[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.342 by root, Wed Nov 10 13:16:44 2010 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	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);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
72		92
73	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
74	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	122	for example).
102		123
…		…
105	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
121	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
155	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
161	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
178	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	203	not a problem.
181		204
182	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
184		208
185	assert (("libev version mismatch",	209	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
188		212
…		…
199	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
201		225
202	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
203		227
204	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
210		235
211	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
212		237
213	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
218		243
219	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
220		245
221	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void (cb)(void *ptr, long size))
222		247
223	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
252	}	277	}
253		278
254	...	279	...
255	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
256		281
257	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (cb)(const char msg))
258		283
259	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
260	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
276	...	301	...
277	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
278		303
279	=back	304	=back
280		305
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		307
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	310	libev 3 had an C<ev_loop> function colliding with the struct name).
286		311
287	The library knows two types of such loops, the I<default> loop, which	312	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	313	supports child process events, and dynamically created event loops which
289	not.	314	do not.
290		315
291	=over 4	316	=over 4
292		317
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		319
295	This will initialise the default event loop if it hasn't been initialised	320	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	321	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	322	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	323	C<ev_loop_new>.
		324
		325	If the default loop is already initialised then this function simply
		326	returns it (and ignores the flags. If that is troubling you, check
		327	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		328	flags, which should almost always be C<0>, unless the caller is also the
		329	one calling C<ev_run> or otherwise qualifies as "the main program".
299		330
300	If you don't know what event loop to use, use the one returned from this	331	If you don't know what event loop to use, use the one returned from this
301	function.	332	function (or via the C<EV_DEFAULT> macro).
302		333
303	Note that this function is I<not> thread-safe, so if you want to use it	334	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	335	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
306		338
307	The default loop is the only loop that can handle C<ev_signal> and	339	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	340	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	341	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	342	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	344
		345	Example: This is the most typical usage.
		346
		347	if (!ev_default_loop (0))
		348	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		349
		350	Example: Restrict libev to the select and poll backends, and do not allow
		351	environment settings to be taken into account:
		352
		353	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		354
		355	=item struct ev_loop *ev_loop_new (unsigned int flags)
		356
		357	This will create and initialise a new event loop object. If the loop
		358	could not be initialised, returns false.
		359
		360	Note that this function I<is> thread-safe, and one common way to use
		361	libev with threads is indeed to create one loop per thread, and using the
		362	default loop in the "main" or "initial" thread.
313		363
314	The flags argument can be used to specify special behaviour or specific	364	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	365	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		366
317	The following flags are supported:	367	The following flags are supported:
…		…
332	useful to try out specific backends to test their performance, or to work	382	useful to try out specific backends to test their performance, or to work
333	around bugs.	383	around bugs.
334		384
335	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
336		386
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	387	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	388	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		389
341	This works by calling C<getpid ()> on every iteration of the loop,	390	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	391	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	392	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	393	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	399	flag.
351		400
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	401	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	402	environment variable.
354		403
		404	=item C<EVFLAG_NOINOTIFY>
		405
		406	When this flag is specified, then libev will not attempt to use the
		407	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		408	testing, this flag can be useful to conserve inotify file descriptors, as
		409	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		410
		411	=item C<EVFLAG_SIGNALFD>
		412
		413	When this flag is specified, then libev will attempt to use the
		414	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		415	delivers signals synchronously, which makes it both faster and might make
		416	it possible to get the queued signal data. It can also simplify signal
		417	handling with threads, as long as you properly block signals in your
		418	threads that are not interested in handling them.
		419
		420	Signalfd will not be used by default as this changes your signal mask, and
		421	there are a lot of shoddy libraries and programs (glib's threadpool for
		422	example) that can't properly initialise their signal masks.
		423
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		425
357	This is your standard select(2) backend. Not I<completely> standard, as	426	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	427	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	428	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	452	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
385		454
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
388	For few fds, this backend is a bit little slower than poll and select,	460	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	462	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	463	epoll scales either O(1) or O(active_fds).
392		464
393	The epoll mechanism deserves honorable mention as the most misdesigned	465	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	466	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	467	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	468	descriptor (and unnecessary guessing of parameters), problems with dup,
		469	returning before the timeout value, resulting in additional iterations
		470	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	471	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	472	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	473	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	474	and is of course hard to detect.
401		475
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	476	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	477	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	478	I<different> file descriptors (even already closed ones, so one cannot
405	even remove them from the set) than registered in the set (especially	479	even remove them from the set) than registered in the set (especially
406	on SMP systems). Libev tries to counter these spurious notifications by	480	on SMP systems). Libev tries to counter these spurious notifications by
407	employing an additional generation counter and comparing that against the	481	employing an additional generation counter and comparing that against the
408	events to filter out spurious ones, recreating the set when required.	482	events to filter out spurious ones, recreating the set when required. Last
		483	not least, it also refuses to work with some file descriptors which work
		484	perfectly fine with C<select> (files, many character devices...).
		485
		486	Epoll is truly the train wreck analog among event poll mechanisms.
409		487
410	While stopping, setting and starting an I/O watcher in the same iteration	488	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	489	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	490	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
506		584
507	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
508		586
509	=back	587	=back
510		588
511	If one or more of these are or'ed into the flags value, then only these	589	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	590	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
514		592	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		593
543	Example: Try to create a event loop that uses epoll and nothing else.	594	Example: Try to create a event loop that uses epoll and nothing else.
544		595
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
546	if (!epoller)	597	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
548		599
		600	Example: Use whatever libev has to offer, but make sure that kqueue is
		601	used if available.
		602
		603	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		604
549	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
550		606
551	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	608	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	609	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	611	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	612	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		614
559	Note that certain global state, such as signal state (and installed signal	615	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	616	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
562		618
563	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	620	C<ev_loop_new>, but it can also be used on the default loop returned by
		621	C<ev_default_loop>, in which case it is not thread-safe.
		622
		623	Note that it is not advisable to call this function on the default loop
		624	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	625	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
567		627
568	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
569		629
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	630	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	632	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	633	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	635
		636	Again, you I<have> to call it on I<any> loop that you want to re-use after
		637	a fork, I<even if you do not plan to use the loop in the parent>. This is
		638	because some kernel interfaces cough I<kqueue> cough do funny things
		639	during fork.
581		640
582	On the other hand, you only need to call this function in the child	641	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	642	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	643	you just fork+exec or create a new loop in the child, you don't have to
		644	call it at all (in fact, C<epoll> is so badly broken that it makes a
		645	difference, but libev will usually detect this case on its own and do a
		646	costly reset of the backend).
585		647
586	The function itself is quite fast and it's usually not a problem to call	648	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		650
		651	Example: Automate calling C<ev_loop_fork> on the default loop when
		652	using pthreads.
		653
		654	static void
		655	post_fork_child (void)
		656	{
		657	ev_loop_fork (EV_DEFAULT);
		658	}
		659
		660	...
590	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		662
599	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
600		664
601	Returns true when the given loop is, in fact, the default loop, and false	665	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	666	otherwise.
603		667
604	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
605		669
606	Returns the count of loop iterations for the loop, which is identical to	670	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	671	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
609		673
610	This value can sometimes be useful as a generation counter of sorts (it	674	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	676	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		677	prepare and check phases.
		678
		679	=item unsigned int ev_depth (loop)
		680
		681	Returns the number of times C<ev_run> was entered minus the number of
		682	times C<ev_run> was exited, in other words, the recursion depth.
		683
		684	Outside C<ev_run>, this number is zero. In a callback, this number is
		685	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		686	in which case it is higher.
		687
		688	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		689	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		690	ungentleman-like behaviour unless it's really convenient.
613		691
614	=item unsigned int ev_backend (loop)	692	=item unsigned int ev_backend (loop)
615		693
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	694	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	695	use.
…		…
626		704
627	=item ev_now_update (loop)	705	=item ev_now_update (loop)
628		706
629	Establishes the current time by querying the kernel, updating the time	707	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	708	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	709	is usually done automatically within C<ev_run ()>.
632		710
633	This function is rarely useful, but when some event callback runs for a	711	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	712	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	713	the current time is a good idea.
636		714
637	See also "The special problem of time updates" in the C<ev_timer> section.	715	See also L<The special problem of time updates> in the C<ev_timer> section.
638		716
639	=item ev_suspend (loop)	717	=item ev_suspend (loop)
640		718
641	=item ev_resume (loop)	719	=item ev_resume (loop)
642		720
643	These two functions suspend and resume a loop, for use when the loop is	721	These two functions suspend and resume an event loop, for use when the
644	not used for a while and timeouts should not be processed.	722	loop is not used for a while and timeouts should not be processed.
645		723
646	A typical use case would be an interactive program such as a game: When	724	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	725	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	726	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>	727	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
651	C<ev_resume> directly afterwards to resume timer processing.	729	C<ev_resume> directly afterwards to resume timer processing.
652		730
653	Effectively, all C<ev_timer> watchers will be delayed by the time spend	731	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	732	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	733	will be rescheduled (that is, they will lose any events that would have
656	occured while suspended).	734	occurred while suspended).
657		735
658	After calling C<ev_suspend> you B<must not> call I<any> function on the	736	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>	737	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>.	738	without a previous call to C<ev_suspend>.
661		739
662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	740	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
663	event loop time (see C<ev_now_update>).	741	event loop time (see C<ev_now_update>).
664		742
665	=item ev_loop (loop, int flags)	743	=item ev_run (loop, int flags)
666		744
667	Finally, this is it, the event handler. This function usually is called	745	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	746	after you have initialised all your watchers and you want to start
669	events.	747	handling events. It will ask the operating system for any new events, call
		748	the watcher callbacks, an then repeat the whole process indefinitely: This
		749	is why event loops are called I<loops>.
670		750
671	If the flags argument is specified as C<0>, it will not return until	751	If the flags argument is specified as C<0>, it will keep handling events
672	either no event watchers are active anymore or C<ev_unloop> was called.	752	until either no event watchers are active anymore or C<ev_break> was
		753	called.
673		754
674	Please note that an explicit C<ev_unloop> is usually better than	755	Please note that an explicit C<ev_break> is usually better than
675	relying on all watchers to be stopped when deciding when a program has	756	relying on all watchers to be stopped when deciding when a program has
676	finished (especially in interactive programs), but having a program	757	finished (especially in interactive programs), but having a program
677	that automatically loops as long as it has to and no longer by virtue	758	that automatically loops as long as it has to and no longer by virtue
678	of relying on its watchers stopping correctly, that is truly a thing of	759	of relying on its watchers stopping correctly, that is truly a thing of
679	beauty.	760	beauty.
680		761
681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	762	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
682	those events and any already outstanding ones, but will not block your	763	those events and any already outstanding ones, but will not wait and
683	process in case there are no events and will return after one iteration of	764	block your process in case there are no events and will return after one
684	the loop.	765	iteration of the loop. This is sometimes useful to poll and handle new
		766	events while doing lengthy calculations, to keep the program responsive.
685		767
686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	768	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
687	necessary) and will handle those and any already outstanding ones. It	769	necessary) and will handle those and any already outstanding ones. It
688	will block your process until at least one new event arrives (which could	770	will block your process until at least one new event arrives (which could
689	be an event internal to libev itself, so there is no guarantee that a	771	be an event internal to libev itself, so there is no guarantee that a
690	user-registered callback will be called), and will return after one	772	user-registered callback will be called), and will return after one
691	iteration of the loop.	773	iteration of the loop.
692		774
693	This is useful if you are waiting for some external event in conjunction	775	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	776	with something not expressible using other libev watchers (i.e. "roll your
695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	777	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
696	usually a better approach for this kind of thing.	778	usually a better approach for this kind of thing.
697		779
698	Here are the gory details of what C<ev_loop> does:	780	Here are the gory details of what C<ev_run> does:
699		781
		782	- Increment loop depth.
		783	- Reset the ev_break status.
700	- Before the first iteration, call any pending watchers.	784	- Before the first iteration, call any pending watchers.
		785	LOOP:
701	* If EVFLAG_FORKCHECK was used, check for a fork.	786	- If EVFLAG_FORKCHECK was used, check for a fork.
702	- If a fork was detected (by any means), queue and call all fork watchers.	787	- If a fork was detected (by any means), queue and call all fork watchers.
703	- Queue and call all prepare watchers.	788	- Queue and call all prepare watchers.
		789	- If ev_break was called, goto FINISH.
704	- If we have been forked, detach and recreate the kernel state	790	- If we have been forked, detach and recreate the kernel state
705	as to not disturb the other process.	791	as to not disturb the other process.
706	- Update the kernel state with all outstanding changes.	792	- Update the kernel state with all outstanding changes.
707	- Update the "event loop time" (ev_now ()).	793	- Update the "event loop time" (ev_now ()).
708	- Calculate for how long to sleep or block, if at all	794	- Calculate for how long to sleep or block, if at all
709	(active idle watchers, EVLOOP_NONBLOCK or not having	795	(active idle watchers, EVRUN_NOWAIT or not having
710	any active watchers at all will result in not sleeping).	796	any active watchers at all will result in not sleeping).
711	- Sleep if the I/O and timer collect interval say so.	797	- Sleep if the I/O and timer collect interval say so.
		798	- Increment loop iteration counter.
