ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC vs.
Revision 1.433 by root, Fri May 2 07:05:42 2014 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
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity 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 (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
134	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	146	time differences (e.g. delays) throughout libev.
136		147
137	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
138		149
139	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	151	and internal errors (bugs).
…		…
164		175
165	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
166		177
167	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
168	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
169	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>.
170		182
171	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
172		184
173	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
174	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
175	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 >>).
176		194
177	=item int ev_version_major ()	195	=item int ev_version_major ()
178		196
179	=item int ev_version_minor ()	197	=item int ev_version_minor ()
180		198
…		…
191	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
192	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
193	not a problem.	211	not a problem.
194		212
195	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
196	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
197		216
198	assert (("libev version mismatch",	217	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
201		220
…		…
212	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
214		233
215	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
216		235
217	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
218	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
219	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
220	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
221	(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
222	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
223		243
224	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
225		245
226	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
227	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
228	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
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
231		251
232	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
233		253
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
235		255
236	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
237	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
238	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
239	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
…		…
265	}	285	}
266		286
267	...	287	...
268	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
269		289
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
271		291
272	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
273	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
274	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
275	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
…		…
287	}	307	}
288		308
289	...	309	...
290	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
291		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
292	=back	325	=back
293		326
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		328
296	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
297	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
298	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
299		332
300	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
301	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
302	not.	335	do not.
303		336
304	=over 4	337	=over 4
305		338
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		340
308	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
309	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
310	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
311	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".
312		351
313	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
314	function.	353	function (or via the C<EV_DEFAULT> macro).
315		354
316	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
317	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
318	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).
319		359
320	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,
321	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
322	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
323	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
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	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.
326		384
327	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
328	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>).
329		387
330	The following flags are supported:	388	The following flags are supported:
…		…
340		398
341	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
342	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
343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
344	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
345	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
346	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).
347		407
348	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
349		409
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	411	make libev check for a fork in each iteration by enabling this flag.
352	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 sequence
…		…
366	environment variable.	425	environment variable.
367		426
368	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
369		428
370	When this flag is specified, then libev will not attempt to use the	429	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	430	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	431	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.	432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		433
375	=item C<EVFLAG_SIGNALFD>	434	=item C<EVFLAG_SIGNALFD>
376		435
377	When this flag is specified, then libev will attempt to use the	436	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	437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes is both faster and might make	438	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data.	439	it possible to get the queued signal data. It can also simplify signal
		440	handling with threads, as long as you properly block signals in your
		441	threads that are not interested in handling them.
381		442
382	Signalfd will not be used by default as this changes your signal mask, and	443	Signalfd will not be used by default as this changes your signal mask, and
383	there are a lot of shoddy libraries and programs (glib's threadpool for	444	there are a lot of shoddy libraries and programs (glib's threadpool for
384	example) that can't properly initialise their signal masks.	445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
385		461
386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
387		463
388	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
389	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
417	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
418		494
419	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
420	kernels).	496	kernels).
421		497
422	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
423	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
424	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
425	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
426		502
427	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
428	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
429	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
430	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
431	so on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
432	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
433	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
434	hard to detect.	512	and is of course hard to detect.
435		513
436	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
437	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
438	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
439	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
440	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
441	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
442	events to filter out spurious ones, recreating the set when required.	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
		524	not least, it also refuses to work with some file descriptors which work
		525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
443		530
444	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
445	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
446	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
447	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
484		571
485	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
486	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
487	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
488	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
489	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
490	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
491	cases	578	drops fds silently in similarly hard-to-detect cases.
492		579
493	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
494		581
495	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
496	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
513	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
514		601
515	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
516	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
517		604
518	Please note that Solaris event ports can deliver a lot of spurious
519	notifications, so you need to use non-blocking I/O or other means to avoid
520	blocking when no data (or space) is available.
521
522	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
523	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
524	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
525	might perform better.	608	might perform better.
526		609
527	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
528	notifications, this backend actually performed fully to specification
529	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
530	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
531		624
532	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
533	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
534		627
535	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
536		629
537	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
538	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
539	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
540		633
541	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
542		643
543	=back	644	=back
544		645
545	If one or more of the backend flags are or'ed into the flags value,	646	If one or more of the backend flags are or'ed into the flags value,
546	then only these backends will be tried (in the reverse order as listed	647	then only these backends will be tried (in the reverse order as listed
547	here). If none are specified, all backends in C<ev_recommended_backends	648	here). If none are specified, all backends in C<ev_recommended_backends
548	()> will be tried.	649	()> will be tried.
549		650
550	Example: This is the most typical usage.
551
552	if (!ev_default_loop (0))
553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
554
555	Example: Restrict libev to the select and poll backends, and do not allow
556	environment settings to be taken into account:
557
558	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
559
560	Example: Use whatever libev has to offer, but make sure that kqueue is
561	used if available (warning, breaks stuff, best use only with your own
562	private event loop and only if you know the OS supports your types of
563	fds):
564
565	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
566
567	=item struct ev_loop *ev_loop_new (unsigned int flags)
568
569	Similar to C<ev_default_loop>, but always creates a new event loop that is
570	always distinct from the default loop. Unlike the default loop, it cannot
571	handle signal and child watchers, and attempts to do so will be greeted by
572	undefined behaviour (or a failed assertion if assertions are enabled).
573
574	Note that this function I<is> thread-safe, and the recommended 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.	651	Example: Try to create a event loop that uses epoll and nothing else.
579		652
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	654	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
583		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
584	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
585		663
586	Destroys the default loop again (frees all memory and kernel state	664	Destroys an event loop object (frees all memory and kernel state
587	etc.). None of the active event watchers will be stopped in the normal	665	etc.). None of the active event watchers will be stopped in the normal
588	sense, so e.g. C<ev_is_active> might still return true. It is your	666	sense, so e.g. C<ev_is_active> might still return true. It is your
589	responsibility to either stop all watchers cleanly yourself I<before>	667	responsibility to either stop all watchers cleanly yourself I<before>
590	calling this function, or cope with the fact afterwards (which is usually	668	calling this function, or cope with the fact afterwards (which is usually
591	the easiest thing, you can just ignore the watchers and/or C<free ()> them	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
593		671
594	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
595	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
596	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
597		675
598	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
599	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
600	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
601	C<ev_loop_new> and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
602		684
603	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
604		686
605	Like C<ev_default_destroy>, but destroys an event loop created by an
606	earlier call to C<ev_loop_new>.
607
608	=item ev_default_fork ()
609
610	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations
611	to reinitialise the kernel state for backends that have one. Despite the	688	to reinitialise the kernel state for backends that have one. Despite
612	name, you can call it anytime, but it makes most sense after forking, in	689	the name, you can call it anytime you are allowed to start or stop
613	the child process (or both child and parent, but that again makes little	690	watchers (except inside an C<ev_prepare> callback), but it makes most
614	sense). You I<must> call it in the child before using any of the libev	691	sense after forking, in the child process. You I<must> call it (or use
615	functions, and it will only take effect at the next C<ev_loop> iteration.	692	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		693
		694	Again, you I<have> to call it on I<any> loop that you want to re-use after
		695	a fork, I<even if you do not plan to use the loop in the parent>. This is
		696	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		697	during fork.
616		698
617	On the other hand, you only need to call this function in the child	699	On the other hand, you only need to call this function in the child
618	process if and only if you want to use the event library in the child. If	700	process if and only if you want to use the event loop in the child. If
619	you just fork+exec, you don't have to call it at all.	701	you just fork+exec or create a new loop in the child, you don't have to
		702	call it at all (in fact, C<epoll> is so badly broken that it makes a
		703	difference, but libev will usually detect this case on its own and do a
		704	costly reset of the backend).
620		705
621	The function itself is quite fast and it's usually not a problem to call	706	The function itself is quite fast and it's usually not a problem to call
622	it just in case after a fork. To make this easy, the function will fit in	707	it just in case after a fork.
623	quite nicely into a call to C<pthread_atfork>:
624		708
		709	Example: Automate calling C<ev_loop_fork> on the default loop when
		710	using pthreads.
		711
		712	static void
		713	post_fork_child (void)
		714	{
		715	ev_loop_fork (EV_DEFAULT);
		716	}
		717
		718	...
625	pthread_atfork (0, 0, ev_default_fork);	719	pthread_atfork (0, 0, post_fork_child);
626
627	=item ev_loop_fork (loop)
628
629	Like C<ev_default_fork>, but acts on an event loop created by
630	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
631	after fork that you want to re-use in the child, and how you do this is
632	entirely your own problem.
633		720
634	=item int ev_is_default_loop (loop)	721	=item int ev_is_default_loop (loop)
635		722
636	Returns true when the given loop is, in fact, the default loop, and false	723	Returns true when the given loop is, in fact, the default loop, and false
637	otherwise.	724	otherwise.
638		725
639	=item unsigned int ev_loop_count (loop)	726	=item unsigned int ev_iteration (loop)
640		727
641	Returns the count of loop iterations for the loop, which is identical to	728	Returns the current iteration count for the event loop, which is identical
642	the number of times libev did poll for new events. It starts at C<0> and	729	to the number of times libev did poll for new events. It starts at C<0>
643	happily wraps around with enough iterations.	730	and happily wraps around with enough iterations.
644		731
645	This value can sometimes be useful as a generation counter of sorts (it	732	This value can sometimes be useful as a generation counter of sorts (it
646	"ticks" the number of loop iterations), as it roughly corresponds with	733	"ticks" the number of loop iterations), as it roughly corresponds with
647	C<ev_prepare> and C<ev_check> calls.	734	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		735	prepare and check phases.
648		736
649	=item unsigned int ev_loop_depth (loop)	737	=item unsigned int ev_depth (loop)
650		738
651	Returns the number of times C<ev_loop> was entered minus the number of	739	Returns the number of times C<ev_run> was entered minus the number of
652	times C<ev_loop> was exited, in other words, the recursion depth.	740	times C<ev_run> was exited normally, in other words, the recursion depth.
653		741
654	Outside C<ev_loop>, this number is zero. In a callback, this number is	742	Outside C<ev_run>, this number is zero. In a callback, this number is
655	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	743	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
656	in which case it is higher.	744	in which case it is higher.
657		745
658	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	746	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
659	etc.), doesn't count as exit.	747	throwing an exception etc.), doesn't count as "exit" - consider this
		748	as a hint to avoid such ungentleman-like behaviour unless it's really
		749	convenient, in which case it is fully supported.
660		750
661	=item unsigned int ev_backend (loop)	751	=item unsigned int ev_backend (loop)
662		752
663	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	753	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
664	use.	754	use.
…		…
673		763
674	=item ev_now_update (loop)	764	=item ev_now_update (loop)
675		765
676	Establishes the current time by querying the kernel, updating the time	766	Establishes the current time by querying the kernel, updating the time
677	returned by C<ev_now ()> in the progress. This is a costly operation and	767	returned by C<ev_now ()> in the progress. This is a costly operation and
678	is usually done automatically within C<ev_loop ()>.	768	is usually done automatically within C<ev_run ()>.
679		769
680	This function is rarely useful, but when some event callback runs for a	770	This function is rarely useful, but when some event callback runs for a
681	very long time without entering the event loop, updating libev's idea of	771	very long time without entering the event loop, updating libev's idea of
682	the current time is a good idea.	772	the current time is a good idea.
683		773
684	See also L<The special problem of time updates> in the C<ev_timer> section.	774	See also L</The special problem of time updates> in the C<ev_timer> section.
685		775
686	=item ev_suspend (loop)	776	=item ev_suspend (loop)
687		777
688	=item ev_resume (loop)	778	=item ev_resume (loop)
689		779
690	These two functions suspend and resume a loop, for use when the loop is	780	These two functions suspend and resume an event loop, for use when the
691	not used for a while and timeouts should not be processed.	781	loop is not used for a while and timeouts should not be processed.
692		782
693	A typical use case would be an interactive program such as a game: When	783	A typical use case would be an interactive program such as a game: When
694	the user presses C<^Z> to suspend the game and resumes it an hour later it	784	the user presses C<^Z> to suspend the game and resumes it an hour later it
695	would be best to handle timeouts as if no time had actually passed while	785	would be best to handle timeouts as if no time had actually passed while
696	the program was suspended. This can be achieved by calling C<ev_suspend>	786	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
698	C<ev_resume> directly afterwards to resume timer processing.	788	C<ev_resume> directly afterwards to resume timer processing.
699		789
700	Effectively, all C<ev_timer> watchers will be delayed by the time spend	790	Effectively, all C<ev_timer> watchers will be delayed by the time spend
701	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	791	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
702	will be rescheduled (that is, they will lose any events that would have	792	will be rescheduled (that is, they will lose any events that would have
703	occured while suspended).	793	occurred while suspended).
704		794
705	After calling C<ev_suspend> you B<must not> call I<any> function on the	795	After calling C<ev_suspend> you B<must not> call I<any> function on the
706	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	796	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
707	without a previous call to C<ev_suspend>.	797	without a previous call to C<ev_suspend>.
708		798
709	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	799	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
710	event loop time (see C<ev_now_update>).	800	event loop time (see C<ev_now_update>).
711		801
712	=item ev_loop (loop, int flags)	802	=item bool ev_run (loop, int flags)
713		803
714	Finally, this is it, the event handler. This function usually is called	804	Finally, this is it, the event handler. This function usually is called
715	after you have initialised all your watchers and you want to start	805	after you have initialised all your watchers and you want to start
716	handling events.	806	handling events. It will ask the operating system for any new events, call
		807	the watcher callbacks, and then repeat the whole process indefinitely: This
		808	is why event loops are called I<loops>.
717		809
718	If the flags argument is specified as C<0>, it will not return until	810	If the flags argument is specified as C<0>, it will keep handling events
719	either no event watchers are active anymore or C<ev_unloop> was called.	811	until either no event watchers are active anymore or C<ev_break> was
		812	called.
720		813
		814	The return value is false if there are no more active watchers (which
		815	usually means "all jobs done" or "deadlock"), and true in all other cases
		816	(which usually means " you should call C<ev_run> again").
		817
721	Please note that an explicit C<ev_unloop> is usually better than	818	Please note that an explicit C<ev_break> is usually better than
722	relying on all watchers to be stopped when deciding when a program has	819	relying on all watchers to be stopped when deciding when a program has
723	finished (especially in interactive programs), but having a program	820	finished (especially in interactive programs), but having a program
724	that automatically loops as long as it has to and no longer by virtue	821	that automatically loops as long as it has to and no longer by virtue
725	of relying on its watchers stopping correctly, that is truly a thing of	822	of relying on its watchers stopping correctly, that is truly a thing of
726	beauty.	823	beauty.
727		824
		825	This function is I<mostly> exception-safe - you can break out of a
		826	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		827	exception and so on. This does not decrement the C<ev_depth> value, nor
		828	will it clear any outstanding C<EVBREAK_ONE> breaks.
		829
728	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	830	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
729	those events and any already outstanding ones, but will not block your	831	those events and any already outstanding ones, but will not wait and
730	process in case there are no events and will return after one iteration of	832	block your process in case there are no events and will return after one
731	the loop.	833	iteration of the loop. This is sometimes useful to poll and handle new
		834	events while doing lengthy calculations, to keep the program responsive.
732		835
733	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	836	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
734	necessary) and will handle those and any already outstanding ones. It	837	necessary) and will handle those and any already outstanding ones. It
735	will block your process until at least one new event arrives (which could	838	will block your process until at least one new event arrives (which could
736	be an event internal to libev itself, so there is no guarantee that a	839	be an event internal to libev itself, so there is no guarantee that a
737	user-registered callback will be called), and will return after one	840	user-registered callback will be called), and will return after one
738	iteration of the loop.	841	iteration of the loop.
739		842
740	This is useful if you are waiting for some external event in conjunction	843	This is useful if you are waiting for some external event in conjunction
741	with something not expressible using other libev watchers (i.e. "roll your	844	with something not expressible using other libev watchers (i.e. "roll your
742	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	845	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
743	usually a better approach for this kind of thing.	846	usually a better approach for this kind of thing.
744		847
745	Here are the gory details of what C<ev_loop> does:	848	Here are the gory details of what C<ev_run> does (this is for your
		849	understanding, not a guarantee that things will work exactly like this in
		850	future versions):
746		851
		852	- Increment loop depth.
		853	- Reset the ev_break status.
747	- Before the first iteration, call any pending watchers.	854	- Before the first iteration, call any pending watchers.
		855	LOOP:
748	* If EVFLAG_FORKCHECK was used, check for a fork.	856	- If EVFLAG_FORKCHECK was used, check for a fork.
749	- If a fork was detected (by any means), queue and call all fork watchers.	857	- If a fork was detected (by any means), queue and call all fork watchers.
750	- Queue and call all prepare watchers.	858	- Queue and call all prepare watchers.
		859	- If ev_break was called, goto FINISH.
751	- If we have been forked, detach and recreate the kernel state	860	- If we have been forked, detach and recreate the kernel state
752	as to not disturb the other process.	861	as to not disturb the other process.
753	- Update the kernel state with all outstanding changes.	862	- Update the kernel state with all outstanding changes.
754	- Update the "event loop time" (ev_now ()).	863	- Update the "event loop time" (ev_now ()).
755	- Calculate for how long to sleep or block, if at all	864	- Calculate for how long to sleep or block, if at all
756	(active idle watchers, EVLOOP_NONBLOCK or not having	865	(active idle watchers, EVRUN_NOWAIT or not having
757	any active watchers at all will result in not sleeping).	866	any active watchers at all will result in not sleeping).
758	- Sleep if the I/O and timer collect interval say so.	867	- Sleep if the I/O and timer collect interval say so.
		868	- Increment loop iteration counter.
759	- Block the process, waiting for any events.	869	- Block the process, waiting for any events.
760	- Queue all outstanding I/O (fd) events.	870	- Queue all outstanding I/O (fd) events.
761	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	871	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
762	- Queue all expired timers.	872	- Queue all expired timers.
763	- Queue all expired periodics.	873	- Queue all expired periodics.
764	- Unless any events are pending now, queue all idle watchers.	874	- Queue all idle watchers with priority higher than that of pending events.
765	- Queue all check watchers.	875	- Queue all check watchers.
766	- Call all queued watchers in reverse order (i.e. check watchers first).	876	- Call all queued watchers in reverse order (i.e. check watchers first).
767	Signals and child watchers are implemented as I/O watchers, and will	877	Signals and child watchers are implemented as I/O watchers, and will
768	be handled here by queueing them when their watcher gets executed.	878	be handled here by queueing them when their watcher gets executed.
769	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	879	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
770	were used, or there are no active watchers, return, otherwise	880	were used, or there are no active watchers, goto FINISH, otherwise
771	continue with step *.	881	continue with step LOOP.
		882	FINISH:
		883	- Reset the ev_break status iff it was EVBREAK_ONE.
		884	- Decrement the loop depth.
		885	- Return.
772		886
773	Example: Queue some jobs and then loop until no events are outstanding	887	Example: Queue some jobs and then loop until no events are outstanding
774	anymore.	888	anymore.
775		889
776	... queue jobs here, make sure they register event watchers as long	890	... queue jobs here, make sure they register event watchers as long
777	... as they still have work to do (even an idle watcher will do..)	891	... as they still have work to do (even an idle watcher will do..)
778	ev_loop (my_loop, 0);	892	ev_run (my_loop, 0);
779	... jobs done or somebody called unloop. yeah!	893	... jobs done or somebody called break. yeah!
780		894
781	=item ev_unloop (loop, how)	895	=item ev_break (loop, how)
782		896
783	Can be used to make a call to C<ev_loop> return early (but only after it	897	Can be used to make a call to C<ev_run> return early (but only after it
784	has processed all outstanding events). The C<how> argument must be either	898	has processed all outstanding events). The C<how> argument must be either
785	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	899	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
786	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	900	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
787		901
788	This "unloop state" will be cleared when entering C<ev_loop> again.	902	This "break state" will be cleared on the next call to C<ev_run>.
789		903
790	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	904	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		905	which case it will have no effect.
