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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,
		512	a frankenpoll, cobbled together in a hurry, no thought to design or
		513	interaction with others.
409		514
410	While stopping, setting and starting an I/O watcher in the same iteration	515	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	516	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	517	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	518	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	584	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		585
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	586	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	587	it's really slow, but it still scales very well (O(active_fds)).
483		588
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	589	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	590	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	591	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	592	might perform better.
492		593
493	On the positive side, with the exception of the spurious readiness	594	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	595	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	596	among the OS-specific backends (I vastly prefer correctness over speed
		597	hacks).
		598
		599	On the negative side, the interface is I<bizarre> - so bizarre that
		600	even sun itself gets it wrong in their code examples: The event polling
		601	function sometimes returning events to the caller even though an error
		602	occurred, but with no indication whether it has done so or not (yes, it's
		603	even documented that way) - deadly for edge-triggered interfaces where
		604	you absolutely have to know whether an event occurred or not because you
		605	have to re-arm the watcher.
		606
		607	Fortunately libev seems to be able to work around these idiocies.
497		608
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	609	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	610	C<EVBACKEND_POLL>.
500		611
501	=item C<EVBACKEND_ALL>	612	=item C<EVBACKEND_ALL>
502		613
503	Try all backends (even potentially broken ones that wouldn't be tried	614	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	615	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	616	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		617
507	It is definitely not recommended to use this flag.	618	It is definitely not recommended to use this flag, use whatever
		619	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		620	at all.
		621
		622	=item C<EVBACKEND_MASK>
		623
		624	Not a backend at all, but a mask to select all backend bits from a
		625	C<flags> value, in case you want to mask out any backends from a flags
		626	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		627
509	=back	628	=back
510		629
511	If one or more of these are or'ed into the flags value, then only these	630	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	631	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.	632	here). If none are specified, all backends in C<ev_recommended_backends
514		633	()> 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		634
543	Example: Try to create a event loop that uses epoll and nothing else.	635	Example: Try to create a event loop that uses epoll and nothing else.
544		636
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	637	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	638	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	639	fatal ("no epoll found here, maybe it hides under your chair");
548		640
		641	Example: Use whatever libev has to offer, but make sure that kqueue is
		642	used if available.
		643
		644	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		645
549	=item ev_default_destroy ()	646	=item ev_loop_destroy (loop)
550		647
551	Destroys the default loop again (frees all memory and kernel state	648	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	649	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	650	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>	651	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	652	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	653	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		655
559	Note that certain global state, such as signal state (and installed signal	656	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	657	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	658	as signal and child watchers) would need to be stopped manually.
562		659
563	In general it is not advisable to call this function except in the	660	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	661	C<ev_loop_new>, but it can also be used on the default loop returned by
		662	C<ev_default_loop>, in which case it is not thread-safe.
		663
		664	Note that it is not advisable to call this function on the default loop
		665	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	666	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>).	667	and C<ev_loop_destroy>.
567		668
568	=item ev_loop_destroy (loop)	669	=item ev_loop_fork (loop)
569		670
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	671	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	672	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	673	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	674	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	675	child before resuming or calling C<ev_run>.
580	functions, and it will only take effect at the next C<ev_loop> iteration.	676
		677	Again, you I<have> to call it on I<any> loop that you want to re-use after
		678	a fork, I<even if you do not plan to use the loop in the parent>. This is
		679	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		680	during fork.
581		681
582	On the other hand, you only need to call this function in the child	682	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	683	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.	684	you just fork+exec or create a new loop in the child, you don't have to
		685	call it at all (in fact, C<epoll> is so badly broken that it makes a
		686	difference, but libev will usually detect this case on its own and do a
		687	costly reset of the backend).
585		688
586	The function itself is quite fast and it's usually not a problem to call	689	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	690	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		691
		692	Example: Automate calling C<ev_loop_fork> on the default loop when
		693	using pthreads.
		694
		695	static void
		696	post_fork_child (void)
		697	{
		698	ev_loop_fork (EV_DEFAULT);
		699	}
		700
		701	...
590	pthread_atfork (0, 0, ev_default_fork);	702	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		703
599	=item int ev_is_default_loop (loop)	704	=item int ev_is_default_loop (loop)
600		705
601	Returns true when the given loop is, in fact, the default loop, and false	706	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	707	otherwise.
603		708
604	=item unsigned int ev_loop_count (loop)	709	=item unsigned int ev_iteration (loop)
605		710
606	Returns the count of loop iterations for the loop, which is identical to	711	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	712	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	713	and happily wraps around with enough iterations.
609		714
610	This value can sometimes be useful as a generation counter of sorts (it	715	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	716	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	717	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		718	prepare and check phases.
		719
		720	=item unsigned int ev_depth (loop)
		721
		722	Returns the number of times C<ev_run> was entered minus the number of
		723	times C<ev_run> was exited normally, in other words, the recursion depth.
		724
		725	Outside C<ev_run>, this number is zero. In a callback, this number is
		726	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		727	in which case it is higher.
		728
		729	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		730	throwing an exception etc.), doesn't count as "exit" - consider this
		731	as a hint to avoid such ungentleman-like behaviour unless it's really
		732	convenient, in which case it is fully supported.
613		733
614	=item unsigned int ev_backend (loop)	734	=item unsigned int ev_backend (loop)
615		735
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	736	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	737	use.
…		…
626		746
627	=item ev_now_update (loop)	747	=item ev_now_update (loop)
628		748
629	Establishes the current time by querying the kernel, updating the time	749	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	750	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	751	is usually done automatically within C<ev_run ()>.
632		752
633	This function is rarely useful, but when some event callback runs for a	753	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	754	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	755	the current time is a good idea.
636		756
637	See also "The special problem of time updates" in the C<ev_timer> section.	757	See also L<The special problem of time updates> in the C<ev_timer> section.
638		758
639	=item ev_suspend (loop)	759	=item ev_suspend (loop)
640		760
641	=item ev_resume (loop)	761	=item ev_resume (loop)
642		762
643	These two functions suspend and resume a loop, for use when the loop is	763	These two functions suspend and resume an event loop, for use when the
644	not used for a while and timeouts should not be processed.	764	loop is not used for a while and timeouts should not be processed.
645		765
646	A typical use case would be an interactive program such as a game: When	766	A typical use case would be an interactive program such as a game: When
647	the user presses C<^Z> to suspend the game and resumes it an hour later it	767	the user presses C<^Z> to suspend the game and resumes it an hour later it
648	would be best to handle timeouts as if no time had actually passed while	768	would be best to handle timeouts as if no time had actually passed while
649	the program was suspended. This can be achieved by calling C<ev_suspend>	769	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
651	C<ev_resume> directly afterwards to resume timer processing.	771	C<ev_resume> directly afterwards to resume timer processing.
652		772
653	Effectively, all C<ev_timer> watchers will be delayed by the time spend	773	Effectively, all C<ev_timer> watchers will be delayed by the time spend
654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	774	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
655	will be rescheduled (that is, they will lose any events that would have	775	will be rescheduled (that is, they will lose any events that would have
656	occured while suspended).	776	occurred while suspended).
657		777
658	After calling C<ev_suspend> you B<must not> call I<any> function on the	778	After calling C<ev_suspend> you B<must not> call I<any> function on the
659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	779	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
660	without a previous call to C<ev_suspend>.	780	without a previous call to C<ev_suspend>.
661		781
662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	782	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
663	event loop time (see C<ev_now_update>).	783	event loop time (see C<ev_now_update>).
664		784
665	=item ev_loop (loop, int flags)	785	=item ev_run (loop, int flags)
666		786
667	Finally, this is it, the event handler. This function usually is called	787	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	788	after you have initialised all your watchers and you want to start
669	events.	789	handling events. It will ask the operating system for any new events, call
		790	the watcher callbacks, an then repeat the whole process indefinitely: This
		791	is why event loops are called I<loops>.
670		792
671	If the flags argument is specified as C<0>, it will not return until	793	If the flags argument is specified as C<0>, it will keep handling events
672	either no event watchers are active anymore or C<ev_unloop> was called.	794	until either no event watchers are active anymore or C<ev_break> was
		795	called.
673		796
674	Please note that an explicit C<ev_unloop> is usually better than	797	Please note that an explicit C<ev_break> is usually better than
675	relying on all watchers to be stopped when deciding when a program has	798	relying on all watchers to be stopped when deciding when a program has
676	finished (especially in interactive programs), but having a program	799	finished (especially in interactive programs), but having a program
677	that automatically loops as long as it has to and no longer by virtue	800	that automatically loops as long as it has to and no longer by virtue
678	of relying on its watchers stopping correctly, that is truly a thing of	801	of relying on its watchers stopping correctly, that is truly a thing of
679	beauty.	802	beauty.
680		803
		804	This function is also I<mostly> exception-safe - you can break out of
		805	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		806	exception and so on. This does not decrement the C<ev_depth> value, nor
		807	will it clear any outstanding C<EVBREAK_ONE> breaks.
		808
681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	809	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
682	those events and any already outstanding ones, but will not block your	810	those events and any already outstanding ones, but will not wait and
683	process in case there are no events and will return after one iteration of	811	block your process in case there are no events and will return after one
684	the loop.	812	iteration of the loop. This is sometimes useful to poll and handle new
		813	events while doing lengthy calculations, to keep the program responsive.
685		814
686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	815	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
687	necessary) and will handle those and any already outstanding ones. It	816	necessary) and will handle those and any already outstanding ones. It
688	will block your process until at least one new event arrives (which could	817	will block your process until at least one new event arrives (which could
689	be an event internal to libev itself, so there is no guarantee that a	818	be an event internal to libev itself, so there is no guarantee that a
690	user-registered callback will be called), and will return after one	819	user-registered callback will be called), and will return after one
691	iteration of the loop.	820	iteration of the loop.
692		821
693	This is useful if you are waiting for some external event in conjunction	822	This is useful if you are waiting for some external event in conjunction
694	with something not expressible using other libev watchers (i.e. "roll your	823	with something not expressible using other libev watchers (i.e. "roll your
695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	824	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
696	usually a better approach for this kind of thing.	825	usually a better approach for this kind of thing.
697		826
698	Here are the gory details of what C<ev_loop> does:	827	Here are the gory details of what C<ev_run> does:
699		828
		829	- Increment loop depth.
		830	- Reset the ev_break status.
700	- Before the first iteration, call any pending watchers.	831	- Before the first iteration, call any pending watchers.
		832	LOOP:
701	* If EVFLAG_FORKCHECK was used, check for a fork.	833	- If EVFLAG_FORKCHECK was used, check for a fork.
702	- If a fork was detected (by any means), queue and call all fork watchers.	834	- If a fork was detected (by any means), queue and call all fork watchers.
703	- Queue and call all prepare watchers.	835	- Queue and call all prepare watchers.
		836	- If ev_break was called, goto FINISH.
704	- If we have been forked, detach and recreate the kernel state	837	- If we have been forked, detach and recreate the kernel state
705	as to not disturb the other process.	838	as to not disturb the other process.
706	- Update the kernel state with all outstanding changes.	839	- Update the kernel state with all outstanding changes.
707	- Update the "event loop time" (ev_now ()).	840	- Update the "event loop time" (ev_now ()).
708	- Calculate for how long to sleep or block, if at all	841	- Calculate for how long to sleep or block, if at all
709	(active idle watchers, EVLOOP_NONBLOCK or not having	842	(active idle watchers, EVRUN_NOWAIT or not having
710	any active watchers at all will result in not sleeping).	843	any active watchers at all will result in not sleeping).
711	- Sleep if the I/O and timer collect interval say so.	844	- Sleep if the I/O and timer collect interval say so.
		845	- Increment loop iteration counter.
712	- Block the process, waiting for any events.	846	- Block the process, waiting for any events.
713	- Queue all outstanding I/O (fd) events.	847	- Queue all outstanding I/O (fd) events.
714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	848	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
715	- Queue all expired timers.	849	- Queue all expired timers.
716	- Queue all expired periodics.	850	- Queue all expired periodics.
717	- Unless any events are pending now, queue all idle watchers.	851	- Queue all idle watchers with priority higher than that of pending events.
718	- Queue all check watchers.	852	- Queue all check watchers.
719	- Call all queued watchers in reverse order (i.e. check watchers first).	853	- Call all queued watchers in reverse order (i.e. check watchers first).
720	Signals and child watchers are implemented as I/O watchers, and will	854	Signals and child watchers are implemented as I/O watchers, and will
721	be handled here by queueing them when their watcher gets executed.	855	be handled here by queueing them when their watcher gets executed.
722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	856	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
723	were used, or there are no active watchers, return, otherwise	857	were used, or there are no active watchers, goto FINISH, otherwise
724	continue with step *.	858	continue with step LOOP.
		859	FINISH:
		860	- Reset the ev_break status iff it was EVBREAK_ONE.
		861	- Decrement the loop depth.
		862	- Return.
725		863
726	Example: Queue some jobs and then loop until no events are outstanding	864	Example: Queue some jobs and then loop until no events are outstanding
727	anymore.	865	anymore.
728		866
729	... queue jobs here, make sure they register event watchers as long	867	... queue jobs here, make sure they register event watchers as long
730	... as they still have work to do (even an idle watcher will do..)	868	... as they still have work to do (even an idle watcher will do..)
731	ev_loop (my_loop, 0);	869	ev_run (my_loop, 0);
732	... jobs done or somebody called unloop. yeah!	870	... jobs done or somebody called unloop. yeah!
733		871
734	=item ev_unloop (loop, how)	872	=item ev_break (loop, how)
735		873
736	Can be used to make a call to C<ev_loop> return early (but only after it	874	Can be used to make a call to C<ev_run> return early (but only after it
737	has processed all outstanding events). The C<how> argument must be either	875	has processed all outstanding events). The C<how> argument must be either
738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	876	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	877	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
740		878
741	This "unloop state" will be cleared when entering C<ev_loop> again.	879	This "break state" will be cleared on the next call to C<ev_run>.
742		880
743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	881	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		882	which case it will have no effect.
744		883
745	=item ev_ref (loop)	884	=item ev_ref (loop)
746		885
747	=item ev_unref (loop)	886	=item ev_unref (loop)
748		887
749	Ref/unref can be used to add or remove a reference count on the event	888	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	889	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	890	count is nonzero, C<ev_run> will not return on its own.
752		891
753	If you have a watcher you never unregister that should not keep C<ev_loop>	892	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	893	unregister, but that nevertheless should not keep C<ev_run> from
		894	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	895	before stopping it.
