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Revision 1.141 by root, Wed Apr 2 19:19:33 2008 UTC vs.
Revision 1.233 by root, Thu Apr 16 07:32:51 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 DESCRIPTION
66		68
67	The newest version of this document is also available as an html-formatted	69	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	70	web page you might find easier to navigate when reading it for the first
69	time: L<http://cvs.schmorp.de/libev/ev.html>.	71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
70		72
71	Libev is an event loop: you register interest in certain events (such as a	73	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	74	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	75	these event sources and provide your program with events.
74		76
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	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	109	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	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	116	(fractional) number of seconds since the (POSIX) epoch (somewhere near
115	the beginning of 1970, details are complicated, don't ask). This type is	117	the beginning of 1970, details are complicated, don't ask). This type is
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	118	called C<ev_tstamp>, which is what you should use too. It usually aliases
117	to the C<double> type in C, and when you need to do any calculations on	119	to the C<double> type in C, and when you need to do any calculations on
118	it, you should treat it as some floatingpoint value. Unlike the name	120	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	121	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	122	throughout libev.
		123
		124	=head1 ERROR HANDLING
		125
		126	Libev knows three classes of errors: operating system errors, usage errors
		127	and internal errors (bugs).
		128
		129	When libev catches an operating system error it cannot handle (for example
		130	a system call indicating a condition libev cannot fix), it calls the callback
		131	set via C<ev_set_syserr_cb>, which is supposed to fix the problem or
		132	abort. The default is to print a diagnostic message and to call C<abort
		133	()>.
		134
		135	When libev detects a usage error such as a negative timer interval, then
		136	it will print a diagnostic message and abort (via the C<assert> mechanism,
		137	so C<NDEBUG> will disable this checking): these are programming errors in
		138	the libev caller and need to be fixed there.
		139
		140	Libev also has a few internal error-checking C<assert>ions, and also has
		141	extensive consistency checking code. These do not trigger under normal
		142	circumstances, as they indicate either a bug in libev or worse.
		143
121		144
122	=head1 GLOBAL FUNCTIONS	145	=head1 GLOBAL FUNCTIONS
123		146
124	These functions can be called anytime, even before initialising the	147	These functions can be called anytime, even before initialising the
125	library in any way.	148	library in any way.
…		…
134		157
135	=item ev_sleep (ev_tstamp interval)	158	=item ev_sleep (ev_tstamp interval)
136		159
137	Sleep for the given interval: The current thread will be blocked until	160	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	161	either it is interrupted or the given time interval has passed. Basically
139	this is a subsecond-resolution C<sleep ()>.	162	this is a sub-second-resolution C<sleep ()>.
140		163
141	=item int ev_version_major ()	164	=item int ev_version_major ()
142		165
143	=item int ev_version_minor ()	166	=item int ev_version_minor ()
144		167
…		…
157	not a problem.	180	not a problem.
158		181
159	Example: Make sure we haven't accidentally been linked against the wrong	182	Example: Make sure we haven't accidentally been linked against the wrong
160	version.	183	version.
161		184
162	assert (("libev version mismatch",	185	assert (("libev version mismatch",
163	ev_version_major () == EV_VERSION_MAJOR	186	ev_version_major () == EV_VERSION_MAJOR
164	&& ev_version_minor () >= EV_VERSION_MINOR));	187	&& ev_version_minor () >= EV_VERSION_MINOR));
165		188
166	=item unsigned int ev_supported_backends ()	189	=item unsigned int ev_supported_backends ()
167		190
168	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>	191	Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*>
169	value) compiled into this binary of libev (independent of their	192	value) compiled into this binary of libev (independent of their
…		…
171	a description of the set values.	194	a description of the set values.
172		195
173	Example: make sure we have the epoll method, because yeah this is cool and	196	Example: make sure we have the epoll method, because yeah this is cool and
174	a must have and can we have a torrent of it please!!!11	197	a must have and can we have a torrent of it please!!!11
175		198
176	assert (("sorry, no epoll, no sex",	199	assert (("sorry, no epoll, no sex",
177	ev_supported_backends () & EVBACKEND_EPOLL));	200	ev_supported_backends () & EVBACKEND_EPOLL));
178		201
179	=item unsigned int ev_recommended_backends ()	202	=item unsigned int ev_recommended_backends ()
180		203
181	Return the set of all backends compiled into this binary of libev and also	204	Return the set of all backends compiled into this binary of libev and also
182	recommended for this platform. This set is often smaller than the one	205	recommended for this platform. This set is often smaller than the one
183	returned by C<ev_supported_backends>, as for example kqueue is broken on	206	returned by C<ev_supported_backends>, as for example kqueue is broken on
184	most BSDs and will not be autodetected unless you explicitly request it	207	most BSDs and will not be auto-detected unless you explicitly request it
185	(assuming you know what you are doing). This is the set of backends that	208	(assuming you know what you are doing). This is the set of backends that
186	libev will probe for if you specify no backends explicitly.	209	libev will probe for if you specify no backends explicitly.
187		210
188	=item unsigned int ev_embeddable_backends ()	211	=item unsigned int ev_embeddable_backends ()
189		212
…		…
193	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
194	recommended ones.	217	recommended ones.
195		218
196	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
197		220
198	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
199		222
200	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
201	semantics is identical - to the realloc C function). It is used to	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
202	allocate and free memory (no surprises here). If it returns zero when	225	used to allocate and free memory (no surprises here). If it returns zero
203	memory needs to be allocated, the library might abort or take some	226	when memory needs to be allocated (C<size != 0>), the library might abort
204	potentially destructive action. The default is your system realloc	227	or take some potentially destructive action.
205	function.	228
		229	Since some systems (at least OpenBSD and Darwin) fail to implement
		230	correct C<realloc> semantics, libev will use a wrapper around the system
		231	C<realloc> and C<free> functions by default.
206		232
207	You could override this function in high-availability programs to, say,	233	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,	234	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.	235	or even to sleep a while and retry until some memory is available.
210		236
211	Example: Replace the libev allocator with one that waits a bit and then	237	Example: Replace the libev allocator with one that waits a bit and then
212	retries).	238	retries (example requires a standards-compliant C<realloc>).
213		239
214	static void *	240	static void *
215	persistent_realloc (void *ptr, size_t size)	241	persistent_realloc (void *ptr, size_t size)
216	{	242	{
217	for (;;)	243	for (;;)
…		…
226	}	252	}
227		253
228	...	254	...
229	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
230		256
231	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
232		258
233	Set the callback function to call on a retryable syscall error (such	259	Set the callback function to call on a retryable system call error (such
234	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
235	indicating the system call or subsystem causing the problem. If this	261	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	262	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	263	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	264	requested operation, or, if the condition doesn't go away, do bad stuff
239	(such as abort).	265	(such as abort).
240		266
241	Example: This is basically the same thing that libev does internally, too.	267	Example: This is basically the same thing that libev does internally, too.
…		…
252		278
253	=back	279	=back
254		280
255	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
256		282
257	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
258	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
259	events, and dynamically created loops which do not.	285	I<function>).
260		286
261	If you use threads, a common model is to run the default event loop	287	The library knows two types of such loops, the I<default> loop, which
262	in your main thread (or in a separate thread) and for each thread you	288	supports signals and child events, and dynamically created loops which do
263	create, you also create another event loop. Libev itself does no locking	289	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		290
268	=over 4	291	=over 4
269		292
270	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
271		294
…		…
277	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
278	function.	301	function.
279		302
280	Note that this function is I<not> thread-safe, so if you want to use it	303	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,	304	from multiple threads, you have to lock (note also that this is unlikely,
282	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
283		306
284	The default loop is the only loop that can handle C<ev_signal> and	307	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	308	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	309	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	310	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	311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
289	C<ev_default_init>.	312	C<ev_default_init>.
290		313
291	The flags argument can be used to specify special behaviour or specific	314	The flags argument can be used to specify special behaviour or specific
…		…
300	The default flags value. Use this if you have no clue (it's the right	323	The default flags value. Use this if you have no clue (it's the right
301	thing, believe me).	324	thing, believe me).
302		325
303	=item C<EVFLAG_NOENV>	326	=item C<EVFLAG_NOENV>
304		327
305	If this flag bit is ored into the flag value (or the program runs setuid	328	If this flag bit is or'ed into the flag value (or the program runs setuid
306	or setgid) then libev will I<not> look at the environment variable	329	or setgid) then libev will I<not> look at the environment variable
307	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
308	override the flags completely if it is found in the environment. This is	331	override the flags completely if it is found in the environment. This is
309	useful to try out specific backends to test their performance, or to work	332	useful to try out specific backends to test their performance, or to work
310	around bugs.	333	around bugs.
…		…
317		340
318	This works by calling C<getpid ()> on every iteration of the loop,	341	This works by calling C<getpid ()> on every iteration of the loop,
319	and thus this might slow down your event loop if you do a lot of loop	342	and thus this might slow down your event loop if you do a lot of loop
320	iterations and little real work, but is usually not noticeable (on my	343	iterations and little real work, but is usually not noticeable (on my
321	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
322	without a syscall and thus I<very> fast, but my GNU/Linux system also has	345	without a system call and thus I<very> fast, but my GNU/Linux system also has
323	C<pthread_atfork> which is even faster).	346	C<pthread_atfork> which is even faster).
324		347
325	The big advantage of this flag is that you can forget about fork (and	348	The big advantage of this flag is that you can forget about fork (and
326	forget about forgetting to tell libev about forking) when you use this	349	forget about forgetting to tell libev about forking) when you use this
327	flag.	350	flag.
328		351
329	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>	352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
330	environment variable.	353	environment variable.
331		354
332	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
333		356
334	This is your standard select(2) backend. Not I<completely> standard, as	357	This is your standard select(2) backend. Not I<completely> standard, as
…		…
336	but if that fails, expect a fairly low limit on the number of fds when	359	but if that fails, expect a fairly low limit on the number of fds when
337	using this backend. It doesn't scale too well (O(highest_fd)), but its	360	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.	361	usually the fastest backend for a low number of (low-numbered :) fds.
339		362
340	To get good performance out of this backend you need a high amount of	363	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	364	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	365	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	366	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	367	a look at C<ev_set_io_collect_interval ()> to increase the amount of
345	readyness notifications you get per iteration.	368	readiness notifications you get per iteration.
		369
		370	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		371	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		372	C<exceptfds> set on that platform).
346		373
347	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	374	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
348		375
349	And this is your standard poll(2) backend. It's more complicated	376	And this is your standard poll(2) backend. It's more complicated
350	than select, but handles sparse fds better and has no artificial	377	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	378	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,	379	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	380	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
354	performance tips.	381	performance tips.
355		382
		383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		385
356	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
357		387
358	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
359	but it scales phenomenally better. While poll and select usually scale	389	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),	390	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	391	epoll scales either O(1) or O(active_fds).
362	of shortcomings, such as silently dropping events in some hard-to-detect	392
363	cases and requiring a syscall per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
364	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
365		409
366	While stopping, setting and starting an I/O watcher in the same iteration	410	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	411	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	412	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	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
370	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
371		415	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		416
376	Best performance from this backend is achieved by not unregistering all	417	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.	418	watchers for a file descriptor until it has been closed, if possible,
378	keep at least one watcher active per fd at all times.	419	i.e. keep at least one watcher active per fd at all times. Stopping and
		420	starting a watcher (without re-setting it) also usually doesn't cause
		421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
379		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
		428
380	While nominally embeddeble in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
381	all kernel versions tested so far.	430	all kernel versions tested so far.
		431
		432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		433	C<EVBACKEND_POLL>.
382		434
383	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
384		436
385	Kqueue deserves special mention, as at the time of this writing, it	437	Kqueue deserves special mention, as at the time of this writing, it
386	was broken on all BSDs except NetBSD (usually it doesn't work reliably	438	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	439	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"	440	it's completely useless). Unlike epoll, however, whose brokenness
		441	is by design, these kqueue bugs can (and eventually will) be fixed
		442	without API changes to existing programs. For this reason it's not being
389	unless you explicitly specify it explicitly in the flags (i.e. using	443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
390	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
391	system like NetBSD.	445	system like NetBSD.
392		446
393	You still can embed kqueue into a normal poll or select backend and use it	447	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	448	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.	449	the target platform). See C<ev_embed> watchers for more info.
396		450
397	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
398	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
399	course). While stopping, setting and starting an I/O watcher does never	453	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	454	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	455	two event changes per incident. Support for C<fork ()> is very bad (but
402	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
403		458
404	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
405		460
406	While nominally embeddable in other event loops, this doesn't work	461	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	462	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	463	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	464	(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	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
411	sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
		467
		468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		470	C<NOTE_EOF>.
412		471
413	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	472	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
414		473
415	This is not implemented yet (and might never be, unless you send me an	474	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	475	implementation). According to reports, C</dev/poll> only supports sockets
…		…
420	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
421		480
422	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	481	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)).	482	it's really slow, but it still scales very well (O(active_fds)).
424		483
425	Please note that solaris event ports can deliver a lot of spurious	484	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	485	notifications, so you need to use non-blocking I/O or other means to avoid
427	blocking when no data (or space) is available.	486	blocking when no data (or space) is available.
428		487
429	While this backend scales well, it requires one system call per active	488	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	489	file descriptor per loop iteration. For small and medium numbers of file
431	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
432	might perform better.	491	might perform better.
433		492
434	On the positive side, ignoring the spurious readyness notifications, this	493	On the positive side, with the exception of the spurious readiness
435	backend actually performed to specification in all tests and is fully	494	notifications, this backend actually performed fully to specification
436	embeddable, which is a rare feat among the OS-specific backends.	495	in all tests and is fully embeddable, which is a rare feat among the
		496	OS-specific backends (I vastly prefer correctness over speed hacks).
		497
		498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		499	C<EVBACKEND_POLL>.
437		500
438	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
439		502
440	Try all backends (even potentially broken ones that wouldn't be tried	503	Try all backends (even potentially broken ones that wouldn't be tried
441	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
443		506
444	It is definitely not recommended to use this flag.	507	It is definitely not recommended to use this flag.
445		508
446	=back	509	=back
447		510
448	If one or more of these are ored into the flags value, then only these	511	If one or more of these are or'ed into the flags value, then only these
449	backends will be tried (in the reverse order as listed here). If none are	512	backends will be tried (in the reverse order as listed here). If none are
450	specified, all backends in C<ev_recommended_backends ()> will be tried.	513	specified, all backends in C<ev_recommended_backends ()> will be tried.
451		514
452	The most typical usage is like this:	515	Example: This is the most typical usage.
453		516
454	if (!ev_default_loop (0))	517	if (!ev_default_loop (0))
455	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
456		519
457	Restrict libev to the select and poll backends, and do not allow	520	Example: Restrict libev to the select and poll backends, and do not allow
458	environment settings to be taken into account:	521	environment settings to be taken into account:
459		522
460	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
461		524
462	Use whatever libev has to offer, but make sure that kqueue is used if	525	Example: Use whatever libev has to offer, but make sure that kqueue is
463	available (warning, breaks stuff, best use only with your own private	526	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):	527	private event loop and only if you know the OS supports your types of
		528	fds):
465		529
466	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
467		531
468	=item struct ev_loop *ev_loop_new (unsigned int flags)	532	=item struct ev_loop *ev_loop_new (unsigned int flags)
469		533
470	Similar to C<ev_default_loop>, but always creates a new event loop that is	534	Similar to C<ev_default_loop>, but always creates a new event loop that is
471	always distinct from the default loop. Unlike the default loop, it cannot	535	always distinct from the default loop. Unlike the default loop, it cannot
…		…
476	libev with threads is indeed to create one loop per thread, and using the	540	libev with threads is indeed to create one loop per thread, and using the
477	default loop in the "main" or "initial" thread.	541	default loop in the "main" or "initial" thread.
478		542
479	Example: Try to create a event loop that uses epoll and nothing else.	543	Example: Try to create a event loop that uses epoll and nothing else.
480		544
481	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
482	if (!epoller)	546	if (!epoller)
483	fatal ("no epoll found here, maybe it hides under your chair");	547	fatal ("no epoll found here, maybe it hides under your chair");
484		548
485	=item ev_default_destroy ()	549	=item ev_default_destroy ()
486		550
487	Destroys the default loop again (frees all memory and kernel state	551	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	552	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	553	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>	554	responsibility to either stop all watchers cleanly yourself I<before>
491	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
492	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
493	for example).	557	for example).
494		558
495	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
496	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
497	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
498		562
499	In general it is not advisable to call this function except in the	563	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	564	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	565	pipe fds. If you need dynamically allocated loops it is better to use
502	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
527		591
528	=item ev_loop_fork (loop)	592	=item ev_loop_fork (loop)
529		593
530	Like C<ev_default_fork>, but acts on an event loop created by	594	Like C<ev_default_fork>, but acts on an event loop created by
531	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
532	after fork, and how you do this is entirely your own problem.	596	after fork that you want to re-use in the child, and how you do this is
		597	entirely your own problem.
533		598
534	=item int ev_is_default_loop (loop)	599	=item int ev_is_default_loop (loop)
535		600
536	Returns true when the given loop actually is the default loop, false otherwise.	601	Returns true when the given loop is, in fact, the default loop, and false
		602	otherwise.
537		603
538	=item unsigned int ev_loop_count (loop)	604	=item unsigned int ev_loop_count (loop)
539		605
540	Returns the count of loop iterations for the loop, which is identical to	606	Returns the count of loop iterations for the loop, which is identical to
541	the number of times libev did poll for new events. It starts at C<0> and	607	the number of times libev did poll for new events. It starts at C<0> and
…		…
556	received events and started processing them. This timestamp does not	622	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	623	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	624	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).	625	event occurring (or more correctly, libev finding out about it).
560		626
		627	=item ev_now_update (loop)
		628
		629	Establishes the current time by querying the kernel, updating the time
		630	returned by C<ev_now ()> in the progress. This is a costly operation and
		631	is usually done automatically within C<ev_loop ()>.
		632
		633	This function is rarely useful, but when some event callback runs for a
		634	very long time without entering the event loop, updating libev's idea of
		635	the current time is a good idea.
		636
		637	See also "The special problem of time updates" in the C<ev_timer> section.
		638
		639	=item ev_suspend (loop)
		640
		641	=item ev_resume (loop)
		642
		643	These two functions suspend and resume a loop, for use when the loop is
		644	not used for a while and timeouts should not be processed.
		645
		646	A typical use case would be an interactive program such as a game: When
		647	the user presses C<^Z> to suspend the game and resumes it an hour later it
		648	would be best to handle timeouts as if no time had actually passed while
		649	the program was suspended. This can be achieved by calling C<ev_suspend>
		650	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		651	C<ev_resume> directly afterwards to resume timer processing.
		652
		653	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		655	will be rescheduled (that is, they will lose any events that would have
		656	occured while suspended).
		657
		658	After calling C<ev_suspend> you B<must not> call I<any> function on the
		659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		660	without a previous call to C<ev_suspend>.
