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Revision 1.271 by root, Fri Sep 18 21:16:10 2009 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	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_loop's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = ev_default_loop (0);
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
52		54
53	// initialise a timer watcher, then start it	55	// initialise a timer watcher, then start it
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_loop (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floatingpoint value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
		136
		137	=head1 ERROR HANDLING
		138
		139	Libev knows three classes of errors: operating system errors, usage errors
		140	and internal errors (bugs).
		141
		142	When libev catches an operating system error it cannot handle (for example
		143	a system call indicating a condition libev cannot fix), it calls the callback
		144	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		145	abort. The default is to print a diagnostic message and to call C<abort
		146	()>.
		147
		148	When libev detects a usage error such as a negative timer interval, then
		149	it will print a diagnostic message and abort (via the C<assert> mechanism,
		150	so C<NDEBUG> will disable this checking): these are programming errors in
		151	the libev caller and need to be fixed there.
		152
		153	Libev also has a few internal error-checking C<assert>ions, and also has
		154	extensive consistency checking code. These do not trigger under normal
		155	circumstances, as they indicate either a bug in libev or worse.
		156
121		157
122	=head1 GLOBAL FUNCTIONS	158	=head1 GLOBAL FUNCTIONS
123		159
124	These functions can be called anytime, even before initialising the	160	These functions can be called anytime, even before initialising the
125	library in any way.	161	library in any way.
…		…
134		170
135	=item ev_sleep (ev_tstamp interval)	171	=item ev_sleep (ev_tstamp interval)
136		172
137	Sleep for the given interval: The current thread will be blocked until	173	Sleep for the given interval: The current thread will be blocked until
138	either it is interrupted or the given time interval has passed. Basically	174	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	175	this is a sub-second-resolution C<sleep ()>.
140		176
141	=item int ev_version_major ()	177	=item int ev_version_major ()
142		178
143	=item int ev_version_minor ()	179	=item int ev_version_minor ()
144		180
…		…
157	not a problem.	193	not a problem.
158		194
159	Example: Make sure we haven't accidentally been linked against the wrong	195	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	196	version.
161		197
162	assert (("libev version mismatch",	198	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	199	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	200	&& ev_version_minor () >= EV_VERSION_MINOR));
165		201
166	=item unsigned int ev_supported_backends ()	202	=item unsigned int ev_supported_backends ()
167		203
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	204	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	205	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	207	a description of the set values.
172		208
173	Example: make sure we have the epoll method, because yeah this is cool and	209	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	210	a must have and can we have a torrent of it please!!!11
175		211
176	assert (("sorry, no epoll, no sex",	212	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	213	ev_supported_backends () & EVBACKEND_EPOLL));
178		214
179	=item unsigned int ev_recommended_backends ()	215	=item unsigned int ev_recommended_backends ()
180		216
181	Return the set of all backends compiled into this binary of libev and also	217	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	218	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	219	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	220	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	221	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	222	libev will probe for if you specify no backends explicitly.
187		223
188	=item unsigned int ev_embeddable_backends ()	224	=item unsigned int ev_embeddable_backends ()
189		225
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	230	recommended ones.
195		231
196	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
197		233
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		235
200	Sets the allocation function to use (the prototype is similar - the	236	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	238	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	239	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	240	or take some potentially destructive action.
205	function.	241
		242	Since some systems (at least OpenBSD and Darwin) fail to implement
		243	correct C<realloc> semantics, libev will use a wrapper around the system
		244	C<realloc> and C<free> functions by default.
206		245
207	You could override this function in high-availability programs to, say,	246	You could override this function in high-availability programs to, say,
208	free some memory if it cannot allocate memory, to use a special allocator,	247	free some memory if it cannot allocate memory, to use a special allocator,
209	or even to sleep a while and retry until some memory is available.	248	or even to sleep a while and retry until some memory is available.
210		249
211	Example: Replace the libev allocator with one that waits a bit and then	250	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	251	retries (example requires a standards-compliant C<realloc>).
213		252
214	static void *	253	static void *
215	persistent_realloc (void *ptr, size_t size)	254	persistent_realloc (void *ptr, size_t size)
216	{	255	{
217	for (;;)	256	for (;;)
…		…
226	}	265	}
227		266
228	...	267	...
229	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
230		269
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		271
233	Set the callback function to call on a retryable syscall error (such	272	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	273	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	274	indicating the system call or subsystem causing the problem. If this
236	callback is set, then libev will expect it to remedy the sitution, no	275	callback is set, then libev will expect it to remedy the situation, no
237	matter what, when it returns. That is, libev will generally retry the	276	matter what, when it returns. That is, libev will generally retry the
238	requested operation, or, if the condition doesn't go away, do bad stuff	277	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	278	(such as abort).
240		279
241	Example: This is basically the same thing that libev does internally, too.	280	Example: This is basically the same thing that libev does internally, too.
…		…
252		291
253	=back	292	=back
254		293
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		295
257	An event loop is described by a C<struct ev_loop *>. The library knows two	296	An event loop is described by a C<struct ev_loop *> (the C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	297	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	298	I<function>).
260		299
261	If you use threads, a common model is to run the default event loop	300	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	301	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	302	not.
264	whatsoever, so if you mix calls to the same event loop in different
265	threads, make sure you lock (this is usually a bad idea, though, even if
266	done correctly, because it's hideous and inefficient).
267		303
268	=over 4	304	=over 4
269		305
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		307
…		…
277	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
278	function.	314	function.
279		315
280	Note that this function is I<not> thread-safe, so if you want to use it	316	Note that this function is I<not> thread-safe, so if you want to use it
281	from multiple threads, you have to lock (note also that this is unlikely,	317	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
283		319
284	The default loop is the only loop that can handle C<ev_signal> and	320	The default loop is the only loop that can handle C<ev_signal> and
285	C<ev_child> watchers, and to do this, it always registers a handler	321	C<ev_child> watchers, and to do this, it always registers a handler
286	for C<SIGCHLD>. If this is a problem for your app you can either	322	for C<SIGCHLD>. If this is a problem for your application you can either
287	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
288	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	325	C<ev_default_init>.
290		326
291	The flags argument can be used to specify special behaviour or specific	327	The flags argument can be used to specify special behaviour or specific
…		…
300	The default flags value. Use this if you have no clue (it's the right	336	The default flags value. Use this if you have no clue (it's the right
301	thing, believe me).	337	thing, believe me).
302		338
303	=item C<EVFLAG_NOENV>	339	=item C<EVFLAG_NOENV>
304		340
305	If this flag bit is ored into the flag value (or the program runs setuid	341	If this flag bit is or'ed into the flag value (or the program runs setuid
306	or setgid) then libev will I<not> look at the environment variable	342	or setgid) then libev will I<not> look at the environment variable
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	override the flags completely if it is found in the environment. This is	344	override the flags completely if it is found in the environment. This is
309	useful to try out specific backends to test their performance, or to work	345	useful to try out specific backends to test their performance, or to work
310	around bugs.	346	around bugs.
…		…
317		353
318	This works by calling C<getpid ()> on every iteration of the loop,	354	This works by calling C<getpid ()> on every iteration of the loop,
319	and thus this might slow down your event loop if you do a lot of loop	355	and thus this might slow down your event loop if you do a lot of loop
320	iterations and little real work, but is usually not noticeable (on my	356	iterations and little real work, but is usually not noticeable (on my
321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
322	without a syscall and thus I<very> fast, but my GNU/Linux system also has	358	without a system call and thus I<very> fast, but my GNU/Linux system also has
323	C<pthread_atfork> which is even faster).	359	C<pthread_atfork> which is even faster).
324		360
325	The big advantage of this flag is that you can forget about fork (and	361	The big advantage of this flag is that you can forget about fork (and
326	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
327	flag.	363	flag.
328		364
329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
330	environment variable.	366	environment variable.
		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
331		382
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		384
334	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
335	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
336	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
337	using this backend. It doesn't scale too well (O(highest_fd)), but its	388	using this backend. It doesn't scale too well (O(highest_fd)), but its
338	usually the fastest backend for a low number of (low-numbered :) fds.	389	usually the fastest backend for a low number of (low-numbered :) fds.
339		390
340	To get good performance out of this backend you need a high amount of	391	To get good performance out of this backend you need a high amount of
341	parallelity (most of the file descriptors should be busy). If you are	392	parallelism (most of the file descriptors should be busy). If you are
342	writing a server, you should C<accept ()> in a loop to accept as many	393	writing a server, you should C<accept ()> in a loop to accept as many
343	connections as possible during one iteration. You might also want to have	394	connections as possible during one iteration. You might also want to have
344	a look at C<ev_set_io_collect_interval ()> to increase the amount of	395	a look at C<ev_set_io_collect_interval ()> to increase the amount of
345	readyness notifications you get per iteration.	396	readiness notifications you get per iteration.
		397
		398	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		399	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		400	C<exceptfds> set on that platform).
346		401
347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	402	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
348		403
349	And this is your standard poll(2) backend. It's more complicated	404	And this is your standard poll(2) backend. It's more complicated
350	than select, but handles sparse fds better and has no artificial	405	than select, but handles sparse fds better and has no artificial
351	limit on the number of fds you can use (except it will slow down	406	limit on the number of fds you can use (except it will slow down
352	considerably with a lot of inactive fds). It scales similarly to select,	407	considerably with a lot of inactive fds). It scales similarly to select,
353	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	408	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
354	performance tips.	409	performance tips.
355		410
		411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		413
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		415
358	For few fds, this backend is a bit little slower than poll and select,	416	For few fds, this backend is a bit little slower than poll and select,
359	but it scales phenomenally better. While poll and select usually scale	417	but it scales phenomenally better. While poll and select usually scale
360	like O(total_fds) where n is the total number of fds (or the highest fd),	418	like O(total_fds) where n is the total number of fds (or the highest fd),
361	epoll scales either O(1) or O(active_fds). The epoll design has a number	419	epoll scales either O(1) or O(active_fds).
362	of shortcomings, such as silently dropping events in some hard-to-detect	420
363	cases and requiring a syscall per fd change, no fork support and bad	421	The epoll mechanism deserves honorable mention as the most misdesigned
364	support for dup.	422	of the more advanced event mechanisms: mere annoyances include silently
		423	dropping file descriptors, requiring a system call per change per file
		424	descriptor (and unnecessary guessing of parameters), problems with dup and
		425	so on. The biggest issue is fork races, however - if a program forks then
		426	I<both> parent and child process have to recreate the epoll set, which can
		427	take considerable time (one syscall per file descriptor) and is of course
		428	hard to detect.
		429
		430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		431	of course I<doesn't>, and epoll just loves to report events for totally
		432	I<different> file descriptors (even already closed ones, so one cannot
		433	even remove them from the set) than registered in the set (especially
		434	on SMP systems). Libev tries to counter these spurious notifications by
		435	employing an additional generation counter and comparing that against the
		436	events to filter out spurious ones, recreating the set when required.
365		437
366	While stopping, setting and starting an I/O watcher in the same iteration	438	While stopping, setting and starting an I/O watcher in the same iteration
367	will result in some caching, there is still a syscall per such incident	439	will result in some caching, there is still a system call per such
368	(because the fd could point to a different file description now), so its	440	incident (because the same I<file descriptor> could point to a different
369	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	441	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
370	very well if you register events for both fds.	442	file descriptors might not work very well if you register events for both
371		443	file descriptors.
372	Please note that epoll sometimes generates spurious notifications, so you
373	need to use non-blocking I/O or other means to avoid blocking when no data
374	(or space) is available.
375		444
376	Best performance from this backend is achieved by not unregistering all	445	Best performance from this backend is achieved by not unregistering all
377	watchers for a file descriptor until it has been closed, if possible, i.e.	446	watchers for a file descriptor until it has been closed, if possible,
378	keep at least one watcher active per fd at all times.	447	i.e. keep at least one watcher active per fd at all times. Stopping and
		448	starting a watcher (without re-setting it) also usually doesn't cause
		449	extra overhead. A fork can both result in spurious notifications as well
		450	as in libev having to destroy and recreate the epoll object, which can
		451	take considerable time and thus should be avoided.
379		452
		453	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		454	faster than epoll for maybe up to a hundred file descriptors, depending on
		455	the usage. So sad.
		456
380	While nominally embeddeble in other event loops, this feature is broken in	457	While nominally embeddable in other event loops, this feature is broken in
381	all kernel versions tested so far.	458	all kernel versions tested so far.
		459
		460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		461	C<EVBACKEND_POLL>.
382		462
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		464
385	Kqueue deserves special mention, as at the time of this writing, it	465	Kqueue deserves special mention, as at the time of this writing, it
386	was broken on all BSDs except NetBSD (usually it doesn't work reliably	466	was broken on all BSDs except NetBSD (usually it doesn't work reliably
387	with anything but sockets and pipes, except on Darwin, where of course	467	with anything but sockets and pipes, except on Darwin, where of course
388	it's completely useless). For this reason it's not being "autodetected"	468	it's completely useless). Unlike epoll, however, whose brokenness
		469	is by design, these kqueue bugs can (and eventually will) be fixed
		470	without API changes to existing programs. For this reason it's not being
389	unless you explicitly specify it explicitly in the flags (i.e. using	471	"auto-detected" unless you explicitly specify it in the flags (i.e. using
390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	472	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
391	system like NetBSD.	473	system like NetBSD.
392		474
393	You still can embed kqueue into a normal poll or select backend and use it	475	You still can embed kqueue into a normal poll or select backend and use it
394	only for sockets (after having made sure that sockets work with kqueue on	476	only for sockets (after having made sure that sockets work with kqueue on
395	the target platform). See C<ev_embed> watchers for more info.	477	the target platform). See C<ev_embed> watchers for more info.
396		478
397	It scales in the same way as the epoll backend, but the interface to the	479	It scales in the same way as the epoll backend, but the interface to the
398	kernel is more efficient (which says nothing about its actual speed, of	480	kernel is more efficient (which says nothing about its actual speed, of
399	course). While stopping, setting and starting an I/O watcher does never	481	course). While stopping, setting and starting an I/O watcher does never
400	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to	482	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
401	two event changes per incident, support for C<fork ()> is very bad and it	483	two event changes per incident. Support for C<fork ()> is very bad (but
402	drops fds silently in similarly hard-to-detect cases.	484	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		485	cases
403		486
404	This backend usually performs well under most conditions.	487	This backend usually performs well under most conditions.
405		488
406	While nominally embeddable in other event loops, this doesn't work	489	While nominally embeddable in other event loops, this doesn't work
407	everywhere, so you might need to test for this. And since it is broken	490	everywhere, so you might need to test for this. And since it is broken
408	almost everywhere, you should only use it when you have a lot of sockets	491	almost everywhere, you should only use it when you have a lot of sockets
409	(for which it usually works), by embedding it into another event loop	492	(for which it usually works), by embedding it into another event loop
410	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	493	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
411	sockets.	494	also broken on OS X)) and, did I mention it, using it only for sockets.
		495
		496	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		497	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		498	C<NOTE_EOF>.
412		499
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	500	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		501
415	This is not implemented yet (and might never be, unless you send me an	502	This is not implemented yet (and might never be, unless you send me an
416	implementation). According to reports, C</dev/poll> only supports sockets	503	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		508
422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	509	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
423	it's really slow, but it still scales very well (O(active_fds)).	510	it's really slow, but it still scales very well (O(active_fds)).
424		511
425	Please note that solaris event ports can deliver a lot of spurious	512	Please note that Solaris event ports can deliver a lot of spurious
426	notifications, so you need to use non-blocking I/O or other means to avoid	513	notifications, so you need to use non-blocking I/O or other means to avoid
427	blocking when no data (or space) is available.	514	blocking when no data (or space) is available.
428		515
429	While this backend scales well, it requires one system call per active	516	While this backend scales well, it requires one system call per active
430	file descriptor per loop iteration. For small and medium numbers of file	517	file descriptor per loop iteration. For small and medium numbers of file
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	519	might perform better.
433		520
434	On the positive side, ignoring the spurious readyness notifications, this	521	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	522	notifications, this backend actually performed fully to specification
436	embeddable, which is a rare feat among the OS-specific backends.	523	in all tests and is fully embeddable, which is a rare feat among the
		524	OS-specific backends (I vastly prefer correctness over speed hacks).
		525
		526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		527	C<EVBACKEND_POLL>.
437		528
438	=item C<EVBACKEND_ALL>	529	=item C<EVBACKEND_ALL>
439		530
440	Try all backends (even potentially broken ones that wouldn't be tried	531	Try all backends (even potentially broken ones that wouldn't be tried
441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	532	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
443		534
444	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
445		536
446	=back	537	=back
447		538
448	If one or more of these are ored into the flags value, then only these	539	If one or more of the backend flags are or'ed into the flags value,
449	backends will be tried (in the reverse order as listed here). If none are	540	then only these backends will be tried (in the reverse order as listed
450	specified, all backends in C<ev_recommended_backends ()> will be tried.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
451		543
452	The most typical usage is like this:	544	Example: This is the most typical usage.
453		545
454	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		548
457	Restrict libev to the select and poll backends, and do not allow	549	Example: Restrict libev to the select and poll backends, and do not allow
458	environment settings to be taken into account:	550	environment settings to be taken into account:
459		551
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		553
462	Use whatever libev has to offer, but make sure that kqueue is used if	554	Example: Use whatever libev has to offer, but make sure that kqueue is
463	available (warning, breaks stuff, best use only with your own private	555	used if available (warning, breaks stuff, best use only with your own
464	event loop and only if you know the OS supports your types of fds):	556	private event loop and only if you know the OS supports your types of
		557	fds):
465		558
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		560
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	561	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		562
470	Similar to C<ev_default_loop>, but always creates a new event loop that is	563	Similar to C<ev_default_loop>, but always creates a new event loop that is
471	always distinct from the default loop. Unlike the default loop, it cannot	564	always distinct from the default loop. Unlike the default loop, it cannot
…		…
476	libev with threads is indeed to create one loop per thread, and using the	569	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	570	default loop in the "main" or "initial" thread.
478		571
479	Example: Try to create a event loop that uses epoll and nothing else.	572	Example: Try to create a event loop that uses epoll and nothing else.
480		573
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	575	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	576	fatal ("no epoll found here, maybe it hides under your chair");
484		577
485	=item ev_default_destroy ()	578	=item ev_default_destroy ()
486		579
487	Destroys the default loop again (frees all memory and kernel state	580	Destroys the default loop again (frees all memory and kernel state
488	etc.). None of the active event watchers will be stopped in the normal	581	etc.). None of the active event watchers will be stopped in the normal
489	sense, so e.g. C<ev_is_active> might still return true. It is your	582	sense, so e.g. C<ev_is_active> might still return true. It is your
490	responsibility to either stop all watchers cleanly yoursef I<before>	583	responsibility to either stop all watchers cleanly yourself I<before>
491	calling this function, or cope with the fact afterwards (which is usually	584	calling this function, or cope with the fact afterwards (which is usually
492	the easiest thing, you can just ignore the watchers and/or C<free ()> them	585	the easiest thing, you can just ignore the watchers and/or C<free ()> them
493	for example).	586	for example).
494		587
495	Note that certain global state, such as signal state, will not be freed by	588	Note that certain global state, such as signal state (and installed signal
496	this function, and related watchers (such as signal and child watchers)	589	handlers), will not be freed by this function, and related watchers (such
497	would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
498		591
499	In general it is not advisable to call this function except in the	592	In general it is not advisable to call this function except in the
500	rare occasion where you really need to free e.g. the signal handling	593	rare occasion where you really need to free e.g. the signal handling
501	pipe fds. If you need dynamically allocated loops it is better to use	594	pipe fds. If you need dynamically allocated loops it is better to use
502	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>.
503		596
504	=item ev_loop_destroy (loop)	597	=item ev_loop_destroy (loop)
505		598
506	Like C<ev_default_destroy>, but destroys an event loop created by an	599	Like C<ev_default_destroy>, but destroys an event loop created by an
507	earlier call to C<ev_loop_new>.	600	earlier call to C<ev_loop_new>.
…		…
527		620
528	=item ev_loop_fork (loop)	621	=item ev_loop_fork (loop)
529		622
530	Like C<ev_default_fork>, but acts on an event loop created by	623	Like C<ev_default_fork>, but acts on an event loop created by
531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
532	after fork, and how you do this is entirely your own problem.	625	after fork that you want to re-use in the child, and how you do this is
		626	entirely your own problem.
533		627
534	=item int ev_is_default_loop (loop)	628	=item int ev_is_default_loop (loop)
535		629
536	Returns true when the given loop actually is the default loop, false otherwise.	630	Returns true when the given loop is, in fact, the default loop, and false
		631	otherwise.
537		632
538	=item unsigned int ev_loop_count (loop)	633	=item unsigned int ev_loop_count (loop)
539		634
540	Returns the count of loop iterations for the loop, which is identical to	635	Returns the count of loop iterations for the loop, which is identical to
541	the number of times libev did poll for new events. It starts at C<0> and	636	the number of times libev did poll for new events. It starts at C<0> and
542	happily wraps around with enough iterations.	637	happily wraps around with enough iterations.
543		638
544	This value can sometimes be useful as a generation counter of sorts (it	639	This value can sometimes be useful as a generation counter of sorts (it
545	"ticks" the number of loop iterations), as it roughly corresponds with	640	"ticks" the number of loop iterations), as it roughly corresponds with
546	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
547		654
548	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
549		656
550	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
551	use.	658	use.
…		…
556	received events and started processing them. This timestamp does not	663	received events and started processing them. This timestamp does not
557	change as long as callbacks are being processed, and this is also the base	664	change as long as callbacks are being processed, and this is also the base
558	time used for relative timers. You can treat it as the timestamp of the	665	time used for relative timers. You can treat it as the timestamp of the
559	event occurring (or more correctly, libev finding out about it).	666	event occurring (or more correctly, libev finding out about it).
560		667
		668	=item ev_now_update (loop)
		669
		670	Establishes the current time by querying the kernel, updating the time
		671	returned by C<ev_now ()> in the progress. This is a costly operation and
		672	is usually done automatically within C<ev_loop ()>.
		673
		674	This function is rarely useful, but when some event callback runs for a
		675	very long time without entering the event loop, updating libev's idea of
		676	the current time is a good idea.
		677
		678	See also L<The special problem of time updates> in the C<ev_timer> section.
		679
		680	=item ev_suspend (loop)
		681
		682	=item ev_resume (loop)
		683
		684	These two functions suspend and resume a loop, for use when the loop is
		685	not used for a while and timeouts should not be processed.
		686
		687	A typical use case would be an interactive program such as a game: When
		688	the user presses C<^Z> to suspend the game and resumes it an hour later it
		689	would be best to handle timeouts as if no time had actually passed while
		690	the program was suspended. This can be achieved by calling C<ev_suspend>
		691	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		692	C<ev_resume> directly afterwards to resume timer processing.
		693
		694	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		696	will be rescheduled (that is, they will lose any events that would have
		697	occured while suspended).
