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Revision 1.84 by root, Wed Dec 12 22:26:37 2007 UTC vs.
Revision 1.220 by root, Thu Nov 20 11:25:15 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	#include <stdio.h> // for puts
		15
		16	// every watcher type has its own typedef'd struct
		17	// with the name ev_TYPE
13	ev_io stdin_watcher;	18	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
15		20
16	/* called when data readable on stdin */	21	// all watcher callbacks have a similar signature
		22	// this callback is called when data is readable on stdin
17	static void	23	static void
18	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
19	{	25	{
20	/* puts ("stdin ready"); */	26	puts ("stdin ready");
21	ev_io_stop (EV_A_ w); /* just a syntax example */	27	// for one-shot events, one must manually stop the watcher
22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */	28	// with its corresponding stop function.
		29	ev_io_stop (EV_A_ w);
		30
		31	// this causes all nested ev_loop's to stop iterating
		32	ev_unloop (EV_A_ EVUNLOOP_ALL);
23	}	33	}
24		34
		35	// another callback, this time for a time-out
25	static void	36	static void
26	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
27	{	38	{
28	/* puts ("timeout"); */	39	puts ("timeout");
29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */	40	// this causes the innermost ev_loop to stop iterating
		41	ev_unloop (EV_A_ EVUNLOOP_ONE);
30	}	42	}
31		43
32	int	44	int
33	main (void)	45	main (void)
34	{	46	{
		47	// use the default event loop unless you have special needs
35	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
36		49
37	/* initialise an io watcher, then start it */	50	// initialise an io watcher, then start it
		51	// this one will watch for stdin to become readable
38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
40		54
		55	// initialise a timer watcher, then start it
41	/* simple non-repeating 5.5 second timeout */	56	// simple non-repeating 5.5 second timeout
42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
44		59
45	/* loop till timeout or data ready */	60	// now wait for events to arrive
46	ev_loop (loop, 0);	61	ev_loop (loop, 0);
47		62
		63	// unloop was called, so exit
48	return 0;	64	return 0;
49	}	65	}
50		66
51	=head1 DESCRIPTION	67	=head1 DESCRIPTION
52		68
53	The newest version of this document is also available as a html-formatted	69	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	70	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
56		72
57	Libev is an event loop: you register interest in certain events (such as a	73	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	74	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	75	these event sources and provide your program with events.
60		76
61	To do this, it must take more or less complete control over your process	77	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	78	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	79	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	81	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	82	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	83	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	84	watcher.
69		85
70	=head1 FEATURES	86	=head2 FEATURES
71		87
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		98
83	It also is quite fast (see this	99	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	101	for example).
86		102
87	=head1 CONVENTIONS	103	=head2 CONVENTIONS
88		104
89	Libev is very configurable. In this manual the default configuration will	105	Libev is very configurable. In this manual the default (and most common)
90	be described, which supports multiple event loops. For more info about	106	configuration will be described, which supports multiple event loops. For
91	various configuration options please have a look at B<EMBED> section in	107	more info about various configuration options please have a look at
92	this manual. If libev was configured without support for multiple event	108	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>	109	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.	110	name C<loop> (which is always of type C<ev_loop *>) will not have
		111	this argument.
95		112
96	=head1 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
97		114
98	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	117	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	118	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	119	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	120	it, you should treat it as some floating point value. Unlike the name
		121	component C<stamp> might indicate, it is also used for time differences
		122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
104		144
105	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
106		146
107	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
108	library in any way.	148	library in any way.
…		…
112	=item ev_tstamp ev_time ()	152	=item ev_tstamp ev_time ()
113		153
114	Returns the current time as libev would use it. Please note that the	154	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	155	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	156	you actually want to know.
		157
		158	=item ev_sleep (ev_tstamp interval)
		159
		160	Sleep for the given interval: The current thread will be blocked until
		161	either it is interrupted or the given time interval has passed. Basically
		162	this is a sub-second-resolution C<sleep ()>.
117		163
118	=item int ev_version_major ()	164	=item int ev_version_major ()
119		165
120	=item int ev_version_minor ()	166	=item int ev_version_minor ()
121		167
…		…
134	not a problem.	180	not a problem.
135		181
136	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
137	version.	183	version.
138		184
139	assert (("libev version mismatch",	185	assert (("libev version mismatch",
140	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
141	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
142		188
143	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
144		190
145	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
146	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
148	a description of the set values.	194	a description of the set values.
149		195
150	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
151	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
152		198
153	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
154	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
155		201
156	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
157		203
158	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
159	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
160	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
161	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
162	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
163	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
164		210
165	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
166		212
…		…
170	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
171	recommended ones.	217	recommended ones.
172		218
173	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
174		220
175	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
176		222
177	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
178	semantics is identical - to the realloc C function). It is used to	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
179	allocate and free memory (no surprises here). If it returns zero when	225	used to allocate and free memory (no surprises here). If it returns zero
180	memory needs to be allocated, the library might abort or take some	226	when memory needs to be allocated (C<size != 0>), the library might abort
181	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
182	function.	228
		229	Since some systems (at least OpenBSD and Darwin) fail to implement
		230	correct C<realloc> semantics, libev will use a wrapper around the system
		231	C<realloc> and C<free> functions by default.
183		232
184	You could override this function in high-availability programs to, say,	233	You could override this function in high-availability programs to, say,
185	free some memory if it cannot allocate memory, to use a special allocator,	234	free some memory if it cannot allocate memory, to use a special allocator,
186	or even to sleep a while and retry until some memory is available.	235	or even to sleep a while and retry until some memory is available.
187		236
188	Example: Replace the libev allocator with one that waits a bit and then	237	Example: Replace the libev allocator with one that waits a bit and then
189	retries).	238	retries (example requires a standards-compliant C<realloc>).
190		239
191	static void *	240	static void *
192	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
193	{	242	{
194	for (;;)	243	for (;;)
…		…
203	}	252	}
204		253
205	...	254	...
206	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
207		256
208	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
209		258
210	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
211	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
212	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
213	callback is set, then libev will expect it to remedy the sitution, no	262	callback is set, then libev will expect it to remedy the situation, no
214	matter what, when it returns. That is, libev will generally retry the	263	matter what, when it returns. That is, libev will generally retry the
215	requested operation, or, if the condition doesn't go away, do bad stuff	264	requested operation, or, if the condition doesn't go away, do bad stuff
216	(such as abort).	265	(such as abort).
217		266
218	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
229		278
230	=back	279	=back
231		280
232	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
233		282
234	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
235	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
236	events, and dynamically created loops which do not.	285	I<function>).
237		286
238	If you use threads, a common model is to run the default event loop	287	The library knows two types of such loops, the I<default> loop, which
239	in your main thread (or in a separate thread) and for each thread you	288	supports signals and child events, and dynamically created loops which do
240	create, you also create another event loop. Libev itself does no locking	289	not.
241	whatsoever, so if you mix calls to the same event loop in different
242	threads, make sure you lock (this is usually a bad idea, though, even if
243	done correctly, because it's hideous and inefficient).
244		290
245	=over 4	291	=over 4
246		292
247	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
248		294
…		…
252	flags. If that is troubling you, check C<ev_backend ()> afterwards).	298	flags. If that is troubling you, check C<ev_backend ()> afterwards).
253		299
254	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
255	function.	301	function.
256		302
		303	Note that this function is I<not> thread-safe, so if you want to use it
		304	from multiple threads, you have to lock (note also that this is unlikely,
		305	as loops cannot be shared easily between threads anyway).
		306
		307	The default loop is the only loop that can handle C<ev_signal> and
		308	C<ev_child> watchers, and to do this, it always registers a handler
		309	for C<SIGCHLD>. If this is a problem for your application you can either
		310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		312	C<ev_default_init>.
		313
257	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
258	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
259		316
260	The following flags are supported:	317	The following flags are supported:
261		318
…		…
266	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
267	thing, believe me).	324	thing, believe me).
268		325
269	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
270		327
271	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
272	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
273	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
274	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
275	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
276	around bugs.	333	around bugs.
…		…
282	enabling this flag.	339	enabling this flag.
283		340
284	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
285	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
286	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
287	Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
288	without a syscall and thus I<very> fast, but my Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
289	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
290		347
291	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
292	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
293	flag.	350	flag.
294		351
295	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
296	environment variable.	353	environment variable.
297		354
298	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299		356
300	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
301	libev tries to roll its own fd_set with no limits on the number of fds,	358	libev tries to roll its own fd_set with no limits on the number of fds,
302	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
303	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	360	using this backend. It doesn't scale too well (O(highest_fd)), but its
304	the fastest backend for a low number of fds.	361	usually the fastest backend for a low number of (low-numbered :) fds.
		362
		363	To get good performance out of this backend you need a high amount of
		364	parallelism (most of the file descriptors should be busy). If you are
		365	writing a server, you should C<accept ()> in a loop to accept as many
		366	connections as possible during one iteration. You might also want to have
		367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
305		373
306	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
307		375
308	And this is your standard poll(2) backend. It's more complicated than	376	And this is your standard poll(2) backend. It's more complicated
309	select, but handles sparse fds better and has no artificial limit on the	377	than select, but handles sparse fds better and has no artificial
310	number of fds you can use (except it will slow down considerably with a	378	limit on the number of fds you can use (except it will slow down
311	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	379	considerably with a lot of inactive fds). It scales similarly to select,
		380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		381	performance tips.
		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
312		385
313	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
314		387
315	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
316	but it scales phenomenally better. While poll and select usually scale like	389	but it scales phenomenally better. While poll and select usually scale
317	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	390	like O(total_fds) where n is the total number of fds (or the highest fd),
318	either O(1) or O(active_fds).	391	epoll scales either O(1) or O(active_fds).
319		392
		393	The epoll mechanism deserves honorable mention as the most misdesigned
		394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
		409
320	While stopping and starting an I/O watcher in the same iteration will	410	While stopping, setting and starting an I/O watcher in the same iteration
321	result in some caching, there is still a syscall per such incident	411	will result in some caching, there is still a system call per such
322	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
323	best to avoid that. Also, dup()ed file descriptors might not work very	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
324	well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
		415	file descriptors.
325		416
326	Please note that epoll sometimes generates spurious notifications, so you	417	Best performance from this backend is achieved by not unregistering all
327	need to use non-blocking I/O or other means to avoid blocking when no data	418	watchers for a file descriptor until it has been closed, if possible,
328	(or space) is available.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
		429	While nominally embeddable in other event loops, this feature is broken in
		430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
329		434
330	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331		436
332	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
333	was broken on all BSDs except NetBSD (usually it doesn't work with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
334	anything but sockets and pipes, except on Darwin, where of course its	439	with anything but sockets and pipes, except on Darwin, where of course
335	completely useless). For this reason its not being "autodetected"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
336	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
337	C<EVBACKEND_KQUEUE>).	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
		446
		447	You still can embed kqueue into a normal poll or select backend and use it
		448	only for sockets (after having made sure that sockets work with kqueue on
		449	the target platform). See C<ev_embed> watchers for more info.
338		450
339	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
340	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
341	course). While starting and stopping an I/O watcher does not cause an	453	course). While stopping, setting and starting an I/O watcher does never
342	extra syscall as with epoll, it still adds up to four event changes per	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
343	incident, so its best to avoid that.	455	two event changes per incident. Support for C<fork ()> is very bad (but
		456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
		458
		459	This backend usually performs well under most conditions.
		460
		461	While nominally embeddable in other event loops, this doesn't work
		462	everywhere, so you might need to test for this. And since it is broken
		463	almost everywhere, you should only use it when you have a lot of sockets
		464	(for which it usually works), by embedding it into another event loop
		465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
		466	using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
344		471
345	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346		473
347	This is not implemented yet (and might never be).	474	This is not implemented yet (and might never be, unless you send me an
		475	implementation). According to reports, C</dev/poll> only supports sockets
		476	and is not embeddable, which would limit the usefulness of this backend
		477	immensely.
348		478
349	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350		480
351	This uses the Solaris 10 port mechanism. As with everything on Solaris,	481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352	it's really slow, but it still scales very well (O(active_fds)).	482	it's really slow, but it still scales very well (O(active_fds)).
353		483
354	Please note that solaris ports can result in a lot of spurious	484	Please note that Solaris event ports can deliver a lot of spurious
355	notifications, so you need to use non-blocking I/O or other means to avoid	485	notifications, so you need to use non-blocking I/O or other means to avoid
356	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
		487
		488	While this backend scales well, it requires one system call per active
		489	file descriptor per loop iteration. For small and medium numbers of file
		490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		491	might perform better.
		492
		493	On the positive side, with the exception of the spurious readiness
		494	notifications, this backend actually performed fully to specification
		495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
357		500
358	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
359		502
360	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
361	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
362	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363		506
		507	It is definitely not recommended to use this flag.
		508
364	=back	509	=back
365		510
366	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
367	backends will be tried (in the reverse order as given here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
368	specified, most compiled-in backend will be tried, usually in reverse	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
369	order of their flag values :)
370		514
371	The most typical usage is like this:	515	Example: This is the most typical usage.
372		516
373	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
374	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
375		519
376	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
377	environment settings to be taken into account:	521	environment settings to be taken into account:
378		522
379	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
380		524
381	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
382	available (warning, breaks stuff, best use only with your own private	526	used if available (warning, breaks stuff, best use only with your own
383	event loop and only if you know the OS supports your types of fds):	527	private event loop and only if you know the OS supports your types of
		528	fds):
384		529
385	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
386		531
387	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
388		533
389	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
390	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
391	handle signal and child watchers, and attempts to do so will be greeted by	536	handle signal and child watchers, and attempts to do so will be greeted by
392	undefined behaviour (or a failed assertion if assertions are enabled).	537	undefined behaviour (or a failed assertion if assertions are enabled).
393		538
		539	Note that this function I<is> thread-safe, and the recommended way to use
		540	libev with threads is indeed to create one loop per thread, and using the
		541	default loop in the "main" or "initial" thread.
		542
394	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
395		544
396	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
397	if (!epoller)	546	if (!epoller)
398	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
399		548
400	=item ev_default_destroy ()	549	=item ev_default_destroy ()
401		550
402	Destroys the default loop again (frees all memory and kernel state	551	Destroys the default loop again (frees all memory and kernel state
403	etc.). None of the active event watchers will be stopped in the normal	552	etc.). None of the active event watchers will be stopped in the normal
404	sense, so e.g. C<ev_is_active> might still return true. It is your	553	sense, so e.g. C<ev_is_active> might still return true. It is your
405	responsibility to either stop all watchers cleanly yoursef I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
406	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
407	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
408	for example).	557	for example).
		558
		559	Note that certain global state, such as signal state (and installed signal
		560	handlers), will not be freed by this function, and related watchers (such
		561	as signal and child watchers) would need to be stopped manually.
		562
		563	In general it is not advisable to call this function except in the
		564	rare occasion where you really need to free e.g. the signal handling
		565	pipe fds. If you need dynamically allocated loops it is better to use
		566	C<ev_loop_new> and C<ev_loop_destroy>).
409		567
410	=item ev_loop_destroy (loop)	568	=item ev_loop_destroy (loop)
411		569
412	Like C<ev_default_destroy>, but destroys an event loop created by an	570	Like C<ev_default_destroy>, but destroys an event loop created by an
413	earlier call to C<ev_loop_new>.	571	earlier call to C<ev_loop_new>.
414		572
415	=item ev_default_fork ()	573	=item ev_default_fork ()
416		574
		575	This function sets a flag that causes subsequent C<ev_loop> iterations
417	This function reinitialises the kernel state for backends that have	576	to reinitialise the kernel state for backends that have one. Despite the
418	one. Despite the name, you can call it anytime, but it makes most sense	577	name, you can call it anytime, but it makes most sense after forking, in
419	after forking, in either the parent or child process (or both, but that	578	the child process (or both child and parent, but that again makes little
420	again makes little sense).	579	sense). You I<must> call it in the child before using any of the libev
		580	functions, and it will only take effect at the next C<ev_loop> iteration.
421		581
422	You I<must> call this function in the child process after forking if and	582	On the other hand, you only need to call this function in the child
423	only if you want to use the event library in both processes. If you just	583	process if and only if you want to use the event library in the child. If
424	fork+exec, you don't have to call it.	584	you just fork+exec, you don't have to call it at all.
425		585
426	The function itself is quite fast and it's usually not a problem to call	586	The function itself is quite fast and it's usually not a problem to call
427	it just in case after a fork. To make this easy, the function will fit in	587	it just in case after a fork. To make this easy, the function will fit in
428	quite nicely into a call to C<pthread_atfork>:	588	quite nicely into a call to C<pthread_atfork>:
429		589
430	pthread_atfork (0, 0, ev_default_fork);	590	pthread_atfork (0, 0, ev_default_fork);
431		591
432	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433	without calling this function, so if you force one of those backends you
434	do not need to care.
435
436	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
437		593
438	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
439	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
440	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
		598
		599	=item int ev_is_default_loop (loop)
		600
		601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
441		603
442	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
443		605
444	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
445	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
458		620
459	Returns the current "event loop time", which is the time the event loop	621	Returns the current "event loop time", which is the time the event loop
460	received events and started processing them. This timestamp does not	622	received events and started processing them. This timestamp does not
461	change as long as callbacks are being processed, and this is also the base	623	change as long as callbacks are being processed, and this is also the base
462	time used for relative timers. You can treat it as the timestamp of the	624	time used for relative timers. You can treat it as the timestamp of the
463	event occuring (or more correctly, libev finding out about it).	625	event occurring (or more correctly, libev finding out about it).
		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
464		638
465	=item ev_loop (loop, int flags)	639	=item ev_loop (loop, int flags)
466		640
467	Finally, this is it, the event handler. This function usually is called	641	Finally, this is it, the event handler. This function usually is called
468	after you initialised all your watchers and you want to start handling	642	after you initialised all your watchers and you want to start handling
…		…
471	If the flags argument is specified as C<0>, it will not return until	645	If the flags argument is specified as C<0>, it will not return until
472	either no event watchers are active anymore or C<ev_unloop> was called.	646	either no event watchers are active anymore or C<ev_unloop> was called.
473		647
474	Please note that an explicit C<ev_unloop> is usually better than	648	Please note that an explicit C<ev_unloop> is usually better than
475	relying on all watchers to be stopped when deciding when a program has	649	relying on all watchers to be stopped when deciding when a program has
476	finished (especially in interactive programs), but having a program that	650	finished (especially in interactive programs), but having a program
477	automatically loops as long as it has to and no longer by virtue of	651	that automatically loops as long as it has to and no longer by virtue
478	relying on its watchers stopping correctly is a thing of beauty.	652	of relying on its watchers stopping correctly, that is truly a thing of
		653	beauty.
479		654
480	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
481	those events and any outstanding ones, but will not block your process in	656	those events and any already outstanding ones, but will not block your
482	case there are no events and will return after one iteration of the loop.	657	process in case there are no events and will return after one iteration of
		658	the loop.
483		659
484	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
485	neccessary) and will handle those and any outstanding ones. It will block	661	necessary) and will handle those and any already outstanding ones. It
486	your process until at least one new event arrives, and will return after	662	will block your process until at least one new event arrives (which could
487	one iteration of the loop. This is useful if you are waiting for some	663	be an event internal to libev itself, so there is no guarantee that a
488	external event in conjunction with something not expressible using other	664	user-registered callback will be called), and will return after one
		665	iteration of the loop.
		666
		667	This is useful if you are waiting for some external event in conjunction
		668	with something not expressible using other libev watchers (i.e. "roll your
489	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
490	usually a better approach for this kind of thing.	670	usually a better approach for this kind of thing.
491		671
492	Here are the gory details of what C<ev_loop> does:	672	Here are the gory details of what C<ev_loop> does:
493		673
494	- Before the first iteration, call any pending watchers.	674	- Before the first iteration, call any pending watchers.
495	* If there are no active watchers (reference count is zero), return.	675	* If EVFLAG_FORKCHECK was used, check for a fork.
496	- Queue all prepare watchers and then call all outstanding watchers.	676	- If a fork was detected (by any means), queue and call all fork watchers.
		677	- Queue and call all prepare watchers.
497	- If we have been forked, recreate the kernel state.	678	- If we have been forked, detach and recreate the kernel state
		679	as to not disturb the other process.
498	- Update the kernel state with all outstanding changes.	680	- Update the kernel state with all outstanding changes.
499	- Update the "event loop time".	681	- Update the "event loop time" (ev_now ()).
500	- Calculate for how long to block.	682	- Calculate for how long to sleep or block, if at all
		683	(active idle watchers, EVLOOP_NONBLOCK or not having
		684	any active watchers at all will result in not sleeping).
		685	- Sleep if the I/O and timer collect interval say so.
501	- Block the process, waiting for any events.	686	- Block the process, waiting for any events.
502	- Queue all outstanding I/O (fd) events.	687	- Queue all outstanding I/O (fd) events.
503	- Update the "event loop time" and do time jump handling.	688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
504	- Queue all outstanding timers.	689	- Queue all expired timers.
505	- Queue all outstanding periodics.	690	- Queue all expired periodics.
506	- If no events are pending now, queue all idle watchers.	691	- Unless any events are pending now, queue all idle watchers.
507	- Queue all check watchers.	692	- Queue all check watchers.
508	- Call all queued watchers in reverse order (i.e. check watchers first).	693	- Call all queued watchers in reverse order (i.e. check watchers first).
