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Revision 1.441 by root, Thu Jul 13 10:46:52 2017 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familiarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
171		182
172	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
173		184
174	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
176	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
177		194
178	=item int ev_version_major ()	195	=item int ev_version_major ()
179		196
180	=item int ev_version_minor ()	197	=item int ev_version_minor ()
181		198
…		…
192	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	211	not a problem.
195		212
196	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
198		216
199	assert (("libev version mismatch",	217	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
202		220
…		…
213	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
215		233
216	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
217		235
218	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
224		243
225	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
226		245
227	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
232		251
233	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
234		253
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		255
237	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	285	}
267		286
268	...	287	...
269	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
270		289
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		291
273	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	307	}
289		308
290	...	309	...
291	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
292		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
293	=back	325	=back
294		326
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		328
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	is I<not> optional in this case, as there is also an C<ev_loop>	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
300		332
301	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
303	not.	335	do not.
304		336
305	=over 4	337	=over 4
306		338
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		340
309	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
313		351
314	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
315	function.	353	function (or via the C<EV_DEFAULT> macro).
316		354
317	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
320		359
321	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
327		384
328	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		387
331	The following flags are supported:	388	The following flags are supported:
…		…
341		398
342	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
343	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
346	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
347	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
348		407
349	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
350		409
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
353		412
354	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
360		420
361	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
363	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
364		424
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	426	environment variable.
367		427
368	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
369		429
370	When this flag is specified, then libev will not attempt to use the	430	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	431	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	432	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	433	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		434
375	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
376		436
377	When this flag is specified, then libev will attempt to use the	437	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	438	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	439	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	440	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	441	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	442	threads that are not interested in handling them.
383		443
384	Signalfd will not be used by default as this changes your signal mask, and	444	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	445	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
387		462
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		464
390	This is your standard select(2) backend. Not I<completely> standard, as	465	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	466	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		495
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	497	kernels).
423		498
424	For few fds, this backend is a bit little slower than poll and select,	499	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	500	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	501	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	502	fd), epoll scales either O(1) or O(active_fds).
428		503
429	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	507	descriptor (and unnecessary guessing of parameters), problems with dup,
		508	returning before the timeout value, resulting in additional iterations
		509	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	510	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	511	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	512	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	513	and is of course hard to detect.
437		514
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	516	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	517	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	518	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	519	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
		525	not least, it also refuses to work with some file descriptors which work
		526	perfectly fine with C<select> (files, many character devices...).
		527
		528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
445		531
446	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
486		572
487	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	579	drops fds silently in similarly hard-to-detect cases.
494		580
495	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
496		582
497	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		602
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	604	it's really slow, but it still scales very well (O(active_fds)).
519		605
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	606	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	607	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	609	might perform better.
528		610
529	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	612	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
533		625
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
536		628
537	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
538		630
539	Try all backends (even potentially broken ones that wouldn't be tried	631	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		634
543	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		644
545	=back	645	=back
546		646
547	If one or more of the backend flags are or'ed into the flags value,	647	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	648	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	649	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	650	()> will be tried.
551		651
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	652	Example: Try to create a event loop that uses epoll and nothing else.
579		653
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	655	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
583		657
		658	Example: Use whatever libev has to offer, but make sure that kqueue is
		659	used if available.
		660
		661	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		662
584	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
585		664
586	Destroys the default loop (frees all memory and kernel state etc.). None	665	Destroys an event loop object (frees all memory and kernel state
587	of the active event watchers will be stopped in the normal sense, so	666	etc.). None of the active event watchers will be stopped in the normal
588	e.g. C<ev_is_active> might still return true. It is your responsibility to	667	sense, so e.g. C<ev_is_active> might still return true. It is your
589	either stop all watchers cleanly yourself I<before> calling this function,	668	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	669	calling this function, or cope with the fact afterwards (which is usually
591	can just ignore the watchers and/or C<free ()> them for example).	670	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		671	for example).
592		672
593	Note that certain global state, such as signal state (and installed signal	673	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	674	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
596		676
597	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	678	C<ev_loop_new>, but it can also be used on the default loop returned by
		679	C<ev_default_loop>, in which case it is not thread-safe.
		680
		681	Note that it is not advisable to call this function on the default loop
		682	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
601		685
602	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
603		687
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	This function sets a flag that causes subsequent C<ev_loop> iterations	688	This function sets a flag that causes subsequent C<ev_run> iterations
610	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
611	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
612	the child process (or both child and parent, but that again makes little	691	watchers (except inside an C<ev_prepare> callback), but it makes most
613	sense). You I<must> call it in the child before using any of the libev	692	sense after forking, in the child process. You I<must> call it (or use
614	functions, and it will only take effect at the next C<ev_loop> iteration.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
615		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	698	Again, you I<have> to call it on I<any> loop that you want to re-use after
617	a fork, I<even if you do not plan to use the loop in the parent>. This is	699	a fork, I<even if you do not plan to use the loop in the parent>. This is
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	700	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	701	during fork.
620		702
621	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	704	process if and only if you want to use the event loop in the child. If
623	just fork+exec or create a new loop in the child, you don't have to call	705	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	706	call it at all (in fact, C<epoll> is so badly broken that it makes a
		707	difference, but libev will usually detect this case on its own and do a
		708	costly reset of the backend).
625		709
626	The function itself is quite fast and it's usually not a problem to call	710	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		712
		713	Example: Automate calling C<ev_loop_fork> on the default loop when
		714	using pthreads.
		715
		716	static void
		717	post_fork_child (void)
		718	{
		719	ev_loop_fork (EV_DEFAULT);
		720	}
		721
		722	...
630	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		724
639	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
640		726
641	Returns true when the given loop is, in fact, the default loop, and false	727	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	728	otherwise.
643		729
644	=item unsigned int ev_iteration (loop)	730	=item unsigned int ev_iteration (loop)
645		731
646	Returns the current iteration count for the loop, which is identical to	732	Returns the current iteration count for the event loop, which is identical
647	the number of times libev did poll for new events. It starts at C<0> and	733	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	734	and happily wraps around with enough iterations.
649		735
650	This value can sometimes be useful as a generation counter of sorts (it	736	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	737	"ticks" the number of loop iterations), as it roughly corresponds with
652	C<ev_prepare> and C<ev_check> calls - and is incremented between the	738	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	739	prepare and check phases.
654		740
655	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
656		742
657	Returns the number of times C<ev_loop> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
659		745
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	748	in which case it is higher.
663		749
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	etc.), doesn't count as "exit" - consider this as a hint to avoid such	751	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
667		754
668	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
669		756
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	758	use.
…		…
680		767
681	=item ev_now_update (loop)	768	=item ev_now_update (loop)
682		769
683	Establishes the current time by querying the kernel, updating the time	770	Establishes the current time by querying the kernel, updating the time
684	returned by C<ev_now ()> in the progress. This is a costly operation and	771	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	772	is usually done automatically within C<ev_run ()>.
686		773
687	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	776	the current time is a good idea.
690		777
691	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
692		779
693	=item ev_suspend (loop)	780	=item ev_suspend (loop)
694		781
695	=item ev_resume (loop)	782	=item ev_resume (loop)
696		783
697	These two functions suspend and resume a loop, for use when the loop is	784	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	785	loop is not used for a while and timeouts should not be processed.
699		786
700	A typical use case would be an interactive program such as a game: When	787	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	788	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	789	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	790	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
714	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
715		802
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
718		805
719	=item ev_loop (loop, int flags)	806	=item bool ev_run (loop, int flags)
720		807
721	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
723	handling events.	810	handling events. It will ask the operating system for any new events, call
		811	the watcher callbacks, and then repeat the whole process indefinitely: This
		812	is why event loops are called I<loops>.
724		813
725	If the flags argument is specified as C<0>, it will not return until	814	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	815	until either no event watchers are active anymore or C<ev_break> was
		816	called.
727		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
		821
728	Please note that an explicit C<ev_unloop> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	827	beauty.
734		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	835	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	836	block your process in case there are no events and will return after one
738	the loop.	837	iteration of the loop. This is sometimes useful to poll and handle new
		838	events while doing lengthy calculations, to keep the program responsive.
739		839
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	840	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	841	necessary) and will handle those and any already outstanding ones. It
742	will block your process until at least one new event arrives (which could	842	will block your process until at least one new event arrives (which could
743	be an event internal to libev itself, so there is no guarantee that a	843	be an event internal to libev itself, so there is no guarantee that a
744	user-registered callback will be called), and will return after one	844	user-registered callback will be called), and will return after one
745	iteration of the loop.	845	iteration of the loop.
746		846
747	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
751		851
752	Here are the gory details of what C<ev_loop> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
753		855
		856	- Increment loop depth.
		857	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
		859	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	860	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	861	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	862	- Queue and call all prepare watchers.
		863	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	864	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	865	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	866	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	867	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	868	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	869	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	870	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	871	- Sleep if the I/O and timer collect interval say so.
		872	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	873	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	874	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	875	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	876	- Queue all expired timers.
770	- Queue all expired periodics.	877	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	878	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	879	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	880	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	881	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	882	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	883	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	884	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	885	continue with step LOOP.
		886	FINISH:
		887	- Reset the ev_break status iff it was EVBREAK_ONE.
		888	- Decrement the loop depth.
		889	- Return.
779		890
780	Example: Queue some jobs and then loop until no events are outstanding	891	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	892	anymore.
782		893
783	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
784	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	896	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
787		898
788	=item ev_unloop (loop, how)	899	=item ev_break (loop, how)
789		900
790	Can be used to make a call to C<ev_loop> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		905
795	This "unloop state" will be cleared when entering C<ev_loop> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
796		907
797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
798		910
799	=item ev_ref (loop)	911	=item ev_ref (loop)
800		912
801	=item ev_unref (loop)	913	=item ev_unref (loop)
802		914
803	Ref/unref can be used to add or remove a reference count on the event	915	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	916	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	917	count is nonzero, C<ev_run> will not return on its own.
806		918
807	This is useful when you have a watcher that you never intend to	919	This is useful when you have a watcher that you never intend to
808	unregister, but that nevertheless should not keep C<ev_loop> from	920	unregister, but that nevertheless should not keep C<ev_run> from
809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	921	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	922	before stopping it.
811		923
812	As an example, libev itself uses this for its internal signal pipe: It	924	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	925	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	926	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	927	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	928	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	929	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	930	before, respectively. Note also that libev might stop watchers itself
819	(e.g. non-repeating timers) in which case you have to C<ev_ref>	931	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	932	in the callback).
821		933
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	934	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	935	running when nothing else is active.
824		936
825	ev_signal exitsig;	937	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	940	ev_unref (loop);
829		941
830	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
831		943
832	ev_ref (loop);	944	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
853	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
854		966
855	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
856	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
858	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
859	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
860	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
861	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
862		975
863	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
864	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
866	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1003	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		1004
892	=item ev_invoke_pending (loop)	1005	=item ev_invoke_pending (loop)
893		1006
894	This call will simply invoke all pending watchers while resetting their	1007	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	1008	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	1009	but when overriding the invoke callback this call comes handy. This
		1010	function can be invoked from a watcher - this can be useful for example
		1011	when you want to do some lengthy calculation and want to pass further
		1012	event handling to another thread (you still have to make sure only one
		1013	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		1014
898	=item int ev_pending_count (loop)	1015	=item int ev_pending_count (loop)
899		1016
900	Returns the number of pending watchers - zero indicates that no watchers	1017	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1018	are pending.
902		1019
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1020	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		1021
905	This overrides the invoke pending functionality of the loop: Instead of	1022	This overrides the invoke pending functionality of the loop: Instead of
906	invoking all pending watchers when there are any, C<ev_loop> will call	1023	invoking all pending watchers when there are any, C<ev_run> will call
907	this callback instead. This is useful, for example, when you want to	1024	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
909		1026
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1028	callback.