756		896
757	As an example, libev itself uses this for its internal signal pipe: It	897	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	898	is not visible to the libev user and should not keep C<ev_run> from
759	exiting if no event watchers registered by it are active. It is also an	899	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	900	excellent way to do this for generic recurring timers or from within
761	third-party libraries. Just remember to I<unref after start> and I<ref	901	third-party libraries. Just remember to I<unref after start> and I<ref
762	before stop> (but only if the watcher wasn't active before, or was active	902	before stop> (but only if the watcher wasn't active before, or was active
763	before, respectively. Note also that libev might stop watchers itself	903	before, respectively. Note also that libev might stop watchers itself
764	(e.g. non-repeating timers) in which case you have to C<ev_ref>	904	(e.g. non-repeating timers) in which case you have to C<ev_ref>
765	in the callback).	905	in the callback).
766		906
767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	907	Example: Create a signal watcher, but keep it from keeping C<ev_run>
768	running when nothing else is active.	908	running when nothing else is active.
769		909
770	ev_signal exitsig;	910	ev_signal exitsig;
771	ev_signal_init (&exitsig, sig_cb, SIGINT);	911	ev_signal_init (&exitsig, sig_cb, SIGINT);
772	ev_signal_start (loop, &exitsig);	912	ev_signal_start (loop, &exitsig);
773	evf_unref (loop);	913	ev_unref (loop);
774		914
775	Example: For some weird reason, unregister the above signal handler again.	915	Example: For some weird reason, unregister the above signal handler again.
776		916
777	ev_ref (loop);	917	ev_ref (loop);
778	ev_signal_stop (loop, &exitsig);	918	ev_signal_stop (loop, &exitsig);
…		…
799		939
800	By setting a higher I<io collect interval> you allow libev to spend more	940	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	941	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	942	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	943	C<ev_timer>) will be not affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	944	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		945	sleep time ensures that libev will not poll for I/O events more often then
		946	once per this interval, on average.
805		947
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	948	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	949	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	950	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	951	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		953
812	Many (busy) programs can usually benefit by setting the I/O collect	954	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	955	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	956	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	957	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	958	as this approaches the timing granularity of most systems. Note that if
		959	you do transactions with the outside world and you can't increase the
		960	parallelity, then this setting will limit your transaction rate (if you
		961	need to poll once per transaction and the I/O collect interval is 0.01,
		962	then you can't do more than 100 transactions per second).
817		963
818	Setting the I<timeout collect interval> can improve the opportunity for	964	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	965	saving power, as the program will "bundle" timer callback invocations that
820	are "near" in time together, by delaying some, thus reducing the number of	966	are "near" in time together, by delaying some, thus reducing the number of
821	times the process sleeps and wakes up again. Another useful technique to	967	times the process sleeps and wakes up again. Another useful technique to
822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	968	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	969	they fire on, say, one-second boundaries only.
824		970
		971	Example: we only need 0.1s timeout granularity, and we wish not to poll
		972	more often than 100 times per second:
		973
		974	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		975	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		976
		977	=item ev_invoke_pending (loop)
		978
		979	This call will simply invoke all pending watchers while resetting their
		980	pending state. Normally, C<ev_run> does this automatically when required,
		981	but when overriding the invoke callback this call comes handy. This
		982	function can be invoked from a watcher - this can be useful for example
		983	when you want to do some lengthy calculation and want to pass further
		984	event handling to another thread (you still have to make sure only one
		985	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		986
		987	=item int ev_pending_count (loop)
		988
		989	Returns the number of pending watchers - zero indicates that no watchers
		990	are pending.
		991
		992	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		993
		994	This overrides the invoke pending functionality of the loop: Instead of
		995	invoking all pending watchers when there are any, C<ev_run> will call
		996	this callback instead. This is useful, for example, when you want to
		997	invoke the actual watchers inside another context (another thread etc.).
		998
		999	If you want to reset the callback, use C<ev_invoke_pending> as new
		1000	callback.
		1001
		1002	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1003
		1004	Sometimes you want to share the same loop between multiple threads. This
		1005	can be done relatively simply by putting mutex_lock/unlock calls around
		1006	each call to a libev function.
		1007
		1008	However, C<ev_run> can run an indefinite time, so it is not feasible
		1009	to wait for it to return. One way around this is to wake up the event
		1010	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1011	I<release> and I<acquire> callbacks on the loop.
		1012
		1013	When set, then C<release> will be called just before the thread is
		1014	suspended waiting for new events, and C<acquire> is called just
		1015	afterwards.
		1016
		1017	Ideally, C<release> will just call your mutex_unlock function, and
		1018	C<acquire> will just call the mutex_lock function again.
		1019
		1020	While event loop modifications are allowed between invocations of
		1021	C<release> and C<acquire> (that's their only purpose after all), no
		1022	modifications done will affect the event loop, i.e. adding watchers will
		1023	have no effect on the set of file descriptors being watched, or the time
		1024	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1025	to take note of any changes you made.
		1026
		1027	In theory, threads executing C<ev_run> will be async-cancel safe between
		1028	invocations of C<release> and C<acquire>.
		1029
		1030	See also the locking example in the C<THREADS> section later in this
		1031	document.
		1032
		1033	=item ev_set_userdata (loop, void *data)
		1034
		1035	=item void *ev_userdata (loop)
		1036
		1037	Set and retrieve a single C<void *> associated with a loop. When
		1038	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1039	C<0>.
		1040
		1041	These two functions can be used to associate arbitrary data with a loop,
		1042	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1043	C<acquire> callbacks described above, but of course can be (ab-)used for
		1044	any other purpose as well.
		1045
825	=item ev_loop_verify (loop)	1046	=item ev_verify (loop)
826		1047
827	This function only does something when C<EV_VERIFY> support has been	1048	This function only does something when C<EV_VERIFY> support has been
828	compiled in, which is the default for non-minimal builds. It tries to go	1049	compiled in, which is the default for non-minimal builds. It tries to go
829	through all internal structures and checks them for validity. If anything	1050	through all internal structures and checks them for validity. If anything
830	is found to be inconsistent, it will print an error message to standard	1051	is found to be inconsistent, it will print an error message to standard
…		…
841		1062
842	In the following description, uppercase C<TYPE> in names stands for the	1063	In the following description, uppercase C<TYPE> in names stands for the
843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1064	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
844	watchers and C<ev_io_start> for I/O watchers.	1065	watchers and C<ev_io_start> for I/O watchers.
845		1066
846	A watcher is a structure that you create and register to record your	1067	A watcher is an opaque structure that you allocate and register to record
847	interest in some event. For instance, if you want to wait for STDIN to	1068	your interest in some event. To make a concrete example, imagine you want
848	become readable, you would create an C<ev_io> watcher for that:	1069	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1070	for that:
849		1071
850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1072	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
851	{	1073	{
852	ev_io_stop (w);	1074	ev_io_stop (w);
853	ev_unloop (loop, EVUNLOOP_ALL);	1075	ev_break (loop, EVBREAK_ALL);
854	}	1076	}
855		1077
856	struct ev_loop *loop = ev_default_loop (0);	1078	struct ev_loop *loop = ev_default_loop (0);
857		1079
858	ev_io stdin_watcher;	1080	ev_io stdin_watcher;
859		1081
860	ev_init (&stdin_watcher, my_cb);	1082	ev_init (&stdin_watcher, my_cb);
861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1083	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
862	ev_io_start (loop, &stdin_watcher);	1084	ev_io_start (loop, &stdin_watcher);
863		1085
864	ev_loop (loop, 0);	1086	ev_run (loop, 0);
865		1087
866	As you can see, you are responsible for allocating the memory for your	1088	As you can see, you are responsible for allocating the memory for your
867	watcher structures (and it is I<usually> a bad idea to do this on the	1089	watcher structures (and it is I<usually> a bad idea to do this on the
868	stack).	1090	stack).
869		1091
870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1092	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1093	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
872		1094
873	Each watcher structure must be initialised by a call to C<ev_init	1095	Each watcher structure must be initialised by a call to C<ev_init (watcher
874	(watcher *, callback)>, which expects a callback to be provided. This	1096	*, callback)>, which expects a callback to be provided. This callback is
875	callback gets invoked each time the event occurs (or, in the case of I/O	1097	invoked each time the event occurs (or, in the case of I/O watchers, each
876	watchers, each time the event loop detects that the file descriptor given	1098	time the event loop detects that the file descriptor given is readable
877	is readable and/or writable).	1099	and/or writable).
878		1100
879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1101	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
880	macro to configure it, with arguments specific to the watcher type. There	1102	macro to configure it, with arguments specific to the watcher type. There
881	is also a macro to combine initialisation and setting in one call: C<<	1103	is also a macro to combine initialisation and setting in one call: C<<
882	ev_TYPE_init (watcher *, callback, ...) >>.	1104	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
905	=item C<EV_WRITE>	1127	=item C<EV_WRITE>
906		1128
907	The file descriptor in the C<ev_io> watcher has become readable and/or	1129	The file descriptor in the C<ev_io> watcher has become readable and/or
908	writable.	1130	writable.
909		1131
910	=item C<EV_TIMEOUT>	1132	=item C<EV_TIMER>
911		1133
912	The C<ev_timer> watcher has timed out.	1134	The C<ev_timer> watcher has timed out.
913		1135
914	=item C<EV_PERIODIC>	1136	=item C<EV_PERIODIC>
915		1137
…		…
933		1155
934	=item C<EV_PREPARE>	1156	=item C<EV_PREPARE>
935		1157
936	=item C<EV_CHECK>	1158	=item C<EV_CHECK>
937		1159
938	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1160	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
939	to gather new events, and all C<ev_check> watchers are invoked just after	1161	to gather new events, and all C<ev_check> watchers are invoked just after
940	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1162	C<ev_run> has gathered them, but before it invokes any callbacks for any
941	received events. Callbacks of both watcher types can start and stop as	1163	received events. Callbacks of both watcher types can start and stop as
942	many watchers as they want, and all of them will be taken into account	1164	many watchers as they want, and all of them will be taken into account
943	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1165	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
944	C<ev_loop> from blocking).	1166	C<ev_run> from blocking).
945		1167
946	=item C<EV_EMBED>	1168	=item C<EV_EMBED>
947		1169
948	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1170	The embedded event loop specified in the C<ev_embed> watcher needs attention.
949		1171
950	=item C<EV_FORK>	1172	=item C<EV_FORK>
951		1173
952	The event loop has been resumed in the child process after fork (see	1174	The event loop has been resumed in the child process after fork (see
953	C<ev_fork>).	1175	C<ev_fork>).
		1176
		1177	=item C<EV_CLEANUP>
		1178
		1179	The event loop is about to be destroyed (see C<ev_cleanup>).
954		1180
955	=item C<EV_ASYNC>	1181	=item C<EV_ASYNC>
956		1182
957	The given async watcher has been asynchronously notified (see C<ev_async>).	1183	The given async watcher has been asynchronously notified (see C<ev_async>).
958		1184
…		…
1005		1231
1006	ev_io w;	1232	ev_io w;
1007	ev_init (&w, my_cb);	1233	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1234	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1235
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1236	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1237
1012	This macro initialises the type-specific parts of a watcher. You need to	1238	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1239	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1240	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1241	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1254
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1255	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1256
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1257	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1258
1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1259	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1260
1035	Starts (activates) the given watcher. Only active watchers will receive	1261	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1262	events. If the watcher is already active nothing will happen.
1037		1263
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1264	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1265	whole section.
1040		1266
1041	ev_io_start (EV_DEFAULT_UC, &w);	1267	ev_io_start (EV_DEFAULT_UC, &w);
1042		1268
1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1269	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1270
1045	Stops the given watcher if active, and clears the pending status (whether	1271	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1272	the watcher was active or not).
1047		1273
1048	It is possible that stopped watchers are pending - for example,	1274	It is possible that stopped watchers are pending - for example,
…		…
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1299	=item ev_cb_set (ev_TYPE *watcher, callback)
1074		1300
1075	Change the callback. You can change the callback at virtually any time	1301	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1302	(modulo threads).
1077		1303
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1304	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1305
1080	=item int ev_priority (ev_TYPE *watcher)	1306	=item int ev_priority (ev_TYPE *watcher)
1081		1307
1082	Set and query the priority of the watcher. The priority is a small	1308	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1309	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1310	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1311	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1312	from being executed (except for C<ev_idle> watchers).
1087		1313
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1314	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1315	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1316
1096	You I<must not> change the priority of a watcher as long as it is active or	1317	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1318	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1319
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1320	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1321	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1322	or might not have been clamped to the valid range.
		1323
		1324	The default priority used by watchers when no priority has been set is
		1325	always C<0>, which is supposed to not be too high and not be too low :).
		1326
		1327	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1328	priorities.
1105		1329
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1330	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1331
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1332	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1333	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1117	watcher isn't pending it does nothing and returns C<0>.	1341	watcher isn't pending it does nothing and returns C<0>.
1118		1342
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1343	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1344	callback to be invoked, which can be accomplished with this function.
1121		1345
		1346	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1347
		1348	Feeds the given event set into the event loop, as if the specified event
		1349	had happened for the specified watcher (which must be a pointer to an
		1350	initialised but not necessarily started event watcher). Obviously you must
		1351	not free the watcher as long as it has pending events.
		1352
		1353	Stopping the watcher, letting libev invoke it, or calling
		1354	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1355	not started in the first place.
		1356
		1357	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1358	functions that do not need a watcher.
		1359
1122	=back	1360	=back
1123		1361
		1362	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1363	OWN COMPOSITE WATCHERS> idioms.
1124		1364
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1365	=head2 WATCHER STATES
1126		1366
1127	Each watcher has, by default, a member C<void *data> that you can change	1367	There are various watcher states mentioned throughout this manual -
1128	and read at any time: libev will completely ignore it. This can be used	1368	active, pending and so on. In this section these states and the rules to
1129	to associate arbitrary data with your watcher. If you need more data and	1369	transition between them will be described in more detail - and while these
1130	don't want to allocate memory and store a pointer to it in that data	1370	rules might look complicated, they usually do "the right thing".
1131	member, you can also "subclass" the watcher type and provide your own
1132	data:
1133		1371
1134	struct my_io	1372	=over 4
		1373
		1374	=item initialiased
		1375
		1376	Before a watcher can be registered with the event looop it has to be
		1377	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1378	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1379
		1380	In this state it is simply some block of memory that is suitable for use
		1381	in an event loop. It can be moved around, freed, reused etc. at will.
		1382
		1383	=item started/running/active
		1384
		1385	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1386	property of the event loop, and is actively waiting for events. While in
		1387	this state it cannot be accessed (except in a few documented ways), moved,
		1388	freed or anything else - the only legal thing is to keep a pointer to it,
		1389	and call libev functions on it that are documented to work on active watchers.
		1390
		1391	=item pending
		1392
		1393	If a watcher is active and libev determines that an event it is interested
		1394	in has occurred (such as a timer expiring), it will become pending. It will
		1395	stay in this pending state until either it is stopped or its callback is
		1396	about to be invoked, so it is not normally pending inside the watcher
		1397	callback.
