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Revision 1.426 by root, Sat Feb 23 23:06:40 2013 UTC

…		…
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_run (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familiarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
124	this argument.	132	this argument.
125		133
126	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
127		135
128	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	138	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	139	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	140	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.	141	any calculations on it, you should treat it as some floating point value.
134		142
…		…
165		173
166	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
167		175
168	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
171		180
172	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
173		182
174	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
176	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
177		192
178	=item int ev_version_major ()	193	=item int ev_version_major ()
179		194
180	=item int ev_version_minor ()	195	=item int ev_version_minor ()
181		196
…		…
192	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	209	not a problem.
195		210
196	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
198		214
199	assert (("libev version mismatch",	215	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
202		218
…		…
213	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
215		231
216	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
217		233
218	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
224		241
225	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
226		243
227	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	245	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	246	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
232		249
233	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
234		251
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		253
237	Sets the allocation function to use (the prototype is similar - the	254	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	255	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	256	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	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	283	}
267		284
268	...	285	...
269	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
270		287
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		289
273	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	292	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	293	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	305	}
289		306
290	...	307	...
291	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
292		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
293	=back	323	=back
294		324
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		326
297	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	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	328	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).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
300		330
301	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
303	which do not.	333	do not.
304		334
305	=over 4	335	=over 4
306		336
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		338
309	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
313		349
314	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
315	function.	351	function (or via the C<EV_DEFAULT> macro).
316		352
317	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
320		357
321	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
327		382
328	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		385
331	The following flags are supported:	386	The following flags are supported:
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	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	434	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	435	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	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	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	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	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),	496	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).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	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	511	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	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
447		526
448	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
488		567
489	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
490	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
491	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
493	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
495	cases	574	drops fds silently in similarly hard-to-detect cases.
496		575
497	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
498		577
499	While nominally embeddable in other event loops, this doesn't work	578	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	579	everywhere, so you might need to test for this. And since it is broken
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		597
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
521		600
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	601	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	602	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	604	might perform better.
530		605
531	On the positive side, with the exception of the spurious readiness	606	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	607	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
535		620
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
538		623
539	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
540		625
541	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		629
545	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		639
547	=back	640	=back
548		641
549	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	645	()> will be tried.
553		646
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.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop (frees all memory and kernel state etc.). None	660	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	661	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	662	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,	663	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	664	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).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
594		667
595	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
598		671
599	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
603		680
604	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
605		682
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
611	This function sets a flag that causes subsequent C<ev_run> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
612	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
613	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
614	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
615	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_run> iteration.
617		688
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	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	690	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	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	692	during fork.
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	697	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	698	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	699	costly reset of the backend).
629		700
630	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
631	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
634	pthread_atfork (0, 0, ev_default_fork);	714	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		715
643	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
644		717
645	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	719	otherwise.
…		…
657	prepare and check phases.	730	prepare and check phases.
658		731
659	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
660		733
661	Returns the number of times C<ev_run> was entered minus the number of	734	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.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
663		736
664	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	739	in which case it is higher.
667		740
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	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	742	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
671		745
672	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
673		747
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	749	use.
…		…
690		764
691	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
692	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
693	the current time is a good idea.	767	the current time is a good idea.
694		768
695	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
696		770
697	=item ev_suspend (loop)	771	=item ev_suspend (loop)
698		772
699	=item ev_resume (loop)	773	=item ev_resume (loop)
700		774
…		…
718	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
719		793
720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
721	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
722		796
723	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
724		798
725	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
726	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
727	handling events. It will ask the operating system for any new events, call	801	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	802	the watcher callbacks, and then repeat the whole process indefinitely: This
729	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
730		804
731	If the flags argument is specified as C<0>, it will keep handling events	805	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	806	until either no event watchers are active anymore or C<ev_break> was
733	called.	807	called.
		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
734		812
735	Please note that an explicit C<ev_break> is usually better than	813	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	814	relying on all watchers to be stopped when deciding when a program has
737	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	818	beauty.
741		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	825	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	826	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	827	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	828	iteration of the loop. This is sometimes useful to poll and handle new
746	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
755	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
756	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
758	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
759		842
760	Here are the gory details of what C<ev_run> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
761		846
762	- Increment loop depth.	847	- Increment loop depth.
763	- Reset the ev_break status.	848	- Reset the ev_break status.
764	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
765	LOOP:	850	LOOP:
…		…
798	anymore.	883	anymore.
799		884
800	... queue jobs here, make sure they register event watchers as long	885	... 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..)	886	... as they still have work to do (even an idle watcher will do..)
802	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
803	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
804		889
805	=item ev_break (loop, how)	890	=item ev_break (loop, how)
806		891
807	Can be used to make a call to C<ev_run> return early (but only after it	892	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	893	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	894	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.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		896
812	This "unloop state" will be cleared when entering C<ev_run> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
813		898
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
815		901
816	=item ev_ref (loop)	902	=item ev_ref (loop)
817		903
818	=item ev_unref (loop)	904	=item ev_unref (loop)
819		905
…		…
840	running when nothing else is active.	926	running when nothing else is active.
841		927
842	ev_signal exitsig;	928	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	931	ev_unref (loop);
846		932
847	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
848		934
849	ev_ref (loop);	935	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
870	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
871		957
872	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
873	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
875	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
876	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
877	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
878	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
879		966
880	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
881	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
882	latency/jitter/inexactness (the watcher callback will be called	969	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	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
908		995
909	=item ev_invoke_pending (loop)	996	=item ev_invoke_pending (loop)
910		997
911	This call will simply invoke all pending watchers while resetting their	998	This call will simply invoke all pending watchers while resetting their
912	pending state. Normally, C<ev_run> does this automatically when required,	999	pending state. Normally, C<ev_run> does this automatically when required,
913	but when overriding the invoke callback this call comes handy.	1000	but when overriding the invoke callback this call comes handy. This
		1001	function can be invoked from a watcher - this can be useful for example
		1002	when you want to do some lengthy calculation and want to pass further
		1003	event handling to another thread (you still have to make sure only one
		1004	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
914		1005
915	=item int ev_pending_count (loop)	1006	=item int ev_pending_count (loop)
916		1007
917	Returns the number of pending watchers - zero indicates that no watchers	1008	Returns the number of pending watchers - zero indicates that no watchers
918	are pending.	1009	are pending.
