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Revision 1.265 by root, Wed Aug 26 17:11:42 2009 UTC vs.
Revision 1.423 by root, Fri Nov 23 12:52:35 2012 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
118	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
119	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
120	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
121	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
122	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
123	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_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_NOSIGNALFD>	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,
…		…
411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413		488
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
416	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
417	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
418	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
419	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
420		498
421	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
422	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
423	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
424	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
425	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
426	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
427	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
428	hard to detect.	508	and is of course hard to detect.
429		509
430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
431	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
432	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
433	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
434	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
435	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
436	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...
437		526
438	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
439	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
440	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
441	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
…		…
478		567
479	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
480	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
481	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
482	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
483	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
484	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
485	cases	574	drops fds silently in similarly hard-to-detect cases.
486		575
487	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
488		577
489	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
490	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
…		…
507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
508		597
509	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,
510	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)).
511		600
512	Please note that Solaris event ports can deliver a lot of spurious
513	notifications, so you need to use non-blocking I/O or other means to avoid
514	blocking when no data (or space) is available.
515
516	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
517	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
518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
519	might perform better.	604	might perform better.
520		605
521	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
522	notifications, this backend actually performed fully to specification
523	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
524	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.
525		620
526	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
527	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
528		623
529	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
530		625
531	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
532	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
533	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
534		629
535	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).
536		639
537	=back	640	=back
538		641
539	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,
540	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
541	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
542	()> will be tried.	645	()> will be tried.
543		646
544	Example: This is the most typical usage.
545
546	if (!ev_default_loop (0))
547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
548
549	Example: Restrict libev to the select and poll backends, and do not allow
550	environment settings to be taken into account:
551
552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
553
554	Example: Use whatever libev has to offer, but make sure that kqueue is
555	used if available (warning, breaks stuff, best use only with your own
556	private event loop and only if you know the OS supports your types of
557	fds):
558
559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
560
561	=item struct ev_loop *ev_loop_new (unsigned int flags)
562
563	Similar to C<ev_default_loop>, but always creates a new event loop that is
564	always distinct from the default loop. Unlike the default loop, it cannot
565	handle signal and child watchers, and attempts to do so will be greeted by
566	undefined behaviour (or a failed assertion if assertions are enabled).
567
568	Note that this function I<is> thread-safe, and the recommended way to use
569	libev with threads is indeed to create one loop per thread, and using the
570	default loop in the "main" or "initial" thread.
571
572	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.
573		648
574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575	if (!epoller)	650	if (!epoller)
576	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
577		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
578	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
579		659
580	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
581	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
582	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
583	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
584	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
585	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
…		…
587		667
588	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
589	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
590	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
591		671
592	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
593	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.
594	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>
595	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
596		680
597	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
598		682
599	Like C<ev_default_destroy>, but destroys an event loop created by an
600	earlier call to C<ev_loop_new>.
601
602	=item ev_default_fork ()
603
604	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
605	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
606	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
607	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
608	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
609	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.
610		693
611	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
612	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
613	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).
614		700
615	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
616	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		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	...
619	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
620
621	=item ev_loop_fork (loop)
622
623	Like C<ev_default_fork>, but acts on an event loop created by
624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
625	after fork that you want to re-use in the child, and how you do this is
626	entirely your own problem.
627		715
628	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
629		717
630	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
631	otherwise.	719	otherwise.
632		720
633	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
634		722
635	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
636	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>
637	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
638		726
639	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
640	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
641	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.
642		731
643	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
644		733
645	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
646	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.
647		736
648	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
649	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),
650	in which case it is higher.	739	in which case it is higher.
651		740
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	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.
654		745
655	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
656		747
657	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
658	use.	749	use.
…		…
667		758
668	=item ev_now_update (loop)	759	=item ev_now_update (loop)
669		760
670	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
671	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
672	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
673		764
674	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
675	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
676	the current time is a good idea.	767	the current time is a good idea.
677		768
678	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.
679		770
680	=item ev_suspend (loop)	771	=item ev_suspend (loop)
681		772
682	=item ev_resume (loop)	773	=item ev_resume (loop)
683		774
684	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
685	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.
686		777
687	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
688	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
689	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
690	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>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
693		784
694	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
695	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
696	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
697	occured while suspended).	788	occurred while suspended).
698		789
699	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
700	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>
701	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
702		793
703	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
704	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
705		796
706	=item ev_loop (loop, int flags)	797	=item bool ev_run (loop, int flags)
707		798
708	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
709	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
710	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>.
711		804
712	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
713	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.
714		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
715	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
716	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
717	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
718	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
719	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
720	beauty.	818	beauty.
721		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
722	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
723	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
724	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
725	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.
726		830
727	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
728	necessary) and will handle those and any already outstanding ones. It	832	necessary) and will handle those and any already outstanding ones. It
729	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
730	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
731	user-registered callback will be called), and will return after one	835	user-registered callback will be called), and will return after one
732	iteration of the loop.	836	iteration of the loop.
733		837
734	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
735	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
736	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
737	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
738		842
739	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):
740		846
		847	- Increment loop depth.
		848	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
		850	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	851	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- 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.
744	- Queue and call all prepare watchers.	853	- Queue and call all prepare watchers.
		854	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	855	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	856	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	857	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	858	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	859	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	860	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	861	any active watchers at all will result in not sleeping).
752	- 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.
753	- Block the process, waiting for any events.	864	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	865	- Queue all outstanding I/O (fd) events.
755	- 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.
756	- Queue all expired timers.	867	- Queue all expired timers.
757	- Queue all expired periodics.	868	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	869	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	870	- Queue all check watchers.
760	- 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).
761	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
762	be handled here by queueing them when their watcher gets executed.	873	be handled here by queueing them when their watcher gets executed.
763	- 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
764	were used, or there are no active watchers, return, otherwise	875	were used, or there are no active watchers, goto FINISH, otherwise
765	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.
766		881
767	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
768	anymore.	883	anymore.
769		884
770	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
771	... 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..)
772	ev_loop (my_loop, 0);	887	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
774		889
775	=item ev_unloop (loop, how)	890	=item ev_break (loop, how)
776		891
777	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
778	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
779	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
780	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.
781		896
782	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>.
783		898
784	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.
785		901
786	=item ev_ref (loop)	902	=item ev_ref (loop)
787		903
788	=item ev_unref (loop)	904	=item ev_unref (loop)
789		905
790	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
791	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
792	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.
793		909
794	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
795	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>
796	stopping it.	913	before stopping it.
797		914
798	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
799	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
800	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
801	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
802	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
803	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
804	before, respectively. Note also that libev might stop watchers itself	921	before, respectively. Note also that libev might stop watchers itself
805	(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>
806	in the callback).	923	in the callback).
807		924
808	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>
809	running when nothing else is active.	926	running when nothing else is active.
810		927
811	ev_signal exitsig;	928	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	931	ev_unref (loop);
815		932
816	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
817		934
818	ev_ref (loop);	935	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
839	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.
840		957
841	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
842	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,
843	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
844	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
845	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
846	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
847	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
848		966
849	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
850	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
852	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
…		…
858	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>,
859	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
860	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
861	parallelity, then this setting will limit your transaction rate (if you	979	parallelity, then this setting will limit your transaction rate (if you
862	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,
863	then you can't do more than 100 transations per second).	981	then you can't do more than 100 transactions per second).
864		982
865	Setting the I<timeout collect interval> can improve the opportunity for	983	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	984	saving power, as the program will "bundle" timer callback invocations that
867	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
868	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
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	994	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		995
878	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
879		997
880	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
882	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).
883		1005
884	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
885		1007
886	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1009	are pending.
888		1010
889	=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))
890		1012
891	This overrides the invoke pending functionality of the loop: Instead of	1013	This overrides the invoke pending functionality of the loop: Instead of
892	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
893	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
894	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
895		1017
896	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
897	callback.	1019	callback.
898		1020
899	=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 ())
900		1022
901	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
902	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
903	each call to a libev function.	1025	each call to a libev function.
904		1026
905	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
906	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
907	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
908	and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
909		1031
910	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
911	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1034	afterwards.
913		1035
…		…
916		1038
917	While event loop modifications are allowed between invocations of	1039	While event loop modifications are allowed between invocations of
918	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
919	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
920	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
921	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
922	to take note of any changes you made.	1044	to take note of any changes you made.
923		1045
924	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
925	invocations of C<release> and C<acquire>.	1047	invocations of C<release> and C<acquire>.
926		1048
927	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
928	document.	1050	document.
929		1051
930	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
931		1053
932	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
933		1055
934	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
935	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
936	C<0.>	1058	C<0>.
937		1059
938	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,
939	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
940	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
941	any other purpose as well.	1063	any other purpose as well.
942		1064
943	=item ev_loop_verify (loop)	1065	=item ev_verify (loop)
944		1066
945	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
946	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
947	through all internal structures and checks them for validity. If anything	1069	through all internal structures and checks them for validity. If anything
948	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
…		…
959		1081
960	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
961	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
962	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
963		1085
964	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
965	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
966	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:
967		1090
968	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)
969	{	1092	{
970	ev_io_stop (w);	1093	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1094	ev_break (loop, EVBREAK_ALL);
972	}	1095	}
973		1096
974	struct ev_loop *loop = ev_default_loop (0);	1097	struct ev_loop *loop = ev_default_loop (0);
975		1098
976	ev_io stdin_watcher;	1099	ev_io stdin_watcher;
977		1100
978	ev_init (&stdin_watcher, my_cb);	1101	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1102	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1103	ev_io_start (loop, &stdin_watcher);
981		1104
982	ev_loop (loop, 0);	1105	ev_run (loop, 0);
983		1106
984	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
985	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
986	stack).	1109	stack).
987		1110
988	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>
989	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).
990		1113
991	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
992	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, callback)>, which expects a callback to be provided. This callback is
993	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
994	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
995	is readable and/or writable).	1118	and/or writable).
996		1119
997	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 *, ...) >>
998	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
999	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<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1023	=item C<EV_WRITE>	1146	=item C<EV_WRITE>
1024		1147
1025	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
1026	writable.	1149	writable.
1027		1150
1028	=item C<EV_TIMEOUT>	1151	=item C<EV_TIMER>
1029		1152
1030	The C<ev_timer> watcher has timed out.	1153	The C<ev_timer> watcher has timed out.
1031		1154
1032	=item C<EV_PERIODIC>	1155	=item C<EV_PERIODIC>
1033		1156
…		…
1051		1174
1052	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1053		1176
1054	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1055		1178
1056	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
1057	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)
1058	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
1059	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
1060	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
1061	(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
1062	C<ev_loop> from blocking).	1190	blocking).
1063		1191
1064	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1065		1193
1066	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.
1067		1195
1068	=item C<EV_FORK>	1196	=item C<EV_FORK>
1069		1197
1070	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
1071	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>).
1072		1204
1073	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1074		1206
1075	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>).
1076		1208
…		…
1123		1255
1124	ev_io w;	1256	ev_io w;
1125	ev_init (&w, my_cb);	1257	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1259
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1261
1130	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
1131	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
1132	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
1133	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
…		…
1146		1278
1147	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.
1148		1280
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1282
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1284
1153	Starts (activates) the given watcher. Only active watchers will receive	1285	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1286	events. If the watcher is already active nothing will happen.
1155		1287
1156	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
1157	whole section.	1289	whole section.
1158		1290
1159	ev_io_start (EV_DEFAULT_UC, &w);	1291	ev_io_start (EV_DEFAULT_UC, &w);
1160		1292
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1294
1163	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
1164	the watcher was active or not).	1296	the watcher was active or not).
1165		1297
1166	It is possible that stopped watchers are pending - for example,	1298	It is possible that stopped watchers are pending - for example,
…		…
1186		1318
1187	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1188		1320
1189	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1190		1322
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1192		1324
1193	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
1194	(modulo threads).	1326	(modulo threads).
1195		1327
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1329
1198	=item int ev_priority (ev_TYPE *watcher)	1330	=item int ev_priority (ev_TYPE *watcher)
1199		1331
1200	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
1201	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>
…		…
1214	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
1215		1347
1216	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
1217	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 :).
1218		1350
1219	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
1220	priorities.	1352	priorities.
1221		1353
1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1223		1355
1224	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
…		…
1233	watcher isn't pending it does nothing and returns C<0>.	1365	watcher isn't pending it does nothing and returns C<0>.
1234		1366
1235	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
1236	callback to be invoked, which can be accomplished with this function.	1368	callback to be invoked, which can be accomplished with this function.
1237		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
1238	=back	1384	=back
1239		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1240		1388
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1242		1390
1243	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1244	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
1245	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
1246	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".
1247	member, you can also "subclass" the watcher type and provide your own
1248	data:
1249		1395
1250	struct my_io	1396	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1397
1258	...	1398	=item initialised
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1399
1262	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
1263	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.
1264		1403
1265	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
1266	{	1405	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1406	will - as long as you either keep the memory contents intact, or call
1268	...	1407	C<ev_TYPE_init> again.