		1398
		1399	The watcher might or might not be active while it is pending (for example,
		1400	an expired non-repeating timer can be pending but no longer active). If it
		1401	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1402	but it is still property of the event loop at this time, so cannot be
		1403	moved, freed or reused. And if it is active the rules described in the
		1404	previous item still apply.
		1405
		1406	It is also possible to feed an event on a watcher that is not active (e.g.
		1407	via C<ev_feed_event>), in which case it becomes pending without being
		1408	active.
		1409
		1410	=item stopped
		1411
		1412	A watcher can be stopped implicitly by libev (in which case it might still
		1413	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1414	latter will clear any pending state the watcher might be in, regardless
		1415	of whether it was active or not, so stopping a watcher explicitly before
		1416	freeing it is often a good idea.
		1417
		1418	While stopped (and not pending) the watcher is essentially in the
		1419	initialised state, that is it can be reused, moved, modified in any way
		1420	you wish.
		1421
		1422	=back
		1423
		1424	=head2 WATCHER PRIORITY MODELS
		1425
		1426	Many event loops support I<watcher priorities>, which are usually small
		1427	integers that influence the ordering of event callback invocation
		1428	between watchers in some way, all else being equal.
		1429
		1430	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1431	description for the more technical details such as the actual priority
		1432	range.
		1433
		1434	There are two common ways how these these priorities are being interpreted
		1435	by event loops:
		1436
		1437	In the more common lock-out model, higher priorities "lock out" invocation
		1438	of lower priority watchers, which means as long as higher priority
		1439	watchers receive events, lower priority watchers are not being invoked.
		1440
		1441	The less common only-for-ordering model uses priorities solely to order
		1442	callback invocation within a single event loop iteration: Higher priority
		1443	watchers are invoked before lower priority ones, but they all get invoked
		1444	before polling for new events.
		1445
		1446	Libev uses the second (only-for-ordering) model for all its watchers
		1447	except for idle watchers (which use the lock-out model).
		1448
		1449	The rationale behind this is that implementing the lock-out model for
		1450	watchers is not well supported by most kernel interfaces, and most event
		1451	libraries will just poll for the same events again and again as long as
		1452	their callbacks have not been executed, which is very inefficient in the
		1453	common case of one high-priority watcher locking out a mass of lower
		1454	priority ones.
		1455
		1456	Static (ordering) priorities are most useful when you have two or more
		1457	watchers handling the same resource: a typical usage example is having an
		1458	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1459	timeouts. Under load, data might be received while the program handles
		1460	other jobs, but since timers normally get invoked first, the timeout
		1461	handler will be executed before checking for data. In that case, giving
		1462	the timer a lower priority than the I/O watcher ensures that I/O will be
		1463	handled first even under adverse conditions (which is usually, but not
		1464	always, what you want).
		1465
		1466	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1467	will only be executed when no same or higher priority watchers have
		1468	received events, they can be used to implement the "lock-out" model when
		1469	required.
		1470
		1471	For example, to emulate how many other event libraries handle priorities,
		1472	you can associate an C<ev_idle> watcher to each such watcher, and in
		1473	the normal watcher callback, you just start the idle watcher. The real
		1474	processing is done in the idle watcher callback. This causes libev to
		1475	continuously poll and process kernel event data for the watcher, but when
		1476	the lock-out case is known to be rare (which in turn is rare :), this is
		1477	workable.
		1478
		1479	Usually, however, the lock-out model implemented that way will perform
		1480	miserably under the type of load it was designed to handle. In that case,
		1481	it might be preferable to stop the real watcher before starting the
		1482	idle watcher, so the kernel will not have to process the event in case
		1483	the actual processing will be delayed for considerable time.
		1484
		1485	Here is an example of an I/O watcher that should run at a strictly lower
		1486	priority than the default, and which should only process data when no
		1487	other events are pending:
		1488
		1489	ev_idle idle; // actual processing watcher
		1490	ev_io io; // actual event watcher
		1491
		1492	static void
		1493	io_cb (EV_P_ ev_io *w, int revents)
1135	{	1494	{
1136	ev_io io;	1495	// stop the I/O watcher, we received the event, but
1137	int otherfd;	1496	// are not yet ready to handle it.
1138	void *somedata;	1497	ev_io_stop (EV_A_ w);
1139	struct whatever *mostinteresting;	1498
		1499	// start the idle watcher to handle the actual event.
		1500	// it will not be executed as long as other watchers
		1501	// with the default priority are receiving events.
		1502	ev_idle_start (EV_A_ &idle);
1140	};	1503	}
1141		1504
1142	...	1505	static void
1143	struct my_io w;	1506	idle_cb (EV_P_ ev_idle *w, int revents)
1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1145
1146	And since your callback will be called with a pointer to the watcher, you
1147	can cast it back to your own type:
1148
1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1150	{	1507	{
1151	struct my_io *w = (struct my_io *)w_;	1508	// actual processing
1152	...	1509	read (STDIN_FILENO, ...);
		1510
		1511	// have to start the I/O watcher again, as
		1512	// we have handled the event
		1513	ev_io_start (EV_P_ &io);
1153	}	1514	}
1154		1515
1155	More interesting and less C-conformant ways of casting your callback type	1516	// initialisation
1156	instead have been omitted.	1517	ev_idle_init (&idle, idle_cb);
		1518	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1519	ev_io_start (EV_DEFAULT_ &io);
1157		1520
1158	Another common scenario is to use some data structure with multiple	1521	In the "real" world, it might also be beneficial to start a timer, so that
1159	embedded watchers:	1522	low-priority connections can not be locked out forever under load. This
1160		1523	enables your program to keep a lower latency for important connections
1161	struct my_biggy	1524	during short periods of high load, while not completely locking out less
1162	{	1525	important ones.
1163	int some_data;
1164	ev_timer t1;
1165	ev_timer t2;
1166	}
1167
1168	In this case getting the pointer to C<my_biggy> is a bit more
1169	complicated: Either you store the address of your C<my_biggy> struct
1170	in the C<data> member of the watcher (for woozies), or you need to use
1171	some pointer arithmetic using C<offsetof> inside your watchers (for real
1172	programmers):
1173
1174	#include <stddef.h>
1175
1176	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{
1179	struct my_biggy big = (struct my_biggy *
1180	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}
1182
1183	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{
1186	struct my_biggy big = (struct my_biggy *
1187	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}
1189		1526
1190		1527
1191	=head1 WATCHER TYPES	1528	=head1 WATCHER TYPES
1192		1529
1193	This section describes each watcher in detail, but will not repeat	1530	This section describes each watcher in detail, but will not repeat
…		…
1217	In general you can register as many read and/or write event watchers per	1554	In general you can register as many read and/or write event watchers per
1218	fd as you want (as long as you don't confuse yourself). Setting all file	1555	fd as you want (as long as you don't confuse yourself). Setting all file
1219	descriptors to non-blocking mode is also usually a good idea (but not	1556	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1557	required if you know what you are doing).
1221		1558
1222	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1225
1226	Another thing you have to watch out for is that it is quite easy to	1559	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1560	receive "spurious" readiness notifications, that is, your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1562	because there is no data. It is very easy to get into this situation even
1230	lot of those (for example Solaris ports), it is very easy to get into	1563	with a relatively standard program structure. Thus it is best to always
1231	this situation even with a relatively standard program structure. Thus	1564	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1232	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1233	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1565	preferable to a program hanging until some data arrives.
1234		1566
1235	If you cannot run the fd in non-blocking mode (for example you should	1567	If you cannot run the fd in non-blocking mode (for example you should
1236	not play around with an Xlib connection), then you have to separately	1568	not play around with an Xlib connection), then you have to separately
1237	re-test whether a file descriptor is really ready with a known-to-be good	1569	re-test whether a file descriptor is really ready with a known-to-be good
1238	interface such as poll (fortunately in our Xlib example, Xlib already	1570	interface such as poll (fortunately in the case of Xlib, it already does
1239	does this on its own, so its quite safe to use). Some people additionally	1571	this on its own, so its quite safe to use). Some people additionally
1240	use C<SIGALRM> and an interval timer, just to be sure you won't block	1572	use C<SIGALRM> and an interval timer, just to be sure you won't block
1241	indefinitely.	1573	indefinitely.
1242		1574
1243	But really, best use non-blocking mode.	1575	But really, best use non-blocking mode.
1244		1576
…		…
1272		1604
1273	There is no workaround possible except not registering events	1605	There is no workaround possible except not registering events
1274	for potentially C<dup ()>'ed file descriptors, or to resort to	1606	for potentially C<dup ()>'ed file descriptors, or to resort to
1275	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1276		1608
		1609	=head3 The special problem of files
		1610
		1611	Many people try to use C<select> (or libev) on file descriptors
		1612	representing files, and expect it to become ready when their program
		1613	doesn't block on disk accesses (which can take a long time on their own).
		1614
		1615	However, this cannot ever work in the "expected" way - you get a readiness
		1616	notification as soon as the kernel knows whether and how much data is
		1617	there, and in the case of open files, that's always the case, so you
		1618	always get a readiness notification instantly, and your read (or possibly
		1619	write) will still block on the disk I/O.
		1620
		1621	Another way to view it is that in the case of sockets, pipes, character
		1622	devices and so on, there is another party (the sender) that delivers data
		1623	on it's own, but in the case of files, there is no such thing: the disk
		1624	will not send data on it's own, simply because it doesn't know what you
		1625	wish to read - you would first have to request some data.
		1626
		1627	Since files are typically not-so-well supported by advanced notification
		1628	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1629	to files, even though you should not use it. The reason for this is
		1630	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1631	usually a tty, often a pipe, but also sometimes files or special devices
		1632	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1633	F</dev/urandom>), and even though the file might better be served with
		1634	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1635	it "just works" instead of freezing.
		1636
		1637	So avoid file descriptors pointing to files when you know it (e.g. use
		1638	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1639	when you rarely read from a file instead of from a socket, and want to
		1640	reuse the same code path.
		1641
1277	=head3 The special problem of fork	1642	=head3 The special problem of fork
1278		1643
1279	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1644	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1280	useless behaviour. Libev fully supports fork, but needs to be told about	1645	useless behaviour. Libev fully supports fork, but needs to be told about
1281	it in the child.	1646	it in the child if you want to continue to use it in the child.
1282		1647
1283	To support fork in your programs, you either have to call	1648	To support fork in your child processes, you have to call C<ev_loop_fork
1284	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1649	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1650	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1286	C<EVBACKEND_POLL>.
1287		1651
1288	=head3 The special problem of SIGPIPE	1652	=head3 The special problem of SIGPIPE
1289		1653
1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1654	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1291	when writing to a pipe whose other end has been closed, your program gets	1655	when writing to a pipe whose other end has been closed, your program gets
…		…
1294		1658
1295	So when you encounter spurious, unexplained daemon exits, make sure you	1659	So when you encounter spurious, unexplained daemon exits, make sure you
1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1660	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1297	somewhere, as that would have given you a big clue).	1661	somewhere, as that would have given you a big clue).
1298		1662
		1663	=head3 The special problem of accept()ing when you can't
		1664
		1665	Many implementations of the POSIX C<accept> function (for example,
		1666	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1667	connection from the pending queue in all error cases.
		1668
		1669	For example, larger servers often run out of file descriptors (because
		1670	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1671	rejecting the connection, leading to libev signalling readiness on
		1672	the next iteration again (the connection still exists after all), and
		1673	typically causing the program to loop at 100% CPU usage.
		1674
		1675	Unfortunately, the set of errors that cause this issue differs between
		1676	operating systems, there is usually little the app can do to remedy the
		1677	situation, and no known thread-safe method of removing the connection to
		1678	cope with overload is known (to me).
		1679
		1680	One of the easiest ways to handle this situation is to just ignore it
		1681	- when the program encounters an overload, it will just loop until the
		1682	situation is over. While this is a form of busy waiting, no OS offers an
		1683	event-based way to handle this situation, so it's the best one can do.
		1684
		1685	A better way to handle the situation is to log any errors other than
		1686	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1687	messages, and continue as usual, which at least gives the user an idea of
		1688	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1689	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1690	usage.
		1691
		1692	If your program is single-threaded, then you could also keep a dummy file
		1693	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1694	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1695	close that fd, and create a new dummy fd. This will gracefully refuse
		1696	clients under typical overload conditions.
		1697
		1698	The last way to handle it is to simply log the error and C<exit>, as
		1699	is often done with C<malloc> failures, but this results in an easy
		1700	opportunity for a DoS attack.
1299		1701
1300	=head3 Watcher-Specific Functions	1702	=head3 Watcher-Specific Functions
1301		1703
1302	=over 4	1704	=over 4
1303		1705
…		…
1335	...	1737	...
1336	struct ev_loop *loop = ev_default_init (0);	1738	struct ev_loop *loop = ev_default_init (0);
1337	ev_io stdin_readable;	1739	ev_io stdin_readable;
1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1740	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1339	ev_io_start (loop, &stdin_readable);	1741	ev_io_start (loop, &stdin_readable);
1340	ev_loop (loop, 0);	1742	ev_run (loop, 0);
1341		1743
1342		1744
1343	=head2 C<ev_timer> - relative and optionally repeating timeouts	1745	=head2 C<ev_timer> - relative and optionally repeating timeouts
1344		1746
1345	Timer watchers are simple relative timers that generate an event after a	1747	Timer watchers are simple relative timers that generate an event after a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1752	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1753	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1754	monotonic clock option helps a lot here).
1353		1755
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1756	The callback is guaranteed to be invoked only I<after> its timeout has
1355	passed. If multiple timers become ready during the same loop iteration	1757	passed (not I<at>, so on systems with very low-resolution clocks this
1356	then the ones with earlier time-out values are invoked before ones with	1758	might introduce a small delay). If multiple timers become ready during the
1357	later time-out values (but this is no longer true when a callback calls	1759	same loop iteration then the ones with earlier time-out values are invoked
1358	C<ev_loop> recursively).	1760	before ones of the same priority with later time-out values (but this is
		1761	no longer true when a callback calls C<ev_run> recursively).
1359		1762
1360	=head3 Be smart about timeouts	1763	=head3 Be smart about timeouts
1361		1764
1362	Many real-world problems involve some kind of timeout, usually for error	1765	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1766	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1810	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1811	member and C<ev_timer_again>.