…		…
925	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
926		1017
927	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
928	callback.	1019	callback.
929		1020
930	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
931		1022
932	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
933	can be done relatively simply by putting mutex_lock/unlock calls around	1024	can be done relatively simply by putting mutex_lock/unlock calls around
934	each call to a libev function.	1025	each call to a libev function.
935		1026
936	However, C<ev_run> can run an indefinite time, so it is not feasible	1027	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	1028	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	1029	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.	1030	I<release> and I<acquire> callbacks on the loop.
940		1031
941	When set, then C<release> will be called just before the thread is	1032	When set, then C<release> will be called just before the thread is
942	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
943	afterwards.	1034	afterwards.
…		…
958	See also the locking example in the C<THREADS> section later in this	1049	See also the locking example in the C<THREADS> section later in this
959	document.	1050	document.
960		1051
961	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
962		1053
963	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
964		1055
965	Set and retrieve a single C<void *> associated with a loop. When	1056	Set and retrieve a single C<void *> associated with a loop. When
966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1057	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
967	C<0.>	1058	C<0>.
968		1059
969	These two functions can be used to associate arbitrary data with a loop,	1060	These two functions can be used to associate arbitrary data with a loop,
970	and are intended solely for the C<invoke_pending_cb>, C<release> and	1061	and are intended solely for the C<invoke_pending_cb>, C<release> and
971	C<acquire> callbacks described above, but of course can be (ab-)used for	1062	C<acquire> callbacks described above, but of course can be (ab-)used for
972	any other purpose as well.	1063	any other purpose as well.
…		…
990		1081
991	In the following description, uppercase C<TYPE> in names stands for the	1082	In the following description, uppercase C<TYPE> in names stands for the
992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1083	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
993	watchers and C<ev_io_start> for I/O watchers.	1084	watchers and C<ev_io_start> for I/O watchers.
994		1085
995	A watcher is a structure that you create and register to record your	1086	A watcher is an opaque structure that you allocate and register to record
996	interest in some event. For instance, if you want to wait for STDIN to	1087	your interest in some event. To make a concrete example, imagine you want
997	become readable, you would create an C<ev_io> watcher for that:	1088	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1089	for that:
998		1090
999	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1091	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
1000	{	1092	{
1001	ev_io_stop (w);	1093	ev_io_stop (w);
1002	ev_break (loop, EVBREAK_ALL);	1094	ev_break (loop, EVBREAK_ALL);
…		…
1017	stack).	1109	stack).
1018		1110
1019	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1111	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1020	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1112	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1021		1113
1022	Each watcher structure must be initialised by a call to C<ev_init	1114	Each watcher structure must be initialised by a call to C<ev_init (watcher
1023	(watcher *, callback)>, which expects a callback to be provided. This	1115	*, 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	1116	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	1117	time the event loop detects that the file descriptor given is readable
1026	is readable and/or writable).	1118	and/or writable).
1027		1119
1028	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1120	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1029	macro to configure it, with arguments specific to the watcher type. There	1121	macro to configure it, with arguments specific to the watcher type. There
1030	is also a macro to combine initialisation and setting in one call: C<<	1122	is also a macro to combine initialisation and setting in one call: C<<
1031	ev_TYPE_init (watcher *, callback, ...) >>.	1123	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1082		1174
1083	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1084		1176
1085	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1086		1178
1087	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1179	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	1180	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	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1090	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1091	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1092	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1093	C<ev_run> from blocking).	1190	blocking).
1094		1191
1095	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1096		1193
1097	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1098		1195
1099	=item C<EV_FORK>	1196	=item C<EV_FORK>
1100		1197
1101	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1102	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1103		1204
1104	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1105		1206
1106	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1107		1208
…		…
1217		1318
1218	=item callback ev_cb (ev_TYPE *watcher)	1319	=item callback ev_cb (ev_TYPE *watcher)
1219		1320
1220	Returns the callback currently set on the watcher.	1321	Returns the callback currently set on the watcher.
1221		1322
1222	=item ev_cb_set (ev_TYPE *watcher, callback)	1323	=item ev_set_cb (ev_TYPE *watcher, callback)
1223		1324
1224	Change the callback. You can change the callback at virtually any time	1325	Change the callback. You can change the callback at virtually any time
1225	(modulo threads).	1326	(modulo threads).
1226		1327
1227	=item ev_set_priority (ev_TYPE *watcher, int priority)	1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1245	or might not have been clamped to the valid range.	1346	or might not have been clamped to the valid range.
1246		1347
1247	The default priority used by watchers when no priority has been set is	1348	The default priority used by watchers when no priority has been set is
1248	always C<0>, which is supposed to not be too high and not be too low :).	1349	always C<0>, which is supposed to not be too high and not be too low :).
1249		1350
1250	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1251	priorities.	1352	priorities.
1252		1353
1253	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1254		1355
1255	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1281	functions that do not need a watcher.	1382	functions that do not need a watcher.
1282		1383
1283	=back	1384	=back
1284		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
1285		1388
1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1389	=head2 WATCHER STATES
1287		1390
1288	Each watcher has, by default, a member C<void *data> that you can change	1391	There are various watcher states mentioned throughout this manual -
1289	and read at any time: libev will completely ignore it. This can be used	1392	active, pending and so on. In this section these states and the rules to
1290	to associate arbitrary data with your watcher. If you need more data and	1393	transition between them will be described in more detail - and while these
1291	don't want to allocate memory and store a pointer to it in that data	1394	rules might look complicated, they usually do "the right thing".
