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Revision 1.373 by root, Sat Jun 4 05:59:50 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
…		…
118	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
119	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
120	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
121	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
122	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
123	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
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_NOSIGFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will not 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 is	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	434	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	435	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		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.
382		457
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		459
385	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
386	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,
…		…
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		490
416	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
417	kernels).	492	kernels).
418		493
419	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
420	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
421	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
422	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
423		498
424	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
425	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
426	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
427	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
428	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
429	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
430	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
431	hard to detect.	508	and is of course hard to detect.
432		509
433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
434	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
435	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
436	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
437	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
438	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
439	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...
440		526
441	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
442	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
443	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
444	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
…		…
510	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
511		597
512	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,
513	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)).
514		600
515	Please note that Solaris event ports can deliver a lot of spurious
516	notifications, so you need to use non-blocking I/O or other means to avoid
517	blocking when no data (or space) is available.
518
519	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
520	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
521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
522	might perform better.	604	might perform better.
523		605
524	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
525	notifications, this backend actually performed fully to specification
526	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
527	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.
528		620
529	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
530	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
531		623
532	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
533		625
534	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
535	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
536	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
537		629
538	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).
539		639
540	=back	640	=back
541		641
542	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,
543	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
544	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
545	()> will be tried.	645	()> will be tried.
546		646
547	Example: This is the most typical usage.
548
549	if (!ev_default_loop (0))
550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
551
552	Example: Restrict libev to the select and poll backends, and do not allow
553	environment settings to be taken into account:
554
555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
556
557	Example: Use whatever libev has to offer, but make sure that kqueue is
558	used if available (warning, breaks stuff, best use only with your own
559	private event loop and only if you know the OS supports your types of
560	fds):
561
562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
563
564	=item struct ev_loop *ev_loop_new (unsigned int flags)
565
566	Similar to C<ev_default_loop>, but always creates a new event loop that is
567	always distinct from the default loop. Unlike the default loop, it cannot
568	handle signal and child watchers, and attempts to do so will be greeted by
569	undefined behaviour (or a failed assertion if assertions are enabled).
570
571	Note that this function I<is> thread-safe, and the recommended way to use
572	libev with threads is indeed to create one loop per thread, and using the
573	default loop in the "main" or "initial" thread.
574
575	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.
576		648
577	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
578	if (!epoller)	650	if (!epoller)
579	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
580		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
581	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
582		659
583	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
584	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
585	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
586	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
587	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
588	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
…		…
590		667
591	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
592	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
593	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
594		671
595	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
596	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.
597	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>
598	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
599		680
600	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
601		682
602	Like C<ev_default_destroy>, but destroys an event loop created by an
603	earlier call to C<ev_loop_new>.
604
605	=item ev_default_fork ()
606
607	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
608	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
609	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
610	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
611	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
612	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.
613		693
614	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
615	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
616	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).
617		700
618	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
619	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
620	quite nicely into a call to C<pthread_atfork>:
621		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	...
622	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
623
624	=item ev_loop_fork (loop)
625
626	Like C<ev_default_fork>, but acts on an event loop created by
627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
628	after fork that you want to re-use in the child, and how you do this is
629	entirely your own problem.
630		715
631	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
632		717
633	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
634	otherwise.	719	otherwise.
635		720
636	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
637		722
638	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
639	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>
640	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
641		726
642	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
643	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
644	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.
645		731
646	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
647		733
648	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
649	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.
650		736
651	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
652	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),
653	in which case it is higher.	739	in which case it is higher.
654		740
655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
656	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.
657		745
658	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
659		747
660	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
661	use.	749	use.
…		…
670		758
671	=item ev_now_update (loop)	759	=item ev_now_update (loop)
672		760
673	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
674	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
675	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
676		764
677	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
678	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
679	the current time is a good idea.	767	the current time is a good idea.
680		768
…		…
682		770
683	=item ev_suspend (loop)	771	=item ev_suspend (loop)
684		772
685	=item ev_resume (loop)	773	=item ev_resume (loop)
686		774
687	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
688	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.
689		777
690	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
691	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
692	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
693	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>
…		…
695	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
696		784
697	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
698	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
699	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
700	occured while suspended).	788	occurred while suspended).
701		789
702	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
703	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>
704	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
705		793
706	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
707	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
708		796
709	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
710		798
711	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
712	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
713	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>.
714		804
715	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
716	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.
717		808
718	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
719	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
720	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
721	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
722	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
723	beauty.	814	beauty.
724		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
725	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
726	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
727	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
728	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.
729		826
730	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
731	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
732	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
733	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
734	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
735	iteration of the loop.	832	iteration of the loop.
736		833
737	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
738	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
739	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
740	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
741		838
742	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):
743		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- 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.
747	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	852	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
755	- 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.
756	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
758	- 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.
759	- Queue all expired timers.	863	- Queue all expired timers.
760	- Queue all expired periodics.	864	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	866	- Queue all check watchers.
763	- 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).
764	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
765	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
766	- 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
767	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
768	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.
769		877
770	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
771	anymore.	879	anymore.
772		880
773	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
774	... 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..)
775	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
777		885
778	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
779		887
780	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
781	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
782	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
783	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.
784		892
785	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>.
786		894
787	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.
788		897
789	=item ev_ref (loop)	898	=item ev_ref (loop)
790		899
791	=item ev_unref (loop)	900	=item ev_unref (loop)
792		901
793	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
794	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
795	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.
796		905
797	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
798	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
799	stopping it.	909	before stopping it.
800		910
801	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
802	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
803	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
804	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
805	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
806	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
807	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
808	(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>
809	in the callback).	919	in the callback).
810		920
811	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>
812	running when nothing else is active.	922	running when nothing else is active.
813		923
814	ev_signal exitsig;	924	ev_signal exitsig;
815	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
816	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
817	evf_unref (loop);	927	ev_unref (loop);
818		928
819	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
820		930
821	ev_ref (loop);	931	ev_ref (loop);
822	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
842	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
843		953
844	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
845	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
847	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
848	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
849	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
850	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
851		962
852	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
853	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
854	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
855	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
861	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
862	as this approaches the timing granularity of most systems. Note that if	973	as this approaches the timing granularity of most systems. Note that if
863	you do transactions with the outside world and you can't increase the	974	you do transactions with the outside world and you can't increase the
864	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
865	need to poll once per transaction and the I/O collect interval is 0.01,	976	need to poll once per transaction and the I/O collect interval is 0.01,
866	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
867		978
868	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
869	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
870	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
871	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
…		…
879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
880		991
881	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
882		993
883	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
884	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
885	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
886		1001
887	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
888		1003
889	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
890	are pending.	1005	are pending.
891		1006
892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
893		1008
894	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
895	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
896	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
897	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
898		1013
899	If you want to reset the callback, use C<ev_invoke_pending> as new	1014	If you want to reset the callback, use C<ev_invoke_pending> as new
900	callback.	1015	callback.
…		…
903		1018
904	Sometimes you want to share the same loop between multiple threads. This	1019	Sometimes you want to share the same loop between multiple threads. This
905	can be done relatively simply by putting mutex_lock/unlock calls around	1020	can be done relatively simply by putting mutex_lock/unlock calls around
906	each call to a libev function.	1021	each call to a libev function.
907		1022
908	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1023	However, C<ev_run> can run an indefinite time, so it is not feasible
909	wait for it to return. One way around this is to wake up the loop via	1024	to wait for it to return. One way around this is to wake up the event
910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<av_async_send>, another way is to set these
911	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
912		1027
913	When set, then C<release> will be called just before the thread is	1028	When set, then C<release> will be called just before the thread is
914	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
915	afterwards.	1030	afterwards.
916		1031
…		…
919		1034
920	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
921	C<release> and C<acquire> (that's their only purpose after all), no	1036	C<release> and C<acquire> (that's their only purpose after all), no
922	modifications done will affect the event loop, i.e. adding watchers will	1037	modifications done will affect the event loop, i.e. adding watchers will
923	have no effect on the set of file descriptors being watched, or the time	1038	have no effect on the set of file descriptors being watched, or the time
924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
925	to take note of any changes you made.	1040	to take note of any changes you made.
926		1041
927	In theory, threads executing C<ev_loop> will be async-cancel safe between	1042	In theory, threads executing C<ev_run> will be async-cancel safe between
928	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
929		1044
930	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
931	document.	1046	document.
932		1047
933	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
934		1049
935	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
936		1051
937	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
939	C<0.>	1054	C<0>.
940		1055
941	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
942	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
943	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
944	any other purpose as well.	1059	any other purpose as well.
945		1060
946	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
947		1062
948	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
949	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
950	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
951	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
962		1077
963	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
965	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
966		1081
967	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
968	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
969	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
970		1086
971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
972	{	1088	{
973	ev_io_stop (w);	1089	ev_io_stop (w);
974	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
975	}	1091	}
976		1092
977	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
978		1094
979	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
980		1096
981	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
983	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
984		1100
985	ev_loop (loop, 0);	1101	ev_run (loop, 0);
986		1102
987	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
988	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
989	stack).	1105	stack).
990		1106
991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
993		1109
994	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
995	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
996	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
997	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
998	is readable and/or writable).	1114	and/or writable).
999		1115
1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1001	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
1002	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
1003	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1026	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1027		1143
1028	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
1029	writable.	1145	writable.
1030		1146
1031	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1032		1148
1033	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1034		1150
1035	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1036		1152
…		…
1054		1170
1055	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1056		1172
1057	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1058		1174
1059	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1060	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
1061	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
1062	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
1063	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
1064	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1065	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1066		1182
1067	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1068		1184
1069	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1070		1186
1071	=item C<EV_FORK>	1187	=item C<EV_FORK>
1072		1188
1073	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1074	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
1075		1195
1076	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1077		1197
1078	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1079		1199
…		…
1126		1246
1127	ev_io w;	1247	ev_io w;
1128	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1129	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1130		1250
1131	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1132		1252
1133	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
1134	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
1135	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
1136	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
1149		1269
1150	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
1151		1271
1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1153		1273
1154	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1155		1275
1156	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1157	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1158		1278
1159	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
1160	whole section.	1280	whole section.
1161		1281
1162	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1163		1283
1164	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1165		1285
1166	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
1167	the watcher was active or not).	1287	the watcher was active or not).
1168		1288
1169	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1194	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1195		1315
1196	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1197	(modulo threads).	1317	(modulo threads).
1198		1318
1199	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1200		1320
1201	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1202		1322
1203	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1236	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1237		1357
1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1239	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1240		1360
1241	=item ev_feed_event (struct ev_loop *, watcher *, int revents)	1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1242		1362
1243	Feeds the given event set into the event loop, as if the specified event	1363	Feeds the given event set into the event loop, as if the specified event
1244	had happened for the specified watcher (which must be a pointer to an	1364	had happened for the specified watcher (which must be a pointer to an
1245	initialised but not necessarily started event watcher). Obviously you must	1365	initialised but not necessarily started event watcher). Obviously you must
1246	not free the watcher as long as it has pending events.	1366	not free the watcher as long as it has pending events.
…		…
1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1253	functions that do not need a watcher.	1373	functions that do not need a watcher.
1254		1374
1255	=back	1375	=back
1256		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1257		1379
1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1259		1381
1260	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1261	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1262	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1263	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1264	member, you can also "subclass" the watcher type and provide your own
1265	data:
1266		1386
1267	struct my_io	1387	=over 4
1268	{
1269	ev_io io;
1270	int otherfd;
1271	void *somedata;
1272	struct whatever *mostinteresting;
1273	};
1274		1388
1275	...	1389	=item initialiased
1276	struct my_io w;
1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1278		1390
1279	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event looop it has to be
1280	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1281		1394
1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1283	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1284	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1285	...	1398	C<ev_TYPE_init> again.
1286	}
1287		1399
1288	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1289	instead have been omitted.
