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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://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
70		92
71	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
72	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
73	these event sources and provide your program with events.	95	these event sources and provide your program with events.
74		96
…		…
84	=head2 FEATURES	106	=head2 FEATURES
85		107
86	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
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	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
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(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>).
96		119
97	It also is quite fast (see this	120	It also is quite fast (see this
98	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
99	for example).	122	for example).
100		123
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	132	this argument.
110		133
111	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
112		135
113	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	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
116	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
117	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
118	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
119	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
120	throughout libev.	144	time differences (e.g. delays) throughout libev.
121		145
122	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
123		147
124	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	149	and internal errors (bugs).
…		…
149		173
150	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
151		175
152	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
153	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
154	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>.
155		180
156	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
157		182
158	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
159	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
…		…
176	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
177	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
178	not a problem.	203	not a problem.
179		204
180	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
181	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
182		208
183	assert (("libev version mismatch",	209	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
186		212
…		…
197	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
199		225
200	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
201		227
202	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
203	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
204	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
205	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
206	(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
207	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
208		235
209	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
210		237
211	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
212	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
213	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
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
216		243
217	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
218		245
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		247
221	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
222	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
223	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
224	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
…		…
250	}	277	}
251		278
252	...	279	...
253	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
254		281
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	282	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		283
257	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
258	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
259	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
260	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
…		…
274	...	301	...
275	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
276		303
277	=back	304	=back
278		305
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	306	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		307
281	An event loop is described by a C<struct ev_loop *>. The library knows two	308	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	309	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	310	libev 3 had an C<ev_loop> function colliding with the struct name).
		311
		312	The library knows two types of such loops, the I<default> loop, which
		313	supports child process events, and dynamically created event loops which
		314	do not.
284		315
285	=over 4	316	=over 4
286		317
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	318	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		319
289	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
290	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
291	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
292	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".
293		330
294	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
295	function.	332	function (or via the C<EV_DEFAULT> macro).
296		333
297	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
298	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
299	as loops cannot bes hared easily between threads anyway).	336	that this case is unlikely, as loops cannot be shared easily between
		337	threads anyway).
300		338
301	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,
302	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
303	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
304	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
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	343	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	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.
307		363
308	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
309	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>).
310		366
311	The following flags are supported:	367	The following flags are supported:
…		…
326	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
327	around bugs.	383	around bugs.
328		384
329	=item C<EVFLAG_FORKCHECK>	385	=item C<EVFLAG_FORKCHECK>
330		386
331	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
332	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.
333	enabling this flag.
334		389
335	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,
336	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
337	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
338	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
…		…
344	flag.	399	flag.
345		400
346	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>
347	environment variable.	402	environment variable.
348		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 it's 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 it's 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
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	424	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		425
351	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
352	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,
353	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
…		…
377	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
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	453	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		454
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	455	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		456
		457	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		458	kernels).
		459
382	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,
383	but it scales phenomenally better. While poll and select usually scale	461	but it scales phenomenally better. While poll and select usually scale
384	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),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	463	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	464
387	cases and requiring a system call per fd change, no fork support and bad	465	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	466	of the more advanced event mechanisms: mere annoyances include silently
		467	dropping file descriptors, requiring a system call per change per file
		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
		471	0.1ms) and so on. The biggest issue is fork races, however - if a program
		472	forks then I<both> parent and child process have to recreate the epoll
		473	set, which can take considerable time (one syscall per file descriptor)
		474	and is of course hard to detect.
		475
		476	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		477	of course I<doesn't>, and epoll just loves to report events for totally
		478	I<different> file descriptors (even already closed ones, so one cannot
		479	even remove them from the set) than registered in the set (especially
		480	on SMP systems). Libev tries to counter these spurious notifications by
		481	employing an additional generation counter and comparing that against the
		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.
389		487
390	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
391	will result in some caching, there is still a system call per such incident	489	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	490	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	491	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	492	file descriptors might not work very well if you register events for both
395		493	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		494
400	Best performance from this backend is achieved by not unregistering all	495	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	496	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	497	i.e. keep at least one watcher active per fd at all times. Stopping and
		498	starting a watcher (without re-setting it) also usually doesn't cause
		499	extra overhead. A fork can both result in spurious notifications as well
		500	as in libev having to destroy and recreate the epoll object, which can
		501	take considerable time and thus should be avoided.
		502
		503	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		504	faster than epoll for maybe up to a hundred file descriptors, depending on
		505	the usage. So sad.
403		506
404	While nominally embeddable in other event loops, this feature is broken in	507	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	508	all kernel versions tested so far.
406		509
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	513	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		514
412	Kqueue deserves special mention, as at the time of this writing, it	515	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	516	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	517	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	518	it's completely useless). Unlike epoll, however, whose brokenness
		519	is by design, these kqueue bugs can (and eventually will) be fixed
		520	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	521	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	522	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	523	system like NetBSD.
419		524
420	You still can embed kqueue into a normal poll or select backend and use it	525	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	526	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		528
424	It scales in the same way as the epoll backend, but the interface to the	529	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	530	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	531	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	532	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	533	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	534	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		535	cases
430		536
431	This backend usually performs well under most conditions.	537	This backend usually performs well under most conditions.
432		538
433	While nominally embeddable in other event loops, this doesn't work	539	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	540	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	541	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	542	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	543	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	544	also broken on OS X)) and, did I mention it, using it only for sockets.
439		545
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	546	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	547	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	548	C<NOTE_EOF>.
443		549
…		…
460	While this backend scales well, it requires one system call per active	566	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	567	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	568	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	569	might perform better.
464		570
465	On the positive side, ignoring the spurious readiness notifications, this	571	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	572	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	573	in all tests and is fully embeddable, which is a rare feat among the
		574	OS-specific backends (I vastly prefer correctness over speed hacks).
468		575
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	576	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	577	C<EVBACKEND_POLL>.
471		578
472	=item C<EVBACKEND_ALL>	579	=item C<EVBACKEND_ALL>
…		…
477		584
478	It is definitely not recommended to use this flag.	585	It is definitely not recommended to use this flag.
479		586
480	=back	587	=back
481		588
482	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,
483	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
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	591	here). If none are specified, all backends in C<ev_recommended_backends
485		592	()> will be tried.
486	The most typical usage is like this:
487
488	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490
491	Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:
493
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495
496	Use whatever libev has to offer, but make sure that kqueue is used if
497	available (warning, breaks stuff, best use only with your own private
498	event loop and only if you know the OS supports your types of fds):
499
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501
502	=item struct ev_loop *ev_loop_new (unsigned int flags)
503
504	Similar to C<ev_default_loop>, but always creates a new event loop that is
505	always distinct from the default loop. Unlike the default loop, it cannot
506	handle signal and child watchers, and attempts to do so will be greeted by
507	undefined behaviour (or a failed assertion if assertions are enabled).
508
509	Note that this function I<is> thread-safe, and the recommended way to use
510	libev with threads is indeed to create one loop per thread, and using the
511	default loop in the "main" or "initial" thread.
512		593
513	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.
514		595
515	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	596	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
516	if (!epoller)	597	if (!epoller)
517	fatal ("no epoll found here, maybe it hides under your chair");	598	fatal ("no epoll found here, maybe it hides under your chair");
518		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
519	=item ev_default_destroy ()	605	=item ev_loop_destroy (loop)
520		606
521	Destroys the default loop again (frees all memory and kernel state	607	Destroys an event loop object (frees all memory and kernel state
522	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
523	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
524	responsibility to either stop all watchers cleanly yourself I<before>	610	responsibility to either stop all watchers cleanly yourself I<before>
525	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
526	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
527	for example).	613	for example).
528		614
529	Note that certain global state, such as signal state, will not be freed by	615	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	616	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	617	as signal and child watchers) would need to be stopped manually.
532		618
533	In general it is not advisable to call this function except in the	619	This function is normally used on loop objects allocated by
534	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 it's resources.
535	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>
536	C<ev_loop_new> and C<ev_loop_destroy>).	626	and C<ev_loop_destroy>.
537		627
538	=item ev_loop_destroy (loop)	628	=item ev_loop_fork (loop)
539		629
540	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.
542
543	=item ev_default_fork ()
544
545	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
546	to reinitialise the kernel state for backends that have one. Despite the	631	reinitialise the kernel state for backends that have one. Despite the
547	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
548	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
549	sense). You I<must> call it in the child before using any of the libev	634	child before resuming or calling C<ev_run>.
550	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.
551		640
552	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
553	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
554	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).
555		647
556	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
557	it just in case after a fork. To make this easy, the function will fit in	649	it just in case after a fork.
558	quite nicely into a call to C<pthread_atfork>:
559		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	...
560	pthread_atfork (0, 0, ev_default_fork);	661	pthread_atfork (0, 0, post_fork_child);
561
562	=item ev_loop_fork (loop)
563
564	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.
567		662
568	=item int ev_is_default_loop (loop)	663	=item int ev_is_default_loop (loop)
569		664
570	Returns true when the given loop actually is the default loop, false otherwise.	665	Returns true when the given loop is, in fact, the default loop, and false
		666	otherwise.
571		667
572	=item unsigned int ev_loop_count (loop)	668	=item unsigned int ev_iteration (loop)
573		669
574	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
575	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>
576	happily wraps around with enough iterations.	672	and happily wraps around with enough iterations.
577		673
578	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
579	"ticks" the number of loop iterations), as it roughly corresponds with	675	"ticks" the number of loop iterations), as it roughly corresponds with
580	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.
581		691
582	=item unsigned int ev_backend (loop)	692	=item unsigned int ev_backend (loop)
583		693
584	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
585	use.	695	use.
…		…
594		704
595	=item ev_now_update (loop)	705	=item ev_now_update (loop)
596		706
597	Establishes the current time by querying the kernel, updating the time	707	Establishes the current time by querying the kernel, updating the time
598	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
599	is usually done automatically within C<ev_loop ()>.	709	is usually done automatically within C<ev_run ()>.
600		710
601	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
602	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
603	the current time is a good idea.	713	the current time is a good idea.
604		714
605	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.
606		716
		717	=item ev_suspend (loop)
		718
		719	=item ev_resume (loop)
		720
		721	These two functions suspend and resume an event loop, for use when the
		722	loop is not used for a while and timeouts should not be processed.
		723
		724	A typical use case would be an interactive program such as a game: When
		725	the user presses C<^Z> to suspend the game and resumes it an hour later it
		726	would be best to handle timeouts as if no time had actually passed while
		727	the program was suspended. This can be achieved by calling C<ev_suspend>
		728	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		729	C<ev_resume> directly afterwards to resume timer processing.
		730
		731	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		732	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		733	will be rescheduled (that is, they will lose any events that would have
		734	occurred while suspended).
		735
		736	After calling C<ev_suspend> you B<must not> call I<any> function on the
		737	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		738	without a previous call to C<ev_suspend>.
		739
		740	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		741	event loop time (see C<ev_now_update>).
		742
607	=item ev_loop (loop, int flags)	743	=item ev_run (loop, int flags)
608		744
609	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
610	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
611	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>.
612		750
613	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
614	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.
615		754
616	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
617	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
618	finished (especially in interactive programs), but having a program that	757	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	758	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	759	of relying on its watchers stopping correctly, that is truly a thing of
		760	beauty.
621		761
622	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
623	those events and any outstanding ones, but will not block your process in	763	those events and any already outstanding ones, but will not wait and
624	case there are no events and will return after one iteration of the loop.	764	block your process in case there are no events and will return after one
		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.
625		767
626	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
627	necessary) and will handle those and any outstanding ones. It will block	769	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	770	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	771	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	772	user-registered callback will be called), and will return after one
		773	iteration of the loop.
		774
		775	This is useful if you are waiting for some external event in conjunction
		776	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. 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
632	usually a better approach for this kind of thing.	778	usually a better approach for this kind of thing.
633		779
634	Here are the gory details of what C<ev_loop> does:	780	Here are the gory details of what C<ev_run> does:
635		781
		782	- Increment loop depth.
		783	- Reset the ev_break status.
636	- Before the first iteration, call any pending watchers.	784	- Before the first iteration, call any pending watchers.
		785	LOOP:
637	* If EVFLAG_FORKCHECK was used, check for a fork.	786	- If EVFLAG_FORKCHECK was used, check for a fork.