791		906
792	=item ev_ref (loop)	907	=item ev_ref (loop)
793		908
794	=item ev_unref (loop)	909	=item ev_unref (loop)
795		910
796	Ref/unref can be used to add or remove a reference count on the event	911	Ref/unref can be used to add or remove a reference count on the event
797	loop: Every watcher keeps one reference, and as long as the reference	912	loop: Every watcher keeps one reference, and as long as the reference
798	count is nonzero, C<ev_loop> will not return on its own.	913	count is nonzero, C<ev_run> will not return on its own.
799		914
800	This is useful when you have a watcher that you never intend to	915	This is useful when you have a watcher that you never intend to
801	unregister, but that nevertheless should not keep C<ev_loop> from	916	unregister, but that nevertheless should not keep C<ev_run> from
802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	917	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
803	before stopping it.	918	before stopping it.
804		919
805	As an example, libev itself uses this for its internal signal pipe: It	920	As an example, libev itself uses this for its internal signal pipe: It
806	is not visible to the libev user and should not keep C<ev_loop> from	921	is not visible to the libev user and should not keep C<ev_run> from
807	exiting if no event watchers registered by it are active. It is also an	922	exiting if no event watchers registered by it are active. It is also an
808	excellent way to do this for generic recurring timers or from within	923	excellent way to do this for generic recurring timers or from within
809	third-party libraries. Just remember to I<unref after start> and I<ref	924	third-party libraries. Just remember to I<unref after start> and I<ref
810	before stop> (but only if the watcher wasn't active before, or was active	925	before stop> (but only if the watcher wasn't active before, or was active
811	before, respectively. Note also that libev might stop watchers itself	926	before, respectively. Note also that libev might stop watchers itself
812	(e.g. non-repeating timers) in which case you have to C<ev_ref>	927	(e.g. non-repeating timers) in which case you have to C<ev_ref>
813	in the callback).	928	in the callback).
814		929
815	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	930	Example: Create a signal watcher, but keep it from keeping C<ev_run>
816	running when nothing else is active.	931	running when nothing else is active.
817		932
818	ev_signal exitsig;	933	ev_signal exitsig;
819	ev_signal_init (&exitsig, sig_cb, SIGINT);	934	ev_signal_init (&exitsig, sig_cb, SIGINT);
820	ev_signal_start (loop, &exitsig);	935	ev_signal_start (loop, &exitsig);
821	evf_unref (loop);	936	ev_unref (loop);
822		937
823	Example: For some weird reason, unregister the above signal handler again.	938	Example: For some weird reason, unregister the above signal handler again.
824		939
825	ev_ref (loop);	940	ev_ref (loop);
826	ev_signal_stop (loop, &exitsig);	941	ev_signal_stop (loop, &exitsig);
…		…
846	overhead for the actual polling but can deliver many events at once.	961	overhead for the actual polling but can deliver many events at once.
847		962
848	By setting a higher I<io collect interval> you allow libev to spend more	963	By setting a higher I<io collect interval> you allow libev to spend more
849	time collecting I/O events, so you can handle more events per iteration,	964	time collecting I/O events, so you can handle more events per iteration,
850	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	965	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
851	C<ev_timer>) will be not affected. Setting this to a non-null value will	966	C<ev_timer>) will not be affected. Setting this to a non-null value will
852	introduce an additional C<ev_sleep ()> call into most loop iterations. The	967	introduce an additional C<ev_sleep ()> call into most loop iterations. The
853	sleep time ensures that libev will not poll for I/O events more often then	968	sleep time ensures that libev will not poll for I/O events more often then
854	once per this interval, on average.	969	once per this interval, on average (as long as the host time resolution is
		970	good enough).
855		971
856	Likewise, by setting a higher I<timeout collect interval> you allow libev	972	Likewise, by setting a higher I<timeout collect interval> you allow libev
857	to spend more time collecting timeouts, at the expense of increased	973	to spend more time collecting timeouts, at the expense of increased
858	latency/jitter/inexactness (the watcher callback will be called	974	latency/jitter/inexactness (the watcher callback will be called
859	later). C<ev_io> watchers will not be affected. Setting this to a non-null	975	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
865	usually doesn't make much sense to set it to a lower value than C<0.01>,	981	usually doesn't make much sense to set it to a lower value than C<0.01>,
866	as this approaches the timing granularity of most systems. Note that if	982	as this approaches the timing granularity of most systems. Note that if
867	you do transactions with the outside world and you can't increase the	983	you do transactions with the outside world and you can't increase the
868	parallelity, then this setting will limit your transaction rate (if you	984	parallelity, then this setting will limit your transaction rate (if you
869	need to poll once per transaction and the I/O collect interval is 0.01,	985	need to poll once per transaction and the I/O collect interval is 0.01,
870	then you can't do more than 100 transations per second).	986	then you can't do more than 100 transactions per second).
871		987
872	Setting the I<timeout collect interval> can improve the opportunity for	988	Setting the I<timeout collect interval> can improve the opportunity for
873	saving power, as the program will "bundle" timer callback invocations that	989	saving power, as the program will "bundle" timer callback invocations that
874	are "near" in time together, by delaying some, thus reducing the number of	990	are "near" in time together, by delaying some, thus reducing the number of
875	times the process sleeps and wakes up again. Another useful technique to	991	times the process sleeps and wakes up again. Another useful technique to
…		…
883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	999	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
884		1000
885	=item ev_invoke_pending (loop)	1001	=item ev_invoke_pending (loop)
886		1002
887	This call will simply invoke all pending watchers while resetting their	1003	This call will simply invoke all pending watchers while resetting their
888	pending state. Normally, C<ev_loop> does this automatically when required,	1004	pending state. Normally, C<ev_run> does this automatically when required,
889	but when overriding the invoke callback this call comes handy.	1005	but when overriding the invoke callback this call comes handy. This
		1006	function can be invoked from a watcher - this can be useful for example
		1007	when you want to do some lengthy calculation and want to pass further
		1008	event handling to another thread (you still have to make sure only one
		1009	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
890		1010
891	=item int ev_pending_count (loop)	1011	=item int ev_pending_count (loop)
892		1012
893	Returns the number of pending watchers - zero indicates that no watchers	1013	Returns the number of pending watchers - zero indicates that no watchers
894	are pending.	1014	are pending.
895		1015
896	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1016	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
897		1017
898	This overrides the invoke pending functionality of the loop: Instead of	1018	This overrides the invoke pending functionality of the loop: Instead of
899	invoking all pending watchers when there are any, C<ev_loop> will call	1019	invoking all pending watchers when there are any, C<ev_run> will call
900	this callback instead. This is useful, for example, when you want to	1020	this callback instead. This is useful, for example, when you want to
901	invoke the actual watchers inside another context (another thread etc.).	1021	invoke the actual watchers inside another context (another thread etc.).
902		1022
903	If you want to reset the callback, use C<ev_invoke_pending> as new	1023	If you want to reset the callback, use C<ev_invoke_pending> as new
904	callback.	1024	callback.
905		1025
906	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1026	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
907		1027
908	Sometimes you want to share the same loop between multiple threads. This	1028	Sometimes you want to share the same loop between multiple threads. This
909	can be done relatively simply by putting mutex_lock/unlock calls around	1029	can be done relatively simply by putting mutex_lock/unlock calls around
910	each call to a libev function.	1030	each call to a libev function.
911		1031
912	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1032	However, C<ev_run> can run an indefinite time, so it is not feasible
913	wait for it to return. One way around this is to wake up the loop via	1033	to wait for it to return. One way around this is to wake up the event
914	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1034	loop via C<ev_break> and C<ev_async_send>, another way is to set these
915	and I<acquire> callbacks on the loop.	1035	I<release> and I<acquire> callbacks on the loop.
916		1036
917	When set, then C<release> will be called just before the thread is	1037	When set, then C<release> will be called just before the thread is
918	suspended waiting for new events, and C<acquire> is called just	1038	suspended waiting for new events, and C<acquire> is called just
919	afterwards.	1039	afterwards.
920		1040
…		…
923		1043
924	While event loop modifications are allowed between invocations of	1044	While event loop modifications are allowed between invocations of
925	C<release> and C<acquire> (that's their only purpose after all), no	1045	C<release> and C<acquire> (that's their only purpose after all), no
926	modifications done will affect the event loop, i.e. adding watchers will	1046	modifications done will affect the event loop, i.e. adding watchers will
927	have no effect on the set of file descriptors being watched, or the time	1047	have no effect on the set of file descriptors being watched, or the time
928	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1048	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
929	to take note of any changes you made.	1049	to take note of any changes you made.
930		1050
931	In theory, threads executing C<ev_loop> will be async-cancel safe between	1051	In theory, threads executing C<ev_run> will be async-cancel safe between
932	invocations of C<release> and C<acquire>.	1052	invocations of C<release> and C<acquire>.
933		1053
934	See also the locking example in the C<THREADS> section later in this	1054	See also the locking example in the C<THREADS> section later in this
935	document.	1055	document.
936		1056
937	=item ev_set_userdata (loop, void *data)	1057	=item ev_set_userdata (loop, void *data)
938		1058
939	=item ev_userdata (loop)	1059	=item void *ev_userdata (loop)
940		1060
941	Set and retrieve a single C<void *> associated with a loop. When	1061	Set and retrieve a single C<void *> associated with a loop. When
942	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1062	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
943	C<0.>	1063	C<0>.
944		1064
945	These two functions can be used to associate arbitrary data with a loop,	1065	These two functions can be used to associate arbitrary data with a loop,
946	and are intended solely for the C<invoke_pending_cb>, C<release> and	1066	and are intended solely for the C<invoke_pending_cb>, C<release> and
947	C<acquire> callbacks described above, but of course can be (ab-)used for	1067	C<acquire> callbacks described above, but of course can be (ab-)used for
948	any other purpose as well.	1068	any other purpose as well.
949		1069
950	=item ev_loop_verify (loop)	1070	=item ev_verify (loop)
951		1071
952	This function only does something when C<EV_VERIFY> support has been	1072	This function only does something when C<EV_VERIFY> support has been
953	compiled in, which is the default for non-minimal builds. It tries to go	1073	compiled in, which is the default for non-minimal builds. It tries to go
954	through all internal structures and checks them for validity. If anything	1074	through all internal structures and checks them for validity. If anything
955	is found to be inconsistent, it will print an error message to standard	1075	is found to be inconsistent, it will print an error message to standard
…		…
966		1086
967	In the following description, uppercase C<TYPE> in names stands for the	1087	In the following description, uppercase C<TYPE> in names stands for the
968	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1088	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
969	watchers and C<ev_io_start> for I/O watchers.	1089	watchers and C<ev_io_start> for I/O watchers.
970		1090
971	A watcher is a structure that you create and register to record your	1091	A watcher is an opaque structure that you allocate and register to record
972	interest in some event. For instance, if you want to wait for STDIN to	1092	your interest in some event. To make a concrete example, imagine you want
973	become readable, you would create an C<ev_io> watcher for that:	1093	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1094	for that:
974		1095
975	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1096	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
976	{	1097	{
977	ev_io_stop (w);	1098	ev_io_stop (w);
978	ev_unloop (loop, EVUNLOOP_ALL);	1099	ev_break (loop, EVBREAK_ALL);
979	}	1100	}
980		1101
981	struct ev_loop *loop = ev_default_loop (0);	1102	struct ev_loop *loop = ev_default_loop (0);
982		1103
983	ev_io stdin_watcher;	1104	ev_io stdin_watcher;
984		1105
985	ev_init (&stdin_watcher, my_cb);	1106	ev_init (&stdin_watcher, my_cb);
986	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1107	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
987	ev_io_start (loop, &stdin_watcher);	1108	ev_io_start (loop, &stdin_watcher);
988		1109
989	ev_loop (loop, 0);	1110	ev_run (loop, 0);
990		1111
991	As you can see, you are responsible for allocating the memory for your	1112	As you can see, you are responsible for allocating the memory for your
992	watcher structures (and it is I<usually> a bad idea to do this on the	1113	watcher structures (and it is I<usually> a bad idea to do this on the
993	stack).	1114	stack).
994		1115
995	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1116	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
996	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1117	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
997		1118
998	Each watcher structure must be initialised by a call to C<ev_init	1119	Each watcher structure must be initialised by a call to C<ev_init (watcher
999	(watcher *, callback)>, which expects a callback to be provided. This	1120	*, callback)>, which expects a callback to be provided. This callback is
1000	callback gets invoked each time the event occurs (or, in the case of I/O	1121	invoked each time the event occurs (or, in the case of I/O watchers, each
1001	watchers, each time the event loop detects that the file descriptor given	1122	time the event loop detects that the file descriptor given is readable
1002	is readable and/or writable).	1123	and/or writable).
1003		1124
1004	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1125	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1005	macro to configure it, with arguments specific to the watcher type. There	1126	macro to configure it, with arguments specific to the watcher type. There
1006	is also a macro to combine initialisation and setting in one call: C<<	1127	is also a macro to combine initialisation and setting in one call: C<<
1007	ev_TYPE_init (watcher *, callback, ...) >>.	1128	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1030	=item C<EV_WRITE>	1151	=item C<EV_WRITE>
1031		1152
1032	The file descriptor in the C<ev_io> watcher has become readable and/or	1153	The file descriptor in the C<ev_io> watcher has become readable and/or
1033	writable.	1154	writable.
1034		1155
1035	=item C<EV_TIMEOUT>	1156	=item C<EV_TIMER>
1036		1157
1037	The C<ev_timer> watcher has timed out.	1158	The C<ev_timer> watcher has timed out.
1038		1159
1039	=item C<EV_PERIODIC>	1160	=item C<EV_PERIODIC>
1040		1161
…		…
1058		1179
1059	=item C<EV_PREPARE>	1180	=item C<EV_PREPARE>
1060		1181
1061	=item C<EV_CHECK>	1182	=item C<EV_CHECK>
1062		1183
1063	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1184	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1064	to gather new events, and all C<ev_check> watchers are invoked just after	1185	gather new events, and all C<ev_check> watchers are queued (not invoked)
1065	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1186	just after C<ev_run> has gathered them, but before it queues any callbacks
		1187	for any received events. That means C<ev_prepare> watchers are the last
		1188	watchers invoked before the event loop sleeps or polls for new events, and
		1189	C<ev_check> watchers will be invoked before any other watchers of the same
		1190	or lower priority within an event loop iteration.
		1191
1066	received events. Callbacks of both watcher types can start and stop as	1192	Callbacks of both watcher types can start and stop as many watchers as
1067	many watchers as they want, and all of them will be taken into account	1193	they want, and all of them will be taken into account (for example, a
1068	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1194	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1069	C<ev_loop> from blocking).	1195	blocking).
1070		1196
1071	=item C<EV_EMBED>	1197	=item C<EV_EMBED>
1072		1198
1073	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1199	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1074		1200
1075	=item C<EV_FORK>	1201	=item C<EV_FORK>
1076		1202
1077	The event loop has been resumed in the child process after fork (see	1203	The event loop has been resumed in the child process after fork (see
1078	C<ev_fork>).	1204	C<ev_fork>).
		1205
		1206	=item C<EV_CLEANUP>
		1207
		1208	The event loop is about to be destroyed (see C<ev_cleanup>).
1079		1209
1080	=item C<EV_ASYNC>	1210	=item C<EV_ASYNC>
1081		1211
1082	The given async watcher has been asynchronously notified (see C<ev_async>).	1212	The given async watcher has been asynchronously notified (see C<ev_async>).
1083		1213
…		…
1193		1323
1194	=item callback ev_cb (ev_TYPE *watcher)	1324	=item callback ev_cb (ev_TYPE *watcher)
1195		1325
1196	Returns the callback currently set on the watcher.	1326	Returns the callback currently set on the watcher.
1197		1327
1198	=item ev_cb_set (ev_TYPE *watcher, callback)	1328	=item ev_set_cb (ev_TYPE *watcher, callback)
1199		1329
1200	Change the callback. You can change the callback at virtually any time	1330	Change the callback. You can change the callback at virtually any time
1201	(modulo threads).	1331	(modulo threads).
1202		1332
1203	=item ev_set_priority (ev_TYPE *watcher, int priority)	1333	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1221	or might not have been clamped to the valid range.	1351	or might not have been clamped to the valid range.
1222		1352
1223	The default priority used by watchers when no priority has been set is	1353	The default priority used by watchers when no priority has been set is
1224	always C<0>, which is supposed to not be too high and not be too low :).	1354	always C<0>, which is supposed to not be too high and not be too low :).
1225		1355
1226	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1356	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1227	priorities.	1357	priorities.
1228		1358
1229	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1359	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1230		1360
1231	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1361	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1256	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1386	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1257	functions that do not need a watcher.	1387	functions that do not need a watcher.
1258		1388
1259	=back	1389	=back
1260		1390
		1391	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1392	OWN COMPOSITE WATCHERS> idioms.
1261		1393
1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1394	=head2 WATCHER STATES
1263		1395
1264	Each watcher has, by default, a member C<void *data> that you can change	1396	There are various watcher states mentioned throughout this manual -
1265	and read at any time: libev will completely ignore it. This can be used	1397	active, pending and so on. In this section these states and the rules to
1266	to associate arbitrary data with your watcher. If you need more data and	1398	transition between them will be described in more detail - and while these
1267	don't want to allocate memory and store a pointer to it in that data	1399	rules might look complicated, they usually do "the right thing".
1268	member, you can also "subclass" the watcher type and provide your own
1269	data:
1270		1400
1271	struct my_io	1401	=over 4
1272	{
1273	ev_io io;
1274	int otherfd;
1275	void *somedata;
1276	struct whatever *mostinteresting;
1277	};
1278		1402
1279	...	1403	=item initialised
1280	struct my_io w;
1281	ev_io_init (&w.io, my_cb, fd, EV_READ);
1282		1404
1283	And since your callback will be called with a pointer to the watcher, you	1405	Before a watcher can be registered with the event loop it has to be
1284	can cast it back to your own type:	1406	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1407	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1285		1408
1286	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1409	In this state it is simply some block of memory that is suitable for
1287	{	1410	use in an event loop. It can be moved around, freed, reused etc. at
1288	struct my_io *w = (struct my_io *)w_;	1411	will - as long as you either keep the memory contents intact, or call
1289	...	1412	C<ev_TYPE_init> again.
1290	}
1291		1413
1292	More interesting and less C-conformant ways of casting your callback type	1414	=item started/running/active
1293	instead have been omitted.
1294		1415
1295	Another common scenario is to use some data structure with multiple	1416	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1296	embedded watchers:	1417	property of the event loop, and is actively waiting for events. While in
		1418	this state it cannot be accessed (except in a few documented ways), moved,
		1419	freed or anything else - the only legal thing is to keep a pointer to it,
		1420	and call libev functions on it that are documented to work on active watchers.
1297		1421
1298	struct my_biggy	1422	=item pending
1299	{
1300	int some_data;
1301	ev_timer t1;
1302	ev_timer t2;
1303	}
1304		1423
1305	In this case getting the pointer to C<my_biggy> is a bit more	1424	If a watcher is active and libev determines that an event it is interested
1306	complicated: Either you store the address of your C<my_biggy> struct	1425	in has occurred (such as a timer expiring), it will become pending. It will
1307	in the C<data> member of the watcher (for woozies), or you need to use	1426	stay in this pending state until either it is stopped or its callback is
1308	some pointer arithmetic using C<offsetof> inside your watchers (for real	1427	about to be invoked, so it is not normally pending inside the watcher
1309	programmers):	1428	callback.
1310		1429
1311	#include <stddef.h>	1430	The watcher might or might not be active while it is pending (for example,
		1431	an expired non-repeating timer can be pending but no longer active). If it
		1432	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1433	but it is still property of the event loop at this time, so cannot be
		1434	moved, freed or reused. And if it is active the rules described in the
		1435	previous item still apply.
1312		1436
1313	static void	1437	It is also possible to feed an event on a watcher that is not active (e.g.
1314	t1_cb (EV_P_ ev_timer *w, int revents)	1438	via C<ev_feed_event>), in which case it becomes pending without being
1315	{	1439	active.
