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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 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	130	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	131	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	132	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	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
149		165
150	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
151		167
152	Returns the current time as libev would use it. Please note that the	168	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	169	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
155		172
156	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
157		174
158	Sleep for the given interval: The current thread will be blocked until	175	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	176	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	195	not a problem.
179		196
180	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
182		200
183	assert (("libev version mismatch",	201	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
186		204
…		…
197	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
199		217
200	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
201		219
202	Return the set of all backends compiled into this binary of libev and also	220	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	221	also recommended for this platform, meaning it will work for most file
		222	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	223	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	224	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	225	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.	226	probe for if you specify no backends explicitly.
208		227
209	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
210		229
211	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	231	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	232	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
216		235
217	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
218		237
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		239
221	Sets the allocation function to use (the prototype is similar - the	240	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	241	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	242	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	243	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	269	}
251		270
252	...	271	...
253	ev_set_allocator (persistent_realloc);	272	ev_set_allocator (persistent_realloc);
254		273
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		275
257	Set the callback function to call on a retryable system call error (such	276	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	277	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	278	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	279	callback is set, then libev will expect it to remedy the situation, no
…		…
274	...	293	...
275	ev_set_syserr_cb (fatal_error);	294	ev_set_syserr_cb (fatal_error);
276		295
277	=back	296	=back
278		297
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		299
281	An event loop is described by a C<struct ev_loop *>. The library knows two	300	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	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	302	libev 3 had an C<ev_loop> function colliding with the struct name).
		303
		304	The library knows two types of such loops, the I<default> loop, which
		305	supports signals and child events, and dynamically created event loops
		306	which do not.
284		307
285	=over 4	308	=over 4
286		309
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		311
289	This will initialise the default event loop if it hasn't been initialised	312	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	313	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	314	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).	315	C<ev_loop_new>.
		316
		317	If the default loop is already initialised then this function simply
		318	returns it (and ignores the flags. If that is troubling you, check
		319	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		320	flags, which should almost always be C<0>, unless the caller is also the
		321	one calling C<ev_run> or otherwise qualifies as "the main program".
293		322
294	If you don't know what event loop to use, use the one returned from this	323	If you don't know what event loop to use, use the one returned from this
295	function.	324	function (or via the C<EV_DEFAULT> macro).
296		325
297	Note that this function is I<not> thread-safe, so if you want to use it	326	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,	327	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
300		330
301	The default loop is the only loop that can handle C<ev_signal> and	331	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	332	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	333	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	334	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	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	336
		337	Example: This is the most typical usage.
		338
		339	if (!ev_default_loop (0))
		340	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		341
		342	Example: Restrict libev to the select and poll backends, and do not allow
		343	environment settings to be taken into account:
		344
		345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		346
		347	Example: Use whatever libev has to offer, but make sure that kqueue is
		348	used if available (warning, breaks stuff, best use only with your own
		349	private event loop and only if you know the OS supports your types of
		350	fds):
		351
		352	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
		353
		354	=item struct ev_loop *ev_loop_new (unsigned int flags)
		355
		356	This will create and initialise a new event loop object. If the loop
		357	could not be initialised, returns false.
		358
		359	Note that this function I<is> thread-safe, and one common way to use
		360	libev with threads is indeed to create one loop per thread, and using the
		361	default loop in the "main" or "initial" thread.
307		362
308	The flags argument can be used to specify special behaviour or specific	363	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>).	364	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		365
311	The following flags are supported:	366	The following flags are supported:
…		…
326	useful to try out specific backends to test their performance, or to work	381	useful to try out specific backends to test their performance, or to work
327	around bugs.	382	around bugs.
328		383
329	=item C<EVFLAG_FORKCHECK>	384	=item C<EVFLAG_FORKCHECK>
330		385
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	386	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	387	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		388
335	This works by calling C<getpid ()> on every iteration of the loop,	389	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	390	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	391	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	392	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
344	flag.	398	flag.
345		399
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	400	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	401	environment variable.
348		402
		403	=item C<EVFLAG_NOINOTIFY>
		404
		405	When this flag is specified, then libev will not attempt to use the
		406	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		407	testing, this flag can be useful to conserve inotify file descriptors, as
		408	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		409
		410	=item C<EVFLAG_SIGNALFD>
		411
		412	When this flag is specified, then libev will attempt to use the
		413	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		414	delivers signals synchronously, which makes it both faster and might make
		415	it possible to get the queued signal data. It can also simplify signal
		416	handling with threads, as long as you properly block signals in your
		417	threads that are not interested in handling them.
		418
		419	Signalfd will not be used by default as this changes your signal mask, and
		420	there are a lot of shoddy libraries and programs (glib's threadpool for
		421	example) that can't properly initialise their signal masks.
		422
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	423	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		424
351	This is your standard select(2) backend. Not I<completely> standard, as	425	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,	426	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	427	but if that fails, expect a fairly low limit on the number of fds when
…		…
359	writing a server, you should C<accept ()> in a loop to accept as many	433	writing a server, you should C<accept ()> in a loop to accept as many
360	connections as possible during one iteration. You might also want to have	434	connections as possible during one iteration. You might also want to have
361	a look at C<ev_set_io_collect_interval ()> to increase the amount of	435	a look at C<ev_set_io_collect_interval ()> to increase the amount of
362	readiness notifications you get per iteration.	436	readiness notifications you get per iteration.
363		437
		438	This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the
		439	C<writefds> set (and to work around Microsoft Windows bugs, also onto the
		440	C<exceptfds> set on that platform).
		441
364	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	442	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
365		443
366	And this is your standard poll(2) backend. It's more complicated	444	And this is your standard poll(2) backend. It's more complicated
367	than select, but handles sparse fds better and has no artificial	445	than select, but handles sparse fds better and has no artificial
368	limit on the number of fds you can use (except it will slow down	446	limit on the number of fds you can use (except it will slow down
369	considerably with a lot of inactive fds). It scales similarly to select,	447	considerably with a lot of inactive fds). It scales similarly to select,
370	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for	448	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
371	performance tips.	449	performance tips.
372		450
		451	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
		452	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
		453
373	=item C<EVBACKEND_EPOLL> (value 4, Linux)	454	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		455
		456	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		457	kernels).
374		458
375	For few fds, this backend is a bit little slower than poll and select,	459	For few fds, this backend is a bit little slower than poll and select,
376	but it scales phenomenally better. While poll and select usually scale	460	but it scales phenomenally better. While poll and select usually scale
377	like O(total_fds) where n is the total number of fds (or the highest fd),	461	like O(total_fds) where n is the total number of fds (or the highest fd),
378	epoll scales either O(1) or O(active_fds). The epoll design has a number	462	epoll scales either O(1) or O(active_fds).
379	of shortcomings, such as silently dropping events in some hard-to-detect	463
380	cases and requiring a system call per fd change, no fork support and bad	464	The epoll mechanism deserves honorable mention as the most misdesigned
381	support for dup.	465	of the more advanced event mechanisms: mere annoyances include silently
		466	dropping file descriptors, requiring a system call per change per file
		467	descriptor (and unnecessary guessing of parameters), problems with dup and
		468	so on. The biggest issue is fork races, however - if a program forks then
		469	I<both> parent and child process have to recreate the epoll set, which can
		470	take considerable time (one syscall per file descriptor) and is of course
		471	hard to detect.
		472
		473	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		474	of course I<doesn't>, and epoll just loves to report events for totally
		475	I<different> file descriptors (even already closed ones, so one cannot
		476	even remove them from the set) than registered in the set (especially
		477	on SMP systems). Libev tries to counter these spurious notifications by
		478	employing an additional generation counter and comparing that against the
		479	events to filter out spurious ones, recreating the set when required. Last
		480	not least, it also refuses to work with some file descriptors which work
		481	perfectly fine with C<select> (files, many character devices...).
382		482
383	While stopping, setting and starting an I/O watcher in the same iteration	483	While stopping, setting and starting an I/O watcher in the same iteration
384	will result in some caching, there is still a system call per such incident	484	will result in some caching, there is still a system call per such
385	(because the fd could point to a different file description now), so its	485	incident (because the same I<file descriptor> could point to a different
386	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	486	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
387	very well if you register events for both fds.	487	file descriptors might not work very well if you register events for both
388		488	file descriptors.
389	Please note that epoll sometimes generates spurious notifications, so you
390	need to use non-blocking I/O or other means to avoid blocking when no data
391	(or space) is available.
392		489
393	Best performance from this backend is achieved by not unregistering all	490	Best performance from this backend is achieved by not unregistering all
394	watchers for a file descriptor until it has been closed, if possible, i.e.	491	watchers for a file descriptor until it has been closed, if possible,
395	keep at least one watcher active per fd at all times.	492	i.e. keep at least one watcher active per fd at all times. Stopping and
		493	starting a watcher (without re-setting it) also usually doesn't cause
		494	extra overhead. A fork can both result in spurious notifications as well
		495	as in libev having to destroy and recreate the epoll object, which can
		496	take considerable time and thus should be avoided.
		497
		498	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		499	faster than epoll for maybe up to a hundred file descriptors, depending on
		500	the usage. So sad.
396		501
397	While nominally embeddable in other event loops, this feature is broken in	502	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	503	all kernel versions tested so far.
		504
		505	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		506	C<EVBACKEND_POLL>.
399		507
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	508	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		509
402	Kqueue deserves special mention, as at the time of this writing, it	510	Kqueue deserves special mention, as at the time of this writing, it
403	was broken on all BSDs except NetBSD (usually it doesn't work reliably	511	was broken on all BSDs except NetBSD (usually it doesn't work reliably
404	with anything but sockets and pipes, except on Darwin, where of course	512	with anything but sockets and pipes, except on Darwin, where of course
405	it's completely useless). For this reason it's not being "auto-detected"	513	it's completely useless). Unlike epoll, however, whose brokenness
		514	is by design, these kqueue bugs can (and eventually will) be fixed
		515	without API changes to existing programs. For this reason it's not being
406	unless you explicitly specify it explicitly in the flags (i.e. using	516	"auto-detected" unless you explicitly specify it in the flags (i.e. using
407	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	517	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	518	system like NetBSD.
409		519
410	You still can embed kqueue into a normal poll or select backend and use it	520	You still can embed kqueue into a normal poll or select backend and use it
411	only for sockets (after having made sure that sockets work with kqueue on	521	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		523
414	It scales in the same way as the epoll backend, but the interface to the	524	It scales in the same way as the epoll backend, but the interface to the
415	kernel is more efficient (which says nothing about its actual speed, of	525	kernel is more efficient (which says nothing about its actual speed, of
416	course). While stopping, setting and starting an I/O watcher does never	526	course). While stopping, setting and starting an I/O watcher does never
417	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	527	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
418	two event changes per incident, support for C<fork ()> is very bad and it	528	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	529	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		530	cases
420		531
421	This backend usually performs well under most conditions.	532	This backend usually performs well under most conditions.
422		533
423	While nominally embeddable in other event loops, this doesn't work	534	While nominally embeddable in other event loops, this doesn't work
424	everywhere, so you might need to test for this. And since it is broken	535	everywhere, so you might need to test for this. And since it is broken
425	almost everywhere, you should only use it when you have a lot of sockets	536	almost everywhere, you should only use it when you have a lot of sockets
426	(for which it usually works), by embedding it into another event loop	537	(for which it usually works), by embedding it into another event loop
427	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	538	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
428	sockets.	539	also broken on OS X)) and, did I mention it, using it only for sockets.
		540
		541	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		542	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		543	C<NOTE_EOF>.
429		544
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	545	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		546
432	This is not implemented yet (and might never be, unless you send me an	547	This is not implemented yet (and might never be, unless you send me an
433	implementation). According to reports, C</dev/poll> only supports sockets	548	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	561	While this backend scales well, it requires one system call per active
447	file descriptor per loop iteration. For small and medium numbers of file	562	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	563	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	564	might perform better.
450		565
451	On the positive side, ignoring the spurious readiness notifications, this	566	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	567	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	568	in all tests and is fully embeddable, which is a rare feat among the
		569	OS-specific backends (I vastly prefer correctness over speed hacks).
		570
		571	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		572	C<EVBACKEND_POLL>.
454		573
455	=item C<EVBACKEND_ALL>	574	=item C<EVBACKEND_ALL>
456		575
457	Try all backends (even potentially broken ones that wouldn't be tried	576	Try all backends (even potentially broken ones that wouldn't be tried
458	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	577	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
460		579
461	It is definitely not recommended to use this flag.	580	It is definitely not recommended to use this flag.
462		581
463	=back	582	=back
464		583
465	If one or more of these are or'ed into the flags value, then only these	584	If one or more of the backend flags are or'ed into the flags value,
466	backends will be tried (in the reverse order as listed here). If none are	585	then only these backends will be tried (in the reverse order as listed
467	specified, all backends in C<ev_recommended_backends ()> will be tried.	586	here). If none are specified, all backends in C<ev_recommended_backends
468		587	()> will be tried.
469	The most typical usage is like this:
470
471	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473
474	Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:
476
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478
479	Use whatever libev has to offer, but make sure that kqueue is used if
480	available (warning, breaks stuff, best use only with your own private
481	event loop and only if you know the OS supports your types of fds):
482
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484
485	=item struct ev_loop *ev_loop_new (unsigned int flags)
486
487	Similar to C<ev_default_loop>, but always creates a new event loop that is
488	always distinct from the default loop. Unlike the default loop, it cannot
489	handle signal and child watchers, and attempts to do so will be greeted by
490	undefined behaviour (or a failed assertion if assertions are enabled).
491
492	Note that this function I<is> thread-safe, and the recommended way to use
493	libev with threads is indeed to create one loop per thread, and using the
494	default loop in the "main" or "initial" thread.
495		588
496	Example: Try to create a event loop that uses epoll and nothing else.	589	Example: Try to create a event loop that uses epoll and nothing else.
497		590
498	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	591	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
499	if (!epoller)	592	if (!epoller)
500	fatal ("no epoll found here, maybe it hides under your chair");	593	fatal ("no epoll found here, maybe it hides under your chair");
501		594
502	=item ev_default_destroy ()	595	=item ev_loop_destroy (loop)
503		596
504	Destroys the default loop again (frees all memory and kernel state	597	Destroys an event loop object (frees all memory and kernel state
505	etc.). None of the active event watchers will be stopped in the normal	598	etc.). None of the active event watchers will be stopped in the normal
506	sense, so e.g. C<ev_is_active> might still return true. It is your	599	sense, so e.g. C<ev_is_active> might still return true. It is your
507	responsibility to either stop all watchers cleanly yourself I<before>	600	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	601	calling this function, or cope with the fact afterwards (which is usually
509	the easiest thing, you can just ignore the watchers and/or C<free ()> them	602	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	603	for example).
511		604
512	Note that certain global state, such as signal state, will not be freed by	605	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	606	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	607	as signal and child watchers) would need to be stopped manually.
515		608
516	In general it is not advisable to call this function except in the	609	This function is normally used on loop objects allocated by
517	rare occasion where you really need to free e.g. the signal handling	610	C<ev_loop_new>, but it can also be used on the default loop returned by
		611	C<ev_default_loop>, in which case it is not thread-safe.
		612
		613	Note that it is not advisable to call this function on the default loop
		614	except in the rare occasion where you really need to free it's resources.
518	pipe fds. If you need dynamically allocated loops it is better to use	615	If you need dynamically allocated loops it is better to use C<ev_loop_new>
519	C<ev_loop_new> and C<ev_loop_destroy>).	616	and C<ev_loop_destroy>.
520		617
521	=item ev_loop_destroy (loop)	618	=item ev_loop_fork (loop)
522		619
523	Like C<ev_default_destroy>, but destroys an event loop created by an
524	earlier call to C<ev_loop_new>.
525
526	=item ev_default_fork ()
527
528	This function sets a flag that causes subsequent C<ev_loop> iterations	620	This function sets a flag that causes subsequent C<ev_run> iterations to
529	to reinitialise the kernel state for backends that have one. Despite the	621	reinitialise the kernel state for backends that have one. Despite the
530	name, you can call it anytime, but it makes most sense after forking, in	622	name, you can call it anytime, but it makes most sense after forking, in
531	the child process (or both child and parent, but that again makes little	623	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
532	sense). You I<must> call it in the child before using any of the libev	624	child before resuming or calling C<ev_run>.
533	functions, and it will only take effect at the next C<ev_loop> iteration.	625
		626	Again, you I<have> to call it on I<any> loop that you want to re-use after
		627	a fork, I<even if you do not plan to use the loop in the parent>. This is
		628	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		629	during fork.
534		630
535	On the other hand, you only need to call this function in the child	631	On the other hand, you only need to call this function in the child
536	process if and only if you want to use the event library in the child. If	632	process if and only if you want to use the event loop in the child. If
537	you just fork+exec, you don't have to call it at all.	633	you just fork+exec or create a new loop in the child, you don't have to
		634	call it at all (in fact, C<epoll> is so badly broken that it makes a
		635	difference, but libev will usually detect this case on its own and do a
		636	costly reset of the backend).
538		637
539	The function itself is quite fast and it's usually not a problem to call	638	The function itself is quite fast and it's usually not a problem to call
540	it just in case after a fork. To make this easy, the function will fit in	639	it just in case after a fork.
541	quite nicely into a call to C<pthread_atfork>:
542		640
		641	Example: Automate calling C<ev_loop_fork> on the default loop when
		642	using pthreads.
		643
		644	static void
		645	post_fork_child (void)
		646	{
		647	ev_loop_fork (EV_DEFAULT);
		648	}
		649
		650	...
543	pthread_atfork (0, 0, ev_default_fork);	651	pthread_atfork (0, 0, post_fork_child);
544
545	=item ev_loop_fork (loop)
546
547	Like C<ev_default_fork>, but acts on an event loop created by
548	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
549	after fork, and how you do this is entirely your own problem.
550		652
551	=item int ev_is_default_loop (loop)	653	=item int ev_is_default_loop (loop)
552		654
553	Returns true when the given loop actually is the default loop, false otherwise.	655	Returns true when the given loop is, in fact, the default loop, and false
		656	otherwise.
554		657
555	=item unsigned int ev_loop_count (loop)	658	=item unsigned int ev_iteration (loop)
556		659
557	Returns the count of loop iterations for the loop, which is identical to	660	Returns the current iteration count for the event loop, which is identical
558	the number of times libev did poll for new events. It starts at C<0> and	661	to the number of times libev did poll for new events. It starts at C<0>
559	happily wraps around with enough iterations.	662	and happily wraps around with enough iterations.
560		663
561	This value can sometimes be useful as a generation counter of sorts (it	664	This value can sometimes be useful as a generation counter of sorts (it
562	"ticks" the number of loop iterations), as it roughly corresponds with	665	"ticks" the number of loop iterations), as it roughly corresponds with
563	C<ev_prepare> and C<ev_check> calls.	666	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		667	prepare and check phases.
		668
		669	=item unsigned int ev_depth (loop)
		670
		671	Returns the number of times C<ev_run> was entered minus the number of
		672	times C<ev_run> was exited, in other words, the recursion depth.
		673
		674	Outside C<ev_run>, this number is zero. In a callback, this number is
		675	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		676	in which case it is higher.
		677
		678	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		679	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		680	ungentleman-like behaviour unless it's really convenient.
564		681
565	=item unsigned int ev_backend (loop)	682	=item unsigned int ev_backend (loop)
566		683
567	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	684	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
568	use.	685	use.
…		…
573	received events and started processing them. This timestamp does not	690	received events and started processing them. This timestamp does not
574	change as long as callbacks are being processed, and this is also the base	691	change as long as callbacks are being processed, and this is also the base
575	time used for relative timers. You can treat it as the timestamp of the	692	time used for relative timers. You can treat it as the timestamp of the
576	event occurring (or more correctly, libev finding out about it).	693	event occurring (or more correctly, libev finding out about it).
577		694
		695	=item ev_now_update (loop)
		696
		697	Establishes the current time by querying the kernel, updating the time
		698	returned by C<ev_now ()> in the progress. This is a costly operation and
		699	is usually done automatically within C<ev_run ()>.
		700
		701	This function is rarely useful, but when some event callback runs for a
		702	very long time without entering the event loop, updating libev's idea of
		703	the current time is a good idea.
		704
		705	See also L<The special problem of time updates> in the C<ev_timer> section.
		706
		707	=item ev_suspend (loop)
		708
		709	=item ev_resume (loop)
		710
		711	These two functions suspend and resume an event loop, for use when the
		712	loop is not used for a while and timeouts should not be processed.
		713
		714	A typical use case would be an interactive program such as a game: When
		715	the user presses C<^Z> to suspend the game and resumes it an hour later it
		716	would be best to handle timeouts as if no time had actually passed while
		717	the program was suspended. This can be achieved by calling C<ev_suspend>
		718	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		719	C<ev_resume> directly afterwards to resume timer processing.
		720
		721	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		722	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		723	will be rescheduled (that is, they will lose any events that would have
		724	occurred while suspended).
		725
		726	After calling C<ev_suspend> you B<must not> call I<any> function on the
		727	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		728	without a previous call to C<ev_suspend>.
		729
		730	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		731	event loop time (see C<ev_now_update>).
		732
578	=item ev_loop (loop, int flags)	733	=item ev_run (loop, int flags)
579		734
580	Finally, this is it, the event handler. This function usually is called	735	Finally, this is it, the event handler. This function usually is called
581	after you initialised all your watchers and you want to start handling	736	after you have initialised all your watchers and you want to start
582	events.	737	handling events. It will ask the operating system for any new events, call
		738	the watcher callbacks, an then repeat the whole process indefinitely: This
		739	is why event loops are called I<loops>.
583		740
584	If the flags argument is specified as C<0>, it will not return until	741	If the flags argument is specified as C<0>, it will keep handling events
585	either no event watchers are active anymore or C<ev_unloop> was called.	742	until either no event watchers are active anymore or C<ev_break> was
		743	called.
586		744
587	Please note that an explicit C<ev_unloop> is usually better than	745	Please note that an explicit C<ev_break> is usually better than
588	relying on all watchers to be stopped when deciding when a program has	746	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	747	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	748	that automatically loops as long as it has to and no longer by virtue
591	relying on its watchers stopping correctly is a thing of beauty.	749	of relying on its watchers stopping correctly, that is truly a thing of
		750	beauty.
592		751
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	752	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
594	those events and any outstanding ones, but will not block your process in	753	those events and any already outstanding ones, but will not wait and
595	case there are no events and will return after one iteration of the loop.	754	block your process in case there are no events and will return after one
		755	iteration of the loop. This is sometimes useful to poll and handle new
		756	events while doing lengthy calculations, to keep the program responsive.
596		757
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	758	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
598	necessary) and will handle those and any outstanding ones. It will block	759	necessary) and will handle those and any already outstanding ones. It
599	your process until at least one new event arrives, and will return after	760	will block your process until at least one new event arrives (which could
600	one iteration of the loop. This is useful if you are waiting for some	761	be an event internal to libev itself, so there is no guarantee that a
601	external event in conjunction with something not expressible using other	762	user-registered callback will be called), and will return after one
		763	iteration of the loop.
		764
		765	This is useful if you are waiting for some external event in conjunction
		766	with something not expressible using other libev watchers (i.e. "roll your
602	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	767	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
603	usually a better approach for this kind of thing.	768	usually a better approach for this kind of thing.
604		769
605	Here are the gory details of what C<ev_loop> does:	770	Here are the gory details of what C<ev_run> does:
606		771
		772	- Increment loop depth.
		773	- Reset the ev_break status.
607	- Before the first iteration, call any pending watchers.	774	- Before the first iteration, call any pending watchers.
		775	LOOP:
608	* If EVFLAG_FORKCHECK was used, check for a fork.	776	- If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	777	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	778	- Queue and call all prepare watchers.
		779	- If ev_break was called, goto FINISH.
611	- If we have been forked, recreate the kernel state.	780	- If we have been forked, detach and recreate the kernel state
		781	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	782	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	783	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	784	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	785	(active idle watchers, EVRUN_NOWAIT or not having
616	any active watchers at all will result in not sleeping).	786	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	787	- Sleep if the I/O and timer collect interval say so.
		788	- Increment loop iteration counter.
618	- Block the process, waiting for any events.	789	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	790	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	791	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	792	- Queue all expired timers.