1290		1401
1291	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1292	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1293		1407
1294	struct my_biggy	1408	=item pending
1295	{
1296	int some_data;
1297	ev_timer t1;
1298	ev_timer t2;
1299	}
1300		1409
1301	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1302	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1303	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1304	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1305	programmers):	1414	callback.
1306		1415
1307	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1308		1422
1309	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1310	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1311	{	1425	active.
1312	struct my_biggy big = (struct my_biggy *)
1313	(((char *)w) - offsetof (struct my_biggy, t1));
1314	}
1315		1426
1316	static void	1427	=item stopped
1317	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1318	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1319	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1320	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1321	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1322		1441
1323	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1324		1443
1325	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1326	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1369		1488
1370	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1371	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1372	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1373	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1374	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1375	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1376	workable.	1495	workable.
1377		1496
1378	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1379	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1393	{	1512	{
1394	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1395	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1396	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1397		1516
1398	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1399	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1400	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1401	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1402	}	1521	}
1403		1522
…		…
1453	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1454	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1455	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1456	required if you know what you are doing).	1575	required if you know what you are doing).
1457		1576
1458	If you cannot use non-blocking mode, then force the use of a
1459	known-to-be-good backend (at the time of this writing, this includes only
1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1461	descriptors for which non-blocking operation makes no sense (such as
1462	files) - libev doesn't guarentee any specific behaviour in that case.
1463
1464	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1465	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1467	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1468	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1469	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1472		1584
1473	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1474	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1475	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1476	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1477	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1478	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1479	indefinitely.	1591	indefinitely.
1480		1592
1481	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1482		1594
…		…
1510		1622
1511	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1512	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1513	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1514		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1515	=head3 The special problem of fork	1660	=head3 The special problem of fork
1516		1661
1517	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1518	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1519	it in the child.	1664	it in the child if you want to continue to use it in the child.
1520		1665
1521	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1522	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524	C<EVBACKEND_POLL>.
1525		1669
1526	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1527		1671
1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1529	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1532		1676
1533	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1535	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1536		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1537		1719
1538	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1539		1721
1540	=over 4	1722	=over 4
1541		1723
…		…
1573	...	1755	...
1574	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1575	ev_io stdin_readable;	1757	ev_io stdin_readable;
1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1577	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1578	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1579		1761
1580		1762
1581	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1582		1764
1583	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1592	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1593	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1594	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay). If multiple timers become ready during the
1595	same loop iteration then the ones with earlier time-out values are invoked	1777	same loop iteration then the ones with earlier time-out values are invoked
1596	before ones of the same priority with later time-out values (but this is	1778	before ones of the same priority with later time-out values (but this is
1597	no longer true when a callback calls C<ev_loop> recursively).	1779	no longer true when a callback calls C<ev_run> recursively).
1598		1780
1599	=head3 Be smart about timeouts	1781	=head3 Be smart about timeouts
1600		1782
1601	Many real-world problems involve some kind of timeout, usually for error	1783	Many real-world problems involve some kind of timeout, usually for error
1602	recovery. A typical example is an HTTP request - if the other side hangs,	1784	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1688	ev_tstamp timeout = last_activity + 60.;	1870	ev_tstamp timeout = last_activity + 60.;
1689		1871
1690	// if last_activity + 60. is older than now, we did time out	1872	// if last_activity + 60. is older than now, we did time out
1691	if (timeout < now)	1873	if (timeout < now)
1692	{	1874	{
1693	// timeout occured, take action	1875	// timeout occurred, take action
1694	}	1876	}
1695	else	1877	else
1696	{	1878	{
1697	// callback was invoked, but there was some activity, re-arm	1879	// callback was invoked, but there was some activity, re-arm
1698	// the watcher to fire in last_activity + 60, which is	1880	// the watcher to fire in last_activity + 60, which is
…		…
1720	to the current time (meaning we just have some activity :), then call the	1902	to the current time (meaning we just have some activity :), then call the
1721	callback, which will "do the right thing" and start the timer:	1903	callback, which will "do the right thing" and start the timer:
1722		1904
1723	ev_init (timer, callback);	1905	ev_init (timer, callback);
1724	last_activity = ev_now (loop);	1906	last_activity = ev_now (loop);
1725	callback (loop, timer, EV_TIMEOUT);	1907	callback (loop, timer, EV_TIMER);
1726		1908
1727	And when there is some activity, simply store the current time in	1909	And when there is some activity, simply store the current time in
1728	C<last_activity>, no libev calls at all:	1910	C<last_activity>, no libev calls at all:
1729		1911
1730	last_actiivty = ev_now (loop);	1912	last_activity = ev_now (loop);
1731		1913
1732	This technique is slightly more complex, but in most cases where the	1914	This technique is slightly more complex, but in most cases where the
1733	time-out is unlikely to be triggered, much more efficient.	1915	time-out is unlikely to be triggered, much more efficient.
1734		1916
1735	Changing the timeout is trivial as well (if it isn't hard-coded in the	1917	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1773		1955
1774	=head3 The special problem of time updates	1956	=head3 The special problem of time updates
1775		1957
1776	Establishing the current time is a costly operation (it usually takes at	1958	Establishing the current time is a costly operation (it usually takes at
1777	least two system calls): EV therefore updates its idea of the current	1959	least two system calls): EV therefore updates its idea of the current
1778	time only before and after C<ev_loop> collects new events, which causes a	1960	time only before and after C<ev_run> collects new events, which causes a
1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1961	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1780	lots of events in one iteration.	1962	lots of events in one iteration.
1781		1963
1782	The relative timeouts are calculated relative to the C<ev_now ()>	1964	The relative timeouts are calculated relative to the C<ev_now ()>
1783	time. This is usually the right thing as this timestamp refers to the time	1965	time. This is usually the right thing as this timestamp refers to the time
…		…
1854	C<repeat> value), or reset the running timer to the C<repeat> value.	2036	C<repeat> value), or reset the running timer to the C<repeat> value.
1855		2037
1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2038	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1857	usage example.	2039	usage example.
1858		2040
1859	=item ev_timer_remaining (loop, ev_timer *)	2041	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1860		2042
1861	Returns the remaining time until a timer fires. If the timer is active,	2043	Returns the remaining time until a timer fires. If the timer is active,
1862	then this time is relative to the current event loop time, otherwise it's	2044	then this time is relative to the current event loop time, otherwise it's
1863	the timeout value currently configured.	2045	the timeout value currently configured.
1864		2046
1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2047	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2048	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1867	will return C<4>. When the timer expires and is restarted, it will return	2049	will return C<4>. When the timer expires and is restarted, it will return
1868	roughly C<7> (likely slightly less as callback invocation takes some time,	2050	roughly C<7> (likely slightly less as callback invocation takes some time,
1869	too), and so on.	2051	too), and so on.
1870		2052
1871	=item ev_tstamp repeat [read-write]	2053	=item ev_tstamp repeat [read-write]
…		…
1900	}	2082	}
1901		2083
1902	ev_timer mytimer;	2084	ev_timer mytimer;
1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2085	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1904	ev_timer_again (&mytimer); /* start timer */	2086	ev_timer_again (&mytimer); /* start timer */
1905	ev_loop (loop, 0);	2087	ev_run (loop, 0);
1906		2088
1907	// and in some piece of code that gets executed on any "activity":	2089	// and in some piece of code that gets executed on any "activity":
1908	// reset the timeout to start ticking again at 10 seconds	2090	// reset the timeout to start ticking again at 10 seconds
1909	ev_timer_again (&mytimer);	2091	ev_timer_again (&mytimer);
1910		2092
…		…
1936		2118
1937	As with timers, the callback is guaranteed to be invoked only when the	2119	As with timers, the callback is guaranteed to be invoked only when the
1938	point in time where it is supposed to trigger has passed. If multiple	2120	point in time where it is supposed to trigger has passed. If multiple
1939	timers become ready during the same loop iteration then the ones with	2121	timers become ready during the same loop iteration then the ones with
1940	earlier time-out values are invoked before ones with later time-out values	2122	earlier time-out values are invoked before ones with later time-out values
1941	(but this is no longer true when a callback calls C<ev_loop> recursively).	2123	(but this is no longer true when a callback calls C<ev_run> recursively).
1942		2124
1943	=head3 Watcher-Specific Functions and Data Members	2125	=head3 Watcher-Specific Functions and Data Members
1944		2126
1945	=over 4	2127	=over 4
1946		2128
…		…
1981		2163
1982	Another way to think about it (for the mathematically inclined) is that	2164	Another way to think about it (for the mathematically inclined) is that
1983	C<ev_periodic> will try to run the callback in this mode at the next possible	2165	C<ev_periodic> will try to run the callback in this mode at the next possible
1984	time where C<time = offset (mod interval)>, regardless of any time jumps.	2166	time where C<time = offset (mod interval)>, regardless of any time jumps.
1985		2167
1986	For numerical stability it is preferable that the C<offset> value is near	2168	The C<interval> I<MUST> be positive, and for numerical stability, the
1987	C<ev_now ()> (the current time), but there is no range requirement for	2169	interval value should be higher than C<1/8192> (which is around 100
1988	this value, and in fact is often specified as zero.	2170	microseconds) and C<offset> should be higher than C<0> and should have
		2171	at most a similar magnitude as the current time (say, within a factor of
		2172	ten). Typical values for offset are, in fact, C<0> or something between
		2173	C<0> and C<interval>, which is also the recommended range.
1989		2174
1990	Note also that there is an upper limit to how often a timer can fire (CPU	2175	Note also that there is an upper limit to how often a timer can fire (CPU
1991	speed for example), so if C<interval> is very small then timing stability	2176	speed for example), so if C<interval> is very small then timing stability
1992	will of course deteriorate. Libev itself tries to be exact to be about one	2177	will of course deteriorate. Libev itself tries to be exact to be about one
1993	millisecond (if the OS supports it and the machine is fast enough).	2178	millisecond (if the OS supports it and the machine is fast enough).
…		…
2074	Example: Call a callback every hour, or, more precisely, whenever the	2259	Example: Call a callback every hour, or, more precisely, whenever the
2075	system time is divisible by 3600. The callback invocation times have	2260	system time is divisible by 3600. The callback invocation times have
2076	potentially a lot of jitter, but good long-term stability.	2261	potentially a lot of jitter, but good long-term stability.
2077		2262
2078	static void	2263	static void
2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2264	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2080	{	2265	{
2081	... its now a full hour (UTC, or TAI or whatever your clock follows)	2266	... its now a full hour (UTC, or TAI or whatever your clock follows)
2082	}	2267	}
2083		2268
2084	ev_periodic hourly_tick;	2269	ev_periodic hourly_tick;
…		…
2107		2292
2108	=head2 C<ev_signal> - signal me when a signal gets signalled!	2293	=head2 C<ev_signal> - signal me when a signal gets signalled!
2109		2294
2110	Signal watchers will trigger an event when the process receives a specific	2295	Signal watchers will trigger an event when the process receives a specific
2111	signal one or more times. Even though signals are very asynchronous, libev	2296	signal one or more times. Even though signals are very asynchronous, libev
2112	will try it's best to deliver signals synchronously, i.e. as part of the	2297	will try its best to deliver signals synchronously, i.e. as part of the
2113	normal event processing, like any other event.	2298	normal event processing, like any other event.
2114		2299
2115	If you want signals to be delivered truly asynchronously, just use	2300	If you want signals to be delivered truly asynchronously, just use
2116	C<sigaction> as you would do without libev and forget about sharing	2301	C<sigaction> as you would do without libev and forget about sharing
2117	the signal. You can even use C<ev_async> from a signal handler to	2302	the signal. You can even use C<ev_async> from a signal handler to
…		…
2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2316	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2132	not be unduly interrupted. If you have a problem with system calls getting	2317	not be unduly interrupted. If you have a problem with system calls getting
2133	interrupted by signals you can block all signals in an C<ev_check> watcher	2318	interrupted by signals you can block all signals in an C<ev_check> watcher
2134	and unblock them in an C<ev_prepare> watcher.	2319	and unblock them in an C<ev_prepare> watcher.