712	- Block the process, waiting for any events.	799	- Block the process, waiting for any events.
713	- Queue all outstanding I/O (fd) events.	800	- Queue all outstanding I/O (fd) events.
714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	801	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
715	- Queue all expired timers.	802	- Queue all expired timers.
716	- Queue all expired periodics.	803	- Queue all expired periodics.
717	- Unless any events are pending now, queue all idle watchers.	804	- Queue all idle watchers with priority higher than that of pending events.
718	- Queue all check watchers.	805	- Queue all check watchers.
719	- Call all queued watchers in reverse order (i.e. check watchers first).	806	- Call all queued watchers in reverse order (i.e. check watchers first).
720	Signals and child watchers are implemented as I/O watchers, and will	807	Signals and child watchers are implemented as I/O watchers, and will
721	be handled here by queueing them when their watcher gets executed.	808	be handled here by queueing them when their watcher gets executed.
722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	809	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
723	were used, or there are no active watchers, return, otherwise	810	were used, or there are no active watchers, goto FINISH, otherwise
724	continue with step *.	811	continue with step LOOP.
		812	FINISH:
		813	- Reset the ev_break status iff it was EVBREAK_ONE.
		814	- Decrement the loop depth.
		815	- Return.
725		816
726	Example: Queue some jobs and then loop until no events are outstanding	817	Example: Queue some jobs and then loop until no events are outstanding
727	anymore.	818	anymore.
728		819
729	... queue jobs here, make sure they register event watchers as long	820	... queue jobs here, make sure they register event watchers as long
730	... as they still have work to do (even an idle watcher will do..)	821	... as they still have work to do (even an idle watcher will do..)
731	ev_loop (my_loop, 0);	822	ev_run (my_loop, 0);
732	... jobs done or somebody called unloop. yeah!	823	... jobs done or somebody called unloop. yeah!
733		824
734	=item ev_unloop (loop, how)	825	=item ev_break (loop, how)
735		826
736	Can be used to make a call to C<ev_loop> return early (but only after it	827	Can be used to make a call to C<ev_run> return early (but only after it
737	has processed all outstanding events). The C<how> argument must be either	828	has processed all outstanding events). The C<how> argument must be either
738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	829	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	830	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
740		831
741	This "unloop state" will be cleared when entering C<ev_loop> again.	832	This "break state" will be cleared when entering C<ev_run> again.
742		833
743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	834	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
744		835
745	=item ev_ref (loop)	836	=item ev_ref (loop)
746		837
747	=item ev_unref (loop)	838	=item ev_unref (loop)
748		839
749	Ref/unref can be used to add or remove a reference count on the event	840	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	841	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	842	count is nonzero, C<ev_run> will not return on its own.
752		843
753	If you have a watcher you never unregister that should not keep C<ev_loop>	844	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	845	unregister, but that nevertheless should not keep C<ev_run> from
		846	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	847	before stopping it.
756		848
757	As an example, libev itself uses this for its internal signal pipe: It	849	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	850	is not visible to the libev user and should not keep C<ev_run> from
759	exiting if no event watchers registered by it are active. It is also an	851	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	852	excellent way to do this for generic recurring timers or from within
761	third-party libraries. Just remember to I<unref after start> and I<ref	853	third-party libraries. Just remember to I<unref after start> and I<ref
762	before stop> (but only if the watcher wasn't active before, or was active	854	before stop> (but only if the watcher wasn't active before, or was active
763	before, respectively. Note also that libev might stop watchers itself	855	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>	856	(e.g. non-repeating timers) in which case you have to C<ev_ref>
765	in the callback).	857	in the callback).
766		858
767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	859	Example: Create a signal watcher, but keep it from keeping C<ev_run>
768	running when nothing else is active.	860	running when nothing else is active.
769		861
770	ev_signal exitsig;	862	ev_signal exitsig;
771	ev_signal_init (&exitsig, sig_cb, SIGINT);	863	ev_signal_init (&exitsig, sig_cb, SIGINT);
772	ev_signal_start (loop, &exitsig);	864	ev_signal_start (loop, &exitsig);
…		…
799		891
800	By setting a higher I<io collect interval> you allow libev to spend more	892	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	893	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	894	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	895	C<ev_timer>) will be not affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	896	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		897	sleep time ensures that libev will not poll for I/O events more often then
		898	once per this interval, on average.
805		899
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	900	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	901	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	902	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	903	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		905
812	Many (busy) programs can usually benefit by setting the I/O collect	906	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	907	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	908	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	909	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	910	as this approaches the timing granularity of most systems. Note that if
		911	you do transactions with the outside world and you can't increase the
		912	parallelity, then this setting will limit your transaction rate (if you
		913	need to poll once per transaction and the I/O collect interval is 0.01,
		914	then you can't do more than 100 transactions per second).
817		915
818	Setting the I<timeout collect interval> can improve the opportunity for	916	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	917	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	918	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	919	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	920	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	921	they fire on, say, one-second boundaries only.
824		922
		923	Example: we only need 0.1s timeout granularity, and we wish not to poll
		924	more often than 100 times per second:
		925
		926	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		927	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		928
		929	=item ev_invoke_pending (loop)
		930
		931	This call will simply invoke all pending watchers while resetting their
		932	pending state. Normally, C<ev_run> does this automatically when required,
		933	but when overriding the invoke callback this call comes handy. This
		934	function can be invoked from a watcher - this can be useful for example
		935	when you want to do some lengthy calculation and want to pass further
		936	event handling to another thread (you still have to make sure only one
		937	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		938
		939	=item int ev_pending_count (loop)
		940
		941	Returns the number of pending watchers - zero indicates that no watchers
		942	are pending.
		943
		944	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		945
		946	This overrides the invoke pending functionality of the loop: Instead of
		947	invoking all pending watchers when there are any, C<ev_run> will call
		948	this callback instead. This is useful, for example, when you want to
		949	invoke the actual watchers inside another context (another thread etc.).
		950
		951	If you want to reset the callback, use C<ev_invoke_pending> as new
		952	callback.
		953
		954	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		955
		956	Sometimes you want to share the same loop between multiple threads. This
		957	can be done relatively simply by putting mutex_lock/unlock calls around
		958	each call to a libev function.
		959
		960	However, C<ev_run> can run an indefinite time, so it is not feasible
		961	to wait for it to return. One way around this is to wake up the event
		962	loop via C<ev_break> and C<av_async_send>, another way is to set these
		963	I<release> and I<acquire> callbacks on the loop.
		964
		965	When set, then C<release> will be called just before the thread is
		966	suspended waiting for new events, and C<acquire> is called just
		967	afterwards.
		968
		969	Ideally, C<release> will just call your mutex_unlock function, and
		970	C<acquire> will just call the mutex_lock function again.
		971
		972	While event loop modifications are allowed between invocations of
		973	C<release> and C<acquire> (that's their only purpose after all), no
		974	modifications done will affect the event loop, i.e. adding watchers will
		975	have no effect on the set of file descriptors being watched, or the time
		976	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		977	to take note of any changes you made.
		978
		979	In theory, threads executing C<ev_run> will be async-cancel safe between
		980	invocations of C<release> and C<acquire>.
		981
		982	See also the locking example in the C<THREADS> section later in this
		983	document.
		984
		985	=item ev_set_userdata (loop, void *data)
		986
		987	=item ev_userdata (loop)
		988
		989	Set and retrieve a single C<void *> associated with a loop. When
		990	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		991	C<0>.
		992
		993	These two functions can be used to associate arbitrary data with a loop,
		994	and are intended solely for the C<invoke_pending_cb>, C<release> and
		995	C<acquire> callbacks described above, but of course can be (ab-)used for
		996	any other purpose as well.
		997
825	=item ev_loop_verify (loop)	998	=item ev_verify (loop)
826		999
827	This function only does something when C<EV_VERIFY> support has been	1000	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	1001	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	1002	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	1003	is found to be inconsistent, it will print an error message to standard
…		…
841		1014
842	In the following description, uppercase C<TYPE> in names stands for the	1015	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	1016	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.	1017	watchers and C<ev_io_start> for I/O watchers.
845		1018
846	A watcher is a structure that you create and register to record your	1019	A watcher is an opaque structure that you allocate and register to record
847	interest in some event. For instance, if you want to wait for STDIN to	1020	your interest in some event. To make a concrete example, imagine you want
848	become readable, you would create an C<ev_io> watcher for that:	1021	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1022	for that:
849		1023
850	static void my_cb (struct ev_loop loop, ev_io w, int revents)	1024	static void my_cb (struct ev_loop loop, ev_io w, int revents)
851	{	1025	{
852	ev_io_stop (w);	1026	ev_io_stop (w);
853	ev_unloop (loop, EVUNLOOP_ALL);	1027	ev_break (loop, EVBREAK_ALL);
854	}	1028	}
855		1029
856	struct ev_loop *loop = ev_default_loop (0);	1030	struct ev_loop *loop = ev_default_loop (0);
857		1031
858	ev_io stdin_watcher;	1032	ev_io stdin_watcher;
859		1033
860	ev_init (&stdin_watcher, my_cb);	1034	ev_init (&stdin_watcher, my_cb);
861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1035	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
862	ev_io_start (loop, &stdin_watcher);	1036	ev_io_start (loop, &stdin_watcher);
863		1037
864	ev_loop (loop, 0);	1038	ev_run (loop, 0);
865		1039
866	As you can see, you are responsible for allocating the memory for your	1040	As you can see, you are responsible for allocating the memory for your
867	watcher structures (and it is I<usually> a bad idea to do this on the	1041	watcher structures (and it is I<usually> a bad idea to do this on the
868	stack).	1042	stack).
869		1043
870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1044	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).	1045	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
872		1046
873	Each watcher structure must be initialised by a call to C<ev_init	1047	Each watcher structure must be initialised by a call to C<ev_init (watcher
874	(watcher *, callback)>, which expects a callback to be provided. This	1048	*, callback)>, which expects a callback to be provided. This callback is
875	callback gets invoked each time the event occurs (or, in the case of I/O	1049	invoked each time the event occurs (or, in the case of I/O watchers, each
876	watchers, each time the event loop detects that the file descriptor given	1050	time the event loop detects that the file descriptor given is readable
877	is readable and/or writable).	1051	and/or writable).
878		1052
879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1053	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
880	macro to configure it, with arguments specific to the watcher type. There	1054	macro to configure it, with arguments specific to the watcher type. There
881	is also a macro to combine initialisation and setting in one call: C<<	1055	is also a macro to combine initialisation and setting in one call: C<<
882	ev_TYPE_init (watcher *, callback, ...) >>.	1056	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
905	=item C<EV_WRITE>	1079	=item C<EV_WRITE>
906		1080
907	The file descriptor in the C<ev_io> watcher has become readable and/or	1081	The file descriptor in the C<ev_io> watcher has become readable and/or
908	writable.	1082	writable.
909		1083
910	=item C<EV_TIMEOUT>	1084	=item C<EV_TIMER>
911		1085
912	The C<ev_timer> watcher has timed out.	1086	The C<ev_timer> watcher has timed out.
913		1087
914	=item C<EV_PERIODIC>	1088	=item C<EV_PERIODIC>
915		1089
…		…
933		1107
934	=item C<EV_PREPARE>	1108	=item C<EV_PREPARE>
935		1109
936	=item C<EV_CHECK>	1110	=item C<EV_CHECK>
937		1111
938	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1112	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
939	to gather new events, and all C<ev_check> watchers are invoked just after	1113	to gather new events, and all C<ev_check> watchers are invoked just after
940	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1114	C<ev_run> has gathered them, but before it invokes any callbacks for any
941	received events. Callbacks of both watcher types can start and stop as	1115	received events. Callbacks of both watcher types can start and stop as
942	many watchers as they want, and all of them will be taken into account	1116	many watchers as they want, and all of them will be taken into account
943	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1117	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
944	C<ev_loop> from blocking).	1118	C<ev_run> from blocking).
945		1119
946	=item C<EV_EMBED>	1120	=item C<EV_EMBED>
947		1121
948	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1122	The embedded event loop specified in the C<ev_embed> watcher needs attention.
949		1123
950	=item C<EV_FORK>	1124	=item C<EV_FORK>
951		1125
952	The event loop has been resumed in the child process after fork (see	1126	The event loop has been resumed in the child process after fork (see
953	C<ev_fork>).	1127	C<ev_fork>).
		1128
		1129	=item C<EV_CLEANUP>
		1130
		1131	The event loop is about to be destroyed (see C<ev_cleanup>).
954		1132
955	=item C<EV_ASYNC>	1133	=item C<EV_ASYNC>
956		1134
957	The given async watcher has been asynchronously notified (see C<ev_async>).	1135	The given async watcher has been asynchronously notified (see C<ev_async>).
958		1136
…		…
1005		1183
1006	ev_io w;	1184	ev_io w;
1007	ev_init (&w, my_cb);	1185	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1186	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1187
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1188	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1189
1012	This macro initialises the type-specific parts of a watcher. You need to	1190	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1191	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1192	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1193	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1206
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1207	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1208
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1209	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1210
1033	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1211	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1212
1035	Starts (activates) the given watcher. Only active watchers will receive	1213	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1214	events. If the watcher is already active nothing will happen.
1037		1215
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1216	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1217	whole section.
