ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.284 by root, Sun Mar 14 21:05:52 2010 UTC vs.
Revision 1.371 by root, Sat Jun 4 05:25:03 2011 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	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	139	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	140	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	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_update_now> and C<ev_now>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
175	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	209	not a problem.
194		210
195	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	Return the set of all backends compiled into this binary of libev and also	234	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	235	also recommended for this platform, meaning it will work for most file
		236	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	237	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	238	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	239	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.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	245	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	246	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		253
236	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
265	}	283	}
266		284
267	...	285	...
268	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
269		287
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		289
272	Set the callback function to call on a retryable system call error (such	290	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	291	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	305	}
288		306
289	...	307	...
290	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
291		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
292	=back	323	=back
293		324
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		326
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	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>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
299		330
300	The library knows two types of such loops, the I<default> loop, which	331	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	332	supports child process events, and dynamically created event loops which
302	not.	333	do not.
303		334
304	=over 4	335	=over 4
305		336
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		338
308	This will initialise the default event loop if it hasn't been initialised	339	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	340	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	341	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).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
312		349
313	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
314	function.	351	function (or via the C<EV_DEFAULT> macro).
315		352
316	Note that this function is I<not> thread-safe, so if you want to use it	353	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,	354	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
319		357
320	The default loop is the only loop that can handle C<ev_signal> and	358	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	359	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	360	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	361	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	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
326		382
327	The flags argument can be used to specify special behaviour or specific	383	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>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		385
330	The following flags are supported:	386	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
346	around bugs.	402	around bugs.
347		403
348	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
349		405
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	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	407	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		408
354	This works by calling C<getpid ()> on every iteration of the loop,	409	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	410	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	411	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	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	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	426	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	427	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.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	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	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you ahve to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also errornously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
445		526
446	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		597
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
519		600
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	604	might perform better.
528		605
529	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returning events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where
		616	you absolutely have to know whether an event occurred or not because you
		617	have to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
533		620
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
536		623
537	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
538		625
539	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		629
543	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		639
545	=back	640	=back
546		641
547	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	645	()> will be tried.
551		646
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		667
596	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
597	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
599		671
600	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
602	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
603	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
604		680
605	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
606		682
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
613	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
614	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
615	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
616	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
617	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
618		693
619	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
620	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
622		700
623	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
624	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
627	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		715
636	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
637		717
638	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	719	otherwise.
640		720
641	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
642		722
643	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
644	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
646		726
647	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
648	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
650		731
651	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
652		733
653	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
654	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
655		736
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	739	in which case it is higher.
659		740
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
662		745
663	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
664		747
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	749	use.
…		…
675		758
676	=item ev_now_update (loop)	759	=item ev_now_update (loop)
677		760
678	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
681		764
682	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
683	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	767	the current time is a good idea.
685		768
…		…
687		770
688	=item ev_suspend (loop)	771	=item ev_suspend (loop)
689		772
690	=item ev_resume (loop)	773	=item ev_resume (loop)
691		774
692	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
693	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
694		777
695	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
696	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
697	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
698	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
701		784
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	788	occurred while suspended).
706		789
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
710		793
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
713		796
714	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
715		798
716	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
717	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
718	handling events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
719		804
720	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
721	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
722		808
723	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
724	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
727	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	814	beauty.
729		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
731	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
732	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
733	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
734		826
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
736	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
740	iteration of the loop.	832	iteration of the loop.
741		833
742	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
743	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
745	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
746		838
747	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
748		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	852	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	863	- Queue all expired timers.
765	- Queue all expired periodics.	864	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	866	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
769	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
770	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
774		877
775	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	879	anymore.
777		880
778	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
782		885
783	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
784		887
785	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
786	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		892
790	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
791		894
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
793		897
794	=item ev_ref (loop)	898	=item ev_ref (loop)
795		899
796	=item ev_unref (loop)	900	=item ev_unref (loop)
797		901
798	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
799	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
800	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
801		905
802	This is useful when you have a watcher that you never intend to	906	This is useful when you have a watcher that you never intend to
803	unregister, but that nevertheless should not keep C<ev_loop> from	907	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	909	before stopping it.
806		910
807	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
808	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
809	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
810	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
811	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
812	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
813	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	919	in the callback).
816		920
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	922	running when nothing else is active.
819		923
820	ev_signal exitsig;	924	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	927	ev_unref (loop);
824		928
825	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
826		930
827	ev_ref (loop);	931	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	971	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	972	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	973	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	974	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	975	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	976	then you can't do more than 100 transactions per second).
873		977
874	Setting the I<timeout collect interval> can improve the opportunity for	978	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	979	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	980	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	981	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	989	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		990
887	=item ev_invoke_pending (loop)	991	=item ev_invoke_pending (loop)
888		992
889	This call will simply invoke all pending watchers while resetting their	993	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	994	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	995	but when overriding the invoke callback this call comes handy. This
		996	function can be invoked from a watcher - this can be useful for example
		997	when you want to do some lengthy calculation and want to pass further
		998	event handling to another thread (you still have to make sure only one
		999	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		1000
893	=item int ev_pending_count (loop)	1001	=item int ev_pending_count (loop)
894		1002
895	Returns the number of pending watchers - zero indicates that no watchers	1003	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	1004	are pending.
897		1005
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1006	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		1007
900	This overrides the invoke pending functionality of the loop: Instead of	1008	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	1009	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	1010	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1011	invoke the actual watchers inside another context (another thread etc.).
904		1012
905	If you want to reset the callback, use C<ev_invoke_pending> as new	1013	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1014	callback.
…		…
909		1017
910	Sometimes you want to share the same loop between multiple threads. This	1018	Sometimes you want to share the same loop between multiple threads. This
911	can be done relatively simply by putting mutex_lock/unlock calls around	1019	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1020	each call to a libev function.
913		1021
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1022	However, C<ev_run> can run an indefinite time, so it is not feasible
915	wait for it to return. One way around this is to wake up the loop via	1023	to wait for it to return. One way around this is to wake up the event
916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1024	loop via C<ev_break> and C<av_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1025	I<release> and I<acquire> callbacks on the loop.
918		1026
919	When set, then C<release> will be called just before the thread is	1027	When set, then C<release> will be called just before the thread is
920	suspended waiting for new events, and C<acquire> is called just	1028	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1029	afterwards.
922		1030
…		…
925		1033
926	While event loop modifications are allowed between invocations of	1034	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1035	C<release> and C<acquire> (that's their only purpose after all), no
928	modifications done will affect the event loop, i.e. adding watchers will	1036	modifications done will affect the event loop, i.e. adding watchers will
929	have no effect on the set of file descriptors being watched, or the time	1037	have no effect on the set of file descriptors being watched, or the time
930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1038	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
931	to take note of any changes you made.	1039	to take note of any changes you made.
932		1040
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1041	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1042	invocations of C<release> and C<acquire>.
935		1043
936	See also the locking example in the C<THREADS> section later in this	1044	See also the locking example in the C<THREADS> section later in this
937	document.	1045	document.
938		1046
939	=item ev_set_userdata (loop, void *data)	1047	=item ev_set_userdata (loop, void *data)
940		1048
941	=item ev_userdata (loop)	1049	=item void *ev_userdata (loop)
942		1050
943	Set and retrieve a single C<void *> associated with a loop. When	1051	Set and retrieve a single C<void *> associated with a loop. When
944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1052	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1053	C<0>.
946		1054
947	These two functions can be used to associate arbitrary data with a loop,	1055	These two functions can be used to associate arbitrary data with a loop,
948	and are intended solely for the C<invoke_pending_cb>, C<release> and	1056	and are intended solely for the C<invoke_pending_cb>, C<release> and
949	C<acquire> callbacks described above, but of course can be (ab-)used for	1057	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1058	any other purpose as well.
951		1059
952	=item ev_loop_verify (loop)	1060	=item ev_verify (loop)
953		1061
954	This function only does something when C<EV_VERIFY> support has been	1062	This function only does something when C<EV_VERIFY> support has been
955	compiled in, which is the default for non-minimal builds. It tries to go	1063	compiled in, which is the default for non-minimal builds. It tries to go
956	through all internal structures and checks them for validity. If anything	1064	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1065	is found to be inconsistent, it will print an error message to standard
…		…
968		1076
969	In the following description, uppercase C<TYPE> in names stands for the	1077	In the following description, uppercase C<TYPE> in names stands for the
970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1078	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
971	watchers and C<ev_io_start> for I/O watchers.	1079	watchers and C<ev_io_start> for I/O watchers.
972		1080
973	A watcher is a structure that you create and register to record your	1081	A watcher is an opaque structure that you allocate and register to record
974	interest in some event. For instance, if you want to wait for STDIN to	1082	your interest in some event. To make a concrete example, imagine you want
975	become readable, you would create an C<ev_io> watcher for that:	1083	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1084	for that:
976		1085
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1086	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1087	{
979	ev_io_stop (w);	1088	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1089	ev_break (loop, EVBREAK_ALL);
981	}	1090	}
982		1091
983	struct ev_loop *loop = ev_default_loop (0);	1092	struct ev_loop *loop = ev_default_loop (0);
984		1093
985	ev_io stdin_watcher;	1094	ev_io stdin_watcher;
986		1095
987	ev_init (&stdin_watcher, my_cb);	1096	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1097	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1098	ev_io_start (loop, &stdin_watcher);
990		1099
991	ev_loop (loop, 0);	1100	ev_run (loop, 0);
992		1101
993	As you can see, you are responsible for allocating the memory for your	1102	As you can see, you are responsible for allocating the memory for your
994	watcher structures (and it is I<usually> a bad idea to do this on the	1103	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1104	stack).
996		1105
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1106	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1107	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1108
1000	Each watcher structure must be initialised by a call to C<ev_init	1109	Each watcher structure must be initialised by a call to C<ev_init (watcher
1001	(watcher *, callback)>, which expects a callback to be provided. This	1110	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1111	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1112	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1113	and/or writable).
1005		1114
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1115	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1007	macro to configure it, with arguments specific to the watcher type. There	1116	macro to configure it, with arguments specific to the watcher type. There
1008	is also a macro to combine initialisation and setting in one call: C<<	1117	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1118	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1032	=item C<EV_WRITE>	1141	=item C<EV_WRITE>
1033		1142
1034	The file descriptor in the C<ev_io> watcher has become readable and/or	1143	The file descriptor in the C<ev_io> watcher has become readable and/or
1035	writable.	1144	writable.
1036		1145
1037	=item C<EV_TIMEOUT>	1146	=item C<EV_TIMER>
1038		1147
1039	The C<ev_timer> watcher has timed out.	1148	The C<ev_timer> watcher has timed out.
1040		1149
1041	=item C<EV_PERIODIC>	1150	=item C<EV_PERIODIC>
1042		1151
…		…
1060		1169
1061	=item C<EV_PREPARE>	1170	=item C<EV_PREPARE>
1062		1171
1063	=item C<EV_CHECK>	1172	=item C<EV_CHECK>
1064		1173
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1174	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1066	to gather new events, and all C<ev_check> watchers are invoked just after	1175	to gather new events, and all C<ev_check> watchers are invoked just after
1067	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1176	C<ev_run> has gathered them, but before it invokes any callbacks for any
1068	received events. Callbacks of both watcher types can start and stop as	1177	received events. Callbacks of both watcher types can start and stop as
1069	many watchers as they want, and all of them will be taken into account	1178	many watchers as they want, and all of them will be taken into account
1070	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1179	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1071	C<ev_loop> from blocking).	1180	C<ev_run> from blocking).
1072		1181
1073	=item C<EV_EMBED>	1182	=item C<EV_EMBED>
1074		1183
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1184	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1185
1077	=item C<EV_FORK>	1186	=item C<EV_FORK>
1078		1187
1079	The event loop has been resumed in the child process after fork (see	1188	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1189	C<ev_fork>).
		1190
		1191	=item C<EV_CLEANUP>
		1192
		1193	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1194
1082	=item C<EV_ASYNC>	1195	=item C<EV_ASYNC>
1083		1196
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1197	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1198
…		…
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1371	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1372	functions that do not need a watcher.
1260		1373
1261	=back	1374	=back
1262		1375
		1376	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1377	OWN COMPOSITE WATCHERS> idioms.
