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Revision 1.432 by root, Sat Apr 26 14:28:48 2014 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
171		182
172	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
173		184
174	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
176	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
177		194
178	=item int ev_version_major ()	195	=item int ev_version_major ()
179		196
180	=item int ev_version_minor ()	197	=item int ev_version_minor ()
181		198
…		…
192	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	211	not a problem.
195		212
196	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
198		216
199	assert (("libev version mismatch",	217	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
202		220
…		…
213	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
215		233
216	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
217		235
218	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
224		243
225	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
226		245
227	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
232		251
233	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
234		253
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		255
237	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	285	}
267		286
268	...	287	...
269	ev_set_allocator (persistent_realloc);	288	ev_set_allocator (persistent_realloc);
270		289
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	290	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		291
273	Set the callback function to call on a retryable system call error (such	292	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	293	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	294	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	295	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	307	}
289		308
290	...	309	...
291	ev_set_syserr_cb (fatal_error);	310	ev_set_syserr_cb (fatal_error);
292		311
		312	=item ev_feed_signal (int signum)
		313
		314	This function can be used to "simulate" a signal receive. It is completely
		315	safe to call this function at any time, from any context, including signal
		316	handlers or random threads.
		317
		318	Its main use is to customise signal handling in your process, especially
		319	in the presence of threads. For example, you could block signals
		320	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		321	creating any loops), and in one thread, use C<sigwait> or any other
		322	mechanism to wait for signals, then "deliver" them to libev by calling
		323	C<ev_feed_signal>.
		324
293	=back	325	=back
294		326
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	327	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		328
297	An event loop is described by a C<struct ev_loop *> (the C<struct>	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	is I<not> optional in this case, as there is also an C<ev_loop>	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	I<function>).	331	libev 3 had an C<ev_loop> function colliding with the struct name).
300		332
301	The library knows two types of such loops, the I<default> loop, which	333	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created loops which do	334	supports child process events, and dynamically created event loops which
303	not.	335	do not.
304		336
305	=over 4	337	=over 4
306		338
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	339	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		340
309	This will initialise the default event loop if it hasn't been initialised	341	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	342	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	343	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	344	C<ev_loop_new>.
		345
		346	If the default loop is already initialised then this function simply
		347	returns it (and ignores the flags. If that is troubling you, check
		348	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		349	flags, which should almost always be C<0>, unless the caller is also the
		350	one calling C<ev_run> or otherwise qualifies as "the main program".
313		351
314	If you don't know what event loop to use, use the one returned from this	352	If you don't know what event loop to use, use the one returned from this
315	function.	353	function (or via the C<EV_DEFAULT> macro).
316		354
317	Note that this function is I<not> thread-safe, so if you want to use it	355	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	356	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	357	that this case is unlikely, as loops cannot be shared easily between
		358	threads anyway).
320		359
321	The default loop is the only loop that can handle C<ev_signal> and	360	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	361	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	362	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	363	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	364	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	365
		366	Example: This is the most typical usage.
		367
		368	if (!ev_default_loop (0))
		369	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		370
		371	Example: Restrict libev to the select and poll backends, and do not allow
		372	environment settings to be taken into account:
		373
		374	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		375
		376	=item struct ev_loop *ev_loop_new (unsigned int flags)
		377
		378	This will create and initialise a new event loop object. If the loop
		379	could not be initialised, returns false.
		380
		381	This function is thread-safe, and one common way to use libev with
		382	threads is indeed to create one loop per thread, and using the default
		383	loop in the "main" or "initial" thread.
327		384
328	The flags argument can be used to specify special behaviour or specific	385	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	386	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		387
331	The following flags are supported:	388	The following flags are supported:
…		…
341		398
342	If this flag bit is or'ed into the flag value (or the program runs setuid	399	If this flag bit is or'ed into the flag value (or the program runs setuid
343	or setgid) then libev will I<not> look at the environment variable	400	or setgid) then libev will I<not> look at the environment variable
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	401	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	override the flags completely if it is found in the environment. This is	402	override the flags completely if it is found in the environment. This is
346	useful to try out specific backends to test their performance, or to work	403	useful to try out specific backends to test their performance, to work
347	around bugs.	404	around bugs, or to make libev threadsafe (accessing environment variables
		405	cannot be done in a threadsafe way, but usually it works if no other
		406	thread modifies them).
348		407
349	=item C<EVFLAG_FORKCHECK>	408	=item C<EVFLAG_FORKCHECK>
350		409
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	410	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	411	make libev check for a fork in each iteration by enabling this flag.
…		…
366	environment variable.	425	environment variable.
367		426
368	=item C<EVFLAG_NOINOTIFY>	427	=item C<EVFLAG_NOINOTIFY>
369		428
370	When this flag is specified, then libev will not attempt to use the	429	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	430	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	431	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	432	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		433
375	=item C<EVFLAG_SIGNALFD>	434	=item C<EVFLAG_SIGNALFD>
376		435
377	When this flag is specified, then libev will attempt to use the	436	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	437	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	438	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	439	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	440	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	441	threads that are not interested in handling them.
383		442
384	Signalfd will not be used by default as this changes your signal mask, and	443	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	444	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	445	example) that can't properly initialise their signal masks.
		446
		447	=item C<EVFLAG_NOSIGMASK>
		448
		449	When this flag is specified, then libev will avoid to modify the signal
		450	mask. Specifically, this means you have to make sure signals are unblocked
		451	when you want to receive them.
		452
		453	This behaviour is useful when you want to do your own signal handling, or
		454	want to handle signals only in specific threads and want to avoid libev
		455	unblocking the signals.
		456
		457	It's also required by POSIX in a threaded program, as libev calls
		458	C<sigprocmask>, whose behaviour is officially unspecified.
		459
		460	This flag's behaviour will become the default in future versions of libev.
387		461
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	462	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		463
390	This is your standard select(2) backend. Not I<completely> standard, as	464	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	465	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	493	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		494
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	495	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	496	kernels).
423		497
424	For few fds, this backend is a bit little slower than poll and select,	498	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	499	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	500	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	501	fd), epoll scales either O(1) or O(active_fds).
428		502
429	The epoll mechanism deserves honorable mention as the most misdesigned	503	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	504	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	505	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	506	descriptor (and unnecessary guessing of parameters), problems with dup,
		507	returning before the timeout value, resulting in additional iterations
		508	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	509	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	510	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	511	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	512	and is of course hard to detect.
437		513
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	514	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	515	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	516	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	517	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	518	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	519	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	520	that against the events to filter out spurious ones, recreating the set
		521	when required. Epoll also erroneously rounds down timeouts, but gives you
		522	no way to know when and by how much, so sometimes you have to busy-wait
		523	because epoll returns immediately despite a nonzero timeout. And last
		524	not least, it also refuses to work with some file descriptors which work
		525	perfectly fine with C<select> (files, many character devices...).
		526
		527	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		528	cobbled together in a hurry, no thought to design or interaction with
		529	others. Oh, the pain, will it ever stop...
445		530
446	While stopping, setting and starting an I/O watcher in the same iteration	531	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	532	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	533	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	534	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
486		571
487	It scales in the same way as the epoll backend, but the interface to the	572	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	573	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	574	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	575	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	576	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	577	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	578	drops fds silently in similarly hard-to-detect cases.
494		579
495	This backend usually performs well under most conditions.	580	This backend usually performs well under most conditions.
496		581
497	While nominally embeddable in other event loops, this doesn't work	582	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	583	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	600	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		601
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	602	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	603	it's really slow, but it still scales very well (O(active_fds)).
519		604
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	605	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	606	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	607	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	608	might perform better.
528		609
529	On the positive side, with the exception of the spurious readiness	610	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	611	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	612	among the OS-specific backends (I vastly prefer correctness over speed
		613	hacks).
		614
		615	On the negative side, the interface is I<bizarre> - so bizarre that
		616	even sun itself gets it wrong in their code examples: The event polling
		617	function sometimes returns events to the caller even though an error
		618	occurred, but with no indication whether it has done so or not (yes, it's
		619	even documented that way) - deadly for edge-triggered interfaces where you
		620	absolutely have to know whether an event occurred or not because you have
		621	to re-arm the watcher.
		622
		623	Fortunately libev seems to be able to work around these idiocies.
533		624
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	625	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	626	C<EVBACKEND_POLL>.
536		627
537	=item C<EVBACKEND_ALL>	628	=item C<EVBACKEND_ALL>
538		629
539	Try all backends (even potentially broken ones that wouldn't be tried	630	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	631	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	632	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		633
543	It is definitely not recommended to use this flag.	634	It is definitely not recommended to use this flag, use whatever
		635	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		636	at all.
		637
		638	=item C<EVBACKEND_MASK>
		639
		640	Not a backend at all, but a mask to select all backend bits from a
		641	C<flags> value, in case you want to mask out any backends from a flags
		642	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		643
545	=back	644	=back
546		645
547	If one or more of the backend flags are or'ed into the flags value,	646	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	647	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	648	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	649	()> will be tried.
551		650
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	651	Example: Try to create a event loop that uses epoll and nothing else.
579		652
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	653	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	654	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	655	fatal ("no epoll found here, maybe it hides under your chair");
583		656
		657	Example: Use whatever libev has to offer, but make sure that kqueue is
		658	used if available.
		659
		660	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		661
584	=item ev_default_destroy ()	662	=item ev_loop_destroy (loop)
585		663
586	Destroys the default loop (frees all memory and kernel state etc.). None	664	Destroys an event loop object (frees all memory and kernel state
587	of the active event watchers will be stopped in the normal sense, so	665	etc.). None of the active event watchers will be stopped in the normal
588	e.g. C<ev_is_active> might still return true. It is your responsibility to	666	sense, so e.g. C<ev_is_active> might still return true. It is your
589	either stop all watchers cleanly yourself I<before> calling this function,	667	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	668	calling this function, or cope with the fact afterwards (which is usually
591	can just ignore the watchers and/or C<free ()> them for example).	669	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		670	for example).
592		671
593	Note that certain global state, such as signal state (and installed signal	672	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	673	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	674	as signal and child watchers) would need to be stopped manually.
596		675
597	In general it is not advisable to call this function except in the	676	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	677	C<ev_loop_new>, but it can also be used on the default loop returned by
		678	C<ev_default_loop>, in which case it is not thread-safe.
		679
		680	Note that it is not advisable to call this function on the default loop
		681	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	682	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	683	and C<ev_loop_destroy>.
601		684
602	=item ev_loop_destroy (loop)	685	=item ev_loop_fork (loop)
603		686
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	This function sets a flag that causes subsequent C<ev_loop> iterations	687	This function sets a flag that causes subsequent C<ev_run> iterations to
610	to reinitialise the kernel state for backends that have one. Despite the	688	reinitialise the kernel state for backends that have one. Despite the
611	name, you can call it anytime, but it makes most sense after forking, in	689	name, you can call it anytime, but it makes most sense after forking, in
612	the child process (or both child and parent, but that again makes little	690	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
613	sense). You I<must> call it in the child before using any of the libev	691	child before resuming or calling C<ev_run>.
614	functions, and it will only take effect at the next C<ev_loop> iteration.
615		692
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	693	Again, you I<have> to call it on I<any> loop that you want to re-use after
617	a fork, I<even if you do not plan to use the loop in the parent>. This is	694	a fork, I<even if you do not plan to use the loop in the parent>. This is
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	695	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	696	during fork.
620		697
621	On the other hand, you only need to call this function in the child	698	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	699	process if and only if you want to use the event loop in the child. If
623	just fork+exec or create a new loop in the child, you don't have to call	700	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	701	call it at all (in fact, C<epoll> is so badly broken that it makes a
		702	difference, but libev will usually detect this case on its own and do a
		703	costly reset of the backend).
625		704
626	The function itself is quite fast and it's usually not a problem to call	705	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	706	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		707
		708	Example: Automate calling C<ev_loop_fork> on the default loop when
		709	using pthreads.
		710
		711	static void
		712	post_fork_child (void)
		713	{
		714	ev_loop_fork (EV_DEFAULT);
		715	}
		716
		717	...
630	pthread_atfork (0, 0, ev_default_fork);	718	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		719
639	=item int ev_is_default_loop (loop)	720	=item int ev_is_default_loop (loop)
640		721
641	Returns true when the given loop is, in fact, the default loop, and false	722	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	723	otherwise.
643		724
644	=item unsigned int ev_iteration (loop)	725	=item unsigned int ev_iteration (loop)
645		726
646	Returns the current iteration count for the loop, which is identical to	727	Returns the current iteration count for the event loop, which is identical
647	the number of times libev did poll for new events. It starts at C<0> and	728	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	729	and happily wraps around with enough iterations.
649		730
650	This value can sometimes be useful as a generation counter of sorts (it	731	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	732	"ticks" the number of loop iterations), as it roughly corresponds with
652	C<ev_prepare> and C<ev_check> calls - and is incremented between the	733	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	734	prepare and check phases.
654		735
655	=item unsigned int ev_depth (loop)	736	=item unsigned int ev_depth (loop)
656		737
657	Returns the number of times C<ev_loop> was entered minus the number of	738	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	739	times C<ev_run> was exited normally, in other words, the recursion depth.
659		740
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	741	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	742	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	743	in which case it is higher.
663		744
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	745	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	etc.), doesn't count as "exit" - consider this as a hint to avoid such	746	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	747	as a hint to avoid such ungentleman-like behaviour unless it's really
		748	convenient, in which case it is fully supported.
667		749
668	=item unsigned int ev_backend (loop)	750	=item unsigned int ev_backend (loop)
669		751
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	752	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	753	use.
…		…
680		762
681	=item ev_now_update (loop)	763	=item ev_now_update (loop)
682		764
683	Establishes the current time by querying the kernel, updating the time	765	Establishes the current time by querying the kernel, updating the time
684	returned by C<ev_now ()> in the progress. This is a costly operation and	766	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	767	is usually done automatically within C<ev_run ()>.
686		768
687	This function is rarely useful, but when some event callback runs for a	769	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	770	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	771	the current time is a good idea.
690		772
691	See also L<The special problem of time updates> in the C<ev_timer> section.	773	See also L</The special problem of time updates> in the C<ev_timer> section.
692		774
693	=item ev_suspend (loop)	775	=item ev_suspend (loop)
694		776
695	=item ev_resume (loop)	777	=item ev_resume (loop)
696		778
697	These two functions suspend and resume a loop, for use when the loop is	779	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	780	loop is not used for a while and timeouts should not be processed.
699		781
700	A typical use case would be an interactive program such as a game: When	782	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	783	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	784	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	785	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
705	C<ev_resume> directly afterwards to resume timer processing.	787	C<ev_resume> directly afterwards to resume timer processing.
706		788
707	Effectively, all C<ev_timer> watchers will be delayed by the time spend	789	Effectively, all C<ev_timer> watchers will be delayed by the time spend
708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	790	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
709	will be rescheduled (that is, they will lose any events that would have	791	will be rescheduled (that is, they will lose any events that would have
710	occured while suspended).	792	occurred while suspended).
711		793
712	After calling C<ev_suspend> you B<must not> call I<any> function on the	794	After calling C<ev_suspend> you B<must not> call I<any> function on the
713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	795	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
714	without a previous call to C<ev_suspend>.	796	without a previous call to C<ev_suspend>.
715		797
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	798	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	799	event loop time (see C<ev_now_update>).
718		800
719	=item ev_loop (loop, int flags)	801	=item bool ev_run (loop, int flags)
720		802
721	Finally, this is it, the event handler. This function usually is called	803	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	804	after you have initialised all your watchers and you want to start
723	handling events.	805	handling events. It will ask the operating system for any new events, call
		806	the watcher callbacks, and then repeat the whole process indefinitely: This
		807	is why event loops are called I<loops>.
724		808
725	If the flags argument is specified as C<0>, it will not return until	809	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	810	until either no event watchers are active anymore or C<ev_break> was
		811	called.
727		812
		813	The return value is false if there are no more active watchers (which
		814	usually means "all jobs done" or "deadlock"), and true in all other cases
		815	(which usually means " you should call C<ev_run> again").
		816
728	Please note that an explicit C<ev_unloop> is usually better than	817	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	818	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	819	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	820	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	821	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	822	beauty.
734		823
		824	This function is I<mostly> exception-safe - you can break out of a
		825	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		826	exception and so on. This does not decrement the C<ev_depth> value, nor
		827	will it clear any outstanding C<EVBREAK_ONE> breaks.