622	- Queue all outstanding periodics.	793	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	794	- Queue all idle watchers with priority higher than that of pending events.
624	- Queue all check watchers.	795	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	796	- Call all queued watchers in reverse order (i.e. check watchers first).
626	Signals and child watchers are implemented as I/O watchers, and will	797	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	798	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	799	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
629	were used, or there are no active watchers, return, otherwise	800	were used, or there are no active watchers, goto FINISH, otherwise
630	continue with step *.	801	continue with step LOOP.
		802	FINISH:
		803	- Reset the ev_break status iff it was EVBREAK_ONE.
		804	- Decrement the loop depth.
		805	- Return.
631		806
632	Example: Queue some jobs and then loop until no events are outstanding	807	Example: Queue some jobs and then loop until no events are outstanding
633	anymore.	808	anymore.
634		809
635	... queue jobs here, make sure they register event watchers as long	810	... queue jobs here, make sure they register event watchers as long
636	... as they still have work to do (even an idle watcher will do..)	811	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	812	ev_run (my_loop, 0);
638	... jobs done. yeah!	813	... jobs done or somebody called unloop. yeah!
639		814
640	=item ev_unloop (loop, how)	815	=item ev_break (loop, how)
641		816
642	Can be used to make a call to C<ev_loop> return early (but only after it	817	Can be used to make a call to C<ev_run> return early (but only after it
643	has processed all outstanding events). The C<how> argument must be either	818	has processed all outstanding events). The C<how> argument must be either
644	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	819	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
645	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	820	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
646		821
647	This "unloop state" will be cleared when entering C<ev_loop> again.	822	This "unloop state" will be cleared when entering C<ev_run> again.
		823
		824	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
648		825
649	=item ev_ref (loop)	826	=item ev_ref (loop)
650		827
651	=item ev_unref (loop)	828	=item ev_unref (loop)
652		829
653	Ref/unref can be used to add or remove a reference count on the event	830	Ref/unref can be used to add or remove a reference count on the event
654	loop: Every watcher keeps one reference, and as long as the reference	831	loop: Every watcher keeps one reference, and as long as the reference
655	count is nonzero, C<ev_loop> will not return on its own. If you have	832	count is nonzero, C<ev_run> will not return on its own.
656	a watcher you never unregister that should not keep C<ev_loop> from	833
657	returning, ev_unref() after starting, and ev_ref() before stopping it. For	834	This is useful when you have a watcher that you never intend to
		835	unregister, but that nevertheless should not keep C<ev_run> from
		836	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
		837	before stopping it.
		838
658	example, libev itself uses this for its internal signal pipe: It is not	839	As an example, libev itself uses this for its internal signal pipe: It
659	visible to the libev user and should not keep C<ev_loop> from exiting if	840	is not visible to the libev user and should not keep C<ev_run> from
660	no event watchers registered by it are active. It is also an excellent	841	exiting if no event watchers registered by it are active. It is also an
661	way to do this for generic recurring timers or from within third-party	842	excellent way to do this for generic recurring timers or from within
662	libraries. Just remember to I<unref after start> and I<ref before stop>	843	third-party libraries. Just remember to I<unref after start> and I<ref
663	(but only if the watcher wasn't active before, or was active before,	844	before stop> (but only if the watcher wasn't active before, or was active
664	respectively).	845	before, respectively. Note also that libev might stop watchers itself
		846	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		847	in the callback).
665		848
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	849	Example: Create a signal watcher, but keep it from keeping C<ev_run>
667	running when nothing else is active.	850	running when nothing else is active.
668		851
669	struct ev_signal exitsig;	852	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	853	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	854	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	855	evf_unref (loop);
673		856
674	Example: For some weird reason, unregister the above signal handler again.	857	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	862	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		863
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	864	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		865
683	These advanced functions influence the time that libev will spend waiting	866	These advanced functions influence the time that libev will spend waiting
684	for events. Both are by default C<0>, meaning that libev will try to	867	for events. Both time intervals are by default C<0>, meaning that libev
685	invoke timer/periodic callbacks and I/O callbacks with minimum latency.	868	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		869	latency.
686		870
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	871	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
688	allows libev to delay invocation of I/O and timer/periodic callbacks to	872	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	873	to increase efficiency of loop iterations (or to increase power-saving
		874	opportunities).
690		875
691	The background is that sometimes your program runs just fast enough to	876	The idea is that sometimes your program runs just fast enough to handle
692	handle one (or very few) event(s) per loop iteration. While this makes	877	one (or very few) event(s) per loop iteration. While this makes the
693	the program responsive, it also wastes a lot of CPU time to poll for new	878	program responsive, it also wastes a lot of CPU time to poll for new
694	events, especially with backends like C<select ()> which have a high	879	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	880	overhead for the actual polling but can deliver many events at once.
696		881
697	By setting a higher I<io collect interval> you allow libev to spend more	882	By setting a higher I<io collect interval> you allow libev to spend more
698	time collecting I/O events, so you can handle more events per iteration,	883	time collecting I/O events, so you can handle more events per iteration,
699	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	884	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
700	C<ev_timer>) will be not affected. Setting this to a non-null value will	885	C<ev_timer>) will be not affected. Setting this to a non-null value will
701	introduce an additional C<ev_sleep ()> call into most loop iterations.	886	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		887	sleep time ensures that libev will not poll for I/O events more often then
		888	once per this interval, on average.
702		889
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	890	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	891	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	892	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	893	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	894	value will not introduce any overhead in libev.
708		895
709	Many (busy) programs can usually benefit by setting the I/O collect	896	Many (busy) programs can usually benefit by setting the I/O collect
710	interval to a value near C<0.1> or so, which is often enough for	897	interval to a value near C<0.1> or so, which is often enough for
711	interactive servers (of course not for games), likewise for timeouts. It	898	interactive servers (of course not for games), likewise for timeouts. It
712	usually doesn't make much sense to set it to a lower value than C<0.01>,	899	usually doesn't make much sense to set it to a lower value than C<0.01>,
713	as this approaches the timing granularity of most systems.	900	as this approaches the timing granularity of most systems. Note that if
		901	you do transactions with the outside world and you can't increase the
		902	parallelity, then this setting will limit your transaction rate (if you
		903	need to poll once per transaction and the I/O collect interval is 0.01,
		904	then you can't do more than 100 transactions per second).
714		905
		906	Setting the I<timeout collect interval> can improve the opportunity for
		907	saving power, as the program will "bundle" timer callback invocations that
		908	are "near" in time together, by delaying some, thus reducing the number of
		909	times the process sleeps and wakes up again. Another useful technique to
		910	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		911	they fire on, say, one-second boundaries only.
		912
		913	Example: we only need 0.1s timeout granularity, and we wish not to poll
		914	more often than 100 times per second:
		915
		916	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		917	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		918
		919	=item ev_invoke_pending (loop)
		920
		921	This call will simply invoke all pending watchers while resetting their
		922	pending state. Normally, C<ev_run> does this automatically when required,
		923	but when overriding the invoke callback this call comes handy. This
		924	function can be invoked from a watcher - this can be useful for example
		925	when you want to do some lengthy calculation and want to pass further
		926	event handling to another thread (you still have to make sure only one
		927	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		928
		929	=item int ev_pending_count (loop)
		930
		931	Returns the number of pending watchers - zero indicates that no watchers
		932	are pending.
		933
		934	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		935
		936	This overrides the invoke pending functionality of the loop: Instead of
		937	invoking all pending watchers when there are any, C<ev_run> will call
		938	this callback instead. This is useful, for example, when you want to
		939	invoke the actual watchers inside another context (another thread etc.).
		940
		941	If you want to reset the callback, use C<ev_invoke_pending> as new
		942	callback.
		943
		944	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		945
		946	Sometimes you want to share the same loop between multiple threads. This
		947	can be done relatively simply by putting mutex_lock/unlock calls around
		948	each call to a libev function.
		949
		950	However, C<ev_run> can run an indefinite time, so it is not feasible
		951	to wait for it to return. One way around this is to wake up the event
		952	loop via C<ev_break> and C<av_async_send>, another way is to set these
		953	I<release> and I<acquire> callbacks on the loop.
		954
		955	When set, then C<release> will be called just before the thread is
		956	suspended waiting for new events, and C<acquire> is called just
		957	afterwards.
		958
		959	Ideally, C<release> will just call your mutex_unlock function, and
		960	C<acquire> will just call the mutex_lock function again.
		961
		962	While event loop modifications are allowed between invocations of
		963	C<release> and C<acquire> (that's their only purpose after all), no
		964	modifications done will affect the event loop, i.e. adding watchers will
		965	have no effect on the set of file descriptors being watched, or the time
		966	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		967	to take note of any changes you made.
		968
		969	In theory, threads executing C<ev_run> will be async-cancel safe between
		970	invocations of C<release> and C<acquire>.
		971
		972	See also the locking example in the C<THREADS> section later in this
		973	document.
		974
		975	=item ev_set_userdata (loop, void *data)
		976
		977	=item ev_userdata (loop)
		978
		979	Set and retrieve a single C<void *> associated with a loop. When
		980	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		981	C<0.>
		982
		983	These two functions can be used to associate arbitrary data with a loop,
		984	and are intended solely for the C<invoke_pending_cb>, C<release> and
		985	C<acquire> callbacks described above, but of course can be (ab-)used for
		986	any other purpose as well.
		987
715	=item ev_loop_verify (loop)	988	=item ev_verify (loop)
716		989
717	This function only does something when C<EV_VERIFY> support has been	990	This function only does something when C<EV_VERIFY> support has been
718	compiled in. It tries to go through all internal structures and checks	991	compiled in, which is the default for non-minimal builds. It tries to go
719	them for validity. If anything is found to be inconsistent, it will print	992	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	993	is found to be inconsistent, it will print an error message to standard
		994	error and call C<abort ()>.
721		995
722	This can be used to catch bugs inside libev itself: under normal	996	This can be used to catch bugs inside libev itself: under normal
723	circumstances, this function will never abort as of course libev keeps its	997	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	998	data structures consistent.
725		999
726	=back	1000	=back
727		1001
728		1002
729	=head1 ANATOMY OF A WATCHER	1003	=head1 ANATOMY OF A WATCHER
730		1004
		1005	In the following description, uppercase C<TYPE> in names stands for the
		1006	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1007	watchers and C<ev_io_start> for I/O watchers.
		1008
731	A watcher is a structure that you create and register to record your	1009	A watcher is an opaque structure that you allocate and register to record
732	interest in some event. For instance, if you want to wait for STDIN to	1010	your interest in some event. To make a concrete example, imagine you want
733	become readable, you would create an C<ev_io> watcher for that:	1011	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1012	for that:
734		1013
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1014	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	1015	{
737	ev_io_stop (w);	1016	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	1017	ev_break (loop, EVBREAK_ALL);
739	}	1018	}
740		1019
741	struct ev_loop *loop = ev_default_loop (0);	1020	struct ev_loop *loop = ev_default_loop (0);
		1021
742	struct ev_io stdin_watcher;	1022	ev_io stdin_watcher;
		1023
743	ev_init (&stdin_watcher, my_cb);	1024	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1025	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	1026	ev_io_start (loop, &stdin_watcher);
		1027
746	ev_loop (loop, 0);	1028	ev_run (loop, 0);
747		1029
748	As you can see, you are responsible for allocating the memory for your	1030	As you can see, you are responsible for allocating the memory for your
749	watcher structures (and it is usually a bad idea to do this on the stack,	1031	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	1032	stack).
751		1033
		1034	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1035	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1036
752	Each watcher structure must be initialised by a call to C<ev_init	1037	Each watcher structure must be initialised by a call to C<ev_init (watcher
753	(watcher *, callback)>, which expects a callback to be provided. This	1038	*, callback)>, which expects a callback to be provided. This callback is
754	callback gets invoked each time the event occurs (or, in the case of I/O	1039	invoked each time the event occurs (or, in the case of I/O watchers, each
755	watchers, each time the event loop detects that the file descriptor given	1040	time the event loop detects that the file descriptor given is readable
756	is readable and/or writable).	1041	and/or writable).
757		1042
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1043	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
759	with arguments specific to this watcher type. There is also a macro	1044	macro to configure it, with arguments specific to the watcher type. There
760	to combine initialisation and setting in one call: C<< ev_<type>_init	1045	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	1046	ev_TYPE_init (watcher *, callback, ...) >>.
762		1047
763	To make the watcher actually watch out for events, you have to start it	1048	To make the watcher actually watch out for events, you have to start it
764	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1049	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
765	*) >>), and you can stop watching for events at any time by calling the	1050	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1051	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		1052
768	As long as your watcher is active (has been started but not stopped) you	1053	As long as your watcher is active (has been started but not stopped) you
769	must not touch the values stored in it. Most specifically you must never	1054	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	1055	reinitialise it or call its C<ev_TYPE_set> macro.
771		1056
772	Each and every callback receives the event loop pointer as first, the	1057	Each and every callback receives the event loop pointer as first, the
773	registered watcher structure as second, and a bitset of received events as	1058	registered watcher structure as second, and a bitset of received events as
774	third argument.	1059	third argument.
775		1060
…		…
784	=item C<EV_WRITE>	1069	=item C<EV_WRITE>
785		1070
786	The file descriptor in the C<ev_io> watcher has become readable and/or	1071	The file descriptor in the C<ev_io> watcher has become readable and/or
787	writable.	1072	writable.
788		1073
789	=item C<EV_TIMEOUT>	1074	=item C<EV_TIMER>
790		1075
791	The C<ev_timer> watcher has timed out.	1076	The C<ev_timer> watcher has timed out.
792		1077
793	=item C<EV_PERIODIC>	1078	=item C<EV_PERIODIC>
794		1079
…		…
812		1097
813	=item C<EV_PREPARE>	1098	=item C<EV_PREPARE>
814		1099
815	=item C<EV_CHECK>	1100	=item C<EV_CHECK>
816		1101
817	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1102	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
818	to gather new events, and all C<ev_check> watchers are invoked just after	1103	to gather new events, and all C<ev_check> watchers are invoked just after
819	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1104	C<ev_run> has gathered them, but before it invokes any callbacks for any
820	received events. Callbacks of both watcher types can start and stop as	1105	received events. Callbacks of both watcher types can start and stop as
821	many watchers as they want, and all of them will be taken into account	1106	many watchers as they want, and all of them will be taken into account
822	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1107	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
823	C<ev_loop> from blocking).	1108	C<ev_run> from blocking).
824		1109
825	=item C<EV_EMBED>	1110	=item C<EV_EMBED>
826		1111
827	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1112	The embedded event loop specified in the C<ev_embed> watcher needs attention.
828		1113
…		…
832	C<ev_fork>).	1117	C<ev_fork>).
833		1118
834	=item C<EV_ASYNC>	1119	=item C<EV_ASYNC>
835		1120
836	The given async watcher has been asynchronously notified (see C<ev_async>).	1121	The given async watcher has been asynchronously notified (see C<ev_async>).
		1122
		1123	=item C<EV_CUSTOM>
		1124
		1125	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1126	by libev users to signal watchers (e.g. via C<ev_feed_event>).
837		1127
838	=item C<EV_ERROR>	1128	=item C<EV_ERROR>
839		1129
840	An unspecified error has occurred, the watcher has been stopped. This might	1130	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	1131	happen because the watcher could not be properly started because libev
842	ran out of memory, a file descriptor was found to be closed or any other	1132	ran out of memory, a file descriptor was found to be closed or any other
		1133	problem. Libev considers these application bugs.
		1134
843	problem. You best act on it by reporting the problem and somehow coping	1135	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	1136	watcher being stopped. Note that well-written programs should not receive
		1137	an error ever, so when your watcher receives it, this usually indicates a
		1138	bug in your program.
845		1139
846	Libev will usually signal a few "dummy" events together with an error,	1140	Libev will usually signal a few "dummy" events together with an error, for
847	for example it might indicate that a fd is readable or writable, and if	1141	example it might indicate that a fd is readable or writable, and if your
848	your callbacks is well-written it can just attempt the operation and cope	1142	callbacks is well-written it can just attempt the operation and cope with
849	with the error from read() or write(). This will not work in multi-threaded	1143	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	1144	programs, though, as the fd could already be closed and reused for another
		1145	thing, so beware.
851		1146
852	=back	1147	=back
853		1148
		1149	=head2 WATCHER STATES
		1150
		1151	There are various watcher states mentioned throughout this manual -
		1152	active, pending and so on. In this section these states and the rules to
		1153	transition between them will be described in more detail - and while these
		1154	rules might look complicated, they usually do "the right thing".
		1155
		1156	=over 4
		1157
		1158	=item initialiased
		1159
		1160	Before a watcher can be registered with the event looop it has to be
		1161	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1162	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1163
		1164	In this state it is simply some block of memory that is suitable for use
		1165	in an event loop. It can be moved around, freed, reused etc. at will.
		1166
		1167	=item started/running/active
		1168
		1169	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1170	property of the event loop, and is actively waiting for events. While in
		1171	this state it cannot be accessed (except in a few documented ways), moved,
		1172	freed or anything else - the only legal thing is to keep a pointer to it,
		1173	and call libev functions on it that are documented to work on active watchers.
		1174
		1175	=item pending
		1176
		1177	If a watcher is active and libev determines that an event it is interested
		1178	in has occurred (such as a timer expiring), it will become pending. It will
		1179	stay in this pending state until either it is stopped or its callback is
		1180	about to be invoked, so it is not normally pending inside the watcher
		1181	callback.
		1182
		1183	The watcher might or might not be active while it is pending (for example,
		1184	an expired non-repeating timer can be pending but no longer active). If it
		1185	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1186	but it is still property of the event loop at this time, so cannot be
		1187	moved, freed or reused. And if it is active the rules described in the
		1188	previous item still apply.
		1189
		1190	It is also possible to feed an event on a watcher that is not active (e.g.
		1191	via C<ev_feed_event>), in which case it becomes pending without being
		1192	active.
		1193
		1194	=item stopped
		1195
		1196	A watcher can be stopped implicitly by libev (in which case it might still
		1197	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1198	latter will clear any pending state the watcher might be in, regardless
		1199	of whether it was active or not, so stopping a watcher explicitly before
		1200	freeing it is often a good idea.
		1201
		1202	While stopped (and not pending) the watcher is essentially in the
		1203	initialised state, that is it can be reused, moved, modified in any way
		1204	you wish.
		1205
		1206	=back
		1207
854	=head2 GENERIC WATCHER FUNCTIONS	1208	=head2 GENERIC WATCHER FUNCTIONS
855
856	In the following description, C<TYPE> stands for the watcher type,
857	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
858		1209
859	=over 4	1210	=over 4
860		1211
861	=item C<ev_init> (ev_TYPE *watcher, callback)	1212	=item C<ev_init> (ev_TYPE *watcher, callback)
862		1213
…		…
868	which rolls both calls into one.	1219	which rolls both calls into one.
869		1220
870	You can reinitialise a watcher at any time as long as it has been stopped	1221	You can reinitialise a watcher at any time as long as it has been stopped
871	(or never started) and there are no pending events outstanding.	1222	(or never started) and there are no pending events outstanding.
872		1223
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1224	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	1225	int revents)>.
875		1226
		1227	Example: Initialise an C<ev_io> watcher in two steps.
		1228
		1229	ev_io w;
		1230	ev_init (&w, my_cb);
		1231	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1232
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1233	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
877		1234
878	This macro initialises the type-specific parts of a watcher. You need to	1235	This macro initialises the type-specific parts of a watcher. You need to
879	call C<ev_init> at least once before you call this macro, but you can	1236	call C<ev_init> at least once before you call this macro, but you can
880	call C<ev_TYPE_set> any number of times. You must not, however, call this	1237	call C<ev_TYPE_set> any number of times. You must not, however, call this
881	macro on a watcher that is active (it can be pending, however, which is a	1238	macro on a watcher that is active (it can be pending, however, which is a
882	difference to the C<ev_init> macro).	1239	difference to the C<ev_init> macro).
883		1240
884	Although some watcher types do not have type-specific arguments	1241	Although some watcher types do not have type-specific arguments
885	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1242	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		1243
		1244	See C<ev_init>, above, for an example.
		1245
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1246	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		1247
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1248	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
890	calls into a single call. This is the most convenient method to initialise	1249	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	1250	a watcher. The same limitations apply, of course.
892		1251
		1252	Example: Initialise and set an C<ev_io> watcher in one step.
		1253
		1254	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1255
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1256	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
894		1257
895	Starts (activates) the given watcher. Only active watchers will receive	1258	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	1259	events. If the watcher is already active nothing will happen.
897		1260
		1261	Example: Start the C<ev_io> watcher that is being abused as example in this
		1262	whole section.
		1263
		1264	ev_io_start (EV_DEFAULT_UC, &w);
		1265
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1266	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
899		1267
900	Stops the given watcher again (if active) and clears the pending	1268	Stops the given watcher if active, and clears the pending status (whether
		1269	the watcher was active or not).
		1270
901	status. It is possible that stopped watchers are pending (for example,	1271	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1272	non-repeating timers are being stopped when they become pending - but
903	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1273	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
904	you want to free or reuse the memory used by the watcher it is therefore a	1274	pending. If you want to free or reuse the memory used by the watcher it is
905	good idea to always call its C<ev_TYPE_stop> function.	1275	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1276
907	=item bool ev_is_active (ev_TYPE *watcher)	1277	=item bool ev_is_active (ev_TYPE *watcher)
908		1278
909	Returns a true value iff the watcher is active (i.e. it has been started	1279	Returns a true value iff the watcher is active (i.e. it has been started
910	and not yet been stopped). As long as a watcher is active you must not modify	1280	and not yet been stopped). As long as a watcher is active you must not modify
…		…
926	=item ev_cb_set (ev_TYPE *watcher, callback)	1296	=item ev_cb_set (ev_TYPE *watcher, callback)
927		1297
928	Change the callback. You can change the callback at virtually any time	1298	Change the callback. You can change the callback at virtually any time
929	(modulo threads).	1299	(modulo threads).
930		1300
931	=item ev_set_priority (ev_TYPE *watcher, priority)	1301	=item ev_set_priority (ev_TYPE *watcher, int priority)
932		1302
933	=item int ev_priority (ev_TYPE *watcher)	1303	=item int ev_priority (ev_TYPE *watcher)
934		1304
935	Set and query the priority of the watcher. The priority is a small	1305	Set and query the priority of the watcher. The priority is a small
936	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1306	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
937	(default: C<-2>). Pending watchers with higher priority will be invoked	1307	(default: C<-2>). Pending watchers with higher priority will be invoked
938	before watchers with lower priority, but priority will not keep watchers	1308	before watchers with lower priority, but priority will not keep watchers
939	from being executed (except for C<ev_idle> watchers).	1309	from being executed (except for C<ev_idle> watchers).
940		1310
941	This means that priorities are I<only> used for ordering callback
942	invocation after new events have been received. This is useful, for
943	example, to reduce latency after idling, or more often, to bind two
944	watchers on the same event and make sure one is called first.
945
946	If you need to suppress invocation when higher priority events are pending	1311	If you need to suppress invocation when higher priority events are pending
947	you need to look at C<ev_idle> watchers, which provide this functionality.	1312	you need to look at C<ev_idle> watchers, which provide this functionality.
948		1313
949	You I<must not> change the priority of a watcher as long as it is active or	1314	You I<must not> change the priority of a watcher as long as it is active or
950	pending.	1315	pending.
951		1316
		1317	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1318	fine, as long as you do not mind that the priority value you query might
		1319	or might not have been clamped to the valid range.
		1320
952	The default priority used by watchers when no priority has been set is	1321	The default priority used by watchers when no priority has been set is
953	always C<0>, which is supposed to not be too high and not be too low :).	1322	always C<0>, which is supposed to not be too high and not be too low :).
954		1323
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1324	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
956	fine, as long as you do not mind that the priority value you query might	1325	priorities.
957	or might not have been adjusted to be within valid range.
958		1326
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1327	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1328
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1329	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
962	C<loop> nor C<revents> need to be valid as long as the watcher callback	1330	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1331	can deal with that fact, as both are simply passed through to the
		1332	callback.
964		1333
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1334	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1335
967	If the watcher is pending, this function returns clears its pending status	1336	If the watcher is pending, this function clears its pending status and
968	and returns its C<revents> bitset (as if its callback was invoked). If the	1337	returns its C<revents> bitset (as if its callback was invoked). If the
969	watcher isn't pending it does nothing and returns C<0>.	1338	watcher isn't pending it does nothing and returns C<0>.
970		1339
		1340	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1341	callback to be invoked, which can be accomplished with this function.
		1342
		1343	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1344
		1345	Feeds the given event set into the event loop, as if the specified event
		1346	had happened for the specified watcher (which must be a pointer to an
		1347	initialised but not necessarily started event watcher). Obviously you must
		1348	not free the watcher as long as it has pending events.
		1349
		1350	Stopping the watcher, letting libev invoke it, or calling
		1351	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1352	not started in the first place.
		1353
		1354	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1355	functions that do not need a watcher.
		1356
971	=back	1357	=back
972		1358
973		1359
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1360	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1361
976	Each watcher has, by default, a member C<void *data> that you can change	1362	Each watcher has, by default, a member C<void *data> that you can change
977	and read at any time, libev will completely ignore it. This can be used	1363	and read at any time: libev will completely ignore it. This can be used
978	to associate arbitrary data with your watcher. If you need more data and	1364	to associate arbitrary data with your watcher. If you need more data and
979	don't want to allocate memory and store a pointer to it in that data	1365	don't want to allocate memory and store a pointer to it in that data
980	member, you can also "subclass" the watcher type and provide your own	1366	member, you can also "subclass" the watcher type and provide your own
981	data:	1367	data:
982		1368
983	struct my_io	1369	struct my_io
984	{	1370	{
985	struct ev_io io;	1371	ev_io io;
986	int otherfd;	1372	int otherfd;
987	void *somedata;	1373	void *somedata;
988	struct whatever *mostinteresting;	1374	struct whatever *mostinteresting;
989	}	1375	};
		1376
		1377	...
		1378	struct my_io w;
		1379	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1380
991	And since your callback will be called with a pointer to the watcher, you	1381	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1382	can cast it back to your own type:
993		1383
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1384	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1385	{
996	struct my_io *w = (struct my_io *)w_;	1386	struct my_io *w = (struct my_io *)w_;
997	...	1387	...
998	}	1388	}
999		1389
1000	More interesting and less C-conformant ways of casting your callback type	1390	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1391	instead have been omitted.
1002		1392
1003	Another common scenario is having some data structure with multiple	1393	Another common scenario is to use some data structure with multiple
1004	watchers:	1394	embedded watchers:
1005		1395
1006	struct my_biggy	1396	struct my_biggy
1007	{	1397	{
1008	int some_data;	1398	int some_data;
1009	ev_timer t1;	1399	ev_timer t1;
1010	ev_timer t2;	1400	ev_timer t2;
1011	}	1401	}
1012		1402
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1403	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1404	complicated: Either you store the address of your C<my_biggy> struct
		1405	in the C<data> member of the watcher (for woozies), or you need to use
		1406	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1407	programmers):
1015		1408
1016	#include <stddef.h>	1409	#include <stddef.h>
1017		1410
1018	static void	1411	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1412	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1413	{
1021	struct my_biggy big = (struct my_biggy *	1414	struct my_biggy big = (struct my_biggy *)
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1415	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1416	}
1024		1417
1025	static void	1418	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1419	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1420	{
1028	struct my_biggy big = (struct my_biggy *	1421	struct my_biggy big = (struct my_biggy *)
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1422	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1423	}
		1424
		1425	=head2 WATCHER PRIORITY MODELS
		1426
		1427	Many event loops support I<watcher priorities>, which are usually small
		1428	integers that influence the ordering of event callback invocation
		1429	between watchers in some way, all else being equal.
		1430
		1431	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1432	description for the more technical details such as the actual priority
		1433	range.
		1434
		1435	There are two common ways how these these priorities are being interpreted
		1436	by event loops:
		1437
		1438	In the more common lock-out model, higher priorities "lock out" invocation
		1439	of lower priority watchers, which means as long as higher priority
		1440	watchers receive events, lower priority watchers are not being invoked.
		1441
		1442	The less common only-for-ordering model uses priorities solely to order
		1443	callback invocation within a single event loop iteration: Higher priority
		1444	watchers are invoked before lower priority ones, but they all get invoked
		1445	before polling for new events.
		1446
		1447	Libev uses the second (only-for-ordering) model for all its watchers
		1448	except for idle watchers (which use the lock-out model).
		1449
		1450	The rationale behind this is that implementing the lock-out model for
		1451	watchers is not well supported by most kernel interfaces, and most event
		1452	libraries will just poll for the same events again and again as long as
		1453	their callbacks have not been executed, which is very inefficient in the
		1454	common case of one high-priority watcher locking out a mass of lower
		1455	priority ones.
		1456
		1457	Static (ordering) priorities are most useful when you have two or more
		1458	watchers handling the same resource: a typical usage example is having an
		1459	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1460	timeouts. Under load, data might be received while the program handles
		1461	other jobs, but since timers normally get invoked first, the timeout
		1462	handler will be executed before checking for data. In that case, giving
		1463	the timer a lower priority than the I/O watcher ensures that I/O will be
		1464	handled first even under adverse conditions (which is usually, but not
		1465	always, what you want).
		1466
		1467	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1468	will only be executed when no same or higher priority watchers have
		1469	received events, they can be used to implement the "lock-out" model when
		1470	required.
		1471
		1472	For example, to emulate how many other event libraries handle priorities,
		1473	you can associate an C<ev_idle> watcher to each such watcher, and in
		1474	the normal watcher callback, you just start the idle watcher. The real
		1475	processing is done in the idle watcher callback. This causes libev to
		1476	continuously poll and process kernel event data for the watcher, but when
		1477	the lock-out case is known to be rare (which in turn is rare :), this is
		1478	workable.
		1479
		1480	Usually, however, the lock-out model implemented that way will perform
		1481	miserably under the type of load it was designed to handle. In that case,
		1482	it might be preferable to stop the real watcher before starting the
		1483	idle watcher, so the kernel will not have to process the event in case
		1484	the actual processing will be delayed for considerable time.
		1485
		1486	Here is an example of an I/O watcher that should run at a strictly lower
		1487	priority than the default, and which should only process data when no
		1488	other events are pending:
		1489
		1490	ev_idle idle; // actual processing watcher
		1491	ev_io io; // actual event watcher
		1492
		1493	static void
		1494	io_cb (EV_P_ ev_io *w, int revents)
		1495	{
		1496	// stop the I/O watcher, we received the event, but
		1497	// are not yet ready to handle it.
		1498	ev_io_stop (EV_A_ w);
		1499
		1500	// start the idle watcher to handle the actual event.
		1501	// it will not be executed as long as other watchers
		1502	// with the default priority are receiving events.
		1503	ev_idle_start (EV_A_ &idle);
		1504	}
		1505
		1506	static void
		1507	idle_cb (EV_P_ ev_idle *w, int revents)
		1508	{
		1509	// actual processing
		1510	read (STDIN_FILENO, ...);
		1511
		1512	// have to start the I/O watcher again, as
		1513	// we have handled the event
		1514	ev_io_start (EV_P_ &io);
		1515	}
		1516
		1517	// initialisation
		1518	ev_idle_init (&idle, idle_cb);
		1519	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1520	ev_io_start (EV_DEFAULT_ &io);
		1521
		1522	In the "real" world, it might also be beneficial to start a timer, so that
		1523	low-priority connections can not be locked out forever under load. This
		1524	enables your program to keep a lower latency for important connections
		1525	during short periods of high load, while not completely locking out less
		1526	important ones.
1031		1527
1032		1528
1033	=head1 WATCHER TYPES	1529	=head1 WATCHER TYPES
1034		1530
1035	This section describes each watcher in detail, but will not repeat	1531	This section describes each watcher in detail, but will not repeat
…		…
1059	In general you can register as many read and/or write event watchers per	1555	In general you can register as many read and/or write event watchers per
1060	fd as you want (as long as you don't confuse yourself). Setting all file	1556	fd as you want (as long as you don't confuse yourself). Setting all file
1061	descriptors to non-blocking mode is also usually a good idea (but not	1557	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1558	required if you know what you are doing).
1063		1559
1064	If you must do this, then force the use of a known-to-be-good backend	1560	If you cannot use non-blocking mode, then force the use of a
1065	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1561	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1562	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1563	descriptors for which non-blocking operation makes no sense (such as
		1564	files) - libev doesn't guarantee any specific behaviour in that case.
1067		1565
1068	Another thing you have to watch out for is that it is quite easy to	1566	Another thing you have to watch out for is that it is quite easy to
1069	receive "spurious" readiness notifications, that is your callback might	1567	receive "spurious" readiness notifications, that is your callback might
1070	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1568	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1071	because there is no data. Not only are some backends known to create a	1569	because there is no data. Not only are some backends known to create a
1072	lot of those (for example Solaris ports), it is very easy to get into	1570	lot of those (for example Solaris ports), it is very easy to get into
1073	this situation even with a relatively standard program structure. Thus	1571	this situation even with a relatively standard program structure. Thus
1074	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1572	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1075	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1573	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1574
1077	If you cannot run the fd in non-blocking mode (for example you should not	1575	If you cannot run the fd in non-blocking mode (for example you should
1078	play around with an Xlib connection), then you have to separately re-test	1576	not play around with an Xlib connection), then you have to separately
1079	whether a file descriptor is really ready with a known-to-be good interface	1577	re-test whether a file descriptor is really ready with a known-to-be good
1080	such as poll (fortunately in our Xlib example, Xlib already does this on	1578	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1579	does this on its own, so its quite safe to use). Some people additionally
		1580	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1581	indefinitely.
		1582
		1583	But really, best use non-blocking mode.
1082		1584
1083	=head3 The special problem of disappearing file descriptors	1585	=head3 The special problem of disappearing file descriptors
1084		1586
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1587	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1086	descriptor (either by calling C<close> explicitly or by any other means,	1588	descriptor (either due to calling C<close> explicitly or any other means,
1087	such as C<dup>). The reason is that you register interest in some file	1589	such as C<dup2>). The reason is that you register interest in some file
1088	descriptor, but when it goes away, the operating system will silently drop	1590	descriptor, but when it goes away, the operating system will silently drop
1089	this interest. If another file descriptor with the same number then is	1591	this interest. If another file descriptor with the same number then is
1090	registered with libev, there is no efficient way to see that this is, in	1592	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1593	fact, a different file descriptor.
1092		1594
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1625	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1626	C<EVBACKEND_POLL>.
1125		1627
1126	=head3 The special problem of SIGPIPE	1628	=head3 The special problem of SIGPIPE
1127		1629
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1630	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1129	when reading from a pipe whose other end has been closed, your program	1631	when writing to a pipe whose other end has been closed, your program gets
1130	gets send a SIGPIPE, which, by default, aborts your program. For most	1632	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1633	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1634
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1635	So when you encounter spurious, unexplained daemon exits, make sure you
1135	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1636	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1136	somewhere, as that would have given you a big clue).	1637	somewhere, as that would have given you a big clue).
1137		1638
		1639	=head3 The special problem of accept()ing when you can't
		1640
		1641	Many implementations of the POSIX C<accept> function (for example,
		1642	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1643	connection from the pending queue in all error cases.
		1644
		1645	For example, larger servers often run out of file descriptors (because
		1646	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1647	rejecting the connection, leading to libev signalling readiness on
		1648	the next iteration again (the connection still exists after all), and
		1649	typically causing the program to loop at 100% CPU usage.
		1650
		1651	Unfortunately, the set of errors that cause this issue differs between
		1652	operating systems, there is usually little the app can do to remedy the
		1653	situation, and no known thread-safe method of removing the connection to
		1654	cope with overload is known (to me).
		1655
		1656	One of the easiest ways to handle this situation is to just ignore it
		1657	- when the program encounters an overload, it will just loop until the
		1658	situation is over. While this is a form of busy waiting, no OS offers an
		1659	event-based way to handle this situation, so it's the best one can do.
		1660
		1661	A better way to handle the situation is to log any errors other than
		1662	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1663	messages, and continue as usual, which at least gives the user an idea of
		1664	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1665	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1666	usage.
		1667
		1668	If your program is single-threaded, then you could also keep a dummy file
		1669	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1670	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1671	close that fd, and create a new dummy fd. This will gracefully refuse
		1672	clients under typical overload conditions.
		1673
		1674	The last way to handle it is to simply log the error and C<exit>, as
		1675	is often done with C<malloc> failures, but this results in an easy
		1676	opportunity for a DoS attack.
1138		1677
1139	=head3 Watcher-Specific Functions	1678	=head3 Watcher-Specific Functions
1140		1679
1141	=over 4	1680	=over 4
1142		1681
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1682	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1683
1145	=item ev_io_set (ev_io *, int fd, int events)	1684	=item ev_io_set (ev_io *, int fd, int events)
1146		1685
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1686	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1148	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1687	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1149	C<EV_READ | EV_WRITE> to receive the given events.	1688	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1689
1151	=item int fd [read-only]	1690	=item int fd [read-only]
1152		1691
1153	The file descriptor being watched.	1692	The file descriptor being watched.
1154		1693
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1702	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1164	readable, but only once. Since it is likely line-buffered, you could	1703	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1704	attempt to read a whole line in the callback.
1166		1705
1167	static void	1706	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1707	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1708	{
1170	ev_io_stop (loop, w);	1709	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1710	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1711	}
1173		1712
1174	...	1713	...
1175	struct ev_loop *loop = ev_default_init (0);	1714	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1715	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1716	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1717	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1718	ev_run (loop, 0);
1180		1719
1181		1720
1182	=head2 C<ev_timer> - relative and optionally repeating timeouts	1721	=head2 C<ev_timer> - relative and optionally repeating timeouts
1183		1722
1184	Timer watchers are simple relative timers that generate an event after a	1723	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1724	given time, and optionally repeating in regular intervals after that.
1186		1725
1187	The timers are based on real time, that is, if you register an event that	1726	The timers are based on real time, that is, if you register an event that
1188	times out after an hour and you reset your system clock to January last	1727	times out after an hour and you reset your system clock to January last
1189	year, it will still time out after (roughly) and hour. "Roughly" because	1728	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1729	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1730	monotonic clock option helps a lot here).
		1731
		1732	The callback is guaranteed to be invoked only I<after> its timeout has
		1733	passed (not I<at>, so on systems with very low-resolution clocks this
		1734	might introduce a small delay). If multiple timers become ready during the
		1735	same loop iteration then the ones with earlier time-out values are invoked
		1736	before ones of the same priority with later time-out values (but this is
		1737	no longer true when a callback calls C<ev_run> recursively).
		1738
		1739	=head3 Be smart about timeouts
		1740
		1741	Many real-world problems involve some kind of timeout, usually for error
		1742	recovery. A typical example is an HTTP request - if the other side hangs,
		1743	you want to raise some error after a while.
		1744
		1745	What follows are some ways to handle this problem, from obvious and
		1746	inefficient to smart and efficient.
		1747
		1748	In the following, a 60 second activity timeout is assumed - a timeout that
		1749	gets reset to 60 seconds each time there is activity (e.g. each time some
		1750	data or other life sign was received).
		1751
		1752	=over 4
		1753
		1754	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1755
		1756	This is the most obvious, but not the most simple way: In the beginning,
		1757	start the watcher:
		1758
		1759	ev_timer_init (timer, callback, 60., 0.);
		1760	ev_timer_start (loop, timer);
		1761
		1762	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1763	and start it again:
		1764
		1765	ev_timer_stop (loop, timer);
		1766	ev_timer_set (timer, 60., 0.);
		1767	ev_timer_start (loop, timer);
		1768
		1769	This is relatively simple to implement, but means that each time there is
		1770	some activity, libev will first have to remove the timer from its internal
		1771	data structure and then add it again. Libev tries to be fast, but it's
		1772	still not a constant-time operation.
		1773
		1774	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1775
		1776	This is the easiest way, and involves using C<ev_timer_again> instead of
		1777	C<ev_timer_start>.
		1778
		1779	To implement this, configure an C<ev_timer> with a C<repeat> value
		1780	of C<60> and then call C<ev_timer_again> at start and each time you
		1781	successfully read or write some data. If you go into an idle state where
		1782	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1783	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1784
		1785	That means you can ignore both the C<ev_timer_start> function and the
		1786	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1787	member and C<ev_timer_again>.
		1788
		1789	At start:
		1790
		1791	ev_init (timer, callback);
		1792	timer->repeat = 60.;
		1793	ev_timer_again (loop, timer);
		1794
		1795	Each time there is some activity:
		1796
		1797	ev_timer_again (loop, timer);
		1798
		1799	It is even possible to change the time-out on the fly, regardless of
		1800	whether the watcher is active or not:
		1801
		1802	timer->repeat = 30.;
		1803	ev_timer_again (loop, timer);
		1804
		1805	This is slightly more efficient then stopping/starting the timer each time
		1806	you want to modify its timeout value, as libev does not have to completely
		1807	remove and re-insert the timer from/into its internal data structure.
		1808
		1809	It is, however, even simpler than the "obvious" way to do it.
		1810
		1811	=item 3. Let the timer time out, but then re-arm it as required.
		1812
		1813	This method is more tricky, but usually most efficient: Most timeouts are
		1814	relatively long compared to the intervals between other activity - in
		1815	our example, within 60 seconds, there are usually many I/O events with
		1816	associated activity resets.
		1817
		1818	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1819	but remember the time of last activity, and check for a real timeout only
		1820	within the callback:
		1821
		1822	ev_tstamp last_activity; // time of last activity
		1823
		1824	static void
		1825	callback (EV_P_ ev_timer *w, int revents)
		1826	{
		1827	ev_tstamp now = ev_now (EV_A);
		1828	ev_tstamp timeout = last_activity + 60.;
		1829
		1830	// if last_activity + 60. is older than now, we did time out
		1831	if (timeout < now)
		1832	{
		1833	// timeout occurred, take action
		1834	}
		1835	else
		1836	{
		1837	// callback was invoked, but there was some activity, re-arm
		1838	// the watcher to fire in last_activity + 60, which is
		1839	// guaranteed to be in the future, so "again" is positive:
		1840	w->repeat = timeout - now;
		1841	ev_timer_again (EV_A_ w);
		1842	}
		1843	}
		1844
		1845	To summarise the callback: first calculate the real timeout (defined
		1846	as "60 seconds after the last activity"), then check if that time has
		1847	been reached, which means something I<did>, in fact, time out. Otherwise
		1848	the callback was invoked too early (C<timeout> is in the future), so
		1849	re-schedule the timer to fire at that future time, to see if maybe we have
		1850	a timeout then.
		1851
		1852	Note how C<ev_timer_again> is used, taking advantage of the
		1853	C<ev_timer_again> optimisation when the timer is already running.
		1854
		1855	This scheme causes more callback invocations (about one every 60 seconds
		1856	minus half the average time between activity), but virtually no calls to
		1857	libev to change the timeout.
		1858
		1859	To start the timer, simply initialise the watcher and set C<last_activity>
		1860	to the current time (meaning we just have some activity :), then call the
		1861	callback, which will "do the right thing" and start the timer:
		1862
		1863	ev_init (timer, callback);
		1864	last_activity = ev_now (loop);
		1865	callback (loop, timer, EV_TIMER);
		1866
		1867	And when there is some activity, simply store the current time in
		1868	C<last_activity>, no libev calls at all:
		1869
		1870	last_activity = ev_now (loop);
		1871
		1872	This technique is slightly more complex, but in most cases where the
		1873	time-out is unlikely to be triggered, much more efficient.
		1874
		1875	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1876	callback :) - just change the timeout and invoke the callback, which will
		1877	fix things for you.
		1878
		1879	=item 4. Wee, just use a double-linked list for your timeouts.
		1880
		1881	If there is not one request, but many thousands (millions...), all
		1882	employing some kind of timeout with the same timeout value, then one can
		1883	do even better:
		1884
		1885	When starting the timeout, calculate the timeout value and put the timeout
		1886	at the I<end> of the list.
		1887
		1888	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1889	the list is expected to fire (for example, using the technique #3).
		1890
		1891	When there is some activity, remove the timer from the list, recalculate
		1892	the timeout, append it to the end of the list again, and make sure to
		1893	update the C<ev_timer> if it was taken from the beginning of the list.
		1894
		1895	This way, one can manage an unlimited number of timeouts in O(1) time for
		1896	starting, stopping and updating the timers, at the expense of a major
		1897	complication, and having to use a constant timeout. The constant timeout
		1898	ensures that the list stays sorted.
		1899
		1900	=back
		1901
		1902	So which method the best?
		1903
		1904	Method #2 is a simple no-brain-required solution that is adequate in most
		1905	situations. Method #3 requires a bit more thinking, but handles many cases
		1906	better, and isn't very complicated either. In most case, choosing either
		1907	one is fine, with #3 being better in typical situations.
		1908
		1909	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1910	rather complicated, but extremely efficient, something that really pays
		1911	off after the first million or so of active timers, i.e. it's usually
		1912	overkill :)
		1913
		1914	=head3 The special problem of time updates
		1915
		1916	Establishing the current time is a costly operation (it usually takes at
		1917	least two system calls): EV therefore updates its idea of the current
		1918	time only before and after C<ev_run> collects new events, which causes a
		1919	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1920	lots of events in one iteration.
1192		1921
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1922	The relative timeouts are calculated relative to the C<ev_now ()>
1194	time. This is usually the right thing as this timestamp refers to the time	1923	time. This is usually the right thing as this timestamp refers to the time
1195	of the event triggering whatever timeout you are modifying/starting. If	1924	of the event triggering whatever timeout you are modifying/starting. If
1196	you suspect event processing to be delayed and you I<need> to base the timeout	1925	you suspect event processing to be delayed and you I<need> to base the
1197	on the current time, use something like this to adjust for this:	1926	timeout on the current time, use something like this to adjust for this:
1198		1927
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1928	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1929
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1930	If the event loop is suspended for a long time, you can also force an
1202	but if multiple timers become ready during the same loop iteration then	1931	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1932	()>.
		1933
		1934	=head3 The special problems of suspended animation
		1935
		1936	When you leave the server world it is quite customary to hit machines that
		1937	can suspend/hibernate - what happens to the clocks during such a suspend?
		1938
		1939	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1940	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1941	to run until the system is suspended, but they will not advance while the
		1942	system is suspended. That means, on resume, it will be as if the program
		1943	was frozen for a few seconds, but the suspend time will not be counted
		1944	towards C<ev_timer> when a monotonic clock source is used. The real time
		1945	clock advanced as expected, but if it is used as sole clocksource, then a
		1946	long suspend would be detected as a time jump by libev, and timers would
		1947	be adjusted accordingly.
		1948
		1949	I would not be surprised to see different behaviour in different between
		1950	operating systems, OS versions or even different hardware.
		1951
		1952	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1953	time jump in the monotonic clocks and the realtime clock. If the program
		1954	is suspended for a very long time, and monotonic clock sources are in use,
		1955	then you can expect C<ev_timer>s to expire as the full suspension time
		1956	will be counted towards the timers. When no monotonic clock source is in
		1957	use, then libev will again assume a timejump and adjust accordingly.
		1958
		1959	It might be beneficial for this latter case to call C<ev_suspend>
		1960	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1961	deterministic behaviour in this case (you can do nothing against
		1962	C<SIGSTOP>).
1204		1963
1205	=head3 Watcher-Specific Functions and Data Members	1964	=head3 Watcher-Specific Functions and Data Members
1206		1965
1207	=over 4	1966	=over 4
1208		1967
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1991	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1992
1234	If the timer is repeating, either start it if necessary (with the	1993	If the timer is repeating, either start it if necessary (with the
1235	C<repeat> value), or reset the running timer to the C<repeat> value.	1994	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1995
1237	This sounds a bit complicated, but here is a useful and typical	1996	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1238	example: Imagine you have a TCP connection and you want a so-called idle	1997	usage example.
1239	timeout, that is, you want to be called when there have been, say, 60
1240	seconds of inactivity on the socket. The easiest way to do this is to
1241	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1242	C<ev_timer_again> each time you successfully read or write some data. If
1243	you go into an idle state where you do not expect data to travel on the
1244	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1245	automatically restart it if need be.
1246		1998
1247	That means you can ignore the C<after> value and C<ev_timer_start>	1999	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1248	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1249		2000
1250	ev_timer_init (timer, callback, 0., 5.);	2001	Returns the remaining time until a timer fires. If the timer is active,
1251	ev_timer_again (loop, timer);	2002	then this time is relative to the current event loop time, otherwise it's
1252	...	2003	the timeout value currently configured.
1253	timer->again = 17.;
1254	ev_timer_again (loop, timer);
1255	...
1256	timer->again = 10.;
1257	ev_timer_again (loop, timer);
1258		2004
1259	This is more slightly efficient then stopping/starting the timer each time	2005	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1260	you want to modify its timeout value.	2006	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2007	will return C<4>. When the timer expires and is restarted, it will return
		2008	roughly C<7> (likely slightly less as callback invocation takes some time,
		2009	too), and so on.
1261		2010
1262	=item ev_tstamp repeat [read-write]	2011	=item ev_tstamp repeat [read-write]
1263		2012
1264	The current C<repeat> value. Will be used each time the watcher times out	2013	The current C<repeat> value. Will be used each time the watcher times out
1265	or C<ev_timer_again> is called and determines the next timeout (if any),	2014	or C<ev_timer_again> is called, and determines the next timeout (if any),
1266	which is also when any modifications are taken into account.	2015	which is also when any modifications are taken into account.
1267		2016
1268	=back	2017	=back
1269		2018
1270	=head3 Examples	2019	=head3 Examples
1271		2020
1272	Example: Create a timer that fires after 60 seconds.	2021	Example: Create a timer that fires after 60 seconds.
1273		2022
1274	static void	2023	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2024	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	2025	{
1277	.. one minute over, w is actually stopped right here	2026	.. one minute over, w is actually stopped right here
1278	}	2027	}
1279		2028
1280	struct ev_timer mytimer;	2029	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2030	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	2031	ev_timer_start (loop, &mytimer);
1283		2032
1284	Example: Create a timeout timer that times out after 10 seconds of	2033	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	2034	inactivity.
1286		2035
1287	static void	2036	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2037	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	2038	{
1290	.. ten seconds without any activity	2039	.. ten seconds without any activity
1291	}	2040	}
1292		2041
1293	struct ev_timer mytimer;	2042	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2043	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	2044	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	2045	ev_run (loop, 0);
1297		2046
1298	// and in some piece of code that gets executed on any "activity":	2047	// and in some piece of code that gets executed on any "activity":
1299	// reset the timeout to start ticking again at 10 seconds	2048	// reset the timeout to start ticking again at 10 seconds
1300	ev_timer_again (&mytimer);	2049	ev_timer_again (&mytimer);
1301		2050
…		…
1303	=head2 C<ev_periodic> - to cron or not to cron?	2052	=head2 C<ev_periodic> - to cron or not to cron?
1304		2053
1305	Periodic watchers are also timers of a kind, but they are very versatile	2054	Periodic watchers are also timers of a kind, but they are very versatile
1306	(and unfortunately a bit complex).	2055	(and unfortunately a bit complex).
1307		2056
1308	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2057	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1309	but on wall clock time (absolute time). You can tell a periodic watcher	2058	relative time, the physical time that passes) but on wall clock time
1310	to trigger after some specific point in time. For example, if you tell a	2059	(absolute time, the thing you can read on your calender or clock). The
1311	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2060	difference is that wall clock time can run faster or slower than real
1312	+ 10.>, that is, an absolute time not a delay) and then reset your system	2061	time, and time jumps are not uncommon (e.g. when you adjust your
1313	clock to January of the previous year, then it will take more than year	2062	wrist-watch).
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).
1316		2063
		2064	You can tell a periodic watcher to trigger after some specific point
		2065	in time: for example, if you tell a periodic watcher to trigger "in 10
		2066	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2067	not a delay) and then reset your system clock to January of the previous
		2068	year, then it will take a year or more to trigger the event (unlike an
		2069	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2070	it, as it uses a relative timeout).
		2071
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	2072	C<ev_periodic> watchers can also be used to implement vastly more complex
1318	such as triggering an event on each "midnight, local time", or other	2073	timers, such as triggering an event on each "midnight, local time", or
1319	complicated, rules.	2074	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2075	those cannot react to time jumps.
1320		2076
1321	As with timers, the callback is guaranteed to be invoked only when the	2077	As with timers, the callback is guaranteed to be invoked only when the
1322	time (C<at>) has passed, but if multiple periodic timers become ready	2078	point in time where it is supposed to trigger has passed. If multiple
1323	during the same loop iteration then order of execution is undefined.	2079	timers become ready during the same loop iteration then the ones with
		2080	earlier time-out values are invoked before ones with later time-out values
		2081	(but this is no longer true when a callback calls C<ev_run> recursively).
1324		2082
1325	=head3 Watcher-Specific Functions and Data Members	2083	=head3 Watcher-Specific Functions and Data Members
1326		2084
1327	=over 4	2085	=over 4
1328		2086
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2087	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1330		2088
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2089	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1332		2090
1333	Lots of arguments, lets sort it out... There are basically three modes of	2091	Lots of arguments, let's sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	2092	operation, and we will explain them from simplest to most complex:
1335		2093
1336	=over 4	2094	=over 4
1337		2095
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2096	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1339		2097
1340	In this configuration the watcher triggers an event after the wall clock	2098	In this configuration the watcher triggers an event after the wall clock
1341	time C<at> has passed and doesn't repeat. It will not adjust when a time	2099	time C<offset> has passed. It will not repeat and will not adjust when a
1342	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2100	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1343	run when the system time reaches or surpasses this time.	2101	will be stopped and invoked when the system clock reaches or surpasses
		2102	this point in time.
1344		2103
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2104	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1346		2105
1347	In this mode the watcher will always be scheduled to time out at the next	2106	In this mode the watcher will always be scheduled to time out at the next
1348	C<at + N * interval> time (for some integer N, which can also be negative)	2107	C<offset + N * interval> time (for some integer N, which can also be
1349	and then repeat, regardless of any time jumps.	2108	negative) and then repeat, regardless of any time jumps. The C<offset>
		2109	argument is merely an offset into the C<interval> periods.
1350		2110
1351	This can be used to create timers that do not drift with respect to system	2111	This can be used to create timers that do not drift with respect to the
1352	time, for example, here is a C<ev_periodic> that triggers each hour, on	2112	system clock, for example, here is an C<ev_periodic> that triggers each
1353	the hour:	2113	hour, on the hour (with respect to UTC):
1354		2114
1355	ev_periodic_set (&periodic, 0., 3600., 0);	2115	ev_periodic_set (&periodic, 0., 3600., 0);
1356		2116
1357	This doesn't mean there will always be 3600 seconds in between triggers,	2117	This doesn't mean there will always be 3600 seconds in between triggers,
1358	but only that the callback will be called when the system time shows a	2118	but only that the callback will be called when the system time shows a
1359	full hour (UTC), or more correctly, when the system time is evenly divisible	2119	full hour (UTC), or more correctly, when the system time is evenly divisible
1360	by 3600.	2120	by 3600.
1361		2121
1362	Another way to think about it (for the mathematically inclined) is that	2122	Another way to think about it (for the mathematically inclined) is that
1363	C<ev_periodic> will try to run the callback in this mode at the next possible	2123	C<ev_periodic> will try to run the callback in this mode at the next possible
1364	time where C<time = at (mod interval)>, regardless of any time jumps.	2124	time where C<time = offset (mod interval)>, regardless of any time jumps.
1365		2125
1366	For numerical stability it is preferable that the C<at> value is near	2126	For numerical stability it is preferable that the C<offset> value is near
1367	C<ev_now ()> (the current time), but there is no range requirement for	2127	C<ev_now ()> (the current time), but there is no range requirement for
1368	this value, and in fact is often specified as zero.	2128	this value, and in fact is often specified as zero.
1369		2129
1370	Note also that there is an upper limit to how often a timer can fire (CPU	2130	Note also that there is an upper limit to how often a timer can fire (CPU
1371	speed for example), so if C<interval> is very small then timing stability	2131	speed for example), so if C<interval> is very small then timing stability
1372	will of course deteriorate. Libev itself tries to be exact to be about one	2132	will of course deteriorate. Libev itself tries to be exact to be about one
1373	millisecond (if the OS supports it and the machine is fast enough).	2133	millisecond (if the OS supports it and the machine is fast enough).
1374		2134
1375	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2135	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1376		2136
1377	In this mode the values for C<interval> and C<at> are both being	2137	In this mode the values for C<interval> and C<offset> are both being
1378	ignored. Instead, each time the periodic watcher gets scheduled, the	2138	ignored. Instead, each time the periodic watcher gets scheduled, the
1379	reschedule callback will be called with the watcher as first, and the	2139	reschedule callback will be called with the watcher as first, and the
1380	current time as second argument.	2140	current time as second argument.
1381		2141
1382	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2142	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1383	ever, or make ANY event loop modifications whatsoever>.	2143	or make ANY other event loop modifications whatsoever, unless explicitly
		2144	allowed by documentation here>.
1384		2145
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2146	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1386	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2147	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	2148	only event loop modification you are allowed to do).
1388		2149
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2150	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	2151	*w, ev_tstamp now)>, e.g.:
1391		2152
		2153	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2154	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	2155	{
1394	return now + 60.;	2156	return now + 60.;
1395	}	2157	}
1396		2158
1397	It must return the next time to trigger, based on the passed time value	2159	It must return the next time to trigger, based on the passed time value
…		…
1417	a different time than the last time it was called (e.g. in a crond like	2179	a different time than the last time it was called (e.g. in a crond like
1418	program when the crontabs have changed).	2180	program when the crontabs have changed).
1419		2181
1420	=item ev_tstamp ev_periodic_at (ev_periodic *)	2182	=item ev_tstamp ev_periodic_at (ev_periodic *)
1421		2183
1422	When active, returns the absolute time that the watcher is supposed to	2184	When active, returns the absolute time that the watcher is supposed
1423	trigger next.	2185	to trigger next. This is not the same as the C<offset> argument to
		2186	C<ev_periodic_set>, but indeed works even in interval and manual
		2187	rescheduling modes.
1424		2188
1425	=item ev_tstamp offset [read-write]	2189	=item ev_tstamp offset [read-write]
1426		2190
1427	When repeating, this contains the offset value, otherwise this is the	2191	When repeating, this contains the offset value, otherwise this is the
1428	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2192	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2193	although libev might modify this value for better numerical stability).
1429		2194
1430	Can be modified any time, but changes only take effect when the periodic	2195	Can be modified any time, but changes only take effect when the periodic
1431	timer fires or C<ev_periodic_again> is being called.	2196	timer fires or C<ev_periodic_again> is being called.
1432		2197
1433	=item ev_tstamp interval [read-write]	2198	=item ev_tstamp interval [read-write]
1434		2199
1435	The current interval value. Can be modified any time, but changes only	2200	The current interval value. Can be modified any time, but changes only
1436	take effect when the periodic timer fires or C<ev_periodic_again> is being	2201	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	2202	called.
1438		2203
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2204	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		2205
1441	The current reschedule callback, or C<0>, if this functionality is	2206	The current reschedule callback, or C<0>, if this functionality is
1442	switched off. Can be changed any time, but changes only take effect when	2207	switched off. Can be changed any time, but changes only take effect when
1443	the periodic timer fires or C<ev_periodic_again> is being called.	2208	the periodic timer fires or C<ev_periodic_again> is being called.
1444		2209
1445	=back	2210	=back
1446		2211
1447	=head3 Examples	2212	=head3 Examples
1448		2213
1449	Example: Call a callback every hour, or, more precisely, whenever the	2214	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	2215	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	2216	potentially a lot of jitter, but good long-term stability.
1452		2217
1453	static void	2218	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2219	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1455	{	2220	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	2221	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	2222	}
1458		2223
1459	struct ev_periodic hourly_tick;	2224	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2225	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	2226	ev_periodic_start (loop, &hourly_tick);
1462		2227
1463	Example: The same as above, but use a reschedule callback to do it:	2228	Example: The same as above, but use a reschedule callback to do it:
1464		2229
1465	#include <math.h>	2230	#include <math.h>
1466		2231
1467	static ev_tstamp	2232	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2233	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	2234	{
1470	return fmod (now, 3600.) + 3600.;	2235	return now + (3600. - fmod (now, 3600.));
1471	}	2236	}
1472		2237
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2238	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		2239
1475	Example: Call a callback every hour, starting now:	2240	Example: Call a callback every hour, starting now:
1476		2241
1477	struct ev_periodic hourly_tick;	2242	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	2243	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	2244	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	2245	ev_periodic_start (loop, &hourly_tick);
1481		2246
1482		2247
…		…
1485	Signal watchers will trigger an event when the process receives a specific	2250	Signal watchers will trigger an event when the process receives a specific
1486	signal one or more times. Even though signals are very asynchronous, libev	2251	signal one or more times. Even though signals are very asynchronous, libev
1487	will try it's best to deliver signals synchronously, i.e. as part of the	2252	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	2253	normal event processing, like any other event.
1489		2254
		2255	If you want signals to be delivered truly asynchronously, just use
		2256	C<sigaction> as you would do without libev and forget about sharing
		2257	the signal. You can even use C<ev_async> from a signal handler to
		2258	synchronously wake up an event loop.
		2259
1490	You can configure as many watchers as you like per signal. Only when the	2260	You can configure as many watchers as you like for the same signal, but
		2261	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2262	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2263	C<SIGINT> in both the default loop and another loop at the same time. At
		2264	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2265
1491	first watcher gets started will libev actually register a signal watcher	2266	When the first watcher gets started will libev actually register something
1492	with the kernel (thus it coexists with your own signal handlers as long	2267	with the kernel (thus it coexists with your own signal handlers as long as
1493	as you don't register any with libev). Similarly, when the last signal	2268	you don't register any with libev for the same signal).
1494	watcher for a signal is stopped libev will reset the signal handler to
1495	SIG_DFL (regardless of what it was set to before).
1496		2269
1497	If possible and supported, libev will install its handlers with	2270	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2271	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1499	interrupted. If you have a problem with system calls getting interrupted by	2272	not be unduly interrupted. If you have a problem with system calls getting
1500	signals you can block all signals in an C<ev_check> watcher and unblock	2273	interrupted by signals you can block all signals in an C<ev_check> watcher
1501	them in an C<ev_prepare> watcher.	2274	and unblock them in an C<ev_prepare> watcher.
		2275
		2276	=head3 The special problem of inheritance over fork/execve/pthread_create
		2277
		2278	Both the signal mask (C<sigprocmask>) and the signal disposition
		2279	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2280	stopping it again), that is, libev might or might not block the signal,
		2281	and might or might not set or restore the installed signal handler.
		2282
		2283	While this does not matter for the signal disposition (libev never
		2284	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2285	C<execve>), this matters for the signal mask: many programs do not expect
		2286	certain signals to be blocked.
		2287
		2288	This means that before calling C<exec> (from the child) you should reset
		2289	the signal mask to whatever "default" you expect (all clear is a good
		2290	choice usually).
		2291
		2292	The simplest way to ensure that the signal mask is reset in the child is
		2293	to install a fork handler with C<pthread_atfork> that resets it. That will
		2294	catch fork calls done by libraries (such as the libc) as well.
		2295
		2296	In current versions of libev, the signal will not be blocked indefinitely
		2297	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2298	the window of opportunity for problems, it will not go away, as libev
		2299	I<has> to modify the signal mask, at least temporarily.
		2300
		2301	So I can't stress this enough: I<If you do not reset your signal mask when
		2302	you expect it to be empty, you have a race condition in your code>. This
		2303	is not a libev-specific thing, this is true for most event libraries.
1502		2304
1503	=head3 Watcher-Specific Functions and Data Members	2305	=head3 Watcher-Specific Functions and Data Members
1504		2306
1505	=over 4	2307	=over 4
1506		2308
…		…
1517		2319
1518	=back	2320	=back
1519		2321
1520	=head3 Examples	2322	=head3 Examples
1521		2323
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	2324	Example: Try to exit cleanly on SIGINT.
1523		2325
1524	static void	2326	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2327	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	2328	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	2329	ev_break (loop, EVBREAK_ALL);
1528	}	2330	}
1529		2331
1530	struct ev_signal signal_watcher;	2332	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2333	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	2334	ev_signal_start (loop, &signal_watcher);
1533		2335
1534		2336
1535	=head2 C<ev_child> - watch out for process status changes	2337	=head2 C<ev_child> - watch out for process status changes
1536		2338
1537	Child watchers trigger when your process receives a SIGCHLD in response to	2339	Child watchers trigger when your process receives a SIGCHLD in response to
1538	some child status changes (most typically when a child of yours dies). It	2340	some child status changes (most typically when a child of yours dies or
1539	is permissible to install a child watcher I<after> the child has been	2341	exits). It is permissible to install a child watcher I<after> the child
1540	forked (which implies it might have already exited), as long as the event	2342	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	2343	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2344	forking and then immediately registering a watcher for the child is fine,
		2345	but forking and registering a watcher a few event loop iterations later or
		2346	in the next callback invocation is not.
1542		2347
1543	Only the default event loop is capable of handling signals, and therefore	2348	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	2349	you can only register child watchers in the default event loop.
1545		2350
		2351	Due to some design glitches inside libev, child watchers will always be
		2352	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2353	libev)
		2354
1546	=head3 Process Interaction	2355	=head3 Process Interaction
1547		2356
1548	Libev grabs C<SIGCHLD> as soon as the default event loop is	2357	Libev grabs C<SIGCHLD> as soon as the default event loop is
1549	initialised. This is necessary to guarantee proper behaviour even if	2358	initialised. This is necessary to guarantee proper behaviour even if the
1550	the first child watcher is started after the child exits. The occurrence	2359	first child watcher is started after the child exits. The occurrence
1551	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2360	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1552	synchronously as part of the event loop processing. Libev always reaps all	2361	synchronously as part of the event loop processing. Libev always reaps all
1553	children, even ones not watched.	2362	children, even ones not watched.
1554		2363
1555	=head3 Overriding the Built-In Processing	2364	=head3 Overriding the Built-In Processing
…		…
1559	handler, you can override it easily by installing your own handler for	2368	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	2369	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	2370	default loop never gets destroyed. You are encouraged, however, to use an
1562	event-based approach to child reaping and thus use libev's support for	2371	event-based approach to child reaping and thus use libev's support for
1563	that, so other libev users can use C<ev_child> watchers freely.	2372	that, so other libev users can use C<ev_child> watchers freely.
		2373
		2374	=head3 Stopping the Child Watcher
		2375
		2376	Currently, the child watcher never gets stopped, even when the
		2377	child terminates, so normally one needs to stop the watcher in the
		2378	callback. Future versions of libev might stop the watcher automatically
		2379	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2380	problem).
1564		2381
1565	=head3 Watcher-Specific Functions and Data Members	2382	=head3 Watcher-Specific Functions and Data Members
1566		2383
1567	=over 4	2384	=over 4
1568		2385
…		…
1600	its completion.	2417	its completion.
1601		2418
1602	ev_child cw;	2419	ev_child cw;
1603		2420
1604	static void	2421	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	2422	child_cb (EV_P_ ev_child *w, int revents)
1606	{	2423	{
1607	ev_child_stop (EV_A_ w);	2424	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2425	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	2426	}
1610		2427
…		…
1625		2442
1626		2443
1627	=head2 C<ev_stat> - did the file attributes just change?	2444	=head2 C<ev_stat> - did the file attributes just change?
1628		2445
1629	This watches a file system path for attribute changes. That is, it calls	2446	This watches a file system path for attribute changes. That is, it calls
1630	C<stat> regularly (or when the OS says it changed) and sees if it changed	2447	C<stat> on that path in regular intervals (or when the OS says it changed)
1631	compared to the last time, invoking the callback if it did.	2448	and sees if it changed compared to the last time, invoking the callback if
		2449	it did.
1632		2450
1633	The path does not need to exist: changing from "path exists" to "path does	2451	The path does not need to exist: changing from "path exists" to "path does
1634	not exist" is a status change like any other. The condition "path does	2452	not exist" is a status change like any other. The condition "path does not
1635	not exist" is signified by the C<st_nlink> field being zero (which is	2453	exist" (or more correctly "path cannot be stat'ed") is signified by the
1636	otherwise always forced to be at least one) and all the other fields of	2454	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	2455	least one) and all the other fields of the stat buffer having unspecified
		2456	contents.
1638		2457
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	2458	The path I<must not> end in a slash or contain special components such as
		2459	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1640	relative and your working directory changes, the behaviour is undefined.	2460	your working directory changes, then the behaviour is undefined.
1641		2461
1642	Since there is no standard to do this, the portable implementation simply	2462	Since there is no portable change notification interface available, the
1643	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2463	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	2464	to see if it changed somehow. You can specify a recommended polling
1645	a polling interval of C<0> (highly recommended!) then a I<suitable,	2465	interval for this case. If you specify a polling interval of C<0> (highly
1646	unspecified default> value will be used (which you can expect to be around	2466	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	2467	(which you can expect to be around five seconds, although this might
1648	impose a minimum interval which is currently around C<0.1>, but thats	2468	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	2469	currently around C<0.1>, but that's usually overkill.
1650		2470
1651	This watcher type is not meant for massive numbers of stat watchers,	2471	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	2472	as even with OS-supported change notifications, this can be
1653	resource-intensive.	2473	resource-intensive.
1654		2474
1655	At the time of this writing, only the Linux inotify interface is	2475	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	2476	is the Linux inotify interface (implementing kqueue support is left as an
1657	reader, note, however, that the author sees no way of implementing ev_stat	2477	exercise for the reader. Note, however, that the author sees no way of
1658	semantics with kqueue). Inotify will be used to give hints only and should	2478	implementing C<ev_stat> semantics with kqueue, except as a hint).
1659	not change the semantics of C<ev_stat> watchers, which means that libev
1660	sometimes needs to fall back to regular polling again even with inotify,
1661	but changes are usually detected immediately, and if the file exists there
1662	will be no polling.
1663		2479
1664	=head3 ABI Issues (Largefile Support)	2480	=head3 ABI Issues (Largefile Support)
1665		2481
1666	Libev by default (unless the user overrides this) uses the default	2482	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with optionally	2483	compilation environment, which means that on systems with large file
1668	disabled large file support, you get the 32 bit version of the stat	2484	support disabled by default, you get the 32 bit version of the stat
1669	structure. When using the library from programs that change the ABI to	2485	structure. When using the library from programs that change the ABI to
1670	use 64 bit file offsets the programs will fail. In that case you have to	2486	use 64 bit file offsets the programs will fail. In that case you have to
1671	compile libev with the same flags to get binary compatibility. This is	2487	compile libev with the same flags to get binary compatibility. This is
1672	obviously the case with any flags that change the ABI, but the problem is	2488	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably with ev_stat and large file support.	2489	most noticeably displayed with ev_stat and large file support.
1674		2490
1675	=head3 Inotify	2491	The solution for this is to lobby your distribution maker to make large
		2492	file interfaces available by default (as e.g. FreeBSD does) and not
		2493	optional. Libev cannot simply switch on large file support because it has
		2494	to exchange stat structures with application programs compiled using the
		2495	default compilation environment.
1676		2496
		2497	=head3 Inotify and Kqueue
		2498
1677	When C<inotify (7)> support has been compiled into libev (generally only	2499	When C<inotify (7)> support has been compiled into libev and present at
1678	available on Linux) and present at runtime, it will be used to speed up	2500	runtime, it will be used to speed up change detection where possible. The
1679	change detection where possible. The inotify descriptor will be created lazily	2501	inotify descriptor will be created lazily when the first C<ev_stat>
1680	when the first C<ev_stat> watcher is being started.	2502	watcher is being started.
1681		2503
1682	Inotify presence does not change the semantics of C<ev_stat> watchers	2504	Inotify presence does not change the semantics of C<ev_stat> watchers
1683	except that changes might be detected earlier, and in some cases, to avoid	2505	except that changes might be detected earlier, and in some cases, to avoid
1684	making regular C<stat> calls. Even in the presence of inotify support	2506	making regular C<stat> calls. Even in the presence of inotify support
1685	there are many cases where libev has to resort to regular C<stat> polling.	2507	there are many cases where libev has to resort to regular C<stat> polling,
		2508	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2509	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2510	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2511	xfs are fully working) libev usually gets away without polling.
1686		2512
1687	(There is no support for kqueue, as apparently it cannot be used to	2513	There is no support for kqueue, as apparently it cannot be used to
1688	implement this functionality, due to the requirement of having a file	2514	implement this functionality, due to the requirement of having a file
1689	descriptor open on the object at all times).	2515	descriptor open on the object at all times, and detecting renames, unlinks
		2516	etc. is difficult.
		2517
		2518	=head3 C<stat ()> is a synchronous operation
		2519
		2520	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2521	the process. The exception are C<ev_stat> watchers - those call C<stat
		2522	()>, which is a synchronous operation.
		2523
		2524	For local paths, this usually doesn't matter: unless the system is very
		2525	busy or the intervals between stat's are large, a stat call will be fast,
		2526	as the path data is usually in memory already (except when starting the
		2527	watcher).
		2528
		2529	For networked file systems, calling C<stat ()> can block an indefinite
		2530	time due to network issues, and even under good conditions, a stat call
		2531	often takes multiple milliseconds.
		2532
		2533	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2534	paths, although this is fully supported by libev.
1690		2535
1691	=head3 The special problem of stat time resolution	2536	=head3 The special problem of stat time resolution
1692		2537
1693	The C<stat ()> system call only supports full-second resolution portably, and	2538	The C<stat ()> system call only supports full-second resolution portably,
1694	even on systems where the resolution is higher, many file systems still	2539	and even on systems where the resolution is higher, most file systems
1695	only support whole seconds.	2540	still only support whole seconds.
1696		2541
1697	That means that, if the time is the only thing that changes, you can	2542	That means that, if the time is the only thing that changes, you can
1698	easily miss updates: on the first update, C<ev_stat> detects a change and	2543	easily miss updates: on the first update, C<ev_stat> detects a change and
1699	calls your callback, which does something. When there is another update	2544	calls your callback, which does something. When there is another update
1700	within the same second, C<ev_stat> will be unable to detect it as the stat	2545	within the same second, C<ev_stat> will be unable to detect unless the
1701	data does not change.	2546	stat data does change in other ways (e.g. file size).
1702		2547
1703	The solution to this is to delay acting on a change for slightly more	2548	The solution to this is to delay acting on a change for slightly more
1704	than a second (or till slightly after the next full second boundary), using	2549	than a second (or till slightly after the next full second boundary), using
1705	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2550	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1706	ev_timer_again (loop, w)>).	2551	ev_timer_again (loop, w)>).
…		…
1726	C<path>. The C<interval> is a hint on how quickly a change is expected to	2571	C<path>. The C<interval> is a hint on how quickly a change is expected to
1727	be detected and should normally be specified as C<0> to let libev choose	2572	be detected and should normally be specified as C<0> to let libev choose
1728	a suitable value. The memory pointed to by C<path> must point to the same	2573	a suitable value. The memory pointed to by C<path> must point to the same
1729	path for as long as the watcher is active.	2574	path for as long as the watcher is active.
1730		2575
1731	The callback will receive C<EV_STAT> when a change was detected, relative	2576	The callback will receive an C<EV_STAT> event when a change was detected,
1732	to the attributes at the time the watcher was started (or the last change	2577	relative to the attributes at the time the watcher was started (or the
1733	was detected).	2578	last change was detected).
1734		2579
1735	=item ev_stat_stat (loop, ev_stat *)	2580	=item ev_stat_stat (loop, ev_stat *)
1736		2581
1737	Updates the stat buffer immediately with new values. If you change the	2582	Updates the stat buffer immediately with new values. If you change the
1738	watched path in your callback, you could call this function to avoid	2583	watched path in your callback, you could call this function to avoid
…		…
1821		2666
1822		2667
1823	=head2 C<ev_idle> - when you've got nothing better to do...	2668	=head2 C<ev_idle> - when you've got nothing better to do...
1824		2669
1825	Idle watchers trigger events when no other events of the same or higher	2670	Idle watchers trigger events when no other events of the same or higher
1826	priority are pending (prepare, check and other idle watchers do not	2671	priority are pending (prepare, check and other idle watchers do not count
1827	count).	2672	as receiving "events").
1828		2673
1829	That is, as long as your process is busy handling sockets or timeouts	2674	That is, as long as your process is busy handling sockets or timeouts
1830	(or even signals, imagine) of the same or higher priority it will not be	2675	(or even signals, imagine) of the same or higher priority it will not be
1831	triggered. But when your process is idle (or only lower-priority watchers	2676	triggered. But when your process is idle (or only lower-priority watchers
1832	are pending), the idle watchers are being called once per event loop	2677	are pending), the idle watchers are being called once per event loop
…		…
1843		2688
1844	=head3 Watcher-Specific Functions and Data Members	2689	=head3 Watcher-Specific Functions and Data Members
1845		2690
1846	=over 4	2691	=over 4
1847		2692
1848	=item ev_idle_init (ev_signal *, callback)	2693	=item ev_idle_init (ev_idle *, callback)
1849		2694
1850	Initialises and configures the idle watcher - it has no parameters of any	2695	Initialises and configures the idle watcher - it has no parameters of any
1851	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2696	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1852	believe me.	2697	believe me.
1853		2698
…		…
1857		2702
1858	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2703	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1859	callback, free it. Also, use no error checking, as usual.	2704	callback, free it. Also, use no error checking, as usual.
1860		2705
1861	static void	2706	static void
1862	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2707	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1863	{	2708	{
1864	free (w);	2709	free (w);
1865	// now do something you wanted to do when the program has	2710	// now do something you wanted to do when the program has
1866	// no longer anything immediate to do.	2711	// no longer anything immediate to do.
1867	}	2712	}
1868		2713
1869	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2714	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1870	ev_idle_init (idle_watcher, idle_cb);	2715	ev_idle_init (idle_watcher, idle_cb);
1871	ev_idle_start (loop, idle_cb);	2716	ev_idle_start (loop, idle_watcher);
1872		2717
1873		2718
1874	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2719	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1875		2720
1876	Prepare and check watchers are usually (but not always) used in tandem:	2721	Prepare and check watchers are usually (but not always) used in pairs:
1877	prepare watchers get invoked before the process blocks and check watchers	2722	prepare watchers get invoked before the process blocks and check watchers
1878	afterwards.	2723	afterwards.
1879		2724
1880	You I<must not> call C<ev_loop> or similar functions that enter	2725	You I<must not> call C<ev_run> or similar functions that enter
1881	the current event loop from either C<ev_prepare> or C<ev_check>	2726	the current event loop from either C<ev_prepare> or C<ev_check>
1882	watchers. Other loops than the current one are fine, however. The	2727	watchers. Other loops than the current one are fine, however. The
1883	rationale behind this is that you do not need to check for recursion in	2728	rationale behind this is that you do not need to check for recursion in
1884	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2729	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1885	C<ev_check> so if you have one watcher of each kind they will always be	2730	C<ev_check> so if you have one watcher of each kind they will always be
1886	called in pairs bracketing the blocking call.	2731	called in pairs bracketing the blocking call.
1887		2732
1888	Their main purpose is to integrate other event mechanisms into libev and	2733	Their main purpose is to integrate other event mechanisms into libev and
1889	their use is somewhat advanced. This could be used, for example, to track	2734	their use is somewhat advanced. They could be used, for example, to track
1890	variable changes, implement your own watchers, integrate net-snmp or a	2735	variable changes, implement your own watchers, integrate net-snmp or a
1891	coroutine library and lots more. They are also occasionally useful if	2736	coroutine library and lots more. They are also occasionally useful if
1892	you cache some data and want to flush it before blocking (for example,	2737	you cache some data and want to flush it before blocking (for example,
1893	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2738	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1894	watcher).	2739	watcher).
1895		2740
1896	This is done by examining in each prepare call which file descriptors need	2741	This is done by examining in each prepare call which file descriptors
1897	to be watched by the other library, registering C<ev_io> watchers for	2742	need to be watched by the other library, registering C<ev_io> watchers
1898	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2743	for them and starting an C<ev_timer> watcher for any timeouts (many
1899	provide just this functionality). Then, in the check watcher you check for	2744	libraries provide exactly this functionality). Then, in the check watcher,
1900	any events that occurred (by checking the pending status of all watchers	2745	you check for any events that occurred (by checking the pending status
1901	and stopping them) and call back into the library. The I/O and timer	2746	of all watchers and stopping them) and call back into the library. The
1902	callbacks will never actually be called (but must be valid nevertheless,	2747	I/O and timer callbacks will never actually be called (but must be valid
1903	because you never know, you know?).	2748	nevertheless, because you never know, you know?).
1904		2749
1905	As another example, the Perl Coro module uses these hooks to integrate	2750	As another example, the Perl Coro module uses these hooks to integrate
1906	coroutines into libev programs, by yielding to other active coroutines	2751	coroutines into libev programs, by yielding to other active coroutines
1907	during each prepare and only letting the process block if no coroutines	2752	during each prepare and only letting the process block if no coroutines
1908	are ready to run (it's actually more complicated: it only runs coroutines	2753	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1911	loop from blocking if lower-priority coroutines are active, thus mapping	2756	loop from blocking if lower-priority coroutines are active, thus mapping
1912	low-priority coroutines to idle/background tasks).	2757	low-priority coroutines to idle/background tasks).
1913		2758
1914	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2759	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1915	priority, to ensure that they are being run before any other watchers	2760	priority, to ensure that they are being run before any other watchers
		2761	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2762
1916	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2763	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1917	too) should not activate ("feed") events into libev. While libev fully	2764	activate ("feed") events into libev. While libev fully supports this, they
1918	supports this, they might get executed before other C<ev_check> watchers	2765	might get executed before other C<ev_check> watchers did their job. As
1919	did their job. As C<ev_check> watchers are often used to embed other	2766	C<ev_check> watchers are often used to embed other (non-libev) event
1920	(non-libev) event loops those other event loops might be in an unusable	2767	loops those other event loops might be in an unusable state until their
1921	state until their C<ev_check> watcher ran (always remind yourself to	2768	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1922	coexist peacefully with others).	2769	others).
1923		2770
1924	=head3 Watcher-Specific Functions and Data Members	2771	=head3 Watcher-Specific Functions and Data Members
1925		2772
1926	=over 4	2773	=over 4
1927		2774
…		…
1929		2776
1930	=item ev_check_init (ev_check *, callback)	2777	=item ev_check_init (ev_check *, callback)
1931		2778
1932	Initialises and configures the prepare or check watcher - they have no	2779	Initialises and configures the prepare or check watcher - they have no
1933	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2780	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1934	macros, but using them is utterly, utterly and completely pointless.	2781	macros, but using them is utterly, utterly, utterly and completely
		2782	pointless.
1935		2783
1936	=back	2784	=back
1937		2785
1938	=head3 Examples	2786	=head3 Examples
1939		2787
…		…
1952		2800
1953	static ev_io iow [nfd];	2801	static ev_io iow [nfd];
1954	static ev_timer tw;	2802	static ev_timer tw;
1955		2803
1956	static void	2804	static void
1957	io_cb (ev_loop *loop, ev_io *w, int revents)	2805	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1958	{	2806	{
1959	}	2807	}
1960		2808
1961	// create io watchers for each fd and a timer before blocking	2809	// create io watchers for each fd and a timer before blocking
1962	static void	2810	static void
1963	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2811	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1964	{	2812	{
1965	int timeout = 3600000;	2813	int timeout = 3600000;
1966	struct pollfd fds [nfd];	2814	struct pollfd fds [nfd];
1967	// actual code will need to loop here and realloc etc.	2815	// actual code will need to loop here and realloc etc.
1968	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2816	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1969		2817
1970	/* the callback is illegal, but won't be called as we stop during check */	2818	/* the callback is illegal, but won't be called as we stop during check */
1971	ev_timer_init (&tw, 0, timeout * 1e-3);	2819	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
1972	ev_timer_start (loop, &tw);	2820	ev_timer_start (loop, &tw);
1973		2821
1974	// create one ev_io per pollfd	2822	// create one ev_io per pollfd
1975	for (int i = 0; i < nfd; ++i)	2823	for (int i = 0; i < nfd; ++i)
1976	{	2824	{
…		…
1983	}	2831	}
1984	}	2832	}
1985		2833
1986	// stop all watchers after blocking	2834	// stop all watchers after blocking
1987	static void	2835	static void
1988	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2836	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1989	{	2837	{
1990	ev_timer_stop (loop, &tw);	2838	ev_timer_stop (loop, &tw);
1991		2839
1992	for (int i = 0; i < nfd; ++i)	2840	for (int i = 0; i < nfd; ++i)
1993	{	2841	{
…		…
2032	}	2880	}
2033		2881
2034	// do not ever call adns_afterpoll	2882	// do not ever call adns_afterpoll
2035		2883
2036	Method 4: Do not use a prepare or check watcher because the module you	2884	Method 4: Do not use a prepare or check watcher because the module you
2037	want to embed is too inflexible to support it. Instead, you can override	2885	want to embed is not flexible enough to support it. Instead, you can
2038	their poll function. The drawback with this solution is that the main	2886	override their poll function. The drawback with this solution is that the
2039	loop is now no longer controllable by EV. The C<Glib::EV> module does	2887	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2040	this.	2888	this approach, effectively embedding EV as a client into the horrible
		2889	libglib event loop.
2041		2890
2042	static gint	2891	static gint
2043	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2892	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2044	{	2893	{
2045	int got_events = 0;	2894	int got_events = 0;
…		…
2049		2898
2050	if (timeout >= 0)	2899	if (timeout >= 0)
2051	// create/start timer	2900	// create/start timer
2052		2901
2053	// poll	2902	// poll
2054	ev_loop (EV_A_ 0);	2903	ev_run (EV_A_ 0);
2055		2904
2056	// stop timer again	2905	// stop timer again
2057	if (timeout >= 0)	2906	if (timeout >= 0)
2058	ev_timer_stop (EV_A_ &to);	2907	ev_timer_stop (EV_A_ &to);
2059		2908
…		…
2076	prioritise I/O.	2925	prioritise I/O.
2077		2926
2078	As an example for a bug workaround, the kqueue backend might only support	2927	As an example for a bug workaround, the kqueue backend might only support
2079	sockets on some platform, so it is unusable as generic backend, but you	2928	sockets on some platform, so it is unusable as generic backend, but you
2080	still want to make use of it because you have many sockets and it scales	2929	still want to make use of it because you have many sockets and it scales
2081	so nicely. In this case, you would create a kqueue-based loop and embed it	2930	so nicely. In this case, you would create a kqueue-based loop and embed
2082	into your default loop (which might use e.g. poll). Overall operation will	2931	it into your default loop (which might use e.g. poll). Overall operation
2083	be a bit slower because first libev has to poll and then call kevent, but	2932	will be a bit slower because first libev has to call C<poll> and then
2084	at least you can use both at what they are best.	2933	C<kevent>, but at least you can use both mechanisms for what they are
		2934	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2085		2935
2086	As for prioritising I/O: rarely you have the case where some fds have	2936	As for prioritising I/O: under rare circumstances you have the case where
2087	to be watched and handled very quickly (with low latency), and even	2937	some fds have to be watched and handled very quickly (with low latency),
2088	priorities and idle watchers might have too much overhead. In this case	2938	and even priorities and idle watchers might have too much overhead. In
2089	you would put all the high priority stuff in one loop and all the rest in	2939	this case you would put all the high priority stuff in one loop and all
2090	a second one, and embed the second one in the first.	2940	the rest in a second one, and embed the second one in the first.
2091		2941
2092	As long as the watcher is active, the callback will be invoked every time	2942	As long as the watcher is active, the callback will be invoked every
2093	there might be events pending in the embedded loop. The callback must then	2943	time there might be events pending in the embedded loop. The callback
2094	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2944	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2095	their callbacks (you could also start an idle watcher to give the embedded	2945	sweep and invoke their callbacks (the callback doesn't need to invoke the
2096	loop strictly lower priority for example). You can also set the callback	2946	C<ev_embed_sweep> function directly, it could also start an idle watcher
2097	to C<0>, in which case the embed watcher will automatically execute the	2947	to give the embedded loop strictly lower priority for example).
2098	embedded loop sweep.
2099		2948
2100	As long as the watcher is started it will automatically handle events. The	2949	You can also set the callback to C<0>, in which case the embed watcher
2101	callback will be invoked whenever some events have been handled. You can	2950	will automatically execute the embedded loop sweep whenever necessary.
2102	set the callback to C<0> to avoid having to specify one if you are not
2103	interested in that.
2104		2951
2105	Also, there have not currently been made special provisions for forking:	2952	Fork detection will be handled transparently while the C<ev_embed> watcher
2106	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2953	is active, i.e., the embedded loop will automatically be forked when the
2107	but you will also have to stop and restart any C<ev_embed> watchers	2954	embedding loop forks. In other cases, the user is responsible for calling
2108	yourself.	2955	C<ev_loop_fork> on the embedded loop.
2109		2956
2110	Unfortunately, not all backends are embeddable, only the ones returned by	2957	Unfortunately, not all backends are embeddable: only the ones returned by
2111	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2958	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2112	portable one.	2959	portable one.
2113		2960
2114	So when you want to use this feature you will always have to be prepared	2961	So when you want to use this feature you will always have to be prepared
2115	that you cannot get an embeddable loop. The recommended way to get around	2962	that you cannot get an embeddable loop. The recommended way to get around
2116	this is to have a separate variables for your embeddable loop, try to	2963	this is to have a separate variables for your embeddable loop, try to
2117	create it, and if that fails, use the normal loop for everything.	2964	create it, and if that fails, use the normal loop for everything.
		2965
		2966	=head3 C<ev_embed> and fork
		2967
		2968	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2969	automatically be applied to the embedded loop as well, so no special
		2970	fork handling is required in that case. When the watcher is not running,
		2971	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2972	as applicable.
2118		2973
2119	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2120		2975
2121	=over 4	2976	=over 4
2122		2977
…		…
2131	if you do not want that, you need to temporarily stop the embed watcher).	2986	if you do not want that, you need to temporarily stop the embed watcher).
2132		2987
2133	=item ev_embed_sweep (loop, ev_embed *)	2988	=item ev_embed_sweep (loop, ev_embed *)
2134		2989
2135	Make a single, non-blocking sweep over the embedded loop. This works	2990	Make a single, non-blocking sweep over the embedded loop. This works
2136	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2991	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2137	appropriate way for embedded loops.	2992	appropriate way for embedded loops.
2138		2993
2139	=item struct ev_loop *other [read-only]	2994	=item struct ev_loop *other [read-only]
2140		2995
2141	The embedded event loop.	2996	The embedded event loop.
…		…
2150	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3005	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2151	used).	3006	used).
2152		3007
2153	struct ev_loop *loop_hi = ev_default_init (0);	3008	struct ev_loop *loop_hi = ev_default_init (0);
2154	struct ev_loop *loop_lo = 0;	3009	struct ev_loop *loop_lo = 0;
2155	struct ev_embed embed;	3010	ev_embed embed;
2156		3011
2157	// see if there is a chance of getting one that works	3012	// see if there is a chance of getting one that works
2158	// (remember that a flags value of 0 means autodetection)	3013	// (remember that a flags value of 0 means autodetection)
2159	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3014	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2160	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3015	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2174	kqueue implementation). Store the kqueue/socket-only event loop in	3029	kqueue implementation). Store the kqueue/socket-only event loop in
2175	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3030	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2176		3031
2177	struct ev_loop *loop = ev_default_init (0);	3032	struct ev_loop *loop = ev_default_init (0);
2178	struct ev_loop *loop_socket = 0;	3033	struct ev_loop *loop_socket = 0;
2179	struct ev_embed embed;	3034	ev_embed embed;
2180		3035
2181	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3036	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2182	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3037	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2183	{	3038	{
2184	ev_embed_init (&embed, 0, loop_socket);	3039	ev_embed_init (&embed, 0, loop_socket);
…		…
2199	event loop blocks next and before C<ev_check> watchers are being called,	3054	event loop blocks next and before C<ev_check> watchers are being called,
2200	and only in the child after the fork. If whoever good citizen calling	3055	and only in the child after the fork. If whoever good citizen calling
2201	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3056	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2202	handlers will be invoked, too, of course.	3057	handlers will be invoked, too, of course.
2203		3058
		3059	=head3 The special problem of life after fork - how is it possible?
		3060
		3061	Most uses of C<fork()> consist of forking, then some simple calls to set
		3062	up/change the process environment, followed by a call to C<exec()>. This
		3063	sequence should be handled by libev without any problems.
		3064
		3065	This changes when the application actually wants to do event handling
		3066	in the child, or both parent in child, in effect "continuing" after the
		3067	fork.
		3068
		3069	The default mode of operation (for libev, with application help to detect
		3070	forks) is to duplicate all the state in the child, as would be expected
		3071	when I<either> the parent I<or> the child process continues.
		3072
		3073	When both processes want to continue using libev, then this is usually the
		3074	wrong result. In that case, usually one process (typically the parent) is
		3075	supposed to continue with all watchers in place as before, while the other
		3076	process typically wants to start fresh, i.e. without any active watchers.
		3077
		3078	The cleanest and most efficient way to achieve that with libev is to
		3079	simply create a new event loop, which of course will be "empty", and
		3080	use that for new watchers. This has the advantage of not touching more
		3081	memory than necessary, and thus avoiding the copy-on-write, and the
		3082	disadvantage of having to use multiple event loops (which do not support
		3083	signal watchers).
		3084
		3085	When this is not possible, or you want to use the default loop for
		3086	other reasons, then in the process that wants to start "fresh", call
		3087	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3088	Destroying the default loop will "orphan" (not stop) all registered
		3089	watchers, so you have to be careful not to execute code that modifies
		3090	those watchers. Note also that in that case, you have to re-register any
		3091	signal watchers.
		3092
2204	=head3 Watcher-Specific Functions and Data Members	3093	=head3 Watcher-Specific Functions and Data Members
2205		3094
2206	=over 4	3095	=over 4
2207		3096
2208	=item ev_fork_init (ev_signal *, callback)	3097	=item ev_fork_init (ev_signal *, callback)
…		…
2212	believe me.	3101	believe me.
2213		3102
2214	=back	3103	=back
2215		3104
2216		3105
2217	=head2 C<ev_async> - how to wake up another event loop	3106	=head2 C<ev_async> - how to wake up an event loop
2218		3107
2219	In general, you cannot use an C<ev_loop> from multiple threads or other	3108	In general, you cannot use an C<ev_run> from multiple threads or other
2220	asynchronous sources such as signal handlers (as opposed to multiple event	3109	asynchronous sources such as signal handlers (as opposed to multiple event
2221	loops - those are of course safe to use in different threads).	3110	loops - those are of course safe to use in different threads).
2222		3111
2223	Sometimes, however, you need to wake up another event loop you do not	3112	Sometimes, however, you need to wake up an event loop you do not control,
2224	control, for example because it belongs to another thread. This is what	3113	for example because it belongs to another thread. This is what C<ev_async>
2225	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3114	watchers do: as long as the C<ev_async> watcher is active, you can signal
2226	can signal it by calling C<ev_async_send>, which is thread- and signal	3115	it by calling C<ev_async_send>, which is thread- and signal safe.
2227	safe.
2228		3116
2229	This functionality is very similar to C<ev_signal> watchers, as signals,	3117	This functionality is very similar to C<ev_signal> watchers, as signals,
2230	too, are asynchronous in nature, and signals, too, will be compressed	3118	too, are asynchronous in nature, and signals, too, will be compressed
2231	(i.e. the number of callback invocations may be less than the number of	3119	(i.e. the number of callback invocations may be less than the number of
2232	C<ev_async_sent> calls).	3120	C<ev_async_sent> calls).
…		…
2237	=head3 Queueing	3125	=head3 Queueing
2238		3126
2239	C<ev_async> does not support queueing of data in any way. The reason	3127	C<ev_async> does not support queueing of data in any way. The reason
2240	is that the author does not know of a simple (or any) algorithm for a	3128	is that the author does not know of a simple (or any) algorithm for a
2241	multiple-writer-single-reader queue that works in all cases and doesn't	3129	multiple-writer-single-reader queue that works in all cases and doesn't
2242	need elaborate support such as pthreads.	3130	need elaborate support such as pthreads or unportable memory access
		3131	semantics.
2243		3132
2244	That means that if you want to queue data, you have to provide your own	3133	That means that if you want to queue data, you have to provide your own
2245	queue. But at least I can tell you would implement locking around your	3134	queue. But at least I can tell you how to implement locking around your
2246	queue:	3135	queue:
2247		3136
2248	=over 4	3137	=over 4
2249		3138
2250	=item queueing from a signal handler context	3139	=item queueing from a signal handler context
2251		3140
2252	To implement race-free queueing, you simply add to the queue in the signal	3141	To implement race-free queueing, you simply add to the queue in the signal
2253	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3142	handler but you block the signal handler in the watcher callback. Here is
2254	some fictitious SIGUSR1 handler:	3143	an example that does that for some fictitious SIGUSR1 handler:
2255		3144
2256	static ev_async mysig;	3145	static ev_async mysig;
2257		3146
2258	static void	3147	static void
2259	sigusr1_handler (void)	3148	sigusr1_handler (void)
…		…
2325	=over 4	3214	=over 4
2326		3215
2327	=item ev_async_init (ev_async *, callback)	3216	=item ev_async_init (ev_async *, callback)
2328		3217
2329	Initialises and configures the async watcher - it has no parameters of any	3218	Initialises and configures the async watcher - it has no parameters of any
2330	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3219	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2331	believe me.	3220	trust me.
2332		3221
2333	=item ev_async_send (loop, ev_async *)	3222	=item ev_async_send (loop, ev_async *)
2334		3223
2335	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3224	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2336	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3225	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2337	C<ev_feed_event>, this call is safe to do in other threads, signal or	3226	C<ev_feed_event>, this call is safe to do from other threads, signal or
2338	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3227	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2339	section below on what exactly this means).	3228	section below on what exactly this means).
2340		3229
		3230	Note that, as with other watchers in libev, multiple events might get
		3231	compressed into a single callback invocation (another way to look at this
		3232	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3233	reset when the event loop detects that).
		3234
2341	This call incurs the overhead of a system call only once per loop iteration,	3235	This call incurs the overhead of a system call only once per event loop
2342	so while the overhead might be noticeable, it doesn't apply to repeated	3236	iteration, so while the overhead might be noticeable, it doesn't apply to
2343	calls to C<ev_async_send>.	3237	repeated calls to C<ev_async_send> for the same event loop.
2344		3238
2345	=item bool = ev_async_pending (ev_async *)	3239	=item bool = ev_async_pending (ev_async *)
2346		3240
2347	Returns a non-zero value when C<ev_async_send> has been called on the	3241	Returns a non-zero value when C<ev_async_send> has been called on the
2348	watcher but the event has not yet been processed (or even noted) by the	3242	watcher but the event has not yet been processed (or even noted) by the
…		…
2351	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3245	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2352	the loop iterates next and checks for the watcher to have become active,	3246	the loop iterates next and checks for the watcher to have become active,
2353	it will reset the flag again. C<ev_async_pending> can be used to very	3247	it will reset the flag again. C<ev_async_pending> can be used to very
2354	quickly check whether invoking the loop might be a good idea.	3248	quickly check whether invoking the loop might be a good idea.
2355		3249
2356	Not that this does I<not> check whether the watcher itself is pending, only	3250	Not that this does I<not> check whether the watcher itself is pending,
2357	whether it has been requested to make this watcher pending.	3251	only whether it has been requested to make this watcher pending: there
		3252	is a time window between the event loop checking and resetting the async
		3253	notification, and the callback being invoked.
2358		3254
2359	=back	3255	=back
2360		3256
2361		3257
2362	=head1 OTHER FUNCTIONS	3258	=head1 OTHER FUNCTIONS
…		…
2366	=over 4	3262	=over 4
2367		3263
2368	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3264	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2369		3265
2370	This function combines a simple timer and an I/O watcher, calls your	3266	This function combines a simple timer and an I/O watcher, calls your
2371	callback on whichever event happens first and automatically stop both	3267	callback on whichever event happens first and automatically stops both
2372	watchers. This is useful if you want to wait for a single event on an fd	3268	watchers. This is useful if you want to wait for a single event on an fd
2373	or timeout without having to allocate/configure/start/stop/free one or	3269	or timeout without having to allocate/configure/start/stop/free one or
2374	more watchers yourself.	3270	more watchers yourself.
2375		3271
2376	If C<fd> is less than 0, then no I/O watcher will be started and events	3272	If C<fd> is less than 0, then no I/O watcher will be started and the
2377	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3273	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2378	C<events> set will be created and started.	3274	the given C<fd> and C<events> set will be created and started.
2379		3275
2380	If C<timeout> is less than 0, then no timeout watcher will be	3276	If C<timeout> is less than 0, then no timeout watcher will be
2381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3277	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2382	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3278	repeat = 0) will be started. C<0> is a valid timeout.
2383	dubious value.
2384		3279
2385	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3280	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2386	passed an C<revents> set like normal event callbacks (a combination of	3281	passed an C<revents> set like normal event callbacks (a combination of
2387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3282	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2388	value passed to C<ev_once>:	3283	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3284	a timeout and an io event at the same time - you probably should give io
		3285	events precedence.
		3286
		3287	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2389		3288
2390	static void stdin_ready (int revents, void *arg)	3289	static void stdin_ready (int revents, void *arg)
2391	{	3290	{
		3291	if (revents & EV_READ)
		3292	/* stdin might have data for us, joy! */;
2392	if (revents & EV_TIMEOUT)	3293	else if (revents & EV_TIMER)
2393	/* doh, nothing entered */;	3294	/* doh, nothing entered */;
2394	else if (revents & EV_READ)
2395	/* stdin might have data for us, joy! */;
2396	}	3295	}
2397		3296
2398	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3297	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2399		3298
2400	=item ev_feed_event (ev_loop *, watcher *, int revents)
2401
2402	Feeds the given event set into the event loop, as if the specified event
2403	had happened for the specified watcher (which must be a pointer to an
2404	initialised but not necessarily started event watcher).
2405
2406	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3299	=item ev_feed_fd_event (loop, int fd, int revents)
2407		3300
2408	Feed an event on the given fd, as if a file descriptor backend detected	3301	Feed an event on the given fd, as if a file descriptor backend detected
2409	the given events it.	3302	the given events it.
2410		3303
2411	=item ev_feed_signal_event (ev_loop *loop, int signum)	3304	=item ev_feed_signal_event (loop, int signum)
2412		3305
2413	Feed an event as if the given signal occurred (C<loop> must be the default	3306	Feed an event as if the given signal occurred (C<loop> must be the default
2414	loop!).	3307	loop!).
2415		3308
2416	=back	3309	=back
…		…
2496		3389
2497	=over 4	3390	=over 4
2498		3391
2499	=item ev::TYPE::TYPE ()	3392	=item ev::TYPE::TYPE ()
2500		3393
2501	=item ev::TYPE::TYPE (struct ev_loop *)	3394	=item ev::TYPE::TYPE (loop)
2502		3395
2503	=item ev::TYPE::~TYPE	3396	=item ev::TYPE::~TYPE
2504		3397
2505	The constructor (optionally) takes an event loop to associate the watcher	3398	The constructor (optionally) takes an event loop to associate the watcher
2506	with. If it is omitted, it will use C<EV_DEFAULT>.	3399	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2538		3431
2539	myclass obj;	3432	myclass obj;
2540	ev::io iow;	3433	ev::io iow;
2541	iow.set <myclass, &myclass::io_cb> (&obj);	3434	iow.set <myclass, &myclass::io_cb> (&obj);
2542		3435
		3436	=item w->set (object *)
		3437
		3438	This is a variation of a method callback - leaving out the method to call
		3439	will default the method to C<operator ()>, which makes it possible to use
		3440	functor objects without having to manually specify the C<operator ()> all
		3441	the time. Incidentally, you can then also leave out the template argument
		3442	list.
		3443
		3444	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3445	int revents)>.
		3446
		3447	See the method-C<set> above for more details.
		3448
		3449	Example: use a functor object as callback.
		3450
		3451	struct myfunctor
		3452	{
		3453	void operator() (ev::io &w, int revents)
		3454	{
		3455	...
		3456	}
		3457	}
		3458
		3459	myfunctor f;
		3460
		3461	ev::io w;
		3462	w.set (&f);
		3463
2543	=item w->set<function> (void *data = 0)	3464	=item w->set<function> (void *data = 0)
2544		3465
2545	Also sets a callback, but uses a static method or plain function as	3466	Also sets a callback, but uses a static method or plain function as
2546	callback. The optional C<data> argument will be stored in the watcher's	3467	callback. The optional C<data> argument will be stored in the watcher's
2547	C<data> member and is free for you to use.	3468	C<data> member and is free for you to use.
2548		3469
2549	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3470	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2550		3471
2551	See the method-C<set> above for more details.	3472	See the method-C<set> above for more details.
2552		3473
2553	Example:	3474	Example: Use a plain function as callback.
2554		3475
2555	static void io_cb (ev::io &w, int revents) { }	3476	static void io_cb (ev::io &w, int revents) { }
2556	iow.set <io_cb> ();	3477	iow.set <io_cb> ();
2557		3478
2558	=item w->set (struct ev_loop *)	3479	=item w->set (loop)
2559		3480
2560	Associates a different C<struct ev_loop> with this watcher. You can only	3481	Associates a different C<struct ev_loop> with this watcher. You can only
2561	do this when the watcher is inactive (and not pending either).	3482	do this when the watcher is inactive (and not pending either).
2562		3483
2563	=item w->set ([arguments])	3484	=item w->set ([arguments])
2564		3485
2565	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3486	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2566	called at least once. Unlike the C counterpart, an active watcher gets	3487	method or a suitable start method must be called at least once. Unlike the
2567	automatically stopped and restarted when reconfiguring it with this	3488	C counterpart, an active watcher gets automatically stopped and restarted
2568	method.	3489	when reconfiguring it with this method.
2569		3490
2570	=item w->start ()	3491	=item w->start ()
2571		3492
2572	Starts the watcher. Note that there is no C<loop> argument, as the	3493	Starts the watcher. Note that there is no C<loop> argument, as the
2573	constructor already stores the event loop.	3494	constructor already stores the event loop.
2574		3495
		3496	=item w->start ([arguments])
		3497
		3498	Instead of calling C<set> and C<start> methods separately, it is often
		3499	convenient to wrap them in one call. Uses the same type of arguments as
		3500	the configure C<set> method of the watcher.
		3501
2575	=item w->stop ()	3502	=item w->stop ()
2576		3503
2577	Stops the watcher if it is active. Again, no C<loop> argument.	3504	Stops the watcher if it is active. Again, no C<loop> argument.
2578		3505
2579	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3506	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2591		3518
2592	=back	3519	=back
2593		3520
2594	=back	3521	=back
2595		3522
2596	Example: Define a class with an IO and idle watcher, start one of them in	3523	Example: Define a class with two I/O and idle watchers, start the I/O
2597	the constructor.	3524	watchers in the constructor.
2598		3525
2599	class myclass	3526	class myclass
2600	{	3527	{
2601	ev::io io; void io_cb (ev::io &w, int revents);	3528	ev::io io ; void io_cb (ev::io &w, int revents);
		3529	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2602	ev:idle idle void idle_cb (ev::idle &w, int revents);	3530	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2603		3531
2604	myclass (int fd)	3532	myclass (int fd)
2605	{	3533	{
2606	io .set <myclass, &myclass::io_cb > (this);	3534	io .set <myclass, &myclass::io_cb > (this);
		3535	io2 .set <myclass, &myclass::io2_cb > (this);
2607	idle.set <myclass, &myclass::idle_cb> (this);	3536	idle.set <myclass, &myclass::idle_cb> (this);
2608		3537
2609	io.start (fd, ev::READ);	3538	io.set (fd, ev::WRITE); // configure the watcher
		3539	io.start (); // start it whenever convenient
		3540
		3541	io2.start (fd, ev::READ); // set + start in one call
2610	}	3542	}
2611	};	3543	};
2612		3544
2613		3545
2614	=head1 OTHER LANGUAGE BINDINGS	3546	=head1 OTHER LANGUAGE BINDINGS
…		…
2623	=item Perl	3555	=item Perl
2624		3556
2625	The EV module implements the full libev API and is actually used to test	3557	The EV module implements the full libev API and is actually used to test
2626	libev. EV is developed together with libev. Apart from the EV core module,	3558	libev. EV is developed together with libev. Apart from the EV core module,
2627	there are additional modules that implement libev-compatible interfaces	3559	there are additional modules that implement libev-compatible interfaces
2628	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3560	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2629	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3561	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3562	and C<EV::Glib>).
2630		3563
2631	It can be found and installed via CPAN, its homepage is found at	3564	It can be found and installed via CPAN, its homepage is at
2632	L<http://software.schmorp.de/pkg/EV>.	3565	L<http://software.schmorp.de/pkg/EV>.
		3566
		3567	=item Python
		3568
		3569	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
		3570	seems to be quite complete and well-documented.
2633		3571
2634	=item Ruby	3572	=item Ruby
2635		3573
2636	Tony Arcieri has written a ruby extension that offers access to a subset	3574	Tony Arcieri has written a ruby extension that offers access to a subset
2637	of the libev API and adds file handle abstractions, asynchronous DNS and	3575	of the libev API and adds file handle abstractions, asynchronous DNS and
2638	more on top of it. It can be found via gem servers. Its homepage is at	3576	more on top of it. It can be found via gem servers. Its homepage is at
2639	L<http://rev.rubyforge.org/>.	3577	L<http://rev.rubyforge.org/>.
2640		3578
		3579	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3580	makes rev work even on mingw.
		3581
		3582	=item Haskell
		3583
		3584	A haskell binding to libev is available at
		3585	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3586
2641	=item D	3587	=item D
2642		3588
2643	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3589	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2644	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	3590	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3591
		3592	=item Ocaml
		3593
		3594	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3595	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3596
		3597	=item Lua
		3598
		3599	Brian Maher has written a partial interface to libev for lua (at the
		3600	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3601	L<http://github.com/brimworks/lua-ev>.
2645		3602
2646	=back	3603	=back
2647		3604
2648		3605
2649	=head1 MACRO MAGIC	3606	=head1 MACRO MAGIC
…		…
2663	loop argument"). The C<EV_A> form is used when this is the sole argument,	3620	loop argument"). The C<EV_A> form is used when this is the sole argument,
2664	C<EV_A_> is used when other arguments are following. Example:	3621	C<EV_A_> is used when other arguments are following. Example:
2665		3622
2666	ev_unref (EV_A);	3623	ev_unref (EV_A);
2667	ev_timer_add (EV_A_ watcher);	3624	ev_timer_add (EV_A_ watcher);
2668	ev_loop (EV_A_ 0);	3625	ev_run (EV_A_ 0);
2669		3626
2670	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3627	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2671	which is often provided by the following macro.	3628	which is often provided by the following macro.
2672		3629
2673	=item C<EV_P>, C<EV_P_>	3630	=item C<EV_P>, C<EV_P_>
…		…
2713	}	3670	}
2714		3671
2715	ev_check check;	3672	ev_check check;
2716	ev_check_init (&check, check_cb);	3673	ev_check_init (&check, check_cb);
2717	ev_check_start (EV_DEFAULT_ &check);	3674	ev_check_start (EV_DEFAULT_ &check);
2718	ev_loop (EV_DEFAULT_ 0);	3675	ev_run (EV_DEFAULT_ 0);
2719		3676
2720	=head1 EMBEDDING	3677	=head1 EMBEDDING
2721		3678
2722	Libev can (and often is) directly embedded into host	3679	Libev can (and often is) directly embedded into host
2723	applications. Examples of applications that embed it include the Deliantra	3680	applications. Examples of applications that embed it include the Deliantra
…		…
2750		3707
2751	#define EV_STANDALONE 1	3708	#define EV_STANDALONE 1
2752	#include "ev.h"	3709	#include "ev.h"
2753		3710
2754	Both header files and implementation files can be compiled with a C++	3711	Both header files and implementation files can be compiled with a C++
2755	compiler (at least, thats a stated goal, and breakage will be treated	3712	compiler (at least, that's a stated goal, and breakage will be treated
2756	as a bug).	3713	as a bug).
2757		3714
2758	You need the following files in your source tree, or in a directory	3715	You need the following files in your source tree, or in a directory
2759	in your include path (e.g. in libev/ when using -Ilibev):	3716	in your include path (e.g. in libev/ when using -Ilibev):
2760		3717
…		…
2803	libev.m4	3760	libev.m4
2804		3761
2805	=head2 PREPROCESSOR SYMBOLS/MACROS	3762	=head2 PREPROCESSOR SYMBOLS/MACROS
2806		3763
2807	Libev can be configured via a variety of preprocessor symbols you have to	3764	Libev can be configured via a variety of preprocessor symbols you have to
2808	define before including any of its files. The default in the absence of	3765	define before including (or compiling) any of its files. The default in
2809	autoconf is noted for every option.	3766	the absence of autoconf is documented for every option.
		3767
		3768	Symbols marked with "(h)" do not change the ABI, and can have different
		3769	values when compiling libev vs. including F<ev.h>, so it is permissible
		3770	to redefine them before including F<ev.h> without breaking compatibility
		3771	to a compiled library. All other symbols change the ABI, which means all
		3772	users of libev and the libev code itself must be compiled with compatible
		3773	settings.
2810		3774
2811	=over 4	3775	=over 4
2812		3776
		3777	=item EV_COMPAT3 (h)
		3778
		3779	Backwards compatibility is a major concern for libev. This is why this
		3780	release of libev comes with wrappers for the functions and symbols that
		3781	have been renamed between libev version 3 and 4.
		3782
		3783	You can disable these wrappers (to test compatibility with future
		3784	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3785	sources. This has the additional advantage that you can drop the C<struct>
		3786	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3787	typedef in that case.
		3788
		3789	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3790	and in some even more future version the compatibility code will be
		3791	removed completely.
		3792
2813	=item EV_STANDALONE	3793	=item EV_STANDALONE (h)
2814		3794
2815	Must always be C<1> if you do not use autoconf configuration, which	3795	Must always be C<1> if you do not use autoconf configuration, which
2816	keeps libev from including F<config.h>, and it also defines dummy	3796	keeps libev from including F<config.h>, and it also defines dummy
2817	implementations for some libevent functions (such as logging, which is not	3797	implementations for some libevent functions (such as logging, which is not
2818	supported). It will also not define any of the structs usually found in	3798	supported). It will also not define any of the structs usually found in
2819	F<event.h> that are not directly supported by the libev core alone.	3799	F<event.h> that are not directly supported by the libev core alone.
2820		3800
		3801	In standalone mode, libev will still try to automatically deduce the
		3802	configuration, but has to be more conservative.
		3803
2821	=item EV_USE_MONOTONIC	3804	=item EV_USE_MONOTONIC
2822		3805
2823	If defined to be C<1>, libev will try to detect the availability of the	3806	If defined to be C<1>, libev will try to detect the availability of the
2824	monotonic clock option at both compile time and runtime. Otherwise no use	3807	monotonic clock option at both compile time and runtime. Otherwise no
2825	of the monotonic clock option will be attempted. If you enable this, you	3808	use of the monotonic clock option will be attempted. If you enable this,
2826	usually have to link against librt or something similar. Enabling it when	3809	you usually have to link against librt or something similar. Enabling it
2827	the functionality isn't available is safe, though, although you have	3810	when the functionality isn't available is safe, though, although you have
2828	to make sure you link against any libraries where the C<clock_gettime>	3811	to make sure you link against any libraries where the C<clock_gettime>
2829	function is hiding in (often F<-lrt>).	3812	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2830		3813
2831	=item EV_USE_REALTIME	3814	=item EV_USE_REALTIME
2832		3815
2833	If defined to be C<1>, libev will try to detect the availability of the	3816	If defined to be C<1>, libev will try to detect the availability of the
2834	real-time clock option at compile time (and assume its availability at	3817	real-time clock option at compile time (and assume its availability
2835	runtime if successful). Otherwise no use of the real-time clock option will	3818	at runtime if successful). Otherwise no use of the real-time clock
2836	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3819	option will be attempted. This effectively replaces C<gettimeofday>
2837	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3820	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2838	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3821	correctness. See the note about libraries in the description of
		3822	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3823	C<EV_USE_CLOCK_SYSCALL>.
		3824
		3825	=item EV_USE_CLOCK_SYSCALL
		3826
		3827	If defined to be C<1>, libev will try to use a direct syscall instead
		3828	of calling the system-provided C<clock_gettime> function. This option
		3829	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3830	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3831	programs needlessly. Using a direct syscall is slightly slower (in
		3832	theory), because no optimised vdso implementation can be used, but avoids
		3833	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3834	higher, as it simplifies linking (no need for C<-lrt>).
2839		3835
2840	=item EV_USE_NANOSLEEP	3836	=item EV_USE_NANOSLEEP
2841		3837
2842	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3838	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2843	and will use it for delays. Otherwise it will use C<select ()>.	3839	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2859		3855
2860	=item EV_SELECT_USE_FD_SET	3856	=item EV_SELECT_USE_FD_SET
2861		3857
2862	If defined to C<1>, then the select backend will use the system C<fd_set>	3858	If defined to C<1>, then the select backend will use the system C<fd_set>
2863	structure. This is useful if libev doesn't compile due to a missing	3859	structure. This is useful if libev doesn't compile due to a missing
2864	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3860	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2865	exotic systems. This usually limits the range of file descriptors to some	3861	on exotic systems. This usually limits the range of file descriptors to
2866	low limit such as 1024 or might have other limitations (winsocket only	3862	some low limit such as 1024 or might have other limitations (winsocket
2867	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3863	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2868	influence the size of the C<fd_set> used.	3864	configures the maximum size of the C<fd_set>.
2869		3865
2870	=item EV_SELECT_IS_WINSOCKET	3866	=item EV_SELECT_IS_WINSOCKET
2871		3867
2872	When defined to C<1>, the select backend will assume that	3868	When defined to C<1>, the select backend will assume that
2873	select/socket/connect etc. don't understand file descriptors but	3869	select/socket/connect etc. don't understand file descriptors but
…		…
2875	be used is the winsock select). This means that it will call	3871	be used is the winsock select). This means that it will call
2876	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3872	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2877	it is assumed that all these functions actually work on fds, even	3873	it is assumed that all these functions actually work on fds, even
2878	on win32. Should not be defined on non-win32 platforms.	3874	on win32. Should not be defined on non-win32 platforms.
2879		3875
2880	=item EV_FD_TO_WIN32_HANDLE	3876	=item EV_FD_TO_WIN32_HANDLE(fd)
2881		3877
2882	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3878	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2883	file descriptors to socket handles. When not defining this symbol (the	3879	file descriptors to socket handles. When not defining this symbol (the
2884	default), then libev will call C<_get_osfhandle>, which is usually	3880	default), then libev will call C<_get_osfhandle>, which is usually
2885	correct. In some cases, programs use their own file descriptor management,	3881	correct. In some cases, programs use their own file descriptor management,
2886	in which case they can provide this function to map fds to socket handles.	3882	in which case they can provide this function to map fds to socket handles.
		3883
		3884	=item EV_WIN32_HANDLE_TO_FD(handle)
		3885
		3886	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3887	using the standard C<_open_osfhandle> function. For programs implementing
		3888	their own fd to handle mapping, overwriting this function makes it easier
		3889	to do so. This can be done by defining this macro to an appropriate value.
		3890
		3891	=item EV_WIN32_CLOSE_FD(fd)
		3892
		3893	If programs implement their own fd to handle mapping on win32, then this
		3894	macro can be used to override the C<close> function, useful to unregister
		3895	file descriptors again. Note that the replacement function has to close
		3896	the underlying OS handle.
2887		3897
2888	=item EV_USE_POLL	3898	=item EV_USE_POLL
2889		3899
2890	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3900	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2891	backend. Otherwise it will be enabled on non-win32 platforms. It	3901	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2938	as well as for signal and thread safety in C<ev_async> watchers.	3948	as well as for signal and thread safety in C<ev_async> watchers.
2939		3949
2940	In the absence of this define, libev will use C<sig_atomic_t volatile>	3950	In the absence of this define, libev will use C<sig_atomic_t volatile>
2941	(from F<signal.h>), which is usually good enough on most platforms.	3951	(from F<signal.h>), which is usually good enough on most platforms.
2942		3952
2943	=item EV_H	3953	=item EV_H (h)
2944		3954
2945	The name of the F<ev.h> header file used to include it. The default if	3955	The name of the F<ev.h> header file used to include it. The default if
2946	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3956	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2947	used to virtually rename the F<ev.h> header file in case of conflicts.	3957	used to virtually rename the F<ev.h> header file in case of conflicts.
2948		3958
2949	=item EV_CONFIG_H	3959	=item EV_CONFIG_H (h)
2950		3960
2951	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3961	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2952	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3962	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2953	C<EV_H>, above.	3963	C<EV_H>, above.
2954		3964
2955	=item EV_EVENT_H	3965	=item EV_EVENT_H (h)
2956		3966
2957	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3967	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2958	of how the F<event.h> header can be found, the default is C<"event.h">.	3968	of how the F<event.h> header can be found, the default is C<"event.h">.
2959		3969
2960	=item EV_PROTOTYPES	3970	=item EV_PROTOTYPES (h)
2961		3971
2962	If defined to be C<0>, then F<ev.h> will not define any function	3972	If defined to be C<0>, then F<ev.h> will not define any function
2963	prototypes, but still define all the structs and other symbols. This is	3973	prototypes, but still define all the structs and other symbols. This is
2964	occasionally useful if you want to provide your own wrapper functions	3974	occasionally useful if you want to provide your own wrapper functions
2965	around libev functions.	3975	around libev functions.
…		…
2984	When doing priority-based operations, libev usually has to linearly search	3994	When doing priority-based operations, libev usually has to linearly search
2985	all the priorities, so having many of them (hundreds) uses a lot of space	3995	all the priorities, so having many of them (hundreds) uses a lot of space
2986	and time, so using the defaults of five priorities (-2 .. +2) is usually	3996	and time, so using the defaults of five priorities (-2 .. +2) is usually
2987	fine.	3997	fine.
2988		3998
2989	If your embedding application does not need any priorities, defining these both to	3999	If your embedding application does not need any priorities, defining these
2990	C<0> will save some memory and CPU.	4000	both to C<0> will save some memory and CPU.
2991		4001
2992	=item EV_PERIODIC_ENABLE	4002	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4003	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4004	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
2993		4005
2994	If undefined or defined to be C<1>, then periodic timers are supported. If	4006	If undefined or defined to be C<1> (and the platform supports it), then
2995	defined to be C<0>, then they are not. Disabling them saves a few kB of	4007	the respective watcher type is supported. If defined to be C<0>, then it
2996	code.	4008	is not. Disabling watcher types mainly saves code size.
2997		4009
2998	=item EV_IDLE_ENABLE	4010	=item EV_FEATURES
2999
3000	If undefined or defined to be C<1>, then idle watchers are supported. If
3001	defined to be C<0>, then they are not. Disabling them saves a few kB of
3002	code.
3003
3004	=item EV_EMBED_ENABLE
3005
3006	If undefined or defined to be C<1>, then embed watchers are supported. If
3007	defined to be C<0>, then they are not.
3008
3009	=item EV_STAT_ENABLE
3010
3011	If undefined or defined to be C<1>, then stat watchers are supported. If
3012	defined to be C<0>, then they are not.
3013
3014	=item EV_FORK_ENABLE
3015
3016	If undefined or defined to be C<1>, then fork watchers are supported. If
3017	defined to be C<0>, then they are not.
3018
3019	=item EV_ASYNC_ENABLE
3020
3021	If undefined or defined to be C<1>, then async watchers are supported. If
3022	defined to be C<0>, then they are not.
3023
3024	=item EV_MINIMAL
3025		4011
3026	If you need to shave off some kilobytes of code at the expense of some	4012	If you need to shave off some kilobytes of code at the expense of some
3027	speed, define this symbol to C<1>. Currently this is used to override some	4013	speed (but with the full API), you can define this symbol to request
3028	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4014	certain subsets of functionality. The default is to enable all features
3029	much smaller 2-heap for timer management over the default 4-heap.	4015	that can be enabled on the platform.
		4016
		4017	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4018	with some broad features you want) and then selectively re-enable
		4019	additional parts you want, for example if you want everything minimal,
		4020	but multiple event loop support, async and child watchers and the poll
		4021	backend, use this:
		4022
		4023	#define EV_FEATURES 0
		4024	#define EV_MULTIPLICITY 1
		4025	#define EV_USE_POLL 1
		4026	#define EV_CHILD_ENABLE 1
		4027	#define EV_ASYNC_ENABLE 1
		4028
		4029	The actual value is a bitset, it can be a combination of the following
		4030	values:
		4031
		4032	=over 4
		4033
		4034	=item C<1> - faster/larger code
		4035
		4036	Use larger code to speed up some operations.
		4037
		4038	Currently this is used to override some inlining decisions (enlarging the
		4039	code size by roughly 30% on amd64).
		4040
		4041	When optimising for size, use of compiler flags such as C<-Os> with
		4042	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4043	assertions.
		4044
		4045	=item C<2> - faster/larger data structures
		4046
		4047	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4048	hash table sizes and so on. This will usually further increase code size
		4049	and can additionally have an effect on the size of data structures at
		4050	runtime.
		4051
		4052	=item C<4> - full API configuration
		4053
		4054	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4055	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4056
		4057	=item C<8> - full API
		4058
		4059	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4060	details on which parts of the API are still available without this
		4061	feature, and do not complain if this subset changes over time.
		4062
		4063	=item C<16> - enable all optional watcher types
		4064
		4065	Enables all optional watcher types. If you want to selectively enable
		4066	only some watcher types other than I/O and timers (e.g. prepare,
		4067	embed, async, child...) you can enable them manually by defining
		4068	C<EV_watchertype_ENABLE> to C<1> instead.
		4069
		4070	=item C<32> - enable all backends
		4071
		4072	This enables all backends - without this feature, you need to enable at
		4073	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4074
		4075	=item C<64> - enable OS-specific "helper" APIs
		4076
		4077	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4078	default.
		4079
		4080	=back
		4081
		4082	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4083	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4084	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4085	watchers, timers and monotonic clock support.
		4086
		4087	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4088	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4089	your program might be left out as well - a binary starting a timer and an
		4090	I/O watcher then might come out at only 5Kb.
		4091
		4092	=item EV_AVOID_STDIO
		4093
		4094	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4095	functions (printf, scanf, perror etc.). This will increase the code size
		4096	somewhat, but if your program doesn't otherwise depend on stdio and your
		4097	libc allows it, this avoids linking in the stdio library which is quite
		4098	big.
		4099
		4100	Note that error messages might become less precise when this option is
		4101	enabled.
		4102
		4103	=item EV_NSIG
		4104
		4105	The highest supported signal number, +1 (or, the number of
		4106	signals): Normally, libev tries to deduce the maximum number of signals
		4107	automatically, but sometimes this fails, in which case it can be
		4108	specified. Also, using a lower number than detected (C<32> should be
		4109	good for about any system in existence) can save some memory, as libev
		4110	statically allocates some 12-24 bytes per signal number.
3030		4111
3031	=item EV_PID_HASHSIZE	4112	=item EV_PID_HASHSIZE
3032		4113
3033	C<ev_child> watchers use a small hash table to distribute workload by	4114	C<ev_child> watchers use a small hash table to distribute workload by
3034	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4115	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3035	than enough. If you need to manage thousands of children you might want to	4116	usually more than enough. If you need to manage thousands of children you
3036	increase this value (I<must> be a power of two).	4117	might want to increase this value (I<must> be a power of two).
3037		4118
3038	=item EV_INOTIFY_HASHSIZE	4119	=item EV_INOTIFY_HASHSIZE
3039		4120
3040	C<ev_stat> watchers use a small hash table to distribute workload by	4121	C<ev_stat> watchers use a small hash table to distribute workload by
3041	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4122	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3042	usually more than enough. If you need to manage thousands of C<ev_stat>	4123	disabled), usually more than enough. If you need to manage thousands of
3043	watchers you might want to increase this value (I<must> be a power of	4124	C<ev_stat> watchers you might want to increase this value (I<must> be a
3044	two).	4125	power of two).
3045		4126
3046	=item EV_USE_4HEAP	4127	=item EV_USE_4HEAP
3047		4128
3048	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4129	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3049	timer and periodics heap, libev uses a 4-heap when this symbol is defined	4130	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3050	to C<1>. The 4-heap uses more complicated (longer) code but has	4131	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3051	noticeably faster performance with many (thousands) of watchers.	4132	faster performance with many (thousands) of watchers.
3052		4133
3053	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4134	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3054	(disabled).	4135	will be C<0>.
3055		4136
3056	=item EV_HEAP_CACHE_AT	4137	=item EV_HEAP_CACHE_AT
3057		4138
3058	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4139	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3059	timer and periodics heap, libev can cache the timestamp (I<at>) within	4140	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3060	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4141	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3061	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4142	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3062	but avoids random read accesses on heap changes. This improves performance	4143	but avoids random read accesses on heap changes. This improves performance
3063	noticeably with with many (hundreds) of watchers.	4144	noticeably with many (hundreds) of watchers.
3064		4145
3065	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4146	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3066	(disabled).	4147	will be C<0>.
3067		4148
3068	=item EV_VERIFY	4149	=item EV_VERIFY
3069		4150
3070	Controls how much internal verification (see C<ev_loop_verify ()>) will	4151	Controls how much internal verification (see C<ev_verify ()>) will
3071	be done: If set to C<0>, no internal verification code will be compiled	4152	be done: If set to C<0>, no internal verification code will be compiled
3072	in. If set to C<1>, then verification code will be compiled in, but not	4153	in. If set to C<1>, then verification code will be compiled in, but not
3073	called. If set to C<2>, then the internal verification code will be	4154	called. If set to C<2>, then the internal verification code will be
3074	called once per loop, which can slow down libev. If set to C<3>, then the	4155	called once per loop, which can slow down libev. If set to C<3>, then the
3075	verification code will be called very frequently, which will slow down	4156	verification code will be called very frequently, which will slow down
3076	libev considerably.	4157	libev considerably.
3077		4158
3078	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4159	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3079	C<0.>	4160	will be C<0>.
3080		4161
3081	=item EV_COMMON	4162	=item EV_COMMON
3082		4163
3083	By default, all watchers have a C<void *data> member. By redefining	4164	By default, all watchers have a C<void *data> member. By redefining
3084	this macro to a something else you can include more and other types of	4165	this macro to something else you can include more and other types of
3085	members. You have to define it each time you include one of the files,	4166	members. You have to define it each time you include one of the files,
3086	though, and it must be identical each time.	4167	though, and it must be identical each time.
3087		4168
3088	For example, the perl EV module uses something like this:	4169	For example, the perl EV module uses something like this:
3089		4170
…		…
3101	and the way callbacks are invoked and set. Must expand to a struct member	4182	and the way callbacks are invoked and set. Must expand to a struct member
3102	definition and a statement, respectively. See the F<ev.h> header file for	4183	definition and a statement, respectively. See the F<ev.h> header file for
3103	their default definitions. One possible use for overriding these is to	4184	their default definitions. One possible use for overriding these is to
3104	avoid the C<struct ev_loop *> as first argument in all cases, or to use	4185	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3105	method calls instead of plain function calls in C++.	4186	method calls instead of plain function calls in C++.
		4187
		4188	=back
3106		4189
3107	=head2 EXPORTED API SYMBOLS	4190	=head2 EXPORTED API SYMBOLS
3108		4191
3109	If you need to re-export the API (e.g. via a DLL) and you need a list of	4192	If you need to re-export the API (e.g. via a DLL) and you need a list of
3110	exported symbols, you can use the provided F<Symbol.*> files which list	4193	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3140	file.	4223	file.
3141		4224
3142	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4225	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3143	that everybody includes and which overrides some configure choices:	4226	that everybody includes and which overrides some configure choices:
3144		4227
3145	#define EV_MINIMAL 1	4228	#define EV_FEATURES 8
3146	#define EV_USE_POLL 0	4229	#define EV_USE_SELECT 1
3147	#define EV_MULTIPLICITY 0
3148	#define EV_PERIODIC_ENABLE 0	4230	#define EV_PREPARE_ENABLE 1
		4231	#define EV_IDLE_ENABLE 1
3149	#define EV_STAT_ENABLE 0	4232	#define EV_SIGNAL_ENABLE 1
3150	#define EV_FORK_ENABLE 0	4233	#define EV_CHILD_ENABLE 1
		4234	#define EV_USE_STDEXCEPT 0
3151	#define EV_CONFIG_H <config.h>	4235	#define EV_CONFIG_H <config.h>
3152	#define EV_MINPRI 0
3153	#define EV_MAXPRI 0
3154		4236
3155	#include "ev++.h"	4237	#include "ev++.h"
3156		4238
3157	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4239	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3158		4240
3159	#include "ev_cpp.h"	4241	#include "ev_cpp.h"
3160	#include "ev.c"	4242	#include "ev.c"
3161		4243
		4244	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3162		4245
3163	=head1 THREADS AND COROUTINES	4246	=head2 THREADS AND COROUTINES
3164		4247
3165	=head2 THREADS	4248	=head3 THREADS
3166		4249
3167	Libev itself is completely thread-safe, but it uses no locking. This	4250	All libev functions are reentrant and thread-safe unless explicitly
		4251	documented otherwise, but libev implements no locking itself. This means
3168	means that you can use as many loops as you want in parallel, as long as	4252	that you can use as many loops as you want in parallel, as long as there
3169	only one thread ever calls into one libev function with the same loop	4253	are no concurrent calls into any libev function with the same loop
3170	parameter.	4254	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		4255	of course): libev guarantees that different event loops share no data
		4256	structures that need any locking.
3171		4257
3172	Or put differently: calls with different loop parameters can be done in	4258	Or to put it differently: calls with different loop parameters can be done
3173	parallel from multiple threads, calls with the same loop parameter must be	4259	concurrently from multiple threads, calls with the same loop parameter
3174	done serially (but can be done from different threads, as long as only one	4260	must be done serially (but can be done from different threads, as long as
3175	thread ever is inside a call at any point in time, e.g. by using a mutex	4261	only one thread ever is inside a call at any point in time, e.g. by using
3176	per loop).	4262	a mutex per loop).
3177		4263
3178	If you want to know which design is best for your problem, then I cannot	4264	Specifically to support threads (and signal handlers), libev implements
		4265	so-called C<ev_async> watchers, which allow some limited form of
		4266	concurrency on the same event loop, namely waking it up "from the
		4267	outside".
		4268
		4269	If you want to know which design (one loop, locking, or multiple loops
		4270	without or something else still) is best for your problem, then I cannot
3179	help you but by giving some generic advice:	4271	help you, but here is some generic advice:
3180		4272
3181	=over 4	4273	=over 4
3182		4274
3183	=item * most applications have a main thread: use the default libev loop	4275	=item * most applications have a main thread: use the default libev loop
3184	in that thread, or create a separate thread running only the default loop.	4276	in that thread, or create a separate thread running only the default loop.
…		…
3196		4288
3197	Choosing a model is hard - look around, learn, know that usually you can do	4289	Choosing a model is hard - look around, learn, know that usually you can do
3198	better than you currently do :-)	4290	better than you currently do :-)
3199		4291
3200	=item * often you need to talk to some other thread which blocks in the	4292	=item * often you need to talk to some other thread which blocks in the
		4293	event loop.
		4294
3201	event loop - C<ev_async> watchers can be used to wake them up from other	4295	C<ev_async> watchers can be used to wake them up from other threads safely
3202	threads safely (or from signal contexts...).	4296	(or from signal contexts...).
		4297
		4298	An example use would be to communicate signals or other events that only
		4299	work in the default loop by registering the signal watcher with the
		4300	default loop and triggering an C<ev_async> watcher from the default loop
		4301	watcher callback into the event loop interested in the signal.
3203		4302
3204	=back	4303	=back
3205		4304
		4305	=head4 THREAD LOCKING EXAMPLE
		4306
		4307	Here is a fictitious example of how to run an event loop in a different
		4308	thread than where callbacks are being invoked and watchers are
		4309	created/added/removed.
		4310
		4311	For a real-world example, see the C<EV::Loop::Async> perl module,
		4312	which uses exactly this technique (which is suited for many high-level
		4313	languages).
		4314
		4315	The example uses a pthread mutex to protect the loop data, a condition
		4316	variable to wait for callback invocations, an async watcher to notify the
		4317	event loop thread and an unspecified mechanism to wake up the main thread.
		4318
		4319	First, you need to associate some data with the event loop:
		4320
		4321	typedef struct {
		4322	mutex_t lock; /* global loop lock */
		4323	ev_async async_w;
		4324	thread_t tid;
		4325	cond_t invoke_cv;
		4326	} userdata;
		4327
		4328	void prepare_loop (EV_P)
		4329	{
		4330	// for simplicity, we use a static userdata struct.
		4331	static userdata u;
		4332
		4333	ev_async_init (&u->async_w, async_cb);
		4334	ev_async_start (EV_A_ &u->async_w);
		4335
		4336	pthread_mutex_init (&u->lock, 0);
		4337	pthread_cond_init (&u->invoke_cv, 0);
		4338
		4339	// now associate this with the loop
		4340	ev_set_userdata (EV_A_ u);
		4341	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4342	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4343
		4344	// then create the thread running ev_loop
		4345	pthread_create (&u->tid, 0, l_run, EV_A);
		4346	}
		4347
		4348	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4349	solely to wake up the event loop so it takes notice of any new watchers
		4350	that might have been added:
		4351
		4352	static void
		4353	async_cb (EV_P_ ev_async *w, int revents)
		4354	{
		4355	// just used for the side effects
		4356	}
		4357
		4358	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4359	protecting the loop data, respectively.
		4360
		4361	static void
		4362	l_release (EV_P)
		4363	{
		4364	userdata *u = ev_userdata (EV_A);
		4365	pthread_mutex_unlock (&u->lock);
		4366	}
		4367
		4368	static void
		4369	l_acquire (EV_P)
		4370	{
		4371	userdata *u = ev_userdata (EV_A);
		4372	pthread_mutex_lock (&u->lock);
		4373	}
		4374
		4375	The event loop thread first acquires the mutex, and then jumps straight
		4376	into C<ev_run>:
		4377
		4378	void *
		4379	l_run (void *thr_arg)
		4380	{
		4381	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4382
		4383	l_acquire (EV_A);
		4384	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4385	ev_run (EV_A_ 0);
		4386	l_release (EV_A);
		4387
		4388	return 0;
		4389	}
		4390
		4391	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4392	signal the main thread via some unspecified mechanism (signals? pipe
		4393	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4394	have been called (in a while loop because a) spurious wakeups are possible
		4395	and b) skipping inter-thread-communication when there are no pending
		4396	watchers is very beneficial):
		4397
		4398	static void
		4399	l_invoke (EV_P)
		4400	{
		4401	userdata *u = ev_userdata (EV_A);
		4402
		4403	while (ev_pending_count (EV_A))
		4404	{
		4405	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4406	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4407	}
		4408	}
		4409
		4410	Now, whenever the main thread gets told to invoke pending watchers, it
		4411	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4412	thread to continue:
		4413
		4414	static void
		4415	real_invoke_pending (EV_P)
		4416	{
		4417	userdata *u = ev_userdata (EV_A);
		4418
		4419	pthread_mutex_lock (&u->lock);
		4420	ev_invoke_pending (EV_A);
		4421	pthread_cond_signal (&u->invoke_cv);
		4422	pthread_mutex_unlock (&u->lock);
		4423	}
		4424
		4425	Whenever you want to start/stop a watcher or do other modifications to an
		4426	event loop, you will now have to lock:
		4427
		4428	ev_timer timeout_watcher;
		4429	userdata *u = ev_userdata (EV_A);
		4430
		4431	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4432
		4433	pthread_mutex_lock (&u->lock);
		4434	ev_timer_start (EV_A_ &timeout_watcher);
		4435	ev_async_send (EV_A_ &u->async_w);
		4436	pthread_mutex_unlock (&u->lock);
		4437
		4438	Note that sending the C<ev_async> watcher is required because otherwise
		4439	an event loop currently blocking in the kernel will have no knowledge
		4440	about the newly added timer. By waking up the loop it will pick up any new
		4441	watchers in the next event loop iteration.
		4442
3206	=head2 COROUTINES	4443	=head3 COROUTINES
3207		4444
3208	Libev is much more accommodating to coroutines ("cooperative threads"):	4445	Libev is very accommodating to coroutines ("cooperative threads"):
3209	libev fully supports nesting calls to it's functions from different	4446	libev fully supports nesting calls to its functions from different
3210	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4447	coroutines (e.g. you can call C<ev_run> on the same loop from two
3211	different coroutines and switch freely between both coroutines running the	4448	different coroutines, and switch freely between both coroutines running
3212	loop, as long as you don't confuse yourself). The only exception is that	4449	the loop, as long as you don't confuse yourself). The only exception is
3213	you must not do this from C<ev_periodic> reschedule callbacks.	4450	that you must not do this from C<ev_periodic> reschedule callbacks.
3214		4451
3215	Care has been invested into making sure that libev does not keep local	4452	Care has been taken to ensure that libev does not keep local state inside
3216	state inside C<ev_loop>, and other calls do not usually allow coroutine	4453	C<ev_run>, and other calls do not usually allow for coroutine switches as
3217	switches.	4454	they do not call any callbacks.
3218		4455
		4456	=head2 COMPILER WARNINGS
3219		4457
3220	=head1 COMPLEXITIES	4458	Depending on your compiler and compiler settings, you might get no or a
		4459	lot of warnings when compiling libev code. Some people are apparently
		4460	scared by this.
3221		4461
3222	In this section the complexities of (many of) the algorithms used inside	4462	However, these are unavoidable for many reasons. For one, each compiler
3223	libev will be explained. For complexity discussions about backends see the	4463	has different warnings, and each user has different tastes regarding
3224	documentation for C<ev_default_init>.	4464	warning options. "Warn-free" code therefore cannot be a goal except when
		4465	targeting a specific compiler and compiler-version.
3225		4466
3226	All of the following are about amortised time: If an array needs to be	4467	Another reason is that some compiler warnings require elaborate
3227	extended, libev needs to realloc and move the whole array, but this	4468	workarounds, or other changes to the code that make it less clear and less
3228	happens asymptotically never with higher number of elements, so O(1) might	4469	maintainable.
3229	mean it might do a lengthy realloc operation in rare cases, but on average
3230	it is much faster and asymptotically approaches constant time.
3231		4470
3232	=over 4	4471	And of course, some compiler warnings are just plain stupid, or simply
		4472	wrong (because they don't actually warn about the condition their message
		4473	seems to warn about). For example, certain older gcc versions had some
		4474	warnings that resulted in an extreme number of false positives. These have
		4475	been fixed, but some people still insist on making code warn-free with
		4476	such buggy versions.
3233		4477
3234	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4478	While libev is written to generate as few warnings as possible,
		4479	"warn-free" code is not a goal, and it is recommended not to build libev
		4480	with any compiler warnings enabled unless you are prepared to cope with
		4481	them (e.g. by ignoring them). Remember that warnings are just that:
		4482	warnings, not errors, or proof of bugs.
3235		4483
3236	This means that, when you have a watcher that triggers in one hour and
3237	there are 100 watchers that would trigger before that then inserting will
3238	have to skip roughly seven (C<ld 100>) of these watchers.
3239		4484
3240	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4485	=head2 VALGRIND
3241		4486
3242	That means that changing a timer costs less than removing/adding them	4487	Valgrind has a special section here because it is a popular tool that is
3243	as only the relative motion in the event queue has to be paid for.	4488	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3244		4489
3245	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4490	If you think you found a bug (memory leak, uninitialised data access etc.)
		4491	in libev, then check twice: If valgrind reports something like:
3246		4492
3247	These just add the watcher into an array or at the head of a list.	4493	==2274== definitely lost: 0 bytes in 0 blocks.
		4494	==2274== possibly lost: 0 bytes in 0 blocks.
		4495	==2274== still reachable: 256 bytes in 1 blocks.
3248		4496
3249	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4497	Then there is no memory leak, just as memory accounted to global variables
		4498	is not a memleak - the memory is still being referenced, and didn't leak.
3250		4499
3251	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4500	Similarly, under some circumstances, valgrind might report kernel bugs
		4501	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4502	although an acceptable workaround has been found here), or it might be
		4503	confused.
3252		4504
3253	These watchers are stored in lists then need to be walked to find the	4505	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3254	correct watcher to remove. The lists are usually short (you don't usually	4506	make it into some kind of religion.
3255	have many watchers waiting for the same fd or signal).
3256		4507
3257	=item Finding the next timer in each loop iteration: O(1)	4508	If you are unsure about something, feel free to contact the mailing list
		4509	with the full valgrind report and an explanation on why you think this
		4510	is a bug in libev (best check the archives, too :). However, don't be
		4511	annoyed when you get a brisk "this is no bug" answer and take the chance
		4512	of learning how to interpret valgrind properly.
3258		4513
3259	By virtue of using a binary or 4-heap, the next timer is always found at a	4514	If you need, for some reason, empty reports from valgrind for your project
3260	fixed position in the storage array.	4515	I suggest using suppression lists.
3261		4516
3262	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3263		4517
3264	A change means an I/O watcher gets started or stopped, which requires	4518	=head1 PORTABILITY NOTES
3265	libev to recalculate its status (and possibly tell the kernel, depending
3266	on backend and whether C<ev_io_set> was used).
3267		4519
3268	=item Activating one watcher (putting it into the pending state): O(1)	4520	=head2 GNU/LINUX 32 BIT LIMITATIONS
3269		4521
3270	=item Priority handling: O(number_of_priorities)	4522	GNU/Linux is the only common platform that supports 64 bit file/large file
		4523	interfaces but I<disables> them by default.
3271		4524
3272	Priorities are implemented by allocating some space for each	4525	That means that libev compiled in the default environment doesn't support
3273	priority. When doing priority-based operations, libev usually has to	4526	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3274	linearly search all the priorities, but starting/stopping and activating
3275	watchers becomes O(1) w.r.t. priority handling.
3276		4527
3277	=item Sending an ev_async: O(1)	4528	Unfortunately, many programs try to work around this GNU/Linux issue
		4529	by enabling the large file API, which makes them incompatible with the
		4530	standard libev compiled for their system.
3278		4531
3279	=item Processing ev_async_send: O(number_of_async_watchers)	4532	Likewise, libev cannot enable the large file API itself as this would
		4533	suddenly make it incompatible to the default compile time environment,
		4534	i.e. all programs not using special compile switches.
3280		4535
3281	=item Processing signals: O(max_signal_number)	4536	=head2 OS/X AND DARWIN BUGS
3282		4537
3283	Sending involves a system call I<iff> there were no other C<ev_async_send>	4538	The whole thing is a bug if you ask me - basically any system interface
3284	calls in the current loop iteration. Checking for async and signal events	4539	you touch is broken, whether it is locales, poll, kqueue or even the
3285	involves iterating over all running async watchers or all signal numbers.	4540	OpenGL drivers.
3286		4541
3287	=back	4542	=head3 C<kqueue> is buggy
3288		4543
		4544	The kqueue syscall is broken in all known versions - most versions support
		4545	only sockets, many support pipes.
3289		4546
		4547	Libev tries to work around this by not using C<kqueue> by default on this
		4548	rotten platform, but of course you can still ask for it when creating a
		4549	loop - embedding a socket-only kqueue loop into a select-based one is
		4550	probably going to work well.
		4551
		4552	=head3 C<poll> is buggy
		4553
		4554	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4555	implementation by something calling C<kqueue> internally around the 10.5.6
		4556	release, so now C<kqueue> I<and> C<poll> are broken.
		4557
		4558	Libev tries to work around this by not using C<poll> by default on
		4559	this rotten platform, but of course you can still ask for it when creating
		4560	a loop.
		4561
		4562	=head3 C<select> is buggy
		4563
		4564	All that's left is C<select>, and of course Apple found a way to fuck this
		4565	one up as well: On OS/X, C<select> actively limits the number of file
		4566	descriptors you can pass in to 1024 - your program suddenly crashes when
		4567	you use more.
		4568
		4569	There is an undocumented "workaround" for this - defining
		4570	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4571	work on OS/X.
		4572
		4573	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4574
		4575	=head3 C<errno> reentrancy
		4576
		4577	The default compile environment on Solaris is unfortunately so
		4578	thread-unsafe that you can't even use components/libraries compiled
		4579	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4580	defined by default. A valid, if stupid, implementation choice.
		4581
		4582	If you want to use libev in threaded environments you have to make sure
		4583	it's compiled with C<_REENTRANT> defined.
		4584
		4585	=head3 Event port backend
		4586
		4587	The scalable event interface for Solaris is called "event
		4588	ports". Unfortunately, this mechanism is very buggy in all major
		4589	releases. If you run into high CPU usage, your program freezes or you get
		4590	a large number of spurious wakeups, make sure you have all the relevant
		4591	and latest kernel patches applied. No, I don't know which ones, but there
		4592	are multiple ones to apply, and afterwards, event ports actually work
		4593	great.
		4594
		4595	If you can't get it to work, you can try running the program by setting
		4596	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4597	C<select> backends.
		4598
		4599	=head2 AIX POLL BUG
		4600
		4601	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4602	this by trying to avoid the poll backend altogether (i.e. it's not even
		4603	compiled in), which normally isn't a big problem as C<select> works fine
		4604	with large bitsets on AIX, and AIX is dead anyway.
		4605
3290	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4606	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4607
		4608	=head3 General issues
3291		4609
3292	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4610	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3293	requires, and its I/O model is fundamentally incompatible with the POSIX	4611	requires, and its I/O model is fundamentally incompatible with the POSIX
3294	model. Libev still offers limited functionality on this platform in	4612	model. Libev still offers limited functionality on this platform in
3295	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4613	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3296	descriptors. This only applies when using Win32 natively, not when using	4614	descriptors. This only applies when using Win32 natively, not when using
3297	e.g. cygwin.	4615	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4616	as every compielr comes with a slightly differently broken/incompatible
		4617	environment.
3298		4618
3299	Lifting these limitations would basically require the full	4619	Lifting these limitations would basically require the full
3300	re-implementation of the I/O system. If you are into these kinds of	4620	re-implementation of the I/O system. If you are into this kind of thing,
3301	things, then note that glib does exactly that for you in a very portable	4621	then note that glib does exactly that for you in a very portable way (note
3302	way (note also that glib is the slowest event library known to man).	4622	also that glib is the slowest event library known to man).
3303		4623
3304	There is no supported compilation method available on windows except	4624	There is no supported compilation method available on windows except
3305	embedding it into other applications.	4625	embedding it into other applications.
		4626
		4627	Sensible signal handling is officially unsupported by Microsoft - libev
		4628	tries its best, but under most conditions, signals will simply not work.
3306		4629
3307	Not a libev limitation but worth mentioning: windows apparently doesn't	4630	Not a libev limitation but worth mentioning: windows apparently doesn't
3308	accept large writes: instead of resulting in a partial write, windows will	4631	accept large writes: instead of resulting in a partial write, windows will
3309	either accept everything or return C<ENOBUFS> if the buffer is too large,	4632	either accept everything or return C<ENOBUFS> if the buffer is too large,
3310	so make sure you only write small amounts into your sockets (less than a	4633	so make sure you only write small amounts into your sockets (less than a
3311	megabyte seems safe, but thsi apparently depends on the amount of memory	4634	megabyte seems safe, but this apparently depends on the amount of memory
3312	available).	4635	available).
3313		4636
3314	Due to the many, low, and arbitrary limits on the win32 platform and	4637	Due to the many, low, and arbitrary limits on the win32 platform and
3315	the abysmal performance of winsockets, using a large number of sockets	4638	the abysmal performance of winsockets, using a large number of sockets
3316	is not recommended (and not reasonable). If your program needs to use	4639	is not recommended (and not reasonable). If your program needs to use
3317	more than a hundred or so sockets, then likely it needs to use a totally	4640	more than a hundred or so sockets, then likely it needs to use a totally
3318	different implementation for windows, as libev offers the POSIX readiness	4641	different implementation for windows, as libev offers the POSIX readiness
3319	notification model, which cannot be implemented efficiently on windows	4642	notification model, which cannot be implemented efficiently on windows
3320	(Microsoft monopoly games).	4643	(due to Microsoft monopoly games).
3321		4644
3322	=over 4	4645	A typical way to use libev under windows is to embed it (see the embedding
		4646	section for details) and use the following F<evwrap.h> header file instead
		4647	of F<ev.h>:
3323		4648
		4649	#define EV_STANDALONE /* keeps ev from requiring config.h */
		4650	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
		4651
		4652	#include "ev.h"
		4653
		4654	And compile the following F<evwrap.c> file into your project (make sure
		4655	you do I<not> compile the F<ev.c> or any other embedded source files!):
		4656
		4657	#include "evwrap.h"
		4658	#include "ev.c"
		4659
3324	=item The winsocket select function	4660	=head3 The winsocket C<select> function
3325		4661
3326	The winsocket C<select> function doesn't follow POSIX in that it	4662	The winsocket C<select> function doesn't follow POSIX in that it
3327	requires socket I<handles> and not socket I<file descriptors> (it is	4663	requires socket I<handles> and not socket I<file descriptors> (it is
3328	also extremely buggy). This makes select very inefficient, and also	4664	also extremely buggy). This makes select very inefficient, and also
3329	requires a mapping from file descriptors to socket handles. See the	4665	requires a mapping from file descriptors to socket handles (the Microsoft
		4666	C runtime provides the function C<_open_osfhandle> for this). See the
3330	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and	4667	discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and
3331	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.	4668	C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info.
3332		4669
3333	The configuration for a "naked" win32 using the Microsoft runtime	4670	The configuration for a "naked" win32 using the Microsoft runtime
3334	libraries and raw winsocket select is:	4671	libraries and raw winsocket select is:
…		…
3337	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4674	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3338		4675
3339	Note that winsockets handling of fd sets is O(n), so you can easily get a	4676	Note that winsockets handling of fd sets is O(n), so you can easily get a
3340	complexity in the O(n²) range when using win32.	4677	complexity in the O(n²) range when using win32.
3341		4678
3342	=item Limited number of file descriptors	4679	=head3 Limited number of file descriptors
3343		4680
3344	Windows has numerous arbitrary (and low) limits on things.	4681	Windows has numerous arbitrary (and low) limits on things.
3345		4682
3346	Early versions of winsocket's select only supported waiting for a maximum	4683	Early versions of winsocket's select only supported waiting for a maximum
3347	of C<64> handles (probably owning to the fact that all windows kernels	4684	of C<64> handles (probably owning to the fact that all windows kernels
3348	can only wait for C<64> things at the same time internally; Microsoft	4685	can only wait for C<64> things at the same time internally; Microsoft
3349	recommends spawning a chain of threads and wait for 63 handles and the	4686	recommends spawning a chain of threads and wait for 63 handles and the
3350	previous thread in each. Great).	4687	previous thread in each. Sounds great!).
3351		4688
3352	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4689	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3353	to some high number (e.g. C<2048>) before compiling the winsocket select	4690	to some high number (e.g. C<2048>) before compiling the winsocket select
3354	call (which might be in libev or elsewhere, for example, perl does its own	4691	call (which might be in libev or elsewhere, for example, perl and many
3355	select emulation on windows).	4692	other interpreters do their own select emulation on windows).
3356		4693
3357	Another limit is the number of file descriptors in the Microsoft runtime	4694	Another limit is the number of file descriptors in the Microsoft runtime
3358	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4695	libraries, which by default is C<64> (there must be a hidden I<64>
3359	or something like this inside Microsoft). You can increase this by calling	4696	fetish or something like this inside Microsoft). You can increase this
3360	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4697	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3361	arbitrary limit), but is broken in many versions of the Microsoft runtime	4698	(another arbitrary limit), but is broken in many versions of the Microsoft
3362	libraries.
3363
3364	This might get you to about C<512> or C<2048> sockets (depending on	4699	runtime libraries. This might get you to about C<512> or C<2048> sockets
3365	windows version and/or the phase of the moon). To get more, you need to	4700	(depending on windows version and/or the phase of the moon). To get more,
3366	wrap all I/O functions and provide your own fd management, but the cost of	4701	you need to wrap all I/O functions and provide your own fd management, but
3367	calling select (O(n²)) will likely make this unworkable.	4702	the cost of calling select (O(n²)) will likely make this unworkable.
3368		4703
3369	=back
3370
3371
3372	=head1 PORTABILITY REQUIREMENTS	4704	=head2 PORTABILITY REQUIREMENTS
3373		4705
3374	In addition to a working ISO-C implementation, libev relies on a few	4706	In addition to a working ISO-C implementation and of course the
3375	additional extensions:	4707	backend-specific APIs, libev relies on a few additional extensions:
3376		4708
3377	=over 4	4709	=over 4
3378		4710
		4711	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
		4712	calling conventions regardless of C<ev_watcher_type *>.
		4713
		4714	Libev assumes not only that all watcher pointers have the same internal
		4715	structure (guaranteed by POSIX but not by ISO C for example), but it also
		4716	assumes that the same (machine) code can be used to call any watcher
		4717	callback: The watcher callbacks have different type signatures, but libev
		4718	calls them using an C<ev_watcher *> internally.
		4719
3379	=item C<sig_atomic_t volatile> must be thread-atomic as well	4720	=item C<sig_atomic_t volatile> must be thread-atomic as well
3380		4721
3381	The type C<sig_atomic_t volatile> (or whatever is defined as	4722	The type C<sig_atomic_t volatile> (or whatever is defined as
3382	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4723	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3383	threads. This is not part of the specification for C<sig_atomic_t>, but is	4724	threads. This is not part of the specification for C<sig_atomic_t>, but is
3384	believed to be sufficiently portable.	4725	believed to be sufficiently portable.
3385		4726
3386	=item C<sigprocmask> must work in a threaded environment	4727	=item C<sigprocmask> must work in a threaded environment
3387		4728
…		…
3396	except the initial one, and run the default loop in the initial thread as	4737	except the initial one, and run the default loop in the initial thread as
3397	well.	4738	well.
3398		4739
3399	=item C<long> must be large enough for common memory allocation sizes	4740	=item C<long> must be large enough for common memory allocation sizes
3400		4741
3401	To improve portability and simplify using libev, libev uses C<long>	4742	To improve portability and simplify its API, libev uses C<long> internally
3402	internally instead of C<size_t> when allocating its data structures. On	4743	instead of C<size_t> when allocating its data structures. On non-POSIX
3403	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4744	systems (Microsoft...) this might be unexpectedly low, but is still at
3404	is still at least 31 bits everywhere, which is enough for hundreds of	4745	least 31 bits everywhere, which is enough for hundreds of millions of
3405	millions of watchers.	4746	watchers.
3406		4747
3407	=item C<double> must hold a time value in seconds with enough accuracy	4748	=item C<double> must hold a time value in seconds with enough accuracy
3408		4749
3409	The type C<double> is used to represent timestamps. It is required to	4750	The type C<double> is used to represent timestamps. It is required to
3410	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4751	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3411	enough for at least into the year 4000. This requirement is fulfilled by	4752	good enough for at least into the year 4000 with millisecond accuracy
		4753	(the design goal for libev). This requirement is overfulfilled by
3412	implementations implementing IEEE 754 (basically all existing ones).	4754	implementations using IEEE 754, which is basically all existing ones. With
		4755	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3413		4756
3414	=back	4757	=back
3415		4758
3416	If you know of other additional requirements drop me a note.	4759	If you know of other additional requirements drop me a note.
3417		4760
3418		4761
3419	=head1 COMPILER WARNINGS	4762	=head1 ALGORITHMIC COMPLEXITIES
3420		4763
3421	Depending on your compiler and compiler settings, you might get no or a	4764	In this section the complexities of (many of) the algorithms used inside
3422	lot of warnings when compiling libev code. Some people are apparently	4765	libev will be documented. For complexity discussions about backends see
3423	scared by this.	4766	the documentation for C<ev_default_init>.
3424		4767
3425	However, these are unavoidable for many reasons. For one, each compiler	4768	All of the following are about amortised time: If an array needs to be
3426	has different warnings, and each user has different tastes regarding	4769	extended, libev needs to realloc and move the whole array, but this
3427	warning options. "Warn-free" code therefore cannot be a goal except when	4770	happens asymptotically rarer with higher number of elements, so O(1) might
3428	targeting a specific compiler and compiler-version.	4771	mean that libev does a lengthy realloc operation in rare cases, but on
		4772	average it is much faster and asymptotically approaches constant time.
3429		4773
3430	Another reason is that some compiler warnings require elaborate	4774	=over 4
3431	workarounds, or other changes to the code that make it less clear and less
3432	maintainable.
3433		4775
3434	And of course, some compiler warnings are just plain stupid, or simply	4776	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3435	wrong (because they don't actually warn about the condition their message
3436	seems to warn about).
3437		4777
3438	While libev is written to generate as few warnings as possible,	4778	This means that, when you have a watcher that triggers in one hour and
3439	"warn-free" code is not a goal, and it is recommended not to build libev	4779	there are 100 watchers that would trigger before that, then inserting will
3440	with any compiler warnings enabled unless you are prepared to cope with	4780	have to skip roughly seven (C<ld 100>) of these watchers.
3441	them (e.g. by ignoring them). Remember that warnings are just that:
3442	warnings, not errors, or proof of bugs.
3443		4781
		4782	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3444		4783
3445	=head1 VALGRIND	4784	That means that changing a timer costs less than removing/adding them,
		4785	as only the relative motion in the event queue has to be paid for.
3446		4786
3447	Valgrind has a special section here because it is a popular tool that is	4787	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3448	highly useful, but valgrind reports are very hard to interpret.
3449		4788
3450	If you think you found a bug (memory leak, uninitialised data access etc.)	4789	These just add the watcher into an array or at the head of a list.
3451	in libev, then check twice: If valgrind reports something like:
3452		4790
3453	==2274== definitely lost: 0 bytes in 0 blocks.	4791	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3454	==2274== possibly lost: 0 bytes in 0 blocks.
3455	==2274== still reachable: 256 bytes in 1 blocks.
3456		4792
3457	Then there is no memory leak. Similarly, under some circumstances,	4793	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3458	valgrind might report kernel bugs as if it were a bug in libev, or it
3459	might be confused (it is a very good tool, but only a tool).
3460		4794
3461	If you are unsure about something, feel free to contact the mailing list	4795	These watchers are stored in lists, so they need to be walked to find the
3462	with the full valgrind report and an explanation on why you think this is	4796	correct watcher to remove. The lists are usually short (you don't usually
3463	a bug in libev. However, don't be annoyed when you get a brisk "this is	4797	have many watchers waiting for the same fd or signal: one is typical, two
3464	no bug" answer and take the chance of learning how to interpret valgrind	4798	is rare).
3465	properly.
3466		4799
3467	If you need, for some reason, empty reports from valgrind for your project	4800	=item Finding the next timer in each loop iteration: O(1)
3468	I suggest using suppression lists.
3469		4801
		4802	By virtue of using a binary or 4-heap, the next timer is always found at a
		4803	fixed position in the storage array.
		4804
		4805	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4806
		4807	A change means an I/O watcher gets started or stopped, which requires
		4808	libev to recalculate its status (and possibly tell the kernel, depending
		4809	on backend and whether C<ev_io_set> was used).
		4810
		4811	=item Activating one watcher (putting it into the pending state): O(1)
		4812
		4813	=item Priority handling: O(number_of_priorities)
		4814
		4815	Priorities are implemented by allocating some space for each
		4816	priority. When doing priority-based operations, libev usually has to
		4817	linearly search all the priorities, but starting/stopping and activating
		4818	watchers becomes O(1) with respect to priority handling.
		4819
		4820	=item Sending an ev_async: O(1)
		4821
		4822	=item Processing ev_async_send: O(number_of_async_watchers)
		4823
		4824	=item Processing signals: O(max_signal_number)
		4825
		4826	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4827	calls in the current loop iteration. Checking for async and signal events
		4828	involves iterating over all running async watchers or all signal numbers.
		4829
		4830	=back
		4831
		4832
		4833	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4834
		4835	The major version 4 introduced some minor incompatible changes to the API.
		4836
		4837	At the moment, the C<ev.h> header file tries to implement superficial
		4838	compatibility, so most programs should still compile. Those might be
		4839	removed in later versions of libev, so better update early than late.
		4840
		4841	=over 4
		4842
		4843	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4844
		4845	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4846
		4847	ev_loop_destroy (EV_DEFAULT);
		4848	ev_loop_fork (EV_DEFAULT);
		4849
		4850	=item function/symbol renames
		4851
		4852	A number of functions and symbols have been renamed:
		4853
		4854	ev_loop => ev_run
		4855	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4856	EVLOOP_ONESHOT => EVRUN_ONCE
		4857
		4858	ev_unloop => ev_break
		4859	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4860	EVUNLOOP_ONE => EVBREAK_ONE
		4861	EVUNLOOP_ALL => EVBREAK_ALL
		4862
		4863	EV_TIMEOUT => EV_TIMER
		4864
		4865	ev_loop_count => ev_iteration
		4866	ev_loop_depth => ev_depth
		4867	ev_loop_verify => ev_verify
		4868
		4869	Most functions working on C<struct ev_loop> objects don't have an
		4870	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4871	associated constants have been renamed to not collide with the C<struct
		4872	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4873	as all other watcher types. Note that C<ev_loop_fork> is still called
		4874	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4875	typedef.
		4876
		4877	=item C<EV_COMPAT3> backwards compatibility mechanism
		4878
		4879	The backward compatibility mechanism can be controlled by
		4880	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4881	section.
		4882
		4883	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4884
		4885	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4886	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4887	and work, but the library code will of course be larger.
		4888
		4889	=back
		4890
		4891
		4892	=head1 GLOSSARY
		4893
		4894	=over 4
		4895
		4896	=item active
		4897
		4898	A watcher is active as long as it has been started and not yet stopped.
		4899	See L<WATCHER STATES> for details.
		4900
		4901	=item application
		4902
		4903	In this document, an application is whatever is using libev.
		4904
		4905	=item backend
		4906
		4907	The part of the code dealing with the operating system interfaces.
		4908
		4909	=item callback
		4910
		4911	The address of a function that is called when some event has been
		4912	detected. Callbacks are being passed the event loop, the watcher that
		4913	received the event, and the actual event bitset.
		4914
		4915	=item callback/watcher invocation
		4916
		4917	The act of calling the callback associated with a watcher.
		4918
		4919	=item event
		4920
		4921	A change of state of some external event, such as data now being available
		4922	for reading on a file descriptor, time having passed or simply not having
		4923	any other events happening anymore.
		4924
		4925	In libev, events are represented as single bits (such as C<EV_READ> or
		4926	C<EV_TIMER>).
		4927
		4928	=item event library
		4929
		4930	A software package implementing an event model and loop.
		4931
		4932	=item event loop
		4933
		4934	An entity that handles and processes external events and converts them
		4935	into callback invocations.
		4936
		4937	=item event model
		4938
		4939	The model used to describe how an event loop handles and processes
		4940	watchers and events.
		4941
		4942	=item pending
		4943
		4944	A watcher is pending as soon as the corresponding event has been
		4945	detected. See L<WATCHER STATES> for details.
		4946
		4947	=item real time
		4948
		4949	The physical time that is observed. It is apparently strictly monotonic :)
		4950
		4951	=item wall-clock time
		4952
		4953	The time and date as shown on clocks. Unlike real time, it can actually
		4954	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4955	clock.
		4956
		4957	=item watcher
		4958
		4959	A data structure that describes interest in certain events. Watchers need
		4960	to be started (attached to an event loop) before they can receive events.
		4961
		4962	=back
3470		4963
3471	=head1 AUTHOR	4964	=head1 AUTHOR
3472		4965
3473	Marc Lehmann <libev@schmorp.de>.	4966	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3474		4967

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