[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.310 by root, Thu Oct 21 12:32:47 2010 UTC vs.
Revision 1.444 by root, Mon Oct 29 00:00:22 2018 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
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);
…		…
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_run (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
…		…
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	Familiarity 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> is	329	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	I<not> optional in case unless libev 3 compatibility is disabled, as libev	330	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	3 had an C<ev_loop> function colliding with the struct name).	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 event loops	334	supports child process events, and dynamically created event loops which
303	which do 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.
353		412
354	This works by calling C<getpid ()> on every iteration of the loop,	413	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	414	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	415	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	416	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	417	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	418	system also has C<pthread_atfork> which is even faster). (Update: glibc
		419	versions 2.25 apparently removed the C<getpid> optimisation again).
360		420
361	The big advantage of this flag is that you can forget about fork (and	421	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	422	forget about forgetting to tell libev about forking, although you still
363	flag.	423	have to ignore C<SIGPIPE>) when you use this flag.
364		424
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	425	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	426	environment variable.
367		427
368	=item C<EVFLAG_NOINOTIFY>	428	=item C<EVFLAG_NOINOTIFY>
369		429
370	When this flag is specified, then libev will not attempt to use the	430	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	431	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	432	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.	433	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		434
375	=item C<EVFLAG_SIGNALFD>	435	=item C<EVFLAG_SIGNALFD>
376		436
377	When this flag is specified, then libev will attempt to use the	437	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	438	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	439	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	440	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	441	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	442	threads that are not interested in handling them.
383		443
384	Signalfd will not be used by default as this changes your signal mask, and	444	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	445	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	446	example) that can't properly initialise their signal masks.
		447
		448	=item C<EVFLAG_NOSIGMASK>
		449
		450	When this flag is specified, then libev will avoid to modify the signal
		451	mask. Specifically, this means you have to make sure signals are unblocked
		452	when you want to receive them.
		453
		454	This behaviour is useful when you want to do your own signal handling, or
		455	want to handle signals only in specific threads and want to avoid libev
		456	unblocking the signals.
		457
		458	It's also required by POSIX in a threaded program, as libev calls
		459	C<sigprocmask>, whose behaviour is officially unspecified.
		460
		461	This flag's behaviour will become the default in future versions of libev.
387		462
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	463	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		464
390	This is your standard select(2) backend. Not I<completely> standard, as	465	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,	466	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	494	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		495
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	496	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	497	kernels).
423		498
424	For few fds, this backend is a bit little slower than poll and select,	499	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	500	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),	501	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).	502	fd), epoll scales either O(1) or O(active_fds).
428		503
429	The epoll mechanism deserves honorable mention as the most misdesigned	504	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	505	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	506	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	507	descriptor (and unnecessary guessing of parameters), problems with dup,
		508	returning before the timeout value, resulting in additional iterations
		509	(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	510	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	511	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	512	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	513	and is of course hard to detect.
437		514
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	515	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	516	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	517	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	518	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	519	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	520	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	521	that against the events to filter out spurious ones, recreating the set
		522	when required. Epoll also erroneously rounds down timeouts, but gives you
		523	no way to know when and by how much, so sometimes you have to busy-wait
		524	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	525	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	526	perfectly fine with C<select> (files, many character devices...).
		527
		528	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		529	cobbled together in a hurry, no thought to design or interaction with
		530	others. Oh, the pain, will it ever stop...
447		531
448	While stopping, setting and starting an I/O watcher in the same iteration	532	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	533	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	534	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	535	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
488		572
489	It scales in the same way as the epoll backend, but the interface to the	573	It scales in the same way as the epoll backend, but the interface to the
490	kernel is more efficient (which says nothing about its actual speed, of	574	kernel is more efficient (which says nothing about its actual speed, of
491	course). While stopping, setting and starting an I/O watcher does never	575	course). While stopping, setting and starting an I/O watcher does never
492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	576	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
493	two event changes per incident. Support for C<fork ()> is very bad (but	577	two event changes per incident. Support for C<fork ()> is very bad (you
494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	578	might have to leak fd's on fork, but it's more sane than epoll) and it
495	cases	579	drops fds silently in similarly hard-to-detect cases.
496		580
497	This backend usually performs well under most conditions.	581	This backend usually performs well under most conditions.
498		582
499	While nominally embeddable in other event loops, this doesn't work	583	While nominally embeddable in other event loops, this doesn't work
500	everywhere, so you might need to test for this. And since it is broken	584	everywhere, so you might need to test for this. And since it is broken
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	601	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		602
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	603	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	604	it's really slow, but it still scales very well (O(active_fds)).
521		605
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	606	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	607	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	608	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	609	might perform better.
530		610
531	On the positive side, with the exception of the spurious readiness	611	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	612	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	613	among the OS-specific backends (I vastly prefer correctness over speed
		614	hacks).
		615
		616	On the negative side, the interface is I<bizarre> - so bizarre that
		617	even sun itself gets it wrong in their code examples: The event polling
		618	function sometimes returns events to the caller even though an error
		619	occurred, but with no indication whether it has done so or not (yes, it's
		620	even documented that way) - deadly for edge-triggered interfaces where you
		621	absolutely have to know whether an event occurred or not because you have
		622	to re-arm the watcher.
		623
		624	Fortunately libev seems to be able to work around these idiocies.
535		625
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	626	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	627	C<EVBACKEND_POLL>.
538		628
539	=item C<EVBACKEND_ALL>	629	=item C<EVBACKEND_ALL>
540		630
541	Try all backends (even potentially broken ones that wouldn't be tried	631	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	632	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	633	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		634
545	It is definitely not recommended to use this flag.	635	It is definitely not recommended to use this flag, use whatever
		636	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		637	at all.
		638
		639	=item C<EVBACKEND_MASK>
		640
		641	Not a backend at all, but a mask to select all backend bits from a
		642	C<flags> value, in case you want to mask out any backends from a flags
		643	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		644
547	=back	645	=back
548		646
549	If one or more of the backend flags are or'ed into the flags value,	647	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	648	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	649	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	650	()> will be tried.
553		651
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	652	Example: Try to create a event loop that uses epoll and nothing else.
581		653
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	654	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
583	if (!epoller)	655	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	656	fatal ("no epoll found here, maybe it hides under your chair");
585		657
		658	Example: Use whatever libev has to offer, but make sure that kqueue is
		659	used if available.
		660
		661	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		662
586	=item ev_default_destroy ()	663	=item ev_loop_destroy (loop)
587		664
588	Destroys the default loop (frees all memory and kernel state etc.). None	665	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	666	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	667	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	668	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	669	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	670	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		671	for example).
594		672
595	Note that certain global state, such as signal state (and installed signal	673	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	674	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	675	as signal and child watchers) would need to be stopped manually.
598		676
599	In general it is not advisable to call this function except in the	677	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	678	C<ev_loop_new>, but it can also be used on the default loop returned by
		679	C<ev_default_loop>, in which case it is not thread-safe.
		680
		681	Note that it is not advisable to call this function on the default loop
		682	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	683	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	684	and C<ev_loop_destroy>.
603		685
604	=item ev_loop_destroy (loop)	686	=item ev_loop_fork (loop)
605
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610		687
611	This function sets a flag that causes subsequent C<ev_run> iterations	688	This function sets a flag that causes subsequent C<ev_run> iterations
612	to reinitialise the kernel state for backends that have one. Despite the	689	to reinitialise the kernel state for backends that have one. Despite
613	name, you can call it anytime, but it makes most sense after forking, in	690	the name, you can call it anytime you are allowed to start or stop
614	the child process (or both child and parent, but that again makes little	691	watchers (except inside an C<ev_prepare> callback), but it makes most
615	sense). You I<must> call it in the child before using any of the libev	692	sense after forking, in the child process. You I<must> call it (or use
616	functions, and it will only take effect at the next C<ev_run> iteration.	693	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
617		694
		695	In addition, if you want to reuse a loop (via this function or
		696	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		697
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	698	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	699	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces cough I<kqueue> cough do funny things	700	because some kernel interfaces cough I<kqueue> cough do funny things
621	during fork.	701	during fork.
622		702
623	On the other hand, you only need to call this function in the child	703	On the other hand, you only need to call this function in the child
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	706	call it at all (in fact, C<epoll> is so badly broken that it makes a
627	difference, but libev will usually detect this case on its own and do a	707	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	708	costly reset of the backend).
629		709
630	The function itself is quite fast and it's usually not a problem to call	710	The function itself is quite fast and it's usually not a problem to call
631	it just in case after a fork. To make this easy, the function will fit in	711	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		712
		713	Example: Automate calling C<ev_loop_fork> on the default loop when
		714	using pthreads.
		715
		716	static void
		717	post_fork_child (void)
		718	{
		719	ev_loop_fork (EV_DEFAULT);
		720	}
		721
		722	...
634	pthread_atfork (0, 0, ev_default_fork);	723	pthread_atfork (0, 0, post_fork_child);
635
636	=item ev_loop_fork (loop)
637
638	Like C<ev_default_fork>, but acts on an event loop created by
639	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
640	after fork that you want to re-use in the child, and how you keep track of
641	them is entirely your own problem.
642		724
643	=item int ev_is_default_loop (loop)	725	=item int ev_is_default_loop (loop)
644		726
645	Returns true when the given loop is, in fact, the default loop, and false	727	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	728	otherwise.
…		…
657	prepare and check phases.	739	prepare and check phases.
658		740
659	=item unsigned int ev_depth (loop)	741	=item unsigned int ev_depth (loop)
660		742
661	Returns the number of times C<ev_run> was entered minus the number of	743	Returns the number of times C<ev_run> was entered minus the number of
662	times C<ev_run> was exited, in other words, the recursion depth.	744	times C<ev_run> was exited normally, in other words, the recursion depth.
663		745
664	Outside C<ev_run>, this number is zero. In a callback, this number is	746	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	747	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	748	in which case it is higher.
667		749
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	750	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
669	etc.), doesn't count as "exit" - consider this as a hint to avoid such	751	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	752	as a hint to avoid such ungentleman-like behaviour unless it's really
		753	convenient, in which case it is fully supported.
671		754
672	=item unsigned int ev_backend (loop)	755	=item unsigned int ev_backend (loop)
673		756
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	757	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	758	use.
…		…
690		773
691	This function is rarely useful, but when some event callback runs for a	774	This function is rarely useful, but when some event callback runs for a
692	very long time without entering the event loop, updating libev's idea of	775	very long time without entering the event loop, updating libev's idea of
693	the current time is a good idea.	776	the current time is a good idea.
694		777
695	See also L<The special problem of time updates> in the C<ev_timer> section.	778	See also L</The special problem of time updates> in the C<ev_timer> section.
696		779
697	=item ev_suspend (loop)	780	=item ev_suspend (loop)
698		781
699	=item ev_resume (loop)	782	=item ev_resume (loop)
700		783
…		…
718	without a previous call to C<ev_suspend>.	801	without a previous call to C<ev_suspend>.
719		802
720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	803	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
721	event loop time (see C<ev_now_update>).	804	event loop time (see C<ev_now_update>).
722		805
723	=item ev_run (loop, int flags)	806	=item bool ev_run (loop, int flags)
724		807
725	Finally, this is it, the event handler. This function usually is called	808	Finally, this is it, the event handler. This function usually is called
726	after you have initialised all your watchers and you want to start	809	after you have initialised all your watchers and you want to start
727	handling events. It will ask the operating system for any new events, call	810	handling events. It will ask the operating system for any new events, call
728	the watcher callbacks, an then repeat the whole process indefinitely: This	811	the watcher callbacks, and then repeat the whole process indefinitely: This
729	is why event loops are called I<loops>.	812	is why event loops are called I<loops>.
730		813
731	If the flags argument is specified as C<0>, it will keep handling events	814	If the flags argument is specified as C<0>, it will keep handling events
732	until either no event watchers are active anymore or C<ev_break> was	815	until either no event watchers are active anymore or C<ev_break> was
733	called.	816	called.
		817
		818	The return value is false if there are no more active watchers (which
		819	usually means "all jobs done" or "deadlock"), and true in all other cases
		820	(which usually means " you should call C<ev_run> again").
734		821
735	Please note that an explicit C<ev_break> is usually better than	822	Please note that an explicit C<ev_break> is usually better than
736	relying on all watchers to be stopped when deciding when a program has	823	relying on all watchers to be stopped when deciding when a program has
737	finished (especially in interactive programs), but having a program	824	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	825	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	826	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	827	beauty.
741		828
		829	This function is I<mostly> exception-safe - you can break out of a
		830	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		831	exception and so on. This does not decrement the C<ev_depth> value, nor
		832	will it clear any outstanding C<EVBREAK_ONE> breaks.
		833
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	834	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
743	those events and any already outstanding ones, but will not wait and	835	those events and any already outstanding ones, but will not wait and
744	block your process in case there are no events and will return after one	836	block your process in case there are no events and will return after one
745	iteration of the loop. This is sometimes useful to poll and handle new	837	iteration of the loop. This is sometimes useful to poll and handle new
746	events while doing lengthy calculations, to keep the program responsive.	838	events while doing lengthy calculations, to keep the program responsive.
…		…
755	This is useful if you are waiting for some external event in conjunction	847	This is useful if you are waiting for some external event in conjunction
756	with something not expressible using other libev watchers (i.e. "roll your	848	with something not expressible using other libev watchers (i.e. "roll your
757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	849	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
758	usually a better approach for this kind of thing.	850	usually a better approach for this kind of thing.
759		851
760	Here are the gory details of what C<ev_run> does:	852	Here are the gory details of what C<ev_run> does (this is for your
		853	understanding, not a guarantee that things will work exactly like this in
		854	future versions):
761		855
762	- Increment loop depth.	856	- Increment loop depth.
763	- Reset the ev_break status.	857	- Reset the ev_break status.
764	- Before the first iteration, call any pending watchers.	858	- Before the first iteration, call any pending watchers.
765	LOOP:	859	LOOP:
…		…
798	anymore.	892	anymore.
799		893
800	... queue jobs here, make sure they register event watchers as long	894	... queue jobs here, make sure they register event watchers as long
801	... as they still have work to do (even an idle watcher will do..)	895	... as they still have work to do (even an idle watcher will do..)
802	ev_run (my_loop, 0);	896	ev_run (my_loop, 0);
803	... jobs done or somebody called unloop. yeah!	897	... jobs done or somebody called break. yeah!
804		898
805	=item ev_break (loop, how)	899	=item ev_break (loop, how)
806		900
807	Can be used to make a call to C<ev_run> return early (but only after it	901	Can be used to make a call to C<ev_run> return early (but only after it
808	has processed all outstanding events). The C<how> argument must be either	902	has processed all outstanding events). The C<how> argument must be either
809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	903	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	904	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		905
812	This "unloop state" will be cleared when entering C<ev_run> again.	906	This "break state" will be cleared on the next call to C<ev_run>.
813		907
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	908	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		909	which case it will have no effect.
815		910
816	=item ev_ref (loop)	911	=item ev_ref (loop)
817		912
818	=item ev_unref (loop)	913	=item ev_unref (loop)
819		914
…		…
840	running when nothing else is active.	935	running when nothing else is active.
841		936
842	ev_signal exitsig;	937	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	938	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	939	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	940	ev_unref (loop);
846		941
847	Example: For some weird reason, unregister the above signal handler again.	942	Example: For some weird reason, unregister the above signal handler again.
848		943
849	ev_ref (loop);	944	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	945	ev_signal_stop (loop, &exitsig);
…		…
870	overhead for the actual polling but can deliver many events at once.	965	overhead for the actual polling but can deliver many events at once.