1409		1812
1410	At start:	1813	At start:
1411		1814
1412	ev_timer_init (timer, callback);	1815	ev_init (timer, callback);
1413	timer->repeat = 60.;	1816	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1817	ev_timer_again (loop, timer);
1415		1818
1416	Each time there is some activity:	1819	Each time there is some activity:
1417		1820
…		…
1449	ev_tstamp timeout = last_activity + 60.;	1852	ev_tstamp timeout = last_activity + 60.;
1450		1853
1451	// if last_activity + 60. is older than now, we did time out	1854	// if last_activity + 60. is older than now, we did time out
1452	if (timeout < now)	1855	if (timeout < now)
1453	{	1856	{
1454	// timeout occured, take action	1857	// timeout occurred, take action
1455	}	1858	}
1456	else	1859	else
1457	{	1860	{
1458	// callback was invoked, but there was some activity, re-arm	1861	// callback was invoked, but there was some activity, re-arm
1459	// the watcher to fire in last_activity + 60, which is	1862	// the watcher to fire in last_activity + 60, which is
…		…
1479		1882
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1883	To start the timer, simply initialise the watcher and set C<last_activity>
1481	to the current time (meaning we just have some activity :), then call the	1884	to the current time (meaning we just have some activity :), then call the
1482	callback, which will "do the right thing" and start the timer:	1885	callback, which will "do the right thing" and start the timer:
1483		1886
1484	ev_timer_init (timer, callback);	1887	ev_init (timer, callback);
1485	last_activity = ev_now (loop);	1888	last_activity = ev_now (loop);
1486	callback (loop, timer, EV_TIMEOUT);	1889	callback (loop, timer, EV_TIMER);
1487		1890
1488	And when there is some activity, simply store the current time in	1891	And when there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1892	C<last_activity>, no libev calls at all:
1490		1893
1491	last_actiivty = ev_now (loop);	1894	last_activity = ev_now (loop);
1492		1895
1493	This technique is slightly more complex, but in most cases where the	1896	This technique is slightly more complex, but in most cases where the
1494	time-out is unlikely to be triggered, much more efficient.	1897	time-out is unlikely to be triggered, much more efficient.
1495		1898
1496	Changing the timeout is trivial as well (if it isn't hard-coded in the	1899	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1534		1937
1535	=head3 The special problem of time updates	1938	=head3 The special problem of time updates
1536		1939
1537	Establishing the current time is a costly operation (it usually takes at	1940	Establishing the current time is a costly operation (it usually takes at
1538	least two system calls): EV therefore updates its idea of the current	1941	least two system calls): EV therefore updates its idea of the current
1539	time only before and after C<ev_loop> collects new events, which causes a	1942	time only before and after C<ev_run> collects new events, which causes a
1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1943	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1541	lots of events in one iteration.	1944	lots of events in one iteration.
1542		1945
1543	The relative timeouts are calculated relative to the C<ev_now ()>	1946	The relative timeouts are calculated relative to the C<ev_now ()>
1544	time. This is usually the right thing as this timestamp refers to the time	1947	time. This is usually the right thing as this timestamp refers to the time
…		…
1550		1953
1551	If the event loop is suspended for a long time, you can also force an	1954	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1955	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	1956	()>.
1554		1957
		1958	=head3 The special problems of suspended animation
		1959
		1960	When you leave the server world it is quite customary to hit machines that
		1961	can suspend/hibernate - what happens to the clocks during such a suspend?
		1962
		1963	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1964	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1965	to run until the system is suspended, but they will not advance while the
		1966	system is suspended. That means, on resume, it will be as if the program
		1967	was frozen for a few seconds, but the suspend time will not be counted
		1968	towards C<ev_timer> when a monotonic clock source is used. The real time
		1969	clock advanced as expected, but if it is used as sole clocksource, then a
		1970	long suspend would be detected as a time jump by libev, and timers would
		1971	be adjusted accordingly.
		1972
		1973	I would not be surprised to see different behaviour in different between
		1974	operating systems, OS versions or even different hardware.
		1975
		1976	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1977	time jump in the monotonic clocks and the realtime clock. If the program
		1978	is suspended for a very long time, and monotonic clock sources are in use,
		1979	then you can expect C<ev_timer>s to expire as the full suspension time
		1980	will be counted towards the timers. When no monotonic clock source is in
		1981	use, then libev will again assume a timejump and adjust accordingly.
		1982
		1983	It might be beneficial for this latter case to call C<ev_suspend>
		1984	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1985	deterministic behaviour in this case (you can do nothing against
		1986	C<SIGSTOP>).
		1987
1555	=head3 Watcher-Specific Functions and Data Members	1988	=head3 Watcher-Specific Functions and Data Members
1556		1989
1557	=over 4	1990	=over 4
1558		1991
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1992	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1582	If the timer is started but non-repeating, stop it (as if it timed out).	2015	If the timer is started but non-repeating, stop it (as if it timed out).
1583		2016
1584	If the timer is repeating, either start it if necessary (with the	2017	If the timer is repeating, either start it if necessary (with the
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	2018	C<repeat> value), or reset the running timer to the C<repeat> value.
1586		2019
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2020	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1588	usage example.	2021	usage example.
		2022
		2023	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2024
		2025	Returns the remaining time until a timer fires. If the timer is active,
		2026	then this time is relative to the current event loop time, otherwise it's
		2027	the timeout value currently configured.
		2028
		2029	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2030	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2031	will return C<4>. When the timer expires and is restarted, it will return
		2032	roughly C<7> (likely slightly less as callback invocation takes some time,
		2033	too), and so on.
1589		2034
1590	=item ev_tstamp repeat [read-write]	2035	=item ev_tstamp repeat [read-write]
1591		2036
1592	The current C<repeat> value. Will be used each time the watcher times out	2037	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	2038	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1619	}	2064	}
1620		2065
1621	ev_timer mytimer;	2066	ev_timer mytimer;
1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2067	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1623	ev_timer_again (&mytimer); /* start timer */	2068	ev_timer_again (&mytimer); /* start timer */
1624	ev_loop (loop, 0);	2069	ev_run (loop, 0);
1625		2070
1626	// and in some piece of code that gets executed on any "activity":	2071	// and in some piece of code that gets executed on any "activity":
1627	// reset the timeout to start ticking again at 10 seconds	2072	// reset the timeout to start ticking again at 10 seconds
1628	ev_timer_again (&mytimer);	2073	ev_timer_again (&mytimer);
1629		2074
…		…
1655		2100
1656	As with timers, the callback is guaranteed to be invoked only when the	2101	As with timers, the callback is guaranteed to be invoked only when the
1657	point in time where it is supposed to trigger has passed. If multiple	2102	point in time where it is supposed to trigger has passed. If multiple
1658	timers become ready during the same loop iteration then the ones with	2103	timers become ready during the same loop iteration then the ones with
1659	earlier time-out values are invoked before ones with later time-out values	2104	earlier time-out values are invoked before ones with later time-out values
1660	(but this is no longer true when a callback calls C<ev_loop> recursively).	2105	(but this is no longer true when a callback calls C<ev_run> recursively).
1661		2106
1662	=head3 Watcher-Specific Functions and Data Members	2107	=head3 Watcher-Specific Functions and Data Members
1663		2108
1664	=over 4	2109	=over 4
1665		2110
…		…
1793	Example: Call a callback every hour, or, more precisely, whenever the	2238	Example: Call a callback every hour, or, more precisely, whenever the
1794	system time is divisible by 3600. The callback invocation times have	2239	system time is divisible by 3600. The callback invocation times have
1795	potentially a lot of jitter, but good long-term stability.	2240	potentially a lot of jitter, but good long-term stability.
1796		2241
1797	static void	2242	static void
1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2243	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1799	{	2244	{
1800	... its now a full hour (UTC, or TAI or whatever your clock follows)	2245	... its now a full hour (UTC, or TAI or whatever your clock follows)
1801	}	2246	}
1802		2247
1803	ev_periodic hourly_tick;	2248	ev_periodic hourly_tick;
…		…
1826		2271
1827	=head2 C<ev_signal> - signal me when a signal gets signalled!	2272	=head2 C<ev_signal> - signal me when a signal gets signalled!
1828		2273
1829	Signal watchers will trigger an event when the process receives a specific	2274	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2275	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2276	will try its best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2277	normal event processing, like any other event.
1833		2278
1834	If you want signals asynchronously, just use C<sigaction> as you would	2279	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2280	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2281	the signal. You can even use C<ev_async> from a signal handler to
		2282	synchronously wake up an event loop.
1837		2283
1838	You can configure as many watchers as you like per signal. Only when the	2284	You can configure as many watchers as you like for the same signal, but
		2285	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2286	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2287	C<SIGINT> in both the default loop and another loop at the same time. At
		2288	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2289
1839	first watcher gets started will libev actually register a signal handler	2290	When the first watcher gets started will libev actually register something
1840	with the kernel (thus it coexists with your own signal handlers as long as	2291	with the kernel (thus it coexists with your own signal handlers as long as
1841	you don't register any with libev for the same signal). Similarly, when	2292	you don't register any with libev for the same signal).
1842	the last signal watcher for a signal is stopped, libev will reset the
1843	signal handler to SIG_DFL (regardless of what it was set to before).
1844		2293
1845	If possible and supported, libev will install its handlers with	2294	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2295	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2296	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2297	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2298	and unblock them in an C<ev_prepare> watcher.
		2299
		2300	=head3 The special problem of inheritance over fork/execve/pthread_create
		2301
		2302	Both the signal mask (C<sigprocmask>) and the signal disposition
		2303	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2304	stopping it again), that is, libev might or might not block the signal,
		2305	and might or might not set or restore the installed signal handler.
		2306
		2307	While this does not matter for the signal disposition (libev never
		2308	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2309	C<execve>), this matters for the signal mask: many programs do not expect
		2310	certain signals to be blocked.
		2311
		2312	This means that before calling C<exec> (from the child) you should reset
		2313	the signal mask to whatever "default" you expect (all clear is a good
		2314	choice usually).
		2315
		2316	The simplest way to ensure that the signal mask is reset in the child is
		2317	to install a fork handler with C<pthread_atfork> that resets it. That will
		2318	catch fork calls done by libraries (such as the libc) as well.
		2319
		2320	In current versions of libev, the signal will not be blocked indefinitely
		2321	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2322	the window of opportunity for problems, it will not go away, as libev
		2323	I<has> to modify the signal mask, at least temporarily.
		2324
		2325	So I can't stress this enough: I<If you do not reset your signal mask when
		2326	you expect it to be empty, you have a race condition in your code>. This
		2327	is not a libev-specific thing, this is true for most event libraries.
		2328
		2329	=head3 The special problem of threads signal handling
		2330
		2331	POSIX threads has problematic signal handling semantics, specifically,
		2332	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2333	threads in a process block signals, which is hard to achieve.
		2334
		2335	When you want to use sigwait (or mix libev signal handling with your own
		2336	for the same signals), you can tackle this problem by globally blocking
		2337	all signals before creating any threads (or creating them with a fully set
		2338	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2339	loops. Then designate one thread as "signal receiver thread" which handles
		2340	these signals. You can pass on any signals that libev might be interested
		2341	in by calling C<ev_feed_signal>.
1850		2342
1851	=head3 Watcher-Specific Functions and Data Members	2343	=head3 Watcher-Specific Functions and Data Members
1852		2344
1853	=over 4	2345	=over 4
1854		2346
…		…
1870	Example: Try to exit cleanly on SIGINT.	2362	Example: Try to exit cleanly on SIGINT.
1871		2363
1872	static void	2364	static void
1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2365	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1874	{	2366	{
1875	ev_unloop (loop, EVUNLOOP_ALL);	2367	ev_break (loop, EVBREAK_ALL);
1876	}	2368	}
1877		2369
1878	ev_signal signal_watcher;	2370	ev_signal signal_watcher;
1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2371	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1880	ev_signal_start (loop, &signal_watcher);	2372	ev_signal_start (loop, &signal_watcher);
…		…
1886	some child status changes (most typically when a child of yours dies or	2378	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2379	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2380	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2381	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2382	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2383	but forking and registering a watcher a few event loop iterations later or
1892	not.	2384	in the next callback invocation is not.
1893		2385
1894	Only the default event loop is capable of handling signals, and therefore	2386	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2387	you can only register child watchers in the default event loop.
1896		2388
		2389	Due to some design glitches inside libev, child watchers will always be
		2390	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2391	libev)
		2392
1897	=head3 Process Interaction	2393	=head3 Process Interaction
1898		2394
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2395	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2396	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2397	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2398	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2399	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2400	children, even ones not watched.
1905		2401
1906	=head3 Overriding the Built-In Processing	2402	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2412	=head3 Stopping the Child Watcher
1917		2413
1918	Currently, the child watcher never gets stopped, even when the	2414	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2415	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2416	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2417	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2418	problem).
1922		2419
1923	=head3 Watcher-Specific Functions and Data Members	2420	=head3 Watcher-Specific Functions and Data Members
1924		2421
1925	=over 4	2422	=over 4
1926		2423
…		…
2252	// no longer anything immediate to do.	2749	// no longer anything immediate to do.
2253	}	2750	}
2254		2751
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2752	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2753	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2754	ev_idle_start (loop, idle_watcher);
2258		2755
2259		2756
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2757	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2758
2262	Prepare and check watchers are usually (but not always) used in pairs:	2759	Prepare and check watchers are usually (but not always) used in pairs:
2263	prepare watchers get invoked before the process blocks and check watchers	2760	prepare watchers get invoked before the process blocks and check watchers
2264	afterwards.	2761	afterwards.
2265		2762
2266	You I<must not> call C<ev_loop> or similar functions that enter	2763	You I<must not> call C<ev_run> or similar functions that enter
2267	the current event loop from either C<ev_prepare> or C<ev_check>	2764	the current event loop from either C<ev_prepare> or C<ev_check>
2268	watchers. Other loops than the current one are fine, however. The	2765	watchers. Other loops than the current one are fine, however. The
2269	rationale behind this is that you do not need to check for recursion in	2766	rationale behind this is that you do not need to check for recursion in
2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2767	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2271	C<ev_check> so if you have one watcher of each kind they will always be	2768	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2355	struct pollfd fds [nfd];	2852	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	2853	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2854	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		2855
2359	/* the callback is illegal, but won't be called as we stop during check */	2856	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	2857	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	2858	ev_timer_start (loop, &tw);
2362		2859
2363	// create one ev_io per pollfd	2860	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	2861	for (int i = 0; i < nfd; ++i)
2365	{	2862	{
…		…
2439		2936
2440	if (timeout >= 0)	2937	if (timeout >= 0)
2441	// create/start timer	2938	// create/start timer
2442		2939
2443	// poll	2940	// poll
2444	ev_loop (EV_A_ 0);	2941	ev_run (EV_A_ 0);
2445		2942
2446	// stop timer again	2943	// stop timer again
2447	if (timeout >= 0)	2944	if (timeout >= 0)
2448	ev_timer_stop (EV_A_ &to);	2945	ev_timer_stop (EV_A_ &to);
2449		2946
…		…
2527	if you do not want that, you need to temporarily stop the embed watcher).	3024	if you do not want that, you need to temporarily stop the embed watcher).