1269	}
1270		1408
1271	More interesting and less C-conformant ways of casting your callback type	1409	=item started/running/active
1272	instead have been omitted.
1273		1410
1274	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
1275	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.
1276		1416
1277	struct my_biggy	1417	=item pending
1278	{
1279	int some_data;
1280	ev_timer t1;
1281	ev_timer t2;
1282	}
1283		1418
1284	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
1285	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
1286	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
1287	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
1288	programmers):	1423	callback.
1289		1424
1290	#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.
1291		1431
1292	static void	1432	It is also possible to feed an event on a watcher that is not active (e.g.
1293	t1_cb (EV_P_ ev_timer *w, int revents)	1433	via C<ev_feed_event>), in which case it becomes pending without being
1294	{	1434	active.
1295	struct my_biggy big = (struct my_biggy *)
1296	(((char *)w) - offsetof (struct my_biggy, t1));
1297	}
1298		1435
1299	static void	1436	=item stopped
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1437
1301	{	1438	A watcher can be stopped implicitly by libev (in which case it might still
1302	struct my_biggy big = (struct my_biggy *)	1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1440	latter will clear any pending state the watcher might be in, regardless
1304	}	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
1305		1450
1306	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1307		1452
1308	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1352		1497
1353	For example, to emulate how many other event libraries handle priorities,	1498	For example, to emulate how many other event libraries handle priorities,
1354	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
1355	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
1356	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
1357	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
1358	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
1359	workable.	1504	workable.
1360		1505
1361	Usually, however, the lock-out model implemented that way will perform	1506	Usually, however, the lock-out model implemented that way will perform
1362	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,
…		…
1376	{	1521	{
1377	// stop the I/O watcher, we received the event, but	1522	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1523	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1524	ev_io_stop (EV_A_ w);
1380		1525
1381	// start the idle watcher to ahndle the actual event.	1526	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1527	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1528	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1529	ev_idle_start (EV_A_ &idle);
1385	}	1530	}
1386		1531
…		…
1436	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
1437	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
1438	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
1439	required if you know what you are doing).	1584	required if you know what you are doing).
1440		1585
1441	If you cannot use non-blocking mode, then force the use of a
1442	known-to-be-good backend (at the time of this writing, this includes only
1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1444	descriptors for which non-blocking operation makes no sense (such as
1445	files) - libev doesn't guarentee any specific behaviour in that case.
1446
1447	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
1448	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1449	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
1450	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
1451	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
1452	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
1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1455		1593
1456	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
1457	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
1458	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
1459	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
1460	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
1461	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
1462	indefinitely.	1600	indefinitely.
1463		1601
1464	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1465		1603
…		…
1493		1631
1494	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		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
1498	=head3 The special problem of fork	1669	=head3 The special problem of fork
1499		1670
1500	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
1501	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
1502	it in the child.	1673	it in the child if you want to continue to use it in the child.
1503		1674
1504	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
1505	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
1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1678
1509	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1510		1680
1511	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>:
1512	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
…		…
1515		1685
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1686	So when you encounter spurious, unexplained daemon exits, make sure you
1517	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
1518	somewhere, as that would have given you a big clue).	1688	somewhere, as that would have given you a big clue).
1519		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.
1520		1728
1521	=head3 Watcher-Specific Functions	1729	=head3 Watcher-Specific Functions
1522		1730
1523	=over 4	1731	=over 4
1524		1732
…		…
1556	...	1764	...
1557	struct ev_loop *loop = ev_default_init (0);	1765	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1766	ev_io stdin_readable;
1559	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);
1560	ev_io_start (loop, &stdin_readable);	1768	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1769	ev_run (loop, 0);
1562		1770
1563		1771
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1772	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1773
1566	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
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1574		1782
1575	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
1576	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
1577	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
1578	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
1579	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
1580	no longer true when a callback calls C<ev_loop> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1581		1790
1582	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1583		1792
1584	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
1585	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,
…		…
1660		1869
1661	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,
1662	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
1663	within the callback:	1872	within the callback:
1664		1873
		1874	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1666		1877
1667	static void	1878	static void
1668	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1669	{	1880	{
1670	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		1883
1673	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1674	if (timeout < now)	1885	if (after < 0.)
1675	{	1886	{
1676	// timeout occured, take action	1887	// timeout occurred, take action
1677	}	1888	}
1678	else	1889	else
1679	{	1890	{
1680	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1685	}	1897	}
1686	}	1898	}
1687		1899
1688	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1689	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,
1690	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
1691	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1692	re-schedule the timer to fire at that future time, to see if maybe we have
1693	a timeout then.
1694		1904
1695	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
1696	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.
1697		1914
1698	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1699	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
1700	libev to change the timeout.	1917	libev to change the timeout.
1701		1918
1702	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1703	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
1704	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:
1705		1923
		1924	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		1927
1710	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1712		1930
		1931	if (activity detected)
1713	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);
1714		1941
1715	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
1716	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1717
1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
1719	callback :) - just change the timeout and invoke the callback, which will
1720	fix things for you.
1721		1944
1722	=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.
1723		1946
1724	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1725	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
…		…
1752	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
1753	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1754	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
1755	overkill :)	1978	overkill :)
1756		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
1757	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1758		2018
1759	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1760	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
1761	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
1762	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
1763	lots of events in one iteration.	2023	lots of events in one iteration.
1764		2024
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
1766	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
…		…
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1772		2032
1773	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
1774	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
1775	()>.	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.
1776		2069
1777	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1778		2071
1779	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
1780	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?
…		…
1824	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
1825	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.
1826		2119
1827	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1828		2121
1829	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
1830	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>.
1831		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
1832	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1833		2132
1834	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).
1835		2135
1836	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
1837	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1838		2138
		2139	=back
		2140
1839	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
1840	usage example.	2142	usage example.
1841		2143
1842	=item ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2145
1844	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,
1845	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
1846	the timeout value currently configured.	2148	the timeout value currently configured.
1847		2149
1848	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
1849	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>
1850	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
1851	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,
1852	too), and so on.	2154	too), and so on.
1853		2155
1854	=item ev_tstamp repeat [read-write]	2156	=item ev_tstamp repeat [read-write]
…		…
1883	}	2185	}
1884		2186
1885	ev_timer mytimer;	2187	ev_timer mytimer;
1886	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 */
1887	ev_timer_again (&mytimer); /* start timer */	2189	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2190	ev_run (loop, 0);
1889		2191
1890	// 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":
1891	// reset the timeout to start ticking again at 10 seconds	2193	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2194	ev_timer_again (&mytimer);
1893		2195
…		…
1919		2221
1920	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
1921	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
1922	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
1923	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
1924	(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).
1925		2227
1926	=head3 Watcher-Specific Functions and Data Members	2228	=head3 Watcher-Specific Functions and Data Members
1927		2229
1928	=over 4	2230	=over 4
1929		2231
…		…
1964		2266
1965	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
1966	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
1967	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.
1968		2270
1969	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
1970	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
1971	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.
1972		2277
1973	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
1974	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
1975	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
1976	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).
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2362	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2363	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2364	potentially a lot of jitter, but good long-term stability.
2060		2365
2061	static void	2366	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2367	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2368	{
2064	... 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)
2065	}	2370	}
2066		2371
2067	ev_periodic hourly_tick;	2372	ev_periodic hourly_tick;
…		…
2090		2395
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2397
2093	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
2094	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
2095	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
2096	normal event processing, like any other event.	2401	normal event processing, like any other event.
2097		2402
2098	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2099	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
2100	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
…		…
2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2419	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2115	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
2116	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
2117	and unblock them in an C<ev_prepare> watcher.	2422	and unblock them in an C<ev_prepare> watcher.
2118		2423
2119	=head3 The special problem of inheritance over execve	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2120		2425
2121	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2122	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2123	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,
2124	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>).
2125		2431
2126	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2127	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
2128	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
2129	many signals to be blocked.	2435	certain signals to be blocked.
2130		2436
2131	This means that before calling C<exec> (from the child) you should reset	2437	This means that before calling C<exec> (from the child) you should reset
2132	the signal mask to whatever "default" you expect (all clear is a good	2438	the signal mask to whatever "default" you expect (all clear is a good
2133	choice usually).	2439	choice usually).
2134		2440
		2441	The simplest way to ensure that the signal mask is reset in the child is
		2442	to install a fork handler with C<pthread_atfork> that resets it. That will
		2443	catch fork calls done by libraries (such as the libc) as well.
		2444
		2445	In current versions of libev, the signal will not be blocked indefinitely
		2446	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2447	the window of opportunity for problems, it will not go away, as libev
		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>.
		2467
2135	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2136		2469
2137	=over 4	2470	=over 4
2138		2471
2139	=item ev_signal_init (ev_signal *, callback, int signum)	2472	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2154	Example: Try to exit cleanly on SIGINT.	2487	Example: Try to exit cleanly on SIGINT.
2155		2488
2156	static void	2489	static void
2157	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2490	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2158	{	2491	{
2159	ev_unloop (loop, EVUNLOOP_ALL);	2492	ev_break (loop, EVBREAK_ALL);
2160	}	2493	}
2161		2494
2162	ev_signal signal_watcher;	2495	ev_signal signal_watcher;
2163	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2496	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2164	ev_signal_start (loop, &signal_watcher);	2497	ev_signal_start (loop, &signal_watcher);
…		…
2514	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2515	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
2516	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2517	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2518		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
2519	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2520		2867
2521	=over 4	2868	=over 4
2522		2869
2523	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2534	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2535		2882
2536	static void	2883	static void
2537	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2538	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2539	free (w);	2890	free (w);
		2891
2540	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2541	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2542	}	2894	}
2543		2895
2544	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2546	ev_idle_start (loop, idle_watcher);	2898	ev_idle_start (loop, idle_watcher);
2547		2899
2548		2900
2549	=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!
2550		2902
2551	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:
2552	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2553	afterwards.	2905	afterwards.
2554		2906
2555	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
2556	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>
2557	watchers. Other loops than the current one are fine, however. The	2909	watchers. Other loops than the current one are fine, however. The
2558	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
2559	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,
2560	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
…		…
2584	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
2585	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
2586	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2587	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2588		2940
2589	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
2590	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
2591	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).
2592		2945
2593	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
2594	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2595	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
2596	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
2597	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
2598	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
2599	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	This is where C<ev_idle> watchers come in handy - all you need is a
		2968	single global idle watcher that is active as long as you have one active
		2969	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2970	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2971	invoked. Neither watcher alone can do that.
2600		2972
2601	=head3 Watcher-Specific Functions and Data Members	2973	=head3 Watcher-Specific Functions and Data Members
2602		2974
2603	=over 4	2975	=over 4
2604		2976
…		…
2728		3100
2729	if (timeout >= 0)	3101	if (timeout >= 0)
2730	// create/start timer	3102	// create/start timer
2731		3103
2732	// poll	3104	// poll
2733	ev_loop (EV_A_ 0);	3105	ev_run (EV_A_ 0);
2734		3106
2735	// stop timer again	3107	// stop timer again
2736	if (timeout >= 0)	3108	if (timeout >= 0)
2737	ev_timer_stop (EV_A_ &to);	3109	ev_timer_stop (EV_A_ &to);
2738		3110
…		…
2816	if you do not want that, you need to temporarily stop the embed watcher).	3188	if you do not want that, you need to temporarily stop the embed watcher).
2817		3189
2818	=item ev_embed_sweep (loop, ev_embed *)	3190	=item ev_embed_sweep (loop, ev_embed *)
2819		3191
2820	Make a single, non-blocking sweep over the embedded loop. This works	3192	Make a single, non-blocking sweep over the embedded loop. This works
2821	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3193	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2822	appropriate way for embedded loops.	3194	appropriate way for embedded loops.
2823		3195
2824	=item struct ev_loop *other [read-only]	3196	=item struct ev_loop *other [read-only]
2825		3197
2826	The embedded event loop.	3198	The embedded event loop.
…		…
2878		3250
2879	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3251	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2880		3252
2881	Fork watchers are called when a C<fork ()> was detected (usually because	3253	Fork watchers are called when a C<fork ()> was detected (usually because
2882	whoever is a good citizen cared to tell libev about it by calling	3254	whoever is a good citizen cared to tell libev about it by calling
2883	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3255	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2884	event loop blocks next and before C<ev_check> watchers are being called,	3256	and before C<ev_check> watchers are being called, and only in the child
2885	and only in the child after the fork. If whoever good citizen calling	3257	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2886	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3258	and calls it in the wrong process, the fork handlers will be invoked, too,
2887	handlers will be invoked, too, of course.	3259	of course.
2888		3260
2889	=head3 The special problem of life after fork - how is it possible?	3261	=head3 The special problem of life after fork - how is it possible?
2890		3262
2891	Most uses of C<fork()> consist of forking, then some simple calls to ste	3263	Most uses of C<fork()> consist of forking, then some simple calls to set
2892	up/change the process environment, followed by a call to C<exec()>. This	3264	up/change the process environment, followed by a call to C<exec()>. This
2893	sequence should be handled by libev without any problems.	3265	sequence should be handled by libev without any problems.
