	=head3 Overriding the Built-In Processing
		1822
		1823	Libev offers no special support for overriding the built-in child
		1824	processing, but if your application collides with libev's default child
		1825	handler, you can override it easily by installing your own handler for
		1826	C<SIGCHLD> after initialising the default loop, and making sure the
		1827	default loop never gets destroyed. You are encouraged, however, to use an
		1828	event-based approach to child reaping and thus use libev's support for
		1829	that, so other libev users can use C<ev_child> watchers freely.
		1830
		1831	=head3 Stopping the Child Watcher
		1832
		1833	Currently, the child watcher never gets stopped, even when the
		1834	child terminates, so normally one needs to stop the watcher in the
		1835	callback. Future versions of libev might stop the watcher automatically
		1836	when a child exit is detected.
		1837
		1838	=head3 Watcher-Specific Functions and Data Members
1251		1839
1252	=over 4	1840	=over 4
1253		1841
1254	=item ev_child_init (ev_child *, callback, int pid)	1842	=item ev_child_init (ev_child *, callback, int pid, int trace)
1255		1843
1256	=item ev_child_set (ev_child *, int pid)	1844	=item ev_child_set (ev_child *, int pid, int trace)
1257		1845
1258	Configures the watcher to wait for status changes of process C<pid> (or	1846	Configures the watcher to wait for status changes of process C<pid> (or
1259	I<any> process if C<pid> is specified as C<0>). The callback can look	1847	I<any> process if C<pid> is specified as C<0>). The callback can look
1260	at the C<rstatus> member of the C<ev_child> watcher structure to see	1848	at the C<rstatus> member of the C<ev_child> watcher structure to see
1261	the status word (use the macros from C<sys/wait.h> and see your systems	1849	the status word (use the macros from C<sys/wait.h> and see your systems
1262	C<waitpid> documentation). The C<rpid> member contains the pid of the	1850	C<waitpid> documentation). The C<rpid> member contains the pid of the
1263	process causing the status change.	1851	process causing the status change. C<trace> must be either C<0> (only
		1852	activate the watcher when the process terminates) or C<1> (additionally
		1853	activate the watcher when the process is stopped or continued).
1264		1854
1265	=item int pid [read-only]	1855	=item int pid [read-only]
1266		1856
1267	The process id this watcher watches out for, or C<0>, meaning any process id.	1857	The process id this watcher watches out for, or C<0>, meaning any process id.
1268		1858
…		…
1275	The process exit/trace status caused by C<rpid> (see your systems	1865	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1866	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1867
1278	=back	1868	=back
1279		1869
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1870	=head3 Examples
1281		1871
		1872	Example: C<fork()> a new process and install a child handler to wait for
		1873	its completion.
		1874
		1875	ev_child cw;
		1876
1282	static void	1877	static void
1283	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1878	child_cb (EV_P_ ev_child *w, int revents)
1284	{	1879	{
1285	ev_unloop (loop, EVUNLOOP_ALL);	1880	ev_child_stop (EV_A_ w);
		1881	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1286	}	1882	}
1287		1883
1288	struct ev_signal signal_watcher;	1884	pid_t pid = fork ();
1289	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1885
1290	ev_signal_start (loop, &sigint_cb);	1886	if (pid < 0)
		1887	// error
		1888	else if (pid == 0)
		1889	{
		1890	// the forked child executes here
		1891	exit (1);
		1892	}
		1893	else
		1894	{
		1895	ev_child_init (&cw, child_cb, pid, 0);
		1896	ev_child_start (EV_DEFAULT_ &cw);
		1897	}
1291		1898
1292		1899
1293	=head2 C<ev_stat> - did the file attributes just change?	1900	=head2 C<ev_stat> - did the file attributes just change?
1294		1901
1295	This watches a filesystem path for attribute changes. That is, it calls	1902	This watches a file system path for attribute changes. That is, it calls
1296	C<stat> regularly (or when the OS says it changed) and sees if it changed	1903	C<stat> regularly (or when the OS says it changed) and sees if it changed
1297	compared to the last time, invoking the callback if it did.	1904	compared to the last time, invoking the callback if it did.
1298		1905
1299	The path does not need to exist: changing from "path exists" to "path does	1906	The path does not need to exist: changing from "path exists" to "path does
1300	not exist" is a status change like any other. The condition "path does	1907	not exist" is a status change like any other. The condition "path does
…		…
1303	the stat buffer having unspecified contents.	1910	the stat buffer having unspecified contents.
1304		1911
1305	The path I<should> be absolute and I<must not> end in a slash. If it is	1912	The path I<should> be absolute and I<must not> end in a slash. If it is
1306	relative and your working directory changes, the behaviour is undefined.	1913	relative and your working directory changes, the behaviour is undefined.
1307		1914
1308	Since there is no standard to do this, the portable implementation simply	1915	Since there is no standard kernel interface to do this, the portable
1309	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1916	implementation simply calls C<stat (2)> regularly on the path to see if
1310	can specify a recommended polling interval for this case. If you specify	1917	it changed somehow. You can specify a recommended polling interval for
1311	a polling interval of C<0> (highly recommended!) then a I<suitable,	1918	this case. If you specify a polling interval of C<0> (highly recommended!)
1312	unspecified default> value will be used (which you can expect to be around	1919	then a I<suitable, unspecified default> value will be used (which
1313	five seconds, although this might change dynamically). Libev will also	1920	you can expect to be around five seconds, although this might change
1314	impose a minimum interval which is currently around C<0.1>, but thats	1921	dynamically). Libev will also impose a minimum interval which is currently
1315	usually overkill.	1922	around C<0.1>, but thats usually overkill.
1316		1923
1317	This watcher type is not meant for massive numbers of stat watchers,	1924	This watcher type is not meant for massive numbers of stat watchers,
1318	as even with OS-supported change notifications, this can be	1925	as even with OS-supported change notifications, this can be
1319	resource-intensive.	1926	resource-intensive.
1320		1927
1321	At the time of this writing, only the Linux inotify interface is	1928	At the time of this writing, the only OS-specific interface implemented
1322	implemented (implementing kqueue support is left as an exercise for the	1929	is the Linux inotify interface (implementing kqueue support is left as
1323	reader). Inotify will be used to give hints only and should not change the	1930	an exercise for the reader. Note, however, that the author sees no way
1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1931	of implementing C<ev_stat> semantics with kqueue).
1325	to fall back to regular polling again even with inotify, but changes are	1932
1326	usually detected immediately, and if the file exists there will be no	1933	=head3 ABI Issues (Largefile Support)
1327	polling.	1934
		1935	Libev by default (unless the user overrides this) uses the default
		1936	compilation environment, which means that on systems with large file
		1937	support disabled by default, you get the 32 bit version of the stat
		1938	structure. When using the library from programs that change the ABI to
		1939	use 64 bit file offsets the programs will fail. In that case you have to
		1940	compile libev with the same flags to get binary compatibility. This is
		1941	obviously the case with any flags that change the ABI, but the problem is
		1942	most noticeably disabled with ev_stat and large file support.
		1943
		1944	The solution for this is to lobby your distribution maker to make large
		1945	file interfaces available by default (as e.g. FreeBSD does) and not
		1946	optional. Libev cannot simply switch on large file support because it has
		1947	to exchange stat structures with application programs compiled using the
		1948	default compilation environment.
		1949
		1950	=head3 Inotify and Kqueue
		1951
		1952	When C<inotify (7)> support has been compiled into libev (generally
		1953	only available with Linux 2.6.25 or above due to bugs in earlier
		1954	implementations) and present at runtime, it will be used to speed up
		1955	change detection where possible. The inotify descriptor will be created
		1956	lazily when the first C<ev_stat> watcher is being started.
		1957
		1958	Inotify presence does not change the semantics of C<ev_stat> watchers
		1959	except that changes might be detected earlier, and in some cases, to avoid
		1960	making regular C<stat> calls. Even in the presence of inotify support
		1961	there are many cases where libev has to resort to regular C<stat> polling,
		1962	but as long as the path exists, libev usually gets away without polling.
		1963
		1964	There is no support for kqueue, as apparently it cannot be used to
		1965	implement this functionality, due to the requirement of having a file
		1966	descriptor open on the object at all times, and detecting renames, unlinks
		1967	etc. is difficult.
		1968
		1969	=head3 The special problem of stat time resolution
		1970
		1971	The C<stat ()> system call only supports full-second resolution portably, and
		1972	even on systems where the resolution is higher, most file systems still
		1973	only support whole seconds.
		1974
		1975	That means that, if the time is the only thing that changes, you can
		1976	easily miss updates: on the first update, C<ev_stat> detects a change and
		1977	calls your callback, which does something. When there is another update
		1978	within the same second, C<ev_stat> will be unable to detect unless the
		1979	stat data does change in other ways (e.g. file size).
		1980
		1981	The solution to this is to delay acting on a change for slightly more
		1982	than a second (or till slightly after the next full second boundary), using
		1983	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		1984	ev_timer_again (loop, w)>).
		1985
		1986	The C<.02> offset is added to work around small timing inconsistencies
		1987	of some operating systems (where the second counter of the current time
		1988	might be be delayed. One such system is the Linux kernel, where a call to
		1989	C<gettimeofday> might return a timestamp with a full second later than
		1990	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		1991	update file times then there will be a small window where the kernel uses
		1992	the previous second to update file times but libev might already execute
		1993	the timer callback).
		1994
		1995	=head3 Watcher-Specific Functions and Data Members
1328		1996
1329	=over 4	1997	=over 4
1330		1998
1331	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1999	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1332		2000
…		…
1336	C<path>. The C<interval> is a hint on how quickly a change is expected to	2004	C<path>. The C<interval> is a hint on how quickly a change is expected to
1337	be detected and should normally be specified as C<0> to let libev choose	2005	be detected and should normally be specified as C<0> to let libev choose
1338	a suitable value. The memory pointed to by C<path> must point to the same	2006	a suitable value. The memory pointed to by C<path> must point to the same
1339	path for as long as the watcher is active.	2007	path for as long as the watcher is active.
1340		2008
1341	The callback will be receive C<EV_STAT> when a change was detected,	2009	The callback will receive an C<EV_STAT> event when a change was detected,
1342	relative to the attributes at the time the watcher was started (or the	2010	relative to the attributes at the time the watcher was started (or the
1343	last change was detected).	2011	last change was detected).
1344		2012
1345	=item ev_stat_stat (ev_stat *)	2013	=item ev_stat_stat (loop, ev_stat *)
1346		2014
1347	Updates the stat buffer immediately with new values. If you change the	2015	Updates the stat buffer immediately with new values. If you change the
1348	watched path in your callback, you could call this fucntion to avoid	2016	watched path in your callback, you could call this function to avoid
1349	detecting this change (while introducing a race condition). Can also be	2017	detecting this change (while introducing a race condition if you are not
1350	useful simply to find out the new values.	2018	the only one changing the path). Can also be useful simply to find out the
		2019	new values.
1351		2020
1352	=item ev_statdata attr [read-only]	2021	=item ev_statdata attr [read-only]
1353		2022
1354	The most-recently detected attributes of the file. Although the type is of	2023	The most-recently detected attributes of the file. Although the type is
1355	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2024	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1356	suitable for your system. If the C<st_nlink> member is C<0>, then there	2025	suitable for your system, but you can only rely on the POSIX-standardised
		2026	members to be present. If the C<st_nlink> member is C<0>, then there was
1357	was some error while C<stat>ing the file.	2027	some error while C<stat>ing the file.