2528		3025
2529	=item ev_embed_sweep (loop, ev_embed *)	3026	=item ev_embed_sweep (loop, ev_embed *)
2530		3027
2531	Make a single, non-blocking sweep over the embedded loop. This works	3028	Make a single, non-blocking sweep over the embedded loop. This works
2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3029	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2533	appropriate way for embedded loops.	3030	appropriate way for embedded loops.
2534		3031
2535	=item struct ev_loop *other [read-only]	3032	=item struct ev_loop *other [read-only]
2536		3033
2537	The embedded event loop.	3034	The embedded event loop.
…		…
2595	event loop blocks next and before C<ev_check> watchers are being called,	3092	event loop blocks next and before C<ev_check> watchers are being called,
2596	and only in the child after the fork. If whoever good citizen calling	3093	and only in the child after the fork. If whoever good citizen calling
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3094	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2598	handlers will be invoked, too, of course.	3095	handlers will be invoked, too, of course.
2599		3096
		3097	=head3 The special problem of life after fork - how is it possible?
		3098
		3099	Most uses of C<fork()> consist of forking, then some simple calls to set
		3100	up/change the process environment, followed by a call to C<exec()>. This
		3101	sequence should be handled by libev without any problems.
		3102
		3103	This changes when the application actually wants to do event handling
		3104	in the child, or both parent in child, in effect "continuing" after the
		3105	fork.
		3106
		3107	The default mode of operation (for libev, with application help to detect
		3108	forks) is to duplicate all the state in the child, as would be expected
		3109	when I<either> the parent I<or> the child process continues.
		3110
		3111	When both processes want to continue using libev, then this is usually the
		3112	wrong result. In that case, usually one process (typically the parent) is
		3113	supposed to continue with all watchers in place as before, while the other
		3114	process typically wants to start fresh, i.e. without any active watchers.
		3115
		3116	The cleanest and most efficient way to achieve that with libev is to
		3117	simply create a new event loop, which of course will be "empty", and
		3118	use that for new watchers. This has the advantage of not touching more
		3119	memory than necessary, and thus avoiding the copy-on-write, and the
		3120	disadvantage of having to use multiple event loops (which do not support
		3121	signal watchers).
		3122
		3123	When this is not possible, or you want to use the default loop for
		3124	other reasons, then in the process that wants to start "fresh", call
		3125	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3126	Destroying the default loop will "orphan" (not stop) all registered
		3127	watchers, so you have to be careful not to execute code that modifies
		3128	those watchers. Note also that in that case, you have to re-register any
		3129	signal watchers.
		3130
2600	=head3 Watcher-Specific Functions and Data Members	3131	=head3 Watcher-Specific Functions and Data Members
2601		3132
2602	=over 4	3133	=over 4
2603		3134
2604	=item ev_fork_init (ev_signal *, callback)	3135	=item ev_fork_init (ev_fork *, callback)
2605		3136
2606	Initialises and configures the fork watcher - it has no parameters of any	3137	Initialises and configures the fork watcher - it has no parameters of any
2607	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3138	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2608	believe me.	3139	really.
2609		3140
2610	=back	3141	=back
2611		3142
2612		3143
		3144	=head2 C<ev_cleanup> - even the best things end
		3145
		3146	Cleanup watchers are called just before the event loop is being destroyed
		3147	by a call to C<ev_loop_destroy>.
		3148
		3149	While there is no guarantee that the event loop gets destroyed, cleanup
		3150	watchers provide a convenient method to install cleanup hooks for your
		3151	program, worker threads and so on - you just to make sure to destroy the
		3152	loop when you want them to be invoked.
		3153
		3154	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3155	all other watchers, they do not keep a reference to the event loop (which
		3156	makes a lot of sense if you think about it). Like all other watchers, you
		3157	can call libev functions in the callback, except C<ev_cleanup_start>.
		3158
		3159	=head3 Watcher-Specific Functions and Data Members
		3160
		3161	=over 4
		3162
		3163	=item ev_cleanup_init (ev_cleanup *, callback)
		3164
		3165	Initialises and configures the cleanup watcher - it has no parameters of
		3166	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3167	pointless, I assure you.
		3168
		3169	=back
		3170
		3171	Example: Register an atexit handler to destroy the default loop, so any
		3172	cleanup functions are called.
		3173
		3174	static void
		3175	program_exits (void)
		3176	{
		3177	ev_loop_destroy (EV_DEFAULT_UC);
		3178	}
		3179
		3180	...
		3181	atexit (program_exits);
		3182
		3183
2613	=head2 C<ev_async> - how to wake up another event loop	3184	=head2 C<ev_async> - how to wake up an event loop
2614		3185
2615	In general, you cannot use an C<ev_loop> from multiple threads or other	3186	In general, you cannot use an C<ev_run> from multiple threads or other
2616	asynchronous sources such as signal handlers (as opposed to multiple event	3187	asynchronous sources such as signal handlers (as opposed to multiple event
2617	loops - those are of course safe to use in different threads).	3188	loops - those are of course safe to use in different threads).
2618		3189
2619	Sometimes, however, you need to wake up another event loop you do not	3190	Sometimes, however, you need to wake up an event loop you do not control,
2620	control, for example because it belongs to another thread. This is what	3191	for example because it belongs to another thread. This is what C<ev_async>
2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3192	watchers do: as long as the C<ev_async> watcher is active, you can signal
2622	can signal it by calling C<ev_async_send>, which is thread- and signal	3193	it by calling C<ev_async_send>, which is thread- and signal safe.
2623	safe.
2624		3194
2625	This functionality is very similar to C<ev_signal> watchers, as signals,	3195	This functionality is very similar to C<ev_signal> watchers, as signals,
2626	too, are asynchronous in nature, and signals, too, will be compressed	3196	too, are asynchronous in nature, and signals, too, will be compressed
2627	(i.e. the number of callback invocations may be less than the number of	3197	(i.e. the number of callback invocations may be less than the number of
2628	C<ev_async_sent> calls).	3198	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3199	of "global async watchers" by using a watcher on an otherwise unused
		3200	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3201	even without knowing which loop owns the signal.
2629		3202
2630	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3203	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2631	just the default loop.	3204	just the default loop.
2632		3205
2633	=head3 Queueing	3206	=head3 Queueing
2634		3207
2635	C<ev_async> does not support queueing of data in any way. The reason	3208	C<ev_async> does not support queueing of data in any way. The reason
2636	is that the author does not know of a simple (or any) algorithm for a	3209	is that the author does not know of a simple (or any) algorithm for a
2637	multiple-writer-single-reader queue that works in all cases and doesn't	3210	multiple-writer-single-reader queue that works in all cases and doesn't
2638	need elaborate support such as pthreads.	3211	need elaborate support such as pthreads or unportable memory access
		3212	semantics.
2639		3213
2640	That means that if you want to queue data, you have to provide your own	3214	That means that if you want to queue data, you have to provide your own
2641	queue. But at least I can tell you how to implement locking around your	3215	queue. But at least I can tell you how to implement locking around your
2642	queue:	3216	queue:
2643		3217
…		…
2782		3356
2783	If C<timeout> is less than 0, then no timeout watcher will be	3357	If C<timeout> is less than 0, then no timeout watcher will be
2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3358	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2785	repeat = 0) will be started. C<0> is a valid timeout.	3359	repeat = 0) will be started. C<0> is a valid timeout.
2786		3360
2787	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3361	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2788	passed an C<revents> set like normal event callbacks (a combination of	3362	passed an C<revents> set like normal event callbacks (a combination of
2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3363	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2790	value passed to C<ev_once>. Note that it is possible to receive I<both>	3364	value passed to C<ev_once>. Note that it is possible to receive I<both>
2791	a timeout and an io event at the same time - you probably should give io	3365	a timeout and an io event at the same time - you probably should give io
2792	events precedence.	3366	events precedence.
2793		3367
2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3368	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2795		3369
2796	static void stdin_ready (int revents, void *arg)	3370	static void stdin_ready (int revents, void *arg)
2797	{	3371	{
2798	if (revents & EV_READ)	3372	if (revents & EV_READ)
2799	/* stdin might have data for us, joy! */;	3373	/* stdin might have data for us, joy! */;
2800	else if (revents & EV_TIMEOUT)	3374	else if (revents & EV_TIMER)
2801	/* doh, nothing entered */;	3375	/* doh, nothing entered */;
2802	}	3376	}
2803		3377
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3378	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805		3379
2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3380	=item ev_feed_fd_event (loop, int fd, int revents)
2813		3381
2814	Feed an event on the given fd, as if a file descriptor backend detected	3382	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3383	the given events it.
2816		3384
2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3385	=item ev_feed_signal_event (loop, int signum)
2818		3386
2819	Feed an event as if the given signal occurred (C<loop> must be the default	3387	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2820	loop!).	3388	which is async-safe.
2821		3389
2822	=back	3390	=back
		3391
		3392
		3393	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3394
		3395	This section explains some common idioms that are not immediately
		3396	obvious. Note that examples are sprinkled over the whole manual, and this
		3397	section only contains stuff that wouldn't fit anywhere else.
		3398
		3399	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3400
		3401	Each watcher has, by default, a C<void *data> member that you can read
		3402	or modify at any time: libev will completely ignore it. This can be used
		3403	to associate arbitrary data with your watcher. If you need more data and
		3404	don't want to allocate memory separately and store a pointer to it in that
		3405	data member, you can also "subclass" the watcher type and provide your own
		3406	data:
		3407
		3408	struct my_io
		3409	{
		3410	ev_io io;
		3411	int otherfd;
		3412	void *somedata;
		3413	struct whatever *mostinteresting;
		3414	};
		3415
		3416	...
		3417	struct my_io w;
		3418	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3419
		3420	And since your callback will be called with a pointer to the watcher, you
		3421	can cast it back to your own type:
		3422
		3423	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3424	{
		3425	struct my_io *w = (struct my_io *)w_;
		3426	...
		3427	}
		3428
		3429	More interesting and less C-conformant ways of casting your callback
		3430	function type instead have been omitted.
		3431
		3432	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3433
		3434	Another common scenario is to use some data structure with multiple
		3435	embedded watchers, in effect creating your own watcher that combines
		3436	multiple libev event sources into one "super-watcher":
		3437
		3438	struct my_biggy
		3439	{
		3440	int some_data;
		3441	ev_timer t1;
		3442	ev_timer t2;
		3443	}
		3444
		3445	In this case getting the pointer to C<my_biggy> is a bit more
		3446	complicated: Either you store the address of your C<my_biggy> struct in
		3447	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3448	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3449	real programmers):
		3450
		3451	#include <stddef.h>
		3452
		3453	static void
		3454	t1_cb (EV_P_ ev_timer *w, int revents)
		3455	{
		3456	struct my_biggy big = (struct my_biggy *)
		3457	(((char *)w) - offsetof (struct my_biggy, t1));
		3458	}
		3459
		3460	static void
		3461	t2_cb (EV_P_ ev_timer *w, int revents)
		3462	{
		3463	struct my_biggy big = (struct my_biggy *)
		3464	(((char *)w) - offsetof (struct my_biggy, t2));
		3465	}
		3466
		3467	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3468
		3469	Often (especially in GUI toolkits) there are places where you have
		3470	I<modal> interaction, which is most easily implemented by recursively
		3471	invoking C<ev_run>.
		3472
		3473	This brings the problem of exiting - a callback might want to finish the
		3474	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3475	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3476	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3477	other combination: In these cases, C<ev_break> will not work alone.
		3478
		3479	The solution is to maintain "break this loop" variable for each C<ev_run>
		3480	invocation, and use a loop around C<ev_run> until the condition is
		3481	triggered, using C<EVRUN_ONCE>:
		3482
		3483	// main loop
		3484	int exit_main_loop = 0;
		3485
		3486	while (!exit_main_loop)
		3487	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3488
		3489	// in a model watcher
		3490	int exit_nested_loop = 0;
		3491
		3492	while (!exit_nested_loop)
		3493	ev_run (EV_A_ EVRUN_ONCE);
		3494
		3495	To exit from any of these loops, just set the corresponding exit variable:
		3496
		3497	// exit modal loop
		3498	exit_nested_loop = 1;
		3499
		3500	// exit main program, after modal loop is finished
		3501	exit_main_loop = 1;
		3502
		3503	// exit both
		3504	exit_main_loop = exit_nested_loop = 1;
		3505
		3506	=head2 THREAD LOCKING EXAMPLE
		3507
		3508	Here is a fictitious example of how to run an event loop in a different
		3509	thread than where callbacks are being invoked and watchers are
		3510	created/added/removed.
		3511
		3512	For a real-world example, see the C<EV::Loop::Async> perl module,
		3513	which uses exactly this technique (which is suited for many high-level
		3514	languages).
		3515
		3516	The example uses a pthread mutex to protect the loop data, a condition
		3517	variable to wait for callback invocations, an async watcher to notify the
		3518	event loop thread and an unspecified mechanism to wake up the main thread.
		3519
		3520	First, you need to associate some data with the event loop:
		3521
		3522	typedef struct {
		3523	mutex_t lock; /* global loop lock */
		3524	ev_async async_w;
		3525	thread_t tid;
		3526	cond_t invoke_cv;
		3527	} userdata;
		3528
		3529	void prepare_loop (EV_P)
		3530	{
		3531	// for simplicity, we use a static userdata struct.
		3532	static userdata u;
		3533
		3534	ev_async_init (&u->async_w, async_cb);
		3535	ev_async_start (EV_A_ &u->async_w);
		3536
		3537	pthread_mutex_init (&u->lock, 0);
		3538	pthread_cond_init (&u->invoke_cv, 0);
		3539
		3540	// now associate this with the loop
		3541	ev_set_userdata (EV_A_ u);
		3542	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3543	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3544
		3545	// then create the thread running ev_loop
		3546	pthread_create (&u->tid, 0, l_run, EV_A);
		3547	}
		3548
		3549	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3550	solely to wake up the event loop so it takes notice of any new watchers
		3551	that might have been added:
		3552
		3553	static void
		3554	async_cb (EV_P_ ev_async *w, int revents)
		3555	{
		3556	// just used for the side effects
		3557	}
		3558
		3559	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3560	protecting the loop data, respectively.