2894		3266
2895	This changes when the application actually wants to do event handling	3267	This changes when the application actually wants to do event handling
2896	in the child, or both parent in child, in effect "continuing" after the	3268	in the child, or both parent in child, in effect "continuing" after the
…		…
2912	disadvantage of having to use multiple event loops (which do not support	3284	disadvantage of having to use multiple event loops (which do not support
2913	signal watchers).	3285	signal watchers).
2914		3286
2915	When this is not possible, or you want to use the default loop for	3287	When this is not possible, or you want to use the default loop for
2916	other reasons, then in the process that wants to start "fresh", call	3288	other reasons, then in the process that wants to start "fresh", call
2917	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3289	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2918	the default loop will "orphan" (not stop) all registered watchers, so you	3290	Destroying the default loop will "orphan" (not stop) all registered
2919	have to be careful not to execute code that modifies those watchers. Note	3291	watchers, so you have to be careful not to execute code that modifies
2920	also that in that case, you have to re-register any signal watchers.	3292	those watchers. Note also that in that case, you have to re-register any
		3293	signal watchers.
2921		3294
2922	=head3 Watcher-Specific Functions and Data Members	3295	=head3 Watcher-Specific Functions and Data Members
2923		3296
2924	=over 4	3297	=over 4
2925		3298
2926	=item ev_fork_init (ev_signal *, callback)	3299	=item ev_fork_init (ev_fork *, callback)
2927		3300
2928	Initialises and configures the fork watcher - it has no parameters of any	3301	Initialises and configures the fork watcher - it has no parameters of any
2929	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3302	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2930	believe me.	3303	really.
2931		3304
2932	=back	3305	=back
2933		3306
2934		3307
		3308	=head2 C<ev_cleanup> - even the best things end
		3309
		3310	Cleanup watchers are called just before the event loop is being destroyed
		3311	by a call to C<ev_loop_destroy>.
		3312
		3313	While there is no guarantee that the event loop gets destroyed, cleanup
		3314	watchers provide a convenient method to install cleanup hooks for your
		3315	program, worker threads and so on - you just to make sure to destroy the
		3316	loop when you want them to be invoked.
		3317
		3318	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3319	all other watchers, they do not keep a reference to the event loop (which
		3320	makes a lot of sense if you think about it). Like all other watchers, you
		3321	can call libev functions in the callback, except C<ev_cleanup_start>.
		3322
		3323	=head3 Watcher-Specific Functions and Data Members
		3324
		3325	=over 4
		3326
		3327	=item ev_cleanup_init (ev_cleanup *, callback)
		3328
		3329	Initialises and configures the cleanup watcher - it has no parameters of
		3330	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3331	pointless, I assure you.
		3332
		3333	=back
		3334
		3335	Example: Register an atexit handler to destroy the default loop, so any
		3336	cleanup functions are called.
		3337
		3338	static void
		3339	program_exits (void)
		3340	{
		3341	ev_loop_destroy (EV_DEFAULT_UC);
		3342	}
		3343
		3344	...
		3345	atexit (program_exits);
		3346
		3347
2935	=head2 C<ev_async> - how to wake up another event loop	3348	=head2 C<ev_async> - how to wake up an event loop
2936		3349
2937	In general, you cannot use an C<ev_loop> from multiple threads or other	3350	In general, you cannot use an C<ev_loop> from multiple threads or other
2938	asynchronous sources such as signal handlers (as opposed to multiple event	3351	asynchronous sources such as signal handlers (as opposed to multiple event
2939	loops - those are of course safe to use in different threads).	3352	loops - those are of course safe to use in different threads).
2940		3353
2941	Sometimes, however, you need to wake up another event loop you do not	3354	Sometimes, however, you need to wake up an event loop you do not control,
2942	control, for example because it belongs to another thread. This is what	3355	for example because it belongs to another thread. This is what C<ev_async>
2943	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3356	watchers do: as long as the C<ev_async> watcher is active, you can signal
2944	can signal it by calling C<ev_async_send>, which is thread- and signal	3357	it by calling C<ev_async_send>, which is thread- and signal safe.
2945	safe.
2946		3358
2947	This functionality is very similar to C<ev_signal> watchers, as signals,	3359	This functionality is very similar to C<ev_signal> watchers, as signals,
2948	too, are asynchronous in nature, and signals, too, will be compressed	3360	too, are asynchronous in nature, and signals, too, will be compressed
2949	(i.e. the number of callback invocations may be less than the number of	3361	(i.e. the number of callback invocations may be less than the number of
2950	C<ev_async_sent> calls).	3362	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2951		3363	of "global async watchers" by using a watcher on an otherwise unused
2952	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3364	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2953	just the default loop.	3365	even without knowing which loop owns the signal.
2954		3366
2955	=head3 Queueing	3367	=head3 Queueing
2956		3368
2957	C<ev_async> does not support queueing of data in any way. The reason	3369	C<ev_async> does not support queueing of data in any way. The reason
2958	is that the author does not know of a simple (or any) algorithm for a	3370	is that the author does not know of a simple (or any) algorithm for a
2959	multiple-writer-single-reader queue that works in all cases and doesn't	3371	multiple-writer-single-reader queue that works in all cases and doesn't
2960	need elaborate support such as pthreads.	3372	need elaborate support such as pthreads or unportable memory access
		3373	semantics.
2961		3374
2962	That means that if you want to queue data, you have to provide your own	3375	That means that if you want to queue data, you have to provide your own
2963	queue. But at least I can tell you how to implement locking around your	3376	queue. But at least I can tell you how to implement locking around your
2964	queue:	3377	queue:
2965		3378
…		…
3049	trust me.	3462	trust me.
3050		3463
3051	=item ev_async_send (loop, ev_async *)	3464	=item ev_async_send (loop, ev_async *)
3052		3465
3053	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3466	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3054	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3467	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3468	returns.
		3469
3055	C<ev_feed_event>, this call is safe to do from other threads, signal or	3470	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3056	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3471	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3057	section below on what exactly this means).	3472	embedding section below on what exactly this means).
3058		3473
3059	Note that, as with other watchers in libev, multiple events might get	3474	Note that, as with other watchers in libev, multiple events might get
3060	compressed into a single callback invocation (another way to look at this	3475	compressed into a single callback invocation (another way to look at
3061	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3476	this is that C<ev_async> watchers are level-triggered: they are set on
3062	reset when the event loop detects that).	3477	C<ev_async_send>, reset when the event loop detects that).
3063		3478
3064	This call incurs the overhead of a system call only once per event loop	3479	This call incurs the overhead of at most one extra system call per event
3065	iteration, so while the overhead might be noticeable, it doesn't apply to	3480	loop iteration, if the event loop is blocked, and no syscall at all if
3066	repeated calls to C<ev_async_send> for the same event loop.	3481	the event loop (or your program) is processing events. That means that
		3482	repeated calls are basically free (there is no need to avoid calls for
		3483	performance reasons) and that the overhead becomes smaller (typically
		3484	zero) under load.
3067		3485
3068	=item bool = ev_async_pending (ev_async *)	3486	=item bool = ev_async_pending (ev_async *)
3069		3487
3070	Returns a non-zero value when C<ev_async_send> has been called on the	3488	Returns a non-zero value when C<ev_async_send> has been called on the
3071	watcher but the event has not yet been processed (or even noted) by the	3489	watcher but the event has not yet been processed (or even noted) by the
…		…
3104		3522
3105	If C<timeout> is less than 0, then no timeout watcher will be	3523	If C<timeout> is less than 0, then no timeout watcher will be
3106	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3524	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3107	repeat = 0) will be started. C<0> is a valid timeout.	3525	repeat = 0) will be started. C<0> is a valid timeout.
3108		3526
3109	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3527	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3110	passed an C<revents> set like normal event callbacks (a combination of	3528	passed an C<revents> set like normal event callbacks (a combination of
3111	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3529	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3112	value passed to C<ev_once>. Note that it is possible to receive I<both>	3530	value passed to C<ev_once>. Note that it is possible to receive I<both>
3113	a timeout and an io event at the same time - you probably should give io	3531	a timeout and an io event at the same time - you probably should give io
3114	events precedence.	3532	events precedence.
3115		3533
3116	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3534	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3117		3535
3118	static void stdin_ready (int revents, void *arg)	3536	static void stdin_ready (int revents, void *arg)
3119	{	3537	{
3120	if (revents & EV_READ)	3538	if (revents & EV_READ)
3121	/* stdin might have data for us, joy! */;	3539	/* stdin might have data for us, joy! */;
3122	else if (revents & EV_TIMEOUT)	3540	else if (revents & EV_TIMER)
3123	/* doh, nothing entered */;	3541	/* doh, nothing entered */;
3124	}	3542	}
3125		3543
3126	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3544	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3127		3545
3128	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3129
3130	Feeds the given event set into the event loop, as if the specified event
3131	had happened for the specified watcher (which must be a pointer to an
3132	initialised but not necessarily started event watcher).
3133
3134	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3546	=item ev_feed_fd_event (loop, int fd, int revents)
3135		3547
3136	Feed an event on the given fd, as if a file descriptor backend detected	3548	Feed an event on the given fd, as if a file descriptor backend detected
3137	the given events it.	3549	the given events.
3138		3550
3139	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3551	=item ev_feed_signal_event (loop, int signum)
3140		3552
3141	Feed an event as if the given signal occurred (C<loop> must be the default	3553	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3142	loop!).	3554	which is async-safe.
3143		3555
3144	=back	3556	=back
		3557
		3558
		3559	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3560
		3561	This section explains some common idioms that are not immediately
		3562	obvious. Note that examples are sprinkled over the whole manual, and this
		3563	section only contains stuff that wouldn't fit anywhere else.
		3564
		3565	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3566
		3567	Each watcher has, by default, a C<void *data> member that you can read
		3568	or modify at any time: libev will completely ignore it. This can be used
		3569	to associate arbitrary data with your watcher. If you need more data and
		3570	don't want to allocate memory separately and store a pointer to it in that
		3571	data member, you can also "subclass" the watcher type and provide your own
		3572	data:
		3573
		3574	struct my_io
		3575	{
		3576	ev_io io;
		3577	int otherfd;
		3578	void *somedata;
		3579	struct whatever *mostinteresting;
		3580	};
		3581
		3582	...
		3583	struct my_io w;
		3584	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3585
		3586	And since your callback will be called with a pointer to the watcher, you
		3587	can cast it back to your own type:
		3588
		3589	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3590	{
		3591	struct my_io *w = (struct my_io *)w_;
		3592	...
		3593	}
		3594
		3595	More interesting and less C-conformant ways of casting your callback
		3596	function type instead have been omitted.
		3597
		3598	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3599
		3600	Another common scenario is to use some data structure with multiple
		3601	embedded watchers, in effect creating your own watcher that combines
		3602	multiple libev event sources into one "super-watcher":
		3603
		3604	struct my_biggy
		3605	{
		3606	int some_data;
		3607	ev_timer t1;
		3608	ev_timer t2;
		3609	}
		3610
		3611	In this case getting the pointer to C<my_biggy> is a bit more
		3612	complicated: Either you store the address of your C<my_biggy> struct in
		3613	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3614	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3615	real programmers):
		3616
		3617	#include <stddef.h>
		3618
		3619	static void
		3620	t1_cb (EV_P_ ev_timer *w, int revents)
		3621	{
		3622	struct my_biggy big = (struct my_biggy *)
		3623	(((char *)w) - offsetof (struct my_biggy, t1));
		3624	}
		3625
		3626	static void
		3627	t2_cb (EV_P_ ev_timer *w, int revents)
		3628	{
		3629	struct my_biggy big = (struct my_biggy *)
		3630	(((char *)w) - offsetof (struct my_biggy, t2));
		3631	}
		3632
		3633	=head2 AVOIDING FINISHING BEFORE RETURNING
		3634
		3635	Often you have structures like this in event-based programs:
		3636
		3637	callback ()
		3638	{
		3639	free (request);
		3640	}
		3641
		3642	request = start_new_request (..., callback);
		3643
		3644	The intent is to start some "lengthy" operation. The C<request> could be
		3645	used to cancel the operation, or do other things with it.
		3646
		3647	It's not uncommon to have code paths in C<start_new_request> that
		3648	immediately invoke the callback, for example, to report errors. Or you add
		3649	some caching layer that finds that it can skip the lengthy aspects of the
		3650	operation and simply invoke the callback with the result.
		3651
		3652	The problem here is that this will happen I<before> C<start_new_request>
		3653	has returned, so C<request> is not set.
		3654
		3655	Even if you pass the request by some safer means to the callback, you
		3656	might want to do something to the request after starting it, such as
		3657	canceling it, which probably isn't working so well when the callback has
		3658	already been invoked.