1358		2028
1359	=item ev_statdata prev [read-only]	2029	=item ev_statdata prev [read-only]
1360		2030
1361	The previous attributes of the file. The callback gets invoked whenever	2031	The previous attributes of the file. The callback gets invoked whenever
1362	C<prev> != C<attr>.	2032	C<prev> != C<attr>, or, more precisely, one or more of these members
		2033	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2034	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1363		2035
1364	=item ev_tstamp interval [read-only]	2036	=item ev_tstamp interval [read-only]
1365		2037
1366	The specified interval.	2038	The specified interval.
1367		2039
1368	=item const char *path [read-only]	2040	=item const char *path [read-only]
1369		2041
1370	The filesystem path that is being watched.	2042	The file system path that is being watched.
1371		2043
1372	=back	2044	=back
1373		2045
		2046	=head3 Examples
		2047
1374	Example: Watch C</etc/passwd> for attribute changes.	2048	Example: Watch C</etc/passwd> for attribute changes.
1375		2049
1376	static void	2050	static void
1377	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2051	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1378	{	2052	{
1379	/* /etc/passwd changed in some way */	2053	/* /etc/passwd changed in some way */
1380	if (w->attr.st_nlink)	2054	if (w->attr.st_nlink)
1381	{	2055	{
1382	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2056	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1383	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2057	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1384	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2058	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1385	}	2059	}
1386	else	2060	else
1387	/* you shalt not abuse printf for puts */	2061	/* you shalt not abuse printf for puts */
1388	puts ("wow, /etc/passwd is not there, expect problems. "	2062	puts ("wow, /etc/passwd is not there, expect problems. "
1389	"if this is windows, they already arrived\n");	2063	"if this is windows, they already arrived\n");
1390	}	2064	}
1391		2065
1392	...	2066	...
1393	ev_stat passwd;	2067	ev_stat passwd;
1394		2068
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2069	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	2070	ev_stat_start (loop, &passwd);
		2071
		2072	Example: Like above, but additionally use a one-second delay so we do not
		2073	miss updates (however, frequent updates will delay processing, too, so
		2074	one might do the work both on C<ev_stat> callback invocation I<and> on
		2075	C<ev_timer> callback invocation).
		2076
		2077	static ev_stat passwd;
		2078	static ev_timer timer;
		2079
		2080	static void
		2081	timer_cb (EV_P_ ev_timer *w, int revents)
		2082	{
		2083	ev_timer_stop (EV_A_ w);
		2084
		2085	/* now it's one second after the most recent passwd change */
		2086	}
		2087
		2088	static void
		2089	stat_cb (EV_P_ ev_stat *w, int revents)
		2090	{
		2091	/* reset the one-second timer */
		2092	ev_timer_again (EV_A_ &timer);
		2093	}
		2094
		2095	...
		2096	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2097	ev_stat_start (loop, &passwd);
		2098	ev_timer_init (&timer, timer_cb, 0., 1.02);
1397		2099
1398		2100
1399	=head2 C<ev_idle> - when you've got nothing better to do...	2101	=head2 C<ev_idle> - when you've got nothing better to do...
1400		2102
1401	Idle watchers trigger events when no other events of the same or higher	2103	Idle watchers trigger events when no other events of the same or higher
1402	priority are pending (prepare, check and other idle watchers do not	2104	priority are pending (prepare, check and other idle watchers do not count
1403	count).	2105	as receiving "events").
1404		2106
1405	That is, as long as your process is busy handling sockets or timeouts	2107	That is, as long as your process is busy handling sockets or timeouts
1406	(or even signals, imagine) of the same or higher priority it will not be	2108	(or even signals, imagine) of the same or higher priority it will not be
1407	triggered. But when your process is idle (or only lower-priority watchers	2109	triggered. But when your process is idle (or only lower-priority watchers
1408	are pending), the idle watchers are being called once per event loop	2110	are pending), the idle watchers are being called once per event loop
…		…
1415	Apart from keeping your process non-blocking (which is a useful	2117	Apart from keeping your process non-blocking (which is a useful
1416	effect on its own sometimes), idle watchers are a good place to do	2118	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	2119	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	2120	event loop has handled all outstanding events.
1419		2121
		2122	=head3 Watcher-Specific Functions and Data Members
		2123
1420	=over 4	2124	=over 4
1421		2125
1422	=item ev_idle_init (ev_signal *, callback)	2126	=item ev_idle_init (ev_signal *, callback)
1423		2127
1424	Initialises and configures the idle watcher - it has no parameters of any	2128	Initialises and configures the idle watcher - it has no parameters of any
1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2129	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	2130	believe me.
1427		2131
1428	=back	2132	=back
1429		2133
		2134	=head3 Examples
		2135
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2136	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	2137	callback, free it. Also, use no error checking, as usual.
1432		2138
1433	static void	2139	static void
1434	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2140	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1435	{	2141	{
1436	free (w);	2142	free (w);
1437	// now do something you wanted to do when the program has	2143	// now do something you wanted to do when the program has
1438	// no longer asnything immediate to do.	2144	// no longer anything immediate to do.
1439	}	2145	}
1440		2146
1441	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2147	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1442	ev_idle_init (idle_watcher, idle_cb);	2148	ev_idle_init (idle_watcher, idle_cb);
1443	ev_idle_start (loop, idle_cb);	2149	ev_idle_start (loop, idle_cb);
1444		2150
1445		2151
1446	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2152	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1447		2153
1448	Prepare and check watchers are usually (but not always) used in tandem:	2154	Prepare and check watchers are usually (but not always) used in pairs:
1449	prepare watchers get invoked before the process blocks and check watchers	2155	prepare watchers get invoked before the process blocks and check watchers
1450	afterwards.	2156	afterwards.
1451		2157
1452	You I<must not> call C<ev_loop> or similar functions that enter	2158	You I<must not> call C<ev_loop> or similar functions that enter
1453	the current event loop from either C<ev_prepare> or C<ev_check>	2159	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1456	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2162	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1457	C<ev_check> so if you have one watcher of each kind they will always be	2163	C<ev_check> so if you have one watcher of each kind they will always be
1458	called in pairs bracketing the blocking call.	2164	called in pairs bracketing the blocking call.
1459		2165
1460	Their main purpose is to integrate other event mechanisms into libev and	2166	Their main purpose is to integrate other event mechanisms into libev and
1461	their use is somewhat advanced. This could be used, for example, to track	2167	their use is somewhat advanced. They could be used, for example, to track
1462	variable changes, implement your own watchers, integrate net-snmp or a	2168	variable changes, implement your own watchers, integrate net-snmp or a
1463	coroutine library and lots more. They are also occasionally useful if	2169	coroutine library and lots more. They are also occasionally useful if
1464	you cache some data and want to flush it before blocking (for example,	2170	you cache some data and want to flush it before blocking (for example,
1465	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2171	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1466	watcher).	2172	watcher).
1467		2173
1468	This is done by examining in each prepare call which file descriptors need	2174	This is done by examining in each prepare call which file descriptors
1469	to be watched by the other library, registering C<ev_io> watchers for	2175	need to be watched by the other library, registering C<ev_io> watchers
1470	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2176	for them and starting an C<ev_timer> watcher for any timeouts (many
1471	provide just this functionality). Then, in the check watcher you check for	2177	libraries provide exactly this functionality). Then, in the check watcher,
1472	any events that occured (by checking the pending status of all watchers	2178	you check for any events that occurred (by checking the pending status
1473	and stopping them) and call back into the library. The I/O and timer	2179	of all watchers and stopping them) and call back into the library. The
1474	callbacks will never actually be called (but must be valid nevertheless,	2180	I/O and timer callbacks will never actually be called (but must be valid
1475	because you never know, you know?).	2181	nevertheless, because you never know, you know?).
1476		2182
1477	As another example, the Perl Coro module uses these hooks to integrate	2183	As another example, the Perl Coro module uses these hooks to integrate
1478	coroutines into libev programs, by yielding to other active coroutines	2184	coroutines into libev programs, by yielding to other active coroutines
1479	during each prepare and only letting the process block if no coroutines	2185	during each prepare and only letting the process block if no coroutines
1480	are ready to run (it's actually more complicated: it only runs coroutines	2186	are ready to run (it's actually more complicated: it only runs coroutines
1481	with priority higher than or equal to the event loop and one coroutine	2187	with priority higher than or equal to the event loop and one coroutine
1482	of lower priority, but only once, using idle watchers to keep the event	2188	of lower priority, but only once, using idle watchers to keep the event
1483	loop from blocking if lower-priority coroutines are active, thus mapping	2189	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	2190	low-priority coroutines to idle/background tasks).
1485		2191
		2192	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		2193	priority, to ensure that they are being run before any other watchers
		2194	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2195
		2196	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
		2197	activate ("feed") events into libev. While libev fully supports this, they
		2198	might get executed before other C<ev_check> watchers did their job. As
		2199	C<ev_check> watchers are often used to embed other (non-libev) event
		2200	loops those other event loops might be in an unusable state until their
		2201	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		2202	others).
		2203
		2204	=head3 Watcher-Specific Functions and Data Members
		2205
1486	=over 4	2206	=over 4
1487		2207
1488	=item ev_prepare_init (ev_prepare *, callback)	2208	=item ev_prepare_init (ev_prepare *, callback)
1489		2209
1490	=item ev_check_init (ev_check *, callback)	2210	=item ev_check_init (ev_check *, callback)
1491		2211
1492	Initialises and configures the prepare or check watcher - they have no	2212	Initialises and configures the prepare or check watcher - they have no
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2213	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1494	macros, but using them is utterly, utterly and completely pointless.	2214	macros, but using them is utterly, utterly, utterly and completely
		2215	pointless.
1495		2216
1496	=back	2217	=back
1497		2218
1498	Example: To include a library such as adns, you would add IO watchers	2219	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	2220
		2221	There are a number of principal ways to embed other event loops or modules
		2222	into libev. Here are some ideas on how to include libadns into libev
		2223	(there is a Perl module named C<EV::ADNS> that does this, which you could
		2224	use as a working example. Another Perl module named C<EV::Glib> embeds a
		2225	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
		2226	Glib event loop).
		2227
		2228	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1500	in a check watcher, destroy them and call into libadns. What follows is	2229	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	2230	is pseudo-code only of course. This requires you to either use a low
		2231	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		2232	the callbacks for the IO/timeout watchers might not have been called yet.
1502		2233
1503	static ev_io iow [nfd];	2234	static ev_io iow [nfd];
1504	static ev_timer tw;	2235	static ev_timer tw;
1505		2236
1506	static void	2237	static void
1507	io_cb (ev_loop *loop, ev_io *w, int revents)	2238	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1508	{	2239	{
1509	// set the relevant poll flags
1510	// could also call adns_processreadable etc. here
1511	struct pollfd *fd = (struct pollfd *)w->data;
1512	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1513	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1514	}	2240	}
1515		2241
1516	// create io watchers for each fd and a timer before blocking	2242	// create io watchers for each fd and a timer before blocking
1517	static void	2243	static void
1518	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2244	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1519	{	2245	{
1520	int timeout = 3600000;	2246	int timeout = 3600000;
1521	struct pollfd fds [nfd];	2247	struct pollfd fds [nfd];
1522	// actual code will need to loop here and realloc etc.	2248	// actual code will need to loop here and realloc etc.