		3561
		3562	static void
		3563	l_release (EV_P)
		3564	{
		3565	userdata *u = ev_userdata (EV_A);
		3566	pthread_mutex_unlock (&u->lock);
		3567	}
		3568
		3569	static void
		3570	l_acquire (EV_P)
		3571	{
		3572	userdata *u = ev_userdata (EV_A);
		3573	pthread_mutex_lock (&u->lock);
		3574	}
		3575
		3576	The event loop thread first acquires the mutex, and then jumps straight
		3577	into C<ev_run>:
		3578
		3579	void *
		3580	l_run (void *thr_arg)
		3581	{
		3582	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3583
		3584	l_acquire (EV_A);
		3585	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3586	ev_run (EV_A_ 0);
		3587	l_release (EV_A);
		3588
		3589	return 0;
		3590	}
		3591
		3592	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3593	signal the main thread via some unspecified mechanism (signals? pipe
		3594	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3595	have been called (in a while loop because a) spurious wakeups are possible
		3596	and b) skipping inter-thread-communication when there are no pending
		3597	watchers is very beneficial):
		3598
		3599	static void
		3600	l_invoke (EV_P)
		3601	{
		3602	userdata *u = ev_userdata (EV_A);
		3603
		3604	while (ev_pending_count (EV_A))
		3605	{
		3606	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3607	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3608	}
		3609	}
		3610
		3611	Now, whenever the main thread gets told to invoke pending watchers, it
		3612	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3613	thread to continue:
		3614
		3615	static void
		3616	real_invoke_pending (EV_P)
		3617	{
		3618	userdata *u = ev_userdata (EV_A);
		3619
		3620	pthread_mutex_lock (&u->lock);
		3621	ev_invoke_pending (EV_A);
		3622	pthread_cond_signal (&u->invoke_cv);
		3623	pthread_mutex_unlock (&u->lock);
		3624	}
		3625
		3626	Whenever you want to start/stop a watcher or do other modifications to an
		3627	event loop, you will now have to lock:
		3628
		3629	ev_timer timeout_watcher;
		3630	userdata *u = ev_userdata (EV_A);
		3631
		3632	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3633
		3634	pthread_mutex_lock (&u->lock);
		3635	ev_timer_start (EV_A_ &timeout_watcher);
		3636	ev_async_send (EV_A_ &u->async_w);
		3637	pthread_mutex_unlock (&u->lock);
		3638
		3639	Note that sending the C<ev_async> watcher is required because otherwise
		3640	an event loop currently blocking in the kernel will have no knowledge
		3641	about the newly added timer. By waking up the loop it will pick up any new
		3642	watchers in the next event loop iteration.
		3643
		3644	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3645
		3646	While the overhead of a callback that e.g. schedules a thread is small, it
		3647	is still an overhead. If you embed libev, and your main usage is with some
		3648	kind of threads or coroutines, you might want to customise libev so that
		3649	doesn't need callbacks anymore.
		3650
		3651	Imagine you have coroutines that you can switch to using a function
		3652	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3653	and that due to some magic, the currently active coroutine is stored in a
		3654	global called C<current_coro>. Then you can build your own "wait for libev
		3655	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3656	the differing C<;> conventions):
		3657
		3658	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3659	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3660
		3661	That means instead of having a C callback function, you store the
		3662	coroutine to switch to in each watcher, and instead of having libev call
		3663	your callback, you instead have it switch to that coroutine.
		3664
		3665	A coroutine might now wait for an event with a function called
		3666	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3667	matter when, or whether the watcher is active or not when this function is
		3668	called):
		3669
		3670	void
		3671	wait_for_event (ev_watcher *w)
		3672	{
		3673	ev_cb_set (w) = current_coro;
		3674	switch_to (libev_coro);
		3675	}
		3676
		3677	That basically suspends the coroutine inside C<wait_for_event> and
		3678	continues the libev coroutine, which, when appropriate, switches back to
		3679	this or any other coroutine. I am sure if you sue this your own :)
		3680
		3681	You can do similar tricks if you have, say, threads with an event queue -
		3682	instead of storing a coroutine, you store the queue object and instead of
		3683	switching to a coroutine, you push the watcher onto the queue and notify
		3684	any waiters.
		3685
		3686	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3687	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3688
		3689	// my_ev.h
		3690	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3691	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3692	#include "../libev/ev.h"
		3693
		3694	// my_ev.c
		3695	#define EV_H "my_ev.h"
		3696	#include "../libev/ev.c"
		3697
		3698	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3699	F<my_ev.c> into your project. When properly specifying include paths, you
		3700	can even use F<ev.h> as header file name directly.
2823		3701
2824		3702
2825	=head1 LIBEVENT EMULATION	3703	=head1 LIBEVENT EMULATION
2826		3704
2827	Libev offers a compatibility emulation layer for libevent. It cannot	3705	Libev offers a compatibility emulation layer for libevent. It cannot
2828	emulate the internals of libevent, so here are some usage hints:	3706	emulate the internals of libevent, so here are some usage hints:
2829		3707
2830	=over 4	3708	=over 4
		3709
		3710	=item * Only the libevent-1.4.1-beta API is being emulated.
		3711
		3712	This was the newest libevent version available when libev was implemented,
		3713	and is still mostly unchanged in 2010.
2831		3714
2832	=item * Use it by including <event.h>, as usual.	3715	=item * Use it by including <event.h>, as usual.
2833		3716
2834	=item * The following members are fully supported: ev_base, ev_callback,	3717	=item * The following members are fully supported: ev_base, ev_callback,
2835	ev_arg, ev_fd, ev_res, ev_events.	3718	ev_arg, ev_fd, ev_res, ev_events.
…		…
2841	=item * Priorities are not currently supported. Initialising priorities	3724	=item * Priorities are not currently supported. Initialising priorities
2842	will fail and all watchers will have the same priority, even though there	3725	will fail and all watchers will have the same priority, even though there
2843	is an ev_pri field.	3726	is an ev_pri field.
2844		3727
2845	=item * In libevent, the last base created gets the signals, in libev, the	3728	=item * In libevent, the last base created gets the signals, in libev, the
2846	first base created (== the default loop) gets the signals.	3729	base that registered the signal gets the signals.
2847		3730
2848	=item * Other members are not supported.	3731	=item * Other members are not supported.
2849		3732
2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3733	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2851	to use the libev header file and library.	3734	to use the libev header file and library.
…		…
2870	Care has been taken to keep the overhead low. The only data member the C++	3753	Care has been taken to keep the overhead low. The only data member the C++
2871	classes add (compared to plain C-style watchers) is the event loop pointer	3754	classes add (compared to plain C-style watchers) is the event loop pointer
2872	that the watcher is associated with (or no additional members at all if	3755	that the watcher is associated with (or no additional members at all if
2873	you disable C<EV_MULTIPLICITY> when embedding libev).	3756	you disable C<EV_MULTIPLICITY> when embedding libev).
2874		3757
2875	Currently, functions, and static and non-static member functions can be	3758	Currently, functions, static and non-static member functions and classes
2876	used as callbacks. Other types should be easy to add as long as they only	3759	with C<operator ()> can be used as callbacks. Other types should be easy
2877	need one additional pointer for context. If you need support for other	3760	to add as long as they only need one additional pointer for context. If
2878	types of functors please contact the author (preferably after implementing	3761	you need support for other types of functors please contact the author
2879	it).	3762	(preferably after implementing it).
2880		3763
2881	Here is a list of things available in the C<ev> namespace:	3764	Here is a list of things available in the C<ev> namespace:
2882		3765
2883	=over 4	3766	=over 4
2884		3767
…		…
2902		3785
2903	=over 4	3786	=over 4
2904		3787
2905	=item ev::TYPE::TYPE ()	3788	=item ev::TYPE::TYPE ()
2906		3789
2907	=item ev::TYPE::TYPE (struct ev_loop *)	3790	=item ev::TYPE::TYPE (loop)
2908		3791
2909	=item ev::TYPE::~TYPE	3792	=item ev::TYPE::~TYPE
2910		3793
2911	The constructor (optionally) takes an event loop to associate the watcher	3794	The constructor (optionally) takes an event loop to associate the watcher
2912	with. If it is omitted, it will use C<EV_DEFAULT>.	3795	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2945	myclass obj;	3828	myclass obj;
2946	ev::io iow;	3829	ev::io iow;
2947	iow.set <myclass, &myclass::io_cb> (&obj);	3830	iow.set <myclass, &myclass::io_cb> (&obj);
2948		3831
2949	=item w->set (object *)	3832	=item w->set (object *)
2950
2951	This is an B<experimental> feature that might go away in a future version.
2952		3833
2953	This is a variation of a method callback - leaving out the method to call	3834	This is a variation of a method callback - leaving out the method to call
2954	will default the method to C<operator ()>, which makes it possible to use	3835	will default the method to C<operator ()>, which makes it possible to use
2955	functor objects without having to manually specify the C<operator ()> all	3836	functor objects without having to manually specify the C<operator ()> all
2956	the time. Incidentally, you can then also leave out the template argument	3837	the time. Incidentally, you can then also leave out the template argument
…		…
2989	Example: Use a plain function as callback.	3870	Example: Use a plain function as callback.
2990		3871
2991	static void io_cb (ev::io &w, int revents) { }	3872	static void io_cb (ev::io &w, int revents) { }
2992	iow.set <io_cb> ();	3873	iow.set <io_cb> ();
2993		3874
2994	=item w->set (struct ev_loop *)	3875	=item w->set (loop)
2995		3876
2996	Associates a different C<struct ev_loop> with this watcher. You can only	3877	Associates a different C<struct ev_loop> with this watcher. You can only
2997	do this when the watcher is inactive (and not pending either).	3878	do this when the watcher is inactive (and not pending either).
2998		3879
2999	=item w->set ([arguments])	3880	=item w->set ([arguments])
3000		3881
3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3882	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3002	called at least once. Unlike the C counterpart, an active watcher gets	3883	method or a suitable start method must be called at least once. Unlike the
3003	automatically stopped and restarted when reconfiguring it with this	3884	C counterpart, an active watcher gets automatically stopped and restarted
3004	method.	3885	when reconfiguring it with this method.
3005		3886
3006	=item w->start ()	3887	=item w->start ()
3007		3888
3008	Starts the watcher. Note that there is no C<loop> argument, as the	3889	Starts the watcher. Note that there is no C<loop> argument, as the
3009	constructor already stores the event loop.	3890	constructor already stores the event loop.
3010		3891
		3892	=item w->start ([arguments])
		3893
		3894	Instead of calling C<set> and C<start> methods separately, it is often
		3895	convenient to wrap them in one call. Uses the same type of arguments as
		3896	the configure C<set> method of the watcher.
		3897
3011	=item w->stop ()	3898	=item w->stop ()
3012		3899
3013	Stops the watcher if it is active. Again, no C<loop> argument.	3900	Stops the watcher if it is active. Again, no C<loop> argument.
3014		3901
3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3902	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3027		3914
3028	=back	3915	=back
3029		3916
3030	=back	3917	=back
3031		3918
3032	Example: Define a class with an IO and idle watcher, start one of them in	3919	Example: Define a class with two I/O and idle watchers, start the I/O
3033	the constructor.	3920	watchers in the constructor.
3034		3921
3035	class myclass	3922	class myclass
3036	{	3923	{
3037	ev::io io ; void io_cb (ev::io &w, int revents);	3924	ev::io io ; void io_cb (ev::io &w, int revents);
		3925	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3926	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3039		3927
3040	myclass (int fd)	3928	myclass (int fd)
3041	{	3929	{
3042	io .set <myclass, &myclass::io_cb > (this);	3930	io .set <myclass, &myclass::io_cb > (this);
		3931	io2 .set <myclass, &myclass::io2_cb > (this);
3043	idle.set <myclass, &myclass::idle_cb> (this);	3932	idle.set <myclass, &myclass::idle_cb> (this);
3044		3933
3045	io.start (fd, ev::READ);	3934	io.set (fd, ev::WRITE); // configure the watcher
		3935	io.start (); // start it whenever convenient
		3936
		3937	io2.start (fd, ev::READ); // set + start in one call
3046	}	3938	}
3047	};	3939	};
3048		3940
3049		3941
3050	=head1 OTHER LANGUAGE BINDINGS	3942	=head1 OTHER LANGUAGE BINDINGS
…		…
3096	=item Ocaml	3988	=item Ocaml
3097		3989
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	3990	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3991	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3100		3992
		3993	=item Lua
		3994
		3995	Brian Maher has written a partial interface to libev for lua (at the
		3996	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3997	L<http://github.com/brimworks/lua-ev>.
		3998
3101	=back	3999	=back
3102		4000
3103		4001
3104	=head1 MACRO MAGIC	4002	=head1 MACRO MAGIC
3105		4003
…		…
3118	loop argument"). The C<EV_A> form is used when this is the sole argument,	4016	loop argument"). The C<EV_A> form is used when this is the sole argument,
3119	C<EV_A_> is used when other arguments are following. Example:	4017	C<EV_A_> is used when other arguments are following. Example:
3120		4018
3121	ev_unref (EV_A);	4019	ev_unref (EV_A);
3122	ev_timer_add (EV_A_ watcher);	4020	ev_timer_add (EV_A_ watcher);
3123	ev_loop (EV_A_ 0);	4021	ev_run (EV_A_ 0);
3124		4022
3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4023	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3126	which is often provided by the following macro.	4024	which is often provided by the following macro.
3127		4025
3128	=item C<EV_P>, C<EV_P_>	4026	=item C<EV_P>, C<EV_P_>
…		…
3168	}	4066	}
3169		4067
3170	ev_check check;	4068	ev_check check;
3171	ev_check_init (&check, check_cb);	4069	ev_check_init (&check, check_cb);
3172	ev_check_start (EV_DEFAULT_ &check);	4070	ev_check_start (EV_DEFAULT_ &check);
3173	ev_loop (EV_DEFAULT_ 0);	4071	ev_run (EV_DEFAULT_ 0);
3174		4072
3175	=head1 EMBEDDING	4073	=head1 EMBEDDING
3176		4074
3177	Libev can (and often is) directly embedded into host	4075	Libev can (and often is) directly embedded into host
3178	applications. Examples of applications that embed it include the Deliantra	4076	applications. Examples of applications that embed it include the Deliantra
…		…
3258	libev.m4	4156	libev.m4
3259		4157
3260	=head2 PREPROCESSOR SYMBOLS/MACROS	4158	=head2 PREPROCESSOR SYMBOLS/MACROS
3261		4159
3262	Libev can be configured via a variety of preprocessor symbols you have to	4160	Libev can be configured via a variety of preprocessor symbols you have to
3263	define before including any of its files. The default in the absence of	4161	define before including (or compiling) any of its files. The default in
3264	autoconf is documented for every option.	4162	the absence of autoconf is documented for every option.
		4163
		4164	Symbols marked with "(h)" do not change the ABI, and can have different
		4165	values when compiling libev vs. including F<ev.h>, so it is permissible
		4166	to redefine them before including F<ev.h> without breaking compatibility
		4167	to a compiled library. All other symbols change the ABI, which means all
		4168	users of libev and the libev code itself must be compiled with compatible
		4169	settings.