509	Signals and child watchers are implemented as I/O watchers, and will	694	Signals and child watchers are implemented as I/O watchers, and will
510	be handled here by queueing them when their watcher gets executed.	695	be handled here by queueing them when their watcher gets executed.
511	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512	were used, return, otherwise continue with step *.	697	were used, or there are no active watchers, return, otherwise
		698	continue with step *.
513		699
514	Example: Queue some jobs and then loop until no events are outsanding	700	Example: Queue some jobs and then loop until no events are outstanding
515	anymore.	701	anymore.
516		702
517	... queue jobs here, make sure they register event watchers as long	703	... queue jobs here, make sure they register event watchers as long
518	... as they still have work to do (even an idle watcher will do..)	704	... as they still have work to do (even an idle watcher will do..)
519	ev_loop (my_loop, 0);	705	ev_loop (my_loop, 0);
520	... jobs done. yeah!	706	... jobs done or somebody called unloop. yeah!
521		707
522	=item ev_unloop (loop, how)	708	=item ev_unloop (loop, how)
523		709
524	Can be used to make a call to C<ev_loop> return early (but only after it	710	Can be used to make a call to C<ev_loop> return early (but only after it
525	has processed all outstanding events). The C<how> argument must be either	711	has processed all outstanding events). The C<how> argument must be either
526	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
528		714
		715	This "unloop state" will be cleared when entering C<ev_loop> again.
		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
529	=item ev_ref (loop)	719	=item ev_ref (loop)
530		720
531	=item ev_unref (loop)	721	=item ev_unref (loop)
532		722
533	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
534	loop: Every watcher keeps one reference, and as long as the reference	724	loop: Every watcher keeps one reference, and as long as the reference
535	count is nonzero, C<ev_loop> will not return on its own. If you have	725	count is nonzero, C<ev_loop> will not return on its own.
		726
536	a watcher you never unregister that should not keep C<ev_loop> from	727	If you have a watcher you never unregister that should not keep C<ev_loop>
537	returning, ev_unref() after starting, and ev_ref() before stopping it. For	728	from returning, call ev_unref() after starting, and ev_ref() before
		729	stopping it.
		730
538	example, libev itself uses this for its internal signal pipe: It is not	731	As an example, libev itself uses this for its internal signal pipe: It is
539	visible to the libev user and should not keep C<ev_loop> from exiting if	732	not visible to the libev user and should not keep C<ev_loop> from exiting
540	no event watchers registered by it are active. It is also an excellent	733	if no event watchers registered by it are active. It is also an excellent
541	way to do this for generic recurring timers or from within third-party	734	way to do this for generic recurring timers or from within third-party
542	libraries. Just remember to I<unref after start> and I<ref before stop>.	735	libraries. Just remember to I<unref after start> and I<ref before stop>
		736	(but only if the watcher wasn't active before, or was active before,
		737	respectively).
543		738
544	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545	running when nothing else is active.	740	running when nothing else is active.
546		741
547	struct ev_signal exitsig;	742	ev_signal exitsig;
548	ev_signal_init (&exitsig, sig_cb, SIGINT);	743	ev_signal_init (&exitsig, sig_cb, SIGINT);
549	ev_signal_start (loop, &exitsig);	744	ev_signal_start (loop, &exitsig);
550	evf_unref (loop);	745	evf_unref (loop);
551		746
552	Example: For some weird reason, unregister the above signal handler again.	747	Example: For some weird reason, unregister the above signal handler again.
553		748
554	ev_ref (loop);	749	ev_ref (loop);
555	ev_signal_stop (loop, &exitsig);	750	ev_signal_stop (loop, &exitsig);
		751
		752	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		753
		754	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		755
		756	These advanced functions influence the time that libev will spend waiting
		757	for events. Both time intervals are by default C<0>, meaning that libev
		758	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		759	latency.
		760
		761	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		762	allows libev to delay invocation of I/O and timer/periodic callbacks
		763	to increase efficiency of loop iterations (or to increase power-saving
		764	opportunities).
		765
		766	The idea is that sometimes your program runs just fast enough to handle
		767	one (or very few) event(s) per loop iteration. While this makes the
		768	program responsive, it also wastes a lot of CPU time to poll for new
		769	events, especially with backends like C<select ()> which have a high
		770	overhead for the actual polling but can deliver many events at once.
		771
		772	By setting a higher I<io collect interval> you allow libev to spend more
		773	time collecting I/O events, so you can handle more events per iteration,
		774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		775	C<ev_timer>) will be not affected. Setting this to a non-null value will
		776	introduce an additional C<ev_sleep ()> call into most loop iterations.
		777
		778	Likewise, by setting a higher I<timeout collect interval> you allow libev
		779	to spend more time collecting timeouts, at the expense of increased
		780	latency/jitter/inexactness (the watcher callback will be called
		781	later). C<ev_io> watchers will not be affected. Setting this to a non-null
		782	value will not introduce any overhead in libev.
		783
		784	Many (busy) programs can usually benefit by setting the I/O collect
		785	interval to a value near C<0.1> or so, which is often enough for
		786	interactive servers (of course not for games), likewise for timeouts. It
		787	usually doesn't make much sense to set it to a lower value than C<0.01>,
		788	as this approaches the timing granularity of most systems.
		789
		790	Setting the I<timeout collect interval> can improve the opportunity for
		791	saving power, as the program will "bundle" timer callback invocations that
		792	are "near" in time together, by delaying some, thus reducing the number of
		793	times the process sleeps and wakes up again. Another useful technique to
		794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		795	they fire on, say, one-second boundaries only.
		796
		797	=item ev_loop_verify (loop)
		798
		799	This function only does something when C<EV_VERIFY> support has been
		800	compiled in, which is the default for non-minimal builds. It tries to go
		801	through all internal structures and checks them for validity. If anything
		802	is found to be inconsistent, it will print an error message to standard
		803	error and call C<abort ()>.
		804
		805	This can be used to catch bugs inside libev itself: under normal
		806	circumstances, this function will never abort as of course libev keeps its
		807	data structures consistent.
556		808
557	=back	809	=back
558		810
559		811
560	=head1 ANATOMY OF A WATCHER	812	=head1 ANATOMY OF A WATCHER
		813
		814	In the following description, uppercase C<TYPE> in names stands for the
		815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		816	watchers and C<ev_io_start> for I/O watchers.
561		817
562	A watcher is a structure that you create and register to record your	818	A watcher is a structure that you create and register to record your
563	interest in some event. For instance, if you want to wait for STDIN to	819	interest in some event. For instance, if you want to wait for STDIN to
564	become readable, you would create an C<ev_io> watcher for that:	820	become readable, you would create an C<ev_io> watcher for that:
565		821
566	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
567	{	823	{
568	ev_io_stop (w);	824	ev_io_stop (w);
569	ev_unloop (loop, EVUNLOOP_ALL);	825	ev_unloop (loop, EVUNLOOP_ALL);
570	}	826	}
571		827
572	struct ev_loop *loop = ev_default_loop (0);	828	struct ev_loop *loop = ev_default_loop (0);
		829
573	struct ev_io stdin_watcher;	830	ev_io stdin_watcher;
		831
574	ev_init (&stdin_watcher, my_cb);	832	ev_init (&stdin_watcher, my_cb);
575	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
576	ev_io_start (loop, &stdin_watcher);	834	ev_io_start (loop, &stdin_watcher);
		835
577	ev_loop (loop, 0);	836	ev_loop (loop, 0);
578		837
579	As you can see, you are responsible for allocating the memory for your	838	As you can see, you are responsible for allocating the memory for your
580	watcher structures (and it is usually a bad idea to do this on the stack,	839	watcher structures (and it is I<usually> a bad idea to do this on the
581	although this can sometimes be quite valid).	840	stack).
		841
		842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
582		844
583	Each watcher structure must be initialised by a call to C<ev_init	845	Each watcher structure must be initialised by a call to C<ev_init
584	(watcher *, callback)>, which expects a callback to be provided. This	846	(watcher *, callback)>, which expects a callback to be provided. This
585	callback gets invoked each time the event occurs (or, in the case of io	847	callback gets invoked each time the event occurs (or, in the case of I/O
586	watchers, each time the event loop detects that the file descriptor given	848	watchers, each time the event loop detects that the file descriptor given
587	is readable and/or writable).	849	is readable and/or writable).
588		850
589	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
590	with arguments specific to this watcher type. There is also a macro	852	macro to configure it, with arguments specific to the watcher type. There
591	to combine initialisation and setting in one call: C<< ev_<type>_init	853	is also a macro to combine initialisation and setting in one call: C<<
592	(watcher *, callback, ...) >>.	854	ev_TYPE_init (watcher *, callback, ...) >>.
593		855
594	To make the watcher actually watch out for events, you have to start it	856	To make the watcher actually watch out for events, you have to start it
595	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
596	*) >>), and you can stop watching for events at any time by calling the	858	*) >>), and you can stop watching for events at any time by calling the
597	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
598		860
599	As long as your watcher is active (has been started but not stopped) you	861	As long as your watcher is active (has been started but not stopped) you
600	must not touch the values stored in it. Most specifically you must never	862	must not touch the values stored in it. Most specifically you must never
601	reinitialise it or call its C<set> macro.	863	reinitialise it or call its C<ev_TYPE_set> macro.
602		864
603	Each and every callback receives the event loop pointer as first, the	865	Each and every callback receives the event loop pointer as first, the
604	registered watcher structure as second, and a bitset of received events as	866	registered watcher structure as second, and a bitset of received events as
605	third argument.	867	third argument.
606		868
…		…
660	=item C<EV_FORK>	922	=item C<EV_FORK>
661		923
662	The event loop has been resumed in the child process after fork (see	924	The event loop has been resumed in the child process after fork (see
663	C<ev_fork>).	925	C<ev_fork>).
664		926
		927	=item C<EV_ASYNC>
		928
		929	The given async watcher has been asynchronously notified (see C<ev_async>).
		930
665	=item C<EV_ERROR>	931	=item C<EV_ERROR>
666		932
667	An unspecified error has occured, the watcher has been stopped. This might	933	An unspecified error has occurred, the watcher has been stopped. This might
668	happen because the watcher could not be properly started because libev	934	happen because the watcher could not be properly started because libev
669	ran out of memory, a file descriptor was found to be closed or any other	935	ran out of memory, a file descriptor was found to be closed or any other
		936	problem. Libev considers these application bugs.
		937
670	problem. You best act on it by reporting the problem and somehow coping	938	You best act on it by reporting the problem and somehow coping with the
671	with the watcher being stopped.	939	watcher being stopped. Note that well-written programs should not receive
		940	an error ever, so when your watcher receives it, this usually indicates a
		941	bug in your program.
672		942
673	Libev will usually signal a few "dummy" events together with an error,	943	Libev will usually signal a few "dummy" events together with an error, for
674	for example it might indicate that a fd is readable or writable, and if	944	example it might indicate that a fd is readable or writable, and if your
675	your callbacks is well-written it can just attempt the operation and cope	945	callbacks is well-written it can just attempt the operation and cope with
676	with the error from read() or write(). This will not work in multithreaded	946	the error from read() or write(). This will not work in multi-threaded
677	programs, though, so beware.	947	programs, though, as the fd could already be closed and reused for another
		948	thing, so beware.
678		949
679	=back	950	=back
680		951
681	=head2 GENERIC WATCHER FUNCTIONS	952	=head2 GENERIC WATCHER FUNCTIONS
682
683	In the following description, C<TYPE> stands for the watcher type,
684	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
685		953
686	=over 4	954	=over 4
687		955
688	=item C<ev_init> (ev_TYPE *watcher, callback)	956	=item C<ev_init> (ev_TYPE *watcher, callback)
689		957
…		…
695	which rolls both calls into one.	963	which rolls both calls into one.
696		964
697	You can reinitialise a watcher at any time as long as it has been stopped	965	You can reinitialise a watcher at any time as long as it has been stopped
698	(or never started) and there are no pending events outstanding.	966	(or never started) and there are no pending events outstanding.
699		967
700	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	968	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
701	int revents)>.	969	int revents)>.
		970
		971	Example: Initialise an C<ev_io> watcher in two steps.
		972
		973	ev_io w;
		974	ev_init (&w, my_cb);
		975	ev_io_set (&w, STDIN_FILENO, EV_READ);
702		976
703	=item C<ev_TYPE_set> (ev_TYPE *, [args])	977	=item C<ev_TYPE_set> (ev_TYPE *, [args])
704		978
705	This macro initialises the type-specific parts of a watcher. You need to	979	This macro initialises the type-specific parts of a watcher. You need to
706	call C<ev_init> at least once before you call this macro, but you can	980	call C<ev_init> at least once before you call this macro, but you can
…		…
709	difference to the C<ev_init> macro).	983	difference to the C<ev_init> macro).
710		984
711	Although some watcher types do not have type-specific arguments	985	Although some watcher types do not have type-specific arguments
712	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	986	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
713		987
		988	See C<ev_init>, above, for an example.
		989
714	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	990	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
715		991
716	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	992	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
717	calls into a single call. This is the most convinient method to initialise	993	calls into a single call. This is the most convenient method to initialise
718	a watcher. The same limitations apply, of course.	994	a watcher. The same limitations apply, of course.
		995
		996	Example: Initialise and set an C<ev_io> watcher in one step.
		997
		998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
719		999
720	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
721		1001
722	Starts (activates) the given watcher. Only active watchers will receive	1002	Starts (activates) the given watcher. Only active watchers will receive
723	events. If the watcher is already active nothing will happen.	1003	events. If the watcher is already active nothing will happen.
724		1004
		1005	Example: Start the C<ev_io> watcher that is being abused as example in this
		1006	whole section.
		1007
		1008	ev_io_start (EV_DEFAULT_UC, &w);
		1009
725	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
726		1011
727	Stops the given watcher again (if active) and clears the pending	1012	Stops the given watcher if active, and clears the pending status (whether
		1013	the watcher was active or not).
		1014
728	status. It is possible that stopped watchers are pending (for example,	1015	It is possible that stopped watchers are pending - for example,
729	non-repeating timers are being stopped when they become pending), but	1016	non-repeating timers are being stopped when they become pending - but
730	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1017	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
731	you want to free or reuse the memory used by the watcher it is therefore a	1018	pending. If you want to free or reuse the memory used by the watcher it is
732	good idea to always call its C<ev_TYPE_stop> function.	1019	therefore a good idea to always call its C<ev_TYPE_stop> function.
733		1020
734	=item bool ev_is_active (ev_TYPE *watcher)	1021	=item bool ev_is_active (ev_TYPE *watcher)
735		1022
736	Returns a true value iff the watcher is active (i.e. it has been started	1023	Returns a true value iff the watcher is active (i.e. it has been started
737	and not yet been stopped). As long as a watcher is active you must not modify	1024	and not yet been stopped). As long as a watcher is active you must not modify
…		…
779	The default priority used by watchers when no priority has been set is	1066	The default priority used by watchers when no priority has been set is
780	always C<0>, which is supposed to not be too high and not be too low :).	1067	always C<0>, which is supposed to not be too high and not be too low :).
781		1068
782	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
783	fine, as long as you do not mind that the priority value you query might	1070	fine, as long as you do not mind that the priority value you query might
784	or might not have been adjusted to be within valid range.	1071	or might not have been clamped to the valid range.
785		1072
786	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
787		1074
788	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
789	C<loop> nor C<revents> need to be valid as long as the watcher callback	1076	C<loop> nor C<revents> need to be valid as long as the watcher callback
790	can deal with that fact.	1077	can deal with that fact, as both are simply passed through to the
		1078	callback.
791		1079
792	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1080	=item int ev_clear_pending (loop, ev_TYPE *watcher)
793		1081
794	If the watcher is pending, this function returns clears its pending status	1082	If the watcher is pending, this function clears its pending status and
795	and returns its C<revents> bitset (as if its callback was invoked). If the	1083	returns its C<revents> bitset (as if its callback was invoked). If the
796	watcher isn't pending it does nothing and returns C<0>.	1084	watcher isn't pending it does nothing and returns C<0>.
797		1085
		1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1087	callback to be invoked, which can be accomplished with this function.
		1088
798	=back	1089	=back
799		1090
800		1091
801	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
802		1093
803	Each watcher has, by default, a member C<void *data> that you can change	1094	Each watcher has, by default, a member C<void *data> that you can change
804	and read at any time, libev will completely ignore it. This can be used	1095	and read at any time: libev will completely ignore it. This can be used
805	to associate arbitrary data with your watcher. If you need more data and	1096	to associate arbitrary data with your watcher. If you need more data and
806	don't want to allocate memory and store a pointer to it in that data	1097	don't want to allocate memory and store a pointer to it in that data
807	member, you can also "subclass" the watcher type and provide your own	1098	member, you can also "subclass" the watcher type and provide your own
808	data:	1099	data:
809		1100
810	struct my_io	1101	struct my_io
811	{	1102	{
812	struct ev_io io;	1103	ev_io io;
813	int otherfd;	1104	int otherfd;
814	void *somedata;	1105	void *somedata;
815	struct whatever *mostinteresting;	1106	struct whatever *mostinteresting;
816	}	1107	};
		1108
		1109	...
		1110	struct my_io w;
		1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
817		1112
818	And since your callback will be called with a pointer to the watcher, you	1113	And since your callback will be called with a pointer to the watcher, you
819	can cast it back to your own type:	1114	can cast it back to your own type:
820		1115
821	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
822	{	1117	{
823	struct my_io *w = (struct my_io *)w_;	1118	struct my_io *w = (struct my_io *)w_;
824	...	1119	...
825	}	1120	}
826		1121
827	More interesting and less C-conformant ways of casting your callback type	1122	More interesting and less C-conformant ways of casting your callback type
828	instead have been omitted.	1123	instead have been omitted.
829		1124
830	Another common scenario is having some data structure with multiple	1125	Another common scenario is to use some data structure with multiple
831	watchers:	1126	embedded watchers:
832		1127
833	struct my_biggy	1128	struct my_biggy
834	{	1129	{
835	int some_data;	1130	int some_data;
836	ev_timer t1;	1131	ev_timer t1;
837	ev_timer t2;	1132	ev_timer t2;
838	}	1133	}
839		1134
840	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1135	In this case getting the pointer to C<my_biggy> is a bit more
841	you need to use C<offsetof>:	1136	complicated: Either you store the address of your C<my_biggy> struct
		1137	in the C<data> member of the watcher (for woozies), or you need to use
		1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1139	programmers):
842		1140
843	#include <stddef.h>	1141	#include <stddef.h>
844		1142
845	static void	1143	static void
846	t1_cb (EV_P_ struct ev_timer *w, int revents)	1144	t1_cb (EV_P_ ev_timer *w, int revents)
847	{	1145	{
848	struct my_biggy big = (struct my_biggy *	1146	struct my_biggy big = (struct my_biggy *
849	(((char *)w) - offsetof (struct my_biggy, t1));	1147	(((char *)w) - offsetof (struct my_biggy, t1));
850	}	1148	}
851		1149
852	static void	1150	static void
853	t2_cb (EV_P_ struct ev_timer *w, int revents)	1151	t2_cb (EV_P_ ev_timer *w, int revents)
854	{	1152	{
855	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
856	(((char *)w) - offsetof (struct my_biggy, t2));	1154	(((char *)w) - offsetof (struct my_biggy, t2));
857	}	1155	}
858		1156
859		1157
860	=head1 WATCHER TYPES	1158	=head1 WATCHER TYPES
861		1159
862	This section describes each watcher in detail, but will not repeat	1160	This section describes each watcher in detail, but will not repeat
…		…
886	In general you can register as many read and/or write event watchers per	1184	In general you can register as many read and/or write event watchers per
887	fd as you want (as long as you don't confuse yourself). Setting all file	1185	fd as you want (as long as you don't confuse yourself). Setting all file
888	descriptors to non-blocking mode is also usually a good idea (but not	1186	descriptors to non-blocking mode is also usually a good idea (but not
889	required if you know what you are doing).	1187	required if you know what you are doing).
890		1188
891	You have to be careful with dup'ed file descriptors, though. Some backends	1189	If you cannot use non-blocking mode, then force the use of a
892	(the linux epoll backend is a notable example) cannot handle dup'ed file	1190	known-to-be-good backend (at the time of this writing, this includes only
893	descriptors correctly if you register interest in two or more fds pointing	1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
894	to the same underlying file/socket/etc. description (that is, they share
895	the same underlying "file open").
896
897	If you must do this, then force the use of a known-to-be-good backend
898	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899	C<EVBACKEND_POLL>).
900		1192
901	Another thing you have to watch out for is that it is quite easy to	1193	Another thing you have to watch out for is that it is quite easy to
902	receive "spurious" readyness notifications, that is your callback might	1194	receive "spurious" readiness notifications, that is your callback might
903	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
904	because there is no data. Not only are some backends known to create a	1196	because there is no data. Not only are some backends known to create a
905	lot of those (for example solaris ports), it is very easy to get into	1197	lot of those (for example Solaris ports), it is very easy to get into
906	this situation even with a relatively standard program structure. Thus	1198	this situation even with a relatively standard program structure. Thus
907	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
908	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.