871		966
872	By setting a higher I<io collect interval> you allow libev to spend more	967	By setting a higher I<io collect interval> you allow libev to spend more
873	time collecting I/O events, so you can handle more events per iteration,	968	time collecting I/O events, so you can handle more events per iteration,
874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	969	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
875	C<ev_timer>) will be not affected. Setting this to a non-null value will	970	C<ev_timer>) will not be affected. Setting this to a non-null value will
876	introduce an additional C<ev_sleep ()> call into most loop iterations. The	971	introduce an additional C<ev_sleep ()> call into most loop iterations. The
877	sleep time ensures that libev will not poll for I/O events more often then	972	sleep time ensures that libev will not poll for I/O events more often then
878	once per this interval, on average.	973	once per this interval, on average (as long as the host time resolution is
		974	good enough).
879		975
880	Likewise, by setting a higher I<timeout collect interval> you allow libev	976	Likewise, by setting a higher I<timeout collect interval> you allow libev
881	to spend more time collecting timeouts, at the expense of increased	977	to spend more time collecting timeouts, at the expense of increased
882	latency/jitter/inexactness (the watcher callback will be called	978	latency/jitter/inexactness (the watcher callback will be called
883	later). C<ev_io> watchers will not be affected. Setting this to a non-null	979	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
908		1004
909	=item ev_invoke_pending (loop)	1005	=item ev_invoke_pending (loop)
910		1006
911	This call will simply invoke all pending watchers while resetting their	1007	This call will simply invoke all pending watchers while resetting their
912	pending state. Normally, C<ev_run> does this automatically when required,	1008	pending state. Normally, C<ev_run> does this automatically when required,
913	but when overriding the invoke callback this call comes handy.	1009	but when overriding the invoke callback this call comes handy. This
		1010	function can be invoked from a watcher - this can be useful for example
		1011	when you want to do some lengthy calculation and want to pass further
		1012	event handling to another thread (you still have to make sure only one
		1013	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
914		1014
915	=item int ev_pending_count (loop)	1015	=item int ev_pending_count (loop)
916		1016
917	Returns the number of pending watchers - zero indicates that no watchers	1017	Returns the number of pending watchers - zero indicates that no watchers
918	are pending.	1018	are pending.
…		…
925	invoke the actual watchers inside another context (another thread etc.).	1025	invoke the actual watchers inside another context (another thread etc.).
926		1026
927	If you want to reset the callback, use C<ev_invoke_pending> as new	1027	If you want to reset the callback, use C<ev_invoke_pending> as new
928	callback.	1028	callback.
929		1029
930	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))	1030	=item ev_set_loop_release_cb (loop, void (release)(EV_P) throw (), void (acquire)(EV_P) throw ())
931		1031
932	Sometimes you want to share the same loop between multiple threads. This	1032	Sometimes you want to share the same loop between multiple threads. This
933	can be done relatively simply by putting mutex_lock/unlock calls around	1033	can be done relatively simply by putting mutex_lock/unlock calls around
934	each call to a libev function.	1034	each call to a libev function.
935		1035
936	However, C<ev_run> can run an indefinite time, so it is not feasible	1036	However, C<ev_run> can run an indefinite time, so it is not feasible
937	to wait for it to return. One way around this is to wake up the event	1037	to wait for it to return. One way around this is to wake up the event
938	loop via C<ev_break> and C<av_async_send>, another way is to set these	1038	loop via C<ev_break> and C<ev_async_send>, another way is to set these
939	I<release> and I<acquire> callbacks on the loop.	1039	I<release> and I<acquire> callbacks on the loop.
940		1040
941	When set, then C<release> will be called just before the thread is	1041	When set, then C<release> will be called just before the thread is
942	suspended waiting for new events, and C<acquire> is called just	1042	suspended waiting for new events, and C<acquire> is called just
943	afterwards.	1043	afterwards.
…		…
958	See also the locking example in the C<THREADS> section later in this	1058	See also the locking example in the C<THREADS> section later in this
959	document.	1059	document.
960		1060
961	=item ev_set_userdata (loop, void *data)	1061	=item ev_set_userdata (loop, void *data)
962		1062
963	=item ev_userdata (loop)	1063	=item void *ev_userdata (loop)
964		1064
965	Set and retrieve a single C<void *> associated with a loop. When	1065	Set and retrieve a single C<void *> associated with a loop. When
966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1066	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
967	C<0.>	1067	C<0>.
968		1068
969	These two functions can be used to associate arbitrary data with a loop,	1069	These two functions can be used to associate arbitrary data with a loop,
970	and are intended solely for the C<invoke_pending_cb>, C<release> and	1070	and are intended solely for the C<invoke_pending_cb>, C<release> and
971	C<acquire> callbacks described above, but of course can be (ab-)used for	1071	C<acquire> callbacks described above, but of course can be (ab-)used for
972	any other purpose as well.	1072	any other purpose as well.
…		…
990		1090
991	In the following description, uppercase C<TYPE> in names stands for the	1091	In the following description, uppercase C<TYPE> in names stands for the
992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1092	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
993	watchers and C<ev_io_start> for I/O watchers.	1093	watchers and C<ev_io_start> for I/O watchers.
994		1094
995	A watcher is a structure that you create and register to record your	1095	A watcher is an opaque structure that you allocate and register to record
996	interest in some event. For instance, if you want to wait for STDIN to	1096	your interest in some event. To make a concrete example, imagine you want
997	become readable, you would create an C<ev_io> watcher for that:	1097	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1098	for that:
998		1099
999	static void my_cb (struct ev_loop loop, ev_io w, int revents)	1100	static void my_cb (struct ev_loop loop, ev_io w, int revents)
1000	{	1101	{
1001	ev_io_stop (w);	1102	ev_io_stop (w);
1002	ev_break (loop, EVBREAK_ALL);	1103	ev_break (loop, EVBREAK_ALL);
…		…
1017	stack).	1118	stack).
1018		1119
1019	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1120	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1020	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1121	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1021		1122
1022	Each watcher structure must be initialised by a call to C<ev_init	1123	Each watcher structure must be initialised by a call to C<ev_init (watcher
1023	(watcher *, callback)>, which expects a callback to be provided. This	1124	*, callback)>, which expects a callback to be provided. This callback is
1024	callback gets invoked each time the event occurs (or, in the case of I/O	1125	invoked each time the event occurs (or, in the case of I/O watchers, each
1025	watchers, each time the event loop detects that the file descriptor given	1126	time the event loop detects that the file descriptor given is readable
1026	is readable and/or writable).	1127	and/or writable).
1027		1128
1028	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1129	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1029	macro to configure it, with arguments specific to the watcher type. There	1130	macro to configure it, with arguments specific to the watcher type. There
1030	is also a macro to combine initialisation and setting in one call: C<<	1131	is also a macro to combine initialisation and setting in one call: C<<
1031	ev_TYPE_init (watcher *, callback, ...) >>.	1132	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1082		1183
1083	=item C<EV_PREPARE>	1184	=item C<EV_PREPARE>
1084		1185
1085	=item C<EV_CHECK>	1186	=item C<EV_CHECK>
1086		1187
1087	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1188	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1088	to gather new events, and all C<ev_check> watchers are invoked just after	1189	gather new events, and all C<ev_check> watchers are queued (not invoked)
1089	C<ev_run> has gathered them, but before it invokes any callbacks for any	1190	just after C<ev_run> has gathered them, but before it queues any callbacks
		1191	for any received events. That means C<ev_prepare> watchers are the last
		1192	watchers invoked before the event loop sleeps or polls for new events, and
		1193	C<ev_check> watchers will be invoked before any other watchers of the same
		1194	or lower priority within an event loop iteration.
		1195
1090	received events. Callbacks of both watcher types can start and stop as	1196	Callbacks of both watcher types can start and stop as many watchers as
1091	many watchers as they want, and all of them will be taken into account	1197	they want, and all of them will be taken into account (for example, a
1092	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1198	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1093	C<ev_run> from blocking).	1199	blocking).
1094		1200
1095	=item C<EV_EMBED>	1201	=item C<EV_EMBED>
1096		1202
1097	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1203	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1098		1204
1099	=item C<EV_FORK>	1205	=item C<EV_FORK>
1100		1206
1101	The event loop has been resumed in the child process after fork (see	1207	The event loop has been resumed in the child process after fork (see
1102	C<ev_fork>).	1208	C<ev_fork>).
		1209
		1210	=item C<EV_CLEANUP>
		1211
		1212	The event loop is about to be destroyed (see C<ev_cleanup>).
1103		1213
1104	=item C<EV_ASYNC>	1214	=item C<EV_ASYNC>
1105		1215
1106	The given async watcher has been asynchronously notified (see C<ev_async>).	1216	The given async watcher has been asynchronously notified (see C<ev_async>).
1107		1217
…		…
1217		1327
1218	=item callback ev_cb (ev_TYPE *watcher)	1328	=item callback ev_cb (ev_TYPE *watcher)
1219		1329
1220	Returns the callback currently set on the watcher.	1330	Returns the callback currently set on the watcher.
1221		1331
1222	=item ev_cb_set (ev_TYPE *watcher, callback)	1332	=item ev_set_cb (ev_TYPE *watcher, callback)
1223		1333
1224	Change the callback. You can change the callback at virtually any time	1334	Change the callback. You can change the callback at virtually any time
1225	(modulo threads).	1335	(modulo threads).
1226		1336
1227	=item ev_set_priority (ev_TYPE *watcher, int priority)	1337	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1245	or might not have been clamped to the valid range.	1355	or might not have been clamped to the valid range.
1246		1356
1247	The default priority used by watchers when no priority has been set is	1357	The default priority used by watchers when no priority has been set is
1248	always C<0>, which is supposed to not be too high and not be too low :).	1358	always C<0>, which is supposed to not be too high and not be too low :).
1249		1359
1250	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1360	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1251	priorities.	1361	priorities.
1252		1362
1253	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1363	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1254		1364
1255	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1365	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1390	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1281	functions that do not need a watcher.	1391	functions that do not need a watcher.
1282		1392
1283	=back	1393	=back
1284		1394
		1395	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1396	OWN COMPOSITE WATCHERS> idioms.
1285		1397
1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1398	=head2 WATCHER STATES
1287		1399
1288	Each watcher has, by default, a member C<void *data> that you can change	1400	There are various watcher states mentioned throughout this manual -
1289	and read at any time: libev will completely ignore it. This can be used	1401	active, pending and so on. In this section these states and the rules to
1290	to associate arbitrary data with your watcher. If you need more data and	1402	transition between them will be described in more detail - and while these
1291	don't want to allocate memory and store a pointer to it in that data	1403	rules might look complicated, they usually do "the right thing".
1292	member, you can also "subclass" the watcher type and provide your own
1293	data:
1294		1404
1295	struct my_io	1405	=over 4
1296	{
1297	ev_io io;
1298	int otherfd;
1299	void *somedata;
1300	struct whatever *mostinteresting;
1301	};
1302		1406
1303	...	1407	=item initialised
1304	struct my_io w;
1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
1306		1408
1307	And since your callback will be called with a pointer to the watcher, you	1409	Before a watcher can be registered with the event loop it has to be
1308	can cast it back to your own type:	1410	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1411	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1309		1412
1310	static void my_cb (struct ev_loop loop, ev_io w_, int revents)	1413	In this state it is simply some block of memory that is suitable for
1311	{	1414	use in an event loop. It can be moved around, freed, reused etc. at
1312	struct my_io w = (struct my_io )w_;	1415	will - as long as you either keep the memory contents intact, or call
1313	...	1416	C<ev_TYPE_init> again.
1314	}
1315		1417
1316	More interesting and less C-conformant ways of casting your callback type	1418	=item started/running/active
1317	instead have been omitted.
1318		1419
1319	Another common scenario is to use some data structure with multiple	1420	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1320	embedded watchers:	1421	property of the event loop, and is actively waiting for events. While in
		1422	this state it cannot be accessed (except in a few documented ways), moved,
		1423	freed or anything else - the only legal thing is to keep a pointer to it,
		1424	and call libev functions on it that are documented to work on active watchers.
1321		1425
1322	struct my_biggy	1426	=item pending
1323	{
1324	int some_data;
1325	ev_timer t1;
1326	ev_timer t2;
1327	}
1328		1427
1329	In this case getting the pointer to C<my_biggy> is a bit more	1428	If a watcher is active and libev determines that an event it is interested
1330	complicated: Either you store the address of your C<my_biggy> struct	1429	in has occurred (such as a timer expiring), it will become pending. It will
1331	in the C<data> member of the watcher (for woozies), or you need to use	1430	stay in this pending state until either it is stopped or its callback is
1332	some pointer arithmetic using C<offsetof> inside your watchers (for real	1431	about to be invoked, so it is not normally pending inside the watcher
1333	programmers):	1432	callback.
1334		1433
1335	#include <stddef.h>	1434	The watcher might or might not be active while it is pending (for example,
		1435	an expired non-repeating timer can be pending but no longer active). If it
		1436	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1437	but it is still property of the event loop at this time, so cannot be
		1438	moved, freed or reused. And if it is active the rules described in the
		1439	previous item still apply.
1336		1440
1337	static void	1441	It is also possible to feed an event on a watcher that is not active (e.g.
1338	t1_cb (EV_P_ ev_timer *w, int revents)	1442	via C<ev_feed_event>), in which case it becomes pending without being
1339	{	1443	active.
1340	struct my_biggy big = (struct my_biggy *)
1341	(((char *)w) - offsetof (struct my_biggy, t1));
1342	}
1343		1444
1344	static void	1445	=item stopped
1345	t2_cb (EV_P_ ev_timer *w, int revents)	1446
1346	{	1447	A watcher can be stopped implicitly by libev (in which case it might still
1347	struct my_biggy big = (struct my_biggy *)	1448	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1348	(((char *)w) - offsetof (struct my_biggy, t2));	1449	latter will clear any pending state the watcher might be in, regardless
1349	}	1450	of whether it was active or not, so stopping a watcher explicitly before
		1451	freeing it is often a good idea.
		1452
		1453	While stopped (and not pending) the watcher is essentially in the
		1454	initialised state, that is, it can be reused, moved, modified in any way
		1455	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1456	it again).
		1457
		1458	=back
1350		1459
1351	=head2 WATCHER PRIORITY MODELS	1460	=head2 WATCHER PRIORITY MODELS
1352		1461
1353	Many event loops support I<watcher priorities>, which are usually small	1462	Many event loops support I<watcher priorities>, which are usually small
1354	integers that influence the ordering of event callback invocation	1463	integers that influence the ordering of event callback invocation
…		…
1481	In general you can register as many read and/or write event watchers per	1590	In general you can register as many read and/or write event watchers per
1482	fd as you want (as long as you don't confuse yourself). Setting all file	1591	fd as you want (as long as you don't confuse yourself). Setting all file
1483	descriptors to non-blocking mode is also usually a good idea (but not	1592	descriptors to non-blocking mode is also usually a good idea (but not
1484	required if you know what you are doing).	1593	required if you know what you are doing).
1485		1594
1486	If you cannot use non-blocking mode, then force the use of a
1487	known-to-be-good backend (at the time of this writing, this includes only
1488	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1489	descriptors for which non-blocking operation makes no sense (such as
1490	files) - libev doesn't guarantee any specific behaviour in that case.
1491
1492	Another thing you have to watch out for is that it is quite easy to	1595	Another thing you have to watch out for is that it is quite easy to
1493	receive "spurious" readiness notifications, that is your callback might	1596	receive "spurious" readiness notifications, that is, your callback might
1494	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1597	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1495	because there is no data. Not only are some backends known to create a	1598	because there is no data. It is very easy to get into this situation even
1496	lot of those (for example Solaris ports), it is very easy to get into	1599	with a relatively standard program structure. Thus it is best to always
1497	this situation even with a relatively standard program structure. Thus	1600	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1498	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1499	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1601	preferable to a program hanging until some data arrives.