638	- 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.
639	- Queue and call all prepare watchers.	788	- Queue and call all prepare watchers.
		789	- If ev_break was called, goto FINISH.
640	- If we have been forked, detach and recreate the kernel state	790	- If we have been forked, detach and recreate the kernel state
641	as to not disturb the other process.	791	as to not disturb the other process.
642	- Update the kernel state with all outstanding changes.	792	- Update the kernel state with all outstanding changes.
643	- Update the "event loop time" (ev_now ()).	793	- Update the "event loop time" (ev_now ()).
644	- Calculate for how long to sleep or block, if at all	794	- Calculate for how long to sleep or block, if at all
645	(active idle watchers, EVLOOP_NONBLOCK or not having	795	(active idle watchers, EVRUN_NOWAIT or not having
646	any active watchers at all will result in not sleeping).	796	any active watchers at all will result in not sleeping).
647	- 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.
648	- Block the process, waiting for any events.	799	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	800	- Queue all outstanding I/O (fd) events.
650	- 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.
651	- Queue all outstanding timers.	802	- Queue all expired timers.
652	- Queue all outstanding periodics.	803	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	804	- Queue all idle watchers with priority higher than that of pending events.
654	- Queue all check watchers.	805	- Queue all check watchers.
655	- 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).
656	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
657	be handled here by queueing them when their watcher gets executed.	808	be handled here by queueing them when their watcher gets executed.
658	- 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
659	were used, or there are no active watchers, return, otherwise	810	were used, or there are no active watchers, goto FINISH, otherwise
660	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.
661		816
662	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
663	anymore.	818	anymore.
664		819
665	... queue jobs here, make sure they register event watchers as long	820	... queue jobs here, make sure they register event watchers as long
666	... 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..)
667	ev_loop (my_loop, 0);	822	ev_run (my_loop, 0);
668	... jobs done or somebody called unloop. yeah!	823	... jobs done or somebody called unloop. yeah!
669		824
670	=item ev_unloop (loop, how)	825	=item ev_break (loop, how)
671		826
672	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
673	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
674	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
675	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.
676		831
677	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.
		833
		834	It is safe to call C<ev_break> from outside any C<ev_run> calls, too.
678		835
679	=item ev_ref (loop)	836	=item ev_ref (loop)
680		837
681	=item ev_unref (loop)	838	=item ev_unref (loop)
682		839
683	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
684	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
685	count is nonzero, C<ev_loop> will not return on its own. If you have	842	count is nonzero, C<ev_run> will not return on its own.
686	a watcher you never unregister that should not keep C<ev_loop> from	843
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	844	This is useful when you have a watcher that you never intend to
		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>
		847	before stopping it.
		848
688	example, libev itself uses this for its internal signal pipe: It is not	849	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	850	is not visible to the libev user and should not keep C<ev_run> from
690	no event watchers registered by it are active. It is also an excellent	851	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	852	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	853	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	854	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	855	before, respectively. Note also that libev might stop watchers itself
		856	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		857	in the callback).
695		858
696	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>
697	running when nothing else is active.	860	running when nothing else is active.
698		861
699	struct ev_signal exitsig;	862	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	863	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	864	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	865	evf_unref (loop);
703		866
704	Example: For some weird reason, unregister the above signal handler again.	867	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	881	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	882	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	883	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	884	opportunities).
722		885
723	The background is that sometimes your program runs just fast enough to	886	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	887	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	888	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	889	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	890	overhead for the actual polling but can deliver many events at once.
728		891
729	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
730	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,
731	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
732	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
733	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.
734		899
735	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
736	to spend more time collecting timeouts, at the expense of increased	901	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	902	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	903	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	904	value will not introduce any overhead in libev.
740		905
741	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
742	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
743	interactive servers (of course not for games), likewise for timeouts. It	908	interactive servers (of course not for games), likewise for timeouts. It
744	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>,
745	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).
746		915
747	Setting the I<timeout collect interval> can improve the opportunity for	916	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	917	saving power, as the program will "bundle" timer callback invocations that
749	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
750	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
751	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
752	they fire on, say, one-second boundaries only.	921	they fire on, say, one-second boundaries only.
753		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
754	=item ev_loop_verify (loop)	998	=item ev_verify (loop)
755		999
756	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
757	compiled in. It tries to go through all internal structures and checks	1001	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	1002	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	1003	is found to be inconsistent, it will print an error message to standard
		1004	error and call C<abort ()>.
760		1005
761	This can be used to catch bugs inside libev itself: under normal	1006	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	1007	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	1008	data structures consistent.
764		1009
765	=back	1010	=back
766		1011
767		1012
768	=head1 ANATOMY OF A WATCHER	1013	=head1 ANATOMY OF A WATCHER
769		1014
		1015	In the following description, uppercase C<TYPE> in names stands for the
		1016	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1017	watchers and C<ev_io_start> for I/O watchers.
		1018
770	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
771	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
772	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:
773		1023
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1024	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	1025	{
776	ev_io_stop (w);	1026	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	1027	ev_break (loop, EVBREAK_ALL);
778	}	1028	}
779		1029
780	struct ev_loop *loop = ev_default_loop (0);	1030	struct ev_loop *loop = ev_default_loop (0);
		1031
781	struct ev_io stdin_watcher;	1032	ev_io stdin_watcher;
		1033
782	ev_init (&stdin_watcher, my_cb);	1034	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1035	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	1036	ev_io_start (loop, &stdin_watcher);
		1037
785	ev_loop (loop, 0);	1038	ev_run (loop, 0);
786		1039
787	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
788	watcher structures (and it is usually a bad idea to do this on the stack,	1041	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	1042	stack).
790		1043
		1044	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1045	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1046
791	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
792	(watcher *, callback)>, which expects a callback to be provided. This	1048	*, callback)>, which expects a callback to be provided. This callback is
793	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
794	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
795	is readable and/or writable).	1051	and/or writable).
796		1052
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1053	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1054	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1055	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1056	ev_TYPE_init (watcher *, callback, ...) >>.
801		1057
802	To make the watcher actually watch out for events, you have to start it	1058	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1059	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1060	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1061	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1062
807	As long as your watcher is active (has been started but not stopped) you	1063	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1064	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1065	reinitialise it or call its C<ev_TYPE_set> macro.
810		1066
811	Each and every callback receives the event loop pointer as first, the	1067	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1068	registered watcher structure as second, and a bitset of received events as
813	third argument.	1069	third argument.
814		1070
…		…
823	=item C<EV_WRITE>	1079	=item C<EV_WRITE>
824		1080
825	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
826	writable.	1082	writable.
827		1083
828	=item C<EV_TIMEOUT>	1084	=item C<EV_TIMER>
829		1085
830	The C<ev_timer> watcher has timed out.	1086	The C<ev_timer> watcher has timed out.
831		1087
832	=item C<EV_PERIODIC>	1088	=item C<EV_PERIODIC>
833		1089
…		…
851		1107
852	=item C<EV_PREPARE>	1108	=item C<EV_PREPARE>
853		1109
854	=item C<EV_CHECK>	1110	=item C<EV_CHECK>
855		1111
856	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
857	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
858	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
859	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
860	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
861	(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
862	C<ev_loop> from blocking).	1118	C<ev_run> from blocking).
863		1119
864	=item C<EV_EMBED>	1120	=item C<EV_EMBED>
865		1121
866	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.
867		1123
868	=item C<EV_FORK>	1124	=item C<EV_FORK>
869		1125
870	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
871	C<ev_fork>).	1127	C<ev_fork>).
872		1128
		1129	=item C<EV_CLEANUP>
		1130
		1131	The event loop is about to be destroyed (see C<ev_cleanup>).
		1132
873	=item C<EV_ASYNC>	1133	=item C<EV_ASYNC>
874		1134
875	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>).
		1136
		1137	=item C<EV_CUSTOM>
		1138
		1139	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1140	by libev users to signal watchers (e.g. via C<ev_feed_event>).
876		1141
877	=item C<EV_ERROR>	1142	=item C<EV_ERROR>
878		1143
879	An unspecified error has occurred, the watcher has been stopped. This might	1144	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1145	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1146	ran out of memory, a file descriptor was found to be closed or any other
		1147	problem. Libev considers these application bugs.
		1148
882	problem. You best act on it by reporting the problem and somehow coping	1149	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1150	watcher being stopped. Note that well-written programs should not receive
		1151	an error ever, so when your watcher receives it, this usually indicates a
		1152	bug in your program.
884		1153
885	Libev will usually signal a few "dummy" events together with an error,	1154	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1155	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1156	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1157	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1158	programs, though, as the fd could already be closed and reused for another
		1159	thing, so beware.
890		1160
891	=back	1161	=back
892		1162
893	=head2 GENERIC WATCHER FUNCTIONS	1163	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1164
898	=over 4	1165	=over 4
899		1166
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1167	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1168
…		…
907	which rolls both calls into one.	1174	which rolls both calls into one.
908		1175
909	You can reinitialise a watcher at any time as long as it has been stopped	1176	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1177	(or never started) and there are no pending events outstanding.
911		1178
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1179	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1180	int revents)>.
914		1181
		1182	Example: Initialise an C<ev_io> watcher in two steps.
		1183
		1184	ev_io w;
		1185	ev_init (&w, my_cb);
		1186	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1187
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1188	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
916		1189
917	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
918	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
919	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
920	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
921	difference to the C<ev_init> macro).	1194	difference to the C<ev_init> macro).
922		1195
923	Although some watcher types do not have type-specific arguments	1196	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1197	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1198
		1199	See C<ev_init>, above, for an example.
		1200
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1201	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1202
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1203	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1204	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1205	a watcher. The same limitations apply, of course.
931		1206
		1207	Example: Initialise and set an C<ev_io> watcher in one step.
		1208
		1209	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1210
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1211	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
933		1212
934	Starts (activates) the given watcher. Only active watchers will receive	1213	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1214	events. If the watcher is already active nothing will happen.
936		1215
		1216	Example: Start the C<ev_io> watcher that is being abused as example in this
		1217	whole section.
		1218
		1219	ev_io_start (EV_DEFAULT_UC, &w);
		1220
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1221	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
938		1222
939	Stops the given watcher again (if active) and clears the pending	1223	Stops the given watcher if active, and clears the pending status (whether
		1224	the watcher was active or not).
		1225
940	status. It is possible that stopped watchers are pending (for example,	1226	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1227	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1228	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1229	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1230	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1231
946	=item bool ev_is_active (ev_TYPE *watcher)	1232	=item bool ev_is_active (ev_TYPE *watcher)
947		1233
948	Returns a true value iff the watcher is active (i.e. it has been started	1234	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1235	and not yet been stopped). As long as a watcher is active you must not modify
…		…
965	=item ev_cb_set (ev_TYPE *watcher, callback)	1251	=item ev_cb_set (ev_TYPE *watcher, callback)
966		1252
967	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
968	(modulo threads).	1254	(modulo threads).
969		1255
970	=item ev_set_priority (ev_TYPE *watcher, priority)	1256	=item ev_set_priority (ev_TYPE *watcher, int priority)
971		1257
972	=item int ev_priority (ev_TYPE *watcher)	1258	=item int ev_priority (ev_TYPE *watcher)
973		1259
974	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
975	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>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1262	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1263	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1264	from being executed (except for C<ev_idle> watchers).
979		1265
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	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
986	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.
987		1268
988	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
989	pending.	1270	pending.
990		1271
		1272	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1273	fine, as long as you do not mind that the priority value you query might
		1274	or might not have been clamped to the valid range.
		1275
991	The default priority used by watchers when no priority has been set is	1276	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1277	always C<0>, which is supposed to not be too high and not be too low :).
993		1278
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1279	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1280	priorities.
996	or might not have been adjusted to be within valid range.
997		1281
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1282	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1283
1000	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
1001	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
1002	can deal with that fact.	1286	can deal with that fact, as both are simply passed through to the
		1287	callback.
1003		1288
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1289	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1290
1006	If the watcher is pending, this function returns clears its pending status	1291	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1292	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1293	watcher isn't pending it does nothing and returns C<0>.
1009		1294
		1295	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1296	callback to be invoked, which can be accomplished with this function.