909		1201
910	If you cannot run the fd in non-blocking mode (for example you should not	1202	If you cannot run the fd in non-blocking mode (for example you should
911	play around with an Xlib connection), then you have to seperately re-test	1203	not play around with an Xlib connection), then you have to separately
912	whether a file descriptor is really ready with a known-to-be good interface	1204	re-test whether a file descriptor is really ready with a known-to-be good
913	such as poll (fortunately in our Xlib example, Xlib already does this on	1205	interface such as poll (fortunately in our Xlib example, Xlib already
914	its own, so its quite safe to use).	1206	does this on its own, so its quite safe to use). Some people additionally
		1207	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1208	indefinitely.
		1209
		1210	But really, best use non-blocking mode.
915		1211
916	=head3 The special problem of disappearing file descriptors	1212	=head3 The special problem of disappearing file descriptors
917		1213
918	Some backends (e.g kqueue, epoll) need to be told about closing a file	1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file
919	descriptor (either by calling C<close> explicitly or by any other means,	1215	descriptor (either due to calling C<close> explicitly or any other means,
920	such as C<dup>). The reason is that you register interest in some file	1216	such as C<dup2>). The reason is that you register interest in some file
921	descriptor, but when it goes away, the operating system will silently drop	1217	descriptor, but when it goes away, the operating system will silently drop
922	this interest. If another file descriptor with the same number then is	1218	this interest. If another file descriptor with the same number then is
923	registered with libev, there is no efficient way to see that this is, in	1219	registered with libev, there is no efficient way to see that this is, in
924	fact, a different file descriptor.	1220	fact, a different file descriptor.
925		1221
…		…
932		1228
933	This is how one would do it normally anyway, the important point is that	1229	This is how one would do it normally anyway, the important point is that
934	the libev application should not optimise around libev but should leave	1230	the libev application should not optimise around libev but should leave
935	optimisations to libev.	1231	optimisations to libev.
936		1232
		1233	=head3 The special problem of dup'ed file descriptors
		1234
		1235	Some backends (e.g. epoll), cannot register events for file descriptors,
		1236	but only events for the underlying file descriptions. That means when you
		1237	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1238	events for them, only one file descriptor might actually receive events.
		1239
		1240	There is no workaround possible except not registering events
		1241	for potentially C<dup ()>'ed file descriptors, or to resort to
		1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1243
		1244	=head3 The special problem of fork
		1245
		1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1247	useless behaviour. Libev fully supports fork, but needs to be told about
		1248	it in the child.
		1249
		1250	To support fork in your programs, you either have to call
		1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1253	C<EVBACKEND_POLL>.
		1254
		1255	=head3 The special problem of SIGPIPE
		1256
		1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
		1258	when writing to a pipe whose other end has been closed, your program gets
		1259	sent a SIGPIPE, which, by default, aborts your program. For most programs
		1260	this is sensible behaviour, for daemons, this is usually undesirable.
		1261
		1262	So when you encounter spurious, unexplained daemon exits, make sure you
		1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
		1264	somewhere, as that would have given you a big clue).
		1265
937		1266
938	=head3 Watcher-Specific Functions	1267	=head3 Watcher-Specific Functions
939		1268
940	=over 4	1269	=over 4
941		1270
942	=item ev_io_init (ev_io *, callback, int fd, int events)	1271	=item ev_io_init (ev_io *, callback, int fd, int events)
943		1272
944	=item ev_io_set (ev_io *, int fd, int events)	1273	=item ev_io_set (ev_io *, int fd, int events)
945		1274
946	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
947	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
948	C<EV_READ | EV_WRITE> to receive the given events.	1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
949		1278
950	=item int fd [read-only]	1279	=item int fd [read-only]
951		1280
952	The file descriptor being watched.	1281	The file descriptor being watched.
953		1282
954	=item int events [read-only]	1283	=item int events [read-only]
955		1284
956	The events being watched.	1285	The events being watched.
957		1286
958	=back	1287	=back
		1288
		1289	=head3 Examples
959		1290
960	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1291	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961	readable, but only once. Since it is likely line-buffered, you could	1292	readable, but only once. Since it is likely line-buffered, you could
962	attempt to read a whole line in the callback.	1293	attempt to read a whole line in the callback.
963		1294
964	static void	1295	static void
965	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1296	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
966	{	1297	{
967	ev_io_stop (loop, w);	1298	ev_io_stop (loop, w);
968	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1299	.. read from stdin here (or from w->fd) and handle any I/O errors
969	}	1300	}
970		1301
971	...	1302	...
972	struct ev_loop *loop = ev_default_init (0);	1303	struct ev_loop *loop = ev_default_init (0);
973	struct ev_io stdin_readable;	1304	ev_io stdin_readable;
974	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
975	ev_io_start (loop, &stdin_readable);	1306	ev_io_start (loop, &stdin_readable);
976	ev_loop (loop, 0);	1307	ev_loop (loop, 0);
977		1308
978		1309
979	=head2 C<ev_timer> - relative and optionally repeating timeouts	1310	=head2 C<ev_timer> - relative and optionally repeating timeouts
980		1311
981	Timer watchers are simple relative timers that generate an event after a	1312	Timer watchers are simple relative timers that generate an event after a
982	given time, and optionally repeating in regular intervals after that.	1313	given time, and optionally repeating in regular intervals after that.
983		1314
984	The timers are based on real time, that is, if you register an event that	1315	The timers are based on real time, that is, if you register an event that
985	times out after an hour and you reset your system clock to last years	1316	times out after an hour and you reset your system clock to January last
986	time, it will still time out after (roughly) and hour. "Roughly" because	1317	year, it will still time out after (roughly) one hour. "Roughly" because
987	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the
988	monotonic clock option helps a lot here).	1319	monotonic clock option helps a lot here).
		1320
		1321	The callback is guaranteed to be invoked only I<after> its timeout has
		1322	passed, but if multiple timers become ready during the same loop iteration
		1323	then order of execution is undefined.
		1324
		1325	=head3 Be smart about timeouts
		1326
		1327	Many real-world problems involve some kind of timeout, usually for error
		1328	recovery. A typical example is an HTTP request - if the other side hangs,
		1329	you want to raise some error after a while.
		1330
		1331	What follows are some ways to handle this problem, from obvious and
		1332	inefficient to smart and efficient.
		1333
		1334	In the following, a 60 second activity timeout is assumed - a timeout that
		1335	gets reset to 60 seconds each time there is activity (e.g. each time some
		1336	data or other life sign was received).
		1337
		1338	=over 4
		1339
		1340	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1341
		1342	This is the most obvious, but not the most simple way: In the beginning,
		1343	start the watcher:
		1344
		1345	ev_timer_init (timer, callback, 60., 0.);
		1346	ev_timer_start (loop, timer);
		1347
		1348	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1349	and start it again:
		1350
		1351	ev_timer_stop (loop, timer);
		1352	ev_timer_set (timer, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	This is relatively simple to implement, but means that each time there is
		1356	some activity, libev will first have to remove the timer from its internal
		1357	data structure and then add it again. Libev tries to be fast, but it's
		1358	still not a constant-time operation.
		1359
		1360	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1361
		1362	This is the easiest way, and involves using C<ev_timer_again> instead of
		1363	C<ev_timer_start>.
		1364
		1365	To implement this, configure an C<ev_timer> with a C<repeat> value
		1366	of C<60> and then call C<ev_timer_again> at start and each time you
		1367	successfully read or write some data. If you go into an idle state where
		1368	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1369	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1370
		1371	That means you can ignore both the C<ev_timer_start> function and the
		1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1373	member and C<ev_timer_again>.
		1374
		1375	At start:
		1376
		1377	ev_timer_init (timer, callback);
		1378	timer->repeat = 60.;
		1379	ev_timer_again (loop, timer);
		1380
		1381	Each time there is some activity:
		1382
		1383	ev_timer_again (loop, timer);
		1384
		1385	It is even possible to change the time-out on the fly, regardless of
		1386	whether the watcher is active or not:
		1387
		1388	timer->repeat = 30.;
		1389	ev_timer_again (loop, timer);
		1390
		1391	This is slightly more efficient then stopping/starting the timer each time
		1392	you want to modify its timeout value, as libev does not have to completely
		1393	remove and re-insert the timer from/into its internal data structure.
		1394
		1395	It is, however, even simpler than the "obvious" way to do it.
		1396
		1397	=item 3. Let the timer time out, but then re-arm it as required.
		1398
		1399	This method is more tricky, but usually most efficient: Most timeouts are
		1400	relatively long compared to the intervals between other activity - in
		1401	our example, within 60 seconds, there are usually many I/O events with
		1402	associated activity resets.
		1403
		1404	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1405	but remember the time of last activity, and check for a real timeout only
		1406	within the callback:
		1407
		1408	ev_tstamp last_activity; // time of last activity
		1409
		1410	static void
		1411	callback (EV_P_ ev_timer *w, int revents)
		1412	{
		1413	ev_tstamp now = ev_now (EV_A);
		1414	ev_tstamp timeout = last_activity + 60.;
		1415
		1416	// if last_activity + 60. is older than now, we did time out
		1417	if (timeout < now)
		1418	{
		1419	// timeout occured, take action
		1420	}
		1421	else
		1422	{
		1423	// callback was invoked, but there was some activity, re-arm
		1424	// the watcher to fire in last_activity + 60, which is
		1425	// guaranteed to be in the future, so "again" is positive:
		1426	w->repeat = timeout - now;
		1427	ev_timer_again (EV_A_ w);
		1428	}
		1429	}
		1430
		1431	To summarise the callback: first calculate the real timeout (defined
		1432	as "60 seconds after the last activity"), then check if that time has
		1433	been reached, which means something I<did>, in fact, time out. Otherwise
		1434	the callback was invoked too early (C<timeout> is in the future), so
		1435	re-schedule the timer to fire at that future time, to see if maybe we have
		1436	a timeout then.
		1437
		1438	Note how C<ev_timer_again> is used, taking advantage of the
		1439	C<ev_timer_again> optimisation when the timer is already running.
		1440
		1441	This scheme causes more callback invocations (about one every 60 seconds
		1442	minus half the average time between activity), but virtually no calls to
		1443	libev to change the timeout.
		1444
		1445	To start the timer, simply initialise the watcher and set C<last_activity>
		1446	to the current time (meaning we just have some activity :), then call the
		1447	callback, which will "do the right thing" and start the timer:
		1448
		1449	ev_timer_init (timer, callback);
		1450	last_activity = ev_now (loop);
		1451	callback (loop, timer, EV_TIMEOUT);
		1452
		1453	And when there is some activity, simply store the current time in
		1454	C<last_activity>, no libev calls at all:
		1455
		1456	last_actiivty = ev_now (loop);
		1457
		1458	This technique is slightly more complex, but in most cases where the
		1459	time-out is unlikely to be triggered, much more efficient.
		1460
		1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1462	callback :) - just change the timeout and invoke the callback, which will
		1463	fix things for you.
		1464
		1465	=item 4. Wee, just use a double-linked list for your timeouts.
		1466
		1467	If there is not one request, but many thousands (millions...), all
		1468	employing some kind of timeout with the same timeout value, then one can
		1469	do even better:
		1470
		1471	When starting the timeout, calculate the timeout value and put the timeout
		1472	at the I<end> of the list.
		1473
		1474	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1475	the list is expected to fire (for example, using the technique #3).
		1476
		1477	When there is some activity, remove the timer from the list, recalculate
		1478	the timeout, append it to the end of the list again, and make sure to
		1479	update the C<ev_timer> if it was taken from the beginning of the list.
		1480
		1481	This way, one can manage an unlimited number of timeouts in O(1) time for
		1482	starting, stopping and updating the timers, at the expense of a major
		1483	complication, and having to use a constant timeout. The constant timeout
		1484	ensures that the list stays sorted.
		1485
		1486	=back
		1487
		1488	So which method the best?
		1489
		1490	Method #2 is a simple no-brain-required solution that is adequate in most
		1491	situations. Method #3 requires a bit more thinking, but handles many cases
		1492	better, and isn't very complicated either. In most case, choosing either
		1493	one is fine, with #3 being better in typical situations.
		1494
		1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1496	rather complicated, but extremely efficient, something that really pays
		1497	off after the first million or so of active timers, i.e. it's usually
		1498	overkill :)
		1499
		1500	=head3 The special problem of time updates
		1501
		1502	Establishing the current time is a costly operation (it usually takes at
		1503	least two system calls): EV therefore updates its idea of the current
		1504	time only before and after C<ev_loop> collects new events, which causes a
		1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1506	lots of events in one iteration.
989		1507
990	The relative timeouts are calculated relative to the C<ev_now ()>	1508	The relative timeouts are calculated relative to the C<ev_now ()>
991	time. This is usually the right thing as this timestamp refers to the time	1509	time. This is usually the right thing as this timestamp refers to the time
992	of the event triggering whatever timeout you are modifying/starting. If	1510	of the event triggering whatever timeout you are modifying/starting. If
993	you suspect event processing to be delayed and you I<need> to base the timeout	1511	you suspect event processing to be delayed and you I<need> to base the
994	on the current time, use something like this to adjust for this:	1512	timeout on the current time, use something like this to adjust for this:
995		1513
996	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
997		1515
998	The callback is guarenteed to be invoked only when its timeout has passed,	1516	If the event loop is suspended for a long time, you can also force an
999	but if multiple timers become ready during the same loop iteration then	1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1000	order of execution is undefined.	1518	()>.
1001		1519
1002	=head3 Watcher-Specific Functions and Data Members	1520	=head3 Watcher-Specific Functions and Data Members
1003		1521
1004	=over 4	1522	=over 4
1005		1523
1006	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1007		1525
1008	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1009		1527
1010	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1528	Configure the timer to trigger after C<after> seconds. If C<repeat>
1011	C<0.>, then it will automatically be stopped. If it is positive, then the	1529	is C<0.>, then it will automatically be stopped once the timeout is
1012	timer will automatically be configured to trigger again C<repeat> seconds	1530	reached. If it is positive, then the timer will automatically be
1013	later, again, and again, until stopped manually.	1531	configured to trigger again C<repeat> seconds later, again, and again,
		1532	until stopped manually.
1014		1533
1015	The timer itself will do a best-effort at avoiding drift, that is, if you	1534	The timer itself will do a best-effort at avoiding drift, that is, if
1016	configure a timer to trigger every 10 seconds, then it will trigger at	1535	you configure a timer to trigger every 10 seconds, then it will normally
1017	exactly 10 second intervals. If, however, your program cannot keep up with	1536	trigger at exactly 10 second intervals. If, however, your program cannot
1018	the timer (because it takes longer than those 10 seconds to do stuff) the	1537	keep up with the timer (because it takes longer than those 10 seconds to
1019	timer will not fire more than once per event loop iteration.	1538	do stuff) the timer will not fire more than once per event loop iteration.
1020		1539
1021	=item ev_timer_again (loop)	1540	=item ev_timer_again (loop, ev_timer *)
1022		1541
1023	This will act as if the timer timed out and restart it again if it is	1542	This will act as if the timer timed out and restart it again if it is
1024	repeating. The exact semantics are:	1543	repeating. The exact semantics are:
1025		1544
1026	If the timer is pending, its pending status is cleared.	1545	If the timer is pending, its pending status is cleared.
1027		1546
1028	If the timer is started but nonrepeating, stop it (as if it timed out).	1547	If the timer is started but non-repeating, stop it (as if it timed out).
1029		1548
1030	If the timer is repeating, either start it if necessary (with the	1549	If the timer is repeating, either start it if necessary (with the
1031	C<repeat> value), or reset the running timer to the C<repeat> value.	1550	C<repeat> value), or reset the running timer to the C<repeat> value.
1032		1551
1033	This sounds a bit complicated, but here is a useful and typical	1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1034	example: Imagine you have a tcp connection and you want a so-called idle	1553	usage example.
1035	timeout, that is, you want to be called when there have been, say, 60
1036	seconds of inactivity on the socket. The easiest way to do this is to
1037	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1038	C<ev_timer_again> each time you successfully read or write some data. If
1039	you go into an idle state where you do not expect data to travel on the
1040	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1041	automatically restart it if need be.
1042
1043	That means you can ignore the C<after> value and C<ev_timer_start>
1044	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1045
1046	ev_timer_init (timer, callback, 0., 5.);
1047	ev_timer_again (loop, timer);
1048	...
1049	timer->again = 17.;
1050	ev_timer_again (loop, timer);
1051	...
1052	timer->again = 10.;
1053	ev_timer_again (loop, timer);
1054
1055	This is more slightly efficient then stopping/starting the timer each time
1056	you want to modify its timeout value.
1057		1554
1058	=item ev_tstamp repeat [read-write]	1555	=item ev_tstamp repeat [read-write]
1059		1556
1060	The current C<repeat> value. Will be used each time the watcher times out	1557	The current C<repeat> value. Will be used each time the watcher times out
1061	or C<ev_timer_again> is called and determines the next timeout (if any),	1558	or C<ev_timer_again> is called, and determines the next timeout (if any),
1062	which is also when any modifications are taken into account.	1559	which is also when any modifications are taken into account.
1063		1560
1064	=back	1561	=back
1065		1562
		1563	=head3 Examples
		1564
1066	Example: Create a timer that fires after 60 seconds.	1565	Example: Create a timer that fires after 60 seconds.
1067		1566
1068	static void	1567	static void
1069	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1568	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1070	{	1569	{
1071	.. one minute over, w is actually stopped right here	1570	.. one minute over, w is actually stopped right here
1072	}	1571	}
1073		1572
1074	struct ev_timer mytimer;	1573	ev_timer mytimer;
1075	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1574	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1076	ev_timer_start (loop, &mytimer);	1575	ev_timer_start (loop, &mytimer);
1077		1576
1078	Example: Create a timeout timer that times out after 10 seconds of	1577	Example: Create a timeout timer that times out after 10 seconds of
1079	inactivity.	1578	inactivity.
1080		1579
1081	static void	1580	static void
1082	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1581	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1083	{	1582	{
1084	.. ten seconds without any activity	1583	.. ten seconds without any activity
1085	}	1584	}
1086		1585
1087	struct ev_timer mytimer;	1586	ev_timer mytimer;
1088	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1089	ev_timer_again (&mytimer); /* start timer */	1588	ev_timer_again (&mytimer); /* start timer */
1090	ev_loop (loop, 0);	1589	ev_loop (loop, 0);
1091		1590
1092	// and in some piece of code that gets executed on any "activity":	1591	// and in some piece of code that gets executed on any "activity":
1093	// reset the timeout to start ticking again at 10 seconds	1592	// reset the timeout to start ticking again at 10 seconds
1094	ev_timer_again (&mytimer);	1593	ev_timer_again (&mytimer);
1095		1594
1096		1595
1097	=head2 C<ev_periodic> - to cron or not to cron?	1596	=head2 C<ev_periodic> - to cron or not to cron?
1098		1597
1099	Periodic watchers are also timers of a kind, but they are very versatile	1598	Periodic watchers are also timers of a kind, but they are very versatile
1100	(and unfortunately a bit complex).	1599	(and unfortunately a bit complex).
1101		1600
1102	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
1103	but on wallclock time (absolute time). You can tell a periodic watcher	1602	but on wall clock time (absolute time). You can tell a periodic watcher
1104	to trigger "at" some specific point in time. For example, if you tell a	1603	to trigger after some specific point in time. For example, if you tell a
1105	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()
1106	+ 10.>) and then reset your system clock to the last year, then it will	1605	+ 10.>, that is, an absolute time not a delay) and then reset your system
		1606	clock to January of the previous year, then it will take more than year
1107	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1108	roughly 10 seconds later).	1608	roughly 10 seconds later as it uses a relative timeout).
1109		1609
1110	They can also be used to implement vastly more complex timers, such as	1610	C<ev_periodic>s can also be used to implement vastly more complex timers,
1111	triggering an event on each midnight, local time or other, complicated,	1611	such as triggering an event on each "midnight, local time", or other
1112	rules.	1612	complicated rules.
1113		1613
1114	As with timers, the callback is guarenteed to be invoked only when the	1614	As with timers, the callback is guaranteed to be invoked only when the
1115	time (C<at>) has been passed, but if multiple periodic timers become ready	1615	time (C<at>) has passed, but if multiple periodic timers become ready
1116	during the same loop iteration then order of execution is undefined.	1616	during the same loop iteration, then order of execution is undefined.
1117		1617
1118	=head3 Watcher-Specific Functions and Data Members	1618	=head3 Watcher-Specific Functions and Data Members
1119		1619
1120	=over 4	1620	=over 4
1121		1621
1122	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1123		1623
1124	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1125		1625
1126	Lots of arguments, lets sort it out... There are basically three modes of	1626	Lots of arguments, lets sort it out... There are basically three modes of
1127	operation, and we will explain them from simplest to complex:	1627	operation, and we will explain them from simplest to most complex:
1128		1628
1129	=over 4	1629	=over 4
1130		1630
1131	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1132		1632
1133	In this configuration the watcher triggers an event at the wallclock time	1633	In this configuration the watcher triggers an event after the wall clock
1134	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1634	time C<at> has passed. It will not repeat and will not adjust when a time
1135	that is, if it is to be run at January 1st 2011 then it will run when the	1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will
1136	system time reaches or surpasses this time.	1636	only run when the system clock reaches or surpasses this time.
1137		1637
1138	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1139		1639
1140	In this mode the watcher will always be scheduled to time out at the next	1640	In this mode the watcher will always be scheduled to time out at the next
1141	C<at + N * interval> time (for some integer N, which can also be negative)	1641	C<at + N * interval> time (for some integer N, which can also be negative)
1142	and then repeat, regardless of any time jumps.	1642	and then repeat, regardless of any time jumps.