1292	member, you can also "subclass" the watcher type and provide your own
1293	data:
1294		1395
1295	struct my_io	1396	=over 4
1296	{
1297	ev_io io;
1298	int otherfd;
1299	void *somedata;
1300	struct whatever *mostinteresting;
1301	};
1302		1397
1303	...	1398	=item initialised
1304	struct my_io w;
1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
1306		1399
1307	And since your callback will be called with a pointer to the watcher, you	1400	Before a watcher can be registered with the event loop it has to be
1308	can cast it back to your own type:	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1309		1403
1310	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1404	In this state it is simply some block of memory that is suitable for
1311	{	1405	use in an event loop. It can be moved around, freed, reused etc. at
1312	struct my_io *w = (struct my_io *)w_;	1406	will - as long as you either keep the memory contents intact, or call
1313	...	1407	C<ev_TYPE_init> again.
1314	}
1315		1408
1316	More interesting and less C-conformant ways of casting your callback type	1409	=item started/running/active
1317	instead have been omitted.
1318		1410
1319	Another common scenario is to use some data structure with multiple	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1320	embedded watchers:	1412	property of the event loop, and is actively waiting for events. While in
		1413	this state it cannot be accessed (except in a few documented ways), moved,
		1414	freed or anything else - the only legal thing is to keep a pointer to it,
		1415	and call libev functions on it that are documented to work on active watchers.
1321		1416
1322	struct my_biggy	1417	=item pending
1323	{
1324	int some_data;
1325	ev_timer t1;
1326	ev_timer t2;
1327	}
1328		1418
1329	In this case getting the pointer to C<my_biggy> is a bit more	1419	If a watcher is active and libev determines that an event it is interested
1330	complicated: Either you store the address of your C<my_biggy> struct	1420	in has occurred (such as a timer expiring), it will become pending. It will
1331	in the C<data> member of the watcher (for woozies), or you need to use	1421	stay in this pending state until either it is stopped or its callback is
1332	some pointer arithmetic using C<offsetof> inside your watchers (for real	1422	about to be invoked, so it is not normally pending inside the watcher
1333	programmers):	1423	callback.
1334		1424
1335	#include <stddef.h>	1425	The watcher might or might not be active while it is pending (for example,
		1426	an expired non-repeating timer can be pending but no longer active). If it
		1427	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1428	but it is still property of the event loop at this time, so cannot be
		1429	moved, freed or reused. And if it is active the rules described in the
		1430	previous item still apply.
1336		1431
1337	static void	1432	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)	1433	via C<ev_feed_event>), in which case it becomes pending without being
1339	{	1434	active.
1340	struct my_biggy big = (struct my_biggy *)
1341	(((char *)w) - offsetof (struct my_biggy, t1));
1342	}
1343		1435
1344	static void	1436	=item stopped
1345	t2_cb (EV_P_ ev_timer *w, int revents)	1437
1346	{	1438	A watcher can be stopped implicitly by libev (in which case it might still
1347	struct my_biggy big = (struct my_biggy *)	1439	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1348	(((char *)w) - offsetof (struct my_biggy, t2));	1440	latter will clear any pending state the watcher might be in, regardless
1349	}	1441	of whether it was active or not, so stopping a watcher explicitly before
		1442	freeing it is often a good idea.
		1443
		1444	While stopped (and not pending) the watcher is essentially in the
		1445	initialised state, that is, it can be reused, moved, modified in any way
		1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
		1448
		1449	=back
1350		1450
1351	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1352		1452
1353	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1354	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1481	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1482	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1483	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1484	required if you know what you are doing).	1584	required if you know what you are doing).
1485		1585
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	1586	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	1587	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	1588	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	1589	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	1590	with a relatively standard program structure. Thus it is best to always
1497	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
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.	1592	preferable to a program hanging until some data arrives.
1500		1593
1501	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1502	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1503	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1504	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1505	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1506	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1507	indefinitely.	1600	indefinitely.
1508		1601
1509	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1510		1603
…		…
1538		1631
1539	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1540	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1541	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1542		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1543	=head3 The special problem of fork	1669	=head3 The special problem of fork
1544		1670
1545	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1546	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1547	it in the child.	1673	it in the child if you want to continue to use it in the child.
1548		1674
1549	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1550	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1551	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1552	C<EVBACKEND_POLL>.
1553		1678
1554	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1555		1680
1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1557	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1655	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1656	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1657		1782
1658	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1659	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1660	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1661	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1662	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1663	no longer true when a callback calls C<ev_run> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1664		1790
1665	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1666		1792
1667	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1668	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1743		1869
1744	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1745	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1746	within the callback:	1872	within the callback:
1747		1873
		1874	ev_tstamp timeout = 60.;
1748	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1749		1877
1750	static void	1878	static void
1751	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1752	{	1880	{
1753	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1754	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1755		1883
1756	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1757	if (timeout < now)	1885	if (after < 0.)
1758	{	1886	{
1759	// timeout occurred, take action	1887	// timeout occurred, take action
1760	}	1888	}
1761	else	1889	else
1762	{	1890	{
1763	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1764	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1765	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1766	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1767	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1768	}	1897	}
1769	}	1898	}
1770		1899
1771	To summarise the callback: first calculate the real timeout (defined	1900	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	1901	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	1902	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	1903	(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		1904
1778	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1779	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1780		1914
1781	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1782	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1783	libev to change the timeout.	1917	libev to change the timeout.