		698
		699	After calling C<ev_suspend> you B<must not> call I<any> function on the
		700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		701	without a previous call to C<ev_suspend>.
		702
		703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		704	event loop time (see C<ev_now_update>).
		705
561	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
562		707
563	Finally, this is it, the event handler. This function usually is called	708	Finally, this is it, the event handler. This function usually is called
564	after you initialised all your watchers and you want to start handling	709	after you have initialised all your watchers and you want to start
565	events.	710	handling events.
566		711
567	If the flags argument is specified as C<0>, it will not return until	712	If the flags argument is specified as C<0>, it will not return until
568	either no event watchers are active anymore or C<ev_unloop> was called.	713	either no event watchers are active anymore or C<ev_unloop> was called.
569		714
570	Please note that an explicit C<ev_unloop> is usually better than	715	Please note that an explicit C<ev_unloop> is usually better than
571	relying on all watchers to be stopped when deciding when a program has	716	relying on all watchers to be stopped when deciding when a program has
572	finished (especially in interactive programs), but having a program that	717	finished (especially in interactive programs), but having a program
573	automatically loops as long as it has to and no longer by virtue of	718	that automatically loops as long as it has to and no longer by virtue
574	relying on its watchers stopping correctly is a thing of beauty.	719	of relying on its watchers stopping correctly, that is truly a thing of
		720	beauty.
575		721
576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
577	those events and any outstanding ones, but will not block your process in	723	those events and any already outstanding ones, but will not block your
578	case there are no events and will return after one iteration of the loop.	724	process in case there are no events and will return after one iteration of
		725	the loop.
579		726
580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
581	neccessary) and will handle those and any outstanding ones. It will block	728	necessary) and will handle those and any already outstanding ones. It
582	your process until at least one new event arrives, and will return after	729	will block your process until at least one new event arrives (which could
583	one iteration of the loop. This is useful if you are waiting for some	730	be an event internal to libev itself, so there is no guarantee that a
584	external event in conjunction with something not expressible using other	731	user-registered callback will be called), and will return after one
		732	iteration of the loop.
		733
		734	This is useful if you are waiting for some external event in conjunction
		735	with something not expressible using other libev watchers (i.e. "roll your
585	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	736	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
586	usually a better approach for this kind of thing.	737	usually a better approach for this kind of thing.
587		738
588	Here are the gory details of what C<ev_loop> does:	739	Here are the gory details of what C<ev_loop> does:
589		740
590	- Before the first iteration, call any pending watchers.	741	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	742	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- If a fork was detected, queue and call all fork watchers.	743	- If a fork was detected (by any means), queue and call all fork watchers.
593	- Queue and call all prepare watchers.	744	- Queue and call all prepare watchers.
594	- If we have been forked, recreate the kernel state.	745	- If we have been forked, detach and recreate the kernel state
		746	as to not disturb the other process.
595	- Update the kernel state with all outstanding changes.	747	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	748	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	749	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	750	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	751	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	752	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	753	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	754	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	756	- Queue all expired timers.
605	- Queue all outstanding periodics.	757	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	758	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	759	- Queue all check watchers.
608	- Call all queued watchers in reverse order (i.e. check watchers first).	760	- Call all queued watchers in reverse order (i.e. check watchers first).
609	Signals and child watchers are implemented as I/O watchers, and will	761	Signals and child watchers are implemented as I/O watchers, and will
610	be handled here by queueing them when their watcher gets executed.	762	be handled here by queueing them when their watcher gets executed.
611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
616	anymore.	768	anymore.
617		769
618	... queue jobs here, make sure they register event watchers as long	770	... queue jobs here, make sure they register event watchers as long
619	... as they still have work to do (even an idle watcher will do..)	771	... as they still have work to do (even an idle watcher will do..)
620	ev_loop (my_loop, 0);	772	ev_loop (my_loop, 0);
621	... jobs done. yeah!	773	... jobs done or somebody called unloop. yeah!
622		774
623	=item ev_unloop (loop, how)	775	=item ev_unloop (loop, how)
624		776
625	Can be used to make a call to C<ev_loop> return early (but only after it	777	Can be used to make a call to C<ev_loop> return early (but only after it
626	has processed all outstanding events). The C<how> argument must be either	778	has processed all outstanding events). The C<how> argument must be either
627	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	779	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
628	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
629		781
630	This "unloop state" will be cleared when entering C<ev_loop> again.	782	This "unloop state" will be cleared when entering C<ev_loop> again.
631		783
		784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		785
632	=item ev_ref (loop)	786	=item ev_ref (loop)
633		787
634	=item ev_unref (loop)	788	=item ev_unref (loop)
635		789
636	Ref/unref can be used to add or remove a reference count on the event	790	Ref/unref can be used to add or remove a reference count on the event
637	loop: Every watcher keeps one reference, and as long as the reference	791	loop: Every watcher keeps one reference, and as long as the reference
638	count is nonzero, C<ev_loop> will not return on its own. If you have	792	count is nonzero, C<ev_loop> will not return on its own.
		793
639	a watcher you never unregister that should not keep C<ev_loop> from	794	If you have a watcher you never unregister that should not keep C<ev_loop>
640	returning, ev_unref() after starting, and ev_ref() before stopping it. For	795	from returning, call ev_unref() after starting, and ev_ref() before
		796	stopping it.
		797
641	example, libev itself uses this for its internal signal pipe: It is not	798	As an example, libev itself uses this for its internal signal pipe: It
642	visible to the libev user and should not keep C<ev_loop> from exiting if	799	is not visible to the libev user and should not keep C<ev_loop> from
643	no event watchers registered by it are active. It is also an excellent	800	exiting if no event watchers registered by it are active. It is also an
644	way to do this for generic recurring timers or from within third-party	801	excellent way to do this for generic recurring timers or from within
645	libraries. Just remember to I<unref after start> and I<ref before stop>	802	third-party libraries. Just remember to I<unref after start> and I<ref
646	(but only if the watcher wasn't active before, or was active before,	803	before stop> (but only if the watcher wasn't active before, or was active
647	respectively).	804	before, respectively. Note also that libev might stop watchers itself
		805	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		806	in the callback).
648		807
649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
650	running when nothing else is active.	809	running when nothing else is active.
651		810
652	struct ev_signal exitsig;	811	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	812	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	813	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	814	evf_unref (loop);
656		815
657	Example: For some weird reason, unregister the above signal handler again.	816	Example: For some weird reason, unregister the above signal handler again.
658		817
659	ev_ref (loop);	818	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	819	ev_signal_stop (loop, &exitsig);
661		820
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	821	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		822
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	823	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		824
666	These advanced functions influence the time that libev will spend waiting	825	These advanced functions influence the time that libev will spend waiting
667	for events. Both are by default C<0>, meaning that libev will try to	826	for events. Both time intervals are by default C<0>, meaning that libev
668	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	827	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		828	latency.
669		829
670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	830	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
671	allows libev to delay invocation of I/O and timer/periodic callbacks to	831	allows libev to delay invocation of I/O and timer/periodic callbacks
672	increase efficiency of loop iterations.	832	to increase efficiency of loop iterations (or to increase power-saving
		833	opportunities).
673		834
674	The background is that sometimes your program runs just fast enough to	835	The idea is that sometimes your program runs just fast enough to handle
675	handle one (or very few) event(s) per loop iteration. While this makes	836	one (or very few) event(s) per loop iteration. While this makes the
676	the program responsive, it also wastes a lot of CPU time to poll for new	837	program responsive, it also wastes a lot of CPU time to poll for new
677	events, especially with backends like C<select ()> which have a high	838	events, especially with backends like C<select ()> which have a high
678	overhead for the actual polling but can deliver many events at once.	839	overhead for the actual polling but can deliver many events at once.
679		840
680	By setting a higher I<io collect interval> you allow libev to spend more	841	By setting a higher I<io collect interval> you allow libev to spend more
681	time collecting I/O events, so you can handle more events per iteration,	842	time collecting I/O events, so you can handle more events per iteration,
682	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	843	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
683	C<ev_timer>) will be not affected. Setting this to a non-null value will	844	C<ev_timer>) will be not affected. Setting this to a non-null value will
684	introduce an additional C<ev_sleep ()> call into most loop iterations.	845	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		846	sleep time ensures that libev will not poll for I/O events more often then
		847	once per this interval, on average.
685		848
686	Likewise, by setting a higher I<timeout collect interval> you allow libev	849	Likewise, by setting a higher I<timeout collect interval> you allow libev
687	to spend more time collecting timeouts, at the expense of increased	850	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	851	latency/jitter/inexactness (the watcher callback will be called
689	will not be affected. Setting this to a non-null value will not introduce	852	later). C<ev_io> watchers will not be affected. Setting this to a non-null
690	any overhead in libev.	853	value will not introduce any overhead in libev.
691		854
692	Many (busy) programs can usually benefit by setting the io collect	855	Many (busy) programs can usually benefit by setting the I/O collect
693	interval to a value near C<0.1> or so, which is often enough for	856	interval to a value near C<0.1> or so, which is often enough for
694	interactive servers (of course not for games), likewise for timeouts. It	857	interactive servers (of course not for games), likewise for timeouts. It
695	usually doesn't make much sense to set it to a lower value than C<0.01>,	858	usually doesn't make much sense to set it to a lower value than C<0.01>,
696	as this approsaches the timing granularity of most systems.	859	as this approaches the timing granularity of most systems. Note that if
		860	you do transactions with the outside world and you can't increase the
		861	parallelity, then this setting will limit your transaction rate (if you
		862	need to poll once per transaction and the I/O collect interval is 0.01,
		863	then you can't do more than 100 transations per second).
		864
		865	Setting the I<timeout collect interval> can improve the opportunity for
		866	saving power, as the program will "bundle" timer callback invocations that
		867	are "near" in time together, by delaying some, thus reducing the number of
		868	times the process sleeps and wakes up again. Another useful technique to
		869	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		870	they fire on, say, one-second boundaries only.
		871
		872	Example: we only need 0.1s timeout granularity, and we wish not to poll
		873	more often than 100 times per second:
		874
		875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
		943	=item ev_loop_verify (loop)
		944
		945	This function only does something when C<EV_VERIFY> support has been
		946	compiled in, which is the default for non-minimal builds. It tries to go
		947	through all internal structures and checks them for validity. If anything
		948	is found to be inconsistent, it will print an error message to standard
		949	error and call C<abort ()>.
		950
		951	This can be used to catch bugs inside libev itself: under normal
		952	circumstances, this function will never abort as of course libev keeps its
		953	data structures consistent.
697		954
698	=back	955	=back
699		956
700		957
701	=head1 ANATOMY OF A WATCHER	958	=head1 ANATOMY OF A WATCHER
		959
		960	In the following description, uppercase C<TYPE> in names stands for the
		961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		962	watchers and C<ev_io_start> for I/O watchers.
702		963
703	A watcher is a structure that you create and register to record your	964	A watcher is a structure that you create and register to record your
704	interest in some event. For instance, if you want to wait for STDIN to	965	interest in some event. For instance, if you want to wait for STDIN to
705	become readable, you would create an C<ev_io> watcher for that:	966	become readable, you would create an C<ev_io> watcher for that:
706		967
707	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
708	{	969	{
709	ev_io_stop (w);	970	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	971	ev_unloop (loop, EVUNLOOP_ALL);
711	}	972	}
712		973
713	struct ev_loop *loop = ev_default_loop (0);	974	struct ev_loop *loop = ev_default_loop (0);
		975
714	struct ev_io stdin_watcher;	976	ev_io stdin_watcher;
		977
715	ev_init (&stdin_watcher, my_cb);	978	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	980	ev_io_start (loop, &stdin_watcher);
		981
718	ev_loop (loop, 0);	982	ev_loop (loop, 0);
719		983
720	As you can see, you are responsible for allocating the memory for your	984	As you can see, you are responsible for allocating the memory for your
721	watcher structures (and it is usually a bad idea to do this on the stack,	985	watcher structures (and it is I<usually> a bad idea to do this on the
722	although this can sometimes be quite valid).	986	stack).
		987
		988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
723		990
724	Each watcher structure must be initialised by a call to C<ev_init	991	Each watcher structure must be initialised by a call to C<ev_init
725	(watcher *, callback)>, which expects a callback to be provided. This	992	(watcher *, callback)>, which expects a callback to be provided. This
726	callback gets invoked each time the event occurs (or, in the case of io	993	callback gets invoked each time the event occurs (or, in the case of I/O
727	watchers, each time the event loop detects that the file descriptor given	994	watchers, each time the event loop detects that the file descriptor given
728	is readable and/or writable).	995	is readable and/or writable).
729		996
730	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
731	with arguments specific to this watcher type. There is also a macro	998	macro to configure it, with arguments specific to the watcher type. There
732	to combine initialisation and setting in one call: C<< ev_<type>_init	999	is also a macro to combine initialisation and setting in one call: C<<
733	(watcher *, callback, ...) >>.	1000	ev_TYPE_init (watcher *, callback, ...) >>.
734		1001
735	To make the watcher actually watch out for events, you have to start it	1002	To make the watcher actually watch out for events, you have to start it
736	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1003	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
737	*) >>), and you can stop watching for events at any time by calling the	1004	*) >>), and you can stop watching for events at any time by calling the
738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
739		1006
740	As long as your watcher is active (has been started but not stopped) you	1007	As long as your watcher is active (has been started but not stopped) you
741	must not touch the values stored in it. Most specifically you must never	1008	must not touch the values stored in it. Most specifically you must never
742	reinitialise it or call its C<set> macro.	1009	reinitialise it or call its C<ev_TYPE_set> macro.
743		1010
744	Each and every callback receives the event loop pointer as first, the	1011	Each and every callback receives the event loop pointer as first, the
745	registered watcher structure as second, and a bitset of received events as	1012	registered watcher structure as second, and a bitset of received events as
746	third argument.	1013	third argument.
747		1014
…		…
805		1072
806	=item C<EV_ASYNC>	1073	=item C<EV_ASYNC>
807		1074
808	The given async watcher has been asynchronously notified (see C<ev_async>).	1075	The given async watcher has been asynchronously notified (see C<ev_async>).
809		1076
		1077	=item C<EV_CUSTOM>
		1078
		1079	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1080	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1081
810	=item C<EV_ERROR>	1082	=item C<EV_ERROR>
811		1083
812	An unspecified error has occured, the watcher has been stopped. This might	1084	An unspecified error has occurred, the watcher has been stopped. This might
813	happen because the watcher could not be properly started because libev	1085	happen because the watcher could not be properly started because libev
814	ran out of memory, a file descriptor was found to be closed or any other	1086	ran out of memory, a file descriptor was found to be closed or any other
		1087	problem. Libev considers these application bugs.
		1088
815	problem. You best act on it by reporting the problem and somehow coping	1089	You best act on it by reporting the problem and somehow coping with the
816	with the watcher being stopped.	1090	watcher being stopped. Note that well-written programs should not receive
		1091	an error ever, so when your watcher receives it, this usually indicates a
		1092	bug in your program.
817		1093
818	Libev will usually signal a few "dummy" events together with an error,	1094	Libev will usually signal a few "dummy" events together with an error, for
819	for example it might indicate that a fd is readable or writable, and if	1095	example it might indicate that a fd is readable or writable, and if your
820	your callbacks is well-written it can just attempt the operation and cope	1096	callbacks is well-written it can just attempt the operation and cope with
821	with the error from read() or write(). This will not work in multithreaded	1097	the error from read() or write(). This will not work in multi-threaded
822	programs, though, so beware.	1098	programs, though, as the fd could already be closed and reused for another
		1099	thing, so beware.
823		1100
824	=back	1101	=back
825		1102
826	=head2 GENERIC WATCHER FUNCTIONS	1103	=head2 GENERIC WATCHER FUNCTIONS
827
828	In the following description, C<TYPE> stands for the watcher type,
829	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
830		1104
831	=over 4	1105	=over 4
832		1106
833	=item C<ev_init> (ev_TYPE *watcher, callback)	1107	=item C<ev_init> (ev_TYPE *watcher, callback)
834		1108
…		…
840	which rolls both calls into one.	1114	which rolls both calls into one.
841		1115
842	You can reinitialise a watcher at any time as long as it has been stopped	1116	You can reinitialise a watcher at any time as long as it has been stopped
843	(or never started) and there are no pending events outstanding.	1117	(or never started) and there are no pending events outstanding.
844		1118
845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1119	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
846	int revents)>.	1120	int revents)>.
		1121
		1122	Example: Initialise an C<ev_io> watcher in two steps.
		1123
		1124	ev_io w;
		1125	ev_init (&w, my_cb);
		1126	ev_io_set (&w, STDIN_FILENO, EV_READ);
847		1127
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		1129
850	This macro initialises the type-specific parts of a watcher. You need to	1130	This macro initialises the type-specific parts of a watcher. You need to
851	call C<ev_init> at least once before you call this macro, but you can	1131	call C<ev_init> at least once before you call this macro, but you can
…		…
854	difference to the C<ev_init> macro).	1134	difference to the C<ev_init> macro).
855		1135
856	Although some watcher types do not have type-specific arguments	1136	Although some watcher types do not have type-specific arguments
857	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1137	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
858		1138
		1139	See C<ev_init>, above, for an example.
		1140
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1141	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		1142
861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1143	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
862	calls into a single call. This is the most convinient method to initialise	1144	calls into a single call. This is the most convenient method to initialise
863	a watcher. The same limitations apply, of course.	1145	a watcher. The same limitations apply, of course.
		1146
		1147	Example: Initialise and set an C<ev_io> watcher in one step.
		1148
		1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
864		1150
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		1152
867	Starts (activates) the given watcher. Only active watchers will receive	1153	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	1154	events. If the watcher is already active nothing will happen.
869		1155
		1156	Example: Start the C<ev_io> watcher that is being abused as example in this
		1157	whole section.
		1158
		1159	ev_io_start (EV_DEFAULT_UC, &w);
		1160
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		1162
872	Stops the given watcher again (if active) and clears the pending	1163	Stops the given watcher if active, and clears the pending status (whether
		1164	the watcher was active or not).
		1165
873	status. It is possible that stopped watchers are pending (for example,	1166	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	1167	non-repeating timers are being stopped when they become pending - but
875	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1168	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
876	you want to free or reuse the memory used by the watcher it is therefore a	1169	pending. If you want to free or reuse the memory used by the watcher it is
877	good idea to always call its C<ev_TYPE_stop> function.	1170	therefore a good idea to always call its C<ev_TYPE_stop> function.
878		1171
879	=item bool ev_is_active (ev_TYPE *watcher)	1172	=item bool ev_is_active (ev_TYPE *watcher)
880		1173
881	Returns a true value iff the watcher is active (i.e. it has been started	1174	Returns a true value iff the watcher is active (i.e. it has been started
882	and not yet been stopped). As long as a watcher is active you must not modify	1175	and not yet been stopped). As long as a watcher is active you must not modify
…		…
908	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
909	(default: C<-2>). Pending watchers with higher priority will be invoked	1202	(default: C<-2>). Pending watchers with higher priority will be invoked
910	before watchers with lower priority, but priority will not keep watchers	1203	before watchers with lower priority, but priority will not keep watchers
911	from being executed (except for C<ev_idle> watchers).	1204	from being executed (except for C<ev_idle> watchers).
912		1205
913	This means that priorities are I<only> used for ordering callback
914	invocation after new events have been received. This is useful, for
915	example, to reduce latency after idling, or more often, to bind two
916	watchers on the same event and make sure one is called first.
917
918	If you need to suppress invocation when higher priority events are pending	1206	If you need to suppress invocation when higher priority events are pending
919	you need to look at C<ev_idle> watchers, which provide this functionality.	1207	you need to look at C<ev_idle> watchers, which provide this functionality.
920		1208
921	You I<must not> change the priority of a watcher as long as it is active or	1209	You I<must not> change the priority of a watcher as long as it is active or
922	pending.	1210	pending.
923		1211
		1212	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1213	fine, as long as you do not mind that the priority value you query might
		1214	or might not have been clamped to the valid range.
		1215
924	The default priority used by watchers when no priority has been set is	1216	The default priority used by watchers when no priority has been set is
925	always C<0>, which is supposed to not be too high and not be too low :).	1217	always C<0>, which is supposed to not be too high and not be too low :).
926		1218
927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
928	fine, as long as you do not mind that the priority value you query might	1220	priorities.
929	or might not have been adjusted to be within valid range.
930		1221
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1223
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
934	C<loop> nor C<revents> need to be valid as long as the watcher callback	1225	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1226	can deal with that fact, as both are simply passed through to the
		1227	callback.
936		1228
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1229	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1230
939	If the watcher is pending, this function returns clears its pending status	1231	If the watcher is pending, this function clears its pending status and
940	and returns its C<revents> bitset (as if its callback was invoked). If the	1232	returns its C<revents> bitset (as if its callback was invoked). If the
941	watcher isn't pending it does nothing and returns C<0>.	1233	watcher isn't pending it does nothing and returns C<0>.
942		1234
		1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1236	callback to be invoked, which can be accomplished with this function.
		1237
943	=back	1238	=back
944		1239
945		1240
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1242
948	Each watcher has, by default, a member C<void *data> that you can change	1243	Each watcher has, by default, a member C<void *data> that you can change
949	and read at any time, libev will completely ignore it. This can be used	1244	and read at any time: libev will completely ignore it. This can be used
950	to associate arbitrary data with your watcher. If you need more data and	1245	to associate arbitrary data with your watcher. If you need more data and
951	don't want to allocate memory and store a pointer to it in that data	1246	don't want to allocate memory and store a pointer to it in that data
952	member, you can also "subclass" the watcher type and provide your own	1247	member, you can also "subclass" the watcher type and provide your own
953	data:	1248	data:
954		1249
955	struct my_io	1250	struct my_io
956	{	1251	{
957	struct ev_io io;	1252	ev_io io;
958	int otherfd;	1253	int otherfd;
959	void *somedata;	1254	void *somedata;
960	struct whatever *mostinteresting;	1255	struct whatever *mostinteresting;
961	}	1256	};
		1257
		1258	...
		1259	struct my_io w;
		1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1261
963	And since your callback will be called with a pointer to the watcher, you	1262	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1263	can cast it back to your own type:
965		1264
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1266	{
968	struct my_io *w = (struct my_io *)w_;	1267	struct my_io *w = (struct my_io *)w_;
969	...	1268	...
970	}	1269	}
971		1270
972	More interesting and less C-conformant ways of casting your callback type	1271	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1272	instead have been omitted.