1143		1643
1144	This can be used to create timers that do not drift with respect to system	1644	This can be used to create timers that do not drift with respect to the
1145	time:	1645	system clock, for example, here is a C<ev_periodic> that triggers each
		1646	hour, on the hour:
1146		1647
1147	ev_periodic_set (&periodic, 0., 3600., 0);	1648	ev_periodic_set (&periodic, 0., 3600., 0);
1148		1649
1149	This doesn't mean there will always be 3600 seconds in between triggers,	1650	This doesn't mean there will always be 3600 seconds in between triggers,
1150	but only that the the callback will be called when the system time shows a	1651	but only that the callback will be called when the system time shows a
1151	full hour (UTC), or more correctly, when the system time is evenly divisible	1652	full hour (UTC), or more correctly, when the system time is evenly divisible
1152	by 3600.	1653	by 3600.
1153		1654
1154	Another way to think about it (for the mathematically inclined) is that	1655	Another way to think about it (for the mathematically inclined) is that
1155	C<ev_periodic> will try to run the callback in this mode at the next possible	1656	C<ev_periodic> will try to run the callback in this mode at the next possible
1156	time where C<time = at (mod interval)>, regardless of any time jumps.	1657	time where C<time = at (mod interval)>, regardless of any time jumps.
1157		1658
1158	For numerical stability it is preferable that the C<at> value is near	1659	For numerical stability it is preferable that the C<at> value is near
1159	C<ev_now ()> (the current time), but there is no range requirement for	1660	C<ev_now ()> (the current time), but there is no range requirement for
1160	this value.	1661	this value, and in fact is often specified as zero.
		1662
		1663	Note also that there is an upper limit to how often a timer can fire (CPU
		1664	speed for example), so if C<interval> is very small then timing stability
		1665	will of course deteriorate. Libev itself tries to be exact to be about one
		1666	millisecond (if the OS supports it and the machine is fast enough).
1161		1667
1162	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1163		1669
1164	In this mode the values for C<interval> and C<at> are both being	1670	In this mode the values for C<interval> and C<at> are both being
1165	ignored. Instead, each time the periodic watcher gets scheduled, the	1671	ignored. Instead, each time the periodic watcher gets scheduled, the
1166	reschedule callback will be called with the watcher as first, and the	1672	reschedule callback will be called with the watcher as first, and the
1167	current time as second argument.	1673	current time as second argument.
1168		1674
1169	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1170	ever, or make any event loop modifications>. If you need to stop it,	1676	ever, or make ANY event loop modifications whatsoever>.
1171	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1172	starting an C<ev_prepare> watcher, which is legal).
1173		1677
		1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1680	only event loop modification you are allowed to do).
		1681
1174	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1682	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1175	ev_tstamp now)>, e.g.:	1683	*w, ev_tstamp now)>, e.g.:
1176		1684
		1685	static ev_tstamp
1177	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1686	my_rescheduler (ev_periodic *w, ev_tstamp now)
1178	{	1687	{
1179	return now + 60.;	1688	return now + 60.;
1180	}	1689	}
1181		1690
1182	It must return the next time to trigger, based on the passed time value	1691	It must return the next time to trigger, based on the passed time value
1183	(that is, the lowest time value larger than to the second argument). It	1692	(that is, the lowest time value larger than to the second argument). It
1184	will usually be called just before the callback will be triggered, but	1693	will usually be called just before the callback will be triggered, but
1185	might be called at other times, too.	1694	might be called at other times, too.
1186		1695
1187	NOTE: I<< This callback must always return a time that is later than the	1696	NOTE: I<< This callback must always return a time that is higher than or
1188	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	1697	equal to the passed C<now> value >>.
1189		1698
1190	This can be used to create very complex timers, such as a timer that	1699	This can be used to create very complex timers, such as a timer that
1191	triggers on each midnight, local time. To do this, you would calculate the	1700	triggers on "next midnight, local time". To do this, you would calculate the
1192	next midnight after C<now> and return the timestamp value for this. How	1701	next midnight after C<now> and return the timestamp value for this. How
1193	you do this is, again, up to you (but it is not trivial, which is the main	1702	you do this is, again, up to you (but it is not trivial, which is the main
1194	reason I omitted it as an example).	1703	reason I omitted it as an example).
1195		1704
1196	=back	1705	=back
…		…
1200	Simply stops and restarts the periodic watcher again. This is only useful	1709	Simply stops and restarts the periodic watcher again. This is only useful
1201	when you changed some parameters or the reschedule callback would return	1710	when you changed some parameters or the reschedule callback would return
1202	a different time than the last time it was called (e.g. in a crond like	1711	a different time than the last time it was called (e.g. in a crond like
1203	program when the crontabs have changed).	1712	program when the crontabs have changed).
1204		1713
		1714	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1715
		1716	When active, returns the absolute time that the watcher is supposed to
		1717	trigger next.
		1718
1205	=item ev_tstamp offset [read-write]	1719	=item ev_tstamp offset [read-write]
1206		1720
1207	When repeating, this contains the offset value, otherwise this is the	1721	When repeating, this contains the offset value, otherwise this is the
1208	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209		1723
…		…
1214		1728
1215	The current interval value. Can be modified any time, but changes only	1729	The current interval value. Can be modified any time, but changes only
1216	take effect when the periodic timer fires or C<ev_periodic_again> is being	1730	take effect when the periodic timer fires or C<ev_periodic_again> is being
1217	called.	1731	called.
1218		1732
1219	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1733	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1220		1734
1221	The current reschedule callback, or C<0>, if this functionality is	1735	The current reschedule callback, or C<0>, if this functionality is
1222	switched off. Can be changed any time, but changes only take effect when	1736	switched off. Can be changed any time, but changes only take effect when
1223	the periodic timer fires or C<ev_periodic_again> is being called.	1737	the periodic timer fires or C<ev_periodic_again> is being called.
1224		1738
1225	=back	1739	=back
1226		1740
		1741	=head3 Examples
		1742
1227	Example: Call a callback every hour, or, more precisely, whenever the	1743	Example: Call a callback every hour, or, more precisely, whenever the
1228	system clock is divisible by 3600. The callback invocation times have	1744	system time is divisible by 3600. The callback invocation times have
1229	potentially a lot of jittering, but good long-term stability.	1745	potentially a lot of jitter, but good long-term stability.
1230		1746
1231	static void	1747	static void
1232	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1233	{	1749	{
1234	... its now a full hour (UTC, or TAI or whatever your clock follows)	1750	... its now a full hour (UTC, or TAI or whatever your clock follows)
1235	}	1751	}
1236		1752
1237	struct ev_periodic hourly_tick;	1753	ev_periodic hourly_tick;
1238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1754	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1239	ev_periodic_start (loop, &hourly_tick);	1755	ev_periodic_start (loop, &hourly_tick);
1240		1756
1241	Example: The same as above, but use a reschedule callback to do it:	1757	Example: The same as above, but use a reschedule callback to do it:
1242		1758
1243	#include <math.h>	1759	#include <math.h>
1244		1760
1245	static ev_tstamp	1761	static ev_tstamp
1246	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1762	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1247	{	1763	{
1248	return fmod (now, 3600.) + 3600.;	1764	return now + (3600. - fmod (now, 3600.));
1249	}	1765	}
1250		1766
1251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1767	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1252		1768
1253	Example: Call a callback every hour, starting now:	1769	Example: Call a callback every hour, starting now:
1254		1770
1255	struct ev_periodic hourly_tick;	1771	ev_periodic hourly_tick;
1256	ev_periodic_init (&hourly_tick, clock_cb,	1772	ev_periodic_init (&hourly_tick, clock_cb,
1257	fmod (ev_now (loop), 3600.), 3600., 0);	1773	fmod (ev_now (loop), 3600.), 3600., 0);
1258	ev_periodic_start (loop, &hourly_tick);	1774	ev_periodic_start (loop, &hourly_tick);
1259		1775
1260		1776
1261	=head2 C<ev_signal> - signal me when a signal gets signalled!	1777	=head2 C<ev_signal> - signal me when a signal gets signalled!
1262		1778
1263	Signal watchers will trigger an event when the process receives a specific	1779	Signal watchers will trigger an event when the process receives a specific
1264	signal one or more times. Even though signals are very asynchronous, libev	1780	signal one or more times. Even though signals are very asynchronous, libev
1265	will try it's best to deliver signals synchronously, i.e. as part of the	1781	will try it's best to deliver signals synchronously, i.e. as part of the
1266	normal event processing, like any other event.	1782	normal event processing, like any other event.
1267		1783
		1784	If you want signals asynchronously, just use C<sigaction> as you would
		1785	do without libev and forget about sharing the signal. You can even use
		1786	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1787
1268	You can configure as many watchers as you like per signal. Only when the	1788	You can configure as many watchers as you like per signal. Only when the
1269	first watcher gets started will libev actually register a signal watcher	1789	first watcher gets started will libev actually register a signal handler
1270	with the kernel (thus it coexists with your own signal handlers as long	1790	with the kernel (thus it coexists with your own signal handlers as long as
1271	as you don't register any with libev). Similarly, when the last signal	1791	you don't register any with libev for the same signal). Similarly, when
1272	watcher for a signal is stopped libev will reset the signal handler to	1792	the last signal watcher for a signal is stopped, libev will reset the
1273	SIG_DFL (regardless of what it was set to before).	1793	signal handler to SIG_DFL (regardless of what it was set to before).
		1794
		1795	If possible and supported, libev will install its handlers with
		1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
		1797	interrupted. If you have a problem with system calls getting interrupted by
		1798	signals you can block all signals in an C<ev_check> watcher and unblock
		1799	them in an C<ev_prepare> watcher.
1274		1800
1275	=head3 Watcher-Specific Functions and Data Members	1801	=head3 Watcher-Specific Functions and Data Members
1276		1802
1277	=over 4	1803	=over 4
1278		1804
…		…
1287		1813
1288	The signal the watcher watches out for.	1814	The signal the watcher watches out for.
1289		1815
1290	=back	1816	=back
1291		1817
		1818	=head3 Examples
		1819
		1820	Example: Try to exit cleanly on SIGINT.
		1821
		1822	static void
		1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
		1824	{
		1825	ev_unloop (loop, EVUNLOOP_ALL);
		1826	}
		1827
		1828	ev_signal signal_watcher;
		1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1830	ev_signal_start (loop, &signal_watcher);
		1831
1292		1832
1293	=head2 C<ev_child> - watch out for process status changes	1833	=head2 C<ev_child> - watch out for process status changes
1294		1834
1295	Child watchers trigger when your process receives a SIGCHLD in response to	1835	Child watchers trigger when your process receives a SIGCHLD in response to
1296	some child status changes (most typically when a child of yours dies).	1836	some child status changes (most typically when a child of yours dies or
		1837	exits). It is permissible to install a child watcher I<after> the child
		1838	has been forked (which implies it might have already exited), as long
		1839	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1840	forking and then immediately registering a watcher for the child is fine,
		1841	but forking and registering a watcher a few event loop iterations later is
		1842	not.
		1843
		1844	Only the default event loop is capable of handling signals, and therefore
		1845	you can only register child watchers in the default event loop.
		1846
		1847	=head3 Process Interaction
		1848
		1849	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1850	initialised. This is necessary to guarantee proper behaviour even if
		1851	the first child watcher is started after the child exits. The occurrence
		1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1853	synchronously as part of the event loop processing. Libev always reaps all
		1854	children, even ones not watched.
		1855
		1856	=head3 Overriding the Built-In Processing
		1857
		1858	Libev offers no special support for overriding the built-in child
		1859	processing, but if your application collides with libev's default child
		1860	handler, you can override it easily by installing your own handler for
		1861	C<SIGCHLD> after initialising the default loop, and making sure the
		1862	default loop never gets destroyed. You are encouraged, however, to use an
		1863	event-based approach to child reaping and thus use libev's support for
		1864	that, so other libev users can use C<ev_child> watchers freely.
		1865
		1866	=head3 Stopping the Child Watcher
		1867
		1868	Currently, the child watcher never gets stopped, even when the
		1869	child terminates, so normally one needs to stop the watcher in the
		1870	callback. Future versions of libev might stop the watcher automatically
		1871	when a child exit is detected.
1297		1872
1298	=head3 Watcher-Specific Functions and Data Members	1873	=head3 Watcher-Specific Functions and Data Members
1299		1874
1300	=over 4	1875	=over 4
1301		1876
1302	=item ev_child_init (ev_child *, callback, int pid)	1877	=item ev_child_init (ev_child *, callback, int pid, int trace)
1303		1878
1304	=item ev_child_set (ev_child *, int pid)	1879	=item ev_child_set (ev_child *, int pid, int trace)
1305		1880
1306	Configures the watcher to wait for status changes of process C<pid> (or	1881	Configures the watcher to wait for status changes of process C<pid> (or
1307	I<any> process if C<pid> is specified as C<0>). The callback can look	1882	I<any> process if C<pid> is specified as C<0>). The callback can look
1308	at the C<rstatus> member of the C<ev_child> watcher structure to see	1883	at the C<rstatus> member of the C<ev_child> watcher structure to see
1309	the status word (use the macros from C<sys/wait.h> and see your systems	1884	the status word (use the macros from C<sys/wait.h> and see your systems
1310	C<waitpid> documentation). The C<rpid> member contains the pid of the	1885	C<waitpid> documentation). The C<rpid> member contains the pid of the
1311	process causing the status change.	1886	process causing the status change. C<trace> must be either C<0> (only
		1887	activate the watcher when the process terminates) or C<1> (additionally
		1888	activate the watcher when the process is stopped or continued).
1312		1889
1313	=item int pid [read-only]	1890	=item int pid [read-only]
1314		1891
1315	The process id this watcher watches out for, or C<0>, meaning any process id.	1892	The process id this watcher watches out for, or C<0>, meaning any process id.
1316		1893
…		…
1323	The process exit/trace status caused by C<rpid> (see your systems	1900	The process exit/trace status caused by C<rpid> (see your systems
1324	C<waitpid> and C<sys/wait.h> documentation for details).	1901	C<waitpid> and C<sys/wait.h> documentation for details).
1325		1902
1326	=back	1903	=back
1327		1904
1328	Example: Try to exit cleanly on SIGINT and SIGTERM.	1905	=head3 Examples
1329		1906
		1907	Example: C<fork()> a new process and install a child handler to wait for
		1908	its completion.
		1909
		1910	ev_child cw;
		1911
1330	static void	1912	static void
1331	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1913	child_cb (EV_P_ ev_child *w, int revents)
1332	{	1914	{
1333	ev_unloop (loop, EVUNLOOP_ALL);	1915	ev_child_stop (EV_A_ w);
		1916	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1334	}	1917	}
1335		1918
1336	struct ev_signal signal_watcher;	1919	pid_t pid = fork ();
1337	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1920
1338	ev_signal_start (loop, &sigint_cb);	1921	if (pid < 0)
		1922	// error
		1923	else if (pid == 0)
		1924	{
		1925	// the forked child executes here
		1926	exit (1);
		1927	}
		1928	else
		1929	{
		1930	ev_child_init (&cw, child_cb, pid, 0);
		1931	ev_child_start (EV_DEFAULT_ &cw);
		1932	}
1339		1933
1340		1934
1341	=head2 C<ev_stat> - did the file attributes just change?	1935	=head2 C<ev_stat> - did the file attributes just change?
1342		1936
1343	This watches a filesystem path for attribute changes. That is, it calls	1937	This watches a file system path for attribute changes. That is, it calls
1344	C<stat> regularly (or when the OS says it changed) and sees if it changed	1938	C<stat> on that path in regular intervals (or when the OS says it changed)
1345	compared to the last time, invoking the callback if it did.	1939	and sees if it changed compared to the last time, invoking the callback if
		1940	it did.
1346		1941
1347	The path does not need to exist: changing from "path exists" to "path does	1942	The path does not need to exist: changing from "path exists" to "path does
1348	not exist" is a status change like any other. The condition "path does	1943	not exist" is a status change like any other. The condition "path does not
1349	not exist" is signified by the C<st_nlink> field being zero (which is	1944	exist" (or more correctly "path cannot be stat'ed") is signified by the
1350	otherwise always forced to be at least one) and all the other fields of	1945	C<st_nlink> field being zero (which is otherwise always forced to be at
1351	the stat buffer having unspecified contents.	1946	least one) and all the other fields of the stat buffer having unspecified
		1947	contents.
1352		1948
1353	The path I<should> be absolute and I<must not> end in a slash. If it is	1949	The path I<must not> end in a slash or contain special components such as
		1950	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1354	relative and your working directory changes, the behaviour is undefined.	1951	your working directory changes, then the behaviour is undefined.
1355		1952
1356	Since there is no standard to do this, the portable implementation simply	1953	Since there is no portable change notification interface available, the
1357	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1954	portable implementation simply calls C<stat(2)> regularly on the path
1358	can specify a recommended polling interval for this case. If you specify	1955	to see if it changed somehow. You can specify a recommended polling
1359	a polling interval of C<0> (highly recommended!) then a I<suitable,	1956	interval for this case. If you specify a polling interval of C<0> (highly
1360	unspecified default> value will be used (which you can expect to be around	1957	recommended!) then a I<suitable, unspecified default> value will be used
1361	five seconds, although this might change dynamically). Libev will also	1958	(which you can expect to be around five seconds, although this might
1362	impose a minimum interval which is currently around C<0.1>, but thats	1959	change dynamically). Libev will also impose a minimum interval which is
1363	usually overkill.	1960	currently around C<0.1>, but that's usually overkill.
1364		1961
1365	This watcher type is not meant for massive numbers of stat watchers,	1962	This watcher type is not meant for massive numbers of stat watchers,
1366	as even with OS-supported change notifications, this can be	1963	as even with OS-supported change notifications, this can be
1367	resource-intensive.	1964	resource-intensive.
1368		1965
1369	At the time of this writing, only the Linux inotify interface is	1966	At the time of this writing, the only OS-specific interface implemented
1370	implemented (implementing kqueue support is left as an exercise for the	1967	is the Linux inotify interface (implementing kqueue support is left as an
1371	reader). Inotify will be used to give hints only and should not change the	1968	exercise for the reader. Note, however, that the author sees no way of
1372	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1969	implementing C<ev_stat> semantics with kqueue, except as a hint).
1373	to fall back to regular polling again even with inotify, but changes are	1970
1374	usually detected immediately, and if the file exists there will be no	1971	=head3 ABI Issues (Largefile Support)
1375	polling.	1972
		1973	Libev by default (unless the user overrides this) uses the default
		1974	compilation environment, which means that on systems with large file
		1975	support disabled by default, you get the 32 bit version of the stat
		1976	structure. When using the library from programs that change the ABI to
		1977	use 64 bit file offsets the programs will fail. In that case you have to
		1978	compile libev with the same flags to get binary compatibility. This is
		1979	obviously the case with any flags that change the ABI, but the problem is
		1980	most noticeably displayed with ev_stat and large file support.
		1981
		1982	The solution for this is to lobby your distribution maker to make large
		1983	file interfaces available by default (as e.g. FreeBSD does) and not
		1984	optional. Libev cannot simply switch on large file support because it has
		1985	to exchange stat structures with application programs compiled using the
		1986	default compilation environment.
		1987
		1988	=head3 Inotify and Kqueue
		1989
		1990	When C<inotify (7)> support has been compiled into libev and present at
		1991	runtime, it will be used to speed up change detection where possible. The
		1992	inotify descriptor will be created lazily when the first C<ev_stat>
		1993	watcher is being started.
		1994
		1995	Inotify presence does not change the semantics of C<ev_stat> watchers
		1996	except that changes might be detected earlier, and in some cases, to avoid
		1997	making regular C<stat> calls. Even in the presence of inotify support
		1998	there are many cases where libev has to resort to regular C<stat> polling,
		1999	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2000	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2001	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2002	xfs are fully working) libev usually gets away without polling.
		2003
		2004	There is no support for kqueue, as apparently it cannot be used to
		2005	implement this functionality, due to the requirement of having a file
		2006	descriptor open on the object at all times, and detecting renames, unlinks
		2007	etc. is difficult.
		2008
		2009	=head3 C<stat ()> is a synchronous operation
		2010
		2011	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2012	the process. The exception are C<ev_stat> watchers - those call C<stat
		2013	()>, which is a synchronous operation.
		2014
		2015	For local paths, this usually doesn't matter: unless the system is very
		2016	busy or the intervals between stat's are large, a stat call will be fast,
		2017	as the path data is suually in memory already (except when starting the
		2018	watcher).
		2019
		2020	For networked file systems, calling C<stat ()> can block an indefinite
		2021	time due to network issues, and even under good conditions, a stat call
		2022	often takes multiple milliseconds.
		2023
		2024	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2025	paths, although this is fully supported by libev.
		2026
		2027	=head3 The special problem of stat time resolution
		2028
		2029	The C<stat ()> system call only supports full-second resolution portably,
		2030	and even on systems where the resolution is higher, most file systems
		2031	still only support whole seconds.
		2032
		2033	That means that, if the time is the only thing that changes, you can
		2034	easily miss updates: on the first update, C<ev_stat> detects a change and
		2035	calls your callback, which does something. When there is another update
		2036	within the same second, C<ev_stat> will be unable to detect unless the
		2037	stat data does change in other ways (e.g. file size).