1263		1378
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1379	=head2 WATCHER STATES
1265		1380
1266	Each watcher has, by default, a member C<void *data> that you can change	1381	There are various watcher states mentioned throughout this manual -
1267	and read at any time: libev will completely ignore it. This can be used	1382	active, pending and so on. In this section these states and the rules to
1268	to associate arbitrary data with your watcher. If you need more data and	1383	transition between them will be described in more detail - and while these
1269	don't want to allocate memory and store a pointer to it in that data	1384	rules might look complicated, they usually do "the right thing".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1385
1273	struct my_io	1386	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1387
1281	...	1388	=item initialiased
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1389
1285	And since your callback will be called with a pointer to the watcher, you	1390	Before a watcher can be registered with the event looop it has to be
1286	can cast it back to your own type:	1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1287		1393
1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1394	In this state it is simply some block of memory that is suitable for
1289	{	1395	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1396	will - as long as you either keep the memory contents intact, or call
1291	...	1397	C<ev_TYPE_init> again.
1292	}
1293		1398
1294	More interesting and less C-conformant ways of casting your callback type	1399	=item started/running/active
1295	instead have been omitted.
1296		1400
1297	Another common scenario is to use some data structure with multiple	1401	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1298	embedded watchers:	1402	property of the event loop, and is actively waiting for events. While in
		1403	this state it cannot be accessed (except in a few documented ways), moved,
		1404	freed or anything else - the only legal thing is to keep a pointer to it,
		1405	and call libev functions on it that are documented to work on active watchers.
1299		1406
1300	struct my_biggy	1407	=item pending
1301	{
1302	int some_data;
1303	ev_timer t1;
1304	ev_timer t2;
1305	}
1306		1408
1307	In this case getting the pointer to C<my_biggy> is a bit more	1409	If a watcher is active and libev determines that an event it is interested
1308	complicated: Either you store the address of your C<my_biggy> struct	1410	in has occurred (such as a timer expiring), it will become pending. It will
1309	in the C<data> member of the watcher (for woozies), or you need to use	1411	stay in this pending state until either it is stopped or its callback is
1310	some pointer arithmetic using C<offsetof> inside your watchers (for real	1412	about to be invoked, so it is not normally pending inside the watcher
1311	programmers):	1413	callback.
1312		1414
1313	#include <stddef.h>	1415	The watcher might or might not be active while it is pending (for example,
		1416	an expired non-repeating timer can be pending but no longer active). If it
		1417	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1418	but it is still property of the event loop at this time, so cannot be
		1419	moved, freed or reused. And if it is active the rules described in the
		1420	previous item still apply.
1314		1421
1315	static void	1422	It is also possible to feed an event on a watcher that is not active (e.g.
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1423	via C<ev_feed_event>), in which case it becomes pending without being
1317	{	1424	active.
1318	struct my_biggy big = (struct my_biggy *)
1319	(((char *)w) - offsetof (struct my_biggy, t1));
1320	}
1321		1425
1322	static void	1426	=item stopped
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1427
1324	{	1428	A watcher can be stopped implicitly by libev (in which case it might still
1325	struct my_biggy big = (struct my_biggy *)	1429	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1430	latter will clear any pending state the watcher might be in, regardless
1327	}	1431	of whether it was active or not, so stopping a watcher explicitly before
		1432	freeing it is often a good idea.
		1433
		1434	While stopped (and not pending) the watcher is essentially in the
		1435	initialised state, that is, it can be reused, moved, modified in any way
		1436	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1437	it again).
		1438
		1439	=back
1328		1440
1329	=head2 WATCHER PRIORITY MODELS	1441	=head2 WATCHER PRIORITY MODELS
1330		1442
1331	Many event loops support I<watcher priorities>, which are usually small	1443	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1444	integers that influence the ordering of event callback invocation
…		…
1375		1487
1376	For example, to emulate how many other event libraries handle priorities,	1488	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1489	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1490	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1491	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1492	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1493	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1494	workable.
1383		1495
1384	Usually, however, the lock-out model implemented that way will perform	1496	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1497	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1511	{
1400	// stop the I/O watcher, we received the event, but	1512	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1513	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1514	ev_io_stop (EV_A_ w);
1403		1515
1404	// start the idle watcher to ahndle the actual event.	1516	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1517	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1518	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1519	ev_idle_start (EV_A_ &idle);
1408	}	1520	}
1409		1521
…		…
1459	In general you can register as many read and/or write event watchers per	1571	In general you can register as many read and/or write event watchers per
1460	fd as you want (as long as you don't confuse yourself). Setting all file	1572	fd as you want (as long as you don't confuse yourself). Setting all file
1461	descriptors to non-blocking mode is also usually a good idea (but not	1573	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1574	required if you know what you are doing).
1463		1575
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1579	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1580	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1581	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	preferable to a program hanging until some data arrives.
1478		1583
1479	If you cannot run the fd in non-blocking mode (for example you should	1584	If you cannot run the fd in non-blocking mode (for example you should
1480	not play around with an Xlib connection), then you have to separately	1585	not play around with an Xlib connection), then you have to separately
1481	re-test whether a file descriptor is really ready with a known-to-be good	1586	re-test whether a file descriptor is really ready with a known-to-be good
1482	interface such as poll (fortunately in our Xlib example, Xlib already	1587	interface such as poll (fortunately in the case of Xlib, it already does
1483	does this on its own, so its quite safe to use). Some people additionally	1588	this on its own, so its quite safe to use). Some people additionally
1484	use C<SIGALRM> and an interval timer, just to be sure you won't block	1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1590	indefinitely.
1486		1591
1487	But really, best use non-blocking mode.	1592	But really, best use non-blocking mode.
1488		1593
…		…
1516		1621
1517	There is no workaround possible except not registering events	1622	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1623	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1624	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1625
		1626	=head3 The special problem of files
		1627
		1628	Many people try to use C<select> (or libev) on file descriptors
		1629	representing files, and expect it to become ready when their program
		1630	doesn't block on disk accesses (which can take a long time on their own).
		1631
		1632	However, this cannot ever work in the "expected" way - you get a readiness
		1633	notification as soon as the kernel knows whether and how much data is
		1634	there, and in the case of open files, that's always the case, so you
		1635	always get a readiness notification instantly, and your read (or possibly
		1636	write) will still block on the disk I/O.
		1637
		1638	Another way to view it is that in the case of sockets, pipes, character
		1639	devices and so on, there is another party (the sender) that delivers data
		1640	on its own, but in the case of files, there is no such thing: the disk
		1641	will not send data on its own, simply because it doesn't know what you
		1642	wish to read - you would first have to request some data.
		1643
		1644	Since files are typically not-so-well supported by advanced notification
		1645	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1646	to files, even though you should not use it. The reason for this is
		1647	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1648	usually a tty, often a pipe, but also sometimes files or special devices
		1649	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1650	F</dev/urandom>), and even though the file might better be served with
		1651	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1652	it "just works" instead of freezing.
		1653
		1654	So avoid file descriptors pointing to files when you know it (e.g. use
		1655	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1656	when you rarely read from a file instead of from a socket, and want to
		1657	reuse the same code path.
		1658
1521	=head3 The special problem of fork	1659	=head3 The special problem of fork
1522		1660
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1661	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1524	useless behaviour. Libev fully supports fork, but needs to be told about	1662	useless behaviour. Libev fully supports fork, but needs to be told about
1525	it in the child.	1663	it in the child if you want to continue to use it in the child.
1526		1664
1527	To support fork in your programs, you either have to call	1665	To support fork in your child processes, you have to call C<ev_loop_fork
1528	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1666	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1667	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1668
1532	=head3 The special problem of SIGPIPE	1669	=head3 The special problem of SIGPIPE
1533		1670
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1671	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1535	when writing to a pipe whose other end has been closed, your program gets	1672	when writing to a pipe whose other end has been closed, your program gets
…		…
1541	somewhere, as that would have given you a big clue).	1678	somewhere, as that would have given you a big clue).
1542		1679
1543	=head3 The special problem of accept()ing when you can't	1680	=head3 The special problem of accept()ing when you can't
1544		1681
1545	Many implementations of the POSIX C<accept> function (for example,	1682	Many implementations of the POSIX C<accept> function (for example,
1546	found in port-2004 Linux) have the peculiar behaviour of not removing a	1683	found in post-2004 Linux) have the peculiar behaviour of not removing a
1547	connection from the pending queue in all error cases.	1684	connection from the pending queue in all error cases.
1548		1685
1549	For example, larger servers often run out of file descriptors (because	1686	For example, larger servers often run out of file descriptors (because
1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not	1687	of resource limits), causing C<accept> to fail with C<ENFILE> but not
1551	rejecting the connection, leading to libev signalling readiness on	1688	rejecting the connection, leading to libev signalling readiness on
…		…
1617	...	1754	...
1618	struct ev_loop *loop = ev_default_init (0);	1755	struct ev_loop *loop = ev_default_init (0);
1619	ev_io stdin_readable;	1756	ev_io stdin_readable;
1620	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1757	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1621	ev_io_start (loop, &stdin_readable);	1758	ev_io_start (loop, &stdin_readable);
1622	ev_loop (loop, 0);	1759	ev_run (loop, 0);
1623		1760
1624		1761
1625	=head2 C<ev_timer> - relative and optionally repeating timeouts	1762	=head2 C<ev_timer> - relative and optionally repeating timeouts
1626		1763
1627	Timer watchers are simple relative timers that generate an event after a	1764	Timer watchers are simple relative timers that generate an event after a
…		…
1636	The callback is guaranteed to be invoked only I<after> its timeout has	1773	The callback is guaranteed to be invoked only I<after> its timeout has
1637	passed (not I<at>, so on systems with very low-resolution clocks this	1774	passed (not I<at>, so on systems with very low-resolution clocks this
1638	might introduce a small delay). If multiple timers become ready during the	1775	might introduce a small delay). If multiple timers become ready during the
1639	same loop iteration then the ones with earlier time-out values are invoked	1776	same loop iteration then the ones with earlier time-out values are invoked
1640	before ones of the same priority with later time-out values (but this is	1777	before ones of the same priority with later time-out values (but this is
1641	no longer true when a callback calls C<ev_loop> recursively).	1778	no longer true when a callback calls C<ev_run> recursively).
1642		1779
1643	=head3 Be smart about timeouts	1780	=head3 Be smart about timeouts
1644		1781
1645	Many real-world problems involve some kind of timeout, usually for error	1782	Many real-world problems involve some kind of timeout, usually for error
1646	recovery. A typical example is an HTTP request - if the other side hangs,	1783	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1732	ev_tstamp timeout = last_activity + 60.;	1869	ev_tstamp timeout = last_activity + 60.;
1733		1870
1734	// if last_activity + 60. is older than now, we did time out	1871	// if last_activity + 60. is older than now, we did time out
1735	if (timeout < now)	1872	if (timeout < now)
1736	{	1873	{
1737	// timeout occured, take action	1874	// timeout occurred, take action
1738	}	1875	}
1739	else	1876	else
1740	{	1877	{
1741	// callback was invoked, but there was some activity, re-arm	1878	// callback was invoked, but there was some activity, re-arm
1742	// the watcher to fire in last_activity + 60, which is	1879	// the watcher to fire in last_activity + 60, which is
…		…
1764	to the current time (meaning we just have some activity :), then call the	1901	to the current time (meaning we just have some activity :), then call the
1765	callback, which will "do the right thing" and start the timer:	1902	callback, which will "do the right thing" and start the timer:
1766		1903
1767	ev_init (timer, callback);	1904	ev_init (timer, callback);
1768	last_activity = ev_now (loop);	1905	last_activity = ev_now (loop);
1769	callback (loop, timer, EV_TIMEOUT);	1906	callback (loop, timer, EV_TIMER);
1770		1907
1771	And when there is some activity, simply store the current time in	1908	And when there is some activity, simply store the current time in
1772	C<last_activity>, no libev calls at all:	1909	C<last_activity>, no libev calls at all:
1773		1910
1774	last_actiivty = ev_now (loop);	1911	last_activity = ev_now (loop);
1775		1912
1776	This technique is slightly more complex, but in most cases where the	1913	This technique is slightly more complex, but in most cases where the
1777	time-out is unlikely to be triggered, much more efficient.	1914	time-out is unlikely to be triggered, much more efficient.