1316	struct my_biggy big = (struct my_biggy *)
1317	(((char *)w) - offsetof (struct my_biggy, t1));
1318	}
1319		1440
1320	static void	1441	=item stopped
1321	t2_cb (EV_P_ ev_timer *w, int revents)	1442
1322	{	1443	A watcher can be stopped implicitly by libev (in which case it might still
1323	struct my_biggy big = (struct my_biggy *)	1444	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1324	(((char *)w) - offsetof (struct my_biggy, t2));	1445	latter will clear any pending state the watcher might be in, regardless
1325	}	1446	of whether it was active or not, so stopping a watcher explicitly before
		1447	freeing it is often a good idea.
		1448
		1449	While stopped (and not pending) the watcher is essentially in the
		1450	initialised state, that is, it can be reused, moved, modified in any way
		1451	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1452	it again).
		1453
		1454	=back
1326		1455
1327	=head2 WATCHER PRIORITY MODELS	1456	=head2 WATCHER PRIORITY MODELS
1328		1457
1329	Many event loops support I<watcher priorities>, which are usually small	1458	Many event loops support I<watcher priorities>, which are usually small
1330	integers that influence the ordering of event callback invocation	1459	integers that influence the ordering of event callback invocation
…		…
1373		1502
1374	For example, to emulate how many other event libraries handle priorities,	1503	For example, to emulate how many other event libraries handle priorities,
1375	you can associate an C<ev_idle> watcher to each such watcher, and in	1504	you can associate an C<ev_idle> watcher to each such watcher, and in
1376	the normal watcher callback, you just start the idle watcher. The real	1505	the normal watcher callback, you just start the idle watcher. The real
1377	processing is done in the idle watcher callback. This causes libev to	1506	processing is done in the idle watcher callback. This causes libev to
1378	continously poll and process kernel event data for the watcher, but when	1507	continuously poll and process kernel event data for the watcher, but when
1379	the lock-out case is known to be rare (which in turn is rare :), this is	1508	the lock-out case is known to be rare (which in turn is rare :), this is
1380	workable.	1509	workable.
1381		1510
1382	Usually, however, the lock-out model implemented that way will perform	1511	Usually, however, the lock-out model implemented that way will perform
1383	miserably under the type of load it was designed to handle. In that case,	1512	miserably under the type of load it was designed to handle. In that case,
…		…
1397	{	1526	{
1398	// stop the I/O watcher, we received the event, but	1527	// stop the I/O watcher, we received the event, but
1399	// are not yet ready to handle it.	1528	// are not yet ready to handle it.
1400	ev_io_stop (EV_A_ w);	1529	ev_io_stop (EV_A_ w);
1401		1530
1402	// start the idle watcher to ahndle the actual event.	1531	// start the idle watcher to handle the actual event.
1403	// it will not be executed as long as other watchers	1532	// it will not be executed as long as other watchers
1404	// with the default priority are receiving events.	1533	// with the default priority are receiving events.
1405	ev_idle_start (EV_A_ &idle);	1534	ev_idle_start (EV_A_ &idle);
1406	}	1535	}
1407		1536
…		…
1457	In general you can register as many read and/or write event watchers per	1586	In general you can register as many read and/or write event watchers per
1458	fd as you want (as long as you don't confuse yourself). Setting all file	1587	fd as you want (as long as you don't confuse yourself). Setting all file
1459	descriptors to non-blocking mode is also usually a good idea (but not	1588	descriptors to non-blocking mode is also usually a good idea (but not
1460	required if you know what you are doing).	1589	required if you know what you are doing).
1461		1590
1462	If you cannot use non-blocking mode, then force the use of a
1463	known-to-be-good backend (at the time of this writing, this includes only
1464	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1465	descriptors for which non-blocking operation makes no sense (such as
1466	files) - libev doesn't guarentee any specific behaviour in that case.
1467
1468	Another thing you have to watch out for is that it is quite easy to	1591	Another thing you have to watch out for is that it is quite easy to
1469	receive "spurious" readiness notifications, that is your callback might	1592	receive "spurious" readiness notifications, that is, your callback might
1470	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1593	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1471	because there is no data. Not only are some backends known to create a	1594	because there is no data. It is very easy to get into this situation even
1472	lot of those (for example Solaris ports), it is very easy to get into	1595	with a relatively standard program structure. Thus it is best to always
1473	this situation even with a relatively standard program structure. Thus	1596	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1474	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1475	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1597	preferable to a program hanging until some data arrives.
1476		1598
1477	If you cannot run the fd in non-blocking mode (for example you should	1599	If you cannot run the fd in non-blocking mode (for example you should
1478	not play around with an Xlib connection), then you have to separately	1600	not play around with an Xlib connection), then you have to separately
1479	re-test whether a file descriptor is really ready with a known-to-be good	1601	re-test whether a file descriptor is really ready with a known-to-be good
1480	interface such as poll (fortunately in our Xlib example, Xlib already	1602	interface such as poll (fortunately in the case of Xlib, it already does
1481	does this on its own, so its quite safe to use). Some people additionally	1603	this on its own, so its quite safe to use). Some people additionally
1482	use C<SIGALRM> and an interval timer, just to be sure you won't block	1604	use C<SIGALRM> and an interval timer, just to be sure you won't block
1483	indefinitely.	1605	indefinitely.
1484		1606
1485	But really, best use non-blocking mode.	1607	But really, best use non-blocking mode.
1486		1608
…		…
1514		1636
1515	There is no workaround possible except not registering events	1637	There is no workaround possible except not registering events
1516	for potentially C<dup ()>'ed file descriptors, or to resort to	1638	for potentially C<dup ()>'ed file descriptors, or to resort to
1517	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1639	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1518		1640
		1641	=head3 The special problem of files
		1642
		1643	Many people try to use C<select> (or libev) on file descriptors
		1644	representing files, and expect it to become ready when their program
		1645	doesn't block on disk accesses (which can take a long time on their own).
		1646
		1647	However, this cannot ever work in the "expected" way - you get a readiness
		1648	notification as soon as the kernel knows whether and how much data is
		1649	there, and in the case of open files, that's always the case, so you
		1650	always get a readiness notification instantly, and your read (or possibly
		1651	write) will still block on the disk I/O.
		1652
		1653	Another way to view it is that in the case of sockets, pipes, character
		1654	devices and so on, there is another party (the sender) that delivers data
		1655	on its own, but in the case of files, there is no such thing: the disk
		1656	will not send data on its own, simply because it doesn't know what you
		1657	wish to read - you would first have to request some data.
		1658
		1659	Since files are typically not-so-well supported by advanced notification
		1660	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1661	to files, even though you should not use it. The reason for this is
		1662	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1663	usually a tty, often a pipe, but also sometimes files or special devices
		1664	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1665	F</dev/urandom>), and even though the file might better be served with
		1666	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1667	it "just works" instead of freezing.
		1668
		1669	So avoid file descriptors pointing to files when you know it (e.g. use
		1670	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1671	when you rarely read from a file instead of from a socket, and want to
		1672	reuse the same code path.
		1673
1519	=head3 The special problem of fork	1674	=head3 The special problem of fork
1520		1675
1521	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1676	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1522	useless behaviour. Libev fully supports fork, but needs to be told about	1677	useless behaviour. Libev fully supports fork, but needs to be told about
1523	it in the child.	1678	it in the child if you want to continue to use it in the child.
1524		1679
1525	To support fork in your programs, you either have to call	1680	To support fork in your child processes, you have to call C<ev_loop_fork
1526	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1681	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1527	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1682	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1528	C<EVBACKEND_POLL>.
1529		1683
1530	=head3 The special problem of SIGPIPE	1684	=head3 The special problem of SIGPIPE
1531		1685
1532	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1686	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1533	when writing to a pipe whose other end has been closed, your program gets	1687	when writing to a pipe whose other end has been closed, your program gets
…		…
1536		1690
1537	So when you encounter spurious, unexplained daemon exits, make sure you	1691	So when you encounter spurious, unexplained daemon exits, make sure you
1538	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1692	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1539	somewhere, as that would have given you a big clue).	1693	somewhere, as that would have given you a big clue).
1540		1694
		1695	=head3 The special problem of accept()ing when you can't
		1696
		1697	Many implementations of the POSIX C<accept> function (for example,
		1698	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1699	connection from the pending queue in all error cases.
		1700
		1701	For example, larger servers often run out of file descriptors (because
		1702	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1703	rejecting the connection, leading to libev signalling readiness on
		1704	the next iteration again (the connection still exists after all), and
		1705	typically causing the program to loop at 100% CPU usage.
		1706
		1707	Unfortunately, the set of errors that cause this issue differs between
		1708	operating systems, there is usually little the app can do to remedy the
		1709	situation, and no known thread-safe method of removing the connection to
		1710	cope with overload is known (to me).
		1711
		1712	One of the easiest ways to handle this situation is to just ignore it
		1713	- when the program encounters an overload, it will just loop until the
		1714	situation is over. While this is a form of busy waiting, no OS offers an
		1715	event-based way to handle this situation, so it's the best one can do.
		1716
		1717	A better way to handle the situation is to log any errors other than
		1718	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1719	messages, and continue as usual, which at least gives the user an idea of
		1720	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1721	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1722	usage.
		1723
		1724	If your program is single-threaded, then you could also keep a dummy file
		1725	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1726	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1727	close that fd, and create a new dummy fd. This will gracefully refuse
		1728	clients under typical overload conditions.
		1729
		1730	The last way to handle it is to simply log the error and C<exit>, as
		1731	is often done with C<malloc> failures, but this results in an easy
		1732	opportunity for a DoS attack.
1541		1733
1542	=head3 Watcher-Specific Functions	1734	=head3 Watcher-Specific Functions
1543		1735
1544	=over 4	1736	=over 4
1545		1737
…		…
1577	...	1769	...
1578	struct ev_loop *loop = ev_default_init (0);	1770	struct ev_loop *loop = ev_default_init (0);
1579	ev_io stdin_readable;	1771	ev_io stdin_readable;
1580	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1772	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1581	ev_io_start (loop, &stdin_readable);	1773	ev_io_start (loop, &stdin_readable);
1582	ev_loop (loop, 0);	1774	ev_run (loop, 0);
1583		1775
1584		1776
1585	=head2 C<ev_timer> - relative and optionally repeating timeouts	1777	=head2 C<ev_timer> - relative and optionally repeating timeouts
1586		1778
1587	Timer watchers are simple relative timers that generate an event after a	1779	Timer watchers are simple relative timers that generate an event after a
…		…
1593	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1785	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1594	monotonic clock option helps a lot here).	1786	monotonic clock option helps a lot here).
1595		1787
1596	The callback is guaranteed to be invoked only I<after> its timeout has	1788	The callback is guaranteed to be invoked only I<after> its timeout has
1597	passed (not I<at>, so on systems with very low-resolution clocks this	1789	passed (not I<at>, so on systems with very low-resolution clocks this
1598	might introduce a small delay). If multiple timers become ready during the	1790	might introduce a small delay, see "the special problem of being too
		1791	early", below). If multiple timers become ready during the same loop
1599	same loop iteration then the ones with earlier time-out values are invoked	1792	iteration then the ones with earlier time-out values are invoked before
1600	before ones of the same priority with later time-out values (but this is	1793	ones of the same priority with later time-out values (but this is no
1601	no longer true when a callback calls C<ev_loop> recursively).	1794	longer true when a callback calls C<ev_run> recursively).
1602		1795
1603	=head3 Be smart about timeouts	1796	=head3 Be smart about timeouts
1604		1797
1605	Many real-world problems involve some kind of timeout, usually for error	1798	Many real-world problems involve some kind of timeout, usually for error
1606	recovery. A typical example is an HTTP request - if the other side hangs,	1799	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1681		1874
1682	In this case, it would be more efficient to leave the C<ev_timer> alone,	1875	In this case, it would be more efficient to leave the C<ev_timer> alone,
1683	but remember the time of last activity, and check for a real timeout only	1876	but remember the time of last activity, and check for a real timeout only
1684	within the callback:	1877	within the callback:
1685		1878
		1879	ev_tstamp timeout = 60.;
1686	ev_tstamp last_activity; // time of last activity	1880	ev_tstamp last_activity; // time of last activity
		1881	ev_timer timer;
1687		1882
1688	static void	1883	static void
1689	callback (EV_P_ ev_timer *w, int revents)	1884	callback (EV_P_ ev_timer *w, int revents)
1690	{	1885	{
1691	ev_tstamp now = ev_now (EV_A);	1886	// calculate when the timeout would happen
1692	ev_tstamp timeout = last_activity + 60.;	1887	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1693		1888
1694	// if last_activity + 60. is older than now, we did time out	1889	// if negative, it means we the timeout already occurred
1695	if (timeout < now)	1890	if (after < 0.)
1696	{	1891	{
1697	// timeout occured, take action	1892	// timeout occurred, take action
1698	}	1893	}
1699	else	1894	else
1700	{	1895	{
1701	// callback was invoked, but there was some activity, re-arm	1896	// callback was invoked, but there was some recent
1702	// the watcher to fire in last_activity + 60, which is	1897	// activity. simply restart the timer to time out
1703	// guaranteed to be in the future, so "again" is positive:	1898	// after "after" seconds, which is the earliest time
1704	w->repeat = timeout - now;	1899	// the timeout can occur.
		1900	ev_timer_set (w, after, 0.);
1705	ev_timer_again (EV_A_ w);	1901	ev_timer_start (EV_A_ w);
1706	}	1902	}
1707	}	1903	}
1708		1904
1709	To summarise the callback: first calculate the real timeout (defined	1905	To summarise the callback: first calculate in how many seconds the
1710	as "60 seconds after the last activity"), then check if that time has	1906	timeout will occur (by calculating the absolute time when it would occur,
1711	been reached, which means something I<did>, in fact, time out. Otherwise	1907	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1712	the callback was invoked too early (C<timeout> is in the future), so	1908	(EV_A)> from that).
1713	re-schedule the timer to fire at that future time, to see if maybe we have
1714	a timeout then.
1715		1909
1716	Note how C<ev_timer_again> is used, taking advantage of the	1910	If this value is negative, then we are already past the timeout, i.e. we
1717	C<ev_timer_again> optimisation when the timer is already running.	1911	timed out, and need to do whatever is needed in this case.
		1912
		1913	Otherwise, we now the earliest time at which the timeout would trigger,
		1914	and simply start the timer with this timeout value.
		1915
		1916	In other words, each time the callback is invoked it will check whether
		1917	the timeout occurred. If not, it will simply reschedule itself to check
		1918	again at the earliest time it could time out. Rinse. Repeat.
1718		1919
1719	This scheme causes more callback invocations (about one every 60 seconds	1920	This scheme causes more callback invocations (about one every 60 seconds
1720	minus half the average time between activity), but virtually no calls to	1921	minus half the average time between activity), but virtually no calls to
1721	libev to change the timeout.	1922	libev to change the timeout.
1722		1923
1723	To start the timer, simply initialise the watcher and set C<last_activity>	1924	To start the machinery, simply initialise the watcher and set
1724	to the current time (meaning we just have some activity :), then call the	1925	C<last_activity> to the current time (meaning there was some activity just
1725	callback, which will "do the right thing" and start the timer:	1926	now), then call the callback, which will "do the right thing" and start
		1927	the timer:
1726		1928
		1929	last_activity = ev_now (EV_A);
1727	ev_init (timer, callback);	1930	ev_init (&timer, callback);
1728	last_activity = ev_now (loop);	1931	callback (EV_A_ &timer, 0);
1729	callback (loop, timer, EV_TIMEOUT);
1730		1932
1731	And when there is some activity, simply store the current time in	1933	When there is some activity, simply store the current time in
1732	C<last_activity>, no libev calls at all:	1934	C<last_activity>, no libev calls at all:
1733		1935
		1936	if (activity detected)
1734	last_actiivty = ev_now (loop);	1937	last_activity = ev_now (EV_A);
		1938
		1939	When your timeout value changes, then the timeout can be changed by simply
		1940	providing a new value, stopping the timer and calling the callback, which
		1941	will again do the right thing (for example, time out immediately :).
		1942
		1943	timeout = new_value;
		1944	ev_timer_stop (EV_A_ &timer);
		1945	callback (EV_A_ &timer, 0);
1735		1946
1736	This technique is slightly more complex, but in most cases where the	1947	This technique is slightly more complex, but in most cases where the
1737	time-out is unlikely to be triggered, much more efficient.	1948	time-out is unlikely to be triggered, much more efficient.
1738
1739	Changing the timeout is trivial as well (if it isn't hard-coded in the
1740	callback :) - just change the timeout and invoke the callback, which will
1741	fix things for you.
1742		1949
1743	=item 4. Wee, just use a double-linked list for your timeouts.	1950	=item 4. Wee, just use a double-linked list for your timeouts.
1744		1951
1745	If there is not one request, but many thousands (millions...), all	1952	If there is not one request, but many thousands (millions...), all
1746	employing some kind of timeout with the same timeout value, then one can	1953	employing some kind of timeout with the same timeout value, then one can
…		…
1773	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1980	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1774	rather complicated, but extremely efficient, something that really pays	1981	rather complicated, but extremely efficient, something that really pays
1775	off after the first million or so of active timers, i.e. it's usually	1982	off after the first million or so of active timers, i.e. it's usually
1776	overkill :)	1983	overkill :)
1777		1984
		1985	=head3 The special problem of being too early
		1986
		1987	If you ask a timer to call your callback after three seconds, then
		1988	you expect it to be invoked after three seconds - but of course, this
		1989	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1990	guaranteed to any precision by libev - imagine somebody suspending the
		1991	process with a STOP signal for a few hours for example.
		1992
		1993	So, libev tries to invoke your callback as soon as possible I<after> the
		1994	delay has occurred, but cannot guarantee this.
		1995
		1996	A less obvious failure mode is calling your callback too early: many event
		1997	loops compare timestamps with a "elapsed delay >= requested delay", but
		1998	this can cause your callback to be invoked much earlier than you would
		1999	expect.
		2000
		2001	To see why, imagine a system with a clock that only offers full second
		2002	resolution (think windows if you can't come up with a broken enough OS
		2003	yourself). If you schedule a one-second timer at the time 500.9, then the
		2004	event loop will schedule your timeout to elapse at a system time of 500
		2005	(500.9 truncated to the resolution) + 1, or 501.
		2006
		2007	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2008	501" and invoke the callback 0.1s after it was started, even though a
		2009	one-second delay was requested - this is being "too early", despite best
		2010	intentions.
		2011
		2012	This is the reason why libev will never invoke the callback if the elapsed
		2013	delay equals the requested delay, but only when the elapsed delay is
		2014	larger than the requested delay. In the example above, libev would only invoke
		2015	the callback at system time 502, or 1.1s after the timer was started.
		2016
		2017	So, while libev cannot guarantee that your callback will be invoked
		2018	exactly when requested, it I<can> and I<does> guarantee that the requested
		2019	delay has actually elapsed, or in other words, it always errs on the "too
		2020	late" side of things.
		2021
1778	=head3 The special problem of time updates	2022	=head3 The special problem of time updates
1779		2023
1780	Establishing the current time is a costly operation (it usually takes at	2024	Establishing the current time is a costly operation (it usually takes
1781	least two system calls): EV therefore updates its idea of the current	2025	at least one system call): EV therefore updates its idea of the current
1782	time only before and after C<ev_loop> collects new events, which causes a	2026	time only before and after C<ev_run> collects new events, which causes a
1783	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2027	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1784	lots of events in one iteration.	2028	lots of events in one iteration.
1785		2029
1786	The relative timeouts are calculated relative to the C<ev_now ()>	2030	The relative timeouts are calculated relative to the C<ev_now ()>
1787	time. This is usually the right thing as this timestamp refers to the time	2031	time. This is usually the right thing as this timestamp refers to the time
…		…
1792	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2036	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1793		2037
1794	If the event loop is suspended for a long time, you can also force an	2038	If the event loop is suspended for a long time, you can also force an
1795	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2039	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1796	()>.	2040	()>.
		2041
		2042	=head3 The special problem of unsynchronised clocks
		2043
		2044	Modern systems have a variety of clocks - libev itself uses the normal
		2045	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2046	jumps).
		2047
		2048	Neither of these clocks is synchronised with each other or any other clock
		2049	on the system, so C<ev_time ()> might return a considerably different time
		2050	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2051	a call to C<gettimeofday> might return a second count that is one higher
		2052	than a directly following call to C<time>.