3265		4170
3266	=over 4	4171	=over 4
3267		4172
		4173	=item EV_COMPAT3 (h)
		4174
		4175	Backwards compatibility is a major concern for libev. This is why this
		4176	release of libev comes with wrappers for the functions and symbols that
		4177	have been renamed between libev version 3 and 4.
		4178
		4179	You can disable these wrappers (to test compatibility with future
		4180	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4181	sources. This has the additional advantage that you can drop the C<struct>
		4182	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4183	typedef in that case.
		4184
		4185	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4186	and in some even more future version the compatibility code will be
		4187	removed completely.
		4188
3268	=item EV_STANDALONE	4189	=item EV_STANDALONE (h)
3269		4190
3270	Must always be C<1> if you do not use autoconf configuration, which	4191	Must always be C<1> if you do not use autoconf configuration, which
3271	keeps libev from including F<config.h>, and it also defines dummy	4192	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	4193	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	4194	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	4195	F<event.h> that are not directly supported by the libev core alone.
3275		4196
3276	In stanbdalone mode, libev will still try to automatically deduce the	4197	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	4198	configuration, but has to be more conservative.
3278		4199
3279	=item EV_USE_MONOTONIC	4200	=item EV_USE_MONOTONIC
3280		4201
3281	If defined to be C<1>, libev will try to detect the availability of the	4202	If defined to be C<1>, libev will try to detect the availability of the
…		…
3346	be used is the winsock select). This means that it will call	4267	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4268	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	4269	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	4270	on win32. Should not be defined on non-win32 platforms.
3350		4271
3351	=item EV_FD_TO_WIN32_HANDLE	4272	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		4273
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4274	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	4275	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	4276	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	4277	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	4278	in which case they can provide this function to map fds to socket handles.
		4279
		4280	=item EV_WIN32_HANDLE_TO_FD(handle)
		4281
		4282	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4283	using the standard C<_open_osfhandle> function. For programs implementing
		4284	their own fd to handle mapping, overwriting this function makes it easier
		4285	to do so. This can be done by defining this macro to an appropriate value.
		4286
		4287	=item EV_WIN32_CLOSE_FD(fd)
		4288
		4289	If programs implement their own fd to handle mapping on win32, then this
		4290	macro can be used to override the C<close> function, useful to unregister
		4291	file descriptors again. Note that the replacement function has to close
		4292	the underlying OS handle.
3358		4293
3359	=item EV_USE_POLL	4294	=item EV_USE_POLL
3360		4295
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4296	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	4297	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3409	as well as for signal and thread safety in C<ev_async> watchers.	4344	as well as for signal and thread safety in C<ev_async> watchers.
3410		4345
3411	In the absence of this define, libev will use C<sig_atomic_t volatile>	4346	In the absence of this define, libev will use C<sig_atomic_t volatile>
3412	(from F<signal.h>), which is usually good enough on most platforms.	4347	(from F<signal.h>), which is usually good enough on most platforms.
3413		4348
3414	=item EV_H	4349	=item EV_H (h)
3415		4350
3416	The name of the F<ev.h> header file used to include it. The default if	4351	The name of the F<ev.h> header file used to include it. The default if
3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4352	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3418	used to virtually rename the F<ev.h> header file in case of conflicts.	4353	used to virtually rename the F<ev.h> header file in case of conflicts.
3419		4354
3420	=item EV_CONFIG_H	4355	=item EV_CONFIG_H (h)
3421		4356
3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4357	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4358	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3424	C<EV_H>, above.	4359	C<EV_H>, above.
3425		4360
3426	=item EV_EVENT_H	4361	=item EV_EVENT_H (h)
3427		4362
3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4363	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3429	of how the F<event.h> header can be found, the default is C<"event.h">.	4364	of how the F<event.h> header can be found, the default is C<"event.h">.
3430		4365
3431	=item EV_PROTOTYPES	4366	=item EV_PROTOTYPES (h)
3432		4367
3433	If defined to be C<0>, then F<ev.h> will not define any function	4368	If defined to be C<0>, then F<ev.h> will not define any function
3434	prototypes, but still define all the structs and other symbols. This is	4369	prototypes, but still define all the structs and other symbols. This is
3435	occasionally useful if you want to provide your own wrapper functions	4370	occasionally useful if you want to provide your own wrapper functions
3436	around libev functions.	4371	around libev functions.
…		…
3458	fine.	4393	fine.
3459		4394
3460	If your embedding application does not need any priorities, defining these	4395	If your embedding application does not need any priorities, defining these
3461	both to C<0> will save some memory and CPU.	4396	both to C<0> will save some memory and CPU.
3462		4397
3463	=item EV_PERIODIC_ENABLE	4398	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4399	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4400	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3464		4401
3465	If undefined or defined to be C<1>, then periodic timers are supported. If	4402	If undefined or defined to be C<1> (and the platform supports it), then
3466	defined to be C<0>, then they are not. Disabling them saves a few kB of	4403	the respective watcher type is supported. If defined to be C<0>, then it
3467	code.	4404	is not. Disabling watcher types mainly saves code size.
3468		4405
3469	=item EV_IDLE_ENABLE	4406	=item EV_FEATURES
3470
3471	If undefined or defined to be C<1>, then idle watchers are supported. If
3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
3473	code.
3474
3475	=item EV_EMBED_ENABLE
3476
3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3478	defined to be C<0>, then they are not. Embed watchers rely on most other
3479	watcher types, which therefore must not be disabled.
3480
3481	=item EV_STAT_ENABLE
3482
3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3484	defined to be C<0>, then they are not.
3485
3486	=item EV_FORK_ENABLE
3487
3488	If undefined or defined to be C<1>, then fork watchers are supported. If
3489	defined to be C<0>, then they are not.
3490
3491	=item EV_ASYNC_ENABLE
3492
3493	If undefined or defined to be C<1>, then async watchers are supported. If
3494	defined to be C<0>, then they are not.
3495
3496	=item EV_MINIMAL
3497		4407
3498	If you need to shave off some kilobytes of code at the expense of some	4408	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	4409	speed (but with the full API), you can define this symbol to request
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4410	certain subsets of functionality. The default is to enable all features
3501	much smaller 2-heap for timer management over the default 4-heap.	4411	that can be enabled on the platform.
		4412
		4413	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4414	with some broad features you want) and then selectively re-enable
		4415	additional parts you want, for example if you want everything minimal,
		4416	but multiple event loop support, async and child watchers and the poll
		4417	backend, use this:
		4418
		4419	#define EV_FEATURES 0
		4420	#define EV_MULTIPLICITY 1
		4421	#define EV_USE_POLL 1
		4422	#define EV_CHILD_ENABLE 1
		4423	#define EV_ASYNC_ENABLE 1
		4424
		4425	The actual value is a bitset, it can be a combination of the following
		4426	values:
		4427
		4428	=over 4
		4429
		4430	=item C<1> - faster/larger code
		4431
		4432	Use larger code to speed up some operations.
		4433
		4434	Currently this is used to override some inlining decisions (enlarging the
		4435	code size by roughly 30% on amd64).
		4436
		4437	When optimising for size, use of compiler flags such as C<-Os> with
		4438	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4439	assertions.
		4440
		4441	=item C<2> - faster/larger data structures
		4442
		4443	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4444	hash table sizes and so on. This will usually further increase code size
		4445	and can additionally have an effect on the size of data structures at
		4446	runtime.
		4447
		4448	=item C<4> - full API configuration
		4449
		4450	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4451	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4452
		4453	=item C<8> - full API
		4454
		4455	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4456	details on which parts of the API are still available without this
		4457	feature, and do not complain if this subset changes over time.
		4458
		4459	=item C<16> - enable all optional watcher types
		4460
		4461	Enables all optional watcher types. If you want to selectively enable
		4462	only some watcher types other than I/O and timers (e.g. prepare,
		4463	embed, async, child...) you can enable them manually by defining
		4464	C<EV_watchertype_ENABLE> to C<1> instead.
		4465
		4466	=item C<32> - enable all backends
		4467
		4468	This enables all backends - without this feature, you need to enable at
		4469	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4470
		4471	=item C<64> - enable OS-specific "helper" APIs
		4472
		4473	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4474	default.
		4475
		4476	=back
		4477
		4478	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4479	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4480	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4481	watchers, timers and monotonic clock support.
		4482
		4483	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4484	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4485	your program might be left out as well - a binary starting a timer and an
		4486	I/O watcher then might come out at only 5Kb.
		4487
		4488	=item EV_AVOID_STDIO
		4489
		4490	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4491	functions (printf, scanf, perror etc.). This will increase the code size
		4492	somewhat, but if your program doesn't otherwise depend on stdio and your
		4493	libc allows it, this avoids linking in the stdio library which is quite
		4494	big.
		4495
		4496	Note that error messages might become less precise when this option is
		4497	enabled.
		4498
		4499	=item EV_NSIG
		4500
		4501	The highest supported signal number, +1 (or, the number of
		4502	signals): Normally, libev tries to deduce the maximum number of signals
		4503	automatically, but sometimes this fails, in which case it can be
		4504	specified. Also, using a lower number than detected (C<32> should be
		4505	good for about any system in existence) can save some memory, as libev
		4506	statically allocates some 12-24 bytes per signal number.
3502		4507
3503	=item EV_PID_HASHSIZE	4508	=item EV_PID_HASHSIZE
3504		4509
3505	C<ev_child> watchers use a small hash table to distribute workload by	4510	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4511	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3507	than enough. If you need to manage thousands of children you might want to	4512	usually more than enough. If you need to manage thousands of children you
3508	increase this value (I<must> be a power of two).	4513	might want to increase this value (I<must> be a power of two).
3509		4514
3510	=item EV_INOTIFY_HASHSIZE	4515	=item EV_INOTIFY_HASHSIZE
3511		4516
3512	C<ev_stat> watchers use a small hash table to distribute workload by	4517	C<ev_stat> watchers use a small hash table to distribute workload by
3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4518	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3514	usually more than enough. If you need to manage thousands of C<ev_stat>	4519	disabled), usually more than enough. If you need to manage thousands of
3515	watchers you might want to increase this value (I<must> be a power of	4520	C<ev_stat> watchers you might want to increase this value (I<must> be a
3516	two).	4521	power of two).
3517		4522
3518	=item EV_USE_4HEAP	4523	=item EV_USE_4HEAP
3519		4524
3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4525	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4526	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4527	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3523	faster performance with many (thousands) of watchers.	4528	faster performance with many (thousands) of watchers.
3524		4529
3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4530	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3526	(disabled).	4531	will be C<0>.
3527		4532
3528	=item EV_HEAP_CACHE_AT	4533	=item EV_HEAP_CACHE_AT
3529		4534
3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4535	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4536	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4537	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4538	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3534	but avoids random read accesses on heap changes. This improves performance	4539	but avoids random read accesses on heap changes. This improves performance
3535	noticeably with many (hundreds) of watchers.	4540	noticeably with many (hundreds) of watchers.
3536		4541
3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4542	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3538	(disabled).	4543	will be C<0>.
3539		4544
3540	=item EV_VERIFY	4545	=item EV_VERIFY
3541		4546
3542	Controls how much internal verification (see C<ev_loop_verify ()>) will	4547	Controls how much internal verification (see C<ev_verify ()>) will
3543	be done: If set to C<0>, no internal verification code will be compiled	4548	be done: If set to C<0>, no internal verification code will be compiled
3544	in. If set to C<1>, then verification code will be compiled in, but not	4549	in. If set to C<1>, then verification code will be compiled in, but not
3545	called. If set to C<2>, then the internal verification code will be	4550	called. If set to C<2>, then the internal verification code will be
3546	called once per loop, which can slow down libev. If set to C<3>, then the	4551	called once per loop, which can slow down libev. If set to C<3>, then the
3547	verification code will be called very frequently, which will slow down	4552	verification code will be called very frequently, which will slow down
3548	libev considerably.	4553	libev considerably.
3549		4554
3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4555	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3551	C<0>.	4556	will be C<0>.
3552		4557
3553	=item EV_COMMON	4558	=item EV_COMMON
3554		4559
3555	By default, all watchers have a C<void *data> member. By redefining	4560	By default, all watchers have a C<void *data> member. By redefining
3556	this macro to a something else you can include more and other types of	4561	this macro to something else you can include more and other types of
3557	members. You have to define it each time you include one of the files,	4562	members. You have to define it each time you include one of the files,
3558	though, and it must be identical each time.	4563	though, and it must be identical each time.
3559		4564
3560	For example, the perl EV module uses something like this:	4565	For example, the perl EV module uses something like this:
3561		4566
…		…
3614	file.	4619	file.
3615		4620
3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4621	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3617	that everybody includes and which overrides some configure choices:	4622	that everybody includes and which overrides some configure choices:
3618		4623
3619	#define EV_MINIMAL 1	4624	#define EV_FEATURES 8
3620	#define EV_USE_POLL 0	4625	#define EV_USE_SELECT 1
3621	#define EV_MULTIPLICITY 0
3622	#define EV_PERIODIC_ENABLE 0	4626	#define EV_PREPARE_ENABLE 1
		4627	#define EV_IDLE_ENABLE 1
3623	#define EV_STAT_ENABLE 0	4628	#define EV_SIGNAL_ENABLE 1
3624	#define EV_FORK_ENABLE 0	4629	#define EV_CHILD_ENABLE 1
		4630	#define EV_USE_STDEXCEPT 0
3625	#define EV_CONFIG_H <config.h>	4631	#define EV_CONFIG_H <config.h>
3626	#define EV_MINPRI 0
3627	#define EV_MAXPRI 0
3628		4632
3629	#include "ev++.h"	4633	#include "ev++.h"
3630		4634
3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4635	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3632		4636
3633	#include "ev_cpp.h"	4637	#include "ev_cpp.h"
3634	#include "ev.c"	4638	#include "ev.c"
3635		4639
3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4640	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3637		4641
3638	=head2 THREADS AND COROUTINES	4642	=head2 THREADS AND COROUTINES
3639		4643
3640	=head3 THREADS	4644	=head3 THREADS
3641		4645
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	4696	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	4697	watcher callback into the event loop interested in the signal.
3694		4698
3695	=back	4699	=back
3696		4700
		4701	See also L<THREAD LOCKING EXAMPLE>.
		4702
3697	=head3 COROUTINES	4703	=head3 COROUTINES
3698		4704
3699	Libev is very accommodating to coroutines ("cooperative threads"):	4705	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	4706	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4707	coroutines (e.g. you can call C<ev_run> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	4708	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	4709	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	4710	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		4711
3706	Care has been taken to ensure that libev does not keep local state inside	4712	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4713	C<ev_run>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	4714	they do not call any callbacks.