912		1029
913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
914		1031
915	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
916	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1034	each call to a libev function.
918		1035
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
920	wait for it to return. One way around this is to wake up the loop via	1037	to wait for it to return. One way around this is to wake up the event
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
923		1040
924	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
925	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1043	afterwards.
927		1044
…		…
930		1047
931	While event loop modifications are allowed between invocations of	1048	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1049	C<release> and C<acquire> (that's their only purpose after all), no
933	modifications done will affect the event loop, i.e. adding watchers will	1050	modifications done will affect the event loop, i.e. adding watchers will
934	have no effect on the set of file descriptors being watched, or the time	1051	have no effect on the set of file descriptors being watched, or the time
935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1052	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
936	to take note of any changes you made.	1053	to take note of any changes you made.
937		1054
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1055	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1056	invocations of C<release> and C<acquire>.
940		1057
941	See also the locking example in the C<THREADS> section later in this	1058	See also the locking example in the C<THREADS> section later in this
942	document.	1059	document.
943		1060
944	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
945		1062
946	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
947		1064
948	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1067	C<0>.
951		1068
952	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
953	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
954	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1072	any other purpose as well.
956		1073
957	=item ev_loop_verify (loop)	1074	=item ev_verify (loop)
958		1075
959	This function only does something when C<EV_VERIFY> support has been	1076	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1077	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1078	through all internal structures and checks them for validity. If anything
962	is found to be inconsistent, it will print an error message to standard	1079	is found to be inconsistent, it will print an error message to standard
…		…
973		1090
974	In the following description, uppercase C<TYPE> in names stands for the	1091	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1092	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1093	watchers and C<ev_io_start> for I/O watchers.
977		1094
978	A watcher is a structure that you create and register to record your	1095	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1096	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1097	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1098	for that:
981		1099
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1100	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1101	{
984	ev_io_stop (w);	1102	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1103	ev_break (loop, EVBREAK_ALL);
986	}	1104	}
987		1105
988	struct ev_loop *loop = ev_default_loop (0);	1106	struct ev_loop *loop = ev_default_loop (0);
989		1107
990	ev_io stdin_watcher;	1108	ev_io stdin_watcher;
991		1109
992	ev_init (&stdin_watcher, my_cb);	1110	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1111	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1112	ev_io_start (loop, &stdin_watcher);
995		1113
996	ev_loop (loop, 0);	1114	ev_run (loop, 0);
997		1115
998	As you can see, you are responsible for allocating the memory for your	1116	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1117	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1118	stack).
1001		1119
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1120	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1121	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1122
1005	Each watcher structure must be initialised by a call to C<ev_init	1123	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1124	*, callback)>, which expects a callback to be provided. This callback is
1007	callback gets invoked each time the event occurs (or, in the case of I/O	1125	invoked each time the event occurs (or, in the case of I/O watchers, each
1008	watchers, each time the event loop detects that the file descriptor given	1126	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1127	and/or writable).
1010		1128
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1129	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1130	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1131	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1132	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1183
1066	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1067		1185
1068	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1069		1187
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1073	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1074	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1076	C<ev_loop> from blocking).	1199	blocking).
1077		1200
1078	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1079		1202
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1204
1082	=item C<EV_FORK>	1205	=item C<EV_FORK>
1083		1206
1084	The event loop has been resumed in the child process after fork (see	1207	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1208	C<ev_fork>).
		1209
		1210	=item C<EV_CLEANUP>
		1211
		1212	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1213
1087	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1088		1215
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1216	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1217
…		…
1200		1327
1201	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1202		1329
1203	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1204		1331
1205	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1206		1333
1207	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1208	(modulo threads).	1335	(modulo threads).
1209		1336
1210	=item ev_set_priority (ev_TYPE *watcher, int priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1228	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1229		1356
1230	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1231	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1232		1359
1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1234	priorities.	1361	priorities.
1235		1362
1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1237		1364
1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1391	functions that do not need a watcher.
1265		1392
1266	=back	1393	=back
1267		1394
		1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1396	OWN COMPOSITE WATCHERS> idioms.
1268		1397
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1398	=head2 WATCHER STATES
1270		1399
1271	Each watcher has, by default, a member C<void *data> that you can change	1400	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1401	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1402	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1403	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1404
1278	struct my_io	1405	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1406
1286	...	1407	=item initialised
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1408
1290	And since your callback will be called with a pointer to the watcher, you	1409	Before a watcher can be registered with the event loop it has to be
1291	can cast it back to your own type:	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1412
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1413	In this state it is simply some block of memory that is suitable for
1294	{	1414	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1415	will - as long as you either keep the memory contents intact, or call
1296	...	1416	C<ev_TYPE_init> again.
1297	}
1298		1417
1299	More interesting and less C-conformant ways of casting your callback type	1418	=item started/running/active
1300	instead have been omitted.
1301		1419
1302	Another common scenario is to use some data structure with multiple	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1421	property of the event loop, and is actively waiting for events. While in
		1422	this state it cannot be accessed (except in a few documented ways), moved,
		1423	freed or anything else - the only legal thing is to keep a pointer to it,
		1424	and call libev functions on it that are documented to work on active watchers.
1304		1425
1305	struct my_biggy	1426	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1427
1312	In this case getting the pointer to C<my_biggy> is a bit more	1428	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1429	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1430	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1431	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1432	callback.
1317		1433
1318	#include <stddef.h>	1434	The watcher might or might not be active while it is pending (for example,
		1435	an expired non-repeating timer can be pending but no longer active). If it
		1436	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1437	but it is still property of the event loop at this time, so cannot be
		1438	moved, freed or reused. And if it is active the rules described in the
		1439	previous item still apply.
1319		1440
1320	static void	1441	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1442	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1443	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1444
1327	static void	1445	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1446
1329	{	1447	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1448	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1449	latter will clear any pending state the watcher might be in, regardless
1332	}	1450	of whether it was active or not, so stopping a watcher explicitly before
		1451	freeing it is often a good idea.
		1452
		1453	While stopped (and not pending) the watcher is essentially in the
		1454	initialised state, that is, it can be reused, moved, modified in any way
		1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
		1457
		1458	=back
1333		1459
1334	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1335		1461
1336	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1464	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1593	required if you know what you are doing).
1468		1594
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarantee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1478	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1479	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1483		1602
1484	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1609	indefinitely.
1491		1610
1492	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1493		1612
…		…
1521		1640
1522	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1526	=head3 The special problem of fork	1678	=head3 The special problem of fork
1527		1679
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1530	it in the child.	1682	it in the child if you want to continue to use it in the child.
1531		1683
1532	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1687
1537	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1538		1689
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1773	...
1623	struct ev_loop *loop = ev_default_init (0);	1774	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1775	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1776	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1777	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1778	ev_run (loop, 0);
1628		1779
1629		1780
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1781	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1782
1632	Timer watchers are simple relative timers that generate an event after a	1783	Timer watchers are simple relative timers that generate an event after a
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1640		1791
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1647		1799
1648	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1649		1801
1650	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1878
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1881	within the callback:
1730		1882
		1883	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1732		1886
1733	static void	1887	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1735	{	1889	{
1736	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1892
1739	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1740	if (timeout < now)	1894	if (after < 0.)
1741	{	1895	{
1742	// timeout occurred, take action	1896	// timeout occurred, take action
1743	}	1897	}
1744	else	1898	else
1745	{	1899	{
1746	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1751	}	1906	}
1752	}	1907	}
1753		1908
1754	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1755	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1756	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1757	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1758	re-schedule the timer to fire at that future time, to see if maybe we have
1759	a timeout then.
1760		1913
1761	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1763		1923
1764	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1926	libev to change the timeout.
1767		1927
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1771		1932
		1933	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		1936
1776	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1778		1939
		1940	if (activity detected)
1779	last_activity = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1780		1950
1781	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1783
1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
1785	callback :) - just change the timeout and invoke the callback, which will
1786	fix things for you.
1787		1953
1788	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1789		1955
1790	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1791	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1819	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1820	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	1987	overkill :)
1822		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1823	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1824		2027
1825	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2032	lots of events in one iteration.
1830		2033
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1833	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1834	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1835	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1836		2040
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1838		2042
1839	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
1842		2080
1843	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1844		2082
1845	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
1846	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1890	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1891	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1892		2130
1893	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1894		2132
1895	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
1896	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
1897		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
1898	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1899		2143
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
1901		2146
1902	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
1903	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1904		2149
		2150	=back
		2151
1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1906	usage example.	2153	usage example.
1907		2154
1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1909		2156
1910	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
1949	}	2196	}
1950		2197
1951	ev_timer mytimer;	2198	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2199	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2200	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2201	ev_run (loop, 0);
1955		2202
1956	// and in some piece of code that gets executed on any "activity":	2203	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2204	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2205	ev_timer_again (&mytimer);
1959		2206
…		…
1963	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
1964	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
1965		2212
1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1967	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
1968	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
1969	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
1970	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
1971	wrist-watch).	2218	wrist-watch).
1972		2219
1973	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
1985		2232
1986	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2237	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2238
1992	=head3 Watcher-Specific Functions and Data Members	2239	=head3 Watcher-Specific Functions and Data Members
1993		2240
1994	=over 4	2241	=over 4
1995		2242
…		…
2030		2277
2031	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2281
2035	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
2038		2288
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2150		2400
2151	ev_periodic hourly_tick;	2401	ev_periodic hourly_tick;
2152	ev_periodic_init (&hourly_tick, clock_cb,	2402	ev_periodic_init (&hourly_tick, clock_cb,
2153	fmod (ev_now (loop), 3600.), 3600., 0);	2403	fmod (ev_now (loop), 3600.), 3600., 0);
2154	ev_periodic_start (loop, &hourly_tick);	2404	ev_periodic_start (loop, &hourly_tick);
2155		2405
2156		2406
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2407	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2408
2159	Signal watchers will trigger an event when the process receives a specific	2409	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2410	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2411	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2412	normal event processing, like any other event.
2163		2413
2164	If you want signals to be delivered truly asynchronously, just use	2414	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2415	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2416	the signal. You can even use C<ev_async> from a signal handler to
…		…
2170	only within the same loop, i.e. you can watch for C<SIGINT> in your	2420	only within the same loop, i.e. you can watch for C<SIGINT> in your
2171	default loop and for C<SIGIO> in another loop, but you cannot watch for	2421	default loop and for C<SIGIO> in another loop, but you cannot watch for
2172	C<SIGINT> in both the default loop and another loop at the same time. At	2422	C<SIGINT> in both the default loop and another loop at the same time. At
2173	the moment, C<SIGCHLD> is permanently tied to the default loop.	2423	the moment, C<SIGCHLD> is permanently tied to the default loop.
2174		2424
2175	When the first watcher gets started will libev actually register something	2425	Only after the first watcher for a signal is started will libev actually
2176	with the kernel (thus it coexists with your own signal handlers as long as	2426	register something with the kernel. It thus coexists with your own signal
2177	you don't register any with libev for the same signal).	2427	handlers as long as you don't register any with libev for the same signal.
2178		2428
2179	If possible and supported, libev will install its handlers with	2429	If possible and supported, libev will install its handlers with
2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2430	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2181	not be unduly interrupted. If you have a problem with system calls getting	2431	not be unduly interrupted. If you have a problem with system calls getting
2182	interrupted by signals you can block all signals in an C<ev_check> watcher	2432	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2435	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2436
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2437	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2438	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2439	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2440	and might or might not set or restore the installed signal handler (but
		2441	see C<EVFLAG_NOSIGMASK>).
2191		2442
2192	While this does not matter for the signal disposition (libev never	2443	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2444	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2445	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2446	certain signals to be blocked.