1523	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2249	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1524		2250
1525	/* the callback is illegal, but won't be called as we stop during check */	2251	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	2252	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	2253	ev_timer_start (loop, &tw);
1528		2254
1529	// create on ev_io per pollfd	2255	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	2256	for (int i = 0; i < nfd; ++i)
1531	{	2257	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	2258	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	2259	((fds [i].events & POLLIN ? EV_READ : 0)
1534	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2260	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		2261
1536	fds [i].revents = 0;	2262	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	2263	ev_io_start (loop, iow + i);
1539	}	2264	}
1540	}	2265	}
1541		2266
1542	// stop all watchers after blocking	2267	// stop all watchers after blocking
1543	static void	2268	static void
1544	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2269	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1545	{	2270	{
1546	ev_timer_stop (loop, &tw);	2271	ev_timer_stop (loop, &tw);
1547		2272
1548	for (int i = 0; i < nfd; ++i)	2273	for (int i = 0; i < nfd; ++i)
		2274	{
		2275	// set the relevant poll flags
		2276	// could also call adns_processreadable etc. here
		2277	struct pollfd *fd = fds + i;
		2278	int revents = ev_clear_pending (iow + i);
		2279	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		2280	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		2281
		2282	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	2283	ev_io_stop (loop, iow + i);
		2284	}
1550		2285
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2286	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1552	}	2287	}
		2288
		2289	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		2290	in the prepare watcher and would dispose of the check watcher.
		2291
		2292	Method 3: If the module to be embedded supports explicit event
		2293	notification (libadns does), you can also make use of the actual watcher
		2294	callbacks, and only destroy/create the watchers in the prepare watcher.
		2295
		2296	static void
		2297	timer_cb (EV_P_ ev_timer *w, int revents)
		2298	{
		2299	adns_state ads = (adns_state)w->data;
		2300	update_now (EV_A);
		2301
		2302	adns_processtimeouts (ads, &tv_now);
		2303	}
		2304
		2305	static void
		2306	io_cb (EV_P_ ev_io *w, int revents)
		2307	{
		2308	adns_state ads = (adns_state)w->data;
		2309	update_now (EV_A);
		2310
		2311	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		2312	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		2313	}
		2314
		2315	// do not ever call adns_afterpoll
		2316
		2317	Method 4: Do not use a prepare or check watcher because the module you
		2318	want to embed is not flexible enough to support it. Instead, you can
		2319	override their poll function. The drawback with this solution is that the
		2320	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
		2321	this approach, effectively embedding EV as a client into the horrible
		2322	libglib event loop.
		2323
		2324	static gint
		2325	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		2326	{
		2327	int got_events = 0;
		2328
		2329	for (n = 0; n < nfds; ++n)
		2330	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		2331
		2332	if (timeout >= 0)
		2333	// create/start timer
		2334
		2335	// poll
		2336	ev_loop (EV_A_ 0);
		2337
		2338	// stop timer again
		2339	if (timeout >= 0)
		2340	ev_timer_stop (EV_A_ &to);
		2341
		2342	// stop io watchers again - their callbacks should have set
		2343	for (n = 0; n < nfds; ++n)
		2344	ev_io_stop (EV_A_ iow [n]);
		2345
		2346	return got_events;
		2347	}
1553		2348
1554		2349
1555	=head2 C<ev_embed> - when one backend isn't enough...	2350	=head2 C<ev_embed> - when one backend isn't enough...
1556		2351
1557	This is a rather advanced watcher type that lets you embed one event loop	2352	This is a rather advanced watcher type that lets you embed one event loop
…		…
1563	prioritise I/O.	2358	prioritise I/O.
1564		2359
1565	As an example for a bug workaround, the kqueue backend might only support	2360	As an example for a bug workaround, the kqueue backend might only support
1566	sockets on some platform, so it is unusable as generic backend, but you	2361	sockets on some platform, so it is unusable as generic backend, but you
1567	still want to make use of it because you have many sockets and it scales	2362	still want to make use of it because you have many sockets and it scales
1568	so nicely. In this case, you would create a kqueue-based loop and embed it	2363	so nicely. In this case, you would create a kqueue-based loop and embed
1569	into your default loop (which might use e.g. poll). Overall operation will	2364	it into your default loop (which might use e.g. poll). Overall operation
1570	be a bit slower because first libev has to poll and then call kevent, but	2365	will be a bit slower because first libev has to call C<poll> and then
1571	at least you can use both at what they are best.	2366	C<kevent>, but at least you can use both mechanisms for what they are
		2367	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1572		2368
1573	As for prioritising I/O: rarely you have the case where some fds have	2369	As for prioritising I/O: under rare circumstances you have the case where
1574	to be watched and handled very quickly (with low latency), and even	2370	some fds have to be watched and handled very quickly (with low latency),
1575	priorities and idle watchers might have too much overhead. In this case	2371	and even priorities and idle watchers might have too much overhead. In
1576	you would put all the high priority stuff in one loop and all the rest in	2372	this case you would put all the high priority stuff in one loop and all
1577	a second one, and embed the second one in the first.	2373	the rest in a second one, and embed the second one in the first.
1578		2374
1579	As long as the watcher is active, the callback will be invoked every time	2375	As long as the watcher is active, the callback will be invoked every time
1580	there might be events pending in the embedded loop. The callback must then	2376	there might be events pending in the embedded loop. The callback must then
1581	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2377	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1582	their callbacks (you could also start an idle watcher to give the embedded	2378	their callbacks (you could also start an idle watcher to give the embedded
…		…
1590	interested in that.	2386	interested in that.
1591		2387
1592	Also, there have not currently been made special provisions for forking:	2388	Also, there have not currently been made special provisions for forking:
1593	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2389	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1594	but you will also have to stop and restart any C<ev_embed> watchers	2390	but you will also have to stop and restart any C<ev_embed> watchers
1595	yourself.	2391	yourself - but you can use a fork watcher to handle this automatically,
		2392	and future versions of libev might do just that.
1596		2393
1597	Unfortunately, not all backends are embeddable, only the ones returned by	2394	Unfortunately, not all backends are embeddable: only the ones returned by
1598	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2395	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1599	portable one.	2396	portable one.
1600		2397
1601	So when you want to use this feature you will always have to be prepared	2398	So when you want to use this feature you will always have to be prepared
1602	that you cannot get an embeddable loop. The recommended way to get around	2399	that you cannot get an embeddable loop. The recommended way to get around
1603	this is to have a separate variables for your embeddable loop, try to	2400	this is to have a separate variables for your embeddable loop, try to
1604	create it, and if that fails, use the normal loop for everything:	2401	create it, and if that fails, use the normal loop for everything.
1605		2402
1606	struct ev_loop *loop_hi = ev_default_init (0);	2403	=head3 C<ev_embed> and fork
1607	struct ev_loop *loop_lo = 0;
1608	struct ev_embed embed;
1609
1610	// see if there is a chance of getting one that works
1611	// (remember that a flags value of 0 means autodetection)
1612	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1613	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1614	: 0;
1615		2404
1616	// if we got one, then embed it, otherwise default to loop_hi	2405	While the C<ev_embed> watcher is running, forks in the embedding loop will
1617	if (loop_lo)	2406	automatically be applied to the embedded loop as well, so no special
1618	{	2407	fork handling is required in that case. When the watcher is not running,
1619	ev_embed_init (&embed, 0, loop_lo);	2408	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1620	ev_embed_start (loop_hi, &embed);	2409	as applicable.
1621	}	2410
1622	else	2411	=head3 Watcher-Specific Functions and Data Members
1623	loop_lo = loop_hi;
1624		2412
1625	=over 4	2413	=over 4
1626		2414
1627	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2415	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1628		2416
…		…
1630		2418
1631	Configures the watcher to embed the given loop, which must be	2419	Configures the watcher to embed the given loop, which must be
1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2420	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1633	invoked automatically, otherwise it is the responsibility of the callback	2421	invoked automatically, otherwise it is the responsibility of the callback
1634	to invoke it (it will continue to be called until the sweep has been done,	2422	to invoke it (it will continue to be called until the sweep has been done,
1635	if you do not want thta, you need to temporarily stop the embed watcher).	2423	if you do not want that, you need to temporarily stop the embed watcher).
1636		2424
1637	=item ev_embed_sweep (loop, ev_embed *)	2425	=item ev_embed_sweep (loop, ev_embed *)
1638		2426
1639	Make a single, non-blocking sweep over the embedded loop. This works	2427	Make a single, non-blocking sweep over the embedded loop. This works
1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2428	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.	2429	appropriate way for embedded loops.
1642		2430
1643	=item struct ev_loop *loop [read-only]	2431	=item struct ev_loop *other [read-only]
1644		2432
1645	The embedded event loop.	2433	The embedded event loop.
1646		2434
1647	=back	2435	=back
		2436
		2437	=head3 Examples
		2438
		2439	Example: Try to get an embeddable event loop and embed it into the default
		2440	event loop. If that is not possible, use the default loop. The default
		2441	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2442	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2443	used).
		2444
		2445	struct ev_loop *loop_hi = ev_default_init (0);
		2446	struct ev_loop *loop_lo = 0;
		2447	ev_embed embed;
		2448
		2449	// see if there is a chance of getting one that works
		2450	// (remember that a flags value of 0 means autodetection)
		2451	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2452	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2453	: 0;
		2454
		2455	// if we got one, then embed it, otherwise default to loop_hi
		2456	if (loop_lo)
		2457	{
		2458	ev_embed_init (&embed, 0, loop_lo);
		2459	ev_embed_start (loop_hi, &embed);
		2460	}
		2461	else
		2462	loop_lo = loop_hi;
		2463
		2464	Example: Check if kqueue is available but not recommended and create
		2465	a kqueue backend for use with sockets (which usually work with any
		2466	kqueue implementation). Store the kqueue/socket-only event loop in
		2467	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2468
		2469	struct ev_loop *loop = ev_default_init (0);
		2470	struct ev_loop *loop_socket = 0;
		2471	ev_embed embed;
		2472
		2473	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2474	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2475	{
		2476	ev_embed_init (&embed, 0, loop_socket);
		2477	ev_embed_start (loop, &embed);
		2478	}
		2479
		2480	if (!loop_socket)
		2481	loop_socket = loop;
		2482
		2483	// now use loop_socket for all sockets, and loop for everything else
1648		2484
1649		2485
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2486	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2487
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2488	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1655	event loop blocks next and before C<ev_check> watchers are being called,	2491	event loop blocks next and before C<ev_check> watchers are being called,
1656	and only in the child after the fork. If whoever good citizen calling	2492	and only in the child after the fork. If whoever good citizen calling
1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2493	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2494	handlers will be invoked, too, of course.
1659		2495
		2496	=head3 Watcher-Specific Functions and Data Members
		2497
1660	=over 4	2498	=over 4
1661		2499
1662	=item ev_fork_init (ev_signal *, callback)	2500	=item ev_fork_init (ev_signal *, callback)
1663		2501
1664	Initialises and configures the fork watcher - it has no parameters of any	2502	Initialises and configures the fork watcher - it has no parameters of any
…		…
1666	believe me.	2504	believe me.