		3659
		3660	A common way around all these issues is to make sure that
		3661	C<start_new_request> I<always> returns before the callback is invoked. If
		3662	C<start_new_request> immediately knows the result, it can artificially
		3663	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3664	example, or more sneakily, by reusing an existing (stopped) watcher and
		3665	pushing it into the pending queue:
		3666
		3667	ev_set_cb (watcher, callback);
		3668	ev_feed_event (EV_A_ watcher, 0);
		3669
		3670	This way, C<start_new_request> can safely return before the callback is
		3671	invoked, while not delaying callback invocation too much.
		3672
		3673	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3674
		3675	Often (especially in GUI toolkits) there are places where you have
		3676	I<modal> interaction, which is most easily implemented by recursively
		3677	invoking C<ev_run>.
		3678
		3679	This brings the problem of exiting - a callback might want to finish the
		3680	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3681	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3682	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3683	other combination: In these cases, a simple C<ev_break> will not work.
		3684
		3685	The solution is to maintain "break this loop" variable for each C<ev_run>
		3686	invocation, and use a loop around C<ev_run> until the condition is
		3687	triggered, using C<EVRUN_ONCE>:
		3688
		3689	// main loop
		3690	int exit_main_loop = 0;
		3691
		3692	while (!exit_main_loop)
		3693	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3694
		3695	// in a modal watcher
		3696	int exit_nested_loop = 0;
		3697
		3698	while (!exit_nested_loop)
		3699	ev_run (EV_A_ EVRUN_ONCE);
		3700
		3701	To exit from any of these loops, just set the corresponding exit variable:
		3702
		3703	// exit modal loop
		3704	exit_nested_loop = 1;
		3705
		3706	// exit main program, after modal loop is finished
		3707	exit_main_loop = 1;
		3708
		3709	// exit both
		3710	exit_main_loop = exit_nested_loop = 1;
		3711
		3712	=head2 THREAD LOCKING EXAMPLE
		3713
		3714	Here is a fictitious example of how to run an event loop in a different
		3715	thread from where callbacks are being invoked and watchers are
		3716	created/added/removed.
		3717
		3718	For a real-world example, see the C<EV::Loop::Async> perl module,
		3719	which uses exactly this technique (which is suited for many high-level
		3720	languages).
		3721
		3722	The example uses a pthread mutex to protect the loop data, a condition
		3723	variable to wait for callback invocations, an async watcher to notify the
		3724	event loop thread and an unspecified mechanism to wake up the main thread.
		3725
		3726	First, you need to associate some data with the event loop:
		3727
		3728	typedef struct {
		3729	mutex_t lock; /* global loop lock */
		3730	ev_async async_w;
		3731	thread_t tid;
		3732	cond_t invoke_cv;
		3733	} userdata;
		3734
		3735	void prepare_loop (EV_P)
		3736	{
		3737	// for simplicity, we use a static userdata struct.
		3738	static userdata u;
		3739
		3740	ev_async_init (&u->async_w, async_cb);
		3741	ev_async_start (EV_A_ &u->async_w);
		3742
		3743	pthread_mutex_init (&u->lock, 0);
		3744	pthread_cond_init (&u->invoke_cv, 0);
		3745
		3746	// now associate this with the loop
		3747	ev_set_userdata (EV_A_ u);
		3748	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3749	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3750
		3751	// then create the thread running ev_run
		3752	pthread_create (&u->tid, 0, l_run, EV_A);
		3753	}
		3754
		3755	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3756	solely to wake up the event loop so it takes notice of any new watchers
		3757	that might have been added:
		3758
		3759	static void
		3760	async_cb (EV_P_ ev_async *w, int revents)
		3761	{
		3762	// just used for the side effects
		3763	}
		3764
		3765	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3766	protecting the loop data, respectively.
		3767
		3768	static void
		3769	l_release (EV_P)
		3770	{
		3771	userdata *u = ev_userdata (EV_A);
		3772	pthread_mutex_unlock (&u->lock);
		3773	}
		3774
		3775	static void
		3776	l_acquire (EV_P)
		3777	{
		3778	userdata *u = ev_userdata (EV_A);
		3779	pthread_mutex_lock (&u->lock);
		3780	}
		3781
		3782	The event loop thread first acquires the mutex, and then jumps straight
		3783	into C<ev_run>:
		3784
		3785	void *
		3786	l_run (void *thr_arg)
		3787	{
		3788	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3789
		3790	l_acquire (EV_A);
		3791	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3792	ev_run (EV_A_ 0);
		3793	l_release (EV_A);
		3794
		3795	return 0;
		3796	}
		3797
		3798	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3799	signal the main thread via some unspecified mechanism (signals? pipe
		3800	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3801	have been called (in a while loop because a) spurious wakeups are possible
		3802	and b) skipping inter-thread-communication when there are no pending
		3803	watchers is very beneficial):
		3804
		3805	static void
		3806	l_invoke (EV_P)
		3807	{
		3808	userdata *u = ev_userdata (EV_A);
		3809
		3810	while (ev_pending_count (EV_A))
		3811	{
		3812	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3813	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3814	}
		3815	}
		3816
		3817	Now, whenever the main thread gets told to invoke pending watchers, it
		3818	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3819	thread to continue:
		3820
		3821	static void
		3822	real_invoke_pending (EV_P)
		3823	{
		3824	userdata *u = ev_userdata (EV_A);
		3825
		3826	pthread_mutex_lock (&u->lock);
		3827	ev_invoke_pending (EV_A);
		3828	pthread_cond_signal (&u->invoke_cv);
		3829	pthread_mutex_unlock (&u->lock);
		3830	}
		3831
		3832	Whenever you want to start/stop a watcher or do other modifications to an
		3833	event loop, you will now have to lock:
		3834
		3835	ev_timer timeout_watcher;
		3836	userdata *u = ev_userdata (EV_A);
		3837
		3838	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3839
		3840	pthread_mutex_lock (&u->lock);
		3841	ev_timer_start (EV_A_ &timeout_watcher);
		3842	ev_async_send (EV_A_ &u->async_w);
		3843	pthread_mutex_unlock (&u->lock);
		3844
		3845	Note that sending the C<ev_async> watcher is required because otherwise
		3846	an event loop currently blocking in the kernel will have no knowledge
		3847	about the newly added timer. By waking up the loop it will pick up any new
		3848	watchers in the next event loop iteration.
		3849
		3850	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3851
		3852	While the overhead of a callback that e.g. schedules a thread is small, it
		3853	is still an overhead. If you embed libev, and your main usage is with some
		3854	kind of threads or coroutines, you might want to customise libev so that
		3855	doesn't need callbacks anymore.
		3856
		3857	Imagine you have coroutines that you can switch to using a function
		3858	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3859	and that due to some magic, the currently active coroutine is stored in a
		3860	global called C<current_coro>. Then you can build your own "wait for libev
		3861	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3862	the differing C<;> conventions):
		3863
		3864	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3865	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3866
		3867	That means instead of having a C callback function, you store the
		3868	coroutine to switch to in each watcher, and instead of having libev call
		3869	your callback, you instead have it switch to that coroutine.
		3870
		3871	A coroutine might now wait for an event with a function called
		3872	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3873	matter when, or whether the watcher is active or not when this function is
		3874	called):
		3875
		3876	void
		3877	wait_for_event (ev_watcher *w)
		3878	{
		3879	ev_set_cb (w, current_coro);
		3880	switch_to (libev_coro);
		3881	}
		3882
		3883	That basically suspends the coroutine inside C<wait_for_event> and
		3884	continues the libev coroutine, which, when appropriate, switches back to
		3885	this or any other coroutine.
		3886
		3887	You can do similar tricks if you have, say, threads with an event queue -
		3888	instead of storing a coroutine, you store the queue object and instead of
		3889	switching to a coroutine, you push the watcher onto the queue and notify
		3890	any waiters.
		3891
		3892	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3893	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3894
		3895	// my_ev.h
		3896	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3897	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3898	#include "../libev/ev.h"
		3899
		3900	// my_ev.c
		3901	#define EV_H "my_ev.h"
		3902	#include "../libev/ev.c"
		3903
		3904	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3905	F<my_ev.c> into your project. When properly specifying include paths, you
		3906	can even use F<ev.h> as header file name directly.
3145		3907
3146		3908
3147	=head1 LIBEVENT EMULATION	3909	=head1 LIBEVENT EMULATION
3148		3910
3149	Libev offers a compatibility emulation layer for libevent. It cannot	3911	Libev offers a compatibility emulation layer for libevent. It cannot
3150	emulate the internals of libevent, so here are some usage hints:	3912	emulate the internals of libevent, so here are some usage hints:
3151		3913
3152	=over 4	3914	=over 4
		3915
		3916	=item * Only the libevent-1.4.1-beta API is being emulated.
		3917
		3918	This was the newest libevent version available when libev was implemented,
		3919	and is still mostly unchanged in 2010.
3153		3920
3154	=item * Use it by including <event.h>, as usual.	3921	=item * Use it by including <event.h>, as usual.
3155		3922
3156	=item * The following members are fully supported: ev_base, ev_callback,	3923	=item * The following members are fully supported: ev_base, ev_callback,
3157	ev_arg, ev_fd, ev_res, ev_events.	3924	ev_arg, ev_fd, ev_res, ev_events.
…		…
3163	=item * Priorities are not currently supported. Initialising priorities	3930	=item * Priorities are not currently supported. Initialising priorities
3164	will fail and all watchers will have the same priority, even though there	3931	will fail and all watchers will have the same priority, even though there
3165	is an ev_pri field.	3932	is an ev_pri field.
3166		3933
3167	=item * In libevent, the last base created gets the signals, in libev, the	3934	=item * In libevent, the last base created gets the signals, in libev, the
3168	first base created (== the default loop) gets the signals.	3935	base that registered the signal gets the signals.
3169		3936
3170	=item * Other members are not supported.	3937	=item * Other members are not supported.
3171		3938
3172	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3939	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3173	to use the libev header file and library.	3940	to use the libev header file and library.
3174		3941
3175	=back	3942	=back
3176		3943
3177	=head1 C++ SUPPORT	3944	=head1 C++ SUPPORT
		3945
		3946	=head2 C API
		3947
		3948	The normal C API should work fine when used from C++: both ev.h and the
		3949	libev sources can be compiled as C++. Therefore, code that uses the C API
		3950	will work fine.
		3951
		3952	Proper exception specifications might have to be added to callbacks passed
		3953	to libev: exceptions may be thrown only from watcher callbacks, all
		3954	other callbacks (allocator, syserr, loop acquire/release and periodic
		3955	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3956	()> specification. If you have code that needs to be compiled as both C
		3957	and C++ you can use the C<EV_THROW> macro for this:
		3958
		3959	static void
		3960	fatal_error (const char *msg) EV_THROW
		3961	{
		3962	perror (msg);
		3963	abort ();
		3964	}
		3965
		3966	...
		3967	ev_set_syserr_cb (fatal_error);
		3968
		3969	The only API functions that can currently throw exceptions are C<ev_run>,
		3970	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3971	because it runs cleanup watchers).
		3972
		3973	Throwing exceptions in watcher callbacks is only supported if libev itself
		3974	is compiled with a C++ compiler or your C and C++ environments allow
		3975	throwing exceptions through C libraries (most do).
		3976
		3977	=head2 C++ API
3178		3978
3179	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3979	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3180	you to use some convenience methods to start/stop watchers and also change	3980	you to use some convenience methods to start/stop watchers and also change
3181	the callback model to a model using method callbacks on objects.	3981	the callback model to a model using method callbacks on objects.
3182		3982
…		…
3192	Care has been taken to keep the overhead low. The only data member the C++	3992	Care has been taken to keep the overhead low. The only data member the C++
3193	classes add (compared to plain C-style watchers) is the event loop pointer	3993	classes add (compared to plain C-style watchers) is the event loop pointer
3194	that the watcher is associated with (or no additional members at all if	3994	that the watcher is associated with (or no additional members at all if
3195	you disable C<EV_MULTIPLICITY> when embedding libev).	3995	you disable C<EV_MULTIPLICITY> when embedding libev).
3196		3996
3197	Currently, functions, and static and non-static member functions can be	3997	Currently, functions, static and non-static member functions and classes
3198	used as callbacks. Other types should be easy to add as long as they only	3998	with C<operator ()> can be used as callbacks. Other types should be easy
3199	need one additional pointer for context. If you need support for other	3999	to add as long as they only need one additional pointer for context. If
3200	types of functors please contact the author (preferably after implementing	4000	you need support for other types of functors please contact the author
3201	it).	4001	(preferably after implementing it).
		4002
		4003	For all this to work, your C++ compiler either has to use the same calling
		4004	conventions as your C compiler (for static member functions), or you have
		4005	to embed libev and compile libev itself as C++.
3202		4006
3203	Here is a list of things available in the C<ev> namespace:	4007	Here is a list of things available in the C<ev> namespace:
3204		4008
3205	=over 4	4009	=over 4
3206		4010
…		…
3216	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4020	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3217		4021
3218	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4022	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3219	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4023	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3220	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4024	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3221	defines by many implementations.	4025	defined by many implementations.
