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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
		90
		91	=head1 ABOUT LIBEV
72		92
73	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
74	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
75	these event sources and provide your program with events.	95	these event sources and provide your program with events.
76		96
…		…
86	=head2 FEATURES	106	=head2 FEATURES
87		107
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
98		119
99	It also is quite fast (see this	120	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	122	for example).
102		123
…		…
105	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	132	this argument.
112		133
113	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
114		135
115	Libev represents time as a single floating point number, representing the	136	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	138	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	139	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	140	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
121	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
122	throughout libev.	144	time differences (e.g. delays) throughout libev.
123		145
124	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
125		147
126	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	149	and internal errors (bugs).
…		…
151		173
152	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
153		175
154	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
155	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
157		180
158	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
159		182
160	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked until
161	either it is interrupted or the given time interval has passed. Basically	184	either it is interrupted or the given time interval has passed. Basically
…		…
178	as this indicates an incompatible change. Minor versions are usually	201	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	202	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	203	not a problem.
181		204
182	Example: Make sure we haven't accidentally been linked against the wrong	205	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	206	version (note, however, that this will not detect other ABI mismatches,
		207	such as LFS or reentrancy).
184		208
185	assert (("libev version mismatch",	209	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	210	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	211	&& ev_version_minor () >= EV_VERSION_MINOR));
188		212
…		…
199	assert (("sorry, no epoll, no sex",	223	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	224	ev_supported_backends () & EVBACKEND_EPOLL));
201		225
202	=item unsigned int ev_recommended_backends ()	226	=item unsigned int ev_recommended_backends ()
203		227
204	Return the set of all backends compiled into this binary of libev and also	228	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	229	also recommended for this platform, meaning it will work for most file
		230	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	231	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	232	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	233	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	234	probe for if you specify no backends explicitly.
210		235
211	=item unsigned int ev_embeddable_backends ()	236	=item unsigned int ev_embeddable_backends ()
212		237
213	Returns the set of backends that are embeddable in other event loops. This	238	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	239	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	240	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	241	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	242	& ev_supported_backends ()>, likewise for recommended ones.
218		243
219	See the description of C<ev_embed> watchers for more info.	244	See the description of C<ev_embed> watchers for more info.
220		245
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	246	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
222		247
223	Sets the allocation function to use (the prototype is similar - the	248	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	249	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	250	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	251	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
252	}	277	}
253		278
254	...	279	...
255	ev_set_allocator (persistent_realloc);	280	ev_set_allocator (persistent_realloc);
256		281
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	282	=item ev_set_syserr_cb (void (*cb)(const char *msg))
258		283
259	Set the callback function to call on a retryable system call error (such	284	Set the callback function to call on a retryable system call error (such
260	as failed select, poll, epoll_wait). The message is a printable string	285	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	286	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	287	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	299	}
275		300
276	...	301	...
277	ev_set_syserr_cb (fatal_error);	302	ev_set_syserr_cb (fatal_error);
278		303
		304	=item ev_feed_signal (int signum)
		305
		306	This function can be used to "simulate" a signal receive. It is completely
		307	safe to call this function at any time, from any context, including signal
		308	handlers or random threads.
		309
		310	Its main use is to customise signal handling in your process, especially
		311	in the presence of threads. For example, you could block signals
		312	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		313	creating any loops), and in one thread, use C<sigwait> or any other
		314	mechanism to wait for signals, then "deliver" them to libev by calling
		315	C<ev_feed_signal>.
		316
279	=back	317	=back
280		318
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	319	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		320
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	321	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	322	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	323	libev 3 had an C<ev_loop> function colliding with the struct name).
286		324
287	The library knows two types of such loops, the I<default> loop, which	325	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	326	supports child process events, and dynamically created event loops which
289	not.	327	do not.
290		328
291	=over 4	329	=over 4
292		330
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	331	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		332
295	This will initialise the default event loop if it hasn't been initialised	333	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	334	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	335	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	336	C<ev_loop_new>.
		337
		338	If the default loop is already initialised then this function simply
		339	returns it (and ignores the flags. If that is troubling you, check
		340	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		341	flags, which should almost always be C<0>, unless the caller is also the
		342	one calling C<ev_run> or otherwise qualifies as "the main program".
299		343
300	If you don't know what event loop to use, use the one returned from this	344	If you don't know what event loop to use, use the one returned from this
301	function.	345	function (or via the C<EV_DEFAULT> macro).
302		346
303	Note that this function is I<not> thread-safe, so if you want to use it	347	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	348	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	349	that this case is unlikely, as loops cannot be shared easily between
		350	threads anyway).
306		351
307	The default loop is the only loop that can handle C<ev_signal> and	352	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	353	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	354	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	355	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	356	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	357
		358	Example: This is the most typical usage.
		359
		360	if (!ev_default_loop (0))
		361	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		362
		363	Example: Restrict libev to the select and poll backends, and do not allow
		364	environment settings to be taken into account:
		365
		366	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		367
		368	=item struct ev_loop *ev_loop_new (unsigned int flags)
		369
		370	This will create and initialise a new event loop object. If the loop
		371	could not be initialised, returns false.
		372
		373	This function is thread-safe, and one common way to use libev with
		374	threads is indeed to create one loop per thread, and using the default
		375	loop in the "main" or "initial" thread.
313		376
314	The flags argument can be used to specify special behaviour or specific	377	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	378	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		379
317	The following flags are supported:	380	The following flags are supported:
…		…
332	useful to try out specific backends to test their performance, or to work	395	useful to try out specific backends to test their performance, or to work
333	around bugs.	396	around bugs.
334		397
335	=item C<EVFLAG_FORKCHECK>	398	=item C<EVFLAG_FORKCHECK>
336		399
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	400	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	401	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		402
341	This works by calling C<getpid ()> on every iteration of the loop,	403	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	404	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	405	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	406	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
350	flag.	412	flag.
351		413
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	414	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	415	environment variable.
354		416
		417	=item C<EVFLAG_NOINOTIFY>
		418
		419	When this flag is specified, then libev will not attempt to use the
		420	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		421	testing, this flag can be useful to conserve inotify file descriptors, as
		422	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		423
		424	=item C<EVFLAG_SIGNALFD>
		425
		426	When this flag is specified, then libev will attempt to use the
		427	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		428	delivers signals synchronously, which makes it both faster and might make
		429	it possible to get the queued signal data. It can also simplify signal
		430	handling with threads, as long as you properly block signals in your
		431	threads that are not interested in handling them.
		432
		433	Signalfd will not be used by default as this changes your signal mask, and
		434	there are a lot of shoddy libraries and programs (glib's threadpool for
		435	example) that can't properly initialise their signal masks.
		436
		437	=item C<EVFLAG_NOSIGMASK>
		438
		439	When this flag is specified, then libev will avoid to modify the signal
		440	mask. Specifically, this means you ahve to make sure signals are unblocked
		441	when you want to receive them.
		442
		443	This behaviour is useful when you want to do your own signal handling, or
		444	want to handle signals only in specific threads and want to avoid libev
		445	unblocking the signals.
		446
		447	This flag's behaviour will become the default in future versions of libev.
		448
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	449	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		450
357	This is your standard select(2) backend. Not I<completely> standard, as	451	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	452	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	453	but if that fails, expect a fairly low limit on the number of fds when
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	477	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	478	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		479
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	480	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		481
		482	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		483	kernels).
		484
388	For few fds, this backend is a bit little slower than poll and select,	485	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	486	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	487	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	488	epoll scales either O(1) or O(active_fds).
392		489
393	The epoll mechanism deserves honorable mention as the most misdesigned	490	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	491	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	492	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	493	descriptor (and unnecessary guessing of parameters), problems with dup,
		494	returning before the timeout value, resulting in additional iterations
		495	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	496	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	497	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	498	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	499	and is of course hard to detect.
401		500
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	501	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
403	of course I<doesn't>, and epoll just loves to report events for totally	502	of course I<doesn't>, and epoll just loves to report events for totally
404	I<different> file descriptors (even already closed ones, so one cannot	503	I<different> file descriptors (even already closed ones, so one cannot
405	even remove them from the set) than registered in the set (especially	504	even remove them from the set) than registered in the set (especially
406	on SMP systems). Libev tries to counter these spurious notifications by	505	on SMP systems). Libev tries to counter these spurious notifications by
407	employing an additional generation counter and comparing that against the	506	employing an additional generation counter and comparing that against the
408	events to filter out spurious ones, recreating the set when required.	507	events to filter out spurious ones, recreating the set when required. Last
		508	not least, it also refuses to work with some file descriptors which work
		509	perfectly fine with C<select> (files, many character devices...).
		510
		511	Epoll is truly the train wreck analog among event poll mechanisms.
409		512
410	While stopping, setting and starting an I/O watcher in the same iteration	513	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	514	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	515	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	516	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
502		605
503	Try all backends (even potentially broken ones that wouldn't be tried	606	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	607	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	608	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		609
507	It is definitely not recommended to use this flag.	610	It is definitely not recommended to use this flag, use whatever
		611	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		612	at all.
		613
		614	=item C<EVBACKEND_MASK>
		615
		616	Not a backend at all, but a mask to select all backend bits from a
		617	C<flags> value, in case you want to mask out any backends from a flags
		618	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		619
509	=back	620	=back
510		621
511	If one or more of these are or'ed into the flags value, then only these	622	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	623	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	624	here). If none are specified, all backends in C<ev_recommended_backends
514		625	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		626
543	Example: Try to create a event loop that uses epoll and nothing else.	627	Example: Try to create a event loop that uses epoll and nothing else.
544		628
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	629	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	630	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	631	fatal ("no epoll found here, maybe it hides under your chair");
548		632
		633	Example: Use whatever libev has to offer, but make sure that kqueue is
		634	used if available.
		635
		636	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		637
549	=item ev_default_destroy ()	638	=item ev_loop_destroy (loop)
550		639
551	Destroys the default loop again (frees all memory and kernel state	640	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	641	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	642	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	643	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	644	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	645	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		647
559	Note that certain global state, such as signal state (and installed signal	648	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	649	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	650	as signal and child watchers) would need to be stopped manually.
562		651
563	In general it is not advisable to call this function except in the	652	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	653	C<ev_loop_new>, but it can also be used on the default loop returned by
		654	C<ev_default_loop>, in which case it is not thread-safe.
		655
		656	Note that it is not advisable to call this function on the default loop
		657	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	658	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	659	and C<ev_loop_destroy>.
567		660
568	=item ev_loop_destroy (loop)	661	=item ev_loop_fork (loop)
569		662
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	663	This function sets a flag that causes subsequent C<ev_run> iterations to
576	to reinitialise the kernel state for backends that have one. Despite the	664	reinitialise the kernel state for backends that have one. Despite the
577	name, you can call it anytime, but it makes most sense after forking, in	665	name, you can call it anytime, but it makes most sense after forking, in
578	the child process (or both child and parent, but that again makes little	666	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
579	sense). You I<must> call it in the child before using any of the libev	667	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	668
		669	Again, you I<have> to call it on I<any> loop that you want to re-use after
		670	a fork, I<even if you do not plan to use the loop in the parent>. This is
		671	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		672	during fork.
581		673
582	On the other hand, you only need to call this function in the child	674	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	675	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	676	you just fork+exec or create a new loop in the child, you don't have to
		677	call it at all (in fact, C<epoll> is so badly broken that it makes a
		678	difference, but libev will usually detect this case on its own and do a
		679	costly reset of the backend).
585		680
586	The function itself is quite fast and it's usually not a problem to call	681	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	682	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		683
		684	Example: Automate calling C<ev_loop_fork> on the default loop when
		685	using pthreads.
		686
		687	static void
		688	post_fork_child (void)
		689	{
		690	ev_loop_fork (EV_DEFAULT);
		691	}
		692
		693	...
590	pthread_atfork (0, 0, ev_default_fork);	694	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		695
599	=item int ev_is_default_loop (loop)	696	=item int ev_is_default_loop (loop)
600		697
601	Returns true when the given loop is, in fact, the default loop, and false	698	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	699	otherwise.
603		700
604	=item unsigned int ev_loop_count (loop)	701	=item unsigned int ev_iteration (loop)
605		702
606	Returns the count of loop iterations for the loop, which is identical to	703	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	704	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	705	and happily wraps around with enough iterations.
609		706
610	This value can sometimes be useful as a generation counter of sorts (it	707	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	708	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	709	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		710	prepare and check phases.
		711
		712	=item unsigned int ev_depth (loop)
		713
		714	Returns the number of times C<ev_run> was entered minus the number of
		715	times C<ev_run> was exited normally, in other words, the recursion depth.
		716
		717	Outside C<ev_run>, this number is zero. In a callback, this number is
		718	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		719	in which case it is higher.
		720
		721	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		722	throwing an exception etc.), doesn't count as "exit" - consider this
		723	as a hint to avoid such ungentleman-like behaviour unless it's really
		724	convenient, in which case it is fully supported.
613		725
614	=item unsigned int ev_backend (loop)	726	=item unsigned int ev_backend (loop)
615		727
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	728	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	729	use.
…		…
626		738
627	=item ev_now_update (loop)	739	=item ev_now_update (loop)
628		740
629	Establishes the current time by querying the kernel, updating the time	741	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	742	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	743	is usually done automatically within C<ev_run ()>.
632		744
633	This function is rarely useful, but when some event callback runs for a	745	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	746	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	747	the current time is a good idea.
636		748
637	See also "The special problem of time updates" in the C<ev_timer> section.	749	See also L<The special problem of time updates> in the C<ev_timer> section.
638		750
		751	=item ev_suspend (loop)
		752
		753	=item ev_resume (loop)
		754
		755	These two functions suspend and resume an event loop, for use when the
		756	loop is not used for a while and timeouts should not be processed.