2135		2320
2136	=head3 The special problem of inheritance over execve	2321	=head3 The special problem of inheritance over fork/execve/pthread_create
2137		2322
2138	Both the signal mask (C<sigprocmask>) and the signal disposition	2323	Both the signal mask (C<sigprocmask>) and the signal disposition
2139	(C<sigaction>) are unspecified after starting a signal watcher (and after	2324	(C<sigaction>) are unspecified after starting a signal watcher (and after
2140	stopping it again), that is, libev might or might not block the signal,	2325	stopping it again), that is, libev might or might not block the signal,
2141	and might or might not set or restore the installed signal handler.	2326	and might or might not set or restore the installed signal handler (but
		2327	see C<EVFLAG_NOSIGMASK>).
2142		2328
2143	While this does not matter for the signal disposition (libev never	2329	While this does not matter for the signal disposition (libev never
2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2330	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2145	C<execve>), this matters for the signal mask: many programs do not expect	2331	C<execve>), this matters for the signal mask: many programs do not expect
2146	certain signals to be blocked.	2332	certain signals to be blocked.
…		…
2151		2337
2152	The simplest way to ensure that the signal mask is reset in the child is	2338	The simplest way to ensure that the signal mask is reset in the child is
2153	to install a fork handler with C<pthread_atfork> that resets it. That will	2339	to install a fork handler with C<pthread_atfork> that resets it. That will
2154	catch fork calls done by libraries (such as the libc) as well.	2340	catch fork calls done by libraries (such as the libc) as well.
2155		2341
2156	In current versions of libev, you can also ensure that the signal mask is	2342	In current versions of libev, the signal will not be blocked indefinitely
2157	not blocking any signals (except temporarily, so thread users watch out)	2343	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This	2344	the window of opportunity for problems, it will not go away, as libev
2159	is not guaranteed for future versions, however.	2345	I<has> to modify the signal mask, at least temporarily.
		2346
		2347	So I can't stress this enough: I<If you do not reset your signal mask when
		2348	you expect it to be empty, you have a race condition in your code>. This
		2349	is not a libev-specific thing, this is true for most event libraries.
		2350
		2351	=head3 The special problem of threads signal handling
		2352
		2353	POSIX threads has problematic signal handling semantics, specifically,
		2354	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2355	threads in a process block signals, which is hard to achieve.
		2356
		2357	When you want to use sigwait (or mix libev signal handling with your own
		2358	for the same signals), you can tackle this problem by globally blocking
		2359	all signals before creating any threads (or creating them with a fully set
		2360	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2361	loops. Then designate one thread as "signal receiver thread" which handles
		2362	these signals. You can pass on any signals that libev might be interested
		2363	in by calling C<ev_feed_signal>.
2160		2364
2161	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2162		2366
2163	=over 4	2367	=over 4
2164		2368
…		…
2180	Example: Try to exit cleanly on SIGINT.	2384	Example: Try to exit cleanly on SIGINT.
2181		2385
2182	static void	2386	static void
2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2387	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2184	{	2388	{
2185	ev_unloop (loop, EVUNLOOP_ALL);	2389	ev_break (loop, EVBREAK_ALL);
2186	}	2390	}
2187		2391
2188	ev_signal signal_watcher;	2392	ev_signal signal_watcher;
2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2393	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2190	ev_signal_start (loop, &signal_watcher);	2394	ev_signal_start (loop, &signal_watcher);
…		…
2576		2780
2577	Prepare and check watchers are usually (but not always) used in pairs:	2781	Prepare and check watchers are usually (but not always) used in pairs:
2578	prepare watchers get invoked before the process blocks and check watchers	2782	prepare watchers get invoked before the process blocks and check watchers
2579	afterwards.	2783	afterwards.
2580		2784
2581	You I<must not> call C<ev_loop> or similar functions that enter	2785	You I<must not> call C<ev_run> or similar functions that enter
2582	the current event loop from either C<ev_prepare> or C<ev_check>	2786	the current event loop from either C<ev_prepare> or C<ev_check>
2583	watchers. Other loops than the current one are fine, however. The	2787	watchers. Other loops than the current one are fine, however. The
2584	rationale behind this is that you do not need to check for recursion in	2788	rationale behind this is that you do not need to check for recursion in
2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2789	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2586	C<ev_check> so if you have one watcher of each kind they will always be	2790	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2754		2958
2755	if (timeout >= 0)	2959	if (timeout >= 0)
2756	// create/start timer	2960	// create/start timer
2757		2961
2758	// poll	2962	// poll
2759	ev_loop (EV_A_ 0);	2963	ev_run (EV_A_ 0);
2760		2964
2761	// stop timer again	2965	// stop timer again
2762	if (timeout >= 0)	2966	if (timeout >= 0)
2763	ev_timer_stop (EV_A_ &to);	2967	ev_timer_stop (EV_A_ &to);
2764		2968
…		…
2842	if you do not want that, you need to temporarily stop the embed watcher).	3046	if you do not want that, you need to temporarily stop the embed watcher).
2843		3047
2844	=item ev_embed_sweep (loop, ev_embed *)	3048	=item ev_embed_sweep (loop, ev_embed *)
2845		3049
2846	Make a single, non-blocking sweep over the embedded loop. This works	3050	Make a single, non-blocking sweep over the embedded loop. This works
2847	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3051	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2848	appropriate way for embedded loops.	3052	appropriate way for embedded loops.
2849		3053
2850	=item struct ev_loop *other [read-only]	3054	=item struct ev_loop *other [read-only]
2851		3055
2852	The embedded event loop.	3056	The embedded event loop.
…		…
2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3116	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2913	handlers will be invoked, too, of course.	3117	handlers will be invoked, too, of course.
2914		3118
2915	=head3 The special problem of life after fork - how is it possible?	3119	=head3 The special problem of life after fork - how is it possible?
2916		3120
2917	Most uses of C<fork()> consist of forking, then some simple calls to ste	3121	Most uses of C<fork()> consist of forking, then some simple calls to set
2918	up/change the process environment, followed by a call to C<exec()>. This	3122	up/change the process environment, followed by a call to C<exec()>. This
2919	sequence should be handled by libev without any problems.	3123	sequence should be handled by libev without any problems.
2920		3124
2921	This changes when the application actually wants to do event handling	3125	This changes when the application actually wants to do event handling
2922	in the child, or both parent in child, in effect "continuing" after the	3126	in the child, or both parent in child, in effect "continuing" after the
…		…
2938	disadvantage of having to use multiple event loops (which do not support	3142	disadvantage of having to use multiple event loops (which do not support
2939	signal watchers).	3143	signal watchers).
2940		3144
2941	When this is not possible, or you want to use the default loop for	3145	When this is not possible, or you want to use the default loop for
2942	other reasons, then in the process that wants to start "fresh", call	3146	other reasons, then in the process that wants to start "fresh", call
2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3147	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2944	the default loop will "orphan" (not stop) all registered watchers, so you	3148	Destroying the default loop will "orphan" (not stop) all registered
2945	have to be careful not to execute code that modifies those watchers. Note	3149	watchers, so you have to be careful not to execute code that modifies
2946	also that in that case, you have to re-register any signal watchers.	3150	those watchers. Note also that in that case, you have to re-register any
		3151	signal watchers.
2947		3152
2948	=head3 Watcher-Specific Functions and Data Members	3153	=head3 Watcher-Specific Functions and Data Members
2949		3154
2950	=over 4	3155	=over 4
2951		3156
2952	=item ev_fork_init (ev_signal *, callback)	3157	=item ev_fork_init (ev_fork *, callback)
2953		3158
2954	Initialises and configures the fork watcher - it has no parameters of any	3159	Initialises and configures the fork watcher - it has no parameters of any
2955	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3160	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2956	believe me.	3161	really.
2957		3162
2958	=back	3163	=back
2959		3164
2960		3165
		3166	=head2 C<ev_cleanup> - even the best things end
		3167
		3168	Cleanup watchers are called just before the event loop is being destroyed
		3169	by a call to C<ev_loop_destroy>.
		3170
		3171	While there is no guarantee that the event loop gets destroyed, cleanup
		3172	watchers provide a convenient method to install cleanup hooks for your
		3173	program, worker threads and so on - you just to make sure to destroy the
		3174	loop when you want them to be invoked.
		3175
		3176	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3177	all other watchers, they do not keep a reference to the event loop (which
		3178	makes a lot of sense if you think about it). Like all other watchers, you
		3179	can call libev functions in the callback, except C<ev_cleanup_start>.
		3180
		3181	=head3 Watcher-Specific Functions and Data Members
		3182
		3183	=over 4
		3184
		3185	=item ev_cleanup_init (ev_cleanup *, callback)
		3186
		3187	Initialises and configures the cleanup watcher - it has no parameters of
		3188	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3189	pointless, I assure you.
		3190
		3191	=back
		3192
		3193	Example: Register an atexit handler to destroy the default loop, so any
		3194	cleanup functions are called.
		3195
		3196	static void
		3197	program_exits (void)
		3198	{
		3199	ev_loop_destroy (EV_DEFAULT_UC);
		3200	}
		3201
		3202	...
		3203	atexit (program_exits);
		3204
		3205
2961	=head2 C<ev_async> - how to wake up another event loop	3206	=head2 C<ev_async> - how to wake up an event loop
2962		3207
2963	In general, you cannot use an C<ev_loop> from multiple threads or other	3208	In general, you cannot use an C<ev_loop> from multiple threads or other
2964	asynchronous sources such as signal handlers (as opposed to multiple event	3209	asynchronous sources such as signal handlers (as opposed to multiple event
2965	loops - those are of course safe to use in different threads).	3210	loops - those are of course safe to use in different threads).
2966		3211
2967	Sometimes, however, you need to wake up another event loop you do not	3212	Sometimes, however, you need to wake up an event loop you do not control,
2968	control, for example because it belongs to another thread. This is what	3213	for example because it belongs to another thread. This is what C<ev_async>
2969	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3214	watchers do: as long as the C<ev_async> watcher is active, you can signal
2970	can signal it by calling C<ev_async_send>, which is thread- and signal	3215	it by calling C<ev_async_send>, which is thread- and signal safe.
2971	safe.
2972		3216
2973	This functionality is very similar to C<ev_signal> watchers, as signals,	3217	This functionality is very similar to C<ev_signal> watchers, as signals,
2974	too, are asynchronous in nature, and signals, too, will be compressed	3218	too, are asynchronous in nature, and signals, too, will be compressed
2975	(i.e. the number of callback invocations may be less than the number of	3219	(i.e. the number of callback invocations may be less than the number of
2976	C<ev_async_sent> calls).	3220	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3221	of "global async watchers" by using a watcher on an otherwise unused
		3222	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3223	even without knowing which loop owns the signal.
2977		3224
2978	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3225	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2979	just the default loop.	3226	just the default loop.
2980		3227
2981	=head3 Queueing	3228	=head3 Queueing
2982		3229
2983	C<ev_async> does not support queueing of data in any way. The reason	3230	C<ev_async> does not support queueing of data in any way. The reason
2984	is that the author does not know of a simple (or any) algorithm for a	3231	is that the author does not know of a simple (or any) algorithm for a
2985	multiple-writer-single-reader queue that works in all cases and doesn't	3232	multiple-writer-single-reader queue that works in all cases and doesn't
2986	need elaborate support such as pthreads.	3233	need elaborate support such as pthreads or unportable memory access
		3234	semantics.
2987		3235
2988	That means that if you want to queue data, you have to provide your own	3236	That means that if you want to queue data, you have to provide your own
2989	queue. But at least I can tell you how to implement locking around your	3237	queue. But at least I can tell you how to implement locking around your
2990	queue:	3238	queue:
2991		3239
…		…
3075	trust me.	3323	trust me.
3076		3324
3077	=item ev_async_send (loop, ev_async *)	3325	=item ev_async_send (loop, ev_async *)
3078		3326
3079	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3327	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3080	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3328	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3329	returns.