3222		4026
3223	All of those classes have these methods:	4027	All of those classes have these methods:
3224		4028
3225	=over 4	4029	=over 4
3226		4030
3227	=item ev::TYPE::TYPE ()	4031	=item ev::TYPE::TYPE ()
3228		4032
3229	=item ev::TYPE::TYPE (struct ev_loop *)	4033	=item ev::TYPE::TYPE (loop)
3230		4034
3231	=item ev::TYPE::~TYPE	4035	=item ev::TYPE::~TYPE
3232		4036
3233	The constructor (optionally) takes an event loop to associate the watcher	4037	The constructor (optionally) takes an event loop to associate the watcher
3234	with. If it is omitted, it will use C<EV_DEFAULT>.	4038	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3267	myclass obj;	4071	myclass obj;
3268	ev::io iow;	4072	ev::io iow;
3269	iow.set <myclass, &myclass::io_cb> (&obj);	4073	iow.set <myclass, &myclass::io_cb> (&obj);
3270		4074
3271	=item w->set (object *)	4075	=item w->set (object *)
3272
3273	This is an B<experimental> feature that might go away in a future version.
3274		4076
3275	This is a variation of a method callback - leaving out the method to call	4077	This is a variation of a method callback - leaving out the method to call
3276	will default the method to C<operator ()>, which makes it possible to use	4078	will default the method to C<operator ()>, which makes it possible to use
3277	functor objects without having to manually specify the C<operator ()> all	4079	functor objects without having to manually specify the C<operator ()> all
3278	the time. Incidentally, you can then also leave out the template argument	4080	the time. Incidentally, you can then also leave out the template argument
…		…
3311	Example: Use a plain function as callback.	4113	Example: Use a plain function as callback.
3312		4114
3313	static void io_cb (ev::io &w, int revents) { }	4115	static void io_cb (ev::io &w, int revents) { }
3314	iow.set <io_cb> ();	4116	iow.set <io_cb> ();
3315		4117
3316	=item w->set (struct ev_loop *)	4118	=item w->set (loop)
3317		4119
3318	Associates a different C<struct ev_loop> with this watcher. You can only	4120	Associates a different C<struct ev_loop> with this watcher. You can only
3319	do this when the watcher is inactive (and not pending either).	4121	do this when the watcher is inactive (and not pending either).
3320		4122
3321	=item w->set ([arguments])	4123	=item w->set ([arguments])
3322		4124
3323	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4125	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4126	with the same arguments. Either this method or a suitable start method
3324	called at least once. Unlike the C counterpart, an active watcher gets	4127	must be called at least once. Unlike the C counterpart, an active watcher
3325	automatically stopped and restarted when reconfiguring it with this	4128	gets automatically stopped and restarted when reconfiguring it with this
3326	method.	4129	method.
		4130
		4131	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4132	clashing with the C<set (loop)> method.
3327		4133
3328	=item w->start ()	4134	=item w->start ()
3329		4135
3330	Starts the watcher. Note that there is no C<loop> argument, as the	4136	Starts the watcher. Note that there is no C<loop> argument, as the
3331	constructor already stores the event loop.	4137	constructor already stores the event loop.
3332		4138
		4139	=item w->start ([arguments])
		4140
		4141	Instead of calling C<set> and C<start> methods separately, it is often
		4142	convenient to wrap them in one call. Uses the same type of arguments as
		4143	the configure C<set> method of the watcher.
		4144
3333	=item w->stop ()	4145	=item w->stop ()
3334		4146
3335	Stops the watcher if it is active. Again, no C<loop> argument.	4147	Stops the watcher if it is active. Again, no C<loop> argument.
3336		4148
3337	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4149	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3349		4161
3350	=back	4162	=back
3351		4163
3352	=back	4164	=back
3353		4165
3354	Example: Define a class with an IO and idle watcher, start one of them in	4166	Example: Define a class with two I/O and idle watchers, start the I/O
3355	the constructor.	4167	watchers in the constructor.
3356		4168
3357	class myclass	4169	class myclass
3358	{	4170	{
3359	ev::io io ; void io_cb (ev::io &w, int revents);	4171	ev::io io ; void io_cb (ev::io &w, int revents);
		4172	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3360	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4173	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3361		4174
3362	myclass (int fd)	4175	myclass (int fd)
3363	{	4176	{
3364	io .set <myclass, &myclass::io_cb > (this);	4177	io .set <myclass, &myclass::io_cb > (this);
		4178	io2 .set <myclass, &myclass::io2_cb > (this);
3365	idle.set <myclass, &myclass::idle_cb> (this);	4179	idle.set <myclass, &myclass::idle_cb> (this);
3366		4180
3367	io.start (fd, ev::READ);	4181	io.set (fd, ev::WRITE); // configure the watcher
		4182	io.start (); // start it whenever convenient
		4183
		4184	io2.start (fd, ev::READ); // set + start in one call
3368	}	4185	}
3369	};	4186	};
3370		4187
3371		4188
3372	=head1 OTHER LANGUAGE BINDINGS	4189	=head1 OTHER LANGUAGE BINDINGS
…		…
3411	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4228	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3412		4229
3413	=item D	4230	=item D
3414		4231
3415	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4232	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3416	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4233	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3417		4234
3418	=item Ocaml	4235	=item Ocaml
3419		4236
3420	Erkki Seppala has written Ocaml bindings for libev, to be found at	4237	Erkki Seppala has written Ocaml bindings for libev, to be found at
3421	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4238	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3422		4239
3423	=item Lua	4240	=item Lua
3424		4241
3425	Brian Maher has written a partial interface to libev	4242	Brian Maher has written a partial interface to libev for lua (at the
3426	for lua (only C<ev_io> and C<ev_timer>), to be found at	4243	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3427	L<http://github.com/brimworks/lua-ev>.	4244	L<http://github.com/brimworks/lua-ev>.
		4245
		4246	=item Javascript
		4247
		4248	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4249
		4250	=item Others
		4251
		4252	There are others, and I stopped counting.
3428		4253
3429	=back	4254	=back
3430		4255
3431		4256
3432	=head1 MACRO MAGIC	4257	=head1 MACRO MAGIC
…		…
3446	loop argument"). The C<EV_A> form is used when this is the sole argument,	4271	loop argument"). The C<EV_A> form is used when this is the sole argument,
3447	C<EV_A_> is used when other arguments are following. Example:	4272	C<EV_A_> is used when other arguments are following. Example:
3448		4273
3449	ev_unref (EV_A);	4274	ev_unref (EV_A);
3450	ev_timer_add (EV_A_ watcher);	4275	ev_timer_add (EV_A_ watcher);
3451	ev_loop (EV_A_ 0);	4276	ev_run (EV_A_ 0);
3452		4277
3453	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4278	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3454	which is often provided by the following macro.	4279	which is often provided by the following macro.
3455		4280
3456	=item C<EV_P>, C<EV_P_>	4281	=item C<EV_P>, C<EV_P_>
…		…
3469	suitable for use with C<EV_A>.	4294	suitable for use with C<EV_A>.
3470		4295
3471	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4296	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3472		4297
3473	Similar to the other two macros, this gives you the value of the default	4298	Similar to the other two macros, this gives you the value of the default
3474	loop, if multiple loops are supported ("ev loop default").	4299	loop, if multiple loops are supported ("ev loop default"). The default loop
		4300	will be initialised if it isn't already initialised.
		4301
		4302	For non-multiplicity builds, these macros do nothing, so you always have
		4303	to initialise the loop somewhere.
3475		4304
3476	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4305	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3477		4306
3478	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4307	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3479	default loop has been initialised (C<UC> == unchecked). Their behaviour	4308	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3496	}	4325	}
3497		4326
3498	ev_check check;	4327	ev_check check;
3499	ev_check_init (&check, check_cb);	4328	ev_check_init (&check, check_cb);
3500	ev_check_start (EV_DEFAULT_ &check);	4329	ev_check_start (EV_DEFAULT_ &check);
3501	ev_loop (EV_DEFAULT_ 0);	4330	ev_run (EV_DEFAULT_ 0);
3502		4331
3503	=head1 EMBEDDING	4332	=head1 EMBEDDING
3504		4333
3505	Libev can (and often is) directly embedded into host	4334	Libev can (and often is) directly embedded into host
3506	applications. Examples of applications that embed it include the Deliantra	4335	applications. Examples of applications that embed it include the Deliantra
…		…
3586	libev.m4	4415	libev.m4
3587		4416
3588	=head2 PREPROCESSOR SYMBOLS/MACROS	4417	=head2 PREPROCESSOR SYMBOLS/MACROS
3589		4418
3590	Libev can be configured via a variety of preprocessor symbols you have to	4419	Libev can be configured via a variety of preprocessor symbols you have to
3591	define before including any of its files. The default in the absence of	4420	define before including (or compiling) any of its files. The default in
3592	autoconf is documented for every option.	4421	the absence of autoconf is documented for every option.
		4422
		4423	Symbols marked with "(h)" do not change the ABI, and can have different
		4424	values when compiling libev vs. including F<ev.h>, so it is permissible
		4425	to redefine them before including F<ev.h> without breaking compatibility
		4426	to a compiled library. All other symbols change the ABI, which means all
		4427	users of libev and the libev code itself must be compiled with compatible
		4428	settings.
3593		4429
3594	=over 4	4430	=over 4
3595		4431
		4432	=item EV_COMPAT3 (h)
		4433
		4434	Backwards compatibility is a major concern for libev. This is why this
		4435	release of libev comes with wrappers for the functions and symbols that
		4436	have been renamed between libev version 3 and 4.
		4437
		4438	You can disable these wrappers (to test compatibility with future
		4439	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4440	sources. This has the additional advantage that you can drop the C<struct>
		4441	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4442	typedef in that case.
		4443
		4444	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4445	and in some even more future version the compatibility code will be
		4446	removed completely.
		4447
3596	=item EV_STANDALONE	4448	=item EV_STANDALONE (h)
3597		4449
3598	Must always be C<1> if you do not use autoconf configuration, which	4450	Must always be C<1> if you do not use autoconf configuration, which
3599	keeps libev from including F<config.h>, and it also defines dummy	4451	keeps libev from including F<config.h>, and it also defines dummy
3600	implementations for some libevent functions (such as logging, which is not	4452	implementations for some libevent functions (such as logging, which is not
3601	supported). It will also not define any of the structs usually found in	4453	supported). It will also not define any of the structs usually found in
3602	F<event.h> that are not directly supported by the libev core alone.	4454	F<event.h> that are not directly supported by the libev core alone.
3603		4455
3604	In standalone mode, libev will still try to automatically deduce the	4456	In standalone mode, libev will still try to automatically deduce the
3605	configuration, but has to be more conservative.	4457	configuration, but has to be more conservative.
		4458
		4459	=item EV_USE_FLOOR
		4460
		4461	If defined to be C<1>, libev will use the C<floor ()> function for its
		4462	periodic reschedule calculations, otherwise libev will fall back on a
		4463	portable (slower) implementation. If you enable this, you usually have to
		4464	link against libm or something equivalent. Enabling this when the C<floor>
		4465	function is not available will fail, so the safe default is to not enable
		4466	this.
3606		4467
3607	=item EV_USE_MONOTONIC	4468	=item EV_USE_MONOTONIC
3608		4469
3609	If defined to be C<1>, libev will try to detect the availability of the	4470	If defined to be C<1>, libev will try to detect the availability of the
3610	monotonic clock option at both compile time and runtime. Otherwise no	4471	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3695		4556
3696	If programs implement their own fd to handle mapping on win32, then this	4557	If programs implement their own fd to handle mapping on win32, then this
3697	macro can be used to override the C<close> function, useful to unregister	4558	macro can be used to override the C<close> function, useful to unregister
3698	file descriptors again. Note that the replacement function has to close	4559	file descriptors again. Note that the replacement function has to close
3699	the underlying OS handle.	4560	the underlying OS handle.
		4561
		4562	=item EV_USE_WSASOCKET
		4563
		4564	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4565	communication socket, which works better in some environments. Otherwise,
		4566	the normal C<socket> function will be used, which works better in other
		4567	environments.
3700		4568
3701	=item EV_USE_POLL	4569	=item EV_USE_POLL
3702		4570
3703	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4571	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3704	backend. Otherwise it will be enabled on non-win32 platforms. It	4572	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3740	If defined to be C<1>, libev will compile in support for the Linux inotify	4608	If defined to be C<1>, libev will compile in support for the Linux inotify
3741	interface to speed up C<ev_stat> watchers. Its actual availability will	4609	interface to speed up C<ev_stat> watchers. Its actual availability will
3742	be detected at runtime. If undefined, it will be enabled if the headers	4610	be detected at runtime. If undefined, it will be enabled if the headers
3743	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4611	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3744		4612
		4613	=item EV_NO_SMP
		4614
		4615	If defined to be C<1>, libev will assume that memory is always coherent
		4616	between threads, that is, threads can be used, but threads never run on
		4617	different cpus (or different cpu cores). This reduces dependencies
		4618	and makes libev faster.