		828
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	829	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	830	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	831	block your process in case there are no events and will return after one
738	the loop.	832	iteration of the loop. This is sometimes useful to poll and handle new
		833	events while doing lengthy calculations, to keep the program responsive.
739		834
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	835	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	836	necessary) and will handle those and any already outstanding ones. It
742	will block your process until at least one new event arrives (which could	837	will block your process until at least one new event arrives (which could
743	be an event internal to libev itself, so there is no guarantee that a	838	be an event internal to libev itself, so there is no guarantee that a
744	user-registered callback will be called), and will return after one	839	user-registered callback will be called), and will return after one
745	iteration of the loop.	840	iteration of the loop.
746		841
747	This is useful if you are waiting for some external event in conjunction	842	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	843	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	844	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	845	usually a better approach for this kind of thing.
751		846
752	Here are the gory details of what C<ev_loop> does:	847	Here are the gory details of what C<ev_run> does (this is for your
		848	understanding, not a guarantee that things will work exactly like this in
		849	future versions):
753		850
		851	- Increment loop depth.
		852	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	853	- Before the first iteration, call any pending watchers.
		854	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	855	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	856	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	857	- Queue and call all prepare watchers.
		858	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	859	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	860	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	861	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	862	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	863	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	864	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	865	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	866	- Sleep if the I/O and timer collect interval say so.
		867	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	868	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	869	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	870	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	871	- Queue all expired timers.
770	- Queue all expired periodics.	872	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	873	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	874	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	875	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	876	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	877	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	878	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	879	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	880	continue with step LOOP.
		881	FINISH:
		882	- Reset the ev_break status iff it was EVBREAK_ONE.
		883	- Decrement the loop depth.
		884	- Return.
779		885
780	Example: Queue some jobs and then loop until no events are outstanding	886	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	887	anymore.
782		888
783	... queue jobs here, make sure they register event watchers as long	889	... queue jobs here, make sure they register event watchers as long
784	... as they still have work to do (even an idle watcher will do..)	890	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	891	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	892	... jobs done or somebody called break. yeah!
787		893
788	=item ev_unloop (loop, how)	894	=item ev_break (loop, how)
789		895
790	Can be used to make a call to C<ev_loop> return early (but only after it	896	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	897	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	898	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	899	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		900
795	This "unloop state" will be cleared when entering C<ev_loop> again.	901	This "break state" will be cleared on the next call to C<ev_run>.
796		902
797	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	903	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		904	which case it will have no effect.
798		905
799	=item ev_ref (loop)	906	=item ev_ref (loop)
800		907
801	=item ev_unref (loop)	908	=item ev_unref (loop)
802		909
803	Ref/unref can be used to add or remove a reference count on the event	910	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	911	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	912	count is nonzero, C<ev_run> will not return on its own.
806		913
807	This is useful when you have a watcher that you never intend to	914	This is useful when you have a watcher that you never intend to
808	unregister, but that nevertheless should not keep C<ev_loop> from	915	unregister, but that nevertheless should not keep C<ev_run> from
809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	916	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	917	before stopping it.
811		918
812	As an example, libev itself uses this for its internal signal pipe: It	919	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	920	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	921	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	922	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	923	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	924	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	925	before, respectively. Note also that libev might stop watchers itself
819	(e.g. non-repeating timers) in which case you have to C<ev_ref>	926	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	927	in the callback).
821		928
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	929	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	930	running when nothing else is active.
824		931
825	ev_signal exitsig;	932	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	933	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	934	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	935	ev_unref (loop);
829		936
830	Example: For some weird reason, unregister the above signal handler again.	937	Example: For some weird reason, unregister the above signal handler again.
831		938
832	ev_ref (loop);	939	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	940	ev_signal_stop (loop, &exitsig);
…		…
853	overhead for the actual polling but can deliver many events at once.	960	overhead for the actual polling but can deliver many events at once.
854		961
855	By setting a higher I<io collect interval> you allow libev to spend more	962	By setting a higher I<io collect interval> you allow libev to spend more
856	time collecting I/O events, so you can handle more events per iteration,	963	time collecting I/O events, so you can handle more events per iteration,
857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	964	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
858	C<ev_timer>) will be not affected. Setting this to a non-null value will	965	C<ev_timer>) will not be affected. Setting this to a non-null value will
859	introduce an additional C<ev_sleep ()> call into most loop iterations. The	966	introduce an additional C<ev_sleep ()> call into most loop iterations. The
860	sleep time ensures that libev will not poll for I/O events more often then	967	sleep time ensures that libev will not poll for I/O events more often then
861	once per this interval, on average.	968	once per this interval, on average (as long as the host time resolution is
		969	good enough).
862		970
863	Likewise, by setting a higher I<timeout collect interval> you allow libev	971	Likewise, by setting a higher I<timeout collect interval> you allow libev
864	to spend more time collecting timeouts, at the expense of increased	972	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	973	latency/jitter/inexactness (the watcher callback will be called
866	later). C<ev_io> watchers will not be affected. Setting this to a non-null	974	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
872	usually doesn't make much sense to set it to a lower value than C<0.01>,	980	usually doesn't make much sense to set it to a lower value than C<0.01>,
873	as this approaches the timing granularity of most systems. Note that if	981	as this approaches the timing granularity of most systems. Note that if
874	you do transactions with the outside world and you can't increase the	982	you do transactions with the outside world and you can't increase the
875	parallelity, then this setting will limit your transaction rate (if you	983	parallelity, then this setting will limit your transaction rate (if you
876	need to poll once per transaction and the I/O collect interval is 0.01,	984	need to poll once per transaction and the I/O collect interval is 0.01,
877	then you can't do more than 100 transations per second).	985	then you can't do more than 100 transactions per second).
878		986
879	Setting the I<timeout collect interval> can improve the opportunity for	987	Setting the I<timeout collect interval> can improve the opportunity for
880	saving power, as the program will "bundle" timer callback invocations that	988	saving power, as the program will "bundle" timer callback invocations that
881	are "near" in time together, by delaying some, thus reducing the number of	989	are "near" in time together, by delaying some, thus reducing the number of
882	times the process sleeps and wakes up again. Another useful technique to	990	times the process sleeps and wakes up again. Another useful technique to
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	998	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		999
892	=item ev_invoke_pending (loop)	1000	=item ev_invoke_pending (loop)
893		1001
894	This call will simply invoke all pending watchers while resetting their	1002	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	1003	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	1004	but when overriding the invoke callback this call comes handy. This
		1005	function can be invoked from a watcher - this can be useful for example
		1006	when you want to do some lengthy calculation and want to pass further
		1007	event handling to another thread (you still have to make sure only one
		1008	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		1009
898	=item int ev_pending_count (loop)	1010	=item int ev_pending_count (loop)
899		1011
900	Returns the number of pending watchers - zero indicates that no watchers	1012	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1013	are pending.
902		1014
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1015	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		1016
905	This overrides the invoke pending functionality of the loop: Instead of	1017	This overrides the invoke pending functionality of the loop: Instead of
906	invoking all pending watchers when there are any, C<ev_loop> will call	1018	invoking all pending watchers when there are any, C<ev_run> will call
907	this callback instead. This is useful, for example, when you want to	1019	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1020	invoke the actual watchers inside another context (another thread etc.).
909		1021
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1022	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1023	callback.
912		1024
913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1025	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
914		1026
915	Sometimes you want to share the same loop between multiple threads. This	1027	Sometimes you want to share the same loop between multiple threads. This
916	can be done relatively simply by putting mutex_lock/unlock calls around	1028	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1029	each call to a libev function.
918		1030
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1031	However, C<ev_run> can run an indefinite time, so it is not feasible
920	wait for it to return. One way around this is to wake up the loop via	1032	to wait for it to return. One way around this is to wake up the event
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1033	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1034	I<release> and I<acquire> callbacks on the loop.
923		1035
924	When set, then C<release> will be called just before the thread is	1036	When set, then C<release> will be called just before the thread is
925	suspended waiting for new events, and C<acquire> is called just	1037	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1038	afterwards.
927		1039
…		…
930		1042
931	While event loop modifications are allowed between invocations of	1043	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1044	C<release> and C<acquire> (that's their only purpose after all), no
933	modifications done will affect the event loop, i.e. adding watchers will	1045	modifications done will affect the event loop, i.e. adding watchers will
934	have no effect on the set of file descriptors being watched, or the time	1046	have no effect on the set of file descriptors being watched, or the time
935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1047	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
936	to take note of any changes you made.	1048	to take note of any changes you made.
937		1049
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1050	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1051	invocations of C<release> and C<acquire>.
940		1052
941	See also the locking example in the C<THREADS> section later in this	1053	See also the locking example in the C<THREADS> section later in this
942	document.	1054	document.
943		1055
944	=item ev_set_userdata (loop, void *data)	1056	=item ev_set_userdata (loop, void *data)
945		1057
946	=item ev_userdata (loop)	1058	=item void *ev_userdata (loop)
947		1059
948	Set and retrieve a single C<void *> associated with a loop. When	1060	Set and retrieve a single C<void *> associated with a loop. When
949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1061	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1062	C<0>.
951		1063
952	These two functions can be used to associate arbitrary data with a loop,	1064	These two functions can be used to associate arbitrary data with a loop,
953	and are intended solely for the C<invoke_pending_cb>, C<release> and	1065	and are intended solely for the C<invoke_pending_cb>, C<release> and
954	C<acquire> callbacks described above, but of course can be (ab-)used for	1066	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1067	any other purpose as well.
956		1068
957	=item ev_loop_verify (loop)	1069	=item ev_verify (loop)
958		1070
959	This function only does something when C<EV_VERIFY> support has been	1071	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1072	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1073	through all internal structures and checks them for validity. If anything
962	is found to be inconsistent, it will print an error message to standard	1074	is found to be inconsistent, it will print an error message to standard
…		…
973		1085
974	In the following description, uppercase C<TYPE> in names stands for the	1086	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1087	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1088	watchers and C<ev_io_start> for I/O watchers.
977		1089
978	A watcher is a structure that you create and register to record your	1090	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1091	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1092	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1093	for that:
981		1094
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1095	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1096	{
984	ev_io_stop (w);	1097	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1098	ev_break (loop, EVBREAK_ALL);
986	}	1099	}
987		1100
988	struct ev_loop *loop = ev_default_loop (0);	1101	struct ev_loop *loop = ev_default_loop (0);
989		1102
990	ev_io stdin_watcher;	1103	ev_io stdin_watcher;
991		1104
992	ev_init (&stdin_watcher, my_cb);	1105	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1106	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1107	ev_io_start (loop, &stdin_watcher);
995		1108
996	ev_loop (loop, 0);	1109	ev_run (loop, 0);
997		1110
998	As you can see, you are responsible for allocating the memory for your	1111	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1112	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1113	stack).
1001		1114
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1115	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1116	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1117
1005	Each watcher structure must be initialised by a call to C<ev_init	1118	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1119	*, callback)>, which expects a callback to be provided. This callback is
1007	callback gets invoked each time the event occurs (or, in the case of I/O	1120	invoked each time the event occurs (or, in the case of I/O watchers, each
1008	watchers, each time the event loop detects that the file descriptor given	1121	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1122	and/or writable).
1010		1123
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1124	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1125	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1126	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1127	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1178
1066	=item C<EV_PREPARE>	1179	=item C<EV_PREPARE>
1067		1180
1068	=item C<EV_CHECK>	1181	=item C<EV_CHECK>
1069		1182
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1183	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1184	gather new events, and all C<ev_check> watchers are queued (not invoked)
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1185	just after C<ev_run> has gathered them, but before it queues any callbacks
		1186	for any received events. That means C<ev_prepare> watchers are the last
		1187	watchers invoked before the event loop sleeps or polls for new events, and
		1188	C<ev_check> watchers will be invoked before any other watchers of the same
		1189	or lower priority within an event loop iteration.
		1190
1073	received events. Callbacks of both watcher types can start and stop as	1191	Callbacks of both watcher types can start and stop as many watchers as
1074	many watchers as they want, and all of them will be taken into account	1192	they want, and all of them will be taken into account (for example, a
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1193	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1076	C<ev_loop> from blocking).	1194	blocking).
1077		1195
1078	=item C<EV_EMBED>	1196	=item C<EV_EMBED>
1079		1197
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1198	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1199
1082	=item C<EV_FORK>	1200	=item C<EV_FORK>
1083		1201
1084	The event loop has been resumed in the child process after fork (see	1202	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1203	C<ev_fork>).
		1204
		1205	=item C<EV_CLEANUP>
		1206
		1207	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1208
1087	=item C<EV_ASYNC>	1209	=item C<EV_ASYNC>
1088		1210
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1211	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1212
…		…
1200		1322
1201	=item callback ev_cb (ev_TYPE *watcher)	1323	=item callback ev_cb (ev_TYPE *watcher)
1202		1324
1203	Returns the callback currently set on the watcher.	1325	Returns the callback currently set on the watcher.
1204		1326
1205	=item ev_cb_set (ev_TYPE *watcher, callback)	1327	=item ev_set_cb (ev_TYPE *watcher, callback)
1206		1328
1207	Change the callback. You can change the callback at virtually any time	1329	Change the callback. You can change the callback at virtually any time
1208	(modulo threads).	1330	(modulo threads).
1209		1331
1210	=item ev_set_priority (ev_TYPE *watcher, int priority)	1332	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1228	or might not have been clamped to the valid range.	1350	or might not have been clamped to the valid range.
1229		1351
1230	The default priority used by watchers when no priority has been set is	1352	The default priority used by watchers when no priority has been set is
1231	always C<0>, which is supposed to not be too high and not be too low :).	1353	always C<0>, which is supposed to not be too high and not be too low :).
1232		1354
1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1355	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1234	priorities.	1356	priorities.
1235		1357
1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1358	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1237		1359
1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1360	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1385	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1386	functions that do not need a watcher.
1265		1387
1266	=back	1388	=back
1267		1389
		1390	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1391	OWN COMPOSITE WATCHERS> idioms.
1268		1392
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1393	=head2 WATCHER STATES
1270		1394
1271	Each watcher has, by default, a member C<void *data> that you can change	1395	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1396	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1397	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1398	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1399
1278	struct my_io	1400	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1401
1286	...	1402	=item initialised
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1403
1290	And since your callback will be called with a pointer to the watcher, you	1404	Before a watcher can be registered with the event loop it has to be
1291	can cast it back to your own type:	1405	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1406	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1407
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1408	In this state it is simply some block of memory that is suitable for
1294	{	1409	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1410	will - as long as you either keep the memory contents intact, or call
1296	...	1411	C<ev_TYPE_init> again.
1297	}
1298		1412
1299	More interesting and less C-conformant ways of casting your callback type	1413	=item started/running/active
1300	instead have been omitted.
1301		1414
1302	Another common scenario is to use some data structure with multiple	1415	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1416	property of the event loop, and is actively waiting for events. While in
		1417	this state it cannot be accessed (except in a few documented ways), moved,
		1418	freed or anything else - the only legal thing is to keep a pointer to it,
		1419	and call libev functions on it that are documented to work on active watchers.
1304		1420
1305	struct my_biggy	1421	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1422
1312	In this case getting the pointer to C<my_biggy> is a bit more	1423	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1424	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1425	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1426	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1427	callback.
1317		1428
1318	#include <stddef.h>	1429	The watcher might or might not be active while it is pending (for example,
		1430	an expired non-repeating timer can be pending but no longer active). If it
		1431	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1432	but it is still property of the event loop at this time, so cannot be
		1433	moved, freed or reused. And if it is active the rules described in the
		1434	previous item still apply.
1319		1435
1320	static void	1436	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1437	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1438	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1439
1327	static void	1440	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1441
1329	{	1442	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1443	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1444	latter will clear any pending state the watcher might be in, regardless
1332	}	1445	of whether it was active or not, so stopping a watcher explicitly before
		1446	freeing it is often a good idea.
		1447
		1448	While stopped (and not pending) the watcher is essentially in the
		1449	initialised state, that is, it can be reused, moved, modified in any way
		1450	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1451	it again).