1040		1218
1041	ev_io_start (EV_DEFAULT_UC, &w);	1219	ev_io_start (EV_DEFAULT_UC, &w);
1042		1220
1043	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1221	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1222
1045	Stops the given watcher if active, and clears the pending status (whether	1223	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1224	the watcher was active or not).
1047		1225
1048	It is possible that stopped watchers are pending - for example,	1226	It is possible that stopped watchers are pending - for example,
…		…
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1251	=item ev_cb_set (ev_TYPE *watcher, callback)
1074		1252
1075	Change the callback. You can change the callback at virtually any time	1253	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1254	(modulo threads).
1077		1255
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1256	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1257
1080	=item int ev_priority (ev_TYPE *watcher)	1258	=item int ev_priority (ev_TYPE *watcher)
1081		1259
1082	Set and query the priority of the watcher. The priority is a small	1260	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1261	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1262	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1263	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1264	from being executed (except for C<ev_idle> watchers).
1087		1265
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1266	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1267	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1268
1096	You I<must not> change the priority of a watcher as long as it is active or	1269	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1270	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1271
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1272	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1273	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1274	or might not have been clamped to the valid range.
		1275
		1276	The default priority used by watchers when no priority has been set is
		1277	always C<0>, which is supposed to not be too high and not be too low :).
		1278
		1279	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1280	priorities.
1105		1281
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1282	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1283
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1284	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1285	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1117	watcher isn't pending it does nothing and returns C<0>.	1293	watcher isn't pending it does nothing and returns C<0>.
1118		1294
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1295	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1296	callback to be invoked, which can be accomplished with this function.
1121		1297
		1298	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1299
		1300	Feeds the given event set into the event loop, as if the specified event
		1301	had happened for the specified watcher (which must be a pointer to an
		1302	initialised but not necessarily started event watcher). Obviously you must
		1303	not free the watcher as long as it has pending events.
		1304
		1305	Stopping the watcher, letting libev invoke it, or calling
		1306	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1307	not started in the first place.
		1308
		1309	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1310	functions that do not need a watcher.
		1311
1122	=back	1312	=back
1123
1124		1313
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1314	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1126		1315
1127	Each watcher has, by default, a member C<void *data> that you can change	1316	Each watcher has, by default, a member C<void *data> that you can change
1128	and read at any time: libev will completely ignore it. This can be used	1317	and read at any time: libev will completely ignore it. This can be used
…		…
1174	#include <stddef.h>	1363	#include <stddef.h>
1175		1364
1176	static void	1365	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)	1366	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{	1367	{
1179	struct my_biggy big = (struct my_biggy *	1368	struct my_biggy big = (struct my_biggy *)
1180	(((char *)w) - offsetof (struct my_biggy, t1));	1369	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}	1370	}
1182		1371
1183	static void	1372	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)	1373	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{	1374	{
1186	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1187	(((char *)w) - offsetof (struct my_biggy, t2));	1376	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}	1377	}
		1378
		1379	=head2 WATCHER STATES
		1380
		1381	There are various watcher states mentioned throughout this manual -
		1382	active, pending and so on. In this section these states and the rules to
		1383	transition between them will be described in more detail - and while these
		1384	rules might look complicated, they usually do "the right thing".
		1385
		1386	=over 4
		1387
		1388	=item initialiased
		1389
		1390	Before a watcher can be registered with the event looop it has to be
		1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1393
		1394	In this state it is simply some block of memory that is suitable for use
		1395	in an event loop. It can be moved around, freed, reused etc. at will.
		1396
		1397	=item started/running/active
		1398
		1399	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1400	property of the event loop, and is actively waiting for events. While in
		1401	this state it cannot be accessed (except in a few documented ways), moved,
		1402	freed or anything else - the only legal thing is to keep a pointer to it,
		1403	and call libev functions on it that are documented to work on active watchers.
		1404
		1405	=item pending
		1406
		1407	If a watcher is active and libev determines that an event it is interested
		1408	in has occurred (such as a timer expiring), it will become pending. It will
		1409	stay in this pending state until either it is stopped or its callback is
		1410	about to be invoked, so it is not normally pending inside the watcher
		1411	callback.
		1412
		1413	The watcher might or might not be active while it is pending (for example,
		1414	an expired non-repeating timer can be pending but no longer active). If it
		1415	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1416	but it is still property of the event loop at this time, so cannot be
		1417	moved, freed or reused. And if it is active the rules described in the
		1418	previous item still apply.
		1419
		1420	It is also possible to feed an event on a watcher that is not active (e.g.
		1421	via C<ev_feed_event>), in which case it becomes pending without being
		1422	active.
		1423
		1424	=item stopped
		1425
		1426	A watcher can be stopped implicitly by libev (in which case it might still
		1427	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1428	latter will clear any pending state the watcher might be in, regardless
		1429	of whether it was active or not, so stopping a watcher explicitly before
		1430	freeing it is often a good idea.
		1431
		1432	While stopped (and not pending) the watcher is essentially in the
		1433	initialised state, that is it can be reused, moved, modified in any way
		1434	you wish.
		1435
		1436	=back
		1437
		1438	=head2 WATCHER PRIORITY MODELS
		1439
		1440	Many event loops support I<watcher priorities>, which are usually small
		1441	integers that influence the ordering of event callback invocation
		1442	between watchers in some way, all else being equal.
		1443
		1444	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1445	description for the more technical details such as the actual priority
		1446	range.
		1447
		1448	There are two common ways how these these priorities are being interpreted
		1449	by event loops:
		1450
		1451	In the more common lock-out model, higher priorities "lock out" invocation
		1452	of lower priority watchers, which means as long as higher priority
		1453	watchers receive events, lower priority watchers are not being invoked.
		1454
		1455	The less common only-for-ordering model uses priorities solely to order
		1456	callback invocation within a single event loop iteration: Higher priority
		1457	watchers are invoked before lower priority ones, but they all get invoked
		1458	before polling for new events.
		1459
		1460	Libev uses the second (only-for-ordering) model for all its watchers
		1461	except for idle watchers (which use the lock-out model).
		1462
		1463	The rationale behind this is that implementing the lock-out model for
		1464	watchers is not well supported by most kernel interfaces, and most event
		1465	libraries will just poll for the same events again and again as long as
		1466	their callbacks have not been executed, which is very inefficient in the
		1467	common case of one high-priority watcher locking out a mass of lower
		1468	priority ones.
		1469
		1470	Static (ordering) priorities are most useful when you have two or more
		1471	watchers handling the same resource: a typical usage example is having an
		1472	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1473	timeouts. Under load, data might be received while the program handles
		1474	other jobs, but since timers normally get invoked first, the timeout
		1475	handler will be executed before checking for data. In that case, giving
		1476	the timer a lower priority than the I/O watcher ensures that I/O will be
		1477	handled first even under adverse conditions (which is usually, but not
		1478	always, what you want).
		1479
		1480	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1481	will only be executed when no same or higher priority watchers have
		1482	received events, they can be used to implement the "lock-out" model when
		1483	required.
		1484
		1485	For example, to emulate how many other event libraries handle priorities,
		1486	you can associate an C<ev_idle> watcher to each such watcher, and in
		1487	the normal watcher callback, you just start the idle watcher. The real
		1488	processing is done in the idle watcher callback. This causes libev to
		1489	continuously poll and process kernel event data for the watcher, but when
		1490	the lock-out case is known to be rare (which in turn is rare :), this is
		1491	workable.
		1492
		1493	Usually, however, the lock-out model implemented that way will perform
		1494	miserably under the type of load it was designed to handle. In that case,
		1495	it might be preferable to stop the real watcher before starting the
		1496	idle watcher, so the kernel will not have to process the event in case
		1497	the actual processing will be delayed for considerable time.
		1498
		1499	Here is an example of an I/O watcher that should run at a strictly lower
		1500	priority than the default, and which should only process data when no
		1501	other events are pending:
		1502
		1503	ev_idle idle; // actual processing watcher
		1504	ev_io io; // actual event watcher
		1505
		1506	static void
		1507	io_cb (EV_P_ ev_io *w, int revents)
		1508	{
		1509	// stop the I/O watcher, we received the event, but
		1510	// are not yet ready to handle it.
		1511	ev_io_stop (EV_A_ w);
		1512
		1513	// start the idle watcher to handle the actual event.
		1514	// it will not be executed as long as other watchers
		1515	// with the default priority are receiving events.
		1516	ev_idle_start (EV_A_ &idle);
		1517	}
		1518
		1519	static void
		1520	idle_cb (EV_P_ ev_idle *w, int revents)
		1521	{
		1522	// actual processing
		1523	read (STDIN_FILENO, ...);
		1524
		1525	// have to start the I/O watcher again, as
		1526	// we have handled the event
		1527	ev_io_start (EV_P_ &io);
		1528	}
		1529
		1530	// initialisation
		1531	ev_idle_init (&idle, idle_cb);
		1532	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1533	ev_io_start (EV_DEFAULT_ &io);
		1534
		1535	In the "real" world, it might also be beneficial to start a timer, so that
		1536	low-priority connections can not be locked out forever under load. This
		1537	enables your program to keep a lower latency for important connections
		1538	during short periods of high load, while not completely locking out less
		1539	important ones.
1189		1540
1190		1541
1191	=head1 WATCHER TYPES	1542	=head1 WATCHER TYPES
1192		1543
1193	This section describes each watcher in detail, but will not repeat	1544	This section describes each watcher in detail, but will not repeat
…		…
1219	descriptors to non-blocking mode is also usually a good idea (but not	1570	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1571	required if you know what you are doing).
1221		1572
1222	If you cannot use non-blocking mode, then force the use of a	1573	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only	1574	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1575	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1576	descriptors for which non-blocking operation makes no sense (such as
		1577	files) - libev doesn't guarantee any specific behaviour in that case.
1225		1578
1226	Another thing you have to watch out for is that it is quite easy to	1579	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1580	receive "spurious" readiness notifications, that is your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1581	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1582	because there is no data. Not only are some backends known to create a
…		…
1294		1647
1295	So when you encounter spurious, unexplained daemon exits, make sure you	1648	So when you encounter spurious, unexplained daemon exits, make sure you
1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1649	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1297	somewhere, as that would have given you a big clue).	1650	somewhere, as that would have given you a big clue).
1298		1651
		1652	=head3 The special problem of accept()ing when you can't
		1653
		1654	Many implementations of the POSIX C<accept> function (for example,
		1655	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1656	connection from the pending queue in all error cases.
		1657
		1658	For example, larger servers often run out of file descriptors (because
		1659	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1660	rejecting the connection, leading to libev signalling readiness on
		1661	the next iteration again (the connection still exists after all), and
		1662	typically causing the program to loop at 100% CPU usage.
		1663
		1664	Unfortunately, the set of errors that cause this issue differs between
		1665	operating systems, there is usually little the app can do to remedy the
		1666	situation, and no known thread-safe method of removing the connection to
		1667	cope with overload is known (to me).
		1668
		1669	One of the easiest ways to handle this situation is to just ignore it
		1670	- when the program encounters an overload, it will just loop until the
		1671	situation is over. While this is a form of busy waiting, no OS offers an
		1672	event-based way to handle this situation, so it's the best one can do.
		1673
		1674	A better way to handle the situation is to log any errors other than
		1675	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1676	messages, and continue as usual, which at least gives the user an idea of
		1677	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1678	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1679	usage.
		1680
		1681	If your program is single-threaded, then you could also keep a dummy file
		1682	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1683	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1684	close that fd, and create a new dummy fd. This will gracefully refuse
		1685	clients under typical overload conditions.
		1686
		1687	The last way to handle it is to simply log the error and C<exit>, as
		1688	is often done with C<malloc> failures, but this results in an easy
		1689	opportunity for a DoS attack.
1299		1690
1300	=head3 Watcher-Specific Functions	1691	=head3 Watcher-Specific Functions
1301		1692
1302	=over 4	1693	=over 4
1303		1694
…		…
1335	...	1726	...
1336	struct ev_loop *loop = ev_default_init (0);	1727	struct ev_loop *loop = ev_default_init (0);
1337	ev_io stdin_readable;	1728	ev_io stdin_readable;
1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1729	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1339	ev_io_start (loop, &stdin_readable);	1730	ev_io_start (loop, &stdin_readable);
1340	ev_loop (loop, 0);	1731	ev_run (loop, 0);
1341		1732
1342		1733
1343	=head2 C<ev_timer> - relative and optionally repeating timeouts	1734	=head2 C<ev_timer> - relative and optionally repeating timeouts
1344		1735
1345	Timer watchers are simple relative timers that generate an event after a	1736	Timer watchers are simple relative timers that generate an event after a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1741	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1742	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1743	monotonic clock option helps a lot here).
1353		1744
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1745	The callback is guaranteed to be invoked only I<after> its timeout has
1355	passed. If multiple timers become ready during the same loop iteration	1746	passed (not I<at>, so on systems with very low-resolution clocks this
1356	then the ones with earlier time-out values are invoked before ones with	1747	might introduce a small delay). If multiple timers become ready during the
1357	later time-out values (but this is no longer true when a callback calls	1748	same loop iteration then the ones with earlier time-out values are invoked
1358	C<ev_loop> recursively).	1749	before ones of the same priority with later time-out values (but this is
		1750	no longer true when a callback calls C<ev_run> recursively).