…		…
2209		2460
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2461	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2462	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2463	is not a libev-specific thing, this is true for most event libraries.
2213		2464
		2465	=head3 The special problem of threads signal handling
		2466
		2467	POSIX threads has problematic signal handling semantics, specifically,
		2468	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2469	threads in a process block signals, which is hard to achieve.
		2470
		2471	When you want to use sigwait (or mix libev signal handling with your own
		2472	for the same signals), you can tackle this problem by globally blocking
		2473	all signals before creating any threads (or creating them with a fully set
		2474	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2475	loops. Then designate one thread as "signal receiver thread" which handles
		2476	these signals. You can pass on any signals that libev might be interested
		2477	in by calling C<ev_feed_signal>.
		2478
2214	=head3 Watcher-Specific Functions and Data Members	2479	=head3 Watcher-Specific Functions and Data Members
2215		2480
2216	=over 4	2481	=over 4
2217		2482
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2483	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2498	Example: Try to exit cleanly on SIGINT.
2234		2499
2235	static void	2500	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2501	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2502	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2503	ev_break (loop, EVBREAK_ALL);
2239	}	2504	}
2240		2505
2241	ev_signal signal_watcher;	2506	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2507	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2508	ev_signal_start (loop, &signal_watcher);
…		…
2352		2617
2353	=head2 C<ev_stat> - did the file attributes just change?	2618	=head2 C<ev_stat> - did the file attributes just change?
2354		2619
2355	This watches a file system path for attribute changes. That is, it calls	2620	This watches a file system path for attribute changes. That is, it calls
2356	C<stat> on that path in regular intervals (or when the OS says it changed)	2621	C<stat> on that path in regular intervals (or when the OS says it changed)
2357	and sees if it changed compared to the last time, invoking the callback if	2622	and sees if it changed compared to the last time, invoking the callback
2358	it did.	2623	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2624	happen after the watcher has been started will be reported.
2359		2625
2360	The path does not need to exist: changing from "path exists" to "path does	2626	The path does not need to exist: changing from "path exists" to "path does
2361	not exist" is a status change like any other. The condition "path does not	2627	not exist" is a status change like any other. The condition "path does not
2362	exist" (or more correctly "path cannot be stat'ed") is signified by the	2628	exist" (or more correctly "path cannot be stat'ed") is signified by the
2363	C<st_nlink> field being zero (which is otherwise always forced to be at	2629	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2593	Apart from keeping your process non-blocking (which is a useful	2859	Apart from keeping your process non-blocking (which is a useful
2594	effect on its own sometimes), idle watchers are a good place to do	2860	effect on its own sometimes), idle watchers are a good place to do
2595	"pseudo-background processing", or delay processing stuff to after the	2861	"pseudo-background processing", or delay processing stuff to after the
2596	event loop has handled all outstanding events.	2862	event loop has handled all outstanding events.
2597		2863
		2864	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2865
		2866	As long as there is at least one active idle watcher, libev will never
		2867	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2868	For this to work, the idle watcher doesn't need to be invoked at all - the
		2869	lowest priority will do.
		2870
		2871	This mode of operation can be useful together with an C<ev_check> watcher,
		2872	to do something on each event loop iteration - for example to balance load
		2873	between different connections.
		2874
		2875	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2876	example.
		2877
2598	=head3 Watcher-Specific Functions and Data Members	2878	=head3 Watcher-Specific Functions and Data Members
2599		2879
2600	=over 4	2880	=over 4
2601		2881
2602	=item ev_idle_init (ev_idle *, callback)	2882	=item ev_idle_init (ev_idle *, callback)
…		…
2613	callback, free it. Also, use no error checking, as usual.	2893	callback, free it. Also, use no error checking, as usual.
2614		2894
2615	static void	2895	static void
2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2896	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2617	{	2897	{
		2898	// stop the watcher
		2899	ev_idle_stop (loop, w);
		2900
		2901	// now we can free it
2618	free (w);	2902	free (w);
		2903
2619	// now do something you wanted to do when the program has	2904	// now do something you wanted to do when the program has
2620	// no longer anything immediate to do.	2905	// no longer anything immediate to do.
2621	}	2906	}
2622		2907
2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2908	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2625	ev_idle_start (loop, idle_watcher);	2910	ev_idle_start (loop, idle_watcher);
2626		2911
2627		2912
2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2913	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2629		2914
2630	Prepare and check watchers are usually (but not always) used in pairs:	2915	Prepare and check watchers are often (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2916	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2917	afterwards.
2633		2918
2634	You I<must not> call C<ev_loop> or similar functions that enter	2919	You I<must not> call C<ev_run> (or similar functions that enter the
2635	the current event loop from either C<ev_prepare> or C<ev_check>	2920	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2636	watchers. Other loops than the current one are fine, however. The	2921	C<ev_check> watchers. Other loops than the current one are fine,
2637	rationale behind this is that you do not need to check for recursion in	2922	however. The rationale behind this is that you do not need to check
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2923	for recursion in those watchers, i.e. the sequence will always be
2639	C<ev_check> so if you have one watcher of each kind they will always be	2924	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2640	called in pairs bracketing the blocking call.	2925	kind they will always be called in pairs bracketing the blocking call.
2641		2926
2642	Their main purpose is to integrate other event mechanisms into libev and	2927	Their main purpose is to integrate other event mechanisms into libev and
2643	their use is somewhat advanced. They could be used, for example, to track	2928	their use is somewhat advanced. They could be used, for example, to track
2644	variable changes, implement your own watchers, integrate net-snmp or a	2929	variable changes, implement your own watchers, integrate net-snmp or a
2645	coroutine library and lots more. They are also occasionally useful if	2930	coroutine library and lots more. They are also occasionally useful if
…		…
2663	with priority higher than or equal to the event loop and one coroutine	2948	with priority higher than or equal to the event loop and one coroutine
2664	of lower priority, but only once, using idle watchers to keep the event	2949	of lower priority, but only once, using idle watchers to keep the event
2665	loop from blocking if lower-priority coroutines are active, thus mapping	2950	loop from blocking if lower-priority coroutines are active, thus mapping
2666	low-priority coroutines to idle/background tasks).	2951	low-priority coroutines to idle/background tasks).
2667		2952
2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2953	When used for this purpose, it is recommended to give C<ev_check> watchers
2669	priority, to ensure that they are being run before any other watchers	2954	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2670	after the poll (this doesn't matter for C<ev_prepare> watchers).	2955	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2956	watchers).
2671		2957
2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2958	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2673	activate ("feed") events into libev. While libev fully supports this, they	2959	activate ("feed") events into libev. While libev fully supports this, they
2674	might get executed before other C<ev_check> watchers did their job. As	2960	might get executed before other C<ev_check> watchers did their job. As
2675	C<ev_check> watchers are often used to embed other (non-libev) event	2961	C<ev_check> watchers are often used to embed other (non-libev) event
2676	loops those other event loops might be in an unusable state until their	2962	loops those other event loops might be in an unusable state until their
2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2963	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2678	others).	2964	others).
		2965
		2966	=head3 Abusing an C<ev_check> watcher for its side-effect
		2967
		2968	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2969	useful because they are called once per event loop iteration. For
		2970	example, if you want to handle a large number of connections fairly, you
		2971	normally only do a bit of work for each active connection, and if there
		2972	is more work to do, you wait for the next event loop iteration, so other
		2973	connections have a chance of making progress.
		2974
		2975	Using an C<ev_check> watcher is almost enough: it will be called on the
		2976	next event loop iteration. However, that isn't as soon as possible -
		2977	without external events, your C<ev_check> watcher will not be invoked.
		2978
		2979	This is where C<ev_idle> watchers come in handy - all you need is a
		2980	single global idle watcher that is active as long as you have one active
		2981	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2982	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2983	invoked. Neither watcher alone can do that.
2679		2984
2680	=head3 Watcher-Specific Functions and Data Members	2985	=head3 Watcher-Specific Functions and Data Members
2681		2986
2682	=over 4	2987	=over 4
2683		2988
…		…
2807		3112
2808	if (timeout >= 0)	3113	if (timeout >= 0)
2809	// create/start timer	3114	// create/start timer
2810		3115
2811	// poll	3116	// poll
2812	ev_loop (EV_A_ 0);	3117	ev_run (EV_A_ 0);
2813		3118
2814	// stop timer again	3119	// stop timer again
2815	if (timeout >= 0)	3120	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3121	ev_timer_stop (EV_A_ &to);
2817		3122
…		…
2884		3189
2885	=over 4	3190	=over 4
2886		3191
2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3192	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2888		3193
2889	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3194	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2890		3195
2891	Configures the watcher to embed the given loop, which must be	3196	Configures the watcher to embed the given loop, which must be
2892	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3197	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2893	invoked automatically, otherwise it is the responsibility of the callback	3198	invoked automatically, otherwise it is the responsibility of the callback
2894	to invoke it (it will continue to be called until the sweep has been done,	3199	to invoke it (it will continue to be called until the sweep has been done,
2895	if you do not want that, you need to temporarily stop the embed watcher).	3200	if you do not want that, you need to temporarily stop the embed watcher).
2896		3201
2897	=item ev_embed_sweep (loop, ev_embed *)	3202	=item ev_embed_sweep (loop, ev_embed *)
2898		3203
2899	Make a single, non-blocking sweep over the embedded loop. This works	3204	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3205	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3206	appropriate way for embedded loops.
2902		3207
2903	=item struct ev_loop *other [read-only]	3208	=item struct ev_loop *other [read-only]
2904		3209
2905	The embedded event loop.	3210	The embedded event loop.
…		…
2915	used).	3220	used).
2916		3221
2917	struct ev_loop *loop_hi = ev_default_init (0);	3222	struct ev_loop *loop_hi = ev_default_init (0);
2918	struct ev_loop *loop_lo = 0;	3223	struct ev_loop *loop_lo = 0;
2919	ev_embed embed;	3224	ev_embed embed;
2920		3225
2921	// see if there is a chance of getting one that works	3226	// see if there is a chance of getting one that works
2922	// (remember that a flags value of 0 means autodetection)	3227	// (remember that a flags value of 0 means autodetection)
2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2925	: 0;	3230	: 0;
…		…
2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2940		3245
2941	struct ev_loop *loop = ev_default_init (0);	3246	struct ev_loop *loop = ev_default_init (0);
2942	struct ev_loop *loop_socket = 0;	3247	struct ev_loop *loop_socket = 0;
2943	ev_embed embed;	3248	ev_embed embed;
2944		3249
2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2947	{	3252	{
2948	ev_embed_init (&embed, 0, loop_socket);	3253	ev_embed_init (&embed, 0, loop_socket);
2949	ev_embed_start (loop, &embed);	3254	ev_embed_start (loop, &embed);
…		…
2957		3262
2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3263	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2959		3264
2960	Fork watchers are called when a C<fork ()> was detected (usually because	3265	Fork watchers are called when a C<fork ()> was detected (usually because
2961	whoever is a good citizen cared to tell libev about it by calling	3266	whoever is a good citizen cared to tell libev about it by calling
2962	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3267	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2963	event loop blocks next and before C<ev_check> watchers are being called,	3268	and before C<ev_check> watchers are being called, and only in the child
2964	and only in the child after the fork. If whoever good citizen calling	3269	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3270	and calls it in the wrong process, the fork handlers will be invoked, too,
2966	handlers will be invoked, too, of course.	3271	of course.
2967		3272
2968	=head3 The special problem of life after fork - how is it possible?	3273	=head3 The special problem of life after fork - how is it possible?
2969		3274
2970	Most uses of C<fork()> consist of forking, then some simple calls to set	3275	Most uses of C<fork ()> consist of forking, then some simple calls to set
2971	up/change the process environment, followed by a call to C<exec()>. This	3276	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3277	sequence should be handled by libev without any problems.