		661
		662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		663	event loop time (see C<ev_now_update>).
		664
561	=item ev_loop (loop, int flags)	665	=item ev_loop (loop, int flags)
562		666
563	Finally, this is it, the event handler. This function usually is called	667	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	668	after you initialised all your watchers and you want to start handling
565	events.	669	events.
…		…
567	If the flags argument is specified as C<0>, it will not return until	671	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.	672	either no event watchers are active anymore or C<ev_unloop> was called.
569		673
570	Please note that an explicit C<ev_unloop> is usually better than	674	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	675	relying on all watchers to be stopped when deciding when a program has
572	finished (especially in interactive programs), but having a program that	676	finished (especially in interactive programs), but having a program
573	automatically loops as long as it has to and no longer by virtue of	677	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.	678	of relying on its watchers stopping correctly, that is truly a thing of
		679	beauty.
575		680
576	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	681	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	682	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.	683	process in case there are no events and will return after one iteration of
		684	the loop.
579		685
580	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	686	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	687	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	688	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	689	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	690	user-registered callback will be called), and will return after one
		691	iteration of the loop.
		692
		693	This is useful if you are waiting for some external event in conjunction
		694	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	695	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.	696	usually a better approach for this kind of thing.
587		697
588	Here are the gory details of what C<ev_loop> does:	698	Here are the gory details of what C<ev_loop> does:
589		699
590	- Before the first iteration, call any pending watchers.	700	- Before the first iteration, call any pending watchers.
591	* If EVFLAG_FORKCHECK was used, check for a fork.	701	* If EVFLAG_FORKCHECK was used, check for a fork.
592	- If a fork was detected, queue and call all fork watchers.	702	- If a fork was detected (by any means), queue and call all fork watchers.
593	- Queue and call all prepare watchers.	703	- Queue and call all prepare watchers.
594	- If we have been forked, recreate the kernel state.	704	- If we have been forked, detach and recreate the kernel state
		705	as to not disturb the other process.
595	- Update the kernel state with all outstanding changes.	706	- Update the kernel state with all outstanding changes.
596	- Update the "event loop time".	707	- Update the "event loop time" (ev_now ()).
597	- Calculate for how long to sleep or block, if at all	708	- Calculate for how long to sleep or block, if at all
598	(active idle watchers, EVLOOP_NONBLOCK or not having	709	(active idle watchers, EVLOOP_NONBLOCK or not having
599	any active watchers at all will result in not sleeping).	710	any active watchers at all will result in not sleeping).
600	- Sleep if the I/O and timer collect interval say so.	711	- Sleep if the I/O and timer collect interval say so.
601	- Block the process, waiting for any events.	712	- Block the process, waiting for any events.
602	- Queue all outstanding I/O (fd) events.	713	- Queue all outstanding I/O (fd) events.
603	- Update the "event loop time" and do time jump handling.	714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
604	- Queue all outstanding timers.	715	- Queue all expired timers.
605	- Queue all outstanding periodics.	716	- Queue all expired periodics.
606	- If no events are pending now, queue all idle watchers.	717	- Unless any events are pending now, queue all idle watchers.
607	- Queue all check watchers.	718	- Queue all check watchers.
608	- Call all queued watchers in reverse order (i.e. check watchers first).	719	- 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	720	Signals and child watchers are implemented as I/O watchers, and will
610	be handled here by queueing them when their watcher gets executed.	721	be handled here by queueing them when their watcher gets executed.
611	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
616	anymore.	727	anymore.
617		728
618	... queue jobs here, make sure they register event watchers as long	729	... 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..)	730	... as they still have work to do (even an idle watcher will do..)
620	ev_loop (my_loop, 0);	731	ev_loop (my_loop, 0);
621	... jobs done. yeah!	732	... jobs done or somebody called unloop. yeah!
622		733
623	=item ev_unloop (loop, how)	734	=item ev_unloop (loop, how)
624		735
625	Can be used to make a call to C<ev_loop> return early (but only after it	736	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	737	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	738	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.	739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
629		740
630	This "unloop state" will be cleared when entering C<ev_loop> again.	741	This "unloop state" will be cleared when entering C<ev_loop> again.
631		742
		743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		744
632	=item ev_ref (loop)	745	=item ev_ref (loop)
633		746
634	=item ev_unref (loop)	747	=item ev_unref (loop)
635		748
636	Ref/unref can be used to add or remove a reference count on the event	749	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	750	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	751	count is nonzero, C<ev_loop> will not return on its own.
		752
639	a watcher you never unregister that should not keep C<ev_loop> from	753	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	754	from returning, call ev_unref() after starting, and ev_ref() before
		755	stopping it.
		756
641	example, libev itself uses this for its internal signal pipe: It is not	757	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	758	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	759	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	760	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>	761	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,	762	before stop> (but only if the watcher wasn't active before, or was active
647	respectively).	763	before, respectively. Note also that libev might stop watchers itself
		764	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		765	in the callback).
648		766
649	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
650	running when nothing else is active.	768	running when nothing else is active.
651		769
652	struct ev_signal exitsig;	770	ev_signal exitsig;
653	ev_signal_init (&exitsig, sig_cb, SIGINT);	771	ev_signal_init (&exitsig, sig_cb, SIGINT);
654	ev_signal_start (loop, &exitsig);	772	ev_signal_start (loop, &exitsig);
655	evf_unref (loop);	773	evf_unref (loop);
656		774
657	Example: For some weird reason, unregister the above signal handler again.	775	Example: For some weird reason, unregister the above signal handler again.
658		776
659	ev_ref (loop);	777	ev_ref (loop);
660	ev_signal_stop (loop, &exitsig);	778	ev_signal_stop (loop, &exitsig);
661		779
662	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	780	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
663		781
664	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	782	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
665		783
666	These advanced functions influence the time that libev will spend waiting	784	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	785	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.	786	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		787	latency.
669		788
670	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	789	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	790	allows libev to delay invocation of I/O and timer/periodic callbacks
672	increase efficiency of loop iterations.	791	to increase efficiency of loop iterations (or to increase power-saving
		792	opportunities).
673		793
674	The background is that sometimes your program runs just fast enough to	794	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	795	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	796	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	797	events, especially with backends like C<select ()> which have a high
678	overhead for the actual polling but can deliver many events at once.	798	overhead for the actual polling but can deliver many events at once.
679		799
680	By setting a higher I<io collect interval> you allow libev to spend more	800	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,	801	time collecting I/O events, so you can handle more events per iteration,
…		…
683	C<ev_timer>) will be not affected. Setting this to a non-null value will	803	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.	804	introduce an additional C<ev_sleep ()> call into most loop iterations.
685		805
686	Likewise, by setting a higher I<timeout collect interval> you allow libev	806	Likewise, by setting a higher I<timeout collect interval> you allow libev
687	to spend more time collecting timeouts, at the expense of increased	807	to spend more time collecting timeouts, at the expense of increased
688	latency (the watcher callback will be called later). C<ev_io> watchers	808	latency/jitter/inexactness (the watcher callback will be called
689	will not be affected. Setting this to a non-null value will not introduce	809	later). C<ev_io> watchers will not be affected. Setting this to a non-null
690	any overhead in libev.	810	value will not introduce any overhead in libev.
691		811
692	Many (busy) programs can usually benefit by setting the io collect	812	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	813	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	814	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>,	815	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.	816	as this approaches the timing granularity of most systems.
		817
		818	Setting the I<timeout collect interval> can improve the opportunity for
		819	saving power, as the program will "bundle" timer callback invocations that
		820	are "near" in time together, by delaying some, thus reducing the number of
		821	times the process sleeps and wakes up again. Another useful technique to
		822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		823	they fire on, say, one-second boundaries only.
		824
		825	=item ev_loop_verify (loop)
		826
		827	This function only does something when C<EV_VERIFY> support has been
		828	compiled in, which is the default for non-minimal builds. It tries to go
		829	through all internal structures and checks them for validity. If anything
		830	is found to be inconsistent, it will print an error message to standard
		831	error and call C<abort ()>.
		832
		833	This can be used to catch bugs inside libev itself: under normal
		834	circumstances, this function will never abort as of course libev keeps its
		835	data structures consistent.
697		836
698	=back	837	=back
699		838
700		839
701	=head1 ANATOMY OF A WATCHER	840	=head1 ANATOMY OF A WATCHER
		841
		842	In the following description, uppercase C<TYPE> in names stands for the
		843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		844	watchers and C<ev_io_start> for I/O watchers.
702		845
703	A watcher is a structure that you create and register to record your	846	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	847	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:	848	become readable, you would create an C<ev_io> watcher for that:
706		849
707	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
708	{	851	{
709	ev_io_stop (w);	852	ev_io_stop (w);
710	ev_unloop (loop, EVUNLOOP_ALL);	853	ev_unloop (loop, EVUNLOOP_ALL);
711	}	854	}
712		855
713	struct ev_loop *loop = ev_default_loop (0);	856	struct ev_loop *loop = ev_default_loop (0);
		857
714	struct ev_io stdin_watcher;	858	ev_io stdin_watcher;
		859
715	ev_init (&stdin_watcher, my_cb);	860	ev_init (&stdin_watcher, my_cb);
716	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
717	ev_io_start (loop, &stdin_watcher);	862	ev_io_start (loop, &stdin_watcher);
		863
718	ev_loop (loop, 0);	864	ev_loop (loop, 0);
719		865
720	As you can see, you are responsible for allocating the memory for your	866	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,	867	watcher structures (and it is I<usually> a bad idea to do this on the
722	although this can sometimes be quite valid).	868	stack).
		869
		870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
723		872
724	Each watcher structure must be initialised by a call to C<ev_init	873	Each watcher structure must be initialised by a call to C<ev_init
725	(watcher *, callback)>, which expects a callback to be provided. This	874	(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	875	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	876	watchers, each time the event loop detects that the file descriptor given
728	is readable and/or writable).	877	is readable and/or writable).
729		878
730	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	879	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	880	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	881	is also a macro to combine initialisation and setting in one call: C<<
733	(watcher *, callback, ...) >>.	882	ev_TYPE_init (watcher *, callback, ...) >>.
734		883
735	To make the watcher actually watch out for events, you have to start it	884	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	885	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	886	*) >>), and you can stop watching for events at any time by calling the
738	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	887	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
739		888
740	As long as your watcher is active (has been started but not stopped) you	889	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	890	must not touch the values stored in it. Most specifically you must never
742	reinitialise it or call its C<set> macro.	891	reinitialise it or call its C<ev_TYPE_set> macro.
743		892
744	Each and every callback receives the event loop pointer as first, the	893	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	894	registered watcher structure as second, and a bitset of received events as
746	third argument.	895	third argument.
747		896
…		…
805		954
806	=item C<EV_ASYNC>	955	=item C<EV_ASYNC>
807		956
808	The given async watcher has been asynchronously notified (see C<ev_async>).	957	The given async watcher has been asynchronously notified (see C<ev_async>).
809		958
		959	=item C<EV_CUSTOM>
		960
		961	Not ever sent (or otherwise used) by libev itself, but can be freely used
		962	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		963
810	=item C<EV_ERROR>	964	=item C<EV_ERROR>
811		965
812	An unspecified error has occured, the watcher has been stopped. This might	966	An unspecified error has occurred, the watcher has been stopped. This might
813	happen because the watcher could not be properly started because libev	967	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	968	ran out of memory, a file descriptor was found to be closed or any other
		969	problem. Libev considers these application bugs.
		970
815	problem. You best act on it by reporting the problem and somehow coping	971	You best act on it by reporting the problem and somehow coping with the
816	with the watcher being stopped.	972	watcher being stopped. Note that well-written programs should not receive
		973	an error ever, so when your watcher receives it, this usually indicates a
		974	bug in your program.
817		975
818	Libev will usually signal a few "dummy" events together with an error,	976	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	977	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	978	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	979	the error from read() or write(). This will not work in multi-threaded
822	programs, though, so beware.	980	programs, though, as the fd could already be closed and reused for another
		981	thing, so beware.
823		982
824	=back	983	=back
825		984
826	=head2 GENERIC WATCHER FUNCTIONS	985	=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		986
831	=over 4	987	=over 4
832		988
833	=item C<ev_init> (ev_TYPE *watcher, callback)	989	=item C<ev_init> (ev_TYPE *watcher, callback)
834		990
…		…
840	which rolls both calls into one.	996	which rolls both calls into one.
841		997
842	You can reinitialise a watcher at any time as long as it has been stopped	998	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.	999	(or never started) and there are no pending events outstanding.
844		1000
845	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1001	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
846	int revents)>.	1002	int revents)>.
		1003
		1004	Example: Initialise an C<ev_io> watcher in two steps.
		1005
		1006	ev_io w;
		1007	ev_init (&w, my_cb);
		1008	ev_io_set (&w, STDIN_FILENO, EV_READ);
847		1009
848	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])
849		1011
850	This macro initialises the type-specific parts of a watcher. You need to	1012	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	1013	call C<ev_init> at least once before you call this macro, but you can
…		…
854	difference to the C<ev_init> macro).	1016	difference to the C<ev_init> macro).
855		1017
856	Although some watcher types do not have type-specific arguments	1018	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.	1019	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
858		1020
		1021	See C<ev_init>, above, for an example.
		1022
859	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1023	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
860		1024
861	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1025	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	1026	calls into a single call. This is the most convenient method to initialise
863	a watcher. The same limitations apply, of course.	1027	a watcher. The same limitations apply, of course.
		1028
		1029	Example: Initialise and set an C<ev_io> watcher in one step.
		1030
		1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
864		1032
865	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
866		1034
867	Starts (activates) the given watcher. Only active watchers will receive	1035	Starts (activates) the given watcher. Only active watchers will receive
868	events. If the watcher is already active nothing will happen.	1036	events. If the watcher is already active nothing will happen.
869		1037
		1038	Example: Start the C<ev_io> watcher that is being abused as example in this
		1039	whole section.
		1040
		1041	ev_io_start (EV_DEFAULT_UC, &w);
		1042
870	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
871		1044
872	Stops the given watcher again (if active) and clears the pending	1045	Stops the given watcher if active, and clears the pending status (whether
		1046	the watcher was active or not).
		1047
873	status. It is possible that stopped watchers are pending (for example,	1048	It is possible that stopped watchers are pending - for example,
874	non-repeating timers are being stopped when they become pending), but	1049	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	1050	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	1051	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.	1052	therefore a good idea to always call its C<ev_TYPE_stop> function.
878		1053
879	=item bool ev_is_active (ev_TYPE *watcher)	1054	=item bool ev_is_active (ev_TYPE *watcher)
880		1055
881	Returns a true value iff the watcher is active (i.e. it has been started	1056	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	1057	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>	1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
909	(default: C<-2>). Pending watchers with higher priority will be invoked	1084	(default: C<-2>). Pending watchers with higher priority will be invoked
910	before watchers with lower priority, but priority will not keep watchers	1085	before watchers with lower priority, but priority will not keep watchers
911	from being executed (except for C<ev_idle> watchers).	1086	from being executed (except for C<ev_idle> watchers).
912		1087
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	1088	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.	1089	you need to look at C<ev_idle> watchers, which provide this functionality.
920		1090
921	You I<must not> change the priority of a watcher as long as it is active or	1091	You I<must not> change the priority of a watcher as long as it is active or
922	pending.	1092	pending.
923		1093
		1094	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1095	fine, as long as you do not mind that the priority value you query might
		1096	or might not have been clamped to the valid range.
		1097
924	The default priority used by watchers when no priority has been set is	1098	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 :).	1099	always C<0>, which is supposed to not be too high and not be too low :).
926		1100
927	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1101	See L<WATCHER PRIORITIES>, below, for a more thorough treatment of
928	fine, as long as you do not mind that the priority value you query might	1102	priorities.
929	or might not have been adjusted to be within valid range.
930		1103
931	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1104	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
932		1105
933	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1106	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	1107	C<loop> nor C<revents> need to be valid as long as the watcher callback
935	can deal with that fact.	1108	can deal with that fact, as both are simply passed through to the
		1109	callback.
936		1110
937	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1111	=item int ev_clear_pending (loop, ev_TYPE *watcher)
938		1112
939	If the watcher is pending, this function returns clears its pending status	1113	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	1114	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>.	1115	watcher isn't pending it does nothing and returns C<0>.
942		1116
		1117	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1118	callback to be invoked, which can be accomplished with this function.
		1119
943	=back	1120	=back
944		1121
945		1122
946	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1123	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
947		1124
948	Each watcher has, by default, a member C<void *data> that you can change	1125	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	1126	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	1127	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	1128	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	1129	member, you can also "subclass" the watcher type and provide your own
953	data:	1130	data:
954		1131
955	struct my_io	1132	struct my_io
956	{	1133	{
957	struct ev_io io;	1134	ev_io io;
958	int otherfd;	1135	int otherfd;
959	void *somedata;	1136	void *somedata;
960	struct whatever *mostinteresting;	1137	struct whatever *mostinteresting;
961	}	1138	};
		1139
		1140	...
		1141	struct my_io w;
		1142	ev_io_init (&w.io, my_cb, fd, EV_READ);
962		1143
963	And since your callback will be called with a pointer to the watcher, you	1144	And since your callback will be called with a pointer to the watcher, you
964	can cast it back to your own type:	1145	can cast it back to your own type:
965		1146
966	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1147	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
967	{	1148	{
968	struct my_io *w = (struct my_io *)w_;	1149	struct my_io *w = (struct my_io *)w_;
969	...	1150	...
970	}	1151	}
971		1152
972	More interesting and less C-conformant ways of casting your callback type	1153	More interesting and less C-conformant ways of casting your callback type
973	instead have been omitted.	1154	instead have been omitted.
974		1155
975	Another common scenario is having some data structure with multiple	1156	Another common scenario is to use some data structure with multiple
976	watchers:	1157	embedded watchers:
977		1158
978	struct my_biggy	1159	struct my_biggy
979	{	1160	{
980	int some_data;	1161	int some_data;
981	ev_timer t1;	1162	ev_timer t1;
982	ev_timer t2;	1163	ev_timer t2;
983	}	1164	}
984		1165
985	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1166	In this case getting the pointer to C<my_biggy> is a bit more
986	you need to use C<offsetof>:	1167	complicated: Either you store the address of your C<my_biggy> struct
		1168	in the C<data> member of the watcher (for woozies), or you need to use
		1169	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1170	programmers):
987		1171
988	#include <stddef.h>	1172	#include <stddef.h>
989		1173
990	static void	1174	static void
991	t1_cb (EV_P_ struct ev_timer *w, int revents)	1175	t1_cb (EV_P_ ev_timer *w, int revents)
992	{	1176	{
993	struct my_biggy big = (struct my_biggy *	1177	struct my_biggy big = (struct my_biggy *
994	(((char *)w) - offsetof (struct my_biggy, t1));	1178	(((char *)w) - offsetof (struct my_biggy, t1));
995	}	1179	}
996		1180
997	static void	1181	static void
998	t2_cb (EV_P_ struct ev_timer *w, int revents)	1182	t2_cb (EV_P_ ev_timer *w, int revents)
999	{	1183	{
1000	struct my_biggy big = (struct my_biggy *	1184	struct my_biggy big = (struct my_biggy *
1001	(((char *)w) - offsetof (struct my_biggy, t2));	1185	(((char *)w) - offsetof (struct my_biggy, t2));
1002	}	1186	}
		1187
		1188	=head2 WATCHER PRIORITY MODELS
		1189
		1190	Many event loops support I<watcher priorities>, which are usually small
		1191	integers that influence the ordering of event callback invocation
		1192	between watchers in some way, all else being equal.