		757
		758	A typical use case would be an interactive program such as a game: When
		759	the user presses C<^Z> to suspend the game and resumes it an hour later it
		760	would be best to handle timeouts as if no time had actually passed while
		761	the program was suspended. This can be achieved by calling C<ev_suspend>
		762	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		763	C<ev_resume> directly afterwards to resume timer processing.
		764
		765	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		766	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		767	will be rescheduled (that is, they will lose any events that would have
		768	occurred while suspended).
		769
		770	After calling C<ev_suspend> you B<must not> call I<any> function on the
		771	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		772	without a previous call to C<ev_suspend>.
		773
		774	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		775	event loop time (see C<ev_now_update>).
		776
639	=item ev_loop (loop, int flags)	777	=item ev_run (loop, int flags)
640		778
641	Finally, this is it, the event handler. This function usually is called	779	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	780	after you have initialised all your watchers and you want to start
643	events.	781	handling events. It will ask the operating system for any new events, call
		782	the watcher callbacks, an then repeat the whole process indefinitely: This
		783	is why event loops are called I<loops>.
644		784
645	If the flags argument is specified as C<0>, it will not return until	785	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	786	until either no event watchers are active anymore or C<ev_break> was
		787	called.
647		788
648	Please note that an explicit C<ev_unloop> is usually better than	789	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	790	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	791	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	792	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	793	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	794	beauty.
654		795
		796	This function is also I<mostly> exception-safe - you can break out of
		797	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		798	exception and so on. This does not decrement the C<ev_depth> value, nor
		799	will it clear any outstanding C<EVBREAK_ONE> breaks.
		800
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	801	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	802	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	803	block your process in case there are no events and will return after one
658	the loop.	804	iteration of the loop. This is sometimes useful to poll and handle new
		805	events while doing lengthy calculations, to keep the program responsive.
659		806
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	807	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	808	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	809	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	810	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	811	user-registered callback will be called), and will return after one
665	iteration of the loop.	812	iteration of the loop.
666		813
667	This is useful if you are waiting for some external event in conjunction	814	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	815	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	816	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	817	usually a better approach for this kind of thing.
671		818
672	Here are the gory details of what C<ev_loop> does:	819	Here are the gory details of what C<ev_run> does:
673		820
		821	- Increment loop depth.
		822	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	823	- Before the first iteration, call any pending watchers.
		824	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	825	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	826	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	827	- Queue and call all prepare watchers.
		828	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	829	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	830	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	831	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	832	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	833	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	834	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	835	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	836	- Sleep if the I/O and timer collect interval say so.
		837	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	838	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	839	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	840	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	841	- Queue all expired timers.
690	- Queue all expired periodics.	842	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	843	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	844	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	845	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	846	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	847	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	848	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	849	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	850	continue with step LOOP.
		851	FINISH:
		852	- Reset the ev_break status iff it was EVBREAK_ONE.
		853	- Decrement the loop depth.
		854	- Return.
699		855
700	Example: Queue some jobs and then loop until no events are outstanding	856	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	857	anymore.
702		858
703	... queue jobs here, make sure they register event watchers as long	859	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	860	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	861	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	862	... jobs done or somebody called unloop. yeah!
707		863
708	=item ev_unloop (loop, how)	864	=item ev_break (loop, how)
709		865
710	Can be used to make a call to C<ev_loop> return early (but only after it	866	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	867	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	868	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	869	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		870
715	This "unloop state" will be cleared when entering C<ev_loop> again.	871	This "break state" will be cleared on the next call to C<ev_run>.
716		872
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	873	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		874	which case it will have no effect.
718		875
719	=item ev_ref (loop)	876	=item ev_ref (loop)
720		877
721	=item ev_unref (loop)	878	=item ev_unref (loop)
722		879
723	Ref/unref can be used to add or remove a reference count on the event	880	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	881	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	882	count is nonzero, C<ev_run> will not return on its own.
726		883
727	If you have a watcher you never unregister that should not keep C<ev_loop>	884	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	885	unregister, but that nevertheless should not keep C<ev_run> from
		886	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	887	before stopping it.
730		888
731	As an example, libev itself uses this for its internal signal pipe: It is	889	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	890	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	891	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	892	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	893	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	894	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	895	before, respectively. Note also that libev might stop watchers itself
		896	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		897	in the callback).
738		898
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	899	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	900	running when nothing else is active.
741		901
742	ev_signal exitsig;	902	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	903	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	904	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	905	ev_unref (loop);
746		906
747	Example: For some weird reason, unregister the above signal handler again.	907	Example: For some weird reason, unregister the above signal handler again.
748		908
749	ev_ref (loop);	909	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	910	ev_signal_stop (loop, &exitsig);
…		…
771		931
772	By setting a higher I<io collect interval> you allow libev to spend more	932	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	933	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	934	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	935	C<ev_timer>) will be not affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	936	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		937	sleep time ensures that libev will not poll for I/O events more often then
		938	once per this interval, on average.
777		939
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	940	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	941	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	942	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	943	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		945
784	Many (busy) programs can usually benefit by setting the I/O collect	946	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	947	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	948	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	949	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	950	as this approaches the timing granularity of most systems. Note that if
		951	you do transactions with the outside world and you can't increase the
		952	parallelity, then this setting will limit your transaction rate (if you
		953	need to poll once per transaction and the I/O collect interval is 0.01,
		954	then you can't do more than 100 transactions per second).
789		955
790	Setting the I<timeout collect interval> can improve the opportunity for	956	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	957	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	958	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	959	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	960	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	961	they fire on, say, one-second boundaries only.
796		962
		963	Example: we only need 0.1s timeout granularity, and we wish not to poll
		964	more often than 100 times per second:
		965
		966	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		967	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		968
		969	=item ev_invoke_pending (loop)
		970
		971	This call will simply invoke all pending watchers while resetting their
		972	pending state. Normally, C<ev_run> does this automatically when required,
		973	but when overriding the invoke callback this call comes handy. This
		974	function can be invoked from a watcher - this can be useful for example
		975	when you want to do some lengthy calculation and want to pass further
		976	event handling to another thread (you still have to make sure only one
		977	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		978
		979	=item int ev_pending_count (loop)
		980
		981	Returns the number of pending watchers - zero indicates that no watchers
		982	are pending.
		983
		984	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		985
		986	This overrides the invoke pending functionality of the loop: Instead of
		987	invoking all pending watchers when there are any, C<ev_run> will call
		988	this callback instead. This is useful, for example, when you want to
		989	invoke the actual watchers inside another context (another thread etc.).
		990
		991	If you want to reset the callback, use C<ev_invoke_pending> as new
		992	callback.
		993
		994	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		995
		996	Sometimes you want to share the same loop between multiple threads. This
		997	can be done relatively simply by putting mutex_lock/unlock calls around
		998	each call to a libev function.
		999
		1000	However, C<ev_run> can run an indefinite time, so it is not feasible
		1001	to wait for it to return. One way around this is to wake up the event
		1002	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1003	I<release> and I<acquire> callbacks on the loop.
		1004
		1005	When set, then C<release> will be called just before the thread is
		1006	suspended waiting for new events, and C<acquire> is called just
		1007	afterwards.
		1008
		1009	Ideally, C<release> will just call your mutex_unlock function, and
		1010	C<acquire> will just call the mutex_lock function again.
		1011
		1012	While event loop modifications are allowed between invocations of
		1013	C<release> and C<acquire> (that's their only purpose after all), no
		1014	modifications done will affect the event loop, i.e. adding watchers will
		1015	have no effect on the set of file descriptors being watched, or the time
		1016	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1017	to take note of any changes you made.
		1018
		1019	In theory, threads executing C<ev_run> will be async-cancel safe between
		1020	invocations of C<release> and C<acquire>.
		1021
		1022	See also the locking example in the C<THREADS> section later in this
		1023	document.
		1024
		1025	=item ev_set_userdata (loop, void *data)
		1026
		1027	=item void *ev_userdata (loop)
		1028
		1029	Set and retrieve a single C<void *> associated with a loop. When
		1030	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1031	C<0>.
		1032
		1033	These two functions can be used to associate arbitrary data with a loop,
		1034	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1035	C<acquire> callbacks described above, but of course can be (ab-)used for
		1036	any other purpose as well.
		1037
797	=item ev_loop_verify (loop)	1038	=item ev_verify (loop)
798		1039
799	This function only does something when C<EV_VERIFY> support has been	1040	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1041	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1042	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1043	is found to be inconsistent, it will print an error message to standard
…		…
813		1054
814	In the following description, uppercase C<TYPE> in names stands for the	1055	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1056	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1057	watchers and C<ev_io_start> for I/O watchers.
817		1058
818	A watcher is a structure that you create and register to record your	1059	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1060	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1061	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1062	for that:
821		1063
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1064	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1065	{
824	ev_io_stop (w);	1066	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1067	ev_break (loop, EVBREAK_ALL);
826	}	1068	}
827		1069
828	struct ev_loop *loop = ev_default_loop (0);	1070	struct ev_loop *loop = ev_default_loop (0);
829		1071
830	ev_io stdin_watcher;	1072	ev_io stdin_watcher;
831		1073
832	ev_init (&stdin_watcher, my_cb);	1074	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1075	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1076	ev_io_start (loop, &stdin_watcher);
835		1077
836	ev_loop (loop, 0);	1078	ev_run (loop, 0);
837		1079
838	As you can see, you are responsible for allocating the memory for your	1080	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1081	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1082	stack).
841		1083
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1084	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1085	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1086
845	Each watcher structure must be initialised by a call to C<ev_init	1087	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1088	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1089	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1090	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1091	and/or writable).
850		1092
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1093	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1094	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1095	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1096	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1119	=item C<EV_WRITE>
878		1120
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1121	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1122	writable.
881		1123
882	=item C<EV_TIMEOUT>	1124	=item C<EV_TIMER>
883		1125
884	The C<ev_timer> watcher has timed out.	1126	The C<ev_timer> watcher has timed out.
885		1127
886	=item C<EV_PERIODIC>	1128	=item C<EV_PERIODIC>
887		1129
…		…
905		1147
906	=item C<EV_PREPARE>	1148	=item C<EV_PREPARE>
907		1149
908	=item C<EV_CHECK>	1150	=item C<EV_CHECK>
909		1151
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1152	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
911	to gather new events, and all C<ev_check> watchers are invoked just after	1153	to gather new events, and all C<ev_check> watchers are invoked just after
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1154	C<ev_run> has gathered them, but before it invokes any callbacks for any
913	received events. Callbacks of both watcher types can start and stop as	1155	received events. Callbacks of both watcher types can start and stop as
914	many watchers as they want, and all of them will be taken into account	1156	many watchers as they want, and all of them will be taken into account
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1157	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
916	C<ev_loop> from blocking).	1158	C<ev_run> from blocking).
917		1159
918	=item C<EV_EMBED>	1160	=item C<EV_EMBED>
919		1161
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1162	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1163
922	=item C<EV_FORK>	1164	=item C<EV_FORK>
923		1165
924	The event loop has been resumed in the child process after fork (see	1166	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1167	C<ev_fork>).
926		1168
		1169	=item C<EV_CLEANUP>
		1170
		1171	The event loop is about to be destroyed (see C<ev_cleanup>).
		1172
927	=item C<EV_ASYNC>	1173	=item C<EV_ASYNC>
928		1174
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1175	The given async watcher has been asynchronously notified (see C<ev_async>).
		1176
		1177	=item C<EV_CUSTOM>
		1178
		1179	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1180	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1181
931	=item C<EV_ERROR>	1182	=item C<EV_ERROR>
932		1183
933	An unspecified error has occurred, the watcher has been stopped. This might	1184	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1185	happen because the watcher could not be properly started because libev
…		…
972		1223
973	ev_io w;	1224	ev_io w;
974	ev_init (&w, my_cb);	1225	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1226	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1227
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1228	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1229
979	This macro initialises the type-specific parts of a watcher. You need to	1230	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1231	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1232	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1233	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1246
996	Example: Initialise and set an C<ev_io> watcher in one step.	1247	Example: Initialise and set an C<ev_io> watcher in one step.
997		1248
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1249	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1250
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1251	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1252
1002	Starts (activates) the given watcher. Only active watchers will receive	1253	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1254	events. If the watcher is already active nothing will happen.
1004		1255
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1256	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1257	whole section.
1007		1258
1008	ev_io_start (EV_DEFAULT_UC, &w);	1259	ev_io_start (EV_DEFAULT_UC, &w);
1009		1260
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1261	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1262
1012	Stops the given watcher if active, and clears the pending status (whether	1263	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1264	the watcher was active or not).
1014		1265
1015	It is possible that stopped watchers are pending - for example,	1266	It is possible that stopped watchers are pending - for example,
…		…
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1291	=item ev_cb_set (ev_TYPE *watcher, callback)
1041		1292
1042	Change the callback. You can change the callback at virtually any time	1293	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1294	(modulo threads).
1044		1295
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1296	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1297
1047	=item int ev_priority (ev_TYPE *watcher)	1298	=item int ev_priority (ev_TYPE *watcher)
1048		1299
1049	Set and query the priority of the watcher. The priority is a small	1300	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1301	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1302	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1303	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1304	from being executed (except for C<ev_idle> watchers).
1054		1305
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1306	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1307	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1308
1063	You I<must not> change the priority of a watcher as long as it is active or	1309	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1310	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1311
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1312	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1313	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1314	or might not have been clamped to the valid range.
		1315
		1316	The default priority used by watchers when no priority has been set is
		1317	always C<0>, which is supposed to not be too high and not be too low :).
		1318
		1319	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1320	priorities.
1072		1321
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1322	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1323
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1324	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1325	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1333	watcher isn't pending it does nothing and returns C<0>.
1085		1334
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1335	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1336	callback to be invoked, which can be accomplished with this function.
1088		1337
		1338	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1339
		1340	Feeds the given event set into the event loop, as if the specified event
		1341	had happened for the specified watcher (which must be a pointer to an
		1342	initialised but not necessarily started event watcher). Obviously you must
		1343	not free the watcher as long as it has pending events.