1784		1918
1785	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1786	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1787	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1788		1923
		1924	last_activity = ev_now (EV_A);
1789	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1790	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1791	callback (loop, timer, EV_TIMER);
1792		1927
1793	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1794	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1795		1930
		1931	if (activity detected)
1796	last_activity = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1797		1941
1798	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1799	time-out is unlikely to be triggered, much more efficient.	1943	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		1944
1805	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1806		1946
1807	If there is not one request, but many thousands (millions...), all	1947	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	1948	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	1975	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	1976	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	1977	off after the first million or so of active timers, i.e. it's usually
1838	overkill :)	1978	overkill :)
1839		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1840	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1841		2018
1842	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1843	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1844	time only before and after C<ev_run> collects new events, which causes a	2021	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	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1846	lots of events in one iteration.	2023	lots of events in one iteration.
1847		2024
1848	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1855		2032
1856	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1857	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1858	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
1859		2069
1860	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1861		2071
1862	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
1863	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1907	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1908	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1909		2119
1910	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1911		2121
1912	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1913	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1914		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1915	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1916		2132
1917	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1918		2135
1919	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1920	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1921		2138
		2139	=back
		2140
1922	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1923	usage example.	2142	usage example.
1924		2143
1925	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1926		2145
1927	Returns the remaining time until a timer fires. If the timer is active,	2146	Returns the remaining time until a timer fires. If the timer is active,
…		…
2047		2266
2048	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
2049	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
2050	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
2051		2270
2052	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
2053	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
2054	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
2055		2277
2056	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
2057	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
2058	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
2059	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2173		2395
2174	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2175		2397
2176	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
2177	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
2178	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
2179	normal event processing, like any other event.	2401	normal event processing, like any other event.
2180		2402
2181	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2182	C<sigaction> as you would do without libev and forget about sharing	2404	C<sigaction> as you would do without libev and forget about sharing
2183	the signal. You can even use C<ev_async> from a signal handler to	2405	the signal. You can even use C<ev_async> from a signal handler to
…		…
2202	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2203		2425
2204	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2205	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(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,	2428	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.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2208		2431
2209	While this does not matter for the signal disposition (libev never	2432	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	2433	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	2434	C<execve>), this matters for the signal mask: many programs do not expect
2212	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2225	I<has> to modify the signal mask, at least temporarily.	2448	I<has> to modify the signal mask, at least temporarily.
2226		2449
2227	So I can't stress this enough: I<If you do not reset your signal mask when	2450	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	2451	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.	2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
2230		2467
2231	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2232		2469
2233	=over 4	2470	=over 4
2234		2471
…		…
2369		2606
2370	=head2 C<ev_stat> - did the file attributes just change?	2607	=head2 C<ev_stat> - did the file attributes just change?
2371		2608
2372	This watches a file system path for attribute changes. That is, it calls	2609	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)	2610	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	2611	and sees if it changed compared to the last time, invoking the callback
2375	it did.	2612	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2613	happen after the watcher has been started will be reported.
2376		2614
2377	The path does not need to exist: changing from "path exists" to "path does	2615	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	2616	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	2617	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	2618	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	2848	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	2849	effect on its own sometimes), idle watchers are a good place to do
2612	"pseudo-background processing", or delay processing stuff to after the	2850	"pseudo-background processing", or delay processing stuff to after the
2613	event loop has handled all outstanding events.	2851	event loop has handled all outstanding events.
2614		2852
		2853	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2854
		2855	As long as there is at least one active idle watcher, libev will never
		2856	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2857	For this to work, the idle watcher doesn't need to be invoked at all - the
		2858	lowest priority will do.
		2859
		2860	This mode of operation can be useful together with an C<ev_check> watcher,
		2861	to do something on each event loop iteration - for example to balance load
		2862	between different connections.
		2863
		2864	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2865	example.
		2866
2615	=head3 Watcher-Specific Functions and Data Members	2867	=head3 Watcher-Specific Functions and Data Members
2616		2868
2617	=over 4	2869	=over 4
2618		2870
2619	=item ev_idle_init (ev_idle *, callback)	2871	=item ev_idle_init (ev_idle *, callback)
…		…
2630	callback, free it. Also, use no error checking, as usual.	2882	callback, free it. Also, use no error checking, as usual.
2631		2883
2632	static void	2884	static void
2633	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2885	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2634	{	2886	{
		2887	// stop the watcher
		2888	ev_idle_stop (loop, w);
		2889
		2890	// now we can free it
2635	free (w);	2891	free (w);
		2892
2636	// now do something you wanted to do when the program has	2893	// now do something you wanted to do when the program has
2637	// no longer anything immediate to do.	2894	// no longer anything immediate to do.
2638	}	2895	}
2639		2896
2640	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2897	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2642	ev_idle_start (loop, idle_watcher);	2899	ev_idle_start (loop, idle_watcher);
2643		2900
2644		2901
2645	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2902	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2646		2903
2647	Prepare and check watchers are usually (but not always) used in pairs:	2904	Prepare and check watchers are often (but not always) used in pairs:
2648	prepare watchers get invoked before the process blocks and check watchers	2905	prepare watchers get invoked before the process blocks and check watchers
2649	afterwards.	2906	afterwards.
2650		2907
2651	You I<must not> call C<ev_run> or similar functions that enter	2908	You I<must not> call C<ev_run> or similar functions that enter
2652	the current event loop from either C<ev_prepare> or C<ev_check>	2909	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2680	with priority higher than or equal to the event loop and one coroutine	2937	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	2938	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	2939	loop from blocking if lower-priority coroutines are active, thus mapping
2683	low-priority coroutines to idle/background tasks).	2940	low-priority coroutines to idle/background tasks).
2684		2941
2685	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2942	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	2943	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).	2944	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2945	watchers).
2688		2946
2689	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2947	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	2948	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	2949	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	2950	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	2951	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	2952	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2695	others).	2953	others).
		2954
		2955	=head3 Abusing an C<ev_check> watcher for its side-effect
		2956
		2957	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2958	useful because they are called once per event loop iteration. For
		2959	example, if you want to handle a large number of connections fairly, you
		2960	normally only do a bit of work for each active connection, and if there
		2961	is more work to do, you wait for the next event loop iteration, so other
		2962	connections have a chance of making progress.
		2963
		2964	Using an C<ev_check> watcher is almost enough: it will be called on the
		2965	next event loop iteration. However, that isn't as soon as possible -
		2966	without external events, your C<ev_check> watcher will not be invoked.
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2696		2973
2697	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2698		2975
2699	=over 4	2976	=over 4
2700		2977
…		…
2901		3178
2902	=over 4	3179	=over 4
2903		3180
2904	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3181	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2905		3182
2906	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2907		3184
2908	Configures the watcher to embed the given loop, which must be	3185	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	3186	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	3187	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,	3188	to invoke it (it will continue to be called until the sweep has been done,
…		…
2974		3251
2975	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3252	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2976		3253
2977	Fork watchers are called when a C<fork ()> was detected (usually because	3254	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	3255	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	3256	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,	3257	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	3258	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	3259	and calls it in the wrong process, the fork handlers will be invoked, too,
2983	handlers will be invoked, too, of course.	3260	of course.
2984		3261
2985	=head3 The special problem of life after fork - how is it possible?	3262	=head3 The special problem of life after fork - how is it possible?
2986		3263
2987	Most uses of C<fork()> consist of forking, then some simple calls to set	3264	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	3265	up/change the process environment, followed by a call to C<exec()>. This
…		…
3008	disadvantage of having to use multiple event loops (which do not support	3285	disadvantage of having to use multiple event loops (which do not support
3009	signal watchers).	3286	signal watchers).
3010		3287
3011	When this is not possible, or you want to use the default loop for	3288	When this is not possible, or you want to use the default loop for
3012	other reasons, then in the process that wants to start "fresh", call	3289	other reasons, then in the process that wants to start "fresh", call
3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3290	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	3291	Destroying the default loop will "orphan" (not stop) all registered
3015	have to be careful not to execute code that modifies those watchers. Note	3292	watchers, so you have to be careful not to execute code that modifies
3016	also that in that case, you have to re-register any signal watchers.	3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
3017		3295
3018	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
3019		3297
3020	=over 4	3298	=over 4
3021		3299
3022	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
3023		3301
3024	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
3025	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3026	believe me.	3304	really.
3027		3305
3028	=back	3306	=back
3029		3307
3030		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
3031	=head2 C<ev_async> - how to wake up an event loop	3349	=head2 C<ev_async> - how to wake up an event loop
3032		3350
3033	In general, you cannot use an C<ev_run> from multiple threads or other	3351	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	3352	asynchronous sources such as signal handlers (as opposed to multiple event
3035	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
3036		3354
3037	Sometimes, however, you need to wake up an event loop you do not control,	3355	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>	3356	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.	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
3041		3359
3042	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
3043	too, are asynchronous in nature, and signals, too, will be compressed	3361	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	3362	(i.e. the number of callback invocations may be less than the number of
3045	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3046		3364	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	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3048	just the default loop.	3366	even without knowing which loop owns the signal.
3049		3367
3050	=head3 Queueing	3368	=head3 Queueing
3051		3369
3052	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
3053	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
…		…
3145	trust me.	3463	trust me.
3146		3464
3147	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3148		3466
3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3150	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3151	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3152	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3153	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3154		3474
3155	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
3156	compressed into a single callback invocation (another way to look at this	3476	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>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3158	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3159		3479
3160	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3161	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3162	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3163		3486
3164	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3165		3488
3166	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3167	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3223		3546
3224	=item ev_feed_fd_event (loop, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3225		3548
3226	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3227	the given events it.	3550	the given events.
3228		3551
3229	=item ev_feed_signal_event (loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3230		3553
3231	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3232	loop!).	3555	which is async-safe.
3233		3556
3234	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3665	example, or more sneakily, by reusing an existing (stopped) watcher and
		3666	pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, a simple C<ev_break> will not work.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3235		3908
3236		3909
3237	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3238		3911
3239	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3240	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3241		3914
3242	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3243		3921
3244	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3245		3923
3246	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3247	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3253	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3254	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3255	is an ev_pri field.	3933	is an ev_pri field.
3256		3934
3257	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3258	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3259		3937
3260	=item * Other members are not supported.	3938	=item * Other members are not supported.
3261		3939
3262	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3263	to use the libev header file and library.	3941	to use the libev header file and library.
3264		3942
3265	=back	3943	=back
3266		3944
3267	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3268		3979
3269	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3270	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3271	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3272		3983
…		…
3282	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
3283	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
3284	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
3285	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3286		3997
3287	Currently, functions, and static and non-static member functions can be	3998	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	3999	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	4000	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	4001	you need support for other types of functors please contact the author
3291	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3292		4007
3293	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3294		4009
3295	=over 4	4010	=over 4
3296		4011
…		…
3306	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3307		4022
3308	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3309	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3310	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3311	defines by many implementations.	4026	defined by many implementations.
3312		4027
3313	All of those classes have these methods:	4028	All of those classes have these methods:
3314		4029
3315	=over 4	4030	=over 4
3316		4031
…		…
3406	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
3407	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
3408		4123
3409	=item w->set ([arguments])	4124	=item w->set ([arguments])
3410		4125
3411	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4126	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	4127	with the same arguments. Either this method or a suitable start method
3413	C counterpart, an active watcher gets automatically stopped and restarted	4128	must be called at least once. Unlike the C counterpart, an active watcher
3414	when reconfiguring it with this method.	4129	gets automatically stopped and restarted when reconfiguring it with this
		4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3415		4134
3416	=item w->start ()	4135	=item w->start ()
3417		4136
3418	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3419	constructor already stores the event loop.	4138	constructor already stores the event loop.
…		…
3449	watchers in the constructor.	4168	watchers in the constructor.
3450		4169
3451	class myclass	4170	class myclass
3452	{	4171	{
3453	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3456		4175
3457	myclass (int fd)	4176	myclass (int fd)
3458	{	4177	{
3459	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
…		…
3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3511		4230
3512	=item D	4231	=item D
3513		4232
3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3515	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3516		4235
3517	=item Ocaml	4236	=item Ocaml
3518		4237
3519	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3523		4242
3524	Brian Maher has written a partial interface to libev for lua (at the	4243	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	4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3526	L<http://github.com/brimworks/lua-ev>.	4245	L<http://github.com/brimworks/lua-ev>.
3527		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
		4254
3528	=back	4255	=back
3529		4256
3530		4257
3531	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
3532		4259
…		…
3568	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3569		4296
3570	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3571		4298
3572	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3573	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3574		4305
3575	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3576		4307
3577	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3578	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3723	supported). It will also not define any of the structs usually found in	4454	supported). It will also not define any of the structs usually found in
3724	F<event.h> that are not directly supported by the libev core alone.	4455	F<event.h> that are not directly supported by the libev core alone.
3725		4456
3726	In standalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3727	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3728		4468
3729	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3730		4470
3731	If defined to be C<1>, libev will try to detect the availability of the	4471	If defined to be C<1>, libev will try to detect the availability of the
3732	monotonic clock option at both compile time and runtime. Otherwise no	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3817		4557
3818	If programs implement their own fd to handle mapping on win32, then this	4558	If programs implement their own fd to handle mapping on win32, then this
3819	macro can be used to override the C<close> function, useful to unregister	4559	macro can be used to override the C<close> function, useful to unregister
3820	file descriptors again. Note that the replacement function has to close	4560	file descriptors again. Note that the replacement function has to close
3821	the underlying OS handle.	4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3822		4569
3823	=item EV_USE_POLL	4570	=item EV_USE_POLL
3824		4571
3825	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3826	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	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	4609	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	4610	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	4611	be detected at runtime. If undefined, it will be enabled if the headers
3865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3866		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called from
		4624	different threads (that includes signal handlers), which is a stronger
		4625	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4626	libev faster.
		4627
3867	=item EV_ATOMIC_T	4628	=item EV_ATOMIC_T
3868		4629
3869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4630	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	4631	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	4632	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"	4633	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.	4634	handler "locking" as well as for signal and thread safety in C<ev_async>
		4635	watchers.
3874		4636
3875	In the absence of this define, libev will use C<sig_atomic_t volatile>	4637	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.	4638	(from F<signal.h>), which is usually good enough on most platforms.
3877		4639
3878	=item EV_H (h)	4640	=item EV_H (h)
…		…
3905	will have the C<struct ev_loop *> as first argument, and you can create	4667	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	4668	additional independent event loops. Otherwise there will be no support
3907	for multiple event loops and there is no first event loop pointer	4669	for multiple event loops and there is no first event loop pointer
3908	argument. Instead, all functions act on the single default loop.	4670	argument. Instead, all functions act on the single default loop.
3909		4671
		4672	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4673	default loop when multiplicity is switched off - you always have to
		4674	initialise the loop manually in this case.
		4675
3910	=item EV_MINPRI	4676	=item EV_MINPRI
3911		4677
3912	=item EV_MAXPRI	4678	=item EV_MAXPRI
3913		4679
3914	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4680	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3950	#define EV_USE_POLL 1	4716	#define EV_USE_POLL 1
3951	#define EV_CHILD_ENABLE 1	4717	#define EV_CHILD_ENABLE 1
3952	#define EV_ASYNC_ENABLE 1	4718	#define EV_ASYNC_ENABLE 1
3953		4719
3954	The actual value is a bitset, it can be a combination of the following	4720	The actual value is a bitset, it can be a combination of the following
3955	values:	4721	values (by default, all of these are enabled):
3956		4722
3957	=over 4	4723	=over 4
3958		4724
3959	=item C<1> - faster/larger code	4725	=item C<1> - faster/larger code
3960		4726
…		…
3964	code size by roughly 30% on amd64).	4730	code size by roughly 30% on amd64).
3965		4731
3966	When optimising for size, use of compiler flags such as C<-Os> with	4732	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	4733	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3968	assertions.	4734	assertions.
		4735
		4736	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4737	(e.g. gcc with C<-Os>).
3969		4738
3970	=item C<2> - faster/larger data structures	4739	=item C<2> - faster/larger data structures
3971		4740
3972	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4741	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	4742	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	4743	and can additionally have an effect on the size of data structures at
3975	runtime.	4744	runtime.
3976		4745
		4746	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4747	(e.g. gcc with C<-Os>).
		4748
3977	=item C<4> - full API configuration	4749	=item C<4> - full API configuration
3978		4750
3979	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4751	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3980	enables multiplicity (C<EV_MULTIPLICITY>=1).	4752	enables multiplicity (C<EV_MULTIPLICITY>=1).
3981		4753
…		…
4011		4783
4012	With an intelligent-enough linker (gcc+binutils are intelligent enough	4784	With an intelligent-enough linker (gcc+binutils are intelligent enough
4013	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4785	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	4786	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.	4787	I/O watcher then might come out at only 5Kb.
		4788
		4789	=item EV_API_STATIC
		4790
		4791	If this symbol is defined (by default it is not), then all identifiers
		4792	will have static linkage. This means that libev will not export any
		4793	identifiers, and you cannot link against libev anymore. This can be useful
		4794	when you embed libev, only want to use libev functions in a single file,
		4795	and do not want its identifiers to be visible.
		4796
		4797	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4798	wants to use libev.
		4799
		4800	This option only works when libev is compiled with a C compiler, as C++
		4801	doesn't support the required declaration syntax.
4016		4802
4017	=item EV_AVOID_STDIO	4803	=item EV_AVOID_STDIO
4018		4804
4019	If this is set to C<1> at compiletime, then libev will avoid using stdio	4805	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	4806	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:	4950	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4165		4951
4166	#include "ev_cpp.h"	4952	#include "ev_cpp.h"
4167	#include "ev.c"	4953	#include "ev.c"
4168		4954
4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4955	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4170		4956
4171	=head2 THREADS AND COROUTINES	4957	=head2 THREADS AND COROUTINES
4172		4958
4173	=head3 THREADS	4959	=head3 THREADS
4174		4960
…		…
4225	default loop and triggering an C<ev_async> watcher from the default loop	5011	default loop and triggering an C<ev_async> watcher from the default loop
4226	watcher callback into the event loop interested in the signal.	5012	watcher callback into the event loop interested in the signal.
4227		5013
4228	=back	5014	=back
4229		5015
4230	=head4 THREAD LOCKING EXAMPLE	5016	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		5017
4368	=head3 COROUTINES	5018	=head3 COROUTINES
4369		5019
4370	Libev is very accommodating to coroutines ("cooperative threads"):	5020	Libev is very accommodating to coroutines ("cooperative threads"):
4371	libev fully supports nesting calls to its functions from different	5021	libev fully supports nesting calls to its functions from different
…		…
4467	=head3 C<kqueue> is buggy	5117	=head3 C<kqueue> is buggy
4468		5118
4469	The kqueue syscall is broken in all known versions - most versions support	5119	The kqueue syscall is broken in all known versions - most versions support
4470	only sockets, many support pipes.	5120	only sockets, many support pipes.
4471		5121
4472	Libev tries to work around this by not using C<kqueue> by default on	5122	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	5123	rotten platform, but of course you can still ask for it when creating a
4474	a loop.	5124	loop - embedding a socket-only kqueue loop into a select-based one is
		5125	probably going to work well.
4475		5126
4476	=head3 C<poll> is buggy	5127	=head3 C<poll> is buggy
4477		5128
4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5129	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4479	implementation by something calling C<kqueue> internally around the 10.5.6	5130	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4498		5149
4499	=head3 C<errno> reentrancy	5150	=head3 C<errno> reentrancy
4500		5151
4501	The default compile environment on Solaris is unfortunately so	5152	The default compile environment on Solaris is unfortunately so
4502	thread-unsafe that you can't even use components/libraries compiled	5153	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,	5154	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4504	isn't defined by default.	5155	defined by default. A valid, if stupid, implementation choice.
4505		5156
4506	If you want to use libev in threaded environments you have to make sure	5157	If you want to use libev in threaded environments you have to make sure
4507	it's compiled with C<_REENTRANT> defined.	5158	it's compiled with C<_REENTRANT> defined.
4508		5159
4509	=head3 Event port backend	5160	=head3 Event port backend
4510		5161
4511	The scalable event interface for Solaris is called "event ports". Unfortunately,	5162	The scalable event interface for Solaris is called "event
4512	this mechanism is very buggy. If you run into high CPU usage, your program	5163	ports". Unfortunately, this mechanism is very buggy in all major
		5164	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	5165	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	5166	and latest kernel patches applied. No, I don't know which ones, but there
4515	ones, but there are multiple ones.	5167	are multiple ones to apply, and afterwards, event ports actually work
		5168	great.
4516		5169
4517	If you can't get it to work, you can try running the program by setting	5170	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	5171	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4519	C<select> backends.	5172	C<select> backends.
4520		5173
4521	=head2 AIX POLL BUG	5174	=head2 AIX POLL BUG
4522		5175
4523	AIX unfortunately has a broken C<poll.h> header. Libev works around	5176	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	5177	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	5178	compiled in), which normally isn't a big problem as C<select> works fine
4526	with large bitsets, and AIX is dead anyway.	5179	with large bitsets on AIX, and AIX is dead anyway.
4527		5180
4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5181	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4529		5182
4530	=head3 General issues	5183	=head3 General issues
4531		5184
…		…
4533	requires, and its I/O model is fundamentally incompatible with the POSIX	5186	requires, and its I/O model is fundamentally incompatible with the POSIX
4534	model. Libev still offers limited functionality on this platform in	5187	model. Libev still offers limited functionality on this platform in
4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5188	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4536	descriptors. This only applies when using Win32 natively, not when using	5189	descriptors. This only applies when using Win32 natively, not when using
4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5190	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4538	as every compielr comes with a slightly differently broken/incompatible	5191	as every compiler comes with a slightly differently broken/incompatible
4539	environment.	5192	environment.
4540		5193
4541	Lifting these limitations would basically require the full	5194	Lifting these limitations would basically require the full
4542	re-implementation of the I/O system. If you are into this kind of thing,	5195	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	5196	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	5290	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	5291	assumes that the same (machine) code can be used to call any watcher
4639	callback: The watcher callbacks have different type signatures, but libev	5292	callback: The watcher callbacks have different type signatures, but libev
4640	calls them using an C<ev_watcher *> internally.	5293	calls them using an C<ev_watcher *> internally.
4641		5294
		5295	=item pointer accesses must be thread-atomic
		5296
		5297	Accessing a pointer value must be atomic, it must both be readable and
		5298	writable in one piece - this is the case on all current architectures.
		5299
4642	=item C<sig_atomic_t volatile> must be thread-atomic as well	5300	=item C<sig_atomic_t volatile> must be thread-atomic as well
4643		5301
4644	The type C<sig_atomic_t volatile> (or whatever is defined as	5302	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	5303	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	5304	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	5312	thread" or will block signals process-wide, both behaviours would
4655	be compatible with libev. Interaction between C<sigprocmask> and	5313	be compatible with libev. Interaction between C<sigprocmask> and
4656	C<pthread_sigmask> could complicate things, however.	5314	C<pthread_sigmask> could complicate things, however.
4657		5315
4658	The most portable way to handle signals is to block signals in all threads	5316	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	5317	except the initial one, and run the signal handling loop in the initial
4660	well.	5318	thread as well.
4661		5319
4662	=item C<long> must be large enough for common memory allocation sizes	5320	=item C<long> must be large enough for common memory allocation sizes
4663		5321
4664	To improve portability and simplify its API, libev uses C<long> internally	5322	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	5323	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4671		5329
4672	The type C<double> is used to represent timestamps. It is required to	5330	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	5331	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	5332	good enough for at least into the year 4000 with millisecond accuracy
4675	(the design goal for libev). This requirement is overfulfilled by	5333	(the design goal for libev). This requirement is overfulfilled by
4676	implementations using IEEE 754, which is basically all existing ones. With	5334	implementations using IEEE 754, which is basically all existing ones.
		5335
4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5336	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5337	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5338	is either obsolete or somebody patched it to use C<long double> or
		5339	something like that, just kidding).
4678		5340
4679	=back	5341	=back
4680		5342
4681	If you know of other additional requirements drop me a note.	5343	If you know of other additional requirements drop me a note.
4682		5344
…		…
4744	=item Processing ev_async_send: O(number_of_async_watchers)	5406	=item Processing ev_async_send: O(number_of_async_watchers)
4745		5407
4746	=item Processing signals: O(max_signal_number)	5408	=item Processing signals: O(max_signal_number)
4747		5409
4748	Sending involves a system call I<iff> there were no other C<ev_async_send>	5410	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	5411	calls in the current loop iteration and the loop is currently
		5412	blocked. Checking for async and signal events involves iterating over all
4750	involves iterating over all running async watchers or all signal numbers.	5413	running async watchers or all signal numbers.
4751		5414
4752	=back	5415	=back
4753		5416
4754		5417
4755	=head1 PORTING FROM LIBEV 3.X TO 4.X	5418	=head1 PORTING FROM LIBEV 3.X TO 4.X
4756		5419
4757	The major version 4 introduced some minor incompatible changes to the API.	5420	The major version 4 introduced some incompatible changes to the API.
4758		5421
4759	At the moment, the C<ev.h> header file tries to implement superficial	5422	At the moment, the C<ev.h> header file provides compatibility definitions
4760	compatibility, so most programs should still compile. Those might be	5423	for all changes, so most programs should still compile. The compatibility
4761	removed in later versions of libev, so better update early than late.	5424	layer might be removed in later versions of libev, so better update to the
		5425	new API early than late.
4762		5426
4763	=over 4	5427	=over 4
		5428
		5429	=item C<EV_COMPAT3> backwards compatibility mechanism
		5430
		5431	The backward compatibility mechanism can be controlled by
		5432	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5433	section.
		5434
		5435	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5436
		5437	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5438
		5439	ev_loop_destroy (EV_DEFAULT_UC);
		5440	ev_loop_fork (EV_DEFAULT);
4764		5441
4765	=item function/symbol renames	5442	=item function/symbol renames
4766		5443
4767	A number of functions and symbols have been renamed:	5444	A number of functions and symbols have been renamed:
4768		5445
…		…
4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5464	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	5465	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>	5466	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4790	typedef.	5467	typedef.
4791		5468
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>	5469	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4799		5470
4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5471	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5472	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4802	and work, but the library code will of course be larger.	5473	and work, but the library code will of course be larger.
…		…
4808		5479
4809	=over 4	5480	=over 4
4810		5481
4811	=item active	5482	=item active
4812		5483
4813	A watcher is active as long as it has been started (has been attached to	5484	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).	5485	See L</WATCHER STATES> for details.
4815		5486
4816	=item application	5487	=item application
4817		5488
4818	In this document, an application is whatever is using libev.	5489	In this document, an application is whatever is using libev.
		5490
		5491	=item backend
		5492
		5493	The part of the code dealing with the operating system interfaces.
4819		5494
4820	=item callback	5495	=item callback
4821		5496
4822	The address of a function that is called when some event has been	5497	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	5498	detected. Callbacks are being passed the event loop, the watcher that
4824	received the event, and the actual event bitset.	5499	received the event, and the actual event bitset.
4825		5500
4826	=item callback invocation	5501	=item callback/watcher invocation
4827		5502
4828	The act of calling the callback associated with a watcher.	5503	The act of calling the callback associated with a watcher.
4829		5504
4830	=item event	5505	=item event
4831		5506
…		…
4850	The model used to describe how an event loop handles and processes	5525	The model used to describe how an event loop handles and processes
4851	watchers and events.	5526	watchers and events.
4852		5527
4853	=item pending	5528	=item pending
4854		5529
4855	A watcher is pending as soon as the corresponding event has been detected,	5530	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	5531	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		5532
4862	=item real time	5533	=item real time
4863		5534
4864	The physical time that is observed. It is apparently strictly monotonic :)	5535	The physical time that is observed. It is apparently strictly monotonic :)
4865		5536
4866	=item wall-clock time	5537	=item wall-clock time
4867		5538
4868	The time and date as shown on clocks. Unlike real time, it can actually	5539	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	5540	be wrong and jump forwards and backwards, e.g. when you adjust your
4870	clock.	5541	clock.
4871		5542
4872	=item watcher	5543	=item watcher
4873		5544
4874	A data structure that describes interest in certain events. Watchers need	5545	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.	5546	to be started (attached to an event loop) before they can receive events.
4876		5547
4877	=item watcher invocation
4878
4879	The act of calling the callback associated with a watcher.
4880
4881	=back	5548	=back
4882		5549
4883	=head1 AUTHOR	5550	=head1 AUTHOR
4884		5551
4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5552	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5553	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4886		5554

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