		1193
		1194	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1195	description for the more technical details such as the actual priority
		1196	range.
		1197
		1198	There are two common ways how these these priorities are being interpreted
		1199	by event loops:
		1200
		1201	In the more common lock-out model, higher priorities "lock out" invocation
		1202	of lower priority watchers, which means as long as higher priority
		1203	watchers receive events, lower priority watchers are not being invoked.
		1204
		1205	The less common only-for-ordering model uses priorities solely to order
		1206	callback invocation within a single event loop iteration: Higher priority
		1207	watchers are invoked before lower priority ones, but they all get invoked
		1208	before polling for new events.
		1209
		1210	Libev uses the second (only-for-ordering) model for all its watchers
		1211	except for idle watchers (which use the lock-out model).
		1212
		1213	The rationale behind this is that implementing the lock-out model for
		1214	watchers is not well supported by most kernel interfaces, and most event
		1215	libraries will just poll for the same events again and again as long as
		1216	their callbacks have not been executed, which is very inefficient in the
		1217	common case of one high-priority watcher locking out a mass of lower
		1218	priority ones.
		1219
		1220	Static (ordering) priorities are most useful when you have two or more
		1221	watchers handling the same resource: a typical usage example is having an
		1222	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1223	timeouts. Under load, data might be received while the program handles
		1224	other jobs, but since timers normally get invoked first, the timeout
		1225	handler will be executed before checking for data. In that case, giving
		1226	the timer a lower priority than the I/O watcher ensures that I/O will be
		1227	handled first even under adverse conditions (which is usually, but not
		1228	always, what you want).
		1229
		1230	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1231	will only be executed when no same or higher priority watchers have
		1232	received events, they can be used to implement the "lock-out" model when
		1233	required.
		1234
		1235	For example, to emulate how many other event libraries handle priorities,
		1236	you can associate an C<ev_idle> watcher to each such watcher, and in
		1237	the normal watcher callback, you just start the idle watcher. The real
		1238	processing is done in the idle watcher callback. This causes libev to
		1239	continously poll and process kernel event data for the watcher, but when
		1240	the lock-out case is known to be rare (which in turn is rare :), this is
		1241	workable.
		1242
		1243	Usually, however, the lock-out model implemented that way will perform
		1244	miserably under the type of load it was designed to handle. In that case,
		1245	it might be preferable to stop the real watcher before starting the
		1246	idle watcher, so the kernel will not have to process the event in case
		1247	the actual processing will be delayed for considerable time.
		1248
		1249	Here is an example of an I/O watcher that should run at a strictly lower
		1250	priority than the default, and which should only process data when no
		1251	other events are pending:
		1252
		1253	ev_idle idle; // actual processing watcher
		1254	ev_io io; // actual event watcher
		1255
		1256	static void
		1257	io_cb (EV_P_ ev_io *w, int revents)
		1258	{
		1259	// stop the I/O watcher, we received the event, but
		1260	// are not yet ready to handle it.
		1261	ev_io_stop (EV_A_ w);
		1262
		1263	// start the idle watcher to ahndle the actual event.
		1264	// it will not be executed as long as other watchers
		1265	// with the default priority are receiving events.
		1266	ev_idle_start (EV_A_ &idle);
		1267	}
		1268
		1269	static void
		1270	idle-cb (EV_P_ ev_idle *w, int revents)
		1271	{
		1272	// actual processing
		1273	read (STDIN_FILENO, ...);
		1274
		1275	// have to start the I/O watcher again, as
		1276	// we have handled the event
		1277	ev_io_start (EV_P_ &io);
		1278	}
		1279
		1280	// initialisation
		1281	ev_idle_init (&idle, idle_cb);
		1282	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1283	ev_io_start (EV_DEFAULT_ &io);
		1284
		1285	In the "real" world, it might also be beneficial to start a timer, so that
		1286	low-priority connections can not be locked out forever under load. This
		1287	enables your program to keep a lower latency for important connections
		1288	during short periods of high load, while not completely locking out less
		1289	important ones.
1003		1290
1004		1291
1005	=head1 WATCHER TYPES	1292	=head1 WATCHER TYPES
1006		1293
1007	This section describes each watcher in detail, but will not repeat	1294	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	1318	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	1319	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	1320	descriptors to non-blocking mode is also usually a good idea (but not
1034	required if you know what you are doing).	1321	required if you know what you are doing).
1035		1322
1036	If you must do this, then force the use of a known-to-be-good backend	1323	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	1324	known-to-be-good backend (at the time of this writing, this includes only
1038	C<EVBACKEND_POLL>).	1325	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1039		1326
1040	Another thing you have to watch out for is that it is quite easy to	1327	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	1328	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	1329	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	1330	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	1331	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	1332	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	1333	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.	1334	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1048		1335
1049	If you cannot run the fd in non-blocking mode (for example you should not	1336	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	1337	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	1338	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	1339	interface such as poll (fortunately in our Xlib example, Xlib already
1053	its own, so its quite safe to use).	1340	does this on its own, so its quite safe to use). Some people additionally
		1341	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1342	indefinitely.
		1343
		1344	But really, best use non-blocking mode.
1054		1345
1055	=head3 The special problem of disappearing file descriptors	1346	=head3 The special problem of disappearing file descriptors
1056		1347
1057	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1348	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,	1349	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	1350	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	1351	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	1352	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	1353	registered with libev, there is no efficient way to see that this is, in
1063	fact, a different file descriptor.	1354	fact, a different file descriptor.
1064		1355
…		…
1095	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1386	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1096	C<EVBACKEND_POLL>.	1387	C<EVBACKEND_POLL>.
1097		1388
1098	=head3 The special problem of SIGPIPE	1389	=head3 The special problem of SIGPIPE
1099		1390
1100	While not really specific to libev, it is easy to forget about SIGPIPE:	1391	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	1392	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	1393	sent a SIGPIPE, which, by default, aborts your program. For most programs
1103	programs this is sensible behaviour, for daemons, this is usually	1394	this is sensible behaviour, for daemons, this is usually undesirable.
1104	undesirable.
1105		1395
1106	So when you encounter spurious, unexplained daemon exits, make sure you	1396	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	1397	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).	1398	somewhere, as that would have given you a big clue).
1109		1399
…		…
1115	=item ev_io_init (ev_io *, callback, int fd, int events)	1405	=item ev_io_init (ev_io *, callback, int fd, int events)
1116		1406
1117	=item ev_io_set (ev_io *, int fd, int events)	1407	=item ev_io_set (ev_io *, int fd, int events)
1118		1408
1119	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1409	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	1410	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.	1411	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1122		1412
1123	=item int fd [read-only]	1413	=item int fd [read-only]
1124		1414
1125	The file descriptor being watched.	1415	The file descriptor being watched.
1126		1416
…		…
1134		1424
1135	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1425	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	1426	readable, but only once. Since it is likely line-buffered, you could
1137	attempt to read a whole line in the callback.	1427	attempt to read a whole line in the callback.
1138		1428
1139	static void	1429	static void
1140	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1430	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1141	{	1431	{
1142	ev_io_stop (loop, w);	1432	ev_io_stop (loop, w);
1143	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1433	.. read from stdin here (or from w->fd) and handle any I/O errors
1144	}	1434	}
1145		1435
1146	...	1436	...
1147	struct ev_loop *loop = ev_default_init (0);	1437	struct ev_loop *loop = ev_default_init (0);
1148	struct ev_io stdin_readable;	1438	ev_io stdin_readable;
1149	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1439	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1150	ev_io_start (loop, &stdin_readable);	1440	ev_io_start (loop, &stdin_readable);
1151	ev_loop (loop, 0);	1441	ev_loop (loop, 0);
1152		1442
1153		1443
1154	=head2 C<ev_timer> - relative and optionally repeating timeouts	1444	=head2 C<ev_timer> - relative and optionally repeating timeouts
1155		1445
1156	Timer watchers are simple relative timers that generate an event after a	1446	Timer watchers are simple relative timers that generate an event after a
1157	given time, and optionally repeating in regular intervals after that.	1447	given time, and optionally repeating in regular intervals after that.
1158		1448
1159	The timers are based on real time, that is, if you register an event that	1449	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	1450	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	1451	year, it will still time out after (roughly) one hour. "Roughly" because
1162	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1452	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1163	monotonic clock option helps a lot here).	1453	monotonic clock option helps a lot here).
		1454
		1455	The callback is guaranteed to be invoked only I<after> its timeout has
		1456	passed. If multiple timers become ready during the same loop iteration
		1457	then the ones with earlier time-out values are invoked before ones with
		1458	later time-out values (but this is no longer true when a callback calls
		1459	C<ev_loop> recursively).
		1460
		1461	=head3 Be smart about timeouts
		1462
		1463	Many real-world problems involve some kind of timeout, usually for error
		1464	recovery. A typical example is an HTTP request - if the other side hangs,
		1465	you want to raise some error after a while.
		1466
		1467	What follows are some ways to handle this problem, from obvious and
		1468	inefficient to smart and efficient.
		1469
		1470	In the following, a 60 second activity timeout is assumed - a timeout that
		1471	gets reset to 60 seconds each time there is activity (e.g. each time some
		1472	data or other life sign was received).
		1473
		1474	=over 4
		1475
		1476	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1477
		1478	This is the most obvious, but not the most simple way: In the beginning,
		1479	start the watcher:
		1480
		1481	ev_timer_init (timer, callback, 60., 0.);
		1482	ev_timer_start (loop, timer);
		1483
		1484	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1485	and start it again:
		1486
		1487	ev_timer_stop (loop, timer);
		1488	ev_timer_set (timer, 60., 0.);
		1489	ev_timer_start (loop, timer);
		1490
		1491	This is relatively simple to implement, but means that each time there is
		1492	some activity, libev will first have to remove the timer from its internal
		1493	data structure and then add it again. Libev tries to be fast, but it's
		1494	still not a constant-time operation.
		1495
		1496	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1497
		1498	This is the easiest way, and involves using C<ev_timer_again> instead of
		1499	C<ev_timer_start>.
		1500
		1501	To implement this, configure an C<ev_timer> with a C<repeat> value
		1502	of C<60> and then call C<ev_timer_again> at start and each time you
		1503	successfully read or write some data. If you go into an idle state where
		1504	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1505	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1506
		1507	That means you can ignore both the C<ev_timer_start> function and the
		1508	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1509	member and C<ev_timer_again>.
		1510
		1511	At start:
		1512
		1513	ev_timer_init (timer, callback);
		1514	timer->repeat = 60.;
		1515	ev_timer_again (loop, timer);
		1516
		1517	Each time there is some activity:
		1518
		1519	ev_timer_again (loop, timer);
		1520
		1521	It is even possible to change the time-out on the fly, regardless of
		1522	whether the watcher is active or not:
		1523
		1524	timer->repeat = 30.;
		1525	ev_timer_again (loop, timer);
		1526
		1527	This is slightly more efficient then stopping/starting the timer each time
		1528	you want to modify its timeout value, as libev does not have to completely
		1529	remove and re-insert the timer from/into its internal data structure.
		1530
		1531	It is, however, even simpler than the "obvious" way to do it.
		1532
		1533	=item 3. Let the timer time out, but then re-arm it as required.
		1534
		1535	This method is more tricky, but usually most efficient: Most timeouts are
		1536	relatively long compared to the intervals between other activity - in
		1537	our example, within 60 seconds, there are usually many I/O events with
		1538	associated activity resets.
		1539
		1540	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1541	but remember the time of last activity, and check for a real timeout only
		1542	within the callback:
		1543
		1544	ev_tstamp last_activity; // time of last activity
		1545
		1546	static void
		1547	callback (EV_P_ ev_timer *w, int revents)
		1548	{
		1549	ev_tstamp now = ev_now (EV_A);
		1550	ev_tstamp timeout = last_activity + 60.;
		1551
		1552	// if last_activity + 60. is older than now, we did time out
		1553	if (timeout < now)
		1554	{
		1555	// timeout occured, take action
		1556	}
		1557	else
		1558	{
		1559	// callback was invoked, but there was some activity, re-arm
		1560	// the watcher to fire in last_activity + 60, which is
		1561	// guaranteed to be in the future, so "again" is positive:
		1562	w->repeat = timeout - now;
		1563	ev_timer_again (EV_A_ w);
		1564	}
		1565	}
		1566
		1567	To summarise the callback: first calculate the real timeout (defined
		1568	as "60 seconds after the last activity"), then check if that time has
		1569	been reached, which means something I<did>, in fact, time out. Otherwise
		1570	the callback was invoked too early (C<timeout> is in the future), so
		1571	re-schedule the timer to fire at that future time, to see if maybe we have
		1572	a timeout then.
		1573
		1574	Note how C<ev_timer_again> is used, taking advantage of the
		1575	C<ev_timer_again> optimisation when the timer is already running.
		1576
		1577	This scheme causes more callback invocations (about one every 60 seconds
		1578	minus half the average time between activity), but virtually no calls to
		1579	libev to change the timeout.
		1580
		1581	To start the timer, simply initialise the watcher and set C<last_activity>
		1582	to the current time (meaning we just have some activity :), then call the
		1583	callback, which will "do the right thing" and start the timer:
		1584
		1585	ev_timer_init (timer, callback);
		1586	last_activity = ev_now (loop);
		1587	callback (loop, timer, EV_TIMEOUT);
		1588
		1589	And when there is some activity, simply store the current time in
		1590	C<last_activity>, no libev calls at all:
		1591
		1592	last_actiivty = ev_now (loop);
		1593
		1594	This technique is slightly more complex, but in most cases where the
		1595	time-out is unlikely to be triggered, much more efficient.
		1596
		1597	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1598	callback :) - just change the timeout and invoke the callback, which will
		1599	fix things for you.
		1600
		1601	=item 4. Wee, just use a double-linked list for your timeouts.
		1602
		1603	If there is not one request, but many thousands (millions...), all
		1604	employing some kind of timeout with the same timeout value, then one can
		1605	do even better:
		1606
		1607	When starting the timeout, calculate the timeout value and put the timeout
		1608	at the I<end> of the list.
		1609
		1610	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1611	the list is expected to fire (for example, using the technique #3).
		1612
		1613	When there is some activity, remove the timer from the list, recalculate
		1614	the timeout, append it to the end of the list again, and make sure to
		1615	update the C<ev_timer> if it was taken from the beginning of the list.
		1616
		1617	This way, one can manage an unlimited number of timeouts in O(1) time for
		1618	starting, stopping and updating the timers, at the expense of a major
		1619	complication, and having to use a constant timeout. The constant timeout
		1620	ensures that the list stays sorted.
		1621
		1622	=back
		1623
		1624	So which method the best?
		1625
		1626	Method #2 is a simple no-brain-required solution that is adequate in most
		1627	situations. Method #3 requires a bit more thinking, but handles many cases
		1628	better, and isn't very complicated either. In most case, choosing either
		1629	one is fine, with #3 being better in typical situations.
		1630
		1631	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1632	rather complicated, but extremely efficient, something that really pays
		1633	off after the first million or so of active timers, i.e. it's usually
		1634	overkill :)
		1635
		1636	=head3 The special problem of time updates
		1637
		1638	Establishing the current time is a costly operation (it usually takes at
		1639	least two system calls): EV therefore updates its idea of the current
		1640	time only before and after C<ev_loop> collects new events, which causes a
		1641	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1642	lots of events in one iteration.
1164		1643
1165	The relative timeouts are calculated relative to the C<ev_now ()>	1644	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	1645	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	1646	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	1647	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:	1648	timeout on the current time, use something like this to adjust for this:
1170		1649
1171	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1650	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1172		1651
1173	The callback is guarenteed to be invoked only when its timeout has passed,	1652	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	1653	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1175	order of execution is undefined.	1654	()>.
1176		1655
1177	=head3 Watcher-Specific Functions and Data Members	1656	=head3 Watcher-Specific Functions and Data Members
1178		1657
1179	=over 4	1658	=over 4
1180		1659
1181	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1660	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1182		1661
1183	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1662	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1184		1663
1185	Configure the timer to trigger after C<after> seconds. If C<repeat> is	1664	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	1665	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	1666	reached. If it is positive, then the timer will automatically be
1188	later, again, and again, until stopped manually.	1667	configured to trigger again C<repeat> seconds later, again, and again,
		1668	until stopped manually.
1189		1669
1190	The timer itself will do a best-effort at avoiding drift, that is, if you	1670	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	1671	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	1672	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	1673	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.	1674	do stuff) the timer will not fire more than once per event loop iteration.
1195		1675
1196	=item ev_timer_again (loop, ev_timer *)	1676	=item ev_timer_again (loop, ev_timer *)
1197		1677
1198	This will act as if the timer timed out and restart it again if it is	1678	This will act as if the timer timed out and restart it again if it is
1199	repeating. The exact semantics are:	1679	repeating. The exact semantics are:
1200		1680
1201	If the timer is pending, its pending status is cleared.	1681	If the timer is pending, its pending status is cleared.
1202		1682
1203	If the timer is started but nonrepeating, stop it (as if it timed out).	1683	If the timer is started but non-repeating, stop it (as if it timed out).
1204		1684
1205	If the timer is repeating, either start it if necessary (with the	1685	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.	1686	C<repeat> value), or reset the running timer to the C<repeat> value.
1207		1687
1208	This sounds a bit complicated, but here is a useful and typical	1688	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	1689	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
1218	That means you can ignore the C<after> value and C<ev_timer_start>
1219	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1220
1221	ev_timer_init (timer, callback, 0., 5.);
1222	ev_timer_again (loop, timer);
1223	...
1224	timer->again = 17.;
1225	ev_timer_again (loop, timer);
1226	...
1227	timer->again = 10.;
1228	ev_timer_again (loop, timer);
1229
1230	This is more slightly efficient then stopping/starting the timer each time
1231	you want to modify its timeout value.
1232		1690
1233	=item ev_tstamp repeat [read-write]	1691	=item ev_tstamp repeat [read-write]
1234		1692
1235	The current C<repeat> value. Will be used each time the watcher times out	1693	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),	1694	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.	1695	which is also when any modifications are taken into account.