1667		2505
1668	=back	2506	=back
1669		2507
1670		2508
		2509	=head2 C<ev_async> - how to wake up another event loop
		2510
		2511	In general, you cannot use an C<ev_loop> from multiple threads or other
		2512	asynchronous sources such as signal handlers (as opposed to multiple event
		2513	loops - those are of course safe to use in different threads).
		2514
		2515	Sometimes, however, you need to wake up another event loop you do not
		2516	control, for example because it belongs to another thread. This is what
		2517	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2518	can signal it by calling C<ev_async_send>, which is thread- and signal
		2519	safe.
		2520
		2521	This functionality is very similar to C<ev_signal> watchers, as signals,
		2522	too, are asynchronous in nature, and signals, too, will be compressed
		2523	(i.e. the number of callback invocations may be less than the number of
		2524	C<ev_async_sent> calls).
		2525
		2526	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2527	just the default loop.
		2528
		2529	=head3 Queueing
		2530
		2531	C<ev_async> does not support queueing of data in any way. The reason
		2532	is that the author does not know of a simple (or any) algorithm for a
		2533	multiple-writer-single-reader queue that works in all cases and doesn't
		2534	need elaborate support such as pthreads.
		2535
		2536	That means that if you want to queue data, you have to provide your own
		2537	queue. But at least I can tell you how to implement locking around your
		2538	queue:
		2539
		2540	=over 4
		2541
		2542	=item queueing from a signal handler context
		2543
		2544	To implement race-free queueing, you simply add to the queue in the signal
		2545	handler but you block the signal handler in the watcher callback. Here is
		2546	an example that does that for some fictitious SIGUSR1 handler:
		2547
		2548	static ev_async mysig;
		2549
		2550	static void
		2551	sigusr1_handler (void)
		2552	{
		2553	sometype data;
		2554
		2555	// no locking etc.
		2556	queue_put (data);
		2557	ev_async_send (EV_DEFAULT_ &mysig);
		2558	}
		2559
		2560	static void
		2561	mysig_cb (EV_P_ ev_async *w, int revents)
		2562	{
		2563	sometype data;
		2564	sigset_t block, prev;
		2565
		2566	sigemptyset (&block);
		2567	sigaddset (&block, SIGUSR1);
		2568	sigprocmask (SIG_BLOCK, &block, &prev);
		2569
		2570	while (queue_get (&data))
		2571	process (data);
		2572
		2573	if (sigismember (&prev, SIGUSR1)
		2574	sigprocmask (SIG_UNBLOCK, &block, 0);
		2575	}
		2576
		2577	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2578	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2579	either...).
		2580
		2581	=item queueing from a thread context
		2582
		2583	The strategy for threads is different, as you cannot (easily) block
		2584	threads but you can easily preempt them, so to queue safely you need to
		2585	employ a traditional mutex lock, such as in this pthread example:
		2586
		2587	static ev_async mysig;
		2588	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2589
		2590	static void
		2591	otherthread (void)
		2592	{
		2593	// only need to lock the actual queueing operation
		2594	pthread_mutex_lock (&mymutex);
		2595	queue_put (data);
		2596	pthread_mutex_unlock (&mymutex);
		2597
		2598	ev_async_send (EV_DEFAULT_ &mysig);
		2599	}
		2600
		2601	static void
		2602	mysig_cb (EV_P_ ev_async *w, int revents)
		2603	{
		2604	pthread_mutex_lock (&mymutex);
		2605
		2606	while (queue_get (&data))
		2607	process (data);
		2608
		2609	pthread_mutex_unlock (&mymutex);
		2610	}
		2611
		2612	=back
		2613
		2614
		2615	=head3 Watcher-Specific Functions and Data Members
		2616
		2617	=over 4
		2618
		2619	=item ev_async_init (ev_async *, callback)
		2620
		2621	Initialises and configures the async watcher - it has no parameters of any
		2622	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2623	trust me.
		2624
		2625	=item ev_async_send (loop, ev_async *)
		2626
		2627	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2628	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2629	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2630	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2631	section below on what exactly this means).
		2632
		2633	This call incurs the overhead of a system call only once per loop iteration,
		2634	so while the overhead might be noticeable, it doesn't apply to repeated
		2635	calls to C<ev_async_send>.
		2636
		2637	=item bool = ev_async_pending (ev_async *)
		2638
		2639	Returns a non-zero value when C<ev_async_send> has been called on the
		2640	watcher but the event has not yet been processed (or even noted) by the
		2641	event loop.
		2642
		2643	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2644	the loop iterates next and checks for the watcher to have become active,
		2645	it will reset the flag again. C<ev_async_pending> can be used to very
		2646	quickly check whether invoking the loop might be a good idea.
		2647
		2648	Not that this does I<not> check whether the watcher itself is pending, only
		2649	whether it has been requested to make this watcher pending.
		2650
		2651	=back
		2652
		2653
1671	=head1 OTHER FUNCTIONS	2654	=head1 OTHER FUNCTIONS
1672		2655
1673	There are some other functions of possible interest. Described. Here. Now.	2656	There are some other functions of possible interest. Described. Here. Now.
1674		2657
1675	=over 4	2658	=over 4
1676		2659
1677	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2660	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1678		2661
1679	This function combines a simple timer and an I/O watcher, calls your	2662	This function combines a simple timer and an I/O watcher, calls your
1680	callback on whichever event happens first and automatically stop both	2663	callback on whichever event happens first and automatically stops both
1681	watchers. This is useful if you want to wait for a single event on an fd	2664	watchers. This is useful if you want to wait for a single event on an fd
1682	or timeout without having to allocate/configure/start/stop/free one or	2665	or timeout without having to allocate/configure/start/stop/free one or
1683	more watchers yourself.	2666	more watchers yourself.
1684		2667
1685	If C<fd> is less than 0, then no I/O watcher will be started and events	2668	If C<fd> is less than 0, then no I/O watcher will be started and the
1686	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2669	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1687	C<events> set will be craeted and started.	2670	the given C<fd> and C<events> set will be created and started.
1688		2671
1689	If C<timeout> is less than 0, then no timeout watcher will be	2672	If C<timeout> is less than 0, then no timeout watcher will be
1690	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2673	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1691	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2674	repeat = 0) will be started. C<0> is a valid timeout.
1692	dubious value.
1693		2675
1694	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2676	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1695	passed an C<revents> set like normal event callbacks (a combination of	2677	passed an C<revents> set like normal event callbacks (a combination of
1696	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2678	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1697	value passed to C<ev_once>:	2679	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2680	a timeout and an io event at the same time - you probably should give io
		2681	events precedence.
1698		2682
		2683	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2684
1699	static void stdin_ready (int revents, void *arg)	2685	static void stdin_ready (int revents, void *arg)
1700	{	2686	{
1701	if (revents & EV_TIMEOUT)
1702	/* doh, nothing entered */;
1703	else if (revents & EV_READ)	2687	if (revents & EV_READ)
1704	/* stdin might have data for us, joy! */;	2688	/* stdin might have data for us, joy! */;
		2689	else if (revents & EV_TIMEOUT)
		2690	/* doh, nothing entered */;
1705	}	2691	}
1706		2692
1707	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2693	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1708		2694
1709	=item ev_feed_event (ev_loop *, watcher *, int revents)	2695	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1710		2696
1711	Feeds the given event set into the event loop, as if the specified event	2697	Feeds the given event set into the event loop, as if the specified event
1712	had happened for the specified watcher (which must be a pointer to an	2698	had happened for the specified watcher (which must be a pointer to an
1713	initialised but not necessarily started event watcher).	2699	initialised but not necessarily started event watcher).
1714		2700
1715	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2701	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1716		2702
1717	Feed an event on the given fd, as if a file descriptor backend detected	2703	Feed an event on the given fd, as if a file descriptor backend detected
1718	the given events it.	2704	the given events it.
1719		2705
1720	=item ev_feed_signal_event (ev_loop *loop, int signum)	2706	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1721		2707
1722	Feed an event as if the given signal occured (C<loop> must be the default	2708	Feed an event as if the given signal occurred (C<loop> must be the default
1723	loop!).	2709	loop!).
1724		2710
1725	=back	2711	=back
1726		2712
1727		2713
…		…
1743		2729
1744	=item * Priorities are not currently supported. Initialising priorities	2730	=item * Priorities are not currently supported. Initialising priorities
1745	will fail and all watchers will have the same priority, even though there	2731	will fail and all watchers will have the same priority, even though there
1746	is an ev_pri field.	2732	is an ev_pri field.
1747		2733
		2734	=item * In libevent, the last base created gets the signals, in libev, the
		2735	first base created (== the default loop) gets the signals.
		2736
1748	=item * Other members are not supported.	2737	=item * Other members are not supported.
1749		2738
1750	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2739	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1751	to use the libev header file and library.	2740	to use the libev header file and library.
1752		2741
1753	=back	2742	=back
1754		2743
1755	=head1 C++ SUPPORT	2744	=head1 C++ SUPPORT
1756		2745
1757	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2746	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1758	you to use some convinience methods to start/stop watchers and also change	2747	you to use some convenience methods to start/stop watchers and also change
1759	the callback model to a model using method callbacks on objects.	2748	the callback model to a model using method callbacks on objects.
1760		2749
1761	To use it,	2750	To use it,
1762		2751
1763	#include <ev++.h>	2752	#include <ev++.h>
1764		2753
1765	This automatically includes F<ev.h> and puts all of its definitions (many	2754	This automatically includes F<ev.h> and puts all of its definitions (many
1766	of them macros) into the global namespace. All C++ specific things are	2755	of them macros) into the global namespace. All C++ specific things are
1767	put into the C<ev> namespace. It should support all the same embedding	2756	put into the C<ev> namespace. It should support all the same embedding
1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2757	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1835	your compiler is good :), then the method will be fully inlined into the	2824	your compiler is good :), then the method will be fully inlined into the
1836	thunking function, making it as fast as a direct C callback.	2825	thunking function, making it as fast as a direct C callback.
1837		2826
1838	Example: simple class declaration and watcher initialisation	2827	Example: simple class declaration and watcher initialisation
1839		2828
1840	struct myclass	2829	struct myclass
1841	{	2830	{
1842	void io_cb (ev::io &w, int revents) { }	2831	void io_cb (ev::io &w, int revents) { }
1843	}	2832	}
1844		2833
1845	myclass obj;	2834	myclass obj;
1846	ev::io iow;	2835	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2836	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2837
1849	=item w->set (void (*function)(watcher &w, int), void *data = 0)	2838	=item w->set<function> (void *data = 0)
1850		2839
1851	Also sets a callback, but uses a static method or plain function as	2840	Also sets a callback, but uses a static method or plain function as
1852	callback. The optional C<data> argument will be stored in the watcher's	2841	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2842	C<data> member and is free for you to use.