		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
1010	=back	1312	=back
1011		1313
1012
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1314	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1315
1015	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
1016	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
1017	to associate arbitrary data with your watcher. If you need more data and	1318	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1319	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1320	member, you can also "subclass" the watcher type and provide your own
1020	data:	1321	data:
1021		1322
1022	struct my_io	1323	struct my_io
1023	{	1324	{
1024	struct ev_io io;	1325	ev_io io;
1025	int otherfd;	1326	int otherfd;
1026	void *somedata;	1327	void *somedata;
1027	struct whatever *mostinteresting;	1328	struct whatever *mostinteresting;
1028	};	1329	};
1029		1330
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1333	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1334
1034	And since your callback will be called with a pointer to the watcher, you	1335	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1336	can cast it back to your own type:
1036		1337
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1338	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1339	{
1039	struct my_io *w = (struct my_io *)w_;	1340	struct my_io *w = (struct my_io *)w_;
1040	...	1341	...
1041	}	1342	}
1042		1343
…		…
1053	ev_timer t2;	1354	ev_timer t2;
1054	}	1355	}
1055		1356
1056	In this case getting the pointer to C<my_biggy> is a bit more	1357	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1358	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1359	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1360	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1361	programmers):
1060		1362
1061	#include <stddef.h>	1363	#include <stddef.h>
1062		1364
1063	static void	1365	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1366	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1367	{
1066	struct my_biggy big = (struct my_biggy *	1368	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1369	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1370	}
1069		1371
1070	static void	1372	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1373	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1374	{
1073	struct my_biggy big = (struct my_biggy *	1375	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1376	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	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.
1076		1540
1077		1541
1078	=head1 WATCHER TYPES	1542	=head1 WATCHER TYPES
1079		1543
1080	This section describes each watcher in detail, but will not repeat	1544	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1568	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1569	fd as you want (as long as you don't confuse yourself). Setting all file
1106	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
1107	required if you know what you are doing).	1571	required if you know what you are doing).
1108		1572
1109	If you must do this, then force the use of a known-to-be-good backend	1573	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1574	known-to-be-good backend (at the time of this writing, this includes only
1111	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.
1112		1578
1113	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
1114	receive "spurious" readiness notifications, that is your callback might	1580	receive "spurious" readiness notifications, that is your callback might
1115	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
1116	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
1117	lot of those (for example Solaris ports), it is very easy to get into	1583	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1584	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1585	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1586	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1587
1122	If you cannot run the fd in non-blocking mode (for example you should not	1588	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1589	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1590	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1591	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1592	does this on its own, so its quite safe to use). Some people additionally
		1593	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1594	indefinitely.
		1595
		1596	But really, best use non-blocking mode.
1127		1597
1128	=head3 The special problem of disappearing file descriptors	1598	=head3 The special problem of disappearing file descriptors
1129		1599
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1600	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1601	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1602	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1603	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1604	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1605	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1606	fact, a different file descriptor.
1137		1607
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1638	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1639	C<EVBACKEND_POLL>.
1170		1640
1171	=head3 The special problem of SIGPIPE	1641	=head3 The special problem of SIGPIPE
1172		1642
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1643	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1644	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1645	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1646	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1647
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1648	So when you encounter spurious, unexplained daemon exits, make sure you
1179	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
1180	somewhere, as that would have given you a big clue).	1650	somewhere, as that would have given you a big clue).
1181		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.
1182		1690
1183	=head3 Watcher-Specific Functions	1691	=head3 Watcher-Specific Functions
1184		1692
1185	=over 4	1693	=over 4
1186		1694
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1695	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1696
1189	=item ev_io_set (ev_io *, int fd, int events)	1697	=item ev_io_set (ev_io *, int fd, int events)
1190		1698
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1699	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1700	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1701	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1702
1195	=item int fd [read-only]	1703	=item int fd [read-only]
1196		1704
1197	The file descriptor being watched.	1705	The file descriptor being watched.
1198		1706
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1715	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1716	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1717	attempt to read a whole line in the callback.
1210		1718
1211	static void	1719	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1720	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1721	{
1214	ev_io_stop (loop, w);	1722	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1723	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1724	}
1217		1725
1218	...	1726	...
1219	struct ev_loop *loop = ev_default_init (0);	1727	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1728	ev_io stdin_readable;
1221	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);
1222	ev_io_start (loop, &stdin_readable);	1730	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1731	ev_run (loop, 0);
1224		1732
1225		1733
1226	=head2 C<ev_timer> - relative and optionally repeating timeouts	1734	=head2 C<ev_timer> - relative and optionally repeating timeouts
1227		1735
1228	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
1229	given time, and optionally repeating in regular intervals after that.	1737	given time, and optionally repeating in regular intervals after that.
1230		1738
1231	The timers are based on real time, that is, if you register an event that	1739	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1740	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1741	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1742	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1743	monotonic clock option helps a lot here).
1236		1744
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1745	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1746	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1747	might introduce a small delay). If multiple timers become ready during the
		1748	same loop iteration then the ones with earlier time-out values are invoked
		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).
		1751
		1752	=head3 Be smart about timeouts
		1753
		1754	Many real-world problems involve some kind of timeout, usually for error
		1755	recovery. A typical example is an HTTP request - if the other side hangs,
		1756	you want to raise some error after a while.
		1757
		1758	What follows are some ways to handle this problem, from obvious and
		1759	inefficient to smart and efficient.
		1760
		1761	In the following, a 60 second activity timeout is assumed - a timeout that
		1762	gets reset to 60 seconds each time there is activity (e.g. each time some
		1763	data or other life sign was received).
		1764
		1765	=over 4
		1766
		1767	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1768
		1769	This is the most obvious, but not the most simple way: In the beginning,
		1770	start the watcher:
		1771
		1772	ev_timer_init (timer, callback, 60., 0.);
		1773	ev_timer_start (loop, timer);
		1774
		1775	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1776	and start it again:
		1777
		1778	ev_timer_stop (loop, timer);
		1779	ev_timer_set (timer, 60., 0.);
		1780	ev_timer_start (loop, timer);
		1781
		1782	This is relatively simple to implement, but means that each time there is
		1783	some activity, libev will first have to remove the timer from its internal
		1784	data structure and then add it again. Libev tries to be fast, but it's
		1785	still not a constant-time operation.
		1786
		1787	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1788
		1789	This is the easiest way, and involves using C<ev_timer_again> instead of
		1790	C<ev_timer_start>.
		1791
		1792	To implement this, configure an C<ev_timer> with a C<repeat> value
		1793	of C<60> and then call C<ev_timer_again> at start and each time you
		1794	successfully read or write some data. If you go into an idle state where
		1795	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1796	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1797
		1798	That means you can ignore both the C<ev_timer_start> function and the
		1799	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1800	member and C<ev_timer_again>.
		1801
		1802	At start:
		1803
		1804	ev_init (timer, callback);
		1805	timer->repeat = 60.;
		1806	ev_timer_again (loop, timer);
		1807
		1808	Each time there is some activity:
		1809
		1810	ev_timer_again (loop, timer);
		1811
		1812	It is even possible to change the time-out on the fly, regardless of
		1813	whether the watcher is active or not:
		1814
		1815	timer->repeat = 30.;
		1816	ev_timer_again (loop, timer);
		1817
		1818	This is slightly more efficient then stopping/starting the timer each time
		1819	you want to modify its timeout value, as libev does not have to completely
		1820	remove and re-insert the timer from/into its internal data structure.
		1821
		1822	It is, however, even simpler than the "obvious" way to do it.
		1823
		1824	=item 3. Let the timer time out, but then re-arm it as required.
		1825
		1826	This method is more tricky, but usually most efficient: Most timeouts are
		1827	relatively long compared to the intervals between other activity - in
		1828	our example, within 60 seconds, there are usually many I/O events with
		1829	associated activity resets.
		1830
		1831	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1832	but remember the time of last activity, and check for a real timeout only
		1833	within the callback:
		1834
		1835	ev_tstamp last_activity; // time of last activity
		1836
		1837	static void
		1838	callback (EV_P_ ev_timer *w, int revents)
		1839	{
		1840	ev_tstamp now = ev_now (EV_A);
		1841	ev_tstamp timeout = last_activity + 60.;
		1842
		1843	// if last_activity + 60. is older than now, we did time out
		1844	if (timeout < now)
		1845	{
		1846	// timeout occurred, take action
		1847	}
		1848	else
		1849	{
		1850	// callback was invoked, but there was some activity, re-arm
		1851	// the watcher to fire in last_activity + 60, which is
		1852	// guaranteed to be in the future, so "again" is positive:
		1853	w->repeat = timeout - now;
		1854	ev_timer_again (EV_A_ w);
		1855	}
		1856	}
		1857
		1858	To summarise the callback: first calculate the real timeout (defined
		1859	as "60 seconds after the last activity"), then check if that time has
		1860	been reached, which means something I<did>, in fact, time out. Otherwise
		1861	the callback was invoked too early (C<timeout> is in the future), so
		1862	re-schedule the timer to fire at that future time, to see if maybe we have
		1863	a timeout then.
		1864
		1865	Note how C<ev_timer_again> is used, taking advantage of the
		1866	C<ev_timer_again> optimisation when the timer is already running.
		1867
		1868	This scheme causes more callback invocations (about one every 60 seconds
		1869	minus half the average time between activity), but virtually no calls to
		1870	libev to change the timeout.
		1871
		1872	To start the timer, simply initialise the watcher and set C<last_activity>
		1873	to the current time (meaning we just have some activity :), then call the
		1874	callback, which will "do the right thing" and start the timer:
		1875
		1876	ev_init (timer, callback);
		1877	last_activity = ev_now (loop);
		1878	callback (loop, timer, EV_TIMER);
		1879
		1880	And when there is some activity, simply store the current time in
		1881	C<last_activity>, no libev calls at all:
		1882
		1883	last_activity = ev_now (loop);
		1884
		1885	This technique is slightly more complex, but in most cases where the
		1886	time-out is unlikely to be triggered, much more efficient.
		1887
		1888	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1889	callback :) - just change the timeout and invoke the callback, which will
		1890	fix things for you.
		1891
		1892	=item 4. Wee, just use a double-linked list for your timeouts.
		1893
		1894	If there is not one request, but many thousands (millions...), all
		1895	employing some kind of timeout with the same timeout value, then one can
		1896	do even better:
		1897
		1898	When starting the timeout, calculate the timeout value and put the timeout
		1899	at the I<end> of the list.
		1900
		1901	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1902	the list is expected to fire (for example, using the technique #3).
		1903
		1904	When there is some activity, remove the timer from the list, recalculate
		1905	the timeout, append it to the end of the list again, and make sure to
		1906	update the C<ev_timer> if it was taken from the beginning of the list.
		1907
		1908	This way, one can manage an unlimited number of timeouts in O(1) time for
		1909	starting, stopping and updating the timers, at the expense of a major
		1910	complication, and having to use a constant timeout. The constant timeout
		1911	ensures that the list stays sorted.
		1912
		1913	=back
		1914
		1915	So which method the best?
		1916
		1917	Method #2 is a simple no-brain-required solution that is adequate in most
		1918	situations. Method #3 requires a bit more thinking, but handles many cases
		1919	better, and isn't very complicated either. In most case, choosing either
		1920	one is fine, with #3 being better in typical situations.
		1921
		1922	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1923	rather complicated, but extremely efficient, something that really pays
		1924	off after the first million or so of active timers, i.e. it's usually
		1925	overkill :)
1240		1926
1241	=head3 The special problem of time updates	1927	=head3 The special problem of time updates
1242		1928
1243	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
1244	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
1245	time only before and after C<ev_loop> polls for new events, which causes	1931	time only before and after C<ev_run> collects new events, which causes a
1246	a 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
1247	lots of events.	1933	lots of events in one iteration.
1248		1934
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1935	The relative timeouts are calculated relative to the C<ev_now ()>
1250	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
1251	of the event triggering whatever timeout you are modifying/starting. If	1937	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1938	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1942
1257	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
1258	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
1259	()>.	1945	()>.
1260		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
1261	=head3 Watcher-Specific Functions and Data Members	1977	=head3 Watcher-Specific Functions and Data Members
1262		1978
1263	=over 4	1979	=over 4
1264		1980
1265	=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)
…		…
1288	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).
1289		2005
1290	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
1291	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.