974		1273
975	Another common scenario is having some data structure with multiple	1274	Another common scenario is to use some data structure with multiple
976	watchers:	1275	embedded watchers:
977		1276
978	struct my_biggy	1277	struct my_biggy
979	{	1278	{
980	int some_data;	1279	int some_data;
981	ev_timer t1;	1280	ev_timer t1;
982	ev_timer t2;	1281	ev_timer t2;
983	}	1282	}
984		1283
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1284	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1285	complicated: Either you store the address of your C<my_biggy> struct
		1286	in the C<data> member of the watcher (for woozies), or you need to use
		1287	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1288	programmers):
987		1289
988	#include <stddef.h>	1290	#include <stddef.h>
989		1291
990	static void	1292	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1293	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1294	{
993	struct my_biggy big = (struct my_biggy *	1295	struct my_biggy big = (struct my_biggy *)
994	(((char *)w) - offsetof (struct my_biggy, t1));	1296	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1297	}
996		1298
997	static void	1299	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1300	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1301	{
1000	struct my_biggy big = (struct my_biggy *	1302	struct my_biggy big = (struct my_biggy *)
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1303	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1304	}
		1305
		1306	=head2 WATCHER PRIORITY MODELS
		1307
		1308	Many event loops support I<watcher priorities>, which are usually small
		1309	integers that influence the ordering of event callback invocation
		1310	between watchers in some way, all else being equal.
		1311
		1312	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1313	description for the more technical details such as the actual priority
		1314	range.
		1315
		1316	There are two common ways how these these priorities are being interpreted
		1317	by event loops:
		1318
		1319	In the more common lock-out model, higher priorities "lock out" invocation
		1320	of lower priority watchers, which means as long as higher priority
		1321	watchers receive events, lower priority watchers are not being invoked.
		1322
		1323	The less common only-for-ordering model uses priorities solely to order
		1324	callback invocation within a single event loop iteration: Higher priority
		1325	watchers are invoked before lower priority ones, but they all get invoked
		1326	before polling for new events.
		1327
		1328	Libev uses the second (only-for-ordering) model for all its watchers
		1329	except for idle watchers (which use the lock-out model).
		1330
		1331	The rationale behind this is that implementing the lock-out model for
		1332	watchers is not well supported by most kernel interfaces, and most event
		1333	libraries will just poll for the same events again and again as long as
		1334	their callbacks have not been executed, which is very inefficient in the
		1335	common case of one high-priority watcher locking out a mass of lower
		1336	priority ones.
		1337
		1338	Static (ordering) priorities are most useful when you have two or more
		1339	watchers handling the same resource: a typical usage example is having an
		1340	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1341	timeouts. Under load, data might be received while the program handles
		1342	other jobs, but since timers normally get invoked first, the timeout
		1343	handler will be executed before checking for data. In that case, giving
		1344	the timer a lower priority than the I/O watcher ensures that I/O will be
		1345	handled first even under adverse conditions (which is usually, but not
		1346	always, what you want).
		1347
		1348	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1349	will only be executed when no same or higher priority watchers have
		1350	received events, they can be used to implement the "lock-out" model when
		1351	required.
		1352
		1353	For example, to emulate how many other event libraries handle priorities,
		1354	you can associate an C<ev_idle> watcher to each such watcher, and in
		1355	the normal watcher callback, you just start the idle watcher. The real
		1356	processing is done in the idle watcher callback. This causes libev to
		1357	continously poll and process kernel event data for the watcher, but when
		1358	the lock-out case is known to be rare (which in turn is rare :), this is
		1359	workable.
		1360
		1361	Usually, however, the lock-out model implemented that way will perform
		1362	miserably under the type of load it was designed to handle. In that case,
		1363	it might be preferable to stop the real watcher before starting the
		1364	idle watcher, so the kernel will not have to process the event in case
		1365	the actual processing will be delayed for considerable time.
		1366
		1367	Here is an example of an I/O watcher that should run at a strictly lower
		1368	priority than the default, and which should only process data when no
		1369	other events are pending:
		1370
		1371	ev_idle idle; // actual processing watcher
		1372	ev_io io; // actual event watcher
		1373
		1374	static void
		1375	io_cb (EV_P_ ev_io *w, int revents)
		1376	{
		1377	// stop the I/O watcher, we received the event, but
		1378	// are not yet ready to handle it.
		1379	ev_io_stop (EV_A_ w);
		1380
		1381	// start the idle watcher to ahndle the actual event.
		1382	// it will not be executed as long as other watchers
		1383	// with the default priority are receiving events.
		1384	ev_idle_start (EV_A_ &idle);
		1385	}
		1386
		1387	static void
		1388	idle_cb (EV_P_ ev_idle *w, int revents)
		1389	{
		1390	// actual processing
		1391	read (STDIN_FILENO, ...);
		1392
		1393	// have to start the I/O watcher again, as
		1394	// we have handled the event
		1395	ev_io_start (EV_P_ &io);
		1396	}
		1397
		1398	// initialisation
		1399	ev_idle_init (&idle, idle_cb);
		1400	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1401	ev_io_start (EV_DEFAULT_ &io);
		1402
		1403	In the "real" world, it might also be beneficial to start a timer, so that
		1404	low-priority connections can not be locked out forever under load. This
		1405	enables your program to keep a lower latency for important connections
		1406	during short periods of high load, while not completely locking out less
		1407	important ones.
1003		1408
1004		1409
1005	=head1 WATCHER TYPES	1410	=head1 WATCHER TYPES
1006		1411
1007	This section describes each watcher in detail, but will not repeat	1412	This section describes each watcher in detail, but will not repeat
…		…
1031	In general you can register as many read and/or write event watchers per	1436	In general you can register as many read and/or write event watchers per
1032	fd as you want (as long as you don't confuse yourself). Setting all file	1437	fd as you want (as long as you don't confuse yourself). Setting all file
1033	descriptors to non-blocking mode is also usually a good idea (but not	1438	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1439	required if you know what you are doing).
1035		1440
1036	If you must do this, then force the use of a known-to-be-good backend	1441	If you cannot use non-blocking mode, then force the use of a
1037	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1442	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1444	descriptors for which non-blocking operation makes no sense (such as
		1445	files) - libev doesn't guarentee any specific behaviour in that case.
1039		1446
1040	Another thing you have to watch out for is that it is quite easy to	1447	Another thing you have to watch out for is that it is quite easy to
1041	receive "spurious" readyness notifications, that is your callback might	1448	receive "spurious" readiness notifications, that is your callback might
1042	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1449	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1043	because there is no data. Not only are some backends known to create a	1450	because there is no data. Not only are some backends known to create a
1044	lot of those (for example solaris ports), it is very easy to get into	1451	lot of those (for example Solaris ports), it is very easy to get into
1045	this situation even with a relatively standard program structure. Thus	1452	this situation even with a relatively standard program structure. Thus
1046	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1047	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1455
1049	If you cannot run the fd in non-blocking mode (for example you should not	1456	If you cannot run the fd in non-blocking mode (for example you should
1050	play around with an Xlib connection), then you have to seperately re-test	1457	not play around with an Xlib connection), then you have to separately
1051	whether a file descriptor is really ready with a known-to-be good interface	1458	re-test whether a file descriptor is really ready with a known-to-be good
1052	such as poll (fortunately in our Xlib example, Xlib already does this on	1459	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1460	does this on its own, so its quite safe to use). Some people additionally
		1461	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1462	indefinitely.
		1463
		1464	But really, best use non-blocking mode.
1054		1465
1055	=head3 The special problem of disappearing file descriptors	1466	=head3 The special problem of disappearing file descriptors
1056		1467
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1468	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1058	descriptor (either by calling C<close> explicitly or by any other means,	1469	descriptor (either due to calling C<close> explicitly or any other means,
1059	such as C<dup>). The reason is that you register interest in some file	1470	such as C<dup2>). The reason is that you register interest in some file
1060	descriptor, but when it goes away, the operating system will silently drop	1471	descriptor, but when it goes away, the operating system will silently drop
1061	this interest. If another file descriptor with the same number then is	1472	this interest. If another file descriptor with the same number then is
1062	registered with libev, there is no efficient way to see that this is, in	1473	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1474	fact, a different file descriptor.
1064		1475
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1507	C<EVBACKEND_POLL>.
1097		1508
1098	=head3 The special problem of SIGPIPE	1509	=head3 The special problem of SIGPIPE
1099		1510
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1101	when reading from a pipe whose other end has been closed, your program	1512	when writing to a pipe whose other end has been closed, your program gets
1102	gets send a SIGPIPE, which, by default, aborts your program. For most	1513	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1514	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1515
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1516	So when you encounter spurious, unexplained daemon exits, make sure you
1107	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1108	somewhere, as that would have given you a big clue).	1518	somewhere, as that would have given you a big clue).
1109		1519
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1525	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1526
1117	=item ev_io_set (ev_io *, int fd, int events)	1527	=item ev_io_set (ev_io *, int fd, int events)
1118		1528
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1529	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1120	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	1530	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1121	C<EV_READ | EV_WRITE> to receive the given events.	1531	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1532
1123	=item int fd [read-only]	1533	=item int fd [read-only]
1124		1534
1125	The file descriptor being watched.	1535	The file descriptor being watched.
1126		1536
…		…
1134		1544
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1545	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1136	readable, but only once. Since it is likely line-buffered, you could	1546	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1547	attempt to read a whole line in the callback.
1138		1548
1139	static void	1549	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1550	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1551	{
1142	ev_io_stop (loop, w);	1552	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1553	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1554	}
1145		1555
1146	...	1556	...
1147	struct ev_loop *loop = ev_default_init (0);	1557	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1558	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1560	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1561	ev_loop (loop, 0);
1152		1562
1153		1563
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1564	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1565
1156	Timer watchers are simple relative timers that generate an event after a	1566	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1567	given time, and optionally repeating in regular intervals after that.
1158		1568
1159	The timers are based on real time, that is, if you register an event that	1569	The timers are based on real time, that is, if you register an event that
1160	times out after an hour and you reset your system clock to last years	1570	times out after an hour and you reset your system clock to January last
1161	time, it will still time out after (roughly) and hour. "Roughly" because	1571	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1573	monotonic clock option helps a lot here).
		1574
		1575	The callback is guaranteed to be invoked only I<after> its timeout has
		1576	passed (not I<at>, so on systems with very low-resolution clocks this
		1577	might introduce a small delay). If multiple timers become ready during the
		1578	same loop iteration then the ones with earlier time-out values are invoked
		1579	before ones of the same priority with later time-out values (but this is
		1580	no longer true when a callback calls C<ev_loop> recursively).
		1581
		1582	=head3 Be smart about timeouts
		1583
		1584	Many real-world problems involve some kind of timeout, usually for error
		1585	recovery. A typical example is an HTTP request - if the other side hangs,
		1586	you want to raise some error after a while.
		1587
		1588	What follows are some ways to handle this problem, from obvious and
		1589	inefficient to smart and efficient.
		1590
		1591	In the following, a 60 second activity timeout is assumed - a timeout that
		1592	gets reset to 60 seconds each time there is activity (e.g. each time some
		1593	data or other life sign was received).
		1594
		1595	=over 4
		1596
		1597	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1598
		1599	This is the most obvious, but not the most simple way: In the beginning,
		1600	start the watcher:
		1601
		1602	ev_timer_init (timer, callback, 60., 0.);
		1603	ev_timer_start (loop, timer);
		1604
		1605	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1606	and start it again:
		1607
		1608	ev_timer_stop (loop, timer);
		1609	ev_timer_set (timer, 60., 0.);
		1610	ev_timer_start (loop, timer);
		1611
		1612	This is relatively simple to implement, but means that each time there is
		1613	some activity, libev will first have to remove the timer from its internal
		1614	data structure and then add it again. Libev tries to be fast, but it's
		1615	still not a constant-time operation.
		1616
		1617	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1618
		1619	This is the easiest way, and involves using C<ev_timer_again> instead of
		1620	C<ev_timer_start>.
		1621
		1622	To implement this, configure an C<ev_timer> with a C<repeat> value
		1623	of C<60> and then call C<ev_timer_again> at start and each time you
		1624	successfully read or write some data. If you go into an idle state where
		1625	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1626	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1627
		1628	That means you can ignore both the C<ev_timer_start> function and the
		1629	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1630	member and C<ev_timer_again>.
		1631
		1632	At start:
		1633
		1634	ev_init (timer, callback);
		1635	timer->repeat = 60.;
		1636	ev_timer_again (loop, timer);
		1637
		1638	Each time there is some activity:
		1639
		1640	ev_timer_again (loop, timer);
		1641
		1642	It is even possible to change the time-out on the fly, regardless of
		1643	whether the watcher is active or not:
		1644
		1645	timer->repeat = 30.;
		1646	ev_timer_again (loop, timer);
		1647
		1648	This is slightly more efficient then stopping/starting the timer each time
		1649	you want to modify its timeout value, as libev does not have to completely
		1650	remove and re-insert the timer from/into its internal data structure.
		1651
		1652	It is, however, even simpler than the "obvious" way to do it.
		1653
		1654	=item 3. Let the timer time out, but then re-arm it as required.
		1655
		1656	This method is more tricky, but usually most efficient: Most timeouts are
		1657	relatively long compared to the intervals between other activity - in
		1658	our example, within 60 seconds, there are usually many I/O events with
		1659	associated activity resets.
		1660
		1661	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1662	but remember the time of last activity, and check for a real timeout only
		1663	within the callback:
		1664
		1665	ev_tstamp last_activity; // time of last activity
		1666
		1667	static void
		1668	callback (EV_P_ ev_timer *w, int revents)
		1669	{
		1670	ev_tstamp now = ev_now (EV_A);
		1671	ev_tstamp timeout = last_activity + 60.;
		1672
		1673	// if last_activity + 60. is older than now, we did time out
		1674	if (timeout < now)
		1675	{
		1676	// timeout occured, take action
		1677	}
		1678	else
		1679	{
		1680	// callback was invoked, but there was some activity, re-arm
		1681	// the watcher to fire in last_activity + 60, which is
		1682	// guaranteed to be in the future, so "again" is positive:
		1683	w->repeat = timeout - now;
		1684	ev_timer_again (EV_A_ w);
		1685	}
		1686	}
		1687
		1688	To summarise the callback: first calculate the real timeout (defined
		1689	as "60 seconds after the last activity"), then check if that time has
		1690	been reached, which means something I<did>, in fact, time out. Otherwise
		1691	the callback was invoked too early (C<timeout> is in the future), so
		1692	re-schedule the timer to fire at that future time, to see if maybe we have
		1693	a timeout then.
		1694
		1695	Note how C<ev_timer_again> is used, taking advantage of the
		1696	C<ev_timer_again> optimisation when the timer is already running.
		1697
		1698	This scheme causes more callback invocations (about one every 60 seconds
		1699	minus half the average time between activity), but virtually no calls to
		1700	libev to change the timeout.
		1701
		1702	To start the timer, simply initialise the watcher and set C<last_activity>
		1703	to the current time (meaning we just have some activity :), then call the
		1704	callback, which will "do the right thing" and start the timer:
		1705
		1706	ev_init (timer, callback);
		1707	last_activity = ev_now (loop);
		1708	callback (loop, timer, EV_TIMEOUT);
		1709
		1710	And when there is some activity, simply store the current time in
		1711	C<last_activity>, no libev calls at all:
		1712
		1713	last_actiivty = ev_now (loop);
		1714
		1715	This technique is slightly more complex, but in most cases where the
		1716	time-out is unlikely to be triggered, much more efficient.
		1717
		1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1719	callback :) - just change the timeout and invoke the callback, which will
		1720	fix things for you.
		1721
		1722	=item 4. Wee, just use a double-linked list for your timeouts.
		1723
		1724	If there is not one request, but many thousands (millions...), all
		1725	employing some kind of timeout with the same timeout value, then one can
		1726	do even better:
		1727
		1728	When starting the timeout, calculate the timeout value and put the timeout
		1729	at the I<end> of the list.
		1730
		1731	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1732	the list is expected to fire (for example, using the technique #3).
		1733
		1734	When there is some activity, remove the timer from the list, recalculate
		1735	the timeout, append it to the end of the list again, and make sure to
		1736	update the C<ev_timer> if it was taken from the beginning of the list.
		1737
		1738	This way, one can manage an unlimited number of timeouts in O(1) time for
		1739	starting, stopping and updating the timers, at the expense of a major
		1740	complication, and having to use a constant timeout. The constant timeout
		1741	ensures that the list stays sorted.
		1742
		1743	=back
		1744
		1745	So which method the best?
		1746
		1747	Method #2 is a simple no-brain-required solution that is adequate in most
		1748	situations. Method #3 requires a bit more thinking, but handles many cases
		1749	better, and isn't very complicated either. In most case, choosing either
		1750	one is fine, with #3 being better in typical situations.
		1751
		1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1753	rather complicated, but extremely efficient, something that really pays
		1754	off after the first million or so of active timers, i.e. it's usually
		1755	overkill :)
		1756
		1757	=head3 The special problem of time updates
		1758
		1759	Establishing the current time is a costly operation (it usually takes at
		1760	least two system calls): EV therefore updates its idea of the current
		1761	time only before and after C<ev_loop> collects new events, which causes a
		1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1763	lots of events in one iteration.
1164		1764
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1765	The relative timeouts are calculated relative to the C<ev_now ()>
1166	time. This is usually the right thing as this timestamp refers to the time	1766	time. This is usually the right thing as this timestamp refers to the time
1167	of the event triggering whatever timeout you are modifying/starting. If	1767	of the event triggering whatever timeout you are modifying/starting. If
1168	you suspect event processing to be delayed and you I<need> to base the timeout	1768	you suspect event processing to be delayed and you I<need> to base the
1169	on the current time, use something like this to adjust for this:	1769	timeout on the current time, use something like this to adjust for this:
1170		1770
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1772
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1773	If the event loop is suspended for a long time, you can also force an
1174	but if multiple timers become ready during the same loop iteration then	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1775	()>.
		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
1176		1806
1177	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1178		1808
1179	=over 4	1809	=over 4
1180		1810
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1812
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1813	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1814
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1815	Configure the timer to trigger after C<after> seconds. If C<repeat>
1186	C<0.>, then it will automatically be stopped. If it is positive, then the	1816	is C<0.>, then it will automatically be stopped once the timeout is
1187	timer will automatically be configured to trigger again C<repeat> seconds	1817	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1818	configured to trigger again C<repeat> seconds later, again, and again,
		1819	until stopped manually.
1189		1820
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1821	The timer itself will do a best-effort at avoiding drift, that is, if
1191	configure a timer to trigger every 10 seconds, then it will trigger at	1822	you configure a timer to trigger every 10 seconds, then it will normally
1192	exactly 10 second intervals. If, however, your program cannot keep up with	1823	trigger at exactly 10 second intervals. If, however, your program cannot
1193	the timer (because it takes longer than those 10 seconds to do stuff) the	1824	keep up with the timer (because it takes longer than those 10 seconds to
1194	timer will not fire more than once per event loop iteration.	1825	do stuff) the timer will not fire more than once per event loop iteration.
1195		1826
1196	=item ev_timer_again (loop, ev_timer *)	1827	=item ev_timer_again (loop, ev_timer *)
1197		1828
1198	This will act as if the timer timed out and restart it again if it is	1829	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1830	repeating. The exact semantics are:
1200		1831
1201	If the timer is pending, its pending status is cleared.	1832	If the timer is pending, its pending status is cleared.
1202		1833
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1834	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1835
1205	If the timer is repeating, either start it if necessary (with the	1836	If the timer is repeating, either start it if necessary (with the
1206	C<repeat> value), or reset the running timer to the C<repeat> value.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1838
1208	This sounds a bit complicated, but here is a useful and typical	1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1209	example: Imagine you have a tcp connection and you want a so-called idle	1840	usage example.
1210	timeout, that is, you want to be called when there have been, say, 60
1211	seconds of inactivity on the socket. The easiest way to do this is to
1212	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1213	C<ev_timer_again> each time you successfully read or write some data. If
1214	you go into an idle state where you do not expect data to travel on the
1215	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1216	automatically restart it if need be.
1217		1841
1218	That means you can ignore the C<after> value and C<ev_timer_start>	1842	=item ev_timer_remaining (loop, ev_timer *)
1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1220		1843
1221	ev_timer_init (timer, callback, 0., 5.);	1844	Returns the remaining time until a timer fires. If the timer is active,
1222	ev_timer_again (loop, timer);	1845	then this time is relative to the current event loop time, otherwise it's
1223	...	1846	the timeout value currently configured.
1224	timer->again = 17.;
1225	ev_timer_again (loop, timer);
1226	...
1227	timer->again = 10.;
1228	ev_timer_again (loop, timer);
1229		1847
1230	This is more slightly efficient then stopping/starting the timer each time	1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1231	you want to modify its timeout value.	1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1232		1853
1233	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1234		1855
1235	The current C<repeat> value. Will be used each time the watcher times out	1856	The current C<repeat> value. Will be used each time the watcher times out
1236	or C<ev_timer_again> is called and determines the next timeout (if any),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
1237	which is also when any modifications are taken into account.	1858	which is also when any modifications are taken into account.
1238		1859
1239	=back	1860	=back
1240		1861
1241	=head3 Examples	1862	=head3 Examples
1242		1863
1243	Example: Create a timer that fires after 60 seconds.	1864	Example: Create a timer that fires after 60 seconds.
1244		1865
1245	static void	1866	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1867	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1868	{
1248	.. one minute over, w is actually stopped right here	1869	.. one minute over, w is actually stopped right here
1249	}	1870	}
1250		1871
1251	struct ev_timer mytimer;	1872	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1873	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1874	ev_timer_start (loop, &mytimer);
1254		1875
1255	Example: Create a timeout timer that times out after 10 seconds of	1876	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1877	inactivity.
1257		1878
1258	static void	1879	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1880	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1881	{
1261	.. ten seconds without any activity	1882	.. ten seconds without any activity
1262	}	1883	}
1263		1884
1264	struct ev_timer mytimer;	1885	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1887	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1888	ev_loop (loop, 0);
1268		1889
1269	// and in some piece of code that gets executed on any "activity":	1890	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1891	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1892	ev_timer_again (&mytimer);
1272		1893
1273		1894
1274	=head2 C<ev_periodic> - to cron or not to cron?	1895	=head2 C<ev_periodic> - to cron or not to cron?
1275		1896
1276	Periodic watchers are also timers of a kind, but they are very versatile	1897	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1898	(and unfortunately a bit complex).
1278		1899
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1900	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1280	but on wallclock time (absolute time). You can tell a periodic watcher	1901	relative time, the physical time that passes) but on wall clock time
1281	to trigger "at" some specific point in time. For example, if you tell a	1902	(absolute time, the thing you can read on your calender or clock). The
1282	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1903	difference is that wall clock time can run faster or slower than real
1283	+ 10.>) and then reset your system clock to the last year, then it will	1904	time, and time jumps are not uncommon (e.g. when you adjust your
1284	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1905	wrist-watch).
1285	roughly 10 seconds later).
1286		1906
1287	They can also be used to implement vastly more complex timers, such as	1907	You can tell a periodic watcher to trigger after some specific point
1288	triggering an event on each midnight, local time or other, complicated,	1908	in time: for example, if you tell a periodic watcher to trigger "in 10
1289	rules.	1909	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1910	not a delay) and then reset your system clock to January of the previous
		1911	year, then it will take a year or more to trigger the event (unlike an
		1912	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1913	it, as it uses a relative timeout).