		2053
		2054	The moral of this is to only compare libev-related timestamps with
		2055	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2056	a second or so.
		2057
		2058	One more problem arises due to this lack of synchronisation: if libev uses
		2059	the system monotonic clock and you compare timestamps from C<ev_time>
		2060	or C<ev_now> from when you started your timer and when your callback is
		2061	invoked, you will find that sometimes the callback is a bit "early".
		2062
		2063	This is because C<ev_timer>s work in real time, not wall clock time, so
		2064	libev makes sure your callback is not invoked before the delay happened,
		2065	I<measured according to the real time>, not the system clock.
		2066
		2067	If your timeouts are based on a physical timescale (e.g. "time out this
		2068	connection after 100 seconds") then this shouldn't bother you as it is
		2069	exactly the right behaviour.
		2070
		2071	If you want to compare wall clock/system timestamps to your timers, then
		2072	you need to use C<ev_periodic>s, as these are based on the wall clock
		2073	time, where your comparisons will always generate correct results.
1797		2074
1798	=head3 The special problems of suspended animation	2075	=head3 The special problems of suspended animation
1799		2076
1800	When you leave the server world it is quite customary to hit machines that	2077	When you leave the server world it is quite customary to hit machines that
1801	can suspend/hibernate - what happens to the clocks during such a suspend?	2078	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1845	keep up with the timer (because it takes longer than those 10 seconds to	2122	keep up with the timer (because it takes longer than those 10 seconds to
1846	do stuff) the timer will not fire more than once per event loop iteration.	2123	do stuff) the timer will not fire more than once per event loop iteration.
1847		2124
1848	=item ev_timer_again (loop, ev_timer *)	2125	=item ev_timer_again (loop, ev_timer *)
1849		2126
1850	This will act as if the timer timed out and restart it again if it is	2127	This will act as if the timer timed out, and restarts it again if it is
1851	repeating. The exact semantics are:	2128	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2129	timeout to the C<repeat> value and calling C<ev_timer_start>.
1852		2130
		2131	The exact semantics are as in the following rules, all of which will be
		2132	applied to the watcher:
		2133
		2134	=over 4
		2135
1853	If the timer is pending, its pending status is cleared.	2136	=item If the timer is pending, the pending status is always cleared.
1854		2137
1855	If the timer is started but non-repeating, stop it (as if it timed out).	2138	=item If the timer is started but non-repeating, stop it (as if it timed
		2139	out, without invoking it).
1856		2140
1857	If the timer is repeating, either start it if necessary (with the	2141	=item If the timer is repeating, make the C<repeat> value the new timeout
1858	C<repeat> value), or reset the running timer to the C<repeat> value.	2142	and start the timer, if necessary.
1859		2143
		2144	=back
		2145
1860	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2146	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1861	usage example.	2147	usage example.
1862		2148
1863	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2149	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1864		2150
1865	Returns the remaining time until a timer fires. If the timer is active,	2151	Returns the remaining time until a timer fires. If the timer is active,
1866	then this time is relative to the current event loop time, otherwise it's	2152	then this time is relative to the current event loop time, otherwise it's
1867	the timeout value currently configured.	2153	the timeout value currently configured.
1868		2154
1869	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2155	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1870	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2156	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1871	will return C<4>. When the timer expires and is restarted, it will return	2157	will return C<4>. When the timer expires and is restarted, it will return
1872	roughly C<7> (likely slightly less as callback invocation takes some time,	2158	roughly C<7> (likely slightly less as callback invocation takes some time,
1873	too), and so on.	2159	too), and so on.
1874		2160
1875	=item ev_tstamp repeat [read-write]	2161	=item ev_tstamp repeat [read-write]
…		…
1904	}	2190	}
1905		2191
1906	ev_timer mytimer;	2192	ev_timer mytimer;
1907	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2193	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1908	ev_timer_again (&mytimer); /* start timer */	2194	ev_timer_again (&mytimer); /* start timer */
1909	ev_loop (loop, 0);	2195	ev_run (loop, 0);
1910		2196
1911	// and in some piece of code that gets executed on any "activity":	2197	// and in some piece of code that gets executed on any "activity":
1912	// reset the timeout to start ticking again at 10 seconds	2198	// reset the timeout to start ticking again at 10 seconds
1913	ev_timer_again (&mytimer);	2199	ev_timer_again (&mytimer);
1914		2200
…		…
1940		2226
1941	As with timers, the callback is guaranteed to be invoked only when the	2227	As with timers, the callback is guaranteed to be invoked only when the
1942	point in time where it is supposed to trigger has passed. If multiple	2228	point in time where it is supposed to trigger has passed. If multiple
1943	timers become ready during the same loop iteration then the ones with	2229	timers become ready during the same loop iteration then the ones with
1944	earlier time-out values are invoked before ones with later time-out values	2230	earlier time-out values are invoked before ones with later time-out values
1945	(but this is no longer true when a callback calls C<ev_loop> recursively).	2231	(but this is no longer true when a callback calls C<ev_run> recursively).
1946		2232
1947	=head3 Watcher-Specific Functions and Data Members	2233	=head3 Watcher-Specific Functions and Data Members
1948		2234
1949	=over 4	2235	=over 4
1950		2236
…		…
1985		2271
1986	Another way to think about it (for the mathematically inclined) is that	2272	Another way to think about it (for the mathematically inclined) is that
1987	C<ev_periodic> will try to run the callback in this mode at the next possible	2273	C<ev_periodic> will try to run the callback in this mode at the next possible
1988	time where C<time = offset (mod interval)>, regardless of any time jumps.	2274	time where C<time = offset (mod interval)>, regardless of any time jumps.
1989		2275
1990	For numerical stability it is preferable that the C<offset> value is near	2276	The C<interval> I<MUST> be positive, and for numerical stability, the
1991	C<ev_now ()> (the current time), but there is no range requirement for	2277	interval value should be higher than C<1/8192> (which is around 100
1992	this value, and in fact is often specified as zero.	2278	microseconds) and C<offset> should be higher than C<0> and should have
		2279	at most a similar magnitude as the current time (say, within a factor of
		2280	ten). Typical values for offset are, in fact, C<0> or something between
		2281	C<0> and C<interval>, which is also the recommended range.
1993		2282
1994	Note also that there is an upper limit to how often a timer can fire (CPU	2283	Note also that there is an upper limit to how often a timer can fire (CPU
1995	speed for example), so if C<interval> is very small then timing stability	2284	speed for example), so if C<interval> is very small then timing stability
1996	will of course deteriorate. Libev itself tries to be exact to be about one	2285	will of course deteriorate. Libev itself tries to be exact to be about one
1997	millisecond (if the OS supports it and the machine is fast enough).	2286	millisecond (if the OS supports it and the machine is fast enough).
…		…
2078	Example: Call a callback every hour, or, more precisely, whenever the	2367	Example: Call a callback every hour, or, more precisely, whenever the
2079	system time is divisible by 3600. The callback invocation times have	2368	system time is divisible by 3600. The callback invocation times have
2080	potentially a lot of jitter, but good long-term stability.	2369	potentially a lot of jitter, but good long-term stability.
2081		2370
2082	static void	2371	static void
2083	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2372	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2084	{	2373	{
2085	... its now a full hour (UTC, or TAI or whatever your clock follows)	2374	... its now a full hour (UTC, or TAI or whatever your clock follows)
2086	}	2375	}
2087		2376
2088	ev_periodic hourly_tick;	2377	ev_periodic hourly_tick;
…		…
2105		2394
2106	ev_periodic hourly_tick;	2395	ev_periodic hourly_tick;
2107	ev_periodic_init (&hourly_tick, clock_cb,	2396	ev_periodic_init (&hourly_tick, clock_cb,
2108	fmod (ev_now (loop), 3600.), 3600., 0);	2397	fmod (ev_now (loop), 3600.), 3600., 0);
2109	ev_periodic_start (loop, &hourly_tick);	2398	ev_periodic_start (loop, &hourly_tick);
2110		2399
2111		2400
2112	=head2 C<ev_signal> - signal me when a signal gets signalled!	2401	=head2 C<ev_signal> - signal me when a signal gets signalled!
2113		2402
2114	Signal watchers will trigger an event when the process receives a specific	2403	Signal watchers will trigger an event when the process receives a specific
2115	signal one or more times. Even though signals are very asynchronous, libev	2404	signal one or more times. Even though signals are very asynchronous, libev
2116	will try it's best to deliver signals synchronously, i.e. as part of the	2405	will try its best to deliver signals synchronously, i.e. as part of the
2117	normal event processing, like any other event.	2406	normal event processing, like any other event.
2118		2407
2119	If you want signals to be delivered truly asynchronously, just use	2408	If you want signals to be delivered truly asynchronously, just use
2120	C<sigaction> as you would do without libev and forget about sharing	2409	C<sigaction> as you would do without libev and forget about sharing
2121	the signal. You can even use C<ev_async> from a signal handler to	2410	the signal. You can even use C<ev_async> from a signal handler to
…		…
2125	only within the same loop, i.e. you can watch for C<SIGINT> in your	2414	only within the same loop, i.e. you can watch for C<SIGINT> in your
2126	default loop and for C<SIGIO> in another loop, but you cannot watch for	2415	default loop and for C<SIGIO> in another loop, but you cannot watch for
2127	C<SIGINT> in both the default loop and another loop at the same time. At	2416	C<SIGINT> in both the default loop and another loop at the same time. At
2128	the moment, C<SIGCHLD> is permanently tied to the default loop.	2417	the moment, C<SIGCHLD> is permanently tied to the default loop.
2129		2418
2130	When the first watcher gets started will libev actually register something	2419	Only after the first watcher for a signal is started will libev actually
2131	with the kernel (thus it coexists with your own signal handlers as long as	2420	register something with the kernel. It thus coexists with your own signal
2132	you don't register any with libev for the same signal).	2421	handlers as long as you don't register any with libev for the same signal.
2133		2422
2134	If possible and supported, libev will install its handlers with	2423	If possible and supported, libev will install its handlers with
2135	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2424	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2136	not be unduly interrupted. If you have a problem with system calls getting	2425	not be unduly interrupted. If you have a problem with system calls getting
2137	interrupted by signals you can block all signals in an C<ev_check> watcher	2426	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2140	=head3 The special problem of inheritance over fork/execve/pthread_create	2429	=head3 The special problem of inheritance over fork/execve/pthread_create
2141		2430
2142	Both the signal mask (C<sigprocmask>) and the signal disposition	2431	Both the signal mask (C<sigprocmask>) and the signal disposition
2143	(C<sigaction>) are unspecified after starting a signal watcher (and after	2432	(C<sigaction>) are unspecified after starting a signal watcher (and after
2144	stopping it again), that is, libev might or might not block the signal,	2433	stopping it again), that is, libev might or might not block the signal,
2145	and might or might not set or restore the installed signal handler.	2434	and might or might not set or restore the installed signal handler (but
		2435	see C<EVFLAG_NOSIGMASK>).
2146		2436
2147	While this does not matter for the signal disposition (libev never	2437	While this does not matter for the signal disposition (libev never
2148	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2438	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2149	C<execve>), this matters for the signal mask: many programs do not expect	2439	C<execve>), this matters for the signal mask: many programs do not expect
2150	certain signals to be blocked.	2440	certain signals to be blocked.
…		…
2160	In current versions of libev, the signal will not be blocked indefinitely	2450	In current versions of libev, the signal will not be blocked indefinitely
2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces	2451	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162	the window of opportunity for problems, it will not go away, as libev	2452	the window of opportunity for problems, it will not go away, as libev
2163	I<has> to modify the signal mask, at least temporarily.	2453	I<has> to modify the signal mask, at least temporarily.
2164		2454
2165	So I can't stress this enough I<if you do not reset your signal mask	2455	So I can't stress this enough: I<If you do not reset your signal mask when
2166	when you expect it to be empty, you have a race condition in your	2456	you expect it to be empty, you have a race condition in your code>. This
2167	program>. This is not a libev-specific thing, this is true for most event	2457	is not a libev-specific thing, this is true for most event libraries.
2168	libraries.	2458
		2459	=head3 The special problem of threads signal handling
		2460
		2461	POSIX threads has problematic signal handling semantics, specifically,
		2462	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2463	threads in a process block signals, which is hard to achieve.
		2464
		2465	When you want to use sigwait (or mix libev signal handling with your own
		2466	for the same signals), you can tackle this problem by globally blocking
		2467	all signals before creating any threads (or creating them with a fully set
		2468	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2469	loops. Then designate one thread as "signal receiver thread" which handles
		2470	these signals. You can pass on any signals that libev might be interested
		2471	in by calling C<ev_feed_signal>.
2169		2472
2170	=head3 Watcher-Specific Functions and Data Members	2473	=head3 Watcher-Specific Functions and Data Members
2171		2474
2172	=over 4	2475	=over 4
2173		2476
…		…
2189	Example: Try to exit cleanly on SIGINT.	2492	Example: Try to exit cleanly on SIGINT.
2190		2493
2191	static void	2494	static void
2192	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2495	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2193	{	2496	{
2194	ev_unloop (loop, EVUNLOOP_ALL);	2497	ev_break (loop, EVBREAK_ALL);
2195	}	2498	}
2196		2499
2197	ev_signal signal_watcher;	2500	ev_signal signal_watcher;
2198	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2501	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2199	ev_signal_start (loop, &signal_watcher);	2502	ev_signal_start (loop, &signal_watcher);
…		…
2308		2611
2309	=head2 C<ev_stat> - did the file attributes just change?	2612	=head2 C<ev_stat> - did the file attributes just change?
2310		2613
2311	This watches a file system path for attribute changes. That is, it calls	2614	This watches a file system path for attribute changes. That is, it calls
2312	C<stat> on that path in regular intervals (or when the OS says it changed)	2615	C<stat> on that path in regular intervals (or when the OS says it changed)
2313	and sees if it changed compared to the last time, invoking the callback if	2616	and sees if it changed compared to the last time, invoking the callback
2314	it did.	2617	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2618	happen after the watcher has been started will be reported.
2315		2619
2316	The path does not need to exist: changing from "path exists" to "path does	2620	The path does not need to exist: changing from "path exists" to "path does
2317	not exist" is a status change like any other. The condition "path does not	2621	not exist" is a status change like any other. The condition "path does not
2318	exist" (or more correctly "path cannot be stat'ed") is signified by the	2622	exist" (or more correctly "path cannot be stat'ed") is signified by the
2319	C<st_nlink> field being zero (which is otherwise always forced to be at	2623	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2549	Apart from keeping your process non-blocking (which is a useful	2853	Apart from keeping your process non-blocking (which is a useful
2550	effect on its own sometimes), idle watchers are a good place to do	2854	effect on its own sometimes), idle watchers are a good place to do
2551	"pseudo-background processing", or delay processing stuff to after the	2855	"pseudo-background processing", or delay processing stuff to after the
2552	event loop has handled all outstanding events.	2856	event loop has handled all outstanding events.
2553		2857
		2858	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2859
		2860	As long as there is at least one active idle watcher, libev will never
		2861	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2862	For this to work, the idle watcher doesn't need to be invoked at all - the
		2863	lowest priority will do.
		2864
		2865	This mode of operation can be useful together with an C<ev_check> watcher,
		2866	to do something on each event loop iteration - for example to balance load
		2867	between different connections.
		2868
		2869	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2870	example.
		2871
2554	=head3 Watcher-Specific Functions and Data Members	2872	=head3 Watcher-Specific Functions and Data Members
2555		2873
2556	=over 4	2874	=over 4
2557		2875
2558	=item ev_idle_init (ev_idle *, callback)	2876	=item ev_idle_init (ev_idle *, callback)
…		…
2569	callback, free it. Also, use no error checking, as usual.	2887	callback, free it. Also, use no error checking, as usual.
2570		2888
2571	static void	2889	static void
2572	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2890	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2573	{	2891	{
		2892	// stop the watcher
		2893	ev_idle_stop (loop, w);
		2894
		2895	// now we can free it
2574	free (w);	2896	free (w);
		2897
2575	// now do something you wanted to do when the program has	2898	// now do something you wanted to do when the program has
2576	// no longer anything immediate to do.	2899	// no longer anything immediate to do.
2577	}	2900	}
2578		2901
2579	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2902	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2581	ev_idle_start (loop, idle_watcher);	2904	ev_idle_start (loop, idle_watcher);
2582		2905
2583		2906
2584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2907	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2585		2908
2586	Prepare and check watchers are usually (but not always) used in pairs:	2909	Prepare and check watchers are often (but not always) used in pairs:
2587	prepare watchers get invoked before the process blocks and check watchers	2910	prepare watchers get invoked before the process blocks and check watchers
2588	afterwards.	2911	afterwards.
2589		2912
2590	You I<must not> call C<ev_loop> or similar functions that enter	2913	You I<must not> call C<ev_run> (or similar functions that enter the
2591	the current event loop from either C<ev_prepare> or C<ev_check>	2914	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2592	watchers. Other loops than the current one are fine, however. The	2915	C<ev_check> watchers. Other loops than the current one are fine,
2593	rationale behind this is that you do not need to check for recursion in	2916	however. The rationale behind this is that you do not need to check
2594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2917	for recursion in those watchers, i.e. the sequence will always be
2595	C<ev_check> so if you have one watcher of each kind they will always be	2918	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2596	called in pairs bracketing the blocking call.	2919	kind they will always be called in pairs bracketing the blocking call.
2597		2920
2598	Their main purpose is to integrate other event mechanisms into libev and	2921	Their main purpose is to integrate other event mechanisms into libev and
2599	their use is somewhat advanced. They could be used, for example, to track	2922	their use is somewhat advanced. They could be used, for example, to track
2600	variable changes, implement your own watchers, integrate net-snmp or a	2923	variable changes, implement your own watchers, integrate net-snmp or a
2601	coroutine library and lots more. They are also occasionally useful if	2924	coroutine library and lots more. They are also occasionally useful if
…		…
2619	with priority higher than or equal to the event loop and one coroutine	2942	with priority higher than or equal to the event loop and one coroutine
2620	of lower priority, but only once, using idle watchers to keep the event	2943	of lower priority, but only once, using idle watchers to keep the event
2621	loop from blocking if lower-priority coroutines are active, thus mapping	2944	loop from blocking if lower-priority coroutines are active, thus mapping
2622	low-priority coroutines to idle/background tasks).	2945	low-priority coroutines to idle/background tasks).
2623		2946
2624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2947	When used for this purpose, it is recommended to give C<ev_check> watchers
2625	priority, to ensure that they are being run before any other watchers	2948	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2626	after the poll (this doesn't matter for C<ev_prepare> watchers).	2949	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2950	watchers).
2627		2951
2628	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2952	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2629	activate ("feed") events into libev. While libev fully supports this, they	2953	activate ("feed") events into libev. While libev fully supports this, they
2630	might get executed before other C<ev_check> watchers did their job. As	2954	might get executed before other C<ev_check> watchers did their job. As
2631	C<ev_check> watchers are often used to embed other (non-libev) event	2955	C<ev_check> watchers are often used to embed other (non-libev) event
2632	loops those other event loops might be in an unusable state until their	2956	loops those other event loops might be in an unusable state until their
2633	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2957	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2634	others).	2958	others).
		2959
		2960	=head3 Abusing an C<ev_check> watcher for its side-effect
		2961
		2962	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2963	useful because they are called once per event loop iteration. For
		2964	example, if you want to handle a large number of connections fairly, you
		2965	normally only do a bit of work for each active connection, and if there
		2966	is more work to do, you wait for the next event loop iteration, so other
		2967	connections have a chance of making progress.
		2968
		2969	Using an C<ev_check> watcher is almost enough: it will be called on the
		2970	next event loop iteration. However, that isn't as soon as possible -
		2971	without external events, your C<ev_check> watcher will not be invoked.
		2972
		2973	This is where C<ev_idle> watchers come in handy - all you need is a
		2974	single global idle watcher that is active as long as you have one active
		2975	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2976	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2977	invoked. Neither watcher alone can do that.