1500		1602
1501	If you cannot run the fd in non-blocking mode (for example you should	1603	If you cannot run the fd in non-blocking mode (for example you should
1502	not play around with an Xlib connection), then you have to separately	1604	not play around with an Xlib connection), then you have to separately
1503	re-test whether a file descriptor is really ready with a known-to-be good	1605	re-test whether a file descriptor is really ready with a known-to-be good
1504	interface such as poll (fortunately in our Xlib example, Xlib already	1606	interface such as poll (fortunately in the case of Xlib, it already does
1505	does this on its own, so its quite safe to use). Some people additionally	1607	this on its own, so its quite safe to use). Some people additionally
1506	use C<SIGALRM> and an interval timer, just to be sure you won't block	1608	use C<SIGALRM> and an interval timer, just to be sure you won't block
1507	indefinitely.	1609	indefinitely.
1508		1610
1509	But really, best use non-blocking mode.	1611	But really, best use non-blocking mode.
1510		1612
…		…
1538		1640
1539	There is no workaround possible except not registering events	1641	There is no workaround possible except not registering events
1540	for potentially C<dup ()>'ed file descriptors, or to resort to	1642	for potentially C<dup ()>'ed file descriptors, or to resort to
1541	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1643	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1542		1644
		1645	=head3 The special problem of files
		1646
		1647	Many people try to use C<select> (or libev) on file descriptors
		1648	representing files, and expect it to become ready when their program
		1649	doesn't block on disk accesses (which can take a long time on their own).
		1650
		1651	However, this cannot ever work in the "expected" way - you get a readiness
		1652	notification as soon as the kernel knows whether and how much data is
		1653	there, and in the case of open files, that's always the case, so you
		1654	always get a readiness notification instantly, and your read (or possibly
		1655	write) will still block on the disk I/O.
		1656
		1657	Another way to view it is that in the case of sockets, pipes, character
		1658	devices and so on, there is another party (the sender) that delivers data
		1659	on its own, but in the case of files, there is no such thing: the disk
		1660	will not send data on its own, simply because it doesn't know what you
		1661	wish to read - you would first have to request some data.
		1662
		1663	Since files are typically not-so-well supported by advanced notification
		1664	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1665	to files, even though you should not use it. The reason for this is
		1666	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1667	usually a tty, often a pipe, but also sometimes files or special devices
		1668	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1669	F</dev/urandom>), and even though the file might better be served with
		1670	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1671	it "just works" instead of freezing.
		1672
		1673	So avoid file descriptors pointing to files when you know it (e.g. use
		1674	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1675	when you rarely read from a file instead of from a socket, and want to
		1676	reuse the same code path.
		1677
1543	=head3 The special problem of fork	1678	=head3 The special problem of fork
1544		1679
1545	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1680	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1546	useless behaviour. Libev fully supports fork, but needs to be told about	1681	useless behaviour. Libev fully supports fork, but needs to be told about
1547	it in the child.	1682	it in the child if you want to continue to use it in the child.
1548		1683
1549	To support fork in your programs, you either have to call	1684	To support fork in your child processes, you have to call C<ev_loop_fork
1550	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1685	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1551	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1686	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1552	C<EVBACKEND_POLL>.
1553		1687
1554	=head3 The special problem of SIGPIPE	1688	=head3 The special problem of SIGPIPE
1555		1689
1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1690	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1557	when writing to a pipe whose other end has been closed, your program gets	1691	when writing to a pipe whose other end has been closed, your program gets
…		…
1655	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1789	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1656	monotonic clock option helps a lot here).	1790	monotonic clock option helps a lot here).
1657		1791
1658	The callback is guaranteed to be invoked only I<after> its timeout has	1792	The callback is guaranteed to be invoked only I<after> its timeout has
1659	passed (not I<at>, so on systems with very low-resolution clocks this	1793	passed (not I<at>, so on systems with very low-resolution clocks this
1660	might introduce a small delay). If multiple timers become ready during the	1794	might introduce a small delay, see "the special problem of being too
		1795	early", below). If multiple timers become ready during the same loop
1661	same loop iteration then the ones with earlier time-out values are invoked	1796	iteration then the ones with earlier time-out values are invoked before
1662	before ones of the same priority with later time-out values (but this is	1797	ones of the same priority with later time-out values (but this is no
1663	no longer true when a callback calls C<ev_run> recursively).	1798	longer true when a callback calls C<ev_run> recursively).
1664		1799
1665	=head3 Be smart about timeouts	1800	=head3 Be smart about timeouts
1666		1801
1667	Many real-world problems involve some kind of timeout, usually for error	1802	Many real-world problems involve some kind of timeout, usually for error
1668	recovery. A typical example is an HTTP request - if the other side hangs,	1803	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1743		1878
1744	In this case, it would be more efficient to leave the C<ev_timer> alone,	1879	In this case, it would be more efficient to leave the C<ev_timer> alone,
1745	but remember the time of last activity, and check for a real timeout only	1880	but remember the time of last activity, and check for a real timeout only
1746	within the callback:	1881	within the callback:
1747		1882
		1883	ev_tstamp timeout = 60.;
1748	ev_tstamp last_activity; // time of last activity	1884	ev_tstamp last_activity; // time of last activity
		1885	ev_timer timer;
1749		1886
1750	static void	1887	static void
1751	callback (EV_P_ ev_timer *w, int revents)	1888	callback (EV_P_ ev_timer *w, int revents)
1752	{	1889	{
1753	ev_tstamp now = ev_now (EV_A);	1890	// calculate when the timeout would happen
1754	ev_tstamp timeout = last_activity + 60.;	1891	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1755		1892
1756	// if last_activity + 60. is older than now, we did time out	1893	// if negative, it means we the timeout already occurred
1757	if (timeout < now)	1894	if (after < 0.)
1758	{	1895	{
1759	// timeout occurred, take action	1896	// timeout occurred, take action
1760	}	1897	}
1761	else	1898	else
1762	{	1899	{
1763	// callback was invoked, but there was some activity, re-arm	1900	// callback was invoked, but there was some recent
1764	// the watcher to fire in last_activity + 60, which is	1901	// activity. simply restart the timer to time out
1765	// guaranteed to be in the future, so "again" is positive:	1902	// after "after" seconds, which is the earliest time
1766	w->repeat = timeout - now;	1903	// the timeout can occur.
		1904	ev_timer_set (w, after, 0.);
1767	ev_timer_again (EV_A_ w);	1905	ev_timer_start (EV_A_ w);
1768	}	1906	}
1769	}	1907	}
1770		1908
1771	To summarise the callback: first calculate the real timeout (defined	1909	To summarise the callback: first calculate in how many seconds the
1772	as "60 seconds after the last activity"), then check if that time has	1910	timeout will occur (by calculating the absolute time when it would occur,
1773	been reached, which means something I<did>, in fact, time out. Otherwise	1911	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1774	the callback was invoked too early (C<timeout> is in the future), so	1912	(EV_A)> from that).
1775	re-schedule the timer to fire at that future time, to see if maybe we have
1776	a timeout then.
1777		1913
1778	Note how C<ev_timer_again> is used, taking advantage of the	1914	If this value is negative, then we are already past the timeout, i.e. we
1779	C<ev_timer_again> optimisation when the timer is already running.	1915	timed out, and need to do whatever is needed in this case.
		1916
		1917	Otherwise, we now the earliest time at which the timeout would trigger,
		1918	and simply start the timer with this timeout value.
		1919
		1920	In other words, each time the callback is invoked it will check whether
		1921	the timeout occurred. If not, it will simply reschedule itself to check
		1922	again at the earliest time it could time out. Rinse. Repeat.
1780		1923
1781	This scheme causes more callback invocations (about one every 60 seconds	1924	This scheme causes more callback invocations (about one every 60 seconds
1782	minus half the average time between activity), but virtually no calls to	1925	minus half the average time between activity), but virtually no calls to
1783	libev to change the timeout.	1926	libev to change the timeout.
1784		1927
1785	To start the timer, simply initialise the watcher and set C<last_activity>	1928	To start the machinery, simply initialise the watcher and set
1786	to the current time (meaning we just have some activity :), then call the	1929	C<last_activity> to the current time (meaning there was some activity just
1787	callback, which will "do the right thing" and start the timer:	1930	now), then call the callback, which will "do the right thing" and start
		1931	the timer:
1788		1932
		1933	last_activity = ev_now (EV_A);
1789	ev_init (timer, callback);	1934	ev_init (&timer, callback);
1790	last_activity = ev_now (loop);	1935	callback (EV_A_ &timer, 0);
1791	callback (loop, timer, EV_TIMER);
1792		1936
1793	And when there is some activity, simply store the current time in	1937	When there is some activity, simply store the current time in
1794	C<last_activity>, no libev calls at all:	1938	C<last_activity>, no libev calls at all:
1795		1939
		1940	if (activity detected)
1796	last_activity = ev_now (loop);	1941	last_activity = ev_now (EV_A);
		1942
		1943	When your timeout value changes, then the timeout can be changed by simply
		1944	providing a new value, stopping the timer and calling the callback, which
		1945	will again do the right thing (for example, time out immediately :).
		1946
		1947	timeout = new_value;
		1948	ev_timer_stop (EV_A_ &timer);
		1949	callback (EV_A_ &timer, 0);
1797		1950
1798	This technique is slightly more complex, but in most cases where the	1951	This technique is slightly more complex, but in most cases where the
1799	time-out is unlikely to be triggered, much more efficient.	1952	time-out is unlikely to be triggered, much more efficient.
1800
1801	Changing the timeout is trivial as well (if it isn't hard-coded in the
1802	callback :) - just change the timeout and invoke the callback, which will
1803	fix things for you.
1804		1953
1805	=item 4. Wee, just use a double-linked list for your timeouts.	1954	=item 4. Wee, just use a double-linked list for your timeouts.
1806		1955
1807	If there is not one request, but many thousands (millions...), all	1956	If there is not one request, but many thousands (millions...), all
1808	employing some kind of timeout with the same timeout value, then one can	1957	employing some kind of timeout with the same timeout value, then one can
…		…
1835	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1984	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1836	rather complicated, but extremely efficient, something that really pays	1985	rather complicated, but extremely efficient, something that really pays
1837	off after the first million or so of active timers, i.e. it's usually	1986	off after the first million or so of active timers, i.e. it's usually
1838	overkill :)	1987	overkill :)
1839		1988
		1989	=head3 The special problem of being too early
		1990
		1991	If you ask a timer to call your callback after three seconds, then
		1992	you expect it to be invoked after three seconds - but of course, this
		1993	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1994	guaranteed to any precision by libev - imagine somebody suspending the
		1995	process with a STOP signal for a few hours for example.
		1996
		1997	So, libev tries to invoke your callback as soon as possible I<after> the
		1998	delay has occurred, but cannot guarantee this.
		1999
		2000	A less obvious failure mode is calling your callback too early: many event
		2001	loops compare timestamps with a "elapsed delay >= requested delay", but
		2002	this can cause your callback to be invoked much earlier than you would
		2003	expect.
		2004
		2005	To see why, imagine a system with a clock that only offers full second
		2006	resolution (think windows if you can't come up with a broken enough OS
		2007	yourself). If you schedule a one-second timer at the time 500.9, then the
		2008	event loop will schedule your timeout to elapse at a system time of 500
		2009	(500.9 truncated to the resolution) + 1, or 501.
		2010
		2011	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2012	501" and invoke the callback 0.1s after it was started, even though a
		2013	one-second delay was requested - this is being "too early", despite best
		2014	intentions.
		2015
		2016	This is the reason why libev will never invoke the callback if the elapsed
		2017	delay equals the requested delay, but only when the elapsed delay is
		2018	larger than the requested delay. In the example above, libev would only invoke
		2019	the callback at system time 502, or 1.1s after the timer was started.
		2020
		2021	So, while libev cannot guarantee that your callback will be invoked
		2022	exactly when requested, it I<can> and I<does> guarantee that the requested
		2023	delay has actually elapsed, or in other words, it always errs on the "too
		2024	late" side of things.
		2025
1840	=head3 The special problem of time updates	2026	=head3 The special problem of time updates
1841		2027
1842	Establishing the current time is a costly operation (it usually takes at	2028	Establishing the current time is a costly operation (it usually takes
1843	least two system calls): EV therefore updates its idea of the current	2029	at least one system call): EV therefore updates its idea of the current
1844	time only before and after C<ev_run> collects new events, which causes a	2030	time only before and after C<ev_run> collects new events, which causes a
1845	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2031	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1846	lots of events in one iteration.	2032	lots of events in one iteration.
1847		2033
1848	The relative timeouts are calculated relative to the C<ev_now ()>	2034	The relative timeouts are calculated relative to the C<ev_now ()>
1849	time. This is usually the right thing as this timestamp refers to the time	2035	time. This is usually the right thing as this timestamp refers to the time
1850	of the event triggering whatever timeout you are modifying/starting. If	2036	of the event triggering whatever timeout you are modifying/starting. If
1851	you suspect event processing to be delayed and you I<need> to base the	2037	you suspect event processing to be delayed and you I<need> to base the
1852	timeout on the current time, use something like this to adjust for this:	2038	timeout on the current time, use something like the following to adjust
		2039	for it:
1853		2040
1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2041	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1855		2042
1856	If the event loop is suspended for a long time, you can also force an	2043	If the event loop is suspended for a long time, you can also force an
1857	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2044	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1858	()>.	2045	()>, although that will push the event time of all outstanding events
		2046	further into the future.
		2047
		2048	=head3 The special problem of unsynchronised clocks
		2049
		2050	Modern systems have a variety of clocks - libev itself uses the normal
		2051	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2052	jumps).
		2053
		2054	Neither of these clocks is synchronised with each other or any other clock
		2055	on the system, so C<ev_time ()> might return a considerably different time
		2056	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2057	a call to C<gettimeofday> might return a second count that is one higher
		2058	than a directly following call to C<time>.
		2059
		2060	The moral of this is to only compare libev-related timestamps with
		2061	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2062	a second or so.
		2063
		2064	One more problem arises due to this lack of synchronisation: if libev uses
		2065	the system monotonic clock and you compare timestamps from C<ev_time>
		2066	or C<ev_now> from when you started your timer and when your callback is
		2067	invoked, you will find that sometimes the callback is a bit "early".
		2068
		2069	This is because C<ev_timer>s work in real time, not wall clock time, so
		2070	libev makes sure your callback is not invoked before the delay happened,
		2071	I<measured according to the real time>, not the system clock.
		2072
		2073	If your timeouts are based on a physical timescale (e.g. "time out this
		2074	connection after 100 seconds") then this shouldn't bother you as it is
		2075	exactly the right behaviour.
		2076
		2077	If you want to compare wall clock/system timestamps to your timers, then
		2078	you need to use C<ev_periodic>s, as these are based on the wall clock
		2079	time, where your comparisons will always generate correct results.
1859		2080
1860	=head3 The special problems of suspended animation	2081	=head3 The special problems of suspended animation
1861		2082
1862	When you leave the server world it is quite customary to hit machines that	2083	When you leave the server world it is quite customary to hit machines that
1863	can suspend/hibernate - what happens to the clocks during such a suspend?	2084	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1893		2114
1894	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2115	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1895		2116
1896	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2117	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1897		2118
1898	Configure the timer to trigger after C<after> seconds. If C<repeat>	2119	Configure the timer to trigger after C<after> seconds (fractional and
1899	is C<0.>, then it will automatically be stopped once the timeout is	2120	negative values are supported). If C<repeat> is C<0.>, then it will
1900	reached. If it is positive, then the timer will automatically be	2121	automatically be stopped once the timeout is reached. If it is positive,
1901	configured to trigger again C<repeat> seconds later, again, and again,	2122	then the timer will automatically be configured to trigger again C<repeat>
1902	until stopped manually.	2123	seconds later, again, and again, until stopped manually.