1359		1751
1360	=head3 Be smart about timeouts	1752	=head3 Be smart about timeouts
1361		1753
1362	Many real-world problems involve some kind of timeout, usually for error	1754	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1755	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1799	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1800	member and C<ev_timer_again>.
1409		1801
1410	At start:	1802	At start:
1411		1803
1412	ev_timer_init (timer, callback);	1804	ev_init (timer, callback);
1413	timer->repeat = 60.;	1805	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1806	ev_timer_again (loop, timer);
1415		1807
1416	Each time there is some activity:	1808	Each time there is some activity:
1417		1809
…		…
1449	ev_tstamp timeout = last_activity + 60.;	1841	ev_tstamp timeout = last_activity + 60.;
1450		1842
1451	// if last_activity + 60. is older than now, we did time out	1843	// if last_activity + 60. is older than now, we did time out
1452	if (timeout < now)	1844	if (timeout < now)
1453	{	1845	{
1454	// timeout occured, take action	1846	// timeout occurred, take action
1455	}	1847	}
1456	else	1848	else
1457	{	1849	{
1458	// callback was invoked, but there was some activity, re-arm	1850	// callback was invoked, but there was some activity, re-arm
1459	// the watcher to fire in last_activity + 60, which is	1851	// the watcher to fire in last_activity + 60, which is
…		…
1479		1871
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1872	To start the timer, simply initialise the watcher and set C<last_activity>
1481	to the current time (meaning we just have some activity :), then call the	1873	to the current time (meaning we just have some activity :), then call the
1482	callback, which will "do the right thing" and start the timer:	1874	callback, which will "do the right thing" and start the timer:
1483		1875
1484	ev_timer_init (timer, callback);	1876	ev_init (timer, callback);
1485	last_activity = ev_now (loop);	1877	last_activity = ev_now (loop);
1486	callback (loop, timer, EV_TIMEOUT);	1878	callback (loop, timer, EV_TIMER);
1487		1879
1488	And when there is some activity, simply store the current time in	1880	And when there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1881	C<last_activity>, no libev calls at all:
1490		1882
1491	last_actiivty = ev_now (loop);	1883	last_activity = ev_now (loop);
1492		1884
1493	This technique is slightly more complex, but in most cases where the	1885	This technique is slightly more complex, but in most cases where the
1494	time-out is unlikely to be triggered, much more efficient.	1886	time-out is unlikely to be triggered, much more efficient.
1495		1887
1496	Changing the timeout is trivial as well (if it isn't hard-coded in the	1888	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1534		1926
1535	=head3 The special problem of time updates	1927	=head3 The special problem of time updates
1536		1928
1537	Establishing the current time is a costly operation (it usually takes at	1929	Establishing the current time is a costly operation (it usually takes at
1538	least two system calls): EV therefore updates its idea of the current	1930	least two system calls): EV therefore updates its idea of the current
1539	time only before and after C<ev_loop> collects new events, which causes a	1931	time only before and after C<ev_run> collects new events, which causes a
1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1932	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1541	lots of events in one iteration.	1933	lots of events in one iteration.
1542		1934
1543	The relative timeouts are calculated relative to the C<ev_now ()>	1935	The relative timeouts are calculated relative to the C<ev_now ()>
1544	time. This is usually the right thing as this timestamp refers to the time	1936	time. This is usually the right thing as this timestamp refers to the time
…		…
1550		1942
1551	If the event loop is suspended for a long time, you can also force an	1943	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1944	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	1945	()>.
1554		1946
		1947	=head3 The special problems of suspended animation
		1948
		1949	When you leave the server world it is quite customary to hit machines that
		1950	can suspend/hibernate - what happens to the clocks during such a suspend?
		1951
		1952	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1953	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1954	to run until the system is suspended, but they will not advance while the
		1955	system is suspended. That means, on resume, it will be as if the program
		1956	was frozen for a few seconds, but the suspend time will not be counted
		1957	towards C<ev_timer> when a monotonic clock source is used. The real time
		1958	clock advanced as expected, but if it is used as sole clocksource, then a
		1959	long suspend would be detected as a time jump by libev, and timers would
		1960	be adjusted accordingly.
		1961
		1962	I would not be surprised to see different behaviour in different between
		1963	operating systems, OS versions or even different hardware.
		1964
		1965	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1966	time jump in the monotonic clocks and the realtime clock. If the program
		1967	is suspended for a very long time, and monotonic clock sources are in use,
		1968	then you can expect C<ev_timer>s to expire as the full suspension time
		1969	will be counted towards the timers. When no monotonic clock source is in
		1970	use, then libev will again assume a timejump and adjust accordingly.
		1971
		1972	It might be beneficial for this latter case to call C<ev_suspend>
		1973	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1974	deterministic behaviour in this case (you can do nothing against
		1975	C<SIGSTOP>).
		1976
1555	=head3 Watcher-Specific Functions and Data Members	1977	=head3 Watcher-Specific Functions and Data Members
1556		1978
1557	=over 4	1979	=over 4
1558		1980
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1981	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1582	If the timer is started but non-repeating, stop it (as if it timed out).	2004	If the timer is started but non-repeating, stop it (as if it timed out).
1583		2005
1584	If the timer is repeating, either start it if necessary (with the	2006	If the timer is repeating, either start it if necessary (with the
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	2007	C<repeat> value), or reset the running timer to the C<repeat> value.
1586		2008
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2009	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1588	usage example.	2010	usage example.
		2011
		2012	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2013
		2014	Returns the remaining time until a timer fires. If the timer is active,
		2015	then this time is relative to the current event loop time, otherwise it's
		2016	the timeout value currently configured.
		2017
		2018	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2019	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2020	will return C<4>. When the timer expires and is restarted, it will return
		2021	roughly C<7> (likely slightly less as callback invocation takes some time,
		2022	too), and so on.
1589		2023
1590	=item ev_tstamp repeat [read-write]	2024	=item ev_tstamp repeat [read-write]
1591		2025
1592	The current C<repeat> value. Will be used each time the watcher times out	2026	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	2027	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1619	}	2053	}
1620		2054
1621	ev_timer mytimer;	2055	ev_timer mytimer;
1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2056	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1623	ev_timer_again (&mytimer); /* start timer */	2057	ev_timer_again (&mytimer); /* start timer */
1624	ev_loop (loop, 0);	2058	ev_run (loop, 0);
1625		2059
1626	// and in some piece of code that gets executed on any "activity":	2060	// and in some piece of code that gets executed on any "activity":
1627	// reset the timeout to start ticking again at 10 seconds	2061	// reset the timeout to start ticking again at 10 seconds
1628	ev_timer_again (&mytimer);	2062	ev_timer_again (&mytimer);
1629		2063
…		…
1655		2089
1656	As with timers, the callback is guaranteed to be invoked only when the	2090	As with timers, the callback is guaranteed to be invoked only when the
1657	point in time where it is supposed to trigger has passed. If multiple	2091	point in time where it is supposed to trigger has passed. If multiple
1658	timers become ready during the same loop iteration then the ones with	2092	timers become ready during the same loop iteration then the ones with
1659	earlier time-out values are invoked before ones with later time-out values	2093	earlier time-out values are invoked before ones with later time-out values
1660	(but this is no longer true when a callback calls C<ev_loop> recursively).	2094	(but this is no longer true when a callback calls C<ev_run> recursively).
1661		2095
1662	=head3 Watcher-Specific Functions and Data Members	2096	=head3 Watcher-Specific Functions and Data Members
1663		2097
1664	=over 4	2098	=over 4
1665		2099
…		…
1793	Example: Call a callback every hour, or, more precisely, whenever the	2227	Example: Call a callback every hour, or, more precisely, whenever the
1794	system time is divisible by 3600. The callback invocation times have	2228	system time is divisible by 3600. The callback invocation times have
1795	potentially a lot of jitter, but good long-term stability.	2229	potentially a lot of jitter, but good long-term stability.
1796		2230
1797	static void	2231	static void
1798	clock_cb (struct ev_loop loop, ev_io w, int revents)	2232	clock_cb (struct ev_loop loop, ev_periodic w, int revents)
1799	{	2233	{
1800	... its now a full hour (UTC, or TAI or whatever your clock follows)	2234	... its now a full hour (UTC, or TAI or whatever your clock follows)
1801	}	2235	}
1802		2236
1803	ev_periodic hourly_tick;	2237	ev_periodic hourly_tick;
…		…
1826		2260
1827	=head2 C<ev_signal> - signal me when a signal gets signalled!	2261	=head2 C<ev_signal> - signal me when a signal gets signalled!
1828		2262
1829	Signal watchers will trigger an event when the process receives a specific	2263	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2264	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2265	will try its best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2266	normal event processing, like any other event.
1833		2267
1834	If you want signals asynchronously, just use C<sigaction> as you would	2268	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2269	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2270	the signal. You can even use C<ev_async> from a signal handler to
		2271	synchronously wake up an event loop.
1837		2272
1838	You can configure as many watchers as you like per signal. Only when the	2273	You can configure as many watchers as you like for the same signal, but
		2274	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2275	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2276	C<SIGINT> in both the default loop and another loop at the same time. At
		2277	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2278
1839	first watcher gets started will libev actually register a signal handler	2279	When the first watcher gets started will libev actually register something
1840	with the kernel (thus it coexists with your own signal handlers as long as	2280	with the kernel (thus it coexists with your own signal handlers as long as
1841	you don't register any with libev for the same signal). Similarly, when	2281	you don't register any with libev for the same signal).
1842	the last signal watcher for a signal is stopped, libev will reset the
1843	signal handler to SIG_DFL (regardless of what it was set to before).
1844		2282
1845	If possible and supported, libev will install its handlers with	2283	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2284	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2285	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2286	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2287	and unblock them in an C<ev_prepare> watcher.
		2288
		2289	=head3 The special problem of inheritance over fork/execve/pthread_create
		2290
		2291	Both the signal mask (C<sigprocmask>) and the signal disposition
		2292	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2293	stopping it again), that is, libev might or might not block the signal,
		2294	and might or might not set or restore the installed signal handler.
		2295
		2296	While this does not matter for the signal disposition (libev never
		2297	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2298	C<execve>), this matters for the signal mask: many programs do not expect
		2299	certain signals to be blocked.
		2300
		2301	This means that before calling C<exec> (from the child) you should reset
		2302	the signal mask to whatever "default" you expect (all clear is a good
		2303	choice usually).
		2304
		2305	The simplest way to ensure that the signal mask is reset in the child is
		2306	to install a fork handler with C<pthread_atfork> that resets it. That will
		2307	catch fork calls done by libraries (such as the libc) as well.
		2308
		2309	In current versions of libev, the signal will not be blocked indefinitely
		2310	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2311	the window of opportunity for problems, it will not go away, as libev
		2312	I<has> to modify the signal mask, at least temporarily.
		2313
		2314	So I can't stress this enough: I<If you do not reset your signal mask when
		2315	you expect it to be empty, you have a race condition in your code>. This
		2316	is not a libev-specific thing, this is true for most event libraries.
1850		2317
1851	=head3 Watcher-Specific Functions and Data Members	2318	=head3 Watcher-Specific Functions and Data Members
1852		2319
1853	=over 4	2320	=over 4
1854		2321
…		…
1870	Example: Try to exit cleanly on SIGINT.	2337	Example: Try to exit cleanly on SIGINT.
1871		2338
1872	static void	2339	static void
1873	sigint_cb (struct ev_loop loop, ev_signal w, int revents)	2340	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1874	{	2341	{
1875	ev_unloop (loop, EVUNLOOP_ALL);	2342	ev_break (loop, EVBREAK_ALL);
1876	}	2343	}
1877		2344
1878	ev_signal signal_watcher;	2345	ev_signal signal_watcher;
1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2346	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1880	ev_signal_start (loop, &signal_watcher);	2347	ev_signal_start (loop, &signal_watcher);
…		…
1886	some child status changes (most typically when a child of yours dies or	2353	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2354	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2355	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2356	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2357	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2358	but forking and registering a watcher a few event loop iterations later or
1892	not.	2359	in the next callback invocation is not.
1893		2360
1894	Only the default event loop is capable of handling signals, and therefore	2361	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2362	you can only register child watchers in the default event loop.
1896		2363
		2364	Due to some design glitches inside libev, child watchers will always be
		2365	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2366	libev)
		2367
1897	=head3 Process Interaction	2368	=head3 Process Interaction
1898		2369
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2370	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2371	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2372	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2373	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2374	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2375	children, even ones not watched.
1905		2376
1906	=head3 Overriding the Built-In Processing	2377	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2387	=head3 Stopping the Child Watcher
1917		2388
1918	Currently, the child watcher never gets stopped, even when the	2389	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2390	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2391	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2392	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2393	problem).
1922		2394
1923	=head3 Watcher-Specific Functions and Data Members	2395	=head3 Watcher-Specific Functions and Data Members
1924		2396
1925	=over 4	2397	=over 4
1926		2398
…		…
2252	// no longer anything immediate to do.	2724	// no longer anything immediate to do.