1290		1914
		1915	C<ev_periodic> watchers can also be used to implement vastly more complex
		1916	timers, such as triggering an event on each "midnight, local time", or
		1917	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1918	those cannot react to time jumps.
		1919
1291	As with timers, the callback is guarenteed to be invoked only when the	1920	As with timers, the callback is guaranteed to be invoked only when the
1292	time (C<at>) has been passed, but if multiple periodic timers become ready	1921	point in time where it is supposed to trigger has passed. If multiple
1293	during the same loop iteration then order of execution is undefined.	1922	timers become ready during the same loop iteration then the ones with
		1923	earlier time-out values are invoked before ones with later time-out values
		1924	(but this is no longer true when a callback calls C<ev_loop> recursively).
1294		1925
1295	=head3 Watcher-Specific Functions and Data Members	1926	=head3 Watcher-Specific Functions and Data Members
1296		1927
1297	=over 4	1928	=over 4
1298		1929
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1930	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		1931
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1932	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1302		1933
1303	Lots of arguments, lets sort it out... There are basically three modes of	1934	Lots of arguments, let's sort it out... There are basically three modes of
1304	operation, and we will explain them from simplest to complex:	1935	operation, and we will explain them from simplest to most complex:
1305		1936
1306	=over 4	1937	=over 4
1307		1938
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1939	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1309		1940
1310	In this configuration the watcher triggers an event at the wallclock time	1941	In this configuration the watcher triggers an event after the wall clock
1311	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1942	time C<offset> has passed. It will not repeat and will not adjust when a
1312	that is, if it is to be run at January 1st 2011 then it will run when the	1943	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1313	system time reaches or surpasses this time.	1944	will be stopped and invoked when the system clock reaches or surpasses
		1945	this point in time.
1314		1946
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1947	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1316		1948
1317	In this mode the watcher will always be scheduled to time out at the next	1949	In this mode the watcher will always be scheduled to time out at the next
1318	C<at + N * interval> time (for some integer N, which can also be negative)	1950	C<offset + N * interval> time (for some integer N, which can also be
1319	and then repeat, regardless of any time jumps.	1951	negative) and then repeat, regardless of any time jumps. The C<offset>
		1952	argument is merely an offset into the C<interval> periods.
1320		1953
1321	This can be used to create timers that do not drift with respect to system	1954	This can be used to create timers that do not drift with respect to the
1322	time:	1955	system clock, for example, here is an C<ev_periodic> that triggers each
		1956	hour, on the hour (with respect to UTC):
1323		1957
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1958	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1959
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1960	This doesn't mean there will always be 3600 seconds in between triggers,
1327	but only that the the callback will be called when the system time shows a	1961	but only that the callback will be called when the system time shows a
1328	full hour (UTC), or more correctly, when the system time is evenly divisible	1962	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1963	by 3600.
1330		1964
1331	Another way to think about it (for the mathematically inclined) is that	1965	Another way to think about it (for the mathematically inclined) is that
1332	C<ev_periodic> will try to run the callback in this mode at the next possible	1966	C<ev_periodic> will try to run the callback in this mode at the next possible
1333	time where C<time = at (mod interval)>, regardless of any time jumps.	1967	time where C<time = offset (mod interval)>, regardless of any time jumps.
1334		1968
1335	For numerical stability it is preferable that the C<at> value is near	1969	For numerical stability it is preferable that the C<offset> value is near
1336	C<ev_now ()> (the current time), but there is no range requirement for	1970	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1971	this value, and in fact is often specified as zero.
1338		1972
		1973	Note also that there is an upper limit to how often a timer can fire (CPU
		1974	speed for example), so if C<interval> is very small then timing stability
		1975	will of course deteriorate. Libev itself tries to be exact to be about one
		1976	millisecond (if the OS supports it and the machine is fast enough).
		1977
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1978	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1340		1979
1341	In this mode the values for C<interval> and C<at> are both being	1980	In this mode the values for C<interval> and C<offset> are both being
1342	ignored. Instead, each time the periodic watcher gets scheduled, the	1981	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1982	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1983	current time as second argument.
1345		1984
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1985	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1347	ever, or make any event loop modifications>. If you need to stop it,	1986	or make ANY other event loop modifications whatsoever, unless explicitly
1348	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1987	allowed by documentation here>.
1349	starting an C<ev_prepare> watcher, which is legal).
1350		1988
		1989	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1990	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1991	only event loop modification you are allowed to do).
		1992
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1993	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1994	*w, ev_tstamp now)>, e.g.:
1353		1995
		1996	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1997	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1998	{
1356	return now + 60.;	1999	return now + 60.;
1357	}	2000	}
1358		2001
1359	It must return the next time to trigger, based on the passed time value	2002	It must return the next time to trigger, based on the passed time value
1360	(that is, the lowest time value larger than to the second argument). It	2003	(that is, the lowest time value larger than to the second argument). It
1361	will usually be called just before the callback will be triggered, but	2004	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	2005	might be called at other times, too.
1363		2006
1364	NOTE: I<< This callback must always return a time that is later than the	2007	NOTE: I<< This callback must always return a time that is higher than or
1365	passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.	2008	equal to the passed C<now> value >>.
1366		2009
1367	This can be used to create very complex timers, such as a timer that	2010	This can be used to create very complex timers, such as a timer that
1368	triggers on each midnight, local time. To do this, you would calculate the	2011	triggers on "next midnight, local time". To do this, you would calculate the
1369	next midnight after C<now> and return the timestamp value for this. How	2012	next midnight after C<now> and return the timestamp value for this. How
1370	you do this is, again, up to you (but it is not trivial, which is the main	2013	you do this is, again, up to you (but it is not trivial, which is the main
1371	reason I omitted it as an example).	2014	reason I omitted it as an example).
1372		2015
1373	=back	2016	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	2020	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	2021	when you changed some parameters or the reschedule callback would return
1379	a different time than the last time it was called (e.g. in a crond like	2022	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	2023	program when the crontabs have changed).
1381		2024
		2025	=item ev_tstamp ev_periodic_at (ev_periodic *)
		2026
		2027	When active, returns the absolute time that the watcher is supposed
		2028	to trigger next. This is not the same as the C<offset> argument to
		2029	C<ev_periodic_set>, but indeed works even in interval and manual
		2030	rescheduling modes.
		2031
1382	=item ev_tstamp offset [read-write]	2032	=item ev_tstamp offset [read-write]
1383		2033
1384	When repeating, this contains the offset value, otherwise this is the	2034	When repeating, this contains the offset value, otherwise this is the
1385	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2035	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2036	although libev might modify this value for better numerical stability).
1386		2037
1387	Can be modified any time, but changes only take effect when the periodic	2038	Can be modified any time, but changes only take effect when the periodic
1388	timer fires or C<ev_periodic_again> is being called.	2039	timer fires or C<ev_periodic_again> is being called.
1389		2040
1390	=item ev_tstamp interval [read-write]	2041	=item ev_tstamp interval [read-write]
1391		2042
1392	The current interval value. Can be modified any time, but changes only	2043	The current interval value. Can be modified any time, but changes only
1393	take effect when the periodic timer fires or C<ev_periodic_again> is being	2044	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	2045	called.
1395		2046
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2047	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		2048
1398	The current reschedule callback, or C<0>, if this functionality is	2049	The current reschedule callback, or C<0>, if this functionality is
1399	switched off. Can be changed any time, but changes only take effect when	2050	switched off. Can be changed any time, but changes only take effect when
1400	the periodic timer fires or C<ev_periodic_again> is being called.	2051	the periodic timer fires or C<ev_periodic_again> is being called.
1401		2052
1402	=item ev_tstamp at [read-only]
1403
1404	When active, contains the absolute time that the watcher is supposed to
1405	trigger next.
1406
1407	=back	2053	=back
1408		2054
1409	=head3 Examples	2055	=head3 Examples
1410		2056
1411	Example: Call a callback every hour, or, more precisely, whenever the	2057	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	2058	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	2059	potentially a lot of jitter, but good long-term stability.
1414		2060
1415	static void	2061	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	2063	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	2064	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	2065	}
1420		2066
1421	struct ev_periodic hourly_tick;	2067	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2068	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	2069	ev_periodic_start (loop, &hourly_tick);
1424		2070
1425	Example: The same as above, but use a reschedule callback to do it:	2071	Example: The same as above, but use a reschedule callback to do it:
1426		2072
1427	#include <math.h>	2073	#include <math.h>
1428		2074
1429	static ev_tstamp	2075	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2076	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	2077	{
1432	return fmod (now, 3600.) + 3600.;	2078	return now + (3600. - fmod (now, 3600.));
1433	}	2079	}
1434		2080
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2081	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		2082
1437	Example: Call a callback every hour, starting now:	2083	Example: Call a callback every hour, starting now:
1438		2084
1439	struct ev_periodic hourly_tick;	2085	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	2086	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	2087	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	2088	ev_periodic_start (loop, &hourly_tick);
1443		2089
1444		2090
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	2091	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		2092
1447	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
1448	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
1449	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	2096	normal event processing, like any other event.
1451		2097
		2098	If you want signals to be delivered truly asynchronously, just use
		2099	C<sigaction> as you would do without libev and forget about sharing
		2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
		2102
1452	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1453	first watcher gets started will libev actually register a signal watcher	2109	When the first watcher gets started will libev actually register something
1454	with the kernel (thus it coexists with your own signal handlers as long	2110	with the kernel (thus it coexists with your own signal handlers as long as
1455	as you don't register any with libev). Similarly, when the last signal	2111	you don't register any with libev for the same signal).
1456	watcher for a signal is stopped libev will reset the signal handler to
1457	SIG_DFL (regardless of what it was set to before).
1458		2112
1459	If possible and supported, libev will install its handlers with	2113	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1461	interrupted. If you have a problem with syscalls getting interrupted by	2115	not be unduly interrupted. If you have a problem with system calls getting
1462	signals you can block all signals in an C<ev_check> watcher and unblock	2116	interrupted by signals you can block all signals in an C<ev_check> watcher
1463	them in an C<ev_prepare> watcher.	2117	and unblock them in an C<ev_prepare> watcher.
		2118
		2119	=head3 The special problem of inheritance over execve
		2120
		2121	Both the signal mask (C<sigprocmask>) and the signal disposition
		2122	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2123	stopping it again), that is, libev might or might not block the signal,
		2124	and might or might not set or restore the installed signal handler.
		2125
		2126	While this does not matter for the signal disposition (libev never
		2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2128	C<execve>), this matters for the signal mask: many programs do not expect
		2129	certain signals to be blocked.
		2130
		2131	This means that before calling C<exec> (from the child) you should reset
		2132	the signal mask to whatever "default" you expect (all clear is a good
		2133	choice usually).
		2134
		2135	The simplest way to ensure that the signal mask is reset in the child is
		2136	to install a fork handler with C<pthread_atfork> that resets it. That will
		2137	catch fork calls done by libraries (such as the libc) as well.
		2138
		2139	In current versions of libev, you can also ensure that the signal mask is
		2140	not blocking any signals (except temporarily, so thread users watch out)
		2141	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2142	is not guaranteed for future versions, however.
1464		2143
1465	=head3 Watcher-Specific Functions and Data Members	2144	=head3 Watcher-Specific Functions and Data Members
1466		2145
1467	=over 4	2146	=over 4
1468		2147
…		…
1479		2158
1480	=back	2159	=back
1481		2160
1482	=head3 Examples	2161	=head3 Examples
1483		2162
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	2163	Example: Try to exit cleanly on SIGINT.
1485		2164
1486	static void	2165	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2166	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	2167	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	2168	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	2169	}
1491		2170
1492	struct ev_signal signal_watcher;	2171	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2172	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	2173	ev_signal_start (loop, &signal_watcher);
1495		2174
1496		2175
1497	=head2 C<ev_child> - watch out for process status changes	2176	=head2 C<ev_child> - watch out for process status changes
1498		2177
1499	Child watchers trigger when your process receives a SIGCHLD in response to	2178	Child watchers trigger when your process receives a SIGCHLD in response to
1500	some child status changes (most typically when a child of yours dies). It	2179	some child status changes (most typically when a child of yours dies or
1501	is permissible to install a child watcher I<after> the child has been	2180	exits). It is permissible to install a child watcher I<after> the child
1502	forked (which implies it might have already exited), as long as the event	2181	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	2182	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2183	forking and then immediately registering a watcher for the child is fine,
		2184	but forking and registering a watcher a few event loop iterations later or
		2185	in the next callback invocation is not.
1504		2186
1505	Only the default event loop is capable of handling signals, and therefore	2187	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	2188	you can only register child watchers in the default event loop.
		2189
		2190	Due to some design glitches inside libev, child watchers will always be
		2191	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2192	libev)
1507		2193
1508	=head3 Process Interaction	2194	=head3 Process Interaction
1509		2195
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	2196	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	2197	initialised. This is necessary to guarantee proper behaviour even if the
1512	the first child watcher is started after the child exits. The occurance	2198	first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2199	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	2200	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	2201	children, even ones not watched.
1516		2202
1517	=head3 Overriding the Built-In Processing	2203	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	2207	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	2208	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	2209	default loop never gets destroyed. You are encouraged, however, to use an
1524	event-based approach to child reaping and thus use libev's support for	2210	event-based approach to child reaping and thus use libev's support for
1525	that, so other libev users can use C<ev_child> watchers freely.	2211	that, so other libev users can use C<ev_child> watchers freely.
		2212
		2213	=head3 Stopping the Child Watcher
		2214
		2215	Currently, the child watcher never gets stopped, even when the
		2216	child terminates, so normally one needs to stop the watcher in the
		2217	callback. Future versions of libev might stop the watcher automatically
		2218	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2219	problem).
1526		2220
1527	=head3 Watcher-Specific Functions and Data Members	2221	=head3 Watcher-Specific Functions and Data Members
1528		2222
1529	=over 4	2223	=over 4
1530		2224
…		…
1559	=head3 Examples	2253	=head3 Examples
1560		2254
1561	Example: C<fork()> a new process and install a child handler to wait for	2255	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	2256	its completion.
1563		2257
1564	ev_child cw;	2258	ev_child cw;
1565		2259
1566	static void	2260	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	2261	child_cb (EV_P_ ev_child *w, int revents)
1568	{	2262	{
1569	ev_child_stop (EV_A_ w);	2263	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2264	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	2265	}
1572		2266
1573	pid_t pid = fork ();	2267	pid_t pid = fork ();
1574		2268
1575	if (pid < 0)	2269	if (pid < 0)
1576	// error	2270	// error
1577	else if (pid == 0)	2271	else if (pid == 0)
1578	{	2272	{
1579	// the forked child executes here	2273	// the forked child executes here
1580	exit (1);	2274	exit (1);
1581	}	2275	}
1582	else	2276	else
1583	{	2277	{
1584	ev_child_init (&cw, child_cb, pid, 0);	2278	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	2279	ev_child_start (EV_DEFAULT_ &cw);
1586	}	2280	}
1587		2281
1588		2282
1589	=head2 C<ev_stat> - did the file attributes just change?	2283	=head2 C<ev_stat> - did the file attributes just change?
1590		2284
1591	This watches a filesystem path for attribute changes. That is, it calls	2285	This watches a file system path for attribute changes. That is, it calls
1592	C<stat> regularly (or when the OS says it changed) and sees if it changed	2286	C<stat> on that path in regular intervals (or when the OS says it changed)
1593	compared to the last time, invoking the callback if it did.	2287	and sees if it changed compared to the last time, invoking the callback if
		2288	it did.
1594		2289
1595	The path does not need to exist: changing from "path exists" to "path does	2290	The path does not need to exist: changing from "path exists" to "path does
1596	not exist" is a status change like any other. The condition "path does	2291	not exist" is a status change like any other. The condition "path does not
1597	not exist" is signified by the C<st_nlink> field being zero (which is	2292	exist" (or more correctly "path cannot be stat'ed") is signified by the
1598	otherwise always forced to be at least one) and all the other fields of	2293	C<st_nlink> field being zero (which is otherwise always forced to be at
1599	the stat buffer having unspecified contents.	2294	least one) and all the other fields of the stat buffer having unspecified
		2295	contents.
1600		2296
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	2297	The path I<must not> end in a slash or contain special components such as
		2298	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1602	relative and your working directory changes, the behaviour is undefined.	2299	your working directory changes, then the behaviour is undefined.
1603		2300
1604	Since there is no standard to do this, the portable implementation simply	2301	Since there is no portable change notification interface available, the
1605	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2302	portable implementation simply calls C<stat(2)> regularly on the path
1606	can specify a recommended polling interval for this case. If you specify	2303	to see if it changed somehow. You can specify a recommended polling
1607	a polling interval of C<0> (highly recommended!) then a I<suitable,	2304	interval for this case. If you specify a polling interval of C<0> (highly
1608	unspecified default> value will be used (which you can expect to be around	2305	recommended!) then a I<suitable, unspecified default> value will be used
1609	five seconds, although this might change dynamically). Libev will also	2306	(which you can expect to be around five seconds, although this might
1610	impose a minimum interval which is currently around C<0.1>, but thats	2307	change dynamically). Libev will also impose a minimum interval which is
1611	usually overkill.	2308	currently around C<0.1>, but that's usually overkill.
1612		2309
1613	This watcher type is not meant for massive numbers of stat watchers,	2310	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	2311	as even with OS-supported change notifications, this can be
1615	resource-intensive.	2312	resource-intensive.
1616		2313
1617	At the time of this writing, only the Linux inotify interface is	2314	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	2315	is the Linux inotify interface (implementing kqueue support is left as an
1619	reader). Inotify will be used to give hints only and should not change the	2316	exercise for the reader. Note, however, that the author sees no way of
1620	semantics of C<ev_stat> watchers, which means that libev sometimes needs	2317	implementing C<ev_stat> semantics with kqueue, except as a hint).
1621	to fall back to regular polling again even with inotify, but changes are
1622	usually detected immediately, and if the file exists there will be no
1623	polling.
1624		2318
1625	=head3 ABI Issues (Largefile Support)	2319	=head3 ABI Issues (Largefile Support)
1626		2320
1627	Libev by default (unless the user overrides this) uses the default	2321	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	2322	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	2323	support disabled by default, you get the 32 bit version of the stat
1630	structure. When using the library from programs that change the ABI to	2324	structure. When using the library from programs that change the ABI to
1631	use 64 bit file offsets the programs will fail. In that case you have to	2325	use 64 bit file offsets the programs will fail. In that case you have to
1632	compile libev with the same flags to get binary compatibility. This is	2326	compile libev with the same flags to get binary compatibility. This is
1633	obviously the case with any flags that change the ABI, but the problem is	2327	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	2328	most noticeably displayed with ev_stat and large file support.
1635		2329
1636	=head3 Inotify	2330	The solution for this is to lobby your distribution maker to make large
		2331	file interfaces available by default (as e.g. FreeBSD does) and not
		2332	optional. Libev cannot simply switch on large file support because it has
		2333	to exchange stat structures with application programs compiled using the
		2334	default compilation environment.
1637		2335
		2336	=head3 Inotify and Kqueue
		2337
1638	When C<inotify (7)> support has been compiled into libev (generally only	2338	When C<inotify (7)> support has been compiled into libev and present at
1639	available on Linux) and present at runtime, it will be used to speed up	2339	runtime, it will be used to speed up change detection where possible. The
1640	change detection where possible. The inotify descriptor will be created lazily	2340	inotify descriptor will be created lazily when the first C<ev_stat>
1641	when the first C<ev_stat> watcher is being started.	2341	watcher is being started.
1642		2342
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	2343	Inotify presence does not change the semantics of C<ev_stat> watchers
1644	except that changes might be detected earlier, and in some cases, to avoid	2344	except that changes might be detected earlier, and in some cases, to avoid
1645	making regular C<stat> calls. Even in the presense of inotify support	2345	making regular C<stat> calls. Even in the presence of inotify support
1646	there are many cases where libev has to resort to regular C<stat> polling.	2346	there are many cases where libev has to resort to regular C<stat> polling,
		2347	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2348	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2349	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2350	xfs are fully working) libev usually gets away without polling.
1647		2351
1648	(There is no support for kqueue, as apparently it cannot be used to	2352	There is no support for kqueue, as apparently it cannot be used to
1649	implement this functionality, due to the requirement of having a file	2353	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	2354	descriptor open on the object at all times, and detecting renames, unlinks
		2355	etc. is difficult.
		2356
		2357	=head3 C<stat ()> is a synchronous operation
		2358
		2359	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2360	the process. The exception are C<ev_stat> watchers - those call C<stat
		2361	()>, which is a synchronous operation.
		2362
		2363	For local paths, this usually doesn't matter: unless the system is very
		2364	busy or the intervals between stat's are large, a stat call will be fast,
		2365	as the path data is usually in memory already (except when starting the
		2366	watcher).
		2367
		2368	For networked file systems, calling C<stat ()> can block an indefinite
		2369	time due to network issues, and even under good conditions, a stat call
		2370	often takes multiple milliseconds.
		2371
		2372	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2373	paths, although this is fully supported by libev.
1651		2374
1652	=head3 The special problem of stat time resolution	2375	=head3 The special problem of stat time resolution
1653		2376
1654	The C<stat ()> syscall only supports full-second resolution portably, and	2377	The C<stat ()> system call only supports full-second resolution portably,
1655	even on systems where the resolution is higher, many filesystems still	2378	and even on systems where the resolution is higher, most file systems
1656	only support whole seconds.	2379	still only support whole seconds.
1657		2380
1658	That means that, if the time is the only thing that changes, you might	2381	That means that, if the time is the only thing that changes, you can
1659	miss updates: on the first update, C<ev_stat> detects a change and calls	2382	easily miss updates: on the first update, C<ev_stat> detects a change and
1660	your callback, which does something. When there is another update within	2383	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	2384	within the same second, C<ev_stat> will be unable to detect unless the
		2385	stat data does change in other ways (e.g. file size).
1662		2386
1663	The solution to this is to delay acting on a change for a second (or till	2387	The solution to this is to delay acting on a change for slightly more
1664	the next second boundary), using a roughly one-second delay C<ev_timer>	2388	than a second (or till slightly after the next full second boundary), using
1665	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>	2389	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1666	is added to work around small timing inconsistencies of some operating	2390	ev_timer_again (loop, w)>).
1667	systems.	2391
		2392	The C<.02> offset is added to work around small timing inconsistencies
		2393	of some operating systems (where the second counter of the current time
		2394	might be be delayed. One such system is the Linux kernel, where a call to
		2395	C<gettimeofday> might return a timestamp with a full second later than
		2396	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2397	update file times then there will be a small window where the kernel uses
		2398	the previous second to update file times but libev might already execute
		2399	the timer callback).
1668		2400
1669	=head3 Watcher-Specific Functions and Data Members	2401	=head3 Watcher-Specific Functions and Data Members
1670		2402
1671	=over 4	2403	=over 4
1672		2404
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2410	C<path>. The C<interval> is a hint on how quickly a change is expected to
1679	be detected and should normally be specified as C<0> to let libev choose	2411	be detected and should normally be specified as C<0> to let libev choose
1680	a suitable value. The memory pointed to by C<path> must point to the same	2412	a suitable value. The memory pointed to by C<path> must point to the same
1681	path for as long as the watcher is active.	2413	path for as long as the watcher is active.