2973		3278
2974	This changes when the application actually wants to do event handling	3279	This changes when the application actually wants to do event handling
2975	in the child, or both parent in child, in effect "continuing" after the	3280	in the child, or both parent in child, in effect "continuing" after the
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3296	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3297	signal watchers).
2993		3298
2994	When this is not possible, or you want to use the default loop for	3299	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3300	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3301	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3302	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3303	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3304	those watchers. Note also that in that case, you have to re-register any
		3305	signal watchers.
3000		3306
3001	=head3 Watcher-Specific Functions and Data Members	3307	=head3 Watcher-Specific Functions and Data Members
3002		3308
3003	=over 4	3309	=over 4
3004		3310
3005	=item ev_fork_init (ev_signal *, callback)	3311	=item ev_fork_init (ev_fork *, callback)
3006		3312
3007	Initialises and configures the fork watcher - it has no parameters of any	3313	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3314	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3315	really.
3010		3316
3011	=back	3317	=back
		3318
		3319
		3320	=head2 C<ev_cleanup> - even the best things end
		3321
		3322	Cleanup watchers are called just before the event loop is being destroyed
		3323	by a call to C<ev_loop_destroy>.
		3324
		3325	While there is no guarantee that the event loop gets destroyed, cleanup
		3326	watchers provide a convenient method to install cleanup hooks for your
		3327	program, worker threads and so on - you just to make sure to destroy the
		3328	loop when you want them to be invoked.
		3329
		3330	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3331	all other watchers, they do not keep a reference to the event loop (which
		3332	makes a lot of sense if you think about it). Like all other watchers, you
		3333	can call libev functions in the callback, except C<ev_cleanup_start>.
		3334
		3335	=head3 Watcher-Specific Functions and Data Members
		3336
		3337	=over 4
		3338
		3339	=item ev_cleanup_init (ev_cleanup *, callback)
		3340
		3341	Initialises and configures the cleanup watcher - it has no parameters of
		3342	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3343	pointless, I assure you.
		3344
		3345	=back
		3346
		3347	Example: Register an atexit handler to destroy the default loop, so any
		3348	cleanup functions are called.
		3349
		3350	static void
		3351	program_exits (void)
		3352	{
		3353	ev_loop_destroy (EV_DEFAULT_UC);
		3354	}
		3355
		3356	...
		3357	atexit (program_exits);
3012		3358
3013		3359
3014	=head2 C<ev_async> - how to wake up an event loop	3360	=head2 C<ev_async> - how to wake up an event loop
3015		3361
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3362	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3023	it by calling C<ev_async_send>, which is thread- and signal safe.	3369	it by calling C<ev_async_send>, which is thread- and signal safe.
3024		3370
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3371	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3372	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3373	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3374	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3029		3375	of "global async watchers" by using a watcher on an otherwise unused
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3376	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3031	just the default loop.	3377	even without knowing which loop owns the signal.
3032		3378
3033	=head3 Queueing	3379	=head3 Queueing
3034		3380
3035	C<ev_async> does not support queueing of data in any way. The reason	3381	C<ev_async> does not support queueing of data in any way. The reason
3036	is that the author does not know of a simple (or any) algorithm for a	3382	is that the author does not know of a simple (or any) algorithm for a
…		…
3128	trust me.	3474	trust me.
3129		3475
3130	=item ev_async_send (loop, ev_async *)	3476	=item ev_async_send (loop, ev_async *)
3131		3477
3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3478	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3479	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3480	returns.
		3481
3134	C<ev_feed_event>, this call is safe to do from other threads, signal or	3482	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3483	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3136	section below on what exactly this means).	3484	embedding section below on what exactly this means).
3137		3485
3138	Note that, as with other watchers in libev, multiple events might get	3486	Note that, as with other watchers in libev, multiple events might get
3139	compressed into a single callback invocation (another way to look at this	3487	compressed into a single callback invocation (another way to look at
3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3488	this is that C<ev_async> watchers are level-triggered: they are set on
3141	reset when the event loop detects that).	3489	C<ev_async_send>, reset when the event loop detects that).
3142		3490
3143	This call incurs the overhead of a system call only once per event loop	3491	This call incurs the overhead of at most one extra system call per event
3144	iteration, so while the overhead might be noticeable, it doesn't apply to	3492	loop iteration, if the event loop is blocked, and no syscall at all if
3145	repeated calls to C<ev_async_send> for the same event loop.	3493	the event loop (or your program) is processing events. That means that
		3494	repeated calls are basically free (there is no need to avoid calls for
		3495	performance reasons) and that the overhead becomes smaller (typically
		3496	zero) under load.
3146		3497
3147	=item bool = ev_async_pending (ev_async *)	3498	=item bool = ev_async_pending (ev_async *)
3148		3499
3149	Returns a non-zero value when C<ev_async_send> has been called on the	3500	Returns a non-zero value when C<ev_async_send> has been called on the
3150	watcher but the event has not yet been processed (or even noted) by the	3501	watcher but the event has not yet been processed (or even noted) by the
…		…
3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3556	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3206		3557
3207	=item ev_feed_fd_event (loop, int fd, int revents)	3558	=item ev_feed_fd_event (loop, int fd, int revents)
3208		3559
3209	Feed an event on the given fd, as if a file descriptor backend detected	3560	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3561	the given events.
3211		3562
3212	=item ev_feed_signal_event (loop, int signum)	3563	=item ev_feed_signal_event (loop, int signum)
3213		3564
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3565	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3566	which is async-safe.
3216		3567
3217	=back	3568	=back
		3569
		3570
		3571	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3572
		3573	This section explains some common idioms that are not immediately
		3574	obvious. Note that examples are sprinkled over the whole manual, and this
		3575	section only contains stuff that wouldn't fit anywhere else.
		3576
		3577	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3578
		3579	Each watcher has, by default, a C<void *data> member that you can read
		3580	or modify at any time: libev will completely ignore it. This can be used
		3581	to associate arbitrary data with your watcher. If you need more data and
		3582	don't want to allocate memory separately and store a pointer to it in that
		3583	data member, you can also "subclass" the watcher type and provide your own
		3584	data:
		3585
		3586	struct my_io
		3587	{
		3588	ev_io io;
		3589	int otherfd;
		3590	void *somedata;
		3591	struct whatever *mostinteresting;
		3592	};
		3593
		3594	...
		3595	struct my_io w;
		3596	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3597
		3598	And since your callback will be called with a pointer to the watcher, you
		3599	can cast it back to your own type:
		3600
		3601	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3602	{
		3603	struct my_io *w = (struct my_io *)w_;
		3604	...
		3605	}
		3606
		3607	More interesting and less C-conformant ways of casting your callback
		3608	function type instead have been omitted.
		3609
		3610	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3611
		3612	Another common scenario is to use some data structure with multiple
		3613	embedded watchers, in effect creating your own watcher that combines
		3614	multiple libev event sources into one "super-watcher":
		3615
		3616	struct my_biggy
		3617	{
		3618	int some_data;
		3619	ev_timer t1;
		3620	ev_timer t2;
		3621	}
		3622
		3623	In this case getting the pointer to C<my_biggy> is a bit more
		3624	complicated: Either you store the address of your C<my_biggy> struct in
		3625	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3626	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3627	real programmers):
		3628
		3629	#include <stddef.h>
		3630
		3631	static void
		3632	t1_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t1));
		3636	}
		3637
		3638	static void
		3639	t2_cb (EV_P_ ev_timer *w, int revents)
		3640	{
		3641	struct my_biggy big = (struct my_biggy *)
		3642	(((char *)w) - offsetof (struct my_biggy, t2));
		3643	}
		3644
		3645	=head2 AVOIDING FINISHING BEFORE RETURNING
		3646
		3647	Often you have structures like this in event-based programs:
		3648
		3649	callback ()
		3650	{
		3651	free (request);
		3652	}
		3653
		3654	request = start_new_request (..., callback);
		3655
		3656	The intent is to start some "lengthy" operation. The C<request> could be
		3657	used to cancel the operation, or do other things with it.
		3658
		3659	It's not uncommon to have code paths in C<start_new_request> that
		3660	immediately invoke the callback, for example, to report errors. Or you add
		3661	some caching layer that finds that it can skip the lengthy aspects of the
		3662	operation and simply invoke the callback with the result.
		3663
		3664	The problem here is that this will happen I<before> C<start_new_request>
		3665	has returned, so C<request> is not set.
		3666
		3667	Even if you pass the request by some safer means to the callback, you
		3668	might want to do something to the request after starting it, such as
		3669	canceling it, which probably isn't working so well when the callback has
		3670	already been invoked.
		3671
		3672	A common way around all these issues is to make sure that
		3673	C<start_new_request> I<always> returns before the callback is invoked. If
		3674	C<start_new_request> immediately knows the result, it can artificially
		3675	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3676	example, or more sneakily, by reusing an existing (stopped) watcher and
		3677	pushing it into the pending queue:
		3678
		3679	ev_set_cb (watcher, callback);
		3680	ev_feed_event (EV_A_ watcher, 0);
		3681
		3682	This way, C<start_new_request> can safely return before the callback is
		3683	invoked, while not delaying callback invocation too much.
		3684
		3685	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3686
		3687	Often (especially in GUI toolkits) there are places where you have
		3688	I<modal> interaction, which is most easily implemented by recursively
		3689	invoking C<ev_run>.
		3690
		3691	This brings the problem of exiting - a callback might want to finish the
		3692	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3693	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3694	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3695	other combination: In these cases, a simple C<ev_break> will not work.
		3696
		3697	The solution is to maintain "break this loop" variable for each C<ev_run>
		3698	invocation, and use a loop around C<ev_run> until the condition is
		3699	triggered, using C<EVRUN_ONCE>:
		3700
		3701	// main loop
		3702	int exit_main_loop = 0;
		3703
		3704	while (!exit_main_loop)
		3705	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3706
		3707	// in a modal watcher
		3708	int exit_nested_loop = 0;
		3709
		3710	while (!exit_nested_loop)
		3711	ev_run (EV_A_ EVRUN_ONCE);
		3712
		3713	To exit from any of these loops, just set the corresponding exit variable:
		3714
		3715	// exit modal loop
		3716	exit_nested_loop = 1;
		3717
		3718	// exit main program, after modal loop is finished
		3719	exit_main_loop = 1;
		3720
		3721	// exit both
		3722	exit_main_loop = exit_nested_loop = 1;
		3723
		3724	=head2 THREAD LOCKING EXAMPLE
		3725
		3726	Here is a fictitious example of how to run an event loop in a different
		3727	thread from where callbacks are being invoked and watchers are
		3728	created/added/removed.
		3729
		3730	For a real-world example, see the C<EV::Loop::Async> perl module,
		3731	which uses exactly this technique (which is suited for many high-level
		3732	languages).
		3733
		3734	The example uses a pthread mutex to protect the loop data, a condition
		3735	variable to wait for callback invocations, an async watcher to notify the
		3736	event loop thread and an unspecified mechanism to wake up the main thread.
		3737
		3738	First, you need to associate some data with the event loop:
		3739
		3740	typedef struct {
		3741	mutex_t lock; /* global loop lock */
		3742	ev_async async_w;
		3743	thread_t tid;
		3744	cond_t invoke_cv;
		3745	} userdata;
		3746
		3747	void prepare_loop (EV_P)
		3748	{
		3749	// for simplicity, we use a static userdata struct.