2253	}	2725	}
2254		2726
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2727	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2728	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2729	ev_idle_start (loop, idle_watcher);
2258		2730
2259		2731
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2732	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2733
2262	Prepare and check watchers are usually (but not always) used in pairs:	2734	Prepare and check watchers are usually (but not always) used in pairs:
2263	prepare watchers get invoked before the process blocks and check watchers	2735	prepare watchers get invoked before the process blocks and check watchers
2264	afterwards.	2736	afterwards.
2265		2737
2266	You I<must not> call C<ev_loop> or similar functions that enter	2738	You I<must not> call C<ev_run> or similar functions that enter
2267	the current event loop from either C<ev_prepare> or C<ev_check>	2739	the current event loop from either C<ev_prepare> or C<ev_check>
2268	watchers. Other loops than the current one are fine, however. The	2740	watchers. Other loops than the current one are fine, however. The
2269	rationale behind this is that you do not need to check for recursion in	2741	rationale behind this is that you do not need to check for recursion in
2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2742	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2271	C<ev_check> so if you have one watcher of each kind they will always be	2743	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2355	struct pollfd fds [nfd];	2827	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	2828	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2829	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		2830
2359	/* the callback is illegal, but won't be called as we stop during check */	2831	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	2832	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	2833	ev_timer_start (loop, &tw);
2362		2834
2363	// create one ev_io per pollfd	2835	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	2836	for (int i = 0; i < nfd; ++i)
2365	{	2837	{
…		…
2439		2911
2440	if (timeout >= 0)	2912	if (timeout >= 0)
2441	// create/start timer	2913	// create/start timer
2442		2914
2443	// poll	2915	// poll
2444	ev_loop (EV_A_ 0);	2916	ev_run (EV_A_ 0);
2445		2917
2446	// stop timer again	2918	// stop timer again
2447	if (timeout >= 0)	2919	if (timeout >= 0)
2448	ev_timer_stop (EV_A_ &to);	2920	ev_timer_stop (EV_A_ &to);
2449		2921
…		…
2527	if you do not want that, you need to temporarily stop the embed watcher).	2999	if you do not want that, you need to temporarily stop the embed watcher).
2528		3000
2529	=item ev_embed_sweep (loop, ev_embed *)	3001	=item ev_embed_sweep (loop, ev_embed *)
2530		3002
2531	Make a single, non-blocking sweep over the embedded loop. This works	3003	Make a single, non-blocking sweep over the embedded loop. This works
2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3004	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2533	appropriate way for embedded loops.	3005	appropriate way for embedded loops.
2534		3006
2535	=item struct ev_loop *other [read-only]	3007	=item struct ev_loop *other [read-only]
2536		3008
2537	The embedded event loop.	3009	The embedded event loop.
…		…
2595	event loop blocks next and before C<ev_check> watchers are being called,	3067	event loop blocks next and before C<ev_check> watchers are being called,
2596	and only in the child after the fork. If whoever good citizen calling	3068	and only in the child after the fork. If whoever good citizen calling
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3069	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2598	handlers will be invoked, too, of course.	3070	handlers will be invoked, too, of course.
2599		3071
		3072	=head3 The special problem of life after fork - how is it possible?
		3073
		3074	Most uses of C<fork()> consist of forking, then some simple calls to set
		3075	up/change the process environment, followed by a call to C<exec()>. This
		3076	sequence should be handled by libev without any problems.
		3077
		3078	This changes when the application actually wants to do event handling
		3079	in the child, or both parent in child, in effect "continuing" after the
		3080	fork.
		3081
		3082	The default mode of operation (for libev, with application help to detect
		3083	forks) is to duplicate all the state in the child, as would be expected
		3084	when I<either> the parent I<or> the child process continues.
		3085
		3086	When both processes want to continue using libev, then this is usually the
		3087	wrong result. In that case, usually one process (typically the parent) is
		3088	supposed to continue with all watchers in place as before, while the other
		3089	process typically wants to start fresh, i.e. without any active watchers.
		3090
		3091	The cleanest and most efficient way to achieve that with libev is to
		3092	simply create a new event loop, which of course will be "empty", and
		3093	use that for new watchers. This has the advantage of not touching more
		3094	memory than necessary, and thus avoiding the copy-on-write, and the
		3095	disadvantage of having to use multiple event loops (which do not support
		3096	signal watchers).
		3097
		3098	When this is not possible, or you want to use the default loop for
		3099	other reasons, then in the process that wants to start "fresh", call
		3100	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3101	Destroying the default loop will "orphan" (not stop) all registered
		3102	watchers, so you have to be careful not to execute code that modifies
		3103	those watchers. Note also that in that case, you have to re-register any
		3104	signal watchers.
		3105
2600	=head3 Watcher-Specific Functions and Data Members	3106	=head3 Watcher-Specific Functions and Data Members
2601		3107
2602	=over 4	3108	=over 4
2603		3109
2604	=item ev_fork_init (ev_signal *, callback)	3110	=item ev_fork_init (ev_fork *, callback)
2605		3111
2606	Initialises and configures the fork watcher - it has no parameters of any	3112	Initialises and configures the fork watcher - it has no parameters of any
2607	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3113	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2608	believe me.	3114	really.
2609		3115
2610	=back	3116	=back
2611		3117
2612		3118
		3119	=head2 C<ev_cleanup> - even the best things end
		3120
		3121	Cleanup watchers are called just before the event loop is being destroyed
		3122	by a call to C<ev_loop_destroy>.
		3123
		3124	While there is no guarantee that the event loop gets destroyed, cleanup
		3125	watchers provide a convenient method to install cleanup hooks for your
		3126	program, worker threads and so on - you just to make sure to destroy the
		3127	loop when you want them to be invoked.
		3128
		3129	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3130	all other watchers, they do not keep a reference to the event loop (which
		3131	makes a lot of sense if you think about it). Like all other watchers, you
		3132	can call libev functions in the callback, except C<ev_cleanup_start>.
		3133
		3134	=head3 Watcher-Specific Functions and Data Members
		3135
		3136	=over 4
		3137
		3138	=item ev_cleanup_init (ev_cleanup *, callback)
		3139
		3140	Initialises and configures the cleanup watcher - it has no parameters of
		3141	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3142	pointless, I assure you.
		3143
		3144	=back
		3145
		3146	Example: Register an atexit handler to destroy the default loop, so any
		3147	cleanup functions are called.
		3148
		3149	static void
		3150	program_exits (void)
		3151	{
		3152	ev_loop_destroy (EV_DEFAULT_UC);
		3153	}
		3154
		3155	...
		3156	atexit (program_exits);
		3157
		3158
2613	=head2 C<ev_async> - how to wake up another event loop	3159	=head2 C<ev_async> - how to wake up an event loop
2614		3160
2615	In general, you cannot use an C<ev_loop> from multiple threads or other	3161	In general, you cannot use an C<ev_run> from multiple threads or other
2616	asynchronous sources such as signal handlers (as opposed to multiple event	3162	asynchronous sources such as signal handlers (as opposed to multiple event
2617	loops - those are of course safe to use in different threads).	3163	loops - those are of course safe to use in different threads).
2618		3164
2619	Sometimes, however, you need to wake up another event loop you do not	3165	Sometimes, however, you need to wake up an event loop you do not control,
2620	control, for example because it belongs to another thread. This is what	3166	for example because it belongs to another thread. This is what C<ev_async>
2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3167	watchers do: as long as the C<ev_async> watcher is active, you can signal
2622	can signal it by calling C<ev_async_send>, which is thread- and signal	3168	it by calling C<ev_async_send>, which is thread- and signal safe.
2623	safe.
2624		3169
2625	This functionality is very similar to C<ev_signal> watchers, as signals,	3170	This functionality is very similar to C<ev_signal> watchers, as signals,
2626	too, are asynchronous in nature, and signals, too, will be compressed	3171	too, are asynchronous in nature, and signals, too, will be compressed
2627	(i.e. the number of callback invocations may be less than the number of	3172	(i.e. the number of callback invocations may be less than the number of
2628	C<ev_async_sent> calls).	3173	C<ev_async_sent> calls).
…		…
2633	=head3 Queueing	3178	=head3 Queueing
2634		3179
2635	C<ev_async> does not support queueing of data in any way. The reason	3180	C<ev_async> does not support queueing of data in any way. The reason
2636	is that the author does not know of a simple (or any) algorithm for a	3181	is that the author does not know of a simple (or any) algorithm for a
2637	multiple-writer-single-reader queue that works in all cases and doesn't	3182	multiple-writer-single-reader queue that works in all cases and doesn't
2638	need elaborate support such as pthreads.	3183	need elaborate support such as pthreads or unportable memory access
		3184	semantics.
2639		3185
2640	That means that if you want to queue data, you have to provide your own	3186	That means that if you want to queue data, you have to provide your own
2641	queue. But at least I can tell you how to implement locking around your	3187	queue. But at least I can tell you how to implement locking around your
2642	queue:	3188	queue:
2643		3189
…		…
2782		3328
2783	If C<timeout> is less than 0, then no timeout watcher will be	3329	If C<timeout> is less than 0, then no timeout watcher will be
2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3330	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2785	repeat = 0) will be started. C<0> is a valid timeout.	3331	repeat = 0) will be started. C<0> is a valid timeout.
2786		3332
2787	The callback has the type C<void (cb)(int revents, void arg)> and gets	3333	The callback has the type C<void (cb)(int revents, void arg)> and is
2788	passed an C<revents> set like normal event callbacks (a combination of	3334	passed an C<revents> set like normal event callbacks (a combination of
2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3335	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2790	value passed to C<ev_once>. Note that it is possible to receive I<both>	3336	value passed to C<ev_once>. Note that it is possible to receive I<both>
2791	a timeout and an io event at the same time - you probably should give io	3337	a timeout and an io event at the same time - you probably should give io
2792	events precedence.	3338	events precedence.
2793		3339
2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3340	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2795		3341
2796	static void stdin_ready (int revents, void *arg)	3342	static void stdin_ready (int revents, void *arg)
2797	{	3343	{
2798	if (revents & EV_READ)	3344	if (revents & EV_READ)
2799	/* stdin might have data for us, joy! */;	3345	/* stdin might have data for us, joy! */;
2800	else if (revents & EV_TIMEOUT)	3346	else if (revents & EV_TIMER)
2801	/* doh, nothing entered */;	3347	/* doh, nothing entered */;
2802	}	3348	}
2803		3349
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3350	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805		3351
2806	=item ev_feed_event (struct ev_loop , watcher , int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3352	=item ev_feed_fd_event (loop, int fd, int revents)
2813		3353
2814	Feed an event on the given fd, as if a file descriptor backend detected	3354	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3355	the given events it.
2816		3356
2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3357	=item ev_feed_signal_event (loop, int signum)
2818		3358
2819	Feed an event as if the given signal occurred (C<loop> must be the default	3359	Feed an event as if the given signal occurred (C<loop> must be the default
2820	loop!).	3360	loop!).
2821		3361
2822	=back	3362	=back
…		…
2841	=item * Priorities are not currently supported. Initialising priorities	3381	=item * Priorities are not currently supported. Initialising priorities
2842	will fail and all watchers will have the same priority, even though there	3382	will fail and all watchers will have the same priority, even though there
2843	is an ev_pri field.	3383	is an ev_pri field.
2844		3384
2845	=item * In libevent, the last base created gets the signals, in libev, the	3385	=item * In libevent, the last base created gets the signals, in libev, the
2846	first base created (== the default loop) gets the signals.	3386	base that registered the signal gets the signals.
2847		3387
2848	=item * Other members are not supported.	3388	=item * Other members are not supported.
2849		3389
2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3390	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2851	to use the libev header file and library.	3391	to use the libev header file and library.
…		…
2902		3442
2903	=over 4	3443	=over 4
2904		3444
2905	=item ev::TYPE::TYPE ()	3445	=item ev::TYPE::TYPE ()
2906		3446
2907	=item ev::TYPE::TYPE (struct ev_loop *)	3447	=item ev::TYPE::TYPE (loop)
2908		3448
2909	=item ev::TYPE::~TYPE	3449	=item ev::TYPE::~TYPE
2910		3450
2911	The constructor (optionally) takes an event loop to associate the watcher	3451	The constructor (optionally) takes an event loop to associate the watcher
2912	with. If it is omitted, it will use C<EV_DEFAULT>.	3452	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2945	myclass obj;	3485	myclass obj;
2946	ev::io iow;	3486	ev::io iow;
2947	iow.set <myclass, &myclass::io_cb> (&obj);	3487	iow.set <myclass, &myclass::io_cb> (&obj);
2948		3488
2949	=item w->set (object *)	3489	=item w->set (object *)
2950
2951	This is an B<experimental> feature that might go away in a future version.
2952		3490
2953	This is a variation of a method callback - leaving out the method to call	3491	This is a variation of a method callback - leaving out the method to call
2954	will default the method to C<operator ()>, which makes it possible to use	3492	will default the method to C<operator ()>, which makes it possible to use
2955	functor objects without having to manually specify the C<operator ()> all	3493	functor objects without having to manually specify the C<operator ()> all
2956	the time. Incidentally, you can then also leave out the template argument	3494	the time. Incidentally, you can then also leave out the template argument
…		…
2989	Example: Use a plain function as callback.	3527	Example: Use a plain function as callback.
2990		3528
2991	static void io_cb (ev::io &w, int revents) { }	3529	static void io_cb (ev::io &w, int revents) { }
2992	iow.set <io_cb> ();	3530	iow.set <io_cb> ();
2993		3531
2994	=item w->set (struct ev_loop *)	3532	=item w->set (loop)
2995		3533
2996	Associates a different C<struct ev_loop> with this watcher. You can only	3534	Associates a different C<struct ev_loop> with this watcher. You can only
2997	do this when the watcher is inactive (and not pending either).	3535	do this when the watcher is inactive (and not pending either).