1854		2843
		2844	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2845
1855	See the method-C<set> above for more details.	2846	See the method-C<set> above for more details.
		2847
		2848	Example: Use a plain function as callback.
		2849
		2850	static void io_cb (ev::io &w, int revents) { }
		2851	iow.set <io_cb> ();
1856		2852
1857	=item w->set (struct ev_loop *)	2853	=item w->set (struct ev_loop *)
1858		2854
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2855	Associates a different C<struct ev_loop> with this watcher. You can only
1860	do this when the watcher is inactive (and not pending either).	2856	do this when the watcher is inactive (and not pending either).
1861		2857
1862	=item w->set ([args])	2858	=item w->set ([arguments])
1863		2859
1864	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2860	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
1865	called at least once. Unlike the C counterpart, an active watcher gets	2861	called at least once. Unlike the C counterpart, an active watcher gets
1866	automatically stopped and restarted when reconfiguring it with this	2862	automatically stopped and restarted when reconfiguring it with this
1867	method.	2863	method.
1868		2864
1869	=item w->start ()	2865	=item w->start ()
…		…
1873		2869
1874	=item w->stop ()	2870	=item w->stop ()
1875		2871
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2872	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2873
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2874	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2875
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2876	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2877	C<ev_TYPE_again> function.
1882		2878
1883	=item w->sweep () C<ev::embed> only	2879	=item w->sweep () (C<ev::embed> only)
1884		2880
1885	Invokes C<ev_embed_sweep>.	2881	Invokes C<ev_embed_sweep>.
1886		2882
1887	=item w->update () C<ev::stat> only	2883	=item w->update () (C<ev::stat> only)
1888		2884
1889	Invokes C<ev_stat_stat>.	2885	Invokes C<ev_stat_stat>.
1890		2886
1891	=back	2887	=back
1892		2888
1893	=back	2889	=back
1894		2890
1895	Example: Define a class with an IO and idle watcher, start one of them in	2891	Example: Define a class with an IO and idle watcher, start one of them in
1896	the constructor.	2892	the constructor.
1897		2893
1898	class myclass	2894	class myclass
1899	{	2895	{
1900	ev_io io; void io_cb (ev::io &w, int revents);	2896	ev::io io ; void io_cb (ev::io &w, int revents);
1901	ev_idle idle void idle_cb (ev::idle &w, int revents);	2897	ev::idle idle; void idle_cb (ev::idle &w, int revents);
1902		2898
1903	myclass ();	2899	myclass (int fd)
1904	}	2900	{
1905
1906	myclass::myclass (int fd)
1907	{
1908	io .set <myclass, &myclass::io_cb > (this);	2901	io .set <myclass, &myclass::io_cb > (this);
1909	idle.set <myclass, &myclass::idle_cb> (this);	2902	idle.set <myclass, &myclass::idle_cb> (this);
1910		2903
1911	io.start (fd, ev::READ);	2904	io.start (fd, ev::READ);
		2905	}
1912	}	2906	};
		2907
		2908
		2909	=head1 OTHER LANGUAGE BINDINGS
		2910
		2911	Libev does not offer other language bindings itself, but bindings for a
		2912	number of languages exist in the form of third-party packages. If you know
		2913	any interesting language binding in addition to the ones listed here, drop
		2914	me a note.
		2915
		2916	=over 4
		2917
		2918	=item Perl
		2919
		2920	The EV module implements the full libev API and is actually used to test
		2921	libev. EV is developed together with libev. Apart from the EV core module,
		2922	there are additional modules that implement libev-compatible interfaces
		2923	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2924	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2925	and C<EV::Glib>).
		2926
		2927	It can be found and installed via CPAN, its homepage is at
		2928	L<http://software.schmorp.de/pkg/EV>.
		2929
		2930	=item Python
		2931
		2932	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2933	seems to be quite complete and well-documented. Note, however, that the
		2934	patch they require for libev is outright dangerous as it breaks the ABI
		2935	for everybody else, and therefore, should never be applied in an installed
		2936	libev (if python requires an incompatible ABI then it needs to embed
		2937	libev).
		2938
		2939	=item Ruby
		2940
		2941	Tony Arcieri has written a ruby extension that offers access to a subset
		2942	of the libev API and adds file handle abstractions, asynchronous DNS and
		2943	more on top of it. It can be found via gem servers. Its homepage is at
		2944	L<http://rev.rubyforge.org/>.
		2945
		2946	=item D
		2947
		2948	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		2949	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2950
		2951	=back
1913		2952
1914		2953
1915	=head1 MACRO MAGIC	2954	=head1 MACRO MAGIC
1916		2955
1917	Libev can be compiled with a variety of options, the most fundemantal is	2956	Libev can be compiled with a variety of options, the most fundamental
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2957	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2958	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2959
1921	To make it easier to write programs that cope with either variant, the	2960	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2961	following macros are defined:
1923		2962
1924	=over 4	2963	=over 4
…		…
1927		2966
1928	This provides the loop I<argument> for functions, if one is required ("ev	2967	This provides the loop I<argument> for functions, if one is required ("ev
1929	loop argument"). The C<EV_A> form is used when this is the sole argument,	2968	loop argument"). The C<EV_A> form is used when this is the sole argument,
1930	C<EV_A_> is used when other arguments are following. Example:	2969	C<EV_A_> is used when other arguments are following. Example:
1931		2970
1932	ev_unref (EV_A);	2971	ev_unref (EV_A);
1933	ev_timer_add (EV_A_ watcher);	2972	ev_timer_add (EV_A_ watcher);
1934	ev_loop (EV_A_ 0);	2973	ev_loop (EV_A_ 0);
1935		2974
1936	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	2975	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1937	which is often provided by the following macro.	2976	which is often provided by the following macro.
1938		2977
1939	=item C<EV_P>, C<EV_P_>	2978	=item C<EV_P>, C<EV_P_>
1940		2979
1941	This provides the loop I<parameter> for functions, if one is required ("ev	2980	This provides the loop I<parameter> for functions, if one is required ("ev
1942	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	2981	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1943	C<EV_P_> is used when other parameters are following. Example:	2982	C<EV_P_> is used when other parameters are following. Example:
1944		2983
1945	// this is how ev_unref is being declared	2984	// this is how ev_unref is being declared
1946	static void ev_unref (EV_P);	2985	static void ev_unref (EV_P);
1947		2986
1948	// this is how you can declare your typical callback	2987	// this is how you can declare your typical callback
1949	static void cb (EV_P_ ev_timer *w, int revents)	2988	static void cb (EV_P_ ev_timer *w, int revents)
1950		2989
1951	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	2990	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1952	suitable for use with C<EV_A>.	2991	suitable for use with C<EV_A>.
1953		2992
1954	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	2993	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1955		2994
1956	Similar to the other two macros, this gives you the value of the default	2995	Similar to the other two macros, this gives you the value of the default
1957	loop, if multiple loops are supported ("ev loop default").	2996	loop, if multiple loops are supported ("ev loop default").
		2997
		2998	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		2999
		3000	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3001	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3002	is undefined when the default loop has not been initialised by a previous
		3003	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3004
		3005	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3006	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
1958		3007
1959	=back	3008	=back
1960		3009
1961	Example: Declare and initialise a check watcher, utilising the above	3010	Example: Declare and initialise a check watcher, utilising the above
1962	macros so it will work regardless of whether multiple loops are supported	3011	macros so it will work regardless of whether multiple loops are supported
1963	or not.	3012	or not.
1964		3013
1965	static void	3014	static void
1966	check_cb (EV_P_ ev_timer *w, int revents)	3015	check_cb (EV_P_ ev_timer *w, int revents)
1967	{	3016	{
1968	ev_check_stop (EV_A_ w);	3017	ev_check_stop (EV_A_ w);
1969	}	3018	}
1970		3019
1971	ev_check check;	3020	ev_check check;
1972	ev_check_init (&check, check_cb);	3021	ev_check_init (&check, check_cb);
1973	ev_check_start (EV_DEFAULT_ &check);	3022	ev_check_start (EV_DEFAULT_ &check);
1974	ev_loop (EV_DEFAULT_ 0);	3023	ev_loop (EV_DEFAULT_ 0);
1975		3024
1976	=head1 EMBEDDING	3025	=head1 EMBEDDING
1977		3026
1978	Libev can (and often is) directly embedded into host	3027	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	3028	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3029	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	3030	and rxvt-unicode.
1982		3031
1983	The goal is to enable you to just copy the neecssary files into your	3032	The goal is to enable you to just copy the necessary files into your
1984	source directory without having to change even a single line in them, so	3033	source directory without having to change even a single line in them, so
1985	you can easily upgrade by simply copying (or having a checked-out copy of	3034	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	3035	libev somewhere in your source tree).
1987		3036
1988	=head2 FILESETS	3037	=head2 FILESETS
1989		3038
1990	Depending on what features you need you need to include one or more sets of files	3039	Depending on what features you need you need to include one or more sets of files
1991	in your app.	3040	in your application.
1992		3041
1993	=head3 CORE EVENT LOOP	3042	=head3 CORE EVENT LOOP
1994		3043
1995	To include only the libev core (all the C<ev_*> functions), with manual	3044	To include only the libev core (all the C<ev_*> functions), with manual
1996	configuration (no autoconf):	3045	configuration (no autoconf):
1997		3046
1998	#define EV_STANDALONE 1	3047	#define EV_STANDALONE 1
1999	#include "ev.c"	3048	#include "ev.c"
2000		3049
2001	This will automatically include F<ev.h>, too, and should be done in a	3050	This will automatically include F<ev.h>, too, and should be done in a
2002	single C source file only to provide the function implementations. To use	3051	single C source file only to provide the function implementations. To use
2003	it, do the same for F<ev.h> in all files wishing to use this API (best	3052	it, do the same for F<ev.h> in all files wishing to use this API (best
2004	done by writing a wrapper around F<ev.h> that you can include instead and	3053	done by writing a wrapper around F<ev.h> that you can include instead and
2005	where you can put other configuration options):	3054	where you can put other configuration options):
2006		3055
2007	#define EV_STANDALONE 1	3056	#define EV_STANDALONE 1
2008	#include "ev.h"	3057	#include "ev.h"
2009		3058
2010	Both header files and implementation files can be compiled with a C++	3059	Both header files and implementation files can be compiled with a C++
2011	compiler (at least, thats a stated goal, and breakage will be treated	3060	compiler (at least, thats a stated goal, and breakage will be treated
2012	as a bug).	3061	as a bug).
2013		3062
2014	You need the following files in your source tree, or in a directory	3063	You need the following files in your source tree, or in a directory
2015	in your include path (e.g. in libev/ when using -Ilibev):	3064	in your include path (e.g. in libev/ when using -Ilibev):
2016		3065
2017	ev.h	3066	ev.h
2018	ev.c	3067	ev.c
2019	ev_vars.h	3068	ev_vars.h
2020	ev_wrap.h	3069	ev_wrap.h
2021		3070
2022	ev_win32.c required on win32 platforms only	3071	ev_win32.c required on win32 platforms only
2023		3072
2024	ev_select.c only when select backend is enabled (which is enabled by default)	3073	ev_select.c only when select backend is enabled (which is enabled by default)
2025	ev_poll.c only when poll backend is enabled (disabled by default)	3074	ev_poll.c only when poll backend is enabled (disabled by default)
2026	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3075	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2027	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3076	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2028	ev_port.c only when the solaris port backend is enabled (disabled by default)	3077	ev_port.c only when the solaris port backend is enabled (disabled by default)
2029		3078
2030	F<ev.c> includes the backend files directly when enabled, so you only need	3079	F<ev.c> includes the backend files directly when enabled, so you only need
2031	to compile this single file.	3080	to compile this single file.