1238		1696
1239	=back	1697	=back
1240		1698
1241	=head3 Examples	1699	=head3 Examples
1242		1700
1243	Example: Create a timer that fires after 60 seconds.	1701	Example: Create a timer that fires after 60 seconds.
1244		1702
1245	static void	1703	static void
1246	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1704	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1247	{	1705	{
1248	.. one minute over, w is actually stopped right here	1706	.. one minute over, w is actually stopped right here
1249	}	1707	}
1250		1708
1251	struct ev_timer mytimer;	1709	ev_timer mytimer;
1252	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1710	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1253	ev_timer_start (loop, &mytimer);	1711	ev_timer_start (loop, &mytimer);
1254		1712
1255	Example: Create a timeout timer that times out after 10 seconds of	1713	Example: Create a timeout timer that times out after 10 seconds of
1256	inactivity.	1714	inactivity.
1257		1715
1258	static void	1716	static void
1259	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1717	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1260	{	1718	{
1261	.. ten seconds without any activity	1719	.. ten seconds without any activity
1262	}	1720	}
1263		1721
1264	struct ev_timer mytimer;	1722	ev_timer mytimer;
1265	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1723	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1266	ev_timer_again (&mytimer); /* start timer */	1724	ev_timer_again (&mytimer); /* start timer */
1267	ev_loop (loop, 0);	1725	ev_loop (loop, 0);
1268		1726
1269	// and in some piece of code that gets executed on any "activity":	1727	// and in some piece of code that gets executed on any "activity":
1270	// reset the timeout to start ticking again at 10 seconds	1728	// reset the timeout to start ticking again at 10 seconds
1271	ev_timer_again (&mytimer);	1729	ev_timer_again (&mytimer);
1272		1730
1273		1731
1274	=head2 C<ev_periodic> - to cron or not to cron?	1732	=head2 C<ev_periodic> - to cron or not to cron?
1275		1733
1276	Periodic watchers are also timers of a kind, but they are very versatile	1734	Periodic watchers are also timers of a kind, but they are very versatile
1277	(and unfortunately a bit complex).	1735	(and unfortunately a bit complex).
1278		1736
1279	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1737	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	1738	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	1739	(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 ()	1740	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	1741	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	1742	wrist-watch).
1285	roughly 10 seconds later).
1286		1743
1287	They can also be used to implement vastly more complex timers, such as	1744	You can tell a periodic watcher to trigger after some specific point
1288	triggering an event on each midnight, local time or other, complicated,	1745	in time: for example, if you tell a periodic watcher to trigger "in 10
1289	rules.	1746	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1747	not a delay) and then reset your system clock to January of the previous
		1748	year, then it will take a year or more to trigger the event (unlike an
		1749	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1750	it, as it uses a relative timeout).
1290		1751
		1752	C<ev_periodic> watchers can also be used to implement vastly more complex
		1753	timers, such as triggering an event on each "midnight, local time", or
		1754	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1755	those cannot react to time jumps.
		1756
1291	As with timers, the callback is guarenteed to be invoked only when the	1757	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	1758	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.	1759	timers become ready during the same loop iteration then the ones with
		1760	earlier time-out values are invoked before ones with later time-out values
		1761	(but this is no longer true when a callback calls C<ev_loop> recursively).
1294		1762
1295	=head3 Watcher-Specific Functions and Data Members	1763	=head3 Watcher-Specific Functions and Data Members
1296		1764
1297	=over 4	1765	=over 4
1298		1766
1299	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1767	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1300		1768
1301	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1769	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1302		1770
1303	Lots of arguments, lets sort it out... There are basically three modes of	1771	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:	1772	operation, and we will explain them from simplest to most complex:
1305		1773
1306	=over 4	1774	=over 4
1307		1775
1308	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1776	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1309		1777
1310	In this configuration the watcher triggers an event at the wallclock time	1778	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,	1779	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	1780	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.	1781	will be stopped and invoked when the system clock reaches or surpasses
		1782	this point in time.
1314		1783
1315	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1784	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1316		1785
1317	In this mode the watcher will always be scheduled to time out at the next	1786	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)	1787	C<offset + N * interval> time (for some integer N, which can also be
1319	and then repeat, regardless of any time jumps.	1788	negative) and then repeat, regardless of any time jumps. The C<offset>
		1789	argument is merely an offset into the C<interval> periods.
1320		1790
1321	This can be used to create timers that do not drift with respect to system	1791	This can be used to create timers that do not drift with respect to the
1322	time:	1792	system clock, for example, here is an C<ev_periodic> that triggers each
		1793	hour, on the hour (with respect to UTC):
1323		1794
1324	ev_periodic_set (&periodic, 0., 3600., 0);	1795	ev_periodic_set (&periodic, 0., 3600., 0);
1325		1796
1326	This doesn't mean there will always be 3600 seconds in between triggers,	1797	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	1798	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	1799	full hour (UTC), or more correctly, when the system time is evenly divisible
1329	by 3600.	1800	by 3600.
1330		1801
1331	Another way to think about it (for the mathematically inclined) is that	1802	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	1803	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.	1804	time where C<time = offset (mod interval)>, regardless of any time jumps.
1334		1805
1335	For numerical stability it is preferable that the C<at> value is near	1806	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	1807	C<ev_now ()> (the current time), but there is no range requirement for
1337	this value.	1808	this value, and in fact is often specified as zero.
1338		1809
		1810	Note also that there is an upper limit to how often a timer can fire (CPU
		1811	speed for example), so if C<interval> is very small then timing stability
		1812	will of course deteriorate. Libev itself tries to be exact to be about one
		1813	millisecond (if the OS supports it and the machine is fast enough).
		1814
1339	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1815	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1340		1816
1341	In this mode the values for C<interval> and C<at> are both being	1817	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	1818	ignored. Instead, each time the periodic watcher gets scheduled, the
1343	reschedule callback will be called with the watcher as first, and the	1819	reschedule callback will be called with the watcher as first, and the
1344	current time as second argument.	1820	current time as second argument.
1345		1821
1346	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1822	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,	1823	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	1824	allowed by documentation here>.
1349	starting an C<ev_prepare> watcher, which is legal).
1350		1825
		1826	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
		1827	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
		1828	only event loop modification you are allowed to do).
		1829
1351	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1830	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1352	ev_tstamp now)>, e.g.:	1831	*w, ev_tstamp now)>, e.g.:
1353		1832
		1833	static ev_tstamp
1354	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1834	my_rescheduler (ev_periodic *w, ev_tstamp now)
1355	{	1835	{
1356	return now + 60.;	1836	return now + 60.;
1357	}	1837	}
1358		1838
1359	It must return the next time to trigger, based on the passed time value	1839	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	1840	(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	1841	will usually be called just before the callback will be triggered, but
1362	might be called at other times, too.	1842	might be called at other times, too.
1363		1843
1364	NOTE: I<< This callback must always return a time that is later than the	1844	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.	1845	equal to the passed C<now> value >>.
1366		1846
1367	This can be used to create very complex timers, such as a timer that	1847	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	1848	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	1849	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	1850	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).	1851	reason I omitted it as an example).
1372		1852
1373	=back	1853	=back
…		…
1377	Simply stops and restarts the periodic watcher again. This is only useful	1857	Simply stops and restarts the periodic watcher again. This is only useful
1378	when you changed some parameters or the reschedule callback would return	1858	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	1859	a different time than the last time it was called (e.g. in a crond like
1380	program when the crontabs have changed).	1860	program when the crontabs have changed).
1381		1861
		1862	=item ev_tstamp ev_periodic_at (ev_periodic *)
		1863
		1864	When active, returns the absolute time that the watcher is supposed
		1865	to trigger next. This is not the same as the C<offset> argument to
		1866	C<ev_periodic_set>, but indeed works even in interval and manual
		1867	rescheduling modes.
		1868
1382	=item ev_tstamp offset [read-write]	1869	=item ev_tstamp offset [read-write]
1383		1870
1384	When repeating, this contains the offset value, otherwise this is the	1871	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>).	1872	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1873	although libev might modify this value for better numerical stability).
1386		1874
1387	Can be modified any time, but changes only take effect when the periodic	1875	Can be modified any time, but changes only take effect when the periodic
1388	timer fires or C<ev_periodic_again> is being called.	1876	timer fires or C<ev_periodic_again> is being called.
1389		1877
1390	=item ev_tstamp interval [read-write]	1878	=item ev_tstamp interval [read-write]
1391		1879
1392	The current interval value. Can be modified any time, but changes only	1880	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	1881	take effect when the periodic timer fires or C<ev_periodic_again> is being
1394	called.	1882	called.
1395		1883
1396	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1884	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1397		1885
1398	The current reschedule callback, or C<0>, if this functionality is	1886	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	1887	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.	1888	the periodic timer fires or C<ev_periodic_again> is being called.
1401		1889
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	1890	=back
1408		1891
1409	=head3 Examples	1892	=head3 Examples
1410		1893
1411	Example: Call a callback every hour, or, more precisely, whenever the	1894	Example: Call a callback every hour, or, more precisely, whenever the
1412	system clock is divisible by 3600. The callback invocation times have	1895	system time is divisible by 3600. The callback invocation times have
1413	potentially a lot of jittering, but good long-term stability.	1896	potentially a lot of jitter, but good long-term stability.
1414		1897
1415	static void	1898	static void
1416	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1899	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1417	{	1900	{
1418	... its now a full hour (UTC, or TAI or whatever your clock follows)	1901	... its now a full hour (UTC, or TAI or whatever your clock follows)
1419	}	1902	}
1420		1903
1421	struct ev_periodic hourly_tick;	1904	ev_periodic hourly_tick;
1422	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1905	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1423	ev_periodic_start (loop, &hourly_tick);	1906	ev_periodic_start (loop, &hourly_tick);
1424		1907
1425	Example: The same as above, but use a reschedule callback to do it:	1908	Example: The same as above, but use a reschedule callback to do it:
1426		1909
1427	#include <math.h>	1910	#include <math.h>
1428		1911
1429	static ev_tstamp	1912	static ev_tstamp
1430	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1913	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1431	{	1914	{
1432	return fmod (now, 3600.) + 3600.;	1915	return now + (3600. - fmod (now, 3600.));
1433	}	1916	}
1434		1917
1435	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1918	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1436		1919
1437	Example: Call a callback every hour, starting now:	1920	Example: Call a callback every hour, starting now:
1438		1921
1439	struct ev_periodic hourly_tick;	1922	ev_periodic hourly_tick;
1440	ev_periodic_init (&hourly_tick, clock_cb,	1923	ev_periodic_init (&hourly_tick, clock_cb,
1441	fmod (ev_now (loop), 3600.), 3600., 0);	1924	fmod (ev_now (loop), 3600.), 3600., 0);
1442	ev_periodic_start (loop, &hourly_tick);	1925	ev_periodic_start (loop, &hourly_tick);
1443		1926
1444		1927
1445	=head2 C<ev_signal> - signal me when a signal gets signalled!	1928	=head2 C<ev_signal> - signal me when a signal gets signalled!
1446		1929
1447	Signal watchers will trigger an event when the process receives a specific	1930	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	1931	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	1932	will try it's best to deliver signals synchronously, i.e. as part of the
1450	normal event processing, like any other event.	1933	normal event processing, like any other event.
1451		1934
		1935	If you want signals asynchronously, just use C<sigaction> as you would
		1936	do without libev and forget about sharing the signal. You can even use
		1937	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1938
1452	You can configure as many watchers as you like per signal. Only when the	1939	You can configure as many watchers as you like per signal. Only when the
1453	first watcher gets started will libev actually register a signal watcher	1940	first watcher gets started will libev actually register a signal handler
1454	with the kernel (thus it coexists with your own signal handlers as long	1941	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	1942	you don't register any with libev for the same signal). Similarly, when
1456	watcher for a signal is stopped libev will reset the signal handler to	1943	the last signal watcher for a signal is stopped, libev will reset the
1457	SIG_DFL (regardless of what it was set to before).	1944	signal handler to SIG_DFL (regardless of what it was set to before).
1458		1945
1459	If possible and supported, libev will install its handlers with	1946	If possible and supported, libev will install its handlers with
1460	C<SA_RESTART> behaviour enabled, so syscalls should not be unduly	1947	C<SA_RESTART> behaviour enabled, so system calls should not be unduly
1461	interrupted. If you have a problem with syscalls getting interrupted by	1948	interrupted. If you have a problem with system calls getting interrupted by
1462	signals you can block all signals in an C<ev_check> watcher and unblock	1949	signals you can block all signals in an C<ev_check> watcher and unblock
1463	them in an C<ev_prepare> watcher.	1950	them in an C<ev_prepare> watcher.
1464		1951
1465	=head3 Watcher-Specific Functions and Data Members	1952	=head3 Watcher-Specific Functions and Data Members
1466		1953
…		…
1479		1966
1480	=back	1967	=back
1481		1968
1482	=head3 Examples	1969	=head3 Examples
1483		1970
1484	Example: Try to exit cleanly on SIGINT and SIGTERM.	1971	Example: Try to exit cleanly on SIGINT.
1485		1972
1486	static void	1973	static void
1487	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1974	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1488	{	1975	{
1489	ev_unloop (loop, EVUNLOOP_ALL);	1976	ev_unloop (loop, EVUNLOOP_ALL);
1490	}	1977	}
1491		1978
1492	struct ev_signal signal_watcher;	1979	ev_signal signal_watcher;
1493	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1980	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1494	ev_signal_start (loop, &sigint_cb);	1981	ev_signal_start (loop, &signal_watcher);
1495		1982
1496		1983
1497	=head2 C<ev_child> - watch out for process status changes	1984	=head2 C<ev_child> - watch out for process status changes
1498		1985
1499	Child watchers trigger when your process receives a SIGCHLD in response to	1986	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	1987	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	1988	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	1989	has been forked (which implies it might have already exited), as long
1503	loop isn't entered (or is continued from a watcher).	1990	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1991	forking and then immediately registering a watcher for the child is fine,
		1992	but forking and registering a watcher a few event loop iterations later is
		1993	not.
1504		1994
1505	Only the default event loop is capable of handling signals, and therefore	1995	Only the default event loop is capable of handling signals, and therefore
1506	you can only rgeister child watchers in the default event loop.	1996	you can only register child watchers in the default event loop.
1507		1997
1508	=head3 Process Interaction	1998	=head3 Process Interaction
1509		1999
1510	Libev grabs C<SIGCHLD> as soon as the default event loop is	2000	Libev grabs C<SIGCHLD> as soon as the default event loop is
1511	initialised. This is necessary to guarantee proper behaviour even if	2001	initialised. This is necessary to guarantee proper behaviour even if
1512	the first child watcher is started after the child exits. The occurance	2002	the first child watcher is started after the child exits. The occurrence
1513	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2003	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1514	synchronously as part of the event loop processing. Libev always reaps all	2004	synchronously as part of the event loop processing. Libev always reaps all
1515	children, even ones not watched.	2005	children, even ones not watched.
1516		2006
1517	=head3 Overriding the Built-In Processing	2007	=head3 Overriding the Built-In Processing
…		…
1521	handler, you can override it easily by installing your own handler for	2011	handler, you can override it easily by installing your own handler for
1522	C<SIGCHLD> after initialising the default loop, and making sure the	2012	C<SIGCHLD> after initialising the default loop, and making sure the
1523	default loop never gets destroyed. You are encouraged, however, to use an	2013	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	2014	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.	2015	that, so other libev users can use C<ev_child> watchers freely.
		2016
		2017	=head3 Stopping the Child Watcher
		2018
		2019	Currently, the child watcher never gets stopped, even when the
		2020	child terminates, so normally one needs to stop the watcher in the
		2021	callback. Future versions of libev might stop the watcher automatically
		2022	when a child exit is detected.
1526		2023
1527	=head3 Watcher-Specific Functions and Data Members	2024	=head3 Watcher-Specific Functions and Data Members
1528		2025
1529	=over 4	2026	=over 4
1530		2027
…		…
1559	=head3 Examples	2056	=head3 Examples
1560		2057
1561	Example: C<fork()> a new process and install a child handler to wait for	2058	Example: C<fork()> a new process and install a child handler to wait for
1562	its completion.	2059	its completion.
1563		2060
1564	ev_child cw;	2061	ev_child cw;
1565		2062
1566	static void	2063	static void
1567	child_cb (EV_P_ struct ev_child *w, int revents)	2064	child_cb (EV_P_ ev_child *w, int revents)
1568	{	2065	{
1569	ev_child_stop (EV_A_ w);	2066	ev_child_stop (EV_A_ w);
1570	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2067	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1571	}	2068	}
1572		2069
1573	pid_t pid = fork ();	2070	pid_t pid = fork ();
1574		2071
1575	if (pid < 0)	2072	if (pid < 0)
1576	// error	2073	// error
1577	else if (pid == 0)	2074	else if (pid == 0)
1578	{	2075	{
1579	// the forked child executes here	2076	// the forked child executes here
1580	exit (1);	2077	exit (1);
1581	}	2078	}
1582	else	2079	else
1583	{	2080	{
1584	ev_child_init (&cw, child_cb, pid, 0);	2081	ev_child_init (&cw, child_cb, pid, 0);
1585	ev_child_start (EV_DEFAULT_ &cw);	2082	ev_child_start (EV_DEFAULT_ &cw);
1586	}	2083	}
1587		2084
1588		2085
1589	=head2 C<ev_stat> - did the file attributes just change?	2086	=head2 C<ev_stat> - did the file attributes just change?
1590		2087
1591	This watches a filesystem path for attribute changes. That is, it calls	2088	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	2089	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.	2090	and sees if it changed compared to the last time, invoking the callback if
		2091	it did.
1594		2092
1595	The path does not need to exist: changing from "path exists" to "path does	2093	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	2094	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	2095	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	2096	C<st_nlink> field being zero (which is otherwise always forced to be at
1599	the stat buffer having unspecified contents.	2097	least one) and all the other fields of the stat buffer having unspecified
		2098	contents.
1600		2099
1601	The path I<should> be absolute and I<must not> end in a slash. If it is	2100	The path I<must not> end in a slash or contain special components such as
		2101	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.	2102	your working directory changes, then the behaviour is undefined.
1603		2103
1604	Since there is no standard to do this, the portable implementation simply	2104	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	2105	portable implementation simply calls C<stat(2)> regularly on the path
1606	can specify a recommended polling interval for this case. If you specify	2106	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,	2107	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	2108	recommended!) then a I<suitable, unspecified default> value will be used
1609	five seconds, although this might change dynamically). Libev will also	2109	(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	2110	change dynamically). Libev will also impose a minimum interval which is
1611	usually overkill.	2111	currently around C<0.1>, but that's usually overkill.
1612		2112
1613	This watcher type is not meant for massive numbers of stat watchers,	2113	This watcher type is not meant for massive numbers of stat watchers,
1614	as even with OS-supported change notifications, this can be	2114	as even with OS-supported change notifications, this can be
1615	resource-intensive.	2115	resource-intensive.