1292		2008
1293	This sounds a bit complicated, but here is a useful and typical	2009	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	2010	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		2011
1303	That means you can ignore the C<after> value and C<ev_timer_start>	2012	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		2013
1306	ev_timer_init (timer, callback, 0., 5.);	2014	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	2015	then this time is relative to the current event loop time, otherwise it's
1308	...	2016	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		2017
1315	This is more slightly efficient then stopping/starting the timer each time	2018	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	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.
1317		2023
1318	=item ev_tstamp repeat [read-write]	2024	=item ev_tstamp repeat [read-write]
1319		2025
1320	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
1321	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),
1322	which is also when any modifications are taken into account.	2028	which is also when any modifications are taken into account.
1323		2029
1324	=back	2030	=back
1325		2031
1326	=head3 Examples	2032	=head3 Examples
1327		2033
1328	Example: Create a timer that fires after 60 seconds.	2034	Example: Create a timer that fires after 60 seconds.
1329		2035
1330	static void	2036	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2037	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	2038	{
1333	.. one minute over, w is actually stopped right here	2039	.. one minute over, w is actually stopped right here
1334	}	2040	}
1335		2041
1336	struct ev_timer mytimer;	2042	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2043	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	2044	ev_timer_start (loop, &mytimer);
1339		2045
1340	Example: Create a timeout timer that times out after 10 seconds of	2046	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	2047	inactivity.
1342		2048
1343	static void	2049	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2050	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	2051	{
1346	.. ten seconds without any activity	2052	.. ten seconds without any activity
1347	}	2053	}
1348		2054
1349	struct ev_timer mytimer;	2055	ev_timer mytimer;
1350	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 */
1351	ev_timer_again (&mytimer); /* start timer */	2057	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	2058	ev_run (loop, 0);
1353		2059
1354	// 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":
1355	// reset the timeout to start ticking again at 10 seconds	2061	// reset the timeout to start ticking again at 10 seconds
1356	ev_timer_again (&mytimer);	2062	ev_timer_again (&mytimer);
1357		2063
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	2065	=head2 C<ev_periodic> - to cron or not to cron?
1360		2066
1361	Periodic watchers are also timers of a kind, but they are very versatile	2067	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	2068	(and unfortunately a bit complex).
1363		2069
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2070	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	2071	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	2072	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2073	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	2074	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	2075	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		2076
		2077	You can tell a periodic watcher to trigger after some specific point
		2078	in time: for example, if you tell a periodic watcher to trigger "in 10
		2079	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2080	not a delay) and then reset your system clock to January of the previous
		2081	year, then it will take a year or more to trigger the event (unlike an
		2082	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2083	it, as it uses a relative timeout).
		2084
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	2085	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	2086	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	2087	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2088	those cannot react to time jumps.
1376		2089
1377	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
1378	time (C<at>) has passed, but if multiple periodic timers become ready	2091	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	2092	timers become ready during the same loop iteration then the ones with
		2093	earlier time-out values are invoked before ones with later time-out values
		2094	(but this is no longer true when a callback calls C<ev_run> recursively).
1380		2095
1381	=head3 Watcher-Specific Functions and Data Members	2096	=head3 Watcher-Specific Functions and Data Members
1382		2097
1383	=over 4	2098	=over 4
1384		2099
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2100	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		2101
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2102	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		2103
1389	Lots of arguments, lets sort it out... There are basically three modes of	2104	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	2105	operation, and we will explain them from simplest to most complex:
1391		2106
1392	=over 4	2107	=over 4
1393		2108
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2109	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		2110
1396	In this configuration the watcher triggers an event after the wall clock	2111	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	2112	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2113	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	2114	will be stopped and invoked when the system clock reaches or surpasses
		2115	this point in time.
1400		2116
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2117	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		2118
1403	In this mode the watcher will always be scheduled to time out at the next	2119	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	2120	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	2121	negative) and then repeat, regardless of any time jumps. The C<offset>
		2122	argument is merely an offset into the C<interval> periods.
1406		2123
1407	This can be used to create timers that do not drift with respect to system	2124	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	2125	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	2126	hour, on the hour (with respect to UTC):
1410		2127
1411	ev_periodic_set (&periodic, 0., 3600., 0);	2128	ev_periodic_set (&periodic, 0., 3600., 0);
1412		2129
1413	This doesn't mean there will always be 3600 seconds in between triggers,	2130	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	2131	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	2132	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	2133	by 3600.
1417		2134
1418	Another way to think about it (for the mathematically inclined) is that	2135	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	2136	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	2137	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		2138
1422	For numerical stability it is preferable that the C<at> value is near	2139	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	2140	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	2141	this value, and in fact is often specified as zero.
1425		2142
1426	Note also that there is an upper limit to how often a timer can fire (CPU	2143	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	2144	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	2145	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	2146	millisecond (if the OS supports it and the machine is fast enough).
1430		2147
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2148	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		2149
1433	In this mode the values for C<interval> and C<at> are both being	2150	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	2151	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	2152	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2153	current time as second argument.
1437		2154
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2155	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2156	or make ANY other event loop modifications whatsoever, unless explicitly
		2157	allowed by documentation here>.
1440		2158
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2159	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2160	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2161	only event loop modification you are allowed to do).
1444		2162
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2163	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2164	*w, ev_tstamp now)>, e.g.:
1447		2165
		2166	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2167	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2168	{
1450	return now + 60.;	2169	return now + 60.;
1451	}	2170	}
1452		2171
1453	It must return the next time to trigger, based on the passed time value	2172	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2192	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2193	program when the crontabs have changed).
1475		2194
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2195	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2196
1478	When active, returns the absolute time that the watcher is supposed to	2197	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2198	to trigger next. This is not the same as the C<offset> argument to
		2199	C<ev_periodic_set>, but indeed works even in interval and manual
		2200	rescheduling modes.
1480		2201
1481	=item ev_tstamp offset [read-write]	2202	=item ev_tstamp offset [read-write]
1482		2203
1483	When repeating, this contains the offset value, otherwise this is the	2204	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2205	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2206	although libev might modify this value for better numerical stability).
1485		2207
1486	Can be modified any time, but changes only take effect when the periodic	2208	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2209	timer fires or C<ev_periodic_again> is being called.
1488		2210
1489	=item ev_tstamp interval [read-write]	2211	=item ev_tstamp interval [read-write]
1490		2212
1491	The current interval value. Can be modified any time, but changes only	2213	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2214	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2215	called.
1494		2216
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2217	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2218
1497	The current reschedule callback, or C<0>, if this functionality is	2219	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2220	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2221	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2222
1501	=back	2223	=back
1502		2224
1503	=head3 Examples	2225	=head3 Examples
1504		2226
1505	Example: Call a callback every hour, or, more precisely, whenever the	2227	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2228	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2229	potentially a lot of jitter, but good long-term stability.
1508		2230
1509	static void	2231	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2232	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1511	{	2233	{
1512	... 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)
1513	}	2235	}
1514		2236
1515	struct ev_periodic hourly_tick;	2237	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2238	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2239	ev_periodic_start (loop, &hourly_tick);
1518		2240
1519	Example: The same as above, but use a reschedule callback to do it:	2241	Example: The same as above, but use a reschedule callback to do it:
1520		2242
1521	#include <math.h>	2243	#include <math.h>
1522		2244
1523	static ev_tstamp	2245	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2246	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2247	{
1526	return fmod (now, 3600.) + 3600.;	2248	return now + (3600. - fmod (now, 3600.));
1527	}	2249	}
1528		2250
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2251	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2252
1531	Example: Call a callback every hour, starting now:	2253	Example: Call a callback every hour, starting now:
1532		2254
1533	struct ev_periodic hourly_tick;	2255	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2256	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2257	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2258	ev_periodic_start (loop, &hourly_tick);
1537		2259
1538		2260
…		…
1541	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
1542	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
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2265	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2266	normal event processing, like any other event.
1545		2267
		2268	If you want signals to be delivered truly asynchronously, just use
		2269	C<sigaction> as you would do without libev and forget about sharing
		2270	the signal. You can even use C<ev_async> from a signal handler to
		2271	synchronously wake up an event loop.
		2272
1546	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
1547	first watcher gets started will libev actually register a signal watcher	2279	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2280	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2281	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2282
1553	If possible and supported, libev will install its handlers with	2283	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2284	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	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
1556	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
1557	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.
1558		2317
1559	=head3 Watcher-Specific Functions and Data Members	2318	=head3 Watcher-Specific Functions and Data Members
1560		2319
1561	=over 4	2320	=over 4
1562		2321
…		…
1573		2332
1574	=back	2333	=back
1575		2334
1576	=head3 Examples	2335	=head3 Examples
1577		2336
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2337	Example: Try to exit cleanly on SIGINT.
1579		2338
1580	static void	2339	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2340	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2341	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2342	ev_break (loop, EVBREAK_ALL);
1584	}	2343	}
1585		2344
1586	struct ev_signal signal_watcher;	2345	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2346	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2347	ev_signal_start (loop, &signal_watcher);
1589		2348
1590		2349
1591	=head2 C<ev_child> - watch out for process status changes	2350	=head2 C<ev_child> - watch out for process status changes
1592		2351
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2352	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2353	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2354	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2355	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2356	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2357	forking and then immediately registering a watcher for the child is fine,
		2358	but forking and registering a watcher a few event loop iterations later or
		2359	in the next callback invocation is not.
1598		2360
1599	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
1600	you can only register child watchers in the default event loop.	2362	you can only register child watchers in the default event loop.
1601		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
1602	=head3 Process Interaction	2368	=head3 Process Interaction
1603		2369
1604	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
1605	initialised. This is necessary to guarantee proper behaviour even if	2371	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2372	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2373	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	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
1609	children, even ones not watched.	2375	children, even ones not watched.
1610		2376
1611	=head3 Overriding the Built-In Processing	2377	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2387	=head3 Stopping the Child Watcher
1622		2388
1623	Currently, the child watcher never gets stopped, even when the	2389	Currently, the child watcher never gets stopped, even when the
1624	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
1625	callback. Future versions of libev might stop the watcher automatically	2391	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2392	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2393	problem).
1627		2394
1628	=head3 Watcher-Specific Functions and Data Members	2395	=head3 Watcher-Specific Functions and Data Members
1629		2396
1630	=over 4	2397	=over 4
1631		2398
…		…
1663	its completion.	2430	its completion.
1664		2431
1665	ev_child cw;	2432	ev_child cw;
1666		2433
1667	static void	2434	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2435	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2436	{
1670	ev_child_stop (EV_A_ w);	2437	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2438	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2439	}
1673		2440
…		…
1688		2455
1689		2456
1690	=head2 C<ev_stat> - did the file attributes just change?	2457	=head2 C<ev_stat> - did the file attributes just change?
1691		2458
1692	This watches a file system path for attribute changes. That is, it calls	2459	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2460	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2461	and sees if it changed compared to the last time, invoking the callback if
		2462	it did.
1695		2463
1696	The path does not need to exist: changing from "path exists" to "path does	2464	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2465	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2466	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2467	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2468	least one) and all the other fields of the stat buffer having unspecified
		2469	contents.
1701		2470
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2471	The path I<must not> end in a slash or contain special components such as
		2472	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2473	your working directory changes, then the behaviour is undefined.
1704		2474
1705	Since there is no standard to do this, the portable implementation simply	2475	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2476	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2477	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2478	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2479	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2480	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2481	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2482	currently around C<0.1>, but that's usually overkill.
1713		2483
1714	This watcher type is not meant for massive numbers of stat watchers,	2484	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2485	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2486	resource-intensive.
1717		2487
1718	At the time of this writing, only the Linux inotify interface is	2488	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2489	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2490	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2491	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2492
1727	=head3 ABI Issues (Largefile Support)	2493	=head3 ABI Issues (Largefile Support)
1728		2494
1729	Libev by default (unless the user overrides this) uses the default	2495	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2496	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2497	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2498	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2499	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2500	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2501	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2502	most noticeably displayed with ev_stat and large file support.
1737		2503
1738	The solution for this is to lobby your distribution maker to make large	2504	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2505	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2506	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2507	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2508	default compilation environment.