		2038
		2039	The solution to this is to delay acting on a change for slightly more
		2040	than a second (or till slightly after the next full second boundary), using
		2041	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
		2042	ev_timer_again (loop, w)>).
		2043
		2044	The C<.02> offset is added to work around small timing inconsistencies
		2045	of some operating systems (where the second counter of the current time
		2046	might be be delayed. One such system is the Linux kernel, where a call to
		2047	C<gettimeofday> might return a timestamp with a full second later than
		2048	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2049	update file times then there will be a small window where the kernel uses
		2050	the previous second to update file times but libev might already execute
		2051	the timer callback).
1376		2052
1377	=head3 Watcher-Specific Functions and Data Members	2053	=head3 Watcher-Specific Functions and Data Members
1378		2054
1379	=over 4	2055	=over 4
1380		2056
…		…
1386	C<path>. The C<interval> is a hint on how quickly a change is expected to	2062	C<path>. The C<interval> is a hint on how quickly a change is expected to
1387	be detected and should normally be specified as C<0> to let libev choose	2063	be detected and should normally be specified as C<0> to let libev choose
1388	a suitable value. The memory pointed to by C<path> must point to the same	2064	a suitable value. The memory pointed to by C<path> must point to the same
1389	path for as long as the watcher is active.	2065	path for as long as the watcher is active.
1390		2066
1391	The callback will be receive C<EV_STAT> when a change was detected,	2067	The callback will receive an C<EV_STAT> event when a change was detected,
1392	relative to the attributes at the time the watcher was started (or the	2068	relative to the attributes at the time the watcher was started (or the
1393	last change was detected).	2069	last change was detected).
1394		2070
1395	=item ev_stat_stat (ev_stat *)	2071	=item ev_stat_stat (loop, ev_stat *)
1396		2072
1397	Updates the stat buffer immediately with new values. If you change the	2073	Updates the stat buffer immediately with new values. If you change the
1398	watched path in your callback, you could call this fucntion to avoid	2074	watched path in your callback, you could call this function to avoid
1399	detecting this change (while introducing a race condition). Can also be	2075	detecting this change (while introducing a race condition if you are not
1400	useful simply to find out the new values.	2076	the only one changing the path). Can also be useful simply to find out the
		2077	new values.
1401		2078
1402	=item ev_statdata attr [read-only]	2079	=item ev_statdata attr [read-only]
1403		2080
1404	The most-recently detected attributes of the file. Although the type is of	2081	The most-recently detected attributes of the file. Although the type is
1405	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2082	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1406	suitable for your system. If the C<st_nlink> member is C<0>, then there	2083	suitable for your system, but you can only rely on the POSIX-standardised
		2084	members to be present. If the C<st_nlink> member is C<0>, then there was
1407	was some error while C<stat>ing the file.	2085	some error while C<stat>ing the file.
1408		2086
1409	=item ev_statdata prev [read-only]	2087	=item ev_statdata prev [read-only]
1410		2088
1411	The previous attributes of the file. The callback gets invoked whenever	2089	The previous attributes of the file. The callback gets invoked whenever
1412	C<prev> != C<attr>.	2090	C<prev> != C<attr>, or, more precisely, one or more of these members
		2091	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2092	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1413		2093
1414	=item ev_tstamp interval [read-only]	2094	=item ev_tstamp interval [read-only]
1415		2095
1416	The specified interval.	2096	The specified interval.
1417		2097
1418	=item const char *path [read-only]	2098	=item const char *path [read-only]
1419		2099
1420	The filesystem path that is being watched.	2100	The file system path that is being watched.
1421		2101
1422	=back	2102	=back
1423		2103
		2104	=head3 Examples
		2105
1424	Example: Watch C</etc/passwd> for attribute changes.	2106	Example: Watch C</etc/passwd> for attribute changes.
1425		2107
1426	static void	2108	static void
1427	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2109	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1428	{	2110	{
1429	/* /etc/passwd changed in some way */	2111	/* /etc/passwd changed in some way */
1430	if (w->attr.st_nlink)	2112	if (w->attr.st_nlink)
1431	{	2113	{
1432	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2114	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1433	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2115	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1434	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2116	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1435	}	2117	}
1436	else	2118	else
1437	/* you shalt not abuse printf for puts */	2119	/* you shalt not abuse printf for puts */
1438	puts ("wow, /etc/passwd is not there, expect problems. "	2120	puts ("wow, /etc/passwd is not there, expect problems. "
1439	"if this is windows, they already arrived\n");	2121	"if this is windows, they already arrived\n");
1440	}	2122	}
1441		2123
1442	...	2124	...
1443	ev_stat passwd;	2125	ev_stat passwd;
1444		2126
1445	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	2127	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1446	ev_stat_start (loop, &passwd);	2128	ev_stat_start (loop, &passwd);
		2129
		2130	Example: Like above, but additionally use a one-second delay so we do not
		2131	miss updates (however, frequent updates will delay processing, too, so
		2132	one might do the work both on C<ev_stat> callback invocation I<and> on
		2133	C<ev_timer> callback invocation).
		2134
		2135	static ev_stat passwd;
		2136	static ev_timer timer;
		2137
		2138	static void
		2139	timer_cb (EV_P_ ev_timer *w, int revents)
		2140	{
		2141	ev_timer_stop (EV_A_ w);
		2142
		2143	/* now it's one second after the most recent passwd change */
		2144	}
		2145
		2146	static void
		2147	stat_cb (EV_P_ ev_stat *w, int revents)
		2148	{
		2149	/* reset the one-second timer */
		2150	ev_timer_again (EV_A_ &timer);
		2151	}
		2152
		2153	...
		2154	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		2155	ev_stat_start (loop, &passwd);
		2156	ev_timer_init (&timer, timer_cb, 0., 1.02);
1447		2157
1448		2158
1449	=head2 C<ev_idle> - when you've got nothing better to do...	2159	=head2 C<ev_idle> - when you've got nothing better to do...
1450		2160
1451	Idle watchers trigger events when no other events of the same or higher	2161	Idle watchers trigger events when no other events of the same or higher
1452	priority are pending (prepare, check and other idle watchers do not	2162	priority are pending (prepare, check and other idle watchers do not count
1453	count).	2163	as receiving "events").
1454		2164
1455	That is, as long as your process is busy handling sockets or timeouts	2165	That is, as long as your process is busy handling sockets or timeouts
1456	(or even signals, imagine) of the same or higher priority it will not be	2166	(or even signals, imagine) of the same or higher priority it will not be
1457	triggered. But when your process is idle (or only lower-priority watchers	2167	triggered. But when your process is idle (or only lower-priority watchers
1458	are pending), the idle watchers are being called once per event loop	2168	are pending), the idle watchers are being called once per event loop
…		…
1477	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1478	believe me.	2188	believe me.
1479		2189
1480	=back	2190	=back
1481		2191
		2192	=head3 Examples
		2193
1482	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2194	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1483	callback, free it. Also, use no error checking, as usual.	2195	callback, free it. Also, use no error checking, as usual.
1484		2196
1485	static void	2197	static void
1486	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1487	{	2199	{
1488	free (w);	2200	free (w);
1489	// now do something you wanted to do when the program has	2201	// now do something you wanted to do when the program has
1490	// no longer asnything immediate to do.	2202	// no longer anything immediate to do.
1491	}	2203	}
1492		2204
1493	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1494	ev_idle_init (idle_watcher, idle_cb);	2206	ev_idle_init (idle_watcher, idle_cb);
1495	ev_idle_start (loop, idle_cb);	2207	ev_idle_start (loop, idle_cb);
1496		2208
1497		2209
1498	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1499		2211
1500	Prepare and check watchers are usually (but not always) used in tandem:	2212	Prepare and check watchers are usually (but not always) used in pairs:
1501	prepare watchers get invoked before the process blocks and check watchers	2213	prepare watchers get invoked before the process blocks and check watchers
1502	afterwards.	2214	afterwards.
1503		2215
1504	You I<must not> call C<ev_loop> or similar functions that enter	2216	You I<must not> call C<ev_loop> or similar functions that enter
1505	the current event loop from either C<ev_prepare> or C<ev_check>	2217	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1508	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1509	C<ev_check> so if you have one watcher of each kind they will always be	2221	C<ev_check> so if you have one watcher of each kind they will always be
1510	called in pairs bracketing the blocking call.	2222	called in pairs bracketing the blocking call.
1511		2223
1512	Their main purpose is to integrate other event mechanisms into libev and	2224	Their main purpose is to integrate other event mechanisms into libev and
1513	their use is somewhat advanced. This could be used, for example, to track	2225	their use is somewhat advanced. They could be used, for example, to track
1514	variable changes, implement your own watchers, integrate net-snmp or a	2226	variable changes, implement your own watchers, integrate net-snmp or a
1515	coroutine library and lots more. They are also occasionally useful if	2227	coroutine library and lots more. They are also occasionally useful if
1516	you cache some data and want to flush it before blocking (for example,	2228	you cache some data and want to flush it before blocking (for example,
1517	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2229	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1518	watcher).	2230	watcher).
1519		2231
1520	This is done by examining in each prepare call which file descriptors need	2232	This is done by examining in each prepare call which file descriptors
1521	to be watched by the other library, registering C<ev_io> watchers for	2233	need to be watched by the other library, registering C<ev_io> watchers
1522	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2234	for them and starting an C<ev_timer> watcher for any timeouts (many
1523	provide just this functionality). Then, in the check watcher you check for	2235	libraries provide exactly this functionality). Then, in the check watcher,
1524	any events that occured (by checking the pending status of all watchers	2236	you check for any events that occurred (by checking the pending status
1525	and stopping them) and call back into the library. The I/O and timer	2237	of all watchers and stopping them) and call back into the library. The
1526	callbacks will never actually be called (but must be valid nevertheless,	2238	I/O and timer callbacks will never actually be called (but must be valid
1527	because you never know, you know?).	2239	nevertheless, because you never know, you know?).
1528		2240
1529	As another example, the Perl Coro module uses these hooks to integrate	2241	As another example, the Perl Coro module uses these hooks to integrate
1530	coroutines into libev programs, by yielding to other active coroutines	2242	coroutines into libev programs, by yielding to other active coroutines
1531	during each prepare and only letting the process block if no coroutines	2243	during each prepare and only letting the process block if no coroutines
1532	are ready to run (it's actually more complicated: it only runs coroutines	2244	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1535	loop from blocking if lower-priority coroutines are active, thus mapping	2247	loop from blocking if lower-priority coroutines are active, thus mapping
1536	low-priority coroutines to idle/background tasks).	2248	low-priority coroutines to idle/background tasks).
1537		2249
1538	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539	priority, to ensure that they are being run before any other watchers	2251	priority, to ensure that they are being run before any other watchers
		2252	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2253
1540	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1541	too) should not activate ("feed") events into libev. While libev fully	2255	activate ("feed") events into libev. While libev fully supports this, they
1542	supports this, they will be called before other C<ev_check> watchers did	2256	might get executed before other C<ev_check> watchers did their job. As
1543	their job. As C<ev_check> watchers are often used to embed other event	2257	C<ev_check> watchers are often used to embed other (non-libev) event
1544	loops those other event loops might be in an unusable state until their	2258	loops those other event loops might be in an unusable state until their
1545	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1546	others).	2260	others).
1547		2261
1548	=head3 Watcher-Specific Functions and Data Members	2262	=head3 Watcher-Specific Functions and Data Members
…		…
1553		2267
1554	=item ev_check_init (ev_check *, callback)	2268	=item ev_check_init (ev_check *, callback)
1555		2269
1556	Initialises and configures the prepare or check watcher - they have no	2270	Initialises and configures the prepare or check watcher - they have no
1557	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2271	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1558	macros, but using them is utterly, utterly and completely pointless.	2272	macros, but using them is utterly, utterly, utterly and completely
		2273	pointless.
1559		2274
1560	=back	2275	=back
		2276
		2277	=head3 Examples
1561		2278
1562	There are a number of principal ways to embed other event loops or modules	2279	There are a number of principal ways to embed other event loops or modules
1563	into libev. Here are some ideas on how to include libadns into libev	2280	into libev. Here are some ideas on how to include libadns into libev
1564	(there is a Perl module named C<EV::ADNS> that does this, which you could	2281	(there is a Perl module named C<EV::ADNS> that does this, which you could
1565	use for an actually working example. Another Perl module named C<EV::Glib>	2282	use as a working example. Another Perl module named C<EV::Glib> embeds a
1566	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2283	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1567	into the Glib event loop).	2284	Glib event loop).
1568		2285
1569	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2286	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1570	and in a check watcher, destroy them and call into libadns. What follows	2287	and in a check watcher, destroy them and call into libadns. What follows
1571	is pseudo-code only of course. This requires you to either use a low	2288	is pseudo-code only of course. This requires you to either use a low
1572	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2289	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573	the callbacks for the IO/timeout watchers might not have been called yet.	2290	the callbacks for the IO/timeout watchers might not have been called yet.
1574		2291
1575	static ev_io iow [nfd];	2292	static ev_io iow [nfd];
1576	static ev_timer tw;	2293	static ev_timer tw;
1577		2294
1578	static void	2295	static void
1579	io_cb (ev_loop *loop, ev_io *w, int revents)	2296	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1580	{	2297	{
1581	}	2298	}
1582		2299
1583	// create io watchers for each fd and a timer before blocking	2300	// create io watchers for each fd and a timer before blocking
1584	static void	2301	static void
1585	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2302	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1586	{	2303	{
1587	int timeout = 3600000;	2304	int timeout = 3600000;
1588	struct pollfd fds [nfd];	2305	struct pollfd fds [nfd];
1589	// actual code will need to loop here and realloc etc.	2306	// actual code will need to loop here and realloc etc.
1590	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1591		2308
1592	/* the callback is illegal, but won't be called as we stop during check */	2309	/* the callback is illegal, but won't be called as we stop during check */
1593	ev_timer_init (&tw, 0, timeout * 1e-3);	2310	ev_timer_init (&tw, 0, timeout * 1e-3);
1594	ev_timer_start (loop, &tw);	2311	ev_timer_start (loop, &tw);
1595		2312
1596	// create one ev_io per pollfd	2313	// create one ev_io per pollfd
1597	for (int i = 0; i < nfd; ++i)	2314	for (int i = 0; i < nfd; ++i)
1598	{	2315	{
1599	ev_io_init (iow + i, io_cb, fds [i].fd,	2316	ev_io_init (iow + i, io_cb, fds [i].fd,
1600	((fds [i].events & POLLIN ? EV_READ : 0)	2317	((fds [i].events & POLLIN ? EV_READ : 0)
1601	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2318	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1602		2319
1603	fds [i].revents = 0;	2320	fds [i].revents = 0;
1604	ev_io_start (loop, iow + i);	2321	ev_io_start (loop, iow + i);
1605	}	2322	}
1606	}	2323	}
1607		2324
1608	// stop all watchers after blocking	2325	// stop all watchers after blocking
1609	static void	2326	static void
1610	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2327	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1611	{	2328	{
1612	ev_timer_stop (loop, &tw);	2329	ev_timer_stop (loop, &tw);
1613		2330
1614	for (int i = 0; i < nfd; ++i)	2331	for (int i = 0; i < nfd; ++i)
1615	{	2332	{
1616	// set the relevant poll flags	2333	// set the relevant poll flags
1617	// could also call adns_processreadable etc. here	2334	// could also call adns_processreadable etc. here
1618	struct pollfd *fd = fds + i;	2335	struct pollfd *fd = fds + i;
1619	int revents = ev_clear_pending (iow + i);	2336	int revents = ev_clear_pending (iow + i);
1620	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2337	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2338	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622		2339
1623	// now stop the watcher	2340	// now stop the watcher
1624	ev_io_stop (loop, iow + i);	2341	ev_io_stop (loop, iow + i);
1625	}	2342	}
1626		2343
1627	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2344	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628	}	2345	}
1629		2346
1630	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2347	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631	in the prepare watcher and would dispose of the check watcher.	2348	in the prepare watcher and would dispose of the check watcher.
1632		2349
1633	Method 3: If the module to be embedded supports explicit event	2350	Method 3: If the module to be embedded supports explicit event
1634	notification (adns does), you can also make use of the actual watcher	2351	notification (libadns does), you can also make use of the actual watcher
1635	callbacks, and only destroy/create the watchers in the prepare watcher.	2352	callbacks, and only destroy/create the watchers in the prepare watcher.
1636		2353
1637	static void	2354	static void
1638	timer_cb (EV_P_ ev_timer *w, int revents)	2355	timer_cb (EV_P_ ev_timer *w, int revents)
1639	{	2356	{
1640	adns_state ads = (adns_state)w->data;	2357	adns_state ads = (adns_state)w->data;
1641	update_now (EV_A);	2358	update_now (EV_A);
1642		2359
1643	adns_processtimeouts (ads, &tv_now);	2360	adns_processtimeouts (ads, &tv_now);
1644	}	2361	}
1645		2362
1646	static void	2363	static void
1647	io_cb (EV_P_ ev_io *w, int revents)	2364	io_cb (EV_P_ ev_io *w, int revents)
1648	{	2365	{
1649	adns_state ads = (adns_state)w->data;	2366	adns_state ads = (adns_state)w->data;
1650	update_now (EV_A);	2367	update_now (EV_A);
1651		2368
1652	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2369	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2370	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654	}	2371	}
1655		2372
1656	// do not ever call adns_afterpoll	2373	// do not ever call adns_afterpoll
1657		2374
1658	Method 4: Do not use a prepare or check watcher because the module you	2375	Method 4: Do not use a prepare or check watcher because the module you
1659	want to embed is too inflexible to support it. Instead, youc na override	2376	want to embed is not flexible enough to support it. Instead, you can
1660	their poll function. The drawback with this solution is that the main	2377	override their poll function. The drawback with this solution is that the
1661	loop is now no longer controllable by EV. The C<Glib::EV> module does	2378	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1662	this.	2379	this approach, effectively embedding EV as a client into the horrible
		2380	libglib event loop.
1663		2381
1664	static gint	2382	static gint
1665	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2383	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666	{	2384	{
1667	int got_events = 0;	2385	int got_events = 0;
1668		2386
1669	for (n = 0; n < nfds; ++n)	2387	for (n = 0; n < nfds; ++n)
1670	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2388	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671		2389
1672	if (timeout >= 0)	2390	if (timeout >= 0)
1673	// create/start timer	2391	// create/start timer
1674		2392
1675	// poll	2393	// poll
1676	ev_loop (EV_A_ 0);	2394	ev_loop (EV_A_ 0);
1677		2395
1678	// stop timer again	2396	// stop timer again
1679	if (timeout >= 0)	2397	if (timeout >= 0)
1680	ev_timer_stop (EV_A_ &to);	2398	ev_timer_stop (EV_A_ &to);
1681		2399
1682	// stop io watchers again - their callbacks should have set	2400	// stop io watchers again - their callbacks should have set
1683	for (n = 0; n < nfds; ++n)	2401	for (n = 0; n < nfds; ++n)
1684	ev_io_stop (EV_A_ iow [n]);	2402	ev_io_stop (EV_A_ iow [n]);
1685		2403
1686	return got_events;	2404	return got_events;
1687	}	2405	}
1688		2406
1689		2407
1690	=head2 C<ev_embed> - when one backend isn't enough...	2408	=head2 C<ev_embed> - when one backend isn't enough...
1691		2409
1692	This is a rather advanced watcher type that lets you embed one event loop	2410	This is a rather advanced watcher type that lets you embed one event loop
…		…
1698	prioritise I/O.	2416	prioritise I/O.
1699		2417
1700	As an example for a bug workaround, the kqueue backend might only support	2418	As an example for a bug workaround, the kqueue backend might only support
1701	sockets on some platform, so it is unusable as generic backend, but you	2419	sockets on some platform, so it is unusable as generic backend, but you
1702	still want to make use of it because you have many sockets and it scales	2420	still want to make use of it because you have many sockets and it scales
1703	so nicely. In this case, you would create a kqueue-based loop and embed it	2421	so nicely. In this case, you would create a kqueue-based loop and embed
1704	into your default loop (which might use e.g. poll). Overall operation will	2422	it into your default loop (which might use e.g. poll). Overall operation
1705	be a bit slower because first libev has to poll and then call kevent, but	2423	will be a bit slower because first libev has to call C<poll> and then
1706	at least you can use both at what they are best.	2424	C<kevent>, but at least you can use both mechanisms for what they are
		2425	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
1707		2426
1708	As for prioritising I/O: rarely you have the case where some fds have	2427	As for prioritising I/O: under rare circumstances you have the case where
1709	to be watched and handled very quickly (with low latency), and even	2428	some fds have to be watched and handled very quickly (with low latency),
1710	priorities and idle watchers might have too much overhead. In this case	2429	and even priorities and idle watchers might have too much overhead. In
1711	you would put all the high priority stuff in one loop and all the rest in	2430	this case you would put all the high priority stuff in one loop and all
1712	a second one, and embed the second one in the first.	2431	the rest in a second one, and embed the second one in the first.