1616		2116
1617	At the time of this writing, only the Linux inotify interface is	2117	At the time of this writing, the only OS-specific interface implemented
1618	implemented (implementing kqueue support is left as an exercise for the	2118	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	2119	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	2120	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		2121
1625	=head3 ABI Issues (Largefile Support)	2122	=head3 ABI Issues (Largefile Support)
1626		2123
1627	Libev by default (unless the user overrides this) uses the default	2124	Libev by default (unless the user overrides this) uses the default
1628	compilation environment, which means that on systems with optionally	2125	compilation environment, which means that on systems with large file
1629	disabled large file support, you get the 32 bit version of the stat	2126	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	2127	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	2128	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	2129	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	2130	obviously the case with any flags that change the ABI, but the problem is
1634	most noticably with ev_stat and largefile support.	2131	most noticeably displayed with ev_stat and large file support.
1635		2132
1636	=head3 Inotify	2133	The solution for this is to lobby your distribution maker to make large
		2134	file interfaces available by default (as e.g. FreeBSD does) and not
		2135	optional. Libev cannot simply switch on large file support because it has
		2136	to exchange stat structures with application programs compiled using the
		2137	default compilation environment.
1637		2138
		2139	=head3 Inotify and Kqueue
		2140
1638	When C<inotify (7)> support has been compiled into libev (generally only	2141	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	2142	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	2143	inotify descriptor will be created lazily when the first C<ev_stat>
1641	when the first C<ev_stat> watcher is being started.	2144	watcher is being started.
1642		2145
1643	Inotify presense does not change the semantics of C<ev_stat> watchers	2146	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	2147	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	2148	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.	2149	there are many cases where libev has to resort to regular C<stat> polling,
		2150	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2151	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2152	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2153	xfs are fully working) libev usually gets away without polling.
1647		2154
1648	(There is no support for kqueue, as apparently it cannot be used to	2155	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	2156	implement this functionality, due to the requirement of having a file
1650	descriptor open on the object at all times).	2157	descriptor open on the object at all times, and detecting renames, unlinks
		2158	etc. is difficult.
		2159
		2160	=head3 C<stat ()> is a synchronous operation
		2161
		2162	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2163	the process. The exception are C<ev_stat> watchers - those call C<stat
		2164	()>, which is a synchronous operation.
		2165
		2166	For local paths, this usually doesn't matter: unless the system is very
		2167	busy or the intervals between stat's are large, a stat call will be fast,
		2168	as the path data is usually in memory already (except when starting the
		2169	watcher).
		2170
		2171	For networked file systems, calling C<stat ()> can block an indefinite
		2172	time due to network issues, and even under good conditions, a stat call
		2173	often takes multiple milliseconds.
		2174
		2175	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2176	paths, although this is fully supported by libev.
1651		2177
1652	=head3 The special problem of stat time resolution	2178	=head3 The special problem of stat time resolution
1653		2179
1654	The C<stat ()> syscall only supports full-second resolution portably, and	2180	The C<stat ()> system call only supports full-second resolution portably,
1655	even on systems where the resolution is higher, many filesystems still	2181	and even on systems where the resolution is higher, most file systems
1656	only support whole seconds.	2182	still only support whole seconds.
1657		2183
1658	That means that, if the time is the only thing that changes, you might	2184	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	2185	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	2186	calls your callback, which does something. When there is another update
1661	the same second, C<ev_stat> will be unable to detect it.	2187	within the same second, C<ev_stat> will be unable to detect unless the
		2188	stat data does change in other ways (e.g. file size).
1662		2189
1663	The solution to this is to delay acting on a change for a second (or till	2190	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>	2191	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>	2192	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	2193	ev_timer_again (loop, w)>).
1667	systems.	2194
		2195	The C<.02> offset is added to work around small timing inconsistencies
		2196	of some operating systems (where the second counter of the current time
		2197	might be be delayed. One such system is the Linux kernel, where a call to
		2198	C<gettimeofday> might return a timestamp with a full second later than
		2199	a subsequent C<time> call - if the equivalent of C<time ()> is used to
		2200	update file times then there will be a small window where the kernel uses
		2201	the previous second to update file times but libev might already execute
		2202	the timer callback).
1668		2203
1669	=head3 Watcher-Specific Functions and Data Members	2204	=head3 Watcher-Specific Functions and Data Members
1670		2205
1671	=over 4	2206	=over 4
1672		2207
…		…
1678	C<path>. The C<interval> is a hint on how quickly a change is expected to	2213	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	2214	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	2215	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.	2216	path for as long as the watcher is active.
1682		2217
1683	The callback will be receive C<EV_STAT> when a change was detected,	2218	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	2219	relative to the attributes at the time the watcher was started (or the
1685	last change was detected).	2220	last change was detected).
1686		2221
1687	=item ev_stat_stat (loop, ev_stat *)	2222	=item ev_stat_stat (loop, ev_stat *)
1688		2223
1689	Updates the stat buffer immediately with new values. If you change the	2224	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	2225	watched path in your callback, you could call this function to avoid
1691	detecting this change (while introducing a race condition). Can also be	2226	detecting this change (while introducing a race condition if you are not
1692	useful simply to find out the new values.	2227	the only one changing the path). Can also be useful simply to find out the
		2228	new values.
1693		2229
1694	=item ev_statdata attr [read-only]	2230	=item ev_statdata attr [read-only]
1695		2231
1696	The most-recently detected attributes of the file. Although the type is of	2232	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	2233	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	2234	suitable for your system, but you can only rely on the POSIX-standardised
		2235	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.	2236	some error while C<stat>ing the file.
1700		2237
1701	=item ev_statdata prev [read-only]	2238	=item ev_statdata prev [read-only]
1702		2239
1703	The previous attributes of the file. The callback gets invoked whenever	2240	The previous attributes of the file. The callback gets invoked whenever
1704	C<prev> != C<attr>.	2241	C<prev> != C<attr>, or, more precisely, one or more of these members
		2242	differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>,
		2243	C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>.
1705		2244
1706	=item ev_tstamp interval [read-only]	2245	=item ev_tstamp interval [read-only]
1707		2246
1708	The specified interval.	2247	The specified interval.
1709		2248
1710	=item const char *path [read-only]	2249	=item const char *path [read-only]
1711		2250
1712	The filesystem path that is being watched.	2251	The file system path that is being watched.
1713		2252
1714	=back	2253	=back
1715		2254
1716	=head3 Examples	2255	=head3 Examples
1717		2256
1718	Example: Watch C</etc/passwd> for attribute changes.	2257	Example: Watch C</etc/passwd> for attribute changes.
1719		2258
1720	static void	2259	static void
1721	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	2260	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1722	{	2261	{
1723	/* /etc/passwd changed in some way */	2262	/* /etc/passwd changed in some way */
1724	if (w->attr.st_nlink)	2263	if (w->attr.st_nlink)
1725	{	2264	{
1726	printf ("passwd current size %ld\n", (long)w->attr.st_size);	2265	printf ("passwd current size %ld\n", (long)w->attr.st_size);
1727	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);	2266	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
1728	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);	2267	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
1729	}	2268	}
1730	else	2269	else
1731	/* you shalt not abuse printf for puts */	2270	/* you shalt not abuse printf for puts */
1732	puts ("wow, /etc/passwd is not there, expect problems. "	2271	puts ("wow, /etc/passwd is not there, expect problems. "
1733	"if this is windows, they already arrived\n");	2272	"if this is windows, they already arrived\n");
1734	}	2273	}
1735		2274
1736	...	2275	...
1737	ev_stat passwd;	2276	ev_stat passwd;
1738		2277
1739	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);	2278	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1740	ev_stat_start (loop, &passwd);	2279	ev_stat_start (loop, &passwd);
1741		2280
1742	Example: Like above, but additionally use a one-second delay so we do not	2281	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	2282	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	2283	one might do the work both on C<ev_stat> callback invocation I<and> on
1745	C<ev_timer> callback invocation).	2284	C<ev_timer> callback invocation).
1746		2285
1747	static ev_stat passwd;	2286	static ev_stat passwd;
1748	static ev_timer timer;	2287	static ev_timer timer;
1749		2288
1750	static void	2289	static void
1751	timer_cb (EV_P_ ev_timer *w, int revents)	2290	timer_cb (EV_P_ ev_timer *w, int revents)
1752	{	2291	{
1753	ev_timer_stop (EV_A_ w);	2292	ev_timer_stop (EV_A_ w);
1754		2293
1755	/* now it's one second after the most recent passwd change */	2294	/* now it's one second after the most recent passwd change */
1756	}	2295	}
1757		2296
1758	static void	2297	static void
1759	stat_cb (EV_P_ ev_stat *w, int revents)	2298	stat_cb (EV_P_ ev_stat *w, int revents)
1760	{	2299	{
1761	/* reset the one-second timer */	2300	/* reset the one-second timer */
1762	ev_timer_again (EV_A_ &timer);	2301	ev_timer_again (EV_A_ &timer);
1763	}	2302	}
1764		2303
1765	...	2304	...
1766	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);	2305	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1767	ev_stat_start (loop, &passwd);	2306	ev_stat_start (loop, &passwd);
1768	ev_timer_init (&timer, timer_cb, 0., 1.01);	2307	ev_timer_init (&timer, timer_cb, 0., 1.02);
1769		2308
1770		2309
1771	=head2 C<ev_idle> - when you've got nothing better to do...	2310	=head2 C<ev_idle> - when you've got nothing better to do...
1772		2311
1773	Idle watchers trigger events when no other events of the same or higher	2312	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	2313	priority are pending (prepare, check and other idle watchers do not count
1775	count).	2314	as receiving "events").
1776		2315
1777	That is, as long as your process is busy handling sockets or timeouts	2316	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	2317	(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	2318	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	2319	are pending), the idle watchers are being called once per event loop
…		…
1791		2330
1792	=head3 Watcher-Specific Functions and Data Members	2331	=head3 Watcher-Specific Functions and Data Members
1793		2332
1794	=over 4	2333	=over 4
1795		2334
1796	=item ev_idle_init (ev_signal *, callback)	2335	=item ev_idle_init (ev_idle *, callback)
1797		2336
1798	Initialises and configures the idle watcher - it has no parameters of any	2337	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,	2338	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1800	believe me.	2339	believe me.
1801		2340
…		…
1804	=head3 Examples	2343	=head3 Examples
1805		2344
1806	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2345	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1807	callback, free it. Also, use no error checking, as usual.	2346	callback, free it. Also, use no error checking, as usual.
1808		2347
1809	static void	2348	static void
1810	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2349	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1811	{	2350	{
1812	free (w);	2351	free (w);
1813	// now do something you wanted to do when the program has	2352	// now do something you wanted to do when the program has
1814	// no longer anything immediate to do.	2353	// no longer anything immediate to do.
1815	}	2354	}
1816		2355
1817	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2356	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1818	ev_idle_init (idle_watcher, idle_cb);	2357	ev_idle_init (idle_watcher, idle_cb);
1819	ev_idle_start (loop, idle_cb);	2358	ev_idle_start (loop, idle_cb);
1820		2359
1821		2360
1822	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2361	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1823		2362
1824	Prepare and check watchers are usually (but not always) used in tandem:	2363	Prepare and check watchers are usually (but not always) used in pairs:
1825	prepare watchers get invoked before the process blocks and check watchers	2364	prepare watchers get invoked before the process blocks and check watchers
1826	afterwards.	2365	afterwards.
1827		2366
1828	You I<must not> call C<ev_loop> or similar functions that enter	2367	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>	2368	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,	2371	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	2372	C<ev_check> so if you have one watcher of each kind they will always be
1834	called in pairs bracketing the blocking call.	2373	called in pairs bracketing the blocking call.
1835		2374
1836	Their main purpose is to integrate other event mechanisms into libev and	2375	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	2376	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	2377	variable changes, implement your own watchers, integrate net-snmp or a
1839	coroutine library and lots more. They are also occasionally useful if	2378	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,	2379	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>	2380	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1842	watcher).	2381	watcher).
1843		2382
1844	This is done by examining in each prepare call which file descriptors need	2383	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	2384	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	2385	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	2386	libraries provide exactly this functionality). Then, in the check watcher,
1848	any events that occured (by checking the pending status of all watchers	2387	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	2388	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,	2389	I/O and timer callbacks will never actually be called (but must be valid
1851	because you never know, you know?).	2390	nevertheless, because you never know, you know?).
1852		2391
1853	As another example, the Perl Coro module uses these hooks to integrate	2392	As another example, the Perl Coro module uses these hooks to integrate
1854	coroutines into libev programs, by yielding to other active coroutines	2393	coroutines into libev programs, by yielding to other active coroutines
1855	during each prepare and only letting the process block if no coroutines	2394	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	2395	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	2398	loop from blocking if lower-priority coroutines are active, thus mapping
1860	low-priority coroutines to idle/background tasks).	2399	low-priority coroutines to idle/background tasks).
1861		2400
1862	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2401	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	2402	priority, to ensure that they are being run before any other watchers
		2403	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2404
1864	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2405	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	2406	activate ("feed") events into libev. While libev fully supports this, they
1866	supports this, they will be called before other C<ev_check> watchers	2407	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	2408	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	2409	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	2410	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1870	coexist peacefully with others).	2411	others).
1871		2412
1872	=head3 Watcher-Specific Functions and Data Members	2413	=head3 Watcher-Specific Functions and Data Members
1873		2414
1874	=over 4	2415	=over 4
1875		2416
…		…
1877		2418
1878	=item ev_check_init (ev_check *, callback)	2419	=item ev_check_init (ev_check *, callback)
1879		2420
1880	Initialises and configures the prepare or check watcher - they have no	2421	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>	2422	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.	2423	macros, but using them is utterly, utterly, utterly and completely
		2424	pointless.
1883		2425
1884	=back	2426	=back
1885		2427
1886	=head3 Examples	2428	=head3 Examples
1887		2429
1888	There are a number of principal ways to embed other event loops or modules	2430	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	2431	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	2432	(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>	2433	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	2434	Glib main context into libev, and finally, C<Glib::EV> embeds EV into the
1893	into the Glib event loop).	2435	Glib event loop).
1894		2436
1895	Method 1: Add IO watchers and a timeout watcher in a prepare handler,	2437	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	2438	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	2439	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	2440	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.	2441	the callbacks for the IO/timeout watchers might not have been called yet.
1900		2442
1901	static ev_io iow [nfd];	2443	static ev_io iow [nfd];
1902	static ev_timer tw;	2444	static ev_timer tw;
1903		2445
1904	static void	2446	static void
1905	io_cb (ev_loop *loop, ev_io *w, int revents)	2447	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1906	{	2448	{
1907	}	2449	}
1908		2450
1909	// create io watchers for each fd and a timer before blocking	2451	// create io watchers for each fd and a timer before blocking
1910	static void	2452	static void
1911	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2453	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1912	{	2454	{
1913	int timeout = 3600000;	2455	int timeout = 3600000;
1914	struct pollfd fds [nfd];	2456	struct pollfd fds [nfd];
1915	// actual code will need to loop here and realloc etc.	2457	// actual code will need to loop here and realloc etc.
1916	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2458	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1917		2459
1918	/* the callback is illegal, but won't be called as we stop during check */	2460	/* the callback is illegal, but won't be called as we stop during check */
1919	ev_timer_init (&tw, 0, timeout * 1e-3);	2461	ev_timer_init (&tw, 0, timeout * 1e-3);
1920	ev_timer_start (loop, &tw);	2462	ev_timer_start (loop, &tw);
1921		2463
1922	// create one ev_io per pollfd	2464	// create one ev_io per pollfd
1923	for (int i = 0; i < nfd; ++i)	2465	for (int i = 0; i < nfd; ++i)
1924	{	2466	{
1925	ev_io_init (iow + i, io_cb, fds [i].fd,	2467	ev_io_init (iow + i, io_cb, fds [i].fd,
1926	((fds [i].events & POLLIN ? EV_READ : 0)	2468	((fds [i].events & POLLIN ? EV_READ : 0)
1927	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	2469	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1928		2470
1929	fds [i].revents = 0;	2471	fds [i].revents = 0;
1930	ev_io_start (loop, iow + i);	2472	ev_io_start (loop, iow + i);
1931	}	2473	}
1932	}	2474	}
1933		2475
1934	// stop all watchers after blocking	2476	// stop all watchers after blocking
1935	static void	2477	static void
1936	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2478	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1937	{	2479	{
1938	ev_timer_stop (loop, &tw);	2480	ev_timer_stop (loop, &tw);
1939		2481
1940	for (int i = 0; i < nfd; ++i)	2482	for (int i = 0; i < nfd; ++i)
1941	{	2483	{
1942	// set the relevant poll flags	2484	// set the relevant poll flags
1943	// could also call adns_processreadable etc. here	2485	// could also call adns_processreadable etc. here
1944	struct pollfd *fd = fds + i;	2486	struct pollfd *fd = fds + i;
1945	int revents = ev_clear_pending (iow + i);	2487	int revents = ev_clear_pending (iow + i);
1946	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;	2488	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1947	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;	2489	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1948		2490
1949	// now stop the watcher	2491	// now stop the watcher
1950	ev_io_stop (loop, iow + i);	2492	ev_io_stop (loop, iow + i);
1951	}	2493	}
1952		2494
1953	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	2495	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1954	}	2496	}
1955		2497
1956	Method 2: This would be just like method 1, but you run C<adns_afterpoll>	2498	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.	2499	in the prepare watcher and would dispose of the check watcher.
1958		2500
1959	Method 3: If the module to be embedded supports explicit event	2501	Method 3: If the module to be embedded supports explicit event
1960	notification (adns does), you can also make use of the actual watcher	2502	notification (libadns does), you can also make use of the actual watcher
1961	callbacks, and only destroy/create the watchers in the prepare watcher.	2503	callbacks, and only destroy/create the watchers in the prepare watcher.
1962		2504
1963	static void	2505	static void
1964	timer_cb (EV_P_ ev_timer *w, int revents)	2506	timer_cb (EV_P_ ev_timer *w, int revents)
1965	{	2507	{
1966	adns_state ads = (adns_state)w->data;	2508	adns_state ads = (adns_state)w->data;
1967	update_now (EV_A);	2509	update_now (EV_A);
1968		2510
1969	adns_processtimeouts (ads, &tv_now);	2511	adns_processtimeouts (ads, &tv_now);
1970	}	2512	}
1971		2513
1972	static void	2514	static void
1973	io_cb (EV_P_ ev_io *w, int revents)	2515	io_cb (EV_P_ ev_io *w, int revents)
1974	{	2516	{
1975	adns_state ads = (adns_state)w->data;	2517	adns_state ads = (adns_state)w->data;
1976	update_now (EV_A);	2518	update_now (EV_A);
1977		2519
1978	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);	2520	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1979	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);	2521	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1980	}	2522	}
1981		2523
1982	// do not ever call adns_afterpoll	2524	// do not ever call adns_afterpoll
1983		2525
1984	Method 4: Do not use a prepare or check watcher because the module you	2526	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	2527	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	2528	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	2529	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
1988	this.	2530	this approach, effectively embedding EV as a client into the horrible
		2531	libglib event loop.