		1452
		1453	=back
1333		1454
1334	=head2 WATCHER PRIORITY MODELS	1455	=head2 WATCHER PRIORITY MODELS
1335		1456
1336	Many event loops support I<watcher priorities>, which are usually small	1457	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1458	integers that influence the ordering of event callback invocation
…		…
1380		1501
1381	For example, to emulate how many other event libraries handle priorities,	1502	For example, to emulate how many other event libraries handle priorities,
1382	you can associate an C<ev_idle> watcher to each such watcher, and in	1503	you can associate an C<ev_idle> watcher to each such watcher, and in
1383	the normal watcher callback, you just start the idle watcher. The real	1504	the normal watcher callback, you just start the idle watcher. The real
1384	processing is done in the idle watcher callback. This causes libev to	1505	processing is done in the idle watcher callback. This causes libev to
1385	continously poll and process kernel event data for the watcher, but when	1506	continuously poll and process kernel event data for the watcher, but when
1386	the lock-out case is known to be rare (which in turn is rare :), this is	1507	the lock-out case is known to be rare (which in turn is rare :), this is
1387	workable.	1508	workable.
1388		1509
1389	Usually, however, the lock-out model implemented that way will perform	1510	Usually, however, the lock-out model implemented that way will perform
1390	miserably under the type of load it was designed to handle. In that case,	1511	miserably under the type of load it was designed to handle. In that case,
…		…
1404	{	1525	{
1405	// stop the I/O watcher, we received the event, but	1526	// stop the I/O watcher, we received the event, but
1406	// are not yet ready to handle it.	1527	// are not yet ready to handle it.
1407	ev_io_stop (EV_A_ w);	1528	ev_io_stop (EV_A_ w);
1408		1529
1409	// start the idle watcher to ahndle the actual event.	1530	// start the idle watcher to handle the actual event.
1410	// it will not be executed as long as other watchers	1531	// it will not be executed as long as other watchers
1411	// with the default priority are receiving events.	1532	// with the default priority are receiving events.
1412	ev_idle_start (EV_A_ &idle);	1533	ev_idle_start (EV_A_ &idle);
1413	}	1534	}
1414		1535
…		…
1464	In general you can register as many read and/or write event watchers per	1585	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1586	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1587	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1588	required if you know what you are doing).
1468		1589
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarentee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1590	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1591	receive "spurious" readiness notifications, that is, your callback might
1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1592	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1478	because there is no data. Not only are some backends known to create a	1593	because there is no data. It is very easy to get into this situation even
1479	lot of those (for example Solaris ports), it is very easy to get into	1594	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1595	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1596	preferable to a program hanging until some data arrives.
1483		1597
1484	If you cannot run the fd in non-blocking mode (for example you should	1598	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1599	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1600	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1601	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1602	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1603	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1604	indefinitely.
1491		1605
1492	But really, best use non-blocking mode.	1606	But really, best use non-blocking mode.
1493		1607
…		…
1521		1635
1522	There is no workaround possible except not registering events	1636	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1637	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1638	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1639
		1640	=head3 The special problem of files
		1641
		1642	Many people try to use C<select> (or libev) on file descriptors
		1643	representing files, and expect it to become ready when their program
		1644	doesn't block on disk accesses (which can take a long time on their own).
		1645
		1646	However, this cannot ever work in the "expected" way - you get a readiness
		1647	notification as soon as the kernel knows whether and how much data is
		1648	there, and in the case of open files, that's always the case, so you
		1649	always get a readiness notification instantly, and your read (or possibly
		1650	write) will still block on the disk I/O.
		1651
		1652	Another way to view it is that in the case of sockets, pipes, character
		1653	devices and so on, there is another party (the sender) that delivers data
		1654	on its own, but in the case of files, there is no such thing: the disk
		1655	will not send data on its own, simply because it doesn't know what you
		1656	wish to read - you would first have to request some data.
		1657
		1658	Since files are typically not-so-well supported by advanced notification
		1659	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1660	to files, even though you should not use it. The reason for this is
		1661	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1662	usually a tty, often a pipe, but also sometimes files or special devices
		1663	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1664	F</dev/urandom>), and even though the file might better be served with
		1665	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1666	it "just works" instead of freezing.
		1667
		1668	So avoid file descriptors pointing to files when you know it (e.g. use
		1669	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1670	when you rarely read from a file instead of from a socket, and want to
		1671	reuse the same code path.
		1672
1526	=head3 The special problem of fork	1673	=head3 The special problem of fork
1527		1674
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1675	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1676	useless behaviour. Libev fully supports fork, but needs to be told about
1530	it in the child.	1677	it in the child if you want to continue to use it in the child.
1531		1678
1532	To support fork in your programs, you either have to call	1679	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1680	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1681	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1682
1537	=head3 The special problem of SIGPIPE	1683	=head3 The special problem of SIGPIPE
1538		1684
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1685	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1686	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1768	...
1623	struct ev_loop *loop = ev_default_init (0);	1769	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1770	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1771	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1772	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1773	ev_run (loop, 0);
1628		1774
1629		1775
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1776	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1777
1632	Timer watchers are simple relative timers that generate an event after a	1778	Timer watchers are simple relative timers that generate an event after a
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1784	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1785	monotonic clock option helps a lot here).
1640		1786
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1787	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1788	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1789	might introduce a small delay, see "the special problem of being too
		1790	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1791	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1792	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1793	longer true when a callback calls C<ev_run> recursively).
1647		1794
1648	=head3 Be smart about timeouts	1795	=head3 Be smart about timeouts
1649		1796
1650	Many real-world problems involve some kind of timeout, usually for error	1797	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1798	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1873
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1874	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1875	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1876	within the callback:
1730		1877
		1878	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1879	ev_tstamp last_activity; // time of last activity
		1880	ev_timer timer;
1732		1881
1733	static void	1882	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1883	callback (EV_P_ ev_timer *w, int revents)
1735	{	1884	{
1736	ev_tstamp now = ev_now (EV_A);	1885	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1886	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1887
1739	// if last_activity + 60. is older than now, we did time out	1888	// if negative, it means we the timeout already occurred
1740	if (timeout < now)	1889	if (after < 0.)
1741	{	1890	{
1742	// timeout occured, take action	1891	// timeout occurred, take action
1743	}	1892	}
1744	else	1893	else
1745	{	1894	{
1746	// callback was invoked, but there was some activity, re-arm	1895	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1896	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1897	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1898	// the timeout can occur.
		1899	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1900	ev_timer_start (EV_A_ w);
1751	}	1901	}
1752	}	1902	}
1753		1903
1754	To summarise the callback: first calculate the real timeout (defined	1904	To summarise the callback: first calculate in how many seconds the
1755	as "60 seconds after the last activity"), then check if that time has	1905	timeout will occur (by calculating the absolute time when it would occur,
1756	been reached, which means something I<did>, in fact, time out. Otherwise	1906	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1757	the callback was invoked too early (C<timeout> is in the future), so	1907	(EV_A)> from that).
1758	re-schedule the timer to fire at that future time, to see if maybe we have
1759	a timeout then.
1760		1908
1761	Note how C<ev_timer_again> is used, taking advantage of the	1909	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1910	timed out, and need to do whatever is needed in this case.
		1911
		1912	Otherwise, we now the earliest time at which the timeout would trigger,
		1913	and simply start the timer with this timeout value.
		1914
		1915	In other words, each time the callback is invoked it will check whether
		1916	the timeout occurred. If not, it will simply reschedule itself to check
		1917	again at the earliest time it could time out. Rinse. Repeat.
1763		1918
1764	This scheme causes more callback invocations (about one every 60 seconds	1919	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1920	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1921	libev to change the timeout.
1767		1922
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1923	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1924	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1925	now), then call the callback, which will "do the right thing" and start
		1926	the timer:
1771		1927
		1928	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	1929	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	1930	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		1931
1776	And when there is some activity, simply store the current time in	1932	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	1933	C<last_activity>, no libev calls at all:
1778		1934
		1935	if (activity detected)
1779	last_actiivty = ev_now (loop);	1936	last_activity = ev_now (EV_A);
		1937
		1938	When your timeout value changes, then the timeout can be changed by simply
		1939	providing a new value, stopping the timer and calling the callback, which
		1940	will again do the right thing (for example, time out immediately :).
		1941
		1942	timeout = new_value;
		1943	ev_timer_stop (EV_A_ &timer);
		1944	callback (EV_A_ &timer, 0);
1780		1945
1781	This technique is slightly more complex, but in most cases where the	1946	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	1947	time-out is unlikely to be triggered, much more efficient.
1783
1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
1785	callback :) - just change the timeout and invoke the callback, which will
1786	fix things for you.
1787		1948
1788	=item 4. Wee, just use a double-linked list for your timeouts.	1949	=item 4. Wee, just use a double-linked list for your timeouts.
1789		1950
1790	If there is not one request, but many thousands (millions...), all	1951	If there is not one request, but many thousands (millions...), all
1791	employing some kind of timeout with the same timeout value, then one can	1952	employing some kind of timeout with the same timeout value, then one can
…		…
1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1979	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1819	rather complicated, but extremely efficient, something that really pays	1980	rather complicated, but extremely efficient, something that really pays
1820	off after the first million or so of active timers, i.e. it's usually	1981	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	1982	overkill :)
1822		1983
		1984	=head3 The special problem of being too early
		1985
		1986	If you ask a timer to call your callback after three seconds, then
		1987	you expect it to be invoked after three seconds - but of course, this
		1988	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1989	guaranteed to any precision by libev - imagine somebody suspending the
		1990	process with a STOP signal for a few hours for example.
		1991
		1992	So, libev tries to invoke your callback as soon as possible I<after> the
		1993	delay has occurred, but cannot guarantee this.
		1994
		1995	A less obvious failure mode is calling your callback too early: many event
		1996	loops compare timestamps with a "elapsed delay >= requested delay", but
		1997	this can cause your callback to be invoked much earlier than you would
		1998	expect.
		1999
		2000	To see why, imagine a system with a clock that only offers full second
		2001	resolution (think windows if you can't come up with a broken enough OS
		2002	yourself). If you schedule a one-second timer at the time 500.9, then the
		2003	event loop will schedule your timeout to elapse at a system time of 500
		2004	(500.9 truncated to the resolution) + 1, or 501.
		2005
		2006	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2007	501" and invoke the callback 0.1s after it was started, even though a
		2008	one-second delay was requested - this is being "too early", despite best
		2009	intentions.
		2010
		2011	This is the reason why libev will never invoke the callback if the elapsed
		2012	delay equals the requested delay, but only when the elapsed delay is
		2013	larger than the requested delay. In the example above, libev would only invoke
		2014	the callback at system time 502, or 1.1s after the timer was started.
		2015
		2016	So, while libev cannot guarantee that your callback will be invoked
		2017	exactly when requested, it I<can> and I<does> guarantee that the requested
		2018	delay has actually elapsed, or in other words, it always errs on the "too
		2019	late" side of things.
		2020
1823	=head3 The special problem of time updates	2021	=head3 The special problem of time updates
1824		2022
1825	Establishing the current time is a costly operation (it usually takes at	2023	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2024	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2025	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2026	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2027	lots of events in one iteration.
1830		2028
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2029	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	2030	time. This is usually the right thing as this timestamp refers to the time
…		…
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2035	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1838		2036
1839	If the event loop is suspended for a long time, you can also force an	2037	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2038	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2039	()>.
		2040
		2041	=head3 The special problem of unsynchronised clocks
		2042
		2043	Modern systems have a variety of clocks - libev itself uses the normal
		2044	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2045	jumps).
		2046
		2047	Neither of these clocks is synchronised with each other or any other clock
		2048	on the system, so C<ev_time ()> might return a considerably different time
		2049	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2050	a call to C<gettimeofday> might return a second count that is one higher
		2051	than a directly following call to C<time>.
		2052
		2053	The moral of this is to only compare libev-related timestamps with
		2054	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2055	a second or so.
		2056
		2057	One more problem arises due to this lack of synchronisation: if libev uses
		2058	the system monotonic clock and you compare timestamps from C<ev_time>
		2059	or C<ev_now> from when you started your timer and when your callback is
		2060	invoked, you will find that sometimes the callback is a bit "early".
		2061
		2062	This is because C<ev_timer>s work in real time, not wall clock time, so
		2063	libev makes sure your callback is not invoked before the delay happened,
		2064	I<measured according to the real time>, not the system clock.
		2065
		2066	If your timeouts are based on a physical timescale (e.g. "time out this
		2067	connection after 100 seconds") then this shouldn't bother you as it is
		2068	exactly the right behaviour.
		2069
		2070	If you want to compare wall clock/system timestamps to your timers, then
		2071	you need to use C<ev_periodic>s, as these are based on the wall clock
		2072	time, where your comparisons will always generate correct results.
1842		2073
1843	=head3 The special problems of suspended animation	2074	=head3 The special problems of suspended animation
1844		2075
1845	When you leave the server world it is quite customary to hit machines that	2076	When you leave the server world it is quite customary to hit machines that
1846	can suspend/hibernate - what happens to the clocks during such a suspend?	2077	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1890	keep up with the timer (because it takes longer than those 10 seconds to	2121	keep up with the timer (because it takes longer than those 10 seconds to
1891	do stuff) the timer will not fire more than once per event loop iteration.	2122	do stuff) the timer will not fire more than once per event loop iteration.
1892		2123
1893	=item ev_timer_again (loop, ev_timer *)	2124	=item ev_timer_again (loop, ev_timer *)
1894		2125
1895	This will act as if the timer timed out and restart it again if it is	2126	This will act as if the timer timed out, and restarts it again if it is
1896	repeating. The exact semantics are:	2127	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2128	timeout to the C<repeat> value and calling C<ev_timer_start>.
1897		2129
		2130	The exact semantics are as in the following rules, all of which will be
		2131	applied to the watcher:
		2132
		2133	=over 4
		2134
1898	If the timer is pending, its pending status is cleared.	2135	=item If the timer is pending, the pending status is always cleared.
1899		2136
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2137	=item If the timer is started but non-repeating, stop it (as if it timed
		2138	out, without invoking it).
1901		2139
1902	If the timer is repeating, either start it if necessary (with the	2140	=item If the timer is repeating, make the C<repeat> value the new timeout
1903	C<repeat> value), or reset the running timer to the C<repeat> value.	2141	and start the timer, if necessary.
1904		2142
		2143	=back
		2144
1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2145	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1906	usage example.	2146	usage example.
1907		2147
1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2148	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1909		2149
1910	Returns the remaining time until a timer fires. If the timer is active,	2150	Returns the remaining time until a timer fires. If the timer is active,
…		…
1949	}	2189	}
1950		2190
1951	ev_timer mytimer;	2191	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2192	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2193	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2194	ev_run (loop, 0);
1955		2195
1956	// and in some piece of code that gets executed on any "activity":	2196	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2197	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2198	ev_timer_again (&mytimer);
1959		2199
…		…
1985		2225
1986	As with timers, the callback is guaranteed to be invoked only when the	2226	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2227	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2228	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2229	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2230	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2231
1992	=head3 Watcher-Specific Functions and Data Members	2232	=head3 Watcher-Specific Functions and Data Members
1993		2233
1994	=over 4	2234	=over 4
1995		2235
…		…
2030		2270
2031	Another way to think about it (for the mathematically inclined) is that	2271	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2272	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2273	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2274
2035	For numerical stability it is preferable that the C<offset> value is near	2275	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2276	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2277	microseconds) and C<offset> should be higher than C<0> and should have
		2278	at most a similar magnitude as the current time (say, within a factor of
		2279	ten). Typical values for offset are, in fact, C<0> or something between
		2280	C<0> and C<interval>, which is also the recommended range.
2038		2281
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2282	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2283	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2284	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2285	millisecond (if the OS supports it and the machine is fast enough).
…		…
2123	Example: Call a callback every hour, or, more precisely, whenever the	2366	Example: Call a callback every hour, or, more precisely, whenever the
2124	system time is divisible by 3600. The callback invocation times have	2367	system time is divisible by 3600. The callback invocation times have
2125	potentially a lot of jitter, but good long-term stability.	2368	potentially a lot of jitter, but good long-term stability.