1778		1915
1779	Changing the timeout is trivial as well (if it isn't hard-coded in the	1916	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1817		1954
1818	=head3 The special problem of time updates	1955	=head3 The special problem of time updates
1819		1956
1820	Establishing the current time is a costly operation (it usually takes at	1957	Establishing the current time is a costly operation (it usually takes at
1821	least two system calls): EV therefore updates its idea of the current	1958	least two system calls): EV therefore updates its idea of the current
1822	time only before and after C<ev_loop> collects new events, which causes a	1959	time only before and after C<ev_run> collects new events, which causes a
1823	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1960	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1824	lots of events in one iteration.	1961	lots of events in one iteration.
1825		1962
1826	The relative timeouts are calculated relative to the C<ev_now ()>	1963	The relative timeouts are calculated relative to the C<ev_now ()>
1827	time. This is usually the right thing as this timestamp refers to the time	1964	time. This is usually the right thing as this timestamp refers to the time
…		…
1944	}	2081	}
1945		2082
1946	ev_timer mytimer;	2083	ev_timer mytimer;
1947	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2084	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1948	ev_timer_again (&mytimer); /* start timer */	2085	ev_timer_again (&mytimer); /* start timer */
1949	ev_loop (loop, 0);	2086	ev_run (loop, 0);
1950		2087
1951	// and in some piece of code that gets executed on any "activity":	2088	// and in some piece of code that gets executed on any "activity":
1952	// reset the timeout to start ticking again at 10 seconds	2089	// reset the timeout to start ticking again at 10 seconds
1953	ev_timer_again (&mytimer);	2090	ev_timer_again (&mytimer);
1954		2091
…		…
1980		2117
1981	As with timers, the callback is guaranteed to be invoked only when the	2118	As with timers, the callback is guaranteed to be invoked only when the
1982	point in time where it is supposed to trigger has passed. If multiple	2119	point in time where it is supposed to trigger has passed. If multiple
1983	timers become ready during the same loop iteration then the ones with	2120	timers become ready during the same loop iteration then the ones with
1984	earlier time-out values are invoked before ones with later time-out values	2121	earlier time-out values are invoked before ones with later time-out values
1985	(but this is no longer true when a callback calls C<ev_loop> recursively).	2122	(but this is no longer true when a callback calls C<ev_run> recursively).
1986		2123
1987	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1988		2125
1989	=over 4	2126	=over 4
1990		2127
…		…
2025		2162
2026	Another way to think about it (for the mathematically inclined) is that	2163	Another way to think about it (for the mathematically inclined) is that
2027	C<ev_periodic> will try to run the callback in this mode at the next possible	2164	C<ev_periodic> will try to run the callback in this mode at the next possible
2028	time where C<time = offset (mod interval)>, regardless of any time jumps.	2165	time where C<time = offset (mod interval)>, regardless of any time jumps.
2029		2166
2030	For numerical stability it is preferable that the C<offset> value is near	2167	The C<interval> I<MUST> be positive, and for numerical stability, the
2031	C<ev_now ()> (the current time), but there is no range requirement for	2168	interval value should be higher than C<1/8192> (which is around 100
2032	this value, and in fact is often specified as zero.	2169	microseconds) and C<offset> should be higher than C<0> and should have
		2170	at most a similar magnitude as the current time (say, within a factor of
		2171	ten). Typical values for offset are, in fact, C<0> or something between
		2172	C<0> and C<interval>, which is also the recommended range.
2033		2173
2034	Note also that there is an upper limit to how often a timer can fire (CPU	2174	Note also that there is an upper limit to how often a timer can fire (CPU
2035	speed for example), so if C<interval> is very small then timing stability	2175	speed for example), so if C<interval> is very small then timing stability
2036	will of course deteriorate. Libev itself tries to be exact to be about one	2176	will of course deteriorate. Libev itself tries to be exact to be about one
2037	millisecond (if the OS supports it and the machine is fast enough).	2177	millisecond (if the OS supports it and the machine is fast enough).
…		…
2118	Example: Call a callback every hour, or, more precisely, whenever the	2258	Example: Call a callback every hour, or, more precisely, whenever the
2119	system time is divisible by 3600. The callback invocation times have	2259	system time is divisible by 3600. The callback invocation times have
2120	potentially a lot of jitter, but good long-term stability.	2260	potentially a lot of jitter, but good long-term stability.
2121		2261
2122	static void	2262	static void
2123	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2263	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2124	{	2264	{
2125	... its now a full hour (UTC, or TAI or whatever your clock follows)	2265	... its now a full hour (UTC, or TAI or whatever your clock follows)
2126	}	2266	}
2127		2267
2128	ev_periodic hourly_tick;	2268	ev_periodic hourly_tick;
…		…
2151		2291
2152	=head2 C<ev_signal> - signal me when a signal gets signalled!	2292	=head2 C<ev_signal> - signal me when a signal gets signalled!
2153		2293
2154	Signal watchers will trigger an event when the process receives a specific	2294	Signal watchers will trigger an event when the process receives a specific
2155	signal one or more times. Even though signals are very asynchronous, libev	2295	signal one or more times. Even though signals are very asynchronous, libev
2156	will try it's best to deliver signals synchronously, i.e. as part of the	2296	will try its best to deliver signals synchronously, i.e. as part of the
2157	normal event processing, like any other event.	2297	normal event processing, like any other event.
2158		2298
2159	If you want signals to be delivered truly asynchronously, just use	2299	If you want signals to be delivered truly asynchronously, just use
2160	C<sigaction> as you would do without libev and forget about sharing	2300	C<sigaction> as you would do without libev and forget about sharing
2161	the signal. You can even use C<ev_async> from a signal handler to	2301	the signal. You can even use C<ev_async> from a signal handler to
…		…
2180	=head3 The special problem of inheritance over fork/execve/pthread_create	2320	=head3 The special problem of inheritance over fork/execve/pthread_create
2181		2321
2182	Both the signal mask (C<sigprocmask>) and the signal disposition	2322	Both the signal mask (C<sigprocmask>) and the signal disposition
2183	(C<sigaction>) are unspecified after starting a signal watcher (and after	2323	(C<sigaction>) are unspecified after starting a signal watcher (and after
2184	stopping it again), that is, libev might or might not block the signal,	2324	stopping it again), that is, libev might or might not block the signal,
2185	and might or might not set or restore the installed signal handler.	2325	and might or might not set or restore the installed signal handler (but
		2326	see C<EVFLAG_NOSIGMASK>).
2186		2327
2187	While this does not matter for the signal disposition (libev never	2328	While this does not matter for the signal disposition (libev never
2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2329	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2189	C<execve>), this matters for the signal mask: many programs do not expect	2330	C<execve>), this matters for the signal mask: many programs do not expect
2190	certain signals to be blocked.	2331	certain signals to be blocked.
…		…
2204		2345
2205	So I can't stress this enough: I<If you do not reset your signal mask when	2346	So I can't stress this enough: I<If you do not reset your signal mask when
2206	you expect it to be empty, you have a race condition in your code>. This	2347	you expect it to be empty, you have a race condition in your code>. This
2207	is not a libev-specific thing, this is true for most event libraries.	2348	is not a libev-specific thing, this is true for most event libraries.
2208		2349
		2350	=head3 The special problem of threads signal handling
		2351
		2352	POSIX threads has problematic signal handling semantics, specifically,
		2353	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2354	threads in a process block signals, which is hard to achieve.
		2355
		2356	When you want to use sigwait (or mix libev signal handling with your own
		2357	for the same signals), you can tackle this problem by globally blocking
		2358	all signals before creating any threads (or creating them with a fully set
		2359	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2360	loops. Then designate one thread as "signal receiver thread" which handles
		2361	these signals. You can pass on any signals that libev might be interested
		2362	in by calling C<ev_feed_signal>.
		2363
2209	=head3 Watcher-Specific Functions and Data Members	2364	=head3 Watcher-Specific Functions and Data Members
2210		2365
2211	=over 4	2366	=over 4
2212		2367
2213	=item ev_signal_init (ev_signal *, callback, int signum)	2368	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2228	Example: Try to exit cleanly on SIGINT.	2383	Example: Try to exit cleanly on SIGINT.
2229		2384
2230	static void	2385	static void
2231	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2386	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2232	{	2387	{
2233	ev_unloop (loop, EVUNLOOP_ALL);	2388	ev_break (loop, EVBREAK_ALL);
2234	}	2389	}
2235		2390
2236	ev_signal signal_watcher;	2391	ev_signal signal_watcher;
2237	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2392	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2238	ev_signal_start (loop, &signal_watcher);	2393	ev_signal_start (loop, &signal_watcher);
…		…
2624		2779
2625	Prepare and check watchers are usually (but not always) used in pairs:	2780	Prepare and check watchers are usually (but not always) used in pairs:
2626	prepare watchers get invoked before the process blocks and check watchers	2781	prepare watchers get invoked before the process blocks and check watchers
2627	afterwards.	2782	afterwards.
2628		2783
2629	You I<must not> call C<ev_loop> or similar functions that enter	2784	You I<must not> call C<ev_run> or similar functions that enter
2630	the current event loop from either C<ev_prepare> or C<ev_check>	2785	the current event loop from either C<ev_prepare> or C<ev_check>
2631	watchers. Other loops than the current one are fine, however. The	2786	watchers. Other loops than the current one are fine, however. The
2632	rationale behind this is that you do not need to check for recursion in	2787	rationale behind this is that you do not need to check for recursion in
2633	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2788	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2634	C<ev_check> so if you have one watcher of each kind they will always be	2789	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2802		2957
2803	if (timeout >= 0)	2958	if (timeout >= 0)
2804	// create/start timer	2959	// create/start timer
2805		2960
2806	// poll	2961	// poll
2807	ev_loop (EV_A_ 0);	2962	ev_run (EV_A_ 0);
2808		2963
2809	// stop timer again	2964	// stop timer again
2810	if (timeout >= 0)	2965	if (timeout >= 0)
2811	ev_timer_stop (EV_A_ &to);	2966	ev_timer_stop (EV_A_ &to);
2812		2967
…		…
2890	if you do not want that, you need to temporarily stop the embed watcher).	3045	if you do not want that, you need to temporarily stop the embed watcher).
2891		3046
2892	=item ev_embed_sweep (loop, ev_embed *)	3047	=item ev_embed_sweep (loop, ev_embed *)
2893		3048
2894	Make a single, non-blocking sweep over the embedded loop. This works	3049	Make a single, non-blocking sweep over the embedded loop. This works
2895	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3050	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2896	appropriate way for embedded loops.	3051	appropriate way for embedded loops.
2897		3052
2898	=item struct ev_loop *other [read-only]	3053	=item struct ev_loop *other [read-only]
2899		3054
2900	The embedded event loop.	3055	The embedded event loop.
…		…
2960	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3115	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2961	handlers will be invoked, too, of course.	3116	handlers will be invoked, too, of course.
2962		3117
2963	=head3 The special problem of life after fork - how is it possible?	3118	=head3 The special problem of life after fork - how is it possible?
2964		3119
2965	Most uses of C<fork()> consist of forking, then some simple calls to ste	3120	Most uses of C<fork()> consist of forking, then some simple calls to set
2966	up/change the process environment, followed by a call to C<exec()>. This	3121	up/change the process environment, followed by a call to C<exec()>. This
2967	sequence should be handled by libev without any problems.	3122	sequence should be handled by libev without any problems.
2968		3123
2969	This changes when the application actually wants to do event handling	3124	This changes when the application actually wants to do event handling
2970	in the child, or both parent in child, in effect "continuing" after the	3125	in the child, or both parent in child, in effect "continuing" after the
…		…
2986	disadvantage of having to use multiple event loops (which do not support	3141	disadvantage of having to use multiple event loops (which do not support
2987	signal watchers).	3142	signal watchers).
2988		3143
2989	When this is not possible, or you want to use the default loop for	3144	When this is not possible, or you want to use the default loop for
2990	other reasons, then in the process that wants to start "fresh", call	3145	other reasons, then in the process that wants to start "fresh", call
2991	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3146	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2992	the default loop will "orphan" (not stop) all registered watchers, so you	3147	Destroying the default loop will "orphan" (not stop) all registered
2993	have to be careful not to execute code that modifies those watchers. Note	3148	watchers, so you have to be careful not to execute code that modifies
2994	also that in that case, you have to re-register any signal watchers.	3149	those watchers. Note also that in that case, you have to re-register any
		3150	signal watchers.
2995		3151
2996	=head3 Watcher-Specific Functions and Data Members	3152	=head3 Watcher-Specific Functions and Data Members
2997		3153
2998	=over 4	3154	=over 4
2999		3155
3000	=item ev_fork_init (ev_signal *, callback)	3156	=item ev_fork_init (ev_fork *, callback)
3001		3157
3002	Initialises and configures the fork watcher - it has no parameters of any	3158	Initialises and configures the fork watcher - it has no parameters of any
3003	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3004	believe me.	3160	really.
3005		3161
3006	=back	3162	=back
3007		3163
3008		3164
		3165	=head2 C<ev_cleanup> - even the best things end
		3166
		3167	Cleanup watchers are called just before the event loop is being destroyed
		3168	by a call to C<ev_loop_destroy>.
		3169
		3170	While there is no guarantee that the event loop gets destroyed, cleanup
		3171	watchers provide a convenient method to install cleanup hooks for your
		3172	program, worker threads and so on - you just to make sure to destroy the
		3173	loop when you want them to be invoked.
		3174
		3175	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3176	all other watchers, they do not keep a reference to the event loop (which
		3177	makes a lot of sense if you think about it). Like all other watchers, you
		3178	can call libev functions in the callback, except C<ev_cleanup_start>.
		3179
		3180	=head3 Watcher-Specific Functions and Data Members
		3181
		3182	=over 4
		3183
		3184	=item ev_cleanup_init (ev_cleanup *, callback)
		3185
		3186	Initialises and configures the cleanup watcher - it has no parameters of
		3187	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3188	pointless, I assure you.
		3189
		3190	=back
		3191
		3192	Example: Register an atexit handler to destroy the default loop, so any
		3193	cleanup functions are called.
		3194
		3195	static void
		3196	program_exits (void)
		3197	{
		3198	ev_loop_destroy (EV_DEFAULT_UC);
		3199	}
		3200
		3201	...
		3202	atexit (program_exits);
		3203
		3204
3009	=head2 C<ev_async> - how to wake up another event loop	3205	=head2 C<ev_async> - how to wake up an event loop
3010		3206
3011	In general, you cannot use an C<ev_loop> from multiple threads or other	3207	In general, you cannot use an C<ev_loop> from multiple threads or other
3012	asynchronous sources such as signal handlers (as opposed to multiple event	3208	asynchronous sources such as signal handlers (as opposed to multiple event
3013	loops - those are of course safe to use in different threads).	3209	loops - those are of course safe to use in different threads).
3014		3210
3015	Sometimes, however, you need to wake up another event loop you do not	3211	Sometimes, however, you need to wake up an event loop you do not control,
3016	control, for example because it belongs to another thread. This is what	3212	for example because it belongs to another thread. This is what C<ev_async>
3017	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3213	watchers do: as long as the C<ev_async> watcher is active, you can signal
3018	can signal it by calling C<ev_async_send>, which is thread- and signal	3214	it by calling C<ev_async_send>, which is thread- and signal safe.
3019	safe.
3020		3215
3021	This functionality is very similar to C<ev_signal> watchers, as signals,	3216	This functionality is very similar to C<ev_signal> watchers, as signals,
3022	too, are asynchronous in nature, and signals, too, will be compressed	3217	too, are asynchronous in nature, and signals, too, will be compressed
3023	(i.e. the number of callback invocations may be less than the number of	3218	(i.e. the number of callback invocations may be less than the number of
3024	C<ev_async_sent> calls).	3219	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3220	of "global async watchers" by using a watcher on an otherwise unused
		3221	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3222	even without knowing which loop owns the signal.
3025		3223
3026	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3224	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
3027	just the default loop.	3225	just the default loop.
3028		3226
3029	=head3 Queueing	3227	=head3 Queueing
…		…
3124	trust me.	3322	trust me.
3125		3323
3126	=item ev_async_send (loop, ev_async *)	3324	=item ev_async_send (loop, ev_async *)
3127		3325
3128	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3326	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3129	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3327	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3328	returns.
		3329
3130	C<ev_feed_event>, this call is safe to do from other threads, signal or	3330	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3131	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3331	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3132	section below on what exactly this means).	3332	embedding section below on what exactly this means).
3133		3333
3134	Note that, as with other watchers in libev, multiple events might get	3334	Note that, as with other watchers in libev, multiple events might get
3135	compressed into a single callback invocation (another way to look at this	3335	compressed into a single callback invocation (another way to look at this
3136	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3336	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3137	reset when the event loop detects that).	3337	reset when the event loop detects that).
…		…
3179		3379
3180	If C<timeout> is less than 0, then no timeout watcher will be	3380	If C<timeout> is less than 0, then no timeout watcher will be
3181	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3182	repeat = 0) will be started. C<0> is a valid timeout.	3382	repeat = 0) will be started. C<0> is a valid timeout.
3183		3383
3184	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3384	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3185	passed an C<revents> set like normal event callbacks (a combination of	3385	passed an C<revents> set like normal event callbacks (a combination of
3186	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3386	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3187	value passed to C<ev_once>. Note that it is possible to receive I<both>	3387	value passed to C<ev_once>. Note that it is possible to receive I<both>
3188	a timeout and an io event at the same time - you probably should give io	3388	a timeout and an io event at the same time - you probably should give io
3189	events precedence.	3389	events precedence.
3190		3390
3191	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3391	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3192		3392
3193	static void stdin_ready (int revents, void *arg)	3393	static void stdin_ready (int revents, void *arg)
3194	{	3394	{
3195	if (revents & EV_READ)	3395	if (revents & EV_READ)
3196	/* stdin might have data for us, joy! */;	3396	/* stdin might have data for us, joy! */;
3197	else if (revents & EV_TIMEOUT)	3397	else if (revents & EV_TIMER)
3198	/* doh, nothing entered */;	3398	/* doh, nothing entered */;
3199	}	3399	}
3200		3400
3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3401	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3202		3402
…		…
3205	Feed an event on the given fd, as if a file descriptor backend detected	3405	Feed an event on the given fd, as if a file descriptor backend detected
3206	the given events it.	3406	the given events it.
3207		3407
3208	=item ev_feed_signal_event (loop, int signum)	3408	=item ev_feed_signal_event (loop, int signum)
3209		3409
3210	Feed an event as if the given signal occurred (C<loop> must be the default	3410	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3211	loop!).	3411	which is async-safe.
3212		3412
3213	=back	3413	=back
		3414
		3415
		3416	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3417
		3418	This section explains some common idioms that are not immediately
		3419	obvious. Note that examples are sprinkled over the whole manual, and this
		3420	section only contains stuff that wouldn't fit anywhere else.
		3421
		3422	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3423
		3424	Each watcher has, by default, a C<void *data> member that you can read
		3425	or modify at any time: libev will completely ignore it. This can be used
		3426	to associate arbitrary data with your watcher. If you need more data and
		3427	don't want to allocate memory separately and store a pointer to it in that
		3428	data member, you can also "subclass" the watcher type and provide your own
		3429	data:
		3430
		3431	struct my_io
		3432	{
		3433	ev_io io;
		3434	int otherfd;
		3435	void *somedata;
		3436	struct whatever *mostinteresting;
		3437	};
		3438
		3439	...
		3440	struct my_io w;
		3441	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3442
		3443	And since your callback will be called with a pointer to the watcher, you
		3444	can cast it back to your own type:
		3445
		3446	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3447	{
		3448	struct my_io *w = (struct my_io *)w_;
		3449	...
		3450	}
		3451
		3452	More interesting and less C-conformant ways of casting your callback
		3453	function type instead have been omitted.
		3454
		3455	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3456
		3457	Another common scenario is to use some data structure with multiple
		3458	embedded watchers, in effect creating your own watcher that combines
		3459	multiple libev event sources into one "super-watcher":
		3460
		3461	struct my_biggy
		3462	{
		3463	int some_data;
		3464	ev_timer t1;
		3465	ev_timer t2;
		3466	}
		3467
		3468	In this case getting the pointer to C<my_biggy> is a bit more
		3469	complicated: Either you store the address of your C<my_biggy> struct in
		3470	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3471	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3472	real programmers):
		3473
		3474	#include <stddef.h>
		3475
		3476	static void
		3477	t1_cb (EV_P_ ev_timer *w, int revents)
		3478	{
		3479	struct my_biggy big = (struct my_biggy *)
		3480	(((char *)w) - offsetof (struct my_biggy, t1));
		3481	}
		3482
		3483	static void
		3484	t2_cb (EV_P_ ev_timer *w, int revents)
		3485	{
		3486	struct my_biggy big = (struct my_biggy *)
		3487	(((char *)w) - offsetof (struct my_biggy, t2));
		3488	}
		3489
		3490	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3491
		3492	Often (especially in GUI toolkits) there are places where you have
		3493	I<modal> interaction, which is most easily implemented by recursively
		3494	invoking C<ev_run>.
		3495
		3496	This brings the problem of exiting - a callback might want to finish the
		3497	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3498	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3499	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3500	other combination: In these cases, C<ev_break> will not work alone.
		3501
		3502	The solution is to maintain "break this loop" variable for each C<ev_run>
		3503	invocation, and use a loop around C<ev_run> until the condition is
		3504	triggered, using C<EVRUN_ONCE>:
		3505
		3506	// main loop
		3507	int exit_main_loop = 0;
		3508
		3509	while (!exit_main_loop)
		3510	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3511
		3512	// in a model watcher
		3513	int exit_nested_loop = 0;
		3514
		3515	while (!exit_nested_loop)
		3516	ev_run (EV_A_ EVRUN_ONCE);
		3517
		3518	To exit from any of these loops, just set the corresponding exit variable:
		3519
		3520	// exit modal loop
		3521	exit_nested_loop = 1;
		3522
		3523	// exit main program, after modal loop is finished
		3524	exit_main_loop = 1;
		3525
		3526	// exit both
		3527	exit_main_loop = exit_nested_loop = 1;
		3528
		3529	=head2 THREAD LOCKING EXAMPLE
		3530
		3531	Here is a fictitious example of how to run an event loop in a different
		3532	thread from where callbacks are being invoked and watchers are
		3533	created/added/removed.
		3534
		3535	For a real-world example, see the C<EV::Loop::Async> perl module,
		3536	which uses exactly this technique (which is suited for many high-level
		3537	languages).
		3538
		3539	The example uses a pthread mutex to protect the loop data, a condition
		3540	variable to wait for callback invocations, an async watcher to notify the
		3541	event loop thread and an unspecified mechanism to wake up the main thread.
		3542
		3543	First, you need to associate some data with the event loop:
		3544
		3545	typedef struct {
		3546	mutex_t lock; /* global loop lock */
		3547	ev_async async_w;
		3548	thread_t tid;
		3549	cond_t invoke_cv;
		3550	} userdata;
		3551
		3552	void prepare_loop (EV_P)
		3553	{
		3554	// for simplicity, we use a static userdata struct.
		3555	static userdata u;
		3556
		3557	ev_async_init (&u->async_w, async_cb);
		3558	ev_async_start (EV_A_ &u->async_w);
		3559
		3560	pthread_mutex_init (&u->lock, 0);
		3561	pthread_cond_init (&u->invoke_cv, 0);
		3562
		3563	// now associate this with the loop
		3564	ev_set_userdata (EV_A_ u);
		3565	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3566	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3567
		3568	// then create the thread running ev_run
		3569	pthread_create (&u->tid, 0, l_run, EV_A);
		3570	}
		3571
		3572	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3573	solely to wake up the event loop so it takes notice of any new watchers
		3574	that might have been added:
		3575
		3576	static void
		3577	async_cb (EV_P_ ev_async *w, int revents)
		3578	{
		3579	// just used for the side effects
		3580	}
		3581
		3582	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3583	protecting the loop data, respectively.
		3584
		3585	static void
		3586	l_release (EV_P)
		3587	{
		3588	userdata *u = ev_userdata (EV_A);
		3589	pthread_mutex_unlock (&u->lock);
		3590	}
		3591
		3592	static void
		3593	l_acquire (EV_P)
		3594	{
		3595	userdata *u = ev_userdata (EV_A);
		3596	pthread_mutex_lock (&u->lock);
		3597	}
		3598
		3599	The event loop thread first acquires the mutex, and then jumps straight
		3600	into C<ev_run>:
		3601
		3602	void *
		3603	l_run (void *thr_arg)
		3604	{
		3605	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3606
		3607	l_acquire (EV_A);
		3608	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3609	ev_run (EV_A_ 0);
		3610	l_release (EV_A);
		3611
		3612	return 0;
		3613	}
		3614
		3615	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3616	signal the main thread via some unspecified mechanism (signals? pipe
		3617	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3618	have been called (in a while loop because a) spurious wakeups are possible
		3619	and b) skipping inter-thread-communication when there are no pending
		3620	watchers is very beneficial):
		3621
		3622	static void
		3623	l_invoke (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	while (ev_pending_count (EV_A))
		3628	{
		3629	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3630	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3631	}
		3632	}
		3633
		3634	Now, whenever the main thread gets told to invoke pending watchers, it
		3635	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3636	thread to continue:
		3637
		3638	static void
		3639	real_invoke_pending (EV_P)
		3640	{
		3641	userdata *u = ev_userdata (EV_A);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_invoke_pending (EV_A);
		3645	pthread_cond_signal (&u->invoke_cv);
		3646	pthread_mutex_unlock (&u->lock);
		3647	}
		3648
		3649	Whenever you want to start/stop a watcher or do other modifications to an
		3650	event loop, you will now have to lock:
		3651
		3652	ev_timer timeout_watcher;
		3653	userdata *u = ev_userdata (EV_A);
		3654
		3655	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3656
		3657	pthread_mutex_lock (&u->lock);
		3658	ev_timer_start (EV_A_ &timeout_watcher);
		3659	ev_async_send (EV_A_ &u->async_w);
		3660	pthread_mutex_unlock (&u->lock);
		3661
		3662	Note that sending the C<ev_async> watcher is required because otherwise
		3663	an event loop currently blocking in the kernel will have no knowledge
		3664	about the newly added timer. By waking up the loop it will pick up any new
		3665	watchers in the next event loop iteration.
		3666
		3667	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3668
		3669	While the overhead of a callback that e.g. schedules a thread is small, it
		3670	is still an overhead. If you embed libev, and your main usage is with some
		3671	kind of threads or coroutines, you might want to customise libev so that
		3672	doesn't need callbacks anymore.
		3673
		3674	Imagine you have coroutines that you can switch to using a function
		3675	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3676	and that due to some magic, the currently active coroutine is stored in a
		3677	global called C<current_coro>. Then you can build your own "wait for libev
		3678	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3679	the differing C<;> conventions):
		3680
		3681	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3682	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3683
		3684	That means instead of having a C callback function, you store the
		3685	coroutine to switch to in each watcher, and instead of having libev call
		3686	your callback, you instead have it switch to that coroutine.
		3687
		3688	A coroutine might now wait for an event with a function called
		3689	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3690	matter when, or whether the watcher is active or not when this function is
		3691	called):
		3692
		3693	void
		3694	wait_for_event (ev_watcher *w)
		3695	{
		3696	ev_cb_set (w) = current_coro;
		3697	switch_to (libev_coro);
		3698	}
		3699
		3700	That basically suspends the coroutine inside C<wait_for_event> and
		3701	continues the libev coroutine, which, when appropriate, switches back to
		3702	this or any other coroutine. I am sure if you sue this your own :)
		3703
		3704	You can do similar tricks if you have, say, threads with an event queue -
		3705	instead of storing a coroutine, you store the queue object and instead of
		3706	switching to a coroutine, you push the watcher onto the queue and notify
		3707	any waiters.
		3708
		3709	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3710	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3711
		3712	// my_ev.h
		3713	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3714	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3715	#include "../libev/ev.h"
		3716
		3717	// my_ev.c
		3718	#define EV_H "my_ev.h"
		3719	#include "../libev/ev.c"
		3720
		3721	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3722	F<my_ev.c> into your project. When properly specifying include paths, you
		3723	can even use F<ev.h> as header file name directly.
3214		3724
3215		3725
3216	=head1 LIBEVENT EMULATION	3726	=head1 LIBEVENT EMULATION
3217		3727
3218	Libev offers a compatibility emulation layer for libevent. It cannot	3728	Libev offers a compatibility emulation layer for libevent. It cannot
3219	emulate the internals of libevent, so here are some usage hints:	3729	emulate the internals of libevent, so here are some usage hints:
3220		3730
3221	=over 4	3731	=over 4
		3732
		3733	=item * Only the libevent-1.4.1-beta API is being emulated.
		3734
		3735	This was the newest libevent version available when libev was implemented,
		3736	and is still mostly unchanged in 2010.
3222		3737
3223	=item * Use it by including <event.h>, as usual.	3738	=item * Use it by including <event.h>, as usual.
3224		3739
3225	=item * The following members are fully supported: ev_base, ev_callback,	3740	=item * The following members are fully supported: ev_base, ev_callback,
3226	ev_arg, ev_fd, ev_res, ev_events.	3741	ev_arg, ev_fd, ev_res, ev_events.
…		…
3232	=item * Priorities are not currently supported. Initialising priorities	3747	=item * Priorities are not currently supported. Initialising priorities
3233	will fail and all watchers will have the same priority, even though there	3748	will fail and all watchers will have the same priority, even though there
3234	is an ev_pri field.	3749	is an ev_pri field.
3235		3750
3236	=item * In libevent, the last base created gets the signals, in libev, the	3751	=item * In libevent, the last base created gets the signals, in libev, the
3237	first base created (== the default loop) gets the signals.	3752	base that registered the signal gets the signals.
3238		3753
3239	=item * Other members are not supported.	3754	=item * Other members are not supported.
3240		3755
3241	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3756	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3242	to use the libev header file and library.	3757	to use the libev header file and library.
…		…
3261	Care has been taken to keep the overhead low. The only data member the C++	3776	Care has been taken to keep the overhead low. The only data member the C++
3262	classes add (compared to plain C-style watchers) is the event loop pointer	3777	classes add (compared to plain C-style watchers) is the event loop pointer
3263	that the watcher is associated with (or no additional members at all if	3778	that the watcher is associated with (or no additional members at all if
3264	you disable C<EV_MULTIPLICITY> when embedding libev).	3779	you disable C<EV_MULTIPLICITY> when embedding libev).
3265		3780
3266	Currently, functions, and static and non-static member functions can be	3781	Currently, functions, static and non-static member functions and classes
3267	used as callbacks. Other types should be easy to add as long as they only	3782	with C<operator ()> can be used as callbacks. Other types should be easy
3268	need one additional pointer for context. If you need support for other	3783	to add as long as they only need one additional pointer for context. If
3269	types of functors please contact the author (preferably after implementing	3784	you need support for other types of functors please contact the author
3270	it).	3785	(preferably after implementing it).
3271		3786
3272	Here is a list of things available in the C<ev> namespace:	3787	Here is a list of things available in the C<ev> namespace:
3273		3788
3274	=over 4	3789	=over 4
3275		3790
…		…
3336	myclass obj;	3851	myclass obj;
3337	ev::io iow;	3852	ev::io iow;
3338	iow.set <myclass, &myclass::io_cb> (&obj);	3853	iow.set <myclass, &myclass::io_cb> (&obj);
3339		3854
3340	=item w->set (object *)	3855	=item w->set (object *)
3341
3342	This is an B<experimental> feature that might go away in a future version.
3343		3856
3344	This is a variation of a method callback - leaving out the method to call	3857	This is a variation of a method callback - leaving out the method to call
3345	will default the method to C<operator ()>, which makes it possible to use	3858	will default the method to C<operator ()>, which makes it possible to use
3346	functor objects without having to manually specify the C<operator ()> all	3859	functor objects without having to manually specify the C<operator ()> all
3347	the time. Incidentally, you can then also leave out the template argument	3860	the time. Incidentally, you can then also leave out the template argument
…		…
3387	Associates a different C<struct ev_loop> with this watcher. You can only	3900	Associates a different C<struct ev_loop> with this watcher. You can only
3388	do this when the watcher is inactive (and not pending either).	3901	do this when the watcher is inactive (and not pending either).
3389		3902
3390	=item w->set ([arguments])	3903	=item w->set ([arguments])
3391		3904
3392	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3905	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3393	called at least once. Unlike the C counterpart, an active watcher gets	3906	method or a suitable start method must be called at least once. Unlike the
3394	automatically stopped and restarted when reconfiguring it with this	3907	C counterpart, an active watcher gets automatically stopped and restarted
3395	method.	3908	when reconfiguring it with this method.
3396		3909
3397	=item w->start ()	3910	=item w->start ()
3398		3911
3399	Starts the watcher. Note that there is no C<loop> argument, as the	3912	Starts the watcher. Note that there is no C<loop> argument, as the
3400	constructor already stores the event loop.	3913	constructor already stores the event loop.
3401		3914
		3915	=item w->start ([arguments])
		3916
		3917	Instead of calling C<set> and C<start> methods separately, it is often
		3918	convenient to wrap them in one call. Uses the same type of arguments as
		3919	the configure C<set> method of the watcher.
		3920
3402	=item w->stop ()	3921	=item w->stop ()
3403		3922
3404	Stops the watcher if it is active. Again, no C<loop> argument.	3923	Stops the watcher if it is active. Again, no C<loop> argument.
3405		3924
3406	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3925	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3418		3937
3419	=back	3938	=back
3420		3939
3421	=back	3940	=back
3422		3941
3423	Example: Define a class with an IO and idle watcher, start one of them in	3942	Example: Define a class with two I/O and idle watchers, start the I/O
3424	the constructor.	3943	watchers in the constructor.
3425		3944
3426	class myclass	3945	class myclass
3427	{	3946	{
3428	ev::io io ; void io_cb (ev::io &w, int revents);	3947	ev::io io ; void io_cb (ev::io &w, int revents);
		3948	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3429	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3430		3950
3431	myclass (int fd)	3951	myclass (int fd)
3432	{	3952	{
3433	io .set <myclass, &myclass::io_cb > (this);	3953	io .set <myclass, &myclass::io_cb > (this);
		3954	io2 .set <myclass, &myclass::io2_cb > (this);
3434	idle.set <myclass, &myclass::idle_cb> (this);	3955	idle.set <myclass, &myclass::idle_cb> (this);
3435		3956
3436	io.start (fd, ev::READ);	3957	io.set (fd, ev::WRITE); // configure the watcher
		3958	io.start (); // start it whenever convenient
		3959
		3960	io2.start (fd, ev::READ); // set + start in one call
3437	}	3961	}
3438	};	3962	};
3439		3963
3440		3964
3441	=head1 OTHER LANGUAGE BINDINGS	3965	=head1 OTHER LANGUAGE BINDINGS
…		…
3515	loop argument"). The C<EV_A> form is used when this is the sole argument,	4039	loop argument"). The C<EV_A> form is used when this is the sole argument,
3516	C<EV_A_> is used when other arguments are following. Example:	4040	C<EV_A_> is used when other arguments are following. Example:
3517		4041
3518	ev_unref (EV_A);	4042	ev_unref (EV_A);
3519	ev_timer_add (EV_A_ watcher);	4043	ev_timer_add (EV_A_ watcher);
3520	ev_loop (EV_A_ 0);	4044	ev_run (EV_A_ 0);
3521		4045
3522	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4046	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3523	which is often provided by the following macro.	4047	which is often provided by the following macro.
3524		4048
3525	=item C<EV_P>, C<EV_P_>	4049	=item C<EV_P>, C<EV_P_>
…		…
3565	}	4089	}
3566		4090
3567	ev_check check;	4091	ev_check check;
3568	ev_check_init (&check, check_cb);	4092	ev_check_init (&check, check_cb);
3569	ev_check_start (EV_DEFAULT_ &check);	4093	ev_check_start (EV_DEFAULT_ &check);
3570	ev_loop (EV_DEFAULT_ 0);	4094	ev_run (EV_DEFAULT_ 0);
3571		4095
3572	=head1 EMBEDDING	4096	=head1 EMBEDDING
3573		4097
3574	Libev can (and often is) directly embedded into host	4098	Libev can (and often is) directly embedded into host
3575	applications. Examples of applications that embed it include the Deliantra	4099	applications. Examples of applications that embed it include the Deliantra
…		…
3660	define before including (or compiling) any of its files. The default in	4184	define before including (or compiling) any of its files. The default in
3661	the absence of autoconf is documented for every option.	4185	the absence of autoconf is documented for every option.
3662		4186
3663	Symbols marked with "(h)" do not change the ABI, and can have different	4187	Symbols marked with "(h)" do not change the ABI, and can have different
3664	values when compiling libev vs. including F<ev.h>, so it is permissible	4188	values when compiling libev vs. including F<ev.h>, so it is permissible
3665	to redefine them before including F<ev.h> without breakign compatibility	4189	to redefine them before including F<ev.h> without breaking compatibility
3666	to a compiled library. All other symbols change the ABI, which means all	4190	to a compiled library. All other symbols change the ABI, which means all
3667	users of libev and the libev code itself must be compiled with compatible	4191	users of libev and the libev code itself must be compiled with compatible
3668	settings.	4192	settings.
3669		4193
3670	=over 4	4194	=over 4
		4195
		4196	=item EV_COMPAT3 (h)
		4197
		4198	Backwards compatibility is a major concern for libev. This is why this
		4199	release of libev comes with wrappers for the functions and symbols that
		4200	have been renamed between libev version 3 and 4.
		4201
		4202	You can disable these wrappers (to test compatibility with future
		4203	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4204	sources. This has the additional advantage that you can drop the C<struct>
		4205	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4206	typedef in that case.
		4207
		4208	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4209	and in some even more future version the compatibility code will be
		4210	removed completely.
3671		4211
3672	=item EV_STANDALONE (h)	4212	=item EV_STANDALONE (h)
3673		4213
3674	Must always be C<1> if you do not use autoconf configuration, which	4214	Must always be C<1> if you do not use autoconf configuration, which
3675	keeps libev from including F<config.h>, and it also defines dummy	4215	keeps libev from including F<config.h>, and it also defines dummy
…		…
3677	supported). It will also not define any of the structs usually found in	4217	supported). It will also not define any of the structs usually found in
3678	F<event.h> that are not directly supported by the libev core alone.	4218	F<event.h> that are not directly supported by the libev core alone.
3679		4219
3680	In standalone mode, libev will still try to automatically deduce the	4220	In standalone mode, libev will still try to automatically deduce the
3681	configuration, but has to be more conservative.	4221	configuration, but has to be more conservative.
		4222
		4223	=item EV_USE_FLOOR
		4224
		4225	If defined to be C<1>, libev will use the C<floor ()> function for its
		4226	periodic reschedule calculations, otherwise libev will fall back on a
		4227	portable (slower) implementation. If you enable this, you usually have to
		4228	link against libm or something equivalent. Enabling this when the C<floor>
		4229	function is not available will fail, so the safe default is to not enable
		4230	this.
3682		4231
3683	=item EV_USE_MONOTONIC	4232	=item EV_USE_MONOTONIC
3684		4233
3685	If defined to be C<1>, libev will try to detect the availability of the	4234	If defined to be C<1>, libev will try to detect the availability of the
3686	monotonic clock option at both compile time and runtime. Otherwise no	4235	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4431	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4432	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3884		4433
3885	If undefined or defined to be C<1> (and the platform supports it), then	4434	If undefined or defined to be C<1> (and the platform supports it), then
3886	the respective watcher type is supported. If defined to be C<0>, then it	4435	the respective watcher type is supported. If defined to be C<0>, then it
3887	is not. Disabling watcher types mainly saves codesize.	4436	is not. Disabling watcher types mainly saves code size.
3888		4437
3889	=item EV_MINIMAL	4438	=item EV_FEATURES
3890		4439
3891	If you need to shave off some kilobytes of code at the expense of some	4440	If you need to shave off some kilobytes of code at the expense of some
3892	speed (but with the full API), define this symbol to C<1>. Currently this	4441	speed (but with the full API), you can define this symbol to request
3893	is used to override some inlining decisions, saves roughly 30% code size	4442	certain subsets of functionality. The default is to enable all features
3894	on amd64. It also selects a much smaller 2-heap for timer management over	4443	that can be enabled on the platform.
3895	the default 4-heap.
3896		4444
3897	You can save even more by disabling watcher types you do not need	4445	A typical way to use this symbol is to define it to C<0> (or to a bitset
3898	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4446	with some broad features you want) and then selectively re-enable
3899	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,	4447	additional parts you want, for example if you want everything minimal,
3900	eventfd and signalfd will further help, and disabling backends one doesn't	4448	but multiple event loop support, async and child watchers and the poll
3901	need (e.g. poll, epoll, kqueue, ports) will help further.	4449	backend, use this:
3902		4450
3903	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4451	#define EV_FEATURES 0
3904	provide a bare-bones event library. See C<ev.h> for details on what parts
3905	of the API are still available, and do not complain if this subset changes
3906	over time.
3907
3908	This example set of settings reduces the compiled size of libev from
3909	23.9Kb to 7.7Kb on my GNU/Linux amd64 system (and leaves little
3910	in - there is also an effect on the amount of memory used). With
3911	an intelligent-enough linker (gcc+binutils do this when you use
3912	C<-Wl,--gc-sections -ffunction-sections>) further unused functions might
3913	be left out as well automatically - a binary starting a timer and an I/O
3914	watcher then might come out at only 5Kb.
3915
3916	// tuning and API changes
3917	#define EV_MINIMAL 2
3918	#define EV_MULTIPLICITY 0	4452	#define EV_MULTIPLICITY 1
3919	#define EV_MINPRI 0
3920	#define EV_MAXPRI 0
3921
3922	// OS-specific backends
3923	#define EV_USE_INOTIFY 0
3924	#define EV_USE_EVENTFD 0
3925	#define EV_USE_SIGNALFD 0
3926	#define EV_USE_REALTIME 0
3927	#define EV_USE_MONOTONIC 0
3928	#define EV_USE_CLOCK_SYSCALL 0
3929
3930	// disable all backends except select
3931	#define EV_USE_POLL 0	4453	#define EV_USE_POLL 1
3932	#define EV_USE_PORT 0
3933	#define EV_USE_KQUEUE 0
3934	#define EV_USE_EPOLL 0
3935
3936	// disable all watcher types that cna be disabled
3937	#define EV_STAT_ENABLE 0
3938	#define EV_PERIODIC_ENABLE 0
3939	#define EV_IDLE_ENABLE 0
3940	#define EV_CHECK_ENABLE 0
3941	#define EV_PREPARE_ENABLE 0
3942	#define EV_FORK_ENABLE 0
3943	#define EV_SIGNAL_ENABLE 0
3944	#define EV_CHILD_ENABLE 0	4454	#define EV_CHILD_ENABLE 1
3945	#define EV_ASYNC_ENABLE 0	4455	#define EV_ASYNC_ENABLE 1
3946	#define EV_EMBED_ENABLE 0	4456
		4457	The actual value is a bitset, it can be a combination of the following
		4458	values:
		4459
		4460	=over 4
		4461
		4462	=item C<1> - faster/larger code
		4463
		4464	Use larger code to speed up some operations.
		4465
		4466	Currently this is used to override some inlining decisions (enlarging the
		4467	code size by roughly 30% on amd64).
		4468
		4469	When optimising for size, use of compiler flags such as C<-Os> with
		4470	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4471	assertions.
		4472
		4473	=item C<2> - faster/larger data structures
		4474
		4475	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4476	hash table sizes and so on. This will usually further increase code size
		4477	and can additionally have an effect on the size of data structures at
		4478	runtime.
		4479
		4480	=item C<4> - full API configuration
		4481
		4482	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4483	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4484
		4485	=item C<8> - full API
		4486
		4487	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4488	details on which parts of the API are still available without this
		4489	feature, and do not complain if this subset changes over time.
		4490
		4491	=item C<16> - enable all optional watcher types
		4492
		4493	Enables all optional watcher types. If you want to selectively enable
		4494	only some watcher types other than I/O and timers (e.g. prepare,
		4495	embed, async, child...) you can enable them manually by defining
		4496	C<EV_watchertype_ENABLE> to C<1> instead.
		4497
		4498	=item C<32> - enable all backends
		4499
		4500	This enables all backends - without this feature, you need to enable at
		4501	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4502
		4503	=item C<64> - enable OS-specific "helper" APIs
		4504
		4505	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4506	default.
		4507
		4508	=back
		4509
		4510	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4511	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4512	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4513	watchers, timers and monotonic clock support.
		4514
		4515	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4516	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4517	your program might be left out as well - a binary starting a timer and an
		4518	I/O watcher then might come out at only 5Kb.
3947		4519
3948	=item EV_AVOID_STDIO	4520	=item EV_AVOID_STDIO
3949		4521
3950	If this is set to C<1> at compiletime, then libev will avoid using stdio	4522	If this is set to C<1> at compiletime, then libev will avoid using stdio
3951	functions (printf, scanf, perror etc.). This will increase the codesize	4523	functions (printf, scanf, perror etc.). This will increase the code size
3952	somewhat, but if your program doesn't otherwise depend on stdio and your	4524	somewhat, but if your program doesn't otherwise depend on stdio and your
3953	libc allows it, this avoids linking in the stdio library which is quite	4525	libc allows it, this avoids linking in the stdio library which is quite
3954	big.	4526	big.
3955		4527
3956	Note that error messages might become less precise when this option is	4528	Note that error messages might become less precise when this option is
…		…
3960		4532
3961	The highest supported signal number, +1 (or, the number of	4533	The highest supported signal number, +1 (or, the number of
3962	signals): Normally, libev tries to deduce the maximum number of signals	4534	signals): Normally, libev tries to deduce the maximum number of signals
3963	automatically, but sometimes this fails, in which case it can be	4535	automatically, but sometimes this fails, in which case it can be
3964	specified. Also, using a lower number than detected (C<32> should be	4536	specified. Also, using a lower number than detected (C<32> should be
3965	good for about any system in existance) can save some memory, as libev	4537	good for about any system in existence) can save some memory, as libev
3966	statically allocates some 12-24 bytes per signal number.	4538	statically allocates some 12-24 bytes per signal number.
3967		4539
3968	=item EV_PID_HASHSIZE	4540	=item EV_PID_HASHSIZE
3969		4541
3970	C<ev_child> watchers use a small hash table to distribute workload by	4542	C<ev_child> watchers use a small hash table to distribute workload by
3971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4543	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3972	than enough. If you need to manage thousands of children you might want to	4544	usually more than enough. If you need to manage thousands of children you
3973	increase this value (I<must> be a power of two).	4545	might want to increase this value (I<must> be a power of two).
3974		4546
3975	=item EV_INOTIFY_HASHSIZE	4547	=item EV_INOTIFY_HASHSIZE
3976		4548
3977	C<ev_stat> watchers use a small hash table to distribute workload by	4549	C<ev_stat> watchers use a small hash table to distribute workload by
3978	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4550	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3979	usually more than enough. If you need to manage thousands of C<ev_stat>	4551	disabled), usually more than enough. If you need to manage thousands of
3980	watchers you might want to increase this value (I<must> be a power of	4552	C<ev_stat> watchers you might want to increase this value (I<must> be a
3981	two).	4553	power of two).
3982		4554
3983	=item EV_USE_4HEAP	4555	=item EV_USE_4HEAP
3984		4556
3985	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4557	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3986	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4558	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3987	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4559	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3988	faster performance with many (thousands) of watchers.	4560	faster performance with many (thousands) of watchers.
3989		4561
3990	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3991	(disabled).	4563	will be C<0>.
3992		4564
3993	=item EV_HEAP_CACHE_AT	4565	=item EV_HEAP_CACHE_AT
3994		4566
3995	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4567	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3996	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4568	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3997	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4569	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3998	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4570	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3999	but avoids random read accesses on heap changes. This improves performance	4571	but avoids random read accesses on heap changes. This improves performance
4000	noticeably with many (hundreds) of watchers.	4572	noticeably with many (hundreds) of watchers.
4001		4573
4002	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4574	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4003	(disabled).	4575	will be C<0>.
4004		4576
4005	=item EV_VERIFY	4577	=item EV_VERIFY
4006		4578
4007	Controls how much internal verification (see C<ev_loop_verify ()>) will	4579	Controls how much internal verification (see C<ev_verify ()>) will
4008	be done: If set to C<0>, no internal verification code will be compiled	4580	be done: If set to C<0>, no internal verification code will be compiled
4009	in. If set to C<1>, then verification code will be compiled in, but not	4581	in. If set to C<1>, then verification code will be compiled in, but not
4010	called. If set to C<2>, then the internal verification code will be	4582	called. If set to C<2>, then the internal verification code will be
4011	called once per loop, which can slow down libev. If set to C<3>, then the	4583	called once per loop, which can slow down libev. If set to C<3>, then the
4012	verification code will be called very frequently, which will slow down	4584	verification code will be called very frequently, which will slow down
4013	libev considerably.	4585	libev considerably.