		4619
		4620	=item EV_NO_THREADS
		4621
		4622	If defined to be C<1>, libev will assume that it will never be called
		4623	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4624	above. This reduces dependencies and makes libev faster.
		4625
3745	=item EV_ATOMIC_T	4626	=item EV_ATOMIC_T
3746		4627
3747	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4628	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3748	access is atomic with respect to other threads or signal contexts. No such	4629	access is atomic with respect to other threads or signal contexts. No
3749	type is easily found in the C language, so you can provide your own type	4630	such type is easily found in the C language, so you can provide your own
3750	that you know is safe for your purposes. It is used both for signal handler "locking"	4631	type that you know is safe for your purposes. It is used both for signal
3751	as well as for signal and thread safety in C<ev_async> watchers.	4632	handler "locking" as well as for signal and thread safety in C<ev_async>
		4633	watchers.
3752		4634
3753	In the absence of this define, libev will use C<sig_atomic_t volatile>	4635	In the absence of this define, libev will use C<sig_atomic_t volatile>
3754	(from F<signal.h>), which is usually good enough on most platforms.	4636	(from F<signal.h>), which is usually good enough on most platforms.
3755		4637
3756	=item EV_H	4638	=item EV_H (h)
3757		4639
3758	The name of the F<ev.h> header file used to include it. The default if	4640	The name of the F<ev.h> header file used to include it. The default if
3759	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4641	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3760	used to virtually rename the F<ev.h> header file in case of conflicts.	4642	used to virtually rename the F<ev.h> header file in case of conflicts.
3761		4643
3762	=item EV_CONFIG_H	4644	=item EV_CONFIG_H (h)
3763		4645
3764	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4646	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3765	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4647	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3766	C<EV_H>, above.	4648	C<EV_H>, above.
3767		4649
3768	=item EV_EVENT_H	4650	=item EV_EVENT_H (h)
3769		4651
3770	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4652	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3771	of how the F<event.h> header can be found, the default is C<"event.h">.	4653	of how the F<event.h> header can be found, the default is C<"event.h">.
3772		4654
3773	=item EV_PROTOTYPES	4655	=item EV_PROTOTYPES (h)
3774		4656
3775	If defined to be C<0>, then F<ev.h> will not define any function	4657	If defined to be C<0>, then F<ev.h> will not define any function
3776	prototypes, but still define all the structs and other symbols. This is	4658	prototypes, but still define all the structs and other symbols. This is
3777	occasionally useful if you want to provide your own wrapper functions	4659	occasionally useful if you want to provide your own wrapper functions
3778	around libev functions.	4660	around libev functions.
…		…
3783	will have the C<struct ev_loop *> as first argument, and you can create	4665	will have the C<struct ev_loop *> as first argument, and you can create
3784	additional independent event loops. Otherwise there will be no support	4666	additional independent event loops. Otherwise there will be no support
3785	for multiple event loops and there is no first event loop pointer	4667	for multiple event loops and there is no first event loop pointer
3786	argument. Instead, all functions act on the single default loop.	4668	argument. Instead, all functions act on the single default loop.
3787		4669
		4670	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4671	default loop when multiplicity is switched off - you always have to
		4672	initialise the loop manually in this case.
		4673
3788	=item EV_MINPRI	4674	=item EV_MINPRI
3789		4675
3790	=item EV_MAXPRI	4676	=item EV_MAXPRI
3791		4677
3792	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4678	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3800	fine.	4686	fine.
3801		4687
3802	If your embedding application does not need any priorities, defining these	4688	If your embedding application does not need any priorities, defining these
3803	both to C<0> will save some memory and CPU.	4689	both to C<0> will save some memory and CPU.
3804		4690
3805	=item EV_PERIODIC_ENABLE	4691	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4692	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4693	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3806		4694
3807	If undefined or defined to be C<1>, then periodic timers are supported. If	4695	If undefined or defined to be C<1> (and the platform supports it), then
3808	defined to be C<0>, then they are not. Disabling them saves a few kB of	4696	the respective watcher type is supported. If defined to be C<0>, then it
3809	code.	4697	is not. Disabling watcher types mainly saves code size.
3810		4698
3811	=item EV_IDLE_ENABLE	4699	=item EV_FEATURES
3812
3813	If undefined or defined to be C<1>, then idle watchers are supported. If
3814	defined to be C<0>, then they are not. Disabling them saves a few kB of
3815	code.
3816
3817	=item EV_EMBED_ENABLE
3818
3819	If undefined or defined to be C<1>, then embed watchers are supported. If
3820	defined to be C<0>, then they are not. Embed watchers rely on most other
3821	watcher types, which therefore must not be disabled.
3822
3823	=item EV_STAT_ENABLE
3824
3825	If undefined or defined to be C<1>, then stat watchers are supported. If
3826	defined to be C<0>, then they are not.
3827
3828	=item EV_FORK_ENABLE
3829
3830	If undefined or defined to be C<1>, then fork watchers are supported. If
3831	defined to be C<0>, then they are not.
3832
3833	=item EV_ASYNC_ENABLE
3834
3835	If undefined or defined to be C<1>, then async watchers are supported. If
3836	defined to be C<0>, then they are not.
3837
3838	=item EV_MINIMAL
3839		4700
3840	If you need to shave off some kilobytes of code at the expense of some	4701	If you need to shave off some kilobytes of code at the expense of some
3841	speed (but with the full API), define this symbol to C<1>. Currently this	4702	speed (but with the full API), you can define this symbol to request
3842	is used to override some inlining decisions, saves roughly 30% code size	4703	certain subsets of functionality. The default is to enable all features
3843	on amd64. It also selects a much smaller 2-heap for timer management over	4704	that can be enabled on the platform.
3844	the default 4-heap.
3845		4705
3846	You can save even more by disabling watcher types you do not need	4706	A typical way to use this symbol is to define it to C<0> (or to a bitset
3847	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4707	with some broad features you want) and then selectively re-enable
3848	(C<-DNDEBUG>) will usually reduce code size a lot.	4708	additional parts you want, for example if you want everything minimal,
		4709	but multiple event loop support, async and child watchers and the poll
		4710	backend, use this:
3849		4711
3850	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4712	#define EV_FEATURES 0
3851	provide a bare-bones event library. See C<ev.h> for details on what parts	4713	#define EV_MULTIPLICITY 1
3852	of the API are still available, and do not complain if this subset changes	4714	#define EV_USE_POLL 1
3853	over time.	4715	#define EV_CHILD_ENABLE 1
		4716	#define EV_ASYNC_ENABLE 1
		4717
		4718	The actual value is a bitset, it can be a combination of the following
		4719	values (by default, all of these are enabled):
		4720
		4721	=over 4
		4722
		4723	=item C<1> - faster/larger code
		4724
		4725	Use larger code to speed up some operations.
		4726
		4727	Currently this is used to override some inlining decisions (enlarging the
		4728	code size by roughly 30% on amd64).
		4729
		4730	When optimising for size, use of compiler flags such as C<-Os> with
		4731	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4732	assertions.
		4733
		4734	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4735	(e.g. gcc with C<-Os>).
		4736
		4737	=item C<2> - faster/larger data structures
		4738
		4739	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4740	hash table sizes and so on. This will usually further increase code size
		4741	and can additionally have an effect on the size of data structures at
		4742	runtime.
		4743
		4744	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4745	(e.g. gcc with C<-Os>).
		4746
		4747	=item C<4> - full API configuration
		4748
		4749	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4750	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4751
		4752	=item C<8> - full API
		4753
		4754	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4755	details on which parts of the API are still available without this
		4756	feature, and do not complain if this subset changes over time.
		4757
		4758	=item C<16> - enable all optional watcher types
		4759
		4760	Enables all optional watcher types. If you want to selectively enable
		4761	only some watcher types other than I/O and timers (e.g. prepare,
		4762	embed, async, child...) you can enable them manually by defining
		4763	C<EV_watchertype_ENABLE> to C<1> instead.
		4764
		4765	=item C<32> - enable all backends
		4766
		4767	This enables all backends - without this feature, you need to enable at
		4768	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4769
		4770	=item C<64> - enable OS-specific "helper" APIs
		4771
		4772	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4773	default.
		4774
		4775	=back
		4776
		4777	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4778	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4779	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4780	watchers, timers and monotonic clock support.
		4781
		4782	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4783	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4784	your program might be left out as well - a binary starting a timer and an
		4785	I/O watcher then might come out at only 5Kb.
		4786
		4787	=item EV_API_STATIC
		4788
		4789	If this symbol is defined (by default it is not), then all identifiers
		4790	will have static linkage. This means that libev will not export any
		4791	identifiers, and you cannot link against libev anymore. This can be useful
		4792	when you embed libev, only want to use libev functions in a single file,
		4793	and do not want its identifiers to be visible.
		4794
		4795	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4796	wants to use libev.
		4797
		4798	This option only works when libev is compiled with a C compiler, as C++
		4799	doesn't support the required declaration syntax.
		4800
		4801	=item EV_AVOID_STDIO
		4802
		4803	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4804	functions (printf, scanf, perror etc.). This will increase the code size
		4805	somewhat, but if your program doesn't otherwise depend on stdio and your
		4806	libc allows it, this avoids linking in the stdio library which is quite
		4807	big.
		4808
		4809	Note that error messages might become less precise when this option is
		4810	enabled.
3854		4811
3855	=item EV_NSIG	4812	=item EV_NSIG
3856		4813
3857	The highest supported signal number, +1 (or, the number of	4814	The highest supported signal number, +1 (or, the number of
3858	signals): Normally, libev tries to deduce the maximum number of signals	4815	signals): Normally, libev tries to deduce the maximum number of signals
3859	automatically, but sometimes this fails, in which case it can be	4816	automatically, but sometimes this fails, in which case it can be
3860	specified. Also, using a lower number than detected (C<32> should be	4817	specified. Also, using a lower number than detected (C<32> should be
3861	good for about any system in existance) can save some memory, as libev	4818	good for about any system in existence) can save some memory, as libev
3862	statically allocates some 12-24 bytes per signal number.	4819	statically allocates some 12-24 bytes per signal number.
3863		4820
3864	=item EV_PID_HASHSIZE	4821	=item EV_PID_HASHSIZE
3865		4822
3866	C<ev_child> watchers use a small hash table to distribute workload by	4823	C<ev_child> watchers use a small hash table to distribute workload by
3867	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4824	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3868	than enough. If you need to manage thousands of children you might want to	4825	usually more than enough. If you need to manage thousands of children you
3869	increase this value (I<must> be a power of two).	4826	might want to increase this value (I<must> be a power of two).
3870		4827
3871	=item EV_INOTIFY_HASHSIZE	4828	=item EV_INOTIFY_HASHSIZE
3872		4829
3873	C<ev_stat> watchers use a small hash table to distribute workload by	4830	C<ev_stat> watchers use a small hash table to distribute workload by
3874	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4831	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3875	usually more than enough. If you need to manage thousands of C<ev_stat>	4832	disabled), usually more than enough. If you need to manage thousands of
3876	watchers you might want to increase this value (I<must> be a power of	4833	C<ev_stat> watchers you might want to increase this value (I<must> be a
3877	two).	4834	power of two).
3878		4835
3879	=item EV_USE_4HEAP	4836	=item EV_USE_4HEAP
3880		4837
3881	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4838	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3882	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4839	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3883	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4840	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3884	faster performance with many (thousands) of watchers.	4841	faster performance with many (thousands) of watchers.
3885		4842
3886	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4843	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3887	(disabled).	4844	will be C<0>.
3888		4845
3889	=item EV_HEAP_CACHE_AT	4846	=item EV_HEAP_CACHE_AT
3890		4847
3891	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4848	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3892	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4849	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3893	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4850	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3894	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4851	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3895	but avoids random read accesses on heap changes. This improves performance	4852	but avoids random read accesses on heap changes. This improves performance
3896	noticeably with many (hundreds) of watchers.	4853	noticeably with many (hundreds) of watchers.
3897		4854
3898	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4855	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3899	(disabled).	4856	will be C<0>.
3900		4857
3901	=item EV_VERIFY	4858	=item EV_VERIFY
3902		4859
3903	Controls how much internal verification (see C<ev_loop_verify ()>) will	4860	Controls how much internal verification (see C<ev_verify ()>) will
3904	be done: If set to C<0>, no internal verification code will be compiled	4861	be done: If set to C<0>, no internal verification code will be compiled
3905	in. If set to C<1>, then verification code will be compiled in, but not	4862	in. If set to C<1>, then verification code will be compiled in, but not
3906	called. If set to C<2>, then the internal verification code will be	4863	called. If set to C<2>, then the internal verification code will be
3907	called once per loop, which can slow down libev. If set to C<3>, then the	4864	called once per loop, which can slow down libev. If set to C<3>, then the
3908	verification code will be called very frequently, which will slow down	4865	verification code will be called very frequently, which will slow down
3909	libev considerably.	4866	libev considerably.