2126		2369
2127	static void	2370	static void
2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2371	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2129	{	2372	{
2130	... its now a full hour (UTC, or TAI or whatever your clock follows)	2373	... its now a full hour (UTC, or TAI or whatever your clock follows)
2131	}	2374	}
2132		2375
2133	ev_periodic hourly_tick;	2376	ev_periodic hourly_tick;
…		…
2150		2393
2151	ev_periodic hourly_tick;	2394	ev_periodic hourly_tick;
2152	ev_periodic_init (&hourly_tick, clock_cb,	2395	ev_periodic_init (&hourly_tick, clock_cb,
2153	fmod (ev_now (loop), 3600.), 3600., 0);	2396	fmod (ev_now (loop), 3600.), 3600., 0);
2154	ev_periodic_start (loop, &hourly_tick);	2397	ev_periodic_start (loop, &hourly_tick);
2155		2398
2156		2399
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2400	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2401
2159	Signal watchers will trigger an event when the process receives a specific	2402	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2403	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2404	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2405	normal event processing, like any other event.
2163		2406
2164	If you want signals to be delivered truly asynchronously, just use	2407	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2408	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2409	the signal. You can even use C<ev_async> from a signal handler to
…		…
2170	only within the same loop, i.e. you can watch for C<SIGINT> in your	2413	only within the same loop, i.e. you can watch for C<SIGINT> in your
2171	default loop and for C<SIGIO> in another loop, but you cannot watch for	2414	default loop and for C<SIGIO> in another loop, but you cannot watch for
2172	C<SIGINT> in both the default loop and another loop at the same time. At	2415	C<SIGINT> in both the default loop and another loop at the same time. At
2173	the moment, C<SIGCHLD> is permanently tied to the default loop.	2416	the moment, C<SIGCHLD> is permanently tied to the default loop.
2174		2417
2175	When the first watcher gets started will libev actually register something	2418	Only after the first watcher for a signal is started will libev actually
2176	with the kernel (thus it coexists with your own signal handlers as long as	2419	register something with the kernel. It thus coexists with your own signal
2177	you don't register any with libev for the same signal).	2420	handlers as long as you don't register any with libev for the same signal.
2178		2421
2179	If possible and supported, libev will install its handlers with	2422	If possible and supported, libev will install its handlers with
2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2423	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2181	not be unduly interrupted. If you have a problem with system calls getting	2424	not be unduly interrupted. If you have a problem with system calls getting
2182	interrupted by signals you can block all signals in an C<ev_check> watcher	2425	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2428	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2429
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2430	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2431	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2432	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2433	and might or might not set or restore the installed signal handler (but
		2434	see C<EVFLAG_NOSIGMASK>).
2191		2435
2192	While this does not matter for the signal disposition (libev never	2436	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2437	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2438	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2439	certain signals to be blocked.
…		…
2209		2453
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2454	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2455	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2456	is not a libev-specific thing, this is true for most event libraries.
2213		2457
		2458	=head3 The special problem of threads signal handling
		2459
		2460	POSIX threads has problematic signal handling semantics, specifically,
		2461	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2462	threads in a process block signals, which is hard to achieve.
		2463
		2464	When you want to use sigwait (or mix libev signal handling with your own
		2465	for the same signals), you can tackle this problem by globally blocking
		2466	all signals before creating any threads (or creating them with a fully set
		2467	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2468	loops. Then designate one thread as "signal receiver thread" which handles
		2469	these signals. You can pass on any signals that libev might be interested
		2470	in by calling C<ev_feed_signal>.
		2471
2214	=head3 Watcher-Specific Functions and Data Members	2472	=head3 Watcher-Specific Functions and Data Members
2215		2473
2216	=over 4	2474	=over 4
2217		2475
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2476	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2491	Example: Try to exit cleanly on SIGINT.
2234		2492
2235	static void	2493	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2494	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2495	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2496	ev_break (loop, EVBREAK_ALL);
2239	}	2497	}
2240		2498
2241	ev_signal signal_watcher;	2499	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2500	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2501	ev_signal_start (loop, &signal_watcher);
…		…
2352		2610
2353	=head2 C<ev_stat> - did the file attributes just change?	2611	=head2 C<ev_stat> - did the file attributes just change?
2354		2612
2355	This watches a file system path for attribute changes. That is, it calls	2613	This watches a file system path for attribute changes. That is, it calls
2356	C<stat> on that path in regular intervals (or when the OS says it changed)	2614	C<stat> on that path in regular intervals (or when the OS says it changed)
2357	and sees if it changed compared to the last time, invoking the callback if	2615	and sees if it changed compared to the last time, invoking the callback
2358	it did.	2616	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2617	happen after the watcher has been started will be reported.
2359		2618
2360	The path does not need to exist: changing from "path exists" to "path does	2619	The path does not need to exist: changing from "path exists" to "path does
2361	not exist" is a status change like any other. The condition "path does not	2620	not exist" is a status change like any other. The condition "path does not
2362	exist" (or more correctly "path cannot be stat'ed") is signified by the	2621	exist" (or more correctly "path cannot be stat'ed") is signified by the
2363	C<st_nlink> field being zero (which is otherwise always forced to be at	2622	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2593	Apart from keeping your process non-blocking (which is a useful	2852	Apart from keeping your process non-blocking (which is a useful
2594	effect on its own sometimes), idle watchers are a good place to do	2853	effect on its own sometimes), idle watchers are a good place to do
2595	"pseudo-background processing", or delay processing stuff to after the	2854	"pseudo-background processing", or delay processing stuff to after the
2596	event loop has handled all outstanding events.	2855	event loop has handled all outstanding events.
2597		2856
		2857	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2858
		2859	As long as there is at least one active idle watcher, libev will never
		2860	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2861	For this to work, the idle watcher doesn't need to be invoked at all - the
		2862	lowest priority will do.
		2863
		2864	This mode of operation can be useful together with an C<ev_check> watcher,
		2865	to do something on each event loop iteration - for example to balance load
		2866	between different connections.
		2867
		2868	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2869	example.
		2870
2598	=head3 Watcher-Specific Functions and Data Members	2871	=head3 Watcher-Specific Functions and Data Members
2599		2872
2600	=over 4	2873	=over 4
2601		2874
2602	=item ev_idle_init (ev_idle *, callback)	2875	=item ev_idle_init (ev_idle *, callback)
…		…
2613	callback, free it. Also, use no error checking, as usual.	2886	callback, free it. Also, use no error checking, as usual.
2614		2887
2615	static void	2888	static void
2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2889	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2617	{	2890	{
		2891	// stop the watcher
		2892	ev_idle_stop (loop, w);
		2893
		2894	// now we can free it
2618	free (w);	2895	free (w);
		2896
2619	// now do something you wanted to do when the program has	2897	// now do something you wanted to do when the program has
2620	// no longer anything immediate to do.	2898	// no longer anything immediate to do.
2621	}	2899	}
2622		2900
2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2901	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2625	ev_idle_start (loop, idle_watcher);	2903	ev_idle_start (loop, idle_watcher);
2626		2904
2627		2905
2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2906	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2629		2907
2630	Prepare and check watchers are usually (but not always) used in pairs:	2908	Prepare and check watchers are often (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2909	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2910	afterwards.
2633		2911
2634	You I<must not> call C<ev_loop> or similar functions that enter	2912	You I<must not> call C<ev_run> or similar functions that enter
2635	the current event loop from either C<ev_prepare> or C<ev_check>	2913	the current event loop from either C<ev_prepare> or C<ev_check>
2636	watchers. Other loops than the current one are fine, however. The	2914	watchers. Other loops than the current one are fine, however. The
2637	rationale behind this is that you do not need to check for recursion in	2915	rationale behind this is that you do not need to check for recursion in
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2916	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2639	C<ev_check> so if you have one watcher of each kind they will always be	2917	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2663	with priority higher than or equal to the event loop and one coroutine	2941	with priority higher than or equal to the event loop and one coroutine
2664	of lower priority, but only once, using idle watchers to keep the event	2942	of lower priority, but only once, using idle watchers to keep the event
2665	loop from blocking if lower-priority coroutines are active, thus mapping	2943	loop from blocking if lower-priority coroutines are active, thus mapping
2666	low-priority coroutines to idle/background tasks).	2944	low-priority coroutines to idle/background tasks).
2667		2945
2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2946	When used for this purpose, it is recommended to give C<ev_check> watchers
2669	priority, to ensure that they are being run before any other watchers	2947	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2670	after the poll (this doesn't matter for C<ev_prepare> watchers).	2948	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2949	watchers).
2671		2950
2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2951	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2673	activate ("feed") events into libev. While libev fully supports this, they	2952	activate ("feed") events into libev. While libev fully supports this, they
2674	might get executed before other C<ev_check> watchers did their job. As	2953	might get executed before other C<ev_check> watchers did their job. As
2675	C<ev_check> watchers are often used to embed other (non-libev) event	2954	C<ev_check> watchers are often used to embed other (non-libev) event
2676	loops those other event loops might be in an unusable state until their	2955	loops those other event loops might be in an unusable state until their
2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2956	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2678	others).	2957	others).
		2958
		2959	=head3 Abusing an C<ev_check> watcher for its side-effect
		2960
		2961	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2962	useful because they are called once per event loop iteration. For
		2963	example, if you want to handle a large number of connections fairly, you
		2964	normally only do a bit of work for each active connection, and if there
		2965	is more work to do, you wait for the next event loop iteration, so other
		2966	connections have a chance of making progress.
		2967
		2968	Using an C<ev_check> watcher is almost enough: it will be called on the
		2969	next event loop iteration. However, that isn't as soon as possible -
		2970	without external events, your C<ev_check> watcher will not be invoked.
		2971
		2972	This is where C<ev_idle> watchers come in handy - all you need is a
		2973	single global idle watcher that is active as long as you have one active
		2974	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2975	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2976	invoked. Neither watcher alone can do that.
2679		2977
2680	=head3 Watcher-Specific Functions and Data Members	2978	=head3 Watcher-Specific Functions and Data Members
2681		2979
2682	=over 4	2980	=over 4
2683		2981
…		…
2807		3105
2808	if (timeout >= 0)	3106	if (timeout >= 0)
2809	// create/start timer	3107	// create/start timer
2810		3108
2811	// poll	3109	// poll
2812	ev_loop (EV_A_ 0);	3110	ev_run (EV_A_ 0);
2813		3111
2814	// stop timer again	3112	// stop timer again
2815	if (timeout >= 0)	3113	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3114	ev_timer_stop (EV_A_ &to);
2817		3115
…		…
2884		3182
2885	=over 4	3183	=over 4
2886		3184
2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2888		3186
2889	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3187	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2890		3188
2891	Configures the watcher to embed the given loop, which must be	3189	Configures the watcher to embed the given loop, which must be
2892	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3190	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2893	invoked automatically, otherwise it is the responsibility of the callback	3191	invoked automatically, otherwise it is the responsibility of the callback
2894	to invoke it (it will continue to be called until the sweep has been done,	3192	to invoke it (it will continue to be called until the sweep has been done,
2895	if you do not want that, you need to temporarily stop the embed watcher).	3193	if you do not want that, you need to temporarily stop the embed watcher).
2896		3194
2897	=item ev_embed_sweep (loop, ev_embed *)	3195	=item ev_embed_sweep (loop, ev_embed *)
2898		3196
2899	Make a single, non-blocking sweep over the embedded loop. This works	3197	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3198	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3199	appropriate way for embedded loops.
2902		3200
2903	=item struct ev_loop *other [read-only]	3201	=item struct ev_loop *other [read-only]
2904		3202
2905	The embedded event loop.	3203	The embedded event loop.
…		…
2915	used).	3213	used).
2916		3214
2917	struct ev_loop *loop_hi = ev_default_init (0);	3215	struct ev_loop *loop_hi = ev_default_init (0);
2918	struct ev_loop *loop_lo = 0;	3216	struct ev_loop *loop_lo = 0;
2919	ev_embed embed;	3217	ev_embed embed;
2920		3218
2921	// see if there is a chance of getting one that works	3219	// see if there is a chance of getting one that works
2922	// (remember that a flags value of 0 means autodetection)	3220	// (remember that a flags value of 0 means autodetection)
2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3221	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3222	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2925	: 0;	3223	: 0;
…		…
2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3237	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2940		3238
2941	struct ev_loop *loop = ev_default_init (0);	3239	struct ev_loop *loop = ev_default_init (0);
2942	struct ev_loop *loop_socket = 0;	3240	struct ev_loop *loop_socket = 0;
2943	ev_embed embed;	3241	ev_embed embed;
2944		3242
2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3243	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3244	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2947	{	3245	{
2948	ev_embed_init (&embed, 0, loop_socket);	3246	ev_embed_init (&embed, 0, loop_socket);
2949	ev_embed_start (loop, &embed);	3247	ev_embed_start (loop, &embed);
…		…
2957		3255
2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3256	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2959		3257
2960	Fork watchers are called when a C<fork ()> was detected (usually because	3258	Fork watchers are called when a C<fork ()> was detected (usually because
2961	whoever is a good citizen cared to tell libev about it by calling	3259	whoever is a good citizen cared to tell libev about it by calling
2962	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3260	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2963	event loop blocks next and before C<ev_check> watchers are being called,	3261	and before C<ev_check> watchers are being called, and only in the child
2964	and only in the child after the fork. If whoever good citizen calling	3262	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3263	and calls it in the wrong process, the fork handlers will be invoked, too,
2966	handlers will be invoked, too, of course.	3264	of course.
2967		3265
2968	=head3 The special problem of life after fork - how is it possible?	3266	=head3 The special problem of life after fork - how is it possible?
2969		3267
2970	Most uses of C<fork()> consist of forking, then some simple calls to ste	3268	Most uses of C<fork()> consist of forking, then some simple calls to set
2971	up/change the process environment, followed by a call to C<exec()>. This	3269	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3270	sequence should be handled by libev without any problems.
2973		3271
2974	This changes when the application actually wants to do event handling	3272	This changes when the application actually wants to do event handling
2975	in the child, or both parent in child, in effect "continuing" after the	3273	in the child, or both parent in child, in effect "continuing" after the
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3289	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3290	signal watchers).
2993		3291
2994	When this is not possible, or you want to use the default loop for	3292	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3293	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3294	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3295	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3296	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3297	those watchers. Note also that in that case, you have to re-register any
		3298	signal watchers.
3000		3299
3001	=head3 Watcher-Specific Functions and Data Members	3300	=head3 Watcher-Specific Functions and Data Members
3002		3301
3003	=over 4	3302	=over 4
3004		3303
3005	=item ev_fork_init (ev_signal *, callback)	3304	=item ev_fork_init (ev_fork *, callback)
3006		3305
3007	Initialises and configures the fork watcher - it has no parameters of any	3306	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3307	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3308	really.
3010		3309
3011	=back	3310	=back
3012		3311
3013		3312
		3313	=head2 C<ev_cleanup> - even the best things end
		3314
		3315	Cleanup watchers are called just before the event loop is being destroyed
		3316	by a call to C<ev_loop_destroy>.
		3317
		3318	While there is no guarantee that the event loop gets destroyed, cleanup
		3319	watchers provide a convenient method to install cleanup hooks for your
		3320	program, worker threads and so on - you just to make sure to destroy the
		3321	loop when you want them to be invoked.
		3322
		3323	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3324	all other watchers, they do not keep a reference to the event loop (which
		3325	makes a lot of sense if you think about it). Like all other watchers, you
		3326	can call libev functions in the callback, except C<ev_cleanup_start>.
		3327
		3328	=head3 Watcher-Specific Functions and Data Members
		3329
		3330	=over 4
		3331
		3332	=item ev_cleanup_init (ev_cleanup *, callback)
		3333
		3334	Initialises and configures the cleanup watcher - it has no parameters of
		3335	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3336	pointless, I assure you.
		3337
		3338	=back
		3339
		3340	Example: Register an atexit handler to destroy the default loop, so any
		3341	cleanup functions are called.
		3342
		3343	static void
		3344	program_exits (void)
		3345	{
		3346	ev_loop_destroy (EV_DEFAULT_UC);
		3347	}
		3348
		3349	...
		3350	atexit (program_exits);
		3351
		3352
3014	=head2 C<ev_async> - how to wake up another event loop	3353	=head2 C<ev_async> - how to wake up an event loop
3015		3354
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3355	In general, you cannot use an C<ev_loop> from multiple threads or other
3017	asynchronous sources such as signal handlers (as opposed to multiple event	3356	asynchronous sources such as signal handlers (as opposed to multiple event
3018	loops - those are of course safe to use in different threads).	3357	loops - those are of course safe to use in different threads).