1713		2432
1714	As long as the watcher is active, the callback will be invoked every time	2433	As long as the watcher is active, the callback will be invoked every time
1715	there might be events pending in the embedded loop. The callback must then	2434	there might be events pending in the embedded loop. The callback must then
1716	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2435	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
1717	their callbacks (you could also start an idle watcher to give the embedded	2436	their callbacks (you could also start an idle watcher to give the embedded
…		…
1725	interested in that.	2444	interested in that.
1726		2445
1727	Also, there have not currently been made special provisions for forking:	2446	Also, there have not currently been made special provisions for forking:
1728	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2447	when you fork, you not only have to call C<ev_loop_fork> on both loops,
1729	but you will also have to stop and restart any C<ev_embed> watchers	2448	but you will also have to stop and restart any C<ev_embed> watchers
1730	yourself.	2449	yourself - but you can use a fork watcher to handle this automatically,
		2450	and future versions of libev might do just that.
1731		2451
1732	Unfortunately, not all backends are embeddable, only the ones returned by	2452	Unfortunately, not all backends are embeddable: only the ones returned by
1733	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2453	C<ev_embeddable_backends> are, which, unfortunately, does not include any
1734	portable one.	2454	portable one.
1735		2455
1736	So when you want to use this feature you will always have to be prepared	2456	So when you want to use this feature you will always have to be prepared
1737	that you cannot get an embeddable loop. The recommended way to get around	2457	that you cannot get an embeddable loop. The recommended way to get around
1738	this is to have a separate variables for your embeddable loop, try to	2458	this is to have a separate variables for your embeddable loop, try to
1739	create it, and if that fails, use the normal loop for everything:	2459	create it, and if that fails, use the normal loop for everything.
1740		2460
1741	struct ev_loop *loop_hi = ev_default_init (0);	2461	=head3 C<ev_embed> and fork
1742	struct ev_loop *loop_lo = 0;
1743	struct ev_embed embed;
1744
1745	// see if there is a chance of getting one that works
1746	// (remember that a flags value of 0 means autodetection)
1747	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1748	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1749	: 0;
1750		2462
1751	// if we got one, then embed it, otherwise default to loop_hi	2463	While the C<ev_embed> watcher is running, forks in the embedding loop will
1752	if (loop_lo)	2464	automatically be applied to the embedded loop as well, so no special
1753	{	2465	fork handling is required in that case. When the watcher is not running,
1754	ev_embed_init (&embed, 0, loop_lo);	2466	however, it is still the task of the libev user to call C<ev_loop_fork ()>
1755	ev_embed_start (loop_hi, &embed);	2467	as applicable.
1756	}
1757	else
1758	loop_lo = loop_hi;
1759		2468
1760	=head3 Watcher-Specific Functions and Data Members	2469	=head3 Watcher-Specific Functions and Data Members
1761		2470
1762	=over 4	2471	=over 4
1763		2472
…		…
1767		2476
1768	Configures the watcher to embed the given loop, which must be	2477	Configures the watcher to embed the given loop, which must be
1769	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2478	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1770	invoked automatically, otherwise it is the responsibility of the callback	2479	invoked automatically, otherwise it is the responsibility of the callback
1771	to invoke it (it will continue to be called until the sweep has been done,	2480	to invoke it (it will continue to be called until the sweep has been done,
1772	if you do not want thta, you need to temporarily stop the embed watcher).	2481	if you do not want that, you need to temporarily stop the embed watcher).
1773		2482
1774	=item ev_embed_sweep (loop, ev_embed *)	2483	=item ev_embed_sweep (loop, ev_embed *)
1775		2484
1776	Make a single, non-blocking sweep over the embedded loop. This works	2485	Make a single, non-blocking sweep over the embedded loop. This works
1777	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2486	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1778	apropriate way for embedded loops.	2487	appropriate way for embedded loops.
1779		2488
1780	=item struct ev_loop *loop [read-only]	2489	=item struct ev_loop *other [read-only]
1781		2490
1782	The embedded event loop.	2491	The embedded event loop.
1783		2492
1784	=back	2493	=back
		2494
		2495	=head3 Examples
		2496
		2497	Example: Try to get an embeddable event loop and embed it into the default
		2498	event loop. If that is not possible, use the default loop. The default
		2499	loop is stored in C<loop_hi>, while the embeddable loop is stored in
		2500	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
		2501	used).
		2502
		2503	struct ev_loop *loop_hi = ev_default_init (0);
		2504	struct ev_loop *loop_lo = 0;
		2505	ev_embed embed;
		2506
		2507	// see if there is a chance of getting one that works
		2508	// (remember that a flags value of 0 means autodetection)
		2509	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		2510	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		2511	: 0;
		2512
		2513	// if we got one, then embed it, otherwise default to loop_hi
		2514	if (loop_lo)
		2515	{
		2516	ev_embed_init (&embed, 0, loop_lo);
		2517	ev_embed_start (loop_hi, &embed);
		2518	}
		2519	else
		2520	loop_lo = loop_hi;
		2521
		2522	Example: Check if kqueue is available but not recommended and create
		2523	a kqueue backend for use with sockets (which usually work with any
		2524	kqueue implementation). Store the kqueue/socket-only event loop in
		2525	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
		2526
		2527	struct ev_loop *loop = ev_default_init (0);
		2528	struct ev_loop *loop_socket = 0;
		2529	ev_embed embed;
		2530
		2531	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2532	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2533	{
		2534	ev_embed_init (&embed, 0, loop_socket);
		2535	ev_embed_start (loop, &embed);
		2536	}
		2537
		2538	if (!loop_socket)
		2539	loop_socket = loop;
		2540
		2541	// now use loop_socket for all sockets, and loop for everything else
1785		2542
1786		2543
1787	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2544	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1788		2545
1789	Fork watchers are called when a C<fork ()> was detected (usually because	2546	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1805	believe me.	2562	believe me.
1806		2563
1807	=back	2564	=back
1808		2565
1809		2566
		2567	=head2 C<ev_async> - how to wake up another event loop
		2568
		2569	In general, you cannot use an C<ev_loop> from multiple threads or other
		2570	asynchronous sources such as signal handlers (as opposed to multiple event
		2571	loops - those are of course safe to use in different threads).
		2572
		2573	Sometimes, however, you need to wake up another event loop you do not
		2574	control, for example because it belongs to another thread. This is what
		2575	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2576	can signal it by calling C<ev_async_send>, which is thread- and signal
		2577	safe.
		2578
		2579	This functionality is very similar to C<ev_signal> watchers, as signals,
		2580	too, are asynchronous in nature, and signals, too, will be compressed
		2581	(i.e. the number of callback invocations may be less than the number of
		2582	C<ev_async_sent> calls).
		2583
		2584	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2585	just the default loop.
		2586
		2587	=head3 Queueing
		2588
		2589	C<ev_async> does not support queueing of data in any way. The reason
		2590	is that the author does not know of a simple (or any) algorithm for a
		2591	multiple-writer-single-reader queue that works in all cases and doesn't
		2592	need elaborate support such as pthreads.
		2593
		2594	That means that if you want to queue data, you have to provide your own
		2595	queue. But at least I can tell you how to implement locking around your
		2596	queue:
		2597
		2598	=over 4
		2599
		2600	=item queueing from a signal handler context
		2601
		2602	To implement race-free queueing, you simply add to the queue in the signal
		2603	handler but you block the signal handler in the watcher callback. Here is
		2604	an example that does that for some fictitious SIGUSR1 handler:
		2605
		2606	static ev_async mysig;
		2607
		2608	static void
		2609	sigusr1_handler (void)
		2610	{
		2611	sometype data;
		2612
		2613	// no locking etc.
		2614	queue_put (data);
		2615	ev_async_send (EV_DEFAULT_ &mysig);
		2616	}
		2617
		2618	static void
		2619	mysig_cb (EV_P_ ev_async *w, int revents)
		2620	{
		2621	sometype data;
		2622	sigset_t block, prev;
		2623
		2624	sigemptyset (&block);
		2625	sigaddset (&block, SIGUSR1);
		2626	sigprocmask (SIG_BLOCK, &block, &prev);
		2627
		2628	while (queue_get (&data))
		2629	process (data);
		2630
		2631	if (sigismember (&prev, SIGUSR1)
		2632	sigprocmask (SIG_UNBLOCK, &block, 0);
		2633	}
		2634
		2635	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2636	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2637	either...).
		2638
		2639	=item queueing from a thread context
		2640
		2641	The strategy for threads is different, as you cannot (easily) block
		2642	threads but you can easily preempt them, so to queue safely you need to
		2643	employ a traditional mutex lock, such as in this pthread example:
		2644
		2645	static ev_async mysig;
		2646	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2647
		2648	static void
		2649	otherthread (void)
		2650	{
		2651	// only need to lock the actual queueing operation
		2652	pthread_mutex_lock (&mymutex);
		2653	queue_put (data);
		2654	pthread_mutex_unlock (&mymutex);
		2655
		2656	ev_async_send (EV_DEFAULT_ &mysig);
		2657	}
		2658
		2659	static void
		2660	mysig_cb (EV_P_ ev_async *w, int revents)
		2661	{
		2662	pthread_mutex_lock (&mymutex);
		2663
		2664	while (queue_get (&data))
		2665	process (data);
		2666
		2667	pthread_mutex_unlock (&mymutex);
		2668	}
		2669
		2670	=back
		2671
		2672
		2673	=head3 Watcher-Specific Functions and Data Members
		2674
		2675	=over 4
		2676
		2677	=item ev_async_init (ev_async *, callback)
		2678
		2679	Initialises and configures the async watcher - it has no parameters of any
		2680	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
		2681	trust me.
		2682
		2683	=item ev_async_send (loop, ev_async *)
		2684
		2685	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2686	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2687	C<ev_feed_event>, this call is safe to do from other threads, signal or
		2688	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
		2689	section below on what exactly this means).
		2690
		2691	This call incurs the overhead of a system call only once per loop iteration,
		2692	so while the overhead might be noticeable, it doesn't apply to repeated
		2693	calls to C<ev_async_send>.
		2694
		2695	=item bool = ev_async_pending (ev_async *)
		2696
		2697	Returns a non-zero value when C<ev_async_send> has been called on the
		2698	watcher but the event has not yet been processed (or even noted) by the
		2699	event loop.
		2700
		2701	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
		2702	the loop iterates next and checks for the watcher to have become active,
		2703	it will reset the flag again. C<ev_async_pending> can be used to very
		2704	quickly check whether invoking the loop might be a good idea.
		2705
		2706	Not that this does I<not> check whether the watcher itself is pending, only
		2707	whether it has been requested to make this watcher pending.
		2708
		2709	=back
		2710
		2711
1810	=head1 OTHER FUNCTIONS	2712	=head1 OTHER FUNCTIONS
1811		2713
1812	There are some other functions of possible interest. Described. Here. Now.	2714	There are some other functions of possible interest. Described. Here. Now.
1813		2715
1814	=over 4	2716	=over 4
1815		2717
1816	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2718	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
1817		2719
1818	This function combines a simple timer and an I/O watcher, calls your	2720	This function combines a simple timer and an I/O watcher, calls your
1819	callback on whichever event happens first and automatically stop both	2721	callback on whichever event happens first and automatically stops both
1820	watchers. This is useful if you want to wait for a single event on an fd	2722	watchers. This is useful if you want to wait for a single event on an fd
1821	or timeout without having to allocate/configure/start/stop/free one or	2723	or timeout without having to allocate/configure/start/stop/free one or
1822	more watchers yourself.	2724	more watchers yourself.
1823		2725
1824	If C<fd> is less than 0, then no I/O watcher will be started and events	2726	If C<fd> is less than 0, then no I/O watcher will be started and the
1825	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2727	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
1826	C<events> set will be craeted and started.	2728	the given C<fd> and C<events> set will be created and started.
1827		2729
1828	If C<timeout> is less than 0, then no timeout watcher will be	2730	If C<timeout> is less than 0, then no timeout watcher will be
1829	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2731	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
1830	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2732	repeat = 0) will be started. C<0> is a valid timeout.
1831	dubious value.
1832		2733
1833	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2734	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
1834	passed an C<revents> set like normal event callbacks (a combination of	2735	passed an C<revents> set like normal event callbacks (a combination of
1835	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2736	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
1836	value passed to C<ev_once>:	2737	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2738	a timeout and an io event at the same time - you probably should give io
		2739	events precedence.
1837		2740
		2741	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2742
1838	static void stdin_ready (int revents, void *arg)	2743	static void stdin_ready (int revents, void *arg)
1839	{	2744	{
1840	if (revents & EV_TIMEOUT)
1841	/* doh, nothing entered */;
1842	else if (revents & EV_READ)	2745	if (revents & EV_READ)
1843	/* stdin might have data for us, joy! */;	2746	/* stdin might have data for us, joy! */;
		2747	else if (revents & EV_TIMEOUT)
		2748	/* doh, nothing entered */;
1844	}	2749	}
1845		2750
1846	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2751	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1847		2752
1848	=item ev_feed_event (ev_loop *, watcher *, int revents)	2753	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
1849		2754
1850	Feeds the given event set into the event loop, as if the specified event	2755	Feeds the given event set into the event loop, as if the specified event
1851	had happened for the specified watcher (which must be a pointer to an	2756	had happened for the specified watcher (which must be a pointer to an
1852	initialised but not necessarily started event watcher).	2757	initialised but not necessarily started event watcher).
1853		2758
1854	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2759	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
1855		2760
1856	Feed an event on the given fd, as if a file descriptor backend detected	2761	Feed an event on the given fd, as if a file descriptor backend detected
1857	the given events it.	2762	the given events it.
1858		2763
1859	=item ev_feed_signal_event (ev_loop *loop, int signum)	2764	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
1860		2765
1861	Feed an event as if the given signal occured (C<loop> must be the default	2766	Feed an event as if the given signal occurred (C<loop> must be the default
1862	loop!).	2767	loop!).
1863		2768
1864	=back	2769	=back
1865		2770
1866		2771
…		…
1882		2787
1883	=item * Priorities are not currently supported. Initialising priorities	2788	=item * Priorities are not currently supported. Initialising priorities
1884	will fail and all watchers will have the same priority, even though there	2789	will fail and all watchers will have the same priority, even though there
1885	is an ev_pri field.	2790	is an ev_pri field.
1886		2791
		2792	=item * In libevent, the last base created gets the signals, in libev, the
		2793	first base created (== the default loop) gets the signals.
		2794
1887	=item * Other members are not supported.	2795	=item * Other members are not supported.
1888		2796
1889	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2797	=item * The libev emulation is I<not> ABI compatible to libevent, you need
1890	to use the libev header file and library.	2798	to use the libev header file and library.
1891		2799
1892	=back	2800	=back
1893		2801
1894	=head1 C++ SUPPORT	2802	=head1 C++ SUPPORT
1895		2803
1896	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2804	Libev comes with some simplistic wrapper classes for C++ that mainly allow
1897	you to use some convinience methods to start/stop watchers and also change	2805	you to use some convenience methods to start/stop watchers and also change
1898	the callback model to a model using method callbacks on objects.	2806	the callback model to a model using method callbacks on objects.
1899		2807
1900	To use it,	2808	To use it,
1901		2809
1902	#include <ev++.h>	2810	#include <ev++.h>
1903		2811
1904	This automatically includes F<ev.h> and puts all of its definitions (many	2812	This automatically includes F<ev.h> and puts all of its definitions (many
1905	of them macros) into the global namespace. All C++ specific things are	2813	of them macros) into the global namespace. All C++ specific things are
1906	put into the C<ev> namespace. It should support all the same embedding	2814	put into the C<ev> namespace. It should support all the same embedding
1907	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2815	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
1974	your compiler is good :), then the method will be fully inlined into the	2882	your compiler is good :), then the method will be fully inlined into the
1975	thunking function, making it as fast as a direct C callback.	2883	thunking function, making it as fast as a direct C callback.
1976		2884
1977	Example: simple class declaration and watcher initialisation	2885	Example: simple class declaration and watcher initialisation
1978		2886
1979	struct myclass	2887	struct myclass
1980	{	2888	{
1981	void io_cb (ev::io &w, int revents) { }	2889	void io_cb (ev::io &w, int revents) { }
1982	}	2890	}
1983		2891
1984	myclass obj;	2892	myclass obj;
1985	ev::io iow;	2893	ev::io iow;
1986	iow.set <myclass, &myclass::io_cb> (&obj);	2894	iow.set <myclass, &myclass::io_cb> (&obj);
1987		2895
1988	=item w->set<function> (void *data = 0)	2896	=item w->set<function> (void *data = 0)
1989		2897
1990	Also sets a callback, but uses a static method or plain function as	2898	Also sets a callback, but uses a static method or plain function as
1991	callback. The optional C<data> argument will be stored in the watcher's	2899	callback. The optional C<data> argument will be stored in the watcher's
…		…
1993		2901
1994	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2902	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
1995		2903
1996	See the method-C<set> above for more details.	2904	See the method-C<set> above for more details.
1997		2905
1998	Example:	2906	Example: Use a plain function as callback.
1999		2907
2000	static void io_cb (ev::io &w, int revents) { }	2908	static void io_cb (ev::io &w, int revents) { }
2001	iow.set <io_cb> ();	2909	iow.set <io_cb> ();
2002		2910
2003	=item w->set (struct ev_loop *)	2911	=item w->set (struct ev_loop *)
2004		2912
2005	Associates a different C<struct ev_loop> with this watcher. You can only	2913	Associates a different C<struct ev_loop> with this watcher. You can only
2006	do this when the watcher is inactive (and not pending either).	2914	do this when the watcher is inactive (and not pending either).
2007		2915
2008	=item w->set ([args])	2916	=item w->set ([arguments])
2009		2917
2010	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2918	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2011	called at least once. Unlike the C counterpart, an active watcher gets	2919	called at least once. Unlike the C counterpart, an active watcher gets
2012	automatically stopped and restarted when reconfiguring it with this	2920	automatically stopped and restarted when reconfiguring it with this
2013	method.	2921	method.
2014		2922
2015	=item w->start ()	2923	=item w->start ()
…		…
2039	=back	2947	=back
2040		2948
2041	Example: Define a class with an IO and idle watcher, start one of them in	2949	Example: Define a class with an IO and idle watcher, start one of them in
2042	the constructor.	2950	the constructor.
2043		2951
2044	class myclass	2952	class myclass
2045	{	2953	{
2046	ev_io io; void io_cb (ev::io &w, int revents);	2954	ev::io io ; void io_cb (ev::io &w, int revents);
2047	ev_idle idle void idle_cb (ev::idle &w, int revents);	2955	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2048		2956
2049	myclass ();	2957	myclass (int fd)
2050	}	2958	{
2051
2052	myclass::myclass (int fd)
2053	{
2054	io .set <myclass, &myclass::io_cb > (this);	2959	io .set <myclass, &myclass::io_cb > (this);
2055	idle.set <myclass, &myclass::idle_cb> (this);	2960	idle.set <myclass, &myclass::idle_cb> (this);
2056		2961
2057	io.start (fd, ev::READ);	2962	io.start (fd, ev::READ);
		2963	}
2058	}	2964	};
		2965
		2966
		2967	=head1 OTHER LANGUAGE BINDINGS
		2968
		2969	Libev does not offer other language bindings itself, but bindings for a
		2970	number of languages exist in the form of third-party packages. If you know
		2971	any interesting language binding in addition to the ones listed here, drop
		2972	me a note.
		2973
		2974	=over 4
		2975
		2976	=item Perl
		2977
		2978	The EV module implements the full libev API and is actually used to test
		2979	libev. EV is developed together with libev. Apart from the EV core module,
		2980	there are additional modules that implement libev-compatible interfaces
		2981	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
		2982	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2983	and C<EV::Glib>).
		2984
		2985	It can be found and installed via CPAN, its homepage is at
		2986	L<http://software.schmorp.de/pkg/EV>.
		2987
		2988	=item Python
		2989
		2990	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		2991	seems to be quite complete and well-documented. Note, however, that the
		2992	patch they require for libev is outright dangerous as it breaks the ABI
		2993	for everybody else, and therefore, should never be applied in an installed
		2994	libev (if python requires an incompatible ABI then it needs to embed
		2995	libev).
		2996
		2997	=item Ruby
		2998
		2999	Tony Arcieri has written a ruby extension that offers access to a subset
		3000	of the libev API and adds file handle abstractions, asynchronous DNS and
		3001	more on top of it. It can be found via gem servers. Its homepage is at
		3002	L<http://rev.rubyforge.org/>.
		3003
		3004	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3005	makes rev work even on mingw.
		3006
		3007	=item D
		3008
		3009	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
		3010	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3011
		3012	=item Ocaml
		3013
		3014	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3016
		3017	=back
2059		3018
2060		3019
2061	=head1 MACRO MAGIC	3020	=head1 MACRO MAGIC
2062		3021
2063	Libev can be compiled with a variety of options, the most fundamantal	3022	Libev can be compiled with a variety of options, the most fundamental
2064	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3023	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2065	functions and callbacks have an initial C<struct ev_loop *> argument.	3024	functions and callbacks have an initial C<struct ev_loop *> argument.