1903		2124
1904	The timer itself will do a best-effort at avoiding drift, that is, if	2125	The timer itself will do a best-effort at avoiding drift, that is, if
1905	you configure a timer to trigger every 10 seconds, then it will normally	2126	you configure a timer to trigger every 10 seconds, then it will normally
1906	trigger at exactly 10 second intervals. If, however, your program cannot	2127	trigger at exactly 10 second intervals. If, however, your program cannot
1907	keep up with the timer (because it takes longer than those 10 seconds to	2128	keep up with the timer (because it takes longer than those 10 seconds to
1908	do stuff) the timer will not fire more than once per event loop iteration.	2129	do stuff) the timer will not fire more than once per event loop iteration.
1909		2130
1910	=item ev_timer_again (loop, ev_timer *)	2131	=item ev_timer_again (loop, ev_timer *)
1911		2132
1912	This will act as if the timer timed out and restart it again if it is	2133	This will act as if the timer timed out, and restarts it again if it is
1913	repeating. The exact semantics are:	2134	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2135	timeout to the C<repeat> value and calling C<ev_timer_start>.
1914		2136
		2137	The exact semantics are as in the following rules, all of which will be
		2138	applied to the watcher:
		2139
		2140	=over 4
		2141
1915	If the timer is pending, its pending status is cleared.	2142	=item If the timer is pending, the pending status is always cleared.
1916		2143
1917	If the timer is started but non-repeating, stop it (as if it timed out).	2144	=item If the timer is started but non-repeating, stop it (as if it timed
		2145	out, without invoking it).
1918		2146
1919	If the timer is repeating, either start it if necessary (with the	2147	=item If the timer is repeating, make the C<repeat> value the new timeout
1920	C<repeat> value), or reset the running timer to the C<repeat> value.	2148	and start the timer, if necessary.
1921		2149
		2150	=back
		2151
1922	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2152	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1923	usage example.	2153	usage example.
1924		2154
1925	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2155	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1926		2156
1927	Returns the remaining time until a timer fires. If the timer is active,	2157	Returns the remaining time until a timer fires. If the timer is active,
…		…
1980	Periodic watchers are also timers of a kind, but they are very versatile	2210	Periodic watchers are also timers of a kind, but they are very versatile
1981	(and unfortunately a bit complex).	2211	(and unfortunately a bit complex).
1982		2212
1983	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2213	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1984	relative time, the physical time that passes) but on wall clock time	2214	relative time, the physical time that passes) but on wall clock time
1985	(absolute time, the thing you can read on your calender or clock). The	2215	(absolute time, the thing you can read on your calendar or clock). The
1986	difference is that wall clock time can run faster or slower than real	2216	difference is that wall clock time can run faster or slower than real
1987	time, and time jumps are not uncommon (e.g. when you adjust your	2217	time, and time jumps are not uncommon (e.g. when you adjust your
1988	wrist-watch).	2218	wrist-watch).
1989		2219
1990	You can tell a periodic watcher to trigger after some specific point	2220	You can tell a periodic watcher to trigger after some specific point
…		…
1995	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2225	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1996	it, as it uses a relative timeout).	2226	it, as it uses a relative timeout).
1997		2227
1998	C<ev_periodic> watchers can also be used to implement vastly more complex	2228	C<ev_periodic> watchers can also be used to implement vastly more complex
1999	timers, such as triggering an event on each "midnight, local time", or	2229	timers, such as triggering an event on each "midnight, local time", or
2000	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2230	other complicated rules. This cannot easily be done with C<ev_timer>
2001	those cannot react to time jumps.	2231	watchers, as those cannot react to time jumps.
2002		2232
2003	As with timers, the callback is guaranteed to be invoked only when the	2233	As with timers, the callback is guaranteed to be invoked only when the
2004	point in time where it is supposed to trigger has passed. If multiple	2234	point in time where it is supposed to trigger has passed. If multiple
2005	timers become ready during the same loop iteration then the ones with	2235	timers become ready during the same loop iteration then the ones with
2006	earlier time-out values are invoked before ones with later time-out values	2236	earlier time-out values are invoked before ones with later time-out values
…		…
2047		2277
2048	Another way to think about it (for the mathematically inclined) is that	2278	Another way to think about it (for the mathematically inclined) is that
2049	C<ev_periodic> will try to run the callback in this mode at the next possible	2279	C<ev_periodic> will try to run the callback in this mode at the next possible
2050	time where C<time = offset (mod interval)>, regardless of any time jumps.	2280	time where C<time = offset (mod interval)>, regardless of any time jumps.
2051		2281
2052	For numerical stability it is preferable that the C<offset> value is near	2282	The C<interval> I<MUST> be positive, and for numerical stability, the
2053	C<ev_now ()> (the current time), but there is no range requirement for	2283	interval value should be higher than C<1/8192> (which is around 100
2054	this value, and in fact is often specified as zero.	2284	microseconds) and C<offset> should be higher than C<0> and should have
		2285	at most a similar magnitude as the current time (say, within a factor of
		2286	ten). Typical values for offset are, in fact, C<0> or something between
		2287	C<0> and C<interval>, which is also the recommended range.
2055		2288
2056	Note also that there is an upper limit to how often a timer can fire (CPU	2289	Note also that there is an upper limit to how often a timer can fire (CPU
2057	speed for example), so if C<interval> is very small then timing stability	2290	speed for example), so if C<interval> is very small then timing stability
2058	will of course deteriorate. Libev itself tries to be exact to be about one	2291	will of course deteriorate. Libev itself tries to be exact to be about one
2059	millisecond (if the OS supports it and the machine is fast enough).	2292	millisecond (if the OS supports it and the machine is fast enough).
…		…
2089		2322
2090	NOTE: I<< This callback must always return a time that is higher than or	2323	NOTE: I<< This callback must always return a time that is higher than or
2091	equal to the passed C<now> value >>.	2324	equal to the passed C<now> value >>.
2092		2325
2093	This can be used to create very complex timers, such as a timer that	2326	This can be used to create very complex timers, such as a timer that
2094	triggers on "next midnight, local time". To do this, you would calculate the	2327	triggers on "next midnight, local time". To do this, you would calculate
2095	next midnight after C<now> and return the timestamp value for this. How	2328	the next midnight after C<now> and return the timestamp value for
2096	you do this is, again, up to you (but it is not trivial, which is the main	2329	this. Here is a (completely untested, no error checking) example on how to
2097	reason I omitted it as an example).	2330	do this:
		2331
		2332	#include <time.h>
		2333
		2334	static ev_tstamp
		2335	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2336	{
		2337	time_t tnow = (time_t)now;
		2338	struct tm tm;
		2339	localtime_r (&tnow, &tm);
		2340
		2341	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2342	++tm.tm_mday; // midnight next day
		2343
		2344	return mktime (&tm);
		2345	}
		2346
		2347	Note: this code might run into trouble on days that have more then two
		2348	midnights (beginning and end).
2098		2349
2099	=back	2350	=back
2100		2351
2101	=item ev_periodic_again (loop, ev_periodic *)	2352	=item ev_periodic_again (loop, ev_periodic *)
2102		2353
…		…
2167		2418
2168	ev_periodic hourly_tick;	2419	ev_periodic hourly_tick;
2169	ev_periodic_init (&hourly_tick, clock_cb,	2420	ev_periodic_init (&hourly_tick, clock_cb,
2170	fmod (ev_now (loop), 3600.), 3600., 0);	2421	fmod (ev_now (loop), 3600.), 3600., 0);
2171	ev_periodic_start (loop, &hourly_tick);	2422	ev_periodic_start (loop, &hourly_tick);
2172		2423
2173		2424
2174	=head2 C<ev_signal> - signal me when a signal gets signalled!	2425	=head2 C<ev_signal> - signal me when a signal gets signalled!
2175		2426
2176	Signal watchers will trigger an event when the process receives a specific	2427	Signal watchers will trigger an event when the process receives a specific
2177	signal one or more times. Even though signals are very asynchronous, libev	2428	signal one or more times. Even though signals are very asynchronous, libev
2178	will try it's best to deliver signals synchronously, i.e. as part of the	2429	will try its best to deliver signals synchronously, i.e. as part of the
2179	normal event processing, like any other event.	2430	normal event processing, like any other event.
2180		2431
2181	If you want signals to be delivered truly asynchronously, just use	2432	If you want signals to be delivered truly asynchronously, just use
2182	C<sigaction> as you would do without libev and forget about sharing	2433	C<sigaction> as you would do without libev and forget about sharing
2183	the signal. You can even use C<ev_async> from a signal handler to	2434	the signal. You can even use C<ev_async> from a signal handler to
…		…
2187	only within the same loop, i.e. you can watch for C<SIGINT> in your	2438	only within the same loop, i.e. you can watch for C<SIGINT> in your
2188	default loop and for C<SIGIO> in another loop, but you cannot watch for	2439	default loop and for C<SIGIO> in another loop, but you cannot watch for
2189	C<SIGINT> in both the default loop and another loop at the same time. At	2440	C<SIGINT> in both the default loop and another loop at the same time. At
2190	the moment, C<SIGCHLD> is permanently tied to the default loop.	2441	the moment, C<SIGCHLD> is permanently tied to the default loop.
2191		2442
2192	When the first watcher gets started will libev actually register something	2443	Only after the first watcher for a signal is started will libev actually
2193	with the kernel (thus it coexists with your own signal handlers as long as	2444	register something with the kernel. It thus coexists with your own signal
2194	you don't register any with libev for the same signal).	2445	handlers as long as you don't register any with libev for the same signal.
2195		2446
2196	If possible and supported, libev will install its handlers with	2447	If possible and supported, libev will install its handlers with
2197	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2448	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2198	not be unduly interrupted. If you have a problem with system calls getting	2449	not be unduly interrupted. If you have a problem with system calls getting
2199	interrupted by signals you can block all signals in an C<ev_check> watcher	2450	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2202	=head3 The special problem of inheritance over fork/execve/pthread_create	2453	=head3 The special problem of inheritance over fork/execve/pthread_create
2203		2454
2204	Both the signal mask (C<sigprocmask>) and the signal disposition	2455	Both the signal mask (C<sigprocmask>) and the signal disposition
2205	(C<sigaction>) are unspecified after starting a signal watcher (and after	2456	(C<sigaction>) are unspecified after starting a signal watcher (and after
2206	stopping it again), that is, libev might or might not block the signal,	2457	stopping it again), that is, libev might or might not block the signal,
2207	and might or might not set or restore the installed signal handler.	2458	and might or might not set or restore the installed signal handler (but
		2459	see C<EVFLAG_NOSIGMASK>).
2208		2460
2209	While this does not matter for the signal disposition (libev never	2461	While this does not matter for the signal disposition (libev never
2210	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2462	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2211	C<execve>), this matters for the signal mask: many programs do not expect	2463	C<execve>), this matters for the signal mask: many programs do not expect
2212	certain signals to be blocked.	2464	certain signals to be blocked.
…		…
2225	I<has> to modify the signal mask, at least temporarily.	2477	I<has> to modify the signal mask, at least temporarily.
2226		2478
2227	So I can't stress this enough: I<If you do not reset your signal mask when	2479	So I can't stress this enough: I<If you do not reset your signal mask when
2228	you expect it to be empty, you have a race condition in your code>. This	2480	you expect it to be empty, you have a race condition in your code>. This
2229	is not a libev-specific thing, this is true for most event libraries.	2481	is not a libev-specific thing, this is true for most event libraries.
		2482
		2483	=head3 The special problem of threads signal handling
		2484
		2485	POSIX threads has problematic signal handling semantics, specifically,
		2486	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2487	threads in a process block signals, which is hard to achieve.
		2488
		2489	When you want to use sigwait (or mix libev signal handling with your own
		2490	for the same signals), you can tackle this problem by globally blocking
		2491	all signals before creating any threads (or creating them with a fully set
		2492	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2493	loops. Then designate one thread as "signal receiver thread" which handles
		2494	these signals. You can pass on any signals that libev might be interested
		2495	in by calling C<ev_feed_signal>.
2230		2496
2231	=head3 Watcher-Specific Functions and Data Members	2497	=head3 Watcher-Specific Functions and Data Members
2232		2498
2233	=over 4	2499	=over 4
2234		2500
…		…
2369		2635
2370	=head2 C<ev_stat> - did the file attributes just change?	2636	=head2 C<ev_stat> - did the file attributes just change?
2371		2637
2372	This watches a file system path for attribute changes. That is, it calls	2638	This watches a file system path for attribute changes. That is, it calls
2373	C<stat> on that path in regular intervals (or when the OS says it changed)	2639	C<stat> on that path in regular intervals (or when the OS says it changed)
2374	and sees if it changed compared to the last time, invoking the callback if	2640	and sees if it changed compared to the last time, invoking the callback
2375	it did.	2641	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2642	happen after the watcher has been started will be reported.
2376		2643
2377	The path does not need to exist: changing from "path exists" to "path does	2644	The path does not need to exist: changing from "path exists" to "path does
2378	not exist" is a status change like any other. The condition "path does not	2645	not exist" is a status change like any other. The condition "path does not
2379	exist" (or more correctly "path cannot be stat'ed") is signified by the	2646	exist" (or more correctly "path cannot be stat'ed") is signified by the
2380	C<st_nlink> field being zero (which is otherwise always forced to be at	2647	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2610	Apart from keeping your process non-blocking (which is a useful	2877	Apart from keeping your process non-blocking (which is a useful
2611	effect on its own sometimes), idle watchers are a good place to do	2878	effect on its own sometimes), idle watchers are a good place to do
2612	"pseudo-background processing", or delay processing stuff to after the	2879	"pseudo-background processing", or delay processing stuff to after the
2613	event loop has handled all outstanding events.	2880	event loop has handled all outstanding events.
2614		2881
		2882	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2883
		2884	As long as there is at least one active idle watcher, libev will never
		2885	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2886	For this to work, the idle watcher doesn't need to be invoked at all - the
		2887	lowest priority will do.
		2888
		2889	This mode of operation can be useful together with an C<ev_check> watcher,
		2890	to do something on each event loop iteration - for example to balance load
		2891	between different connections.
		2892
		2893	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2894	example.
		2895
2615	=head3 Watcher-Specific Functions and Data Members	2896	=head3 Watcher-Specific Functions and Data Members
2616		2897
2617	=over 4	2898	=over 4
2618		2899
2619	=item ev_idle_init (ev_idle *, callback)	2900	=item ev_idle_init (ev_idle *, callback)
…		…
2630	callback, free it. Also, use no error checking, as usual.	2911	callback, free it. Also, use no error checking, as usual.
2631		2912
2632	static void	2913	static void
2633	idle_cb (struct ev_loop loop, ev_idle w, int revents)	2914	idle_cb (struct ev_loop loop, ev_idle w, int revents)
2634	{	2915	{
		2916	// stop the watcher
		2917	ev_idle_stop (loop, w);
		2918
		2919	// now we can free it
2635	free (w);	2920	free (w);
		2921
2636	// now do something you wanted to do when the program has	2922	// now do something you wanted to do when the program has
2637	// no longer anything immediate to do.	2923	// no longer anything immediate to do.
2638	}	2924	}
2639		2925
2640	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2926	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2642	ev_idle_start (loop, idle_watcher);	2928	ev_idle_start (loop, idle_watcher);
2643		2929
2644		2930
2645	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2931	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2646		2932
2647	Prepare and check watchers are usually (but not always) used in pairs:	2933	Prepare and check watchers are often (but not always) used in pairs:
2648	prepare watchers get invoked before the process blocks and check watchers	2934	prepare watchers get invoked before the process blocks and check watchers
2649	afterwards.	2935	afterwards.