		3750	static userdata u;
		3751
		3752	ev_async_init (&u->async_w, async_cb);
		3753	ev_async_start (EV_A_ &u->async_w);
		3754
		3755	pthread_mutex_init (&u->lock, 0);
		3756	pthread_cond_init (&u->invoke_cv, 0);
		3757
		3758	// now associate this with the loop
		3759	ev_set_userdata (EV_A_ u);
		3760	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3761	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3762
		3763	// then create the thread running ev_run
		3764	pthread_create (&u->tid, 0, l_run, EV_A);
		3765	}
		3766
		3767	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3768	solely to wake up the event loop so it takes notice of any new watchers
		3769	that might have been added:
		3770
		3771	static void
		3772	async_cb (EV_P_ ev_async *w, int revents)
		3773	{
		3774	// just used for the side effects
		3775	}
		3776
		3777	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3778	protecting the loop data, respectively.
		3779
		3780	static void
		3781	l_release (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_unlock (&u->lock);
		3785	}
		3786
		3787	static void
		3788	l_acquire (EV_P)
		3789	{
		3790	userdata *u = ev_userdata (EV_A);
		3791	pthread_mutex_lock (&u->lock);
		3792	}
		3793
		3794	The event loop thread first acquires the mutex, and then jumps straight
		3795	into C<ev_run>:
		3796
		3797	void *
		3798	l_run (void *thr_arg)
		3799	{
		3800	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3801
		3802	l_acquire (EV_A);
		3803	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3804	ev_run (EV_A_ 0);
		3805	l_release (EV_A);
		3806
		3807	return 0;
		3808	}
		3809
		3810	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3811	signal the main thread via some unspecified mechanism (signals? pipe
		3812	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3813	have been called (in a while loop because a) spurious wakeups are possible
		3814	and b) skipping inter-thread-communication when there are no pending
		3815	watchers is very beneficial):
		3816
		3817	static void
		3818	l_invoke (EV_P)
		3819	{
		3820	userdata *u = ev_userdata (EV_A);
		3821
		3822	while (ev_pending_count (EV_A))
		3823	{
		3824	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3825	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3826	}
		3827	}
		3828
		3829	Now, whenever the main thread gets told to invoke pending watchers, it
		3830	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3831	thread to continue:
		3832
		3833	static void
		3834	real_invoke_pending (EV_P)
		3835	{
		3836	userdata *u = ev_userdata (EV_A);
		3837
		3838	pthread_mutex_lock (&u->lock);
		3839	ev_invoke_pending (EV_A);
		3840	pthread_cond_signal (&u->invoke_cv);
		3841	pthread_mutex_unlock (&u->lock);
		3842	}
		3843
		3844	Whenever you want to start/stop a watcher or do other modifications to an
		3845	event loop, you will now have to lock:
		3846
		3847	ev_timer timeout_watcher;
		3848	userdata *u = ev_userdata (EV_A);
		3849
		3850	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3851
		3852	pthread_mutex_lock (&u->lock);
		3853	ev_timer_start (EV_A_ &timeout_watcher);
		3854	ev_async_send (EV_A_ &u->async_w);
		3855	pthread_mutex_unlock (&u->lock);
		3856
		3857	Note that sending the C<ev_async> watcher is required because otherwise
		3858	an event loop currently blocking in the kernel will have no knowledge
		3859	about the newly added timer. By waking up the loop it will pick up any new
		3860	watchers in the next event loop iteration.
		3861
		3862	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3863
		3864	While the overhead of a callback that e.g. schedules a thread is small, it
		3865	is still an overhead. If you embed libev, and your main usage is with some
		3866	kind of threads or coroutines, you might want to customise libev so that
		3867	doesn't need callbacks anymore.
		3868
		3869	Imagine you have coroutines that you can switch to using a function
		3870	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3871	and that due to some magic, the currently active coroutine is stored in a
		3872	global called C<current_coro>. Then you can build your own "wait for libev
		3873	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3874	the differing C<;> conventions):
		3875
		3876	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3877	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3878
		3879	That means instead of having a C callback function, you store the
		3880	coroutine to switch to in each watcher, and instead of having libev call
		3881	your callback, you instead have it switch to that coroutine.
		3882
		3883	A coroutine might now wait for an event with a function called
		3884	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3885	matter when, or whether the watcher is active or not when this function is
		3886	called):
		3887
		3888	void
		3889	wait_for_event (ev_watcher *w)
		3890	{
		3891	ev_set_cb (w, current_coro);
		3892	switch_to (libev_coro);
		3893	}
		3894
		3895	That basically suspends the coroutine inside C<wait_for_event> and
		3896	continues the libev coroutine, which, when appropriate, switches back to
		3897	this or any other coroutine.
		3898
		3899	You can do similar tricks if you have, say, threads with an event queue -
		3900	instead of storing a coroutine, you store the queue object and instead of
		3901	switching to a coroutine, you push the watcher onto the queue and notify
		3902	any waiters.
		3903
		3904	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3905	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3906
		3907	// my_ev.h
		3908	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3909	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3910	#include "../libev/ev.h"
		3911
		3912	// my_ev.c
		3913	#define EV_H "my_ev.h"
		3914	#include "../libev/ev.c"
		3915
		3916	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3917	F<my_ev.c> into your project. When properly specifying include paths, you
		3918	can even use F<ev.h> as header file name directly.
3218		3919
3219		3920
3220	=head1 LIBEVENT EMULATION	3921	=head1 LIBEVENT EMULATION
3221		3922
3222	Libev offers a compatibility emulation layer for libevent. It cannot	3923	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	3924	emulate the internals of libevent, so here are some usage hints:
3224		3925
3225	=over 4	3926	=over 4
		3927
		3928	=item * Only the libevent-1.4.1-beta API is being emulated.
		3929
		3930	This was the newest libevent version available when libev was implemented,
		3931	and is still mostly unchanged in 2010.
3226		3932
3227	=item * Use it by including <event.h>, as usual.	3933	=item * Use it by including <event.h>, as usual.
3228		3934
3229	=item * The following members are fully supported: ev_base, ev_callback,	3935	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	3936	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	3942	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	3943	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	3944	is an ev_pri field.
3239		3945
3240	=item * In libevent, the last base created gets the signals, in libev, the	3946	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	3947	base that registered the signal gets the signals.
3242		3948
3243	=item * Other members are not supported.	3949	=item * Other members are not supported.
3244		3950
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3951	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	3952	to use the libev header file and library.
3247		3953
3248	=back	3954	=back
3249		3955
3250	=head1 C++ SUPPORT	3956	=head1 C++ SUPPORT
		3957
		3958	=head2 C API
		3959
		3960	The normal C API should work fine when used from C++: both ev.h and the
		3961	libev sources can be compiled as C++. Therefore, code that uses the C API
		3962	will work fine.
		3963
		3964	Proper exception specifications might have to be added to callbacks passed
		3965	to libev: exceptions may be thrown only from watcher callbacks, all
		3966	other callbacks (allocator, syserr, loop acquire/release and periodic
		3967	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3968	()> specification. If you have code that needs to be compiled as both C
		3969	and C++ you can use the C<EV_THROW> macro for this:
		3970
		3971	static void
		3972	fatal_error (const char *msg) EV_THROW
		3973	{
		3974	perror (msg);
		3975	abort ();
		3976	}
		3977
		3978	...
		3979	ev_set_syserr_cb (fatal_error);
		3980
		3981	The only API functions that can currently throw exceptions are C<ev_run>,
		3982	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3983	because it runs cleanup watchers).
		3984
		3985	Throwing exceptions in watcher callbacks is only supported if libev itself
		3986	is compiled with a C++ compiler or your C and C++ environments allow
		3987	throwing exceptions through C libraries (most do).
		3988
		3989	=head2 C++ API
3251		3990
3252	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3991	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3253	you to use some convenience methods to start/stop watchers and also change	3992	you to use some convenience methods to start/stop watchers and also change
3254	the callback model to a model using method callbacks on objects.	3993	the callback model to a model using method callbacks on objects.
3255		3994
3256	To use it,	3995	To use it,
3257		3996
3258	#include <ev++.h>	3997	#include <ev++.h>
3259		3998
3260	This automatically includes F<ev.h> and puts all of its definitions (many	3999	This automatically includes F<ev.h> and puts all of its definitions (many
3261	of them macros) into the global namespace. All C++ specific things are	4000	of them macros) into the global namespace. All C++ specific things are
3262	put into the C<ev> namespace. It should support all the same embedding	4001	put into the C<ev> namespace. It should support all the same embedding
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	4004	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	4005	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	4006	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	4007	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		4008
3270	Currently, functions, and static and non-static member functions can be	4009	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	4010	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	4011	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	4012	you need support for other types of functors please contact the author
3274	it).	4013	(preferably after implementing it).
		4014
		4015	For all this to work, your C++ compiler either has to use the same calling
		4016	conventions as your C compiler (for static member functions), or you have
		4017	to embed libev and compile libev itself as C++.
3275		4018
3276	Here is a list of things available in the C<ev> namespace:	4019	Here is a list of things available in the C<ev> namespace:
3277		4020
3278	=over 4	4021	=over 4
3279		4022
…		…
3289	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4032	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3290		4033
3291	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4034	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3292	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4035	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3293	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4036	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3294	defines by many implementations.	4037	defined by many implementations.
3295		4038
3296	All of those classes have these methods:	4039	All of those classes have these methods:
3297		4040
3298	=over 4	4041	=over 4
3299		4042
…		…
3361	void operator() (ev::io &w, int revents)	4104	void operator() (ev::io &w, int revents)
3362	{	4105	{
3363	...	4106	...
3364	}	4107	}
3365	}	4108	}
3366		4109
3367	myfunctor f;	4110	myfunctor f;
3368		4111
3369	ev::io w;	4112	ev::io w;
3370	w.set (&f);	4113	w.set (&f);
3371		4114
…		…
3389	Associates a different C<struct ev_loop> with this watcher. You can only	4132	Associates a different C<struct ev_loop> with this watcher. You can only
3390	do this when the watcher is inactive (and not pending either).	4133	do this when the watcher is inactive (and not pending either).
3391		4134
3392	=item w->set ([arguments])	4135	=item w->set ([arguments])
3393		4136
3394	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4137	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4138	with the same arguments. Either this method or a suitable start method
3395	called at least once. Unlike the C counterpart, an active watcher gets	4139	must be called at least once. Unlike the C counterpart, an active watcher
3396	automatically stopped and restarted when reconfiguring it with this	4140	gets automatically stopped and restarted when reconfiguring it with this
3397	method.	4141	method.
		4142
		4143	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4144	clashing with the C<set (loop)> method.
3398		4145
3399	=item w->start ()	4146	=item w->start ()
3400		4147
3401	Starts the watcher. Note that there is no C<loop> argument, as the	4148	Starts the watcher. Note that there is no C<loop> argument, as the
3402	constructor already stores the event loop.	4149	constructor already stores the event loop.
3403		4150
		4151	=item w->start ([arguments])
		4152
		4153	Instead of calling C<set> and C<start> methods separately, it is often
		4154	convenient to wrap them in one call. Uses the same type of arguments as
		4155	the configure C<set> method of the watcher.
		4156
3404	=item w->stop ()	4157	=item w->stop ()
3405		4158
3406	Stops the watcher if it is active. Again, no C<loop> argument.	4159	Stops the watcher if it is active. Again, no C<loop> argument.
3407		4160
3408	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4161	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3420		4173
3421	=back	4174	=back
3422		4175
3423	=back	4176	=back
3424		4177
3425	Example: Define a class with an IO and idle watcher, start one of them in	4178	Example: Define a class with two I/O and idle watchers, start the I/O
3426	the constructor.	4179	watchers in the constructor.