1743		2509
1744	=head3 Inotify	2510	=head3 Inotify and Kqueue
1745		2511
1746	When C<inotify (7)> support has been compiled into libev (generally only	2512	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2513	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2514	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2515	watcher is being started.
1750		2516
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2517	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2518	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2519	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2520	there are many cases where libev has to resort to regular C<stat> polling,
		2521	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2522	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2523	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2524	xfs are fully working) libev usually gets away without polling.
1755		2525
1756	(There is no support for kqueue, as apparently it cannot be used to	2526	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2527	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2528	descriptor open on the object at all times, and detecting renames, unlinks
		2529	etc. is difficult.
		2530
		2531	=head3 C<stat ()> is a synchronous operation
		2532
		2533	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2534	the process. The exception are C<ev_stat> watchers - those call C<stat
		2535	()>, which is a synchronous operation.
		2536
		2537	For local paths, this usually doesn't matter: unless the system is very
		2538	busy or the intervals between stat's are large, a stat call will be fast,
		2539	as the path data is usually in memory already (except when starting the
		2540	watcher).
		2541
		2542	For networked file systems, calling C<stat ()> can block an indefinite
		2543	time due to network issues, and even under good conditions, a stat call
		2544	often takes multiple milliseconds.
		2545
		2546	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2547	paths, although this is fully supported by libev.
1759		2548
1760	=head3 The special problem of stat time resolution	2549	=head3 The special problem of stat time resolution
1761		2550
1762	The C<stat ()> system call only supports full-second resolution portably, and	2551	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2552	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2553	still only support whole seconds.
1765		2554
1766	That means that, if the time is the only thing that changes, you can	2555	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2556	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2557	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2558	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2559	stat data does change in other ways (e.g. file size).
1771		2560
1772	The solution to this is to delay acting on a change for slightly more	2561	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2562	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2563	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2564	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2584	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2585	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2586	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2587	path for as long as the watcher is active.
1799		2588
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2589	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2590	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2591	last change was detected).
1803		2592
1804	=item ev_stat_stat (loop, ev_stat *)	2593	=item ev_stat_stat (loop, ev_stat *)
1805		2594
1806	Updates the stat buffer immediately with new values. If you change the	2595	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2596	watched path in your callback, you could call this function to avoid
…		…
1890		2679
1891		2680
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2681	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2682
1894	Idle watchers trigger events when no other events of the same or higher	2683	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2684	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2685	as receiving "events").
1897		2686
1898	That is, as long as your process is busy handling sockets or timeouts	2687	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2688	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2689	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2690	are pending), the idle watchers are being called once per event loop
…		…
1912		2701
1913	=head3 Watcher-Specific Functions and Data Members	2702	=head3 Watcher-Specific Functions and Data Members
1914		2703
1915	=over 4	2704	=over 4
1916		2705
1917	=item ev_idle_init (ev_signal *, callback)	2706	=item ev_idle_init (ev_idle *, callback)
1918		2707
1919	Initialises and configures the idle watcher - it has no parameters of any	2708	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2709	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2710	believe me.
1922		2711
…		…
1926		2715
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2716	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2717	callback, free it. Also, use no error checking, as usual.
1929		2718
1930	static void	2719	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2720	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2721	{
1933	free (w);	2722	free (w);
1934	// now do something you wanted to do when the program has	2723	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2724	// no longer anything immediate to do.
1936	}	2725	}
1937		2726
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2727	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2728	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2729	ev_idle_start (loop, idle_watcher);
1941		2730
1942		2731
1943	=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!
1944		2733
1945	Prepare and check watchers are usually (but not always) used in tandem:	2734	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2735	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2736	afterwards.
1948		2737
1949	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
1950	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>
1951	watchers. Other loops than the current one are fine, however. The	2740	watchers. Other loops than the current one are fine, however. The
1952	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
1953	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,
1954	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
1955	called in pairs bracketing the blocking call.	2744	called in pairs bracketing the blocking call.
1956		2745
1957	Their main purpose is to integrate other event mechanisms into libev and	2746	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2747	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2748	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2749	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2750	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2751	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2752	watcher).
1964		2753
1965	This is done by examining in each prepare call which file descriptors need	2754	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2755	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2756	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2757	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2758	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2759	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2760	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2761	nevertheless, because you never know, you know?).
1973		2762
1974	As another example, the Perl Coro module uses these hooks to integrate	2763	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2764	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2765	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2766	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2769	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2770	low-priority coroutines to idle/background tasks).
1982		2771
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2772	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2773	priority, to ensure that they are being run before any other watchers
		2774	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2775
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2776	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2777	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2778	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2779	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2780	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2781	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2782	others).
1992		2783
1993	=head3 Watcher-Specific Functions and Data Members	2784	=head3 Watcher-Specific Functions and Data Members
1994		2785
1995	=over 4	2786	=over 4
1996		2787
…		…
1998		2789
1999	=item ev_check_init (ev_check *, callback)	2790	=item ev_check_init (ev_check *, callback)
2000		2791
2001	Initialises and configures the prepare or check watcher - they have no	2792	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2793	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2794	macros, but using them is utterly, utterly, utterly and completely
		2795	pointless.
2004		2796
2005	=back	2797	=back
2006		2798
2007	=head3 Examples	2799	=head3 Examples
2008		2800
…		…
2021		2813
2022	static ev_io iow [nfd];	2814	static ev_io iow [nfd];
2023	static ev_timer tw;	2815	static ev_timer tw;
2024		2816
2025	static void	2817	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2818	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2819	{
2028	}	2820	}
2029		2821
2030	// create io watchers for each fd and a timer before blocking	2822	// create io watchers for each fd and a timer before blocking
2031	static void	2823	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2824	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2825	{
2034	int timeout = 3600000;	2826	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2827	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2828	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2829	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2830
2039	/* 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 */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2832	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2833	ev_timer_start (loop, &tw);
2042		2834
2043	// create one ev_io per pollfd	2835	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2836	for (int i = 0; i < nfd; ++i)
2045	{	2837	{
…		…
2052	}	2844	}
2053	}	2845	}
2054		2846
2055	// stop all watchers after blocking	2847	// stop all watchers after blocking
2056	static void	2848	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2849	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2850	{
2059	ev_timer_stop (loop, &tw);	2851	ev_timer_stop (loop, &tw);
2060		2852
2061	for (int i = 0; i < nfd; ++i)	2853	for (int i = 0; i < nfd; ++i)
2062	{	2854	{
…		…
2101	}	2893	}
2102		2894
2103	// do not ever call adns_afterpoll	2895	// do not ever call adns_afterpoll
2104		2896
2105	Method 4: Do not use a prepare or check watcher because the module you	2897	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2898	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2899	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2900	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2901	this approach, effectively embedding EV as a client into the horrible
		2902	libglib event loop.
2110		2903
2111	static gint	2904	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2905	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2906	{
2114	int got_events = 0;	2907	int got_events = 0;
…		…
2118		2911
2119	if (timeout >= 0)	2912	if (timeout >= 0)
2120	// create/start timer	2913	// create/start timer
2121		2914
2122	// poll	2915	// poll
2123	ev_loop (EV_A_ 0);	2916	ev_run (EV_A_ 0);
2124		2917
2125	// stop timer again	2918	// stop timer again
2126	if (timeout >= 0)	2919	if (timeout >= 0)
2127	ev_timer_stop (EV_A_ &to);	2920	ev_timer_stop (EV_A_ &to);
2128		2921
…		…
2145	prioritise I/O.	2938	prioritise I/O.
2146		2939
2147	As an example for a bug workaround, the kqueue backend might only support	2940	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2941	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2942	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2943	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2944	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2945	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2946	C<kevent>, but at least you can use both mechanisms for what they are
		2947	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2948
2155	As for prioritising I/O: rarely you have the case where some fds have	2949	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2950	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2951	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2952	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2953	the rest in a second one, and embed the second one in the first.
2160		2954
2161	As long as the watcher is active, the callback will be invoked every time	2955	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2956	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2957	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2958	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2959	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2960	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2961
2169	As long as the watcher is started it will automatically handle events. The	2962	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2963	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2964
2174	Also, there have not currently been made special provisions for forking:	2965	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2966	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2967	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2968	C<ev_loop_fork> on the embedded loop.
2178		2969
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2970	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2971	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2972	portable one.
2182		2973
2183	So when you want to use this feature you will always have to be prepared	2974	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2975	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2976	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2977	create it, and if that fails, use the normal loop for everything.
		2978
		2979	=head3 C<ev_embed> and fork
		2980
		2981	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2982	automatically be applied to the embedded loop as well, so no special
		2983	fork handling is required in that case. When the watcher is not running,
		2984	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2985	as applicable.
2187		2986
2188	=head3 Watcher-Specific Functions and Data Members	2987	=head3 Watcher-Specific Functions and Data Members
2189		2988
2190	=over 4	2989	=over 4
2191		2990
…		…
2200	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).
2201		3000
2202	=item ev_embed_sweep (loop, ev_embed *)	3001	=item ev_embed_sweep (loop, ev_embed *)
2203		3002
2204	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
2205	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
2206	appropriate way for embedded loops.	3005	appropriate way for embedded loops.
2207		3006
2208	=item struct ev_loop *other [read-only]	3007	=item struct ev_loop *other [read-only]
2209		3008
2210	The embedded event loop.	3009	The embedded event loop.
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3018	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	3019	used).
2221		3020
2222	struct ev_loop *loop_hi = ev_default_init (0);	3021	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	3022	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	3023	ev_embed embed;
2225		3024
2226	// see if there is a chance of getting one that works	3025	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	3026	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3027	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3028	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	3042	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3043	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		3044
2246	struct ev_loop *loop = ev_default_init (0);	3045	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	3046	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	3047	ev_embed embed;
2249		3048
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3049	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3050	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	3051	{
2253	ev_embed_init (&embed, 0, loop_socket);	3052	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	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,
2269	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
2270	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
2271	handlers will be invoked, too, of course.	3070	handlers will be invoked, too, of course.
2272		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
2273	=head3 Watcher-Specific Functions and Data Members	3106	=head3 Watcher-Specific Functions and Data Members
2274		3107
2275	=over 4	3108	=over 4
2276		3109
2277	=item ev_fork_init (ev_signal *, callback)	3110	=item ev_fork_init (ev_fork *, callback)
2278		3111
2279	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
2280	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,
2281	believe me.	3114	really.
2282		3115
2283	=back	3116	=back
2284		3117
2285		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
2286	=head2 C<ev_async> - how to wake up another event loop	3159	=head2 C<ev_async> - how to wake up an event loop
2287		3160
2288	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
2289	asynchronous sources such as signal handlers (as opposed to multiple event	3162	asynchronous sources such as signal handlers (as opposed to multiple event
2290	loops - those are of course safe to use in different threads).	3163	loops - those are of course safe to use in different threads).
2291		3164
2292	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,
2293	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>
2294	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
2295	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.
2296	safe.
2297		3169
2298	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,
2299	too, are asynchronous in nature, and signals, too, will be compressed	3171	too, are asynchronous in nature, and signals, too, will be compressed
2300	(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
2301	C<ev_async_sent> calls).	3173	C<ev_async_sent> calls).
…		…
2306	=head3 Queueing	3178	=head3 Queueing
2307		3179
2308	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
2309	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
2310	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
2311	need elaborate support such as pthreads.	3183	need elaborate support such as pthreads or unportable memory access
		3184	semantics.
2312		3185
2313	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
2314	queue. But at least I can tell you would implement locking around your	3187	queue. But at least I can tell you how to implement locking around your
2315	queue:	3188	queue:
2316		3189
2317	=over 4	3190	=over 4
2318		3191
2319	=item queueing from a signal handler context	3192	=item queueing from a signal handler context
2320		3193
2321	To implement race-free queueing, you simply add to the queue in the signal	3194	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3195	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	3196	an example that does that for some fictitious SIGUSR1 handler:
2324		3197
2325	static ev_async mysig;	3198	static ev_async mysig;
2326		3199
2327	static void	3200	static void
2328	sigusr1_handler (void)	3201	sigusr1_handler (void)
…		…
2394	=over 4	3267	=over 4
2395		3268
2396	=item ev_async_init (ev_async *, callback)	3269	=item ev_async_init (ev_async *, callback)
2397		3270
2398	Initialises and configures the async watcher - it has no parameters of any	3271	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3272	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3273	trust me.