1682		2414
1683	The callback will be receive C<EV_STAT> when a change was detected,	2415	The callback will receive an C<EV_STAT> event when a change was detected,
1684	relative to the attributes at the time the watcher was started (or the	2416	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2417	last change was detected).
1686		2418
1687	=item ev_stat_stat (loop, ev_stat *)	2419	=item ev_stat_stat (loop, ev_stat *)
1688		2420
1689	Updates the stat buffer immediately with new values. If you change the	2421	Updates the stat buffer immediately with new values. If you change the
1690	watched path in your callback, you could call this fucntion to avoid	2422	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2423	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2424	the only one changing the path). Can also be useful simply to find out the
		2425	new values.
1693		2426
1694	=item ev_statdata attr [read-only]	2427	=item ev_statdata attr [read-only]
1695		2428
1696	The most-recently detected attributes of the file. Although the type is of	2429	The most-recently detected attributes of the file. Although the type is
1697	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types	2430	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
1698	suitable for your system. If the C<st_nlink> member is C<0>, then there	2431	suitable for your system, but you can only rely on the POSIX-standardised
		2432	members to be present. If the C<st_nlink> member is C<0>, then there was
1699	was some error while C<stat>ing the file.	2433	some error while C<stat>ing the file.
1700		2434
1701	=item ev_statdata prev [read-only]	2435	=item ev_statdata prev [read-only]
1702		2436
1703	The previous attributes of the file. The callback gets invoked whenever	2437	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2438	C<prev> != C<attr>, or, more precisely, one or more of these members
		2439	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2440	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2441
1706	=item ev_tstamp interval [read-only]	2442	=item ev_tstamp interval [read-only]
1707		2443
1708	The specified interval.	2444	The specified interval.
1709		2445
1710	=item const char *path [read-only]	2446	=item const char *path [read-only]
1711		2447
1712	The filesystem path that is being watched.	2448	The file system path that is being watched.
1713		2449
1714	=back	2450	=back
1715		2451
1716	=head3 Examples	2452	=head3 Examples
1717		2453
1718	Example: Watch C</etc/passwd> for attribute changes.	2454	Example: Watch C</etc/passwd> for attribute changes.
1719		2455
1720	static void	2456	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2457	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2458	{
1723	/* /etc/passwd changed in some way */	2459	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2460	if (w->attr.st_nlink)
1725	{	2461	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2462	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2463	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2464	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2465	}
1730	else	2466	else
1731	/* you shalt not abuse printf for puts */	2467	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2468	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2469	"if this is windows, they already arrived\n");
1734	}	2470	}
1735		2471
1736	...	2472	...
1737	ev_stat passwd;	2473	ev_stat passwd;
1738		2474
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2475	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2476	ev_stat_start (loop, &passwd);
1741		2477
1742	Example: Like above, but additionally use a one-second delay so we do not	2478	Example: Like above, but additionally use a one-second delay so we do not
1743	miss updates (however, frequent updates will delay processing, too, so	2479	miss updates (however, frequent updates will delay processing, too, so
1744	one might do the work both on C<ev_stat> callback invocation I<and> on	2480	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2481	C<ev_timer> callback invocation).
1746		2482
1747	static ev_stat passwd;	2483	static ev_stat passwd;
1748	static ev_timer timer;	2484	static ev_timer timer;
1749		2485
1750	static void	2486	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2487	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2488	{
1753	ev_timer_stop (EV_A_ w);	2489	ev_timer_stop (EV_A_ w);
1754		2490
1755	/* now it's one second after the most recent passwd change */	2491	/* now it's one second after the most recent passwd change */
1756	}	2492	}
1757		2493
1758	static void	2494	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2495	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2496	{
1761	/* reset the one-second timer */	2497	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2498	ev_timer_again (EV_A_ &timer);
1763	}	2499	}
1764		2500
1765	...	2501	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2502	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2503	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2504	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2505
1770		2506
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2507	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2508
1773	Idle watchers trigger events when no other events of the same or higher	2509	Idle watchers trigger events when no other events of the same or higher
1774	priority are pending (prepare, check and other idle watchers do not	2510	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2511	as receiving "events").
1776		2512
1777	That is, as long as your process is busy handling sockets or timeouts	2513	That is, as long as your process is busy handling sockets or timeouts
1778	(or even signals, imagine) of the same or higher priority it will not be	2514	(or even signals, imagine) of the same or higher priority it will not be
1779	triggered. But when your process is idle (or only lower-priority watchers	2515	triggered. But when your process is idle (or only lower-priority watchers
1780	are pending), the idle watchers are being called once per event loop	2516	are pending), the idle watchers are being called once per event loop
…		…
1791		2527
1792	=head3 Watcher-Specific Functions and Data Members	2528	=head3 Watcher-Specific Functions and Data Members
1793		2529
1794	=over 4	2530	=over 4
1795		2531
1796	=item ev_idle_init (ev_signal *, callback)	2532	=item ev_idle_init (ev_idle *, callback)
1797		2533
1798	Initialises and configures the idle watcher - it has no parameters of any	2534	Initialises and configures the idle watcher - it has no parameters of any
1799	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2535	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1800	believe me.	2536	believe me.
1801		2537
…		…
1804	=head3 Examples	2540	=head3 Examples
1805		2541
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2542	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2543	callback, free it. Also, use no error checking, as usual.
1808		2544
1809	static void	2545	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2546	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2547	{
1812	free (w);	2548	free (w);
1813	// now do something you wanted to do when the program has	2549	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2550	// no longer anything immediate to do.
1815	}	2551	}
1816		2552
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2553	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2554	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2555	ev_idle_start (loop, idle_watcher);
1820		2556
1821		2557
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2558	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2559
1824	Prepare and check watchers are usually (but not always) used in tandem:	2560	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2561	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2562	afterwards.
1827		2563
1828	You I<must not> call C<ev_loop> or similar functions that enter	2564	You I<must not> call C<ev_loop> or similar functions that enter
1829	the current event loop from either C<ev_prepare> or C<ev_check>	2565	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1832	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2568	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1833	C<ev_check> so if you have one watcher of each kind they will always be	2569	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2570	called in pairs bracketing the blocking call.
1835		2571
1836	Their main purpose is to integrate other event mechanisms into libev and	2572	Their main purpose is to integrate other event mechanisms into libev and
1837	their use is somewhat advanced. This could be used, for example, to track	2573	their use is somewhat advanced. They could be used, for example, to track
1838	variable changes, implement your own watchers, integrate net-snmp or a	2574	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2575	coroutine library and lots more. They are also occasionally useful if
1840	you cache some data and want to flush it before blocking (for example,	2576	you cache some data and want to flush it before blocking (for example,
1841	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2577	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2578	watcher).
1843		2579
1844	This is done by examining in each prepare call which file descriptors need	2580	This is done by examining in each prepare call which file descriptors
1845	to be watched by the other library, registering C<ev_io> watchers for	2581	need to be watched by the other library, registering C<ev_io> watchers
1846	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2582	for them and starting an C<ev_timer> watcher for any timeouts (many
1847	provide just this functionality). Then, in the check watcher you check for	2583	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2584	you check for any events that occurred (by checking the pending status
1849	and stopping them) and call back into the library. The I/O and timer	2585	of all watchers and stopping them) and call back into the library. The
1850	callbacks will never actually be called (but must be valid nevertheless,	2586	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2587	nevertheless, because you never know, you know?).
1852		2588
1853	As another example, the Perl Coro module uses these hooks to integrate	2589	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2590	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2591	during each prepare and only letting the process block if no coroutines
1856	are ready to run (it's actually more complicated: it only runs coroutines	2592	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1859	loop from blocking if lower-priority coroutines are active, thus mapping	2595	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2596	low-priority coroutines to idle/background tasks).
1861		2597
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2598	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1863	priority, to ensure that they are being run before any other watchers	2599	priority, to ensure that they are being run before any other watchers
		2600	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2601
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2602	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1865	too) should not activate ("feed") events into libev. While libev fully	2603	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2604	might get executed before other C<ev_check> watchers did their job. As
1867	did their job. As C<ev_check> watchers are often used to embed other	2605	C<ev_check> watchers are often used to embed other (non-libev) event
1868	(non-libev) event loops those other event loops might be in an unusable	2606	loops those other event loops might be in an unusable state until their
1869	state until their C<ev_check> watcher ran (always remind yourself to	2607	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2608	others).
1871		2609
1872	=head3 Watcher-Specific Functions and Data Members	2610	=head3 Watcher-Specific Functions and Data Members
1873		2611
1874	=over 4	2612	=over 4
1875		2613
…		…
1877		2615
1878	=item ev_check_init (ev_check *, callback)	2616	=item ev_check_init (ev_check *, callback)
1879		2617
1880	Initialises and configures the prepare or check watcher - they have no	2618	Initialises and configures the prepare or check watcher - they have no
1881	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2619	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1882	macros, but using them is utterly, utterly and completely pointless.	2620	macros, but using them is utterly, utterly, utterly and completely
		2621	pointless.
1883		2622
1884	=back	2623	=back
1885		2624
1886	=head3 Examples	2625	=head3 Examples
1887		2626
1888	There are a number of principal ways to embed other event loops or modules	2627	There are a number of principal ways to embed other event loops or modules
1889	into libev. Here are some ideas on how to include libadns into libev	2628	into libev. Here are some ideas on how to include libadns into libev
1890	(there is a Perl module named C<EV::ADNS> that does this, which you could	2629	(there is a Perl module named C<EV::ADNS> that does this, which you could
1891	use for an actually working example. Another Perl module named C<EV::Glib>	2630	use as a working example. Another Perl module named C<EV::Glib> embeds a
1892	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV	2631	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2632	Glib event loop).
1894		2633
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2634	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1896	and in a check watcher, destroy them and call into libadns. What follows	2635	and in a check watcher, destroy them and call into libadns. What follows
1897	is pseudo-code only of course. This requires you to either use a low	2636	is pseudo-code only of course. This requires you to either use a low
1898	priority for the check watcher or use C<ev_clear_pending> explicitly, as	2637	priority for the check watcher or use C<ev_clear_pending> explicitly, as
1899	the callbacks for the IO/timeout watchers might not have been called yet.	2638	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2639
1901	static ev_io iow [nfd];	2640	static ev_io iow [nfd];
1902	static ev_timer tw;	2641	static ev_timer tw;
1903		2642
1904	static void	2643	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2644	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2645	{
1907	}	2646	}
1908		2647
1909	// create io watchers for each fd and a timer before blocking	2648	// create io watchers for each fd and a timer before blocking
1910	static void	2649	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2650	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2651	{
1913	int timeout = 3600000;	2652	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2653	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2654	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2655	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2656
1918	/* the callback is illegal, but won't be called as we stop during check */	2657	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2658	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1920	ev_timer_start (loop, &tw);	2659	ev_timer_start (loop, &tw);
1921		2660
1922	// create one ev_io per pollfd	2661	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2662	for (int i = 0; i < nfd; ++i)
1924	{	2663	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2664	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2665	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2666	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2667
1929	fds [i].revents = 0;	2668	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2669	ev_io_start (loop, iow + i);
1931	}	2670	}
1932	}	2671	}
1933		2672
1934	// stop all watchers after blocking	2673	// stop all watchers after blocking
1935	static void	2674	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2675	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2676	{
1938	ev_timer_stop (loop, &tw);	2677	ev_timer_stop (loop, &tw);
1939		2678
1940	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
1941	{	2680	{
1942	// set the relevant poll flags	2681	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2682	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2683	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2684	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2685	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2686	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2687
1949	// now stop the watcher	2688	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2689	ev_io_stop (loop, iow + i);
1951	}	2690	}
1952		2691
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2692	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2693	}
1955		2694
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2695	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1957	in the prepare watcher and would dispose of the check watcher.	2696	in the prepare watcher and would dispose of the check watcher.
1958		2697
1959	Method 3: If the module to be embedded supports explicit event	2698	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2699	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2700	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2701
1963	static void	2702	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2703	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2704	{
1966	adns_state ads = (adns_state)w->data;	2705	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2706	update_now (EV_A);
1968		2707
1969	adns_processtimeouts (ads, &tv_now);	2708	adns_processtimeouts (ads, &tv_now);
1970	}	2709	}
1971		2710
1972	static void	2711	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2712	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2713	{
1975	adns_state ads = (adns_state)w->data;	2714	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2715	update_now (EV_A);
1977		2716
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2717	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2718	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2719	}
1981		2720
1982	// do not ever call adns_afterpoll	2721	// do not ever call adns_afterpoll
1983		2722
1984	Method 4: Do not use a prepare or check watcher because the module you	2723	Method 4: Do not use a prepare or check watcher because the module you
1985	want to embed is too inflexible to support it. Instead, youc na override	2724	want to embed is not flexible enough to support it. Instead, you can
1986	their poll function. The drawback with this solution is that the main	2725	override their poll function. The drawback with this solution is that the
1987	loop is now no longer controllable by EV. The C<Glib::EV> module does	2726	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2727	this approach, effectively embedding EV as a client into the horrible
		2728	libglib event loop.
1989		2729
1990	static gint	2730	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2731	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2732	{
1993	int got_events = 0;	2733	int got_events = 0;
1994		2734
1995	for (n = 0; n < nfds; ++n)	2735	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2736	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2737
1998	if (timeout >= 0)	2738	if (timeout >= 0)
1999	// create/start timer	2739	// create/start timer
2000		2740
2001	// poll	2741	// poll
2002	ev_loop (EV_A_ 0);	2742	ev_loop (EV_A_ 0);
2003		2743
2004	// stop timer again	2744	// stop timer again
2005	if (timeout >= 0)	2745	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2746	ev_timer_stop (EV_A_ &to);
2007		2747
2008	// stop io watchers again - their callbacks should have set	2748	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2749	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2750	ev_io_stop (EV_A_ iow [n]);
2011		2751
2012	return got_events;	2752	return got_events;
2013	}	2753	}
2014		2754
2015		2755
2016	=head2 C<ev_embed> - when one backend isn't enough...	2756	=head2 C<ev_embed> - when one backend isn't enough...
2017		2757
2018	This is a rather advanced watcher type that lets you embed one event loop	2758	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2764	prioritise I/O.
2025		2765
2026	As an example for a bug workaround, the kqueue backend might only support	2766	As an example for a bug workaround, the kqueue backend might only support
2027	sockets on some platform, so it is unusable as generic backend, but you	2767	sockets on some platform, so it is unusable as generic backend, but you
2028	still want to make use of it because you have many sockets and it scales	2768	still want to make use of it because you have many sockets and it scales
2029	so nicely. In this case, you would create a kqueue-based loop and embed it	2769	so nicely. In this case, you would create a kqueue-based loop and embed
2030	into your default loop (which might use e.g. poll). Overall operation will	2770	it into your default loop (which might use e.g. poll). Overall operation
2031	be a bit slower because first libev has to poll and then call kevent, but	2771	will be a bit slower because first libev has to call C<poll> and then
2032	at least you can use both at what they are best.	2772	C<kevent>, but at least you can use both mechanisms for what they are
		2773	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2774
2034	As for prioritising I/O: rarely you have the case where some fds have	2775	As for prioritising I/O: under rare circumstances you have the case where
2035	to be watched and handled very quickly (with low latency), and even	2776	some fds have to be watched and handled very quickly (with low latency),
2036	priorities and idle watchers might have too much overhead. In this case	2777	and even priorities and idle watchers might have too much overhead. In
2037	you would put all the high priority stuff in one loop and all the rest in	2778	this case you would put all the high priority stuff in one loop and all
2038	a second one, and embed the second one in the first.	2779	the rest in a second one, and embed the second one in the first.
2039		2780
2040	As long as the watcher is active, the callback will be invoked every time	2781	As long as the watcher is active, the callback will be invoked every
2041	there might be events pending in the embedded loop. The callback must then	2782	time there might be events pending in the embedded loop. The callback
2042	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2783	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2043	their callbacks (you could also start an idle watcher to give the embedded	2784	sweep and invoke their callbacks (the callback doesn't need to invoke the
2044	loop strictly lower priority for example). You can also set the callback	2785	C<ev_embed_sweep> function directly, it could also start an idle watcher
2045	to C<0>, in which case the embed watcher will automatically execute the	2786	to give the embedded loop strictly lower priority for example).
2046	embedded loop sweep.
2047		2787
2048	As long as the watcher is started it will automatically handle events. The	2788	You can also set the callback to C<0>, in which case the embed watcher
2049	callback will be invoked whenever some events have been handled. You can	2789	will automatically execute the embedded loop sweep whenever necessary.
2050	set the callback to C<0> to avoid having to specify one if you are not
2051	interested in that.
2052		2790
2053	Also, there have not currently been made special provisions for forking:	2791	Fork detection will be handled transparently while the C<ev_embed> watcher
2054	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2792	is active, i.e., the embedded loop will automatically be forked when the
2055	but you will also have to stop and restart any C<ev_embed> watchers	2793	embedding loop forks. In other cases, the user is responsible for calling
2056	yourself.	2794	C<ev_loop_fork> on the embedded loop.
2057		2795
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2796	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2797	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2798	portable one.
2061		2799
2062	So when you want to use this feature you will always have to be prepared	2800	So when you want to use this feature you will always have to be prepared
2063	that you cannot get an embeddable loop. The recommended way to get around	2801	that you cannot get an embeddable loop. The recommended way to get around
2064	this is to have a separate variables for your embeddable loop, try to	2802	this is to have a separate variables for your embeddable loop, try to
2065	create it, and if that fails, use the normal loop for everything.	2803	create it, and if that fails, use the normal loop for everything.
2066		2804
		2805	=head3 C<ev_embed> and fork
		2806
		2807	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2808	automatically be applied to the embedded loop as well, so no special
		2809	fork handling is required in that case. When the watcher is not running,
		2810	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2811	as applicable.
		2812
2067	=head3 Watcher-Specific Functions and Data Members	2813	=head3 Watcher-Specific Functions and Data Members
2068		2814
2069	=over 4	2815	=over 4
2070		2816
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2817	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2820
2075	Configures the watcher to embed the given loop, which must be	2821	Configures the watcher to embed the given loop, which must be
2076	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	2822	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2077	invoked automatically, otherwise it is the responsibility of the callback	2823	invoked automatically, otherwise it is the responsibility of the callback
2078	to invoke it (it will continue to be called until the sweep has been done,	2824	to invoke it (it will continue to be called until the sweep has been done,
2079	if you do not want thta, you need to temporarily stop the embed watcher).	2825	if you do not want that, you need to temporarily stop the embed watcher).
2080		2826
2081	=item ev_embed_sweep (loop, ev_embed *)	2827	=item ev_embed_sweep (loop, ev_embed *)
2082		2828
2083	Make a single, non-blocking sweep over the embedded loop. This works	2829	Make a single, non-blocking sweep over the embedded loop. This works
2084	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2830	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2831	appropriate way for embedded loops.
2086		2832
2087	=item struct ev_loop *other [read-only]	2833	=item struct ev_loop *other [read-only]
2088		2834
2089	The embedded event loop.	2835	The embedded event loop.
2090		2836
…		…
2092		2838
2093	=head3 Examples	2839	=head3 Examples
2094		2840
2095	Example: Try to get an embeddable event loop and embed it into the default	2841	Example: Try to get an embeddable event loop and embed it into the default
2096	event loop. If that is not possible, use the default loop. The default	2842	event loop. If that is not possible, use the default loop. The default
2097	loop is stored in C<loop_hi>, while the mebeddable loop is stored in	2843	loop is stored in C<loop_hi>, while the embeddable loop is stored in
2098	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be	2844	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2845	used).
2100		2846
2101	struct ev_loop *loop_hi = ev_default_init (0);	2847	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2848	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2849	ev_embed embed;
2104		2850
2105	// see if there is a chance of getting one that works	2851	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2852	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2853	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2854	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2855	: 0;
2110		2856
2111	// if we got one, then embed it, otherwise default to loop_hi	2857	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2858	if (loop_lo)
2113	{	2859	{
2114	ev_embed_init (&embed, 0, loop_lo);	2860	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2861	ev_embed_start (loop_hi, &embed);
2116	}	2862	}
2117	else	2863	else
2118	loop_lo = loop_hi;	2864	loop_lo = loop_hi;
2119		2865
2120	Example: Check if kqueue is available but not recommended and create	2866	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2867	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2868	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2869	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2870
2125	struct ev_loop *loop = ev_default_init (0);	2871	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2872	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2873	ev_embed embed;
2128		2874
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2875	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2876	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2877	{
2132	ev_embed_init (&embed, 0, loop_socket);	2878	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2879	ev_embed_start (loop, &embed);
2134	}	2880	}
2135		2881
2136	if (!loop_socket)	2882	if (!loop_socket)
2137	loop_socket = loop;	2883	loop_socket = loop;
2138		2884
2139	// now use loop_socket for all sockets, and loop for everything else	2885	// now use loop_socket for all sockets, and loop for everything else
2140		2886
2141		2887
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2888	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2889
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2890	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2147	event loop blocks next and before C<ev_check> watchers are being called,	2893	event loop blocks next and before C<ev_check> watchers are being called,
2148	and only in the child after the fork. If whoever good citizen calling	2894	and only in the child after the fork. If whoever good citizen calling
2149	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2895	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2150	handlers will be invoked, too, of course.	2896	handlers will be invoked, too, of course.
2151		2897
		2898	=head3 The special problem of life after fork - how is it possible?
		2899
		2900	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2901	up/change the process environment, followed by a call to C<exec()>. This
		2902	sequence should be handled by libev without any problems.
		2903
		2904	This changes when the application actually wants to do event handling
		2905	in the child, or both parent in child, in effect "continuing" after the
		2906	fork.
		2907
		2908	The default mode of operation (for libev, with application help to detect
		2909	forks) is to duplicate all the state in the child, as would be expected
		2910	when I<either> the parent I<or> the child process continues.
		2911
		2912	When both processes want to continue using libev, then this is usually the
		2913	wrong result. In that case, usually one process (typically the parent) is
		2914	supposed to continue with all watchers in place as before, while the other
		2915	process typically wants to start fresh, i.e. without any active watchers.
		2916
		2917	The cleanest and most efficient way to achieve that with libev is to
		2918	simply create a new event loop, which of course will be "empty", and
		2919	use that for new watchers. This has the advantage of not touching more
		2920	memory than necessary, and thus avoiding the copy-on-write, and the
		2921	disadvantage of having to use multiple event loops (which do not support
		2922	signal watchers).
		2923
		2924	When this is not possible, or you want to use the default loop for
		2925	other reasons, then in the process that wants to start "fresh", call
		2926	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2927	the default loop will "orphan" (not stop) all registered watchers, so you
		2928	have to be careful not to execute code that modifies those watchers. Note
		2929	also that in that case, you have to re-register any signal watchers.