3019		3358
3020	Sometimes, however, you need to wake up another event loop you do not	3359	Sometimes, however, you need to wake up an event loop you do not control,
3021	control, for example because it belongs to another thread. This is what	3360	for example because it belongs to another thread. This is what C<ev_async>
3022	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3361	watchers do: as long as the C<ev_async> watcher is active, you can signal
3023	can signal it by calling C<ev_async_send>, which is thread- and signal	3362	it by calling C<ev_async_send>, which is thread- and signal safe.
3024	safe.
3025		3363
3026	This functionality is very similar to C<ev_signal> watchers, as signals,	3364	This functionality is very similar to C<ev_signal> watchers, as signals,
3027	too, are asynchronous in nature, and signals, too, will be compressed	3365	too, are asynchronous in nature, and signals, too, will be compressed
3028	(i.e. the number of callback invocations may be less than the number of	3366	(i.e. the number of callback invocations may be less than the number of
3029	C<ev_async_sent> calls).	3367	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3030		3368	of "global async watchers" by using a watcher on an otherwise unused
3031	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3369	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3032	just the default loop.	3370	even without knowing which loop owns the signal.
3033		3371
3034	=head3 Queueing	3372	=head3 Queueing
3035		3373
3036	C<ev_async> does not support queueing of data in any way. The reason	3374	C<ev_async> does not support queueing of data in any way. The reason
3037	is that the author does not know of a simple (or any) algorithm for a	3375	is that the author does not know of a simple (or any) algorithm for a
…		…
3129	trust me.	3467	trust me.
3130		3468
3131	=item ev_async_send (loop, ev_async *)	3469	=item ev_async_send (loop, ev_async *)
3132		3470
3133	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3471	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3134	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3472	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3473	returns.
		3474
3135	C<ev_feed_event>, this call is safe to do from other threads, signal or	3475	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3136	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3476	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3137	section below on what exactly this means).	3477	embedding section below on what exactly this means).
3138		3478
3139	Note that, as with other watchers in libev, multiple events might get	3479	Note that, as with other watchers in libev, multiple events might get
3140	compressed into a single callback invocation (another way to look at this	3480	compressed into a single callback invocation (another way to look at
3141	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3481	this is that C<ev_async> watchers are level-triggered: they are set on
3142	reset when the event loop detects that).	3482	C<ev_async_send>, reset when the event loop detects that).
3143		3483
3144	This call incurs the overhead of a system call only once per event loop	3484	This call incurs the overhead of at most one extra system call per event
3145	iteration, so while the overhead might be noticeable, it doesn't apply to	3485	loop iteration, if the event loop is blocked, and no syscall at all if
3146	repeated calls to C<ev_async_send> for the same event loop.	3486	the event loop (or your program) is processing events. That means that
		3487	repeated calls are basically free (there is no need to avoid calls for
		3488	performance reasons) and that the overhead becomes smaller (typically
		3489	zero) under load.
3147		3490
3148	=item bool = ev_async_pending (ev_async *)	3491	=item bool = ev_async_pending (ev_async *)
3149		3492
3150	Returns a non-zero value when C<ev_async_send> has been called on the	3493	Returns a non-zero value when C<ev_async_send> has been called on the
3151	watcher but the event has not yet been processed (or even noted) by the	3494	watcher but the event has not yet been processed (or even noted) by the
…		…
3206	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3549	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3207		3550
3208	=item ev_feed_fd_event (loop, int fd, int revents)	3551	=item ev_feed_fd_event (loop, int fd, int revents)
3209		3552
3210	Feed an event on the given fd, as if a file descriptor backend detected	3553	Feed an event on the given fd, as if a file descriptor backend detected
3211	the given events it.	3554	the given events.
3212		3555
3213	=item ev_feed_signal_event (loop, int signum)	3556	=item ev_feed_signal_event (loop, int signum)
3214		3557
3215	Feed an event as if the given signal occurred (C<loop> must be the default	3558	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3216	loop!).	3559	which is async-safe.
3217		3560
3218	=back	3561	=back
		3562
		3563
		3564	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3565
		3566	This section explains some common idioms that are not immediately
		3567	obvious. Note that examples are sprinkled over the whole manual, and this
		3568	section only contains stuff that wouldn't fit anywhere else.
		3569
		3570	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3571
		3572	Each watcher has, by default, a C<void *data> member that you can read
		3573	or modify at any time: libev will completely ignore it. This can be used
		3574	to associate arbitrary data with your watcher. If you need more data and
		3575	don't want to allocate memory separately and store a pointer to it in that
		3576	data member, you can also "subclass" the watcher type and provide your own
		3577	data:
		3578
		3579	struct my_io
		3580	{
		3581	ev_io io;
		3582	int otherfd;
		3583	void *somedata;
		3584	struct whatever *mostinteresting;
		3585	};
		3586
		3587	...
		3588	struct my_io w;
		3589	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3590
		3591	And since your callback will be called with a pointer to the watcher, you
		3592	can cast it back to your own type:
		3593
		3594	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3595	{
		3596	struct my_io *w = (struct my_io *)w_;
		3597	...
		3598	}
		3599
		3600	More interesting and less C-conformant ways of casting your callback
		3601	function type instead have been omitted.
		3602
		3603	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3604
		3605	Another common scenario is to use some data structure with multiple
		3606	embedded watchers, in effect creating your own watcher that combines
		3607	multiple libev event sources into one "super-watcher":
		3608
		3609	struct my_biggy
		3610	{
		3611	int some_data;
		3612	ev_timer t1;
		3613	ev_timer t2;
		3614	}
		3615
		3616	In this case getting the pointer to C<my_biggy> is a bit more
		3617	complicated: Either you store the address of your C<my_biggy> struct in
		3618	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3619	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3620	real programmers):
		3621
		3622	#include <stddef.h>
		3623
		3624	static void
		3625	t1_cb (EV_P_ ev_timer *w, int revents)
		3626	{
		3627	struct my_biggy big = (struct my_biggy *)
		3628	(((char *)w) - offsetof (struct my_biggy, t1));
		3629	}
		3630
		3631	static void
		3632	t2_cb (EV_P_ ev_timer *w, int revents)
		3633	{
		3634	struct my_biggy big = (struct my_biggy *)
		3635	(((char *)w) - offsetof (struct my_biggy, t2));
		3636	}
		3637
		3638	=head2 AVOIDING FINISHING BEFORE RETURNING
		3639
		3640	Often you have structures like this in event-based programs:
		3641
		3642	callback ()
		3643	{
		3644	free (request);
		3645	}
		3646
		3647	request = start_new_request (..., callback);
		3648
		3649	The intent is to start some "lengthy" operation. The C<request> could be
		3650	used to cancel the operation, or do other things with it.
		3651
		3652	It's not uncommon to have code paths in C<start_new_request> that
		3653	immediately invoke the callback, for example, to report errors. Or you add
		3654	some caching layer that finds that it can skip the lengthy aspects of the
		3655	operation and simply invoke the callback with the result.
		3656
		3657	The problem here is that this will happen I<before> C<start_new_request>
		3658	has returned, so C<request> is not set.
		3659
		3660	Even if you pass the request by some safer means to the callback, you
		3661	might want to do something to the request after starting it, such as
		3662	canceling it, which probably isn't working so well when the callback has
		3663	already been invoked.
		3664
		3665	A common way around all these issues is to make sure that
		3666	C<start_new_request> I<always> returns before the callback is invoked. If
		3667	C<start_new_request> immediately knows the result, it can artificially
		3668	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3669	example, or more sneakily, by reusing an existing (stopped) watcher and
		3670	pushing it into the pending queue:
		3671
		3672	ev_set_cb (watcher, callback);
		3673	ev_feed_event (EV_A_ watcher, 0);
		3674
		3675	This way, C<start_new_request> can safely return before the callback is
		3676	invoked, while not delaying callback invocation too much.
		3677
		3678	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3679
		3680	Often (especially in GUI toolkits) there are places where you have
		3681	I<modal> interaction, which is most easily implemented by recursively
		3682	invoking C<ev_run>.
		3683
		3684	This brings the problem of exiting - a callback might want to finish the
		3685	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3686	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3687	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3688	other combination: In these cases, a simple C<ev_break> will not work.
		3689
		3690	The solution is to maintain "break this loop" variable for each C<ev_run>
		3691	invocation, and use a loop around C<ev_run> until the condition is
		3692	triggered, using C<EVRUN_ONCE>:
		3693
		3694	// main loop
		3695	int exit_main_loop = 0;
		3696
		3697	while (!exit_main_loop)
		3698	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3699
		3700	// in a modal watcher
		3701	int exit_nested_loop = 0;
		3702
		3703	while (!exit_nested_loop)
		3704	ev_run (EV_A_ EVRUN_ONCE);
		3705
		3706	To exit from any of these loops, just set the corresponding exit variable:
		3707
		3708	// exit modal loop
		3709	exit_nested_loop = 1;
		3710
		3711	// exit main program, after modal loop is finished
		3712	exit_main_loop = 1;
		3713
		3714	// exit both
		3715	exit_main_loop = exit_nested_loop = 1;
		3716
		3717	=head2 THREAD LOCKING EXAMPLE
		3718
		3719	Here is a fictitious example of how to run an event loop in a different
		3720	thread from where callbacks are being invoked and watchers are
		3721	created/added/removed.
		3722
		3723	For a real-world example, see the C<EV::Loop::Async> perl module,
		3724	which uses exactly this technique (which is suited for many high-level
		3725	languages).
		3726
		3727	The example uses a pthread mutex to protect the loop data, a condition
		3728	variable to wait for callback invocations, an async watcher to notify the
		3729	event loop thread and an unspecified mechanism to wake up the main thread.
		3730
		3731	First, you need to associate some data with the event loop:
		3732
		3733	typedef struct {
		3734	mutex_t lock; /* global loop lock */
		3735	ev_async async_w;
		3736	thread_t tid;
		3737	cond_t invoke_cv;
		3738	} userdata;
		3739
		3740	void prepare_loop (EV_P)
		3741	{
		3742	// for simplicity, we use a static userdata struct.
		3743	static userdata u;
		3744
		3745	ev_async_init (&u->async_w, async_cb);
		3746	ev_async_start (EV_A_ &u->async_w);
		3747
		3748	pthread_mutex_init (&u->lock, 0);
		3749	pthread_cond_init (&u->invoke_cv, 0);
		3750
		3751	// now associate this with the loop
		3752	ev_set_userdata (EV_A_ u);
		3753	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3754	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3755
		3756	// then create the thread running ev_run
		3757	pthread_create (&u->tid, 0, l_run, EV_A);
		3758	}
		3759
		3760	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3761	solely to wake up the event loop so it takes notice of any new watchers
		3762	that might have been added:
		3763
		3764	static void
		3765	async_cb (EV_P_ ev_async *w, int revents)
		3766	{
		3767	// just used for the side effects
		3768	}
		3769
		3770	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3771	protecting the loop data, respectively.
		3772
		3773	static void
		3774	l_release (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777	pthread_mutex_unlock (&u->lock);
		3778	}
		3779
		3780	static void
		3781	l_acquire (EV_P)
		3782	{
		3783	userdata *u = ev_userdata (EV_A);
		3784	pthread_mutex_lock (&u->lock);
		3785	}
		3786
		3787	The event loop thread first acquires the mutex, and then jumps straight
		3788	into C<ev_run>:
		3789
		3790	void *
		3791	l_run (void *thr_arg)
		3792	{
		3793	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3794
		3795	l_acquire (EV_A);
		3796	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3797	ev_run (EV_A_ 0);
		3798	l_release (EV_A);
		3799
		3800	return 0;
		3801	}
		3802
		3803	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3804	signal the main thread via some unspecified mechanism (signals? pipe
		3805	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3806	have been called (in a while loop because a) spurious wakeups are possible
		3807	and b) skipping inter-thread-communication when there are no pending
		3808	watchers is very beneficial):
		3809
		3810	static void
		3811	l_invoke (EV_P)
		3812	{
		3813	userdata *u = ev_userdata (EV_A);
		3814
		3815	while (ev_pending_count (EV_A))
		3816	{
		3817	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3818	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3819	}
		3820	}
		3821
		3822	Now, whenever the main thread gets told to invoke pending watchers, it
		3823	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3824	thread to continue:
		3825
		3826	static void
		3827	real_invoke_pending (EV_P)
		3828	{
		3829	userdata *u = ev_userdata (EV_A);
		3830
		3831	pthread_mutex_lock (&u->lock);
		3832	ev_invoke_pending (EV_A);
		3833	pthread_cond_signal (&u->invoke_cv);
		3834	pthread_mutex_unlock (&u->lock);
		3835	}
		3836
		3837	Whenever you want to start/stop a watcher or do other modifications to an
		3838	event loop, you will now have to lock:
		3839
		3840	ev_timer timeout_watcher;
		3841	userdata *u = ev_userdata (EV_A);
		3842
		3843	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3844
		3845	pthread_mutex_lock (&u->lock);
		3846	ev_timer_start (EV_A_ &timeout_watcher);
		3847	ev_async_send (EV_A_ &u->async_w);
		3848	pthread_mutex_unlock (&u->lock);
		3849
		3850	Note that sending the C<ev_async> watcher is required because otherwise
		3851	an event loop currently blocking in the kernel will have no knowledge
		3852	about the newly added timer. By waking up the loop it will pick up any new
		3853	watchers in the next event loop iteration.
		3854
		3855	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3856
		3857	While the overhead of a callback that e.g. schedules a thread is small, it
		3858	is still an overhead. If you embed libev, and your main usage is with some
		3859	kind of threads or coroutines, you might want to customise libev so that
		3860	doesn't need callbacks anymore.
		3861
		3862	Imagine you have coroutines that you can switch to using a function
		3863	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3864	and that due to some magic, the currently active coroutine is stored in a
		3865	global called C<current_coro>. Then you can build your own "wait for libev
		3866	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3867	the differing C<;> conventions):
		3868
		3869	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3870	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3871
		3872	That means instead of having a C callback function, you store the
		3873	coroutine to switch to in each watcher, and instead of having libev call
		3874	your callback, you instead have it switch to that coroutine.
		3875
		3876	A coroutine might now wait for an event with a function called
		3877	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3878	matter when, or whether the watcher is active or not when this function is
		3879	called):
		3880
		3881	void
		3882	wait_for_event (ev_watcher *w)
		3883	{
		3884	ev_set_cb (w, current_coro);
		3885	switch_to (libev_coro);
		3886	}
		3887
		3888	That basically suspends the coroutine inside C<wait_for_event> and
		3889	continues the libev coroutine, which, when appropriate, switches back to
		3890	this or any other coroutine.
		3891
		3892	You can do similar tricks if you have, say, threads with an event queue -
		3893	instead of storing a coroutine, you store the queue object and instead of
		3894	switching to a coroutine, you push the watcher onto the queue and notify
		3895	any waiters.
		3896
		3897	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3898	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3899
		3900	// my_ev.h
		3901	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3902	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3903	#include "../libev/ev.h"
		3904
		3905	// my_ev.c
		3906	#define EV_H "my_ev.h"
		3907	#include "../libev/ev.c"
		3908
		3909	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3910	F<my_ev.c> into your project. When properly specifying include paths, you
		3911	can even use F<ev.h> as header file name directly.
3219		3912
3220		3913
3221	=head1 LIBEVENT EMULATION	3914	=head1 LIBEVENT EMULATION
3222		3915
3223	Libev offers a compatibility emulation layer for libevent. It cannot	3916	Libev offers a compatibility emulation layer for libevent. It cannot
3224	emulate the internals of libevent, so here are some usage hints:	3917	emulate the internals of libevent, so here are some usage hints:
3225		3918
3226	=over 4	3919	=over 4
		3920
		3921	=item * Only the libevent-1.4.1-beta API is being emulated.
		3922
		3923	This was the newest libevent version available when libev was implemented,
		3924	and is still mostly unchanged in 2010.
3227		3925
3228	=item * Use it by including <event.h>, as usual.	3926	=item * Use it by including <event.h>, as usual.
3229		3927
3230	=item * The following members are fully supported: ev_base, ev_callback,	3928	=item * The following members are fully supported: ev_base, ev_callback,
3231	ev_arg, ev_fd, ev_res, ev_events.	3929	ev_arg, ev_fd, ev_res, ev_events.
…		…
3237	=item * Priorities are not currently supported. Initialising priorities	3935	=item * Priorities are not currently supported. Initialising priorities
3238	will fail and all watchers will have the same priority, even though there	3936	will fail and all watchers will have the same priority, even though there
3239	is an ev_pri field.	3937	is an ev_pri field.