2635		2978
2636	=head3 Watcher-Specific Functions and Data Members	2979	=head3 Watcher-Specific Functions and Data Members
2637		2980
2638	=over 4	2981	=over 4
2639		2982
…		…
2763		3106
2764	if (timeout >= 0)	3107	if (timeout >= 0)
2765	// create/start timer	3108	// create/start timer
2766		3109
2767	// poll	3110	// poll
2768	ev_loop (EV_A_ 0);	3111	ev_run (EV_A_ 0);
2769		3112
2770	// stop timer again	3113	// stop timer again
2771	if (timeout >= 0)	3114	if (timeout >= 0)
2772	ev_timer_stop (EV_A_ &to);	3115	ev_timer_stop (EV_A_ &to);
2773		3116
…		…
2840		3183
2841	=over 4	3184	=over 4
2842		3185
2843	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3186	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2844		3187
2845	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3188	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2846		3189
2847	Configures the watcher to embed the given loop, which must be	3190	Configures the watcher to embed the given loop, which must be
2848	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3191	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2849	invoked automatically, otherwise it is the responsibility of the callback	3192	invoked automatically, otherwise it is the responsibility of the callback
2850	to invoke it (it will continue to be called until the sweep has been done,	3193	to invoke it (it will continue to be called until the sweep has been done,
2851	if you do not want that, you need to temporarily stop the embed watcher).	3194	if you do not want that, you need to temporarily stop the embed watcher).
2852		3195
2853	=item ev_embed_sweep (loop, ev_embed *)	3196	=item ev_embed_sweep (loop, ev_embed *)
2854		3197
2855	Make a single, non-blocking sweep over the embedded loop. This works	3198	Make a single, non-blocking sweep over the embedded loop. This works
2856	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3199	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2857	appropriate way for embedded loops.	3200	appropriate way for embedded loops.
2858		3201
2859	=item struct ev_loop *other [read-only]	3202	=item struct ev_loop *other [read-only]
2860		3203
2861	The embedded event loop.	3204	The embedded event loop.
…		…
2871	used).	3214	used).
2872		3215
2873	struct ev_loop *loop_hi = ev_default_init (0);	3216	struct ev_loop *loop_hi = ev_default_init (0);
2874	struct ev_loop *loop_lo = 0;	3217	struct ev_loop *loop_lo = 0;
2875	ev_embed embed;	3218	ev_embed embed;
2876		3219
2877	// see if there is a chance of getting one that works	3220	// see if there is a chance of getting one that works
2878	// (remember that a flags value of 0 means autodetection)	3221	// (remember that a flags value of 0 means autodetection)
2879	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3222	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2880	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3223	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2881	: 0;	3224	: 0;
…		…
2895	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3238	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2896		3239
2897	struct ev_loop *loop = ev_default_init (0);	3240	struct ev_loop *loop = ev_default_init (0);
2898	struct ev_loop *loop_socket = 0;	3241	struct ev_loop *loop_socket = 0;
2899	ev_embed embed;	3242	ev_embed embed;
2900		3243
2901	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3244	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2902	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3245	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2903	{	3246	{
2904	ev_embed_init (&embed, 0, loop_socket);	3247	ev_embed_init (&embed, 0, loop_socket);
2905	ev_embed_start (loop, &embed);	3248	ev_embed_start (loop, &embed);
…		…
2913		3256
2914	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3257	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2915		3258
2916	Fork watchers are called when a C<fork ()> was detected (usually because	3259	Fork watchers are called when a C<fork ()> was detected (usually because
2917	whoever is a good citizen cared to tell libev about it by calling	3260	whoever is a good citizen cared to tell libev about it by calling
2918	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3261	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2919	event loop blocks next and before C<ev_check> watchers are being called,	3262	and before C<ev_check> watchers are being called, and only in the child
2920	and only in the child after the fork. If whoever good citizen calling	3263	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2921	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3264	and calls it in the wrong process, the fork handlers will be invoked, too,
2922	handlers will be invoked, too, of course.	3265	of course.
2923		3266
2924	=head3 The special problem of life after fork - how is it possible?	3267	=head3 The special problem of life after fork - how is it possible?
2925		3268
2926	Most uses of C<fork()> consist of forking, then some simple calls to ste	3269	Most uses of C<fork ()> consist of forking, then some simple calls to set
2927	up/change the process environment, followed by a call to C<exec()>. This	3270	up/change the process environment, followed by a call to C<exec()>. This
2928	sequence should be handled by libev without any problems.	3271	sequence should be handled by libev without any problems.
2929		3272
2930	This changes when the application actually wants to do event handling	3273	This changes when the application actually wants to do event handling
2931	in the child, or both parent in child, in effect "continuing" after the	3274	in the child, or both parent in child, in effect "continuing" after the
…		…
2947	disadvantage of having to use multiple event loops (which do not support	3290	disadvantage of having to use multiple event loops (which do not support
2948	signal watchers).	3291	signal watchers).
2949		3292
2950	When this is not possible, or you want to use the default loop for	3293	When this is not possible, or you want to use the default loop for
2951	other reasons, then in the process that wants to start "fresh", call	3294	other reasons, then in the process that wants to start "fresh", call
2952	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3295	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2953	the default loop will "orphan" (not stop) all registered watchers, so you	3296	Destroying the default loop will "orphan" (not stop) all registered
2954	have to be careful not to execute code that modifies those watchers. Note	3297	watchers, so you have to be careful not to execute code that modifies
2955	also that in that case, you have to re-register any signal watchers.	3298	those watchers. Note also that in that case, you have to re-register any
		3299	signal watchers.
2956		3300
2957	=head3 Watcher-Specific Functions and Data Members	3301	=head3 Watcher-Specific Functions and Data Members
2958		3302
2959	=over 4	3303	=over 4
2960		3304
2961	=item ev_fork_init (ev_signal *, callback)	3305	=item ev_fork_init (ev_fork *, callback)
2962		3306
2963	Initialises and configures the fork watcher - it has no parameters of any	3307	Initialises and configures the fork watcher - it has no parameters of any
2964	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3308	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2965	believe me.	3309	really.
2966		3310
2967	=back	3311	=back
2968		3312
2969		3313
		3314	=head2 C<ev_cleanup> - even the best things end
		3315
		3316	Cleanup watchers are called just before the event loop is being destroyed
		3317	by a call to C<ev_loop_destroy>.
		3318
		3319	While there is no guarantee that the event loop gets destroyed, cleanup
		3320	watchers provide a convenient method to install cleanup hooks for your
		3321	program, worker threads and so on - you just to make sure to destroy the
		3322	loop when you want them to be invoked.
		3323
		3324	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3325	all other watchers, they do not keep a reference to the event loop (which
		3326	makes a lot of sense if you think about it). Like all other watchers, you
		3327	can call libev functions in the callback, except C<ev_cleanup_start>.
		3328
		3329	=head3 Watcher-Specific Functions and Data Members
		3330
		3331	=over 4
		3332
		3333	=item ev_cleanup_init (ev_cleanup *, callback)
		3334
		3335	Initialises and configures the cleanup watcher - it has no parameters of
		3336	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3337	pointless, I assure you.
		3338
		3339	=back
		3340
		3341	Example: Register an atexit handler to destroy the default loop, so any
		3342	cleanup functions are called.
		3343
		3344	static void
		3345	program_exits (void)
		3346	{
		3347	ev_loop_destroy (EV_DEFAULT_UC);
		3348	}
		3349
		3350	...
		3351	atexit (program_exits);
		3352
		3353
2970	=head2 C<ev_async> - how to wake up another event loop	3354	=head2 C<ev_async> - how to wake up an event loop
2971		3355
2972	In general, you cannot use an C<ev_loop> from multiple threads or other	3356	In general, you cannot use an C<ev_loop> from multiple threads or other
2973	asynchronous sources such as signal handlers (as opposed to multiple event	3357	asynchronous sources such as signal handlers (as opposed to multiple event
2974	loops - those are of course safe to use in different threads).	3358	loops - those are of course safe to use in different threads).
2975		3359
2976	Sometimes, however, you need to wake up another event loop you do not	3360	Sometimes, however, you need to wake up an event loop you do not control,
2977	control, for example because it belongs to another thread. This is what	3361	for example because it belongs to another thread. This is what C<ev_async>
2978	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3362	watchers do: as long as the C<ev_async> watcher is active, you can signal
2979	can signal it by calling C<ev_async_send>, which is thread- and signal	3363	it by calling C<ev_async_send>, which is thread- and signal safe.
2980	safe.
2981		3364
2982	This functionality is very similar to C<ev_signal> watchers, as signals,	3365	This functionality is very similar to C<ev_signal> watchers, as signals,
2983	too, are asynchronous in nature, and signals, too, will be compressed	3366	too, are asynchronous in nature, and signals, too, will be compressed
2984	(i.e. the number of callback invocations may be less than the number of	3367	(i.e. the number of callback invocations may be less than the number of
2985	C<ev_async_sent> calls).	3368	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2986		3369	of "global async watchers" by using a watcher on an otherwise unused
2987	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3370	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2988	just the default loop.	3371	even without knowing which loop owns the signal.
2989		3372
2990	=head3 Queueing	3373	=head3 Queueing
2991		3374
2992	C<ev_async> does not support queueing of data in any way. The reason	3375	C<ev_async> does not support queueing of data in any way. The reason
2993	is that the author does not know of a simple (or any) algorithm for a	3376	is that the author does not know of a simple (or any) algorithm for a
…		…
3085	trust me.	3468	trust me.
3086		3469
3087	=item ev_async_send (loop, ev_async *)	3470	=item ev_async_send (loop, ev_async *)
3088		3471
3089	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3472	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3090	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3473	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3474	returns.
		3475
3091	C<ev_feed_event>, this call is safe to do from other threads, signal or	3476	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3092	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3477	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3093	section below on what exactly this means).	3478	embedding section below on what exactly this means).
3094		3479
3095	Note that, as with other watchers in libev, multiple events might get	3480	Note that, as with other watchers in libev, multiple events might get
3096	compressed into a single callback invocation (another way to look at this	3481	compressed into a single callback invocation (another way to look at
3097	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3482	this is that C<ev_async> watchers are level-triggered: they are set on
3098	reset when the event loop detects that).	3483	C<ev_async_send>, reset when the event loop detects that).
3099		3484
3100	This call incurs the overhead of a system call only once per event loop	3485	This call incurs the overhead of at most one extra system call per event
3101	iteration, so while the overhead might be noticeable, it doesn't apply to	3486	loop iteration, if the event loop is blocked, and no syscall at all if
3102	repeated calls to C<ev_async_send> for the same event loop.	3487	the event loop (or your program) is processing events. That means that
		3488	repeated calls are basically free (there is no need to avoid calls for
		3489	performance reasons) and that the overhead becomes smaller (typically
		3490	zero) under load.
3103		3491
3104	=item bool = ev_async_pending (ev_async *)	3492	=item bool = ev_async_pending (ev_async *)
3105		3493
3106	Returns a non-zero value when C<ev_async_send> has been called on the	3494	Returns a non-zero value when C<ev_async_send> has been called on the
3107	watcher but the event has not yet been processed (or even noted) by the	3495	watcher but the event has not yet been processed (or even noted) by the
…		…
3140		3528
3141	If C<timeout> is less than 0, then no timeout watcher will be	3529	If C<timeout> is less than 0, then no timeout watcher will be
3142	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3530	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3143	repeat = 0) will be started. C<0> is a valid timeout.	3531	repeat = 0) will be started. C<0> is a valid timeout.
3144		3532
3145	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3533	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3146	passed an C<revents> set like normal event callbacks (a combination of	3534	passed an C<revents> set like normal event callbacks (a combination of
3147	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3535	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3148	value passed to C<ev_once>. Note that it is possible to receive I<both>	3536	value passed to C<ev_once>. Note that it is possible to receive I<both>
3149	a timeout and an io event at the same time - you probably should give io	3537	a timeout and an io event at the same time - you probably should give io
3150	events precedence.	3538	events precedence.
3151		3539
3152	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3540	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3153		3541
3154	static void stdin_ready (int revents, void *arg)	3542	static void stdin_ready (int revents, void *arg)
3155	{	3543	{
3156	if (revents & EV_READ)	3544	if (revents & EV_READ)
3157	/* stdin might have data for us, joy! */;	3545	/* stdin might have data for us, joy! */;
3158	else if (revents & EV_TIMEOUT)	3546	else if (revents & EV_TIMER)
3159	/* doh, nothing entered */;	3547	/* doh, nothing entered */;
3160	}	3548	}
3161		3549
3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3550	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3163		3551
3164	=item ev_feed_fd_event (loop, int fd, int revents)	3552	=item ev_feed_fd_event (loop, int fd, int revents)
3165		3553
3166	Feed an event on the given fd, as if a file descriptor backend detected	3554	Feed an event on the given fd, as if a file descriptor backend detected
3167	the given events it.	3555	the given events.
3168		3556
3169	=item ev_feed_signal_event (loop, int signum)	3557	=item ev_feed_signal_event (loop, int signum)
3170		3558
3171	Feed an event as if the given signal occurred (C<loop> must be the default	3559	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3172	loop!).	3560	which is async-safe.
3173		3561
3174	=back	3562	=back
		3563
		3564
		3565	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3566
		3567	This section explains some common idioms that are not immediately
		3568	obvious. Note that examples are sprinkled over the whole manual, and this
		3569	section only contains stuff that wouldn't fit anywhere else.
		3570
		3571	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3572
		3573	Each watcher has, by default, a C<void *data> member that you can read
		3574	or modify at any time: libev will completely ignore it. This can be used
		3575	to associate arbitrary data with your watcher. If you need more data and
		3576	don't want to allocate memory separately and store a pointer to it in that
		3577	data member, you can also "subclass" the watcher type and provide your own
		3578	data:
		3579
		3580	struct my_io
		3581	{
		3582	ev_io io;
		3583	int otherfd;
		3584	void *somedata;
		3585	struct whatever *mostinteresting;
		3586	};
		3587
		3588	...
		3589	struct my_io w;
		3590	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3591
		3592	And since your callback will be called with a pointer to the watcher, you
		3593	can cast it back to your own type:
		3594
		3595	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3596	{
		3597	struct my_io *w = (struct my_io *)w_;
		3598	...
		3599	}
		3600
		3601	More interesting and less C-conformant ways of casting your callback
		3602	function type instead have been omitted.
		3603
		3604	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3605
		3606	Another common scenario is to use some data structure with multiple
		3607	embedded watchers, in effect creating your own watcher that combines
		3608	multiple libev event sources into one "super-watcher":
		3609
		3610	struct my_biggy
		3611	{
		3612	int some_data;
		3613	ev_timer t1;
		3614	ev_timer t2;
		3615	}
		3616
		3617	In this case getting the pointer to C<my_biggy> is a bit more
		3618	complicated: Either you store the address of your C<my_biggy> struct in
		3619	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3620	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3621	real programmers):
		3622
		3623	#include <stddef.h>
		3624
		3625	static void
		3626	t1_cb (EV_P_ ev_timer *w, int revents)
		3627	{
		3628	struct my_biggy big = (struct my_biggy *)
		3629	(((char *)w) - offsetof (struct my_biggy, t1));
		3630	}
		3631
		3632	static void
		3633	t2_cb (EV_P_ ev_timer *w, int revents)
		3634	{
		3635	struct my_biggy big = (struct my_biggy *)
		3636	(((char *)w) - offsetof (struct my_biggy, t2));
		3637	}
		3638
		3639	=head2 AVOIDING FINISHING BEFORE RETURNING
		3640
		3641	Often you have structures like this in event-based programs:
		3642
		3643	callback ()
		3644	{
		3645	free (request);
		3646	}
		3647
		3648	request = start_new_request (..., callback);
		3649
		3650	The intent is to start some "lengthy" operation. The C<request> could be
		3651	used to cancel the operation, or do other things with it.
		3652
		3653	It's not uncommon to have code paths in C<start_new_request> that
		3654	immediately invoke the callback, for example, to report errors. Or you add
		3655	some caching layer that finds that it can skip the lengthy aspects of the
		3656	operation and simply invoke the callback with the result.
		3657
		3658	The problem here is that this will happen I<before> C<start_new_request>
		3659	has returned, so C<request> is not set.
		3660
		3661	Even if you pass the request by some safer means to the callback, you
		3662	might want to do something to the request after starting it, such as
		3663	canceling it, which probably isn't working so well when the callback has
		3664	already been invoked.
		3665
		3666	A common way around all these issues is to make sure that
		3667	C<start_new_request> I<always> returns before the callback is invoked. If
		3668	C<start_new_request> immediately knows the result, it can artificially
		3669	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3670	example, or more sneakily, by reusing an existing (stopped) watcher and
		3671	pushing it into the pending queue:
		3672
		3673	ev_set_cb (watcher, callback);
		3674	ev_feed_event (EV_A_ watcher, 0);
		3675
		3676	This way, C<start_new_request> can safely return before the callback is
		3677	invoked, while not delaying callback invocation too much.
		3678
		3679	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3680
		3681	Often (especially in GUI toolkits) there are places where you have
		3682	I<modal> interaction, which is most easily implemented by recursively
		3683	invoking C<ev_run>.
		3684
		3685	This brings the problem of exiting - a callback might want to finish the
		3686	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3687	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3688	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3689	other combination: In these cases, a simple C<ev_break> will not work.
		3690
		3691	The solution is to maintain "break this loop" variable for each C<ev_run>
		3692	invocation, and use a loop around C<ev_run> until the condition is
		3693	triggered, using C<EVRUN_ONCE>:
		3694
		3695	// main loop
		3696	int exit_main_loop = 0;
		3697
		3698	while (!exit_main_loop)
		3699	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3700
		3701	// in a modal watcher
		3702	int exit_nested_loop = 0;
		3703
		3704	while (!exit_nested_loop)
		3705	ev_run (EV_A_ EVRUN_ONCE);
		3706
		3707	To exit from any of these loops, just set the corresponding exit variable:
		3708
		3709	// exit modal loop
		3710	exit_nested_loop = 1;
		3711
		3712	// exit main program, after modal loop is finished
		3713	exit_main_loop = 1;
		3714
		3715	// exit both
		3716	exit_main_loop = exit_nested_loop = 1;
		3717
		3718	=head2 THREAD LOCKING EXAMPLE
		3719
		3720	Here is a fictitious example of how to run an event loop in a different
		3721	thread from where callbacks are being invoked and watchers are
		3722	created/added/removed.
		3723
		3724	For a real-world example, see the C<EV::Loop::Async> perl module,
		3725	which uses exactly this technique (which is suited for many high-level
		3726	languages).
		3727
		3728	The example uses a pthread mutex to protect the loop data, a condition
		3729	variable to wait for callback invocations, an async watcher to notify the
		3730	event loop thread and an unspecified mechanism to wake up the main thread.
		3731
		3732	First, you need to associate some data with the event loop:
		3733
		3734	typedef struct {
		3735	mutex_t lock; /* global loop lock */
		3736	ev_async async_w;
		3737	thread_t tid;
		3738	cond_t invoke_cv;
		3739	} userdata;
		3740
		3741	void prepare_loop (EV_P)
		3742	{
		3743	// for simplicity, we use a static userdata struct.
		3744	static userdata u;
		3745
		3746	ev_async_init (&u->async_w, async_cb);
		3747	ev_async_start (EV_A_ &u->async_w);
		3748
		3749	pthread_mutex_init (&u->lock, 0);
		3750	pthread_cond_init (&u->invoke_cv, 0);
		3751
		3752	// now associate this with the loop
		3753	ev_set_userdata (EV_A_ u);
		3754	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3755	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3756
		3757	// then create the thread running ev_run
		3758	pthread_create (&u->tid, 0, l_run, EV_A);
		3759	}
		3760
		3761	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3762	solely to wake up the event loop so it takes notice of any new watchers
		3763	that might have been added:
		3764
		3765	static void
		3766	async_cb (EV_P_ ev_async *w, int revents)
		3767	{
		3768	// just used for the side effects
		3769	}
		3770
		3771	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3772	protecting the loop data, respectively.