3427		4180
3428	class myclass	4181	class myclass
3429	{	4182	{
3430	ev::io io ; void io_cb (ev::io &w, int revents);	4183	ev::io io ; void io_cb (ev::io &w, int revents);
		4184	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3431	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4185	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3432		4186
3433	myclass (int fd)	4187	myclass (int fd)
3434	{	4188	{
3435	io .set <myclass, &myclass::io_cb > (this);	4189	io .set <myclass, &myclass::io_cb > (this);
		4190	io2 .set <myclass, &myclass::io2_cb > (this);
3436	idle.set <myclass, &myclass::idle_cb> (this);	4191	idle.set <myclass, &myclass::idle_cb> (this);
3437		4192
3438	io.start (fd, ev::READ);	4193	io.set (fd, ev::WRITE); // configure the watcher
		4194	io.start (); // start it whenever convenient
		4195
		4196	io2.start (fd, ev::READ); // set + start in one call
3439	}	4197	}
3440	};	4198	};
3441		4199
3442		4200
3443	=head1 OTHER LANGUAGE BINDINGS	4201	=head1 OTHER LANGUAGE BINDINGS
…		…
3482	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4240	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3483		4241
3484	=item D	4242	=item D
3485		4243
3486	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4244	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3487	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4245	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3488		4246
3489	=item Ocaml	4247	=item Ocaml
3490		4248
3491	Erkki Seppala has written Ocaml bindings for libev, to be found at	4249	Erkki Seppala has written Ocaml bindings for libev, to be found at
3492	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4250	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3495		4253
3496	Brian Maher has written a partial interface to libev for lua (at the	4254	Brian Maher has written a partial interface to libev for lua (at the
3497	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4255	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3498	L<http://github.com/brimworks/lua-ev>.	4256	L<http://github.com/brimworks/lua-ev>.
3499		4257
		4258	=item Javascript
		4259
		4260	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4261
		4262	=item Others
		4263
		4264	There are others, and I stopped counting.
		4265
3500	=back	4266	=back
3501		4267
3502		4268
3503	=head1 MACRO MAGIC	4269	=head1 MACRO MAGIC
3504		4270
…		…
3517	loop argument"). The C<EV_A> form is used when this is the sole argument,	4283	loop argument"). The C<EV_A> form is used when this is the sole argument,
3518	C<EV_A_> is used when other arguments are following. Example:	4284	C<EV_A_> is used when other arguments are following. Example:
3519		4285
3520	ev_unref (EV_A);	4286	ev_unref (EV_A);
3521	ev_timer_add (EV_A_ watcher);	4287	ev_timer_add (EV_A_ watcher);
3522	ev_loop (EV_A_ 0);	4288	ev_run (EV_A_ 0);
3523		4289
3524	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4290	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3525	which is often provided by the following macro.	4291	which is often provided by the following macro.
3526		4292
3527	=item C<EV_P>, C<EV_P_>	4293	=item C<EV_P>, C<EV_P_>
…		…
3540	suitable for use with C<EV_A>.	4306	suitable for use with C<EV_A>.
3541		4307
3542	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4308	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3543		4309
3544	Similar to the other two macros, this gives you the value of the default	4310	Similar to the other two macros, this gives you the value of the default
3545	loop, if multiple loops are supported ("ev loop default").	4311	loop, if multiple loops are supported ("ev loop default"). The default loop
		4312	will be initialised if it isn't already initialised.
		4313
		4314	For non-multiplicity builds, these macros do nothing, so you always have
		4315	to initialise the loop somewhere.
3546		4316
3547	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4317	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3548		4318
3549	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4319	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3550	default loop has been initialised (C<UC> == unchecked). Their behaviour	4320	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3567	}	4337	}
3568		4338
3569	ev_check check;	4339	ev_check check;
3570	ev_check_init (&check, check_cb);	4340	ev_check_init (&check, check_cb);
3571	ev_check_start (EV_DEFAULT_ &check);	4341	ev_check_start (EV_DEFAULT_ &check);
3572	ev_loop (EV_DEFAULT_ 0);	4342	ev_run (EV_DEFAULT_ 0);
3573		4343
3574	=head1 EMBEDDING	4344	=head1 EMBEDDING
3575		4345
3576	Libev can (and often is) directly embedded into host	4346	Libev can (and often is) directly embedded into host
3577	applications. Examples of applications that embed it include the Deliantra	4347	applications. Examples of applications that embed it include the Deliantra
…		…
3617	ev_vars.h	4387	ev_vars.h
3618	ev_wrap.h	4388	ev_wrap.h
3619		4389
3620	ev_win32.c required on win32 platforms only	4390	ev_win32.c required on win32 platforms only
3621		4391
3622	ev_select.c only when select backend is enabled (which is enabled by default)	4392	ev_select.c only when select backend is enabled
3623	ev_poll.c only when poll backend is enabled (disabled by default)	4393	ev_poll.c only when poll backend is enabled
3624	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4394	ev_epoll.c only when the epoll backend is enabled
3625	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4395	ev_kqueue.c only when the kqueue backend is enabled
3626	ev_port.c only when the solaris port backend is enabled (disabled by default)	4396	ev_port.c only when the solaris port backend is enabled
3627		4397
3628	F<ev.c> includes the backend files directly when enabled, so you only need	4398	F<ev.c> includes the backend files directly when enabled, so you only need
3629	to compile this single file.	4399	to compile this single file.
3630		4400
3631	=head3 LIBEVENT COMPATIBILITY API	4401	=head3 LIBEVENT COMPATIBILITY API
…		…
3669	users of libev and the libev code itself must be compiled with compatible	4439	users of libev and the libev code itself must be compiled with compatible
3670	settings.	4440	settings.
3671		4441
3672	=over 4	4442	=over 4
3673		4443
		4444	=item EV_COMPAT3 (h)
		4445
		4446	Backwards compatibility is a major concern for libev. This is why this
		4447	release of libev comes with wrappers for the functions and symbols that
		4448	have been renamed between libev version 3 and 4.
		4449
		4450	You can disable these wrappers (to test compatibility with future
		4451	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4452	sources. This has the additional advantage that you can drop the C<struct>
		4453	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4454	typedef in that case.
		4455
		4456	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4457	and in some even more future version the compatibility code will be
		4458	removed completely.
		4459
3674	=item EV_STANDALONE (h)	4460	=item EV_STANDALONE (h)
3675		4461
3676	Must always be C<1> if you do not use autoconf configuration, which	4462	Must always be C<1> if you do not use autoconf configuration, which
3677	keeps libev from including F<config.h>, and it also defines dummy	4463	keeps libev from including F<config.h>, and it also defines dummy
3678	implementations for some libevent functions (such as logging, which is not	4464	implementations for some libevent functions (such as logging, which is not
3679	supported). It will also not define any of the structs usually found in	4465	supported). It will also not define any of the structs usually found in
3680	F<event.h> that are not directly supported by the libev core alone.	4466	F<event.h> that are not directly supported by the libev core alone.
3681		4467
3682	In standalone mode, libev will still try to automatically deduce the	4468	In standalone mode, libev will still try to automatically deduce the
3683	configuration, but has to be more conservative.	4469	configuration, but has to be more conservative.
		4470
		4471	=item EV_USE_FLOOR
		4472
		4473	If defined to be C<1>, libev will use the C<floor ()> function for its
		4474	periodic reschedule calculations, otherwise libev will fall back on a
		4475	portable (slower) implementation. If you enable this, you usually have to
		4476	link against libm or something equivalent. Enabling this when the C<floor>
		4477	function is not available will fail, so the safe default is to not enable
		4478	this.
3684		4479
3685	=item EV_USE_MONOTONIC	4480	=item EV_USE_MONOTONIC
3686		4481
3687	If defined to be C<1>, libev will try to detect the availability of the	4482	If defined to be C<1>, libev will try to detect the availability of the
3688	monotonic clock option at both compile time and runtime. Otherwise no	4483	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3773		4568
3774	If programs implement their own fd to handle mapping on win32, then this	4569	If programs implement their own fd to handle mapping on win32, then this
3775	macro can be used to override the C<close> function, useful to unregister	4570	macro can be used to override the C<close> function, useful to unregister
3776	file descriptors again. Note that the replacement function has to close	4571	file descriptors again. Note that the replacement function has to close
3777	the underlying OS handle.	4572	the underlying OS handle.
		4573
		4574	=item EV_USE_WSASOCKET
		4575
		4576	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4577	communication socket, which works better in some environments. Otherwise,
		4578	the normal C<socket> function will be used, which works better in other
		4579	environments.
3778		4580
3779	=item EV_USE_POLL	4581	=item EV_USE_POLL
3780		4582
3781	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4583	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3782	backend. Otherwise it will be enabled on non-win32 platforms. It	4584	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3818	If defined to be C<1>, libev will compile in support for the Linux inotify	4620	If defined to be C<1>, libev will compile in support for the Linux inotify
3819	interface to speed up C<ev_stat> watchers. Its actual availability will	4621	interface to speed up C<ev_stat> watchers. Its actual availability will
3820	be detected at runtime. If undefined, it will be enabled if the headers	4622	be detected at runtime. If undefined, it will be enabled if the headers
3821	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4623	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3822		4624
		4625	=item EV_NO_SMP
		4626
		4627	If defined to be C<1>, libev will assume that memory is always coherent
		4628	between threads, that is, threads can be used, but threads never run on
		4629	different cpus (or different cpu cores). This reduces dependencies
		4630	and makes libev faster.
		4631
		4632	=item EV_NO_THREADS
		4633
		4634	If defined to be C<1>, libev will assume that it will never be called from
		4635	different threads (that includes signal handlers), which is a stronger
		4636	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4637	libev faster.
		4638
3823	=item EV_ATOMIC_T	4639	=item EV_ATOMIC_T
3824		4640
3825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4641	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3826	access is atomic with respect to other threads or signal contexts. No such	4642	access is atomic with respect to other threads or signal contexts. No
3827	type is easily found in the C language, so you can provide your own type	4643	such type is easily found in the C language, so you can provide your own
3828	that you know is safe for your purposes. It is used both for signal handler "locking"	4644	type that you know is safe for your purposes. It is used both for signal
3829	as well as for signal and thread safety in C<ev_async> watchers.	4645	handler "locking" as well as for signal and thread safety in C<ev_async>
		4646	watchers.
3830		4647
3831	In the absence of this define, libev will use C<sig_atomic_t volatile>	4648	In the absence of this define, libev will use C<sig_atomic_t volatile>
3832	(from F<signal.h>), which is usually good enough on most platforms.	4649	(from F<signal.h>), which is usually good enough on most platforms.
3833		4650
3834	=item EV_H (h)	4651	=item EV_H (h)
…		…
3861	will have the C<struct ev_loop *> as first argument, and you can create	4678	will have the C<struct ev_loop *> as first argument, and you can create
3862	additional independent event loops. Otherwise there will be no support	4679	additional independent event loops. Otherwise there will be no support
3863	for multiple event loops and there is no first event loop pointer	4680	for multiple event loops and there is no first event loop pointer
3864	argument. Instead, all functions act on the single default loop.	4681	argument. Instead, all functions act on the single default loop.
3865		4682
		4683	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4684	default loop when multiplicity is switched off - you always have to
		4685	initialise the loop manually in this case.
		4686
3866	=item EV_MINPRI	4687	=item EV_MINPRI
3867		4688
3868	=item EV_MAXPRI	4689	=item EV_MAXPRI
3869		4690
3870	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4691	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3906	#define EV_USE_POLL 1	4727	#define EV_USE_POLL 1
3907	#define EV_CHILD_ENABLE 1	4728	#define EV_CHILD_ENABLE 1
3908	#define EV_ASYNC_ENABLE 1	4729	#define EV_ASYNC_ENABLE 1
3909		4730
3910	The actual value is a bitset, it can be a combination of the following	4731	The actual value is a bitset, it can be a combination of the following
3911	values:	4732	values (by default, all of these are enabled):
3912		4733
3913	=over 4	4734	=over 4
3914		4735
3915	=item C<1> - faster/larger code	4736	=item C<1> - faster/larger code
3916		4737
…		…
3920	code size by roughly 30% on amd64).	4741	code size by roughly 30% on amd64).