		2930
2152	=head3 Watcher-Specific Functions and Data Members	2931	=head3 Watcher-Specific Functions and Data Members
2153		2932
2154	=over 4	2933	=over 4
2155		2934
2156	=item ev_fork_init (ev_signal *, callback)	2935	=item ev_fork_init (ev_signal *, callback)
…		…
2188	is that the author does not know of a simple (or any) algorithm for a	2967	is that the author does not know of a simple (or any) algorithm for a
2189	multiple-writer-single-reader queue that works in all cases and doesn't	2968	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2969	need elaborate support such as pthreads.
2191		2970
2192	That means that if you want to queue data, you have to provide your own	2971	That means that if you want to queue data, you have to provide your own
2193	queue. But at least I can tell you would implement locking around your	2972	queue. But at least I can tell you how to implement locking around your
2194	queue:	2973	queue:
2195		2974
2196	=over 4	2975	=over 4
2197		2976
2198	=item queueing from a signal handler context	2977	=item queueing from a signal handler context
2199		2978
2200	To implement race-free queueing, you simply add to the queue in the signal	2979	To implement race-free queueing, you simply add to the queue in the signal
2201	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2980	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2981	an example that does that for some fictitious SIGUSR1 handler:
2203		2982
2204	static ev_async mysig;	2983	static ev_async mysig;
2205		2984
2206	static void	2985	static void
2207	sigusr1_handler (void)	2986	sigusr1_handler (void)
…		…
2273	=over 4	3052	=over 4
2274		3053
2275	=item ev_async_init (ev_async *, callback)	3054	=item ev_async_init (ev_async *, callback)
2276		3055
2277	Initialises and configures the async watcher - it has no parameters of any	3056	Initialises and configures the async watcher - it has no parameters of any
2278	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3057	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2279	believe me.	3058	trust me.
2280		3059
2281	=item ev_async_send (loop, ev_async *)	3060	=item ev_async_send (loop, ev_async *)
2282		3061
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3062	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2284	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3063	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2285	C<ev_feed_event>, this call is safe to do in other threads, signal or	3064	C<ev_feed_event>, this call is safe to do from other threads, signal or
2286	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding	3065	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	3066	section below on what exactly this means).
2288		3067
		3068	Note that, as with other watchers in libev, multiple events might get
		3069	compressed into a single callback invocation (another way to look at this
		3070	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3071	reset when the event loop detects that).
		3072
2289	This call incurs the overhead of a syscall only once per loop iteration,	3073	This call incurs the overhead of a system call only once per event loop
2290	so while the overhead might be noticable, it doesn't apply to repeated	3074	iteration, so while the overhead might be noticeable, it doesn't apply to
2291	calls to C<ev_async_send>.	3075	repeated calls to C<ev_async_send> for the same event loop.
2292		3076
2293	=item bool = ev_async_pending (ev_async *)	3077	=item bool = ev_async_pending (ev_async *)
2294		3078
2295	Returns a non-zero value when C<ev_async_send> has been called on the	3079	Returns a non-zero value when C<ev_async_send> has been called on the
2296	watcher but the event has not yet been processed (or even noted) by the	3080	watcher but the event has not yet been processed (or even noted) by the
2297	event loop.	3081	event loop.
2298		3082
2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3083	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2300	the loop iterates next and checks for the watcher to have become active,	3084	the loop iterates next and checks for the watcher to have become active,
2301	it will reset the flag again. C<ev_async_pending> can be used to very	3085	it will reset the flag again. C<ev_async_pending> can be used to very
2302	quickly check wether invoking the loop might be a good idea.	3086	quickly check whether invoking the loop might be a good idea.
2303		3087
2304	Not that this does I<not> check wether the watcher itself is pending, only	3088	Not that this does I<not> check whether the watcher itself is pending,
2305	wether it has been requested to make this watcher pending.	3089	only whether it has been requested to make this watcher pending: there
		3090	is a time window between the event loop checking and resetting the async
		3091	notification, and the callback being invoked.
2306		3092
2307	=back	3093	=back
2308		3094
2309		3095
2310	=head1 OTHER FUNCTIONS	3096	=head1 OTHER FUNCTIONS
…		…
2314	=over 4	3100	=over 4
2315		3101
2316	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3102	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2317		3103
2318	This function combines a simple timer and an I/O watcher, calls your	3104	This function combines a simple timer and an I/O watcher, calls your
2319	callback on whichever event happens first and automatically stop both	3105	callback on whichever event happens first and automatically stops both
2320	watchers. This is useful if you want to wait for a single event on an fd	3106	watchers. This is useful if you want to wait for a single event on an fd
2321	or timeout without having to allocate/configure/start/stop/free one or	3107	or timeout without having to allocate/configure/start/stop/free one or
2322	more watchers yourself.	3108	more watchers yourself.
2323		3109
2324	If C<fd> is less than 0, then no I/O watcher will be started and events	3110	If C<fd> is less than 0, then no I/O watcher will be started and the
2325	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3111	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2326	C<events> set will be craeted and started.	3112	the given C<fd> and C<events> set will be created and started.
2327		3113
2328	If C<timeout> is less than 0, then no timeout watcher will be	3114	If C<timeout> is less than 0, then no timeout watcher will be
2329	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3115	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2330	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3116	repeat = 0) will be started. C<0> is a valid timeout.
2331	dubious value.
2332		3117
2333	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3118	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2334	passed an C<revents> set like normal event callbacks (a combination of	3119	passed an C<revents> set like normal event callbacks (a combination of
2335	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3120	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2336	value passed to C<ev_once>:	3121	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3122	a timeout and an io event at the same time - you probably should give io
		3123	events precedence.
2337		3124
		3125	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		3126
2338	static void stdin_ready (int revents, void *arg)	3127	static void stdin_ready (int revents, void *arg)
2339	{	3128	{
2340	if (revents & EV_TIMEOUT)
2341	/* doh, nothing entered */;
2342	else if (revents & EV_READ)	3129	if (revents & EV_READ)
2343	/* stdin might have data for us, joy! */;	3130	/* stdin might have data for us, joy! */;
		3131	else if (revents & EV_TIMEOUT)
		3132	/* doh, nothing entered */;
2344	}	3133	}
2345		3134
2346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3135	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2347		3136
2348	=item ev_feed_event (ev_loop *, watcher *, int revents)	3137	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2349		3138
2350	Feeds the given event set into the event loop, as if the specified event	3139	Feeds the given event set into the event loop, as if the specified event
2351	had happened for the specified watcher (which must be a pointer to an	3140	had happened for the specified watcher (which must be a pointer to an
2352	initialised but not necessarily started event watcher).	3141	initialised but not necessarily started event watcher).
2353		3142
2354	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3143	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2355		3144
2356	Feed an event on the given fd, as if a file descriptor backend detected	3145	Feed an event on the given fd, as if a file descriptor backend detected
2357	the given events it.	3146	the given events it.
2358		3147
2359	=item ev_feed_signal_event (ev_loop *loop, int signum)	3148	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2360		3149
2361	Feed an event as if the given signal occured (C<loop> must be the default	3150	Feed an event as if the given signal occurred (C<loop> must be the default
2362	loop!).	3151	loop!).
2363		3152
2364	=back	3153	=back
2365		3154
2366		3155
…		…
2382		3171
2383	=item * Priorities are not currently supported. Initialising priorities	3172	=item * Priorities are not currently supported. Initialising priorities
2384	will fail and all watchers will have the same priority, even though there	3173	will fail and all watchers will have the same priority, even though there
2385	is an ev_pri field.	3174	is an ev_pri field.
2386		3175
		3176	=item * In libevent, the last base created gets the signals, in libev, the
		3177	first base created (== the default loop) gets the signals.
		3178
2387	=item * Other members are not supported.	3179	=item * Other members are not supported.
2388		3180
2389	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3181	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2390	to use the libev header file and library.	3182	to use the libev header file and library.
2391		3183
2392	=back	3184	=back
2393		3185
2394	=head1 C++ SUPPORT	3186	=head1 C++ SUPPORT
2395		3187
2396	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3188	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2397	you to use some convinience methods to start/stop watchers and also change	3189	you to use some convenience methods to start/stop watchers and also change
2398	the callback model to a model using method callbacks on objects.	3190	the callback model to a model using method callbacks on objects.
2399		3191
2400	To use it,	3192	To use it,
2401		3193
2402	#include <ev++.h>	3194	#include <ev++.h>
2403		3195
2404	This automatically includes F<ev.h> and puts all of its definitions (many	3196	This automatically includes F<ev.h> and puts all of its definitions (many
2405	of them macros) into the global namespace. All C++ specific things are	3197	of them macros) into the global namespace. All C++ specific things are
2406	put into the C<ev> namespace. It should support all the same embedding	3198	put into the C<ev> namespace. It should support all the same embedding
2407	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	3199	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2474	your compiler is good :), then the method will be fully inlined into the	3266	your compiler is good :), then the method will be fully inlined into the
2475	thunking function, making it as fast as a direct C callback.	3267	thunking function, making it as fast as a direct C callback.
2476		3268
2477	Example: simple class declaration and watcher initialisation	3269	Example: simple class declaration and watcher initialisation
2478		3270
2479	struct myclass	3271	struct myclass
2480	{	3272	{
2481	void io_cb (ev::io &w, int revents) { }	3273	void io_cb (ev::io &w, int revents) { }
2482	}	3274	}
2483		3275
2484	myclass obj;	3276	myclass obj;
2485	ev::io iow;	3277	ev::io iow;
2486	iow.set <myclass, &myclass::io_cb> (&obj);	3278	iow.set <myclass, &myclass::io_cb> (&obj);
		3279
		3280	=item w->set (object *)
		3281
		3282	This is an B<experimental> feature that might go away in a future version.
		3283
		3284	This is a variation of a method callback - leaving out the method to call
		3285	will default the method to C<operator ()>, which makes it possible to use
		3286	functor objects without having to manually specify the C<operator ()> all
		3287	the time. Incidentally, you can then also leave out the template argument
		3288	list.
		3289
		3290	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3291	int revents)>.
		3292
		3293	See the method-C<set> above for more details.
		3294
		3295	Example: use a functor object as callback.
		3296
		3297	struct myfunctor
		3298	{
		3299	void operator() (ev::io &w, int revents)
		3300	{
		3301	...
		3302	}
		3303	}
		3304
		3305	myfunctor f;
		3306
		3307	ev::io w;
		3308	w.set (&f);
2487		3309
2488	=item w->set<function> (void *data = 0)	3310	=item w->set<function> (void *data = 0)
2489		3311
2490	Also sets a callback, but uses a static method or plain function as	3312	Also sets a callback, but uses a static method or plain function as
2491	callback. The optional C<data> argument will be stored in the watcher's	3313	callback. The optional C<data> argument will be stored in the watcher's
…		…
2493		3315
2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3316	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2495		3317
2496	See the method-C<set> above for more details.	3318	See the method-C<set> above for more details.
2497		3319
2498	Example:	3320	Example: Use a plain function as callback.
2499		3321
2500	static void io_cb (ev::io &w, int revents) { }	3322	static void io_cb (ev::io &w, int revents) { }
2501	iow.set <io_cb> ();	3323	iow.set <io_cb> ();
2502		3324
2503	=item w->set (struct ev_loop *)	3325	=item w->set (struct ev_loop *)
2504		3326
2505	Associates a different C<struct ev_loop> with this watcher. You can only	3327	Associates a different C<struct ev_loop> with this watcher. You can only
2506	do this when the watcher is inactive (and not pending either).	3328	do this when the watcher is inactive (and not pending either).
2507		3329
2508	=item w->set ([args])	3330	=item w->set ([arguments])
2509		3331
2510	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3332	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be
2511	called at least once. Unlike the C counterpart, an active watcher gets	3333	called at least once. Unlike the C counterpart, an active watcher gets
2512	automatically stopped and restarted when reconfiguring it with this	3334	automatically stopped and restarted when reconfiguring it with this
2513	method.	3335	method.
2514		3336
2515	=item w->start ()	3337	=item w->start ()
…		…
2539	=back	3361	=back
2540		3362
2541	Example: Define a class with an IO and idle watcher, start one of them in	3363	Example: Define a class with an IO and idle watcher, start one of them in
2542	the constructor.	3364	the constructor.
2543		3365
2544	class myclass	3366	class myclass
2545	{	3367	{
2546	ev::io io; void io_cb (ev::io &w, int revents);	3368	ev::io io ; void io_cb (ev::io &w, int revents);
2547	ev:idle idle void idle_cb (ev::idle &w, int revents);	3369	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2548		3370
2549	myclass (int fd)	3371	myclass (int fd)
2550	{	3372	{
2551	io .set <myclass, &myclass::io_cb > (this);	3373	io .set <myclass, &myclass::io_cb > (this);
2552	idle.set <myclass, &myclass::idle_cb> (this);	3374	idle.set <myclass, &myclass::idle_cb> (this);
2553		3375
2554	io.start (fd, ev::READ);	3376	io.start (fd, ev::READ);
2555	}	3377	}
2556	};	3378	};
2557		3379
2558		3380
2559	=head1 OTHER LANGUAGE BINDINGS	3381	=head1 OTHER LANGUAGE BINDINGS
2560		3382
2561	Libev does not offer other language bindings itself, but bindings for a	3383	Libev does not offer other language bindings itself, but bindings for a
2562	numbe rof languages exist in the form of third-party packages. If you know	3384	number of languages exist in the form of third-party packages. If you know
2563	any interesting language binding in addition to the ones listed here, drop	3385	any interesting language binding in addition to the ones listed here, drop
2564	me a note.	3386	me a note.
2565		3387
2566	=over 4	3388	=over 4
2567		3389
2568	=item Perl	3390	=item Perl
2569		3391
2570	The EV module implements the full libev API and is actually used to test	3392	The EV module implements the full libev API and is actually used to test
2571	libev. EV is developed together with libev. Apart from the EV core module,	3393	libev. EV is developed together with libev. Apart from the EV core module,
2572	there are additional modules that implement libev-compatible interfaces	3394	there are additional modules that implement libev-compatible interfaces
2573	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3395	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2574	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3396	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3397	and C<EV::Glib>).
2575		3398
2576	It can be found and installed via CPAN, its homepage is found at	3399	It can be found and installed via CPAN, its homepage is at
2577	L<http://software.schmorp.de/pkg/EV>.	3400	L<http://software.schmorp.de/pkg/EV>.
2578		3401
		3402	=item Python
		3403
		3404	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3405	seems to be quite complete and well-documented.
		3406
2579	=item Ruby	3407	=item Ruby
2580		3408
2581	Tony Arcieri has written a ruby extension that offers access to a subset	3409	Tony Arcieri has written a ruby extension that offers access to a subset
2582	of the libev API and adds filehandle abstractions, asynchronous DNS and	3410	of the libev API and adds file handle abstractions, asynchronous DNS and
2583	more on top of it. It can be found via gem servers. Its homepage is at	3411	more on top of it. It can be found via gem servers. Its homepage is at
2584	L<http://rev.rubyforge.org/>.	3412	L<http://rev.rubyforge.org/>.
2585		3413
		3414	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3415	makes rev work even on mingw.
		3416
		3417	=item Haskell
		3418
		3419	A haskell binding to libev is available at
		3420	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3421
2586	=item D	3422	=item D
2587		3423
2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3424	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2589	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3425	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3426
		3427	=item Ocaml
		3428
		3429	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3430	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3431
		3432	=item Lua
		3433
		3434	Brian Maher has written a partial interface to libev
		3435	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3436	L<http://github.com/brimworks/lua-ev>.
2590		3437
2591	=back	3438	=back
2592		3439
2593		3440
2594	=head1 MACRO MAGIC	3441	=head1 MACRO MAGIC
2595		3442
2596	Libev can be compiled with a variety of options, the most fundamantal	3443	Libev can be compiled with a variety of options, the most fundamental
2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3444	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2598	functions and callbacks have an initial C<struct ev_loop *> argument.	3445	functions and callbacks have an initial C<struct ev_loop *> argument.
2599		3446
2600	To make it easier to write programs that cope with either variant, the	3447	To make it easier to write programs that cope with either variant, the
2601	following macros are defined:	3448	following macros are defined:
…		…
2606		3453
2607	This provides the loop I<argument> for functions, if one is required ("ev	3454	This provides the loop I<argument> for functions, if one is required ("ev
2608	loop argument"). The C<EV_A> form is used when this is the sole argument,	3455	loop argument"). The C<EV_A> form is used when this is the sole argument,
2609	C<EV_A_> is used when other arguments are following. Example:	3456	C<EV_A_> is used when other arguments are following. Example:
2610		3457
2611	ev_unref (EV_A);	3458	ev_unref (EV_A);
2612	ev_timer_add (EV_A_ watcher);	3459	ev_timer_add (EV_A_ watcher);
2613	ev_loop (EV_A_ 0);	3460	ev_loop (EV_A_ 0);
2614		3461
2615	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3462	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2616	which is often provided by the following macro.	3463	which is often provided by the following macro.
2617		3464
2618	=item C<EV_P>, C<EV_P_>	3465	=item C<EV_P>, C<EV_P_>
2619		3466
2620	This provides the loop I<parameter> for functions, if one is required ("ev	3467	This provides the loop I<parameter> for functions, if one is required ("ev
2621	loop parameter"). The C<EV_P> form is used when this is the sole parameter,	3468	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
2622	C<EV_P_> is used when other parameters are following. Example:	3469	C<EV_P_> is used when other parameters are following. Example:
2623		3470
2624	// this is how ev_unref is being declared	3471	// this is how ev_unref is being declared
2625	static void ev_unref (EV_P);	3472	static void ev_unref (EV_P);
2626		3473
2627	// this is how you can declare your typical callback	3474	// this is how you can declare your typical callback
2628	static void cb (EV_P_ ev_timer *w, int revents)	3475	static void cb (EV_P_ ev_timer *w, int revents)
2629		3476
2630	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3477	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2631	suitable for use with C<EV_A>.	3478	suitable for use with C<EV_A>.
2632		3479
2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3480	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2634		3481
2635	Similar to the other two macros, this gives you the value of the default	3482	Similar to the other two macros, this gives you the value of the default
2636	loop, if multiple loops are supported ("ev loop default").	3483	loop, if multiple loops are supported ("ev loop default").
		3484
		3485	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3486
		3487	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3488	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3489	is undefined when the default loop has not been initialised by a previous
		3490	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3491
		3492	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3493	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2637		3494
2638	=back	3495	=back
2639		3496
2640	Example: Declare and initialise a check watcher, utilising the above	3497	Example: Declare and initialise a check watcher, utilising the above
2641	macros so it will work regardless of whether multiple loops are supported	3498	macros so it will work regardless of whether multiple loops are supported
2642	or not.	3499	or not.
2643		3500
2644	static void	3501	static void
2645	check_cb (EV_P_ ev_timer *w, int revents)	3502	check_cb (EV_P_ ev_timer *w, int revents)
2646	{	3503	{
2647	ev_check_stop (EV_A_ w);	3504	ev_check_stop (EV_A_ w);
2648	}	3505	}
2649		3506
2650	ev_check check;	3507	ev_check check;
2651	ev_check_init (&check, check_cb);	3508	ev_check_init (&check, check_cb);
2652	ev_check_start (EV_DEFAULT_ &check);	3509	ev_check_start (EV_DEFAULT_ &check);
2653	ev_loop (EV_DEFAULT_ 0);	3510	ev_loop (EV_DEFAULT_ 0);
2654		3511
2655	=head1 EMBEDDING	3512	=head1 EMBEDDING
2656		3513
2657	Libev can (and often is) directly embedded into host	3514	Libev can (and often is) directly embedded into host
2658	applications. Examples of applications that embed it include the Deliantra	3515	applications. Examples of applications that embed it include the Deliantra
…		…
2665	libev somewhere in your source tree).	3522	libev somewhere in your source tree).
2666		3523
2667	=head2 FILESETS	3524	=head2 FILESETS
2668		3525
2669	Depending on what features you need you need to include one or more sets of files	3526	Depending on what features you need you need to include one or more sets of files
2670	in your app.	3527	in your application.
2671		3528
2672	=head3 CORE EVENT LOOP	3529	=head3 CORE EVENT LOOP
2673		3530
2674	To include only the libev core (all the C<ev_*> functions), with manual	3531	To include only the libev core (all the C<ev_*> functions), with manual
2675	configuration (no autoconf):	3532	configuration (no autoconf):
2676		3533
2677	#define EV_STANDALONE 1	3534	#define EV_STANDALONE 1
2678	#include "ev.c"	3535	#include "ev.c"
2679		3536
2680	This will automatically include F<ev.h>, too, and should be done in a	3537	This will automatically include F<ev.h>, too, and should be done in a
2681	single C source file only to provide the function implementations. To use	3538	single C source file only to provide the function implementations. To use
2682	it, do the same for F<ev.h> in all files wishing to use this API (best	3539	it, do the same for F<ev.h> in all files wishing to use this API (best
2683	done by writing a wrapper around F<ev.h> that you can include instead and	3540	done by writing a wrapper around F<ev.h> that you can include instead and
2684	where you can put other configuration options):	3541	where you can put other configuration options):
2685		3542
2686	#define EV_STANDALONE 1	3543	#define EV_STANDALONE 1
2687	#include "ev.h"	3544	#include "ev.h"
2688		3545
2689	Both header files and implementation files can be compiled with a C++	3546	Both header files and implementation files can be compiled with a C++
2690	compiler (at least, thats a stated goal, and breakage will be treated	3547	compiler (at least, that's a stated goal, and breakage will be treated
2691	as a bug).	3548	as a bug).
2692		3549
2693	You need the following files in your source tree, or in a directory	3550	You need the following files in your source tree, or in a directory
2694	in your include path (e.g. in libev/ when using -Ilibev):	3551	in your include path (e.g. in libev/ when using -Ilibev):
2695		3552
2696	ev.h	3553	ev.h
2697	ev.c	3554	ev.c
2698	ev_vars.h	3555	ev_vars.h
2699	ev_wrap.h	3556	ev_wrap.h
2700		3557
2701	ev_win32.c required on win32 platforms only	3558	ev_win32.c required on win32 platforms only
2702		3559
2703	ev_select.c only when select backend is enabled (which is enabled by default)	3560	ev_select.c only when select backend is enabled (which is enabled by default)
2704	ev_poll.c only when poll backend is enabled (disabled by default)	3561	ev_poll.c only when poll backend is enabled (disabled by default)
2705	ev_epoll.c only when the epoll backend is enabled (disabled by default)	3562	ev_epoll.c only when the epoll backend is enabled (disabled by default)
2706	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	3563	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2707	ev_port.c only when the solaris port backend is enabled (disabled by default)	3564	ev_port.c only when the solaris port backend is enabled (disabled by default)
2708		3565
2709	F<ev.c> includes the backend files directly when enabled, so you only need	3566	F<ev.c> includes the backend files directly when enabled, so you only need
2710	to compile this single file.	3567	to compile this single file.