		3773
		3774	static void
		3775	l_release (EV_P)
		3776	{
		3777	userdata *u = ev_userdata (EV_A);
		3778	pthread_mutex_unlock (&u->lock);
		3779	}
		3780
		3781	static void
		3782	l_acquire (EV_P)
		3783	{
		3784	userdata *u = ev_userdata (EV_A);
		3785	pthread_mutex_lock (&u->lock);
		3786	}
		3787
		3788	The event loop thread first acquires the mutex, and then jumps straight
		3789	into C<ev_run>:
		3790
		3791	void *
		3792	l_run (void *thr_arg)
		3793	{
		3794	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3795
		3796	l_acquire (EV_A);
		3797	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3798	ev_run (EV_A_ 0);
		3799	l_release (EV_A);
		3800
		3801	return 0;
		3802	}
		3803
		3804	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3805	signal the main thread via some unspecified mechanism (signals? pipe
		3806	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3807	have been called (in a while loop because a) spurious wakeups are possible
		3808	and b) skipping inter-thread-communication when there are no pending
		3809	watchers is very beneficial):
		3810
		3811	static void
		3812	l_invoke (EV_P)
		3813	{
		3814	userdata *u = ev_userdata (EV_A);
		3815
		3816	while (ev_pending_count (EV_A))
		3817	{
		3818	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3819	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3820	}
		3821	}
		3822
		3823	Now, whenever the main thread gets told to invoke pending watchers, it
		3824	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3825	thread to continue:
		3826
		3827	static void
		3828	real_invoke_pending (EV_P)
		3829	{
		3830	userdata *u = ev_userdata (EV_A);
		3831
		3832	pthread_mutex_lock (&u->lock);
		3833	ev_invoke_pending (EV_A);
		3834	pthread_cond_signal (&u->invoke_cv);
		3835	pthread_mutex_unlock (&u->lock);
		3836	}
		3837
		3838	Whenever you want to start/stop a watcher or do other modifications to an
		3839	event loop, you will now have to lock:
		3840
		3841	ev_timer timeout_watcher;
		3842	userdata *u = ev_userdata (EV_A);
		3843
		3844	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3845
		3846	pthread_mutex_lock (&u->lock);
		3847	ev_timer_start (EV_A_ &timeout_watcher);
		3848	ev_async_send (EV_A_ &u->async_w);
		3849	pthread_mutex_unlock (&u->lock);
		3850
		3851	Note that sending the C<ev_async> watcher is required because otherwise
		3852	an event loop currently blocking in the kernel will have no knowledge
		3853	about the newly added timer. By waking up the loop it will pick up any new
		3854	watchers in the next event loop iteration.
		3855
		3856	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3857
		3858	While the overhead of a callback that e.g. schedules a thread is small, it
		3859	is still an overhead. If you embed libev, and your main usage is with some
		3860	kind of threads or coroutines, you might want to customise libev so that
		3861	doesn't need callbacks anymore.
		3862
		3863	Imagine you have coroutines that you can switch to using a function
		3864	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3865	and that due to some magic, the currently active coroutine is stored in a
		3866	global called C<current_coro>. Then you can build your own "wait for libev
		3867	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3868	the differing C<;> conventions):
		3869
		3870	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3871	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3872
		3873	That means instead of having a C callback function, you store the
		3874	coroutine to switch to in each watcher, and instead of having libev call
		3875	your callback, you instead have it switch to that coroutine.
		3876
		3877	A coroutine might now wait for an event with a function called
		3878	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3879	matter when, or whether the watcher is active or not when this function is
		3880	called):
		3881
		3882	void
		3883	wait_for_event (ev_watcher *w)
		3884	{
		3885	ev_set_cb (w, current_coro);
		3886	switch_to (libev_coro);
		3887	}
		3888
		3889	That basically suspends the coroutine inside C<wait_for_event> and
		3890	continues the libev coroutine, which, when appropriate, switches back to
		3891	this or any other coroutine.
		3892
		3893	You can do similar tricks if you have, say, threads with an event queue -
		3894	instead of storing a coroutine, you store the queue object and instead of
		3895	switching to a coroutine, you push the watcher onto the queue and notify
		3896	any waiters.
		3897
		3898	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3899	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3900
		3901	// my_ev.h
		3902	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3903	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3904	#include "../libev/ev.h"
		3905
		3906	// my_ev.c
		3907	#define EV_H "my_ev.h"
		3908	#include "../libev/ev.c"
		3909
		3910	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3911	F<my_ev.c> into your project. When properly specifying include paths, you
		3912	can even use F<ev.h> as header file name directly.
3175		3913
3176		3914
3177	=head1 LIBEVENT EMULATION	3915	=head1 LIBEVENT EMULATION
3178		3916
3179	Libev offers a compatibility emulation layer for libevent. It cannot	3917	Libev offers a compatibility emulation layer for libevent. It cannot
3180	emulate the internals of libevent, so here are some usage hints:	3918	emulate the internals of libevent, so here are some usage hints:
3181		3919
3182	=over 4	3920	=over 4
		3921
		3922	=item * Only the libevent-1.4.1-beta API is being emulated.
		3923
		3924	This was the newest libevent version available when libev was implemented,
		3925	and is still mostly unchanged in 2010.
3183		3926
3184	=item * Use it by including <event.h>, as usual.	3927	=item * Use it by including <event.h>, as usual.
3185		3928
3186	=item * The following members are fully supported: ev_base, ev_callback,	3929	=item * The following members are fully supported: ev_base, ev_callback,
3187	ev_arg, ev_fd, ev_res, ev_events.	3930	ev_arg, ev_fd, ev_res, ev_events.
…		…
3193	=item * Priorities are not currently supported. Initialising priorities	3936	=item * Priorities are not currently supported. Initialising priorities
3194	will fail and all watchers will have the same priority, even though there	3937	will fail and all watchers will have the same priority, even though there
3195	is an ev_pri field.	3938	is an ev_pri field.
3196		3939
3197	=item * In libevent, the last base created gets the signals, in libev, the	3940	=item * In libevent, the last base created gets the signals, in libev, the
3198	first base created (== the default loop) gets the signals.	3941	base that registered the signal gets the signals.
3199		3942
3200	=item * Other members are not supported.	3943	=item * Other members are not supported.
3201		3944
3202	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3945	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3203	to use the libev header file and library.	3946	to use the libev header file and library.
3204		3947
3205	=back	3948	=back
3206		3949
3207	=head1 C++ SUPPORT	3950	=head1 C++ SUPPORT
		3951
		3952	=head2 C API
		3953
		3954	The normal C API should work fine when used from C++: both ev.h and the
		3955	libev sources can be compiled as C++. Therefore, code that uses the C API
		3956	will work fine.
		3957
		3958	Proper exception specifications might have to be added to callbacks passed
		3959	to libev: exceptions may be thrown only from watcher callbacks, all
		3960	other callbacks (allocator, syserr, loop acquire/release and periodic
		3961	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3962	()> specification. If you have code that needs to be compiled as both C
		3963	and C++ you can use the C<EV_THROW> macro for this:
		3964
		3965	static void
		3966	fatal_error (const char *msg) EV_THROW
		3967	{
		3968	perror (msg);
		3969	abort ();
		3970	}
		3971
		3972	...
		3973	ev_set_syserr_cb (fatal_error);
		3974
		3975	The only API functions that can currently throw exceptions are C<ev_run>,
		3976	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3977	because it runs cleanup watchers).
		3978
		3979	Throwing exceptions in watcher callbacks is only supported if libev itself
		3980	is compiled with a C++ compiler or your C and C++ environments allow
		3981	throwing exceptions through C libraries (most do).
		3982
		3983	=head2 C++ API
3208		3984
3209	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3985	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3210	you to use some convenience methods to start/stop watchers and also change	3986	you to use some convenience methods to start/stop watchers and also change
3211	the callback model to a model using method callbacks on objects.	3987	the callback model to a model using method callbacks on objects.
3212		3988
3213	To use it,	3989	To use it,
3214		3990
3215	#include <ev++.h>	3991	#include <ev++.h>
3216		3992
3217	This automatically includes F<ev.h> and puts all of its definitions (many	3993	This automatically includes F<ev.h> and puts all of its definitions (many
3218	of them macros) into the global namespace. All C++ specific things are	3994	of them macros) into the global namespace. All C++ specific things are
3219	put into the C<ev> namespace. It should support all the same embedding	3995	put into the C<ev> namespace. It should support all the same embedding
…		…
3222	Care has been taken to keep the overhead low. The only data member the C++	3998	Care has been taken to keep the overhead low. The only data member the C++
3223	classes add (compared to plain C-style watchers) is the event loop pointer	3999	classes add (compared to plain C-style watchers) is the event loop pointer
3224	that the watcher is associated with (or no additional members at all if	4000	that the watcher is associated with (or no additional members at all if
3225	you disable C<EV_MULTIPLICITY> when embedding libev).	4001	you disable C<EV_MULTIPLICITY> when embedding libev).
3226		4002
3227	Currently, functions, and static and non-static member functions can be	4003	Currently, functions, static and non-static member functions and classes
3228	used as callbacks. Other types should be easy to add as long as they only	4004	with C<operator ()> can be used as callbacks. Other types should be easy
3229	need one additional pointer for context. If you need support for other	4005	to add as long as they only need one additional pointer for context. If
3230	types of functors please contact the author (preferably after implementing	4006	you need support for other types of functors please contact the author
3231	it).	4007	(preferably after implementing it).
		4008
		4009	For all this to work, your C++ compiler either has to use the same calling
		4010	conventions as your C compiler (for static member functions), or you have
		4011	to embed libev and compile libev itself as C++.
3232		4012
3233	Here is a list of things available in the C<ev> namespace:	4013	Here is a list of things available in the C<ev> namespace:
3234		4014
3235	=over 4	4015	=over 4
3236		4016
…		…
3246	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4026	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3247		4027
3248	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4028	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3249	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4029	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3250	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4030	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3251	defines by many implementations.	4031	defined by many implementations.
3252		4032
3253	All of those classes have these methods:	4033	All of those classes have these methods:
3254		4034
3255	=over 4	4035	=over 4
3256		4036
…		…
3297	myclass obj;	4077	myclass obj;
3298	ev::io iow;	4078	ev::io iow;
3299	iow.set <myclass, &myclass::io_cb> (&obj);	4079	iow.set <myclass, &myclass::io_cb> (&obj);
3300		4080
3301	=item w->set (object *)	4081	=item w->set (object *)
3302
3303	This is an B<experimental> feature that might go away in a future version.
3304		4082
3305	This is a variation of a method callback - leaving out the method to call	4083	This is a variation of a method callback - leaving out the method to call
3306	will default the method to C<operator ()>, which makes it possible to use	4084	will default the method to C<operator ()>, which makes it possible to use
3307	functor objects without having to manually specify the C<operator ()> all	4085	functor objects without having to manually specify the C<operator ()> all
3308	the time. Incidentally, you can then also leave out the template argument	4086	the time. Incidentally, you can then also leave out the template argument
…		…
3320	void operator() (ev::io &w, int revents)	4098	void operator() (ev::io &w, int revents)
3321	{	4099	{
3322	...	4100	...
3323	}	4101	}
3324	}	4102	}
3325		4103
3326	myfunctor f;	4104	myfunctor f;
3327		4105
3328	ev::io w;	4106	ev::io w;
3329	w.set (&f);	4107	w.set (&f);
3330		4108
…		…
3348	Associates a different C<struct ev_loop> with this watcher. You can only	4126	Associates a different C<struct ev_loop> with this watcher. You can only
3349	do this when the watcher is inactive (and not pending either).	4127	do this when the watcher is inactive (and not pending either).
3350		4128
3351	=item w->set ([arguments])	4129	=item w->set ([arguments])
3352		4130
3353	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4131	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4132	with the same arguments. Either this method or a suitable start method
3354	called at least once. Unlike the C counterpart, an active watcher gets	4133	must be called at least once. Unlike the C counterpart, an active watcher
3355	automatically stopped and restarted when reconfiguring it with this	4134	gets automatically stopped and restarted when reconfiguring it with this
3356	method.	4135	method.
		4136
		4137	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4138	clashing with the C<set (loop)> method.
3357		4139
3358	=item w->start ()	4140	=item w->start ()
3359		4141
3360	Starts the watcher. Note that there is no C<loop> argument, as the	4142	Starts the watcher. Note that there is no C<loop> argument, as the
3361	constructor already stores the event loop.	4143	constructor already stores the event loop.
3362		4144
		4145	=item w->start ([arguments])
		4146
		4147	Instead of calling C<set> and C<start> methods separately, it is often
		4148	convenient to wrap them in one call. Uses the same type of arguments as
		4149	the configure C<set> method of the watcher.
		4150
3363	=item w->stop ()	4151	=item w->stop ()
3364		4152
3365	Stops the watcher if it is active. Again, no C<loop> argument.	4153	Stops the watcher if it is active. Again, no C<loop> argument.
3366		4154
3367	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4155	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3379		4167
3380	=back	4168	=back
3381		4169
3382	=back	4170	=back
3383		4171
3384	Example: Define a class with an IO and idle watcher, start one of them in	4172	Example: Define a class with two I/O and idle watchers, start the I/O
3385	the constructor.	4173	watchers in the constructor.
3386		4174
3387	class myclass	4175	class myclass
3388	{	4176	{
3389	ev::io io ; void io_cb (ev::io &w, int revents);	4177	ev::io io ; void io_cb (ev::io &w, int revents);
		4178	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3390	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4179	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3391		4180
3392	myclass (int fd)	4181	myclass (int fd)
3393	{	4182	{
3394	io .set <myclass, &myclass::io_cb > (this);	4183	io .set <myclass, &myclass::io_cb > (this);
		4184	io2 .set <myclass, &myclass::io2_cb > (this);
3395	idle.set <myclass, &myclass::idle_cb> (this);	4185	idle.set <myclass, &myclass::idle_cb> (this);
3396		4186
3397	io.start (fd, ev::READ);	4187	io.set (fd, ev::WRITE); // configure the watcher
		4188	io.start (); // start it whenever convenient
		4189
		4190	io2.start (fd, ev::READ); // set + start in one call
3398	}	4191	}
3399	};	4192	};
3400		4193
3401		4194
3402	=head1 OTHER LANGUAGE BINDINGS	4195	=head1 OTHER LANGUAGE BINDINGS
…		…
3441	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4234	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3442		4235
3443	=item D	4236	=item D
3444		4237
3445	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4238	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3446	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4239	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3447		4240
3448	=item Ocaml	4241	=item Ocaml
3449		4242
3450	Erkki Seppala has written Ocaml bindings for libev, to be found at	4243	Erkki Seppala has written Ocaml bindings for libev, to be found at
3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4244	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3452		4245
3453	=item Lua	4246	=item Lua
3454		4247
3455	Brian Maher has written a partial interface to libev	4248	Brian Maher has written a partial interface to libev for lua (at the
3456	for lua (only C<ev_io> and C<ev_timer>), to be found at	4249	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3457	L<http://github.com/brimworks/lua-ev>.	4250	L<http://github.com/brimworks/lua-ev>.
		4251
		4252	=item Javascript
		4253
		4254	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4255
		4256	=item Others
		4257
		4258	There are others, and I stopped counting.
3458		4259
3459	=back	4260	=back
3460		4261
3461		4262
3462	=head1 MACRO MAGIC	4263	=head1 MACRO MAGIC
…		…
3476	loop argument"). The C<EV_A> form is used when this is the sole argument,	4277	loop argument"). The C<EV_A> form is used when this is the sole argument,
3477	C<EV_A_> is used when other arguments are following. Example:	4278	C<EV_A_> is used when other arguments are following. Example:
3478		4279
3479	ev_unref (EV_A);	4280	ev_unref (EV_A);
3480	ev_timer_add (EV_A_ watcher);	4281	ev_timer_add (EV_A_ watcher);
3481	ev_loop (EV_A_ 0);	4282	ev_run (EV_A_ 0);
3482		4283
3483	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4284	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3484	which is often provided by the following macro.	4285	which is often provided by the following macro.
3485		4286
3486	=item C<EV_P>, C<EV_P_>	4287	=item C<EV_P>, C<EV_P_>
…		…
3499	suitable for use with C<EV_A>.	4300	suitable for use with C<EV_A>.
3500		4301
3501	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4302	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3502		4303
3503	Similar to the other two macros, this gives you the value of the default	4304	Similar to the other two macros, this gives you the value of the default
3504	loop, if multiple loops are supported ("ev loop default").	4305	loop, if multiple loops are supported ("ev loop default"). The default loop
		4306	will be initialised if it isn't already initialised.
		4307
		4308	For non-multiplicity builds, these macros do nothing, so you always have
		4309	to initialise the loop somewhere.
3505		4310
3506	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4311	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3507		4312
3508	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4313	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3509	default loop has been initialised (C<UC> == unchecked). Their behaviour	4314	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3526	}	4331	}
3527		4332
3528	ev_check check;	4333	ev_check check;
3529	ev_check_init (&check, check_cb);	4334	ev_check_init (&check, check_cb);
3530	ev_check_start (EV_DEFAULT_ &check);	4335	ev_check_start (EV_DEFAULT_ &check);
3531	ev_loop (EV_DEFAULT_ 0);	4336	ev_run (EV_DEFAULT_ 0);
3532		4337
3533	=head1 EMBEDDING	4338	=head1 EMBEDDING
3534		4339
3535	Libev can (and often is) directly embedded into host	4340	Libev can (and often is) directly embedded into host
3536	applications. Examples of applications that embed it include the Deliantra	4341	applications. Examples of applications that embed it include the Deliantra
…		…
3616	libev.m4	4421	libev.m4
3617		4422
3618	=head2 PREPROCESSOR SYMBOLS/MACROS	4423	=head2 PREPROCESSOR SYMBOLS/MACROS
3619		4424
3620	Libev can be configured via a variety of preprocessor symbols you have to	4425	Libev can be configured via a variety of preprocessor symbols you have to
3621	define before including any of its files. The default in the absence of	4426	define before including (or compiling) any of its files. The default in
3622	autoconf is documented for every option.	4427	the absence of autoconf is documented for every option.
		4428
		4429	Symbols marked with "(h)" do not change the ABI, and can have different
		4430	values when compiling libev vs. including F<ev.h>, so it is permissible
		4431	to redefine them before including F<ev.h> without breaking compatibility
		4432	to a compiled library. All other symbols change the ABI, which means all
		4433	users of libev and the libev code itself must be compiled with compatible
		4434	settings.
3623		4435
3624	=over 4	4436	=over 4
3625		4437
		4438	=item EV_COMPAT3 (h)
		4439
		4440	Backwards compatibility is a major concern for libev. This is why this
		4441	release of libev comes with wrappers for the functions and symbols that
		4442	have been renamed between libev version 3 and 4.
		4443
		4444	You can disable these wrappers (to test compatibility with future
		4445	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4446	sources. This has the additional advantage that you can drop the C<struct>
		4447	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4448	typedef in that case.
		4449
		4450	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4451	and in some even more future version the compatibility code will be
		4452	removed completely.
		4453
3626	=item EV_STANDALONE	4454	=item EV_STANDALONE (h)
3627		4455
3628	Must always be C<1> if you do not use autoconf configuration, which	4456	Must always be C<1> if you do not use autoconf configuration, which
3629	keeps libev from including F<config.h>, and it also defines dummy	4457	keeps libev from including F<config.h>, and it also defines dummy
3630	implementations for some libevent functions (such as logging, which is not	4458	implementations for some libevent functions (such as logging, which is not
3631	supported). It will also not define any of the structs usually found in	4459	supported). It will also not define any of the structs usually found in
3632	F<event.h> that are not directly supported by the libev core alone.	4460	F<event.h> that are not directly supported by the libev core alone.
3633		4461
3634	In standalone mode, libev will still try to automatically deduce the	4462	In standalone mode, libev will still try to automatically deduce the
3635	configuration, but has to be more conservative.	4463	configuration, but has to be more conservative.
		4464
		4465	=item EV_USE_FLOOR
		4466
		4467	If defined to be C<1>, libev will use the C<floor ()> function for its
		4468	periodic reschedule calculations, otherwise libev will fall back on a
		4469	portable (slower) implementation. If you enable this, you usually have to
		4470	link against libm or something equivalent. Enabling this when the C<floor>
		4471	function is not available will fail, so the safe default is to not enable
		4472	this.