1989		2532
1990	static gint	2533	static gint
1991	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2534	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1992	{	2535	{
1993	int got_events = 0;	2536	int got_events = 0;
1994		2537
1995	for (n = 0; n < nfds; ++n)	2538	for (n = 0; n < nfds; ++n)
1996	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events	2539	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1997		2540
1998	if (timeout >= 0)	2541	if (timeout >= 0)
1999	// create/start timer	2542	// create/start timer
2000		2543
2001	// poll	2544	// poll
2002	ev_loop (EV_A_ 0);	2545	ev_loop (EV_A_ 0);
2003		2546
2004	// stop timer again	2547	// stop timer again
2005	if (timeout >= 0)	2548	if (timeout >= 0)
2006	ev_timer_stop (EV_A_ &to);	2549	ev_timer_stop (EV_A_ &to);
2007		2550
2008	// stop io watchers again - their callbacks should have set	2551	// stop io watchers again - their callbacks should have set
2009	for (n = 0; n < nfds; ++n)	2552	for (n = 0; n < nfds; ++n)
2010	ev_io_stop (EV_A_ iow [n]);	2553	ev_io_stop (EV_A_ iow [n]);
2011		2554
2012	return got_events;	2555	return got_events;
2013	}	2556	}
2014		2557
2015		2558
2016	=head2 C<ev_embed> - when one backend isn't enough...	2559	=head2 C<ev_embed> - when one backend isn't enough...
2017		2560
2018	This is a rather advanced watcher type that lets you embed one event loop	2561	This is a rather advanced watcher type that lets you embed one event loop
…		…
2024	prioritise I/O.	2567	prioritise I/O.
2025		2568
2026	As an example for a bug workaround, the kqueue backend might only support	2569	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	2570	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	2571	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	2572	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	2573	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	2574	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.	2575	C<kevent>, but at least you can use both mechanisms for what they are
		2576	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2033		2577
2034	As for prioritising I/O: rarely you have the case where some fds have	2578	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	2579	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	2580	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	2581	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.	2582	the rest in a second one, and embed the second one in the first.
2039		2583
2040	As long as the watcher is active, the callback will be invoked every time	2584	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	2585	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	2586	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	2587	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	2588	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	2589	to give the embedded loop strictly lower priority for example).
2046	embedded loop sweep.
2047		2590
2048	As long as the watcher is started it will automatically handle events. The	2591	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	2592	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		2593
2053	Also, there have not currently been made special provisions for forking:	2594	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,	2595	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	2596	embedding loop forks. In other cases, the user is responsible for calling
2056	yourself.	2597	C<ev_loop_fork> on the embedded loop.
2057		2598
2058	Unfortunately, not all backends are embeddable, only the ones returned by	2599	Unfortunately, not all backends are embeddable: only the ones returned by
2059	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2600	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2060	portable one.	2601	portable one.
2061		2602
2062	So when you want to use this feature you will always have to be prepared	2603	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	2604	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	2605	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.	2606	create it, and if that fails, use the normal loop for everything.
2066		2607
		2608	=head3 C<ev_embed> and fork
		2609
		2610	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2611	automatically be applied to the embedded loop as well, so no special
		2612	fork handling is required in that case. When the watcher is not running,
		2613	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2614	as applicable.
		2615
2067	=head3 Watcher-Specific Functions and Data Members	2616	=head3 Watcher-Specific Functions and Data Members
2068		2617
2069	=over 4	2618	=over 4
2070		2619
2071	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2620	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
2074		2623
2075	Configures the watcher to embed the given loop, which must be	2624	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	2625	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	2626	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,	2627	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).	2628	if you do not want that, you need to temporarily stop the embed watcher).
2080		2629
2081	=item ev_embed_sweep (loop, ev_embed *)	2630	=item ev_embed_sweep (loop, ev_embed *)
2082		2631
2083	Make a single, non-blocking sweep over the embedded loop. This works	2632	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	2633	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
2085	apropriate way for embedded loops.	2634	appropriate way for embedded loops.
2086		2635
2087	=item struct ev_loop *other [read-only]	2636	=item struct ev_loop *other [read-only]
2088		2637
2089	The embedded event loop.	2638	The embedded event loop.
2090		2639
…		…
2092		2641
2093	=head3 Examples	2642	=head3 Examples
2094		2643
2095	Example: Try to get an embeddable event loop and embed it into the default	2644	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	2645	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	2646	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	2647	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2099	used).	2648	used).
2100		2649
2101	struct ev_loop *loop_hi = ev_default_init (0);	2650	struct ev_loop *loop_hi = ev_default_init (0);
2102	struct ev_loop *loop_lo = 0;	2651	struct ev_loop *loop_lo = 0;
2103	struct ev_embed embed;	2652	ev_embed embed;
2104		2653
2105	// see if there is a chance of getting one that works	2654	// see if there is a chance of getting one that works
2106	// (remember that a flags value of 0 means autodetection)	2655	// (remember that a flags value of 0 means autodetection)
2107	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2656	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2108	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2657	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2109	: 0;	2658	: 0;
2110		2659
2111	// if we got one, then embed it, otherwise default to loop_hi	2660	// if we got one, then embed it, otherwise default to loop_hi
2112	if (loop_lo)	2661	if (loop_lo)
2113	{	2662	{
2114	ev_embed_init (&embed, 0, loop_lo);	2663	ev_embed_init (&embed, 0, loop_lo);
2115	ev_embed_start (loop_hi, &embed);	2664	ev_embed_start (loop_hi, &embed);
2116	}	2665	}
2117	else	2666	else
2118	loop_lo = loop_hi;	2667	loop_lo = loop_hi;
2119		2668
2120	Example: Check if kqueue is available but not recommended and create	2669	Example: Check if kqueue is available but not recommended and create
2121	a kqueue backend for use with sockets (which usually work with any	2670	a kqueue backend for use with sockets (which usually work with any
2122	kqueue implementation). Store the kqueue/socket-only event loop in	2671	kqueue implementation). Store the kqueue/socket-only event loop in
2123	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2672	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2124		2673
2125	struct ev_loop *loop = ev_default_init (0);	2674	struct ev_loop *loop = ev_default_init (0);
2126	struct ev_loop *loop_socket = 0;	2675	struct ev_loop *loop_socket = 0;
2127	struct ev_embed embed;	2676	ev_embed embed;
2128		2677
2129	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2678	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2130	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2679	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2131	{	2680	{
2132	ev_embed_init (&embed, 0, loop_socket);	2681	ev_embed_init (&embed, 0, loop_socket);
2133	ev_embed_start (loop, &embed);	2682	ev_embed_start (loop, &embed);
2134	}	2683	}
2135		2684
2136	if (!loop_socket)	2685	if (!loop_socket)
2137	loop_socket = loop;	2686	loop_socket = loop;
2138		2687
2139	// now use loop_socket for all sockets, and loop for everything else	2688	// now use loop_socket for all sockets, and loop for everything else
2140		2689
2141		2690
2142	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2691	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2143		2692
2144	Fork watchers are called when a C<fork ()> was detected (usually because	2693	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
2188	is that the author does not know of a simple (or any) algorithm for a	2737	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	2738	multiple-writer-single-reader queue that works in all cases and doesn't
2190	need elaborate support such as pthreads.	2739	need elaborate support such as pthreads.
2191		2740
2192	That means that if you want to queue data, you have to provide your own	2741	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	2742	queue. But at least I can tell you how to implement locking around your
2194	queue:	2743	queue:
2195		2744
2196	=over 4	2745	=over 4
2197		2746
2198	=item queueing from a signal handler context	2747	=item queueing from a signal handler context
2199		2748
2200	To implement race-free queueing, you simply add to the queue in the signal	2749	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	2750	handler but you block the signal handler in the watcher callback. Here is
2202	some fictitiuous SIGUSR1 handler:	2751	an example that does that for some fictitious SIGUSR1 handler:
2203		2752
2204	static ev_async mysig;	2753	static ev_async mysig;
2205		2754
2206	static void	2755	static void
2207	sigusr1_handler (void)	2756	sigusr1_handler (void)
…		…
2273	=over 4	2822	=over 4
2274		2823
2275	=item ev_async_init (ev_async *, callback)	2824	=item ev_async_init (ev_async *, callback)
2276		2825
2277	Initialises and configures the async watcher - it has no parameters of any	2826	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,	2827	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2279	believe me.	2828	trust me.
2280		2829
2281	=item ev_async_send (loop, ev_async *)	2830	=item ev_async_send (loop, ev_async *)
2282		2831
2283	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2832	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	2833	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	2834	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	2835	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2287	section below on what exactly this means).	2836	section below on what exactly this means).
2288		2837
		2838	Note that, as with other watchers in libev, multiple events might get
		2839	compressed into a single callback invocation (another way to look at this
		2840	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2841	reset when the event loop detects that).
		2842
2289	This call incurs the overhead of a syscall only once per loop iteration,	2843	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	2844	iteration, so while the overhead might be noticeable, it doesn't apply to
2291	calls to C<ev_async_send>.	2845	repeated calls to C<ev_async_send> for the same event loop.
2292		2846
2293	=item bool = ev_async_pending (ev_async *)	2847	=item bool = ev_async_pending (ev_async *)
2294		2848
2295	Returns a non-zero value when C<ev_async_send> has been called on the	2849	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	2850	watcher but the event has not yet been processed (or even noted) by the
2297	event loop.	2851	event loop.
2298		2852
2299	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2853	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,	2854	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	2855	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.	2856	quickly check whether invoking the loop might be a good idea.
2303		2857
2304	Not that this does I<not> check wether the watcher itself is pending, only	2858	Not that this does I<not> check whether the watcher itself is pending,
2305	wether it has been requested to make this watcher pending.	2859	only whether it has been requested to make this watcher pending: there
		2860	is a time window between the event loop checking and resetting the async
		2861	notification, and the callback being invoked.
2306		2862
2307	=back	2863	=back
2308		2864
2309		2865
2310	=head1 OTHER FUNCTIONS	2866	=head1 OTHER FUNCTIONS
…		…
2314	=over 4	2870	=over 4
2315		2871
2316	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2872	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2317		2873
2318	This function combines a simple timer and an I/O watcher, calls your	2874	This function combines a simple timer and an I/O watcher, calls your
2319	callback on whichever event happens first and automatically stop both	2875	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	2876	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	2877	or timeout without having to allocate/configure/start/stop/free one or
2322	more watchers yourself.	2878	more watchers yourself.
2323		2879
2324	If C<fd> is less than 0, then no I/O watcher will be started and events	2880	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	2881	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2326	C<events> set will be craeted and started.	2882	the given C<fd> and C<events> set will be created and started.
2327		2883
2328	If C<timeout> is less than 0, then no timeout watcher will be	2884	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	2885	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	2886	repeat = 0) will be started. C<0> is a valid timeout.
2331	dubious value.
2332		2887
2333	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2888	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	2889	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>	2890	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2336	value passed to C<ev_once>:	2891	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2892	a timeout and an io event at the same time - you probably should give io
		2893	events precedence.
2337		2894
		2895	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
		2896
2338	static void stdin_ready (int revents, void *arg)	2897	static void stdin_ready (int revents, void *arg)
2339	{	2898	{
2340	if (revents & EV_TIMEOUT)
2341	/* doh, nothing entered */;
2342	else if (revents & EV_READ)	2899	if (revents & EV_READ)
2343	/* stdin might have data for us, joy! */;	2900	/* stdin might have data for us, joy! */;
		2901	else if (revents & EV_TIMEOUT)
		2902	/* doh, nothing entered */;
2344	}	2903	}
2345		2904
2346	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2905	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2347		2906
2348	=item ev_feed_event (ev_loop *, watcher *, int revents)	2907	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2349		2908
2350	Feeds the given event set into the event loop, as if the specified event	2909	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	2910	had happened for the specified watcher (which must be a pointer to an
2352	initialised but not necessarily started event watcher).	2911	initialised but not necessarily started event watcher).
2353		2912
2354	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2913	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2355		2914
2356	Feed an event on the given fd, as if a file descriptor backend detected	2915	Feed an event on the given fd, as if a file descriptor backend detected
2357	the given events it.	2916	the given events it.
2358		2917
2359	=item ev_feed_signal_event (ev_loop *loop, int signum)	2918	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2360		2919
2361	Feed an event as if the given signal occured (C<loop> must be the default	2920	Feed an event as if the given signal occurred (C<loop> must be the default
2362	loop!).	2921	loop!).
2363		2922
2364	=back	2923	=back
2365		2924
2366		2925
…		…
2382		2941
2383	=item * Priorities are not currently supported. Initialising priorities	2942	=item * Priorities are not currently supported. Initialising priorities
2384	will fail and all watchers will have the same priority, even though there	2943	will fail and all watchers will have the same priority, even though there
2385	is an ev_pri field.	2944	is an ev_pri field.
2386		2945
		2946	=item * In libevent, the last base created gets the signals, in libev, the
		2947	first base created (== the default loop) gets the signals.
		2948
2387	=item * Other members are not supported.	2949	=item * Other members are not supported.
2388		2950
2389	=item * The libev emulation is I<not> ABI compatible to libevent, you need	2951	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2390	to use the libev header file and library.	2952	to use the libev header file and library.
2391		2953
2392	=back	2954	=back
2393		2955
2394	=head1 C++ SUPPORT	2956	=head1 C++ SUPPORT
2395		2957
2396	Libev comes with some simplistic wrapper classes for C++ that mainly allow	2958	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	2959	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.	2960	the callback model to a model using method callbacks on objects.
2399		2961
2400	To use it,	2962	To use it,
2401		2963
2402	#include <ev++.h>	2964	#include <ev++.h>
2403		2965
2404	This automatically includes F<ev.h> and puts all of its definitions (many	2966	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	2967	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	2968	put into the C<ev> namespace. It should support all the same embedding
2407	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.	2969	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
…		…
2474	your compiler is good :), then the method will be fully inlined into the	3036	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.	3037	thunking function, making it as fast as a direct C callback.
2476		3038
2477	Example: simple class declaration and watcher initialisation	3039	Example: simple class declaration and watcher initialisation
2478		3040
2479	struct myclass	3041	struct myclass
2480	{	3042	{
2481	void io_cb (ev::io &w, int revents) { }	3043	void io_cb (ev::io &w, int revents) { }
2482	}	3044	}
2483		3045
2484	myclass obj;	3046	myclass obj;
2485	ev::io iow;	3047	ev::io iow;
2486	iow.set <myclass, &myclass::io_cb> (&obj);	3048	iow.set <myclass, &myclass::io_cb> (&obj);
		3049
		3050	=item w->set (object *)
		3051
		3052	This is an B<experimental> feature that might go away in a future version.
		3053
		3054	This is a variation of a method callback - leaving out the method to call
		3055	will default the method to C<operator ()>, which makes it possible to use
		3056	functor objects without having to manually specify the C<operator ()> all
		3057	the time. Incidentally, you can then also leave out the template argument
		3058	list.
		3059
		3060	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3061	int revents)>.
		3062
		3063	See the method-C<set> above for more details.
		3064
		3065	Example: use a functor object as callback.
		3066
		3067	struct myfunctor
		3068	{
		3069	void operator() (ev::io &w, int revents)
		3070	{
		3071	...
		3072	}
		3073	}
		3074
		3075	myfunctor f;
		3076
		3077	ev::io w;
		3078	w.set (&f);
2487		3079
2488	=item w->set<function> (void *data = 0)	3080	=item w->set<function> (void *data = 0)
2489		3081
2490	Also sets a callback, but uses a static method or plain function as	3082	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	3083	callback. The optional C<data> argument will be stored in the watcher's
…		…
2493		3085
2494	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3086	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2495		3087
2496	See the method-C<set> above for more details.	3088	See the method-C<set> above for more details.
2497		3089
2498	Example:	3090	Example: Use a plain function as callback.
2499		3091
2500	static void io_cb (ev::io &w, int revents) { }	3092	static void io_cb (ev::io &w, int revents) { }
2501	iow.set <io_cb> ();	3093	iow.set <io_cb> ();
2502		3094
2503	=item w->set (struct ev_loop *)	3095	=item w->set (struct ev_loop *)
2504		3096
2505	Associates a different C<struct ev_loop> with this watcher. You can only	3097	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).	3098	do this when the watcher is inactive (and not pending either).
2507		3099
2508	=item w->set ([args])	3100	=item w->set ([arguments])
2509		3101
2510	Basically the same as C<ev_TYPE_set>, with the same args. Must be	3102	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	3103	called at least once. Unlike the C counterpart, an active watcher gets
2512	automatically stopped and restarted when reconfiguring it with this	3104	automatically stopped and restarted when reconfiguring it with this
2513	method.	3105	method.
2514		3106
2515	=item w->start ()	3107	=item w->start ()
…		…
2539	=back	3131	=back
2540		3132
2541	Example: Define a class with an IO and idle watcher, start one of them in	3133	Example: Define a class with an IO and idle watcher, start one of them in
2542	the constructor.	3134	the constructor.
2543		3135
2544	class myclass	3136	class myclass
2545	{	3137	{
2546	ev::io io; void io_cb (ev::io &w, int revents);	3138	ev::io io ; void io_cb (ev::io &w, int revents);
2547	ev:idle idle void idle_cb (ev::idle &w, int revents);	3139	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2548		3140
2549	myclass (int fd)	3141	myclass (int fd)
2550	{	3142	{
2551	io .set <myclass, &myclass::io_cb > (this);	3143	io .set <myclass, &myclass::io_cb > (this);
2552	idle.set <myclass, &myclass::idle_cb> (this);	3144	idle.set <myclass, &myclass::idle_cb> (this);
2553		3145
2554	io.start (fd, ev::READ);	3146	io.start (fd, ev::READ);
2555	}	3147	}
2556	};	3148	};
2557		3149
2558		3150
2559	=head1 OTHER LANGUAGE BINDINGS	3151	=head1 OTHER LANGUAGE BINDINGS
2560		3152
2561	Libev does not offer other language bindings itself, but bindings for a	3153	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	3154	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	3155	any interesting language binding in addition to the ones listed here, drop
2564	me a note.	3156	me a note.
2565		3157
2566	=over 4	3158	=over 4
2567		3159
2568	=item Perl	3160	=item Perl
2569		3161
2570	The EV module implements the full libev API and is actually used to test	3162	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,	3163	libev. EV is developed together with libev. Apart from the EV core module,
2572	there are additional modules that implement libev-compatible interfaces	3164	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	3165	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>).	3166	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3167	and C<EV::Glib>).
2575		3168
2576	It can be found and installed via CPAN, its homepage is found at	3169	It can be found and installed via CPAN, its homepage is at
2577	L<http://software.schmorp.de/pkg/EV>.	3170	L<http://software.schmorp.de/pkg/EV>.
2578		3171
		3172	=item Python
		3173
		3174	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3175	seems to be quite complete and well-documented.