2711		3568
2712	=head3 LIBEVENT COMPATIBILITY API	3569	=head3 LIBEVENT COMPATIBILITY API
2713		3570
2714	To include the libevent compatibility API, also include:	3571	To include the libevent compatibility API, also include:
2715		3572
2716	#include "event.c"	3573	#include "event.c"
2717		3574
2718	in the file including F<ev.c>, and:	3575	in the file including F<ev.c>, and:
2719		3576
2720	#include "event.h"	3577	#include "event.h"
2721		3578
2722	in the files that want to use the libevent API. This also includes F<ev.h>.	3579	in the files that want to use the libevent API. This also includes F<ev.h>.
2723		3580
2724	You need the following additional files for this:	3581	You need the following additional files for this:
2725		3582
2726	event.h	3583	event.h
2727	event.c	3584	event.c
2728		3585
2729	=head3 AUTOCONF SUPPORT	3586	=head3 AUTOCONF SUPPORT
2730		3587
2731	Instead of using C<EV_STANDALONE=1> and providing your config in	3588	Instead of using C<EV_STANDALONE=1> and providing your configuration in
2732	whatever way you want, you can also C<m4_include([libev.m4])> in your	3589	whatever way you want, you can also C<m4_include([libev.m4])> in your
2733	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then	3590	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2734	include F<config.h> and configure itself accordingly.	3591	include F<config.h> and configure itself accordingly.
2735		3592
2736	For this of course you need the m4 file:	3593	For this of course you need the m4 file:
2737		3594
2738	libev.m4	3595	libev.m4
2739		3596
2740	=head2 PREPROCESSOR SYMBOLS/MACROS	3597	=head2 PREPROCESSOR SYMBOLS/MACROS
2741		3598
2742	Libev can be configured via a variety of preprocessor symbols you have to define	3599	Libev can be configured via a variety of preprocessor symbols you have to
2743	before including any of its files. The default is not to build for multiplicity	3600	define before including any of its files. The default in the absence of
2744	and only include the select backend.	3601	autoconf is documented for every option.
2745		3602
2746	=over 4	3603	=over 4
2747		3604
2748	=item EV_STANDALONE	3605	=item EV_STANDALONE
2749		3606
…		…
2751	keeps libev from including F<config.h>, and it also defines dummy	3608	keeps libev from including F<config.h>, and it also defines dummy
2752	implementations for some libevent functions (such as logging, which is not	3609	implementations for some libevent functions (such as logging, which is not
2753	supported). It will also not define any of the structs usually found in	3610	supported). It will also not define any of the structs usually found in
2754	F<event.h> that are not directly supported by the libev core alone.	3611	F<event.h> that are not directly supported by the libev core alone.
2755		3612
		3613	In standalone mode, libev will still try to automatically deduce the
		3614	configuration, but has to be more conservative.
		3615
2756	=item EV_USE_MONOTONIC	3616	=item EV_USE_MONOTONIC
2757		3617
2758	If defined to be C<1>, libev will try to detect the availability of the	3618	If defined to be C<1>, libev will try to detect the availability of the
2759	monotonic clock option at both compiletime and runtime. Otherwise no use	3619	monotonic clock option at both compile time and runtime. Otherwise no
2760	of the monotonic clock option will be attempted. If you enable this, you	3620	use of the monotonic clock option will be attempted. If you enable this,
2761	usually have to link against librt or something similar. Enabling it when	3621	you usually have to link against librt or something similar. Enabling it
2762	the functionality isn't available is safe, though, although you have	3622	when the functionality isn't available is safe, though, although you have
2763	to make sure you link against any libraries where the C<clock_gettime>	3623	to make sure you link against any libraries where the C<clock_gettime>
2764	function is hiding in (often F<-lrt>).	3624	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2765		3625
2766	=item EV_USE_REALTIME	3626	=item EV_USE_REALTIME
2767		3627
2768	If defined to be C<1>, libev will try to detect the availability of the	3628	If defined to be C<1>, libev will try to detect the availability of the
2769	realtime clock option at compiletime (and assume its availability at	3629	real-time clock option at compile time (and assume its availability
2770	runtime if successful). Otherwise no use of the realtime clock option will	3630	at runtime if successful). Otherwise no use of the real-time clock
2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3631	option will be attempted. This effectively replaces C<gettimeofday>
2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3632	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2773	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3633	correctness. See the note about libraries in the description of
		3634	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3635	C<EV_USE_CLOCK_SYSCALL>.
		3636
		3637	=item EV_USE_CLOCK_SYSCALL
		3638
		3639	If defined to be C<1>, libev will try to use a direct syscall instead
		3640	of calling the system-provided C<clock_gettime> function. This option
		3641	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3642	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3643	programs needlessly. Using a direct syscall is slightly slower (in
		3644	theory), because no optimised vdso implementation can be used, but avoids
		3645	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3646	higher, as it simplifies linking (no need for C<-lrt>).
2774		3647
2775	=item EV_USE_NANOSLEEP	3648	=item EV_USE_NANOSLEEP
2776		3649
2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3650	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2778	and will use it for delays. Otherwise it will use C<select ()>.	3651	and will use it for delays. Otherwise it will use C<select ()>.
2779		3652
		3653	=item EV_USE_EVENTFD
		3654
		3655	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3656	available and will probe for kernel support at runtime. This will improve
		3657	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3658	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3659	2.7 or newer, otherwise disabled.
		3660
2780	=item EV_USE_SELECT	3661	=item EV_USE_SELECT
2781		3662
2782	If undefined or defined to be C<1>, libev will compile in support for the	3663	If undefined or defined to be C<1>, libev will compile in support for the
2783	C<select>(2) backend. No attempt at autodetection will be done: if no	3664	C<select>(2) backend. No attempt at auto-detection will be done: if no
2784	other method takes over, select will be it. Otherwise the select backend	3665	other method takes over, select will be it. Otherwise the select backend
2785	will not be compiled in.	3666	will not be compiled in.
2786		3667
2787	=item EV_SELECT_USE_FD_SET	3668	=item EV_SELECT_USE_FD_SET
2788		3669
2789	If defined to C<1>, then the select backend will use the system C<fd_set>	3670	If defined to C<1>, then the select backend will use the system C<fd_set>
2790	structure. This is useful if libev doesn't compile due to a missing	3671	structure. This is useful if libev doesn't compile due to a missing
2791	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on	3672	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2792	exotic systems. This usually limits the range of file descriptors to some	3673	on exotic systems. This usually limits the range of file descriptors to
2793	low limit such as 1024 or might have other limitations (winsocket only	3674	some low limit such as 1024 or might have other limitations (winsocket
2794	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3675	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2795	influence the size of the C<fd_set> used.	3676	configures the maximum size of the C<fd_set>.
2796		3677
2797	=item EV_SELECT_IS_WINSOCKET	3678	=item EV_SELECT_IS_WINSOCKET
2798		3679
2799	When defined to C<1>, the select backend will assume that	3680	When defined to C<1>, the select backend will assume that
2800	select/socket/connect etc. don't understand file descriptors but	3681	select/socket/connect etc. don't understand file descriptors but
…		…
2802	be used is the winsock select). This means that it will call	3683	be used is the winsock select). This means that it will call
2803	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3684	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2804	it is assumed that all these functions actually work on fds, even	3685	it is assumed that all these functions actually work on fds, even
2805	on win32. Should not be defined on non-win32 platforms.	3686	on win32. Should not be defined on non-win32 platforms.
2806		3687
2807	=item EV_FD_TO_WIN32_HANDLE	3688	=item EV_FD_TO_WIN32_HANDLE(fd)
2808		3689
2809	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3690	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2810	file descriptors to socket handles. When not defining this symbol (the	3691	file descriptors to socket handles. When not defining this symbol (the
2811	default), then libev will call C<_get_osfhandle>, which is usually	3692	default), then libev will call C<_get_osfhandle>, which is usually
2812	correct. In some cases, programs use their own file descriptor management,	3693	correct. In some cases, programs use their own file descriptor management,
2813	in which case they can provide this function to map fds to socket handles.	3694	in which case they can provide this function to map fds to socket handles.
2814		3695
		3696	=item EV_WIN32_HANDLE_TO_FD(handle)
		3697
		3698	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3699	using the standard C<_open_osfhandle> function. For programs implementing
		3700	their own fd to handle mapping, overwriting this function makes it easier
		3701	to do so. This can be done by defining this macro to an appropriate value.
		3702
		3703	=item EV_WIN32_CLOSE_FD(fd)
		3704
		3705	If programs implement their own fd to handle mapping on win32, then this
		3706	macro can be used to override the C<close> function, useful to unregister
		3707	file descriptors again. Note that the replacement function has to close
		3708	the underlying OS handle.
		3709
2815	=item EV_USE_POLL	3710	=item EV_USE_POLL
2816		3711
2817	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3712	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2818	backend. Otherwise it will be enabled on non-win32 platforms. It	3713	backend. Otherwise it will be enabled on non-win32 platforms. It
2819	takes precedence over select.	3714	takes precedence over select.
2820		3715
2821	=item EV_USE_EPOLL	3716	=item EV_USE_EPOLL
2822		3717
2823	If defined to be C<1>, libev will compile in support for the Linux	3718	If defined to be C<1>, libev will compile in support for the Linux
2824	C<epoll>(7) backend. Its availability will be detected at runtime,	3719	C<epoll>(7) backend. Its availability will be detected at runtime,
2825	otherwise another method will be used as fallback. This is the	3720	otherwise another method will be used as fallback. This is the preferred
2826	preferred backend for GNU/Linux systems.	3721	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3722	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2827		3723
2828	=item EV_USE_KQUEUE	3724	=item EV_USE_KQUEUE
2829		3725
2830	If defined to be C<1>, libev will compile in support for the BSD style	3726	If defined to be C<1>, libev will compile in support for the BSD style
2831	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	3727	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
2844	otherwise another method will be used as fallback. This is the preferred	3740	otherwise another method will be used as fallback. This is the preferred
2845	backend for Solaris 10 systems.	3741	backend for Solaris 10 systems.
2846		3742
2847	=item EV_USE_DEVPOLL	3743	=item EV_USE_DEVPOLL
2848		3744
2849	reserved for future expansion, works like the USE symbols above.	3745	Reserved for future expansion, works like the USE symbols above.
2850		3746
2851	=item EV_USE_INOTIFY	3747	=item EV_USE_INOTIFY
2852		3748
2853	If defined to be C<1>, libev will compile in support for the Linux inotify	3749	If defined to be C<1>, libev will compile in support for the Linux inotify
2854	interface to speed up C<ev_stat> watchers. Its actual availability will	3750	interface to speed up C<ev_stat> watchers. Its actual availability will
2855	be detected at runtime.	3751	be detected at runtime. If undefined, it will be enabled if the headers
		3752	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2856		3753
2857	=item EV_ATOMIC_T	3754	=item EV_ATOMIC_T
2858		3755
2859	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3756	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2860	access is atomic with respect to other threads or signal contexts. No such	3757	access is atomic with respect to other threads or signal contexts. No such
2861	type is easily found in the C language, so you can provide your own type	3758	type is easily found in the C language, so you can provide your own type
2862	that you know is safe for your purposes. It is used both for signal handler "locking"	3759	that you know is safe for your purposes. It is used both for signal handler "locking"
2863	as well as for signal and thread safety in C<ev_async> watchers.	3760	as well as for signal and thread safety in C<ev_async> watchers.
2864		3761
2865	In the absense of this define, libev will use C<sig_atomic_t volatile>	3762	In the absence of this define, libev will use C<sig_atomic_t volatile>
2866	(from F<signal.h>), which is usually good enough on most platforms.	3763	(from F<signal.h>), which is usually good enough on most platforms.
2867		3764
2868	=item EV_H	3765	=item EV_H
2869		3766
2870	The name of the F<ev.h> header file used to include it. The default if	3767	The name of the F<ev.h> header file used to include it. The default if
…		…
2909	When doing priority-based operations, libev usually has to linearly search	3806	When doing priority-based operations, libev usually has to linearly search
2910	all the priorities, so having many of them (hundreds) uses a lot of space	3807	all the priorities, so having many of them (hundreds) uses a lot of space
2911	and time, so using the defaults of five priorities (-2 .. +2) is usually	3808	and time, so using the defaults of five priorities (-2 .. +2) is usually
2912	fine.	3809	fine.
2913		3810
2914	If your embedding app does not need any priorities, defining these both to	3811	If your embedding application does not need any priorities, defining these
2915	C<0> will save some memory and cpu.	3812	both to C<0> will save some memory and CPU.
2916		3813
2917	=item EV_PERIODIC_ENABLE	3814	=item EV_PERIODIC_ENABLE
2918		3815
2919	If undefined or defined to be C<1>, then periodic timers are supported. If	3816	If undefined or defined to be C<1>, then periodic timers are supported. If
2920	defined to be C<0>, then they are not. Disabling them saves a few kB of	3817	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2927	code.	3824	code.
2928		3825
2929	=item EV_EMBED_ENABLE	3826	=item EV_EMBED_ENABLE
2930		3827
2931	If undefined or defined to be C<1>, then embed watchers are supported. If	3828	If undefined or defined to be C<1>, then embed watchers are supported. If
2932	defined to be C<0>, then they are not.	3829	defined to be C<0>, then they are not. Embed watchers rely on most other
		3830	watcher types, which therefore must not be disabled.
2933		3831
2934	=item EV_STAT_ENABLE	3832	=item EV_STAT_ENABLE
2935		3833
2936	If undefined or defined to be C<1>, then stat watchers are supported. If	3834	If undefined or defined to be C<1>, then stat watchers are supported. If
2937	defined to be C<0>, then they are not.	3835	defined to be C<0>, then they are not.
…		…
2947	defined to be C<0>, then they are not.	3845	defined to be C<0>, then they are not.
2948		3846
2949	=item EV_MINIMAL	3847	=item EV_MINIMAL
2950		3848
2951	If you need to shave off some kilobytes of code at the expense of some	3849	If you need to shave off some kilobytes of code at the expense of some
2952	speed, define this symbol to C<1>. Currently only used for gcc to override	3850	speed (but with the full API), define this symbol to C<1>. Currently this
2953	some inlining decisions, saves roughly 30% codesize of amd64.	3851	is used to override some inlining decisions, saves roughly 30% code size
		3852	on amd64. It also selects a much smaller 2-heap for timer management over
		3853	the default 4-heap.
		3854
		3855	You can save even more by disabling watcher types you do not need
		3856	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3857	(C<-DNDEBUG>) will usually reduce code size a lot.
		3858
		3859	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3860	provide a bare-bones event library. See C<ev.h> for details on what parts
		3861	of the API are still available, and do not complain if this subset changes
		3862	over time.
		3863
		3864	=item EV_NSIG
		3865
		3866	The highest supported signal number, +1 (or, the number of
		3867	signals): Normally, libev tries to deduce the maximum number of signals
		3868	automatically, but sometimes this fails, in which case it can be
		3869	specified. Also, using a lower number than detected (C<32> should be
		3870	good for about any system in existance) can save some memory, as libev
		3871	statically allocates some 12-24 bytes per signal number.
2954		3872
2955	=item EV_PID_HASHSIZE	3873	=item EV_PID_HASHSIZE
2956		3874
2957	C<ev_child> watchers use a small hash table to distribute workload by	3875	C<ev_child> watchers use a small hash table to distribute workload by
2958	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3876	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
2965	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	3883	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2966	usually more than enough. If you need to manage thousands of C<ev_stat>	3884	usually more than enough. If you need to manage thousands of C<ev_stat>
2967	watchers you might want to increase this value (I<must> be a power of	3885	watchers you might want to increase this value (I<must> be a power of
2968	two).	3886	two).
2969		3887
		3888	=item EV_USE_4HEAP
		3889
		3890	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3891	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3892	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3893	faster performance with many (thousands) of watchers.
		3894
		3895	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3896	(disabled).
		3897
		3898	=item EV_HEAP_CACHE_AT
		3899
		3900	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3901	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3902	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3903	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3904	but avoids random read accesses on heap changes. This improves performance
		3905	noticeably with many (hundreds) of watchers.
		3906
		3907	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3908	(disabled).
		3909
		3910	=item EV_VERIFY
		3911
		3912	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3913	be done: If set to C<0>, no internal verification code will be compiled
		3914	in. If set to C<1>, then verification code will be compiled in, but not
		3915	called. If set to C<2>, then the internal verification code will be
		3916	called once per loop, which can slow down libev. If set to C<3>, then the
		3917	verification code will be called very frequently, which will slow down
		3918	libev considerably.
		3919
		3920	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3921	C<0>.
		3922
2970	=item EV_COMMON	3923	=item EV_COMMON
2971		3924
2972	By default, all watchers have a C<void *data> member. By redefining	3925	By default, all watchers have a C<void *data> member. By redefining
2973	this macro to a something else you can include more and other types of	3926	this macro to a something else you can include more and other types of
2974	members. You have to define it each time you include one of the files,	3927	members. You have to define it each time you include one of the files,
2975	though, and it must be identical each time.	3928	though, and it must be identical each time.
2976		3929
2977	For example, the perl EV module uses something like this:	3930	For example, the perl EV module uses something like this:
2978		3931
2979	#define EV_COMMON \	3932	#define EV_COMMON \
2980	SV *self; /* contains this struct */ \	3933	SV *self; /* contains this struct */ \
2981	SV *cb_sv, *fh /* note no trailing ";" */	3934	SV *cb_sv, *fh /* note no trailing ";" */
2982		3935
2983	=item EV_CB_DECLARE (type)	3936	=item EV_CB_DECLARE (type)
2984		3937
2985	=item EV_CB_INVOKE (watcher, revents)	3938	=item EV_CB_INVOKE (watcher, revents)
2986		3939
…		…
2991	definition and a statement, respectively. See the F<ev.h> header file for	3944	definition and a statement, respectively. See the F<ev.h> header file for
2992	their default definitions. One possible use for overriding these is to	3945	their default definitions. One possible use for overriding these is to
2993	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3946	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2994	method calls instead of plain function calls in C++.	3947	method calls instead of plain function calls in C++.
2995		3948
		3949	=back
		3950
2996	=head2 EXPORTED API SYMBOLS	3951	=head2 EXPORTED API SYMBOLS
2997		3952
2998	If you need to re-export the API (e.g. via a dll) and you need a list of	3953	If you need to re-export the API (e.g. via a DLL) and you need a list of
2999	exported symbols, you can use the provided F<Symbol.*> files which list	3954	exported symbols, you can use the provided F<Symbol.*> files which list
3000	all public symbols, one per line:	3955	all public symbols, one per line:
3001		3956
3002	Symbols.ev for libev proper	3957	Symbols.ev for libev proper
3003	Symbols.event for the libevent emulation	3958	Symbols.event for the libevent emulation
3004		3959
3005	This can also be used to rename all public symbols to avoid clashes with	3960	This can also be used to rename all public symbols to avoid clashes with
3006	multiple versions of libev linked together (which is obviously bad in	3961	multiple versions of libev linked together (which is obviously bad in
3007	itself, but sometimes it is inconvinient to avoid this).	3962	itself, but sometimes it is inconvenient to avoid this).
3008		3963
3009	A sed command like this will create wrapper C<#define>'s that you need to	3964	A sed command like this will create wrapper C<#define>'s that you need to
3010	include before including F<ev.h>:	3965	include before including F<ev.h>:
3011		3966
3012	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3967	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3029	file.	3984	file.
3030		3985
3031	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3986	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3032	that everybody includes and which overrides some configure choices:	3987	that everybody includes and which overrides some configure choices:
3033		3988
3034	#define EV_MINIMAL 1	3989	#define EV_MINIMAL 1
3035	#define EV_USE_POLL 0	3990	#define EV_USE_POLL 0
3036	#define EV_MULTIPLICITY 0	3991	#define EV_MULTIPLICITY 0
3037	#define EV_PERIODIC_ENABLE 0	3992	#define EV_PERIODIC_ENABLE 0
3038	#define EV_STAT_ENABLE 0	3993	#define EV_STAT_ENABLE 0
3039	#define EV_FORK_ENABLE 0	3994	#define EV_FORK_ENABLE 0
3040	#define EV_CONFIG_H <config.h>	3995	#define EV_CONFIG_H <config.h>
3041	#define EV_MINPRI 0	3996	#define EV_MINPRI 0
3042	#define EV_MAXPRI 0	3997	#define EV_MAXPRI 0
3043		3998
3044	#include "ev++.h"	3999	#include "ev++.h"
3045		4000
3046	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4001	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3047		4002
3048	#include "ev_cpp.h"	4003	#include "ev_cpp.h"
3049	#include "ev.c"	4004	#include "ev.c"
3050		4005
		4006	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3051		4007
3052	=head1 COMPLEXITIES	4008	=head2 THREADS AND COROUTINES
3053		4009
3054	In this section the complexities of (many of) the algorithms used inside	4010	=head3 THREADS
3055	libev will be explained. For complexity discussions about backends see the
3056	documentation for C<ev_default_init>.
3057		4011
3058	All of the following are about amortised time: If an array needs to be	4012	All libev functions are reentrant and thread-safe unless explicitly
3059	extended, libev needs to realloc and move the whole array, but this	4013	documented otherwise, but libev implements no locking itself. This means
3060	happens asymptotically never with higher number of elements, so O(1) might	4014	that you can use as many loops as you want in parallel, as long as there
3061	mean it might do a lengthy realloc operation in rare cases, but on average	4015	are no concurrent calls into any libev function with the same loop
3062	it is much faster and asymptotically approaches constant time.	4016	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4017	of course): libev guarantees that different event loops share no data
		4018	structures that need any locking.
		4019
		4020	Or to put it differently: calls with different loop parameters can be done
		4021	concurrently from multiple threads, calls with the same loop parameter
		4022	must be done serially (but can be done from different threads, as long as
		4023	only one thread ever is inside a call at any point in time, e.g. by using
		4024	a mutex per loop).
		4025
		4026	Specifically to support threads (and signal handlers), libev implements
		4027	so-called C<ev_async> watchers, which allow some limited form of
		4028	concurrency on the same event loop, namely waking it up "from the
		4029	outside".
		4030
		4031	If you want to know which design (one loop, locking, or multiple loops
		4032	without or something else still) is best for your problem, then I cannot
		4033	help you, but here is some generic advice:
3063		4034
3064	=over 4	4035	=over 4
3065		4036
3066	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4037	=item * most applications have a main thread: use the default libev loop
		4038	in that thread, or create a separate thread running only the default loop.
3067		4039
3068	This means that, when you have a watcher that triggers in one hour and	4040	This helps integrating other libraries or software modules that use libev
3069	there are 100 watchers that would trigger before that then inserting will	4041	themselves and don't care/know about threading.
3070	have to skip roughly seven (C<ld 100>) of these watchers.
3071		4042
3072	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4043	=item * one loop per thread is usually a good model.
3073		4044
3074	That means that changing a timer costs less than removing/adding them	4045	Doing this is almost never wrong, sometimes a better-performance model
3075	as only the relative motion in the event queue has to be paid for.	4046	exists, but it is always a good start.