		3330
3081	C<ev_feed_event>, this call is safe to do from other threads, signal or	3331	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3082	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3332	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3083	section below on what exactly this means).	3333	embedding section below on what exactly this means).
3084		3334
3085	Note that, as with other watchers in libev, multiple events might get	3335	Note that, as with other watchers in libev, multiple events might get
3086	compressed into a single callback invocation (another way to look at this	3336	compressed into a single callback invocation (another way to look at this
3087	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3337	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
3088	reset when the event loop detects that).	3338	reset when the event loop detects that).
…		…
3130		3380
3131	If C<timeout> is less than 0, then no timeout watcher will be	3381	If C<timeout> is less than 0, then no timeout watcher will be
3132	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3382	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3133	repeat = 0) will be started. C<0> is a valid timeout.	3383	repeat = 0) will be started. C<0> is a valid timeout.
3134		3384
3135	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3385	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3136	passed an C<revents> set like normal event callbacks (a combination of	3386	passed an C<revents> set like normal event callbacks (a combination of
3137	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3138	value passed to C<ev_once>. Note that it is possible to receive I<both>	3388	value passed to C<ev_once>. Note that it is possible to receive I<both>
3139	a timeout and an io event at the same time - you probably should give io	3389	a timeout and an io event at the same time - you probably should give io
3140	events precedence.	3390	events precedence.
3141		3391
3142	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3392	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3143		3393
3144	static void stdin_ready (int revents, void *arg)	3394	static void stdin_ready (int revents, void *arg)
3145	{	3395	{
3146	if (revents & EV_READ)	3396	if (revents & EV_READ)
3147	/* stdin might have data for us, joy! */;	3397	/* stdin might have data for us, joy! */;
3148	else if (revents & EV_TIMEOUT)	3398	else if (revents & EV_TIMER)
3149	/* doh, nothing entered */;	3399	/* doh, nothing entered */;
3150	}	3400	}
3151		3401
3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3402	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3153		3403
3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3404	=item ev_feed_fd_event (loop, int fd, int revents)
3155		3405
3156	Feed an event on the given fd, as if a file descriptor backend detected	3406	Feed an event on the given fd, as if a file descriptor backend detected
3157	the given events it.	3407	the given events it.
3158		3408
3159	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3409	=item ev_feed_signal_event (loop, int signum)
3160		3410
3161	Feed an event as if the given signal occurred (C<loop> must be the default	3411	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3162	loop!).	3412	which is async-safe.
3163		3413
3164	=back	3414	=back
		3415
		3416
		3417	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3418
		3419	This section explains some common idioms that are not immediately
		3420	obvious. Note that examples are sprinkled over the whole manual, and this
		3421	section only contains stuff that wouldn't fit anywhere else.
		3422
		3423	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3424
		3425	Each watcher has, by default, a C<void *data> member that you can read
		3426	or modify at any time: libev will completely ignore it. This can be used
		3427	to associate arbitrary data with your watcher. If you need more data and
		3428	don't want to allocate memory separately and store a pointer to it in that
		3429	data member, you can also "subclass" the watcher type and provide your own
		3430	data:
		3431
		3432	struct my_io
		3433	{
		3434	ev_io io;
		3435	int otherfd;
		3436	void *somedata;
		3437	struct whatever *mostinteresting;
		3438	};
		3439
		3440	...
		3441	struct my_io w;
		3442	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3443
		3444	And since your callback will be called with a pointer to the watcher, you
		3445	can cast it back to your own type:
		3446
		3447	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3448	{
		3449	struct my_io *w = (struct my_io *)w_;
		3450	...
		3451	}
		3452
		3453	More interesting and less C-conformant ways of casting your callback
		3454	function type instead have been omitted.
		3455
		3456	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3457
		3458	Another common scenario is to use some data structure with multiple
		3459	embedded watchers, in effect creating your own watcher that combines
		3460	multiple libev event sources into one "super-watcher":
		3461
		3462	struct my_biggy
		3463	{
		3464	int some_data;
		3465	ev_timer t1;
		3466	ev_timer t2;
		3467	}
		3468
		3469	In this case getting the pointer to C<my_biggy> is a bit more
		3470	complicated: Either you store the address of your C<my_biggy> struct in
		3471	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3472	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3473	real programmers):
		3474
		3475	#include <stddef.h>
		3476
		3477	static void
		3478	t1_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t1));
		3482	}
		3483
		3484	static void
		3485	t2_cb (EV_P_ ev_timer *w, int revents)
		3486	{
		3487	struct my_biggy big = (struct my_biggy *)
		3488	(((char *)w) - offsetof (struct my_biggy, t2));
		3489	}
		3490
		3491	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3492
		3493	Often (especially in GUI toolkits) there are places where you have
		3494	I<modal> interaction, which is most easily implemented by recursively
		3495	invoking C<ev_run>.
		3496
		3497	This brings the problem of exiting - a callback might want to finish the
		3498	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3499	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3500	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3501	other combination: In these cases, C<ev_break> will not work alone.
		3502
		3503	The solution is to maintain "break this loop" variable for each C<ev_run>
		3504	invocation, and use a loop around C<ev_run> until the condition is
		3505	triggered, using C<EVRUN_ONCE>:
		3506
		3507	// main loop
		3508	int exit_main_loop = 0;
		3509
		3510	while (!exit_main_loop)
		3511	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3512
		3513	// in a model watcher
		3514	int exit_nested_loop = 0;
		3515
		3516	while (!exit_nested_loop)
		3517	ev_run (EV_A_ EVRUN_ONCE);
		3518
		3519	To exit from any of these loops, just set the corresponding exit variable:
		3520
		3521	// exit modal loop
		3522	exit_nested_loop = 1;
		3523
		3524	// exit main program, after modal loop is finished
		3525	exit_main_loop = 1;
		3526
		3527	// exit both
		3528	exit_main_loop = exit_nested_loop = 1;
		3529
		3530	=head2 THREAD LOCKING EXAMPLE
		3531
		3532	Here is a fictitious example of how to run an event loop in a different
		3533	thread from where callbacks are being invoked and watchers are
		3534	created/added/removed.
		3535
		3536	For a real-world example, see the C<EV::Loop::Async> perl module,
		3537	which uses exactly this technique (which is suited for many high-level
		3538	languages).
		3539
		3540	The example uses a pthread mutex to protect the loop data, a condition
		3541	variable to wait for callback invocations, an async watcher to notify the
		3542	event loop thread and an unspecified mechanism to wake up the main thread.
		3543
		3544	First, you need to associate some data with the event loop:
		3545
		3546	typedef struct {
		3547	mutex_t lock; /* global loop lock */
		3548	ev_async async_w;
		3549	thread_t tid;
		3550	cond_t invoke_cv;
		3551	} userdata;
		3552
		3553	void prepare_loop (EV_P)
		3554	{
		3555	// for simplicity, we use a static userdata struct.
		3556	static userdata u;
		3557
		3558	ev_async_init (&u->async_w, async_cb);
		3559	ev_async_start (EV_A_ &u->async_w);
		3560
		3561	pthread_mutex_init (&u->lock, 0);
		3562	pthread_cond_init (&u->invoke_cv, 0);
		3563
		3564	// now associate this with the loop
		3565	ev_set_userdata (EV_A_ u);
		3566	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3567	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3568
		3569	// then create the thread running ev_run
		3570	pthread_create (&u->tid, 0, l_run, EV_A);
		3571	}
		3572
		3573	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3574	solely to wake up the event loop so it takes notice of any new watchers
		3575	that might have been added:
		3576
		3577	static void
		3578	async_cb (EV_P_ ev_async *w, int revents)
		3579	{
		3580	// just used for the side effects
		3581	}
		3582
		3583	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3584	protecting the loop data, respectively.
		3585
		3586	static void
		3587	l_release (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_unlock (&u->lock);
		3591	}
		3592
		3593	static void
		3594	l_acquire (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597	pthread_mutex_lock (&u->lock);
		3598	}
		3599
		3600	The event loop thread first acquires the mutex, and then jumps straight
		3601	into C<ev_run>:
		3602
		3603	void *
		3604	l_run (void *thr_arg)
		3605	{
		3606	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3607
		3608	l_acquire (EV_A);
		3609	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3610	ev_run (EV_A_ 0);
		3611	l_release (EV_A);
		3612
		3613	return 0;
		3614	}
		3615
		3616	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3617	signal the main thread via some unspecified mechanism (signals? pipe
		3618	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3619	have been called (in a while loop because a) spurious wakeups are possible
		3620	and b) skipping inter-thread-communication when there are no pending
		3621	watchers is very beneficial):
		3622
		3623	static void
		3624	l_invoke (EV_P)
		3625	{
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	while (ev_pending_count (EV_A))
		3629	{
		3630	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3631	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3632	}
		3633	}
		3634
		3635	Now, whenever the main thread gets told to invoke pending watchers, it
		3636	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3637	thread to continue:
		3638
		3639	static void
		3640	real_invoke_pending (EV_P)
		3641	{
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	pthread_mutex_lock (&u->lock);
		3645	ev_invoke_pending (EV_A);
		3646	pthread_cond_signal (&u->invoke_cv);
		3647	pthread_mutex_unlock (&u->lock);
		3648	}
		3649
		3650	Whenever you want to start/stop a watcher or do other modifications to an
		3651	event loop, you will now have to lock:
		3652
		3653	ev_timer timeout_watcher;
		3654	userdata *u = ev_userdata (EV_A);
		3655
		3656	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3657
		3658	pthread_mutex_lock (&u->lock);
		3659	ev_timer_start (EV_A_ &timeout_watcher);
		3660	ev_async_send (EV_A_ &u->async_w);
		3661	pthread_mutex_unlock (&u->lock);
		3662
		3663	Note that sending the C<ev_async> watcher is required because otherwise
		3664	an event loop currently blocking in the kernel will have no knowledge
		3665	about the newly added timer. By waking up the loop it will pick up any new
		3666	watchers in the next event loop iteration.
		3667
		3668	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3669
		3670	While the overhead of a callback that e.g. schedules a thread is small, it
		3671	is still an overhead. If you embed libev, and your main usage is with some
		3672	kind of threads or coroutines, you might want to customise libev so that
		3673	doesn't need callbacks anymore.
		3674
		3675	Imagine you have coroutines that you can switch to using a function
		3676	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3677	and that due to some magic, the currently active coroutine is stored in a
		3678	global called C<current_coro>. Then you can build your own "wait for libev
		3679	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3680	the differing C<;> conventions):
		3681
		3682	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3683	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3684
		3685	That means instead of having a C callback function, you store the
		3686	coroutine to switch to in each watcher, and instead of having libev call
		3687	your callback, you instead have it switch to that coroutine.
		3688
		3689	A coroutine might now wait for an event with a function called
		3690	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3691	matter when, or whether the watcher is active or not when this function is
		3692	called):
		3693
		3694	void
		3695	wait_for_event (ev_watcher *w)
		3696	{
		3697	ev_cb_set (w) = current_coro;
		3698	switch_to (libev_coro);
		3699	}
		3700
		3701	That basically suspends the coroutine inside C<wait_for_event> and
		3702	continues the libev coroutine, which, when appropriate, switches back to
		3703	this or any other coroutine. I am sure if you sue this your own :)
		3704
		3705	You can do similar tricks if you have, say, threads with an event queue -
		3706	instead of storing a coroutine, you store the queue object and instead of
		3707	switching to a coroutine, you push the watcher onto the queue and notify
		3708	any waiters.
		3709
		3710	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3711	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3712
		3713	// my_ev.h
		3714	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3715	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3716	#include "../libev/ev.h"
		3717
		3718	// my_ev.c
		3719	#define EV_H "my_ev.h"
		3720	#include "../libev/ev.c"
		3721
		3722	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3723	F<my_ev.c> into your project. When properly specifying include paths, you
		3724	can even use F<ev.h> as header file name directly.