4014		4586
4015	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4587	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4016	C<0>.	4588	will be C<0>.
4017		4589
4018	=item EV_COMMON	4590	=item EV_COMMON
4019		4591
4020	By default, all watchers have a C<void *data> member. By redefining	4592	By default, all watchers have a C<void *data> member. By redefining
4021	this macro to a something else you can include more and other types of	4593	this macro to something else you can include more and other types of
4022	members. You have to define it each time you include one of the files,	4594	members. You have to define it each time you include one of the files,
4023	though, and it must be identical each time.	4595	though, and it must be identical each time.
4024		4596
4025	For example, the perl EV module uses something like this:	4597	For example, the perl EV module uses something like this:
4026		4598
…		…
4079	file.	4651	file.
4080		4652
4081	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4653	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4082	that everybody includes and which overrides some configure choices:	4654	that everybody includes and which overrides some configure choices:
4083		4655
4084	#define EV_MINIMAL 1	4656	#define EV_FEATURES 8
4085	#define EV_USE_POLL 0	4657	#define EV_USE_SELECT 1
4086	#define EV_MULTIPLICITY 0
4087	#define EV_PERIODIC_ENABLE 0	4658	#define EV_PREPARE_ENABLE 1
		4659	#define EV_IDLE_ENABLE 1
4088	#define EV_STAT_ENABLE 0	4660	#define EV_SIGNAL_ENABLE 1
4089	#define EV_FORK_ENABLE 0	4661	#define EV_CHILD_ENABLE 1
		4662	#define EV_USE_STDEXCEPT 0
4090	#define EV_CONFIG_H <config.h>	4663	#define EV_CONFIG_H <config.h>
4091	#define EV_MINPRI 0
4092	#define EV_MAXPRI 0
4093		4664
4094	#include "ev++.h"	4665	#include "ev++.h"
4095		4666
4096	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4667	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4097		4668
4098	#include "ev_cpp.h"	4669	#include "ev_cpp.h"
4099	#include "ev.c"	4670	#include "ev.c"
4100		4671
4101	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4672	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4102		4673
4103	=head2 THREADS AND COROUTINES	4674	=head2 THREADS AND COROUTINES
4104		4675
4105	=head3 THREADS	4676	=head3 THREADS
4106		4677
…		…
4157	default loop and triggering an C<ev_async> watcher from the default loop	4728	default loop and triggering an C<ev_async> watcher from the default loop
4158	watcher callback into the event loop interested in the signal.	4729	watcher callback into the event loop interested in the signal.
4159		4730
4160	=back	4731	=back
4161		4732
4162	=head4 THREAD LOCKING EXAMPLE	4733	See also L<THREAD LOCKING EXAMPLE>.
4163
4164	Here is a fictitious example of how to run an event loop in a different
4165	thread than where callbacks are being invoked and watchers are
4166	created/added/removed.
4167
4168	For a real-world example, see the C<EV::Loop::Async> perl module,
4169	which uses exactly this technique (which is suited for many high-level
4170	languages).
4171
4172	The example uses a pthread mutex to protect the loop data, a condition
4173	variable to wait for callback invocations, an async watcher to notify the
4174	event loop thread and an unspecified mechanism to wake up the main thread.
4175
4176	First, you need to associate some data with the event loop:
4177
4178	typedef struct {
4179	mutex_t lock; /* global loop lock */
4180	ev_async async_w;
4181	thread_t tid;
4182	cond_t invoke_cv;
4183	} userdata;
4184
4185	void prepare_loop (EV_P)
4186	{
4187	// for simplicity, we use a static userdata struct.
4188	static userdata u;
4189
4190	ev_async_init (&u->async_w, async_cb);
4191	ev_async_start (EV_A_ &u->async_w);
4192
4193	pthread_mutex_init (&u->lock, 0);
4194	pthread_cond_init (&u->invoke_cv, 0);
4195
4196	// now associate this with the loop
4197	ev_set_userdata (EV_A_ u);
4198	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4199	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4200
4201	// then create the thread running ev_loop
4202	pthread_create (&u->tid, 0, l_run, EV_A);
4203	}
4204
4205	The callback for the C<ev_async> watcher does nothing: the watcher is used
4206	solely to wake up the event loop so it takes notice of any new watchers
4207	that might have been added:
4208
4209	static void
4210	async_cb (EV_P_ ev_async *w, int revents)
4211	{
4212	// just used for the side effects
4213	}
4214
4215	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4216	protecting the loop data, respectively.
4217
4218	static void
4219	l_release (EV_P)
4220	{
4221	userdata *u = ev_userdata (EV_A);
4222	pthread_mutex_unlock (&u->lock);
4223	}
4224
4225	static void
4226	l_acquire (EV_P)
4227	{
4228	userdata *u = ev_userdata (EV_A);
4229	pthread_mutex_lock (&u->lock);
4230	}
4231
4232	The event loop thread first acquires the mutex, and then jumps straight
4233	into C<ev_loop>:
4234
4235	void *
4236	l_run (void *thr_arg)
4237	{
4238	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4239
4240	l_acquire (EV_A);
4241	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4242	ev_loop (EV_A_ 0);
4243	l_release (EV_A);
4244
4245	return 0;
4246	}
4247
4248	Instead of invoking all pending watchers, the C<l_invoke> callback will
4249	signal the main thread via some unspecified mechanism (signals? pipe
4250	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4251	have been called (in a while loop because a) spurious wakeups are possible
4252	and b) skipping inter-thread-communication when there are no pending
4253	watchers is very beneficial):
4254
4255	static void
4256	l_invoke (EV_P)
4257	{
4258	userdata *u = ev_userdata (EV_A);
4259
4260	while (ev_pending_count (EV_A))
4261	{
4262	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4263	pthread_cond_wait (&u->invoke_cv, &u->lock);
4264	}
4265	}
4266
4267	Now, whenever the main thread gets told to invoke pending watchers, it
4268	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4269	thread to continue:
4270
4271	static void
4272	real_invoke_pending (EV_P)
4273	{
4274	userdata *u = ev_userdata (EV_A);
4275
4276	pthread_mutex_lock (&u->lock);
4277	ev_invoke_pending (EV_A);
4278	pthread_cond_signal (&u->invoke_cv);
4279	pthread_mutex_unlock (&u->lock);
4280	}
4281
4282	Whenever you want to start/stop a watcher or do other modifications to an
4283	event loop, you will now have to lock:
4284
4285	ev_timer timeout_watcher;
4286	userdata *u = ev_userdata (EV_A);
4287
4288	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4289
4290	pthread_mutex_lock (&u->lock);
4291	ev_timer_start (EV_A_ &timeout_watcher);
4292	ev_async_send (EV_A_ &u->async_w);
4293	pthread_mutex_unlock (&u->lock);
4294
4295	Note that sending the C<ev_async> watcher is required because otherwise
4296	an event loop currently blocking in the kernel will have no knowledge
4297	about the newly added timer. By waking up the loop it will pick up any new
4298	watchers in the next event loop iteration.
4299		4734
4300	=head3 COROUTINES	4735	=head3 COROUTINES
4301		4736
4302	Libev is very accommodating to coroutines ("cooperative threads"):	4737	Libev is very accommodating to coroutines ("cooperative threads"):
4303	libev fully supports nesting calls to its functions from different	4738	libev fully supports nesting calls to its functions from different
4304	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4739	coroutines (e.g. you can call C<ev_run> on the same loop from two
4305	different coroutines, and switch freely between both coroutines running	4740	different coroutines, and switch freely between both coroutines running
4306	the loop, as long as you don't confuse yourself). The only exception is	4741	the loop, as long as you don't confuse yourself). The only exception is
4307	that you must not do this from C<ev_periodic> reschedule callbacks.	4742	that you must not do this from C<ev_periodic> reschedule callbacks.
4308		4743
4309	Care has been taken to ensure that libev does not keep local state inside	4744	Care has been taken to ensure that libev does not keep local state inside
4310	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4745	C<ev_run>, and other calls do not usually allow for coroutine switches as
4311	they do not call any callbacks.	4746	they do not call any callbacks.
4312		4747
4313	=head2 COMPILER WARNINGS	4748	=head2 COMPILER WARNINGS
4314		4749
4315	Depending on your compiler and compiler settings, you might get no or a	4750	Depending on your compiler and compiler settings, you might get no or a
…		…
4326	maintainable.	4761	maintainable.
4327		4762
4328	And of course, some compiler warnings are just plain stupid, or simply	4763	And of course, some compiler warnings are just plain stupid, or simply
4329	wrong (because they don't actually warn about the condition their message	4764	wrong (because they don't actually warn about the condition their message
4330	seems to warn about). For example, certain older gcc versions had some	4765	seems to warn about). For example, certain older gcc versions had some
4331	warnings that resulted an extreme number of false positives. These have	4766	warnings that resulted in an extreme number of false positives. These have
4332	been fixed, but some people still insist on making code warn-free with	4767	been fixed, but some people still insist on making code warn-free with
4333	such buggy versions.	4768	such buggy versions.
4334		4769
4335	While libev is written to generate as few warnings as possible,	4770	While libev is written to generate as few warnings as possible,
4336	"warn-free" code is not a goal, and it is recommended not to build libev	4771	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4372	I suggest using suppression lists.	4807	I suggest using suppression lists.
4373		4808
4374		4809
4375	=head1 PORTABILITY NOTES	4810	=head1 PORTABILITY NOTES
4376		4811
		4812	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4813
		4814	GNU/Linux is the only common platform that supports 64 bit file/large file
		4815	interfaces but I<disables> them by default.
		4816
		4817	That means that libev compiled in the default environment doesn't support
		4818	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4819
		4820	Unfortunately, many programs try to work around this GNU/Linux issue
		4821	by enabling the large file API, which makes them incompatible with the
		4822	standard libev compiled for their system.
		4823
		4824	Likewise, libev cannot enable the large file API itself as this would
		4825	suddenly make it incompatible to the default compile time environment,
		4826	i.e. all programs not using special compile switches.
		4827
		4828	=head2 OS/X AND DARWIN BUGS
		4829
		4830	The whole thing is a bug if you ask me - basically any system interface
		4831	you touch is broken, whether it is locales, poll, kqueue or even the
		4832	OpenGL drivers.
		4833
		4834	=head3 C<kqueue> is buggy
		4835
		4836	The kqueue syscall is broken in all known versions - most versions support
		4837	only sockets, many support pipes.
		4838
		4839	Libev tries to work around this by not using C<kqueue> by default on this
		4840	rotten platform, but of course you can still ask for it when creating a
		4841	loop - embedding a socket-only kqueue loop into a select-based one is
		4842	probably going to work well.
		4843
		4844	=head3 C<poll> is buggy
		4845
		4846	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4847	implementation by something calling C<kqueue> internally around the 10.5.6
		4848	release, so now C<kqueue> I<and> C<poll> are broken.
		4849
		4850	Libev tries to work around this by not using C<poll> by default on
		4851	this rotten platform, but of course you can still ask for it when creating
		4852	a loop.
		4853
		4854	=head3 C<select> is buggy
		4855
		4856	All that's left is C<select>, and of course Apple found a way to fuck this
		4857	one up as well: On OS/X, C<select> actively limits the number of file
		4858	descriptors you can pass in to 1024 - your program suddenly crashes when
		4859	you use more.
		4860
		4861	There is an undocumented "workaround" for this - defining
		4862	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4863	work on OS/X.
		4864
		4865	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4866
		4867	=head3 C<errno> reentrancy
		4868
		4869	The default compile environment on Solaris is unfortunately so
		4870	thread-unsafe that you can't even use components/libraries compiled
		4871	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4872	defined by default. A valid, if stupid, implementation choice.
		4873
		4874	If you want to use libev in threaded environments you have to make sure
		4875	it's compiled with C<_REENTRANT> defined.