2032		3081
2033	=head3 LIBEVENT COMPATIBILITY API	3082	=head3 LIBEVENT COMPATIBILITY API
2034		3083
2035	To include the libevent compatibility API, also include:	3084	To include the libevent compatibility API, also include:
2036		3085
2037	#include "event.c"	3086	#include "event.c"
2038		3087
2039	in the file including F<ev.c>, and:	3088	in the file including F<ev.c>, and:
2040		3089
2041	#include "event.h"	3090	#include "event.h"
2042		3091
2043	in the files that want to use the libevent API. This also includes F<ev.h>.	3092	in the files that want to use the libevent API. This also includes F<ev.h>.
2044		3093
2045	You need the following additional files for this:	3094	You need the following additional files for this:
2046		3095
2047	event.h	3096	event.h
2048	event.c	3097	event.c
2049		3098
2050	=head3 AUTOCONF SUPPORT	3099	=head3 AUTOCONF SUPPORT
2051		3100
2052	Instead of using C<EV_STANDALONE=1> and providing your config in	3101	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2053	whatever way you want, you can also C<m4_include([libev.m4])> in your	3102	whatever way you want, you can also C<m4_include([libev.m4])> in your
2054	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3103	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2055	include F<config.h> and configure itself accordingly.	3104	include F<config.h> and configure itself accordingly.
2056		3105
2057	For this of course you need the m4 file:	3106	For this of course you need the m4 file:
2058		3107
2059	libev.m4	3108	libev.m4
2060		3109
2061	=head2 PREPROCESSOR SYMBOLS/MACROS	3110	=head2 PREPROCESSOR SYMBOLS/MACROS
2062		3111
2063	Libev can be configured via a variety of preprocessor symbols you have to define	3112	Libev can be configured via a variety of preprocessor symbols you have to
2064	before including any of its files. The default is not to build for multiplicity	3113	define before including any of its files. The default in the absence of
2065	and only include the select backend.	3114	autoconf is documented for every option.
2066		3115
2067	=over 4	3116	=over 4
2068		3117
2069	=item EV_STANDALONE	3118	=item EV_STANDALONE
2070		3119
…		…
2075	F<event.h> that are not directly supported by the libev core alone.	3124	F<event.h> that are not directly supported by the libev core alone.
2076		3125
2077	=item EV_USE_MONOTONIC	3126	=item EV_USE_MONOTONIC
2078		3127
2079	If defined to be C<1>, libev will try to detect the availability of the	3128	If defined to be C<1>, libev will try to detect the availability of the
2080	monotonic clock option at both compiletime and runtime. Otherwise no use	3129	monotonic clock option at both compile time and runtime. Otherwise no use
2081	of the monotonic clock option will be attempted. If you enable this, you	3130	of the monotonic clock option will be attempted. If you enable this, you
2082	usually have to link against librt or something similar. Enabling it when	3131	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	3132	the functionality isn't available is safe, though, although you have
2084	to make sure you link against any libraries where the C<clock_gettime>	3133	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	3134	function is hiding in (often F<-lrt>).
2086		3135
2087	=item EV_USE_REALTIME	3136	=item EV_USE_REALTIME
2088		3137
2089	If defined to be C<1>, libev will try to detect the availability of the	3138	If defined to be C<1>, libev will try to detect the availability of the
2090	realtime clock option at compiletime (and assume its availability at	3139	real-time clock option at compile time (and assume its availability at
2091	runtime if successful). Otherwise no use of the realtime clock option will	3140	runtime if successful). Otherwise no use of the real-time clock option will
2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3141	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3142	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	3143	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3144
		3145	=item EV_USE_NANOSLEEP
		3146
		3147	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3148	and will use it for delays. Otherwise it will use C<select ()>.
		3149
		3150	=item EV_USE_EVENTFD
		3151
		3152	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3153	available and will probe for kernel support at runtime. This will improve
		3154	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3155	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3156	2.7 or newer, otherwise disabled.
2095		3157
2096	=item EV_USE_SELECT	3158	=item EV_USE_SELECT
2097		3159
2098	If undefined or defined to be C<1>, libev will compile in support for the	3160	If undefined or defined to be C<1>, libev will compile in support for the
2099	C<select>(2) backend. No attempt at autodetection will be done: if no	3161	C<select>(2) backend. No attempt at auto-detection will be done: if no
2100	other method takes over, select will be it. Otherwise the select backend	3162	other method takes over, select will be it. Otherwise the select backend
2101	will not be compiled in.	3163	will not be compiled in.
2102		3164
2103	=item EV_SELECT_USE_FD_SET	3165	=item EV_SELECT_USE_FD_SET
2104		3166
2105	If defined to C<1>, then the select backend will use the system C<fd_set>	3167	If defined to C<1>, then the select backend will use the system C<fd_set>
2106	structure. This is useful if libev doesn't compile due to a missing	3168	structure. This is useful if libev doesn't compile due to a missing
2107	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3169	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on
2108	exotic systems. This usually limits the range of file descriptors to some	3170	exotic systems. This usually limits the range of file descriptors to some
2109	low limit such as 1024 or might have other limitations (winsocket only	3171	low limit such as 1024 or might have other limitations (winsocket only
2110	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3172	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
2111	influence the size of the C<fd_set> used.	3173	influence the size of the C<fd_set> used.
2112		3174
…		…
2118	be used is the winsock select). This means that it will call	3180	be used is the winsock select). This means that it will call
2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3181	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2120	it is assumed that all these functions actually work on fds, even	3182	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	3183	on win32. Should not be defined on non-win32 platforms.
2122		3184
		3185	=item EV_FD_TO_WIN32_HANDLE
		3186
		3187	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3188	file descriptors to socket handles. When not defining this symbol (the
		3189	default), then libev will call C<_get_osfhandle>, which is usually
		3190	correct. In some cases, programs use their own file descriptor management,
		3191	in which case they can provide this function to map fds to socket handles.
		3192
2123	=item EV_USE_POLL	3193	=item EV_USE_POLL
2124		3194
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3195	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2126	backend. Otherwise it will be enabled on non-win32 platforms. It	3196	backend. Otherwise it will be enabled on non-win32 platforms. It
2127	takes precedence over select.	3197	takes precedence over select.
2128		3198
2129	=item EV_USE_EPOLL	3199	=item EV_USE_EPOLL
2130		3200
2131	If defined to be C<1>, libev will compile in support for the Linux	3201	If defined to be C<1>, libev will compile in support for the Linux
2132	C<epoll>(7) backend. Its availability will be detected at runtime,	3202	C<epoll>(7) backend. Its availability will be detected at runtime,
2133	otherwise another method will be used as fallback. This is the	3203	otherwise another method will be used as fallback. This is the preferred
2134	preferred backend for GNU/Linux systems.	3204	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3205	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2135		3206
2136	=item EV_USE_KQUEUE	3207	=item EV_USE_KQUEUE
2137		3208
2138	If defined to be C<1>, libev will compile in support for the BSD style	3209	If defined to be C<1>, libev will compile in support for the BSD style
2139	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3210	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2152	otherwise another method will be used as fallback. This is the preferred	3223	otherwise another method will be used as fallback. This is the preferred
2153	backend for Solaris 10 systems.	3224	backend for Solaris 10 systems.
2154		3225
2155	=item EV_USE_DEVPOLL	3226	=item EV_USE_DEVPOLL
2156		3227
2157	reserved for future expansion, works like the USE symbols above.	3228	Reserved for future expansion, works like the USE symbols above.
2158		3229
2159	=item EV_USE_INOTIFY	3230	=item EV_USE_INOTIFY
2160		3231
2161	If defined to be C<1>, libev will compile in support for the Linux inotify	3232	If defined to be C<1>, libev will compile in support for the Linux inotify
2162	interface to speed up C<ev_stat> watchers. Its actual availability will	3233	interface to speed up C<ev_stat> watchers. Its actual availability will
2163	be detected at runtime.	3234	be detected at runtime. If undefined, it will be enabled if the headers
		3235	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3236
		3237	=item EV_ATOMIC_T
		3238
		3239	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3240	access is atomic with respect to other threads or signal contexts. No such
		3241	type is easily found in the C language, so you can provide your own type
		3242	that you know is safe for your purposes. It is used both for signal handler "locking"
		3243	as well as for signal and thread safety in C<ev_async> watchers.
		3244
		3245	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3246	(from F<signal.h>), which is usually good enough on most platforms.
2164		3247
2165	=item EV_H	3248	=item EV_H
2166		3249
2167	The name of the F<ev.h> header file used to include it. The default if	3250	The name of the F<ev.h> header file used to include it. The default if
2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3251	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3252	used to virtually rename the F<ev.h> header file in case of conflicts.
2170		3253
2171	=item EV_CONFIG_H	3254	=item EV_CONFIG_H
2172		3255
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3256	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3257	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	3258	C<EV_H>, above.
2176		3259
2177	=item EV_EVENT_H	3260	=item EV_EVENT_H
2178		3261
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3262	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2180	of how the F<event.h> header can be found.	3263	of how the F<event.h> header can be found, the default is C<"event.h">.
2181		3264
2182	=item EV_PROTOTYPES	3265	=item EV_PROTOTYPES
2183		3266
2184	If defined to be C<0>, then F<ev.h> will not define any function	3267	If defined to be C<0>, then F<ev.h> will not define any function
2185	prototypes, but still define all the structs and other symbols. This is	3268	prototypes, but still define all the structs and other symbols. This is
…		…
2206	When doing priority-based operations, libev usually has to linearly search	3289	When doing priority-based operations, libev usually has to linearly search
2207	all the priorities, so having many of them (hundreds) uses a lot of space	3290	all the priorities, so having many of them (hundreds) uses a lot of space
2208	and time, so using the defaults of five priorities (-2 .. +2) is usually	3291	and time, so using the defaults of five priorities (-2 .. +2) is usually
2209	fine.	3292	fine.
2210		3293
2211	If your embedding app does not need any priorities, defining these both to	3294	If your embedding application does not need any priorities, defining these
2212	C<0> will save some memory and cpu.	3295	both to C<0> will save some memory and CPU.
2213		3296
2214	=item EV_PERIODIC_ENABLE	3297	=item EV_PERIODIC_ENABLE
2215		3298
2216	If undefined or defined to be C<1>, then periodic timers are supported. If	3299	If undefined or defined to be C<1>, then periodic timers are supported. If
2217	defined to be C<0>, then they are not. Disabling them saves a few kB of	3300	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2224	code.	3307	code.
2225		3308
2226	=item EV_EMBED_ENABLE	3309	=item EV_EMBED_ENABLE
2227		3310
2228	If undefined or defined to be C<1>, then embed watchers are supported. If	3311	If undefined or defined to be C<1>, then embed watchers are supported. If
2229	defined to be C<0>, then they are not.	3312	defined to be C<0>, then they are not. Embed watchers rely on most other
		3313	watcher types, which therefore must not be disabled.