2998		3536
2999	=item w->set ([arguments])	3537	=item w->set ([arguments])
3000		3538
3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3539	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3002	called at least once. Unlike the C counterpart, an active watcher gets	3540	method or a suitable start method must be called at least once. Unlike the
3003	automatically stopped and restarted when reconfiguring it with this	3541	C counterpart, an active watcher gets automatically stopped and restarted
3004	method.	3542	when reconfiguring it with this method.
3005		3543
3006	=item w->start ()	3544	=item w->start ()
3007		3545
3008	Starts the watcher. Note that there is no C<loop> argument, as the	3546	Starts the watcher. Note that there is no C<loop> argument, as the
3009	constructor already stores the event loop.	3547	constructor already stores the event loop.
3010		3548
		3549	=item w->start ([arguments])
		3550
		3551	Instead of calling C<set> and C<start> methods separately, it is often
		3552	convenient to wrap them in one call. Uses the same type of arguments as
		3553	the configure C<set> method of the watcher.
		3554
3011	=item w->stop ()	3555	=item w->stop ()
3012		3556
3013	Stops the watcher if it is active. Again, no C<loop> argument.	3557	Stops the watcher if it is active. Again, no C<loop> argument.
3014		3558
3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3559	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3027		3571
3028	=back	3572	=back
3029		3573
3030	=back	3574	=back
3031		3575
3032	Example: Define a class with an IO and idle watcher, start one of them in	3576	Example: Define a class with two I/O and idle watchers, start the I/O
3033	the constructor.	3577	watchers in the constructor.
3034		3578
3035	class myclass	3579	class myclass
3036	{	3580	{
3037	ev::io io ; void io_cb (ev::io &w, int revents);	3581	ev::io io ; void io_cb (ev::io &w, int revents);
		3582	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3583	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3039		3584
3040	myclass (int fd)	3585	myclass (int fd)
3041	{	3586	{
3042	io .set <myclass, &myclass::io_cb > (this);	3587	io .set <myclass, &myclass::io_cb > (this);
		3588	io2 .set <myclass, &myclass::io2_cb > (this);
3043	idle.set <myclass, &myclass::idle_cb> (this);	3589	idle.set <myclass, &myclass::idle_cb> (this);
3044		3590
3045	io.start (fd, ev::READ);	3591	io.set (fd, ev::WRITE); // configure the watcher
		3592	io.start (); // start it whenever convenient
		3593
		3594	io2.start (fd, ev::READ); // set + start in one call
3046	}	3595	}
3047	};	3596	};
3048		3597
3049		3598
3050	=head1 OTHER LANGUAGE BINDINGS	3599	=head1 OTHER LANGUAGE BINDINGS
…		…
3096	=item Ocaml	3645	=item Ocaml
3097		3646
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	3647	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3648	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3100		3649
		3650	=item Lua
		3651
		3652	Brian Maher has written a partial interface to libev for lua (at the
		3653	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3654	L<http://github.com/brimworks/lua-ev>.
		3655
3101	=back	3656	=back
3102		3657
3103		3658
3104	=head1 MACRO MAGIC	3659	=head1 MACRO MAGIC
3105		3660
…		…
3118	loop argument"). The C<EV_A> form is used when this is the sole argument,	3673	loop argument"). The C<EV_A> form is used when this is the sole argument,
3119	C<EV_A_> is used when other arguments are following. Example:	3674	C<EV_A_> is used when other arguments are following. Example:
3120		3675
3121	ev_unref (EV_A);	3676	ev_unref (EV_A);
3122	ev_timer_add (EV_A_ watcher);	3677	ev_timer_add (EV_A_ watcher);
3123	ev_loop (EV_A_ 0);	3678	ev_run (EV_A_ 0);
3124		3679
3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3680	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3126	which is often provided by the following macro.	3681	which is often provided by the following macro.
3127		3682
3128	=item C<EV_P>, C<EV_P_>	3683	=item C<EV_P>, C<EV_P_>
…		…
3168	}	3723	}
3169		3724
3170	ev_check check;	3725	ev_check check;
3171	ev_check_init (&check, check_cb);	3726	ev_check_init (&check, check_cb);
3172	ev_check_start (EV_DEFAULT_ &check);	3727	ev_check_start (EV_DEFAULT_ &check);
3173	ev_loop (EV_DEFAULT_ 0);	3728	ev_run (EV_DEFAULT_ 0);
3174		3729
3175	=head1 EMBEDDING	3730	=head1 EMBEDDING
3176		3731
3177	Libev can (and often is) directly embedded into host	3732	Libev can (and often is) directly embedded into host
3178	applications. Examples of applications that embed it include the Deliantra	3733	applications. Examples of applications that embed it include the Deliantra
…		…
3258	libev.m4	3813	libev.m4
3259		3814
3260	=head2 PREPROCESSOR SYMBOLS/MACROS	3815	=head2 PREPROCESSOR SYMBOLS/MACROS
3261		3816
3262	Libev can be configured via a variety of preprocessor symbols you have to	3817	Libev can be configured via a variety of preprocessor symbols you have to
3263	define before including any of its files. The default in the absence of	3818	define before including (or compiling) any of its files. The default in
3264	autoconf is documented for every option.	3819	the absence of autoconf is documented for every option.
		3820
		3821	Symbols marked with "(h)" do not change the ABI, and can have different
		3822	values when compiling libev vs. including F<ev.h>, so it is permissible
		3823	to redefine them before including F<ev.h> without breaking compatibility
		3824	to a compiled library. All other symbols change the ABI, which means all
		3825	users of libev and the libev code itself must be compiled with compatible
		3826	settings.
3265		3827
3266	=over 4	3828	=over 4
3267		3829
		3830	=item EV_COMPAT3 (h)
		3831
		3832	Backwards compatibility is a major concern for libev. This is why this
		3833	release of libev comes with wrappers for the functions and symbols that
		3834	have been renamed between libev version 3 and 4.
		3835
		3836	You can disable these wrappers (to test compatibility with future
		3837	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3838	sources. This has the additional advantage that you can drop the C<struct>
		3839	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3840	typedef in that case.
		3841
		3842	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3843	and in some even more future version the compatibility code will be
		3844	removed completely.
		3845
3268	=item EV_STANDALONE	3846	=item EV_STANDALONE (h)
3269		3847
3270	Must always be C<1> if you do not use autoconf configuration, which	3848	Must always be C<1> if you do not use autoconf configuration, which
3271	keeps libev from including F<config.h>, and it also defines dummy	3849	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	3850	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	3851	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	3852	F<event.h> that are not directly supported by the libev core alone.
3275		3853
3276	In stanbdalone mode, libev will still try to automatically deduce the	3854	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	3855	configuration, but has to be more conservative.
3278		3856
3279	=item EV_USE_MONOTONIC	3857	=item EV_USE_MONOTONIC
3280		3858
3281	If defined to be C<1>, libev will try to detect the availability of the	3859	If defined to be C<1>, libev will try to detect the availability of the
…		…
3346	be used is the winsock select). This means that it will call	3924	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3925	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	3926	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	3927	on win32. Should not be defined on non-win32 platforms.
3350		3928
3351	=item EV_FD_TO_WIN32_HANDLE	3929	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		3930
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3931	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	3932	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	3933	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	3934	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	3935	in which case they can provide this function to map fds to socket handles.
		3936
		3937	=item EV_WIN32_HANDLE_TO_FD(handle)
		3938
		3939	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3940	using the standard C<_open_osfhandle> function. For programs implementing
		3941	their own fd to handle mapping, overwriting this function makes it easier
		3942	to do so. This can be done by defining this macro to an appropriate value.
		3943
		3944	=item EV_WIN32_CLOSE_FD(fd)
		3945
		3946	If programs implement their own fd to handle mapping on win32, then this
		3947	macro can be used to override the C<close> function, useful to unregister
		3948	file descriptors again. Note that the replacement function has to close
		3949	the underlying OS handle.
3358		3950
3359	=item EV_USE_POLL	3951	=item EV_USE_POLL
3360		3952
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3953	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	3954	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3409	as well as for signal and thread safety in C<ev_async> watchers.	4001	as well as for signal and thread safety in C<ev_async> watchers.
3410		4002
3411	In the absence of this define, libev will use C<sig_atomic_t volatile>	4003	In the absence of this define, libev will use C<sig_atomic_t volatile>
3412	(from F<signal.h>), which is usually good enough on most platforms.	4004	(from F<signal.h>), which is usually good enough on most platforms.
3413		4005
3414	=item EV_H	4006	=item EV_H (h)
3415		4007
3416	The name of the F<ev.h> header file used to include it. The default if	4008	The name of the F<ev.h> header file used to include it. The default if
3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4009	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3418	used to virtually rename the F<ev.h> header file in case of conflicts.	4010	used to virtually rename the F<ev.h> header file in case of conflicts.
3419		4011
3420	=item EV_CONFIG_H	4012	=item EV_CONFIG_H (h)
3421		4013
3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4014	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4015	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3424	C<EV_H>, above.	4016	C<EV_H>, above.
3425		4017
3426	=item EV_EVENT_H	4018	=item EV_EVENT_H (h)
3427		4019
3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4020	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3429	of how the F<event.h> header can be found, the default is C<"event.h">.	4021	of how the F<event.h> header can be found, the default is C<"event.h">.
3430		4022
3431	=item EV_PROTOTYPES	4023	=item EV_PROTOTYPES (h)
3432		4024
3433	If defined to be C<0>, then F<ev.h> will not define any function	4025	If defined to be C<0>, then F<ev.h> will not define any function
3434	prototypes, but still define all the structs and other symbols. This is	4026	prototypes, but still define all the structs and other symbols. This is
3435	occasionally useful if you want to provide your own wrapper functions	4027	occasionally useful if you want to provide your own wrapper functions
3436	around libev functions.	4028	around libev functions.
…		…
3458	fine.	4050	fine.
3459		4051
3460	If your embedding application does not need any priorities, defining these	4052	If your embedding application does not need any priorities, defining these
3461	both to C<0> will save some memory and CPU.	4053	both to C<0> will save some memory and CPU.
3462		4054
3463	=item EV_PERIODIC_ENABLE	4055	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4056	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4057	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3464		4058
3465	If undefined or defined to be C<1>, then periodic timers are supported. If	4059	If undefined or defined to be C<1> (and the platform supports it), then
3466	defined to be C<0>, then they are not. Disabling them saves a few kB of	4060	the respective watcher type is supported. If defined to be C<0>, then it
3467	code.	4061	is not. Disabling watcher types mainly saves code size.
3468		4062
3469	=item EV_IDLE_ENABLE	4063	=item EV_FEATURES
3470
3471	If undefined or defined to be C<1>, then idle watchers are supported. If
3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
3473	code.
3474
3475	=item EV_EMBED_ENABLE
3476
3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3478	defined to be C<0>, then they are not. Embed watchers rely on most other
3479	watcher types, which therefore must not be disabled.
3480
3481	=item EV_STAT_ENABLE
3482
3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3484	defined to be C<0>, then they are not.
3485
3486	=item EV_FORK_ENABLE
3487
3488	If undefined or defined to be C<1>, then fork watchers are supported. If
3489	defined to be C<0>, then they are not.
3490
3491	=item EV_ASYNC_ENABLE
3492
3493	If undefined or defined to be C<1>, then async watchers are supported. If
3494	defined to be C<0>, then they are not.
3495
3496	=item EV_MINIMAL
3497		4064
3498	If you need to shave off some kilobytes of code at the expense of some	4065	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	4066	speed (but with the full API), you can define this symbol to request
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4067	certain subsets of functionality. The default is to enable all features
3501	much smaller 2-heap for timer management over the default 4-heap.	4068	that can be enabled on the platform.
		4069
		4070	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4071	with some broad features you want) and then selectively re-enable
		4072	additional parts you want, for example if you want everything minimal,
		4073	but multiple event loop support, async and child watchers and the poll
		4074	backend, use this:
		4075
		4076	#define EV_FEATURES 0
		4077	#define EV_MULTIPLICITY 1
		4078	#define EV_USE_POLL 1
		4079	#define EV_CHILD_ENABLE 1
		4080	#define EV_ASYNC_ENABLE 1
		4081
		4082	The actual value is a bitset, it can be a combination of the following
		4083	values:
		4084
		4085	=over 4
		4086
		4087	=item C<1> - faster/larger code
		4088
		4089	Use larger code to speed up some operations.
		4090
		4091	Currently this is used to override some inlining decisions (enlarging the
		4092	code size by roughly 30% on amd64).
		4093
		4094	When optimising for size, use of compiler flags such as C<-Os> with
		4095	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4096	assertions.