2650		2936
2651	You I<must not> call C<ev_run> or similar functions that enter	2937	You I<must not> call C<ev_run> (or similar functions that enter the
2652	the current event loop from either C<ev_prepare> or C<ev_check>	2938	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2653	watchers. Other loops than the current one are fine, however. The	2939	C<ev_check> watchers. Other loops than the current one are fine,
2654	rationale behind this is that you do not need to check for recursion in	2940	however. The rationale behind this is that you do not need to check
2655	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2941	for recursion in those watchers, i.e. the sequence will always be
2656	C<ev_check> so if you have one watcher of each kind they will always be	2942	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2657	called in pairs bracketing the blocking call.	2943	kind they will always be called in pairs bracketing the blocking call.
2658		2944
2659	Their main purpose is to integrate other event mechanisms into libev and	2945	Their main purpose is to integrate other event mechanisms into libev and
2660	their use is somewhat advanced. They could be used, for example, to track	2946	their use is somewhat advanced. They could be used, for example, to track
2661	variable changes, implement your own watchers, integrate net-snmp or a	2947	variable changes, implement your own watchers, integrate net-snmp or a
2662	coroutine library and lots more. They are also occasionally useful if	2948	coroutine library and lots more. They are also occasionally useful if
…		…
2680	with priority higher than or equal to the event loop and one coroutine	2966	with priority higher than or equal to the event loop and one coroutine
2681	of lower priority, but only once, using idle watchers to keep the event	2967	of lower priority, but only once, using idle watchers to keep the event
2682	loop from blocking if lower-priority coroutines are active, thus mapping	2968	loop from blocking if lower-priority coroutines are active, thus mapping
2683	low-priority coroutines to idle/background tasks).	2969	low-priority coroutines to idle/background tasks).
2684		2970
2685	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2971	When used for this purpose, it is recommended to give C<ev_check> watchers
2686	priority, to ensure that they are being run before any other watchers	2972	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2687	after the poll (this doesn't matter for C<ev_prepare> watchers).	2973	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2974	watchers).
2688		2975
2689	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2976	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2690	activate ("feed") events into libev. While libev fully supports this, they	2977	activate ("feed") events into libev. While libev fully supports this, they
2691	might get executed before other C<ev_check> watchers did their job. As	2978	might get executed before other C<ev_check> watchers did their job. As
2692	C<ev_check> watchers are often used to embed other (non-libev) event	2979	C<ev_check> watchers are often used to embed other (non-libev) event
2693	loops those other event loops might be in an unusable state until their	2980	loops those other event loops might be in an unusable state until their
2694	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2981	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2695	others).	2982	others).
		2983
		2984	=head3 Abusing an C<ev_check> watcher for its side-effect
		2985
		2986	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2987	useful because they are called once per event loop iteration. For
		2988	example, if you want to handle a large number of connections fairly, you
		2989	normally only do a bit of work for each active connection, and if there
		2990	is more work to do, you wait for the next event loop iteration, so other
		2991	connections have a chance of making progress.
		2992
		2993	Using an C<ev_check> watcher is almost enough: it will be called on the
		2994	next event loop iteration. However, that isn't as soon as possible -
		2995	without external events, your C<ev_check> watcher will not be invoked.
		2996
		2997	This is where C<ev_idle> watchers come in handy - all you need is a
		2998	single global idle watcher that is active as long as you have one active
		2999	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3000	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3001	invoked. Neither watcher alone can do that.
2696		3002
2697	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2698		3004
2699	=over 4	3005	=over 4
2700		3006
…		…
2901		3207
2902	=over 4	3208	=over 4
2903		3209
2904	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	3210	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
2905		3211
2906	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	3212	=item ev_embed_set (ev_embed , struct ev_loop embedded_loop)
2907		3213
2908	Configures the watcher to embed the given loop, which must be	3214	Configures the watcher to embed the given loop, which must be
2909	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2910	invoked automatically, otherwise it is the responsibility of the callback	3216	invoked automatically, otherwise it is the responsibility of the callback
2911	to invoke it (it will continue to be called until the sweep has been done,	3217	to invoke it (it will continue to be called until the sweep has been done,
…		…
2932	used).	3238	used).
2933		3239
2934	struct ev_loop *loop_hi = ev_default_init (0);	3240	struct ev_loop *loop_hi = ev_default_init (0);
2935	struct ev_loop *loop_lo = 0;	3241	struct ev_loop *loop_lo = 0;
2936	ev_embed embed;	3242	ev_embed embed;
2937		3243
2938	// see if there is a chance of getting one that works	3244	// see if there is a chance of getting one that works
2939	// (remember that a flags value of 0 means autodetection)	3245	// (remember that a flags value of 0 means autodetection)
2940	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3246	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2941	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3247	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2942	: 0;	3248	: 0;
…		…
2956	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3262	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2957		3263
2958	struct ev_loop *loop = ev_default_init (0);	3264	struct ev_loop *loop = ev_default_init (0);
2959	struct ev_loop *loop_socket = 0;	3265	struct ev_loop *loop_socket = 0;
2960	ev_embed embed;	3266	ev_embed embed;
2961		3267
2962	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3268	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2963	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3269	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2964	{	3270	{
2965	ev_embed_init (&embed, 0, loop_socket);	3271	ev_embed_init (&embed, 0, loop_socket);
2966	ev_embed_start (loop, &embed);	3272	ev_embed_start (loop, &embed);
…		…
2974		3280
2975	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3281	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2976		3282
2977	Fork watchers are called when a C<fork ()> was detected (usually because	3283	Fork watchers are called when a C<fork ()> was detected (usually because
2978	whoever is a good citizen cared to tell libev about it by calling	3284	whoever is a good citizen cared to tell libev about it by calling
2979	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3285	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2980	event loop blocks next and before C<ev_check> watchers are being called,	3286	and before C<ev_check> watchers are being called, and only in the child
2981	and only in the child after the fork. If whoever good citizen calling	3287	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2982	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3288	and calls it in the wrong process, the fork handlers will be invoked, too,
2983	handlers will be invoked, too, of course.	3289	of course.
2984		3290
2985	=head3 The special problem of life after fork - how is it possible?	3291	=head3 The special problem of life after fork - how is it possible?
2986		3292
2987	Most uses of C<fork()> consist of forking, then some simple calls to set	3293	Most uses of C<fork ()> consist of forking, then some simple calls to set
2988	up/change the process environment, followed by a call to C<exec()>. This	3294	up/change the process environment, followed by a call to C<exec()>. This
2989	sequence should be handled by libev without any problems.	3295	sequence should be handled by libev without any problems.
2990		3296
2991	This changes when the application actually wants to do event handling	3297	This changes when the application actually wants to do event handling
2992	in the child, or both parent in child, in effect "continuing" after the	3298	in the child, or both parent in child, in effect "continuing" after the
…		…
3008	disadvantage of having to use multiple event loops (which do not support	3314	disadvantage of having to use multiple event loops (which do not support
3009	signal watchers).	3315	signal watchers).
3010		3316
3011	When this is not possible, or you want to use the default loop for	3317	When this is not possible, or you want to use the default loop for
3012	other reasons, then in the process that wants to start "fresh", call	3318	other reasons, then in the process that wants to start "fresh", call
3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3319	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3014	the default loop will "orphan" (not stop) all registered watchers, so you	3320	Destroying the default loop will "orphan" (not stop) all registered
3015	have to be careful not to execute code that modifies those watchers. Note	3321	watchers, so you have to be careful not to execute code that modifies
3016	also that in that case, you have to re-register any signal watchers.	3322	those watchers. Note also that in that case, you have to re-register any
		3323	signal watchers.
3017		3324
3018	=head3 Watcher-Specific Functions and Data Members	3325	=head3 Watcher-Specific Functions and Data Members
3019		3326
3020	=over 4	3327	=over 4
3021		3328
3022	=item ev_fork_init (ev_signal *, callback)	3329	=item ev_fork_init (ev_fork *, callback)
3023		3330
3024	Initialises and configures the fork watcher - it has no parameters of any	3331	Initialises and configures the fork watcher - it has no parameters of any
3025	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3332	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3026	believe me.	3333	really.
3027		3334
3028	=back	3335	=back
3029		3336
3030		3337
		3338	=head2 C<ev_cleanup> - even the best things end
		3339
		3340	Cleanup watchers are called just before the event loop is being destroyed
		3341	by a call to C<ev_loop_destroy>.
		3342
		3343	While there is no guarantee that the event loop gets destroyed, cleanup
		3344	watchers provide a convenient method to install cleanup hooks for your
		3345	program, worker threads and so on - you just to make sure to destroy the
		3346	loop when you want them to be invoked.
		3347
		3348	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3349	all other watchers, they do not keep a reference to the event loop (which
		3350	makes a lot of sense if you think about it). Like all other watchers, you
		3351	can call libev functions in the callback, except C<ev_cleanup_start>.
		3352
		3353	=head3 Watcher-Specific Functions and Data Members
		3354
		3355	=over 4
		3356
		3357	=item ev_cleanup_init (ev_cleanup *, callback)
		3358
		3359	Initialises and configures the cleanup watcher - it has no parameters of
		3360	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3361	pointless, I assure you.
		3362
		3363	=back
		3364
		3365	Example: Register an atexit handler to destroy the default loop, so any
		3366	cleanup functions are called.
		3367
		3368	static void
		3369	program_exits (void)
		3370	{
		3371	ev_loop_destroy (EV_DEFAULT_UC);
		3372	}
		3373
		3374	...
		3375	atexit (program_exits);
		3376
		3377
3031	=head2 C<ev_async> - how to wake up an event loop	3378	=head2 C<ev_async> - how to wake up an event loop
3032		3379
3033	In general, you cannot use an C<ev_run> from multiple threads or other	3380	In general, you cannot use an C<ev_loop> from multiple threads or other
3034	asynchronous sources such as signal handlers (as opposed to multiple event	3381	asynchronous sources such as signal handlers (as opposed to multiple event
3035	loops - those are of course safe to use in different threads).	3382	loops - those are of course safe to use in different threads).
3036		3383
3037	Sometimes, however, you need to wake up an event loop you do not control,	3384	Sometimes, however, you need to wake up an event loop you do not control,
3038	for example because it belongs to another thread. This is what C<ev_async>	3385	for example because it belongs to another thread. This is what C<ev_async>
…		…
3040	it by calling C<ev_async_send>, which is thread- and signal safe.	3387	it by calling C<ev_async_send>, which is thread- and signal safe.
3041		3388
3042	This functionality is very similar to C<ev_signal> watchers, as signals,	3389	This functionality is very similar to C<ev_signal> watchers, as signals,
3043	too, are asynchronous in nature, and signals, too, will be compressed	3390	too, are asynchronous in nature, and signals, too, will be compressed
3044	(i.e. the number of callback invocations may be less than the number of	3391	(i.e. the number of callback invocations may be less than the number of
3045	C<ev_async_sent> calls).	3392	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3046		3393	of "global async watchers" by using a watcher on an otherwise unused
3047	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3394	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3048	just the default loop.	3395	even without knowing which loop owns the signal.
3049		3396
3050	=head3 Queueing	3397	=head3 Queueing
3051		3398
3052	C<ev_async> does not support queueing of data in any way. The reason	3399	C<ev_async> does not support queueing of data in any way. The reason
3053	is that the author does not know of a simple (or any) algorithm for a	3400	is that the author does not know of a simple (or any) algorithm for a
…		…
3145	trust me.	3492	trust me.
3146		3493
3147	=item ev_async_send (loop, ev_async *)	3494	=item ev_async_send (loop, ev_async *)
3148		3495
3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3496	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3150	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3497	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3498	returns.
		3499
3151	C<ev_feed_event>, this call is safe to do from other threads, signal or	3500	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3152	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3501	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3153	section below on what exactly this means).	3502	embedding section below on what exactly this means).
3154		3503
3155	Note that, as with other watchers in libev, multiple events might get	3504	Note that, as with other watchers in libev, multiple events might get
3156	compressed into a single callback invocation (another way to look at this	3505	compressed into a single callback invocation (another way to look at
3157	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3506	this is that C<ev_async> watchers are level-triggered: they are set on
3158	reset when the event loop detects that).	3507	C<ev_async_send>, reset when the event loop detects that).
3159		3508
3160	This call incurs the overhead of a system call only once per event loop	3509	This call incurs the overhead of at most one extra system call per event
3161	iteration, so while the overhead might be noticeable, it doesn't apply to	3510	loop iteration, if the event loop is blocked, and no syscall at all if
3162	repeated calls to C<ev_async_send> for the same event loop.	3511	the event loop (or your program) is processing events. That means that
		3512	repeated calls are basically free (there is no need to avoid calls for
		3513	performance reasons) and that the overhead becomes smaller (typically
		3514	zero) under load.
3163		3515
3164	=item bool = ev_async_pending (ev_async *)	3516	=item bool = ev_async_pending (ev_async *)
3165		3517
3166	Returns a non-zero value when C<ev_async_send> has been called on the	3518	Returns a non-zero value when C<ev_async_send> has been called on the
3167	watcher but the event has not yet been processed (or even noted) by the	3519	watcher but the event has not yet been processed (or even noted) by the
…		…
3184		3536
3185	There are some other functions of possible interest. Described. Here. Now.	3537	There are some other functions of possible interest. Described. Here. Now.
3186		3538
3187	=over 4	3539	=over 4
3188		3540
3189	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3541	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3190		3542
3191	This function combines a simple timer and an I/O watcher, calls your	3543	This function combines a simple timer and an I/O watcher, calls your
3192	callback on whichever event happens first and automatically stops both	3544	callback on whichever event happens first and automatically stops both
3193	watchers. This is useful if you want to wait for a single event on an fd	3545	watchers. This is useful if you want to wait for a single event on an fd
3194	or timeout without having to allocate/configure/start/stop/free one or	3546	or timeout without having to allocate/configure/start/stop/free one or
…		…
3222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3574	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3223		3575
3224	=item ev_feed_fd_event (loop, int fd, int revents)	3576	=item ev_feed_fd_event (loop, int fd, int revents)
3225		3577
3226	Feed an event on the given fd, as if a file descriptor backend detected	3578	Feed an event on the given fd, as if a file descriptor backend detected
3227	the given events it.	3579	the given events.
3228		3580
3229	=item ev_feed_signal_event (loop, int signum)	3581	=item ev_feed_signal_event (loop, int signum)
3230		3582
3231	Feed an event as if the given signal occurred (C<loop> must be the default	3583	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3232	loop!).	3584	which is async-safe.
3233		3585
3234	=back	3586	=back
		3587
		3588
		3589	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3590
		3591	This section explains some common idioms that are not immediately
		3592	obvious. Note that examples are sprinkled over the whole manual, and this
		3593	section only contains stuff that wouldn't fit anywhere else.
		3594
		3595	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3596
		3597	Each watcher has, by default, a C<void *data> member that you can read
		3598	or modify at any time: libev will completely ignore it. This can be used
		3599	to associate arbitrary data with your watcher. If you need more data and
		3600	don't want to allocate memory separately and store a pointer to it in that
		3601	data member, you can also "subclass" the watcher type and provide your own
		3602	data:
		3603
		3604	struct my_io
		3605	{
		3606	ev_io io;
		3607	int otherfd;
		3608	void *somedata;
		3609	struct whatever *mostinteresting;
		3610	};
		3611
		3612	...
		3613	struct my_io w;
		3614	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3615
		3616	And since your callback will be called with a pointer to the watcher, you
		3617	can cast it back to your own type:
		3618
		3619	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
		3620	{
		3621	struct my_io w = (struct my_io )w_;
		3622	...
		3623	}
		3624
		3625	More interesting and less C-conformant ways of casting your callback
		3626	function type instead have been omitted.