2230		3314
2231	=item EV_STAT_ENABLE	3315	=item EV_STAT_ENABLE
2232		3316
2233	If undefined or defined to be C<1>, then stat watchers are supported. If	3317	If undefined or defined to be C<1>, then stat watchers are supported. If
2234	defined to be C<0>, then they are not.	3318	defined to be C<0>, then they are not.
…		…
2236	=item EV_FORK_ENABLE	3320	=item EV_FORK_ENABLE
2237		3321
2238	If undefined or defined to be C<1>, then fork watchers are supported. If	3322	If undefined or defined to be C<1>, then fork watchers are supported. If
2239	defined to be C<0>, then they are not.	3323	defined to be C<0>, then they are not.
2240		3324
		3325	=item EV_ASYNC_ENABLE
		3326
		3327	If undefined or defined to be C<1>, then async watchers are supported. If
		3328	defined to be C<0>, then they are not.
		3329
2241	=item EV_MINIMAL	3330	=item EV_MINIMAL
2242		3331
2243	If you need to shave off some kilobytes of code at the expense of some	3332	If you need to shave off some kilobytes of code at the expense of some
2244	speed, define this symbol to C<1>. Currently only used for gcc to override	3333	speed, define this symbol to C<1>. Currently this is used to override some
2245	some inlining decisions, saves roughly 30% codesize of amd64.	3334	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3335	much smaller 2-heap for timer management over the default 4-heap.
2246		3336
2247	=item EV_PID_HASHSIZE	3337	=item EV_PID_HASHSIZE
2248		3338
2249	C<ev_child> watchers use a small hash table to distribute workload by	3339	C<ev_child> watchers use a small hash table to distribute workload by
2250	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3340	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2251	than enough. If you need to manage thousands of children you might want to	3341	than enough. If you need to manage thousands of children you might want to
2252	increase this value (I<must> be a power of two).	3342	increase this value (I<must> be a power of two).
2253		3343
2254	=item EV_INOTIFY_HASHSIZE	3344	=item EV_INOTIFY_HASHSIZE
2255		3345
2256	C<ev_staz> watchers use a small hash table to distribute workload by	3346	C<ev_stat> watchers use a small hash table to distribute workload by
2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3347	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2258	usually more than enough. If you need to manage thousands of C<ev_stat>	3348	usually more than enough. If you need to manage thousands of C<ev_stat>
2259	watchers you might want to increase this value (I<must> be a power of	3349	watchers you might want to increase this value (I<must> be a power of
2260	two).	3350	two).
2261		3351
		3352	=item EV_USE_4HEAP
		3353
		3354	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3355	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3356	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3357	faster performance with many (thousands) of watchers.
		3358
		3359	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3360	(disabled).
		3361
		3362	=item EV_HEAP_CACHE_AT
		3363
		3364	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3365	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3366	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3367	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3368	but avoids random read accesses on heap changes. This improves performance
		3369	noticeably with many (hundreds) of watchers.
		3370
		3371	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3372	(disabled).
		3373
		3374	=item EV_VERIFY
		3375
		3376	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3377	be done: If set to C<0>, no internal verification code will be compiled
		3378	in. If set to C<1>, then verification code will be compiled in, but not
		3379	called. If set to C<2>, then the internal verification code will be
		3380	called once per loop, which can slow down libev. If set to C<3>, then the
		3381	verification code will be called very frequently, which will slow down
		3382	libev considerably.
		3383
		3384	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3385	C<0>.
		3386
2262	=item EV_COMMON	3387	=item EV_COMMON
2263		3388
2264	By default, all watchers have a C<void *data> member. By redefining	3389	By default, all watchers have a C<void *data> member. By redefining
2265	this macro to a something else you can include more and other types of	3390	this macro to a something else you can include more and other types of
2266	members. You have to define it each time you include one of the files,	3391	members. You have to define it each time you include one of the files,
2267	though, and it must be identical each time.	3392	though, and it must be identical each time.
2268		3393
2269	For example, the perl EV module uses something like this:	3394	For example, the perl EV module uses something like this:
2270		3395
2271	#define EV_COMMON \	3396	#define EV_COMMON \
2272	SV *self; /* contains this struct */ \	3397	SV *self; /* contains this struct */ \
2273	SV *cb_sv, *fh /* note no trailing ";" */	3398	SV *cb_sv, *fh /* note no trailing ";" */
2274		3399
2275	=item EV_CB_DECLARE (type)	3400	=item EV_CB_DECLARE (type)
2276		3401
2277	=item EV_CB_INVOKE (watcher, revents)	3402	=item EV_CB_INVOKE (watcher, revents)
2278		3403
2279	=item ev_set_cb (ev, cb)	3404	=item ev_set_cb (ev, cb)
2280		3405
2281	Can be used to change the callback member declaration in each watcher,	3406	Can be used to change the callback member declaration in each watcher,
2282	and the way callbacks are invoked and set. Must expand to a struct member	3407	and the way callbacks are invoked and set. Must expand to a struct member
2283	definition and a statement, respectively. See the F<ev.v> header file for	3408	definition and a statement, respectively. See the F<ev.h> header file for
2284	their default definitions. One possible use for overriding these is to	3409	their default definitions. One possible use for overriding these is to
2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3410	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2286	method calls instead of plain function calls in C++.	3411	method calls instead of plain function calls in C++.
		3412
		3413	=back
		3414
		3415	=head2 EXPORTED API SYMBOLS
		3416
		3417	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3418	exported symbols, you can use the provided F<Symbol.*> files which list
		3419	all public symbols, one per line:
		3420
		3421	Symbols.ev for libev proper
		3422	Symbols.event for the libevent emulation
		3423
		3424	This can also be used to rename all public symbols to avoid clashes with
		3425	multiple versions of libev linked together (which is obviously bad in
		3426	itself, but sometimes it is inconvenient to avoid this).
		3427
		3428	A sed command like this will create wrapper C<#define>'s that you need to
		3429	include before including F<ev.h>:
		3430
		3431	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3432
		3433	This would create a file F<wrap.h> which essentially looks like this:
		3434
		3435	#define ev_backend myprefix_ev_backend
		3436	#define ev_check_start myprefix_ev_check_start
		3437	#define ev_check_stop myprefix_ev_check_stop
		3438	...
2287		3439
2288	=head2 EXAMPLES	3440	=head2 EXAMPLES
2289		3441
2290	For a real-world example of a program the includes libev	3442	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	3443	verbatim, you can have a look at the EV perl module
…		…
2296	file.	3448	file.
2297		3449
2298	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3450	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2299	that everybody includes and which overrides some configure choices:	3451	that everybody includes and which overrides some configure choices:
2300		3452
2301	#define EV_MINIMAL 1	3453	#define EV_MINIMAL 1
2302	#define EV_USE_POLL 0	3454	#define EV_USE_POLL 0
2303	#define EV_MULTIPLICITY 0	3455	#define EV_MULTIPLICITY 0
2304	#define EV_PERIODIC_ENABLE 0	3456	#define EV_PERIODIC_ENABLE 0
2305	#define EV_STAT_ENABLE 0	3457	#define EV_STAT_ENABLE 0
2306	#define EV_FORK_ENABLE 0	3458	#define EV_FORK_ENABLE 0
2307	#define EV_CONFIG_H <config.h>	3459	#define EV_CONFIG_H <config.h>
2308	#define EV_MINPRI 0	3460	#define EV_MINPRI 0
2309	#define EV_MAXPRI 0	3461	#define EV_MAXPRI 0
2310		3462
2311	#include "ev++.h"	3463	#include "ev++.h"
2312		3464
2313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3465	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2314		3466
2315	#include "ev_cpp.h"	3467	#include "ev_cpp.h"
2316	#include "ev.c"	3468	#include "ev.c"
2317		3469
		3470	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2318		3471
		3472	=head2 THREADS AND COROUTINES
		3473
		3474	=head3 THREADS
		3475
		3476	All libev functions are reentrant and thread-safe unless explicitly
		3477	documented otherwise, but libev implements no locking itself. This means
		3478	that you can use as many loops as you want in parallel, as long as there
		3479	are no concurrent calls into any libev function with the same loop
		3480	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3481	of course): libev guarantees that different event loops share no data
		3482	structures that need any locking.
		3483
		3484	Or to put it differently: calls with different loop parameters can be done
		3485	concurrently from multiple threads, calls with the same loop parameter
		3486	must be done serially (but can be done from different threads, as long as
		3487	only one thread ever is inside a call at any point in time, e.g. by using
		3488	a mutex per loop).
		3489
		3490	Specifically to support threads (and signal handlers), libev implements
		3491	so-called C<ev_async> watchers, which allow some limited form of
		3492	concurrency on the same event loop, namely waking it up "from the
		3493	outside".
		3494
		3495	If you want to know which design (one loop, locking, or multiple loops
		3496	without or something else still) is best for your problem, then I cannot
		3497	help you, but here is some generic advice:
		3498
		3499	=over 4
		3500
		3501	=item * most applications have a main thread: use the default libev loop
		3502	in that thread, or create a separate thread running only the default loop.
		3503
		3504	This helps integrating other libraries or software modules that use libev
		3505	themselves and don't care/know about threading.
		3506
		3507	=item * one loop per thread is usually a good model.
		3508
		3509	Doing this is almost never wrong, sometimes a better-performance model
		3510	exists, but it is always a good start.
		3511
		3512	=item * other models exist, such as the leader/follower pattern, where one
		3513	loop is handed through multiple threads in a kind of round-robin fashion.
		3514
		3515	Choosing a model is hard - look around, learn, know that usually you can do
		3516	better than you currently do :-)
		3517
		3518	=item * often you need to talk to some other thread which blocks in the
		3519	event loop.
		3520
		3521	C<ev_async> watchers can be used to wake them up from other threads safely
		3522	(or from signal contexts...).
		3523
		3524	An example use would be to communicate signals or other events that only
		3525	work in the default loop by registering the signal watcher with the
		3526	default loop and triggering an C<ev_async> watcher from the default loop
		3527	watcher callback into the event loop interested in the signal.
		3528
		3529	=back
		3530
		3531	=head3 COROUTINES
		3532
		3533	Libev is very accommodating to coroutines ("cooperative threads"):
		3534	libev fully supports nesting calls to its functions from different
		3535	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3536	different coroutines, and switch freely between both coroutines running the
		3537	loop, as long as you don't confuse yourself). The only exception is that
		3538	you must not do this from C<ev_periodic> reschedule callbacks.
		3539
		3540	Care has been taken to ensure that libev does not keep local state inside
		3541	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3542	they do not clal any callbacks.
		3543
		3544	=head2 COMPILER WARNINGS
		3545
		3546	Depending on your compiler and compiler settings, you might get no or a
		3547	lot of warnings when compiling libev code. Some people are apparently
		3548	scared by this.
		3549
		3550	However, these are unavoidable for many reasons. For one, each compiler
		3551	has different warnings, and each user has different tastes regarding
		3552	warning options. "Warn-free" code therefore cannot be a goal except when
		3553	targeting a specific compiler and compiler-version.
		3554
		3555	Another reason is that some compiler warnings require elaborate
		3556	workarounds, or other changes to the code that make it less clear and less
		3557	maintainable.
		3558
		3559	And of course, some compiler warnings are just plain stupid, or simply
		3560	wrong (because they don't actually warn about the condition their message
		3561	seems to warn about). For example, certain older gcc versions had some
		3562	warnings that resulted an extreme number of false positives. These have
		3563	been fixed, but some people still insist on making code warn-free with
		3564	such buggy versions.