3240		3938
3241	=item * In libevent, the last base created gets the signals, in libev, the	3939	=item * In libevent, the last base created gets the signals, in libev, the
3242	first base created (== the default loop) gets the signals.	3940	base that registered the signal gets the signals.
3243		3941
3244	=item * Other members are not supported.	3942	=item * Other members are not supported.
3245		3943
3246	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3944	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3247	to use the libev header file and library.	3945	to use the libev header file and library.
3248		3946
3249	=back	3947	=back
3250		3948
3251	=head1 C++ SUPPORT	3949	=head1 C++ SUPPORT
		3950
		3951	=head2 C API
		3952
		3953	The normal C API should work fine when used from C++: both ev.h and the
		3954	libev sources can be compiled as C++. Therefore, code that uses the C API
		3955	will work fine.
		3956
		3957	Proper exception specifications might have to be added to callbacks passed
		3958	to libev: exceptions may be thrown only from watcher callbacks, all
		3959	other callbacks (allocator, syserr, loop acquire/release and periodic
		3960	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3961	()> specification. If you have code that needs to be compiled as both C
		3962	and C++ you can use the C<EV_THROW> macro for this:
		3963
		3964	static void
		3965	fatal_error (const char *msg) EV_THROW
		3966	{
		3967	perror (msg);
		3968	abort ();
		3969	}
		3970
		3971	...
		3972	ev_set_syserr_cb (fatal_error);
		3973
		3974	The only API functions that can currently throw exceptions are C<ev_run>,
		3975	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3976	because it runs cleanup watchers).
		3977
		3978	Throwing exceptions in watcher callbacks is only supported if libev itself
		3979	is compiled with a C++ compiler or your C and C++ environments allow
		3980	throwing exceptions through C libraries (most do).
		3981
		3982	=head2 C++ API
3252		3983
3253	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3984	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3254	you to use some convenience methods to start/stop watchers and also change	3985	you to use some convenience methods to start/stop watchers and also change
3255	the callback model to a model using method callbacks on objects.	3986	the callback model to a model using method callbacks on objects.
3256		3987
3257	To use it,	3988	To use it,
3258		3989
3259	#include <ev++.h>	3990	#include <ev++.h>
3260		3991
3261	This automatically includes F<ev.h> and puts all of its definitions (many	3992	This automatically includes F<ev.h> and puts all of its definitions (many
3262	of them macros) into the global namespace. All C++ specific things are	3993	of them macros) into the global namespace. All C++ specific things are
3263	put into the C<ev> namespace. It should support all the same embedding	3994	put into the C<ev> namespace. It should support all the same embedding
…		…
3266	Care has been taken to keep the overhead low. The only data member the C++	3997	Care has been taken to keep the overhead low. The only data member the C++
3267	classes add (compared to plain C-style watchers) is the event loop pointer	3998	classes add (compared to plain C-style watchers) is the event loop pointer
3268	that the watcher is associated with (or no additional members at all if	3999	that the watcher is associated with (or no additional members at all if
3269	you disable C<EV_MULTIPLICITY> when embedding libev).	4000	you disable C<EV_MULTIPLICITY> when embedding libev).
3270		4001
3271	Currently, functions, and static and non-static member functions can be	4002	Currently, functions, static and non-static member functions and classes
3272	used as callbacks. Other types should be easy to add as long as they only	4003	with C<operator ()> can be used as callbacks. Other types should be easy
3273	need one additional pointer for context. If you need support for other	4004	to add as long as they only need one additional pointer for context. If
3274	types of functors please contact the author (preferably after implementing	4005	you need support for other types of functors please contact the author
3275	it).	4006	(preferably after implementing it).
		4007
		4008	For all this to work, your C++ compiler either has to use the same calling
		4009	conventions as your C compiler (for static member functions), or you have
		4010	to embed libev and compile libev itself as C++.
3276		4011
3277	Here is a list of things available in the C<ev> namespace:	4012	Here is a list of things available in the C<ev> namespace:
3278		4013
3279	=over 4	4014	=over 4
3280		4015
…		…
3290	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4025	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3291		4026
3292	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4027	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3293	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4028	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3294	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4029	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3295	defines by many implementations.	4030	defined by many implementations.
3296		4031
3297	All of those classes have these methods:	4032	All of those classes have these methods:
3298		4033
3299	=over 4	4034	=over 4
3300		4035
…		…
3341	myclass obj;	4076	myclass obj;
3342	ev::io iow;	4077	ev::io iow;
3343	iow.set <myclass, &myclass::io_cb> (&obj);	4078	iow.set <myclass, &myclass::io_cb> (&obj);
3344		4079
3345	=item w->set (object *)	4080	=item w->set (object *)
3346
3347	This is an B<experimental> feature that might go away in a future version.
3348		4081
3349	This is a variation of a method callback - leaving out the method to call	4082	This is a variation of a method callback - leaving out the method to call
3350	will default the method to C<operator ()>, which makes it possible to use	4083	will default the method to C<operator ()>, which makes it possible to use
3351	functor objects without having to manually specify the C<operator ()> all	4084	functor objects without having to manually specify the C<operator ()> all
3352	the time. Incidentally, you can then also leave out the template argument	4085	the time. Incidentally, you can then also leave out the template argument
…		…
3364	void operator() (ev::io &w, int revents)	4097	void operator() (ev::io &w, int revents)
3365	{	4098	{
3366	...	4099	...
3367	}	4100	}
3368	}	4101	}
3369		4102
3370	myfunctor f;	4103	myfunctor f;
3371		4104
3372	ev::io w;	4105	ev::io w;
3373	w.set (&f);	4106	w.set (&f);
3374		4107
…		…
3392	Associates a different C<struct ev_loop> with this watcher. You can only	4125	Associates a different C<struct ev_loop> with this watcher. You can only
3393	do this when the watcher is inactive (and not pending either).	4126	do this when the watcher is inactive (and not pending either).
3394		4127
3395	=item w->set ([arguments])	4128	=item w->set ([arguments])
3396		4129
3397	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4130	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4131	with the same arguments. Either this method or a suitable start method
3398	called at least once. Unlike the C counterpart, an active watcher gets	4132	must be called at least once. Unlike the C counterpart, an active watcher
3399	automatically stopped and restarted when reconfiguring it with this	4133	gets automatically stopped and restarted when reconfiguring it with this
3400	method.	4134	method.
		4135
		4136	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4137	clashing with the C<set (loop)> method.
3401		4138
3402	=item w->start ()	4139	=item w->start ()
3403		4140
3404	Starts the watcher. Note that there is no C<loop> argument, as the	4141	Starts the watcher. Note that there is no C<loop> argument, as the
3405	constructor already stores the event loop.	4142	constructor already stores the event loop.
3406		4143
		4144	=item w->start ([arguments])
		4145
		4146	Instead of calling C<set> and C<start> methods separately, it is often
		4147	convenient to wrap them in one call. Uses the same type of arguments as
		4148	the configure C<set> method of the watcher.
		4149
3407	=item w->stop ()	4150	=item w->stop ()
3408		4151
3409	Stops the watcher if it is active. Again, no C<loop> argument.	4152	Stops the watcher if it is active. Again, no C<loop> argument.
3410		4153
3411	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4154	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3423		4166
3424	=back	4167	=back
3425		4168
3426	=back	4169	=back
3427		4170
3428	Example: Define a class with an IO and idle watcher, start one of them in	4171	Example: Define a class with two I/O and idle watchers, start the I/O
3429	the constructor.	4172	watchers in the constructor.
3430		4173
3431	class myclass	4174	class myclass
3432	{	4175	{
3433	ev::io io ; void io_cb (ev::io &w, int revents);	4176	ev::io io ; void io_cb (ev::io &w, int revents);
		4177	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3434	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4178	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3435		4179
3436	myclass (int fd)	4180	myclass (int fd)
3437	{	4181	{
3438	io .set <myclass, &myclass::io_cb > (this);	4182	io .set <myclass, &myclass::io_cb > (this);
		4183	io2 .set <myclass, &myclass::io2_cb > (this);
3439	idle.set <myclass, &myclass::idle_cb> (this);	4184	idle.set <myclass, &myclass::idle_cb> (this);
3440		4185
3441	io.start (fd, ev::READ);	4186	io.set (fd, ev::WRITE); // configure the watcher
		4187	io.start (); // start it whenever convenient
		4188
		4189	io2.start (fd, ev::READ); // set + start in one call
3442	}	4190	}
3443	};	4191	};
3444		4192
3445		4193
3446	=head1 OTHER LANGUAGE BINDINGS	4194	=head1 OTHER LANGUAGE BINDINGS
…		…
3485	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4233	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3486		4234
3487	=item D	4235	=item D
3488		4236
3489	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4237	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3490	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4238	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3491		4239
3492	=item Ocaml	4240	=item Ocaml
3493		4241
3494	Erkki Seppala has written Ocaml bindings for libev, to be found at	4242	Erkki Seppala has written Ocaml bindings for libev, to be found at
3495	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4243	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3498		4246
3499	Brian Maher has written a partial interface to libev for lua (at the	4247	Brian Maher has written a partial interface to libev for lua (at the
3500	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4248	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3501	L<http://github.com/brimworks/lua-ev>.	4249	L<http://github.com/brimworks/lua-ev>.
3502		4250
		4251	=item Javascript
		4252
		4253	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4254
		4255	=item Others
		4256
		4257	There are others, and I stopped counting.
		4258
3503	=back	4259	=back
3504		4260
3505		4261
3506	=head1 MACRO MAGIC	4262	=head1 MACRO MAGIC
3507		4263
…		…
3520	loop argument"). The C<EV_A> form is used when this is the sole argument,	4276	loop argument"). The C<EV_A> form is used when this is the sole argument,
3521	C<EV_A_> is used when other arguments are following. Example:	4277	C<EV_A_> is used when other arguments are following. Example:
3522		4278
3523	ev_unref (EV_A);	4279	ev_unref (EV_A);
3524	ev_timer_add (EV_A_ watcher);	4280	ev_timer_add (EV_A_ watcher);
3525	ev_loop (EV_A_ 0);	4281	ev_run (EV_A_ 0);
3526		4282
3527	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4283	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3528	which is often provided by the following macro.	4284	which is often provided by the following macro.
3529		4285
3530	=item C<EV_P>, C<EV_P_>	4286	=item C<EV_P>, C<EV_P_>
…		…
3543	suitable for use with C<EV_A>.	4299	suitable for use with C<EV_A>.
3544		4300
3545	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4301	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3546		4302
3547	Similar to the other two macros, this gives you the value of the default	4303	Similar to the other two macros, this gives you the value of the default
3548	loop, if multiple loops are supported ("ev loop default").	4304	loop, if multiple loops are supported ("ev loop default"). The default loop
		4305	will be initialised if it isn't already initialised.
		4306
		4307	For non-multiplicity builds, these macros do nothing, so you always have
		4308	to initialise the loop somewhere.
3549		4309
3550	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4310	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3551		4311
3552	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4312	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3553	default loop has been initialised (C<UC> == unchecked). Their behaviour	4313	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3570	}	4330	}
3571		4331
3572	ev_check check;	4332	ev_check check;
3573	ev_check_init (&check, check_cb);	4333	ev_check_init (&check, check_cb);
3574	ev_check_start (EV_DEFAULT_ &check);	4334	ev_check_start (EV_DEFAULT_ &check);
3575	ev_loop (EV_DEFAULT_ 0);	4335	ev_run (EV_DEFAULT_ 0);
3576		4336
3577	=head1 EMBEDDING	4337	=head1 EMBEDDING
3578		4338
3579	Libev can (and often is) directly embedded into host	4339	Libev can (and often is) directly embedded into host
3580	applications. Examples of applications that embed it include the Deliantra	4340	applications. Examples of applications that embed it include the Deliantra
…		…
3672	users of libev and the libev code itself must be compiled with compatible	4432	users of libev and the libev code itself must be compiled with compatible
3673	settings.	4433	settings.
3674		4434
3675	=over 4	4435	=over 4
3676		4436
		4437	=item EV_COMPAT3 (h)
		4438
		4439	Backwards compatibility is a major concern for libev. This is why this
		4440	release of libev comes with wrappers for the functions and symbols that
		4441	have been renamed between libev version 3 and 4.
		4442
		4443	You can disable these wrappers (to test compatibility with future
		4444	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4445	sources. This has the additional advantage that you can drop the C<struct>
		4446	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4447	typedef in that case.
		4448
		4449	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4450	and in some even more future version the compatibility code will be
		4451	removed completely.
		4452
3677	=item EV_STANDALONE (h)	4453	=item EV_STANDALONE (h)
3678		4454
3679	Must always be C<1> if you do not use autoconf configuration, which	4455	Must always be C<1> if you do not use autoconf configuration, which
3680	keeps libev from including F<config.h>, and it also defines dummy	4456	keeps libev from including F<config.h>, and it also defines dummy
3681	implementations for some libevent functions (such as logging, which is not	4457	implementations for some libevent functions (such as logging, which is not
3682	supported). It will also not define any of the structs usually found in	4458	supported). It will also not define any of the structs usually found in
3683	F<event.h> that are not directly supported by the libev core alone.	4459	F<event.h> that are not directly supported by the libev core alone.
3684		4460
3685	In standalone mode, libev will still try to automatically deduce the	4461	In standalone mode, libev will still try to automatically deduce the
3686	configuration, but has to be more conservative.	4462	configuration, but has to be more conservative.
		4463
		4464	=item EV_USE_FLOOR
		4465
		4466	If defined to be C<1>, libev will use the C<floor ()> function for its
		4467	periodic reschedule calculations, otherwise libev will fall back on a
		4468	portable (slower) implementation. If you enable this, you usually have to
		4469	link against libm or something equivalent. Enabling this when the C<floor>
		4470	function is not available will fail, so the safe default is to not enable
		4471	this.
3687		4472
3688	=item EV_USE_MONOTONIC	4473	=item EV_USE_MONOTONIC
3689		4474
3690	If defined to be C<1>, libev will try to detect the availability of the	4475	If defined to be C<1>, libev will try to detect the availability of the
3691	monotonic clock option at both compile time and runtime. Otherwise no	4476	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3776		4561
3777	If programs implement their own fd to handle mapping on win32, then this	4562	If programs implement their own fd to handle mapping on win32, then this
3778	macro can be used to override the C<close> function, useful to unregister	4563	macro can be used to override the C<close> function, useful to unregister
3779	file descriptors again. Note that the replacement function has to close	4564	file descriptors again. Note that the replacement function has to close
3780	the underlying OS handle.	4565	the underlying OS handle.
		4566
		4567	=item EV_USE_WSASOCKET
		4568
		4569	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4570	communication socket, which works better in some environments. Otherwise,
		4571	the normal C<socket> function will be used, which works better in other
		4572	environments.
3781		4573
3782	=item EV_USE_POLL	4574	=item EV_USE_POLL
3783		4575
3784	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4576	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3785	backend. Otherwise it will be enabled on non-win32 platforms. It	4577	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3821	If defined to be C<1>, libev will compile in support for the Linux inotify	4613	If defined to be C<1>, libev will compile in support for the Linux inotify
3822	interface to speed up C<ev_stat> watchers. Its actual availability will	4614	interface to speed up C<ev_stat> watchers. Its actual availability will
3823	be detected at runtime. If undefined, it will be enabled if the headers	4615	be detected at runtime. If undefined, it will be enabled if the headers
3824	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4616	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3825		4617
		4618	=item EV_NO_SMP
		4619
		4620	If defined to be C<1>, libev will assume that memory is always coherent
		4621	between threads, that is, threads can be used, but threads never run on
		4622	different cpus (or different cpu cores). This reduces dependencies
		4623	and makes libev faster.
		4624
		4625	=item EV_NO_THREADS
		4626
		4627	If defined to be C<1>, libev will assume that it will never be called from
		4628	different threads (that includes signal handlers), which is a stronger
		4629	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4630	libev faster.
		4631
3826	=item EV_ATOMIC_T	4632	=item EV_ATOMIC_T
3827		4633
3828	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4634	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3829	access is atomic with respect to other threads or signal contexts. No such	4635	access is atomic with respect to other threads or signal contexts. No
3830	type is easily found in the C language, so you can provide your own type	4636	such type is easily found in the C language, so you can provide your own
3831	that you know is safe for your purposes. It is used both for signal handler "locking"	4637	type that you know is safe for your purposes. It is used both for signal
3832	as well as for signal and thread safety in C<ev_async> watchers.	4638	handler "locking" as well as for signal and thread safety in C<ev_async>
		4639	watchers.