2066		3025
2067	To make it easier to write programs that cope with either variant, the	3026	To make it easier to write programs that cope with either variant, the
2068	following macros are defined:	3027	following macros are defined:
…		…
2073		3032
2074	This provides the loop I<argument> for functions, if one is required ("ev	3033	This provides the loop I<argument> for functions, if one is required ("ev
2075	loop argument"). The C<EV_A> form is used when this is the sole argument,	3034	loop argument"). The C<EV_A> form is used when this is the sole argument,
2076	C<EV_A_> is used when other arguments are following. Example:	3035	C<EV_A_> is used when other arguments are following. Example:
2077		3036
2078	ev_unref (EV_A);	3037	ev_unref (EV_A);
2079	ev_timer_add (EV_A_ watcher);	3038	ev_timer_add (EV_A_ watcher);
2080	ev_loop (EV_A_ 0);	3039	ev_loop (EV_A_ 0);
2081		3040
2082	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3041	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2083	which is often provided by the following macro.	3042	which is often provided by the following macro.
2084		3043
2085	=item C<EV_P>, C<EV_P_>	3044	=item C<EV_P>, C<EV_P_>
2086		3045
2087	This provides the loop I<parameter> for functions, if one is required ("ev	3046	This provides the loop I<parameter> for functions, if one is required ("ev
2088	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3047	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2089	C<EV_P_> is used when other parameters are following. Example:	3048	C<EV_P_> is used when other parameters are following. Example:
2090		3049
2091	// this is how ev_unref is being declared	3050	// this is how ev_unref is being declared
2092	static void ev_unref (EV_P);	3051	static void ev_unref (EV_P);
2093		3052
2094	// this is how you can declare your typical callback	3053	// this is how you can declare your typical callback
2095	static void cb (EV_P_ ev_timer *w, int revents)	3054	static void cb (EV_P_ ev_timer *w, int revents)
2096		3055
2097	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3056	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2098	suitable for use with C<EV_A>.	3057	suitable for use with C<EV_A>.
2099		3058
2100	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3059	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2101		3060
2102	Similar to the other two macros, this gives you the value of the default	3061	Similar to the other two macros, this gives you the value of the default
2103	loop, if multiple loops are supported ("ev loop default").	3062	loop, if multiple loops are supported ("ev loop default").
		3063
		3064	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3065
		3066	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3067	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3068	is undefined when the default loop has not been initialised by a previous
		3069	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3070
		3071	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3072	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2104		3073
2105	=back	3074	=back
2106		3075
2107	Example: Declare and initialise a check watcher, utilising the above	3076	Example: Declare and initialise a check watcher, utilising the above
2108	macros so it will work regardless of whether multiple loops are supported	3077	macros so it will work regardless of whether multiple loops are supported
2109	or not.	3078	or not.
2110		3079
2111	static void	3080	static void
2112	check_cb (EV_P_ ev_timer *w, int revents)	3081	check_cb (EV_P_ ev_timer *w, int revents)
2113	{	3082	{
2114	ev_check_stop (EV_A_ w);	3083	ev_check_stop (EV_A_ w);
2115	}	3084	}
2116		3085
2117	ev_check check;	3086	ev_check check;
2118	ev_check_init (&check, check_cb);	3087	ev_check_init (&check, check_cb);
2119	ev_check_start (EV_DEFAULT_ &check);	3088	ev_check_start (EV_DEFAULT_ &check);
2120	ev_loop (EV_DEFAULT_ 0);	3089	ev_loop (EV_DEFAULT_ 0);
2121		3090
2122	=head1 EMBEDDING	3091	=head1 EMBEDDING
2123		3092
2124	Libev can (and often is) directly embedded into host	3093	Libev can (and often is) directly embedded into host
2125	applications. Examples of applications that embed it include the Deliantra	3094	applications. Examples of applications that embed it include the Deliantra
2126	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	3095	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2127	and rxvt-unicode.	3096	and rxvt-unicode.
2128		3097
2129	The goal is to enable you to just copy the neecssary files into your	3098	The goal is to enable you to just copy the necessary files into your
2130	source directory without having to change even a single line in them, so	3099	source directory without having to change even a single line in them, so
2131	you can easily upgrade by simply copying (or having a checked-out copy of	3100	you can easily upgrade by simply copying (or having a checked-out copy of
2132	libev somewhere in your source tree).	3101	libev somewhere in your source tree).
2133		3102
2134	=head2 FILESETS	3103	=head2 FILESETS
2135		3104
2136	Depending on what features you need you need to include one or more sets of files	3105	Depending on what features you need you need to include one or more sets of files
2137	in your app.	3106	in your application.
2138		3107
2139	=head3 CORE EVENT LOOP	3108	=head3 CORE EVENT LOOP
2140		3109
2141	To include only the libev core (all the C<ev_*> functions), with manual	3110	To include only the libev core (all the C<ev_*> functions), with manual
2142	configuration (no autoconf):	3111	configuration (no autoconf):
2143		3112
2144	#define EV_STANDALONE 1	3113	#define EV_STANDALONE 1
2145	#include "ev.c"	3114	#include "ev.c"
2146		3115
2147	This will automatically include F<ev.h>, too, and should be done in a	3116	This will automatically include F<ev.h>, too, and should be done in a
2148	single C source file only to provide the function implementations. To use	3117	single C source file only to provide the function implementations. To use
2149	it, do the same for F<ev.h> in all files wishing to use this API (best	3118	it, do the same for F<ev.h> in all files wishing to use this API (best
2150	done by writing a wrapper around F<ev.h> that you can include instead and	3119	done by writing a wrapper around F<ev.h> that you can include instead and
2151	where you can put other configuration options):	3120	where you can put other configuration options):
2152		3121
2153	#define EV_STANDALONE 1	3122	#define EV_STANDALONE 1
2154	#include "ev.h"	3123	#include "ev.h"
2155		3124
2156	Both header files and implementation files can be compiled with a C++	3125	Both header files and implementation files can be compiled with a C++
2157	compiler (at least, thats a stated goal, and breakage will be treated	3126	compiler (at least, that's a stated goal, and breakage will be treated
2158	as a bug).	3127	as a bug).
2159		3128
2160	You need the following files in your source tree, or in a directory	3129	You need the following files in your source tree, or in a directory
2161	in your include path (e.g. in libev/ when using -Ilibev):	3130	in your include path (e.g. in libev/ when using -Ilibev):
2162		3131
2163	ev.h	3132	ev.h
2164	ev.c	3133	ev.c
2165	ev_vars.h	3134	ev_vars.h
2166	ev_wrap.h	3135	ev_wrap.h
2167		3136
2168	ev_win32.c required on win32 platforms only	3137	ev_win32.c required on win32 platforms only
2169		3138
2170	ev_select.c only when select backend is enabled (which is enabled by default)	3139	ev_select.c only when select backend is enabled (which is enabled by default)
2171	ev_poll.c only when poll backend is enabled (disabled by default)	3140	ev_poll.c only when poll backend is enabled (disabled by default)
2172	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3141	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2173	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3142	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2174	ev_port.c only when the solaris port backend is enabled (disabled by default)	3143	ev_port.c only when the solaris port backend is enabled (disabled by default)
2175		3144
2176	F<ev.c> includes the backend files directly when enabled, so you only need	3145	F<ev.c> includes the backend files directly when enabled, so you only need
2177	to compile this single file.	3146	to compile this single file.
2178		3147
2179	=head3 LIBEVENT COMPATIBILITY API	3148	=head3 LIBEVENT COMPATIBILITY API
2180		3149
2181	To include the libevent compatibility API, also include:	3150	To include the libevent compatibility API, also include:
2182		3151
2183	#include "event.c"	3152	#include "event.c"
2184		3153
2185	in the file including F<ev.c>, and:	3154	in the file including F<ev.c>, and:
2186		3155
2187	#include "event.h"	3156	#include "event.h"
2188		3157
2189	in the files that want to use the libevent API. This also includes F<ev.h>.	3158	in the files that want to use the libevent API. This also includes F<ev.h>.
2190		3159
2191	You need the following additional files for this:	3160	You need the following additional files for this:
2192		3161
2193	event.h	3162	event.h
2194	event.c	3163	event.c
2195		3164
2196	=head3 AUTOCONF SUPPORT	3165	=head3 AUTOCONF SUPPORT
2197		3166
2198	Instead of using C<EV_STANDALONE=1> and providing your config in	3167	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2199	whatever way you want, you can also C<m4_include([libev.m4])> in your	3168	whatever way you want, you can also C<m4_include([libev.m4])> in your
2200	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3169	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2201	include F<config.h> and configure itself accordingly.	3170	include F<config.h> and configure itself accordingly.
2202		3171
2203	For this of course you need the m4 file:	3172	For this of course you need the m4 file:
2204		3173
2205	libev.m4	3174	libev.m4
2206		3175
2207	=head2 PREPROCESSOR SYMBOLS/MACROS	3176	=head2 PREPROCESSOR SYMBOLS/MACROS
2208		3177
2209	Libev can be configured via a variety of preprocessor symbols you have to define	3178	Libev can be configured via a variety of preprocessor symbols you have to
2210	before including any of its files. The default is not to build for multiplicity	3179	define before including any of its files. The default in the absence of
2211	and only include the select backend.	3180	autoconf is documented for every option.
2212		3181
2213	=over 4	3182	=over 4
2214		3183
2215	=item EV_STANDALONE	3184	=item EV_STANDALONE
2216		3185
…		…
2218	keeps libev from including F<config.h>, and it also defines dummy	3187	keeps libev from including F<config.h>, and it also defines dummy
2219	implementations for some libevent functions (such as logging, which is not	3188	implementations for some libevent functions (such as logging, which is not
2220	supported). It will also not define any of the structs usually found in	3189	supported). It will also not define any of the structs usually found in
2221	F<event.h> that are not directly supported by the libev core alone.	3190	F<event.h> that are not directly supported by the libev core alone.
2222		3191
		3192	In stanbdalone mode, libev will still try to automatically deduce the
		3193	configuration, but has to be more conservative.
		3194
2223	=item EV_USE_MONOTONIC	3195	=item EV_USE_MONOTONIC
2224		3196
2225	If defined to be C<1>, libev will try to detect the availability of the	3197	If defined to be C<1>, libev will try to detect the availability of the
2226	monotonic clock option at both compiletime and runtime. Otherwise no use	3198	monotonic clock option at both compile time and runtime. Otherwise no
2227	of the monotonic clock option will be attempted. If you enable this, you	3199	use of the monotonic clock option will be attempted. If you enable this,
2228	usually have to link against librt or something similar. Enabling it when	3200	you usually have to link against librt or something similar. Enabling it
2229	the functionality isn't available is safe, though, althoguh you have	3201	when the functionality isn't available is safe, though, although you have
2230	to make sure you link against any libraries where the C<clock_gettime>	3202	to make sure you link against any libraries where the C<clock_gettime>
2231	function is hiding in (often F<-lrt>).	3203	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2232		3204
2233	=item EV_USE_REALTIME	3205	=item EV_USE_REALTIME
2234		3206
2235	If defined to be C<1>, libev will try to detect the availability of the	3207	If defined to be C<1>, libev will try to detect the availability of the
2236	realtime clock option at compiletime (and assume its availability at	3208	real-time clock option at compile time (and assume its availability at
2237	runtime if successful). Otherwise no use of the realtime clock option will	3209	runtime if successful). Otherwise no use of the real-time clock option will
2238	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3210	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2239	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	3211	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2240	in the description of C<EV_USE_MONOTONIC>, though.	3212	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		3213
		3214	=item EV_USE_CLOCK_SYSCALL
		3215
		3216	If defined to be C<1>, libev will try to use a direct syscall instead
		3217	of calling the system-provided C<clock_gettime> function. This option
		3218	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3219	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3220	programs needlessly. Using a direct syscall is slightly slower (in
		3221	theory), because no optimised vdso implementation can be used, but avoids
		3222	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3223	higher, as it simplifies linking (no need for C<-lrt>).
		3224
		3225	=item EV_USE_NANOSLEEP
		3226
		3227	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		3228	and will use it for delays. Otherwise it will use C<select ()>.
		3229
		3230	=item EV_USE_EVENTFD
		3231
		3232	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3233	available and will probe for kernel support at runtime. This will improve
		3234	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3235	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3236	2.7 or newer, otherwise disabled.
2241		3237
2242	=item EV_USE_SELECT	3238	=item EV_USE_SELECT
2243		3239
2244	If undefined or defined to be C<1>, libev will compile in support for the	3240	If undefined or defined to be C<1>, libev will compile in support for the
2245	C<select>(2) backend. No attempt at autodetection will be done: if no	3241	C<select>(2) backend. No attempt at auto-detection will be done: if no
2246	other method takes over, select will be it. Otherwise the select backend	3242	other method takes over, select will be it. Otherwise the select backend
2247	will not be compiled in.	3243	will not be compiled in.
2248		3244
2249	=item EV_SELECT_USE_FD_SET	3245	=item EV_SELECT_USE_FD_SET
2250		3246
2251	If defined to C<1>, then the select backend will use the system C<fd_set>	3247	If defined to C<1>, then the select backend will use the system C<fd_set>
2252	structure. This is useful if libev doesn't compile due to a missing	3248	structure. This is useful if libev doesn't compile due to a missing
2253	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3249	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2254	exotic systems. This usually limits the range of file descriptors to some	3250	on exotic systems. This usually limits the range of file descriptors to
2255	low limit such as 1024 or might have other limitations (winsocket only	3251	some low limit such as 1024 or might have other limitations (winsocket
2256	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3252	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2257	influence the size of the C<fd_set> used.	3253	configures the maximum size of the C<fd_set>.
2258		3254
2259	=item EV_SELECT_IS_WINSOCKET	3255	=item EV_SELECT_IS_WINSOCKET
2260		3256
2261	When defined to C<1>, the select backend will assume that	3257	When defined to C<1>, the select backend will assume that
2262	select/socket/connect etc. don't understand file descriptors but	3258	select/socket/connect etc. don't understand file descriptors but
…		…
2264	be used is the winsock select). This means that it will call	3260	be used is the winsock select). This means that it will call
2265	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3261	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2266	it is assumed that all these functions actually work on fds, even	3262	it is assumed that all these functions actually work on fds, even
2267	on win32. Should not be defined on non-win32 platforms.	3263	on win32. Should not be defined on non-win32 platforms.
2268		3264
		3265	=item EV_FD_TO_WIN32_HANDLE
		3266
		3267	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		3268	file descriptors to socket handles. When not defining this symbol (the
		3269	default), then libev will call C<_get_osfhandle>, which is usually
		3270	correct. In some cases, programs use their own file descriptor management,
		3271	in which case they can provide this function to map fds to socket handles.
		3272
2269	=item EV_USE_POLL	3273	=item EV_USE_POLL
2270		3274
2271	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3275	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2272	backend. Otherwise it will be enabled on non-win32 platforms. It	3276	backend. Otherwise it will be enabled on non-win32 platforms. It
2273	takes precedence over select.	3277	takes precedence over select.
2274		3278
2275	=item EV_USE_EPOLL	3279	=item EV_USE_EPOLL
2276		3280
2277	If defined to be C<1>, libev will compile in support for the Linux	3281	If defined to be C<1>, libev will compile in support for the Linux
2278	C<epoll>(7) backend. Its availability will be detected at runtime,	3282	C<epoll>(7) backend. Its availability will be detected at runtime,
2279	otherwise another method will be used as fallback. This is the	3283	otherwise another method will be used as fallback. This is the preferred
2280	preferred backend for GNU/Linux systems.	3284	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3285	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2281		3286
2282	=item EV_USE_KQUEUE	3287	=item EV_USE_KQUEUE
2283		3288
2284	If defined to be C<1>, libev will compile in support for the BSD style	3289	If defined to be C<1>, libev will compile in support for the BSD style
2285	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3290	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2298	otherwise another method will be used as fallback. This is the preferred	3303	otherwise another method will be used as fallback. This is the preferred
2299	backend for Solaris 10 systems.	3304	backend for Solaris 10 systems.
2300		3305
2301	=item EV_USE_DEVPOLL	3306	=item EV_USE_DEVPOLL
2302		3307
2303	reserved for future expansion, works like the USE symbols above.	3308	Reserved for future expansion, works like the USE symbols above.
2304		3309
2305	=item EV_USE_INOTIFY	3310	=item EV_USE_INOTIFY
2306		3311
2307	If defined to be C<1>, libev will compile in support for the Linux inotify	3312	If defined to be C<1>, libev will compile in support for the Linux inotify
2308	interface to speed up C<ev_stat> watchers. Its actual availability will	3313	interface to speed up C<ev_stat> watchers. Its actual availability will
2309	be detected at runtime.	3314	be detected at runtime. If undefined, it will be enabled if the headers
		3315	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		3316
		3317	=item EV_ATOMIC_T
		3318
		3319	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		3320	access is atomic with respect to other threads or signal contexts. No such
		3321	type is easily found in the C language, so you can provide your own type
		3322	that you know is safe for your purposes. It is used both for signal handler "locking"
		3323	as well as for signal and thread safety in C<ev_async> watchers.
		3324
		3325	In the absence of this define, libev will use C<sig_atomic_t volatile>
		3326	(from F<signal.h>), which is usually good enough on most platforms.
2310		3327
2311	=item EV_H	3328	=item EV_H
2312		3329
2313	The name of the F<ev.h> header file used to include it. The default if	3330	The name of the F<ev.h> header file used to include it. The default if
2314	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	3331	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2315	can be used to virtually rename the F<ev.h> header file in case of conflicts.	3332	used to virtually rename the F<ev.h> header file in case of conflicts.
2316		3333
2317	=item EV_CONFIG_H	3334	=item EV_CONFIG_H
2318		3335
2319	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3336	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2320	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3337	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2321	C<EV_H>, above.	3338	C<EV_H>, above.
2322		3339
2323	=item EV_EVENT_H	3340	=item EV_EVENT_H
2324		3341
2325	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3342	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2326	of how the F<event.h> header can be found.	3343	of how the F<event.h> header can be found, the default is C<"event.h">.
2327		3344
2328	=item EV_PROTOTYPES	3345	=item EV_PROTOTYPES
2329		3346
2330	If defined to be C<0>, then F<ev.h> will not define any function	3347	If defined to be C<0>, then F<ev.h> will not define any function
2331	prototypes, but still define all the structs and other symbols. This is	3348	prototypes, but still define all the structs and other symbols. This is
…		…
2352	When doing priority-based operations, libev usually has to linearly search	3369	When doing priority-based operations, libev usually has to linearly search
2353	all the priorities, so having many of them (hundreds) uses a lot of space	3370	all the priorities, so having many of them (hundreds) uses a lot of space
2354	and time, so using the defaults of five priorities (-2 .. +2) is usually	3371	and time, so using the defaults of five priorities (-2 .. +2) is usually
2355	fine.	3372	fine.
2356		3373
2357	If your embedding app does not need any priorities, defining these both to	3374	If your embedding application does not need any priorities, defining these
2358	C<0> will save some memory and cpu.	3375	both to C<0> will save some memory and CPU.
2359		3376
2360	=item EV_PERIODIC_ENABLE	3377	=item EV_PERIODIC_ENABLE
2361		3378
2362	If undefined or defined to be C<1>, then periodic timers are supported. If	3379	If undefined or defined to be C<1>, then periodic timers are supported. If
2363	defined to be C<0>, then they are not. Disabling them saves a few kB of	3380	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2370	code.	3387	code.
2371		3388
2372	=item EV_EMBED_ENABLE	3389	=item EV_EMBED_ENABLE
2373		3390
2374	If undefined or defined to be C<1>, then embed watchers are supported. If	3391	If undefined or defined to be C<1>, then embed watchers are supported. If
2375	defined to be C<0>, then they are not.	3392	defined to be C<0>, then they are not. Embed watchers rely on most other
		3393	watcher types, which therefore must not be disabled.
2376		3394
2377	=item EV_STAT_ENABLE	3395	=item EV_STAT_ENABLE
2378		3396
2379	If undefined or defined to be C<1>, then stat watchers are supported. If	3397	If undefined or defined to be C<1>, then stat watchers are supported. If
2380	defined to be C<0>, then they are not.	3398	defined to be C<0>, then they are not.
…		…
2382	=item EV_FORK_ENABLE	3400	=item EV_FORK_ENABLE
2383		3401
2384	If undefined or defined to be C<1>, then fork watchers are supported. If	3402	If undefined or defined to be C<1>, then fork watchers are supported. If
2385	defined to be C<0>, then they are not.	3403	defined to be C<0>, then they are not.
2386		3404
		3405	=item EV_ASYNC_ENABLE
		3406
		3407	If undefined or defined to be C<1>, then async watchers are supported. If
		3408	defined to be C<0>, then they are not.
		3409
2387	=item EV_MINIMAL	3410	=item EV_MINIMAL
2388		3411
2389	If you need to shave off some kilobytes of code at the expense of some	3412	If you need to shave off some kilobytes of code at the expense of some
2390	speed, define this symbol to C<1>. Currently only used for gcc to override	3413	speed, define this symbol to C<1>. Currently this is used to override some
2391	some inlining decisions, saves roughly 30% codesize of amd64.	3414	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3415	much smaller 2-heap for timer management over the default 4-heap.
2392		3416
2393	=item EV_PID_HASHSIZE	3417	=item EV_PID_HASHSIZE
2394		3418
2395	C<ev_child> watchers use a small hash table to distribute workload by	3419	C<ev_child> watchers use a small hash table to distribute workload by
2396	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3420	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2397	than enough. If you need to manage thousands of children you might want to	3421	than enough. If you need to manage thousands of children you might want to
2398	increase this value (I<must> be a power of two).	3422	increase this value (I<must> be a power of two).