		3565
		3566	While libev is written to generate as few warnings as possible,
		3567	"warn-free" code is not a goal, and it is recommended not to build libev
		3568	with any compiler warnings enabled unless you are prepared to cope with
		3569	them (e.g. by ignoring them). Remember that warnings are just that:
		3570	warnings, not errors, or proof of bugs.
		3571
		3572
		3573	=head2 VALGRIND
		3574
		3575	Valgrind has a special section here because it is a popular tool that is
		3576	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3577
		3578	If you think you found a bug (memory leak, uninitialised data access etc.)
		3579	in libev, then check twice: If valgrind reports something like:
		3580
		3581	==2274== definitely lost: 0 bytes in 0 blocks.
		3582	==2274== possibly lost: 0 bytes in 0 blocks.
		3583	==2274== still reachable: 256 bytes in 1 blocks.
		3584
		3585	Then there is no memory leak, just as memory accounted to global variables
		3586	is not a memleak - the memory is still being refernced, and didn't leak.
		3587
		3588	Similarly, under some circumstances, valgrind might report kernel bugs
		3589	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3590	although an acceptable workaround has been found here), or it might be
		3591	confused.
		3592
		3593	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3594	make it into some kind of religion.
		3595
		3596	If you are unsure about something, feel free to contact the mailing list
		3597	with the full valgrind report and an explanation on why you think this
		3598	is a bug in libev (best check the archives, too :). However, don't be
		3599	annoyed when you get a brisk "this is no bug" answer and take the chance
		3600	of learning how to interpret valgrind properly.
		3601
		3602	If you need, for some reason, empty reports from valgrind for your project
		3603	I suggest using suppression lists.
		3604
		3605
		3606	=head1 PORTABILITY NOTES
		3607
		3608	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3609
		3610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3611	requires, and its I/O model is fundamentally incompatible with the POSIX
		3612	model. Libev still offers limited functionality on this platform in
		3613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3614	descriptors. This only applies when using Win32 natively, not when using
		3615	e.g. cygwin.
		3616
		3617	Lifting these limitations would basically require the full
		3618	re-implementation of the I/O system. If you are into these kinds of
		3619	things, then note that glib does exactly that for you in a very portable
		3620	way (note also that glib is the slowest event library known to man).
		3621
		3622	There is no supported compilation method available on windows except
		3623	embedding it into other applications.
		3624
		3625	Not a libev limitation but worth mentioning: windows apparently doesn't
		3626	accept large writes: instead of resulting in a partial write, windows will
		3627	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3628	so make sure you only write small amounts into your sockets (less than a
		3629	megabyte seems safe, but this apparently depends on the amount of memory
		3630	available).
		3631
		3632	Due to the many, low, and arbitrary limits on the win32 platform and
		3633	the abysmal performance of winsockets, using a large number of sockets
		3634	is not recommended (and not reasonable). If your program needs to use
		3635	more than a hundred or so sockets, then likely it needs to use a totally
		3636	different implementation for windows, as libev offers the POSIX readiness
		3637	notification model, which cannot be implemented efficiently on windows
		3638	(Microsoft monopoly games).
		3639
		3640	A typical way to use libev under windows is to embed it (see the embedding
		3641	section for details) and use the following F<evwrap.h> header file instead
		3642	of F<ev.h>:
		3643
		3644	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3645	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3646
		3647	#include "ev.h"
		3648
		3649	And compile the following F<evwrap.c> file into your project (make sure
		3650	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3651
		3652	#include "evwrap.h"
		3653	#include "ev.c"
		3654
		3655	=over 4
		3656
		3657	=item The winsocket select function
		3658
		3659	The winsocket C<select> function doesn't follow POSIX in that it
		3660	requires socket I<handles> and not socket I<file descriptors> (it is
		3661	also extremely buggy). This makes select very inefficient, and also
		3662	requires a mapping from file descriptors to socket handles (the Microsoft
		3663	C runtime provides the function C<_open_osfhandle> for this). See the
		3664	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3665	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3666
		3667	The configuration for a "naked" win32 using the Microsoft runtime
		3668	libraries and raw winsocket select is:
		3669
		3670	#define EV_USE_SELECT 1
		3671	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3672
		3673	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3674	complexity in the O(n²) range when using win32.
		3675
		3676	=item Limited number of file descriptors
		3677
		3678	Windows has numerous arbitrary (and low) limits on things.
		3679
		3680	Early versions of winsocket's select only supported waiting for a maximum
		3681	of C<64> handles (probably owning to the fact that all windows kernels
		3682	can only wait for C<64> things at the same time internally; Microsoft
		3683	recommends spawning a chain of threads and wait for 63 handles and the
		3684	previous thread in each. Great).
		3685
		3686	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3687	to some high number (e.g. C<2048>) before compiling the winsocket select
		3688	call (which might be in libev or elsewhere, for example, perl does its own
		3689	select emulation on windows).
		3690
		3691	Another limit is the number of file descriptors in the Microsoft runtime
		3692	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3693	or something like this inside Microsoft). You can increase this by calling
		3694	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3695	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3696	libraries.
		3697
		3698	This might get you to about C<512> or C<2048> sockets (depending on
		3699	windows version and/or the phase of the moon). To get more, you need to
		3700	wrap all I/O functions and provide your own fd management, but the cost of
		3701	calling select (O(n²)) will likely make this unworkable.
		3702
		3703	=back
		3704
		3705	=head2 PORTABILITY REQUIREMENTS
		3706
		3707	In addition to a working ISO-C implementation and of course the
		3708	backend-specific APIs, libev relies on a few additional extensions:
		3709
		3710	=over 4
		3711
		3712	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3713	calling conventions regardless of C<ev_watcher_type *>.
		3714
		3715	Libev assumes not only that all watcher pointers have the same internal
		3716	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3717	assumes that the same (machine) code can be used to call any watcher
		3718	callback: The watcher callbacks have different type signatures, but libev
		3719	calls them using an C<ev_watcher *> internally.
		3720
		3721	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3722
		3723	The type C<sig_atomic_t volatile> (or whatever is defined as
		3724	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3725	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3726	believed to be sufficiently portable.
		3727
		3728	=item C<sigprocmask> must work in a threaded environment
		3729
		3730	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3731	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3732	pthread implementations will either allow C<sigprocmask> in the "main
		3733	thread" or will block signals process-wide, both behaviours would
		3734	be compatible with libev. Interaction between C<sigprocmask> and
		3735	C<pthread_sigmask> could complicate things, however.
		3736
		3737	The most portable way to handle signals is to block signals in all threads
		3738	except the initial one, and run the default loop in the initial thread as
		3739	well.
		3740
		3741	=item C<long> must be large enough for common memory allocation sizes
		3742
		3743	To improve portability and simplify its API, libev uses C<long> internally
		3744	instead of C<size_t> when allocating its data structures. On non-POSIX
		3745	systems (Microsoft...) this might be unexpectedly low, but is still at
		3746	least 31 bits everywhere, which is enough for hundreds of millions of
		3747	watchers.
		3748
		3749	=item C<double> must hold a time value in seconds with enough accuracy
		3750
		3751	The type C<double> is used to represent timestamps. It is required to
		3752	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3753	enough for at least into the year 4000. This requirement is fulfilled by
		3754	implementations implementing IEEE 754 (basically all existing ones).
		3755
		3756	=back
		3757
		3758	If you know of other additional requirements drop me a note.
		3759
		3760
2319	=head1 COMPLEXITIES	3761	=head1 ALGORITHMIC COMPLEXITIES
2320		3762
2321	In this section the complexities of (many of) the algorithms used inside	3763	In this section the complexities of (many of) the algorithms used inside
2322	libev will be explained. For complexity discussions about backends see the	3764	libev will be documented. For complexity discussions about backends see
2323	documentation for C<ev_default_init>.	3765	the documentation for C<ev_default_init>.
2324		3766
2325	All of the following are about amortised time: If an array needs to be	3767	All of the following are about amortised time: If an array needs to be
2326	extended, libev needs to realloc and move the whole array, but this	3768	extended, libev needs to realloc and move the whole array, but this
2327	happens asymptotically never with higher number of elements, so O(1) might	3769	happens asymptotically rarer with higher number of elements, so O(1) might
2328	mean it might do a lengthy realloc operation in rare cases, but on average	3770	mean that libev does a lengthy realloc operation in rare cases, but on
2329	it is much faster and asymptotically approaches constant time.	3771	average it is much faster and asymptotically approaches constant time.
2330		3772
2331	=over 4	3773	=over 4
2332		3774
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3775	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		3776
2335	This means that, when you have a watcher that triggers in one hour and	3777	This means that, when you have a watcher that triggers in one hour and
2336	there are 100 watchers that would trigger before that then inserting will	3778	there are 100 watchers that would trigger before that, then inserting will
2337	have to skip those 100 watchers.	3779	have to skip roughly seven (C<ld 100>) of these watchers.
2338		3780
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3781	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		3782
2341	That means that for changing a timer costs less than removing/adding them	3783	That means that changing a timer costs less than removing/adding them,
2342	as only the relative motion in the event queue has to be paid for.	3784	as only the relative motion in the event queue has to be paid for.
2343		3785
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3786	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2345		3787
2346	These just add the watcher into an array or at the head of a list.	3788	These just add the watcher into an array or at the head of a list.
		3789
2347	=item Stopping check/prepare/idle watchers: O(1)	3790	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2348		3791
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3792	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		3793
2351	These watchers are stored in lists then need to be walked to find the	3794	These watchers are stored in lists, so they need to be walked to find the
2352	correct watcher to remove. The lists are usually short (you don't usually	3795	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	3796	have many watchers waiting for the same fd or signal: one is typical, two
		3797	is rare).
2354		3798
2355	=item Finding the next timer per loop iteration: O(1)	3799	=item Finding the next timer in each loop iteration: O(1)
		3800
		3801	By virtue of using a binary or 4-heap, the next timer is always found at a
		3802	fixed position in the storage array.
2356		3803
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3804	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		3805
2359	A change means an I/O watcher gets started or stopped, which requires	3806	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	3807	libev to recalculate its status (and possibly tell the kernel, depending
		3808	on backend and whether C<ev_io_set> was used).
2361		3809
2362	=item Activating one watcher: O(1)	3810	=item Activating one watcher (putting it into the pending state): O(1)
2363		3811
2364	=item Priority handling: O(number_of_priorities)	3812	=item Priority handling: O(number_of_priorities)
2365		3813
2366	Priorities are implemented by allocating some space for each	3814	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	3815	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	3816	linearly search all the priorities, but starting/stopping and activating
		3817	watchers becomes O(1) with respect to priority handling.
		3818
		3819	=item Sending an ev_async: O(1)
		3820
		3821	=item Processing ev_async_send: O(number_of_async_watchers)
		3822
		3823	=item Processing signals: O(max_signal_number)
		3824
		3825	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3826	calls in the current loop iteration. Checking for async and signal events
		3827	involves iterating over all running async watchers or all signal numbers.
2369		3828
2370	=back	3829	=back
2371		3830
2372		3831
2373	=head1 AUTHOR	3832	=head1 AUTHOR

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