		4097
		4098	=item C<2> - faster/larger data structures
		4099
		4100	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4101	hash table sizes and so on. This will usually further increase code size
		4102	and can additionally have an effect on the size of data structures at
		4103	runtime.
		4104
		4105	=item C<4> - full API configuration
		4106
		4107	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4108	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4109
		4110	=item C<8> - full API
		4111
		4112	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4113	details on which parts of the API are still available without this
		4114	feature, and do not complain if this subset changes over time.
		4115
		4116	=item C<16> - enable all optional watcher types
		4117
		4118	Enables all optional watcher types. If you want to selectively enable
		4119	only some watcher types other than I/O and timers (e.g. prepare,
		4120	embed, async, child...) you can enable them manually by defining
		4121	C<EV_watchertype_ENABLE> to C<1> instead.
		4122
		4123	=item C<32> - enable all backends
		4124
		4125	This enables all backends - without this feature, you need to enable at
		4126	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4127
		4128	=item C<64> - enable OS-specific "helper" APIs
		4129
		4130	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4131	default.
		4132
		4133	=back
		4134
		4135	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4136	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4137	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4138	watchers, timers and monotonic clock support.
		4139
		4140	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4141	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4142	your program might be left out as well - a binary starting a timer and an
		4143	I/O watcher then might come out at only 5Kb.
		4144
		4145	=item EV_AVOID_STDIO
		4146
		4147	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4148	functions (printf, scanf, perror etc.). This will increase the code size
		4149	somewhat, but if your program doesn't otherwise depend on stdio and your
		4150	libc allows it, this avoids linking in the stdio library which is quite
		4151	big.
		4152
		4153	Note that error messages might become less precise when this option is
		4154	enabled.
		4155
		4156	=item EV_NSIG
		4157
		4158	The highest supported signal number, +1 (or, the number of
		4159	signals): Normally, libev tries to deduce the maximum number of signals
		4160	automatically, but sometimes this fails, in which case it can be
		4161	specified. Also, using a lower number than detected (C<32> should be
		4162	good for about any system in existence) can save some memory, as libev
		4163	statically allocates some 12-24 bytes per signal number.
3502		4164
3503	=item EV_PID_HASHSIZE	4165	=item EV_PID_HASHSIZE
3504		4166
3505	C<ev_child> watchers use a small hash table to distribute workload by	4167	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4168	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3507	than enough. If you need to manage thousands of children you might want to	4169	usually more than enough. If you need to manage thousands of children you
3508	increase this value (I<must> be a power of two).	4170	might want to increase this value (I<must> be a power of two).
3509		4171
3510	=item EV_INOTIFY_HASHSIZE	4172	=item EV_INOTIFY_HASHSIZE
3511		4173
3512	C<ev_stat> watchers use a small hash table to distribute workload by	4174	C<ev_stat> watchers use a small hash table to distribute workload by
3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4175	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3514	usually more than enough. If you need to manage thousands of C<ev_stat>	4176	disabled), usually more than enough. If you need to manage thousands of
3515	watchers you might want to increase this value (I<must> be a power of	4177	C<ev_stat> watchers you might want to increase this value (I<must> be a
3516	two).	4178	power of two).
3517		4179
3518	=item EV_USE_4HEAP	4180	=item EV_USE_4HEAP
3519		4181
3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4182	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4183	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4184	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3523	faster performance with many (thousands) of watchers.	4185	faster performance with many (thousands) of watchers.
3524		4186
3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4187	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3526	(disabled).	4188	will be C<0>.
3527		4189
3528	=item EV_HEAP_CACHE_AT	4190	=item EV_HEAP_CACHE_AT
3529		4191
3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4192	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4193	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4194	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4195	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3534	but avoids random read accesses on heap changes. This improves performance	4196	but avoids random read accesses on heap changes. This improves performance
3535	noticeably with many (hundreds) of watchers.	4197	noticeably with many (hundreds) of watchers.
3536		4198
3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4199	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3538	(disabled).	4200	will be C<0>.
3539		4201
3540	=item EV_VERIFY	4202	=item EV_VERIFY
3541		4203
3542	Controls how much internal verification (see C<ev_loop_verify ()>) will	4204	Controls how much internal verification (see C<ev_verify ()>) will
3543	be done: If set to C<0>, no internal verification code will be compiled	4205	be done: If set to C<0>, no internal verification code will be compiled
3544	in. If set to C<1>, then verification code will be compiled in, but not	4206	in. If set to C<1>, then verification code will be compiled in, but not
3545	called. If set to C<2>, then the internal verification code will be	4207	called. If set to C<2>, then the internal verification code will be
3546	called once per loop, which can slow down libev. If set to C<3>, then the	4208	called once per loop, which can slow down libev. If set to C<3>, then the
3547	verification code will be called very frequently, which will slow down	4209	verification code will be called very frequently, which will slow down
3548	libev considerably.	4210	libev considerably.
3549		4211
3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4212	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3551	C<0>.	4213	will be C<0>.
3552		4214
3553	=item EV_COMMON	4215	=item EV_COMMON
3554		4216
3555	By default, all watchers have a C<void *data> member. By redefining	4217	By default, all watchers have a C<void *data> member. By redefining
3556	this macro to a something else you can include more and other types of	4218	this macro to something else you can include more and other types of
3557	members. You have to define it each time you include one of the files,	4219	members. You have to define it each time you include one of the files,
3558	though, and it must be identical each time.	4220	though, and it must be identical each time.
3559		4221
3560	For example, the perl EV module uses something like this:	4222	For example, the perl EV module uses something like this:
3561		4223
…		…
3614	file.	4276	file.
3615		4277
3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4278	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3617	that everybody includes and which overrides some configure choices:	4279	that everybody includes and which overrides some configure choices:
3618		4280
3619	#define EV_MINIMAL 1	4281	#define EV_FEATURES 8
3620	#define EV_USE_POLL 0	4282	#define EV_USE_SELECT 1
3621	#define EV_MULTIPLICITY 0
3622	#define EV_PERIODIC_ENABLE 0	4283	#define EV_PREPARE_ENABLE 1
		4284	#define EV_IDLE_ENABLE 1
3623	#define EV_STAT_ENABLE 0	4285	#define EV_SIGNAL_ENABLE 1
3624	#define EV_FORK_ENABLE 0	4286	#define EV_CHILD_ENABLE 1
		4287	#define EV_USE_STDEXCEPT 0
3625	#define EV_CONFIG_H <config.h>	4288	#define EV_CONFIG_H <config.h>
3626	#define EV_MINPRI 0
3627	#define EV_MAXPRI 0
3628		4289
3629	#include "ev++.h"	4290	#include "ev++.h"
3630		4291
3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4292	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3632		4293
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	4353	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	4354	watcher callback into the event loop interested in the signal.
3694		4355
3695	=back	4356	=back
3696		4357
		4358	=head4 THREAD LOCKING EXAMPLE
		4359
		4360	Here is a fictitious example of how to run an event loop in a different
		4361	thread than where callbacks are being invoked and watchers are
		4362	created/added/removed.
		4363
		4364	For a real-world example, see the C<EV::Loop::Async> perl module,
		4365	which uses exactly this technique (which is suited for many high-level
		4366	languages).
		4367
		4368	The example uses a pthread mutex to protect the loop data, a condition
		4369	variable to wait for callback invocations, an async watcher to notify the
		4370	event loop thread and an unspecified mechanism to wake up the main thread.
		4371
		4372	First, you need to associate some data with the event loop:
		4373
		4374	typedef struct {
		4375	mutex_t lock; /* global loop lock */
		4376	ev_async async_w;
		4377	thread_t tid;
		4378	cond_t invoke_cv;
		4379	} userdata;
		4380
		4381	void prepare_loop (EV_P)
		4382	{
		4383	// for simplicity, we use a static userdata struct.
		4384	static userdata u;
		4385
		4386	ev_async_init (&u->async_w, async_cb);
		4387	ev_async_start (EV_A_ &u->async_w);
		4388
		4389	pthread_mutex_init (&u->lock, 0);
		4390	pthread_cond_init (&u->invoke_cv, 0);
		4391
		4392	// now associate this with the loop
		4393	ev_set_userdata (EV_A_ u);
		4394	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4395	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4396
		4397	// then create the thread running ev_loop
		4398	pthread_create (&u->tid, 0, l_run, EV_A);
		4399	}
		4400
		4401	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4402	solely to wake up the event loop so it takes notice of any new watchers
		4403	that might have been added:
		4404
		4405	static void
		4406	async_cb (EV_P_ ev_async *w, int revents)
		4407	{
		4408	// just used for the side effects
		4409	}
		4410
		4411	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4412	protecting the loop data, respectively.
		4413
		4414	static void
		4415	l_release (EV_P)
		4416	{
		4417	userdata *u = ev_userdata (EV_A);
		4418	pthread_mutex_unlock (&u->lock);
		4419	}
		4420
		4421	static void
		4422	l_acquire (EV_P)
		4423	{
		4424	userdata *u = ev_userdata (EV_A);
		4425	pthread_mutex_lock (&u->lock);
		4426	}
		4427
		4428	The event loop thread first acquires the mutex, and then jumps straight
		4429	into C<ev_run>:
		4430
		4431	void *
		4432	l_run (void *thr_arg)
		4433	{
		4434	struct ev_loop loop = (struct ev_loop )thr_arg;
		4435
		4436	l_acquire (EV_A);
		4437	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4438	ev_run (EV_A_ 0);
		4439	l_release (EV_A);
		4440
		4441	return 0;
		4442	}
		4443
		4444	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4445	signal the main thread via some unspecified mechanism (signals? pipe
		4446	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4447	have been called (in a while loop because a) spurious wakeups are possible
		4448	and b) skipping inter-thread-communication when there are no pending
		4449	watchers is very beneficial):
		4450
		4451	static void
		4452	l_invoke (EV_P)
		4453	{
		4454	userdata *u = ev_userdata (EV_A);
		4455
		4456	while (ev_pending_count (EV_A))
		4457	{
		4458	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4459	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4460	}
		4461	}
		4462
		4463	Now, whenever the main thread gets told to invoke pending watchers, it
		4464	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4465	thread to continue:
		4466
		4467	static void
		4468	real_invoke_pending (EV_P)
		4469	{
		4470	userdata *u = ev_userdata (EV_A);
		4471
		4472	pthread_mutex_lock (&u->lock);
		4473	ev_invoke_pending (EV_A);
		4474	pthread_cond_signal (&u->invoke_cv);
		4475	pthread_mutex_unlock (&u->lock);
		4476	}
		4477
		4478	Whenever you want to start/stop a watcher or do other modifications to an
		4479	event loop, you will now have to lock:
		4480
		4481	ev_timer timeout_watcher;
		4482	userdata *u = ev_userdata (EV_A);
		4483
		4484	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4485
		4486	pthread_mutex_lock (&u->lock);
		4487	ev_timer_start (EV_A_ &timeout_watcher);
		4488	ev_async_send (EV_A_ &u->async_w);
		4489	pthread_mutex_unlock (&u->lock);
		4490
		4491	Note that sending the C<ev_async> watcher is required because otherwise
		4492	an event loop currently blocking in the kernel will have no knowledge
		4493	about the newly added timer. By waking up the loop it will pick up any new
		4494	watchers in the next event loop iteration.
		4495
3697	=head3 COROUTINES	4496	=head3 COROUTINES
3698		4497
3699	Libev is very accommodating to coroutines ("cooperative threads"):	4498	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	4499	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4500	coroutines (e.g. you can call C<ev_run> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	4501	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	4502	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	4503	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		4504
3706	Care has been taken to ensure that libev does not keep local state inside	4505	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4506	C<ev_run>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	4507	they do not call any callbacks.
3709		4508
3710	=head2 COMPILER WARNINGS	4509	=head2 COMPILER WARNINGS
3711		4510
3712	Depending on your compiler and compiler settings, you might get no or a	4511	Depending on your compiler and compiler settings, you might get no or a
…		…
3723	maintainable.	4522	maintainable.
3724		4523
3725	And of course, some compiler warnings are just plain stupid, or simply	4524	And of course, some compiler warnings are just plain stupid, or simply
3726	wrong (because they don't actually warn about the condition their message	4525	wrong (because they don't actually warn about the condition their message
3727	seems to warn about). For example, certain older gcc versions had some	4526	seems to warn about). For example, certain older gcc versions had some
3728	warnings that resulted an extreme number of false positives. These have	4527	warnings that resulted in an extreme number of false positives. These have
3729	been fixed, but some people still insist on making code warn-free with	4528	been fixed, but some people still insist on making code warn-free with
3730	such buggy versions.	4529	such buggy versions.
3731		4530
3732	While libev is written to generate as few warnings as possible,	4531	While libev is written to generate as few warnings as possible,
3733	"warn-free" code is not a goal, and it is recommended not to build libev	4532	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3769	I suggest using suppression lists.	4568	I suggest using suppression lists.
3770		4569
3771		4570
3772	=head1 PORTABILITY NOTES	4571	=head1 PORTABILITY NOTES
3773		4572
		4573	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4574
		4575	GNU/Linux is the only common platform that supports 64 bit file/large file
		4576	interfaces but I<disables> them by default.