3921		4742
3922	When optimising for size, use of compiler flags such as C<-Os> with	4743	When optimising for size, use of compiler flags such as C<-Os> with
3923	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4744	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3924	assertions.	4745	assertions.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
3925		4749
3926	=item C<2> - faster/larger data structures	4750	=item C<2> - faster/larger data structures
3927		4751
3928	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4752	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3929	hash table sizes and so on. This will usually further increase code size	4753	hash table sizes and so on. This will usually further increase code size
3930	and can additionally have an effect on the size of data structures at	4754	and can additionally have an effect on the size of data structures at
3931	runtime.	4755	runtime.
3932		4756
		4757	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4758	(e.g. gcc with C<-Os>).
		4759
3933	=item C<4> - full API configuration	4760	=item C<4> - full API configuration
3934		4761
3935	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4762	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3936	enables multiplicity (C<EV_MULTIPLICITY>=1).	4763	enables multiplicity (C<EV_MULTIPLICITY>=1).
3937		4764
…		…
3967		4794
3968	With an intelligent-enough linker (gcc+binutils are intelligent enough	4795	With an intelligent-enough linker (gcc+binutils are intelligent enough
3969	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4796	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3970	your program might be left out as well - a binary starting a timer and an	4797	your program might be left out as well - a binary starting a timer and an
3971	I/O watcher then might come out at only 5Kb.	4798	I/O watcher then might come out at only 5Kb.
		4799
		4800	=item EV_API_STATIC
		4801
		4802	If this symbol is defined (by default it is not), then all identifiers
		4803	will have static linkage. This means that libev will not export any
		4804	identifiers, and you cannot link against libev anymore. This can be useful
		4805	when you embed libev, only want to use libev functions in a single file,
		4806	and do not want its identifiers to be visible.
		4807
		4808	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4809	wants to use libev.
		4810
		4811	This option only works when libev is compiled with a C compiler, as C++
		4812	doesn't support the required declaration syntax.
3972		4813
3973	=item EV_AVOID_STDIO	4814	=item EV_AVOID_STDIO
3974		4815
3975	If this is set to C<1> at compiletime, then libev will avoid using stdio	4816	If this is set to C<1> at compiletime, then libev will avoid using stdio
3976	functions (printf, scanf, perror etc.). This will increase the code size	4817	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4868	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4028	will be C<0>.	4869	will be C<0>.
4029		4870
4030	=item EV_VERIFY	4871	=item EV_VERIFY
4031		4872
4032	Controls how much internal verification (see C<ev_loop_verify ()>) will	4873	Controls how much internal verification (see C<ev_verify ()>) will
4033	be done: If set to C<0>, no internal verification code will be compiled	4874	be done: If set to C<0>, no internal verification code will be compiled
4034	in. If set to C<1>, then verification code will be compiled in, but not	4875	in. If set to C<1>, then verification code will be compiled in, but not
4035	called. If set to C<2>, then the internal verification code will be	4876	called. If set to C<2>, then the internal verification code will be
4036	called once per loop, which can slow down libev. If set to C<3>, then the	4877	called once per loop, which can slow down libev. If set to C<3>, then the
4037	verification code will be called very frequently, which will slow down	4878	verification code will be called very frequently, which will slow down
…		…
4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4961	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4121		4962
4122	#include "ev_cpp.h"	4963	#include "ev_cpp.h"
4123	#include "ev.c"	4964	#include "ev.c"
4124		4965
4125	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4966	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4126		4967
4127	=head2 THREADS AND COROUTINES	4968	=head2 THREADS AND COROUTINES
4128		4969
4129	=head3 THREADS	4970	=head3 THREADS
4130		4971
…		…
4181	default loop and triggering an C<ev_async> watcher from the default loop	5022	default loop and triggering an C<ev_async> watcher from the default loop
4182	watcher callback into the event loop interested in the signal.	5023	watcher callback into the event loop interested in the signal.
4183		5024
4184	=back	5025	=back
4185		5026
4186	=head4 THREAD LOCKING EXAMPLE	5027	See also L</THREAD LOCKING EXAMPLE>.
4187
4188	Here is a fictitious example of how to run an event loop in a different
4189	thread than where callbacks are being invoked and watchers are
4190	created/added/removed.
4191
4192	For a real-world example, see the C<EV::Loop::Async> perl module,
4193	which uses exactly this technique (which is suited for many high-level
4194	languages).
4195
4196	The example uses a pthread mutex to protect the loop data, a condition
4197	variable to wait for callback invocations, an async watcher to notify the
4198	event loop thread and an unspecified mechanism to wake up the main thread.
4199
4200	First, you need to associate some data with the event loop:
4201
4202	typedef struct {
4203	mutex_t lock; /* global loop lock */
4204	ev_async async_w;
4205	thread_t tid;
4206	cond_t invoke_cv;
4207	} userdata;
4208
4209	void prepare_loop (EV_P)
4210	{
4211	// for simplicity, we use a static userdata struct.
4212	static userdata u;
4213
4214	ev_async_init (&u->async_w, async_cb);
4215	ev_async_start (EV_A_ &u->async_w);
4216
4217	pthread_mutex_init (&u->lock, 0);
4218	pthread_cond_init (&u->invoke_cv, 0);
4219
4220	// now associate this with the loop
4221	ev_set_userdata (EV_A_ u);
4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4224
4225	// then create the thread running ev_loop
4226	pthread_create (&u->tid, 0, l_run, EV_A);
4227	}
4228
4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
4230	solely to wake up the event loop so it takes notice of any new watchers
4231	that might have been added:
4232
4233	static void
4234	async_cb (EV_P_ ev_async *w, int revents)
4235	{
4236	// just used for the side effects
4237	}
4238
4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4240	protecting the loop data, respectively.
4241
4242	static void
4243	l_release (EV_P)
4244	{
4245	userdata *u = ev_userdata (EV_A);
4246	pthread_mutex_unlock (&u->lock);
4247	}
4248
4249	static void
4250	l_acquire (EV_P)
4251	{
4252	userdata *u = ev_userdata (EV_A);
4253	pthread_mutex_lock (&u->lock);
4254	}
4255
4256	The event loop thread first acquires the mutex, and then jumps straight
4257	into C<ev_loop>:
4258
4259	void *
4260	l_run (void *thr_arg)
4261	{
4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4263
4264	l_acquire (EV_A);
4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4266	ev_loop (EV_A_ 0);
4267	l_release (EV_A);
4268
4269	return 0;
4270	}
4271
4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
4273	signal the main thread via some unspecified mechanism (signals? pipe
4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4275	have been called (in a while loop because a) spurious wakeups are possible
4276	and b) skipping inter-thread-communication when there are no pending
4277	watchers is very beneficial):
4278
4279	static void
4280	l_invoke (EV_P)
4281	{
4282	userdata *u = ev_userdata (EV_A);
4283
4284	while (ev_pending_count (EV_A))
4285	{
4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
4288	}
4289	}
4290
4291	Now, whenever the main thread gets told to invoke pending watchers, it
4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4293	thread to continue:
4294
4295	static void
4296	real_invoke_pending (EV_P)
4297	{
4298	userdata *u = ev_userdata (EV_A);
4299
4300	pthread_mutex_lock (&u->lock);
4301	ev_invoke_pending (EV_A);
4302	pthread_cond_signal (&u->invoke_cv);
4303	pthread_mutex_unlock (&u->lock);
4304	}
4305
4306	Whenever you want to start/stop a watcher or do other modifications to an
4307	event loop, you will now have to lock:
4308
4309	ev_timer timeout_watcher;
4310	userdata *u = ev_userdata (EV_A);
4311
4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4313
4314	pthread_mutex_lock (&u->lock);
4315	ev_timer_start (EV_A_ &timeout_watcher);
4316	ev_async_send (EV_A_ &u->async_w);
4317	pthread_mutex_unlock (&u->lock);
4318
4319	Note that sending the C<ev_async> watcher is required because otherwise
4320	an event loop currently blocking in the kernel will have no knowledge
4321	about the newly added timer. By waking up the loop it will pick up any new
4322	watchers in the next event loop iteration.
4323		5028
4324	=head3 COROUTINES	5029	=head3 COROUTINES
4325		5030
4326	Libev is very accommodating to coroutines ("cooperative threads"):	5031	Libev is very accommodating to coroutines ("cooperative threads"):
4327	libev fully supports nesting calls to its functions from different	5032	libev fully supports nesting calls to its functions from different
4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5033	coroutines (e.g. you can call C<ev_run> on the same loop from two
4329	different coroutines, and switch freely between both coroutines running	5034	different coroutines, and switch freely between both coroutines running
4330	the loop, as long as you don't confuse yourself). The only exception is	5035	the loop, as long as you don't confuse yourself). The only exception is
4331	that you must not do this from C<ev_periodic> reschedule callbacks.	5036	that you must not do this from C<ev_periodic> reschedule callbacks.
4332		5037
4333	Care has been taken to ensure that libev does not keep local state inside	5038	Care has been taken to ensure that libev does not keep local state inside
4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5039	C<ev_run>, and other calls do not usually allow for coroutine switches as
4335	they do not call any callbacks.	5040	they do not call any callbacks.
4336		5041
4337	=head2 COMPILER WARNINGS	5042	=head2 COMPILER WARNINGS
4338		5043
4339	Depending on your compiler and compiler settings, you might get no or a	5044	Depending on your compiler and compiler settings, you might get no or a
…		…
4423	=head3 C<kqueue> is buggy	5128	=head3 C<kqueue> is buggy
4424		5129
4425	The kqueue syscall is broken in all known versions - most versions support	5130	The kqueue syscall is broken in all known versions - most versions support
4426	only sockets, many support pipes.	5131	only sockets, many support pipes.
4427		5132
4428	Libev tries to work around this by not using C<kqueue> by default on	5133	Libev tries to work around this by not using C<kqueue> by default on this
4429	this rotten platform, but of course you can still ask for it when creating	5134	rotten platform, but of course you can still ask for it when creating a
4430	a loop.	5135	loop - embedding a socket-only kqueue loop into a select-based one is
		5136	probably going to work well.
4431		5137
4432	=head3 C<poll> is buggy	5138	=head3 C<poll> is buggy
4433		5139
4434	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5140	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4435	implementation by something calling C<kqueue> internally around the 10.5.6	5141	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4454		5160
4455	=head3 C<errno> reentrancy	5161	=head3 C<errno> reentrancy
4456		5162
4457	The default compile environment on Solaris is unfortunately so	5163	The default compile environment on Solaris is unfortunately so
4458	thread-unsafe that you can't even use components/libraries compiled	5164	thread-unsafe that you can't even use components/libraries compiled
4459	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5165	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4460	isn't defined by default.	5166	defined by default. A valid, if stupid, implementation choice.
4461		5167
4462	If you want to use libev in threaded environments you have to make sure	5168	If you want to use libev in threaded environments you have to make sure
4463	it's compiled with C<_REENTRANT> defined.	5169	it's compiled with C<_REENTRANT> defined.
4464		5170
4465	=head3 Event port backend	5171	=head3 Event port backend
4466		5172
4467	The scalable event interface for Solaris is called "event ports". Unfortunately,	5173	The scalable event interface for Solaris is called "event
4468	this mechanism is very buggy. If you run into high CPU usage, your program	5174	ports". Unfortunately, this mechanism is very buggy in all major
		5175	releases. If you run into high CPU usage, your program freezes or you get
4469	freezes or you get a large number of spurious wakeups, make sure you have	5176	a large number of spurious wakeups, make sure you have all the relevant
4470	all the relevant and latest kernel patches applied. No, I don't know which	5177	and latest kernel patches applied. No, I don't know which ones, but there
4471	ones, but there are multiple ones.	5178	are multiple ones to apply, and afterwards, event ports actually work
		5179	great.