3910		4867
3911	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4868	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3912	C<0>.	4869	will be C<0>.
3913		4870
3914	=item EV_COMMON	4871	=item EV_COMMON
3915		4872
3916	By default, all watchers have a C<void *data> member. By redefining	4873	By default, all watchers have a C<void *data> member. By redefining
3917	this macro to a something else you can include more and other types of	4874	this macro to something else you can include more and other types of
3918	members. You have to define it each time you include one of the files,	4875	members. You have to define it each time you include one of the files,
3919	though, and it must be identical each time.	4876	though, and it must be identical each time.
3920		4877
3921	For example, the perl EV module uses something like this:	4878	For example, the perl EV module uses something like this:
3922		4879
…		…
3975	file.	4932	file.
3976		4933
3977	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4934	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3978	that everybody includes and which overrides some configure choices:	4935	that everybody includes and which overrides some configure choices:
3979		4936
3980	#define EV_MINIMAL 1	4937	#define EV_FEATURES 8
3981	#define EV_USE_POLL 0	4938	#define EV_USE_SELECT 1
3982	#define EV_MULTIPLICITY 0
3983	#define EV_PERIODIC_ENABLE 0	4939	#define EV_PREPARE_ENABLE 1
		4940	#define EV_IDLE_ENABLE 1
3984	#define EV_STAT_ENABLE 0	4941	#define EV_SIGNAL_ENABLE 1
3985	#define EV_FORK_ENABLE 0	4942	#define EV_CHILD_ENABLE 1
		4943	#define EV_USE_STDEXCEPT 0
3986	#define EV_CONFIG_H <config.h>	4944	#define EV_CONFIG_H <config.h>
3987	#define EV_MINPRI 0
3988	#define EV_MAXPRI 0
3989		4945
3990	#include "ev++.h"	4946	#include "ev++.h"
3991		4947
3992	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4948	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3993		4949
3994	#include "ev_cpp.h"	4950	#include "ev_cpp.h"
3995	#include "ev.c"	4951	#include "ev.c"
3996		4952
3997	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4953	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3998		4954
3999	=head2 THREADS AND COROUTINES	4955	=head2 THREADS AND COROUTINES
4000		4956
4001	=head3 THREADS	4957	=head3 THREADS
4002		4958
…		…
4053	default loop and triggering an C<ev_async> watcher from the default loop	5009	default loop and triggering an C<ev_async> watcher from the default loop
4054	watcher callback into the event loop interested in the signal.	5010	watcher callback into the event loop interested in the signal.
4055		5011
4056	=back	5012	=back
4057		5013
4058	=head4 THREAD LOCKING EXAMPLE	5014	See also L</THREAD LOCKING EXAMPLE>.
4059
4060	Here is a fictitious example of how to run an event loop in a different
4061	thread than where callbacks are being invoked and watchers are
4062	created/added/removed.
4063
4064	For a real-world example, see the C<EV::Loop::Async> perl module,
4065	which uses exactly this technique (which is suited for many high-level
4066	languages).
4067
4068	The example uses a pthread mutex to protect the loop data, a condition
4069	variable to wait for callback invocations, an async watcher to notify the
4070	event loop thread and an unspecified mechanism to wake up the main thread.
4071
4072	First, you need to associate some data with the event loop:
4073
4074	typedef struct {
4075	mutex_t lock; /* global loop lock */
4076	ev_async async_w;
4077	thread_t tid;
4078	cond_t invoke_cv;
4079	} userdata;
4080
4081	void prepare_loop (EV_P)
4082	{
4083	// for simplicity, we use a static userdata struct.
4084	static userdata u;
4085
4086	ev_async_init (&u->async_w, async_cb);
4087	ev_async_start (EV_A_ &u->async_w);
4088
4089	pthread_mutex_init (&u->lock, 0);
4090	pthread_cond_init (&u->invoke_cv, 0);
4091
4092	// now associate this with the loop
4093	ev_set_userdata (EV_A_ u);
4094	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4095	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4096
4097	// then create the thread running ev_loop
4098	pthread_create (&u->tid, 0, l_run, EV_A);
4099	}
4100
4101	The callback for the C<ev_async> watcher does nothing: the watcher is used
4102	solely to wake up the event loop so it takes notice of any new watchers
4103	that might have been added:
4104
4105	static void
4106	async_cb (EV_P_ ev_async *w, int revents)
4107	{
4108	// just used for the side effects
4109	}
4110
4111	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4112	protecting the loop data, respectively.
4113
4114	static void
4115	l_release (EV_P)
4116	{
4117	userdata *u = ev_userdata (EV_A);
4118	pthread_mutex_unlock (&u->lock);
4119	}
4120
4121	static void
4122	l_acquire (EV_P)
4123	{
4124	userdata *u = ev_userdata (EV_A);
4125	pthread_mutex_lock (&u->lock);
4126	}
4127
4128	The event loop thread first acquires the mutex, and then jumps straight
4129	into C<ev_loop>:
4130
4131	void *
4132	l_run (void *thr_arg)
4133	{
4134	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4135
4136	l_acquire (EV_A);
4137	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4138	ev_loop (EV_A_ 0);
4139	l_release (EV_A);
4140
4141	return 0;
4142	}
4143
4144	Instead of invoking all pending watchers, the C<l_invoke> callback will
4145	signal the main thread via some unspecified mechanism (signals? pipe
4146	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4147	have been called (in a while loop because a) spurious wakeups are possible
4148	and b) skipping inter-thread-communication when there are no pending
4149	watchers is very beneficial):
4150
4151	static void
4152	l_invoke (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155
4156	while (ev_pending_count (EV_A))
4157	{
4158	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4159	pthread_cond_wait (&u->invoke_cv, &u->lock);
4160	}
4161	}
4162
4163	Now, whenever the main thread gets told to invoke pending watchers, it
4164	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4165	thread to continue:
4166
4167	static void
4168	real_invoke_pending (EV_P)
4169	{
4170	userdata *u = ev_userdata (EV_A);
4171
4172	pthread_mutex_lock (&u->lock);
4173	ev_invoke_pending (EV_A);
4174	pthread_cond_signal (&u->invoke_cv);
4175	pthread_mutex_unlock (&u->lock);
4176	}
4177
4178	Whenever you want to start/stop a watcher or do other modifications to an
4179	event loop, you will now have to lock:
4180
4181	ev_timer timeout_watcher;
4182	userdata *u = ev_userdata (EV_A);
4183
4184	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4185
4186	pthread_mutex_lock (&u->lock);
4187	ev_timer_start (EV_A_ &timeout_watcher);
4188	ev_async_send (EV_A_ &u->async_w);
4189	pthread_mutex_unlock (&u->lock);
4190
4191	Note that sending the C<ev_async> watcher is required because otherwise
4192	an event loop currently blocking in the kernel will have no knowledge
4193	about the newly added timer. By waking up the loop it will pick up any new
4194	watchers in the next event loop iteration.
4195		5015
4196	=head3 COROUTINES	5016	=head3 COROUTINES
4197		5017
4198	Libev is very accommodating to coroutines ("cooperative threads"):	5018	Libev is very accommodating to coroutines ("cooperative threads"):
4199	libev fully supports nesting calls to its functions from different	5019	libev fully supports nesting calls to its functions from different
4200	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5020	coroutines (e.g. you can call C<ev_run> on the same loop from two
4201	different coroutines, and switch freely between both coroutines running	5021	different coroutines, and switch freely between both coroutines running
4202	the loop, as long as you don't confuse yourself). The only exception is	5022	the loop, as long as you don't confuse yourself). The only exception is
4203	that you must not do this from C<ev_periodic> reschedule callbacks.	5023	that you must not do this from C<ev_periodic> reschedule callbacks.
4204		5024
4205	Care has been taken to ensure that libev does not keep local state inside	5025	Care has been taken to ensure that libev does not keep local state inside
4206	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5026	C<ev_run>, and other calls do not usually allow for coroutine switches as
4207	they do not call any callbacks.	5027	they do not call any callbacks.
4208		5028
4209	=head2 COMPILER WARNINGS	5029	=head2 COMPILER WARNINGS
4210		5030
4211	Depending on your compiler and compiler settings, you might get no or a	5031	Depending on your compiler and compiler settings, you might get no or a
…		…
4222	maintainable.	5042	maintainable.
4223		5043
4224	And of course, some compiler warnings are just plain stupid, or simply	5044	And of course, some compiler warnings are just plain stupid, or simply
4225	wrong (because they don't actually warn about the condition their message	5045	wrong (because they don't actually warn about the condition their message
4226	seems to warn about). For example, certain older gcc versions had some	5046	seems to warn about). For example, certain older gcc versions had some
4227	warnings that resulted an extreme number of false positives. These have	5047	warnings that resulted in an extreme number of false positives. These have
4228	been fixed, but some people still insist on making code warn-free with	5048	been fixed, but some people still insist on making code warn-free with
4229	such buggy versions.	5049	such buggy versions.
4230		5050
4231	While libev is written to generate as few warnings as possible,	5051	While libev is written to generate as few warnings as possible,
4232	"warn-free" code is not a goal, and it is recommended not to build libev	5052	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4268	I suggest using suppression lists.	5088	I suggest using suppression lists.
4269		5089
4270		5090
4271	=head1 PORTABILITY NOTES	5091	=head1 PORTABILITY NOTES
4272		5092
		5093	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5094
		5095	GNU/Linux is the only common platform that supports 64 bit file/large file
		5096	interfaces but I<disables> them by default.
		5097
		5098	That means that libev compiled in the default environment doesn't support
		5099	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5100
		5101	Unfortunately, many programs try to work around this GNU/Linux issue
		5102	by enabling the large file API, which makes them incompatible with the
		5103	standard libev compiled for their system.
		5104
		5105	Likewise, libev cannot enable the large file API itself as this would
		5106	suddenly make it incompatible to the default compile time environment,
		5107	i.e. all programs not using special compile switches.
		5108
		5109	=head2 OS/X AND DARWIN BUGS
		5110
		5111	The whole thing is a bug if you ask me - basically any system interface
		5112	you touch is broken, whether it is locales, poll, kqueue or even the
		5113	OpenGL drivers.
		5114
		5115	=head3 C<kqueue> is buggy
		5116
		5117	The kqueue syscall is broken in all known versions - most versions support
		5118	only sockets, many support pipes.
		5119
		5120	Libev tries to work around this by not using C<kqueue> by default on this
		5121	rotten platform, but of course you can still ask for it when creating a
		5122	loop - embedding a socket-only kqueue loop into a select-based one is
		5123	probably going to work well.
		5124
		5125	=head3 C<poll> is buggy
		5126
		5127	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5128	implementation by something calling C<kqueue> internally around the 10.5.6
		5129	release, so now C<kqueue> I<and> C<poll> are broken.
		5130
		5131	Libev tries to work around this by not using C<poll> by default on
		5132	this rotten platform, but of course you can still ask for it when creating
		5133	a loop.
		5134
		5135	=head3 C<select> is buggy
		5136
		5137	All that's left is C<select>, and of course Apple found a way to fuck this
		5138	one up as well: On OS/X, C<select> actively limits the number of file
		5139	descriptors you can pass in to 1024 - your program suddenly crashes when
		5140	you use more.
		5141
		5142	There is an undocumented "workaround" for this - defining
		5143	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5144	work on OS/X.
		5145
		5146	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5147
		5148	=head3 C<errno> reentrancy
		5149
		5150	The default compile environment on Solaris is unfortunately so
		5151	thread-unsafe that you can't even use components/libraries compiled
		5152	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5153	defined by default. A valid, if stupid, implementation choice.
		5154
		5155	If you want to use libev in threaded environments you have to make sure
		5156	it's compiled with C<_REENTRANT> defined.
		5157
		5158	=head3 Event port backend
		5159
		5160	The scalable event interface for Solaris is called "event
		5161	ports". Unfortunately, this mechanism is very buggy in all major
		5162	releases. If you run into high CPU usage, your program freezes or you get
		5163	a large number of spurious wakeups, make sure you have all the relevant
		5164	and latest kernel patches applied. No, I don't know which ones, but there
		5165	are multiple ones to apply, and afterwards, event ports actually work
		5166	great.
		5167
		5168	If you can't get it to work, you can try running the program by setting
		5169	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5170	C<select> backends.
		5171
		5172	=head2 AIX POLL BUG
		5173
		5174	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5175	this by trying to avoid the poll backend altogether (i.e. it's not even
		5176	compiled in), which normally isn't a big problem as C<select> works fine
		5177	with large bitsets on AIX, and AIX is dead anyway.
		5178
4273	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5179	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5180
		5181	=head3 General issues
4274		5182
4275	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5183	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4276	requires, and its I/O model is fundamentally incompatible with the POSIX	5184	requires, and its I/O model is fundamentally incompatible with the POSIX
4277	model. Libev still offers limited functionality on this platform in	5185	model. Libev still offers limited functionality on this platform in
4278	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5186	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4279	descriptors. This only applies when using Win32 natively, not when using	5187	descriptors. This only applies when using Win32 natively, not when using
4280	e.g. cygwin.	5188	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5189	as every compiler comes with a slightly differently broken/incompatible
		5190	environment.