3165		3725
3166		3726
3167	=head1 LIBEVENT EMULATION	3727	=head1 LIBEVENT EMULATION
3168		3728
3169	Libev offers a compatibility emulation layer for libevent. It cannot	3729	Libev offers a compatibility emulation layer for libevent. It cannot
3170	emulate the internals of libevent, so here are some usage hints:	3730	emulate the internals of libevent, so here are some usage hints:
3171		3731
3172	=over 4	3732	=over 4
		3733
		3734	=item * Only the libevent-1.4.1-beta API is being emulated.
		3735
		3736	This was the newest libevent version available when libev was implemented,
		3737	and is still mostly unchanged in 2010.
3173		3738
3174	=item * Use it by including <event.h>, as usual.	3739	=item * Use it by including <event.h>, as usual.
3175		3740
3176	=item * The following members are fully supported: ev_base, ev_callback,	3741	=item * The following members are fully supported: ev_base, ev_callback,
3177	ev_arg, ev_fd, ev_res, ev_events.	3742	ev_arg, ev_fd, ev_res, ev_events.
…		…
3183	=item * Priorities are not currently supported. Initialising priorities	3748	=item * Priorities are not currently supported. Initialising priorities
3184	will fail and all watchers will have the same priority, even though there	3749	will fail and all watchers will have the same priority, even though there
3185	is an ev_pri field.	3750	is an ev_pri field.
3186		3751
3187	=item * In libevent, the last base created gets the signals, in libev, the	3752	=item * In libevent, the last base created gets the signals, in libev, the
3188	first base created (== the default loop) gets the signals.	3753	base that registered the signal gets the signals.
3189		3754
3190	=item * Other members are not supported.	3755	=item * Other members are not supported.
3191		3756
3192	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3757	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3193	to use the libev header file and library.	3758	to use the libev header file and library.
…		…
3212	Care has been taken to keep the overhead low. The only data member the C++	3777	Care has been taken to keep the overhead low. The only data member the C++
3213	classes add (compared to plain C-style watchers) is the event loop pointer	3778	classes add (compared to plain C-style watchers) is the event loop pointer
3214	that the watcher is associated with (or no additional members at all if	3779	that the watcher is associated with (or no additional members at all if
3215	you disable C<EV_MULTIPLICITY> when embedding libev).	3780	you disable C<EV_MULTIPLICITY> when embedding libev).
3216		3781
3217	Currently, functions, and static and non-static member functions can be	3782	Currently, functions, static and non-static member functions and classes
3218	used as callbacks. Other types should be easy to add as long as they only	3783	with C<operator ()> can be used as callbacks. Other types should be easy
3219	need one additional pointer for context. If you need support for other	3784	to add as long as they only need one additional pointer for context. If
3220	types of functors please contact the author (preferably after implementing	3785	you need support for other types of functors please contact the author
3221	it).	3786	(preferably after implementing it).
3222		3787
3223	Here is a list of things available in the C<ev> namespace:	3788	Here is a list of things available in the C<ev> namespace:
3224		3789
3225	=over 4	3790	=over 4
3226		3791
…		…
3244		3809
3245	=over 4	3810	=over 4
3246		3811
3247	=item ev::TYPE::TYPE ()	3812	=item ev::TYPE::TYPE ()
3248		3813
3249	=item ev::TYPE::TYPE (struct ev_loop *)	3814	=item ev::TYPE::TYPE (loop)
3250		3815
3251	=item ev::TYPE::~TYPE	3816	=item ev::TYPE::~TYPE
3252		3817
3253	The constructor (optionally) takes an event loop to associate the watcher	3818	The constructor (optionally) takes an event loop to associate the watcher
3254	with. If it is omitted, it will use C<EV_DEFAULT>.	3819	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3287	myclass obj;	3852	myclass obj;
3288	ev::io iow;	3853	ev::io iow;
3289	iow.set <myclass, &myclass::io_cb> (&obj);	3854	iow.set <myclass, &myclass::io_cb> (&obj);
3290		3855
3291	=item w->set (object *)	3856	=item w->set (object *)
3292
3293	This is an B<experimental> feature that might go away in a future version.
3294		3857
3295	This is a variation of a method callback - leaving out the method to call	3858	This is a variation of a method callback - leaving out the method to call
3296	will default the method to C<operator ()>, which makes it possible to use	3859	will default the method to C<operator ()>, which makes it possible to use
3297	functor objects without having to manually specify the C<operator ()> all	3860	functor objects without having to manually specify the C<operator ()> all
3298	the time. Incidentally, you can then also leave out the template argument	3861	the time. Incidentally, you can then also leave out the template argument
…		…
3331	Example: Use a plain function as callback.	3894	Example: Use a plain function as callback.
3332		3895
3333	static void io_cb (ev::io &w, int revents) { }	3896	static void io_cb (ev::io &w, int revents) { }
3334	iow.set <io_cb> ();	3897	iow.set <io_cb> ();
3335		3898
3336	=item w->set (struct ev_loop *)	3899	=item w->set (loop)
3337		3900
3338	Associates a different C<struct ev_loop> with this watcher. You can only	3901	Associates a different C<struct ev_loop> with this watcher. You can only
3339	do this when the watcher is inactive (and not pending either).	3902	do this when the watcher is inactive (and not pending either).
3340		3903
3341	=item w->set ([arguments])	3904	=item w->set ([arguments])
3342		3905
3343	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3906	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3344	called at least once. Unlike the C counterpart, an active watcher gets	3907	method or a suitable start method must be called at least once. Unlike the
3345	automatically stopped and restarted when reconfiguring it with this	3908	C counterpart, an active watcher gets automatically stopped and restarted
3346	method.	3909	when reconfiguring it with this method.
3347		3910
3348	=item w->start ()	3911	=item w->start ()
3349		3912
3350	Starts the watcher. Note that there is no C<loop> argument, as the	3913	Starts the watcher. Note that there is no C<loop> argument, as the
3351	constructor already stores the event loop.	3914	constructor already stores the event loop.
3352		3915
		3916	=item w->start ([arguments])
		3917
		3918	Instead of calling C<set> and C<start> methods separately, it is often
		3919	convenient to wrap them in one call. Uses the same type of arguments as
		3920	the configure C<set> method of the watcher.
		3921
3353	=item w->stop ()	3922	=item w->stop ()
3354		3923
3355	Stops the watcher if it is active. Again, no C<loop> argument.	3924	Stops the watcher if it is active. Again, no C<loop> argument.
3356		3925
3357	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3926	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3369		3938
3370	=back	3939	=back
3371		3940
3372	=back	3941	=back
3373		3942
3374	Example: Define a class with an IO and idle watcher, start one of them in	3943	Example: Define a class with two I/O and idle watchers, start the I/O
3375	the constructor.	3944	watchers in the constructor.
3376		3945
3377	class myclass	3946	class myclass
3378	{	3947	{
3379	ev::io io ; void io_cb (ev::io &w, int revents);	3948	ev::io io ; void io_cb (ev::io &w, int revents);
		3949	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3380	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3950	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3381		3951
3382	myclass (int fd)	3952	myclass (int fd)
3383	{	3953	{
3384	io .set <myclass, &myclass::io_cb > (this);	3954	io .set <myclass, &myclass::io_cb > (this);
		3955	io2 .set <myclass, &myclass::io2_cb > (this);
3385	idle.set <myclass, &myclass::idle_cb> (this);	3956	idle.set <myclass, &myclass::idle_cb> (this);
3386		3957
3387	io.start (fd, ev::READ);	3958	io.set (fd, ev::WRITE); // configure the watcher
		3959	io.start (); // start it whenever convenient
		3960
		3961	io2.start (fd, ev::READ); // set + start in one call
3388	}	3962	}
3389	};	3963	};
3390		3964
3391		3965
3392	=head1 OTHER LANGUAGE BINDINGS	3966	=head1 OTHER LANGUAGE BINDINGS
…		…
3440	Erkki Seppala has written Ocaml bindings for libev, to be found at	4014	Erkki Seppala has written Ocaml bindings for libev, to be found at
3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3442		4016
3443	=item Lua	4017	=item Lua
3444		4018
3445	Brian Maher has written a partial interface to libev	4019	Brian Maher has written a partial interface to libev for lua (at the
3446	for lua (only C<ev_io> and C<ev_timer>), to be found at	4020	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3447	L<http://github.com/brimworks/lua-ev>.	4021	L<http://github.com/brimworks/lua-ev>.
3448		4022
3449	=back	4023	=back
3450		4024
3451		4025
…		…
3466	loop argument"). The C<EV_A> form is used when this is the sole argument,	4040	loop argument"). The C<EV_A> form is used when this is the sole argument,
3467	C<EV_A_> is used when other arguments are following. Example:	4041	C<EV_A_> is used when other arguments are following. Example:
3468		4042
3469	ev_unref (EV_A);	4043	ev_unref (EV_A);
3470	ev_timer_add (EV_A_ watcher);	4044	ev_timer_add (EV_A_ watcher);
3471	ev_loop (EV_A_ 0);	4045	ev_run (EV_A_ 0);
3472		4046
3473	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4047	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3474	which is often provided by the following macro.	4048	which is often provided by the following macro.
3475		4049
3476	=item C<EV_P>, C<EV_P_>	4050	=item C<EV_P>, C<EV_P_>
…		…
3516	}	4090	}
3517		4091
3518	ev_check check;	4092	ev_check check;
3519	ev_check_init (&check, check_cb);	4093	ev_check_init (&check, check_cb);
3520	ev_check_start (EV_DEFAULT_ &check);	4094	ev_check_start (EV_DEFAULT_ &check);
3521	ev_loop (EV_DEFAULT_ 0);	4095	ev_run (EV_DEFAULT_ 0);
3522		4096
3523	=head1 EMBEDDING	4097	=head1 EMBEDDING
3524		4098
3525	Libev can (and often is) directly embedded into host	4099	Libev can (and often is) directly embedded into host
3526	applications. Examples of applications that embed it include the Deliantra	4100	applications. Examples of applications that embed it include the Deliantra
…		…
3606	libev.m4	4180	libev.m4
3607		4181
3608	=head2 PREPROCESSOR SYMBOLS/MACROS	4182	=head2 PREPROCESSOR SYMBOLS/MACROS
3609		4183
3610	Libev can be configured via a variety of preprocessor symbols you have to	4184	Libev can be configured via a variety of preprocessor symbols you have to
3611	define before including any of its files. The default in the absence of	4185	define before including (or compiling) any of its files. The default in
3612	autoconf is documented for every option.	4186	the absence of autoconf is documented for every option.
		4187
		4188	Symbols marked with "(h)" do not change the ABI, and can have different
		4189	values when compiling libev vs. including F<ev.h>, so it is permissible
		4190	to redefine them before including F<ev.h> without breaking compatibility
		4191	to a compiled library. All other symbols change the ABI, which means all
		4192	users of libev and the libev code itself must be compiled with compatible
		4193	settings.
3613		4194
3614	=over 4	4195	=over 4
3615		4196
		4197	=item EV_COMPAT3 (h)
		4198
		4199	Backwards compatibility is a major concern for libev. This is why this
		4200	release of libev comes with wrappers for the functions and symbols that
		4201	have been renamed between libev version 3 and 4.
		4202
		4203	You can disable these wrappers (to test compatibility with future
		4204	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4205	sources. This has the additional advantage that you can drop the C<struct>
		4206	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4207	typedef in that case.
		4208
		4209	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4210	and in some even more future version the compatibility code will be
		4211	removed completely.
		4212
3616	=item EV_STANDALONE	4213	=item EV_STANDALONE (h)
3617		4214
3618	Must always be C<1> if you do not use autoconf configuration, which	4215	Must always be C<1> if you do not use autoconf configuration, which
3619	keeps libev from including F<config.h>, and it also defines dummy	4216	keeps libev from including F<config.h>, and it also defines dummy
3620	implementations for some libevent functions (such as logging, which is not	4217	implementations for some libevent functions (such as logging, which is not
3621	supported). It will also not define any of the structs usually found in	4218	supported). It will also not define any of the structs usually found in
3622	F<event.h> that are not directly supported by the libev core alone.	4219	F<event.h> that are not directly supported by the libev core alone.