		3627
		3628	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3629
		3630	Another common scenario is to use some data structure with multiple
		3631	embedded watchers, in effect creating your own watcher that combines
		3632	multiple libev event sources into one "super-watcher":
		3633
		3634	struct my_biggy
		3635	{
		3636	int some_data;
		3637	ev_timer t1;
		3638	ev_timer t2;
		3639	}
		3640
		3641	In this case getting the pointer to C<my_biggy> is a bit more
		3642	complicated: Either you store the address of your C<my_biggy> struct in
		3643	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3644	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3645	real programmers):
		3646
		3647	#include <stddef.h>
		3648
		3649	static void
		3650	t1_cb (EV_P_ ev_timer *w, int revents)
		3651	{
		3652	struct my_biggy big = (struct my_biggy *)
		3653	(((char *)w) - offsetof (struct my_biggy, t1));
		3654	}
		3655
		3656	static void
		3657	t2_cb (EV_P_ ev_timer *w, int revents)
		3658	{
		3659	struct my_biggy big = (struct my_biggy *)
		3660	(((char *)w) - offsetof (struct my_biggy, t2));
		3661	}
		3662
		3663	=head2 AVOIDING FINISHING BEFORE RETURNING
		3664
		3665	Often you have structures like this in event-based programs:
		3666
		3667	callback ()
		3668	{
		3669	free (request);
		3670	}
		3671
		3672	request = start_new_request (..., callback);
		3673
		3674	The intent is to start some "lengthy" operation. The C<request> could be
		3675	used to cancel the operation, or do other things with it.
		3676
		3677	It's not uncommon to have code paths in C<start_new_request> that
		3678	immediately invoke the callback, for example, to report errors. Or you add
		3679	some caching layer that finds that it can skip the lengthy aspects of the
		3680	operation and simply invoke the callback with the result.
		3681
		3682	The problem here is that this will happen I<before> C<start_new_request>
		3683	has returned, so C<request> is not set.
		3684
		3685	Even if you pass the request by some safer means to the callback, you
		3686	might want to do something to the request after starting it, such as
		3687	canceling it, which probably isn't working so well when the callback has
		3688	already been invoked.
		3689
		3690	A common way around all these issues is to make sure that
		3691	C<start_new_request> I<always> returns before the callback is invoked. If
		3692	C<start_new_request> immediately knows the result, it can artificially
		3693	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3694	example, or more sneakily, by reusing an existing (stopped) watcher and
		3695	pushing it into the pending queue:
		3696
		3697	ev_set_cb (watcher, callback);
		3698	ev_feed_event (EV_A_ watcher, 0);
		3699
		3700	This way, C<start_new_request> can safely return before the callback is
		3701	invoked, while not delaying callback invocation too much.
		3702
		3703	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3704
		3705	Often (especially in GUI toolkits) there are places where you have
		3706	I<modal> interaction, which is most easily implemented by recursively
		3707	invoking C<ev_run>.
		3708
		3709	This brings the problem of exiting - a callback might want to finish the
		3710	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3711	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3712	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3713	other combination: In these cases, a simple C<ev_break> will not work.
		3714
		3715	The solution is to maintain "break this loop" variable for each C<ev_run>
		3716	invocation, and use a loop around C<ev_run> until the condition is
		3717	triggered, using C<EVRUN_ONCE>:
		3718
		3719	// main loop
		3720	int exit_main_loop = 0;
		3721
		3722	while (!exit_main_loop)
		3723	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3724
		3725	// in a modal watcher
		3726	int exit_nested_loop = 0;
		3727
		3728	while (!exit_nested_loop)
		3729	ev_run (EV_A_ EVRUN_ONCE);
		3730
		3731	To exit from any of these loops, just set the corresponding exit variable:
		3732
		3733	// exit modal loop
		3734	exit_nested_loop = 1;
		3735
		3736	// exit main program, after modal loop is finished
		3737	exit_main_loop = 1;
		3738
		3739	// exit both
		3740	exit_main_loop = exit_nested_loop = 1;
		3741
		3742	=head2 THREAD LOCKING EXAMPLE
		3743
		3744	Here is a fictitious example of how to run an event loop in a different
		3745	thread from where callbacks are being invoked and watchers are
		3746	created/added/removed.
		3747
		3748	For a real-world example, see the C<EV::Loop::Async> perl module,
		3749	which uses exactly this technique (which is suited for many high-level
		3750	languages).
		3751
		3752	The example uses a pthread mutex to protect the loop data, a condition
		3753	variable to wait for callback invocations, an async watcher to notify the
		3754	event loop thread and an unspecified mechanism to wake up the main thread.
		3755
		3756	First, you need to associate some data with the event loop:
		3757
		3758	typedef struct {
		3759	mutex_t lock; /* global loop lock */
		3760	ev_async async_w;
		3761	thread_t tid;
		3762	cond_t invoke_cv;
		3763	} userdata;
		3764
		3765	void prepare_loop (EV_P)
		3766	{
		3767	// for simplicity, we use a static userdata struct.
		3768	static userdata u;
		3769
		3770	ev_async_init (&u->async_w, async_cb);
		3771	ev_async_start (EV_A_ &u->async_w);
		3772
		3773	pthread_mutex_init (&u->lock, 0);
		3774	pthread_cond_init (&u->invoke_cv, 0);
		3775
		3776	// now associate this with the loop
		3777	ev_set_userdata (EV_A_ u);
		3778	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3779	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3780
		3781	// then create the thread running ev_run
		3782	pthread_create (&u->tid, 0, l_run, EV_A);
		3783	}
		3784
		3785	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3786	solely to wake up the event loop so it takes notice of any new watchers
		3787	that might have been added:
		3788
		3789	static void
		3790	async_cb (EV_P_ ev_async *w, int revents)
		3791	{
		3792	// just used for the side effects
		3793	}
		3794
		3795	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3796	protecting the loop data, respectively.
		3797
		3798	static void
		3799	l_release (EV_P)
		3800	{
		3801	userdata *u = ev_userdata (EV_A);
		3802	pthread_mutex_unlock (&u->lock);
		3803	}
		3804
		3805	static void
		3806	l_acquire (EV_P)
		3807	{
		3808	userdata *u = ev_userdata (EV_A);
		3809	pthread_mutex_lock (&u->lock);
		3810	}
		3811
		3812	The event loop thread first acquires the mutex, and then jumps straight
		3813	into C<ev_run>:
		3814
		3815	void *
		3816	l_run (void *thr_arg)
		3817	{
		3818	struct ev_loop loop = (struct ev_loop )thr_arg;
		3819
		3820	l_acquire (EV_A);
		3821	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3822	ev_run (EV_A_ 0);
		3823	l_release (EV_A);
		3824
		3825	return 0;
		3826	}
		3827
		3828	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3829	signal the main thread via some unspecified mechanism (signals? pipe
		3830	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3831	have been called (in a while loop because a) spurious wakeups are possible
		3832	and b) skipping inter-thread-communication when there are no pending
		3833	watchers is very beneficial):
		3834
		3835	static void
		3836	l_invoke (EV_P)
		3837	{
		3838	userdata *u = ev_userdata (EV_A);
		3839
		3840	while (ev_pending_count (EV_A))
		3841	{
		3842	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3843	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3844	}
		3845	}
		3846
		3847	Now, whenever the main thread gets told to invoke pending watchers, it
		3848	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3849	thread to continue:
		3850
		3851	static void
		3852	real_invoke_pending (EV_P)
		3853	{
		3854	userdata *u = ev_userdata (EV_A);
		3855
		3856	pthread_mutex_lock (&u->lock);
		3857	ev_invoke_pending (EV_A);
		3858	pthread_cond_signal (&u->invoke_cv);
		3859	pthread_mutex_unlock (&u->lock);
		3860	}
		3861
		3862	Whenever you want to start/stop a watcher or do other modifications to an
		3863	event loop, you will now have to lock:
		3864
		3865	ev_timer timeout_watcher;
		3866	userdata *u = ev_userdata (EV_A);
		3867
		3868	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3869
		3870	pthread_mutex_lock (&u->lock);
		3871	ev_timer_start (EV_A_ &timeout_watcher);
		3872	ev_async_send (EV_A_ &u->async_w);
		3873	pthread_mutex_unlock (&u->lock);
		3874
		3875	Note that sending the C<ev_async> watcher is required because otherwise
		3876	an event loop currently blocking in the kernel will have no knowledge
		3877	about the newly added timer. By waking up the loop it will pick up any new
		3878	watchers in the next event loop iteration.
		3879
		3880	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3881
		3882	While the overhead of a callback that e.g. schedules a thread is small, it
		3883	is still an overhead. If you embed libev, and your main usage is with some
		3884	kind of threads or coroutines, you might want to customise libev so that
		3885	doesn't need callbacks anymore.
		3886
		3887	Imagine you have coroutines that you can switch to using a function
		3888	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3889	and that due to some magic, the currently active coroutine is stored in a
		3890	global called C<current_coro>. Then you can build your own "wait for libev
		3891	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3892	the differing C<;> conventions):
		3893
		3894	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3895	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3896
		3897	That means instead of having a C callback function, you store the
		3898	coroutine to switch to in each watcher, and instead of having libev call
		3899	your callback, you instead have it switch to that coroutine.
		3900
		3901	A coroutine might now wait for an event with a function called
		3902	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3903	matter when, or whether the watcher is active or not when this function is
		3904	called):
		3905
		3906	void
		3907	wait_for_event (ev_watcher *w)
		3908	{
		3909	ev_set_cb (w, current_coro);
		3910	switch_to (libev_coro);
		3911	}
		3912
		3913	That basically suspends the coroutine inside C<wait_for_event> and
		3914	continues the libev coroutine, which, when appropriate, switches back to
		3915	this or any other coroutine.
		3916
		3917	You can do similar tricks if you have, say, threads with an event queue -
		3918	instead of storing a coroutine, you store the queue object and instead of
		3919	switching to a coroutine, you push the watcher onto the queue and notify
		3920	any waiters.
		3921
		3922	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3923	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3924
		3925	// my_ev.h
		3926	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3927	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3928	#include "../libev/ev.h"
		3929
		3930	// my_ev.c
		3931	#define EV_H "my_ev.h"
		3932	#include "../libev/ev.c"
		3933
		3934	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3935	F<my_ev.c> into your project. When properly specifying include paths, you
		3936	can even use F<ev.h> as header file name directly.
3235		3937
3236		3938
3237	=head1 LIBEVENT EMULATION	3939	=head1 LIBEVENT EMULATION
3238		3940
3239	Libev offers a compatibility emulation layer for libevent. It cannot	3941	Libev offers a compatibility emulation layer for libevent. It cannot
3240	emulate the internals of libevent, so here are some usage hints:	3942	emulate the internals of libevent, so here are some usage hints:
3241		3943
3242	=over 4	3944	=over 4
		3945
		3946	=item * Only the libevent-1.4.1-beta API is being emulated.
		3947
		3948	This was the newest libevent version available when libev was implemented,
		3949	and is still mostly unchanged in 2010.
3243		3950
3244	=item * Use it by including <event.h>, as usual.	3951	=item * Use it by including <event.h>, as usual.
3245		3952
3246	=item * The following members are fully supported: ev_base, ev_callback,	3953	=item * The following members are fully supported: ev_base, ev_callback,
3247	ev_arg, ev_fd, ev_res, ev_events.	3954	ev_arg, ev_fd, ev_res, ev_events.
…		…
3253	=item * Priorities are not currently supported. Initialising priorities	3960	=item * Priorities are not currently supported. Initialising priorities
3254	will fail and all watchers will have the same priority, even though there	3961	will fail and all watchers will have the same priority, even though there
3255	is an ev_pri field.	3962	is an ev_pri field.
3256		3963
3257	=item * In libevent, the last base created gets the signals, in libev, the	3964	=item * In libevent, the last base created gets the signals, in libev, the
3258	first base created (== the default loop) gets the signals.	3965	base that registered the signal gets the signals.
3259		3966
3260	=item * Other members are not supported.	3967	=item * Other members are not supported.
3261		3968
3262	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3969	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3263	to use the libev header file and library.	3970	to use the libev header file and library.
3264		3971
3265	=back	3972	=back
3266		3973
3267	=head1 C++ SUPPORT	3974	=head1 C++ SUPPORT
		3975
		3976	=head2 C API
		3977
		3978	The normal C API should work fine when used from C++: both ev.h and the
		3979	libev sources can be compiled as C++. Therefore, code that uses the C API
		3980	will work fine.
		3981
		3982	Proper exception specifications might have to be added to callbacks passed
		3983	to libev: exceptions may be thrown only from watcher callbacks, all
		3984	other callbacks (allocator, syserr, loop acquire/release and periodic
		3985	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3986	()> specification. If you have code that needs to be compiled as both C
		3987	and C++ you can use the C<EV_THROW> macro for this:
		3988
		3989	static void
		3990	fatal_error (const char *msg) EV_THROW
		3991	{
		3992	perror (msg);
		3993	abort ();
		3994	}
		3995
		3996	...
		3997	ev_set_syserr_cb (fatal_error);
		3998
		3999	The only API functions that can currently throw exceptions are C<ev_run>,
		4000	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4001	because it runs cleanup watchers).
		4002
		4003	Throwing exceptions in watcher callbacks is only supported if libev itself
		4004	is compiled with a C++ compiler or your C and C++ environments allow
		4005	throwing exceptions through C libraries (most do).
		4006
		4007	=head2 C++ API
3268		4008
3269	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4009	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3270	you to use some convenience methods to start/stop watchers and also change	4010	you to use some convenience methods to start/stop watchers and also change
3271	the callback model to a model using method callbacks on objects.	4011	the callback model to a model using method callbacks on objects.
3272		4012
3273	To use it,	4013	To use it,
3274		4014
3275	#include <ev++.h>	4015	#include <ev++.h>
3276		4016
3277	This automatically includes F<ev.h> and puts all of its definitions (many	4017	This automatically includes F<ev.h> and puts all of its definitions (many
3278	of them macros) into the global namespace. All C++ specific things are	4018	of them macros) into the global namespace. All C++ specific things are
3279	put into the C<ev> namespace. It should support all the same embedding	4019	put into the C<ev> namespace. It should support all the same embedding
…		…
3282	Care has been taken to keep the overhead low. The only data member the C++	4022	Care has been taken to keep the overhead low. The only data member the C++
3283	classes add (compared to plain C-style watchers) is the event loop pointer	4023	classes add (compared to plain C-style watchers) is the event loop pointer
3284	that the watcher is associated with (or no additional members at all if	4024	that the watcher is associated with (or no additional members at all if
3285	you disable C<EV_MULTIPLICITY> when embedding libev).	4025	you disable C<EV_MULTIPLICITY> when embedding libev).
3286		4026
3287	Currently, functions, and static and non-static member functions can be	4027	Currently, functions, static and non-static member functions and classes
3288	used as callbacks. Other types should be easy to add as long as they only	4028	with C<operator ()> can be used as callbacks. Other types should be easy
3289	need one additional pointer for context. If you need support for other	4029	to add as long as they only need one additional pointer for context. If
3290	types of functors please contact the author (preferably after implementing	4030	you need support for other types of functors please contact the author
3291	it).	4031	(preferably after implementing it).
		4032
		4033	For all this to work, your C++ compiler either has to use the same calling
		4034	conventions as your C compiler (for static member functions), or you have
		4035	to embed libev and compile libev itself as C++.
3292		4036
3293	Here is a list of things available in the C<ev> namespace:	4037	Here is a list of things available in the C<ev> namespace:
3294		4038
3295	=over 4	4039	=over 4
3296		4040
…		…
3306	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4050	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3307		4051
3308	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4052	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3309	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4053	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3310	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4054	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3311	defines by many implementations.	4055	defined by many implementations.
3312		4056
3313	All of those classes have these methods:	4057	All of those classes have these methods:
3314		4058
3315	=over 4	4059	=over 4
3316		4060
…		…
3378	void operator() (ev::io &w, int revents)	4122	void operator() (ev::io &w, int revents)
3379	{	4123	{
3380	...	4124	...
3381	}	4125	}
3382	}	4126	}
3383		4127
3384	myfunctor f;	4128	myfunctor f;
3385		4129
3386	ev::io w;	4130	ev::io w;
3387	w.set (&f);	4131	w.set (&f);
3388		4132
…		…
3406	Associates a different C<struct ev_loop> with this watcher. You can only	4150	Associates a different C<struct ev_loop> with this watcher. You can only
3407	do this when the watcher is inactive (and not pending either).	4151	do this when the watcher is inactive (and not pending either).
3408		4152
3409	=item w->set ([arguments])	4153	=item w->set ([arguments])
3410		4154
3411	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4155	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3412	method or a suitable start method must be called at least once. Unlike the	4156	with the same arguments. Either this method or a suitable start method
3413	C counterpart, an active watcher gets automatically stopped and restarted	4157	must be called at least once. Unlike the C counterpart, an active watcher
3414	when reconfiguring it with this method.	4158	gets automatically stopped and restarted when reconfiguring it with this
		4159	method.
		4160
		4161	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4162	clashing with the C<set (loop)> method.
3415		4163
3416	=item w->start ()	4164	=item w->start ()
3417		4165
3418	Starts the watcher. Note that there is no C<loop> argument, as the	4166	Starts the watcher. Note that there is no C<loop> argument, as the
3419	constructor already stores the event loop.	4167	constructor already stores the event loop.
…		…
3449	watchers in the constructor.	4197	watchers in the constructor.
3450		4198
3451	class myclass	4199	class myclass
3452	{	4200	{
3453	ev::io io ; void io_cb (ev::io &w, int revents);	4201	ev::io io ; void io_cb (ev::io &w, int revents);
3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4202	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4203	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3456		4204
3457	myclass (int fd)	4205	myclass (int fd)
3458	{	4206	{
3459	io .set <myclass, &myclass::io_cb > (this);	4207	io .set <myclass, &myclass::io_cb > (this);
…		…
3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4258	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3511		4259
3512	=item D	4260	=item D
3513		4261
3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4262	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3515	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4263	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3516		4264
3517	=item Ocaml	4265	=item Ocaml
3518		4266
3519	Erkki Seppala has written Ocaml bindings for libev, to be found at	4267	Erkki Seppala has written Ocaml bindings for libev, to be found at
3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4268	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3523		4271
3524	Brian Maher has written a partial interface to libev for lua (at the	4272	Brian Maher has written a partial interface to libev for lua (at the
3525	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4273	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3526	L<http://github.com/brimworks/lua-ev>.	4274	L<http://github.com/brimworks/lua-ev>.
3527		4275
		4276	=item Javascript
		4277
		4278	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4279
		4280	=item Others
		4281
		4282	There are others, and I stopped counting.
		4283
3528	=back	4284	=back
3529		4285
3530		4286
3531	=head1 MACRO MAGIC	4287	=head1 MACRO MAGIC
3532		4288
…		…
3568	suitable for use with C<EV_A>.	4324	suitable for use with C<EV_A>.
3569		4325
3570	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4326	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3571		4327
3572	Similar to the other two macros, this gives you the value of the default	4328	Similar to the other two macros, this gives you the value of the default
3573	loop, if multiple loops are supported ("ev loop default").	4329	loop, if multiple loops are supported ("ev loop default"). The default loop
		4330	will be initialised if it isn't already initialised.
		4331
		4332	For non-multiplicity builds, these macros do nothing, so you always have
		4333	to initialise the loop somewhere.
3574		4334
3575	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4335	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3576		4336
3577	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4337	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3578	default loop has been initialised (C<UC> == unchecked). Their behaviour	4338	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3645	ev_vars.h	4405	ev_vars.h
3646	ev_wrap.h	4406	ev_wrap.h
3647		4407
3648	ev_win32.c required on win32 platforms only	4408	ev_win32.c required on win32 platforms only
3649		4409
3650	ev_select.c only when select backend is enabled (which is enabled by default)	4410	ev_select.c only when select backend is enabled
3651	ev_poll.c only when poll backend is enabled (disabled by default)	4411	ev_poll.c only when poll backend is enabled
3652	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4412	ev_epoll.c only when the epoll backend is enabled
3653	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4413	ev_kqueue.c only when the kqueue backend is enabled
3654	ev_port.c only when the solaris port backend is enabled (disabled by default)	4414	ev_port.c only when the solaris port backend is enabled
3655		4415
3656	F<ev.c> includes the backend files directly when enabled, so you only need	4416	F<ev.c> includes the backend files directly when enabled, so you only need
3657	to compile this single file.	4417	to compile this single file.
3658		4418
3659	=head3 LIBEVENT COMPATIBILITY API	4419	=head3 LIBEVENT COMPATIBILITY API
…		…
3723	supported). It will also not define any of the structs usually found in	4483	supported). It will also not define any of the structs usually found in
3724	F<event.h> that are not directly supported by the libev core alone.	4484	F<event.h> that are not directly supported by the libev core alone.
3725		4485
3726	In standalone mode, libev will still try to automatically deduce the	4486	In standalone mode, libev will still try to automatically deduce the
3727	configuration, but has to be more conservative.	4487	configuration, but has to be more conservative.
		4488
		4489	=item EV_USE_FLOOR
		4490
		4491	If defined to be C<1>, libev will use the C<floor ()> function for its
		4492	periodic reschedule calculations, otherwise libev will fall back on a
		4493	portable (slower) implementation. If you enable this, you usually have to
		4494	link against libm or something equivalent. Enabling this when the C<floor>
		4495	function is not available will fail, so the safe default is to not enable
		4496	this.
3728		4497
3729	=item EV_USE_MONOTONIC	4498	=item EV_USE_MONOTONIC
3730		4499
3731	If defined to be C<1>, libev will try to detect the availability of the	4500	If defined to be C<1>, libev will try to detect the availability of the
3732	monotonic clock option at both compile time and runtime. Otherwise no	4501	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3817		4586
3818	If programs implement their own fd to handle mapping on win32, then this	4587	If programs implement their own fd to handle mapping on win32, then this
3819	macro can be used to override the C<close> function, useful to unregister	4588	macro can be used to override the C<close> function, useful to unregister
3820	file descriptors again. Note that the replacement function has to close	4589	file descriptors again. Note that the replacement function has to close
3821	the underlying OS handle.	4590	the underlying OS handle.
		4591
		4592	=item EV_USE_WSASOCKET
		4593
		4594	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4595	communication socket, which works better in some environments. Otherwise,
		4596	the normal C<socket> function will be used, which works better in other
		4597	environments.
3822		4598
3823	=item EV_USE_POLL	4599	=item EV_USE_POLL
3824		4600
3825	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4601	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3826	backend. Otherwise it will be enabled on non-win32 platforms. It	4602	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3862	If defined to be C<1>, libev will compile in support for the Linux inotify	4638	If defined to be C<1>, libev will compile in support for the Linux inotify
3863	interface to speed up C<ev_stat> watchers. Its actual availability will	4639	interface to speed up C<ev_stat> watchers. Its actual availability will
3864	be detected at runtime. If undefined, it will be enabled if the headers	4640	be detected at runtime. If undefined, it will be enabled if the headers
3865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4641	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3866		4642
		4643	=item EV_NO_SMP
		4644
		4645	If defined to be C<1>, libev will assume that memory is always coherent
		4646	between threads, that is, threads can be used, but threads never run on
		4647	different cpus (or different cpu cores). This reduces dependencies
		4648	and makes libev faster.
		4649
		4650	=item EV_NO_THREADS
		4651
		4652	If defined to be C<1>, libev will assume that it will never be called from
		4653	different threads (that includes signal handlers), which is a stronger
		4654	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4655	libev faster.
		4656
3867	=item EV_ATOMIC_T	4657	=item EV_ATOMIC_T
3868		4658
3869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4659	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3870	access is atomic with respect to other threads or signal contexts. No such	4660	access is atomic with respect to other threads or signal contexts. No
3871	type is easily found in the C language, so you can provide your own type	4661	such type is easily found in the C language, so you can provide your own
3872	that you know is safe for your purposes. It is used both for signal handler "locking"	4662	type that you know is safe for your purposes. It is used both for signal
3873	as well as for signal and thread safety in C<ev_async> watchers.	4663	handler "locking" as well as for signal and thread safety in C<ev_async>
		4664	watchers.
3874		4665
3875	In the absence of this define, libev will use C<sig_atomic_t volatile>	4666	In the absence of this define, libev will use C<sig_atomic_t volatile>
3876	(from F<signal.h>), which is usually good enough on most platforms.	4667	(from F<signal.h>), which is usually good enough on most platforms.
3877		4668
3878	=item EV_H (h)	4669	=item EV_H (h)
…		…
3905	will have the C<struct ev_loop *> as first argument, and you can create	4696	will have the C<struct ev_loop *> as first argument, and you can create
3906	additional independent event loops. Otherwise there will be no support	4697	additional independent event loops. Otherwise there will be no support
3907	for multiple event loops and there is no first event loop pointer	4698	for multiple event loops and there is no first event loop pointer
3908	argument. Instead, all functions act on the single default loop.	4699	argument. Instead, all functions act on the single default loop.
3909		4700
		4701	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4702	default loop when multiplicity is switched off - you always have to
		4703	initialise the loop manually in this case.
		4704
3910	=item EV_MINPRI	4705	=item EV_MINPRI
3911		4706
3912	=item EV_MAXPRI	4707	=item EV_MAXPRI
3913		4708
3914	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4709	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3950	#define EV_USE_POLL 1	4745	#define EV_USE_POLL 1
3951	#define EV_CHILD_ENABLE 1	4746	#define EV_CHILD_ENABLE 1
3952	#define EV_ASYNC_ENABLE 1	4747	#define EV_ASYNC_ENABLE 1
3953		4748
3954	The actual value is a bitset, it can be a combination of the following	4749	The actual value is a bitset, it can be a combination of the following
3955	values:	4750	values (by default, all of these are enabled):
3956		4751
3957	=over 4	4752	=over 4
3958		4753
3959	=item C<1> - faster/larger code	4754	=item C<1> - faster/larger code
3960		4755
…		…
3964	code size by roughly 30% on amd64).	4759	code size by roughly 30% on amd64).
3965		4760
3966	When optimising for size, use of compiler flags such as C<-Os> with	4761	When optimising for size, use of compiler flags such as C<-Os> with
3967	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4762	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3968	assertions.	4763	assertions.
		4764
		4765	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4766	(e.g. gcc with C<-Os>).
3969		4767
3970	=item C<2> - faster/larger data structures	4768	=item C<2> - faster/larger data structures
3971		4769
3972	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4770	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3973	hash table sizes and so on. This will usually further increase code size	4771	hash table sizes and so on. This will usually further increase code size
3974	and can additionally have an effect on the size of data structures at	4772	and can additionally have an effect on the size of data structures at
3975	runtime.	4773	runtime.
3976		4774
		4775	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4776	(e.g. gcc with C<-Os>).
		4777
3977	=item C<4> - full API configuration	4778	=item C<4> - full API configuration
3978		4779
3979	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4780	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3980	enables multiplicity (C<EV_MULTIPLICITY>=1).	4781	enables multiplicity (C<EV_MULTIPLICITY>=1).
3981		4782
…		…
4011		4812
4012	With an intelligent-enough linker (gcc+binutils are intelligent enough	4813	With an intelligent-enough linker (gcc+binutils are intelligent enough
4013	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4814	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4014	your program might be left out as well - a binary starting a timer and an	4815	your program might be left out as well - a binary starting a timer and an
4015	I/O watcher then might come out at only 5Kb.	4816	I/O watcher then might come out at only 5Kb.
		4817
		4818	=item EV_API_STATIC
		4819
		4820	If this symbol is defined (by default it is not), then all identifiers
		4821	will have static linkage. This means that libev will not export any
		4822	identifiers, and you cannot link against libev anymore. This can be useful
		4823	when you embed libev, only want to use libev functions in a single file,
		4824	and do not want its identifiers to be visible.
		4825
		4826	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4827	wants to use libev.
		4828
		4829	This option only works when libev is compiled with a C compiler, as C++
		4830	doesn't support the required declaration syntax.
4016		4831
4017	=item EV_AVOID_STDIO	4832	=item EV_AVOID_STDIO
4018		4833
4019	If this is set to C<1> at compiletime, then libev will avoid using stdio	4834	If this is set to C<1> at compiletime, then libev will avoid using stdio
4020	functions (printf, scanf, perror etc.). This will increase the code size	4835	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4164	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4979	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4165		4980
4166	#include "ev_cpp.h"	4981	#include "ev_cpp.h"
4167	#include "ev.c"	4982	#include "ev.c"
4168		4983
4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4984	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4170		4985
4171	=head2 THREADS AND COROUTINES	4986	=head2 THREADS AND COROUTINES
4172		4987
4173	=head3 THREADS	4988	=head3 THREADS
4174		4989
…		…
4225	default loop and triggering an C<ev_async> watcher from the default loop	5040	default loop and triggering an C<ev_async> watcher from the default loop
4226	watcher callback into the event loop interested in the signal.	5041	watcher callback into the event loop interested in the signal.
4227		5042
4228	=back	5043	=back
4229		5044
4230	=head4 THREAD LOCKING EXAMPLE	5045	See also L</THREAD LOCKING EXAMPLE>.
4231
4232	Here is a fictitious example of how to run an event loop in a different
4233	thread than where callbacks are being invoked and watchers are
4234	created/added/removed.
4235
4236	For a real-world example, see the C<EV::Loop::Async> perl module,
4237	which uses exactly this technique (which is suited for many high-level
4238	languages).
4239
4240	The example uses a pthread mutex to protect the loop data, a condition
4241	variable to wait for callback invocations, an async watcher to notify the
4242	event loop thread and an unspecified mechanism to wake up the main thread.
4243
4244	First, you need to associate some data with the event loop:
4245
4246	typedef struct {
4247	mutex_t lock; /* global loop lock */
4248	ev_async async_w;
4249	thread_t tid;
4250	cond_t invoke_cv;
4251	} userdata;
4252
4253	void prepare_loop (EV_P)
4254	{
4255	// for simplicity, we use a static userdata struct.
4256	static userdata u;
4257
4258	ev_async_init (&u->async_w, async_cb);
4259	ev_async_start (EV_A_ &u->async_w);
4260
4261	pthread_mutex_init (&u->lock, 0);
4262	pthread_cond_init (&u->invoke_cv, 0);
4263
4264	// now associate this with the loop
4265	ev_set_userdata (EV_A_ u);
4266	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4267	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4268
4269	// then create the thread running ev_loop
4270	pthread_create (&u->tid, 0, l_run, EV_A);
4271	}
4272
4273	The callback for the C<ev_async> watcher does nothing: the watcher is used
4274	solely to wake up the event loop so it takes notice of any new watchers
4275	that might have been added:
4276
4277	static void
4278	async_cb (EV_P_ ev_async *w, int revents)
4279	{
4280	// just used for the side effects
4281	}
4282
4283	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4284	protecting the loop data, respectively.
4285
4286	static void
4287	l_release (EV_P)
4288	{
4289	userdata *u = ev_userdata (EV_A);
4290	pthread_mutex_unlock (&u->lock);
4291	}
4292
4293	static void
4294	l_acquire (EV_P)
4295	{
4296	userdata *u = ev_userdata (EV_A);
4297	pthread_mutex_lock (&u->lock);
4298	}
4299
4300	The event loop thread first acquires the mutex, and then jumps straight
4301	into C<ev_run>:
4302
4303	void *
4304	l_run (void *thr_arg)
4305	{
4306	struct ev_loop loop = (struct ev_loop )thr_arg;
4307
4308	l_acquire (EV_A);
4309	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4310	ev_run (EV_A_ 0);
4311	l_release (EV_A);
4312
4313	return 0;
4314	}
4315
4316	Instead of invoking all pending watchers, the C<l_invoke> callback will
4317	signal the main thread via some unspecified mechanism (signals? pipe
4318	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4319	have been called (in a while loop because a) spurious wakeups are possible
4320	and b) skipping inter-thread-communication when there are no pending
4321	watchers is very beneficial):
4322
4323	static void
4324	l_invoke (EV_P)
4325	{
4326	userdata *u = ev_userdata (EV_A);
4327
4328	while (ev_pending_count (EV_A))
4329	{
4330	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4331	pthread_cond_wait (&u->invoke_cv, &u->lock);
4332	}
4333	}
4334
4335	Now, whenever the main thread gets told to invoke pending watchers, it
4336	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4337	thread to continue:
4338
4339	static void
4340	real_invoke_pending (EV_P)
4341	{
4342	userdata *u = ev_userdata (EV_A);
4343
4344	pthread_mutex_lock (&u->lock);
4345	ev_invoke_pending (EV_A);
4346	pthread_cond_signal (&u->invoke_cv);
4347	pthread_mutex_unlock (&u->lock);
4348	}
4349
4350	Whenever you want to start/stop a watcher or do other modifications to an
4351	event loop, you will now have to lock:
4352
4353	ev_timer timeout_watcher;
4354	userdata *u = ev_userdata (EV_A);
4355
4356	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4357
4358	pthread_mutex_lock (&u->lock);
4359	ev_timer_start (EV_A_ &timeout_watcher);
4360	ev_async_send (EV_A_ &u->async_w);
4361	pthread_mutex_unlock (&u->lock);
4362
4363	Note that sending the C<ev_async> watcher is required because otherwise
4364	an event loop currently blocking in the kernel will have no knowledge
4365	about the newly added timer. By waking up the loop it will pick up any new
4366	watchers in the next event loop iteration.
4367		5046
4368	=head3 COROUTINES	5047	=head3 COROUTINES
4369		5048
4370	Libev is very accommodating to coroutines ("cooperative threads"):	5049	Libev is very accommodating to coroutines ("cooperative threads"):
4371	libev fully supports nesting calls to its functions from different	5050	libev fully supports nesting calls to its functions from different
…		…
4467	=head3 C<kqueue> is buggy	5146	=head3 C<kqueue> is buggy
4468		5147
4469	The kqueue syscall is broken in all known versions - most versions support	5148	The kqueue syscall is broken in all known versions - most versions support
4470	only sockets, many support pipes.	5149	only sockets, many support pipes.
4471		5150
4472	Libev tries to work around this by not using C<kqueue> by default on	5151	Libev tries to work around this by not using C<kqueue> by default on this
4473	this rotten platform, but of course you can still ask for it when creating	5152	rotten platform, but of course you can still ask for it when creating a
4474	a loop.	5153	loop - embedding a socket-only kqueue loop into a select-based one is
		5154	probably going to work well.
4475		5155
4476	=head3 C<poll> is buggy	5156	=head3 C<poll> is buggy
4477		5157
4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5158	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4479	implementation by something calling C<kqueue> internally around the 10.5.6	5159	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4498		5178
4499	=head3 C<errno> reentrancy	5179	=head3 C<errno> reentrancy
4500		5180
4501	The default compile environment on Solaris is unfortunately so	5181	The default compile environment on Solaris is unfortunately so
4502	thread-unsafe that you can't even use components/libraries compiled	5182	thread-unsafe that you can't even use components/libraries compiled
4503	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5183	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4504	isn't defined by default.	5184	defined by default. A valid, if stupid, implementation choice.
4505		5185
4506	If you want to use libev in threaded environments you have to make sure	5186	If you want to use libev in threaded environments you have to make sure
4507	it's compiled with C<_REENTRANT> defined.	5187	it's compiled with C<_REENTRANT> defined.
4508		5188
4509	=head3 Event port backend	5189	=head3 Event port backend
4510		5190
4511	The scalable event interface for Solaris is called "event ports". Unfortunately,	5191	The scalable event interface for Solaris is called "event
4512	this mechanism is very buggy. If you run into high CPU usage, your program	5192	ports". Unfortunately, this mechanism is very buggy in all major
		5193	releases. If you run into high CPU usage, your program freezes or you get
4513	freezes or you get a large number of spurious wakeups, make sure you have	5194	a large number of spurious wakeups, make sure you have all the relevant
4514	all the relevant and latest kernel patches applied. No, I don't know which	5195	and latest kernel patches applied. No, I don't know which ones, but there
4515	ones, but there are multiple ones.	5196	are multiple ones to apply, and afterwards, event ports actually work
		5197	great.
4516		5198
4517	If you can't get it to work, you can try running the program by setting	5199	If you can't get it to work, you can try running the program by setting
4518	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	5200	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4519	C<select> backends.	5201	C<select> backends.
4520		5202
4521	=head2 AIX POLL BUG	5203	=head2 AIX POLL BUG
4522		5204
4523	AIX unfortunately has a broken C<poll.h> header. Libev works around	5205	AIX unfortunately has a broken C<poll.h> header. Libev works around
4524	this by trying to avoid the poll backend altogether (i.e. it's not even	5206	this by trying to avoid the poll backend altogether (i.e. it's not even
4525	compiled in), which normally isn't a big problem as C<select> works fine	5207	compiled in), which normally isn't a big problem as C<select> works fine
4526	with large bitsets, and AIX is dead anyway.	5208	with large bitsets on AIX, and AIX is dead anyway.
4527		5209
4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5210	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4529		5211
4530	=head3 General issues	5212	=head3 General issues
4531		5213
…		…
4533	requires, and its I/O model is fundamentally incompatible with the POSIX	5215	requires, and its I/O model is fundamentally incompatible with the POSIX
4534	model. Libev still offers limited functionality on this platform in	5216	model. Libev still offers limited functionality on this platform in
4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5217	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4536	descriptors. This only applies when using Win32 natively, not when using	5218	descriptors. This only applies when using Win32 natively, not when using
4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5219	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4538	as every compielr comes with a slightly differently broken/incompatible	5220	as every compiler comes with a slightly differently broken/incompatible
4539	environment.	5221	environment.
4540		5222
4541	Lifting these limitations would basically require the full	5223	Lifting these limitations would basically require the full
4542	re-implementation of the I/O system. If you are into this kind of thing,	5224	re-implementation of the I/O system. If you are into this kind of thing,
4543	then note that glib does exactly that for you in a very portable way (note	5225	then note that glib does exactly that for you in a very portable way (note
…		…
4637	structure (guaranteed by POSIX but not by ISO C for example), but it also	5319	structure (guaranteed by POSIX but not by ISO C for example), but it also
4638	assumes that the same (machine) code can be used to call any watcher	5320	assumes that the same (machine) code can be used to call any watcher
4639	callback: The watcher callbacks have different type signatures, but libev	5321	callback: The watcher callbacks have different type signatures, but libev
4640	calls them using an C<ev_watcher *> internally.	5322	calls them using an C<ev_watcher *> internally.
4641		5323
		5324	=item null pointers and integer zero are represented by 0 bytes
		5325
		5326	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5327	relies on this setting pointers and integers to null.
		5328
		5329	=item pointer accesses must be thread-atomic
		5330
		5331	Accessing a pointer value must be atomic, it must both be readable and
		5332	writable in one piece - this is the case on all current architectures.
		5333
4642	=item C<sig_atomic_t volatile> must be thread-atomic as well	5334	=item C<sig_atomic_t volatile> must be thread-atomic as well
4643		5335
4644	The type C<sig_atomic_t volatile> (or whatever is defined as	5336	The type C<sig_atomic_t volatile> (or whatever is defined as
4645	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5337	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4646	threads. This is not part of the specification for C<sig_atomic_t>, but is	5338	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4654	thread" or will block signals process-wide, both behaviours would	5346	thread" or will block signals process-wide, both behaviours would
4655	be compatible with libev. Interaction between C<sigprocmask> and	5347	be compatible with libev. Interaction between C<sigprocmask> and
4656	C<pthread_sigmask> could complicate things, however.	5348	C<pthread_sigmask> could complicate things, however.
4657		5349
4658	The most portable way to handle signals is to block signals in all threads	5350	The most portable way to handle signals is to block signals in all threads
4659	except the initial one, and run the default loop in the initial thread as	5351	except the initial one, and run the signal handling loop in the initial
4660	well.	5352	thread as well.
4661		5353
4662	=item C<long> must be large enough for common memory allocation sizes	5354	=item C<long> must be large enough for common memory allocation sizes
4663		5355
4664	To improve portability and simplify its API, libev uses C<long> internally	5356	To improve portability and simplify its API, libev uses C<long> internally
4665	instead of C<size_t> when allocating its data structures. On non-POSIX	5357	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4671		5363
4672	The type C<double> is used to represent timestamps. It is required to	5364	The type C<double> is used to represent timestamps. It is required to
4673	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5365	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4674	good enough for at least into the year 4000 with millisecond accuracy	5366	good enough for at least into the year 4000 with millisecond accuracy
4675	(the design goal for libev). This requirement is overfulfilled by	5367	(the design goal for libev). This requirement is overfulfilled by
4676	implementations using IEEE 754, which is basically all existing ones. With	5368	implementations using IEEE 754, which is basically all existing ones.
		5369
4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5370	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5371	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5372	is either obsolete or somebody patched it to use C<long double> or
		5373	something like that, just kidding).
4678		5374
4679	=back	5375	=back
4680		5376
4681	If you know of other additional requirements drop me a note.	5377	If you know of other additional requirements drop me a note.
4682		5378
…		…
4744	=item Processing ev_async_send: O(number_of_async_watchers)	5440	=item Processing ev_async_send: O(number_of_async_watchers)
4745		5441
4746	=item Processing signals: O(max_signal_number)	5442	=item Processing signals: O(max_signal_number)
4747		5443
4748	Sending involves a system call I<iff> there were no other C<ev_async_send>	5444	Sending involves a system call I<iff> there were no other C<ev_async_send>
4749	calls in the current loop iteration. Checking for async and signal events	5445	calls in the current loop iteration and the loop is currently
		5446	blocked. Checking for async and signal events involves iterating over all
4750	involves iterating over all running async watchers or all signal numbers.	5447	running async watchers or all signal numbers.
4751		5448
4752	=back	5449	=back
4753		5450
4754		5451
4755	=head1 PORTING FROM LIBEV 3.X TO 4.X	5452	=head1 PORTING FROM LIBEV 3.X TO 4.X
4756		5453
4757	The major version 4 introduced some minor incompatible changes to the API.	5454	The major version 4 introduced some incompatible changes to the API.
4758		5455
4759	At the moment, the C<ev.h> header file tries to implement superficial	5456	At the moment, the C<ev.h> header file provides compatibility definitions
4760	compatibility, so most programs should still compile. Those might be	5457	for all changes, so most programs should still compile. The compatibility
4761	removed in later versions of libev, so better update early than late.	5458	layer might be removed in later versions of libev, so better update to the
		5459	new API early than late.
4762		5460
4763	=over 4	5461	=over 4
		5462
		5463	=item C<EV_COMPAT3> backwards compatibility mechanism
		5464
		5465	The backward compatibility mechanism can be controlled by
		5466	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5467	section.
		5468
		5469	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5470
		5471	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5472
		5473	ev_loop_destroy (EV_DEFAULT_UC);
		5474	ev_loop_fork (EV_DEFAULT);
4764		5475
4765	=item function/symbol renames	5476	=item function/symbol renames
4766		5477
4767	A number of functions and symbols have been renamed:	5478	A number of functions and symbols have been renamed:
4768		5479
…		…
4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5498	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4788	as all other watcher types. Note that C<ev_loop_fork> is still called	5499	as all other watcher types. Note that C<ev_loop_fork> is still called
4789	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5500	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4790	typedef.	5501	typedef.
4791		5502
4792	=item C<EV_COMPAT3> backwards compatibility mechanism
4793
4794	The backward compatibility mechanism can be controlled by
4795	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4796	section.
4797
4798	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5503	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4799		5504
4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5505	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5506	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4802	and work, but the library code will of course be larger.	5507	and work, but the library code will of course be larger.
…		…
4808		5513
4809	=over 4	5514	=over 4
4810		5515
4811	=item active	5516	=item active
4812		5517
4813	A watcher is active as long as it has been started (has been attached to	5518	A watcher is active as long as it has been started and not yet stopped.
4814	an event loop) but not yet stopped (disassociated from the event loop).	5519	See L</WATCHER STATES> for details.
4815		5520
4816	=item application	5521	=item application
4817		5522
4818	In this document, an application is whatever is using libev.	5523	In this document, an application is whatever is using libev.
		5524
		5525	=item backend
		5526
		5527	The part of the code dealing with the operating system interfaces.
4819		5528
4820	=item callback	5529	=item callback
4821		5530
4822	The address of a function that is called when some event has been	5531	The address of a function that is called when some event has been
4823	detected. Callbacks are being passed the event loop, the watcher that	5532	detected. Callbacks are being passed the event loop, the watcher that
4824	received the event, and the actual event bitset.	5533	received the event, and the actual event bitset.
4825		5534
4826	=item callback invocation	5535	=item callback/watcher invocation
4827		5536
4828	The act of calling the callback associated with a watcher.	5537	The act of calling the callback associated with a watcher.
4829		5538
4830	=item event	5539	=item event
4831		5540
…		…
4850	The model used to describe how an event loop handles and processes	5559	The model used to describe how an event loop handles and processes
4851	watchers and events.	5560	watchers and events.
4852		5561
4853	=item pending	5562	=item pending
4854		5563
4855	A watcher is pending as soon as the corresponding event has been detected,	5564	A watcher is pending as soon as the corresponding event has been
4856	and stops being pending as soon as the watcher will be invoked or its	5565	detected. See L</WATCHER STATES> for details.
4857	pending status is explicitly cleared by the application.
4858
4859	A watcher can be pending, but not active. Stopping a watcher also clears
4860	its pending status.
4861		5566
4862	=item real time	5567	=item real time
4863		5568
4864	The physical time that is observed. It is apparently strictly monotonic :)	5569	The physical time that is observed. It is apparently strictly monotonic :)
4865		5570
4866	=item wall-clock time	5571	=item wall-clock time
4867		5572
4868	The time and date as shown on clocks. Unlike real time, it can actually	5573	The time and date as shown on clocks. Unlike real time, it can actually
4869	be wrong and jump forwards and backwards, e.g. when the you adjust your	5574	be wrong and jump forwards and backwards, e.g. when you adjust your
4870	clock.	5575	clock.
4871		5576
4872	=item watcher	5577	=item watcher
4873		5578
4874	A data structure that describes interest in certain events. Watchers need	5579	A data structure that describes interest in certain events. Watchers need
4875	to be started (attached to an event loop) before they can receive events.	5580	to be started (attached to an event loop) before they can receive events.
4876		5581
4877	=item watcher invocation
4878
4879	The act of calling the callback associated with a watcher.
4880
4881	=back	5582	=back
4882		5583
4883	=head1 AUTHOR	5584	=head1 AUTHOR
4884		5585
4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5586	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5587	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4886		5588

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Comparing libev/ev.pod (file contents): Revision 1.310 by root, Thu Oct 21 12:32:47 2010 UTC vs. Revision 1.444 by root, Mon Oct 29 00:00:22 2018 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.310 by root, Thu Oct 21 12:32:47 2010 UTC vs.
Revision 1.444 by root, Mon Oct 29 00:00:22 2018 UTC