4281		5191
4282	Lifting these limitations would basically require the full	5192	Lifting these limitations would basically require the full
4283	re-implementation of the I/O system. If you are into these kinds of	5193	re-implementation of the I/O system. If you are into this kind of thing,
4284	things, then note that glib does exactly that for you in a very portable	5194	then note that glib does exactly that for you in a very portable way (note
4285	way (note also that glib is the slowest event library known to man).	5195	also that glib is the slowest event library known to man).
4286		5196
4287	There is no supported compilation method available on windows except	5197	There is no supported compilation method available on windows except
4288	embedding it into other applications.	5198	embedding it into other applications.
4289		5199
4290	Sensible signal handling is officially unsupported by Microsoft - libev	5200	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4318	you do I<not> compile the F<ev.c> or any other embedded source files!):	5228	you do I<not> compile the F<ev.c> or any other embedded source files!):
4319		5229
4320	#include "evwrap.h"	5230	#include "evwrap.h"
4321	#include "ev.c"	5231	#include "ev.c"
4322		5232
4323	=over 4
4324
4325	=item The winsocket select function	5233	=head3 The winsocket C<select> function
4326		5234
4327	The winsocket C<select> function doesn't follow POSIX in that it	5235	The winsocket C<select> function doesn't follow POSIX in that it
4328	requires socket I<handles> and not socket I<file descriptors> (it is	5236	requires socket I<handles> and not socket I<file descriptors> (it is
4329	also extremely buggy). This makes select very inefficient, and also	5237	also extremely buggy). This makes select very inefficient, and also
4330	requires a mapping from file descriptors to socket handles (the Microsoft	5238	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4339	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5247	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4340		5248
4341	Note that winsockets handling of fd sets is O(n), so you can easily get a	5249	Note that winsockets handling of fd sets is O(n), so you can easily get a
4342	complexity in the O(n²) range when using win32.	5250	complexity in the O(n²) range when using win32.
4343		5251
4344	=item Limited number of file descriptors	5252	=head3 Limited number of file descriptors
4345		5253
4346	Windows has numerous arbitrary (and low) limits on things.	5254	Windows has numerous arbitrary (and low) limits on things.
4347		5255
4348	Early versions of winsocket's select only supported waiting for a maximum	5256	Early versions of winsocket's select only supported waiting for a maximum
4349	of C<64> handles (probably owning to the fact that all windows kernels	5257	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4364	runtime libraries. This might get you to about C<512> or C<2048> sockets	5272	runtime libraries. This might get you to about C<512> or C<2048> sockets
4365	(depending on windows version and/or the phase of the moon). To get more,	5273	(depending on windows version and/or the phase of the moon). To get more,
4366	you need to wrap all I/O functions and provide your own fd management, but	5274	you need to wrap all I/O functions and provide your own fd management, but
4367	the cost of calling select (O(n²)) will likely make this unworkable.	5275	the cost of calling select (O(n²)) will likely make this unworkable.
4368		5276
4369	=back
4370
4371	=head2 PORTABILITY REQUIREMENTS	5277	=head2 PORTABILITY REQUIREMENTS
4372		5278
4373	In addition to a working ISO-C implementation and of course the	5279	In addition to a working ISO-C implementation and of course the
4374	backend-specific APIs, libev relies on a few additional extensions:	5280	backend-specific APIs, libev relies on a few additional extensions:
4375		5281
…		…
4381	Libev assumes not only that all watcher pointers have the same internal	5287	Libev assumes not only that all watcher pointers have the same internal
4382	structure (guaranteed by POSIX but not by ISO C for example), but it also	5288	structure (guaranteed by POSIX but not by ISO C for example), but it also
4383	assumes that the same (machine) code can be used to call any watcher	5289	assumes that the same (machine) code can be used to call any watcher
4384	callback: The watcher callbacks have different type signatures, but libev	5290	callback: The watcher callbacks have different type signatures, but libev
4385	calls them using an C<ev_watcher *> internally.	5291	calls them using an C<ev_watcher *> internally.
		5292
		5293	=item pointer accesses must be thread-atomic
		5294
		5295	Accessing a pointer value must be atomic, it must both be readable and
		5296	writable in one piece - this is the case on all current architectures.
4386		5297
4387	=item C<sig_atomic_t volatile> must be thread-atomic as well	5298	=item C<sig_atomic_t volatile> must be thread-atomic as well
4388		5299
4389	The type C<sig_atomic_t volatile> (or whatever is defined as	5300	The type C<sig_atomic_t volatile> (or whatever is defined as
4390	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5301	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4399	thread" or will block signals process-wide, both behaviours would	5310	thread" or will block signals process-wide, both behaviours would
4400	be compatible with libev. Interaction between C<sigprocmask> and	5311	be compatible with libev. Interaction between C<sigprocmask> and
4401	C<pthread_sigmask> could complicate things, however.	5312	C<pthread_sigmask> could complicate things, however.
4402		5313
4403	The most portable way to handle signals is to block signals in all threads	5314	The most portable way to handle signals is to block signals in all threads
4404	except the initial one, and run the default loop in the initial thread as	5315	except the initial one, and run the signal handling loop in the initial
4405	well.	5316	thread as well.
4406		5317
4407	=item C<long> must be large enough for common memory allocation sizes	5318	=item C<long> must be large enough for common memory allocation sizes
4408		5319
4409	To improve portability and simplify its API, libev uses C<long> internally	5320	To improve portability and simplify its API, libev uses C<long> internally
4410	instead of C<size_t> when allocating its data structures. On non-POSIX	5321	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4413	watchers.	5324	watchers.
4414		5325
4415	=item C<double> must hold a time value in seconds with enough accuracy	5326	=item C<double> must hold a time value in seconds with enough accuracy
4416		5327
4417	The type C<double> is used to represent timestamps. It is required to	5328	The type C<double> is used to represent timestamps. It is required to
4418	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5329	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4419	enough for at least into the year 4000. This requirement is fulfilled by	5330	good enough for at least into the year 4000 with millisecond accuracy
		5331	(the design goal for libev). This requirement is overfulfilled by
4420	implementations implementing IEEE 754, which is basically all existing	5332	implementations using IEEE 754, which is basically all existing ones.
		5333
4421	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5334	With IEEE 754 doubles, you get microsecond accuracy until at least the
4422	2200.	5335	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5336	is either obsolete or somebody patched it to use C<long double> or
		5337	something like that, just kidding).
4423		5338
4424	=back	5339	=back
4425		5340
4426	If you know of other additional requirements drop me a note.	5341	If you know of other additional requirements drop me a note.
4427		5342
…		…
4489	=item Processing ev_async_send: O(number_of_async_watchers)	5404	=item Processing ev_async_send: O(number_of_async_watchers)
4490		5405
4491	=item Processing signals: O(max_signal_number)	5406	=item Processing signals: O(max_signal_number)
4492		5407
4493	Sending involves a system call I<iff> there were no other C<ev_async_send>	5408	Sending involves a system call I<iff> there were no other C<ev_async_send>
4494	calls in the current loop iteration. Checking for async and signal events	5409	calls in the current loop iteration and the loop is currently
		5410	blocked. Checking for async and signal events involves iterating over all
4495	involves iterating over all running async watchers or all signal numbers.	5411	running async watchers or all signal numbers.
4496		5412
4497	=back	5413	=back
4498		5414
4499		5415
		5416	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5417
		5418	The major version 4 introduced some incompatible changes to the API.
		5419
		5420	At the moment, the C<ev.h> header file provides compatibility definitions
		5421	for all changes, so most programs should still compile. The compatibility
		5422	layer might be removed in later versions of libev, so better update to the
		5423	new API early than late.
		5424
		5425	=over 4
		5426
		5427	=item C<EV_COMPAT3> backwards compatibility mechanism
		5428
		5429	The backward compatibility mechanism can be controlled by
		5430	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5431	section.
		5432
		5433	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5434
		5435	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5436
		5437	ev_loop_destroy (EV_DEFAULT_UC);
		5438	ev_loop_fork (EV_DEFAULT);
		5439
		5440	=item function/symbol renames
		5441
		5442	A number of functions and symbols have been renamed:
		5443
		5444	ev_loop => ev_run
		5445	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5446	EVLOOP_ONESHOT => EVRUN_ONCE
		5447
		5448	ev_unloop => ev_break
		5449	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5450	EVUNLOOP_ONE => EVBREAK_ONE
		5451	EVUNLOOP_ALL => EVBREAK_ALL
		5452
		5453	EV_TIMEOUT => EV_TIMER
		5454
		5455	ev_loop_count => ev_iteration
		5456	ev_loop_depth => ev_depth
		5457	ev_loop_verify => ev_verify
		5458
		5459	Most functions working on C<struct ev_loop> objects don't have an
		5460	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5461	associated constants have been renamed to not collide with the C<struct
		5462	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5463	as all other watcher types. Note that C<ev_loop_fork> is still called
		5464	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5465	typedef.
		5466
		5467	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5468
		5469	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5470	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5471	and work, but the library code will of course be larger.
		5472
		5473	=back
		5474
		5475
4500	=head1 GLOSSARY	5476	=head1 GLOSSARY
4501		5477
4502	=over 4	5478	=over 4
4503		5479
4504	=item active	5480	=item active
4505		5481
4506	A watcher is active as long as it has been started (has been attached to	5482	A watcher is active as long as it has been started and not yet stopped.
4507	an event loop) but not yet stopped (disassociated from the event loop).	5483	See L</WATCHER STATES> for details.
4508		5484
4509	=item application	5485	=item application
4510		5486
4511	In this document, an application is whatever is using libev.	5487	In this document, an application is whatever is using libev.
		5488
		5489	=item backend
		5490
		5491	The part of the code dealing with the operating system interfaces.
4512		5492
4513	=item callback	5493	=item callback
4514		5494
4515	The address of a function that is called when some event has been	5495	The address of a function that is called when some event has been
4516	detected. Callbacks are being passed the event loop, the watcher that	5496	detected. Callbacks are being passed the event loop, the watcher that
4517	received the event, and the actual event bitset.	5497	received the event, and the actual event bitset.
4518		5498
4519	=item callback invocation	5499	=item callback/watcher invocation
4520		5500
4521	The act of calling the callback associated with a watcher.	5501	The act of calling the callback associated with a watcher.
4522		5502
4523	=item event	5503	=item event
4524		5504
4525	A change of state of some external event, such as data now being available	5505	A change of state of some external event, such as data now being available
4526	for reading on a file descriptor, time having passed or simply not having	5506	for reading on a file descriptor, time having passed or simply not having
4527	any other events happening anymore.	5507	any other events happening anymore.
4528		5508
4529	In libev, events are represented as single bits (such as C<EV_READ> or	5509	In libev, events are represented as single bits (such as C<EV_READ> or
4530	C<EV_TIMEOUT>).	5510	C<EV_TIMER>).
4531		5511
4532	=item event library	5512	=item event library
4533		5513
4534	A software package implementing an event model and loop.	5514	A software package implementing an event model and loop.
4535		5515
…		…
4543	The model used to describe how an event loop handles and processes	5523	The model used to describe how an event loop handles and processes
4544	watchers and events.	5524	watchers and events.
4545		5525
4546	=item pending	5526	=item pending
4547		5527
4548	A watcher is pending as soon as the corresponding event has been detected,	5528	A watcher is pending as soon as the corresponding event has been
4549	and stops being pending as soon as the watcher will be invoked or its	5529	detected. See L</WATCHER STATES> for details.
4550	pending status is explicitly cleared by the application.
4551
4552	A watcher can be pending, but not active. Stopping a watcher also clears
4553	its pending status.
4554		5530
4555	=item real time	5531	=item real time
4556		5532
4557	The physical time that is observed. It is apparently strictly monotonic :)	5533	The physical time that is observed. It is apparently strictly monotonic :)
4558		5534
4559	=item wall-clock time	5535	=item wall-clock time
4560		5536
4561	The time and date as shown on clocks. Unlike real time, it can actually	5537	The time and date as shown on clocks. Unlike real time, it can actually
4562	be wrong and jump forwards and backwards, e.g. when the you adjust your	5538	be wrong and jump forwards and backwards, e.g. when you adjust your
4563	clock.	5539	clock.
4564		5540
4565	=item watcher	5541	=item watcher
4566		5542
4567	A data structure that describes interest in certain events. Watchers need	5543	A data structure that describes interest in certain events. Watchers need
4568	to be started (attached to an event loop) before they can receive events.	5544	to be started (attached to an event loop) before they can receive events.
4569		5545
4570	=item watcher invocation
4571
4572	The act of calling the callback associated with a watcher.
4573
4574	=back	5546	=back
4575		5547
4576	=head1 AUTHOR	5548	=head1 AUTHOR
4577		5549
4578	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5550	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5551	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4579		5552

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