2399		3423
2400	=item EV_INOTIFY_HASHSIZE	3424	=item EV_INOTIFY_HASHSIZE
2401		3425
2402	C<ev_staz> watchers use a small hash table to distribute workload by	3426	C<ev_stat> watchers use a small hash table to distribute workload by
2403	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3427	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2404	usually more than enough. If you need to manage thousands of C<ev_stat>	3428	usually more than enough. If you need to manage thousands of C<ev_stat>
2405	watchers you might want to increase this value (I<must> be a power of	3429	watchers you might want to increase this value (I<must> be a power of
2406	two).	3430	two).
2407		3431
		3432	=item EV_USE_4HEAP
		3433
		3434	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3435	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3436	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3437	faster performance with many (thousands) of watchers.
		3438
		3439	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3440	(disabled).
		3441
		3442	=item EV_HEAP_CACHE_AT
		3443
		3444	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3445	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3446	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3447	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3448	but avoids random read accesses on heap changes. This improves performance
		3449	noticeably with many (hundreds) of watchers.
		3450
		3451	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3452	(disabled).
		3453
		3454	=item EV_VERIFY
		3455
		3456	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3457	be done: If set to C<0>, no internal verification code will be compiled
		3458	in. If set to C<1>, then verification code will be compiled in, but not
		3459	called. If set to C<2>, then the internal verification code will be
		3460	called once per loop, which can slow down libev. If set to C<3>, then the
		3461	verification code will be called very frequently, which will slow down
		3462	libev considerably.
		3463
		3464	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3465	C<0>.
		3466
2408	=item EV_COMMON	3467	=item EV_COMMON
2409		3468
2410	By default, all watchers have a C<void *data> member. By redefining	3469	By default, all watchers have a C<void *data> member. By redefining
2411	this macro to a something else you can include more and other types of	3470	this macro to a something else you can include more and other types of
2412	members. You have to define it each time you include one of the files,	3471	members. You have to define it each time you include one of the files,
2413	though, and it must be identical each time.	3472	though, and it must be identical each time.
2414		3473
2415	For example, the perl EV module uses something like this:	3474	For example, the perl EV module uses something like this:
2416		3475
2417	#define EV_COMMON \	3476	#define EV_COMMON \
2418	SV *self; /* contains this struct */ \	3477	SV *self; /* contains this struct */ \
2419	SV *cb_sv, *fh /* note no trailing ";" */	3478	SV *cb_sv, *fh /* note no trailing ";" */
2420		3479
2421	=item EV_CB_DECLARE (type)	3480	=item EV_CB_DECLARE (type)
2422		3481
2423	=item EV_CB_INVOKE (watcher, revents)	3482	=item EV_CB_INVOKE (watcher, revents)
2424		3483
2425	=item ev_set_cb (ev, cb)	3484	=item ev_set_cb (ev, cb)
2426		3485
2427	Can be used to change the callback member declaration in each watcher,	3486	Can be used to change the callback member declaration in each watcher,
2428	and the way callbacks are invoked and set. Must expand to a struct member	3487	and the way callbacks are invoked and set. Must expand to a struct member
2429	definition and a statement, respectively. See the F<ev.v> header file for	3488	definition and a statement, respectively. See the F<ev.h> header file for
2430	their default definitions. One possible use for overriding these is to	3489	their default definitions. One possible use for overriding these is to
2431	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3490	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2432	method calls instead of plain function calls in C++.	3491	method calls instead of plain function calls in C++.
		3492
		3493	=back
		3494
		3495	=head2 EXPORTED API SYMBOLS
		3496
		3497	If you need to re-export the API (e.g. via a DLL) and you need a list of
		3498	exported symbols, you can use the provided F<Symbol.*> files which list
		3499	all public symbols, one per line:
		3500
		3501	Symbols.ev for libev proper
		3502	Symbols.event for the libevent emulation
		3503
		3504	This can also be used to rename all public symbols to avoid clashes with
		3505	multiple versions of libev linked together (which is obviously bad in
		3506	itself, but sometimes it is inconvenient to avoid this).
		3507
		3508	A sed command like this will create wrapper C<#define>'s that you need to
		3509	include before including F<ev.h>:
		3510
		3511	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		3512
		3513	This would create a file F<wrap.h> which essentially looks like this:
		3514
		3515	#define ev_backend myprefix_ev_backend
		3516	#define ev_check_start myprefix_ev_check_start
		3517	#define ev_check_stop myprefix_ev_check_stop
		3518	...
2433		3519
2434	=head2 EXAMPLES	3520	=head2 EXAMPLES
2435		3521
2436	For a real-world example of a program the includes libev	3522	For a real-world example of a program the includes libev
2437	verbatim, you can have a look at the EV perl module	3523	verbatim, you can have a look at the EV perl module
…		…
2442	file.	3528	file.
2443		3529
2444	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3530	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2445	that everybody includes and which overrides some configure choices:	3531	that everybody includes and which overrides some configure choices:
2446		3532
2447	#define EV_MINIMAL 1	3533	#define EV_MINIMAL 1
2448	#define EV_USE_POLL 0	3534	#define EV_USE_POLL 0
2449	#define EV_MULTIPLICITY 0	3535	#define EV_MULTIPLICITY 0
2450	#define EV_PERIODIC_ENABLE 0	3536	#define EV_PERIODIC_ENABLE 0
2451	#define EV_STAT_ENABLE 0	3537	#define EV_STAT_ENABLE 0
2452	#define EV_FORK_ENABLE 0	3538	#define EV_FORK_ENABLE 0
2453	#define EV_CONFIG_H <config.h>	3539	#define EV_CONFIG_H <config.h>
2454	#define EV_MINPRI 0	3540	#define EV_MINPRI 0
2455	#define EV_MAXPRI 0	3541	#define EV_MAXPRI 0
2456		3542
2457	#include "ev++.h"	3543	#include "ev++.h"
2458		3544
2459	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3545	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2460		3546
2461	#include "ev_cpp.h"	3547	#include "ev_cpp.h"
2462	#include "ev.c"	3548	#include "ev.c"
2463		3549
		3550	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
2464		3551
		3552	=head2 THREADS AND COROUTINES
		3553
		3554	=head3 THREADS
		3555
		3556	All libev functions are reentrant and thread-safe unless explicitly
		3557	documented otherwise, but libev implements no locking itself. This means
		3558	that you can use as many loops as you want in parallel, as long as there
		3559	are no concurrent calls into any libev function with the same loop
		3560	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3561	of course): libev guarantees that different event loops share no data
		3562	structures that need any locking.
		3563
		3564	Or to put it differently: calls with different loop parameters can be done
		3565	concurrently from multiple threads, calls with the same loop parameter
		3566	must be done serially (but can be done from different threads, as long as
		3567	only one thread ever is inside a call at any point in time, e.g. by using
		3568	a mutex per loop).
		3569
		3570	Specifically to support threads (and signal handlers), libev implements
		3571	so-called C<ev_async> watchers, which allow some limited form of
		3572	concurrency on the same event loop, namely waking it up "from the
		3573	outside".
		3574
		3575	If you want to know which design (one loop, locking, or multiple loops
		3576	without or something else still) is best for your problem, then I cannot
		3577	help you, but here is some generic advice:
		3578
		3579	=over 4
		3580
		3581	=item * most applications have a main thread: use the default libev loop
		3582	in that thread, or create a separate thread running only the default loop.
		3583
		3584	This helps integrating other libraries or software modules that use libev
		3585	themselves and don't care/know about threading.
		3586
		3587	=item * one loop per thread is usually a good model.
		3588
		3589	Doing this is almost never wrong, sometimes a better-performance model
		3590	exists, but it is always a good start.
		3591
		3592	=item * other models exist, such as the leader/follower pattern, where one
		3593	loop is handed through multiple threads in a kind of round-robin fashion.
		3594
		3595	Choosing a model is hard - look around, learn, know that usually you can do
		3596	better than you currently do :-)
		3597
		3598	=item * often you need to talk to some other thread which blocks in the
		3599	event loop.
		3600
		3601	C<ev_async> watchers can be used to wake them up from other threads safely
		3602	(or from signal contexts...).
		3603
		3604	An example use would be to communicate signals or other events that only
		3605	work in the default loop by registering the signal watcher with the
		3606	default loop and triggering an C<ev_async> watcher from the default loop
		3607	watcher callback into the event loop interested in the signal.
		3608
		3609	=back
		3610
		3611	=head3 COROUTINES
		3612
		3613	Libev is very accommodating to coroutines ("cooperative threads"):
		3614	libev fully supports nesting calls to its functions from different
		3615	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3616	different coroutines, and switch freely between both coroutines running the
		3617	loop, as long as you don't confuse yourself). The only exception is that
		3618	you must not do this from C<ev_periodic> reschedule callbacks.
		3619
		3620	Care has been taken to ensure that libev does not keep local state inside
		3621	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3622	they do not call any callbacks.
		3623
		3624	=head2 COMPILER WARNINGS
		3625
		3626	Depending on your compiler and compiler settings, you might get no or a
		3627	lot of warnings when compiling libev code. Some people are apparently
		3628	scared by this.
		3629
		3630	However, these are unavoidable for many reasons. For one, each compiler
		3631	has different warnings, and each user has different tastes regarding
		3632	warning options. "Warn-free" code therefore cannot be a goal except when
		3633	targeting a specific compiler and compiler-version.
		3634
		3635	Another reason is that some compiler warnings require elaborate
		3636	workarounds, or other changes to the code that make it less clear and less
		3637	maintainable.
		3638
		3639	And of course, some compiler warnings are just plain stupid, or simply
		3640	wrong (because they don't actually warn about the condition their message
		3641	seems to warn about). For example, certain older gcc versions had some
		3642	warnings that resulted an extreme number of false positives. These have
		3643	been fixed, but some people still insist on making code warn-free with
		3644	such buggy versions.
		3645
		3646	While libev is written to generate as few warnings as possible,
		3647	"warn-free" code is not a goal, and it is recommended not to build libev
		3648	with any compiler warnings enabled unless you are prepared to cope with
		3649	them (e.g. by ignoring them). Remember that warnings are just that:
		3650	warnings, not errors, or proof of bugs.
		3651
		3652
		3653	=head2 VALGRIND
		3654
		3655	Valgrind has a special section here because it is a popular tool that is
		3656	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3657
		3658	If you think you found a bug (memory leak, uninitialised data access etc.)
		3659	in libev, then check twice: If valgrind reports something like:
		3660
		3661	==2274== definitely lost: 0 bytes in 0 blocks.
		3662	==2274== possibly lost: 0 bytes in 0 blocks.
		3663	==2274== still reachable: 256 bytes in 1 blocks.
		3664
		3665	Then there is no memory leak, just as memory accounted to global variables
		3666	is not a memleak - the memory is still being referenced, and didn't leak.
		3667
		3668	Similarly, under some circumstances, valgrind might report kernel bugs
		3669	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3670	although an acceptable workaround has been found here), or it might be
		3671	confused.
		3672
		3673	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3674	make it into some kind of religion.
		3675
		3676	If you are unsure about something, feel free to contact the mailing list
		3677	with the full valgrind report and an explanation on why you think this
		3678	is a bug in libev (best check the archives, too :). However, don't be
		3679	annoyed when you get a brisk "this is no bug" answer and take the chance
		3680	of learning how to interpret valgrind properly.
		3681
		3682	If you need, for some reason, empty reports from valgrind for your project
		3683	I suggest using suppression lists.
		3684
		3685
		3686	=head1 PORTABILITY NOTES
		3687
		3688	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		3689
		3690	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3691	requires, and its I/O model is fundamentally incompatible with the POSIX
		3692	model. Libev still offers limited functionality on this platform in
		3693	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3694	descriptors. This only applies when using Win32 natively, not when using
		3695	e.g. cygwin.
		3696
		3697	Lifting these limitations would basically require the full
		3698	re-implementation of the I/O system. If you are into these kinds of
		3699	things, then note that glib does exactly that for you in a very portable
		3700	way (note also that glib is the slowest event library known to man).
		3701
		3702	There is no supported compilation method available on windows except
		3703	embedding it into other applications.
		3704
		3705	Not a libev limitation but worth mentioning: windows apparently doesn't
		3706	accept large writes: instead of resulting in a partial write, windows will
		3707	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3708	so make sure you only write small amounts into your sockets (less than a
		3709	megabyte seems safe, but this apparently depends on the amount of memory
		3710	available).
		3711
		3712	Due to the many, low, and arbitrary limits on the win32 platform and
		3713	the abysmal performance of winsockets, using a large number of sockets
		3714	is not recommended (and not reasonable). If your program needs to use
		3715	more than a hundred or so sockets, then likely it needs to use a totally
		3716	different implementation for windows, as libev offers the POSIX readiness
		3717	notification model, which cannot be implemented efficiently on windows
		3718	(Microsoft monopoly games).
		3719
		3720	A typical way to use libev under windows is to embed it (see the embedding
		3721	section for details) and use the following F<evwrap.h> header file instead
		3722	of F<ev.h>:
		3723
		3724	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3725	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3726
		3727	#include "ev.h"
		3728
		3729	And compile the following F<evwrap.c> file into your project (make sure
		3730	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3731
		3732	#include "evwrap.h"
		3733	#include "ev.c"
		3734
		3735	=over 4
		3736
		3737	=item The winsocket select function
		3738
		3739	The winsocket C<select> function doesn't follow POSIX in that it
		3740	requires socket I<handles> and not socket I<file descriptors> (it is
		3741	also extremely buggy). This makes select very inefficient, and also
		3742	requires a mapping from file descriptors to socket handles (the Microsoft
		3743	C runtime provides the function C<_open_osfhandle> for this). See the
		3744	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3745	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
		3746
		3747	The configuration for a "naked" win32 using the Microsoft runtime
		3748	libraries and raw winsocket select is:
		3749
		3750	#define EV_USE_SELECT 1
		3751	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3752
		3753	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3754	complexity in the O(n²) range when using win32.
		3755
		3756	=item Limited number of file descriptors
		3757
		3758	Windows has numerous arbitrary (and low) limits on things.
		3759
		3760	Early versions of winsocket's select only supported waiting for a maximum
		3761	of C<64> handles (probably owning to the fact that all windows kernels
		3762	can only wait for C<64> things at the same time internally; Microsoft
		3763	recommends spawning a chain of threads and wait for 63 handles and the
		3764	previous thread in each. Great).
		3765
		3766	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3767	to some high number (e.g. C<2048>) before compiling the winsocket select
		3768	call (which might be in libev or elsewhere, for example, perl does its own
		3769	select emulation on windows).
		3770
		3771	Another limit is the number of file descriptors in the Microsoft runtime
		3772	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3773	or something like this inside Microsoft). You can increase this by calling
		3774	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3775	arbitrary limit), but is broken in many versions of the Microsoft runtime
		3776	libraries.
		3777
		3778	This might get you to about C<512> or C<2048> sockets (depending on
		3779	windows version and/or the phase of the moon). To get more, you need to
		3780	wrap all I/O functions and provide your own fd management, but the cost of
		3781	calling select (O(n²)) will likely make this unworkable.
		3782
		3783	=back
		3784
		3785	=head2 PORTABILITY REQUIREMENTS
		3786
		3787	In addition to a working ISO-C implementation and of course the
		3788	backend-specific APIs, libev relies on a few additional extensions:
		3789
		3790	=over 4
		3791
		3792	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3793	calling conventions regardless of C<ev_watcher_type *>.
		3794
		3795	Libev assumes not only that all watcher pointers have the same internal
		3796	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3797	assumes that the same (machine) code can be used to call any watcher
		3798	callback: The watcher callbacks have different type signatures, but libev
		3799	calls them using an C<ev_watcher *> internally.
		3800
		3801	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3802
		3803	The type C<sig_atomic_t volatile> (or whatever is defined as
		3804	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3805	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3806	believed to be sufficiently portable.
		3807
		3808	=item C<sigprocmask> must work in a threaded environment
		3809
		3810	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3811	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3812	pthread implementations will either allow C<sigprocmask> in the "main
		3813	thread" or will block signals process-wide, both behaviours would
		3814	be compatible with libev. Interaction between C<sigprocmask> and
		3815	C<pthread_sigmask> could complicate things, however.
		3816
		3817	The most portable way to handle signals is to block signals in all threads
		3818	except the initial one, and run the default loop in the initial thread as
		3819	well.
		3820
		3821	=item C<long> must be large enough for common memory allocation sizes
		3822
		3823	To improve portability and simplify its API, libev uses C<long> internally
		3824	instead of C<size_t> when allocating its data structures. On non-POSIX
		3825	systems (Microsoft...) this might be unexpectedly low, but is still at
		3826	least 31 bits everywhere, which is enough for hundreds of millions of
		3827	watchers.
		3828
		3829	=item C<double> must hold a time value in seconds with enough accuracy
		3830
		3831	The type C<double> is used to represent timestamps. It is required to
		3832	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		3833	enough for at least into the year 4000. This requirement is fulfilled by
		3834	implementations implementing IEEE 754 (basically all existing ones).
		3835
		3836	=back
		3837
		3838	If you know of other additional requirements drop me a note.
		3839
		3840
2465	=head1 COMPLEXITIES	3841	=head1 ALGORITHMIC COMPLEXITIES
2466		3842
2467	In this section the complexities of (many of) the algorithms used inside	3843	In this section the complexities of (many of) the algorithms used inside
2468	libev will be explained. For complexity discussions about backends see the	3844	libev will be documented. For complexity discussions about backends see
2469	documentation for C<ev_default_init>.	3845	the documentation for C<ev_default_init>.
2470		3846
2471	All of the following are about amortised time: If an array needs to be	3847	All of the following are about amortised time: If an array needs to be
2472	extended, libev needs to realloc and move the whole array, but this	3848	extended, libev needs to realloc and move the whole array, but this
2473	happens asymptotically never with higher number of elements, so O(1) might	3849	happens asymptotically rarer with higher number of elements, so O(1) might
2474	mean it might do a lengthy realloc operation in rare cases, but on average	3850	mean that libev does a lengthy realloc operation in rare cases, but on
2475	it is much faster and asymptotically approaches constant time.	3851	average it is much faster and asymptotically approaches constant time.
2476		3852
2477	=over 4	3853	=over 4
2478		3854
2479	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3855	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2480		3856
2481	This means that, when you have a watcher that triggers in one hour and	3857	This means that, when you have a watcher that triggers in one hour and
2482	there are 100 watchers that would trigger before that then inserting will	3858	there are 100 watchers that would trigger before that, then inserting will
2483	have to skip those 100 watchers.	3859	have to skip roughly seven (C<ld 100>) of these watchers.
2484		3860
2485	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	3861	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2486		3862
2487	That means that for changing a timer costs less than removing/adding them	3863	That means that changing a timer costs less than removing/adding them,
2488	as only the relative motion in the event queue has to be paid for.	3864	as only the relative motion in the event queue has to be paid for.
2489		3865
2490	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	3866	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2491		3867
2492	These just add the watcher into an array or at the head of a list.	3868	These just add the watcher into an array or at the head of a list.
		3869
2493	=item Stopping check/prepare/idle watchers: O(1)	3870	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2494		3871
2495	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3872	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2496		3873
2497	These watchers are stored in lists then need to be walked to find the	3874	These watchers are stored in lists, so they need to be walked to find the
2498	correct watcher to remove. The lists are usually short (you don't usually	3875	correct watcher to remove. The lists are usually short (you don't usually
2499	have many watchers waiting for the same fd or signal).	3876	have many watchers waiting for the same fd or signal: one is typical, two
		3877	is rare).
2500		3878
2501	=item Finding the next timer per loop iteration: O(1)	3879	=item Finding the next timer in each loop iteration: O(1)
		3880
		3881	By virtue of using a binary or 4-heap, the next timer is always found at a
		3882	fixed position in the storage array.
2502		3883
2503	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	3884	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2504		3885
2505	A change means an I/O watcher gets started or stopped, which requires	3886	A change means an I/O watcher gets started or stopped, which requires
2506	libev to recalculate its status (and possibly tell the kernel).	3887	libev to recalculate its status (and possibly tell the kernel, depending
		3888	on backend and whether C<ev_io_set> was used).
2507		3889
2508	=item Activating one watcher: O(1)	3890	=item Activating one watcher (putting it into the pending state): O(1)
2509		3891
2510	=item Priority handling: O(number_of_priorities)	3892	=item Priority handling: O(number_of_priorities)
2511		3893
2512	Priorities are implemented by allocating some space for each	3894	Priorities are implemented by allocating some space for each
2513	priority. When doing priority-based operations, libev usually has to	3895	priority. When doing priority-based operations, libev usually has to
2514	linearly search all the priorities.	3896	linearly search all the priorities, but starting/stopping and activating
		3897	watchers becomes O(1) with respect to priority handling.
		3898
		3899	=item Sending an ev_async: O(1)
		3900
		3901	=item Processing ev_async_send: O(number_of_async_watchers)
		3902
		3903	=item Processing signals: O(max_signal_number)
		3904
		3905	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3906	calls in the current loop iteration. Checking for async and signal events
		3907	involves iterating over all running async watchers or all signal numbers.
2515		3908
2516	=back	3909	=back
2517		3910
2518		3911
2519	=head1 AUTHOR	3912	=head1 AUTHOR
2520		3913
2521	Marc Lehmann <libev@schmorp.de>.	3914	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
2522		3915

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