3636		4473
3637	=item EV_USE_MONOTONIC	4474	=item EV_USE_MONOTONIC
3638		4475
3639	If defined to be C<1>, libev will try to detect the availability of the	4476	If defined to be C<1>, libev will try to detect the availability of the
3640	monotonic clock option at both compile time and runtime. Otherwise no	4477	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3725		4562
3726	If programs implement their own fd to handle mapping on win32, then this	4563	If programs implement their own fd to handle mapping on win32, then this
3727	macro can be used to override the C<close> function, useful to unregister	4564	macro can be used to override the C<close> function, useful to unregister
3728	file descriptors again. Note that the replacement function has to close	4565	file descriptors again. Note that the replacement function has to close
3729	the underlying OS handle.	4566	the underlying OS handle.
		4567
		4568	=item EV_USE_WSASOCKET
		4569
		4570	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4571	communication socket, which works better in some environments. Otherwise,
		4572	the normal C<socket> function will be used, which works better in other
		4573	environments.
3730		4574
3731	=item EV_USE_POLL	4575	=item EV_USE_POLL
3732		4576
3733	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4577	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3734	backend. Otherwise it will be enabled on non-win32 platforms. It	4578	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3770	If defined to be C<1>, libev will compile in support for the Linux inotify	4614	If defined to be C<1>, libev will compile in support for the Linux inotify
3771	interface to speed up C<ev_stat> watchers. Its actual availability will	4615	interface to speed up C<ev_stat> watchers. Its actual availability will
3772	be detected at runtime. If undefined, it will be enabled if the headers	4616	be detected at runtime. If undefined, it will be enabled if the headers
3773	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4617	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3774		4618
		4619	=item EV_NO_SMP
		4620
		4621	If defined to be C<1>, libev will assume that memory is always coherent
		4622	between threads, that is, threads can be used, but threads never run on
		4623	different cpus (or different cpu cores). This reduces dependencies
		4624	and makes libev faster.
		4625
		4626	=item EV_NO_THREADS
		4627
		4628	If defined to be C<1>, libev will assume that it will never be called from
		4629	different threads (that includes signal handlers), which is a stronger
		4630	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4631	libev faster.
		4632
3775	=item EV_ATOMIC_T	4633	=item EV_ATOMIC_T
3776		4634
3777	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4635	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3778	access is atomic with respect to other threads or signal contexts. No such	4636	access is atomic with respect to other threads or signal contexts. No
3779	type is easily found in the C language, so you can provide your own type	4637	such type is easily found in the C language, so you can provide your own
3780	that you know is safe for your purposes. It is used both for signal handler "locking"	4638	type that you know is safe for your purposes. It is used both for signal
3781	as well as for signal and thread safety in C<ev_async> watchers.	4639	handler "locking" as well as for signal and thread safety in C<ev_async>
		4640	watchers.
3782		4641
3783	In the absence of this define, libev will use C<sig_atomic_t volatile>	4642	In the absence of this define, libev will use C<sig_atomic_t volatile>
3784	(from F<signal.h>), which is usually good enough on most platforms.	4643	(from F<signal.h>), which is usually good enough on most platforms.
3785		4644
3786	=item EV_H	4645	=item EV_H (h)
3787		4646
3788	The name of the F<ev.h> header file used to include it. The default if	4647	The name of the F<ev.h> header file used to include it. The default if
3789	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4648	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3790	used to virtually rename the F<ev.h> header file in case of conflicts.	4649	used to virtually rename the F<ev.h> header file in case of conflicts.
3791		4650
3792	=item EV_CONFIG_H	4651	=item EV_CONFIG_H (h)
3793		4652
3794	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4653	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3795	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4654	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3796	C<EV_H>, above.	4655	C<EV_H>, above.
3797		4656
3798	=item EV_EVENT_H	4657	=item EV_EVENT_H (h)
3799		4658
3800	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4659	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3801	of how the F<event.h> header can be found, the default is C<"event.h">.	4660	of how the F<event.h> header can be found, the default is C<"event.h">.
3802		4661
3803	=item EV_PROTOTYPES	4662	=item EV_PROTOTYPES (h)
3804		4663
3805	If defined to be C<0>, then F<ev.h> will not define any function	4664	If defined to be C<0>, then F<ev.h> will not define any function
3806	prototypes, but still define all the structs and other symbols. This is	4665	prototypes, but still define all the structs and other symbols. This is
3807	occasionally useful if you want to provide your own wrapper functions	4666	occasionally useful if you want to provide your own wrapper functions
3808	around libev functions.	4667	around libev functions.
…		…
3813	will have the C<struct ev_loop *> as first argument, and you can create	4672	will have the C<struct ev_loop *> as first argument, and you can create
3814	additional independent event loops. Otherwise there will be no support	4673	additional independent event loops. Otherwise there will be no support
3815	for multiple event loops and there is no first event loop pointer	4674	for multiple event loops and there is no first event loop pointer
3816	argument. Instead, all functions act on the single default loop.	4675	argument. Instead, all functions act on the single default loop.
3817		4676
		4677	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4678	default loop when multiplicity is switched off - you always have to
		4679	initialise the loop manually in this case.
		4680
3818	=item EV_MINPRI	4681	=item EV_MINPRI
3819		4682
3820	=item EV_MAXPRI	4683	=item EV_MAXPRI
3821		4684
3822	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4685	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3830	fine.	4693	fine.
3831		4694
3832	If your embedding application does not need any priorities, defining these	4695	If your embedding application does not need any priorities, defining these
3833	both to C<0> will save some memory and CPU.	4696	both to C<0> will save some memory and CPU.
3834		4697
3835	=item EV_PERIODIC_ENABLE	4698	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4699	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4700	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3836		4701
3837	If undefined or defined to be C<1>, then periodic timers are supported. If	4702	If undefined or defined to be C<1> (and the platform supports it), then
3838	defined to be C<0>, then they are not. Disabling them saves a few kB of	4703	the respective watcher type is supported. If defined to be C<0>, then it
3839	code.	4704	is not. Disabling watcher types mainly saves code size.
3840		4705
3841	=item EV_IDLE_ENABLE	4706	=item EV_FEATURES
3842
3843	If undefined or defined to be C<1>, then idle watchers are supported. If
3844	defined to be C<0>, then they are not. Disabling them saves a few kB of
3845	code.
3846
3847	=item EV_EMBED_ENABLE
3848
3849	If undefined or defined to be C<1>, then embed watchers are supported. If
3850	defined to be C<0>, then they are not. Embed watchers rely on most other
3851	watcher types, which therefore must not be disabled.
3852
3853	=item EV_STAT_ENABLE
3854
3855	If undefined or defined to be C<1>, then stat watchers are supported. If
3856	defined to be C<0>, then they are not.
3857
3858	=item EV_FORK_ENABLE
3859
3860	If undefined or defined to be C<1>, then fork watchers are supported. If
3861	defined to be C<0>, then they are not.
3862
3863	=item EV_ASYNC_ENABLE
3864
3865	If undefined or defined to be C<1>, then async watchers are supported. If
3866	defined to be C<0>, then they are not.
3867
3868	=item EV_MINIMAL
3869		4707
3870	If you need to shave off some kilobytes of code at the expense of some	4708	If you need to shave off some kilobytes of code at the expense of some
3871	speed (but with the full API), define this symbol to C<1>. Currently this	4709	speed (but with the full API), you can define this symbol to request
3872	is used to override some inlining decisions, saves roughly 30% code size	4710	certain subsets of functionality. The default is to enable all features
3873	on amd64. It also selects a much smaller 2-heap for timer management over	4711	that can be enabled on the platform.
3874	the default 4-heap.
3875		4712
3876	You can save even more by disabling watcher types you do not need	4713	A typical way to use this symbol is to define it to C<0> (or to a bitset
3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4714	with some broad features you want) and then selectively re-enable
3878	(C<-DNDEBUG>) will usually reduce code size a lot.	4715	additional parts you want, for example if you want everything minimal,
		4716	but multiple event loop support, async and child watchers and the poll
		4717	backend, use this:
3879		4718
3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4719	#define EV_FEATURES 0
3881	provide a bare-bones event library. See C<ev.h> for details on what parts	4720	#define EV_MULTIPLICITY 1
3882	of the API are still available, and do not complain if this subset changes	4721	#define EV_USE_POLL 1
3883	over time.	4722	#define EV_CHILD_ENABLE 1
		4723	#define EV_ASYNC_ENABLE 1
		4724
		4725	The actual value is a bitset, it can be a combination of the following
		4726	values (by default, all of these are enabled):
		4727
		4728	=over 4
		4729
		4730	=item C<1> - faster/larger code
		4731
		4732	Use larger code to speed up some operations.
		4733
		4734	Currently this is used to override some inlining decisions (enlarging the
		4735	code size by roughly 30% on amd64).
		4736
		4737	When optimising for size, use of compiler flags such as C<-Os> with
		4738	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4739	assertions.
		4740
		4741	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4742	(e.g. gcc with C<-Os>).
		4743
		4744	=item C<2> - faster/larger data structures
		4745
		4746	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4747	hash table sizes and so on. This will usually further increase code size
		4748	and can additionally have an effect on the size of data structures at
		4749	runtime.
		4750
		4751	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4752	(e.g. gcc with C<-Os>).
		4753
		4754	=item C<4> - full API configuration
		4755
		4756	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4757	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4758
		4759	=item C<8> - full API
		4760
		4761	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4762	details on which parts of the API are still available without this
		4763	feature, and do not complain if this subset changes over time.
		4764
		4765	=item C<16> - enable all optional watcher types
		4766
		4767	Enables all optional watcher types. If you want to selectively enable
		4768	only some watcher types other than I/O and timers (e.g. prepare,
		4769	embed, async, child...) you can enable them manually by defining
		4770	C<EV_watchertype_ENABLE> to C<1> instead.
		4771
		4772	=item C<32> - enable all backends
		4773
		4774	This enables all backends - without this feature, you need to enable at
		4775	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4776
		4777	=item C<64> - enable OS-specific "helper" APIs
		4778
		4779	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4780	default.
		4781
		4782	=back
		4783
		4784	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4785	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4786	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4787	watchers, timers and monotonic clock support.
		4788
		4789	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4790	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4791	your program might be left out as well - a binary starting a timer and an
		4792	I/O watcher then might come out at only 5Kb.
		4793
		4794	=item EV_API_STATIC
		4795
		4796	If this symbol is defined (by default it is not), then all identifiers
		4797	will have static linkage. This means that libev will not export any
		4798	identifiers, and you cannot link against libev anymore. This can be useful
		4799	when you embed libev, only want to use libev functions in a single file,
		4800	and do not want its identifiers to be visible.
		4801
		4802	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4803	wants to use libev.
		4804
		4805	This option only works when libev is compiled with a C compiler, as C++
		4806	doesn't support the required declaration syntax.
		4807
		4808	=item EV_AVOID_STDIO
		4809
		4810	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4811	functions (printf, scanf, perror etc.). This will increase the code size
		4812	somewhat, but if your program doesn't otherwise depend on stdio and your
		4813	libc allows it, this avoids linking in the stdio library which is quite
		4814	big.
		4815
		4816	Note that error messages might become less precise when this option is
		4817	enabled.
3884		4818
3885	=item EV_NSIG	4819	=item EV_NSIG
3886		4820
3887	The highest supported signal number, +1 (or, the number of	4821	The highest supported signal number, +1 (or, the number of
3888	signals): Normally, libev tries to deduce the maximum number of signals	4822	signals): Normally, libev tries to deduce the maximum number of signals
3889	automatically, but sometimes this fails, in which case it can be	4823	automatically, but sometimes this fails, in which case it can be
3890	specified. Also, using a lower number than detected (C<32> should be	4824	specified. Also, using a lower number than detected (C<32> should be
3891	good for about any system in existance) can save some memory, as libev	4825	good for about any system in existence) can save some memory, as libev
3892	statically allocates some 12-24 bytes per signal number.	4826	statically allocates some 12-24 bytes per signal number.
3893		4827
3894	=item EV_PID_HASHSIZE	4828	=item EV_PID_HASHSIZE
3895		4829
3896	C<ev_child> watchers use a small hash table to distribute workload by	4830	C<ev_child> watchers use a small hash table to distribute workload by
3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4831	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3898	than enough. If you need to manage thousands of children you might want to	4832	usually more than enough. If you need to manage thousands of children you
3899	increase this value (I<must> be a power of two).	4833	might want to increase this value (I<must> be a power of two).
3900		4834
3901	=item EV_INOTIFY_HASHSIZE	4835	=item EV_INOTIFY_HASHSIZE
3902		4836
3903	C<ev_stat> watchers use a small hash table to distribute workload by	4837	C<ev_stat> watchers use a small hash table to distribute workload by
3904	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4838	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3905	usually more than enough. If you need to manage thousands of C<ev_stat>	4839	disabled), usually more than enough. If you need to manage thousands of
3906	watchers you might want to increase this value (I<must> be a power of	4840	C<ev_stat> watchers you might want to increase this value (I<must> be a
3907	two).	4841	power of two).
3908		4842
3909	=item EV_USE_4HEAP	4843	=item EV_USE_4HEAP
3910		4844
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4845	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4846	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3913	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4847	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3914	faster performance with many (thousands) of watchers.	4848	faster performance with many (thousands) of watchers.
3915		4849
3916	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4850	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3917	(disabled).	4851	will be C<0>.
3918		4852
3919	=item EV_HEAP_CACHE_AT	4853	=item EV_HEAP_CACHE_AT
3920		4854
3921	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4855	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3922	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4856	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3923	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4857	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3924	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4858	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3925	but avoids random read accesses on heap changes. This improves performance	4859	but avoids random read accesses on heap changes. This improves performance
3926	noticeably with many (hundreds) of watchers.	4860	noticeably with many (hundreds) of watchers.
3927		4861
3928	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4862	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3929	(disabled).	4863	will be C<0>.
3930		4864
3931	=item EV_VERIFY	4865	=item EV_VERIFY
3932		4866
3933	Controls how much internal verification (see C<ev_loop_verify ()>) will	4867	Controls how much internal verification (see C<ev_verify ()>) will
3934	be done: If set to C<0>, no internal verification code will be compiled	4868	be done: If set to C<0>, no internal verification code will be compiled
3935	in. If set to C<1>, then verification code will be compiled in, but not	4869	in. If set to C<1>, then verification code will be compiled in, but not
3936	called. If set to C<2>, then the internal verification code will be	4870	called. If set to C<2>, then the internal verification code will be
3937	called once per loop, which can slow down libev. If set to C<3>, then the	4871	called once per loop, which can slow down libev. If set to C<3>, then the
3938	verification code will be called very frequently, which will slow down	4872	verification code will be called very frequently, which will slow down
3939	libev considerably.	4873	libev considerably.
3940		4874
3941	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4875	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3942	C<0>.	4876	will be C<0>.
3943		4877
3944	=item EV_COMMON	4878	=item EV_COMMON
3945		4879
3946	By default, all watchers have a C<void *data> member. By redefining	4880	By default, all watchers have a C<void *data> member. By redefining
3947	this macro to a something else you can include more and other types of	4881	this macro to something else you can include more and other types of
3948	members. You have to define it each time you include one of the files,	4882	members. You have to define it each time you include one of the files,
3949	though, and it must be identical each time.	4883	though, and it must be identical each time.
3950		4884
3951	For example, the perl EV module uses something like this:	4885	For example, the perl EV module uses something like this:
3952		4886
…		…
4005	file.	4939	file.
4006		4940
4007	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4941	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4008	that everybody includes and which overrides some configure choices:	4942	that everybody includes and which overrides some configure choices:
4009		4943
4010	#define EV_MINIMAL 1	4944	#define EV_FEATURES 8
4011	#define EV_USE_POLL 0	4945	#define EV_USE_SELECT 1
4012	#define EV_MULTIPLICITY 0
4013	#define EV_PERIODIC_ENABLE 0	4946	#define EV_PREPARE_ENABLE 1
		4947	#define EV_IDLE_ENABLE 1
4014	#define EV_STAT_ENABLE 0	4948	#define EV_SIGNAL_ENABLE 1
4015	#define EV_FORK_ENABLE 0	4949	#define EV_CHILD_ENABLE 1
		4950	#define EV_USE_STDEXCEPT 0
4016	#define EV_CONFIG_H <config.h>	4951	#define EV_CONFIG_H <config.h>
4017	#define EV_MINPRI 0
4018	#define EV_MAXPRI 0
4019		4952
4020	#include "ev++.h"	4953	#include "ev++.h"
4021		4954
4022	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4955	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4023		4956
4024	#include "ev_cpp.h"	4957	#include "ev_cpp.h"
4025	#include "ev.c"	4958	#include "ev.c"
4026		4959
4027	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4960	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4028		4961
4029	=head2 THREADS AND COROUTINES	4962	=head2 THREADS AND COROUTINES
4030		4963
4031	=head3 THREADS	4964	=head3 THREADS
4032		4965
…		…
4083	default loop and triggering an C<ev_async> watcher from the default loop	5016	default loop and triggering an C<ev_async> watcher from the default loop
4084	watcher callback into the event loop interested in the signal.	5017	watcher callback into the event loop interested in the signal.
4085		5018
4086	=back	5019	=back
4087		5020
4088	=head4 THREAD LOCKING EXAMPLE	5021	See also L</THREAD LOCKING EXAMPLE>.
4089
4090	Here is a fictitious example of how to run an event loop in a different
4091	thread than where callbacks are being invoked and watchers are
4092	created/added/removed.
4093
4094	For a real-world example, see the C<EV::Loop::Async> perl module,
4095	which uses exactly this technique (which is suited for many high-level
4096	languages).
4097
4098	The example uses a pthread mutex to protect the loop data, a condition
4099	variable to wait for callback invocations, an async watcher to notify the
4100	event loop thread and an unspecified mechanism to wake up the main thread.
4101
4102	First, you need to associate some data with the event loop:
4103
4104	typedef struct {
4105	mutex_t lock; /* global loop lock */
4106	ev_async async_w;
4107	thread_t tid;
4108	cond_t invoke_cv;
4109	} userdata;
4110
4111	void prepare_loop (EV_P)
4112	{
4113	// for simplicity, we use a static userdata struct.
4114	static userdata u;
4115
4116	ev_async_init (&u->async_w, async_cb);
4117	ev_async_start (EV_A_ &u->async_w);
4118
4119	pthread_mutex_init (&u->lock, 0);
4120	pthread_cond_init (&u->invoke_cv, 0);
4121
4122	// now associate this with the loop
4123	ev_set_userdata (EV_A_ u);
4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4126
4127	// then create the thread running ev_loop
4128	pthread_create (&u->tid, 0, l_run, EV_A);
4129	}
4130
4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
4132	solely to wake up the event loop so it takes notice of any new watchers
4133	that might have been added:
4134
4135	static void
4136	async_cb (EV_P_ ev_async *w, int revents)
4137	{
4138	// just used for the side effects
4139	}
4140
4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4142	protecting the loop data, respectively.