		3176
2579	=item Ruby	3177	=item Ruby
2580		3178
2581	Tony Arcieri has written a ruby extension that offers access to a subset	3179	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	3180	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	3181	more on top of it. It can be found via gem servers. Its homepage is at
2584	L<http://rev.rubyforge.org/>.	3182	L<http://rev.rubyforge.org/>.
2585		3183
		3184	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3185	makes rev work even on mingw.
		3186
		3187	=item Haskell
		3188
		3189	A haskell binding to libev is available at
		3190	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3191
2586	=item D	3192	=item D
2587		3193
2588	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3194	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>.	3195	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3196
		3197	=item Ocaml
		3198
		3199	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3200	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2590		3201
2591	=back	3202	=back
2592		3203
2593		3204
2594	=head1 MACRO MAGIC	3205	=head1 MACRO MAGIC
2595		3206
2596	Libev can be compiled with a variety of options, the most fundamantal	3207	Libev can be compiled with a variety of options, the most fundamental
2597	of which is C<EV_MULTIPLICITY>. This option determines whether (most)	3208	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2598	functions and callbacks have an initial C<struct ev_loop *> argument.	3209	functions and callbacks have an initial C<struct ev_loop *> argument.
2599		3210
2600	To make it easier to write programs that cope with either variant, the	3211	To make it easier to write programs that cope with either variant, the
2601	following macros are defined:	3212	following macros are defined:
…		…
2606		3217
2607	This provides the loop I<argument> for functions, if one is required ("ev	3218	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,	3219	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:	3220	C<EV_A_> is used when other arguments are following. Example:
2610		3221
2611	ev_unref (EV_A);	3222	ev_unref (EV_A);
2612	ev_timer_add (EV_A_ watcher);	3223	ev_timer_add (EV_A_ watcher);
2613	ev_loop (EV_A_ 0);	3224	ev_loop (EV_A_ 0);
2614		3225
2615	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3226	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2616	which is often provided by the following macro.	3227	which is often provided by the following macro.
2617		3228
2618	=item C<EV_P>, C<EV_P_>	3229	=item C<EV_P>, C<EV_P_>
2619		3230
2620	This provides the loop I<parameter> for functions, if one is required ("ev	3231	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,	3232	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:	3233	C<EV_P_> is used when other parameters are following. Example:
2623		3234
2624	// this is how ev_unref is being declared	3235	// this is how ev_unref is being declared
2625	static void ev_unref (EV_P);	3236	static void ev_unref (EV_P);
2626		3237
2627	// this is how you can declare your typical callback	3238	// this is how you can declare your typical callback
2628	static void cb (EV_P_ ev_timer *w, int revents)	3239	static void cb (EV_P_ ev_timer *w, int revents)
2629		3240
2630	It declares a parameter C<loop> of type C<struct ev_loop *>, quite	3241	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
2631	suitable for use with C<EV_A>.	3242	suitable for use with C<EV_A>.
2632		3243
2633	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	3244	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2634		3245
2635	Similar to the other two macros, this gives you the value of the default	3246	Similar to the other two macros, this gives you the value of the default
2636	loop, if multiple loops are supported ("ev loop default").	3247	loop, if multiple loops are supported ("ev loop default").
		3248
		3249	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
		3250
		3251	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
		3252	default loop has been initialised (C<UC> == unchecked). Their behaviour
		3253	is undefined when the default loop has not been initialised by a previous
		3254	execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>.
		3255
		3256	It is often prudent to use C<EV_DEFAULT> when initialising the first
		3257	watcher in a function but use C<EV_DEFAULT_UC> afterwards.
2637		3258
2638	=back	3259	=back
2639		3260
2640	Example: Declare and initialise a check watcher, utilising the above	3261	Example: Declare and initialise a check watcher, utilising the above
2641	macros so it will work regardless of whether multiple loops are supported	3262	macros so it will work regardless of whether multiple loops are supported
2642	or not.	3263	or not.
2643		3264
2644	static void	3265	static void
2645	check_cb (EV_P_ ev_timer *w, int revents)	3266	check_cb (EV_P_ ev_timer *w, int revents)
2646	{	3267	{
2647	ev_check_stop (EV_A_ w);	3268	ev_check_stop (EV_A_ w);
2648	}	3269	}
2649		3270
2650	ev_check check;	3271	ev_check check;
2651	ev_check_init (&check, check_cb);	3272	ev_check_init (&check, check_cb);
2652	ev_check_start (EV_DEFAULT_ &check);	3273	ev_check_start (EV_DEFAULT_ &check);
2653	ev_loop (EV_DEFAULT_ 0);	3274	ev_loop (EV_DEFAULT_ 0);
2654		3275
2655	=head1 EMBEDDING	3276	=head1 EMBEDDING
2656		3277
2657	Libev can (and often is) directly embedded into host	3278	Libev can (and often is) directly embedded into host
2658	applications. Examples of applications that embed it include the Deliantra	3279	applications. Examples of applications that embed it include the Deliantra
…		…
2665	libev somewhere in your source tree).	3286	libev somewhere in your source tree).
2666		3287
2667	=head2 FILESETS	3288	=head2 FILESETS
2668		3289
2669	Depending on what features you need you need to include one or more sets of files	3290	Depending on what features you need you need to include one or more sets of files
2670	in your app.	3291	in your application.
2671		3292
2672	=head3 CORE EVENT LOOP	3293	=head3 CORE EVENT LOOP
2673		3294
2674	To include only the libev core (all the C<ev_*> functions), with manual	3295	To include only the libev core (all the C<ev_*> functions), with manual
2675	configuration (no autoconf):	3296	configuration (no autoconf):
2676		3297
2677	#define EV_STANDALONE 1	3298	#define EV_STANDALONE 1
2678	#include "ev.c"	3299	#include "ev.c"
2679		3300
2680	This will automatically include F<ev.h>, too, and should be done in a	3301	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	3302	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	3303	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	3304	done by writing a wrapper around F<ev.h> that you can include instead and
2684	where you can put other configuration options):	3305	where you can put other configuration options):
2685		3306
2686	#define EV_STANDALONE 1	3307	#define EV_STANDALONE 1
2687	#include "ev.h"	3308	#include "ev.h"
2688		3309
2689	Both header files and implementation files can be compiled with a C++	3310	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	3311	compiler (at least, that's a stated goal, and breakage will be treated
2691	as a bug).	3312	as a bug).
2692		3313
2693	You need the following files in your source tree, or in a directory	3314	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):	3315	in your include path (e.g. in libev/ when using -Ilibev):
2695		3316
2696	ev.h	3317	ev.h
2697	ev.c	3318	ev.c
2698	ev_vars.h	3319	ev_vars.h
2699	ev_wrap.h	3320	ev_wrap.h
2700		3321
2701	ev_win32.c required on win32 platforms only	3322	ev_win32.c required on win32 platforms only
2702		3323
2703	ev_select.c only when select backend is enabled (which is enabled by default)	3324	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)	3325	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)	3326	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)	3327	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)	3328	ev_port.c only when the solaris port backend is enabled (disabled by default)
2708		3329
2709	F<ev.c> includes the backend files directly when enabled, so you only need	3330	F<ev.c> includes the backend files directly when enabled, so you only need
2710	to compile this single file.	3331	to compile this single file.
2711		3332
2712	=head3 LIBEVENT COMPATIBILITY API	3333	=head3 LIBEVENT COMPATIBILITY API
2713		3334
2714	To include the libevent compatibility API, also include:	3335	To include the libevent compatibility API, also include:
2715		3336
2716	#include "event.c"	3337	#include "event.c"
2717		3338
2718	in the file including F<ev.c>, and:	3339	in the file including F<ev.c>, and:
2719		3340
2720	#include "event.h"	3341	#include "event.h"
2721		3342
2722	in the files that want to use the libevent API. This also includes F<ev.h>.	3343	in the files that want to use the libevent API. This also includes F<ev.h>.
2723		3344
2724	You need the following additional files for this:	3345	You need the following additional files for this:
2725		3346
2726	event.h	3347	event.h
2727	event.c	3348	event.c
2728		3349
2729	=head3 AUTOCONF SUPPORT	3350	=head3 AUTOCONF SUPPORT
2730		3351
2731	Instead of using C<EV_STANDALONE=1> and providing your config in	3352	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	3353	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	3354	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
2734	include F<config.h> and configure itself accordingly.	3355	include F<config.h> and configure itself accordingly.
2735		3356
2736	For this of course you need the m4 file:	3357	For this of course you need the m4 file:
2737		3358
2738	libev.m4	3359	libev.m4
2739		3360
2740	=head2 PREPROCESSOR SYMBOLS/MACROS	3361	=head2 PREPROCESSOR SYMBOLS/MACROS
2741		3362
2742	Libev can be configured via a variety of preprocessor symbols you have to define	3363	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	3364	define before including any of its files. The default in the absence of
2744	and only include the select backend.	3365	autoconf is documented for every option.
2745		3366
2746	=over 4	3367	=over 4
2747		3368
2748	=item EV_STANDALONE	3369	=item EV_STANDALONE
2749		3370
…		…
2751	keeps libev from including F<config.h>, and it also defines dummy	3372	keeps libev from including F<config.h>, and it also defines dummy
2752	implementations for some libevent functions (such as logging, which is not	3373	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	3374	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.	3375	F<event.h> that are not directly supported by the libev core alone.
2755		3376
		3377	In stanbdalone mode, libev will still try to automatically deduce the
		3378	configuration, but has to be more conservative.
		3379
2756	=item EV_USE_MONOTONIC	3380	=item EV_USE_MONOTONIC
2757		3381
2758	If defined to be C<1>, libev will try to detect the availability of the	3382	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	3383	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	3384	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	3385	you usually have to link against librt or something similar. Enabling it
2762	the functionality isn't available is safe, though, although you have	3386	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>	3387	to make sure you link against any libraries where the C<clock_gettime>
2764	function is hiding in (often F<-lrt>).	3388	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2765		3389
2766	=item EV_USE_REALTIME	3390	=item EV_USE_REALTIME
2767		3391
2768	If defined to be C<1>, libev will try to detect the availability of the	3392	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	3393	real-time clock option at compile time (and assume its availability
2770	runtime if successful). Otherwise no use of the realtime clock option will	3394	at runtime if successful). Otherwise no use of the real-time clock
2771	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3395	option will be attempted. This effectively replaces C<gettimeofday>
2772	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3396	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2773	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3397	correctness. See the note about libraries in the description of
		3398	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3399	C<EV_USE_CLOCK_SYSCALL>.
		3400
		3401	=item EV_USE_CLOCK_SYSCALL
		3402
		3403	If defined to be C<1>, libev will try to use a direct syscall instead
		3404	of calling the system-provided C<clock_gettime> function. This option
		3405	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3406	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3407	programs needlessly. Using a direct syscall is slightly slower (in
		3408	theory), because no optimised vdso implementation can be used, but avoids
		3409	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3410	higher, as it simplifies linking (no need for C<-lrt>).
2774		3411
2775	=item EV_USE_NANOSLEEP	3412	=item EV_USE_NANOSLEEP
2776		3413
2777	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3414	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 ()>.	3415	and will use it for delays. Otherwise it will use C<select ()>.
2779		3416
		3417	=item EV_USE_EVENTFD
		3418
		3419	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		3420	available and will probe for kernel support at runtime. This will improve
		3421	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		3422	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		3423	2.7 or newer, otherwise disabled.
		3424
2780	=item EV_USE_SELECT	3425	=item EV_USE_SELECT
2781		3426
2782	If undefined or defined to be C<1>, libev will compile in support for the	3427	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	3428	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	3429	other method takes over, select will be it. Otherwise the select backend
2785	will not be compiled in.	3430	will not be compiled in.
2786		3431
2787	=item EV_SELECT_USE_FD_SET	3432	=item EV_SELECT_USE_FD_SET
2788		3433
2789	If defined to C<1>, then the select backend will use the system C<fd_set>	3434	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	3435	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	3436	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	3437	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	3438	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	3439	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2795	influence the size of the C<fd_set> used.	3440	configures the maximum size of the C<fd_set>.
2796		3441
2797	=item EV_SELECT_IS_WINSOCKET	3442	=item EV_SELECT_IS_WINSOCKET
2798		3443
2799	When defined to C<1>, the select backend will assume that	3444	When defined to C<1>, the select backend will assume that
2800	select/socket/connect etc. don't understand file descriptors but	3445	select/socket/connect etc. don't understand file descriptors but
…		…
2820		3465
2821	=item EV_USE_EPOLL	3466	=item EV_USE_EPOLL
2822		3467
2823	If defined to be C<1>, libev will compile in support for the Linux	3468	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,	3469	C<epoll>(7) backend. Its availability will be detected at runtime,
2825	otherwise another method will be used as fallback. This is the	3470	otherwise another method will be used as fallback. This is the preferred
2826	preferred backend for GNU/Linux systems.	3471	backend for GNU/Linux systems. If undefined, it will be enabled if the
		3472	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2827		3473
2828	=item EV_USE_KQUEUE	3474	=item EV_USE_KQUEUE
2829		3475
2830	If defined to be C<1>, libev will compile in support for the BSD style	3476	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,	3477	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	3490	otherwise another method will be used as fallback. This is the preferred
2845	backend for Solaris 10 systems.	3491	backend for Solaris 10 systems.
2846		3492
2847	=item EV_USE_DEVPOLL	3493	=item EV_USE_DEVPOLL
2848		3494
2849	reserved for future expansion, works like the USE symbols above.	3495	Reserved for future expansion, works like the USE symbols above.
2850		3496
2851	=item EV_USE_INOTIFY	3497	=item EV_USE_INOTIFY
2852		3498
2853	If defined to be C<1>, libev will compile in support for the Linux inotify	3499	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	3500	interface to speed up C<ev_stat> watchers. Its actual availability will
2855	be detected at runtime.	3501	be detected at runtime. If undefined, it will be enabled if the headers
		3502	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
2856		3503
2857	=item EV_ATOMIC_T	3504	=item EV_ATOMIC_T
2858		3505
2859	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	3506	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	3507	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	3508	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"	3509	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.	3510	as well as for signal and thread safety in C<ev_async> watchers.
2864		3511
2865	In the absense of this define, libev will use C<sig_atomic_t volatile>	3512	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.	3513	(from F<signal.h>), which is usually good enough on most platforms.
2867		3514
2868	=item EV_H	3515	=item EV_H
2869		3516
2870	The name of the F<ev.h> header file used to include it. The default if	3517	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	3556	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	3557	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	3558	and time, so using the defaults of five priorities (-2 .. +2) is usually
2912	fine.	3559	fine.
2913		3560
2914	If your embedding app does not need any priorities, defining these both to	3561	If your embedding application does not need any priorities, defining these
2915	C<0> will save some memory and cpu.	3562	both to C<0> will save some memory and CPU.
2916		3563
2917	=item EV_PERIODIC_ENABLE	3564	=item EV_PERIODIC_ENABLE
2918		3565
2919	If undefined or defined to be C<1>, then periodic timers are supported. If	3566	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	3567	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
2927	code.	3574	code.
2928		3575
2929	=item EV_EMBED_ENABLE	3576	=item EV_EMBED_ENABLE
2930		3577
2931	If undefined or defined to be C<1>, then embed watchers are supported. If	3578	If undefined or defined to be C<1>, then embed watchers are supported. If
2932	defined to be C<0>, then they are not.	3579	defined to be C<0>, then they are not. Embed watchers rely on most other
		3580	watcher types, which therefore must not be disabled.
2933		3581
2934	=item EV_STAT_ENABLE	3582	=item EV_STAT_ENABLE
2935		3583
2936	If undefined or defined to be C<1>, then stat watchers are supported. If	3584	If undefined or defined to be C<1>, then stat watchers are supported. If
2937	defined to be C<0>, then they are not.	3585	defined to be C<0>, then they are not.
…		…
2947	defined to be C<0>, then they are not.	3595	defined to be C<0>, then they are not.
2948		3596
2949	=item EV_MINIMAL	3597	=item EV_MINIMAL
2950		3598
2951	If you need to shave off some kilobytes of code at the expense of some	3599	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	3600	speed, define this symbol to C<1>. Currently this is used to override some
2953	some inlining decisions, saves roughly 30% codesize of amd64.	3601	inlining decisions, saves roughly 30% code size on amd64. It also selects a
		3602	much smaller 2-heap for timer management over the default 4-heap.
2954		3603
2955	=item EV_PID_HASHSIZE	3604	=item EV_PID_HASHSIZE
2956		3605
2957	C<ev_child> watchers use a small hash table to distribute workload by	3606	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	3607	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>),	3614	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>	3615	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	3616	watchers you might want to increase this value (I<must> be a power of
2968	two).	3617	two).
2969		3618
		3619	=item EV_USE_4HEAP
		3620
		3621	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3622	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
		3623	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
		3624	faster performance with many (thousands) of watchers.
		3625
		3626	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3627	(disabled).
		3628
		3629	=item EV_HEAP_CACHE_AT
		3630
		3631	Heaps are not very cache-efficient. To improve the cache-efficiency of the
		3632	timer and periodics heaps, libev can cache the timestamp (I<at>) within
		3633	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
		3634	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
		3635	but avoids random read accesses on heap changes. This improves performance
		3636	noticeably with many (hundreds) of watchers.
		3637
		3638	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
		3639	(disabled).
		3640
		3641	=item EV_VERIFY
		3642
		3643	Controls how much internal verification (see C<ev_loop_verify ()>) will
		3644	be done: If set to C<0>, no internal verification code will be compiled
		3645	in. If set to C<1>, then verification code will be compiled in, but not
		3646	called. If set to C<2>, then the internal verification code will be
		3647	called once per loop, which can slow down libev. If set to C<3>, then the
		3648	verification code will be called very frequently, which will slow down
		3649	libev considerably.
		3650
		3651	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
		3652	C<0>.
		3653
2970	=item EV_COMMON	3654	=item EV_COMMON
2971		3655
2972	By default, all watchers have a C<void *data> member. By redefining	3656	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	3657	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,	3658	members. You have to define it each time you include one of the files,
2975	though, and it must be identical each time.	3659	though, and it must be identical each time.
2976		3660
2977	For example, the perl EV module uses something like this:	3661	For example, the perl EV module uses something like this:
2978		3662
2979	#define EV_COMMON \	3663	#define EV_COMMON \
2980	SV *self; /* contains this struct */ \	3664	SV *self; /* contains this struct */ \
2981	SV *cb_sv, *fh /* note no trailing ";" */	3665	SV *cb_sv, *fh /* note no trailing ";" */
2982		3666
2983	=item EV_CB_DECLARE (type)	3667	=item EV_CB_DECLARE (type)
2984		3668
2985	=item EV_CB_INVOKE (watcher, revents)	3669	=item EV_CB_INVOKE (watcher, revents)
2986		3670
…		…
2991	definition and a statement, respectively. See the F<ev.h> header file for	3675	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	3676	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	3677	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++.	3678	method calls instead of plain function calls in C++.