3623		4220
3624	In standalone mode, libev will still try to automatically deduce the	4221	In standalone mode, libev will still try to automatically deduce the
3625	configuration, but has to be more conservative.	4222	configuration, but has to be more conservative.
		4223
		4224	=item EV_USE_FLOOR
		4225
		4226	If defined to be C<1>, libev will use the C<floor ()> function for its
		4227	periodic reschedule calculations, otherwise libev will fall back on a
		4228	portable (slower) implementation. If you enable this, you usually have to
		4229	link against libm or something equivalent. Enabling this when the C<floor>
		4230	function is not available will fail, so the safe default is to not enable
		4231	this.
3626		4232
3627	=item EV_USE_MONOTONIC	4233	=item EV_USE_MONOTONIC
3628		4234
3629	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
3630	monotonic clock option at both compile time and runtime. Otherwise no	4236	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3771	as well as for signal and thread safety in C<ev_async> watchers.	4377	as well as for signal and thread safety in C<ev_async> watchers.
3772		4378
3773	In the absence of this define, libev will use C<sig_atomic_t volatile>	4379	In the absence of this define, libev will use C<sig_atomic_t volatile>
3774	(from F<signal.h>), which is usually good enough on most platforms.	4380	(from F<signal.h>), which is usually good enough on most platforms.
3775		4381
3776	=item EV_H	4382	=item EV_H (h)
3777		4383
3778	The name of the F<ev.h> header file used to include it. The default if	4384	The name of the F<ev.h> header file used to include it. The default if
3779	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4385	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3780	used to virtually rename the F<ev.h> header file in case of conflicts.	4386	used to virtually rename the F<ev.h> header file in case of conflicts.
3781		4387
3782	=item EV_CONFIG_H	4388	=item EV_CONFIG_H (h)
3783		4389
3784	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4390	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3785	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4391	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3786	C<EV_H>, above.	4392	C<EV_H>, above.
3787		4393
3788	=item EV_EVENT_H	4394	=item EV_EVENT_H (h)
3789		4395
3790	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4396	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3791	of how the F<event.h> header can be found, the default is C<"event.h">.	4397	of how the F<event.h> header can be found, the default is C<"event.h">.
3792		4398
3793	=item EV_PROTOTYPES	4399	=item EV_PROTOTYPES (h)
3794		4400
3795	If defined to be C<0>, then F<ev.h> will not define any function	4401	If defined to be C<0>, then F<ev.h> will not define any function
3796	prototypes, but still define all the structs and other symbols. This is	4402	prototypes, but still define all the structs and other symbols. This is
3797	occasionally useful if you want to provide your own wrapper functions	4403	occasionally useful if you want to provide your own wrapper functions
3798	around libev functions.	4404	around libev functions.
…		…
3820	fine.	4426	fine.
3821		4427
3822	If your embedding application does not need any priorities, defining these	4428	If your embedding application does not need any priorities, defining these
3823	both to C<0> will save some memory and CPU.	4429	both to C<0> will save some memory and CPU.
3824		4430
3825	=item EV_PERIODIC_ENABLE	4431	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4432	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4433	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3826		4434
3827	If undefined or defined to be C<1>, then periodic timers are supported. If	4435	If undefined or defined to be C<1> (and the platform supports it), then
3828	defined to be C<0>, then they are not. Disabling them saves a few kB of	4436	the respective watcher type is supported. If defined to be C<0>, then it
3829	code.	4437	is not. Disabling watcher types mainly saves code size.
3830		4438
3831	=item EV_IDLE_ENABLE	4439	=item EV_FEATURES
3832
3833	If undefined or defined to be C<1>, then idle watchers are supported. If
3834	defined to be C<0>, then they are not. Disabling them saves a few kB of
3835	code.
3836
3837	=item EV_EMBED_ENABLE
3838
3839	If undefined or defined to be C<1>, then embed watchers are supported. If
3840	defined to be C<0>, then they are not. Embed watchers rely on most other
3841	watcher types, which therefore must not be disabled.
3842
3843	=item EV_STAT_ENABLE
3844
3845	If undefined or defined to be C<1>, then stat watchers are supported. If
3846	defined to be C<0>, then they are not.
3847
3848	=item EV_FORK_ENABLE
3849
3850	If undefined or defined to be C<1>, then fork watchers are supported. If
3851	defined to be C<0>, then they are not.
3852
3853	=item EV_ASYNC_ENABLE
3854
3855	If undefined or defined to be C<1>, then async watchers are supported. If
3856	defined to be C<0>, then they are not.
3857
3858	=item EV_MINIMAL
3859		4440
3860	If you need to shave off some kilobytes of code at the expense of some	4441	If you need to shave off some kilobytes of code at the expense of some
3861	speed (but with the full API), define this symbol to C<1>. Currently this	4442	speed (but with the full API), you can define this symbol to request
3862	is used to override some inlining decisions, saves roughly 30% code size	4443	certain subsets of functionality. The default is to enable all features
3863	on amd64. It also selects a much smaller 2-heap for timer management over	4444	that can be enabled on the platform.
3864	the default 4-heap.
3865		4445
3866	You can save even more by disabling watcher types you do not need	4446	A typical way to use this symbol is to define it to C<0> (or to a bitset
3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4447	with some broad features you want) and then selectively re-enable
3868	(C<-DNDEBUG>) will usually reduce code size a lot.	4448	additional parts you want, for example if you want everything minimal,
		4449	but multiple event loop support, async and child watchers and the poll
		4450	backend, use this:
3869		4451
3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4452	#define EV_FEATURES 0
3871	provide a bare-bones event library. See C<ev.h> for details on what parts	4453	#define EV_MULTIPLICITY 1
3872	of the API are still available, and do not complain if this subset changes	4454	#define EV_USE_POLL 1
3873	over time.	4455	#define EV_CHILD_ENABLE 1
		4456	#define EV_ASYNC_ENABLE 1
		4457
		4458	The actual value is a bitset, it can be a combination of the following
		4459	values:
		4460
		4461	=over 4
		4462
		4463	=item C<1> - faster/larger code
		4464
		4465	Use larger code to speed up some operations.
		4466
		4467	Currently this is used to override some inlining decisions (enlarging the
		4468	code size by roughly 30% on amd64).
		4469
		4470	When optimising for size, use of compiler flags such as C<-Os> with
		4471	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4472	assertions.
		4473
		4474	=item C<2> - faster/larger data structures
		4475
		4476	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4477	hash table sizes and so on. This will usually further increase code size
		4478	and can additionally have an effect on the size of data structures at
		4479	runtime.
		4480
		4481	=item C<4> - full API configuration
		4482
		4483	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4484	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4485
		4486	=item C<8> - full API
		4487
		4488	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4489	details on which parts of the API are still available without this
		4490	feature, and do not complain if this subset changes over time.
		4491
		4492	=item C<16> - enable all optional watcher types
		4493
		4494	Enables all optional watcher types. If you want to selectively enable
		4495	only some watcher types other than I/O and timers (e.g. prepare,
		4496	embed, async, child...) you can enable them manually by defining
		4497	C<EV_watchertype_ENABLE> to C<1> instead.
		4498
		4499	=item C<32> - enable all backends
		4500
		4501	This enables all backends - without this feature, you need to enable at
		4502	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4503
		4504	=item C<64> - enable OS-specific "helper" APIs
		4505
		4506	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4507	default.
		4508
		4509	=back
		4510
		4511	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4512	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4513	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4514	watchers, timers and monotonic clock support.
		4515
		4516	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4517	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4518	your program might be left out as well - a binary starting a timer and an
		4519	I/O watcher then might come out at only 5Kb.
		4520
		4521	=item EV_AVOID_STDIO
		4522
		4523	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4524	functions (printf, scanf, perror etc.). This will increase the code size
		4525	somewhat, but if your program doesn't otherwise depend on stdio and your
		4526	libc allows it, this avoids linking in the stdio library which is quite
		4527	big.
		4528
		4529	Note that error messages might become less precise when this option is
		4530	enabled.
3874		4531
3875	=item EV_NSIG	4532	=item EV_NSIG
3876		4533
3877	The highest supported signal number, +1 (or, the number of	4534	The highest supported signal number, +1 (or, the number of
3878	signals): Normally, libev tries to deduce the maximum number of signals	4535	signals): Normally, libev tries to deduce the maximum number of signals
3879	automatically, but sometimes this fails, in which case it can be	4536	automatically, but sometimes this fails, in which case it can be
3880	specified. Also, using a lower number than detected (C<32> should be	4537	specified. Also, using a lower number than detected (C<32> should be
3881	good for about any system in existance) can save some memory, as libev	4538	good for about any system in existence) can save some memory, as libev
3882	statically allocates some 12-24 bytes per signal number.	4539	statically allocates some 12-24 bytes per signal number.
3883		4540
3884	=item EV_PID_HASHSIZE	4541	=item EV_PID_HASHSIZE
3885		4542
3886	C<ev_child> watchers use a small hash table to distribute workload by	4543	C<ev_child> watchers use a small hash table to distribute workload by
3887	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4544	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3888	than enough. If you need to manage thousands of children you might want to	4545	usually more than enough. If you need to manage thousands of children you
3889	increase this value (I<must> be a power of two).	4546	might want to increase this value (I<must> be a power of two).
3890		4547
3891	=item EV_INOTIFY_HASHSIZE	4548	=item EV_INOTIFY_HASHSIZE
3892		4549
3893	C<ev_stat> watchers use a small hash table to distribute workload by	4550	C<ev_stat> watchers use a small hash table to distribute workload by
3894	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4551	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3895	usually more than enough. If you need to manage thousands of C<ev_stat>	4552	disabled), usually more than enough. If you need to manage thousands of
3896	watchers you might want to increase this value (I<must> be a power of	4553	C<ev_stat> watchers you might want to increase this value (I<must> be a
3897	two).	4554	power of two).
3898		4555
3899	=item EV_USE_4HEAP	4556	=item EV_USE_4HEAP
3900		4557
3901	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4558	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3902	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4559	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3903	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4560	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3904	faster performance with many (thousands) of watchers.	4561	faster performance with many (thousands) of watchers.
3905		4562
3906	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4563	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3907	(disabled).	4564	will be C<0>.
3908		4565
3909	=item EV_HEAP_CACHE_AT	4566	=item EV_HEAP_CACHE_AT
3910		4567
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4568	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4569	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3913	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4570	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3914	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4571	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3915	but avoids random read accesses on heap changes. This improves performance	4572	but avoids random read accesses on heap changes. This improves performance
3916	noticeably with many (hundreds) of watchers.	4573	noticeably with many (hundreds) of watchers.
3917		4574
3918	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4575	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3919	(disabled).	4576	will be C<0>.
3920		4577
3921	=item EV_VERIFY	4578	=item EV_VERIFY
3922		4579
3923	Controls how much internal verification (see C<ev_loop_verify ()>) will	4580	Controls how much internal verification (see C<ev_verify ()>) will
3924	be done: If set to C<0>, no internal verification code will be compiled	4581	be done: If set to C<0>, no internal verification code will be compiled
3925	in. If set to C<1>, then verification code will be compiled in, but not	4582	in. If set to C<1>, then verification code will be compiled in, but not
3926	called. If set to C<2>, then the internal verification code will be	4583	called. If set to C<2>, then the internal verification code will be
3927	called once per loop, which can slow down libev. If set to C<3>, then the	4584	called once per loop, which can slow down libev. If set to C<3>, then the
3928	verification code will be called very frequently, which will slow down	4585	verification code will be called very frequently, which will slow down
3929	libev considerably.	4586	libev considerably.
3930		4587
3931	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4588	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3932	C<0>.	4589	will be C<0>.
3933		4590
3934	=item EV_COMMON	4591	=item EV_COMMON
3935		4592
3936	By default, all watchers have a C<void *data> member. By redefining	4593	By default, all watchers have a C<void *data> member. By redefining
3937	this macro to a something else you can include more and other types of	4594	this macro to something else you can include more and other types of
3938	members. You have to define it each time you include one of the files,	4595	members. You have to define it each time you include one of the files,
3939	though, and it must be identical each time.	4596	though, and it must be identical each time.
3940		4597
3941	For example, the perl EV module uses something like this:	4598	For example, the perl EV module uses something like this:
3942		4599
…		…
3995	file.	4652	file.
3996		4653
3997	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4654	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3998	that everybody includes and which overrides some configure choices:	4655	that everybody includes and which overrides some configure choices:
3999		4656
4000	#define EV_MINIMAL 1	4657	#define EV_FEATURES 8
4001	#define EV_USE_POLL 0	4658	#define EV_USE_SELECT 1
4002	#define EV_MULTIPLICITY 0
4003	#define EV_PERIODIC_ENABLE 0	4659	#define EV_PREPARE_ENABLE 1
		4660	#define EV_IDLE_ENABLE 1
4004	#define EV_STAT_ENABLE 0	4661	#define EV_SIGNAL_ENABLE 1
4005	#define EV_FORK_ENABLE 0	4662	#define EV_CHILD_ENABLE 1
		4663	#define EV_USE_STDEXCEPT 0
4006	#define EV_CONFIG_H <config.h>	4664	#define EV_CONFIG_H <config.h>
4007	#define EV_MINPRI 0
4008	#define EV_MAXPRI 0
4009		4665
4010	#include "ev++.h"	4666	#include "ev++.h"
4011		4667
4012	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4668	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4013		4669
4014	#include "ev_cpp.h"	4670	#include "ev_cpp.h"
4015	#include "ev.c"	4671	#include "ev.c"
4016		4672
4017	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4673	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4018		4674
4019	=head2 THREADS AND COROUTINES	4675	=head2 THREADS AND COROUTINES
4020		4676
4021	=head3 THREADS	4677	=head3 THREADS
4022		4678
…		…
4073	default loop and triggering an C<ev_async> watcher from the default loop	4729	default loop and triggering an C<ev_async> watcher from the default loop
4074	watcher callback into the event loop interested in the signal.	4730	watcher callback into the event loop interested in the signal.
4075		4731
4076	=back	4732	=back
4077		4733
4078	=head4 THREAD LOCKING EXAMPLE	4734	See also L<THREAD LOCKING EXAMPLE>.
4079
4080	Here is a fictitious example of how to run an event loop in a different
4081	thread than where callbacks are being invoked and watchers are
4082	created/added/removed.
4083
4084	For a real-world example, see the C<EV::Loop::Async> perl module,
4085	which uses exactly this technique (which is suited for many high-level
4086	languages).
4087
4088	The example uses a pthread mutex to protect the loop data, a condition
4089	variable to wait for callback invocations, an async watcher to notify the
4090	event loop thread and an unspecified mechanism to wake up the main thread.
4091
4092	First, you need to associate some data with the event loop:
4093
4094	typedef struct {
4095	mutex_t lock; /* global loop lock */
4096	ev_async async_w;
4097	thread_t tid;
4098	cond_t invoke_cv;
4099	} userdata;
4100
4101	void prepare_loop (EV_P)
4102	{
4103	// for simplicity, we use a static userdata struct.
4104	static userdata u;
4105
4106	ev_async_init (&u->async_w, async_cb);
4107	ev_async_start (EV_A_ &u->async_w);
4108
4109	pthread_mutex_init (&u->lock, 0);
4110	pthread_cond_init (&u->invoke_cv, 0);
4111
4112	// now associate this with the loop
4113	ev_set_userdata (EV_A_ u);
4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4116
4117	// then create the thread running ev_loop
4118	pthread_create (&u->tid, 0, l_run, EV_A);
4119	}
4120
4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
4122	solely to wake up the event loop so it takes notice of any new watchers
4123	that might have been added:
4124
4125	static void
4126	async_cb (EV_P_ ev_async *w, int revents)
4127	{
4128	// just used for the side effects
4129	}
4130
4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4132	protecting the loop data, respectively.
4133
4134	static void
4135	l_release (EV_P)
4136	{
4137	userdata *u = ev_userdata (EV_A);
4138	pthread_mutex_unlock (&u->lock);
4139	}
4140
4141	static void
4142	l_acquire (EV_P)
4143	{
4144	userdata *u = ev_userdata (EV_A);
4145	pthread_mutex_lock (&u->lock);
4146	}
4147
4148	The event loop thread first acquires the mutex, and then jumps straight
4149	into C<ev_loop>:
4150
4151	void *
4152	l_run (void *thr_arg)
4153	{
4154	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4155
4156	l_acquire (EV_A);
4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4158	ev_loop (EV_A_ 0);
4159	l_release (EV_A);
4160
4161	return 0;
4162	}
4163
4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
4165	signal the main thread via some unspecified mechanism (signals? pipe
4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4167	have been called (in a while loop because a) spurious wakeups are possible
4168	and b) skipping inter-thread-communication when there are no pending
4169	watchers is very beneficial):
4170
4171	static void
4172	l_invoke (EV_P)
4173	{
4174	userdata *u = ev_userdata (EV_A);
4175
4176	while (ev_pending_count (EV_A))
4177	{
4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
4180	}
4181	}
4182
4183	Now, whenever the main thread gets told to invoke pending watchers, it
4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4185	thread to continue:
4186
4187	static void
4188	real_invoke_pending (EV_P)
4189	{
4190	userdata *u = ev_userdata (EV_A);
4191
4192	pthread_mutex_lock (&u->lock);
4193	ev_invoke_pending (EV_A);
4194	pthread_cond_signal (&u->invoke_cv);
4195	pthread_mutex_unlock (&u->lock);
4196	}
4197
4198	Whenever you want to start/stop a watcher or do other modifications to an
4199	event loop, you will now have to lock:
4200
4201	ev_timer timeout_watcher;
4202	userdata *u = ev_userdata (EV_A);
4203
4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4205
4206	pthread_mutex_lock (&u->lock);
4207	ev_timer_start (EV_A_ &timeout_watcher);
4208	ev_async_send (EV_A_ &u->async_w);
4209	pthread_mutex_unlock (&u->lock);
4210
4211	Note that sending the C<ev_async> watcher is required because otherwise
4212	an event loop currently blocking in the kernel will have no knowledge
4213	about the newly added timer. By waking up the loop it will pick up any new
4214	watchers in the next event loop iteration.
4215		4735
4216	=head3 COROUTINES	4736	=head3 COROUTINES
4217		4737
4218	Libev is very accommodating to coroutines ("cooperative threads"):	4738	Libev is very accommodating to coroutines ("cooperative threads"):
4219	libev fully supports nesting calls to its functions from different	4739	libev fully supports nesting calls to its functions from different
4220	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4740	coroutines (e.g. you can call C<ev_run> on the same loop from two
4221	different coroutines, and switch freely between both coroutines running	4741	different coroutines, and switch freely between both coroutines running
4222	the loop, as long as you don't confuse yourself). The only exception is	4742	the loop, as long as you don't confuse yourself). The only exception is
4223	that you must not do this from C<ev_periodic> reschedule callbacks.	4743	that you must not do this from C<ev_periodic> reschedule callbacks.
4224		4744
4225	Care has been taken to ensure that libev does not keep local state inside	4745	Care has been taken to ensure that libev does not keep local state inside
4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4746	C<ev_run>, and other calls do not usually allow for coroutine switches as
4227	they do not call any callbacks.	4747	they do not call any callbacks.
4228		4748
4229	=head2 COMPILER WARNINGS	4749	=head2 COMPILER WARNINGS
4230		4750
4231	Depending on your compiler and compiler settings, you might get no or a	4751	Depending on your compiler and compiler settings, you might get no or a
…		…
4242	maintainable.	4762	maintainable.
4243		4763
4244	And of course, some compiler warnings are just plain stupid, or simply	4764	And of course, some compiler warnings are just plain stupid, or simply
4245	wrong (because they don't actually warn about the condition their message	4765	wrong (because they don't actually warn about the condition their message
4246	seems to warn about). For example, certain older gcc versions had some	4766	seems to warn about). For example, certain older gcc versions had some
4247	warnings that resulted an extreme number of false positives. These have	4767	warnings that resulted in an extreme number of false positives. These have
4248	been fixed, but some people still insist on making code warn-free with	4768	been fixed, but some people still insist on making code warn-free with
4249	such buggy versions.	4769	such buggy versions.
4250		4770
4251	While libev is written to generate as few warnings as possible,	4771	While libev is written to generate as few warnings as possible,
4252	"warn-free" code is not a goal, and it is recommended not to build libev	4772	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4288	I suggest using suppression lists.	4808	I suggest using suppression lists.
4289		4809
4290		4810
4291	=head1 PORTABILITY NOTES	4811	=head1 PORTABILITY NOTES
4292		4812
		4813	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4814
		4815	GNU/Linux is the only common platform that supports 64 bit file/large file
		4816	interfaces but I<disables> them by default.
		4817
		4818	That means that libev compiled in the default environment doesn't support
		4819	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4820
		4821	Unfortunately, many programs try to work around this GNU/Linux issue
		4822	by enabling the large file API, which makes them incompatible with the
		4823	standard libev compiled for their system.
		4824
		4825	Likewise, libev cannot enable the large file API itself as this would
		4826	suddenly make it incompatible to the default compile time environment,
		4827	i.e. all programs not using special compile switches.
		4828
		4829	=head2 OS/X AND DARWIN BUGS
		4830
		4831	The whole thing is a bug if you ask me - basically any system interface
		4832	you touch is broken, whether it is locales, poll, kqueue or even the
		4833	OpenGL drivers.
		4834
		4835	=head3 C<kqueue> is buggy
		4836
		4837	The kqueue syscall is broken in all known versions - most versions support
		4838	only sockets, many support pipes.
		4839
		4840	Libev tries to work around this by not using C<kqueue> by default on this
		4841	rotten platform, but of course you can still ask for it when creating a
		4842	loop - embedding a socket-only kqueue loop into a select-based one is
		4843	probably going to work well.
		4844
		4845	=head3 C<poll> is buggy
		4846
		4847	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4848	implementation by something calling C<kqueue> internally around the 10.5.6
		4849	release, so now C<kqueue> I<and> C<poll> are broken.
		4850
		4851	Libev tries to work around this by not using C<poll> by default on
		4852	this rotten platform, but of course you can still ask for it when creating
		4853	a loop.
		4854
		4855	=head3 C<select> is buggy
		4856
		4857	All that's left is C<select>, and of course Apple found a way to fuck this
		4858	one up as well: On OS/X, C<select> actively limits the number of file
		4859	descriptors you can pass in to 1024 - your program suddenly crashes when
		4860	you use more.
		4861
		4862	There is an undocumented "workaround" for this - defining
		4863	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4864	work on OS/X.
		4865
		4866	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4867
		4868	=head3 C<errno> reentrancy
		4869
		4870	The default compile environment on Solaris is unfortunately so
		4871	thread-unsafe that you can't even use components/libraries compiled
		4872	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4873	defined by default. A valid, if stupid, implementation choice.
		4874
		4875	If you want to use libev in threaded environments you have to make sure
		4876	it's compiled with C<_REENTRANT> defined.
		4877
		4878	=head3 Event port backend
		4879
		4880	The scalable event interface for Solaris is called "event
		4881	ports". Unfortunately, this mechanism is very buggy in all major
		4882	releases. If you run into high CPU usage, your program freezes or you get
		4883	a large number of spurious wakeups, make sure you have all the relevant
		4884	and latest kernel patches applied. No, I don't know which ones, but there
		4885	are multiple ones to apply, and afterwards, event ports actually work
		4886	great.
		4887
		4888	If you can't get it to work, you can try running the program by setting
		4889	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4890	C<select> backends.