4143
4144	static void
4145	l_release (EV_P)
4146	{
4147	userdata *u = ev_userdata (EV_A);
4148	pthread_mutex_unlock (&u->lock);
4149	}
4150
4151	static void
4152	l_acquire (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155	pthread_mutex_lock (&u->lock);
4156	}
4157
4158	The event loop thread first acquires the mutex, and then jumps straight
4159	into C<ev_loop>:
4160
4161	void *
4162	l_run (void *thr_arg)
4163	{
4164	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4165
4166	l_acquire (EV_A);
4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4168	ev_loop (EV_A_ 0);
4169	l_release (EV_A);
4170
4171	return 0;
4172	}
4173
4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
4175	signal the main thread via some unspecified mechanism (signals? pipe
4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4177	have been called (in a while loop because a) spurious wakeups are possible
4178	and b) skipping inter-thread-communication when there are no pending
4179	watchers is very beneficial):
4180
4181	static void
4182	l_invoke (EV_P)
4183	{
4184	userdata *u = ev_userdata (EV_A);
4185
4186	while (ev_pending_count (EV_A))
4187	{
4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
4190	}
4191	}
4192
4193	Now, whenever the main thread gets told to invoke pending watchers, it
4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4195	thread to continue:
4196
4197	static void
4198	real_invoke_pending (EV_P)
4199	{
4200	userdata *u = ev_userdata (EV_A);
4201
4202	pthread_mutex_lock (&u->lock);
4203	ev_invoke_pending (EV_A);
4204	pthread_cond_signal (&u->invoke_cv);
4205	pthread_mutex_unlock (&u->lock);
4206	}
4207
4208	Whenever you want to start/stop a watcher or do other modifications to an
4209	event loop, you will now have to lock:
4210
4211	ev_timer timeout_watcher;
4212	userdata *u = ev_userdata (EV_A);
4213
4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4215
4216	pthread_mutex_lock (&u->lock);
4217	ev_timer_start (EV_A_ &timeout_watcher);
4218	ev_async_send (EV_A_ &u->async_w);
4219	pthread_mutex_unlock (&u->lock);
4220
4221	Note that sending the C<ev_async> watcher is required because otherwise
4222	an event loop currently blocking in the kernel will have no knowledge
4223	about the newly added timer. By waking up the loop it will pick up any new
4224	watchers in the next event loop iteration.
4225		5022
4226	=head3 COROUTINES	5023	=head3 COROUTINES
4227		5024
4228	Libev is very accommodating to coroutines ("cooperative threads"):	5025	Libev is very accommodating to coroutines ("cooperative threads"):
4229	libev fully supports nesting calls to its functions from different	5026	libev fully supports nesting calls to its functions from different
4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5027	coroutines (e.g. you can call C<ev_run> on the same loop from two
4231	different coroutines, and switch freely between both coroutines running	5028	different coroutines, and switch freely between both coroutines running
4232	the loop, as long as you don't confuse yourself). The only exception is	5029	the loop, as long as you don't confuse yourself). The only exception is
4233	that you must not do this from C<ev_periodic> reschedule callbacks.	5030	that you must not do this from C<ev_periodic> reschedule callbacks.
4234		5031
4235	Care has been taken to ensure that libev does not keep local state inside	5032	Care has been taken to ensure that libev does not keep local state inside
4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5033	C<ev_run>, and other calls do not usually allow for coroutine switches as
4237	they do not call any callbacks.	5034	they do not call any callbacks.
4238		5035
4239	=head2 COMPILER WARNINGS	5036	=head2 COMPILER WARNINGS
4240		5037
4241	Depending on your compiler and compiler settings, you might get no or a	5038	Depending on your compiler and compiler settings, you might get no or a
…		…
4252	maintainable.	5049	maintainable.
4253		5050
4254	And of course, some compiler warnings are just plain stupid, or simply	5051	And of course, some compiler warnings are just plain stupid, or simply
4255	wrong (because they don't actually warn about the condition their message	5052	wrong (because they don't actually warn about the condition their message
4256	seems to warn about). For example, certain older gcc versions had some	5053	seems to warn about). For example, certain older gcc versions had some
4257	warnings that resulted an extreme number of false positives. These have	5054	warnings that resulted in an extreme number of false positives. These have
4258	been fixed, but some people still insist on making code warn-free with	5055	been fixed, but some people still insist on making code warn-free with
4259	such buggy versions.	5056	such buggy versions.
4260		5057
4261	While libev is written to generate as few warnings as possible,	5058	While libev is written to generate as few warnings as possible,
4262	"warn-free" code is not a goal, and it is recommended not to build libev	5059	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4298	I suggest using suppression lists.	5095	I suggest using suppression lists.
4299		5096
4300		5097
4301	=head1 PORTABILITY NOTES	5098	=head1 PORTABILITY NOTES
4302		5099
		5100	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5101
		5102	GNU/Linux is the only common platform that supports 64 bit file/large file
		5103	interfaces but I<disables> them by default.
		5104
		5105	That means that libev compiled in the default environment doesn't support
		5106	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5107
		5108	Unfortunately, many programs try to work around this GNU/Linux issue
		5109	by enabling the large file API, which makes them incompatible with the
		5110	standard libev compiled for their system.
		5111
		5112	Likewise, libev cannot enable the large file API itself as this would
		5113	suddenly make it incompatible to the default compile time environment,
		5114	i.e. all programs not using special compile switches.
		5115
		5116	=head2 OS/X AND DARWIN BUGS
		5117
		5118	The whole thing is a bug if you ask me - basically any system interface
		5119	you touch is broken, whether it is locales, poll, kqueue or even the
		5120	OpenGL drivers.
		5121
		5122	=head3 C<kqueue> is buggy
		5123
		5124	The kqueue syscall is broken in all known versions - most versions support
		5125	only sockets, many support pipes.
		5126
		5127	Libev tries to work around this by not using C<kqueue> by default on this
		5128	rotten platform, but of course you can still ask for it when creating a
		5129	loop - embedding a socket-only kqueue loop into a select-based one is
		5130	probably going to work well.
		5131
		5132	=head3 C<poll> is buggy
		5133
		5134	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5135	implementation by something calling C<kqueue> internally around the 10.5.6
		5136	release, so now C<kqueue> I<and> C<poll> are broken.
		5137
		5138	Libev tries to work around this by not using C<poll> by default on
		5139	this rotten platform, but of course you can still ask for it when creating
		5140	a loop.
		5141
		5142	=head3 C<select> is buggy
		5143
		5144	All that's left is C<select>, and of course Apple found a way to fuck this
		5145	one up as well: On OS/X, C<select> actively limits the number of file
		5146	descriptors you can pass in to 1024 - your program suddenly crashes when
		5147	you use more.
		5148
		5149	There is an undocumented "workaround" for this - defining
		5150	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5151	work on OS/X.
		5152
		5153	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5154
		5155	=head3 C<errno> reentrancy
		5156
		5157	The default compile environment on Solaris is unfortunately so
		5158	thread-unsafe that you can't even use components/libraries compiled
		5159	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5160	defined by default. A valid, if stupid, implementation choice.
		5161
		5162	If you want to use libev in threaded environments you have to make sure
		5163	it's compiled with C<_REENTRANT> defined.
		5164
		5165	=head3 Event port backend
		5166
		5167	The scalable event interface for Solaris is called "event
		5168	ports". Unfortunately, this mechanism is very buggy in all major
		5169	releases. If you run into high CPU usage, your program freezes or you get
		5170	a large number of spurious wakeups, make sure you have all the relevant
		5171	and latest kernel patches applied. No, I don't know which ones, but there
		5172	are multiple ones to apply, and afterwards, event ports actually work
		5173	great.
		5174
		5175	If you can't get it to work, you can try running the program by setting
		5176	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5177	C<select> backends.
		5178
		5179	=head2 AIX POLL BUG
		5180
		5181	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5182	this by trying to avoid the poll backend altogether (i.e. it's not even
		5183	compiled in), which normally isn't a big problem as C<select> works fine
		5184	with large bitsets on AIX, and AIX is dead anyway.
		5185
4303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5186	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5187
		5188	=head3 General issues
4304		5189
4305	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5190	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4306	requires, and its I/O model is fundamentally incompatible with the POSIX	5191	requires, and its I/O model is fundamentally incompatible with the POSIX
4307	model. Libev still offers limited functionality on this platform in	5192	model. Libev still offers limited functionality on this platform in
4308	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5193	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4309	descriptors. This only applies when using Win32 natively, not when using	5194	descriptors. This only applies when using Win32 natively, not when using
4310	e.g. cygwin.	5195	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5196	as every compiler comes with a slightly differently broken/incompatible
		5197	environment.
4311		5198
4312	Lifting these limitations would basically require the full	5199	Lifting these limitations would basically require the full
4313	re-implementation of the I/O system. If you are into these kinds of	5200	re-implementation of the I/O system. If you are into this kind of thing,
4314	things, then note that glib does exactly that for you in a very portable	5201	then note that glib does exactly that for you in a very portable way (note
4315	way (note also that glib is the slowest event library known to man).	5202	also that glib is the slowest event library known to man).
4316		5203
4317	There is no supported compilation method available on windows except	5204	There is no supported compilation method available on windows except
4318	embedding it into other applications.	5205	embedding it into other applications.
4319		5206
4320	Sensible signal handling is officially unsupported by Microsoft - libev	5207	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4348	you do I<not> compile the F<ev.c> or any other embedded source files!):	5235	you do I<not> compile the F<ev.c> or any other embedded source files!):
4349		5236
4350	#include "evwrap.h"	5237	#include "evwrap.h"
4351	#include "ev.c"	5238	#include "ev.c"
4352		5239
4353	=over 4
4354
4355	=item The winsocket select function	5240	=head3 The winsocket C<select> function
4356		5241
4357	The winsocket C<select> function doesn't follow POSIX in that it	5242	The winsocket C<select> function doesn't follow POSIX in that it
4358	requires socket I<handles> and not socket I<file descriptors> (it is	5243	requires socket I<handles> and not socket I<file descriptors> (it is
4359	also extremely buggy). This makes select very inefficient, and also	5244	also extremely buggy). This makes select very inefficient, and also
4360	requires a mapping from file descriptors to socket handles (the Microsoft	5245	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4369	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5254	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4370		5255
4371	Note that winsockets handling of fd sets is O(n), so you can easily get a	5256	Note that winsockets handling of fd sets is O(n), so you can easily get a
4372	complexity in the O(n²) range when using win32.	5257	complexity in the O(n²) range when using win32.
4373		5258
4374	=item Limited number of file descriptors	5259	=head3 Limited number of file descriptors
4375		5260
4376	Windows has numerous arbitrary (and low) limits on things.	5261	Windows has numerous arbitrary (and low) limits on things.
4377		5262
4378	Early versions of winsocket's select only supported waiting for a maximum	5263	Early versions of winsocket's select only supported waiting for a maximum
4379	of C<64> handles (probably owning to the fact that all windows kernels	5264	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4394	runtime libraries. This might get you to about C<512> or C<2048> sockets	5279	runtime libraries. This might get you to about C<512> or C<2048> sockets
4395	(depending on windows version and/or the phase of the moon). To get more,	5280	(depending on windows version and/or the phase of the moon). To get more,
4396	you need to wrap all I/O functions and provide your own fd management, but	5281	you need to wrap all I/O functions and provide your own fd management, but
4397	the cost of calling select (O(n²)) will likely make this unworkable.	5282	the cost of calling select (O(n²)) will likely make this unworkable.
4398		5283
4399	=back
4400
4401	=head2 PORTABILITY REQUIREMENTS	5284	=head2 PORTABILITY REQUIREMENTS
4402		5285
4403	In addition to a working ISO-C implementation and of course the	5286	In addition to a working ISO-C implementation and of course the
4404	backend-specific APIs, libev relies on a few additional extensions:	5287	backend-specific APIs, libev relies on a few additional extensions:
4405		5288
…		…
4411	Libev assumes not only that all watcher pointers have the same internal	5294	Libev assumes not only that all watcher pointers have the same internal
4412	structure (guaranteed by POSIX but not by ISO C for example), but it also	5295	structure (guaranteed by POSIX but not by ISO C for example), but it also
4413	assumes that the same (machine) code can be used to call any watcher	5296	assumes that the same (machine) code can be used to call any watcher
4414	callback: The watcher callbacks have different type signatures, but libev	5297	callback: The watcher callbacks have different type signatures, but libev
4415	calls them using an C<ev_watcher *> internally.	5298	calls them using an C<ev_watcher *> internally.
		5299
		5300	=item pointer accesses must be thread-atomic
		5301
		5302	Accessing a pointer value must be atomic, it must both be readable and
		5303	writable in one piece - this is the case on all current architectures.
4416		5304
4417	=item C<sig_atomic_t volatile> must be thread-atomic as well	5305	=item C<sig_atomic_t volatile> must be thread-atomic as well
4418		5306
4419	The type C<sig_atomic_t volatile> (or whatever is defined as	5307	The type C<sig_atomic_t volatile> (or whatever is defined as
4420	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5308	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4429	thread" or will block signals process-wide, both behaviours would	5317	thread" or will block signals process-wide, both behaviours would
4430	be compatible with libev. Interaction between C<sigprocmask> and	5318	be compatible with libev. Interaction between C<sigprocmask> and
4431	C<pthread_sigmask> could complicate things, however.	5319	C<pthread_sigmask> could complicate things, however.
4432		5320
4433	The most portable way to handle signals is to block signals in all threads	5321	The most portable way to handle signals is to block signals in all threads
4434	except the initial one, and run the default loop in the initial thread as	5322	except the initial one, and run the signal handling loop in the initial
4435	well.	5323	thread as well.
4436		5324
4437	=item C<long> must be large enough for common memory allocation sizes	5325	=item C<long> must be large enough for common memory allocation sizes
4438		5326
4439	To improve portability and simplify its API, libev uses C<long> internally	5327	To improve portability and simplify its API, libev uses C<long> internally
4440	instead of C<size_t> when allocating its data structures. On non-POSIX	5328	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4443	watchers.	5331	watchers.
4444		5332
4445	=item C<double> must hold a time value in seconds with enough accuracy	5333	=item C<double> must hold a time value in seconds with enough accuracy
4446		5334
4447	The type C<double> is used to represent timestamps. It is required to	5335	The type C<double> is used to represent timestamps. It is required to
4448	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5336	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4449	enough for at least into the year 4000. This requirement is fulfilled by	5337	good enough for at least into the year 4000 with millisecond accuracy
		5338	(the design goal for libev). This requirement is overfulfilled by
4450	implementations implementing IEEE 754, which is basically all existing	5339	implementations using IEEE 754, which is basically all existing ones.
		5340
4451	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5341	With IEEE 754 doubles, you get microsecond accuracy until at least the
4452	2200.	5342	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5343	is either obsolete or somebody patched it to use C<long double> or
		5344	something like that, just kidding).
4453		5345
4454	=back	5346	=back
4455		5347
4456	If you know of other additional requirements drop me a note.	5348	If you know of other additional requirements drop me a note.
4457		5349
…		…
4519	=item Processing ev_async_send: O(number_of_async_watchers)	5411	=item Processing ev_async_send: O(number_of_async_watchers)
4520		5412
4521	=item Processing signals: O(max_signal_number)	5413	=item Processing signals: O(max_signal_number)
4522		5414
4523	Sending involves a system call I<iff> there were no other C<ev_async_send>	5415	Sending involves a system call I<iff> there were no other C<ev_async_send>
4524	calls in the current loop iteration. Checking for async and signal events	5416	calls in the current loop iteration and the loop is currently
		5417	blocked. Checking for async and signal events involves iterating over all
4525	involves iterating over all running async watchers or all signal numbers.	5418	running async watchers or all signal numbers.
4526		5419
4527	=back	5420	=back
4528		5421
4529		5422
		5423	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5424
		5425	The major version 4 introduced some incompatible changes to the API.
		5426
		5427	At the moment, the C<ev.h> header file provides compatibility definitions
		5428	for all changes, so most programs should still compile. The compatibility
		5429	layer might be removed in later versions of libev, so better update to the
		5430	new API early than late.
		5431
		5432	=over 4
		5433
		5434	=item C<EV_COMPAT3> backwards compatibility mechanism
		5435
		5436	The backward compatibility mechanism can be controlled by
		5437	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5438	section.
		5439
		5440	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5441
		5442	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5443
		5444	ev_loop_destroy (EV_DEFAULT_UC);
		5445	ev_loop_fork (EV_DEFAULT);
		5446
		5447	=item function/symbol renames
		5448
		5449	A number of functions and symbols have been renamed:
		5450
		5451	ev_loop => ev_run
		5452	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5453	EVLOOP_ONESHOT => EVRUN_ONCE
		5454
		5455	ev_unloop => ev_break
		5456	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5457	EVUNLOOP_ONE => EVBREAK_ONE
		5458	EVUNLOOP_ALL => EVBREAK_ALL
		5459
		5460	EV_TIMEOUT => EV_TIMER
		5461
		5462	ev_loop_count => ev_iteration
		5463	ev_loop_depth => ev_depth
		5464	ev_loop_verify => ev_verify
		5465
		5466	Most functions working on C<struct ev_loop> objects don't have an
		5467	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5468	associated constants have been renamed to not collide with the C<struct
		5469	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5470	as all other watcher types. Note that C<ev_loop_fork> is still called
		5471	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5472	typedef.
		5473
		5474	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5475
		5476	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5477	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5478	and work, but the library code will of course be larger.
		5479
		5480	=back
		5481
		5482
4530	=head1 GLOSSARY	5483	=head1 GLOSSARY
4531		5484
4532	=over 4	5485	=over 4
4533		5486
4534	=item active	5487	=item active
4535		5488
4536	A watcher is active as long as it has been started (has been attached to	5489	A watcher is active as long as it has been started and not yet stopped.
4537	an event loop) but not yet stopped (disassociated from the event loop).	5490	See L</WATCHER STATES> for details.
4538		5491
4539	=item application	5492	=item application
4540		5493
4541	In this document, an application is whatever is using libev.	5494	In this document, an application is whatever is using libev.
		5495
		5496	=item backend
		5497
		5498	The part of the code dealing with the operating system interfaces.
4542		5499
4543	=item callback	5500	=item callback
4544		5501
4545	The address of a function that is called when some event has been	5502	The address of a function that is called when some event has been
4546	detected. Callbacks are being passed the event loop, the watcher that	5503	detected. Callbacks are being passed the event loop, the watcher that
4547	received the event, and the actual event bitset.	5504	received the event, and the actual event bitset.
4548		5505
4549	=item callback invocation	5506	=item callback/watcher invocation
4550		5507
4551	The act of calling the callback associated with a watcher.	5508	The act of calling the callback associated with a watcher.
4552		5509
4553	=item event	5510	=item event
4554		5511
4555	A change of state of some external event, such as data now being available	5512	A change of state of some external event, such as data now being available
4556	for reading on a file descriptor, time having passed or simply not having	5513	for reading on a file descriptor, time having passed or simply not having
4557	any other events happening anymore.	5514	any other events happening anymore.
4558		5515
4559	In libev, events are represented as single bits (such as C<EV_READ> or	5516	In libev, events are represented as single bits (such as C<EV_READ> or
4560	C<EV_TIMEOUT>).	5517	C<EV_TIMER>).
4561		5518
4562	=item event library	5519	=item event library
4563		5520
4564	A software package implementing an event model and loop.	5521	A software package implementing an event model and loop.
4565		5522
…		…
4573	The model used to describe how an event loop handles and processes	5530	The model used to describe how an event loop handles and processes
4574	watchers and events.	5531	watchers and events.
4575		5532
4576	=item pending	5533	=item pending
4577		5534
4578	A watcher is pending as soon as the corresponding event has been detected,	5535	A watcher is pending as soon as the corresponding event has been
4579	and stops being pending as soon as the watcher will be invoked or its	5536	detected. See L</WATCHER STATES> for details.
4580	pending status is explicitly cleared by the application.
4581
4582	A watcher can be pending, but not active. Stopping a watcher also clears
4583	its pending status.
4584		5537
4585	=item real time	5538	=item real time
4586		5539
4587	The physical time that is observed. It is apparently strictly monotonic :)	5540	The physical time that is observed. It is apparently strictly monotonic :)
4588		5541
4589	=item wall-clock time	5542	=item wall-clock time
4590		5543
4591	The time and date as shown on clocks. Unlike real time, it can actually	5544	The time and date as shown on clocks. Unlike real time, it can actually
4592	be wrong and jump forwards and backwards, e.g. when the you adjust your	5545	be wrong and jump forwards and backwards, e.g. when you adjust your
4593	clock.	5546	clock.
4594		5547
4595	=item watcher	5548	=item watcher
4596		5549
4597	A data structure that describes interest in certain events. Watchers need	5550	A data structure that describes interest in certain events. Watchers need
4598	to be started (attached to an event loop) before they can receive events.	5551	to be started (attached to an event loop) before they can receive events.
4599		5552
4600	=item watcher invocation
4601
4602	The act of calling the callback associated with a watcher.
4603
4604	=back	5553	=back
4605		5554
4606	=head1 AUTHOR	5555	=head1 AUTHOR
4607		5556
4608	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5557	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5558	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4609		5559

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines