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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// 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_now_update> 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) throw ())
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) throw ())
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 have 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 erroneously 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
…		…
481		567
482	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
483	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
484	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
485	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
486	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
488	cases	574	drops fds silently in similarly hard-to-detect cases
489		575
490	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
491		577
492	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
493	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
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 returns 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 you
		616	absolutely have to know whether an event occurred or not because you have
		617	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
681	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
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 bool 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, and 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
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
		812
718	Please note that an explicit C<ev_unloop> is usually better than	813	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	814	relying on all watchers to be stopped when deciding when a program has
720	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
721	that automatically loops as long as it has to and no longer by virtue	816	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	817	of relying on its watchers stopping correctly, that is truly a thing of
723	beauty.	818	beauty.
724		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	825	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	826	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	827	block your process in case there are no events and will return after one
728	the loop.	828	iteration of the loop. This is sometimes useful to poll and handle new
		829	events while doing lengthy calculations, to keep the program responsive.
729		830
730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	831	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	832	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	833	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	834	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	835	user-registered callback will be called), and will return after one
735	iteration of the loop.	836	iteration of the loop.
736		837
737	This is useful if you are waiting for some external event in conjunction	838	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	839	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	840	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.	841	usually a better approach for this kind of thing.
741		842
742	Here are the gory details of what C<ev_loop> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
743		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
744	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
745	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
746	- If a fork was detected (by any means), queue and call all fork watchers.	852	- If a fork was detected (by any means), queue and call all fork watchers.
747	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
748	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
749	as to not disturb the other process.	856	as to not disturb the other process.
750	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
751	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
752	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
753	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
754	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
755	- Sleep if the I/O and timer collect interval say so.	862	- Sleep if the I/O and timer collect interval say so.
		863	- Increment loop iteration counter.
756	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
757	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	866	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
759	- Queue all expired timers.	867	- Queue all expired timers.
760	- Queue all expired periodics.	868	- Queue all expired periodics.
761	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
762	- Queue all check watchers.	870	- Queue all check watchers.
763	- Call all queued watchers in reverse order (i.e. check watchers first).	871	- 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	872	Signals and child watchers are implemented as I/O watchers, and will
765	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
766	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	874	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
767	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
768	continue with step *.	876	continue with step LOOP.
		877	FINISH:
		878	- Reset the ev_break status iff it was EVBREAK_ONE.
		879	- Decrement the loop depth.
		880	- Return.
769		881
770	Example: Queue some jobs and then loop until no events are outstanding	882	Example: Queue some jobs and then loop until no events are outstanding
771	anymore.	883	anymore.
772		884
773	... queue jobs here, make sure they register event watchers as long	885	... 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..)	886	... as they still have work to do (even an idle watcher will do..)
775	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
776	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
777		889
778	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
779		891
780	Can be used to make a call to C<ev_loop> return early (but only after it	892	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	893	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	894	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.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
784		896
785	This "unloop state" will be cleared when entering C<ev_loop> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
786		898
787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
788		901
789	=item ev_ref (loop)	902	=item ev_ref (loop)
790		903
791	=item ev_unref (loop)	904	=item ev_unref (loop)
792		905
793	Ref/unref can be used to add or remove a reference count on the event	906	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	907	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.	908	count is nonzero, C<ev_run> will not return on its own.
796		909
797	If you have a watcher you never unregister that should not keep C<ev_loop>	910	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	911	unregister, but that nevertheless should not keep C<ev_run> from
		912	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
799	stopping it.	913	before stopping it.
800		914
801	As an example, libev itself uses this for its internal signal pipe: It	915	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	916	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	917	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	918	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	919	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	920	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	921	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>	922	(e.g. non-repeating timers) in which case you have to C<ev_ref>
809	in the callback).	923	in the callback).
810		924
811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	925	Example: Create a signal watcher, but keep it from keeping C<ev_run>
812	running when nothing else is active.	926	running when nothing else is active.
813		927
814	ev_signal exitsig;	928	ev_signal exitsig;
815	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
816	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
817	evf_unref (loop);	931	ev_unref (loop);
818		932
819	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
820		934
821	ev_ref (loop);	935	ev_ref (loop);
822	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
842	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
843		957
844	By setting a higher I<io collect interval> you allow libev to spend more	958	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,	959	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	960	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	961	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	962	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	963	sleep time ensures that libev will not poll for I/O events more often then
850	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
851		966
852	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
853	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
854	latency/jitter/inexactness (the watcher callback will be called	969	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	970	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>,	976	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	977	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	978	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	979	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,	980	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).	981	then you can't do more than 100 transactions per second).
867		982
868	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
869	saving power, as the program will "bundle" timer callback invocations that	984	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	985	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	986	times the process sleeps and wakes up again. Another useful technique to
…		…
879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
880		995
881	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
882		997
883	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
884	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
885	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
886		1005
887	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
888		1007
889	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
890	are pending.	1009	are pending.
891		1010
892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1011	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
893		1012
894	This overrides the invoke pending functionality of the loop: Instead of	1013	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	1014	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	1015	this callback instead. This is useful, for example, when you want to
897	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
898		1017
899	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
900	callback.	1019	callback.
901		1020
902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
903		1022
904	Sometimes you want to share the same loop between multiple threads. This	1023	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	1024	can be done relatively simply by putting mutex_lock/unlock calls around
906	each call to a libev function.	1025	each call to a libev function.
907		1026
908	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1027	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	1028	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>	1029	loop via C<ev_break> and C<ev_async_send>, another way is to set these
911	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
912		1031
913	When set, then C<release> will be called just before the thread is	1032	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	1033	suspended waiting for new events, and C<acquire> is called just
915	afterwards.	1034	afterwards.
916		1035
…		…
919		1038
920	While event loop modifications are allowed between invocations of	1039	While event loop modifications are allowed between invocations of
921	C<release> and C<acquire> (that's their only purpose after all), no	1040	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	1041	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	1042	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	1043	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.	1044	to take note of any changes you made.
926		1045
927	In theory, threads executing C<ev_loop> will be async-cancel safe between	1046	In theory, threads executing C<ev_run> will be async-cancel safe between
928	invocations of C<release> and C<acquire>.	1047	invocations of C<release> and C<acquire>.
929		1048
930	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
931	document.	1050	document.
932		1051
933	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
934		1053
935	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
936		1055
937	Set and retrieve a single C<void *> associated with a loop. When	1056	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	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
939	C<0.>	1058	C<0>.
940		1059
941	These two functions can be used to associate arbitrary data with a loop,	1060	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	1061	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	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
944	any other purpose as well.	1063	any other purpose as well.
945		1064
946	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
947		1066
948	This function only does something when C<EV_VERIFY> support has been	1067	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	1068	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	1069	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	1070	is found to be inconsistent, it will print an error message to standard
…		…
962		1081
963	In the following description, uppercase C<TYPE> in names stands for the	1082	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	1083	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.	1084	watchers and C<ev_io_start> for I/O watchers.
966		1085
967	A watcher is a structure that you create and register to record your	1086	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	1087	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:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
970		1090
971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
972	{	1092	{
973	ev_io_stop (w);	1093	ev_io_stop (w);
974	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
975	}	1095	}
976		1096
977	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
978		1098
979	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
980		1100
981	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
983	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
984		1104
985	ev_loop (loop, 0);	1105	ev_run (loop, 0);
986		1106
987	As you can see, you are responsible for allocating the memory for your	1107	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	1108	watcher structures (and it is I<usually> a bad idea to do this on the
989	stack).	1109	stack).
990		1110
991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	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).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
993		1113
994	Each watcher structure must be initialised by a call to C<ev_init	1114	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	1115	*, 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	1116	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	1117	time the event loop detects that the file descriptor given is readable
998	is readable and/or writable).	1118	and/or writable).
999		1119
1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	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	1121	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<<	1122	is also a macro to combine initialisation and setting in one call: C<<
1003	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1026	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
1027		1147
1028	The file descriptor in the C<ev_io> watcher has become readable and/or	1148	The file descriptor in the C<ev_io> watcher has become readable and/or
1029	writable.	1149	writable.
1030		1150
1031	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
1032		1152
1033	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
1034		1154
1035	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
1036		1156
…		…
1054		1174
1055	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1056		1176
1057	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1058		1178
1059	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1060	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1061	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1062	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1063	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1064	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1065	C<ev_loop> from blocking).	1190	blocking).
1066		1191
1067	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1068		1193
1069	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1070		1195
1071	=item C<EV_FORK>	1196	=item C<EV_FORK>
1072		1197
1073	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1074	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1075		1204
1076	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1077		1206
1078	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1079		1208
…		…
1126		1255
1127	ev_io w;	1256	ev_io w;
1128	ev_init (&w, my_cb);	1257	ev_init (&w, my_cb);
1129	ev_io_set (&w, STDIN_FILENO, EV_READ);	1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
1130		1259
1131	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1132		1261
1133	This macro initialises the type-specific parts of a watcher. You need to	1262	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	1263	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	1264	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	1265	macro on a watcher that is active (it can be pending, however, which is a
…		…
1149		1278
1150	Example: Initialise and set an C<ev_io> watcher in one step.	1279	Example: Initialise and set an C<ev_io> watcher in one step.
1151		1280
1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1153		1282
1154	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1155		1284
1156	Starts (activates) the given watcher. Only active watchers will receive	1285	Starts (activates) the given watcher. Only active watchers will receive
1157	events. If the watcher is already active nothing will happen.	1286	events. If the watcher is already active nothing will happen.
1158		1287
1159	Example: Start the C<ev_io> watcher that is being abused as example in this	1288	Example: Start the C<ev_io> watcher that is being abused as example in this
1160	whole section.	1289	whole section.
1161		1290
1162	ev_io_start (EV_DEFAULT_UC, &w);	1291	ev_io_start (EV_DEFAULT_UC, &w);
1163		1292
1164	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1165		1294
1166	Stops the given watcher if active, and clears the pending status (whether	1295	Stops the given watcher if active, and clears the pending status (whether
1167	the watcher was active or not).	1296	the watcher was active or not).
1168		1297
1169	It is possible that stopped watchers are pending - for example,	1298	It is possible that stopped watchers are pending - for example,
…		…
1189		1318
1190	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1191		1320
1192	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1193		1322
1194	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1195		1324
1196	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1197	(modulo threads).	1326	(modulo threads).
1198		1327
1199	=item ev_set_priority (ev_TYPE *watcher, priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
1200		1329
1201	=item int ev_priority (ev_TYPE *watcher)	1330	=item int ev_priority (ev_TYPE *watcher)
1202		1331
1203	Set and query the priority of the watcher. The priority is a small	1332	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>	1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1217	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
1218		1347
1219	The default priority used by watchers when no priority has been set is	1348	The default priority used by watchers when no priority has been set is
1220	always C<0>, which is supposed to not be too high and not be too low :).	1349	always C<0>, which is supposed to not be too high and not be too low :).
1221		1350
1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1223	priorities.	1352	priorities.
1224		1353
1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1226		1355
1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1236	watcher isn't pending it does nothing and returns C<0>.	1365	watcher isn't pending it does nothing and returns C<0>.
1237		1366
1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1367	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.	1368	callback to be invoked, which can be accomplished with this function.
1240		1369
1241	=item ev_feed_event (struct ev_loop *, watcher *, int revents)	1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1242		1371
1243	Feeds the given event set into the event loop, as if the specified event	1372	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	1373	had happened for the specified watcher (which must be a pointer to an
1245	initialised but not necessarily started event watcher). Obviously you must	1374	initialised but not necessarily started event watcher). Obviously you must
1246	not free the watcher as long as it has pending events.	1375	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	1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1253	functions that do not need a watcher.	1382	functions that do not need a watcher.
1254		1383
1255	=back	1384	=back
1256		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1257		1388
1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1259		1390
1260	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1261	and read at any time: libev will completely ignore it. This can be used	1392	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	1393	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	1394	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		1395
1267	struct my_io	1396	=over 4
1268	{
1269	ev_io io;
1270	int otherfd;
1271	void *somedata;
1272	struct whatever *mostinteresting;
1273	};
1274		1397
1275	...	1398	=item initialiased
1276	struct my_io w;
1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1278		1399
1279	And since your callback will be called with a pointer to the watcher, you	1400	Before a watcher can be registered with the event loop it has to be
1280	can cast it back to your own type:	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1281		1403
1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1404	In this state it is simply some block of memory that is suitable for
1283	{	1405	use in an event loop. It can be moved around, freed, reused etc. at
1284	struct my_io *w = (struct my_io *)w_;	1406	will - as long as you either keep the memory contents intact, or call
1285	...	1407	C<ev_TYPE_init> again.
1286	}
1287		1408
1288	More interesting and less C-conformant ways of casting your callback type	1409	=item started/running/active
1289	instead have been omitted.
1290		1410
1291	Another common scenario is to use some data structure with multiple	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1292	embedded watchers:	1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
1293		1416
1294	struct my_biggy	1417	=item pending
1295	{
1296	int some_data;
1297	ev_timer t1;
1298	ev_timer t2;
1299	}
1300		1418
1301	In this case getting the pointer to C<my_biggy> is a bit more	1419	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	1420	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	1421	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	1422	about to be invoked, so it is not normally pending inside the watcher
1305	programmers):	1423	callback.
1306		1424
1307	#include <stddef.h>	1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
1308		1431
1309	static void	1432	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)	1433	via C<ev_feed_event>), in which case it becomes pending without being
1311	{	1434	active.
1312	struct my_biggy big = (struct my_biggy *)
1313	(((char *)w) - offsetof (struct my_biggy, t1));
1314	}
1315		1435
1316	static void	1436	=item stopped
1317	t2_cb (EV_P_ ev_timer *w, int revents)	1437
1318	{	1438	A watcher can be stopped implicitly by libev (in which case it might still
1319	struct my_biggy big = (struct my_biggy *)	1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1320	(((char *)w) - offsetof (struct my_biggy, t2));	1440	latter will clear any pending state the watcher might be in, regardless
1321	}	1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
1322		1450
1323	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1324		1452
1325	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1326	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1369		1497
1370	For example, to emulate how many other event libraries handle priorities,	1498	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	1499	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	1500	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	1501	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	1502	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	1503	the lock-out case is known to be rare (which in turn is rare :), this is
1376	workable.	1504	workable.
1377		1505
1378	Usually, however, the lock-out model implemented that way will perform	1506	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,	1507	miserably under the type of load it was designed to handle. In that case,
…		…
1393	{	1521	{
1394	// stop the I/O watcher, we received the event, but	1522	// stop the I/O watcher, we received the event, but
1395	// are not yet ready to handle it.	1523	// are not yet ready to handle it.
1396	ev_io_stop (EV_A_ w);	1524	ev_io_stop (EV_A_ w);
1397		1525
1398	// start the idle watcher to ahndle the actual event.	1526	// start the idle watcher to handle the actual event.
1399	// it will not be executed as long as other watchers	1527	// it will not be executed as long as other watchers
1400	// with the default priority are receiving events.	1528	// with the default priority are receiving events.
1401	ev_idle_start (EV_A_ &idle);	1529	ev_idle_start (EV_A_ &idle);
1402	}	1530	}
1403		1531
…		…
1453	In general you can register as many read and/or write event watchers per	1581	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	1582	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	1583	descriptors to non-blocking mode is also usually a good idea (but not
1456	required if you know what you are doing).	1584	required if you know what you are doing).
1457		1585
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	1586	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	1587	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	1588	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	1589	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	1590	with a relatively standard program structure. Thus it is best to always
1469	this situation even with a relatively standard program structure. Thus	1591	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.	1592	preferable to a program hanging until some data arrives.
1472		1593
1473	If you cannot run the fd in non-blocking mode (for example you should	1594	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	1595	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	1596	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	1597	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	1598	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	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1479	indefinitely.	1600	indefinitely.
1480		1601
1481	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1482		1603
…		…
1510		1631
1511	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1512	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1513	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1514		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1515	=head3 The special problem of fork	1669	=head3 The special problem of fork
1516		1670
1517	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	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	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1519	it in the child.	1673	it in the child if you want to continue to use it in the child.
1520		1674
1521	To support fork in your programs, you either have to call	1675	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,	1676	()> 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	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1524	C<EVBACKEND_POLL>.
1525		1678
1526	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1527		1680
1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	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	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1532		1685
1533	So when you encounter spurious, unexplained daemon exits, make sure you	1686	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	1687	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).	1688	somewhere, as that would have given you a big clue).
1536		1689
		1690	=head3 The special problem of accept()ing when you can't
		1691
		1692	Many implementations of the POSIX C<accept> function (for example,
		1693	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1694	connection from the pending queue in all error cases.
		1695
		1696	For example, larger servers often run out of file descriptors (because
		1697	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1698	rejecting the connection, leading to libev signalling readiness on
		1699	the next iteration again (the connection still exists after all), and
		1700	typically causing the program to loop at 100% CPU usage.
		1701
		1702	Unfortunately, the set of errors that cause this issue differs between
		1703	operating systems, there is usually little the app can do to remedy the
		1704	situation, and no known thread-safe method of removing the connection to
		1705	cope with overload is known (to me).
		1706
		1707	One of the easiest ways to handle this situation is to just ignore it
		1708	- when the program encounters an overload, it will just loop until the
		1709	situation is over. While this is a form of busy waiting, no OS offers an
		1710	event-based way to handle this situation, so it's the best one can do.
		1711
		1712	A better way to handle the situation is to log any errors other than
		1713	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1714	messages, and continue as usual, which at least gives the user an idea of
		1715	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1716	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1717	usage.
		1718
		1719	If your program is single-threaded, then you could also keep a dummy file
		1720	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1721	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1722	close that fd, and create a new dummy fd. This will gracefully refuse
		1723	clients under typical overload conditions.
		1724
		1725	The last way to handle it is to simply log the error and C<exit>, as
		1726	is often done with C<malloc> failures, but this results in an easy
		1727	opportunity for a DoS attack.
1537		1728
1538	=head3 Watcher-Specific Functions	1729	=head3 Watcher-Specific Functions
1539		1730
1540	=over 4	1731	=over 4
1541		1732
…		…
1573	...	1764	...
1574	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1575	ev_io stdin_readable;	1766	ev_io stdin_readable;
1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1767	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1577	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1578	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1579		1770
1580		1771
1581	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1582		1773
1583	Timer watchers are simple relative timers that generate an event after a	1774	Timer watchers are simple relative timers that generate an event after a
…		…
1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1590	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1591		1782
1592	The callback is guaranteed to be invoked only I<after> its timeout has	1783	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	1784	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	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1595	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1596	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1597	no longer true when a callback calls C<ev_loop> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1598		1790
1599	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1600		1792
1601	Many real-world problems involve some kind of timeout, usually for error	1793	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,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1677		1869
1678	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1679	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1680	within the callback:	1872	within the callback:
1681		1873
		1874	ev_tstamp timeout = 60.;
1682	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1683		1877
1684	static void	1878	static void
1685	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1686	{	1880	{
1687	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1688	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1689		1883
1690	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1691	if (timeout < now)	1885	if (after < 0.)
1692	{	1886	{
1693	// timeout occured, take action	1887	// timeout occurred, take action
1694	}	1888	}
1695	else	1889	else
1696	{	1890	{
1697	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1698	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1699	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1700	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1701	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1702	}	1897	}
1703	}	1898	}
1704		1899
1705	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1706	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1707	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1708	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1709	re-schedule the timer to fire at that future time, to see if maybe we have
1710	a timeout then.
1711		1904
1712	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1713	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1714		1914
1715	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1716	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1717	libev to change the timeout.	1917	libev to change the timeout.
1718		1918
1719	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1720	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1721	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1722		1923
		1924	last_activity = ev_now (EV_A);
1723	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1724	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1725	callback (loop, timer, EV_TIMEOUT);
1726		1927
1727	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1728	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1729		1930
		1931	if (activity detected)
1730	last_actiivty = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1731		1941
1732	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1733	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1734
1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
1736	callback :) - just change the timeout and invoke the callback, which will
1737	fix things for you.
1738		1944
1739	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1740		1946
1741	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1742	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1770	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1771	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1772	overkill :)	1978	overkill :)
1773		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1774	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1775		2018
1776	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1777	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1778	time only before and after C<ev_loop> collects new events, which causes a	2021	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	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1780	lots of events in one iteration.	2023	lots of events in one iteration.
1781		2024
1782	The relative timeouts are calculated relative to the C<ev_now ()>	2025	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	2026	time. This is usually the right thing as this timestamp refers to the time
…		…
1788	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1789		2032
1790	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1792	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
1793		2069
1794	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1795		2071
1796	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
1797	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1841	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1842	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1843		2119
1844	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1845		2121
1846	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1847	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1848		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1849	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1850		2132
1851	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1852		2135
1853	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1854	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1855		2138
		2139	=back
		2140
1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1857	usage example.	2142	usage example.
1858		2143
1859	=item ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1860		2145
1861	Returns the remaining time until a timer fires. If the timer is active,	2146	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	2147	then this time is relative to the current event loop time, otherwise it's
1863	the timeout value currently configured.	2148	the timeout value currently configured.
1864		2149
1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2150	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>	2151	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	2152	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,	2153	roughly C<7> (likely slightly less as callback invocation takes some time,
1869	too), and so on.	2154	too), and so on.
1870		2155
1871	=item ev_tstamp repeat [read-write]	2156	=item ev_tstamp repeat [read-write]
…		…
1900	}	2185	}
1901		2186
1902	ev_timer mytimer;	2187	ev_timer mytimer;
1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2188	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1904	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1905	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1906		2191
1907	// and in some piece of code that gets executed on any "activity":	2192	// and in some piece of code that gets executed on any "activity":
1908	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1909	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1910		2195
…		…
1936		2221
1937	As with timers, the callback is guaranteed to be invoked only when the	2222	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	2223	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	2224	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	2225	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).	2226	(but this is no longer true when a callback calls C<ev_run> recursively).
1942		2227
1943	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1944		2229
1945	=over 4	2230	=over 4
1946		2231
…		…
1981		2266
1982	Another way to think about it (for the mathematically inclined) is that	2267	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	2268	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.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
1985		2270
1986	For numerical stability it is preferable that the C<offset> value is near	2271	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	2272	interval value should be higher than C<1/8192> (which is around 100
1988	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
1989		2277
1990	Note also that there is an upper limit to how often a timer can fire (CPU	2278	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	2279	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	2280	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).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2074	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
2075	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
2076	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
2077		2365
2078	static void	2366	static void
2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2080	{	2368	{
2081	... its now a full hour (UTC, or TAI or whatever your clock follows)	2369	... its now a full hour (UTC, or TAI or whatever your clock follows)
2082	}	2370	}
2083		2371
2084	ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
…		…
2107		2395
2108	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2109		2397
2110	Signal watchers will trigger an event when the process receives a specific	2398	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	2399	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	2400	will try its best to deliver signals synchronously, i.e. as part of the
2113	normal event processing, like any other event.	2401	normal event processing, like any other event.
2114		2402
2115	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2116	C<sigaction> as you would do without libev and forget about sharing	2404	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	2405	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	2419	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	2420	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	2421	interrupted by signals you can block all signals in an C<ev_check> watcher
2134	and unblock them in an C<ev_prepare> watcher.	2422	and unblock them in an C<ev_prepare> watcher.
2135		2423
2136	=head3 The special problem of inheritance over execve	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2137		2425
2138	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2139	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(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,	2428	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.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2142		2431
2143	While this does not matter for the signal disposition (libev never	2432	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	2433	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	2434	C<execve>), this matters for the signal mask: many programs do not expect
2146	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2151		2440
2152	The simplest way to ensure that the signal mask is reset in the child is	2441	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	2442	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.	2443	catch fork calls done by libraries (such as the libc) as well.
2155		2444
2156	In current versions of libev, you can also ensure that the signal mask is	2445	In current versions of libev, the signal will not be blocked indefinitely
2157	not blocking any signals (except temporarily, so thread users watch out)	2446	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	2447	the window of opportunity for problems, it will not go away, as libev
2159	is not guaranteed for future versions, however.	2448	I<has> to modify the signal mask, at least temporarily.
		2449
		2450	So I can't stress this enough: I<If you do not reset your signal mask when
		2451	you expect it to be empty, you have a race condition in your code>. This
		2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
2160		2467
2161	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2162		2469
2163	=over 4	2470	=over 4
2164		2471
…		…
2180	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
2181		2488
2182	static void	2489	static void
2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2184	{	2491	{
2185	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
2186	}	2493	}
2187		2494
2188	ev_signal signal_watcher;	2495	ev_signal signal_watcher;
2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2190	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
…		…
2540	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2541	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2542	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2543	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2544		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2864	example.
		2865
2545	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2546		2867
2547	=over 4	2868	=over 4
2548		2869
2549	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2560	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2561		2882
2562	static void	2883	static void
2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2564	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2565	free (w);	2890	free (w);
		2891
2566	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2567	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2568	}	2894	}
2569		2895
2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2572	ev_idle_start (loop, idle_watcher);	2898	ev_idle_start (loop, idle_watcher);
2573		2899
2574		2900
2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2576		2902
2577	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2578	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2579	afterwards.	2905	afterwards.
2580		2906
2581	You I<must not> call C<ev_loop> or similar functions that enter	2907	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>	2908	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	2909	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	2910	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,	2911	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	2912	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2610	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2611	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2612	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2613	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2614		2940
2615	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2616	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2617	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2618		2945
2619	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2620	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2621	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2622	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2623	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2624	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2625	others).	2952	others).
		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2626		2973
2627	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2628		2975
2629	=over 4	2976	=over 4
2630		2977
…		…
2754		3101
2755	if (timeout >= 0)	3102	if (timeout >= 0)
2756	// create/start timer	3103	// create/start timer
2757		3104
2758	// poll	3105	// poll
2759	ev_loop (EV_A_ 0);	3106	ev_run (EV_A_ 0);
2760		3107
2761	// stop timer again	3108	// stop timer again
2762	if (timeout >= 0)	3109	if (timeout >= 0)
2763	ev_timer_stop (EV_A_ &to);	3110	ev_timer_stop (EV_A_ &to);
2764		3111
…		…
2842	if you do not want that, you need to temporarily stop the embed watcher).	3189	if you do not want that, you need to temporarily stop the embed watcher).
2843		3190
2844	=item ev_embed_sweep (loop, ev_embed *)	3191	=item ev_embed_sweep (loop, ev_embed *)
2845		3192
2846	Make a single, non-blocking sweep over the embedded loop. This works	3193	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	3194	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2848	appropriate way for embedded loops.	3195	appropriate way for embedded loops.
2849		3196
2850	=item struct ev_loop *other [read-only]	3197	=item struct ev_loop *other [read-only]
2851		3198
2852	The embedded event loop.	3199	The embedded event loop.
…		…
2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3259	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2913	handlers will be invoked, too, of course.	3260	handlers will be invoked, too, of course.
2914		3261
2915	=head3 The special problem of life after fork - how is it possible?	3262	=head3 The special problem of life after fork - how is it possible?
2916		3263
2917	Most uses of C<fork()> consist of forking, then some simple calls to ste	3264	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	3265	up/change the process environment, followed by a call to C<exec()>. This
2919	sequence should be handled by libev without any problems.	3266	sequence should be handled by libev without any problems.
2920		3267
2921	This changes when the application actually wants to do event handling	3268	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	3269	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	3285	disadvantage of having to use multiple event loops (which do not support
2939	signal watchers).	3286	signal watchers).
2940		3287
2941	When this is not possible, or you want to use the default loop for	3288	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	3289	other reasons, then in the process that wants to start "fresh", call
2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3290	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	3291	Destroying the default loop will "orphan" (not stop) all registered
2945	have to be careful not to execute code that modifies those watchers. Note	3292	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.	3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
2947		3295
2948	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
2949		3297
2950	=over 4	3298	=over 4
2951		3299
2952	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
2953		3301
2954	Initialises and configures the fork watcher - it has no parameters of any	3302	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,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2956	believe me.	3304	really.
2957		3305
2958	=back	3306	=back
2959		3307
2960		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
2961	=head2 C<ev_async> - how to wake up another event loop	3349	=head2 C<ev_async> - how to wake up an event loop
2962		3350
2963	In general, you cannot use an C<ev_loop> from multiple threads or other	3351	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	3352	asynchronous sources such as signal handlers (as opposed to multiple event
2965	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
2966		3354
2967	Sometimes, however, you need to wake up another event loop you do not	3355	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	3356	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	3357	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	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
2971	safe.
2972		3359
2973	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
2974	too, are asynchronous in nature, and signals, too, will be compressed	3361	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	3362	(i.e. the number of callback invocations may be less than the number of
2976	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2977		3364	of "global async watchers" by using a watcher on an otherwise unused
2978	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2979	just the default loop.	3366	even without knowing which loop owns the signal.
2980		3367
2981	=head3 Queueing	3368	=head3 Queueing
2982		3369
2983	C<ev_async> does not support queueing of data in any way. The reason	3370	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	3371	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	3372	multiple-writer-single-reader queue that works in all cases and doesn't
2986	need elaborate support such as pthreads.	3373	need elaborate support such as pthreads or unportable memory access
		3374	semantics.
2987		3375
2988	That means that if you want to queue data, you have to provide your own	3376	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	3377	queue. But at least I can tell you how to implement locking around your
2990	queue:	3378	queue:
2991		3379
…		…
3075	trust me.	3463	trust me.
3076		3464
3077	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3078		3466
3079	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	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	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3081	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	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	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3083	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3084		3474
3085	Note that, as with other watchers in libev, multiple events might get	3475	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	3476	compressed into a single callback invocation (another way to look at
3087	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3088	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3089		3479
3090	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3091	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3092	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3093		3486
3094	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3095		3488
3096	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3097	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3130		3523
3131	If C<timeout> is less than 0, then no timeout watcher will be	3524	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	3525	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3133	repeat = 0) will be started. C<0> is a valid timeout.	3526	repeat = 0) will be started. C<0> is a valid timeout.
3134		3527
3135	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3528	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	3529	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>	3530	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>	3531	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	3532	a timeout and an io event at the same time - you probably should give io
3140	events precedence.	3533	events precedence.
3141		3534
3142	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3535	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3143		3536
3144	static void stdin_ready (int revents, void *arg)	3537	static void stdin_ready (int revents, void *arg)
3145	{	3538	{
3146	if (revents & EV_READ)	3539	if (revents & EV_READ)
3147	/* stdin might have data for us, joy! */;	3540	/* stdin might have data for us, joy! */;
3148	else if (revents & EV_TIMEOUT)	3541	else if (revents & EV_TIMER)
3149	/* doh, nothing entered */;	3542	/* doh, nothing entered */;
3150	}	3543	}
3151		3544
3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3153		3546
3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3155		3548
3156	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3157	the given events it.	3550	the given events.
3158		3551
3159	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3160		3553
3161	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3162	loop!).	3555	which is async-safe.
3163		3556
3164	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, C<ev_break> will not work alone.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3165		3908
3166		3909
3167	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3168		3911
3169	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3170	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3171		3914
3172	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3173		3921
3174	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3175		3923
3176	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3177	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3183	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3184	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3185	is an ev_pri field.	3933	is an ev_pri field.
3186		3934
3187	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3188	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3189		3937
3190	=item * Other members are not supported.	3938	=item * Other members are not supported.
3191		3939
3192	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3193	to use the libev header file and library.	3941	to use the libev header file and library.
3194		3942
3195	=back	3943	=back
3196		3944
3197	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3198		3979
3199	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3200	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3201	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3202		3983
…		…
3212	Care has been taken to keep the overhead low. The only data member the C++	3993	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	3994	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	3995	that the watcher is associated with (or no additional members at all if
3215	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3216		3997
3217	Currently, functions, and static and non-static member functions can be	3998	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	3999	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	4000	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	4001	you need support for other types of functors please contact the author
3221	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3222		4007
3223	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3224		4009
3225	=over 4	4010	=over 4
3226		4011
…		…
3236	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3237		4022
3238	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3239	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3240	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3241	defines by many implementations.	4026	defined by many implementations.
3242		4027
3243	All of those classes have these methods:	4028	All of those classes have these methods:
3244		4029
3245	=over 4	4030	=over 4
3246		4031
3247	=item ev::TYPE::TYPE ()	4032	=item ev::TYPE::TYPE ()
3248		4033
3249	=item ev::TYPE::TYPE (struct ev_loop *)	4034	=item ev::TYPE::TYPE (loop)
3250		4035
3251	=item ev::TYPE::~TYPE	4036	=item ev::TYPE::~TYPE
3252		4037
3253	The constructor (optionally) takes an event loop to associate the watcher	4038	The constructor (optionally) takes an event loop to associate the watcher
3254	with. If it is omitted, it will use C<EV_DEFAULT>.	4039	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3287	myclass obj;	4072	myclass obj;
3288	ev::io iow;	4073	ev::io iow;
3289	iow.set <myclass, &myclass::io_cb> (&obj);	4074	iow.set <myclass, &myclass::io_cb> (&obj);
3290		4075
3291	=item w->set (object *)	4076	=item w->set (object *)
3292
3293	This is an B<experimental> feature that might go away in a future version.
3294		4077
3295	This is a variation of a method callback - leaving out the method to call	4078	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	4079	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	4080	functor objects without having to manually specify the C<operator ()> all
3298	the time. Incidentally, you can then also leave out the template argument	4081	the time. Incidentally, you can then also leave out the template argument
…		…
3331	Example: Use a plain function as callback.	4114	Example: Use a plain function as callback.
3332		4115
3333	static void io_cb (ev::io &w, int revents) { }	4116	static void io_cb (ev::io &w, int revents) { }
3334	iow.set <io_cb> ();	4117	iow.set <io_cb> ();
3335		4118
3336	=item w->set (struct ev_loop *)	4119	=item w->set (loop)
3337		4120
3338	Associates a different C<struct ev_loop> with this watcher. You can only	4121	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).	4122	do this when the watcher is inactive (and not pending either).
3340		4123
3341	=item w->set ([arguments])	4124	=item w->set ([arguments])
3342		4125
3343	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4126	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4127	with the same arguments. Either this method or a suitable start method
3344	called at least once. Unlike the C counterpart, an active watcher gets	4128	must be called at least once. Unlike the C counterpart, an active watcher
3345	automatically stopped and restarted when reconfiguring it with this	4129	gets automatically stopped and restarted when reconfiguring it with this
3346	method.	4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3347		4134
3348	=item w->start ()	4135	=item w->start ()
3349		4136
3350	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3351	constructor already stores the event loop.	4138	constructor already stores the event loop.
3352		4139
		4140	=item w->start ([arguments])
		4141
		4142	Instead of calling C<set> and C<start> methods separately, it is often
		4143	convenient to wrap them in one call. Uses the same type of arguments as
		4144	the configure C<set> method of the watcher.
		4145
3353	=item w->stop ()	4146	=item w->stop ()
3354		4147
3355	Stops the watcher if it is active. Again, no C<loop> argument.	4148	Stops the watcher if it is active. Again, no C<loop> argument.
3356		4149
3357	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4150	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3369		4162
3370	=back	4163	=back
3371		4164
3372	=back	4165	=back
3373		4166
3374	Example: Define a class with an IO and idle watcher, start one of them in	4167	Example: Define a class with two I/O and idle watchers, start the I/O
3375	the constructor.	4168	watchers in the constructor.
3376		4169
3377	class myclass	4170	class myclass
3378	{	4171	{
3379	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
		4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3380	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3381		4175
3382	myclass (int fd)	4176	myclass (int fd)
3383	{	4177	{
3384	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
		4179	io2 .set <myclass, &myclass::io2_cb > (this);
3385	idle.set <myclass, &myclass::idle_cb> (this);	4180	idle.set <myclass, &myclass::idle_cb> (this);
3386		4181
3387	io.start (fd, ev::READ);	4182	io.set (fd, ev::WRITE); // configure the watcher
		4183	io.start (); // start it whenever convenient
		4184
		4185	io2.start (fd, ev::READ); // set + start in one call
3388	}	4186	}
3389	};	4187	};
3390		4188
3391		4189
3392	=head1 OTHER LANGUAGE BINDINGS	4190	=head1 OTHER LANGUAGE BINDINGS
…		…
3431	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3432		4230
3433	=item D	4231	=item D
3434		4232
3435	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3436	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3437		4235
3438	=item Ocaml	4236	=item Ocaml
3439		4237
3440	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3442		4240
3443	=item Lua	4241	=item Lua
3444		4242
3445	Brian Maher has written a partial interface to libev	4243	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	4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3447	L<http://github.com/brimworks/lua-ev>.	4245	L<http://github.com/brimworks/lua-ev>.
		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
3448		4254
3449	=back	4255	=back
3450		4256
3451		4257
3452	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
…		…
3466	loop argument"). The C<EV_A> form is used when this is the sole argument,	4272	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:	4273	C<EV_A_> is used when other arguments are following. Example:
3468		4274
3469	ev_unref (EV_A);	4275	ev_unref (EV_A);
3470	ev_timer_add (EV_A_ watcher);	4276	ev_timer_add (EV_A_ watcher);
3471	ev_loop (EV_A_ 0);	4277	ev_run (EV_A_ 0);
3472		4278
3473	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4279	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3474	which is often provided by the following macro.	4280	which is often provided by the following macro.
3475		4281
3476	=item C<EV_P>, C<EV_P_>	4282	=item C<EV_P>, C<EV_P_>
…		…
3489	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3490		4296
3491	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3492		4298
3493	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3494	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3495		4305
3496	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3497		4307
3498	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3499	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3516	}	4326	}
3517		4327
3518	ev_check check;	4328	ev_check check;
3519	ev_check_init (&check, check_cb);	4329	ev_check_init (&check, check_cb);
3520	ev_check_start (EV_DEFAULT_ &check);	4330	ev_check_start (EV_DEFAULT_ &check);
3521	ev_loop (EV_DEFAULT_ 0);	4331	ev_run (EV_DEFAULT_ 0);
3522		4332
3523	=head1 EMBEDDING	4333	=head1 EMBEDDING
3524		4334
3525	Libev can (and often is) directly embedded into host	4335	Libev can (and often is) directly embedded into host
3526	applications. Examples of applications that embed it include the Deliantra	4336	applications. Examples of applications that embed it include the Deliantra
…		…
3606	libev.m4	4416	libev.m4
3607		4417
3608	=head2 PREPROCESSOR SYMBOLS/MACROS	4418	=head2 PREPROCESSOR SYMBOLS/MACROS
3609		4419
3610	Libev can be configured via a variety of preprocessor symbols you have to	4420	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	4421	define before including (or compiling) any of its files. The default in
3612	autoconf is documented for every option.	4422	the absence of autoconf is documented for every option.
		4423
		4424	Symbols marked with "(h)" do not change the ABI, and can have different
		4425	values when compiling libev vs. including F<ev.h>, so it is permissible
		4426	to redefine them before including F<ev.h> without breaking compatibility
		4427	to a compiled library. All other symbols change the ABI, which means all
		4428	users of libev and the libev code itself must be compiled with compatible
		4429	settings.
3613		4430
3614	=over 4	4431	=over 4
3615		4432
		4433	=item EV_COMPAT3 (h)
		4434
		4435	Backwards compatibility is a major concern for libev. This is why this
		4436	release of libev comes with wrappers for the functions and symbols that
		4437	have been renamed between libev version 3 and 4.
		4438
		4439	You can disable these wrappers (to test compatibility with future
		4440	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4441	sources. This has the additional advantage that you can drop the C<struct>
		4442	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4443	typedef in that case.
		4444
		4445	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4446	and in some even more future version the compatibility code will be
		4447	removed completely.
		4448
3616	=item EV_STANDALONE	4449	=item EV_STANDALONE (h)
3617		4450
3618	Must always be C<1> if you do not use autoconf configuration, which	4451	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	4452	keeps libev from including F<config.h>, and it also defines dummy
3620	implementations for some libevent functions (such as logging, which is not	4453	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	4454	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.	4455	F<event.h> that are not directly supported by the libev core alone.
3623		4456
3624	In standalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3625	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3626		4468
3627	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3628		4470
3629	If defined to be C<1>, libev will try to detect the availability of the	4471	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	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3715		4557
3716	If programs implement their own fd to handle mapping on win32, then this	4558	If programs implement their own fd to handle mapping on win32, then this
3717	macro can be used to override the C<close> function, useful to unregister	4559	macro can be used to override the C<close> function, useful to unregister
3718	file descriptors again. Note that the replacement function has to close	4560	file descriptors again. Note that the replacement function has to close
3719	the underlying OS handle.	4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3720		4569
3721	=item EV_USE_POLL	4570	=item EV_USE_POLL
3722		4571
3723	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3724	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3760	If defined to be C<1>, libev will compile in support for the Linux inotify	4609	If defined to be C<1>, libev will compile in support for the Linux inotify
3761	interface to speed up C<ev_stat> watchers. Its actual availability will	4610	interface to speed up C<ev_stat> watchers. Its actual availability will
3762	be detected at runtime. If undefined, it will be enabled if the headers	4611	be detected at runtime. If undefined, it will be enabled if the headers
3763	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3764		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called
		4624	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4625	above. This reduces dependencies and makes libev faster.
		4626
3765	=item EV_ATOMIC_T	4627	=item EV_ATOMIC_T
3766		4628
3767	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3768	access is atomic with respect to other threads or signal contexts. No such	4630	access is atomic and serialised with respect to other threads or signal
3769	type is easily found in the C language, so you can provide your own type	4631	contexts. No such type is easily found in the C language, so you can
3770	that you know is safe for your purposes. It is used both for signal handler "locking"	4632	provide your own type that you know is safe for your purposes. It is used
3771	as well as for signal and thread safety in C<ev_async> watchers.	4633	both for signal handler "locking" as well as for signal and thread safety
		4634	in C<ev_async> watchers.
3772		4635
3773	In the absence of this define, libev will use C<sig_atomic_t volatile>	4636	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.	4637	(from F<signal.h>), which is usually good enough on most platforms,
		4638	although strictly speaking using a type that also implies a memory fence
		4639	is required.
3775		4640
3776	=item EV_H	4641	=item EV_H (h)
3777		4642
3778	The name of the F<ev.h> header file used to include it. The default if	4643	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	4644	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.	4645	used to virtually rename the F<ev.h> header file in case of conflicts.
3781		4646
3782	=item EV_CONFIG_H	4647	=item EV_CONFIG_H (h)
3783		4648
3784	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4649	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	4650	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3786	C<EV_H>, above.	4651	C<EV_H>, above.
3787		4652
3788	=item EV_EVENT_H	4653	=item EV_EVENT_H (h)
3789		4654
3790	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4655	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">.	4656	of how the F<event.h> header can be found, the default is C<"event.h">.
3792		4657
3793	=item EV_PROTOTYPES	4658	=item EV_PROTOTYPES (h)
3794		4659
3795	If defined to be C<0>, then F<ev.h> will not define any function	4660	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	4661	prototypes, but still define all the structs and other symbols. This is
3797	occasionally useful if you want to provide your own wrapper functions	4662	occasionally useful if you want to provide your own wrapper functions
3798	around libev functions.	4663	around libev functions.
…		…
3803	will have the C<struct ev_loop *> as first argument, and you can create	4668	will have the C<struct ev_loop *> as first argument, and you can create
3804	additional independent event loops. Otherwise there will be no support	4669	additional independent event loops. Otherwise there will be no support
3805	for multiple event loops and there is no first event loop pointer	4670	for multiple event loops and there is no first event loop pointer
3806	argument. Instead, all functions act on the single default loop.	4671	argument. Instead, all functions act on the single default loop.
3807		4672
		4673	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4674	default loop when multiplicity is switched off - you always have to
		4675	initialise the loop manually in this case.
		4676
3808	=item EV_MINPRI	4677	=item EV_MINPRI
3809		4678
3810	=item EV_MAXPRI	4679	=item EV_MAXPRI
3811		4680
3812	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4681	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3820	fine.	4689	fine.
3821		4690
3822	If your embedding application does not need any priorities, defining these	4691	If your embedding application does not need any priorities, defining these
3823	both to C<0> will save some memory and CPU.	4692	both to C<0> will save some memory and CPU.
3824		4693
3825	=item EV_PERIODIC_ENABLE	4694	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4695	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4696	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3826		4697
3827	If undefined or defined to be C<1>, then periodic timers are supported. If	4698	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	4699	the respective watcher type is supported. If defined to be C<0>, then it
3829	code.	4700	is not. Disabling watcher types mainly saves code size.
3830		4701
3831	=item EV_IDLE_ENABLE	4702	=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		4703
3860	If you need to shave off some kilobytes of code at the expense of some	4704	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	4705	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	4706	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	4707	that can be enabled on the platform.
3864	the default 4-heap.
3865		4708
3866	You can save even more by disabling watcher types you do not need	4709	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>	4710	with some broad features you want) and then selectively re-enable
3868	(C<-DNDEBUG>) will usually reduce code size a lot.	4711	additional parts you want, for example if you want everything minimal,
		4712	but multiple event loop support, async and child watchers and the poll
		4713	backend, use this:
3869		4714
3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4715	#define EV_FEATURES 0
3871	provide a bare-bones event library. See C<ev.h> for details on what parts	4716	#define EV_MULTIPLICITY 1
3872	of the API are still available, and do not complain if this subset changes	4717	#define EV_USE_POLL 1
3873	over time.	4718	#define EV_CHILD_ENABLE 1
		4719	#define EV_ASYNC_ENABLE 1
		4720
		4721	The actual value is a bitset, it can be a combination of the following
		4722	values (by default, all of these are enabled):
		4723
		4724	=over 4
		4725
		4726	=item C<1> - faster/larger code
		4727
		4728	Use larger code to speed up some operations.
		4729
		4730	Currently this is used to override some inlining decisions (enlarging the
		4731	code size by roughly 30% on amd64).
		4732
		4733	When optimising for size, use of compiler flags such as C<-Os> with
		4734	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4735	assertions.
		4736
		4737	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4738	(e.g. gcc with C<-Os>).
		4739
		4740	=item C<2> - faster/larger data structures
		4741
		4742	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4743	hash table sizes and so on. This will usually further increase code size
		4744	and can additionally have an effect on the size of data structures at
		4745	runtime.
		4746
		4747	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4748	(e.g. gcc with C<-Os>).
		4749
		4750	=item C<4> - full API configuration
		4751
		4752	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4753	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4754
		4755	=item C<8> - full API
		4756
		4757	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4758	details on which parts of the API are still available without this
		4759	feature, and do not complain if this subset changes over time.
		4760
		4761	=item C<16> - enable all optional watcher types
		4762
		4763	Enables all optional watcher types. If you want to selectively enable
		4764	only some watcher types other than I/O and timers (e.g. prepare,
		4765	embed, async, child...) you can enable them manually by defining
		4766	C<EV_watchertype_ENABLE> to C<1> instead.
		4767
		4768	=item C<32> - enable all backends
		4769
		4770	This enables all backends - without this feature, you need to enable at
		4771	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4772
		4773	=item C<64> - enable OS-specific "helper" APIs
		4774
		4775	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4776	default.
		4777
		4778	=back
		4779
		4780	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4781	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4782	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4783	watchers, timers and monotonic clock support.
		4784
		4785	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4786	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4787	your program might be left out as well - a binary starting a timer and an
		4788	I/O watcher then might come out at only 5Kb.
		4789
		4790	=item EV_API_STATIC
		4791
		4792	If this symbol is defined (by default it is not), then all identifiers
		4793	will have static linkage. This means that libev will not export any
		4794	identifiers, and you cannot link against libev anymore. This can be useful
		4795	when you embed libev, only want to use libev functions in a single file,
		4796	and do not want its identifiers to be visible.
		4797
		4798	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4799	wants to use libev.
		4800
		4801	This option only works when libev is compiled with a C compiler, as C++
		4802	doesn't support the required declaration syntax.
		4803
		4804	=item EV_AVOID_STDIO
		4805
		4806	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4807	functions (printf, scanf, perror etc.). This will increase the code size
		4808	somewhat, but if your program doesn't otherwise depend on stdio and your
		4809	libc allows it, this avoids linking in the stdio library which is quite
		4810	big.
		4811
		4812	Note that error messages might become less precise when this option is
		4813	enabled.
3874		4814
3875	=item EV_NSIG	4815	=item EV_NSIG
3876		4816
3877	The highest supported signal number, +1 (or, the number of	4817	The highest supported signal number, +1 (or, the number of
3878	signals): Normally, libev tries to deduce the maximum number of signals	4818	signals): Normally, libev tries to deduce the maximum number of signals
3879	automatically, but sometimes this fails, in which case it can be	4819	automatically, but sometimes this fails, in which case it can be
3880	specified. Also, using a lower number than detected (C<32> should be	4820	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	4821	good for about any system in existence) can save some memory, as libev
3882	statically allocates some 12-24 bytes per signal number.	4822	statically allocates some 12-24 bytes per signal number.
3883		4823
3884	=item EV_PID_HASHSIZE	4824	=item EV_PID_HASHSIZE
3885		4825
3886	C<ev_child> watchers use a small hash table to distribute workload by	4826	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	4827	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	4828	usually more than enough. If you need to manage thousands of children you
3889	increase this value (I<must> be a power of two).	4829	might want to increase this value (I<must> be a power of two).
3890		4830
3891	=item EV_INOTIFY_HASHSIZE	4831	=item EV_INOTIFY_HASHSIZE
3892		4832
3893	C<ev_stat> watchers use a small hash table to distribute workload by	4833	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>),	4834	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>	4835	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	4836	C<ev_stat> watchers you might want to increase this value (I<must> be a
3897	two).	4837	power of two).
3898		4838
3899	=item EV_USE_4HEAP	4839	=item EV_USE_4HEAP
3900		4840
3901	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4841	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	4842	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	4843	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3904	faster performance with many (thousands) of watchers.	4844	faster performance with many (thousands) of watchers.
3905		4845
3906	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4846	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3907	(disabled).	4847	will be C<0>.
3908		4848
3909	=item EV_HEAP_CACHE_AT	4849	=item EV_HEAP_CACHE_AT
3910		4850
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4851	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	4852	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>),	4853	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,	4854	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	4855	but avoids random read accesses on heap changes. This improves performance
3916	noticeably with many (hundreds) of watchers.	4856	noticeably with many (hundreds) of watchers.
3917		4857
3918	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4858	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3919	(disabled).	4859	will be C<0>.
3920		4860
3921	=item EV_VERIFY	4861	=item EV_VERIFY
3922		4862
3923	Controls how much internal verification (see C<ev_loop_verify ()>) will	4863	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	4864	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	4865	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	4866	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	4867	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	4868	verification code will be called very frequently, which will slow down
3929	libev considerably.	4869	libev considerably.
3930		4870
3931	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4871	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3932	C<0>.	4872	will be C<0>.
3933		4873
3934	=item EV_COMMON	4874	=item EV_COMMON
3935		4875
3936	By default, all watchers have a C<void *data> member. By redefining	4876	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	4877	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,	4878	members. You have to define it each time you include one of the files,
3939	though, and it must be identical each time.	4879	though, and it must be identical each time.
3940		4880
3941	For example, the perl EV module uses something like this:	4881	For example, the perl EV module uses something like this:
3942		4882
…		…
3995	file.	4935	file.
3996		4936
3997	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4937	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:	4938	that everybody includes and which overrides some configure choices:
3999		4939
4000	#define EV_MINIMAL 1	4940	#define EV_FEATURES 8
4001	#define EV_USE_POLL 0	4941	#define EV_USE_SELECT 1
4002	#define EV_MULTIPLICITY 0
4003	#define EV_PERIODIC_ENABLE 0	4942	#define EV_PREPARE_ENABLE 1
		4943	#define EV_IDLE_ENABLE 1
4004	#define EV_STAT_ENABLE 0	4944	#define EV_SIGNAL_ENABLE 1
4005	#define EV_FORK_ENABLE 0	4945	#define EV_CHILD_ENABLE 1
		4946	#define EV_USE_STDEXCEPT 0
4006	#define EV_CONFIG_H <config.h>	4947	#define EV_CONFIG_H <config.h>
4007	#define EV_MINPRI 0
4008	#define EV_MAXPRI 0
4009		4948
4010	#include "ev++.h"	4949	#include "ev++.h"
4011		4950
4012	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4951	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4013		4952
4014	#include "ev_cpp.h"	4953	#include "ev_cpp.h"
4015	#include "ev.c"	4954	#include "ev.c"
4016		4955
4017	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4956	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4018		4957
4019	=head2 THREADS AND COROUTINES	4958	=head2 THREADS AND COROUTINES
4020		4959
4021	=head3 THREADS	4960	=head3 THREADS
4022		4961
…		…
4073	default loop and triggering an C<ev_async> watcher from the default loop	5012	default loop and triggering an C<ev_async> watcher from the default loop
4074	watcher callback into the event loop interested in the signal.	5013	watcher callback into the event loop interested in the signal.
4075		5014
4076	=back	5015	=back
4077		5016
4078	=head4 THREAD LOCKING EXAMPLE	5017	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		5018
4216	=head3 COROUTINES	5019	=head3 COROUTINES
4217		5020
4218	Libev is very accommodating to coroutines ("cooperative threads"):	5021	Libev is very accommodating to coroutines ("cooperative threads"):
4219	libev fully supports nesting calls to its functions from different	5022	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	5023	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	5024	different coroutines, and switch freely between both coroutines running
4222	the loop, as long as you don't confuse yourself). The only exception is	5025	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.	5026	that you must not do this from C<ev_periodic> reschedule callbacks.
4224		5027
4225	Care has been taken to ensure that libev does not keep local state inside	5028	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	5029	C<ev_run>, and other calls do not usually allow for coroutine switches as
4227	they do not call any callbacks.	5030	they do not call any callbacks.
4228		5031
4229	=head2 COMPILER WARNINGS	5032	=head2 COMPILER WARNINGS
4230		5033
4231	Depending on your compiler and compiler settings, you might get no or a	5034	Depending on your compiler and compiler settings, you might get no or a
…		…
4242	maintainable.	5045	maintainable.
4243		5046
4244	And of course, some compiler warnings are just plain stupid, or simply	5047	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	5048	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	5049	seems to warn about). For example, certain older gcc versions had some
4247	warnings that resulted an extreme number of false positives. These have	5050	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	5051	been fixed, but some people still insist on making code warn-free with
4249	such buggy versions.	5052	such buggy versions.
4250		5053
4251	While libev is written to generate as few warnings as possible,	5054	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	5055	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4288	I suggest using suppression lists.	5091	I suggest using suppression lists.
4289		5092
4290		5093
4291	=head1 PORTABILITY NOTES	5094	=head1 PORTABILITY NOTES
4292		5095
		5096	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5097
		5098	GNU/Linux is the only common platform that supports 64 bit file/large file
		5099	interfaces but I<disables> them by default.
		5100
		5101	That means that libev compiled in the default environment doesn't support
		5102	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5103
		5104	Unfortunately, many programs try to work around this GNU/Linux issue
		5105	by enabling the large file API, which makes them incompatible with the
		5106	standard libev compiled for their system.
		5107
		5108	Likewise, libev cannot enable the large file API itself as this would
		5109	suddenly make it incompatible to the default compile time environment,
		5110	i.e. all programs not using special compile switches.
		5111
		5112	=head2 OS/X AND DARWIN BUGS
		5113
		5114	The whole thing is a bug if you ask me - basically any system interface
		5115	you touch is broken, whether it is locales, poll, kqueue or even the
		5116	OpenGL drivers.
		5117
		5118	=head3 C<kqueue> is buggy
		5119
		5120	The kqueue syscall is broken in all known versions - most versions support
		5121	only sockets, many support pipes.
		5122
		5123	Libev tries to work around this by not using C<kqueue> by default on this
		5124	rotten platform, but of course you can still ask for it when creating a
		5125	loop - embedding a socket-only kqueue loop into a select-based one is
		5126	probably going to work well.
		5127
		5128	=head3 C<poll> is buggy
		5129
		5130	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5131	implementation by something calling C<kqueue> internally around the 10.5.6
		5132	release, so now C<kqueue> I<and> C<poll> are broken.
		5133
		5134	Libev tries to work around this by not using C<poll> by default on
		5135	this rotten platform, but of course you can still ask for it when creating
		5136	a loop.
		5137
		5138	=head3 C<select> is buggy
		5139
		5140	All that's left is C<select>, and of course Apple found a way to fuck this
		5141	one up as well: On OS/X, C<select> actively limits the number of file
		5142	descriptors you can pass in to 1024 - your program suddenly crashes when
		5143	you use more.
		5144
		5145	There is an undocumented "workaround" for this - defining
		5146	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5147	work on OS/X.
		5148
		5149	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5150
		5151	=head3 C<errno> reentrancy
		5152
		5153	The default compile environment on Solaris is unfortunately so
		5154	thread-unsafe that you can't even use components/libraries compiled
		5155	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5156	defined by default. A valid, if stupid, implementation choice.
		5157
		5158	If you want to use libev in threaded environments you have to make sure
		5159	it's compiled with C<_REENTRANT> defined.
		5160
		5161	=head3 Event port backend
		5162
		5163	The scalable event interface for Solaris is called "event
		5164	ports". Unfortunately, this mechanism is very buggy in all major
		5165	releases. If you run into high CPU usage, your program freezes or you get
		5166	a large number of spurious wakeups, make sure you have all the relevant
		5167	and latest kernel patches applied. No, I don't know which ones, but there
		5168	are multiple ones to apply, and afterwards, event ports actually work
		5169	great.
		5170
		5171	If you can't get it to work, you can try running the program by setting
		5172	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5173	C<select> backends.
		5174
		5175	=head2 AIX POLL BUG
		5176
		5177	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5178	this by trying to avoid the poll backend altogether (i.e. it's not even
		5179	compiled in), which normally isn't a big problem as C<select> works fine
		5180	with large bitsets on AIX, and AIX is dead anyway.
		5181
4293	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5182	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5183
		5184	=head3 General issues
4294		5185
4295	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5186	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	5187	requires, and its I/O model is fundamentally incompatible with the POSIX
4297	model. Libev still offers limited functionality on this platform in	5188	model. Libev still offers limited functionality on this platform in
4298	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5189	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4299	descriptors. This only applies when using Win32 natively, not when using	5190	descriptors. This only applies when using Win32 natively, not when using
4300	e.g. cygwin.	5191	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5192	as every compiler comes with a slightly differently broken/incompatible
		5193	environment.
4301		5194
4302	Lifting these limitations would basically require the full	5195	Lifting these limitations would basically require the full
4303	re-implementation of the I/O system. If you are into these kinds of	5196	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	5197	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).	5198	also that glib is the slowest event library known to man).
4306		5199
4307	There is no supported compilation method available on windows except	5200	There is no supported compilation method available on windows except
4308	embedding it into other applications.	5201	embedding it into other applications.
4309		5202
4310	Sensible signal handling is officially unsupported by Microsoft - libev	5203	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!):	5231	you do I<not> compile the F<ev.c> or any other embedded source files!):
4339		5232
4340	#include "evwrap.h"	5233	#include "evwrap.h"
4341	#include "ev.c"	5234	#include "ev.c"
4342		5235
4343	=over 4
4344
4345	=item The winsocket select function	5236	=head3 The winsocket C<select> function
4346		5237
4347	The winsocket C<select> function doesn't follow POSIX in that it	5238	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	5239	requires socket I<handles> and not socket I<file descriptors> (it is
4349	also extremely buggy). This makes select very inefficient, and also	5240	also extremely buggy). This makes select very inefficient, and also
4350	requires a mapping from file descriptors to socket handles (the Microsoft	5241	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 */	5250	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4360		5251
4361	Note that winsockets handling of fd sets is O(n), so you can easily get a	5252	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.	5253	complexity in the O(n²) range when using win32.
4363		5254
4364	=item Limited number of file descriptors	5255	=head3 Limited number of file descriptors
4365		5256
4366	Windows has numerous arbitrary (and low) limits on things.	5257	Windows has numerous arbitrary (and low) limits on things.
4367		5258
4368	Early versions of winsocket's select only supported waiting for a maximum	5259	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	5260	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	5275	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,	5276	(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	5277	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.	5278	the cost of calling select (O(n²)) will likely make this unworkable.
4388		5279
4389	=back
4390
4391	=head2 PORTABILITY REQUIREMENTS	5280	=head2 PORTABILITY REQUIREMENTS
4392		5281
4393	In addition to a working ISO-C implementation and of course the	5282	In addition to a working ISO-C implementation and of course the
4394	backend-specific APIs, libev relies on a few additional extensions:	5283	backend-specific APIs, libev relies on a few additional extensions:
4395		5284
…		…
4401	Libev assumes not only that all watcher pointers have the same internal	5290	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	5291	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	5292	assumes that the same (machine) code can be used to call any watcher
4404	callback: The watcher callbacks have different type signatures, but libev	5293	callback: The watcher callbacks have different type signatures, but libev
4405	calls them using an C<ev_watcher *> internally.	5294	calls them using an C<ev_watcher *> internally.
		5295
		5296	=item pointer accesses must be thread-atomic
		5297
		5298	Accessing a pointer value must be atomic, it must both be readable and
		5299	writable in one piece - this is the case on all current architectures.
4406		5300
4407	=item C<sig_atomic_t volatile> must be thread-atomic as well	5301	=item C<sig_atomic_t volatile> must be thread-atomic as well
4408		5302
4409	The type C<sig_atomic_t volatile> (or whatever is defined as	5303	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	5304	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4433	watchers.	5327	watchers.
4434		5328
4435	=item C<double> must hold a time value in seconds with enough accuracy	5329	=item C<double> must hold a time value in seconds with enough accuracy
4436		5330
4437	The type C<double> is used to represent timestamps. It is required to	5331	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	5332	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	5333	good enough for at least into the year 4000 with millisecond accuracy
		5334	(the design goal for libev). This requirement is overfulfilled by
4440	implementations implementing IEEE 754, which is basically all existing	5335	implementations using IEEE 754, which is basically all existing ones.
		5336
4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5337	With IEEE 754 doubles, you get microsecond accuracy until at least the
4442	2200.	5338	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5339	is either obsolete or somebody patched it to use C<long double> or
		5340	something like that, just kidding).
4443		5341
4444	=back	5342	=back
4445		5343
4446	If you know of other additional requirements drop me a note.	5344	If you know of other additional requirements drop me a note.
4447		5345
…		…
4509	=item Processing ev_async_send: O(number_of_async_watchers)	5407	=item Processing ev_async_send: O(number_of_async_watchers)
4510		5408
4511	=item Processing signals: O(max_signal_number)	5409	=item Processing signals: O(max_signal_number)
4512		5410
4513	Sending involves a system call I<iff> there were no other C<ev_async_send>	5411	Sending involves a system call I<iff> there were no other C<ev_async_send>
4514	calls in the current loop iteration. Checking for async and signal events	5412	calls in the current loop iteration and the loop is currently
		5413	blocked. Checking for async and signal events involves iterating over all
4515	involves iterating over all running async watchers or all signal numbers.	5414	running async watchers or all signal numbers.
4516		5415
4517	=back	5416	=back
4518		5417
4519		5418
		5419	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5420
		5421	The major version 4 introduced some incompatible changes to the API.
		5422
		5423	At the moment, the C<ev.h> header file provides compatibility definitions
		5424	for all changes, so most programs should still compile. The compatibility
		5425	layer might be removed in later versions of libev, so better update to the
		5426	new API early than late.
		5427
		5428	=over 4
		5429
		5430	=item C<EV_COMPAT3> backwards compatibility mechanism
		5431
		5432	The backward compatibility mechanism can be controlled by
		5433	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5434	section.
		5435
		5436	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5437
		5438	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5439
		5440	ev_loop_destroy (EV_DEFAULT_UC);
		5441	ev_loop_fork (EV_DEFAULT);
		5442
		5443	=item function/symbol renames
		5444
		5445	A number of functions and symbols have been renamed:
		5446
		5447	ev_loop => ev_run
		5448	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5449	EVLOOP_ONESHOT => EVRUN_ONCE
		5450
		5451	ev_unloop => ev_break
		5452	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5453	EVUNLOOP_ONE => EVBREAK_ONE
		5454	EVUNLOOP_ALL => EVBREAK_ALL
		5455
		5456	EV_TIMEOUT => EV_TIMER
		5457
		5458	ev_loop_count => ev_iteration
		5459	ev_loop_depth => ev_depth
		5460	ev_loop_verify => ev_verify
		5461
		5462	Most functions working on C<struct ev_loop> objects don't have an
		5463	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5464	associated constants have been renamed to not collide with the C<struct
		5465	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5466	as all other watcher types. Note that C<ev_loop_fork> is still called
		5467	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5468	typedef.
		5469
		5470	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5471
		5472	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5473	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5474	and work, but the library code will of course be larger.
		5475
		5476	=back
		5477
		5478
4520	=head1 GLOSSARY	5479	=head1 GLOSSARY
4521		5480
4522	=over 4	5481	=over 4
4523		5482
4524	=item active	5483	=item active
4525		5484
4526	A watcher is active as long as it has been started (has been attached to	5485	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).	5486	See L</WATCHER STATES> for details.
4528		5487
4529	=item application	5488	=item application
4530		5489
4531	In this document, an application is whatever is using libev.	5490	In this document, an application is whatever is using libev.
		5491
		5492	=item backend
		5493
		5494	The part of the code dealing with the operating system interfaces.
4532		5495
4533	=item callback	5496	=item callback
4534		5497
4535	The address of a function that is called when some event has been	5498	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	5499	detected. Callbacks are being passed the event loop, the watcher that
4537	received the event, and the actual event bitset.	5500	received the event, and the actual event bitset.
4538		5501
4539	=item callback invocation	5502	=item callback/watcher invocation
4540		5503
4541	The act of calling the callback associated with a watcher.	5504	The act of calling the callback associated with a watcher.
4542		5505
4543	=item event	5506	=item event
4544		5507
4545	A change of state of some external event, such as data now being available	5508	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	5509	for reading on a file descriptor, time having passed or simply not having
4547	any other events happening anymore.	5510	any other events happening anymore.
4548		5511
4549	In libev, events are represented as single bits (such as C<EV_READ> or	5512	In libev, events are represented as single bits (such as C<EV_READ> or
4550	C<EV_TIMEOUT>).	5513	C<EV_TIMER>).
4551		5514
4552	=item event library	5515	=item event library
4553		5516
4554	A software package implementing an event model and loop.	5517	A software package implementing an event model and loop.
4555		5518
…		…
4563	The model used to describe how an event loop handles and processes	5526	The model used to describe how an event loop handles and processes
4564	watchers and events.	5527	watchers and events.
4565		5528
4566	=item pending	5529	=item pending
4567		5530
4568	A watcher is pending as soon as the corresponding event has been detected,	5531	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	5532	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		5533
4575	=item real time	5534	=item real time
4576		5535
4577	The physical time that is observed. It is apparently strictly monotonic :)	5536	The physical time that is observed. It is apparently strictly monotonic :)
4578		5537
4579	=item wall-clock time	5538	=item wall-clock time
4580		5539
4581	The time and date as shown on clocks. Unlike real time, it can actually	5540	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	5541	be wrong and jump forwards and backwards, e.g. when you adjust your
4583	clock.	5542	clock.
4584		5543
4585	=item watcher	5544	=item watcher
4586		5545
4587	A data structure that describes interest in certain events. Watchers need	5546	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.	5547	to be started (attached to an event loop) before they can receive events.
4589		5548
4590	=item watcher invocation
4591
4592	The act of calling the callback associated with a watcher.
4593
4594	=back	5549	=back
4595		5550
4596	=head1 AUTHOR	5551	=head1 AUTHOR
4597		5552
4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5553	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5554	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4599		5555

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