		4891
		4892	=head2 AIX POLL BUG
		4893
		4894	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4895	this by trying to avoid the poll backend altogether (i.e. it's not even
		4896	compiled in), which normally isn't a big problem as C<select> works fine
		4897	with large bitsets on AIX, and AIX is dead anyway.
		4898
4293	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4899	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4900
		4901	=head3 General issues
4294		4902
4295	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4903	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4296	requires, and its I/O model is fundamentally incompatible with the POSIX	4904	requires, and its I/O model is fundamentally incompatible with the POSIX
4297	model. Libev still offers limited functionality on this platform in	4905	model. Libev still offers limited functionality on this platform in
4298	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4906	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4299	descriptors. This only applies when using Win32 natively, not when using	4907	descriptors. This only applies when using Win32 natively, not when using
4300	e.g. cygwin.	4908	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4909	as every compielr comes with a slightly differently broken/incompatible
		4910	environment.
4301		4911
4302	Lifting these limitations would basically require the full	4912	Lifting these limitations would basically require the full
4303	re-implementation of the I/O system. If you are into these kinds of	4913	re-implementation of the I/O system. If you are into this kind of thing,
4304	things, then note that glib does exactly that for you in a very portable	4914	then note that glib does exactly that for you in a very portable way (note
4305	way (note also that glib is the slowest event library known to man).	4915	also that glib is the slowest event library known to man).
4306		4916
4307	There is no supported compilation method available on windows except	4917	There is no supported compilation method available on windows except
4308	embedding it into other applications.	4918	embedding it into other applications.
4309		4919
4310	Sensible signal handling is officially unsupported by Microsoft - libev	4920	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4338	you do I<not> compile the F<ev.c> or any other embedded source files!):	4948	you do I<not> compile the F<ev.c> or any other embedded source files!):
4339		4949
4340	#include "evwrap.h"	4950	#include "evwrap.h"
4341	#include "ev.c"	4951	#include "ev.c"
4342		4952
4343	=over 4
4344
4345	=item The winsocket select function	4953	=head3 The winsocket C<select> function
4346		4954
4347	The winsocket C<select> function doesn't follow POSIX in that it	4955	The winsocket C<select> function doesn't follow POSIX in that it
4348	requires socket I<handles> and not socket I<file descriptors> (it is	4956	requires socket I<handles> and not socket I<file descriptors> (it is
4349	also extremely buggy). This makes select very inefficient, and also	4957	also extremely buggy). This makes select very inefficient, and also
4350	requires a mapping from file descriptors to socket handles (the Microsoft	4958	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4359	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4967	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4360		4968
4361	Note that winsockets handling of fd sets is O(n), so you can easily get a	4969	Note that winsockets handling of fd sets is O(n), so you can easily get a
4362	complexity in the O(n²) range when using win32.	4970	complexity in the O(n²) range when using win32.
4363		4971
4364	=item Limited number of file descriptors	4972	=head3 Limited number of file descriptors
4365		4973
4366	Windows has numerous arbitrary (and low) limits on things.	4974	Windows has numerous arbitrary (and low) limits on things.
4367		4975
4368	Early versions of winsocket's select only supported waiting for a maximum	4976	Early versions of winsocket's select only supported waiting for a maximum
4369	of C<64> handles (probably owning to the fact that all windows kernels	4977	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4384	runtime libraries. This might get you to about C<512> or C<2048> sockets	4992	runtime libraries. This might get you to about C<512> or C<2048> sockets
4385	(depending on windows version and/or the phase of the moon). To get more,	4993	(depending on windows version and/or the phase of the moon). To get more,
4386	you need to wrap all I/O functions and provide your own fd management, but	4994	you need to wrap all I/O functions and provide your own fd management, but
4387	the cost of calling select (O(n²)) will likely make this unworkable.	4995	the cost of calling select (O(n²)) will likely make this unworkable.
4388		4996
4389	=back
4390
4391	=head2 PORTABILITY REQUIREMENTS	4997	=head2 PORTABILITY REQUIREMENTS
4392		4998
4393	In addition to a working ISO-C implementation and of course the	4999	In addition to a working ISO-C implementation and of course the
4394	backend-specific APIs, libev relies on a few additional extensions:	5000	backend-specific APIs, libev relies on a few additional extensions:
4395		5001
…		…
4401	Libev assumes not only that all watcher pointers have the same internal	5007	Libev assumes not only that all watcher pointers have the same internal
4402	structure (guaranteed by POSIX but not by ISO C for example), but it also	5008	structure (guaranteed by POSIX but not by ISO C for example), but it also
4403	assumes that the same (machine) code can be used to call any watcher	5009	assumes that the same (machine) code can be used to call any watcher
4404	callback: The watcher callbacks have different type signatures, but libev	5010	callback: The watcher callbacks have different type signatures, but libev
4405	calls them using an C<ev_watcher *> internally.	5011	calls them using an C<ev_watcher *> internally.
		5012
		5013	=item pointer accesses must be thread-atomic
		5014
		5015	Accessing a pointer value must be atomic, it must both be readable and
		5016	writable in one piece - this is the case on all current architectures.
4406		5017
4407	=item C<sig_atomic_t volatile> must be thread-atomic as well	5018	=item C<sig_atomic_t volatile> must be thread-atomic as well
4408		5019
4409	The type C<sig_atomic_t volatile> (or whatever is defined as	5020	The type C<sig_atomic_t volatile> (or whatever is defined as
4410	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5021	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4433	watchers.	5044	watchers.
4434		5045
4435	=item C<double> must hold a time value in seconds with enough accuracy	5046	=item C<double> must hold a time value in seconds with enough accuracy
4436		5047
4437	The type C<double> is used to represent timestamps. It is required to	5048	The type C<double> is used to represent timestamps. It is required to
4438	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5049	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4439	enough for at least into the year 4000. This requirement is fulfilled by	5050	good enough for at least into the year 4000 with millisecond accuracy
		5051	(the design goal for libev). This requirement is overfulfilled by
4440	implementations implementing IEEE 754, which is basically all existing	5052	implementations using IEEE 754, which is basically all existing ones. With
4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5053	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4442	2200.
4443		5054
4444	=back	5055	=back
4445		5056
4446	If you know of other additional requirements drop me a note.	5057	If you know of other additional requirements drop me a note.
4447		5058
…		…
4515	involves iterating over all running async watchers or all signal numbers.	5126	involves iterating over all running async watchers or all signal numbers.
4516		5127
4517	=back	5128	=back
4518		5129
4519		5130
		5131	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5132
		5133	The major version 4 introduced some incompatible changes to the API.
		5134
		5135	At the moment, the C<ev.h> header file provides compatibility definitions
		5136	for all changes, so most programs should still compile. The compatibility
		5137	layer might be removed in later versions of libev, so better update to the
		5138	new API early than late.
		5139
		5140	=over 4
		5141
		5142	=item C<EV_COMPAT3> backwards compatibility mechanism
		5143
		5144	The backward compatibility mechanism can be controlled by
		5145	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5146	section.
		5147
		5148	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5149
		5150	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5151
		5152	ev_loop_destroy (EV_DEFAULT_UC);
		5153	ev_loop_fork (EV_DEFAULT);
		5154
		5155	=item function/symbol renames
		5156
		5157	A number of functions and symbols have been renamed:
		5158
		5159	ev_loop => ev_run
		5160	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5161	EVLOOP_ONESHOT => EVRUN_ONCE
		5162
		5163	ev_unloop => ev_break
		5164	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5165	EVUNLOOP_ONE => EVBREAK_ONE
		5166	EVUNLOOP_ALL => EVBREAK_ALL
		5167
		5168	EV_TIMEOUT => EV_TIMER
		5169
		5170	ev_loop_count => ev_iteration
		5171	ev_loop_depth => ev_depth
		5172	ev_loop_verify => ev_verify
		5173
		5174	Most functions working on C<struct ev_loop> objects don't have an
		5175	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5176	associated constants have been renamed to not collide with the C<struct
		5177	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5178	as all other watcher types. Note that C<ev_loop_fork> is still called
		5179	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5180	typedef.
		5181
		5182	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5183
		5184	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5185	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5186	and work, but the library code will of course be larger.
		5187
		5188	=back
		5189
		5190
4520	=head1 GLOSSARY	5191	=head1 GLOSSARY
4521		5192
4522	=over 4	5193	=over 4
4523		5194
4524	=item active	5195	=item active
4525		5196
4526	A watcher is active as long as it has been started (has been attached to	5197	A watcher is active as long as it has been started and not yet stopped.
4527	an event loop) but not yet stopped (disassociated from the event loop).	5198	See L<WATCHER STATES> for details.
4528		5199
4529	=item application	5200	=item application
4530		5201
4531	In this document, an application is whatever is using libev.	5202	In this document, an application is whatever is using libev.
		5203
		5204	=item backend
		5205
		5206	The part of the code dealing with the operating system interfaces.
4532		5207
4533	=item callback	5208	=item callback
4534		5209
4535	The address of a function that is called when some event has been	5210	The address of a function that is called when some event has been
4536	detected. Callbacks are being passed the event loop, the watcher that	5211	detected. Callbacks are being passed the event loop, the watcher that
4537	received the event, and the actual event bitset.	5212	received the event, and the actual event bitset.
4538		5213
4539	=item callback invocation	5214	=item callback/watcher invocation
4540		5215
4541	The act of calling the callback associated with a watcher.	5216	The act of calling the callback associated with a watcher.
4542		5217
4543	=item event	5218	=item event
4544		5219
4545	A change of state of some external event, such as data now being available	5220	A change of state of some external event, such as data now being available
4546	for reading on a file descriptor, time having passed or simply not having	5221	for reading on a file descriptor, time having passed or simply not having
4547	any other events happening anymore.	5222	any other events happening anymore.
4548		5223
4549	In libev, events are represented as single bits (such as C<EV_READ> or	5224	In libev, events are represented as single bits (such as C<EV_READ> or
4550	C<EV_TIMEOUT>).	5225	C<EV_TIMER>).
4551		5226
4552	=item event library	5227	=item event library
4553		5228
4554	A software package implementing an event model and loop.	5229	A software package implementing an event model and loop.
4555		5230
…		…
4563	The model used to describe how an event loop handles and processes	5238	The model used to describe how an event loop handles and processes
4564	watchers and events.	5239	watchers and events.
4565		5240
4566	=item pending	5241	=item pending
4567		5242
4568	A watcher is pending as soon as the corresponding event has been detected,	5243	A watcher is pending as soon as the corresponding event has been
4569	and stops being pending as soon as the watcher will be invoked or its	5244	detected. See L<WATCHER STATES> for details.
4570	pending status is explicitly cleared by the application.
4571
4572	A watcher can be pending, but not active. Stopping a watcher also clears
4573	its pending status.
4574		5245
4575	=item real time	5246	=item real time
4576		5247
4577	The physical time that is observed. It is apparently strictly monotonic :)	5248	The physical time that is observed. It is apparently strictly monotonic :)
4578		5249
4579	=item wall-clock time	5250	=item wall-clock time
4580		5251
4581	The time and date as shown on clocks. Unlike real time, it can actually	5252	The time and date as shown on clocks. Unlike real time, it can actually
4582	be wrong and jump forwards and backwards, e.g. when the you adjust your	5253	be wrong and jump forwards and backwards, e.g. when you adjust your
4583	clock.	5254	clock.
4584		5255
4585	=item watcher	5256	=item watcher
4586		5257
4587	A data structure that describes interest in certain events. Watchers need	5258	A data structure that describes interest in certain events. Watchers need
4588	to be started (attached to an event loop) before they can receive events.	5259	to be started (attached to an event loop) before they can receive events.
4589		5260
4590	=item watcher invocation
4591
4592	The act of calling the callback associated with a watcher.
4593
4594	=back	5261	=back
4595		5262
4596	=head1 AUTHOR	5263	=head1 AUTHOR
4597		5264
4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5265	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5266	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4599		5267

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