3709		4715
3710	=head2 COMPILER WARNINGS	4716	=head2 COMPILER WARNINGS
3711		4717
3712	Depending on your compiler and compiler settings, you might get no or a	4718	Depending on your compiler and compiler settings, you might get no or a
…		…
3723	maintainable.	4729	maintainable.
3724		4730
3725	And of course, some compiler warnings are just plain stupid, or simply	4731	And of course, some compiler warnings are just plain stupid, or simply
3726	wrong (because they don't actually warn about the condition their message	4732	wrong (because they don't actually warn about the condition their message
3727	seems to warn about). For example, certain older gcc versions had some	4733	seems to warn about). For example, certain older gcc versions had some
3728	warnings that resulted an extreme number of false positives. These have	4734	warnings that resulted in an extreme number of false positives. These have
3729	been fixed, but some people still insist on making code warn-free with	4735	been fixed, but some people still insist on making code warn-free with
3730	such buggy versions.	4736	such buggy versions.
3731		4737
3732	While libev is written to generate as few warnings as possible,	4738	While libev is written to generate as few warnings as possible,
3733	"warn-free" code is not a goal, and it is recommended not to build libev	4739	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3769	I suggest using suppression lists.	4775	I suggest using suppression lists.
3770		4776
3771		4777
3772	=head1 PORTABILITY NOTES	4778	=head1 PORTABILITY NOTES
3773		4779
		4780	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4781
		4782	GNU/Linux is the only common platform that supports 64 bit file/large file
		4783	interfaces but I<disables> them by default.
		4784
		4785	That means that libev compiled in the default environment doesn't support
		4786	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4787
		4788	Unfortunately, many programs try to work around this GNU/Linux issue
		4789	by enabling the large file API, which makes them incompatible with the
		4790	standard libev compiled for their system.
		4791
		4792	Likewise, libev cannot enable the large file API itself as this would
		4793	suddenly make it incompatible to the default compile time environment,
		4794	i.e. all programs not using special compile switches.
		4795
		4796	=head2 OS/X AND DARWIN BUGS
		4797
		4798	The whole thing is a bug if you ask me - basically any system interface
		4799	you touch is broken, whether it is locales, poll, kqueue or even the
		4800	OpenGL drivers.
		4801
		4802	=head3 C<kqueue> is buggy
		4803
		4804	The kqueue syscall is broken in all known versions - most versions support
		4805	only sockets, many support pipes.
		4806
		4807	Libev tries to work around this by not using C<kqueue> by default on this
		4808	rotten platform, but of course you can still ask for it when creating a
		4809	loop - embedding a socket-only kqueue loop into a select-based one is
		4810	probably going to work well.
		4811
		4812	=head3 C<poll> is buggy
		4813
		4814	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4815	implementation by something calling C<kqueue> internally around the 10.5.6
		4816	release, so now C<kqueue> I<and> C<poll> are broken.
		4817
		4818	Libev tries to work around this by not using C<poll> by default on
		4819	this rotten platform, but of course you can still ask for it when creating
		4820	a loop.
		4821
		4822	=head3 C<select> is buggy
		4823
		4824	All that's left is C<select>, and of course Apple found a way to fuck this
		4825	one up as well: On OS/X, C<select> actively limits the number of file
		4826	descriptors you can pass in to 1024 - your program suddenly crashes when
		4827	you use more.
		4828
		4829	There is an undocumented "workaround" for this - defining
		4830	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4831	work on OS/X.
		4832
		4833	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4834
		4835	=head3 C<errno> reentrancy
		4836
		4837	The default compile environment on Solaris is unfortunately so
		4838	thread-unsafe that you can't even use components/libraries compiled
		4839	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4840	defined by default. A valid, if stupid, implementation choice.
		4841
		4842	If you want to use libev in threaded environments you have to make sure
		4843	it's compiled with C<_REENTRANT> defined.
		4844
		4845	=head3 Event port backend
		4846
		4847	The scalable event interface for Solaris is called "event
		4848	ports". Unfortunately, this mechanism is very buggy in all major
		4849	releases. If you run into high CPU usage, your program freezes or you get
		4850	a large number of spurious wakeups, make sure you have all the relevant
		4851	and latest kernel patches applied. No, I don't know which ones, but there
		4852	are multiple ones to apply, and afterwards, event ports actually work
		4853	great.
		4854
		4855	If you can't get it to work, you can try running the program by setting
		4856	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4857	C<select> backends.
		4858
		4859	=head2 AIX POLL BUG
		4860
		4861	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4862	this by trying to avoid the poll backend altogether (i.e. it's not even
		4863	compiled in), which normally isn't a big problem as C<select> works fine
		4864	with large bitsets on AIX, and AIX is dead anyway.
		4865
3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4866	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4867
		4868	=head3 General issues
3775		4869
3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4870	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3777	requires, and its I/O model is fundamentally incompatible with the POSIX	4871	requires, and its I/O model is fundamentally incompatible with the POSIX
3778	model. Libev still offers limited functionality on this platform in	4872	model. Libev still offers limited functionality on this platform in
3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4873	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3780	descriptors. This only applies when using Win32 natively, not when using	4874	descriptors. This only applies when using Win32 natively, not when using
3781	e.g. cygwin.	4875	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4876	as every compielr comes with a slightly differently broken/incompatible
		4877	environment.
3782		4878
3783	Lifting these limitations would basically require the full	4879	Lifting these limitations would basically require the full
3784	re-implementation of the I/O system. If you are into these kinds of	4880	re-implementation of the I/O system. If you are into this kind of thing,
3785	things, then note that glib does exactly that for you in a very portable	4881	then note that glib does exactly that for you in a very portable way (note
3786	way (note also that glib is the slowest event library known to man).	4882	also that glib is the slowest event library known to man).
3787		4883
3788	There is no supported compilation method available on windows except	4884	There is no supported compilation method available on windows except
3789	embedding it into other applications.	4885	embedding it into other applications.
		4886
		4887	Sensible signal handling is officially unsupported by Microsoft - libev
		4888	tries its best, but under most conditions, signals will simply not work.
3790		4889
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	4890	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	4891	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	4892	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	4893	so make sure you only write small amounts into your sockets (less than a
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	4898	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	4899	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	4900	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	4901	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	4902	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	4903	(due to Microsoft monopoly games).
3805		4904
3806	A typical way to use libev under windows is to embed it (see the embedding	4905	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	4906	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	4907	of F<ev.h>:
3809		4908
…		…
3816	you do I<not> compile the F<ev.c> or any other embedded source files!):	4915	you do I<not> compile the F<ev.c> or any other embedded source files!):
3817		4916
3818	#include "evwrap.h"	4917	#include "evwrap.h"
3819	#include "ev.c"	4918	#include "ev.c"
3820		4919
3821	=over 4
3822
3823	=item The winsocket select function	4920	=head3 The winsocket C<select> function
3824		4921
3825	The winsocket C<select> function doesn't follow POSIX in that it	4922	The winsocket C<select> function doesn't follow POSIX in that it
3826	requires socket I<handles> and not socket I<file descriptors> (it is	4923	requires socket I<handles> and not socket I<file descriptors> (it is
3827	also extremely buggy). This makes select very inefficient, and also	4924	also extremely buggy). This makes select very inefficient, and also
3828	requires a mapping from file descriptors to socket handles (the Microsoft	4925	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4934	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3838		4935
3839	Note that winsockets handling of fd sets is O(n), so you can easily get a	4936	Note that winsockets handling of fd sets is O(n), so you can easily get a
3840	complexity in the O(n²) range when using win32.	4937	complexity in the O(n²) range when using win32.
3841		4938
3842	=item Limited number of file descriptors	4939	=head3 Limited number of file descriptors
3843		4940
3844	Windows has numerous arbitrary (and low) limits on things.	4941	Windows has numerous arbitrary (and low) limits on things.
3845		4942
3846	Early versions of winsocket's select only supported waiting for a maximum	4943	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	4944	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	4945	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	4946	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	4947	previous thread in each. Sounds great!).
3851		4948
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4949	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	4950	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	4951	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	4952	other interpreters do their own select emulation on windows).
3856		4953
3857	Another limit is the number of file descriptors in the Microsoft runtime	4954	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4955	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	4956	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4957	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	4958	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	4959	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	4960	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	4961	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	4962	the cost of calling select (O(n²)) will likely make this unworkable.
3868
3869	=back
3870		4963
3871	=head2 PORTABILITY REQUIREMENTS	4964	=head2 PORTABILITY REQUIREMENTS
3872		4965
3873	In addition to a working ISO-C implementation and of course the	4966	In addition to a working ISO-C implementation and of course the
3874	backend-specific APIs, libev relies on a few additional extensions:	4967	backend-specific APIs, libev relies on a few additional extensions:
…		…
3881	Libev assumes not only that all watcher pointers have the same internal	4974	Libev assumes not only that all watcher pointers have the same internal
3882	structure (guaranteed by POSIX but not by ISO C for example), but it also	4975	structure (guaranteed by POSIX but not by ISO C for example), but it also
3883	assumes that the same (machine) code can be used to call any watcher	4976	assumes that the same (machine) code can be used to call any watcher
3884	callback: The watcher callbacks have different type signatures, but libev	4977	callback: The watcher callbacks have different type signatures, but libev
3885	calls them using an C<ev_watcher *> internally.	4978	calls them using an C<ev_watcher *> internally.
		4979
		4980	=item pointer accesses must be thread-atomic
		4981
		4982	Accessing a pointer value must be atomic, it must both be readable and
		4983	writable in one piece - this is the case on all current architectures.
3886		4984
3887	=item C<sig_atomic_t volatile> must be thread-atomic as well	4985	=item C<sig_atomic_t volatile> must be thread-atomic as well
3888		4986
3889	The type C<sig_atomic_t volatile> (or whatever is defined as	4987	The type C<sig_atomic_t volatile> (or whatever is defined as
3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	4988	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3913	watchers.	5011	watchers.
3914		5012
3915	=item C<double> must hold a time value in seconds with enough accuracy	5013	=item C<double> must hold a time value in seconds with enough accuracy
3916		5014
3917	The type C<double> is used to represent timestamps. It is required to	5015	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5016	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3919	enough for at least into the year 4000. This requirement is fulfilled by	5017	good enough for at least into the year 4000 with millisecond accuracy
		5018	(the design goal for libev). This requirement is overfulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	5019	implementations using IEEE 754, which is basically all existing ones. With
		5020	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3921		5021
3922	=back	5022	=back
3923		5023
3924	If you know of other additional requirements drop me a note.	5024	If you know of other additional requirements drop me a note.
3925		5025
…		…
3993	involves iterating over all running async watchers or all signal numbers.	5093	involves iterating over all running async watchers or all signal numbers.
3994		5094
3995	=back	5095	=back
3996		5096
3997		5097
		5098	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5099
		5100	The major version 4 introduced some incompatible changes to the API.
		5101
		5102	At the moment, the C<ev.h> header file provides compatibility definitions
		5103	for all changes, so most programs should still compile. The compatibility
		5104	layer might be removed in later versions of libev, so better update to the
		5105	new API early than late.
		5106
		5107	=over 4
		5108
		5109	=item C<EV_COMPAT3> backwards compatibility mechanism
		5110
		5111	The backward compatibility mechanism can be controlled by
		5112	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5113	section.
		5114
		5115	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5116
		5117	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5118
		5119	ev_loop_destroy (EV_DEFAULT_UC);
		5120	ev_loop_fork (EV_DEFAULT);
		5121
		5122	=item function/symbol renames
		5123
		5124	A number of functions and symbols have been renamed:
		5125
		5126	ev_loop => ev_run
		5127	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5128	EVLOOP_ONESHOT => EVRUN_ONCE
		5129
		5130	ev_unloop => ev_break
		5131	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5132	EVUNLOOP_ONE => EVBREAK_ONE
		5133	EVUNLOOP_ALL => EVBREAK_ALL
		5134
		5135	EV_TIMEOUT => EV_TIMER
		5136
		5137	ev_loop_count => ev_iteration
		5138	ev_loop_depth => ev_depth
		5139	ev_loop_verify => ev_verify
		5140
		5141	Most functions working on C<struct ev_loop> objects don't have an
		5142	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5143	associated constants have been renamed to not collide with the C<struct
		5144	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5145	as all other watcher types. Note that C<ev_loop_fork> is still called
		5146	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5147	typedef.
		5148
		5149	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5150
		5151	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5152	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5153	and work, but the library code will of course be larger.
		5154
		5155	=back
		5156
		5157
		5158	=head1 GLOSSARY
		5159
		5160	=over 4
		5161
		5162	=item active
		5163
		5164	A watcher is active as long as it has been started and not yet stopped.
		5165	See L<WATCHER STATES> for details.
		5166
		5167	=item application
		5168
		5169	In this document, an application is whatever is using libev.
		5170
		5171	=item backend
		5172
		5173	The part of the code dealing with the operating system interfaces.
		5174
		5175	=item callback
		5176
		5177	The address of a function that is called when some event has been
		5178	detected. Callbacks are being passed the event loop, the watcher that
		5179	received the event, and the actual event bitset.
		5180
		5181	=item callback/watcher invocation
		5182
		5183	The act of calling the callback associated with a watcher.
		5184
		5185	=item event
		5186
		5187	A change of state of some external event, such as data now being available
		5188	for reading on a file descriptor, time having passed or simply not having
		5189	any other events happening anymore.
		5190
		5191	In libev, events are represented as single bits (such as C<EV_READ> or
		5192	C<EV_TIMER>).
		5193
		5194	=item event library
		5195
		5196	A software package implementing an event model and loop.
		5197
		5198	=item event loop
		5199
		5200	An entity that handles and processes external events and converts them
		5201	into callback invocations.
		5202
		5203	=item event model
		5204
		5205	The model used to describe how an event loop handles and processes
		5206	watchers and events.
		5207
		5208	=item pending
		5209
		5210	A watcher is pending as soon as the corresponding event has been
		5211	detected. See L<WATCHER STATES> for details.
		5212
		5213	=item real time
		5214
		5215	The physical time that is observed. It is apparently strictly monotonic :)
		5216
		5217	=item wall-clock time
		5218
		5219	The time and date as shown on clocks. Unlike real time, it can actually
		5220	be wrong and jump forwards and backwards, e.g. when the you adjust your
		5221	clock.
		5222
		5223	=item watcher
		5224
		5225	A data structure that describes interest in certain events. Watchers need
		5226	to be started (attached to an event loop) before they can receive events.
		5227
		5228	=back
		5229
3998	=head1 AUTHOR	5230	=head1 AUTHOR
3999		5231
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5232	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5233	Magnusson and Emanuele Giaquinta.
4001		5234

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