		4577
		4578	That means that libev compiled in the default environment doesn't support
		4579	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4580
		4581	Unfortunately, many programs try to work around this GNU/Linux issue
		4582	by enabling the large file API, which makes them incompatible with the
		4583	standard libev compiled for their system.
		4584
		4585	Likewise, libev cannot enable the large file API itself as this would
		4586	suddenly make it incompatible to the default compile time environment,
		4587	i.e. all programs not using special compile switches.
		4588
		4589	=head2 OS/X AND DARWIN BUGS
		4590
		4591	The whole thing is a bug if you ask me - basically any system interface
		4592	you touch is broken, whether it is locales, poll, kqueue or even the
		4593	OpenGL drivers.
		4594
		4595	=head3 C<kqueue> is buggy
		4596
		4597	The kqueue syscall is broken in all known versions - most versions support
		4598	only sockets, many support pipes.
		4599
		4600	Libev tries to work around this by not using C<kqueue> by default on this
		4601	rotten platform, but of course you can still ask for it when creating a
		4602	loop - embedding a socket-only kqueue loop into a select-based one is
		4603	probably going to work well.
		4604
		4605	=head3 C<poll> is buggy
		4606
		4607	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4608	implementation by something calling C<kqueue> internally around the 10.5.6
		4609	release, so now C<kqueue> I<and> C<poll> are broken.
		4610
		4611	Libev tries to work around this by not using C<poll> by default on
		4612	this rotten platform, but of course you can still ask for it when creating
		4613	a loop.
		4614
		4615	=head3 C<select> is buggy
		4616
		4617	All that's left is C<select>, and of course Apple found a way to fuck this
		4618	one up as well: On OS/X, C<select> actively limits the number of file
		4619	descriptors you can pass in to 1024 - your program suddenly crashes when
		4620	you use more.
		4621
		4622	There is an undocumented "workaround" for this - defining
		4623	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4624	work on OS/X.
		4625
		4626	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4627
		4628	=head3 C<errno> reentrancy
		4629
		4630	The default compile environment on Solaris is unfortunately so
		4631	thread-unsafe that you can't even use components/libraries compiled
		4632	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4633	defined by default. A valid, if stupid, implementation choice.
		4634
		4635	If you want to use libev in threaded environments you have to make sure
		4636	it's compiled with C<_REENTRANT> defined.
		4637
		4638	=head3 Event port backend
		4639
		4640	The scalable event interface for Solaris is called "event
		4641	ports". Unfortunately, this mechanism is very buggy in all major
		4642	releases. If you run into high CPU usage, your program freezes or you get
		4643	a large number of spurious wakeups, make sure you have all the relevant
		4644	and latest kernel patches applied. No, I don't know which ones, but there
		4645	are multiple ones to apply, and afterwards, event ports actually work
		4646	great.
		4647
		4648	If you can't get it to work, you can try running the program by setting
		4649	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4650	C<select> backends.
		4651
		4652	=head2 AIX POLL BUG
		4653
		4654	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4655	this by trying to avoid the poll backend altogether (i.e. it's not even
		4656	compiled in), which normally isn't a big problem as C<select> works fine
		4657	with large bitsets on AIX, and AIX is dead anyway.
		4658
3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4659	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4660
		4661	=head3 General issues
3775		4662
3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4663	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3777	requires, and its I/O model is fundamentally incompatible with the POSIX	4664	requires, and its I/O model is fundamentally incompatible with the POSIX
3778	model. Libev still offers limited functionality on this platform in	4665	model. Libev still offers limited functionality on this platform in
3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4666	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3780	descriptors. This only applies when using Win32 natively, not when using	4667	descriptors. This only applies when using Win32 natively, not when using
3781	e.g. cygwin.	4668	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4669	as every compielr comes with a slightly differently broken/incompatible
		4670	environment.
3782		4671
3783	Lifting these limitations would basically require the full	4672	Lifting these limitations would basically require the full
3784	re-implementation of the I/O system. If you are into these kinds of	4673	re-implementation of the I/O system. If you are into this kind of thing,
3785	things, then note that glib does exactly that for you in a very portable	4674	then note that glib does exactly that for you in a very portable way (note
3786	way (note also that glib is the slowest event library known to man).	4675	also that glib is the slowest event library known to man).
3787		4676
3788	There is no supported compilation method available on windows except	4677	There is no supported compilation method available on windows except
3789	embedding it into other applications.	4678	embedding it into other applications.
		4679
		4680	Sensible signal handling is officially unsupported by Microsoft - libev
		4681	tries its best, but under most conditions, signals will simply not work.
3790		4682
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	4683	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	4684	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	4685	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	4686	so make sure you only write small amounts into your sockets (less than a
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	4691	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	4692	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	4693	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	4694	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	4695	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	4696	(due to Microsoft monopoly games).
3805		4697
3806	A typical way to use libev under windows is to embed it (see the embedding	4698	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	4699	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	4700	of F<ev.h>:
3809		4701
…		…
3816	you do I<not> compile the F<ev.c> or any other embedded source files!):	4708	you do I<not> compile the F<ev.c> or any other embedded source files!):
3817		4709
3818	#include "evwrap.h"	4710	#include "evwrap.h"
3819	#include "ev.c"	4711	#include "ev.c"
3820		4712
3821	=over 4
3822
3823	=item The winsocket select function	4713	=head3 The winsocket C<select> function
3824		4714
3825	The winsocket C<select> function doesn't follow POSIX in that it	4715	The winsocket C<select> function doesn't follow POSIX in that it
3826	requires socket I<handles> and not socket I<file descriptors> (it is	4716	requires socket I<handles> and not socket I<file descriptors> (it is
3827	also extremely buggy). This makes select very inefficient, and also	4717	also extremely buggy). This makes select very inefficient, and also
3828	requires a mapping from file descriptors to socket handles (the Microsoft	4718	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4727	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3838		4728
3839	Note that winsockets handling of fd sets is O(n), so you can easily get a	4729	Note that winsockets handling of fd sets is O(n), so you can easily get a
3840	complexity in the O(n²) range when using win32.	4730	complexity in the O(n²) range when using win32.
3841		4731
3842	=item Limited number of file descriptors	4732	=head3 Limited number of file descriptors
3843		4733
3844	Windows has numerous arbitrary (and low) limits on things.	4734	Windows has numerous arbitrary (and low) limits on things.
3845		4735
3846	Early versions of winsocket's select only supported waiting for a maximum	4736	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	4737	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	4738	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	4739	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	4740	previous thread in each. Sounds great!).
3851		4741
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4742	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	4743	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	4744	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	4745	other interpreters do their own select emulation on windows).
3856		4746
3857	Another limit is the number of file descriptors in the Microsoft runtime	4747	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4748	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	4749	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4750	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	4751	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	4752	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	4753	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	4754	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	4755	the cost of calling select (O(n²)) will likely make this unworkable.
3868
3869	=back
3870		4756
3871	=head2 PORTABILITY REQUIREMENTS	4757	=head2 PORTABILITY REQUIREMENTS
3872		4758
3873	In addition to a working ISO-C implementation and of course the	4759	In addition to a working ISO-C implementation and of course the
3874	backend-specific APIs, libev relies on a few additional extensions:	4760	backend-specific APIs, libev relies on a few additional extensions:
…		…
3881	Libev assumes not only that all watcher pointers have the same internal	4767	Libev assumes not only that all watcher pointers have the same internal
3882	structure (guaranteed by POSIX but not by ISO C for example), but it also	4768	structure (guaranteed by POSIX but not by ISO C for example), but it also
3883	assumes that the same (machine) code can be used to call any watcher	4769	assumes that the same (machine) code can be used to call any watcher
3884	callback: The watcher callbacks have different type signatures, but libev	4770	callback: The watcher callbacks have different type signatures, but libev
3885	calls them using an C<ev_watcher *> internally.	4771	calls them using an C<ev_watcher *> internally.
		4772
		4773	=item pointer accesses must be thread-atomic
		4774
		4775	Accessing a pointer value must be atomic, it must both be readable and
		4776	writable in one piece - this is the case on all current architectures.
3886		4777
3887	=item C<sig_atomic_t volatile> must be thread-atomic as well	4778	=item C<sig_atomic_t volatile> must be thread-atomic as well
3888		4779
3889	The type C<sig_atomic_t volatile> (or whatever is defined as	4780	The type C<sig_atomic_t volatile> (or whatever is defined as
3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3913	watchers.	4804	watchers.
3914		4805
3915	=item C<double> must hold a time value in seconds with enough accuracy	4806	=item C<double> must hold a time value in seconds with enough accuracy
3916		4807
3917	The type C<double> is used to represent timestamps. It is required to	4808	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4809	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3919	enough for at least into the year 4000. This requirement is fulfilled by	4810	good enough for at least into the year 4000 with millisecond accuracy
		4811	(the design goal for libev). This requirement is overfulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	4812	implementations using IEEE 754, which is basically all existing ones. With
		4813	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3921		4814
3922	=back	4815	=back
3923		4816
3924	If you know of other additional requirements drop me a note.	4817	If you know of other additional requirements drop me a note.
3925		4818
…		…
3993	involves iterating over all running async watchers or all signal numbers.	4886	involves iterating over all running async watchers or all signal numbers.
3994		4887
3995	=back	4888	=back
3996		4889
3997		4890
		4891	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4892
		4893	The major version 4 introduced some incompatible changes to the API.
		4894
		4895	At the moment, the C<ev.h> header file provides compatibility definitions
		4896	for all changes, so most programs should still compile. The compatibility
		4897	layer might be removed in later versions of libev, so better update to the
		4898	new API early than late.
		4899
		4900	=over 4
		4901
		4902	=item C<EV_COMPAT3> backwards compatibility mechanism
		4903
		4904	The backward compatibility mechanism can be controlled by
		4905	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4906	section.
		4907
		4908	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4909
		4910	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4911
		4912	ev_loop_destroy (EV_DEFAULT_UC);
		4913	ev_loop_fork (EV_DEFAULT);
		4914
		4915	=item function/symbol renames
		4916
		4917	A number of functions and symbols have been renamed:
		4918
		4919	ev_loop => ev_run
		4920	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4921	EVLOOP_ONESHOT => EVRUN_ONCE
		4922
		4923	ev_unloop => ev_break
		4924	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4925	EVUNLOOP_ONE => EVBREAK_ONE
		4926	EVUNLOOP_ALL => EVBREAK_ALL
		4927
		4928	EV_TIMEOUT => EV_TIMER
		4929
		4930	ev_loop_count => ev_iteration
		4931	ev_loop_depth => ev_depth
		4932	ev_loop_verify => ev_verify
		4933
		4934	Most functions working on C<struct ev_loop> objects don't have an
		4935	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4936	associated constants have been renamed to not collide with the C<struct
		4937	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4938	as all other watcher types. Note that C<ev_loop_fork> is still called
		4939	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4940	typedef.
		4941
		4942	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4943
		4944	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4945	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4946	and work, but the library code will of course be larger.
		4947
		4948	=back
		4949
		4950
		4951	=head1 GLOSSARY
		4952
		4953	=over 4
		4954
		4955	=item active
		4956
		4957	A watcher is active as long as it has been started and not yet stopped.
		4958	See L<WATCHER STATES> for details.
		4959
		4960	=item application
		4961
		4962	In this document, an application is whatever is using libev.
		4963
		4964	=item backend
		4965
		4966	The part of the code dealing with the operating system interfaces.
		4967
		4968	=item callback
		4969
		4970	The address of a function that is called when some event has been
		4971	detected. Callbacks are being passed the event loop, the watcher that
		4972	received the event, and the actual event bitset.
		4973
		4974	=item callback/watcher invocation
		4975
		4976	The act of calling the callback associated with a watcher.
		4977
		4978	=item event
		4979
		4980	A change of state of some external event, such as data now being available
		4981	for reading on a file descriptor, time having passed or simply not having
		4982	any other events happening anymore.
		4983
		4984	In libev, events are represented as single bits (such as C<EV_READ> or
		4985	C<EV_TIMER>).
		4986
		4987	=item event library
		4988
		4989	A software package implementing an event model and loop.
		4990
		4991	=item event loop
		4992
		4993	An entity that handles and processes external events and converts them
		4994	into callback invocations.
		4995
		4996	=item event model
		4997
		4998	The model used to describe how an event loop handles and processes
		4999	watchers and events.
		5000
		5001	=item pending
		5002
		5003	A watcher is pending as soon as the corresponding event has been
		5004	detected. See L<WATCHER STATES> for details.
		5005
		5006	=item real time
		5007
		5008	The physical time that is observed. It is apparently strictly monotonic :)
		5009
		5010	=item wall-clock time
		5011
		5012	The time and date as shown on clocks. Unlike real time, it can actually
		5013	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5014	clock.
		5015
		5016	=item watcher
		5017
		5018	A data structure that describes interest in certain events. Watchers need
		5019	to be started (attached to an event loop) before they can receive events.
		5020
		5021	=back
		5022
3998	=head1 AUTHOR	5023	=head1 AUTHOR
3999		5024
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5025	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5026	Magnusson and Emanuele Giaquinta.
4001		5027

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Comparing libev/ev.pod (file contents): Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs. Revision 1.342 by root, Wed Nov 10 13:16:44 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.342 by root, Wed Nov 10 13:16:44 2010 UTC