2401		3274
2402	=item ev_async_send (loop, ev_async *)	3275	=item ev_async_send (loop, ev_async *)
2403		3276
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3277	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3278	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3279	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3280	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3281	section below on what exactly this means).
2409		3282
		3283	Note that, as with other watchers in libev, multiple events might get
		3284	compressed into a single callback invocation (another way to look at this
		3285	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3286	reset when the event loop detects that).
		3287
2410	This call incurs the overhead of a system call only once per loop iteration,	3288	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3289	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3290	repeated calls to C<ev_async_send> for the same event loop.
2413		3291
2414	=item bool = ev_async_pending (ev_async *)	3292	=item bool = ev_async_pending (ev_async *)
2415		3293
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3294	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3295	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3298	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3299	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3300	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3301	quickly check whether invoking the loop might be a good idea.
2424		3302
2425	Not that this does I<not> check whether the watcher itself is pending, only	3303	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3304	only whether it has been requested to make this watcher pending: there
		3305	is a time window between the event loop checking and resetting the async
		3306	notification, and the callback being invoked.
2427		3307
2428	=back	3308	=back
2429		3309
2430		3310
2431	=head1 OTHER FUNCTIONS	3311	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3315	=over 4
2436		3316
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3317	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3318
2439	This function combines a simple timer and an I/O watcher, calls your	3319	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3320	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3321	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3322	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3323	more watchers yourself.
2444		3324
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3325	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3326	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3327	the given C<fd> and C<events> set will be created and started.
2448		3328
2449	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
2450	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
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3331	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3332
2454	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
2455	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
2456	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>
2457	value passed to C<ev_once>:	3336	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3337	a timeout and an io event at the same time - you probably should give io
		3338	events precedence.
		3339
		3340	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3341
2459	static void stdin_ready (int revents, void *arg)	3342	static void stdin_ready (int revents, void *arg)
2460	{	3343	{
		3344	if (revents & EV_READ)
		3345	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3346	else if (revents & EV_TIMER)
2462	/* doh, nothing entered */;	3347	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3348	}
2466		3349
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3350	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3351
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3352	=item ev_feed_fd_event (loop, int fd, int revents)
2476		3353
2477	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
2478	the given events it.	3355	the given events it.
2479		3356
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3357	=item ev_feed_signal_event (loop, int signum)
2481		3358
2482	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
2483	loop!).	3360	loop!).
2484		3361
2485	=back	3362	=back
…		…
2565		3442
2566	=over 4	3443	=over 4
2567		3444
2568	=item ev::TYPE::TYPE ()	3445	=item ev::TYPE::TYPE ()
2569		3446
2570	=item ev::TYPE::TYPE (struct ev_loop *)	3447	=item ev::TYPE::TYPE (loop)
2571		3448
2572	=item ev::TYPE::~TYPE	3449	=item ev::TYPE::~TYPE
2573		3450
2574	The constructor (optionally) takes an event loop to associate the watcher	3451	The constructor (optionally) takes an event loop to associate the watcher
2575	with. If it is omitted, it will use C<EV_DEFAULT>.	3452	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2607		3484
2608	myclass obj;	3485	myclass obj;
2609	ev::io iow;	3486	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3487	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3488
		3489	=item w->set (object *)
		3490
		3491	This is a variation of a method callback - leaving out the method to call
		3492	will default the method to C<operator ()>, which makes it possible to use
		3493	functor objects without having to manually specify the C<operator ()> all
		3494	the time. Incidentally, you can then also leave out the template argument
		3495	list.
		3496
		3497	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3498	int revents)>.
		3499
		3500	See the method-C<set> above for more details.
		3501
		3502	Example: use a functor object as callback.
		3503
		3504	struct myfunctor
		3505	{
		3506	void operator() (ev::io &w, int revents)
		3507	{
		3508	...
		3509	}
		3510	}
		3511
		3512	myfunctor f;
		3513
		3514	ev::io w;
		3515	w.set (&f);
		3516
2612	=item w->set<function> (void *data = 0)	3517	=item w->set<function> (void *data = 0)
2613		3518
2614	Also sets a callback, but uses a static method or plain function as	3519	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3520	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3521	C<data> member and is free for you to use.
2617		3522
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3523	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3524
2620	See the method-C<set> above for more details.	3525	See the method-C<set> above for more details.
2621		3526
2622	Example:	3527	Example: Use a plain function as callback.
2623		3528
2624	static void io_cb (ev::io &w, int revents) { }	3529	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3530	iow.set <io_cb> ();
2626		3531
2627	=item w->set (struct ev_loop *)	3532	=item w->set (loop)
2628		3533
2629	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
2630	do this when the watcher is inactive (and not pending either).	3535	do this when the watcher is inactive (and not pending either).
2631		3536
2632	=item w->set ([arguments])	3537	=item w->set ([arguments])
2633		3538
2634	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
2635	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
2636	automatically stopped and restarted when reconfiguring it with this	3541	C counterpart, an active watcher gets automatically stopped and restarted
2637	method.	3542	when reconfiguring it with this method.
2638		3543
2639	=item w->start ()	3544	=item w->start ()
2640		3545
2641	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
2642	constructor already stores the event loop.	3547	constructor already stores the event loop.
2643		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
2644	=item w->stop ()	3555	=item w->stop ()
2645		3556
2646	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.
2647		3558
2648	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3559	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2660		3571
2661	=back	3572	=back
2662		3573
2663	=back	3574	=back
2664		3575
2665	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
2666	the constructor.	3577	watchers in the constructor.
2667		3578
2668	class myclass	3579	class myclass
2669	{	3580	{
2670	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);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3583	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3584
2673	myclass (int fd)	3585	myclass (int fd)
2674	{	3586	{
2675	io .set <myclass, &myclass::io_cb > (this);	3587	io .set <myclass, &myclass::io_cb > (this);
		3588	io2 .set <myclass, &myclass::io2_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3589	idle.set <myclass, &myclass::idle_cb> (this);
2677		3590
2678	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
2679	}	3595	}
2680	};	3596	};
2681		3597
2682		3598
2683	=head1 OTHER LANGUAGE BINDINGS	3599	=head1 OTHER LANGUAGE BINDINGS
…		…
2692	=item Perl	3608	=item Perl
2693		3609
2694	The EV module implements the full libev API and is actually used to test	3610	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3611	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3612	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3613	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3614	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3615	and C<EV::Glib>).
2699		3616
2700	It can be found and installed via CPAN, its homepage is at	3617	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3618	L<http://software.schmorp.de/pkg/EV>.
2702		3619
2703	=item Python	3620	=item Python
2704		3621
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3622	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3623	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3624
2712	=item Ruby	3625	=item Ruby
2713		3626
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3627	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3628	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3629	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3630	L<http://rev.rubyforge.org/>.
2718		3631
		3632	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3633	makes rev work even on mingw.
		3634
		3635	=item Haskell
		3636
		3637	A haskell binding to libev is available at
		3638	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3639
2719	=item D	3640	=item D
2720		3641
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3642	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3643	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3644
		3645	=item Ocaml
		3646
		3647	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3648	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		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>.
2723		3655
2724	=back	3656	=back
2725		3657
2726		3658
2727	=head1 MACRO MAGIC	3659	=head1 MACRO MAGIC
…		…
2741	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,
2742	C<EV_A_> is used when other arguments are following. Example:	3674	C<EV_A_> is used when other arguments are following. Example:
2743		3675
2744	ev_unref (EV_A);	3676	ev_unref (EV_A);
2745	ev_timer_add (EV_A_ watcher);	3677	ev_timer_add (EV_A_ watcher);
2746	ev_loop (EV_A_ 0);	3678	ev_run (EV_A_ 0);
2747		3679
2748	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,
2749	which is often provided by the following macro.	3681	which is often provided by the following macro.
2750		3682
2751	=item C<EV_P>, C<EV_P_>	3683	=item C<EV_P>, C<EV_P_>
…		…
2791	}	3723	}
2792		3724
2793	ev_check check;	3725	ev_check check;
2794	ev_check_init (&check, check_cb);	3726	ev_check_init (&check, check_cb);
2795	ev_check_start (EV_DEFAULT_ &check);	3727	ev_check_start (EV_DEFAULT_ &check);
2796	ev_loop (EV_DEFAULT_ 0);	3728	ev_run (EV_DEFAULT_ 0);
2797		3729
2798	=head1 EMBEDDING	3730	=head1 EMBEDDING
2799		3731
2800	Libev can (and often is) directly embedded into host	3732	Libev can (and often is) directly embedded into host
2801	applications. Examples of applications that embed it include the Deliantra	3733	applications. Examples of applications that embed it include the Deliantra
…		…
2828		3760
2829	#define EV_STANDALONE 1	3761	#define EV_STANDALONE 1
2830	#include "ev.h"	3762	#include "ev.h"
2831		3763
2832	Both header files and implementation files can be compiled with a C++	3764	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3765	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3766	as a bug).
2835		3767
2836	You need the following files in your source tree, or in a directory	3768	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3769	in your include path (e.g. in libev/ when using -Ilibev):
2838		3770
…		…
2881	libev.m4	3813	libev.m4
2882		3814
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3815	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3816
2885	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
2886	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
2887	autoconf is noted 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.
2888		3827
2889	=over 4	3828	=over 4
2890		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
2891	=item EV_STANDALONE	3846	=item EV_STANDALONE (h)
2892		3847
2893	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
2894	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
2895	implementations for some libevent functions (such as logging, which is not	3850	implementations for some libevent functions (such as logging, which is not
2896	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
2897	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.
2898		3853
		3854	In standalone mode, libev will still try to automatically deduce the
		3855	configuration, but has to be more conservative.
		3856
2899	=item EV_USE_MONOTONIC	3857	=item EV_USE_MONOTONIC
2900		3858
2901	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
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3860	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3861	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3862	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3863	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3864	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3865	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3866
2909	=item EV_USE_REALTIME	3867	=item EV_USE_REALTIME
2910		3868
2911	If defined to be C<1>, libev will try to detect the availability of the	3869	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3870	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3871	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3872	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3873	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3874	correctness. See the note about libraries in the description of
		3875	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3876	C<EV_USE_CLOCK_SYSCALL>.
		3877
		3878	=item EV_USE_CLOCK_SYSCALL
		3879
		3880	If defined to be C<1>, libev will try to use a direct syscall instead
		3881	of calling the system-provided C<clock_gettime> function. This option
		3882	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3883	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3884	programs needlessly. Using a direct syscall is slightly slower (in
		3885	theory), because no optimised vdso implementation can be used, but avoids
		3886	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3887	higher, as it simplifies linking (no need for C<-lrt>).
2917		3888
2918	=item EV_USE_NANOSLEEP	3889	=item EV_USE_NANOSLEEP
2919		3890
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3891	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3892	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3908
2938	=item EV_SELECT_USE_FD_SET	3909	=item EV_SELECT_USE_FD_SET
2939		3910
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3911	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3912	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3913	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3914	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3915	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3916	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3917	configures the maximum size of the C<fd_set>.
2947		3918
2948	=item EV_SELECT_IS_WINSOCKET	3919	=item EV_SELECT_IS_WINSOCKET
2949		3920
2950	When defined to C<1>, the select backend will assume that	3921	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3922	select/socket/connect etc. don't understand file descriptors but
…		…
2953	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
2954	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,
2955	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
2956	on win32. Should not be defined on non-win32 platforms.	3927	on win32. Should not be defined on non-win32 platforms.
2957		3928
2958	=item EV_FD_TO_WIN32_HANDLE	3929	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		3930
2960	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
2961	file descriptors to socket handles. When not defining this symbol (the	3932	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	3933	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	3934	correct. In some cases, programs use their own file descriptor management,
2964	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.
2965		3950
2966	=item EV_USE_POLL	3951	=item EV_USE_POLL
2967		3952
2968	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)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	3954	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3016	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.
3017		4002
3018	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>
3019	(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.
3020		4005
3021	=item EV_H	4006	=item EV_H (h)
3022		4007
3023	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
3024	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
3025	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.
3026		4011
3027	=item EV_CONFIG_H	4012	=item EV_CONFIG_H (h)
3028		4013
3029	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
3030	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
3031	C<EV_H>, above.	4016	C<EV_H>, above.
3032		4017
3033	=item EV_EVENT_H	4018	=item EV_EVENT_H (h)
3034		4019
3035	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
3036	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">.