4472		5180
4473	If you can't get it to work, you can try running the program by setting	5181	If you can't get it to work, you can try running the program by setting
4474	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	5182	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4475	C<select> backends.	5183	C<select> backends.
4476		5184
4477	=head2 AIX POLL BUG	5185	=head2 AIX POLL BUG
4478		5186
4479	AIX unfortunately has a broken C<poll.h> header. Libev works around	5187	AIX unfortunately has a broken C<poll.h> header. Libev works around
4480	this by trying to avoid the poll backend altogether (i.e. it's not even	5188	this by trying to avoid the poll backend altogether (i.e. it's not even
4481	compiled in), which normally isn't a big problem as C<select> works fine	5189	compiled in), which normally isn't a big problem as C<select> works fine
4482	with large bitsets, and AIX is dead anyway.	5190	with large bitsets on AIX, and AIX is dead anyway.
4483		5191
4484	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5192	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4485		5193
4486	=head3 General issues	5194	=head3 General issues
4487		5195
…		…
4489	requires, and its I/O model is fundamentally incompatible with the POSIX	5197	requires, and its I/O model is fundamentally incompatible with the POSIX
4490	model. Libev still offers limited functionality on this platform in	5198	model. Libev still offers limited functionality on this platform in
4491	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4492	descriptors. This only applies when using Win32 natively, not when using	5200	descriptors. This only applies when using Win32 natively, not when using
4493	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5201	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4494	as every compielr comes with a slightly differently broken/incompatible	5202	as every compiler comes with a slightly differently broken/incompatible
4495	environment.	5203	environment.
4496		5204
4497	Lifting these limitations would basically require the full	5205	Lifting these limitations would basically require the full
4498	re-implementation of the I/O system. If you are into this kind of thing,	5206	re-implementation of the I/O system. If you are into this kind of thing,
4499	then note that glib does exactly that for you in a very portable way (note	5207	then note that glib does exactly that for you in a very portable way (note
…		…
4593	structure (guaranteed by POSIX but not by ISO C for example), but it also	5301	structure (guaranteed by POSIX but not by ISO C for example), but it also
4594	assumes that the same (machine) code can be used to call any watcher	5302	assumes that the same (machine) code can be used to call any watcher
4595	callback: The watcher callbacks have different type signatures, but libev	5303	callback: The watcher callbacks have different type signatures, but libev
4596	calls them using an C<ev_watcher *> internally.	5304	calls them using an C<ev_watcher *> internally.
4597		5305
		5306	=item null pointers and integer zero are represented by 0 bytes
		5307
		5308	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5309	relies on this setting pointers and integers to null.
		5310
		5311	=item pointer accesses must be thread-atomic
		5312
		5313	Accessing a pointer value must be atomic, it must both be readable and
		5314	writable in one piece - this is the case on all current architectures.
		5315
4598	=item C<sig_atomic_t volatile> must be thread-atomic as well	5316	=item C<sig_atomic_t volatile> must be thread-atomic as well
4599		5317
4600	The type C<sig_atomic_t volatile> (or whatever is defined as	5318	The type C<sig_atomic_t volatile> (or whatever is defined as
4601	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5319	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4602	threads. This is not part of the specification for C<sig_atomic_t>, but is	5320	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4610	thread" or will block signals process-wide, both behaviours would	5328	thread" or will block signals process-wide, both behaviours would
4611	be compatible with libev. Interaction between C<sigprocmask> and	5329	be compatible with libev. Interaction between C<sigprocmask> and
4612	C<pthread_sigmask> could complicate things, however.	5330	C<pthread_sigmask> could complicate things, however.
4613		5331
4614	The most portable way to handle signals is to block signals in all threads	5332	The most portable way to handle signals is to block signals in all threads
4615	except the initial one, and run the default loop in the initial thread as	5333	except the initial one, and run the signal handling loop in the initial
4616	well.	5334	thread as well.
4617		5335
4618	=item C<long> must be large enough for common memory allocation sizes	5336	=item C<long> must be large enough for common memory allocation sizes
4619		5337
4620	To improve portability and simplify its API, libev uses C<long> internally	5338	To improve portability and simplify its API, libev uses C<long> internally
4621	instead of C<size_t> when allocating its data structures. On non-POSIX	5339	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4624	watchers.	5342	watchers.
4625		5343
4626	=item C<double> must hold a time value in seconds with enough accuracy	5344	=item C<double> must hold a time value in seconds with enough accuracy
4627		5345
4628	The type C<double> is used to represent timestamps. It is required to	5346	The type C<double> is used to represent timestamps. It is required to
4629	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5347	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4630	enough for at least into the year 4000. This requirement is fulfilled by	5348	good enough for at least into the year 4000 with millisecond accuracy
		5349	(the design goal for libev). This requirement is overfulfilled by
4631	implementations implementing IEEE 754, which is basically all existing	5350	implementations using IEEE 754, which is basically all existing ones.
		5351
4632	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5352	With IEEE 754 doubles, you get microsecond accuracy until at least the
4633	2200.	5353	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5354	is either obsolete or somebody patched it to use C<long double> or
		5355	something like that, just kidding).
4634		5356
4635	=back	5357	=back
4636		5358
4637	If you know of other additional requirements drop me a note.	5359	If you know of other additional requirements drop me a note.
4638		5360
…		…
4700	=item Processing ev_async_send: O(number_of_async_watchers)	5422	=item Processing ev_async_send: O(number_of_async_watchers)
4701		5423
4702	=item Processing signals: O(max_signal_number)	5424	=item Processing signals: O(max_signal_number)
4703		5425
4704	Sending involves a system call I<iff> there were no other C<ev_async_send>	5426	Sending involves a system call I<iff> there were no other C<ev_async_send>
4705	calls in the current loop iteration. Checking for async and signal events	5427	calls in the current loop iteration and the loop is currently
		5428	blocked. Checking for async and signal events involves iterating over all
4706	involves iterating over all running async watchers or all signal numbers.	5429	running async watchers or all signal numbers.
4707		5430
4708	=back	5431	=back
4709		5432
4710		5433
4711	=head1 PORTING FROM LIBEV 3.X TO 4.X	5434	=head1 PORTING FROM LIBEV 3.X TO 4.X
4712		5435
4713	The major version 4 introduced some minor incompatible changes to the API.	5436	The major version 4 introduced some incompatible changes to the API.
4714		5437
4715	At the moment, the C<ev.h> header file tries to implement superficial	5438	At the moment, the C<ev.h> header file provides compatibility definitions
4716	compatibility, so most programs should still compile. Those might be	5439	for all changes, so most programs should still compile. The compatibility
4717	removed in later versions of libev, so better update early than late.	5440	layer might be removed in later versions of libev, so better update to the
		5441	new API early than late.
4718		5442
4719	=over 4	5443	=over 4
4720		5444
4721	=item C<ev_loop_count> renamed to C<ev_iteration>	5445	=item C<EV_COMPAT3> backwards compatibility mechanism
4722		5446
4723	=item C<ev_loop_depth> renamed to C<ev_depth>	5447	The backward compatibility mechanism can be controlled by
		5448	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5449	section.
4724		5450
4725	=item C<ev_loop_verify> renamed to C<ev_verify>	5451	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5452
		5453	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5454
		5455	ev_loop_destroy (EV_DEFAULT_UC);
		5456	ev_loop_fork (EV_DEFAULT);
		5457
		5458	=item function/symbol renames
		5459
		5460	A number of functions and symbols have been renamed:
		5461
		5462	ev_loop => ev_run
		5463	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5464	EVLOOP_ONESHOT => EVRUN_ONCE
		5465
		5466	ev_unloop => ev_break
		5467	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5468	EVUNLOOP_ONE => EVBREAK_ONE
		5469	EVUNLOOP_ALL => EVBREAK_ALL
		5470
		5471	EV_TIMEOUT => EV_TIMER
		5472
		5473	ev_loop_count => ev_iteration
		5474	ev_loop_depth => ev_depth
		5475	ev_loop_verify => ev_verify
4726		5476
4727	Most functions working on C<struct ev_loop> objects don't have an	5477	Most functions working on C<struct ev_loop> objects don't have an
4728	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5478	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5479	associated constants have been renamed to not collide with the C<struct
		5480	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5481	as all other watcher types. Note that C<ev_loop_fork> is still called
4729	still called C<ev_loop_fork> because it would otherwise clash with the	5482	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4730	C<ev_fork> typedef.	5483	typedef.
4731
4732	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4733
4734	This is a simple rename - all other watcher types use their name
4735	as revents flag, and now C<ev_timer> does, too.
4736
4737	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4738	and continue to be present for the foreseeable future, so this is mostly a
4739	documentation change.
4740		5484
4741	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5485	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4742		5486
4743	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5487	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4744	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5488	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4751		5495
4752	=over 4	5496	=over 4
4753		5497
4754	=item active	5498	=item active
4755		5499
4756	A watcher is active as long as it has been started (has been attached to	5500	A watcher is active as long as it has been started and not yet stopped.
4757	an event loop) but not yet stopped (disassociated from the event loop).	5501	See L</WATCHER STATES> for details.
4758		5502
4759	=item application	5503	=item application
4760		5504
4761	In this document, an application is whatever is using libev.	5505	In this document, an application is whatever is using libev.
		5506
		5507	=item backend
		5508
		5509	The part of the code dealing with the operating system interfaces.
4762		5510
4763	=item callback	5511	=item callback
4764		5512
4765	The address of a function that is called when some event has been	5513	The address of a function that is called when some event has been
4766	detected. Callbacks are being passed the event loop, the watcher that	5514	detected. Callbacks are being passed the event loop, the watcher that
4767	received the event, and the actual event bitset.	5515	received the event, and the actual event bitset.
4768		5516
4769	=item callback invocation	5517	=item callback/watcher invocation
4770		5518
4771	The act of calling the callback associated with a watcher.	5519	The act of calling the callback associated with a watcher.
4772		5520
4773	=item event	5521	=item event
4774		5522
…		…
4793	The model used to describe how an event loop handles and processes	5541	The model used to describe how an event loop handles and processes
4794	watchers and events.	5542	watchers and events.
4795		5543
4796	=item pending	5544	=item pending
4797		5545
4798	A watcher is pending as soon as the corresponding event has been detected,	5546	A watcher is pending as soon as the corresponding event has been
4799	and stops being pending as soon as the watcher will be invoked or its	5547	detected. See L</WATCHER STATES> for details.
4800	pending status is explicitly cleared by the application.
4801
4802	A watcher can be pending, but not active. Stopping a watcher also clears
4803	its pending status.
4804		5548
4805	=item real time	5549	=item real time
4806		5550
4807	The physical time that is observed. It is apparently strictly monotonic :)	5551	The physical time that is observed. It is apparently strictly monotonic :)
4808		5552
4809	=item wall-clock time	5553	=item wall-clock time
4810		5554
4811	The time and date as shown on clocks. Unlike real time, it can actually	5555	The time and date as shown on clocks. Unlike real time, it can actually
4812	be wrong and jump forwards and backwards, e.g. when the you adjust your	5556	be wrong and jump forwards and backwards, e.g. when you adjust your
4813	clock.	5557	clock.
4814		5558
4815	=item watcher	5559	=item watcher
4816		5560
4817	A data structure that describes interest in certain events. Watchers need	5561	A data structure that describes interest in certain events. Watchers need
4818	to be started (attached to an event loop) before they can receive events.	5562	to be started (attached to an event loop) before they can receive events.
4819		5563
4820	=item watcher invocation
4821
4822	The act of calling the callback associated with a watcher.
4823
4824	=back	5564	=back
4825		5565
4826	=head1 AUTHOR	5566	=head1 AUTHOR
4827		5567
4828	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5568	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5569	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4829		5570

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