3833		4640
3834	In the absence of this define, libev will use C<sig_atomic_t volatile>	4641	In the absence of this define, libev will use C<sig_atomic_t volatile>
3835	(from F<signal.h>), which is usually good enough on most platforms.	4642	(from F<signal.h>), which is usually good enough on most platforms.
3836		4643
3837	=item EV_H (h)	4644	=item EV_H (h)
…		…
3864	will have the C<struct ev_loop *> as first argument, and you can create	4671	will have the C<struct ev_loop *> as first argument, and you can create
3865	additional independent event loops. Otherwise there will be no support	4672	additional independent event loops. Otherwise there will be no support
3866	for multiple event loops and there is no first event loop pointer	4673	for multiple event loops and there is no first event loop pointer
3867	argument. Instead, all functions act on the single default loop.	4674	argument. Instead, all functions act on the single default loop.
3868		4675
		4676	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4677	default loop when multiplicity is switched off - you always have to
		4678	initialise the loop manually in this case.
		4679
3869	=item EV_MINPRI	4680	=item EV_MINPRI
3870		4681
3871	=item EV_MAXPRI	4682	=item EV_MAXPRI
3872		4683
3873	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4684	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3887	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4698	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3888	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4699	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3889		4700
3890	If undefined or defined to be C<1> (and the platform supports it), then	4701	If undefined or defined to be C<1> (and the platform supports it), then
3891	the respective watcher type is supported. If defined to be C<0>, then it	4702	the respective watcher type is supported. If defined to be C<0>, then it
3892	is not. Disabling watcher types mainly saves codesize.	4703	is not. Disabling watcher types mainly saves code size.
3893		4704
3894	=item EV_FEATURES	4705	=item EV_FEATURES
3895		4706
3896	If you need to shave off some kilobytes of code at the expense of some	4707	If you need to shave off some kilobytes of code at the expense of some
3897	speed (but with the full API), you can define this symbol to request	4708	speed (but with the full API), you can define this symbol to request
…		…
3909	#define EV_USE_POLL 1	4720	#define EV_USE_POLL 1
3910	#define EV_CHILD_ENABLE 1	4721	#define EV_CHILD_ENABLE 1
3911	#define EV_ASYNC_ENABLE 1	4722	#define EV_ASYNC_ENABLE 1
3912		4723
3913	The actual value is a bitset, it can be a combination of the following	4724	The actual value is a bitset, it can be a combination of the following
3914	values:	4725	values (by default, all of these are enabled):
3915		4726
3916	=over 4	4727	=over 4
3917		4728
3918	=item C<1> - faster/larger code	4729	=item C<1> - faster/larger code
3919		4730
3920	Use larger code to speed up some operations.	4731	Use larger code to speed up some operations.
3921		4732
3922	Currently this is used to override some inlining decisions (enlarging the roughly	4733	Currently this is used to override some inlining decisions (enlarging the
3923	30% code size on amd64.	4734	code size by roughly 30% on amd64).
3924		4735
3925	When optimising for size, use of compiler flags such as C<-Os> with	4736	When optimising for size, use of compiler flags such as C<-Os> with
3926	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4737	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3927	assertions.	4738	assertions.
3928		4739
		4740	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4741	(e.g. gcc with C<-Os>).
		4742
3929	=item C<2> - faster/larger data structures	4743	=item C<2> - faster/larger data structures
3930		4744
3931	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4745	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3932	hash table sizes and so on. This will usually further increase codesize	4746	hash table sizes and so on. This will usually further increase code size
3933	and can additionally have an effect on the size of data structures at	4747	and can additionally have an effect on the size of data structures at
3934	runtime.	4748	runtime.
		4749
		4750	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4751	(e.g. gcc with C<-Os>).
3935		4752
3936	=item C<4> - full API configuration	4753	=item C<4> - full API configuration
3937		4754
3938	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4755	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3939	enables multiplicity (C<EV_MULTIPLICITY>=1).	4756	enables multiplicity (C<EV_MULTIPLICITY>=1).
…		…
3971	With an intelligent-enough linker (gcc+binutils are intelligent enough	4788	With an intelligent-enough linker (gcc+binutils are intelligent enough
3972	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4789	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3973	your program might be left out as well - a binary starting a timer and an	4790	your program might be left out as well - a binary starting a timer and an
3974	I/O watcher then might come out at only 5Kb.	4791	I/O watcher then might come out at only 5Kb.
3975		4792
		4793	=item EV_API_STATIC
		4794
		4795	If this symbol is defined (by default it is not), then all identifiers
		4796	will have static linkage. This means that libev will not export any
		4797	identifiers, and you cannot link against libev anymore. This can be useful
		4798	when you embed libev, only want to use libev functions in a single file,
		4799	and do not want its identifiers to be visible.
		4800
		4801	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4802	wants to use libev.
		4803
		4804	This option only works when libev is compiled with a C compiler, as C++
		4805	doesn't support the required declaration syntax.
		4806
3976	=item EV_AVOID_STDIO	4807	=item EV_AVOID_STDIO
3977		4808
3978	If this is set to C<1> at compiletime, then libev will avoid using stdio	4809	If this is set to C<1> at compiletime, then libev will avoid using stdio
3979	functions (printf, scanf, perror etc.). This will increase the codesize	4810	functions (printf, scanf, perror etc.). This will increase the code size
3980	somewhat, but if your program doesn't otherwise depend on stdio and your	4811	somewhat, but if your program doesn't otherwise depend on stdio and your
3981	libc allows it, this avoids linking in the stdio library which is quite	4812	libc allows it, this avoids linking in the stdio library which is quite
3982	big.	4813	big.
3983		4814
3984	Note that error messages might become less precise when this option is	4815	Note that error messages might become less precise when this option is
…		…
3988		4819
3989	The highest supported signal number, +1 (or, the number of	4820	The highest supported signal number, +1 (or, the number of
3990	signals): Normally, libev tries to deduce the maximum number of signals	4821	signals): Normally, libev tries to deduce the maximum number of signals
3991	automatically, but sometimes this fails, in which case it can be	4822	automatically, but sometimes this fails, in which case it can be
3992	specified. Also, using a lower number than detected (C<32> should be	4823	specified. Also, using a lower number than detected (C<32> should be
3993	good for about any system in existance) can save some memory, as libev	4824	good for about any system in existence) can save some memory, as libev
3994	statically allocates some 12-24 bytes per signal number.	4825	statically allocates some 12-24 bytes per signal number.
3995		4826
3996	=item EV_PID_HASHSIZE	4827	=item EV_PID_HASHSIZE
3997		4828
3998	C<ev_child> watchers use a small hash table to distribute workload by	4829	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4030	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4861	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4031	will be C<0>.	4862	will be C<0>.
4032		4863
4033	=item EV_VERIFY	4864	=item EV_VERIFY
4034		4865
4035	Controls how much internal verification (see C<ev_loop_verify ()>) will	4866	Controls how much internal verification (see C<ev_verify ()>) will
4036	be done: If set to C<0>, no internal verification code will be compiled	4867	be done: If set to C<0>, no internal verification code will be compiled
4037	in. If set to C<1>, then verification code will be compiled in, but not	4868	in. If set to C<1>, then verification code will be compiled in, but not
4038	called. If set to C<2>, then the internal verification code will be	4869	called. If set to C<2>, then the internal verification code will be
4039	called once per loop, which can slow down libev. If set to C<3>, then the	4870	called once per loop, which can slow down libev. If set to C<3>, then the
4040	verification code will be called very frequently, which will slow down	4871	verification code will be called very frequently, which will slow down
…		…
4044	will be C<0>.	4875	will be C<0>.
4045		4876
4046	=item EV_COMMON	4877	=item EV_COMMON
4047		4878
4048	By default, all watchers have a C<void *data> member. By redefining	4879	By default, all watchers have a C<void *data> member. By redefining
4049	this macro to a something else you can include more and other types of	4880	this macro to something else you can include more and other types of
4050	members. You have to define it each time you include one of the files,	4881	members. You have to define it each time you include one of the files,
4051	though, and it must be identical each time.	4882	though, and it must be identical each time.
4052		4883
4053	For example, the perl EV module uses something like this:	4884	For example, the perl EV module uses something like this:
4054		4885
…		…
4123	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4954	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4124		4955
4125	#include "ev_cpp.h"	4956	#include "ev_cpp.h"
4126	#include "ev.c"	4957	#include "ev.c"
4127		4958
4128	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4959	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4129		4960
4130	=head2 THREADS AND COROUTINES	4961	=head2 THREADS AND COROUTINES
4131		4962
4132	=head3 THREADS	4963	=head3 THREADS
4133		4964
…		…
4184	default loop and triggering an C<ev_async> watcher from the default loop	5015	default loop and triggering an C<ev_async> watcher from the default loop
4185	watcher callback into the event loop interested in the signal.	5016	watcher callback into the event loop interested in the signal.
4186		5017
4187	=back	5018	=back
4188		5019
4189	=head4 THREAD LOCKING EXAMPLE	5020	See also L</THREAD LOCKING EXAMPLE>.
4190
4191	Here is a fictitious example of how to run an event loop in a different
4192	thread than where callbacks are being invoked and watchers are
4193	created/added/removed.
4194
4195	For a real-world example, see the C<EV::Loop::Async> perl module,
4196	which uses exactly this technique (which is suited for many high-level
4197	languages).
4198
4199	The example uses a pthread mutex to protect the loop data, a condition
4200	variable to wait for callback invocations, an async watcher to notify the
4201	event loop thread and an unspecified mechanism to wake up the main thread.
4202
4203	First, you need to associate some data with the event loop:
4204
4205	typedef struct {
4206	mutex_t lock; /* global loop lock */
4207	ev_async async_w;
4208	thread_t tid;
4209	cond_t invoke_cv;
4210	} userdata;
4211
4212	void prepare_loop (EV_P)
4213	{
4214	// for simplicity, we use a static userdata struct.
4215	static userdata u;
4216
4217	ev_async_init (&u->async_w, async_cb);
4218	ev_async_start (EV_A_ &u->async_w);
4219
4220	pthread_mutex_init (&u->lock, 0);
4221	pthread_cond_init (&u->invoke_cv, 0);
4222
4223	// now associate this with the loop
4224	ev_set_userdata (EV_A_ u);
4225	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4226	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4227
4228	// then create the thread running ev_loop
4229	pthread_create (&u->tid, 0, l_run, EV_A);
4230	}
4231
4232	The callback for the C<ev_async> watcher does nothing: the watcher is used
4233	solely to wake up the event loop so it takes notice of any new watchers
4234	that might have been added:
4235
4236	static void
4237	async_cb (EV_P_ ev_async *w, int revents)
4238	{
4239	// just used for the side effects
4240	}
4241
4242	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4243	protecting the loop data, respectively.
4244
4245	static void
4246	l_release (EV_P)
4247	{
4248	userdata *u = ev_userdata (EV_A);
4249	pthread_mutex_unlock (&u->lock);
4250	}
4251
4252	static void
4253	l_acquire (EV_P)
4254	{
4255	userdata *u = ev_userdata (EV_A);
4256	pthread_mutex_lock (&u->lock);
4257	}
4258
4259	The event loop thread first acquires the mutex, and then jumps straight
4260	into C<ev_loop>:
4261
4262	void *
4263	l_run (void *thr_arg)
4264	{
4265	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4266
4267	l_acquire (EV_A);
4268	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4269	ev_loop (EV_A_ 0);
4270	l_release (EV_A);
4271
4272	return 0;
4273	}
4274
4275	Instead of invoking all pending watchers, the C<l_invoke> callback will
4276	signal the main thread via some unspecified mechanism (signals? pipe
4277	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4278	have been called (in a while loop because a) spurious wakeups are possible
4279	and b) skipping inter-thread-communication when there are no pending
4280	watchers is very beneficial):
4281
4282	static void
4283	l_invoke (EV_P)
4284	{
4285	userdata *u = ev_userdata (EV_A);
4286
4287	while (ev_pending_count (EV_A))
4288	{
4289	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4290	pthread_cond_wait (&u->invoke_cv, &u->lock);
4291	}
4292	}
4293
4294	Now, whenever the main thread gets told to invoke pending watchers, it
4295	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4296	thread to continue:
4297
4298	static void
4299	real_invoke_pending (EV_P)
4300	{
4301	userdata *u = ev_userdata (EV_A);
4302
4303	pthread_mutex_lock (&u->lock);
4304	ev_invoke_pending (EV_A);
4305	pthread_cond_signal (&u->invoke_cv);
4306	pthread_mutex_unlock (&u->lock);
4307	}
4308
4309	Whenever you want to start/stop a watcher or do other modifications to an
4310	event loop, you will now have to lock:
4311
4312	ev_timer timeout_watcher;
4313	userdata *u = ev_userdata (EV_A);
4314
4315	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4316
4317	pthread_mutex_lock (&u->lock);
4318	ev_timer_start (EV_A_ &timeout_watcher);
4319	ev_async_send (EV_A_ &u->async_w);
4320	pthread_mutex_unlock (&u->lock);
4321
4322	Note that sending the C<ev_async> watcher is required because otherwise
4323	an event loop currently blocking in the kernel will have no knowledge
4324	about the newly added timer. By waking up the loop it will pick up any new
4325	watchers in the next event loop iteration.
4326		5021
4327	=head3 COROUTINES	5022	=head3 COROUTINES
4328		5023
4329	Libev is very accommodating to coroutines ("cooperative threads"):	5024	Libev is very accommodating to coroutines ("cooperative threads"):
4330	libev fully supports nesting calls to its functions from different	5025	libev fully supports nesting calls to its functions from different
4331	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5026	coroutines (e.g. you can call C<ev_run> on the same loop from two
4332	different coroutines, and switch freely between both coroutines running	5027	different coroutines, and switch freely between both coroutines running
4333	the loop, as long as you don't confuse yourself). The only exception is	5028	the loop, as long as you don't confuse yourself). The only exception is
4334	that you must not do this from C<ev_periodic> reschedule callbacks.	5029	that you must not do this from C<ev_periodic> reschedule callbacks.
4335		5030
4336	Care has been taken to ensure that libev does not keep local state inside	5031	Care has been taken to ensure that libev does not keep local state inside
4337	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5032	C<ev_run>, and other calls do not usually allow for coroutine switches as
4338	they do not call any callbacks.	5033	they do not call any callbacks.
4339		5034
4340	=head2 COMPILER WARNINGS	5035	=head2 COMPILER WARNINGS
4341		5036
4342	Depending on your compiler and compiler settings, you might get no or a	5037	Depending on your compiler and compiler settings, you might get no or a
…		…
4353	maintainable.	5048	maintainable.
4354		5049
4355	And of course, some compiler warnings are just plain stupid, or simply	5050	And of course, some compiler warnings are just plain stupid, or simply
4356	wrong (because they don't actually warn about the condition their message	5051	wrong (because they don't actually warn about the condition their message
4357	seems to warn about). For example, certain older gcc versions had some	5052	seems to warn about). For example, certain older gcc versions had some
4358	warnings that resulted an extreme number of false positives. These have	5053	warnings that resulted in an extreme number of false positives. These have
4359	been fixed, but some people still insist on making code warn-free with	5054	been fixed, but some people still insist on making code warn-free with
4360	such buggy versions.	5055	such buggy versions.
4361		5056
4362	While libev is written to generate as few warnings as possible,	5057	While libev is written to generate as few warnings as possible,
4363	"warn-free" code is not a goal, and it is recommended not to build libev	5058	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4399	I suggest using suppression lists.	5094	I suggest using suppression lists.
4400		5095
4401		5096
4402	=head1 PORTABILITY NOTES	5097	=head1 PORTABILITY NOTES
4403		5098
		5099	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5100
		5101	GNU/Linux is the only common platform that supports 64 bit file/large file
		5102	interfaces but I<disables> them by default.
		5103
		5104	That means that libev compiled in the default environment doesn't support
		5105	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5106
		5107	Unfortunately, many programs try to work around this GNU/Linux issue
		5108	by enabling the large file API, which makes them incompatible with the
		5109	standard libev compiled for their system.
		5110
		5111	Likewise, libev cannot enable the large file API itself as this would
		5112	suddenly make it incompatible to the default compile time environment,
		5113	i.e. all programs not using special compile switches.
		5114
		5115	=head2 OS/X AND DARWIN BUGS
		5116
		5117	The whole thing is a bug if you ask me - basically any system interface
		5118	you touch is broken, whether it is locales, poll, kqueue or even the
		5119	OpenGL drivers.
		5120
		5121	=head3 C<kqueue> is buggy
		5122
		5123	The kqueue syscall is broken in all known versions - most versions support
		5124	only sockets, many support pipes.
		5125
		5126	Libev tries to work around this by not using C<kqueue> by default on this
		5127	rotten platform, but of course you can still ask for it when creating a
		5128	loop - embedding a socket-only kqueue loop into a select-based one is
		5129	probably going to work well.
		5130
		5131	=head3 C<poll> is buggy
		5132
		5133	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5134	implementation by something calling C<kqueue> internally around the 10.5.6
		5135	release, so now C<kqueue> I<and> C<poll> are broken.
		5136
		5137	Libev tries to work around this by not using C<poll> by default on
		5138	this rotten platform, but of course you can still ask for it when creating
		5139	a loop.
		5140
		5141	=head3 C<select> is buggy
		5142
		5143	All that's left is C<select>, and of course Apple found a way to fuck this
		5144	one up as well: On OS/X, C<select> actively limits the number of file
		5145	descriptors you can pass in to 1024 - your program suddenly crashes when
		5146	you use more.
		5147
		5148	There is an undocumented "workaround" for this - defining
		5149	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5150	work on OS/X.
		5151
		5152	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5153
		5154	=head3 C<errno> reentrancy
		5155
		5156	The default compile environment on Solaris is unfortunately so
		5157	thread-unsafe that you can't even use components/libraries compiled
		5158	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5159	defined by default. A valid, if stupid, implementation choice.
		5160
		5161	If you want to use libev in threaded environments you have to make sure
		5162	it's compiled with C<_REENTRANT> defined.
		5163
		5164	=head3 Event port backend
		5165
		5166	The scalable event interface for Solaris is called "event
		5167	ports". Unfortunately, this mechanism is very buggy in all major
		5168	releases. If you run into high CPU usage, your program freezes or you get
		5169	a large number of spurious wakeups, make sure you have all the relevant
		5170	and latest kernel patches applied. No, I don't know which ones, but there
		5171	are multiple ones to apply, and afterwards, event ports actually work
		5172	great.
		5173
		5174	If you can't get it to work, you can try running the program by setting
		5175	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5176	C<select> backends.
		5177
		5178	=head2 AIX POLL BUG
		5179
		5180	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5181	this by trying to avoid the poll backend altogether (i.e. it's not even
		5182	compiled in), which normally isn't a big problem as C<select> works fine
		5183	with large bitsets on AIX, and AIX is dead anyway.
		5184
4404	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5185	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5186
		5187	=head3 General issues
4405		5188
4406	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5189	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4407	requires, and its I/O model is fundamentally incompatible with the POSIX	5190	requires, and its I/O model is fundamentally incompatible with the POSIX
4408	model. Libev still offers limited functionality on this platform in	5191	model. Libev still offers limited functionality on this platform in
4409	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5192	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4410	descriptors. This only applies when using Win32 natively, not when using	5193	descriptors. This only applies when using Win32 natively, not when using
4411	e.g. cygwin.	5194	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5195	as every compiler comes with a slightly differently broken/incompatible
		5196	environment.
4412		5197
4413	Lifting these limitations would basically require the full	5198	Lifting these limitations would basically require the full
4414	re-implementation of the I/O system. If you are into these kinds of	5199	re-implementation of the I/O system. If you are into this kind of thing,
4415	things, then note that glib does exactly that for you in a very portable	5200	then note that glib does exactly that for you in a very portable way (note
4416	way (note also that glib is the slowest event library known to man).	5201	also that glib is the slowest event library known to man).
4417		5202
4418	There is no supported compilation method available on windows except	5203	There is no supported compilation method available on windows except
4419	embedding it into other applications.	5204	embedding it into other applications.
4420		5205
4421	Sensible signal handling is officially unsupported by Microsoft - libev	5206	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4449	you do I<not> compile the F<ev.c> or any other embedded source files!):	5234	you do I<not> compile the F<ev.c> or any other embedded source files!):
4450		5235
4451	#include "evwrap.h"	5236	#include "evwrap.h"
4452	#include "ev.c"	5237	#include "ev.c"
4453		5238
4454	=over 4
4455
4456	=item The winsocket select function	5239	=head3 The winsocket C<select> function
4457		5240
4458	The winsocket C<select> function doesn't follow POSIX in that it	5241	The winsocket C<select> function doesn't follow POSIX in that it
4459	requires socket I<handles> and not socket I<file descriptors> (it is	5242	requires socket I<handles> and not socket I<file descriptors> (it is
4460	also extremely buggy). This makes select very inefficient, and also	5243	also extremely buggy). This makes select very inefficient, and also
4461	requires a mapping from file descriptors to socket handles (the Microsoft	5244	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4470	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5253	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4471		5254
4472	Note that winsockets handling of fd sets is O(n), so you can easily get a	5255	Note that winsockets handling of fd sets is O(n), so you can easily get a
4473	complexity in the O(n²) range when using win32.	5256	complexity in the O(n²) range when using win32.
4474		5257
4475	=item Limited number of file descriptors	5258	=head3 Limited number of file descriptors
4476		5259
4477	Windows has numerous arbitrary (and low) limits on things.	5260	Windows has numerous arbitrary (and low) limits on things.
4478		5261
4479	Early versions of winsocket's select only supported waiting for a maximum	5262	Early versions of winsocket's select only supported waiting for a maximum
4480	of C<64> handles (probably owning to the fact that all windows kernels	5263	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4495	runtime libraries. This might get you to about C<512> or C<2048> sockets	5278	runtime libraries. This might get you to about C<512> or C<2048> sockets
4496	(depending on windows version and/or the phase of the moon). To get more,	5279	(depending on windows version and/or the phase of the moon). To get more,
4497	you need to wrap all I/O functions and provide your own fd management, but	5280	you need to wrap all I/O functions and provide your own fd management, but
4498	the cost of calling select (O(n²)) will likely make this unworkable.	5281	the cost of calling select (O(n²)) will likely make this unworkable.
4499		5282
4500	=back
4501
4502	=head2 PORTABILITY REQUIREMENTS	5283	=head2 PORTABILITY REQUIREMENTS
4503		5284
4504	In addition to a working ISO-C implementation and of course the	5285	In addition to a working ISO-C implementation and of course the
4505	backend-specific APIs, libev relies on a few additional extensions:	5286	backend-specific APIs, libev relies on a few additional extensions:
4506		5287
…		…
4512	Libev assumes not only that all watcher pointers have the same internal	5293	Libev assumes not only that all watcher pointers have the same internal
4513	structure (guaranteed by POSIX but not by ISO C for example), but it also	5294	structure (guaranteed by POSIX but not by ISO C for example), but it also
4514	assumes that the same (machine) code can be used to call any watcher	5295	assumes that the same (machine) code can be used to call any watcher
4515	callback: The watcher callbacks have different type signatures, but libev	5296	callback: The watcher callbacks have different type signatures, but libev
4516	calls them using an C<ev_watcher *> internally.	5297	calls them using an C<ev_watcher *> internally.
		5298
		5299	=item pointer accesses must be thread-atomic
		5300
		5301	Accessing a pointer value must be atomic, it must both be readable and
		5302	writable in one piece - this is the case on all current architectures.
4517		5303
4518	=item C<sig_atomic_t volatile> must be thread-atomic as well	5304	=item C<sig_atomic_t volatile> must be thread-atomic as well
4519		5305
4520	The type C<sig_atomic_t volatile> (or whatever is defined as	5306	The type C<sig_atomic_t volatile> (or whatever is defined as
4521	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5307	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4530	thread" or will block signals process-wide, both behaviours would	5316	thread" or will block signals process-wide, both behaviours would
4531	be compatible with libev. Interaction between C<sigprocmask> and	5317	be compatible with libev. Interaction between C<sigprocmask> and
4532	C<pthread_sigmask> could complicate things, however.	5318	C<pthread_sigmask> could complicate things, however.
4533		5319
4534	The most portable way to handle signals is to block signals in all threads	5320	The most portable way to handle signals is to block signals in all threads
4535	except the initial one, and run the default loop in the initial thread as	5321	except the initial one, and run the signal handling loop in the initial
4536	well.	5322	thread as well.
4537		5323
4538	=item C<long> must be large enough for common memory allocation sizes	5324	=item C<long> must be large enough for common memory allocation sizes
4539		5325
4540	To improve portability and simplify its API, libev uses C<long> internally	5326	To improve portability and simplify its API, libev uses C<long> internally
4541	instead of C<size_t> when allocating its data structures. On non-POSIX	5327	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4544	watchers.	5330	watchers.
4545		5331
4546	=item C<double> must hold a time value in seconds with enough accuracy	5332	=item C<double> must hold a time value in seconds with enough accuracy
4547		5333
4548	The type C<double> is used to represent timestamps. It is required to	5334	The type C<double> is used to represent timestamps. It is required to
4549	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5335	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4550	enough for at least into the year 4000. This requirement is fulfilled by	5336	good enough for at least into the year 4000 with millisecond accuracy
		5337	(the design goal for libev). This requirement is overfulfilled by
4551	implementations implementing IEEE 754, which is basically all existing	5338	implementations using IEEE 754, which is basically all existing ones.
		5339
4552	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5340	With IEEE 754 doubles, you get microsecond accuracy until at least the
4553	2200.	5341	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5342	is either obsolete or somebody patched it to use C<long double> or
		5343	something like that, just kidding).
4554		5344
4555	=back	5345	=back
4556		5346
4557	If you know of other additional requirements drop me a note.	5347	If you know of other additional requirements drop me a note.
4558		5348
…		…
4620	=item Processing ev_async_send: O(number_of_async_watchers)	5410	=item Processing ev_async_send: O(number_of_async_watchers)
4621		5411
4622	=item Processing signals: O(max_signal_number)	5412	=item Processing signals: O(max_signal_number)
4623		5413
4624	Sending involves a system call I<iff> there were no other C<ev_async_send>	5414	Sending involves a system call I<iff> there were no other C<ev_async_send>
4625	calls in the current loop iteration. Checking for async and signal events	5415	calls in the current loop iteration and the loop is currently
		5416	blocked. Checking for async and signal events involves iterating over all
4626	involves iterating over all running async watchers or all signal numbers.	5417	running async watchers or all signal numbers.
4627		5418
4628	=back	5419	=back
4629		5420
4630		5421
4631	=head1 PORTING FROM LIBEV 3.X TO 4.X	5422	=head1 PORTING FROM LIBEV 3.X TO 4.X
4632		5423
4633	The major version 4 introduced some minor incompatible changes to the API.	5424	The major version 4 introduced some incompatible changes to the API.
4634		5425
4635	At the moment, the C<ev.h> header file tries to implement superficial	5426	At the moment, the C<ev.h> header file provides compatibility definitions
4636	compatibility, so most programs should still compile. Those might be	5427	for all changes, so most programs should still compile. The compatibility
4637	removed in later versions of libev, so better update early than late.	5428	layer might be removed in later versions of libev, so better update to the
		5429	new API early than late.
4638		5430
4639	=over 4	5431	=over 4
4640		5432
4641	=item C<ev_loop_count> renamed to C<ev_iteration>	5433	=item C<EV_COMPAT3> backwards compatibility mechanism
4642		5434
4643	=item C<ev_loop_depth> renamed to C<ev_depth>	5435	The backward compatibility mechanism can be controlled by
		5436	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5437	section.
4644		5438
4645	=item C<ev_loop_verify> renamed to C<ev_verify>	5439	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5440
		5441	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5442
		5443	ev_loop_destroy (EV_DEFAULT_UC);
		5444	ev_loop_fork (EV_DEFAULT);
		5445
		5446	=item function/symbol renames
		5447
		5448	A number of functions and symbols have been renamed:
		5449
		5450	ev_loop => ev_run
		5451	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5452	EVLOOP_ONESHOT => EVRUN_ONCE
		5453
		5454	ev_unloop => ev_break
		5455	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5456	EVUNLOOP_ONE => EVBREAK_ONE
		5457	EVUNLOOP_ALL => EVBREAK_ALL
		5458
		5459	EV_TIMEOUT => EV_TIMER
		5460
		5461	ev_loop_count => ev_iteration
		5462	ev_loop_depth => ev_depth
		5463	ev_loop_verify => ev_verify
4646		5464
4647	Most functions working on C<struct ev_loop> objects don't have an	5465	Most functions working on C<struct ev_loop> objects don't have an
4648	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5466	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5467	associated constants have been renamed to not collide with the C<struct
		5468	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5469	as all other watcher types. Note that C<ev_loop_fork> is still called
4649	still called C<ev_loop_fork> because it would otherwise clash with the	5470	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4650	C<ev_fork> typedef.	5471	typedef.
4651
4652	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4653
4654	This is a simple rename - all other watcher types use their name
4655	as revents flag, and now C<ev_timer> does, too.
4656
4657	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4658	and continue to be present for the forseeable future, so this is mostly a
4659	documentation change.
4660		5472
4661	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5473	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4662		5474
4663	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5475	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4664	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5476	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4671		5483
4672	=over 4	5484	=over 4
4673		5485
4674	=item active	5486	=item active
4675		5487
4676	A watcher is active as long as it has been started (has been attached to	5488	A watcher is active as long as it has been started and not yet stopped.
4677	an event loop) but not yet stopped (disassociated from the event loop).	5489	See L</WATCHER STATES> for details.
4678		5490
4679	=item application	5491	=item application
4680		5492
4681	In this document, an application is whatever is using libev.	5493	In this document, an application is whatever is using libev.
		5494
		5495	=item backend
		5496
		5497	The part of the code dealing with the operating system interfaces.
4682		5498
4683	=item callback	5499	=item callback
4684		5500
4685	The address of a function that is called when some event has been	5501	The address of a function that is called when some event has been
4686	detected. Callbacks are being passed the event loop, the watcher that	5502	detected. Callbacks are being passed the event loop, the watcher that
4687	received the event, and the actual event bitset.	5503	received the event, and the actual event bitset.
4688		5504
4689	=item callback invocation	5505	=item callback/watcher invocation
4690		5506
4691	The act of calling the callback associated with a watcher.	5507	The act of calling the callback associated with a watcher.
4692		5508
4693	=item event	5509	=item event
4694		5510
…		…
4713	The model used to describe how an event loop handles and processes	5529	The model used to describe how an event loop handles and processes
4714	watchers and events.	5530	watchers and events.
4715		5531
4716	=item pending	5532	=item pending
4717		5533
4718	A watcher is pending as soon as the corresponding event has been detected,	5534	A watcher is pending as soon as the corresponding event has been
4719	and stops being pending as soon as the watcher will be invoked or its	5535	detected. See L</WATCHER STATES> for details.
4720	pending status is explicitly cleared by the application.
4721
4722	A watcher can be pending, but not active. Stopping a watcher also clears
4723	its pending status.
4724		5536
4725	=item real time	5537	=item real time
4726		5538
4727	The physical time that is observed. It is apparently strictly monotonic :)	5539	The physical time that is observed. It is apparently strictly monotonic :)
4728		5540
4729	=item wall-clock time	5541	=item wall-clock time
4730		5542
4731	The time and date as shown on clocks. Unlike real time, it can actually	5543	The time and date as shown on clocks. Unlike real time, it can actually
4732	be wrong and jump forwards and backwards, e.g. when the you adjust your	5544	be wrong and jump forwards and backwards, e.g. when you adjust your
4733	clock.	5545	clock.
4734		5546
4735	=item watcher	5547	=item watcher
4736		5548
4737	A data structure that describes interest in certain events. Watchers need	5549	A data structure that describes interest in certain events. Watchers need
4738	to be started (attached to an event loop) before they can receive events.	5550	to be started (attached to an event loop) before they can receive events.
4739		5551
4740	=item watcher invocation
4741
4742	The act of calling the callback associated with a watcher.
4743
4744	=back	5552	=back
4745		5553
4746	=head1 AUTHOR	5554	=head1 AUTHOR
4747		5555
4748	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5556	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5557	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4749		5558

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