2995		3679
		3680	=back
		3681
2996	=head2 EXPORTED API SYMBOLS	3682	=head2 EXPORTED API SYMBOLS
2997		3683
2998	If you need to re-export the API (e.g. via a dll) and you need a list of	3684	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	3685	exported symbols, you can use the provided F<Symbol.*> files which list
3000	all public symbols, one per line:	3686	all public symbols, one per line:
3001		3687
3002	Symbols.ev for libev proper	3688	Symbols.ev for libev proper
3003	Symbols.event for the libevent emulation	3689	Symbols.event for the libevent emulation
3004		3690
3005	This can also be used to rename all public symbols to avoid clashes with	3691	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	3692	multiple versions of libev linked together (which is obviously bad in
3007	itself, but sometimes it is inconvinient to avoid this).	3693	itself, but sometimes it is inconvenient to avoid this).
3008		3694
3009	A sed command like this will create wrapper C<#define>'s that you need to	3695	A sed command like this will create wrapper C<#define>'s that you need to
3010	include before including F<ev.h>:	3696	include before including F<ev.h>:
3011		3697
3012	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h	3698	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
…		…
3029	file.	3715	file.
3030		3716
3031	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	3717	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:	3718	that everybody includes and which overrides some configure choices:
3033		3719
3034	#define EV_MINIMAL 1	3720	#define EV_MINIMAL 1
3035	#define EV_USE_POLL 0	3721	#define EV_USE_POLL 0
3036	#define EV_MULTIPLICITY 0	3722	#define EV_MULTIPLICITY 0
3037	#define EV_PERIODIC_ENABLE 0	3723	#define EV_PERIODIC_ENABLE 0
3038	#define EV_STAT_ENABLE 0	3724	#define EV_STAT_ENABLE 0
3039	#define EV_FORK_ENABLE 0	3725	#define EV_FORK_ENABLE 0
3040	#define EV_CONFIG_H <config.h>	3726	#define EV_CONFIG_H <config.h>
3041	#define EV_MINPRI 0	3727	#define EV_MINPRI 0
3042	#define EV_MAXPRI 0	3728	#define EV_MAXPRI 0
3043		3729
3044	#include "ev++.h"	3730	#include "ev++.h"
3045		3731
3046	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3732	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3047		3733
3048	#include "ev_cpp.h"	3734	#include "ev_cpp.h"
3049	#include "ev.c"	3735	#include "ev.c"
3050		3736
		3737	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3051		3738
3052	=head1 COMPLEXITIES	3739	=head2 THREADS AND COROUTINES
3053		3740
3054	In this section the complexities of (many of) the algorithms used inside	3741	=head3 THREADS
3055	libev will be explained. For complexity discussions about backends see the
3056	documentation for C<ev_default_init>.
3057		3742
3058	All of the following are about amortised time: If an array needs to be	3743	All libev functions are reentrant and thread-safe unless explicitly
3059	extended, libev needs to realloc and move the whole array, but this	3744	documented otherwise, but libev implements no locking itself. This means
3060	happens asymptotically never with higher number of elements, so O(1) might	3745	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	3746	are no concurrent calls into any libev function with the same loop
3062	it is much faster and asymptotically approaches constant time.	3747	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3748	of course): libev guarantees that different event loops share no data
		3749	structures that need any locking.
		3750
		3751	Or to put it differently: calls with different loop parameters can be done
		3752	concurrently from multiple threads, calls with the same loop parameter
		3753	must be done serially (but can be done from different threads, as long as
		3754	only one thread ever is inside a call at any point in time, e.g. by using
		3755	a mutex per loop).
		3756
		3757	Specifically to support threads (and signal handlers), libev implements
		3758	so-called C<ev_async> watchers, which allow some limited form of
		3759	concurrency on the same event loop, namely waking it up "from the
		3760	outside".
		3761
		3762	If you want to know which design (one loop, locking, or multiple loops
		3763	without or something else still) is best for your problem, then I cannot
		3764	help you, but here is some generic advice:
3063		3765
3064	=over 4	3766	=over 4
3065		3767
3066	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3768	=item * most applications have a main thread: use the default libev loop
		3769	in that thread, or create a separate thread running only the default loop.
3067		3770
3068	This means that, when you have a watcher that triggers in one hour and	3771	This helps integrating other libraries or software modules that use libev
3069	there are 100 watchers that would trigger before that then inserting will	3772	themselves and don't care/know about threading.
3070	have to skip roughly seven (C<ld 100>) of these watchers.
3071		3773
3072	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3774	=item * one loop per thread is usually a good model.
3073		3775
3074	That means that changing a timer costs less than removing/adding them	3776	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.	3777	exists, but it is always a good start.
3076		3778
3077	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3779	=item * other models exist, such as the leader/follower pattern, where one
		3780	loop is handed through multiple threads in a kind of round-robin fashion.
3078		3781
3079	These just add the watcher into an array or at the head of a list.	3782	Choosing a model is hard - look around, learn, know that usually you can do
		3783	better than you currently do :-)
3080		3784
3081	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3785	=item * often you need to talk to some other thread which blocks in the
		3786	event loop.
3082		3787
3083	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3788	C<ev_async> watchers can be used to wake them up from other threads safely
		3789	(or from signal contexts...).
3084		3790
3085	These watchers are stored in lists then need to be walked to find the	3791	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	3792	work in the default loop by registering the signal watcher with the
3087	have many watchers waiting for the same fd or signal).	3793	default loop and triggering an C<ev_async> watcher from the default loop
3088		3794	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		3795
3119	=back	3796	=back
3120		3797
		3798	=head3 COROUTINES
3121		3799
3122	=head1 Win32 platform limitations and workarounds	3800	Libev is very accommodating to coroutines ("cooperative threads"):
		3801	libev fully supports nesting calls to its functions from different
		3802	coroutines (e.g. you can call C<ev_loop> on the same loop from two
		3803	different coroutines, and switch freely between both coroutines running the
		3804	loop, as long as you don't confuse yourself). The only exception is that
		3805	you must not do this from C<ev_periodic> reschedule callbacks.
		3806
		3807	Care has been taken to ensure that libev does not keep local state inside
		3808	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3809	they do not call any callbacks.
		3810
		3811	=head2 COMPILER WARNINGS
		3812
		3813	Depending on your compiler and compiler settings, you might get no or a
		3814	lot of warnings when compiling libev code. Some people are apparently
		3815	scared by this.
		3816
		3817	However, these are unavoidable for many reasons. For one, each compiler
		3818	has different warnings, and each user has different tastes regarding
		3819	warning options. "Warn-free" code therefore cannot be a goal except when
		3820	targeting a specific compiler and compiler-version.
		3821
		3822	Another reason is that some compiler warnings require elaborate
		3823	workarounds, or other changes to the code that make it less clear and less
		3824	maintainable.
		3825
		3826	And of course, some compiler warnings are just plain stupid, or simply
		3827	wrong (because they don't actually warn about the condition their message
		3828	seems to warn about). For example, certain older gcc versions had some
		3829	warnings that resulted an extreme number of false positives. These have
		3830	been fixed, but some people still insist on making code warn-free with
		3831	such buggy versions.
		3832
		3833	While libev is written to generate as few warnings as possible,
		3834	"warn-free" code is not a goal, and it is recommended not to build libev
		3835	with any compiler warnings enabled unless you are prepared to cope with
		3836	them (e.g. by ignoring them). Remember that warnings are just that:
		3837	warnings, not errors, or proof of bugs.
		3838
		3839
		3840	=head2 VALGRIND
		3841
		3842	Valgrind has a special section here because it is a popular tool that is
		3843	highly useful. Unfortunately, valgrind reports are very hard to interpret.
		3844
		3845	If you think you found a bug (memory leak, uninitialised data access etc.)
		3846	in libev, then check twice: If valgrind reports something like:
		3847
		3848	==2274== definitely lost: 0 bytes in 0 blocks.
		3849	==2274== possibly lost: 0 bytes in 0 blocks.
		3850	==2274== still reachable: 256 bytes in 1 blocks.
		3851
		3852	Then there is no memory leak, just as memory accounted to global variables
		3853	is not a memleak - the memory is still being referenced, and didn't leak.
		3854
		3855	Similarly, under some circumstances, valgrind might report kernel bugs
		3856	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3857	although an acceptable workaround has been found here), or it might be
		3858	confused.
		3859
		3860	Keep in mind that valgrind is a very good tool, but only a tool. Don't
		3861	make it into some kind of religion.
		3862
		3863	If you are unsure about something, feel free to contact the mailing list
		3864	with the full valgrind report and an explanation on why you think this
		3865	is a bug in libev (best check the archives, too :). However, don't be
		3866	annoyed when you get a brisk "this is no bug" answer and take the chance
		3867	of learning how to interpret valgrind properly.
		3868
		3869	If you need, for some reason, empty reports from valgrind for your project
		3870	I suggest using suppression lists.
		3871
		3872
		3873	=head1 PORTABILITY NOTES
		3874
		3875	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3123		3876
3124	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3877	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	3878	requires, and its I/O model is fundamentally incompatible with the POSIX
3126	model. Libev still offers limited functionality on this platform in	3879	model. Libev still offers limited functionality on this platform in
3127	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3880	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3128	descriptors. This only applies when using Win32 natively, not when using	3881	descriptors. This only applies when using Win32 natively, not when using
3129	e.g. cygwin.	3882	e.g. cygwin.
3130		3883
		3884	Lifting these limitations would basically require the full
		3885	re-implementation of the I/O system. If you are into these kinds of
		3886	things, then note that glib does exactly that for you in a very portable
		3887	way (note also that glib is the slowest event library known to man).
		3888
3131	There is no supported compilation method available on windows except	3889	There is no supported compilation method available on windows except
3132	embedding it into other applications.	3890	embedding it into other applications.
3133		3891
		3892	Not a libev limitation but worth mentioning: windows apparently doesn't
		3893	accept large writes: instead of resulting in a partial write, windows will
		3894	either accept everything or return C<ENOBUFS> if the buffer is too large,
		3895	so make sure you only write small amounts into your sockets (less than a
		3896	megabyte seems safe, but this apparently depends on the amount of memory
		3897	available).
		3898
3134	Due to the many, low, and arbitrary limits on the win32 platform and the	3899	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	3900	the abysmal performance of winsockets, using a large number of sockets
3136	recommended (and not reasonable). If your program needs to use more than	3901	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	3902	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	3903	different implementation for windows, as libev offers the POSIX readiness
3139	be implemented efficiently on windows (microsoft monopoly games).	3904	notification model, which cannot be implemented efficiently on windows
		3905	(Microsoft monopoly games).
		3906
		3907	A typical way to use libev under windows is to embed it (see the embedding
		3908	section for details) and use the following F<evwrap.h> header file instead
		3909	of F<ev.h>:
		3910
		3911	#define EV_STANDALONE /* keeps ev from requiring config.h */
		3912	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		3913
		3914	#include "ev.h"
		3915
		3916	And compile the following F<evwrap.c> file into your project (make sure
		3917	you do I<not> compile the F<ev.c> or any other embedded source files!):
		3918
		3919	#include "evwrap.h"
		3920	#include "ev.c"
3140		3921
3141	=over 4	3922	=over 4
3142		3923
3143	=item The winsocket select function	3924	=item The winsocket select function
3144		3925
3145	The winsocket C<select> function doesn't follow POSIX in that it requires	3926	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	3927	requires socket I<handles> and not socket I<file descriptors> (it is
3147	very inefficient, and also requires a mapping from file descriptors	3928	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>,	3929	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	3930	C runtime provides the function C<_open_osfhandle> for this). See the
3150	symbols for more info.	3931	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
		3932	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3151		3933
3152	The configuration for a "naked" win32 using the microsoft runtime	3934	The configuration for a "naked" win32 using the Microsoft runtime
3153	libraries and raw winsocket select is:	3935	libraries and raw winsocket select is:
3154		3936
3155	#define EV_USE_SELECT 1	3937	#define EV_USE_SELECT 1
3156	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	3938	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3157		3939
3158	Note that winsockets handling of fd sets is O(n), so you can easily get a	3940	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.	3941	complexity in the O(n²) range when using win32.
3160		3942
3161	=item Limited number of file descriptors	3943	=item Limited number of file descriptors
3162		3944
3163	Windows has numerous arbitrary (and low) limits on things. Early versions	3945	Windows has numerous arbitrary (and low) limits on things.
3164	of winsocket's select only supported waiting for a max. of C<64> handles	3946
		3947	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	3948	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	3949	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).	3950	recommends spawning a chain of threads and wait for 63 handles and the
		3951	previous thread in each. Great).
3168		3952
3169	Newer versions support more handles, but you need to define C<FD_SETSIZE>	3953	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	3954	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	3955	call (which might be in libev or elsewhere, for example, perl does its own
3172	select emulation on windows).	3956	select emulation on windows).
3173		3957
3174	Another limit is the number of file descriptors in the microsoft runtime	3958	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	3959	libraries, which by default is C<64> (there must be a hidden I<64> fetish
3176	or something like this inside microsoft). You can increase this by calling	3960	or something like this inside Microsoft). You can increase this by calling
3177	C<_setmaxstdio>, which can increase this limit to C<2048> (another	3961	C<_setmaxstdio>, which can increase this limit to C<2048> (another
3178	arbitrary limit), but is broken in many versions of the microsoft runtime	3962	arbitrary limit), but is broken in many versions of the Microsoft runtime
3179	libraries.	3963	libraries.
3180		3964
3181	This might get you to about C<512> or C<2048> sockets (depending on	3965	This might get you to about C<512> or C<2048> sockets (depending on
3182	windows version and/or the phase of the moon). To get more, you need to	3966	windows version and/or the phase of the moon). To get more, you need to
3183	wrap all I/O functions and provide your own fd management, but the cost of	3967	wrap all I/O functions and provide your own fd management, but the cost of
3184	calling select (O(n²)) will likely make this unworkable.	3968	calling select (O(n²)) will likely make this unworkable.
3185		3969
3186	=back	3970	=back
3187		3971
		3972	=head2 PORTABILITY REQUIREMENTS
		3973
		3974	In addition to a working ISO-C implementation and of course the
		3975	backend-specific APIs, libev relies on a few additional extensions:
		3976
		3977	=over 4
		3978
		3979	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		3980	calling conventions regardless of C<ev_watcher_type *>.
		3981
		3982	Libev assumes not only that all watcher pointers have the same internal
		3983	structure (guaranteed by POSIX but not by ISO C for example), but it also
		3984	assumes that the same (machine) code can be used to call any watcher
		3985	callback: The watcher callbacks have different type signatures, but libev
		3986	calls them using an C<ev_watcher *> internally.
		3987
		3988	=item C<sig_atomic_t volatile> must be thread-atomic as well
		3989
		3990	The type C<sig_atomic_t volatile> (or whatever is defined as
		3991	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
		3992	threads. This is not part of the specification for C<sig_atomic_t>, but is
		3993	believed to be sufficiently portable.
		3994
		3995	=item C<sigprocmask> must work in a threaded environment
		3996
		3997	Libev uses C<sigprocmask> to temporarily block signals. This is not
		3998	allowed in a threaded program (C<pthread_sigmask> has to be used). Typical
		3999	pthread implementations will either allow C<sigprocmask> in the "main
		4000	thread" or will block signals process-wide, both behaviours would
		4001	be compatible with libev. Interaction between C<sigprocmask> and
		4002	C<pthread_sigmask> could complicate things, however.
		4003
		4004	The most portable way to handle signals is to block signals in all threads
		4005	except the initial one, and run the default loop in the initial thread as
		4006	well.
		4007
		4008	=item C<long> must be large enough for common memory allocation sizes
		4009
		4010	To improve portability and simplify its API, libev uses C<long> internally
		4011	instead of C<size_t> when allocating its data structures. On non-POSIX
		4012	systems (Microsoft...) this might be unexpectedly low, but is still at
		4013	least 31 bits everywhere, which is enough for hundreds of millions of
		4014	watchers.
		4015
		4016	=item C<double> must hold a time value in seconds with enough accuracy
		4017
		4018	The type C<double> is used to represent timestamps. It is required to
		4019	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
		4020	enough for at least into the year 4000. This requirement is fulfilled by
		4021	implementations implementing IEEE 754 (basically all existing ones).
		4022
		4023	=back
		4024
		4025	If you know of other additional requirements drop me a note.
		4026
		4027
		4028	=head1 ALGORITHMIC COMPLEXITIES
		4029
		4030	In this section the complexities of (many of) the algorithms used inside
		4031	libev will be documented. For complexity discussions about backends see
		4032	the documentation for C<ev_default_init>.
		4033
		4034	All of the following are about amortised time: If an array needs to be
		4035	extended, libev needs to realloc and move the whole array, but this
		4036	happens asymptotically rarer with higher number of elements, so O(1) might
		4037	mean that libev does a lengthy realloc operation in rare cases, but on
		4038	average it is much faster and asymptotically approaches constant time.
		4039
		4040	=over 4
		4041
		4042	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		4043
		4044	This means that, when you have a watcher that triggers in one hour and
		4045	there are 100 watchers that would trigger before that, then inserting will
		4046	have to skip roughly seven (C<ld 100>) of these watchers.
		4047
		4048	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		4049
		4050	That means that changing a timer costs less than removing/adding them,
		4051	as only the relative motion in the event queue has to be paid for.
		4052
		4053	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
		4054
		4055	These just add the watcher into an array or at the head of a list.
		4056
		4057	=item Stopping check/prepare/idle/fork/async watchers: O(1)
		4058
		4059	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		4060
		4061	These watchers are stored in lists, so they need to be walked to find the
		4062	correct watcher to remove. The lists are usually short (you don't usually
		4063	have many watchers waiting for the same fd or signal: one is typical, two
		4064	is rare).
		4065
		4066	=item Finding the next timer in each loop iteration: O(1)
		4067
		4068	By virtue of using a binary or 4-heap, the next timer is always found at a
		4069	fixed position in the storage array.
		4070
		4071	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4072
		4073	A change means an I/O watcher gets started or stopped, which requires
		4074	libev to recalculate its status (and possibly tell the kernel, depending
		4075	on backend and whether C<ev_io_set> was used).
		4076
		4077	=item Activating one watcher (putting it into the pending state): O(1)
		4078
		4079	=item Priority handling: O(number_of_priorities)
		4080
		4081	Priorities are implemented by allocating some space for each
		4082	priority. When doing priority-based operations, libev usually has to
		4083	linearly search all the priorities, but starting/stopping and activating
		4084	watchers becomes O(1) with respect to priority handling.
		4085
		4086	=item Sending an ev_async: O(1)
		4087
		4088	=item Processing ev_async_send: O(number_of_async_watchers)
		4089
		4090	=item Processing signals: O(max_signal_number)
		4091
		4092	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4093	calls in the current loop iteration. Checking for async and signal events
		4094	involves iterating over all running async watchers or all signal numbers.
		4095
		4096	=back
		4097
3188		4098
3189	=head1 AUTHOR	4099	=head1 AUTHOR
3190		4100
3191	Marc Lehmann <libev@schmorp.de>.	4101	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3192		4102

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