3037		4022
3038	=item EV_PROTOTYPES	4023	=item EV_PROTOTYPES (h)
3039		4024
3040	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
3041	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
3042	occasionally useful if you want to provide your own wrapper functions	4027	occasionally useful if you want to provide your own wrapper functions
3043	around libev functions.	4028	around libev functions.
…		…
3062	When doing priority-based operations, libev usually has to linearly search	4047	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	4048	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	4049	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	4050	fine.
3066		4051
3067	If your embedding application does not need any priorities, defining these both to	4052	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	4053	both to C<0> will save some memory and CPU.
3069		4054
3070	=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.
3071		4058
3072	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
3073	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
3074	code.	4061	is not. Disabling watcher types mainly saves code size.
3075		4062
3076	=item EV_IDLE_ENABLE	4063	=item EV_FEATURES
3077
3078	If undefined or defined to be C<1>, then idle watchers are supported. If
3079	defined to be C<0>, then they are not. Disabling them saves a few kB of
3080	code.
3081
3082	=item EV_EMBED_ENABLE
3083
3084	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.
3086
3087	=item EV_STAT_ENABLE
3088
3089	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.
3091
3092	=item EV_FORK_ENABLE
3093
3094	If undefined or defined to be C<1>, then fork watchers are supported. If
3095	defined to be C<0>, then they are not.
3096
3097	=item EV_ASYNC_ENABLE
3098
3099	If undefined or defined to be C<1>, then async watchers are supported. If
3100	defined to be C<0>, then they are not.
3101
3102	=item EV_MINIMAL
3103		4064
3104	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
3105	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
3106	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
3107	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.
3108		4164
3109	=item EV_PID_HASHSIZE	4165	=item EV_PID_HASHSIZE
3110		4166
3111	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
3112	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),
3113	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
3114	increase this value (I<must> be a power of two).	4170	might want to increase this value (I<must> be a power of two).
3115		4171
3116	=item EV_INOTIFY_HASHSIZE	4172	=item EV_INOTIFY_HASHSIZE
3117		4173
3118	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
3119	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>
3120	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
3121	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
3122	two).	4178	power of two).
3123		4179
3124	=item EV_USE_4HEAP	4180	=item EV_USE_4HEAP
3125		4181
3126	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
3127	timer and periodics heap, 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
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	4184	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	4185	faster performance with many (thousands) of watchers.
3130		4186
3131	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
3132	(disabled).	4188	will be C<0>.
3133		4189
3134	=item EV_HEAP_CACHE_AT	4190	=item EV_HEAP_CACHE_AT
3135		4191
3136	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
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	4193	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	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>),
3139	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,
3140	but avoids random read accesses on heap changes. This improves performance	4196	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	4197	noticeably with many (hundreds) of watchers.
3142		4198
3143	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
3144	(disabled).	4200	will be C<0>.
3145		4201
3146	=item EV_VERIFY	4202	=item EV_VERIFY
3147		4203
3148	Controls how much internal verification (see C<ev_loop_verify ()>) will	4204	Controls how much internal verification (see C<ev_verify ()>) will
3149	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
3150	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
3151	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
3152	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
3153	verification code will be called very frequently, which will slow down	4209	verification code will be called very frequently, which will slow down
3154	libev considerably.	4210	libev considerably.
3155		4211
3156	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
3157	C<0.>	4213	will be C<0>.
3158		4214
3159	=item EV_COMMON	4215	=item EV_COMMON
3160		4216
3161	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
3162	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
3163	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,
3164	though, and it must be identical each time.	4220	though, and it must be identical each time.
3165		4221
3166	For example, the perl EV module uses something like this:	4222	For example, the perl EV module uses something like this:
3167		4223
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	4235	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	4236	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	4237	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4238	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	4239	method calls instead of plain function calls in C++.
		4240
		4241	=back
3184		4242
3185	=head2 EXPORTED API SYMBOLS	4243	=head2 EXPORTED API SYMBOLS
3186		4244
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	4245	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	4246	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3218	file.	4276	file.
3219		4277
3220	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
3221	that everybody includes and which overrides some configure choices:	4279	that everybody includes and which overrides some configure choices:
3222		4280
3223	#define EV_MINIMAL 1	4281	#define EV_FEATURES 8
3224	#define EV_USE_POLL 0	4282	#define EV_USE_SELECT 1
3225	#define EV_MULTIPLICITY 0
3226	#define EV_PERIODIC_ENABLE 0	4283	#define EV_PREPARE_ENABLE 1
		4284	#define EV_IDLE_ENABLE 1
3227	#define EV_STAT_ENABLE 0	4285	#define EV_SIGNAL_ENABLE 1
3228	#define EV_FORK_ENABLE 0	4286	#define EV_CHILD_ENABLE 1
		4287	#define EV_USE_STDEXCEPT 0
3229	#define EV_CONFIG_H <config.h>	4288	#define EV_CONFIG_H <config.h>
3230	#define EV_MINPRI 0
3231	#define EV_MAXPRI 0
3232		4289
3233	#include "ev++.h"	4290	#include "ev++.h"
3234		4291
3235	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:
3236		4293
3237	#include "ev_cpp.h"	4294	#include "ev_cpp.h"
3238	#include "ev.c"	4295	#include "ev.c"
3239		4296
		4297	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4298
3241	=head1 THREADS AND COROUTINES	4299	=head2 THREADS AND COROUTINES
3242		4300
3243	=head2 THREADS	4301	=head3 THREADS
3244		4302
3245	Libev itself is thread-safe (unless the opposite is specifically	4303	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4304	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	4305	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	4306	are no concurrent calls into any libev function with the same loop
		4307	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4308	of course): libev guarantees that different event loops share no data
3250	need locking.	4309	structures that need any locking.
3251		4310
3252	Or to put it differently: calls with different loop parameters can be done	4311	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4312	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	4313	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	4314	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4315	a mutex per loop).
3257		4316
3258	Specifically to support threads (and signal handlers), libev implements	4317	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4318	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4319	concurrency on the same event loop, namely waking it up "from the
		4320	outside".
3261		4321
3262	If you want to know which design (one loop, locking, or multiple loops	4322	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	4323	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4324	help you, but here is some generic advice:
3265		4325
3266	=over 4	4326	=over 4
3267		4327
3268	=item * most applications have a main thread: use the default libev loop	4328	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	4329	in that thread, or create a separate thread running only the default loop.
…		…
3281		4341
3282	Choosing a model is hard - look around, learn, know that usually you can do	4342	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	4343	better than you currently do :-)
3284		4344
3285	=item * often you need to talk to some other thread which blocks in the	4345	=item * often you need to talk to some other thread which blocks in the
		4346	event loop.
		4347
3286	event loop - C<ev_async> watchers can be used to wake them up from other	4348	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	4349	(or from signal contexts...).
3288		4350
3289	=item * some watcher types are only supported in the default loop - use	4351	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	4352	work in the default loop by registering the signal watcher with the
		4353	default loop and triggering an C<ev_async> watcher from the default loop
		4354	watcher callback into the event loop interested in the signal.
3291		4355
3292	=back	4356	=back
3293		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
3294	=head2 COROUTINES	4496	=head3 COROUTINES
3295		4497
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	4498	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	4499	libev fully supports nesting calls to its functions from different
3298	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
3299	different coroutines and switch freely between both coroutines running the	4501	different coroutines, and switch freely between both coroutines running
3300	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
3301	you must not do this from C<ev_periodic> reschedule callbacks.	4503	that you must not do this from C<ev_periodic> reschedule callbacks.
3302		4504
3303	Care has been invested into making sure that libev does not keep local	4505	Care has been taken to ensure that libev does not keep local state inside
3304	state inside C<ev_loop>, and other calls do not usually allow coroutine	4506	C<ev_run>, and other calls do not usually allow for coroutine switches as
3305	switches.	4507	they do not call any callbacks.
3306		4508
		4509	=head2 COMPILER WARNINGS
3307		4510
3308	=head1 COMPLEXITIES	4511	Depending on your compiler and compiler settings, you might get no or a
		4512	lot of warnings when compiling libev code. Some people are apparently
		4513	scared by this.
3309		4514
3310	In this section the complexities of (many of) the algorithms used inside	4515	However, these are unavoidable for many reasons. For one, each compiler
3311	libev will be explained. For complexity discussions about backends see the	4516	has different warnings, and each user has different tastes regarding
3312	documentation for C<ev_default_init>.	4517	warning options. "Warn-free" code therefore cannot be a goal except when
		4518	targeting a specific compiler and compiler-version.
3313		4519
3314	All of the following are about amortised time: If an array needs to be	4520	Another reason is that some compiler warnings require elaborate
3315	extended, libev needs to realloc and move the whole array, but this	4521	workarounds, or other changes to the code that make it less clear and less
3316	happens asymptotically never with higher number of elements, so O(1) might	4522	maintainable.
3317	mean it might do a lengthy realloc operation in rare cases, but on average
3318	it is much faster and asymptotically approaches constant time.
3319		4523
3320	=over 4	4524	And of course, some compiler warnings are just plain stupid, or simply
		4525	wrong (because they don't actually warn about the condition their message
		4526	seems to warn about). For example, certain older gcc versions had some
		4527	warnings that resulted in an extreme number of false positives. These have
		4528	been fixed, but some people still insist on making code warn-free with
		4529	such buggy versions.
3321		4530
3322	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4531	While libev is written to generate as few warnings as possible,
		4532	"warn-free" code is not a goal, and it is recommended not to build libev
		4533	with any compiler warnings enabled unless you are prepared to cope with
		4534	them (e.g. by ignoring them). Remember that warnings are just that:
		4535	warnings, not errors, or proof of bugs.
3323		4536
3324	This means that, when you have a watcher that triggers in one hour and
3325	there are 100 watchers that would trigger before that then inserting will
3326	have to skip roughly seven (C<ld 100>) of these watchers.
3327		4537
3328	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4538	=head2 VALGRIND
3329		4539
3330	That means that changing a timer costs less than removing/adding them	4540	Valgrind has a special section here because it is a popular tool that is
3331	as only the relative motion in the event queue has to be paid for.	4541	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3332		4542
3333	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4543	If you think you found a bug (memory leak, uninitialised data access etc.)
		4544	in libev, then check twice: If valgrind reports something like:
3334		4545
3335	These just add the watcher into an array or at the head of a list.	4546	==2274== definitely lost: 0 bytes in 0 blocks.
		4547	==2274== possibly lost: 0 bytes in 0 blocks.
		4548	==2274== still reachable: 256 bytes in 1 blocks.
3336		4549
3337	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4550	Then there is no memory leak, just as memory accounted to global variables
		4551	is not a memleak - the memory is still being referenced, and didn't leak.
3338		4552
3339	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4553	Similarly, under some circumstances, valgrind might report kernel bugs
		4554	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4555	although an acceptable workaround has been found here), or it might be
		4556	confused.
3340		4557
3341	These watchers are stored in lists then need to be walked to find the	4558	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3342	correct watcher to remove. The lists are usually short (you don't usually	4559	make it into some kind of religion.
3343	have many watchers waiting for the same fd or signal).
3344		4560
3345	=item Finding the next timer in each loop iteration: O(1)	4561	If you are unsure about something, feel free to contact the mailing list
		4562	with the full valgrind report and an explanation on why you think this
		4563	is a bug in libev (best check the archives, too :). However, don't be
		4564	annoyed when you get a brisk "this is no bug" answer and take the chance
		4565	of learning how to interpret valgrind properly.
3346		4566
3347	By virtue of using a binary or 4-heap, the next timer is always found at a	4567	If you need, for some reason, empty reports from valgrind for your project
3348	fixed position in the storage array.	4568	I suggest using suppression lists.
3349		4569
3350	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3351		4570
3352	A change means an I/O watcher gets started or stopped, which requires	4571	=head1 PORTABILITY NOTES
3353	libev to recalculate its status (and possibly tell the kernel, depending
3354	on backend and whether C<ev_io_set> was used).