		4876
		4877	=head3 Event port backend
		4878
		4879	The scalable event interface for Solaris is called "event
		4880	ports". Unfortunately, this mechanism is very buggy in all major
		4881	releases. If you run into high CPU usage, your program freezes or you get
		4882	a large number of spurious wakeups, make sure you have all the relevant
		4883	and latest kernel patches applied. No, I don't know which ones, but there
		4884	are multiple ones to apply, and afterwards, event ports actually work
		4885	great.
		4886
		4887	If you can't get it to work, you can try running the program by setting
		4888	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4889	C<select> backends.
		4890
		4891	=head2 AIX POLL BUG
		4892
		4893	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4894	this by trying to avoid the poll backend altogether (i.e. it's not even
		4895	compiled in), which normally isn't a big problem as C<select> works fine
		4896	with large bitsets on AIX, and AIX is dead anyway.
		4897
4377	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4898	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4899
		4900	=head3 General issues
4378		4901
4379	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4902	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4380	requires, and its I/O model is fundamentally incompatible with the POSIX	4903	requires, and its I/O model is fundamentally incompatible with the POSIX
4381	model. Libev still offers limited functionality on this platform in	4904	model. Libev still offers limited functionality on this platform in
4382	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4905	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4383	descriptors. This only applies when using Win32 natively, not when using	4906	descriptors. This only applies when using Win32 natively, not when using
4384	e.g. cygwin.	4907	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4908	as every compielr comes with a slightly differently broken/incompatible
		4909	environment.
4385		4910
4386	Lifting these limitations would basically require the full	4911	Lifting these limitations would basically require the full
4387	re-implementation of the I/O system. If you are into these kinds of	4912	re-implementation of the I/O system. If you are into this kind of thing,
4388	things, then note that glib does exactly that for you in a very portable	4913	then note that glib does exactly that for you in a very portable way (note
4389	way (note also that glib is the slowest event library known to man).	4914	also that glib is the slowest event library known to man).
4390		4915
4391	There is no supported compilation method available on windows except	4916	There is no supported compilation method available on windows except
4392	embedding it into other applications.	4917	embedding it into other applications.
4393		4918
4394	Sensible signal handling is officially unsupported by Microsoft - libev	4919	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4422	you do I<not> compile the F<ev.c> or any other embedded source files!):	4947	you do I<not> compile the F<ev.c> or any other embedded source files!):
4423		4948
4424	#include "evwrap.h"	4949	#include "evwrap.h"
4425	#include "ev.c"	4950	#include "ev.c"
4426		4951
4427	=over 4
4428
4429	=item The winsocket select function	4952	=head3 The winsocket C<select> function
4430		4953
4431	The winsocket C<select> function doesn't follow POSIX in that it	4954	The winsocket C<select> function doesn't follow POSIX in that it
4432	requires socket I<handles> and not socket I<file descriptors> (it is	4955	requires socket I<handles> and not socket I<file descriptors> (it is
4433	also extremely buggy). This makes select very inefficient, and also	4956	also extremely buggy). This makes select very inefficient, and also
4434	requires a mapping from file descriptors to socket handles (the Microsoft	4957	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4443	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4966	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4444		4967
4445	Note that winsockets handling of fd sets is O(n), so you can easily get a	4968	Note that winsockets handling of fd sets is O(n), so you can easily get a
4446	complexity in the O(n²) range when using win32.	4969	complexity in the O(n²) range when using win32.
4447		4970
4448	=item Limited number of file descriptors	4971	=head3 Limited number of file descriptors
4449		4972
4450	Windows has numerous arbitrary (and low) limits on things.	4973	Windows has numerous arbitrary (and low) limits on things.
4451		4974
4452	Early versions of winsocket's select only supported waiting for a maximum	4975	Early versions of winsocket's select only supported waiting for a maximum
4453	of C<64> handles (probably owning to the fact that all windows kernels	4976	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4468	runtime libraries. This might get you to about C<512> or C<2048> sockets	4991	runtime libraries. This might get you to about C<512> or C<2048> sockets
4469	(depending on windows version and/or the phase of the moon). To get more,	4992	(depending on windows version and/or the phase of the moon). To get more,
4470	you need to wrap all I/O functions and provide your own fd management, but	4993	you need to wrap all I/O functions and provide your own fd management, but
4471	the cost of calling select (O(n²)) will likely make this unworkable.	4994	the cost of calling select (O(n²)) will likely make this unworkable.
4472		4995
4473	=back
4474
4475	=head2 PORTABILITY REQUIREMENTS	4996	=head2 PORTABILITY REQUIREMENTS
4476		4997
4477	In addition to a working ISO-C implementation and of course the	4998	In addition to a working ISO-C implementation and of course the
4478	backend-specific APIs, libev relies on a few additional extensions:	4999	backend-specific APIs, libev relies on a few additional extensions:
4479		5000
…		…
4485	Libev assumes not only that all watcher pointers have the same internal	5006	Libev assumes not only that all watcher pointers have the same internal
4486	structure (guaranteed by POSIX but not by ISO C for example), but it also	5007	structure (guaranteed by POSIX but not by ISO C for example), but it also
4487	assumes that the same (machine) code can be used to call any watcher	5008	assumes that the same (machine) code can be used to call any watcher
4488	callback: The watcher callbacks have different type signatures, but libev	5009	callback: The watcher callbacks have different type signatures, but libev
4489	calls them using an C<ev_watcher *> internally.	5010	calls them using an C<ev_watcher *> internally.
		5011
		5012	=item pointer accesses must be thread-atomic
		5013
		5014	Accessing a pointer value must be atomic, it must both be readable and
		5015	writable in one piece - this is the case on all current architectures.
4490		5016
4491	=item C<sig_atomic_t volatile> must be thread-atomic as well	5017	=item C<sig_atomic_t volatile> must be thread-atomic as well
4492		5018
4493	The type C<sig_atomic_t volatile> (or whatever is defined as	5019	The type C<sig_atomic_t volatile> (or whatever is defined as
4494	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5020	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4517	watchers.	5043	watchers.
4518		5044
4519	=item C<double> must hold a time value in seconds with enough accuracy	5045	=item C<double> must hold a time value in seconds with enough accuracy
4520		5046
4521	The type C<double> is used to represent timestamps. It is required to	5047	The type C<double> is used to represent timestamps. It is required to
4522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5048	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4523	enough for at least into the year 4000. This requirement is fulfilled by	5049	good enough for at least into the year 4000 with millisecond accuracy
		5050	(the design goal for libev). This requirement is overfulfilled by
4524	implementations implementing IEEE 754, which is basically all existing	5051	implementations using IEEE 754, which is basically all existing ones. With
4525	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5052	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4526	2200.
4527		5053
4528	=back	5054	=back
4529		5055
4530	If you know of other additional requirements drop me a note.	5056	If you know of other additional requirements drop me a note.
4531		5057
…		…
4599	involves iterating over all running async watchers or all signal numbers.	5125	involves iterating over all running async watchers or all signal numbers.
4600		5126
4601	=back	5127	=back
4602		5128
4603		5129
		5130	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5131
		5132	The major version 4 introduced some incompatible changes to the API.
		5133
		5134	At the moment, the C<ev.h> header file provides compatibility definitions
		5135	for all changes, so most programs should still compile. The compatibility
		5136	layer might be removed in later versions of libev, so better update to the
		5137	new API early than late.
		5138
		5139	=over 4
		5140
		5141	=item C<EV_COMPAT3> backwards compatibility mechanism
		5142
		5143	The backward compatibility mechanism can be controlled by
		5144	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5145	section.
		5146
		5147	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5148
		5149	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5150
		5151	ev_loop_destroy (EV_DEFAULT_UC);
		5152	ev_loop_fork (EV_DEFAULT);
		5153
		5154	=item function/symbol renames
		5155
		5156	A number of functions and symbols have been renamed:
		5157
		5158	ev_loop => ev_run
		5159	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5160	EVLOOP_ONESHOT => EVRUN_ONCE
		5161
		5162	ev_unloop => ev_break
		5163	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5164	EVUNLOOP_ONE => EVBREAK_ONE
		5165	EVUNLOOP_ALL => EVBREAK_ALL
		5166
		5167	EV_TIMEOUT => EV_TIMER
		5168
		5169	ev_loop_count => ev_iteration
		5170	ev_loop_depth => ev_depth
		5171	ev_loop_verify => ev_verify
		5172
		5173	Most functions working on C<struct ev_loop> objects don't have an
		5174	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5175	associated constants have been renamed to not collide with the C<struct
		5176	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5177	as all other watcher types. Note that C<ev_loop_fork> is still called
		5178	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5179	typedef.
		5180
		5181	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5182
		5183	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5184	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5185	and work, but the library code will of course be larger.
		5186
		5187	=back
		5188
		5189
4604	=head1 GLOSSARY	5190	=head1 GLOSSARY
4605		5191
4606	=over 4	5192	=over 4
4607		5193
4608	=item active	5194	=item active
4609		5195
4610	A watcher is active as long as it has been started (has been attached to	5196	A watcher is active as long as it has been started and not yet stopped.
4611	an event loop) but not yet stopped (disassociated from the event loop).	5197	See L<WATCHER STATES> for details.
4612		5198
4613	=item application	5199	=item application
4614		5200
4615	In this document, an application is whatever is using libev.	5201	In this document, an application is whatever is using libev.
		5202
		5203	=item backend
		5204
		5205	The part of the code dealing with the operating system interfaces.
4616		5206
4617	=item callback	5207	=item callback
4618		5208
4619	The address of a function that is called when some event has been	5209	The address of a function that is called when some event has been
4620	detected. Callbacks are being passed the event loop, the watcher that	5210	detected. Callbacks are being passed the event loop, the watcher that
4621	received the event, and the actual event bitset.	5211	received the event, and the actual event bitset.
4622		5212
4623	=item callback invocation	5213	=item callback/watcher invocation
4624		5214
4625	The act of calling the callback associated with a watcher.	5215	The act of calling the callback associated with a watcher.
4626		5216
4627	=item event	5217	=item event
4628		5218
4629	A change of state of some external event, such as data now being available	5219	A change of state of some external event, such as data now being available
4630	for reading on a file descriptor, time having passed or simply not having	5220	for reading on a file descriptor, time having passed or simply not having
4631	any other events happening anymore.	5221	any other events happening anymore.
4632		5222
4633	In libev, events are represented as single bits (such as C<EV_READ> or	5223	In libev, events are represented as single bits (such as C<EV_READ> or
4634	C<EV_TIMEOUT>).	5224	C<EV_TIMER>).
4635		5225
4636	=item event library	5226	=item event library
4637		5227
4638	A software package implementing an event model and loop.	5228	A software package implementing an event model and loop.
4639		5229
…		…
4647	The model used to describe how an event loop handles and processes	5237	The model used to describe how an event loop handles and processes
4648	watchers and events.	5238	watchers and events.
4649		5239
4650	=item pending	5240	=item pending
4651		5241
4652	A watcher is pending as soon as the corresponding event has been detected,	5242	A watcher is pending as soon as the corresponding event has been
4653	and stops being pending as soon as the watcher will be invoked or its	5243	detected. See L<WATCHER STATES> for details.
4654	pending status is explicitly cleared by the application.
4655
4656	A watcher can be pending, but not active. Stopping a watcher also clears
4657	its pending status.
4658		5244
4659	=item real time	5245	=item real time
4660		5246
4661	The physical time that is observed. It is apparently strictly monotonic :)	5247	The physical time that is observed. It is apparently strictly monotonic :)
4662		5248
4663	=item wall-clock time	5249	=item wall-clock time
4664		5250
4665	The time and date as shown on clocks. Unlike real time, it can actually	5251	The time and date as shown on clocks. Unlike real time, it can actually
4666	be wrong and jump forwards and backwards, e.g. when the you adjust your	5252	be wrong and jump forwards and backwards, e.g. when you adjust your
4667	clock.	5253	clock.
4668		5254
4669	=item watcher	5255	=item watcher
4670		5256
4671	A data structure that describes interest in certain events. Watchers need	5257	A data structure that describes interest in certain events. Watchers need
4672	to be started (attached to an event loop) before they can receive events.	5258	to be started (attached to an event loop) before they can receive events.
4673		5259
4674	=item watcher invocation
4675
4676	The act of calling the callback associated with a watcher.
4677
4678	=back	5260	=back
4679		5261
4680	=head1 AUTHOR	5262	=head1 AUTHOR
4681		5263
4682	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5264	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5265	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4683		5266

Diff Legend

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