		1344
		1345	Stopping the watcher, letting libev invoke it, or calling
		1346	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1347	not started in the first place.
		1348
		1349	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1350	functions that do not need a watcher.
		1351
1089	=back	1352	=back
1090
1091		1353
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1354	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1093		1355
1094	Each watcher has, by default, a member C<void *data> that you can change	1356	Each watcher has, by default, a member C<void *data> that you can change
1095	and read at any time: libev will completely ignore it. This can be used	1357	and read at any time: libev will completely ignore it. This can be used
…		…
1141	#include <stddef.h>	1403	#include <stddef.h>
1142		1404
1143	static void	1405	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)	1406	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{	1407	{
1146	struct my_biggy big = (struct my_biggy *	1408	struct my_biggy big = (struct my_biggy *)
1147	(((char *)w) - offsetof (struct my_biggy, t1));	1409	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}	1410	}
1149		1411
1150	static void	1412	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)	1413	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{	1414	{
1153	struct my_biggy big = (struct my_biggy *	1415	struct my_biggy big = (struct my_biggy *)
1154	(((char *)w) - offsetof (struct my_biggy, t2));	1416	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}	1417	}
		1418
		1419	=head2 WATCHER STATES
		1420
		1421	There are various watcher states mentioned throughout this manual -
		1422	active, pending and so on. In this section these states and the rules to
		1423	transition between them will be described in more detail - and while these
		1424	rules might look complicated, they usually do "the right thing".
		1425
		1426	=over 4
		1427
		1428	=item initialiased
		1429
		1430	Before a watcher can be registered with the event looop it has to be
		1431	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1432	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1433
		1434	In this state it is simply some block of memory that is suitable for use
		1435	in an event loop. It can be moved around, freed, reused etc. at will.
		1436
		1437	=item started/running/active
		1438
		1439	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1440	property of the event loop, and is actively waiting for events. While in
		1441	this state it cannot be accessed (except in a few documented ways), moved,
		1442	freed or anything else - the only legal thing is to keep a pointer to it,
		1443	and call libev functions on it that are documented to work on active watchers.
		1444
		1445	=item pending
		1446
		1447	If a watcher is active and libev determines that an event it is interested
		1448	in has occurred (such as a timer expiring), it will become pending. It will
		1449	stay in this pending state until either it is stopped or its callback is
		1450	about to be invoked, so it is not normally pending inside the watcher
		1451	callback.
		1452
		1453	The watcher might or might not be active while it is pending (for example,
		1454	an expired non-repeating timer can be pending but no longer active). If it
		1455	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1456	but it is still property of the event loop at this time, so cannot be
		1457	moved, freed or reused. And if it is active the rules described in the
		1458	previous item still apply.
		1459
		1460	It is also possible to feed an event on a watcher that is not active (e.g.
		1461	via C<ev_feed_event>), in which case it becomes pending without being
		1462	active.
		1463
		1464	=item stopped
		1465
		1466	A watcher can be stopped implicitly by libev (in which case it might still
		1467	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1468	latter will clear any pending state the watcher might be in, regardless
		1469	of whether it was active or not, so stopping a watcher explicitly before
		1470	freeing it is often a good idea.
		1471
		1472	While stopped (and not pending) the watcher is essentially in the
		1473	initialised state, that is it can be reused, moved, modified in any way
		1474	you wish.
		1475
		1476	=back
		1477
		1478	=head2 WATCHER PRIORITY MODELS
		1479
		1480	Many event loops support I<watcher priorities>, which are usually small
		1481	integers that influence the ordering of event callback invocation
		1482	between watchers in some way, all else being equal.
		1483
		1484	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1485	description for the more technical details such as the actual priority
		1486	range.
		1487
		1488	There are two common ways how these these priorities are being interpreted
		1489	by event loops:
		1490
		1491	In the more common lock-out model, higher priorities "lock out" invocation
		1492	of lower priority watchers, which means as long as higher priority
		1493	watchers receive events, lower priority watchers are not being invoked.
		1494
		1495	The less common only-for-ordering model uses priorities solely to order
		1496	callback invocation within a single event loop iteration: Higher priority
		1497	watchers are invoked before lower priority ones, but they all get invoked
		1498	before polling for new events.
		1499
		1500	Libev uses the second (only-for-ordering) model for all its watchers
		1501	except for idle watchers (which use the lock-out model).
		1502
		1503	The rationale behind this is that implementing the lock-out model for
		1504	watchers is not well supported by most kernel interfaces, and most event
		1505	libraries will just poll for the same events again and again as long as
		1506	their callbacks have not been executed, which is very inefficient in the
		1507	common case of one high-priority watcher locking out a mass of lower
		1508	priority ones.
		1509
		1510	Static (ordering) priorities are most useful when you have two or more
		1511	watchers handling the same resource: a typical usage example is having an
		1512	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1513	timeouts. Under load, data might be received while the program handles
		1514	other jobs, but since timers normally get invoked first, the timeout
		1515	handler will be executed before checking for data. In that case, giving
		1516	the timer a lower priority than the I/O watcher ensures that I/O will be
		1517	handled first even under adverse conditions (which is usually, but not
		1518	always, what you want).
		1519
		1520	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1521	will only be executed when no same or higher priority watchers have
		1522	received events, they can be used to implement the "lock-out" model when
		1523	required.
		1524
		1525	For example, to emulate how many other event libraries handle priorities,
		1526	you can associate an C<ev_idle> watcher to each such watcher, and in
		1527	the normal watcher callback, you just start the idle watcher. The real
		1528	processing is done in the idle watcher callback. This causes libev to
		1529	continuously poll and process kernel event data for the watcher, but when
		1530	the lock-out case is known to be rare (which in turn is rare :), this is
		1531	workable.
		1532
		1533	Usually, however, the lock-out model implemented that way will perform
		1534	miserably under the type of load it was designed to handle. In that case,
		1535	it might be preferable to stop the real watcher before starting the
		1536	idle watcher, so the kernel will not have to process the event in case
		1537	the actual processing will be delayed for considerable time.
		1538
		1539	Here is an example of an I/O watcher that should run at a strictly lower
		1540	priority than the default, and which should only process data when no
		1541	other events are pending:
		1542
		1543	ev_idle idle; // actual processing watcher
		1544	ev_io io; // actual event watcher
		1545
		1546	static void
		1547	io_cb (EV_P_ ev_io *w, int revents)
		1548	{
		1549	// stop the I/O watcher, we received the event, but
		1550	// are not yet ready to handle it.
		1551	ev_io_stop (EV_A_ w);
		1552
		1553	// start the idle watcher to handle the actual event.
		1554	// it will not be executed as long as other watchers
		1555	// with the default priority are receiving events.
		1556	ev_idle_start (EV_A_ &idle);
		1557	}
		1558
		1559	static void
		1560	idle_cb (EV_P_ ev_idle *w, int revents)
		1561	{
		1562	// actual processing
		1563	read (STDIN_FILENO, ...);
		1564
		1565	// have to start the I/O watcher again, as
		1566	// we have handled the event
		1567	ev_io_start (EV_P_ &io);
		1568	}
		1569
		1570	// initialisation
		1571	ev_idle_init (&idle, idle_cb);
		1572	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1573	ev_io_start (EV_DEFAULT_ &io);
		1574
		1575	In the "real" world, it might also be beneficial to start a timer, so that
		1576	low-priority connections can not be locked out forever under load. This
		1577	enables your program to keep a lower latency for important connections
		1578	during short periods of high load, while not completely locking out less
		1579	important ones.
1156		1580
1157		1581
1158	=head1 WATCHER TYPES	1582	=head1 WATCHER TYPES
1159		1583
1160	This section describes each watcher in detail, but will not repeat	1584	This section describes each watcher in detail, but will not repeat
…		…
1186	descriptors to non-blocking mode is also usually a good idea (but not	1610	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1611	required if you know what you are doing).
1188		1612
1189	If you cannot use non-blocking mode, then force the use of a	1613	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only	1614	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1615	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1616	descriptors for which non-blocking operation makes no sense (such as
		1617	files) - libev doesn't guarantee any specific behaviour in that case.
1192		1618
1193	Another thing you have to watch out for is that it is quite easy to	1619	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1620	receive "spurious" readiness notifications, that is your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1621	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1622	because there is no data. Not only are some backends known to create a
…		…
1261		1687
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1688	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1689	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1690	somewhere, as that would have given you a big clue).
1265		1691
		1692	=head3 The special problem of accept()ing when you can't
		1693
		1694	Many implementations of the POSIX C<accept> function (for example,
		1695	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1696	connection from the pending queue in all error cases.
		1697
		1698	For example, larger servers often run out of file descriptors (because
		1699	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1700	rejecting the connection, leading to libev signalling readiness on
		1701	the next iteration again (the connection still exists after all), and
		1702	typically causing the program to loop at 100% CPU usage.
		1703
		1704	Unfortunately, the set of errors that cause this issue differs between
		1705	operating systems, there is usually little the app can do to remedy the
		1706	situation, and no known thread-safe method of removing the connection to
		1707	cope with overload is known (to me).
		1708
		1709	One of the easiest ways to handle this situation is to just ignore it
		1710	- when the program encounters an overload, it will just loop until the
		1711	situation is over. While this is a form of busy waiting, no OS offers an
		1712	event-based way to handle this situation, so it's the best one can do.
		1713
		1714	A better way to handle the situation is to log any errors other than
		1715	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1716	messages, and continue as usual, which at least gives the user an idea of
		1717	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1718	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1719	usage.
		1720
		1721	If your program is single-threaded, then you could also keep a dummy file
		1722	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1723	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1724	close that fd, and create a new dummy fd. This will gracefully refuse
		1725	clients under typical overload conditions.
		1726
		1727	The last way to handle it is to simply log the error and C<exit>, as
		1728	is often done with C<malloc> failures, but this results in an easy
		1729	opportunity for a DoS attack.
1266		1730
1267	=head3 Watcher-Specific Functions	1731	=head3 Watcher-Specific Functions
1268		1732
1269	=over 4	1733	=over 4
1270		1734
…		…
1302	...	1766	...
1303	struct ev_loop *loop = ev_default_init (0);	1767	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1768	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1769	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1770	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1771	ev_run (loop, 0);
1308		1772
1309		1773
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1774	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1775
1312	Timer watchers are simple relative timers that generate an event after a	1776	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1781	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1320		1784
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1785	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1786	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1787	might introduce a small delay). If multiple timers become ready during the
		1788	same loop iteration then the ones with earlier time-out values are invoked
		1789	before ones of the same priority with later time-out values (but this is
		1790	no longer true when a callback calls C<ev_run> recursively).
1324		1791
1325	=head3 Be smart about timeouts	1792	=head3 Be smart about timeouts
1326		1793
1327	Many real-world problems involve some kind of timeout, usually for error	1794	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1795	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1839	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1840	member and C<ev_timer_again>.
1374		1841
1375	At start:	1842	At start:
1376		1843
1377	ev_timer_init (timer, callback);	1844	ev_init (timer, callback);
1378	timer->repeat = 60.;	1845	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1846	ev_timer_again (loop, timer);
1380		1847
1381	Each time there is some activity:	1848	Each time there is some activity:
1382		1849
…		…
1414	ev_tstamp timeout = last_activity + 60.;	1881	ev_tstamp timeout = last_activity + 60.;
1415		1882
1416	// if last_activity + 60. is older than now, we did time out	1883	// if last_activity + 60. is older than now, we did time out
1417	if (timeout < now)	1884	if (timeout < now)
1418	{	1885	{
1419	// timeout occured, take action	1886	// timeout occurred, take action
1420	}	1887	}
1421	else	1888	else
1422	{	1889	{
1423	// callback was invoked, but there was some activity, re-arm	1890	// callback was invoked, but there was some activity, re-arm
1424	// the watcher to fire in last_activity + 60, which is	1891	// the watcher to fire in last_activity + 60, which is
…		…
1444		1911
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1912	To start the timer, simply initialise the watcher and set C<last_activity>
1446	to the current time (meaning we just have some activity :), then call the	1913	to the current time (meaning we just have some activity :), then call the
1447	callback, which will "do the right thing" and start the timer:	1914	callback, which will "do the right thing" and start the timer:
1448		1915
1449	ev_timer_init (timer, callback);	1916	ev_init (timer, callback);
1450	last_activity = ev_now (loop);	1917	last_activity = ev_now (loop);
1451	callback (loop, timer, EV_TIMEOUT);	1918	callback (loop, timer, EV_TIMER);
1452		1919
1453	And when there is some activity, simply store the current time in	1920	And when there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1921	C<last_activity>, no libev calls at all:
1455		1922
1456	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (loop);
1457		1924
1458	This technique is slightly more complex, but in most cases where the	1925	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1926	time-out is unlikely to be triggered, much more efficient.
1460		1927
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the	1928	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1499		1966
1500	=head3 The special problem of time updates	1967	=head3 The special problem of time updates
1501		1968
1502	Establishing the current time is a costly operation (it usually takes at	1969	Establishing the current time is a costly operation (it usually takes at
1503	least two system calls): EV therefore updates its idea of the current	1970	least two system calls): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	1971	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1972	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	1973	lots of events in one iteration.
1507		1974
1508	The relative timeouts are calculated relative to the C<ev_now ()>	1975	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	1976	time. This is usually the right thing as this timestamp refers to the time
…		…
1515		1982
1516	If the event loop is suspended for a long time, you can also force an	1983	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1984	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	1985	()>.
1519		1986
		1987	=head3 The special problems of suspended animation
		1988
		1989	When you leave the server world it is quite customary to hit machines that
		1990	can suspend/hibernate - what happens to the clocks during such a suspend?
		1991
		1992	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1993	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1994	to run until the system is suspended, but they will not advance while the
		1995	system is suspended. That means, on resume, it will be as if the program
		1996	was frozen for a few seconds, but the suspend time will not be counted
		1997	towards C<ev_timer> when a monotonic clock source is used. The real time
		1998	clock advanced as expected, but if it is used as sole clocksource, then a
		1999	long suspend would be detected as a time jump by libev, and timers would
		2000	be adjusted accordingly.
		2001
		2002	I would not be surprised to see different behaviour in different between
		2003	operating systems, OS versions or even different hardware.
		2004
		2005	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2006	time jump in the monotonic clocks and the realtime clock. If the program
		2007	is suspended for a very long time, and monotonic clock sources are in use,
		2008	then you can expect C<ev_timer>s to expire as the full suspension time
		2009	will be counted towards the timers. When no monotonic clock source is in
		2010	use, then libev will again assume a timejump and adjust accordingly.
		2011
		2012	It might be beneficial for this latter case to call C<ev_suspend>
		2013	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2014	deterministic behaviour in this case (you can do nothing against
		2015	C<SIGSTOP>).
		2016
1520	=head3 Watcher-Specific Functions and Data Members	2017	=head3 Watcher-Specific Functions and Data Members
1521		2018
1522	=over 4	2019	=over 4
1523		2020
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2021	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2044	If the timer is started but non-repeating, stop it (as if it timed out).
1548		2045
1549	If the timer is repeating, either start it if necessary (with the	2046	If the timer is repeating, either start it if necessary (with the
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2047	C<repeat> value), or reset the running timer to the C<repeat> value.
1551		2048
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2049	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1553	usage example.	2050	usage example.
		2051
		2052	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2053
		2054	Returns the remaining time until a timer fires. If the timer is active,
		2055	then this time is relative to the current event loop time, otherwise it's
		2056	the timeout value currently configured.
		2057
		2058	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2059	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2060	will return C<4>. When the timer expires and is restarted, it will return
		2061	roughly C<7> (likely slightly less as callback invocation takes some time,
		2062	too), and so on.
1554		2063
1555	=item ev_tstamp repeat [read-write]	2064	=item ev_tstamp repeat [read-write]
1556		2065
1557	The current C<repeat> value. Will be used each time the watcher times out	2066	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2067	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2093	}
1585		2094
1586	ev_timer mytimer;	2095	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2096	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2097	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2098	ev_run (loop, 0);
1590		2099
1591	// and in some piece of code that gets executed on any "activity":	2100	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2101	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2102	ev_timer_again (&mytimer);
1594		2103
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2105	=head2 C<ev_periodic> - to cron or not to cron?
1597		2106
1598	Periodic watchers are also timers of a kind, but they are very versatile	2107	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2108	(and unfortunately a bit complex).
1600		2109
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2110	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2111	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2112	(absolute time, the thing you can read on your calender or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2113	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2114	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2115	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2116
		2117	You can tell a periodic watcher to trigger after some specific point
		2118	in time: for example, if you tell a periodic watcher to trigger "in 10
		2119	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2120	not a delay) and then reset your system clock to January of the previous
		2121	year, then it will take a year or more to trigger the event (unlike an
		2122	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2123	it, as it uses a relative timeout).
		2124
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2125	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2126	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2127	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2128	those cannot react to time jumps.
1613		2129
1614	As with timers, the callback is guaranteed to be invoked only when the	2130	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2131	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2132	timers become ready during the same loop iteration then the ones with
		2133	earlier time-out values are invoked before ones with later time-out values
		2134	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2135
1618	=head3 Watcher-Specific Functions and Data Members	2136	=head3 Watcher-Specific Functions and Data Members
1619		2137
1620	=over 4	2138	=over 4
1621		2139
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2140	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2141
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2142	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2143
1626	Lots of arguments, lets sort it out... There are basically three modes of	2144	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2145	operation, and we will explain them from simplest to most complex:
1628		2146
1629	=over 4	2147	=over 4
1630		2148
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2149	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2150
1633	In this configuration the watcher triggers an event after the wall clock	2151	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2152	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2153	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2154	will be stopped and invoked when the system clock reaches or surpasses
		2155	this point in time.
1637		2156
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2157	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2158
1640	In this mode the watcher will always be scheduled to time out at the next	2159	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2160	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2161	negative) and then repeat, regardless of any time jumps. The C<offset>
		2162	argument is merely an offset into the C<interval> periods.
1643		2163
1644	This can be used to create timers that do not drift with respect to the	2164	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2165	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2166	hour, on the hour (with respect to UTC):
1647		2167
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2168	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2169
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2170	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2171	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2172	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2173	by 3600.
1654		2174
1655	Another way to think about it (for the mathematically inclined) is that	2175	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2176	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2177	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2178
1659	For numerical stability it is preferable that the C<at> value is near	2179	For numerical stability it is preferable that the C<offset> value is near
1660	C<ev_now ()> (the current time), but there is no range requirement for	2180	C<ev_now ()> (the current time), but there is no range requirement for
1661	this value, and in fact is often specified as zero.	2181	this value, and in fact is often specified as zero.
1662		2182
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2183	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2184	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2185	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2186	millisecond (if the OS supports it and the machine is fast enough).
1667		2187
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2188	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2189
1670	In this mode the values for C<interval> and C<at> are both being	2190	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2191	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2192	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2193	current time as second argument.
1674		2194
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2195	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY event loop modifications whatsoever>.	2196	or make ANY other event loop modifications whatsoever, unless explicitly
		2197	allowed by documentation here>.
1677		2198
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2199	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2200	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2201	only event loop modification you are allowed to do).
1681		2202
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2232	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2233	program when the crontabs have changed).
1713		2234
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2235	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2236
1716	When active, returns the absolute time that the watcher is supposed to	2237	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2238	to trigger next. This is not the same as the C<offset> argument to
		2239	C<ev_periodic_set>, but indeed works even in interval and manual
		2240	rescheduling modes.
1718		2241
1719	=item ev_tstamp offset [read-write]	2242	=item ev_tstamp offset [read-write]
1720		2243
1721	When repeating, this contains the offset value, otherwise this is the	2244	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2245	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2246	although libev might modify this value for better numerical stability).
1723		2247
1724	Can be modified any time, but changes only take effect when the periodic	2248	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2249	timer fires or C<ev_periodic_again> is being called.
1726		2250
1727	=item ev_tstamp interval [read-write]	2251	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2267	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2268	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2269	potentially a lot of jitter, but good long-term stability.
1746		2270
1747	static void	2271	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2272	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2273	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2274	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2275	}
1752		2276
1753	ev_periodic hourly_tick;	2277	ev_periodic hourly_tick;
…		…
1776		2300
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2301	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2302
1779	Signal watchers will trigger an event when the process receives a specific	2303	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2304	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2305	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2306	normal event processing, like any other event.
1783		2307
1784	If you want signals asynchronously, just use C<sigaction> as you would	2308	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2309	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2310	the signal. You can even use C<ev_async> from a signal handler to
		2311	synchronously wake up an event loop.
1787		2312
1788	You can configure as many watchers as you like per signal. Only when the	2313	You can configure as many watchers as you like for the same signal, but
		2314	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2315	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2316	C<SIGINT> in both the default loop and another loop at the same time. At
		2317	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2318
1789	first watcher gets started will libev actually register a signal handler	2319	When the first watcher gets started will libev actually register something
1790	with the kernel (thus it coexists with your own signal handlers as long as	2320	with the kernel (thus it coexists with your own signal handlers as long as
1791	you don't register any with libev for the same signal). Similarly, when	2321	you don't register any with libev for the same signal).
1792	the last signal watcher for a signal is stopped, libev will reset the
1793	signal handler to SIG_DFL (regardless of what it was set to before).
1794		2322
1795	If possible and supported, libev will install its handlers with	2323	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2324	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2325	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2326	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2327	and unblock them in an C<ev_prepare> watcher.
		2328
		2329	=head3 The special problem of inheritance over fork/execve/pthread_create
		2330
		2331	Both the signal mask (C<sigprocmask>) and the signal disposition
		2332	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2333	stopping it again), that is, libev might or might not block the signal,
		2334	and might or might not set or restore the installed signal handler.
		2335
		2336	While this does not matter for the signal disposition (libev never
		2337	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2338	C<execve>), this matters for the signal mask: many programs do not expect
		2339	certain signals to be blocked.
		2340
		2341	This means that before calling C<exec> (from the child) you should reset
		2342	the signal mask to whatever "default" you expect (all clear is a good
		2343	choice usually).
		2344
		2345	The simplest way to ensure that the signal mask is reset in the child is
		2346	to install a fork handler with C<pthread_atfork> that resets it. That will
		2347	catch fork calls done by libraries (such as the libc) as well.
		2348
		2349	In current versions of libev, the signal will not be blocked indefinitely
		2350	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2351	the window of opportunity for problems, it will not go away, as libev
		2352	I<has> to modify the signal mask, at least temporarily.
		2353
		2354	So I can't stress this enough: I<If you do not reset your signal mask when
		2355	you expect it to be empty, you have a race condition in your code>. This
		2356	is not a libev-specific thing, this is true for most event libraries.
		2357
		2358	=head3 The special problem of threads signal handling
		2359
		2360	POSIX threads has problematic signal handling semantics, specifically,
		2361	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2362	threads in a process block signals, which is hard to achieve.
		2363
		2364	When you want to use sigwait (or mix libev signal handling with your own
		2365	for the same signals), you can tackle this problem by globally blocking
		2366	all signals before creating any threads (or creating them with a fully set
		2367	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2368	loops. Then designate one thread as "signal receiver thread" which handles
		2369	these signals. You can pass on any signals that libev might be interested
		2370	in by calling C<ev_feed_signal>.
1800		2371
1801	=head3 Watcher-Specific Functions and Data Members	2372	=head3 Watcher-Specific Functions and Data Members
1802		2373
1803	=over 4	2374	=over 4
1804		2375
…		…
1820	Example: Try to exit cleanly on SIGINT.	2391	Example: Try to exit cleanly on SIGINT.
1821		2392
1822	static void	2393	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2394	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2395	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2396	ev_break (loop, EVBREAK_ALL);
1826	}	2397	}
1827		2398
1828	ev_signal signal_watcher;	2399	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2400	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2401	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2407	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2408	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2409	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2410	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2411	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2412	but forking and registering a watcher a few event loop iterations later or
1842	not.	2413	in the next callback invocation is not.
1843		2414
1844	Only the default event loop is capable of handling signals, and therefore	2415	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2416	you can only register child watchers in the default event loop.
1846		2417
		2418	Due to some design glitches inside libev, child watchers will always be
		2419	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2420	libev)
		2421
1847	=head3 Process Interaction	2422	=head3 Process Interaction
1848		2423
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2424	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2425	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2426	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2427	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2428	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2429	children, even ones not watched.
1855		2430
1856	=head3 Overriding the Built-In Processing	2431	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2441	=head3 Stopping the Child Watcher
1867		2442
1868	Currently, the child watcher never gets stopped, even when the	2443	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2444	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2445	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2446	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2447	problem).
1872		2448
1873	=head3 Watcher-Specific Functions and Data Members	2449	=head3 Watcher-Specific Functions and Data Members
1874		2450
1875	=over 4	2451	=over 4
1876		2452
…		…
2179		2755
2180	=head3 Watcher-Specific Functions and Data Members	2756	=head3 Watcher-Specific Functions and Data Members
2181		2757
2182	=over 4	2758	=over 4
2183		2759
2184	=item ev_idle_init (ev_signal *, callback)	2760	=item ev_idle_init (ev_idle *, callback)
2185		2761
2186	Initialises and configures the idle watcher - it has no parameters of any	2762	Initialises and configures the idle watcher - it has no parameters of any
2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2763	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2188	believe me.	2764	believe me.
2189		2765
…		…
2202	// no longer anything immediate to do.	2778	// no longer anything immediate to do.
2203	}	2779	}
2204		2780
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2781	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2782	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2783	ev_idle_start (loop, idle_watcher);
2208		2784
2209		2785
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2786	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2787
2212	Prepare and check watchers are usually (but not always) used in pairs:	2788	Prepare and check watchers are usually (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2789	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2790	afterwards.
2215		2791
2216	You I<must not> call C<ev_loop> or similar functions that enter	2792	You I<must not> call C<ev_run> or similar functions that enter
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2793	the current event loop from either C<ev_prepare> or C<ev_check>
2218	watchers. Other loops than the current one are fine, however. The	2794	watchers. Other loops than the current one are fine, however. The
2219	rationale behind this is that you do not need to check for recursion in	2795	rationale behind this is that you do not need to check for recursion in
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2796	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2221	C<ev_check> so if you have one watcher of each kind they will always be	2797	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2305	struct pollfd fds [nfd];	2881	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	2882	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2883	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		2884
2309	/* the callback is illegal, but won't be called as we stop during check */	2885	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	2886	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	2887	ev_timer_start (loop, &tw);
2312		2888
2313	// create one ev_io per pollfd	2889	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	2890	for (int i = 0; i < nfd; ++i)
2315	{	2891	{
…		…
2389		2965
2390	if (timeout >= 0)	2966	if (timeout >= 0)
2391	// create/start timer	2967	// create/start timer
2392		2968
2393	// poll	2969	// poll
2394	ev_loop (EV_A_ 0);	2970	ev_run (EV_A_ 0);
2395		2971
2396	// stop timer again	2972	// stop timer again
2397	if (timeout >= 0)	2973	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	2974	ev_timer_stop (EV_A_ &to);
2399		2975
…		…
2477	if you do not want that, you need to temporarily stop the embed watcher).	3053	if you do not want that, you need to temporarily stop the embed watcher).
2478		3054
2479	=item ev_embed_sweep (loop, ev_embed *)	3055	=item ev_embed_sweep (loop, ev_embed *)
2480		3056
2481	Make a single, non-blocking sweep over the embedded loop. This works	3057	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3058	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3059	appropriate way for embedded loops.
2484		3060
2485	=item struct ev_loop *other [read-only]	3061	=item struct ev_loop *other [read-only]
2486		3062
2487	The embedded event loop.	3063	The embedded event loop.
…		…
2545	event loop blocks next and before C<ev_check> watchers are being called,	3121	event loop blocks next and before C<ev_check> watchers are being called,
2546	and only in the child after the fork. If whoever good citizen calling	3122	and only in the child after the fork. If whoever good citizen calling
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3123	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2548	handlers will be invoked, too, of course.	3124	handlers will be invoked, too, of course.
2549		3125
		3126	=head3 The special problem of life after fork - how is it possible?
		3127
		3128	Most uses of C<fork()> consist of forking, then some simple calls to set
		3129	up/change the process environment, followed by a call to C<exec()>. This
		3130	sequence should be handled by libev without any problems.
		3131
		3132	This changes when the application actually wants to do event handling
		3133	in the child, or both parent in child, in effect "continuing" after the
		3134	fork.
		3135
		3136	The default mode of operation (for libev, with application help to detect
		3137	forks) is to duplicate all the state in the child, as would be expected
		3138	when I<either> the parent I<or> the child process continues.
		3139
		3140	When both processes want to continue using libev, then this is usually the
		3141	wrong result. In that case, usually one process (typically the parent) is
		3142	supposed to continue with all watchers in place as before, while the other
		3143	process typically wants to start fresh, i.e. without any active watchers.
		3144
		3145	The cleanest and most efficient way to achieve that with libev is to
		3146	simply create a new event loop, which of course will be "empty", and
		3147	use that for new watchers. This has the advantage of not touching more
		3148	memory than necessary, and thus avoiding the copy-on-write, and the
		3149	disadvantage of having to use multiple event loops (which do not support
		3150	signal watchers).
		3151
		3152	When this is not possible, or you want to use the default loop for
		3153	other reasons, then in the process that wants to start "fresh", call
		3154	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3155	Destroying the default loop will "orphan" (not stop) all registered
		3156	watchers, so you have to be careful not to execute code that modifies
		3157	those watchers. Note also that in that case, you have to re-register any
		3158	signal watchers.
		3159
2550	=head3 Watcher-Specific Functions and Data Members	3160	=head3 Watcher-Specific Functions and Data Members
2551		3161
2552	=over 4	3162	=over 4
2553		3163
2554	=item ev_fork_init (ev_signal *, callback)	3164	=item ev_fork_init (ev_fork *, callback)
2555		3165
2556	Initialises and configures the fork watcher - it has no parameters of any	3166	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3167	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3168	really.
2559		3169
2560	=back	3170	=back
2561		3171
2562		3172
		3173	=head2 C<ev_cleanup> - even the best things end
		3174
		3175	Cleanup watchers are called just before the event loop is being destroyed
		3176	by a call to C<ev_loop_destroy>.
		3177
		3178	While there is no guarantee that the event loop gets destroyed, cleanup
		3179	watchers provide a convenient method to install cleanup hooks for your
		3180	program, worker threads and so on - you just to make sure to destroy the
		3181	loop when you want them to be invoked.
		3182
		3183	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3184	all other watchers, they do not keep a reference to the event loop (which
		3185	makes a lot of sense if you think about it). Like all other watchers, you
		3186	can call libev functions in the callback, except C<ev_cleanup_start>.
		3187
		3188	=head3 Watcher-Specific Functions and Data Members
		3189
		3190	=over 4
		3191
		3192	=item ev_cleanup_init (ev_cleanup *, callback)
		3193
		3194	Initialises and configures the cleanup watcher - it has no parameters of
		3195	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3196	pointless, I assure you.
		3197
		3198	=back
		3199
		3200	Example: Register an atexit handler to destroy the default loop, so any
		3201	cleanup functions are called.
		3202
		3203	static void
		3204	program_exits (void)
		3205	{
		3206	ev_loop_destroy (EV_DEFAULT_UC);
		3207	}
		3208
		3209	...
		3210	atexit (program_exits);
		3211
		3212
2563	=head2 C<ev_async> - how to wake up another event loop	3213	=head2 C<ev_async> - how to wake up an event loop
2564		3214
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3215	In general, you cannot use an C<ev_run> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3216	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3217	loops - those are of course safe to use in different threads).
2568		3218
2569	Sometimes, however, you need to wake up another event loop you do not	3219	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3220	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3221	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3222	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3223
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3224	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3225	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3226	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3227	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3228	of "global async watchers" by using a watcher on an otherwise unused
		3229	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3230	even without knowing which loop owns the signal.
2579		3231
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3232	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2581	just the default loop.	3233	just the default loop.
2582		3234
2583	=head3 Queueing	3235	=head3 Queueing
2584		3236
2585	C<ev_async> does not support queueing of data in any way. The reason	3237	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3238	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3239	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3240	need elaborate support such as pthreads or unportable memory access
		3241	semantics.
2589		3242
2590	That means that if you want to queue data, you have to provide your own	3243	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3244	queue. But at least I can tell you how to implement locking around your
2592	queue:	3245	queue:
2593		3246
…		…
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3335	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3336	C<ev_feed_event>, this call is safe to do from other threads, signal or
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3337	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2685	section below on what exactly this means).	3338	section below on what exactly this means).
2686		3339
		3340	Note that, as with other watchers in libev, multiple events might get
		3341	compressed into a single callback invocation (another way to look at this
		3342	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3343	reset when the event loop detects that).
		3344
2687	This call incurs the overhead of a system call only once per loop iteration,	3345	This call incurs the overhead of a system call only once per event loop
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3346	iteration, so while the overhead might be noticeable, it doesn't apply to
2689	calls to C<ev_async_send>.	3347	repeated calls to C<ev_async_send> for the same event loop.
2690		3348
2691	=item bool = ev_async_pending (ev_async *)	3349	=item bool = ev_async_pending (ev_async *)
2692		3350
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3351	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3352	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3355	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3356	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3357	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3358	quickly check whether invoking the loop might be a good idea.
2701		3359
2702	Not that this does I<not> check whether the watcher itself is pending, only	3360	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3361	only whether it has been requested to make this watcher pending: there
		3362	is a time window between the event loop checking and resetting the async
		3363	notification, and the callback being invoked.
2704		3364
2705	=back	3365	=back
2706		3366
2707		3367
2708	=head1 OTHER FUNCTIONS	3368	=head1 OTHER FUNCTIONS
…		…
2725		3385
2726	If C<timeout> is less than 0, then no timeout watcher will be	3386	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3387	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3388	repeat = 0) will be started. C<0> is a valid timeout.
2729		3389
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3390	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3391	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3392	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3393	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3394	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3395	events precedence.
2736		3396
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3397	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3398
2739	static void stdin_ready (int revents, void *arg)	3399	static void stdin_ready (int revents, void *arg)
2740	{	3400	{
2741	if (revents & EV_READ)	3401	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3402	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3403	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3404	/* doh, nothing entered */;
2745	}	3405	}
2746		3406
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3407	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3408
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3409	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3410
2757	Feed an event on the given fd, as if a file descriptor backend detected	3411	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3412	the given events it.
2759		3413
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3414	=item ev_feed_signal_event (loop, int signum)
2761		3415
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3416	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3417	which is async-safe.
		3418
		3419	=back
		3420
		3421
		3422	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3423
		3424	This section explains some common idioms that are not immediately
		3425	obvious. Note that examples are sprinkled over the whole manual, and this
		3426	section only contains stuff that wouldn't fit anywhere else.
		3427
		3428	=over 4
		3429
		3430	=item Model/nested event loop invocations and exit conditions.
		3431
		3432	Often (especially in GUI toolkits) there are places where you have
		3433	I<modal> interaction, which is most easily implemented by recursively
		3434	invoking C<ev_run>.
		3435
		3436	This brings the problem of exiting - a callback might want to finish the
		3437	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3438	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3439	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3440	other combination: In these cases, C<ev_break> will not work alone.
		3441
		3442	The solution is to maintain "break this loop" variable for each C<ev_run>
		3443	invocation, and use a loop around C<ev_run> until the condition is
		3444	triggered, using C<EVRUN_ONCE>:
		3445
		3446	// main loop
		3447	int exit_main_loop = 0;
		3448
		3449	while (!exit_main_loop)
		3450	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3451
		3452	// in a model watcher
		3453	int exit_nested_loop = 0;
		3454
		3455	while (!exit_nested_loop)
		3456	ev_run (EV_A_ EVRUN_ONCE);
		3457
		3458	To exit from any of these loops, just set the corresponding exit variable:
		3459
		3460	// exit modal loop
		3461	exit_nested_loop = 1;
		3462
		3463	// exit main program, after modal loop is finished
		3464	exit_main_loop = 1;
		3465
		3466	// exit both
		3467	exit_main_loop = exit_nested_loop = 1;
2764		3468
2765	=back	3469	=back
2766		3470
2767		3471
2768	=head1 LIBEVENT EMULATION	3472	=head1 LIBEVENT EMULATION
2769		3473
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3474	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3475	emulate the internals of libevent, so here are some usage hints:
2772		3476
2773	=over 4	3477	=over 4
		3478
		3479	=item * Only the libevent-1.4.1-beta API is being emulated.
		3480
		3481	This was the newest libevent version available when libev was implemented,
		3482	and is still mostly unchanged in 2010.
2774		3483
2775	=item * Use it by including <event.h>, as usual.	3484	=item * Use it by including <event.h>, as usual.
2776		3485
2777	=item * The following members are fully supported: ev_base, ev_callback,	3486	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3487	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3493	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3494	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3495	is an ev_pri field.
2787		3496
2788	=item * In libevent, the last base created gets the signals, in libev, the	3497	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3498	base that registered the signal gets the signals.
2790		3499
2791	=item * Other members are not supported.	3500	=item * Other members are not supported.
2792		3501
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3502	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3503	to use the libev header file and library.
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	3522	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	3523	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	3524	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	3525	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		3526
2818	Currently, functions, and static and non-static member functions can be	3527	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	3528	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	3529	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	3530	you need support for other types of functors please contact the author
2822	it).	3531	(preferably after implementing it).
2823		3532
2824	Here is a list of things available in the C<ev> namespace:	3533	Here is a list of things available in the C<ev> namespace:
2825		3534
2826	=over 4	3535	=over 4
2827		3536
…		…
2845		3554
2846	=over 4	3555	=over 4
2847		3556
2848	=item ev::TYPE::TYPE ()	3557	=item ev::TYPE::TYPE ()
2849		3558
2850	=item ev::TYPE::TYPE (struct ev_loop *)	3559	=item ev::TYPE::TYPE (loop)
2851		3560
2852	=item ev::TYPE::~TYPE	3561	=item ev::TYPE::~TYPE
2853		3562
2854	The constructor (optionally) takes an event loop to associate the watcher	3563	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	3564	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	3597	myclass obj;
2889	ev::io iow;	3598	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	3599	iow.set <myclass, &myclass::io_cb> (&obj);
2891		3600
2892	=item w->set (object *)	3601	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		3602
2896	This is a variation of a method callback - leaving out the method to call	3603	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	3604	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	3605	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	3606	the time. Incidentally, you can then also leave out the template argument
…		…
2932	Example: Use a plain function as callback.	3639	Example: Use a plain function as callback.
2933		3640
2934	static void io_cb (ev::io &w, int revents) { }	3641	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	3642	iow.set <io_cb> ();
2936		3643
2937	=item w->set (struct ev_loop *)	3644	=item w->set (loop)
2938		3645
2939	Associates a different C<struct ev_loop> with this watcher. You can only	3646	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	3647	do this when the watcher is inactive (and not pending either).
2941		3648
2942	=item w->set ([arguments])	3649	=item w->set ([arguments])
2943		3650
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3651	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2945	called at least once. Unlike the C counterpart, an active watcher gets	3652	method or a suitable start method must be called at least once. Unlike the
2946	automatically stopped and restarted when reconfiguring it with this	3653	C counterpart, an active watcher gets automatically stopped and restarted
2947	method.	3654	when reconfiguring it with this method.
2948		3655
2949	=item w->start ()	3656	=item w->start ()
2950		3657
2951	Starts the watcher. Note that there is no C<loop> argument, as the	3658	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	3659	constructor already stores the event loop.
2953		3660
		3661	=item w->start ([arguments])
		3662
		3663	Instead of calling C<set> and C<start> methods separately, it is often
		3664	convenient to wrap them in one call. Uses the same type of arguments as
		3665	the configure C<set> method of the watcher.
		3666
2954	=item w->stop ()	3667	=item w->stop ()
2955		3668
2956	Stops the watcher if it is active. Again, no C<loop> argument.	3669	Stops the watcher if it is active. Again, no C<loop> argument.
2957		3670
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3671	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		3683
2971	=back	3684	=back
2972		3685
2973	=back	3686	=back
2974		3687
2975	Example: Define a class with an IO and idle watcher, start one of them in	3688	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	3689	watchers in the constructor.
2977		3690
2978	class myclass	3691	class myclass
2979	{	3692	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	3693	ev::io io ; void io_cb (ev::io &w, int revents);
		3694	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3695	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		3696
2983	myclass (int fd)	3697	myclass (int fd)
2984	{	3698	{
2985	io .set <myclass, &myclass::io_cb > (this);	3699	io .set <myclass, &myclass::io_cb > (this);
		3700	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	3701	idle.set <myclass, &myclass::idle_cb> (this);
2987		3702
2988	io.start (fd, ev::READ);	3703	io.set (fd, ev::WRITE); // configure the watcher
		3704	io.start (); // start it whenever convenient
		3705
		3706	io2.start (fd, ev::READ); // set + start in one call
2989	}	3707	}
2990	};	3708	};
2991		3709
2992		3710
2993	=head1 OTHER LANGUAGE BINDINGS	3711	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	3730	L<http://software.schmorp.de/pkg/EV>.
3013		3731
3014	=item Python	3732	=item Python
3015		3733
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3734	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	3735	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		3736
3023	=item Ruby	3737	=item Ruby
3024		3738
3025	Tony Arcieri has written a ruby extension that offers access to a subset	3739	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	3740	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	3742	L<http://rev.rubyforge.org/>.
3029		3743
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	3744	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	3745	makes rev work even on mingw.
3032		3746
		3747	=item Haskell
		3748
		3749	A haskell binding to libev is available at
		3750	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3751
3033	=item D	3752	=item D
3034		3753
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3754	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3755	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3037		3756
3038	=item Ocaml	3757	=item Ocaml
3039		3758
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	3759	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3760	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3761
		3762	=item Lua
		3763
		3764	Brian Maher has written a partial interface to libev for lua (at the
		3765	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3766	L<http://github.com/brimworks/lua-ev>.
3042		3767
3043	=back	3768	=back
3044		3769
3045		3770
3046	=head1 MACRO MAGIC	3771	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	3785	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	3786	C<EV_A_> is used when other arguments are following. Example:
3062		3787
3063	ev_unref (EV_A);	3788	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	3789	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	3790	ev_run (EV_A_ 0);
3066		3791
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3792	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	3793	which is often provided by the following macro.
3069		3794
3070	=item C<EV_P>, C<EV_P_>	3795	=item C<EV_P>, C<EV_P_>
…		…
3110	}	3835	}
3111		3836
3112	ev_check check;	3837	ev_check check;
3113	ev_check_init (&check, check_cb);	3838	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	3839	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	3840	ev_run (EV_DEFAULT_ 0);
3116		3841
3117	=head1 EMBEDDING	3842	=head1 EMBEDDING
3118		3843
3119	Libev can (and often is) directly embedded into host	3844	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	3845	applications. Examples of applications that embed it include the Deliantra
…		…
3200	libev.m4	3925	libev.m4
3201		3926
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	3927	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		3928
3204	Libev can be configured via a variety of preprocessor symbols you have to	3929	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	3930	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	3931	the absence of autoconf is documented for every option.
		3932
		3933	Symbols marked with "(h)" do not change the ABI, and can have different
		3934	values when compiling libev vs. including F<ev.h>, so it is permissible
		3935	to redefine them before including F<ev.h> without breaking compatibility
		3936	to a compiled library. All other symbols change the ABI, which means all
		3937	users of libev and the libev code itself must be compiled with compatible
		3938	settings.
3207		3939
3208	=over 4	3940	=over 4
3209		3941
		3942	=item EV_COMPAT3 (h)
		3943
		3944	Backwards compatibility is a major concern for libev. This is why this
		3945	release of libev comes with wrappers for the functions and symbols that
		3946	have been renamed between libev version 3 and 4.
		3947
		3948	You can disable these wrappers (to test compatibility with future
		3949	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3950	sources. This has the additional advantage that you can drop the C<struct>
		3951	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3952	typedef in that case.
		3953
		3954	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3955	and in some even more future version the compatibility code will be
		3956	removed completely.
		3957
3210	=item EV_STANDALONE	3958	=item EV_STANDALONE (h)
3211		3959
3212	Must always be C<1> if you do not use autoconf configuration, which	3960	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	3961	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	3962	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	3963	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	3964	F<event.h> that are not directly supported by the libev core alone.
3217		3965
3218	In stanbdalone mode, libev will still try to automatically deduce the	3966	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	3967	configuration, but has to be more conservative.
3220		3968
3221	=item EV_USE_MONOTONIC	3969	=item EV_USE_MONOTONIC
3222		3970
3223	If defined to be C<1>, libev will try to detect the availability of the	3971	If defined to be C<1>, libev will try to detect the availability of the
…		…
3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.	3977	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3230		3978
3231	=item EV_USE_REALTIME	3979	=item EV_USE_REALTIME
3232		3980
3233	If defined to be C<1>, libev will try to detect the availability of the	3981	If defined to be C<1>, libev will try to detect the availability of the
3234	real-time clock option at compile time (and assume its availability at	3982	real-time clock option at compile time (and assume its availability
3235	runtime if successful). Otherwise no use of the real-time clock option will	3983	at runtime if successful). Otherwise no use of the real-time clock
3236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3984	option will be attempted. This effectively replaces C<gettimeofday>
3237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3985	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3238	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3986	correctness. See the note about libraries in the description of
		3987	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3988	C<EV_USE_CLOCK_SYSCALL>.
3239		3989
3240	=item EV_USE_CLOCK_SYSCALL	3990	=item EV_USE_CLOCK_SYSCALL
3241		3991
3242	If defined to be C<1>, libev will try to use a direct syscall instead	3992	If defined to be C<1>, libev will try to use a direct syscall instead
3243	of calling the system-provided C<clock_gettime> function. This option	3993	of calling the system-provided C<clock_gettime> function. This option
…		…
3286	be used is the winsock select). This means that it will call	4036	be used is the winsock select). This means that it will call
3287	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4037	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3288	it is assumed that all these functions actually work on fds, even	4038	it is assumed that all these functions actually work on fds, even
3289	on win32. Should not be defined on non-win32 platforms.	4039	on win32. Should not be defined on non-win32 platforms.
3290		4040
3291	=item EV_FD_TO_WIN32_HANDLE	4041	=item EV_FD_TO_WIN32_HANDLE(fd)
3292		4042
3293	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4043	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3294	file descriptors to socket handles. When not defining this symbol (the	4044	file descriptors to socket handles. When not defining this symbol (the
3295	default), then libev will call C<_get_osfhandle>, which is usually	4045	default), then libev will call C<_get_osfhandle>, which is usually
3296	correct. In some cases, programs use their own file descriptor management,	4046	correct. In some cases, programs use their own file descriptor management,
3297	in which case they can provide this function to map fds to socket handles.	4047	in which case they can provide this function to map fds to socket handles.
		4048
		4049	=item EV_WIN32_HANDLE_TO_FD(handle)
		4050
		4051	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4052	using the standard C<_open_osfhandle> function. For programs implementing
		4053	their own fd to handle mapping, overwriting this function makes it easier
		4054	to do so. This can be done by defining this macro to an appropriate value.
		4055
		4056	=item EV_WIN32_CLOSE_FD(fd)
		4057
		4058	If programs implement their own fd to handle mapping on win32, then this
		4059	macro can be used to override the C<close> function, useful to unregister
		4060	file descriptors again. Note that the replacement function has to close
		4061	the underlying OS handle.
3298		4062
3299	=item EV_USE_POLL	4063	=item EV_USE_POLL
3300		4064
3301	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4065	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3302	backend. Otherwise it will be enabled on non-win32 platforms. It	4066	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3349	as well as for signal and thread safety in C<ev_async> watchers.	4113	as well as for signal and thread safety in C<ev_async> watchers.
3350		4114
3351	In the absence of this define, libev will use C<sig_atomic_t volatile>	4115	In the absence of this define, libev will use C<sig_atomic_t volatile>
3352	(from F<signal.h>), which is usually good enough on most platforms.	4116	(from F<signal.h>), which is usually good enough on most platforms.
3353		4117
3354	=item EV_H	4118	=item EV_H (h)
3355		4119
3356	The name of the F<ev.h> header file used to include it. The default if	4120	The name of the F<ev.h> header file used to include it. The default if
3357	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4121	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3358	used to virtually rename the F<ev.h> header file in case of conflicts.	4122	used to virtually rename the F<ev.h> header file in case of conflicts.
3359		4123
3360	=item EV_CONFIG_H	4124	=item EV_CONFIG_H (h)
3361		4125
3362	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4126	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3363	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4127	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3364	C<EV_H>, above.	4128	C<EV_H>, above.
3365		4129
3366	=item EV_EVENT_H	4130	=item EV_EVENT_H (h)
3367		4131
3368	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4132	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3369	of how the F<event.h> header can be found, the default is C<"event.h">.	4133	of how the F<event.h> header can be found, the default is C<"event.h">.
3370		4134
3371	=item EV_PROTOTYPES	4135	=item EV_PROTOTYPES (h)
3372		4136
3373	If defined to be C<0>, then F<ev.h> will not define any function	4137	If defined to be C<0>, then F<ev.h> will not define any function
3374	prototypes, but still define all the structs and other symbols. This is	4138	prototypes, but still define all the structs and other symbols. This is
3375	occasionally useful if you want to provide your own wrapper functions	4139	occasionally useful if you want to provide your own wrapper functions
3376	around libev functions.	4140	around libev functions.
…		…
3398	fine.	4162	fine.
3399		4163
3400	If your embedding application does not need any priorities, defining these	4164	If your embedding application does not need any priorities, defining these
3401	both to C<0> will save some memory and CPU.	4165	both to C<0> will save some memory and CPU.
3402		4166
3403	=item EV_PERIODIC_ENABLE	4167	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4168	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4169	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3404		4170
3405	If undefined or defined to be C<1>, then periodic timers are supported. If	4171	If undefined or defined to be C<1> (and the platform supports it), then
3406	defined to be C<0>, then they are not. Disabling them saves a few kB of	4172	the respective watcher type is supported. If defined to be C<0>, then it
3407	code.	4173	is not. Disabling watcher types mainly saves code size.
3408		4174
3409	=item EV_IDLE_ENABLE	4175	=item EV_FEATURES
3410
3411	If undefined or defined to be C<1>, then idle watchers are supported. If
3412	defined to be C<0>, then they are not. Disabling them saves a few kB of
3413	code.
3414
3415	=item EV_EMBED_ENABLE
3416
3417	If undefined or defined to be C<1>, then embed watchers are supported. If
3418	defined to be C<0>, then they are not. Embed watchers rely on most other
3419	watcher types, which therefore must not be disabled.
3420
3421	=item EV_STAT_ENABLE
3422
3423	If undefined or defined to be C<1>, then stat watchers are supported. If
3424	defined to be C<0>, then they are not.
3425
3426	=item EV_FORK_ENABLE
3427
3428	If undefined or defined to be C<1>, then fork watchers are supported. If
3429	defined to be C<0>, then they are not.
3430
3431	=item EV_ASYNC_ENABLE
3432
3433	If undefined or defined to be C<1>, then async watchers are supported. If
3434	defined to be C<0>, then they are not.
3435
3436	=item EV_MINIMAL
3437		4176
3438	If you need to shave off some kilobytes of code at the expense of some	4177	If you need to shave off some kilobytes of code at the expense of some
3439	speed, define this symbol to C<1>. Currently this is used to override some	4178	speed (but with the full API), you can define this symbol to request
3440	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4179	certain subsets of functionality. The default is to enable all features
3441	much smaller 2-heap for timer management over the default 4-heap.	4180	that can be enabled on the platform.
		4181
		4182	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4183	with some broad features you want) and then selectively re-enable
		4184	additional parts you want, for example if you want everything minimal,
		4185	but multiple event loop support, async and child watchers and the poll
		4186	backend, use this:
		4187
		4188	#define EV_FEATURES 0
		4189	#define EV_MULTIPLICITY 1
		4190	#define EV_USE_POLL 1
		4191	#define EV_CHILD_ENABLE 1
		4192	#define EV_ASYNC_ENABLE 1
		4193
		4194	The actual value is a bitset, it can be a combination of the following
		4195	values:
		4196
		4197	=over 4
		4198
		4199	=item C<1> - faster/larger code
		4200
		4201	Use larger code to speed up some operations.
		4202
		4203	Currently this is used to override some inlining decisions (enlarging the
		4204	code size by roughly 30% on amd64).
		4205
		4206	When optimising for size, use of compiler flags such as C<-Os> with
		4207	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4208	assertions.
		4209
		4210	=item C<2> - faster/larger data structures
		4211
		4212	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4213	hash table sizes and so on. This will usually further increase code size
		4214	and can additionally have an effect on the size of data structures at
		4215	runtime.
		4216
		4217	=item C<4> - full API configuration
		4218
		4219	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4220	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4221
		4222	=item C<8> - full API
		4223
		4224	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4225	details on which parts of the API are still available without this
		4226	feature, and do not complain if this subset changes over time.
		4227
		4228	=item C<16> - enable all optional watcher types
		4229
		4230	Enables all optional watcher types. If you want to selectively enable
		4231	only some watcher types other than I/O and timers (e.g. prepare,
		4232	embed, async, child...) you can enable them manually by defining
		4233	C<EV_watchertype_ENABLE> to C<1> instead.
		4234
		4235	=item C<32> - enable all backends
		4236
		4237	This enables all backends - without this feature, you need to enable at
		4238	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4239
		4240	=item C<64> - enable OS-specific "helper" APIs
		4241
		4242	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4243	default.
		4244
		4245	=back
		4246
		4247	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4248	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4249	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4250	watchers, timers and monotonic clock support.
		4251
		4252	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4253	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4254	your program might be left out as well - a binary starting a timer and an
		4255	I/O watcher then might come out at only 5Kb.
		4256
		4257	=item EV_AVOID_STDIO
		4258
		4259	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4260	functions (printf, scanf, perror etc.). This will increase the code size
		4261	somewhat, but if your program doesn't otherwise depend on stdio and your
		4262	libc allows it, this avoids linking in the stdio library which is quite
		4263	big.
		4264
		4265	Note that error messages might become less precise when this option is
		4266	enabled.
		4267
		4268	=item EV_NSIG
		4269
		4270	The highest supported signal number, +1 (or, the number of
		4271	signals): Normally, libev tries to deduce the maximum number of signals
		4272	automatically, but sometimes this fails, in which case it can be
		4273	specified. Also, using a lower number than detected (C<32> should be
		4274	good for about any system in existence) can save some memory, as libev
		4275	statically allocates some 12-24 bytes per signal number.
3442		4276
3443	=item EV_PID_HASHSIZE	4277	=item EV_PID_HASHSIZE
3444		4278
3445	C<ev_child> watchers use a small hash table to distribute workload by	4279	C<ev_child> watchers use a small hash table to distribute workload by
3446	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4280	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3447	than enough. If you need to manage thousands of children you might want to	4281	usually more than enough. If you need to manage thousands of children you
3448	increase this value (I<must> be a power of two).	4282	might want to increase this value (I<must> be a power of two).
3449		4283
3450	=item EV_INOTIFY_HASHSIZE	4284	=item EV_INOTIFY_HASHSIZE
3451		4285
3452	C<ev_stat> watchers use a small hash table to distribute workload by	4286	C<ev_stat> watchers use a small hash table to distribute workload by
3453	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4287	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3454	usually more than enough. If you need to manage thousands of C<ev_stat>	4288	disabled), usually more than enough. If you need to manage thousands of
3455	watchers you might want to increase this value (I<must> be a power of	4289	C<ev_stat> watchers you might want to increase this value (I<must> be a
3456	two).	4290	power of two).
3457		4291
3458	=item EV_USE_4HEAP	4292	=item EV_USE_4HEAP
3459		4293
3460	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4294	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3461	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4295	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3462	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4296	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3463	faster performance with many (thousands) of watchers.	4297	faster performance with many (thousands) of watchers.
3464		4298
3465	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4299	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3466	(disabled).	4300	will be C<0>.
3467		4301
3468	=item EV_HEAP_CACHE_AT	4302	=item EV_HEAP_CACHE_AT
3469		4303
3470	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4304	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3471	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4305	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3472	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4306	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3473	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4307	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3474	but avoids random read accesses on heap changes. This improves performance	4308	but avoids random read accesses on heap changes. This improves performance
3475	noticeably with many (hundreds) of watchers.	4309	noticeably with many (hundreds) of watchers.
3476		4310
3477	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4311	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3478	(disabled).	4312	will be C<0>.
3479		4313
3480	=item EV_VERIFY	4314	=item EV_VERIFY
3481		4315
3482	Controls how much internal verification (see C<ev_loop_verify ()>) will	4316	Controls how much internal verification (see C<ev_verify ()>) will
3483	be done: If set to C<0>, no internal verification code will be compiled	4317	be done: If set to C<0>, no internal verification code will be compiled
3484	in. If set to C<1>, then verification code will be compiled in, but not	4318	in. If set to C<1>, then verification code will be compiled in, but not
3485	called. If set to C<2>, then the internal verification code will be	4319	called. If set to C<2>, then the internal verification code will be
3486	called once per loop, which can slow down libev. If set to C<3>, then the	4320	called once per loop, which can slow down libev. If set to C<3>, then the
3487	verification code will be called very frequently, which will slow down	4321	verification code will be called very frequently, which will slow down
3488	libev considerably.	4322	libev considerably.
3489		4323
3490	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4324	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3491	C<0>.	4325	will be C<0>.
3492		4326
3493	=item EV_COMMON	4327	=item EV_COMMON
3494		4328
3495	By default, all watchers have a C<void *data> member. By redefining	4329	By default, all watchers have a C<void *data> member. By redefining
3496	this macro to a something else you can include more and other types of	4330	this macro to something else you can include more and other types of
3497	members. You have to define it each time you include one of the files,	4331	members. You have to define it each time you include one of the files,
3498	though, and it must be identical each time.	4332	though, and it must be identical each time.
3499		4333
3500	For example, the perl EV module uses something like this:	4334	For example, the perl EV module uses something like this:
3501		4335
…		…
3554	file.	4388	file.
3555		4389
3556	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4390	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3557	that everybody includes and which overrides some configure choices:	4391	that everybody includes and which overrides some configure choices:
3558		4392
3559	#define EV_MINIMAL 1	4393	#define EV_FEATURES 8
3560	#define EV_USE_POLL 0	4394	#define EV_USE_SELECT 1
3561	#define EV_MULTIPLICITY 0
3562	#define EV_PERIODIC_ENABLE 0	4395	#define EV_PREPARE_ENABLE 1
		4396	#define EV_IDLE_ENABLE 1
3563	#define EV_STAT_ENABLE 0	4397	#define EV_SIGNAL_ENABLE 1
3564	#define EV_FORK_ENABLE 0	4398	#define EV_CHILD_ENABLE 1
		4399	#define EV_USE_STDEXCEPT 0
3565	#define EV_CONFIG_H <config.h>	4400	#define EV_CONFIG_H <config.h>
3566	#define EV_MINPRI 0
3567	#define EV_MAXPRI 0
3568		4401
3569	#include "ev++.h"	4402	#include "ev++.h"
3570		4403
3571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4404	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3572		4405
…		…
3632	default loop and triggering an C<ev_async> watcher from the default loop	4465	default loop and triggering an C<ev_async> watcher from the default loop
3633	watcher callback into the event loop interested in the signal.	4466	watcher callback into the event loop interested in the signal.
3634		4467
3635	=back	4468	=back
3636		4469
		4470	=head4 THREAD LOCKING EXAMPLE
		4471
		4472	Here is a fictitious example of how to run an event loop in a different
		4473	thread than where callbacks are being invoked and watchers are
		4474	created/added/removed.
		4475
		4476	For a real-world example, see the C<EV::Loop::Async> perl module,
		4477	which uses exactly this technique (which is suited for many high-level
		4478	languages).
		4479
		4480	The example uses a pthread mutex to protect the loop data, a condition
		4481	variable to wait for callback invocations, an async watcher to notify the
		4482	event loop thread and an unspecified mechanism to wake up the main thread.
		4483
		4484	First, you need to associate some data with the event loop:
		4485
		4486	typedef struct {
		4487	mutex_t lock; /* global loop lock */
		4488	ev_async async_w;
		4489	thread_t tid;
		4490	cond_t invoke_cv;
		4491	} userdata;
		4492
		4493	void prepare_loop (EV_P)
		4494	{
		4495	// for simplicity, we use a static userdata struct.
		4496	static userdata u;
		4497
		4498	ev_async_init (&u->async_w, async_cb);
		4499	ev_async_start (EV_A_ &u->async_w);
		4500
		4501	pthread_mutex_init (&u->lock, 0);
		4502	pthread_cond_init (&u->invoke_cv, 0);
		4503
		4504	// now associate this with the loop
		4505	ev_set_userdata (EV_A_ u);
		4506	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4507	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4508
		4509	// then create the thread running ev_loop
		4510	pthread_create (&u->tid, 0, l_run, EV_A);
		4511	}
		4512
		4513	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4514	solely to wake up the event loop so it takes notice of any new watchers
		4515	that might have been added:
		4516
		4517	static void
		4518	async_cb (EV_P_ ev_async *w, int revents)
		4519	{
		4520	// just used for the side effects
		4521	}
		4522
		4523	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4524	protecting the loop data, respectively.
		4525
		4526	static void
		4527	l_release (EV_P)
		4528	{
		4529	userdata *u = ev_userdata (EV_A);
		4530	pthread_mutex_unlock (&u->lock);
		4531	}
		4532
		4533	static void
		4534	l_acquire (EV_P)
		4535	{
		4536	userdata *u = ev_userdata (EV_A);
		4537	pthread_mutex_lock (&u->lock);
		4538	}
		4539
		4540	The event loop thread first acquires the mutex, and then jumps straight
		4541	into C<ev_run>:
		4542
		4543	void *
		4544	l_run (void *thr_arg)
		4545	{
		4546	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4547
		4548	l_acquire (EV_A);
		4549	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4550	ev_run (EV_A_ 0);
		4551	l_release (EV_A);
		4552
		4553	return 0;
		4554	}
		4555
		4556	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4557	signal the main thread via some unspecified mechanism (signals? pipe
		4558	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4559	have been called (in a while loop because a) spurious wakeups are possible
		4560	and b) skipping inter-thread-communication when there are no pending
		4561	watchers is very beneficial):
		4562
		4563	static void
		4564	l_invoke (EV_P)
		4565	{
		4566	userdata *u = ev_userdata (EV_A);
		4567
		4568	while (ev_pending_count (EV_A))
		4569	{
		4570	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4571	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4572	}
		4573	}
		4574
		4575	Now, whenever the main thread gets told to invoke pending watchers, it
		4576	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4577	thread to continue:
		4578
		4579	static void
		4580	real_invoke_pending (EV_P)
		4581	{
		4582	userdata *u = ev_userdata (EV_A);
		4583
		4584	pthread_mutex_lock (&u->lock);
		4585	ev_invoke_pending (EV_A);
		4586	pthread_cond_signal (&u->invoke_cv);
		4587	pthread_mutex_unlock (&u->lock);
		4588	}
		4589
		4590	Whenever you want to start/stop a watcher or do other modifications to an
		4591	event loop, you will now have to lock:
		4592
		4593	ev_timer timeout_watcher;
		4594	userdata *u = ev_userdata (EV_A);
		4595
		4596	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4597
		4598	pthread_mutex_lock (&u->lock);
		4599	ev_timer_start (EV_A_ &timeout_watcher);
		4600	ev_async_send (EV_A_ &u->async_w);
		4601	pthread_mutex_unlock (&u->lock);
		4602
		4603	Note that sending the C<ev_async> watcher is required because otherwise
		4604	an event loop currently blocking in the kernel will have no knowledge
		4605	about the newly added timer. By waking up the loop it will pick up any new
		4606	watchers in the next event loop iteration.
		4607
3637	=head3 COROUTINES	4608	=head3 COROUTINES
3638		4609
3639	Libev is very accommodating to coroutines ("cooperative threads"):	4610	Libev is very accommodating to coroutines ("cooperative threads"):
3640	libev fully supports nesting calls to its functions from different	4611	libev fully supports nesting calls to its functions from different
3641	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4612	coroutines (e.g. you can call C<ev_run> on the same loop from two
3642	different coroutines, and switch freely between both coroutines running the	4613	different coroutines, and switch freely between both coroutines running
3643	loop, as long as you don't confuse yourself). The only exception is that	4614	the loop, as long as you don't confuse yourself). The only exception is
3644	you must not do this from C<ev_periodic> reschedule callbacks.	4615	that you must not do this from C<ev_periodic> reschedule callbacks.
3645		4616
3646	Care has been taken to ensure that libev does not keep local state inside	4617	Care has been taken to ensure that libev does not keep local state inside
3647	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4618	C<ev_run>, and other calls do not usually allow for coroutine switches as
3648	they do not call any callbacks.	4619	they do not call any callbacks.
3649		4620
3650	=head2 COMPILER WARNINGS	4621	=head2 COMPILER WARNINGS
3651		4622
3652	Depending on your compiler and compiler settings, you might get no or a	4623	Depending on your compiler and compiler settings, you might get no or a
…		…
3663	maintainable.	4634	maintainable.
3664		4635
3665	And of course, some compiler warnings are just plain stupid, or simply	4636	And of course, some compiler warnings are just plain stupid, or simply
3666	wrong (because they don't actually warn about the condition their message	4637	wrong (because they don't actually warn about the condition their message
3667	seems to warn about). For example, certain older gcc versions had some	4638	seems to warn about). For example, certain older gcc versions had some
3668	warnings that resulted an extreme number of false positives. These have	4639	warnings that resulted in an extreme number of false positives. These have
3669	been fixed, but some people still insist on making code warn-free with	4640	been fixed, but some people still insist on making code warn-free with
3670	such buggy versions.	4641	such buggy versions.
3671		4642
3672	While libev is written to generate as few warnings as possible,	4643	While libev is written to generate as few warnings as possible,
3673	"warn-free" code is not a goal, and it is recommended not to build libev	4644	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3709	I suggest using suppression lists.	4680	I suggest using suppression lists.
3710		4681
3711		4682
3712	=head1 PORTABILITY NOTES	4683	=head1 PORTABILITY NOTES
3713		4684
		4685	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4686
		4687	GNU/Linux is the only common platform that supports 64 bit file/large file
		4688	interfaces but I<disables> them by default.
		4689
		4690	That means that libev compiled in the default environment doesn't support
		4691	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4692
		4693	Unfortunately, many programs try to work around this GNU/Linux issue
		4694	by enabling the large file API, which makes them incompatible with the
		4695	standard libev compiled for their system.
		4696
		4697	Likewise, libev cannot enable the large file API itself as this would
		4698	suddenly make it incompatible to the default compile time environment,
		4699	i.e. all programs not using special compile switches.
		4700
		4701	=head2 OS/X AND DARWIN BUGS
		4702
		4703	The whole thing is a bug if you ask me - basically any system interface
		4704	you touch is broken, whether it is locales, poll, kqueue or even the
		4705	OpenGL drivers.
		4706
		4707	=head3 C<kqueue> is buggy
		4708
		4709	The kqueue syscall is broken in all known versions - most versions support
		4710	only sockets, many support pipes.
		4711
		4712	Libev tries to work around this by not using C<kqueue> by default on this
		4713	rotten platform, but of course you can still ask for it when creating a
		4714	loop - embedding a socket-only kqueue loop into a select-based one is
		4715	probably going to work well.
		4716
		4717	=head3 C<poll> is buggy
		4718
		4719	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4720	implementation by something calling C<kqueue> internally around the 10.5.6
		4721	release, so now C<kqueue> I<and> C<poll> are broken.
		4722
		4723	Libev tries to work around this by not using C<poll> by default on
		4724	this rotten platform, but of course you can still ask for it when creating
		4725	a loop.
		4726
		4727	=head3 C<select> is buggy
		4728
		4729	All that's left is C<select>, and of course Apple found a way to fuck this
		4730	one up as well: On OS/X, C<select> actively limits the number of file
		4731	descriptors you can pass in to 1024 - your program suddenly crashes when
		4732	you use more.
		4733
		4734	There is an undocumented "workaround" for this - defining
		4735	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4736	work on OS/X.
		4737
		4738	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4739
		4740	=head3 C<errno> reentrancy
		4741
		4742	The default compile environment on Solaris is unfortunately so
		4743	thread-unsafe that you can't even use components/libraries compiled
		4744	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4745	defined by default. A valid, if stupid, implementation choice.
		4746
		4747	If you want to use libev in threaded environments you have to make sure
		4748	it's compiled with C<_REENTRANT> defined.
		4749
		4750	=head3 Event port backend
		4751
		4752	The scalable event interface for Solaris is called "event
		4753	ports". Unfortunately, this mechanism is very buggy in all major
		4754	releases. If you run into high CPU usage, your program freezes or you get
		4755	a large number of spurious wakeups, make sure you have all the relevant
		4756	and latest kernel patches applied. No, I don't know which ones, but there
		4757	are multiple ones to apply, and afterwards, event ports actually work
		4758	great.
		4759
		4760	If you can't get it to work, you can try running the program by setting
		4761	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4762	C<select> backends.
		4763
		4764	=head2 AIX POLL BUG
		4765
		4766	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4767	this by trying to avoid the poll backend altogether (i.e. it's not even
		4768	compiled in), which normally isn't a big problem as C<select> works fine
		4769	with large bitsets on AIX, and AIX is dead anyway.
		4770
3714	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4771	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4772
		4773	=head3 General issues
3715		4774
3716	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4775	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3717	requires, and its I/O model is fundamentally incompatible with the POSIX	4776	requires, and its I/O model is fundamentally incompatible with the POSIX
3718	model. Libev still offers limited functionality on this platform in	4777	model. Libev still offers limited functionality on this platform in
3719	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4778	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3720	descriptors. This only applies when using Win32 natively, not when using	4779	descriptors. This only applies when using Win32 natively, not when using
3721	e.g. cygwin.	4780	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4781	as every compielr comes with a slightly differently broken/incompatible
		4782	environment.
3722		4783
3723	Lifting these limitations would basically require the full	4784	Lifting these limitations would basically require the full
3724	re-implementation of the I/O system. If you are into these kinds of	4785	re-implementation of the I/O system. If you are into this kind of thing,
3725	things, then note that glib does exactly that for you in a very portable	4786	then note that glib does exactly that for you in a very portable way (note
3726	way (note also that glib is the slowest event library known to man).	4787	also that glib is the slowest event library known to man).
3727		4788
3728	There is no supported compilation method available on windows except	4789	There is no supported compilation method available on windows except
3729	embedding it into other applications.	4790	embedding it into other applications.
		4791
		4792	Sensible signal handling is officially unsupported by Microsoft - libev
		4793	tries its best, but under most conditions, signals will simply not work.
3730		4794
3731	Not a libev limitation but worth mentioning: windows apparently doesn't	4795	Not a libev limitation but worth mentioning: windows apparently doesn't
3732	accept large writes: instead of resulting in a partial write, windows will	4796	accept large writes: instead of resulting in a partial write, windows will
3733	either accept everything or return C<ENOBUFS> if the buffer is too large,	4797	either accept everything or return C<ENOBUFS> if the buffer is too large,
3734	so make sure you only write small amounts into your sockets (less than a	4798	so make sure you only write small amounts into your sockets (less than a
…		…
3739	the abysmal performance of winsockets, using a large number of sockets	4803	the abysmal performance of winsockets, using a large number of sockets
3740	is not recommended (and not reasonable). If your program needs to use	4804	is not recommended (and not reasonable). If your program needs to use
3741	more than a hundred or so sockets, then likely it needs to use a totally	4805	more than a hundred or so sockets, then likely it needs to use a totally
3742	different implementation for windows, as libev offers the POSIX readiness	4806	different implementation for windows, as libev offers the POSIX readiness
3743	notification model, which cannot be implemented efficiently on windows	4807	notification model, which cannot be implemented efficiently on windows
3744	(Microsoft monopoly games).	4808	(due to Microsoft monopoly games).
3745		4809
3746	A typical way to use libev under windows is to embed it (see the embedding	4810	A typical way to use libev under windows is to embed it (see the embedding
3747	section for details) and use the following F<evwrap.h> header file instead	4811	section for details) and use the following F<evwrap.h> header file instead
3748	of F<ev.h>:	4812	of F<ev.h>:
3749		4813
…		…
3756	you do I<not> compile the F<ev.c> or any other embedded source files!):	4820	you do I<not> compile the F<ev.c> or any other embedded source files!):
3757		4821
3758	#include "evwrap.h"	4822	#include "evwrap.h"
3759	#include "ev.c"	4823	#include "ev.c"
3760		4824
3761	=over 4
3762
3763	=item The winsocket select function	4825	=head3 The winsocket C<select> function
3764		4826
3765	The winsocket C<select> function doesn't follow POSIX in that it	4827	The winsocket C<select> function doesn't follow POSIX in that it
3766	requires socket I<handles> and not socket I<file descriptors> (it is	4828	requires socket I<handles> and not socket I<file descriptors> (it is
3767	also extremely buggy). This makes select very inefficient, and also	4829	also extremely buggy). This makes select very inefficient, and also
3768	requires a mapping from file descriptors to socket handles (the Microsoft	4830	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3777	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4839	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3778		4840
3779	Note that winsockets handling of fd sets is O(n), so you can easily get a	4841	Note that winsockets handling of fd sets is O(n), so you can easily get a
3780	complexity in the O(n²) range when using win32.	4842	complexity in the O(n²) range when using win32.
3781		4843
3782	=item Limited number of file descriptors	4844	=head3 Limited number of file descriptors
3783		4845
3784	Windows has numerous arbitrary (and low) limits on things.	4846	Windows has numerous arbitrary (and low) limits on things.
3785		4847
3786	Early versions of winsocket's select only supported waiting for a maximum	4848	Early versions of winsocket's select only supported waiting for a maximum
3787	of C<64> handles (probably owning to the fact that all windows kernels	4849	of C<64> handles (probably owning to the fact that all windows kernels
3788	can only wait for C<64> things at the same time internally; Microsoft	4850	can only wait for C<64> things at the same time internally; Microsoft
3789	recommends spawning a chain of threads and wait for 63 handles and the	4851	recommends spawning a chain of threads and wait for 63 handles and the
3790	previous thread in each. Great).	4852	previous thread in each. Sounds great!).
3791		4853
3792	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4854	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3793	to some high number (e.g. C<2048>) before compiling the winsocket select	4855	to some high number (e.g. C<2048>) before compiling the winsocket select
3794	call (which might be in libev or elsewhere, for example, perl does its own	4856	call (which might be in libev or elsewhere, for example, perl and many
3795	select emulation on windows).	4857	other interpreters do their own select emulation on windows).
3796		4858
3797	Another limit is the number of file descriptors in the Microsoft runtime	4859	Another limit is the number of file descriptors in the Microsoft runtime
3798	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4860	libraries, which by default is C<64> (there must be a hidden I<64>
3799	or something like this inside Microsoft). You can increase this by calling	4861	fetish or something like this inside Microsoft). You can increase this
3800	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4862	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3801	arbitrary limit), but is broken in many versions of the Microsoft runtime	4863	(another arbitrary limit), but is broken in many versions of the Microsoft
3802	libraries.
3803
3804	This might get you to about C<512> or C<2048> sockets (depending on	4864	runtime libraries. This might get you to about C<512> or C<2048> sockets
3805	windows version and/or the phase of the moon). To get more, you need to	4865	(depending on windows version and/or the phase of the moon). To get more,
3806	wrap all I/O functions and provide your own fd management, but the cost of	4866	you need to wrap all I/O functions and provide your own fd management, but
3807	calling select (O(n²)) will likely make this unworkable.	4867	the cost of calling select (O(n²)) will likely make this unworkable.
3808
3809	=back
3810		4868
3811	=head2 PORTABILITY REQUIREMENTS	4869	=head2 PORTABILITY REQUIREMENTS
3812		4870
3813	In addition to a working ISO-C implementation and of course the	4871	In addition to a working ISO-C implementation and of course the
3814	backend-specific APIs, libev relies on a few additional extensions:	4872	backend-specific APIs, libev relies on a few additional extensions:
…		…
3821	Libev assumes not only that all watcher pointers have the same internal	4879	Libev assumes not only that all watcher pointers have the same internal
3822	structure (guaranteed by POSIX but not by ISO C for example), but it also	4880	structure (guaranteed by POSIX but not by ISO C for example), but it also
3823	assumes that the same (machine) code can be used to call any watcher	4881	assumes that the same (machine) code can be used to call any watcher
3824	callback: The watcher callbacks have different type signatures, but libev	4882	callback: The watcher callbacks have different type signatures, but libev
3825	calls them using an C<ev_watcher *> internally.	4883	calls them using an C<ev_watcher *> internally.
		4884
		4885	=item pointer accesses must be thread-atomic
		4886
		4887	Accessing a pointer value must be atomic, it must both be readable and
		4888	writable in one piece - this is the case on all current architectures.
3826		4889
3827	=item C<sig_atomic_t volatile> must be thread-atomic as well	4890	=item C<sig_atomic_t volatile> must be thread-atomic as well
3828		4891
3829	The type C<sig_atomic_t volatile> (or whatever is defined as	4892	The type C<sig_atomic_t volatile> (or whatever is defined as
3830	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4893	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3853	watchers.	4916	watchers.
3854		4917
3855	=item C<double> must hold a time value in seconds with enough accuracy	4918	=item C<double> must hold a time value in seconds with enough accuracy
3856		4919
3857	The type C<double> is used to represent timestamps. It is required to	4920	The type C<double> is used to represent timestamps. It is required to
3858	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4921	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3859	enough for at least into the year 4000. This requirement is fulfilled by	4922	good enough for at least into the year 4000 with millisecond accuracy
		4923	(the design goal for libev). This requirement is overfulfilled by
3860	implementations implementing IEEE 754 (basically all existing ones).	4924	implementations using IEEE 754, which is basically all existing ones. With
		4925	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3861		4926
3862	=back	4927	=back
3863		4928
3864	If you know of other additional requirements drop me a note.	4929	If you know of other additional requirements drop me a note.
3865		4930
…		…
3933	involves iterating over all running async watchers or all signal numbers.	4998	involves iterating over all running async watchers or all signal numbers.
3934		4999
3935	=back	5000	=back
3936		5001
3937		5002
		5003	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5004
		5005	The major version 4 introduced some incompatible changes to the API.
		5006
		5007	At the moment, the C<ev.h> header file provides compatibility definitions
		5008	for all changes, so most programs should still compile. The compatibility
		5009	layer might be removed in later versions of libev, so better update to the
		5010	new API early than late.
		5011
		5012	=over 4
		5013
		5014	=item C<EV_COMPAT3> backwards compatibility mechanism
		5015
		5016	The backward compatibility mechanism can be controlled by
		5017	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5018	section.
		5019
		5020	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5021
		5022	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5023
		5024	ev_loop_destroy (EV_DEFAULT_UC);
		5025	ev_loop_fork (EV_DEFAULT);
		5026
		5027	=item function/symbol renames
		5028
		5029	A number of functions and symbols have been renamed:
		5030
		5031	ev_loop => ev_run
		5032	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5033	EVLOOP_ONESHOT => EVRUN_ONCE
		5034
		5035	ev_unloop => ev_break
		5036	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5037	EVUNLOOP_ONE => EVBREAK_ONE
		5038	EVUNLOOP_ALL => EVBREAK_ALL
		5039
		5040	EV_TIMEOUT => EV_TIMER
		5041
		5042	ev_loop_count => ev_iteration
		5043	ev_loop_depth => ev_depth
		5044	ev_loop_verify => ev_verify
		5045
		5046	Most functions working on C<struct ev_loop> objects don't have an
		5047	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5048	associated constants have been renamed to not collide with the C<struct
		5049	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5050	as all other watcher types. Note that C<ev_loop_fork> is still called
		5051	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5052	typedef.
		5053
		5054	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5055
		5056	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5057	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5058	and work, but the library code will of course be larger.
		5059
		5060	=back
		5061
		5062
		5063	=head1 GLOSSARY
		5064
		5065	=over 4
		5066
		5067	=item active
		5068
		5069	A watcher is active as long as it has been started and not yet stopped.
		5070	See L<WATCHER STATES> for details.
		5071
		5072	=item application
		5073
		5074	In this document, an application is whatever is using libev.
		5075
		5076	=item backend
		5077
		5078	The part of the code dealing with the operating system interfaces.
		5079
		5080	=item callback
		5081
		5082	The address of a function that is called when some event has been
		5083	detected. Callbacks are being passed the event loop, the watcher that
		5084	received the event, and the actual event bitset.
		5085
		5086	=item callback/watcher invocation
		5087
		5088	The act of calling the callback associated with a watcher.
		5089
		5090	=item event
		5091
		5092	A change of state of some external event, such as data now being available
		5093	for reading on a file descriptor, time having passed or simply not having
		5094	any other events happening anymore.
		5095
		5096	In libev, events are represented as single bits (such as C<EV_READ> or
		5097	C<EV_TIMER>).
		5098
		5099	=item event library
		5100
		5101	A software package implementing an event model and loop.
		5102
		5103	=item event loop
		5104
		5105	An entity that handles and processes external events and converts them
		5106	into callback invocations.
		5107
		5108	=item event model
		5109
		5110	The model used to describe how an event loop handles and processes
		5111	watchers and events.
		5112
		5113	=item pending
		5114
		5115	A watcher is pending as soon as the corresponding event has been
		5116	detected. See L<WATCHER STATES> for details.
		5117
		5118	=item real time
		5119
		5120	The physical time that is observed. It is apparently strictly monotonic :)
		5121
		5122	=item wall-clock time
		5123
		5124	The time and date as shown on clocks. Unlike real time, it can actually
		5125	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5126	clock.
		5127
		5128	=item watcher
		5129
		5130	A data structure that describes interest in certain events. Watchers need
		5131	to be started (attached to an event loop) before they can receive events.
		5132
		5133	=back
		5134
3938	=head1 AUTHOR	5135	=head1 AUTHOR
3939		5136
3940	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5137	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5138	Magnusson and Emanuele Giaquinta.
3941		5139

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