3076		4047
3077	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4048	=item * other models exist, such as the leader/follower pattern, where one
		4049	loop is handed through multiple threads in a kind of round-robin fashion.
3078		4050
3079	These just add the watcher into an array or at the head of a list.	4051	Choosing a model is hard - look around, learn, know that usually you can do
		4052	better than you currently do :-)
3080		4053
3081	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4054	=item * often you need to talk to some other thread which blocks in the
		4055	event loop.
3082		4056
3083	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4057	C<ev_async> watchers can be used to wake them up from other threads safely
		4058	(or from signal contexts...).
3084		4059
3085	These watchers are stored in lists then need to be walked to find the	4060	An example use would be to communicate signals or other events that only
3086	correct watcher to remove. The lists are usually short (you don't usually	4061	work in the default loop by registering the signal watcher with the
3087	have many watchers waiting for the same fd or signal).	4062	default loop and triggering an C<ev_async> watcher from the default loop
3088		4063	watcher callback into the event loop interested in the signal.
3089	=item Finding the next timer in each loop iteration: O(1)
3090
3091	By virtue of using a binary heap, the next timer is always found at the
3092	beginning of the storage array.
3093
3094	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3095
3096	A change means an I/O watcher gets started or stopped, which requires
3097	libev to recalculate its status (and possibly tell the kernel, depending
3098	on backend and wether C<ev_io_set> was used).
3099
3100	=item Activating one watcher (putting it into the pending state): O(1)
3101
3102	=item Priority handling: O(number_of_priorities)
3103
3104	Priorities are implemented by allocating some space for each
3105	priority. When doing priority-based operations, libev usually has to
3106	linearly search all the priorities, but starting/stopping and activating
3107	watchers becomes O(1) w.r.t. priority handling.
3108
3109	=item Sending an ev_async: O(1)
3110
3111	=item Processing ev_async_send: O(number_of_async_watchers)
3112
3113	=item Processing signals: O(max_signal_number)
3114
3115	Sending involves a syscall I<iff> there were no other C<ev_async_send>
3116	calls in the current loop iteration. Checking for async and signal events
3117	involves iterating over all running async watchers or all signal numbers.
3118		4064
3119	=back	4065	=back
3120		4066
		4067	=head4 THREAD LOCKING EXAMPLE
3121		4068
3122	=head1 Win32 platform limitations and workarounds	4069	Here is a fictitious example of how to run an event loop in a different
		4070	thread than where callbacks are being invoked and watchers are
		4071	created/added/removed.
		4072
		4073	For a real-world example, see the C<EV::Loop::Async> perl module,
		4074	which uses exactly this technique (which is suited for many high-level
		4075	languages).
		4076
		4077	The example uses a pthread mutex to protect the loop data, a condition
		4078	variable to wait for callback invocations, an async watcher to notify the
		4079	event loop thread and an unspecified mechanism to wake up the main thread.
		4080
		4081	First, you need to associate some data with the event loop:
		4082
		4083	typedef struct {
		4084	mutex_t lock; /* global loop lock */
		4085	ev_async async_w;
		4086	thread_t tid;
		4087	cond_t invoke_cv;
		4088	} userdata;
		4089
		4090	void prepare_loop (EV_P)
		4091	{
		4092	// for simplicity, we use a static userdata struct.
		4093	static userdata u;
		4094
		4095	ev_async_init (&u->async_w, async_cb);
		4096	ev_async_start (EV_A_ &u->async_w);
		4097
		4098	pthread_mutex_init (&u->lock, 0);
		4099	pthread_cond_init (&u->invoke_cv, 0);
		4100
		4101	// now associate this with the loop
		4102	ev_set_userdata (EV_A_ u);
		4103	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4104	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4105
		4106	// then create the thread running ev_loop
		4107	pthread_create (&u->tid, 0, l_run, EV_A);
		4108	}
		4109
		4110	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4111	solely to wake up the event loop so it takes notice of any new watchers
		4112	that might have been added:
		4113
		4114	static void
		4115	async_cb (EV_P_ ev_async *w, int revents)
		4116	{
		4117	// just used for the side effects
		4118	}
		4119
		4120	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4121	protecting the loop data, respectively.
		4122
		4123	static void
		4124	l_release (EV_P)
		4125	{
		4126	userdata *u = ev_userdata (EV_A);
		4127	pthread_mutex_unlock (&u->lock);
		4128	}
		4129
		4130	static void
		4131	l_acquire (EV_P)
		4132	{
		4133	userdata *u = ev_userdata (EV_A);
		4134	pthread_mutex_lock (&u->lock);
		4135	}
		4136
		4137	The event loop thread first acquires the mutex, and then jumps straight
		4138	into C<ev_loop>:
		4139
		4140	void *
		4141	l_run (void *thr_arg)
		4142	{
		4143	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4144
		4145	l_acquire (EV_A);
		4146	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4147	ev_loop (EV_A_ 0);
		4148	l_release (EV_A);
		4149
		4150	return 0;
		4151	}
		4152
		4153	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4154	signal the main thread via some unspecified mechanism (signals? pipe
		4155	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4156	have been called (in a while loop because a) spurious wakeups are possible
		4157	and b) skipping inter-thread-communication when there are no pending
		4158	watchers is very beneficial):
		4159
		4160	static void
		4161	l_invoke (EV_P)
		4162	{
		4163	userdata *u = ev_userdata (EV_A);
		4164
		4165	while (ev_pending_count (EV_A))
		4166	{
		4167	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4168	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4169	}
		4170	}
		4171
		4172	Now, whenever the main thread gets told to invoke pending watchers, it
		4173	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4174	thread to continue:
		4175
		4176	static void
		4177	real_invoke_pending (EV_P)
		4178	{
		4179	userdata *u = ev_userdata (EV_A);
		4180
		4181	pthread_mutex_lock (&u->lock);
		4182	ev_invoke_pending (EV_A);
		4183	pthread_cond_signal (&u->invoke_cv);
		4184	pthread_mutex_unlock (&u->lock);
		4185	}
		4186
		4187	Whenever you want to start/stop a watcher or do other modifications to an
		4188	event loop, you will now have to lock:
		4189
		4190	ev_timer timeout_watcher;
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4194
		4195	pthread_mutex_lock (&u->lock);
		4196	ev_timer_start (EV_A_ &timeout_watcher);
		4197	ev_async_send (EV_A_ &u->async_w);
		4198	pthread_mutex_unlock (&u->lock);
		4199
		4200	Note that sending the C<ev_async> watcher is required because otherwise
		4201	an event loop currently blocking in the kernel will have no knowledge
		4202	about the newly added timer. By waking up the loop it will pick up any new
		4203	watchers in the next event loop iteration.
		4204
		4205	=head3 COROUTINES
		4206
		4207	Libev is very accommodating to coroutines ("cooperative threads"):
		4208	libev fully supports nesting calls to its functions from different
		4209	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		4210	different coroutines, and switch freely between both coroutines running
		4211	the loop, as long as you don't confuse yourself). The only exception is
		4212	that you must not do this from C<ev_periodic> reschedule callbacks.
		4213
		4214	Care has been taken to ensure that libev does not keep local state inside
		4215	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4216	they do not call any callbacks.
		4217
		4218	=head2 COMPILER WARNINGS
		4219
		4220	Depending on your compiler and compiler settings, you might get no or a
		4221	lot of warnings when compiling libev code. Some people are apparently
		4222	scared by this.
		4223
		4224	However, these are unavoidable for many reasons. For one, each compiler
		4225	has different warnings, and each user has different tastes regarding
		4226	warning options. "Warn-free" code therefore cannot be a goal except when
		4227	targeting a specific compiler and compiler-version.
		4228
		4229	Another reason is that some compiler warnings require elaborate
		4230	workarounds, or other changes to the code that make it less clear and less
		4231	maintainable.
		4232
		4233	And of course, some compiler warnings are just plain stupid, or simply
		4234	wrong (because they don't actually warn about the condition their message
		4235	seems to warn about). For example, certain older gcc versions had some
		4236	warnings that resulted an extreme number of false positives. These have
		4237	been fixed, but some people still insist on making code warn-free with
		4238	such buggy versions.
		4239
		4240	While libev is written to generate as few warnings as possible,
		4241	"warn-free" code is not a goal, and it is recommended not to build libev
		4242	with any compiler warnings enabled unless you are prepared to cope with
		4243	them (e.g. by ignoring them). Remember that warnings are just that:
		4244	warnings, not errors, or proof of bugs.
		4245
		4246
		4247	=head2 VALGRIND
		4248
		4249	Valgrind has a special section here because it is a popular tool that is
		4250	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		4251
		4252	If you think you found a bug (memory leak, uninitialised data access etc.)
		4253	in libev, then check twice: If valgrind reports something like:
		4254
		4255	==2274== definitely lost: 0 bytes in 0 blocks.
		4256	==2274== possibly lost: 0 bytes in 0 blocks.
		4257	==2274== still reachable: 256 bytes in 1 blocks.
		4258
		4259	Then there is no memory leak, just as memory accounted to global variables
		4260	is not a memleak - the memory is still being referenced, and didn't leak.
		4261
		4262	Similarly, under some circumstances, valgrind might report kernel bugs
		4263	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4264	although an acceptable workaround has been found here), or it might be
		4265	confused.
		4266
		4267	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		4268	make it into some kind of religion.
		4269
		4270	If you are unsure about something, feel free to contact the mailing list
		4271	with the full valgrind report and an explanation on why you think this
		4272	is a bug in libev (best check the archives, too :). However, don't be
		4273	annoyed when you get a brisk "this is no bug" answer and take the chance
		4274	of learning how to interpret valgrind properly.
		4275
		4276	If you need, for some reason, empty reports from valgrind for your project
		4277	I suggest using suppression lists.
		4278
		4279
		4280	=head1 PORTABILITY NOTES
		4281
		4282	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3123		4283
3124	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4284	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3125	requires, and its I/O model is fundamentally incompatible with the POSIX	4285	requires, and its I/O model is fundamentally incompatible with the POSIX
3126	model. Libev still offers limited functionality on this platform in	4286	model. Libev still offers limited functionality on this platform in
3127	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4287	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3128	descriptors. This only applies when using Win32 natively, not when using	4288	descriptors. This only applies when using Win32 natively, not when using
3129	e.g. cygwin.	4289	e.g. cygwin.
3130		4290
		4291	Lifting these limitations would basically require the full
		4292	re-implementation of the I/O system. If you are into these kinds of
		4293	things, then note that glib does exactly that for you in a very portable
		4294	way (note also that glib is the slowest event library known to man).
		4295
3131	There is no supported compilation method available on windows except	4296	There is no supported compilation method available on windows except
3132	embedding it into other applications.	4297	embedding it into other applications.
3133		4298
		4299	Sensible signal handling is officially unsupported by Microsoft - libev
		4300	tries its best, but under most conditions, signals will simply not work.
		4301
		4302	Not a libev limitation but worth mentioning: windows apparently doesn't
		4303	accept large writes: instead of resulting in a partial write, windows will
		4304	either accept everything or return C<ENOBUFS> if the buffer is too large,
		4305	so make sure you only write small amounts into your sockets (less than a
		4306	megabyte seems safe, but this apparently depends on the amount of memory
		4307	available).
		4308
3134	Due to the many, low, and arbitrary limits on the win32 platform and the	4309	Due to the many, low, and arbitrary limits on the win32 platform and
3135	abysmal performance of winsockets, using a large number of sockets is not	4310	the abysmal performance of winsockets, using a large number of sockets
3136	recommended (and not reasonable). If your program needs to use more than	4311	is not recommended (and not reasonable). If your program needs to use
3137	a hundred or so sockets, then likely it needs to use a totally different	4312	more than a hundred or so sockets, then likely it needs to use a totally
3138	implementation for windows, as libev offers the POSIX model, which cannot	4313	different implementation for windows, as libev offers the POSIX readiness
3139	be implemented efficiently on windows (microsoft monopoly games).	4314	notification model, which cannot be implemented efficiently on windows
		4315	(due to Microsoft monopoly games).
		4316
		4317	A typical way to use libev under windows is to embed it (see the embedding
		4318	section for details) and use the following F<evwrap.h> header file instead
		4319	of F<ev.h>:
		4320
		4321	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4322	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4323
		4324	#include "ev.h"
		4325
		4326	And compile the following F<evwrap.c> file into your project (make sure
		4327	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4328
		4329	#include "evwrap.h"
		4330	#include "ev.c"
3140		4331
3141	=over 4	4332	=over 4
3142		4333
3143	=item The winsocket select function	4334	=item The winsocket select function
3144		4335
3145	The winsocket C<select> function doesn't follow POSIX in that it requires	4336	The winsocket C<select> function doesn't follow POSIX in that it
3146	socket I<handles> and not socket I<file descriptors>. This makes select	4337	requires socket I<handles> and not socket I<file descriptors> (it is
3147	very inefficient, and also requires a mapping from file descriptors	4338	also extremely buggy). This makes select very inefficient, and also
3148	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,	4339	requires a mapping from file descriptors to socket handles (the Microsoft
3149	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor	4340	C runtime provides the function C<_open_osfhandle> for this). See the
3150	symbols for more info.	4341	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		4342	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3151		4343
3152	The configuration for a "naked" win32 using the microsoft runtime	4344	The configuration for a "naked" win32 using the Microsoft runtime
3153	libraries and raw winsocket select is:	4345	libraries and raw winsocket select is:
3154		4346
3155	#define EV_USE_SELECT 1	4347	#define EV_USE_SELECT 1
3156	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4348	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3157		4349
3158	Note that winsockets handling of fd sets is O(n), so you can easily get a	4350	Note that winsockets handling of fd sets is O(n), so you can easily get a
3159	complexity in the O(n²) range when using win32.	4351	complexity in the O(n²) range when using win32.
3160		4352
3161	=item Limited number of file descriptors	4353	=item Limited number of file descriptors
3162		4354
3163	Windows has numerous arbitrary (and low) limits on things. Early versions	4355	Windows has numerous arbitrary (and low) limits on things.
3164	of winsocket's select only supported waiting for a max. of C<64> handles	4356
		4357	Early versions of winsocket's select only supported waiting for a maximum
3165	(probably owning to the fact that all windows kernels can only wait for	4358	of C<64> handles (probably owning to the fact that all windows kernels
3166	C<64> things at the same time internally; microsoft recommends spawning a	4359	can only wait for C<64> things at the same time internally; Microsoft
3167	chain of threads and wait for 63 handles and the previous thread in each).	4360	recommends spawning a chain of threads and wait for 63 handles and the
		4361	previous thread in each. Sounds great!).
3168		4362
3169	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4363	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3170	to some high number (e.g. C<2048>) before compiling the winsocket select	4364	to some high number (e.g. C<2048>) before compiling the winsocket select
3171	call (which might be in libev or elsewhere, for example, perl does its own	4365	call (which might be in libev or elsewhere, for example, perl and many
3172	select emulation on windows).	4366	other interpreters do their own select emulation on windows).
3173		4367
3174	Another limit is the number of file descriptors in the microsoft runtime	4368	Another limit is the number of file descriptors in the Microsoft runtime
3175	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4369	libraries, which by default is C<64> (there must be a hidden I<64>
3176	or something like this inside microsoft). You can increase this by calling	4370	fetish or something like this inside Microsoft). You can increase this
3177	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4371	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3178	arbitrary limit), but is broken in many versions of the microsoft runtime	4372	(another arbitrary limit), but is broken in many versions of the Microsoft
3179	libraries.
3180
3181	This might get you to about C<512> or C<2048> sockets (depending on	4373	runtime libraries. This might get you to about C<512> or C<2048> sockets
3182	windows version and/or the phase of the moon). To get more, you need to	4374	(depending on windows version and/or the phase of the moon). To get more,
3183	wrap all I/O functions and provide your own fd management, but the cost of	4375	you need to wrap all I/O functions and provide your own fd management, but
3184	calling select (O(n²)) will likely make this unworkable.	4376	the cost of calling select (O(n²)) will likely make this unworkable.
3185		4377
3186	=back	4378	=back
3187		4379
		4380	=head2 PORTABILITY REQUIREMENTS
		4381
		4382	In addition to a working ISO-C implementation and of course the
		4383	backend-specific APIs, libev relies on a few additional extensions:
		4384
		4385	=over 4
		4386
		4387	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4388	calling conventions regardless of C<ev_watcher_type *>.
		4389
		4390	Libev assumes not only that all watcher pointers have the same internal
		4391	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4392	assumes that the same (machine) code can be used to call any watcher
		4393	callback: The watcher callbacks have different type signatures, but libev
		4394	calls them using an C<ev_watcher *> internally.
		4395
		4396	=item C<sig_atomic_t volatile> must be thread-atomic as well
		4397
		4398	The type C<sig_atomic_t volatile> (or whatever is defined as
		4399	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		4400	threads. This is not part of the specification for C<sig_atomic_t>, but is
		4401	believed to be sufficiently portable.
		4402
		4403	=item C<sigprocmask> must work in a threaded environment
		4404
		4405	Libev uses C<sigprocmask> to temporarily block signals. This is not
		4406	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		4407	pthread implementations will either allow C<sigprocmask> in the "main
		4408	thread" or will block signals process-wide, both behaviours would
		4409	be compatible with libev. Interaction between C<sigprocmask> and
		4410	C<pthread_sigmask> could complicate things, however.
		4411
		4412	The most portable way to handle signals is to block signals in all threads
		4413	except the initial one, and run the default loop in the initial thread as
		4414	well.
		4415
		4416	=item C<long> must be large enough for common memory allocation sizes
		4417
		4418	To improve portability and simplify its API, libev uses C<long> internally
		4419	instead of C<size_t> when allocating its data structures. On non-POSIX
		4420	systems (Microsoft...) this might be unexpectedly low, but is still at
		4421	least 31 bits everywhere, which is enough for hundreds of millions of
		4422	watchers.
		4423
		4424	=item C<double> must hold a time value in seconds with enough accuracy
		4425
		4426	The type C<double> is used to represent timestamps. It is required to
		4427	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4428	enough for at least into the year 4000. This requirement is fulfilled by
		4429	implementations implementing IEEE 754, which is basically all existing
		4430	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4431	2200.
		4432
		4433	=back
		4434
		4435	If you know of other additional requirements drop me a note.
		4436
		4437
		4438	=head1 ALGORITHMIC COMPLEXITIES
		4439
		4440	In this section the complexities of (many of) the algorithms used inside
		4441	libev will be documented. For complexity discussions about backends see
		4442	the documentation for C<ev_default_init>.
		4443
		4444	All of the following are about amortised time: If an array needs to be
		4445	extended, libev needs to realloc and move the whole array, but this
		4446	happens asymptotically rarer with higher number of elements, so O(1) might
		4447	mean that libev does a lengthy realloc operation in rare cases, but on
		4448	average it is much faster and asymptotically approaches constant time.
		4449
		4450	=over 4
		4451
		4452	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4453
		4454	This means that, when you have a watcher that triggers in one hour and
		4455	there are 100 watchers that would trigger before that, then inserting will
		4456	have to skip roughly seven (C<ld 100>) of these watchers.
		4457
		4458	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4459
		4460	That means that changing a timer costs less than removing/adding them,
		4461	as only the relative motion in the event queue has to be paid for.
		4462
		4463	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4464
		4465	These just add the watcher into an array or at the head of a list.
		4466
		4467	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4468
		4469	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4470
		4471	These watchers are stored in lists, so they need to be walked to find the
		4472	correct watcher to remove. The lists are usually short (you don't usually
		4473	have many watchers waiting for the same fd or signal: one is typical, two
		4474	is rare).
		4475
		4476	=item Finding the next timer in each loop iteration: O(1)
		4477
		4478	By virtue of using a binary or 4-heap, the next timer is always found at a
		4479	fixed position in the storage array.
		4480
		4481	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4482
		4483	A change means an I/O watcher gets started or stopped, which requires
		4484	libev to recalculate its status (and possibly tell the kernel, depending
		4485	on backend and whether C<ev_io_set> was used).
		4486
		4487	=item Activating one watcher (putting it into the pending state): O(1)
		4488
		4489	=item Priority handling: O(number_of_priorities)
		4490
		4491	Priorities are implemented by allocating some space for each
		4492	priority. When doing priority-based operations, libev usually has to
		4493	linearly search all the priorities, but starting/stopping and activating
		4494	watchers becomes O(1) with respect to priority handling.
		4495
		4496	=item Sending an ev_async: O(1)
		4497
		4498	=item Processing ev_async_send: O(number_of_async_watchers)
		4499
		4500	=item Processing signals: O(max_signal_number)
		4501
		4502	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4503	calls in the current loop iteration. Checking for async and signal events
		4504	involves iterating over all running async watchers or all signal numbers.
		4505
		4506	=back
		4507
		4508
		4509	=head1 GLOSSARY
		4510
		4511	=over 4
		4512
		4513	=item active
		4514
		4515	A watcher is active as long as it has been started (has been attached to
		4516	an event loop) but not yet stopped (disassociated from the event loop).
		4517
		4518	=item application
		4519
		4520	In this document, an application is whatever is using libev.
		4521
		4522	=item callback
		4523
		4524	The address of a function that is called when some event has been
		4525	detected. Callbacks are being passed the event loop, the watcher that
		4526	received the event, and the actual event bitset.
		4527
		4528	=item callback invocation
		4529
		4530	The act of calling the callback associated with a watcher.
		4531
		4532	=item event
		4533
		4534	A change of state of some external event, such as data now being available
		4535	for reading on a file descriptor, time having passed or simply not having
		4536	any other events happening anymore.
		4537
		4538	In libev, events are represented as single bits (such as C<EV_READ> or
		4539	C<EV_TIMEOUT>).
		4540
		4541	=item event library
		4542
		4543	A software package implementing an event model and loop.
		4544
		4545	=item event loop
		4546
		4547	An entity that handles and processes external events and converts them
		4548	into callback invocations.
		4549
		4550	=item event model
		4551
		4552	The model used to describe how an event loop handles and processes
		4553	watchers and events.
		4554
		4555	=item pending
		4556
		4557	A watcher is pending as soon as the corresponding event has been detected,
		4558	and stops being pending as soon as the watcher will be invoked or its
		4559	pending status is explicitly cleared by the application.
		4560
		4561	A watcher can be pending, but not active. Stopping a watcher also clears
		4562	its pending status.
		4563
		4564	=item real time
		4565
		4566	The physical time that is observed. It is apparently strictly monotonic :)
		4567
		4568	=item wall-clock time
		4569
		4570	The time and date as shown on clocks. Unlike real time, it can actually
		4571	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4572	clock.
		4573
		4574	=item watcher
		4575
		4576	A data structure that describes interest in certain events. Watchers need
		4577	to be started (attached to an event loop) before they can receive events.
		4578
		4579	=item watcher invocation
		4580
		4581	The act of calling the callback associated with a watcher.
		4582
		4583	=back
3188		4584
3189	=head1 AUTHOR	4585	=head1 AUTHOR
3190		4586
3191	Marc Lehmann <libev@schmorp.de>.	4587	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3192		4588

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