3355		4572
3356	=item Activating one watcher (putting it into the pending state): O(1)	4573	=head2 GNU/LINUX 32 BIT LIMITATIONS
3357		4574
3358	=item Priority handling: O(number_of_priorities)	4575	GNU/Linux is the only common platform that supports 64 bit file/large file
		4576	interfaces but I<disables> them by default.
3359		4577
3360	Priorities are implemented by allocating some space for each	4578	That means that libev compiled in the default environment doesn't support
3361	priority. When doing priority-based operations, libev usually has to	4579	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3362	linearly search all the priorities, but starting/stopping and activating
3363	watchers becomes O(1) w.r.t. priority handling.
3364		4580
3365	=item Sending an ev_async: O(1)	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.
3366		4584
3367	=item Processing ev_async_send: O(number_of_async_watchers)	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.
3368		4588
3369	=item Processing signals: O(max_signal_number)	4589	=head2 OS/X AND DARWIN BUGS
3370		4590
3371	Sending involves a system call I<iff> there were no other C<ev_async_send>	4591	The whole thing is a bug if you ask me - basically any system interface
3372	calls in the current loop iteration. Checking for async and signal events	4592	you touch is broken, whether it is locales, poll, kqueue or even the
3373	involves iterating over all running async watchers or all signal numbers.	4593	OpenGL drivers.
3374		4594
3375	=back	4595	=head3 C<kqueue> is buggy
3376		4596
		4597	The kqueue syscall is broken in all known versions - most versions support
		4598	only sockets, many support pipes.
3377		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
3378	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4659	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4660
		4661	=head3 General issues
3379		4662
3380	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
3381	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
3382	model. Libev still offers limited functionality on this platform in	4665	model. Libev still offers limited functionality on this platform in
3383	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
3384	descriptors. This only applies when using Win32 natively, not when using	4667	descriptors. This only applies when using Win32 natively, not when using
3385	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.
3386		4671
3387	Lifting these limitations would basically require the full	4672	Lifting these limitations would basically require the full
3388	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,
3389	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
3390	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).
3391		4676
3392	There is no supported compilation method available on windows except	4677	There is no supported compilation method available on windows except
3393	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.
3394		4682
3395	Not a libev limitation but worth mentioning: windows apparently doesn't	4683	Not a libev limitation but worth mentioning: windows apparently doesn't
3396	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
3397	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,
3398	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
3399	megabyte seems safe, but thsi apparently depends on the amount of memory	4687	megabyte seems safe, but this apparently depends on the amount of memory
3400	available).	4688	available).
3401		4689
3402	Due to the many, low, and arbitrary limits on the win32 platform and	4690	Due to the many, low, and arbitrary limits on the win32 platform and
3403	the abysmal performance of winsockets, using a large number of sockets	4691	the abysmal performance of winsockets, using a large number of sockets
3404	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
3405	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
3406	different implementation for windows, as libev offers the POSIX readiness	4694	different implementation for windows, as libev offers the POSIX readiness
3407	notification model, which cannot be implemented efficiently on windows	4695	notification model, which cannot be implemented efficiently on windows
3408	(Microsoft monopoly games).	4696	(due to Microsoft monopoly games).
3409		4697
3410	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
3411	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
3412	of F<ev.h>:	4700	of F<ev.h>:
3413		4701
…		…
3415	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4703	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3416		4704
3417	#include "ev.h"	4705	#include "ev.h"
3418		4706
3419	And compile the following F<evwrap.c> file into your project (make sure	4707	And compile the following F<evwrap.c> file into your project (make sure
3420	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4708	you do I<not> compile the F<ev.c> or any other embedded source files!):
3421		4709
3422	#include "evwrap.h"	4710	#include "evwrap.h"
3423	#include "ev.c"	4711	#include "ev.c"
3424		4712
3425	=over 4
3426
3427	=item The winsocket select function	4713	=head3 The winsocket C<select> function
3428		4714
3429	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
3430	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
3431	also extremely buggy). This makes select very inefficient, and also	4717	also extremely buggy). This makes select very inefficient, and also
3432	requires a mapping from file descriptors to socket handles (the Microsoft	4718	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3441	#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 */
3442		4728
3443	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
3444	complexity in the O(n²) range when using win32.	4730	complexity in the O(n²) range when using win32.
3445		4731
3446	=item Limited number of file descriptors	4732	=head3 Limited number of file descriptors
3447		4733
3448	Windows has numerous arbitrary (and low) limits on things.	4734	Windows has numerous arbitrary (and low) limits on things.
3449		4735
3450	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
3451	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
3452	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
3453	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
3454	previous thread in each. Great).	4740	previous thread in each. Sounds great!).
3455		4741
3456	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>
3457	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
3458	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
3459	select emulation on windows).	4745	other interpreters do their own select emulation on windows).
3460		4746
3461	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
3462	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>
3463	or something like this inside Microsoft). You can increase this by calling	4749	fetish or something like this inside Microsoft). You can increase this
3464	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4750	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3465	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
3466	libraries.
3467
3468	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
3469	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,
3470	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
3471	calling select (O(n²)) will likely make this unworkable.	4755	the cost of calling select (O(n²)) will likely make this unworkable.
3472		4756
3473	=back
3474
3475
3476	=head1 PORTABILITY REQUIREMENTS	4757	=head2 PORTABILITY REQUIREMENTS
3477		4758
3478	In addition to a working ISO-C implementation, libev relies on a few	4759	In addition to a working ISO-C implementation and of course the
3479	additional extensions:	4760	backend-specific APIs, libev relies on a few additional extensions:
3480		4761
3481	=over 4	4762	=over 4
3482		4763
3483	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4764	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3484	calling conventions regardless of C<ev_watcher_type *>.	4765	calling conventions regardless of C<ev_watcher_type *>.
…		…
3487	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
3488	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
3489	callback: The watcher callbacks have different type signatures, but libev	4770	callback: The watcher callbacks have different type signatures, but libev
3490	calls them using an C<ev_watcher *> internally.	4771	calls them using an C<ev_watcher *> internally.
3491		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.
		4777
3492	=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
3493		4779
3494	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
3495	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4781	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3496	threads. This is not part of the specification for C<sig_atomic_t>, but is	4782	threads. This is not part of the specification for C<sig_atomic_t>, but is
3497	believed to be sufficiently portable.	4783	believed to be sufficiently portable.
3498		4784
3499	=item C<sigprocmask> must work in a threaded environment	4785	=item C<sigprocmask> must work in a threaded environment
3500		4786
…		…
3509	except the initial one, and run the default loop in the initial thread as	4795	except the initial one, and run the default loop in the initial thread as
3510	well.	4796	well.
3511		4797
3512	=item C<long> must be large enough for common memory allocation sizes	4798	=item C<long> must be large enough for common memory allocation sizes
3513		4799
3514	To improve portability and simplify using libev, libev uses C<long>	4800	To improve portability and simplify its API, libev uses C<long> internally
3515	internally instead of C<size_t> when allocating its data structures. On	4801	instead of C<size_t> when allocating its data structures. On non-POSIX
3516	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4802	systems (Microsoft...) this might be unexpectedly low, but is still at
3517	is still at least 31 bits everywhere, which is enough for hundreds of	4803	least 31 bits everywhere, which is enough for hundreds of millions of
3518	millions of watchers.	4804	watchers.
3519		4805
3520	=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
3521		4807
3522	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
3523	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
3524	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
3525	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.
3526		4814
3527	=back	4815	=back
3528		4816
3529	If you know of other additional requirements drop me a note.	4817	If you know of other additional requirements drop me a note.
3530		4818
3531		4819
3532	=head1 COMPILER WARNINGS	4820	=head1 ALGORITHMIC COMPLEXITIES
3533		4821
3534	Depending on your compiler and compiler settings, you might get no or a	4822	In this section the complexities of (many of) the algorithms used inside
3535	lot of warnings when compiling libev code. Some people are apparently	4823	libev will be documented. For complexity discussions about backends see
3536	scared by this.	4824	the documentation for C<ev_default_init>.
3537		4825
3538	However, these are unavoidable for many reasons. For one, each compiler	4826	All of the following are about amortised time: If an array needs to be
3539	has different warnings, and each user has different tastes regarding	4827	extended, libev needs to realloc and move the whole array, but this
3540	warning options. "Warn-free" code therefore cannot be a goal except when	4828	happens asymptotically rarer with higher number of elements, so O(1) might
3541	targeting a specific compiler and compiler-version.	4829	mean that libev does a lengthy realloc operation in rare cases, but on
		4830	average it is much faster and asymptotically approaches constant time.
3542		4831
3543	Another reason is that some compiler warnings require elaborate	4832	=over 4
3544	workarounds, or other changes to the code that make it less clear and less
3545	maintainable.
3546		4833
3547	And of course, some compiler warnings are just plain stupid, or simply	4834	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3548	wrong (because they don't actually warn about the condition their message
3549	seems to warn about).
3550		4835
3551	While libev is written to generate as few warnings as possible,	4836	This means that, when you have a watcher that triggers in one hour and
3552	"warn-free" code is not a goal, and it is recommended not to build libev	4837	there are 100 watchers that would trigger before that, then inserting will
3553	with any compiler warnings enabled unless you are prepared to cope with	4838	have to skip roughly seven (C<ld 100>) of these watchers.
3554	them (e.g. by ignoring them). Remember that warnings are just that:
3555	warnings, not errors, or proof of bugs.
3556		4839
		4840	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3557		4841
3558	=head1 VALGRIND	4842	That means that changing a timer costs less than removing/adding them,
		4843	as only the relative motion in the event queue has to be paid for.
3559		4844
3560	Valgrind has a special section here because it is a popular tool that is	4845	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3561	highly useful, but valgrind reports are very hard to interpret.
3562		4846
3563	If you think you found a bug (memory leak, uninitialised data access etc.)	4847	These just add the watcher into an array or at the head of a list.
3564	in libev, then check twice: If valgrind reports something like:
3565		4848
3566	==2274== definitely lost: 0 bytes in 0 blocks.	4849	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3567	==2274== possibly lost: 0 bytes in 0 blocks.
3568	==2274== still reachable: 256 bytes in 1 blocks.
3569		4850
3570	Then there is no memory leak. Similarly, under some circumstances,	4851	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3571	valgrind might report kernel bugs as if it were a bug in libev, or it
3572	might be confused (it is a very good tool, but only a tool).
3573		4852
3574	If you are unsure about something, feel free to contact the mailing list	4853	These watchers are stored in lists, so they need to be walked to find the
3575	with the full valgrind report and an explanation on why you think this is	4854	correct watcher to remove. The lists are usually short (you don't usually
3576	a bug in libev. However, don't be annoyed when you get a brisk "this is	4855	have many watchers waiting for the same fd or signal: one is typical, two
3577	no bug" answer and take the chance of learning how to interpret valgrind	4856	is rare).
3578	properly.
3579		4857
3580	If you need, for some reason, empty reports from valgrind for your project	4858	=item Finding the next timer in each loop iteration: O(1)
3581	I suggest using suppression lists.
3582		4859
		4860	By virtue of using a binary or 4-heap, the next timer is always found at a
		4861	fixed position in the storage array.
		4862
		4863	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4864
		4865	A change means an I/O watcher gets started or stopped, which requires
		4866	libev to recalculate its status (and possibly tell the kernel, depending
		4867	on backend and whether C<ev_io_set> was used).
		4868
		4869	=item Activating one watcher (putting it into the pending state): O(1)
		4870
		4871	=item Priority handling: O(number_of_priorities)
		4872
		4873	Priorities are implemented by allocating some space for each
		4874	priority. When doing priority-based operations, libev usually has to
		4875	linearly search all the priorities, but starting/stopping and activating
		4876	watchers becomes O(1) with respect to priority handling.
		4877
		4878	=item Sending an ev_async: O(1)
		4879
		4880	=item Processing ev_async_send: O(number_of_async_watchers)
		4881
		4882	=item Processing signals: O(max_signal_number)
		4883
		4884	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4885	calls in the current loop iteration. Checking for async and signal events
		4886	involves iterating over all running async watchers or all signal numbers.
		4887
		4888	=back
		4889
		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
3583		5022
3584	=head1 AUTHOR	5023	=head1 AUTHOR
3585		5024
3586	Marc Lehmann <libev@schmorp.de>.	5025	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5026	Magnusson and Emanuele Giaquinta.
3587		5027

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