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Revision 1.399 by root, Mon Apr 2 23:14:41 2012 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))
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))
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.
…		…
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.
…		…
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, ...) >>.
…		…
1099	=item C<EV_FORK>	1191	=item C<EV_FORK>
1100		1192
1101	The event loop has been resumed in the child process after fork (see	1193	The event loop has been resumed in the child process after fork (see
1102	C<ev_fork>).	1194	C<ev_fork>).
1103		1195
		1196	=item C<EV_CLEANUP>
		1197
		1198	The event loop is about to be destroyed (see C<ev_cleanup>).
		1199
1104	=item C<EV_ASYNC>	1200	=item C<EV_ASYNC>
1105		1201
1106	The given async watcher has been asynchronously notified (see C<ev_async>).	1202	The given async watcher has been asynchronously notified (see C<ev_async>).
1107		1203
1108	=item C<EV_CUSTOM>	1204	=item C<EV_CUSTOM>
…		…
1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1376	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1281	functions that do not need a watcher.	1377	functions that do not need a watcher.
1282		1378
1283	=back	1379	=back
1284		1380
		1381	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1382	OWN COMPOSITE WATCHERS> idioms.
1285		1383
1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1384	=head2 WATCHER STATES
1287		1385
1288	Each watcher has, by default, a member C<void *data> that you can change	1386	There are various watcher states mentioned throughout this manual -
1289	and read at any time: libev will completely ignore it. This can be used	1387	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	1388	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	1389	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		1390
1295	struct my_io	1391	=over 4
1296	{
1297	ev_io io;
1298	int otherfd;
1299	void *somedata;
1300	struct whatever *mostinteresting;
1301	};
1302		1392
1303	...	1393	=item initialiased
1304	struct my_io w;
1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
1306		1394
1307	And since your callback will be called with a pointer to the watcher, you	1395	Before a watcher can be registered with the event loop it has to be
1308	can cast it back to your own type:	1396	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1397	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1309		1398
1310	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1399	In this state it is simply some block of memory that is suitable for
1311	{	1400	use in an event loop. It can be moved around, freed, reused etc. at
1312	struct my_io *w = (struct my_io *)w_;	1401	will - as long as you either keep the memory contents intact, or call
1313	...	1402	C<ev_TYPE_init> again.
1314	}
1315		1403
1316	More interesting and less C-conformant ways of casting your callback type	1404	=item started/running/active
1317	instead have been omitted.
1318		1405
1319	Another common scenario is to use some data structure with multiple	1406	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1320	embedded watchers:	1407	property of the event loop, and is actively waiting for events. While in
		1408	this state it cannot be accessed (except in a few documented ways), moved,
		1409	freed or anything else - the only legal thing is to keep a pointer to it,
		1410	and call libev functions on it that are documented to work on active watchers.
1321		1411
1322	struct my_biggy	1412	=item pending
1323	{
1324	int some_data;
1325	ev_timer t1;
1326	ev_timer t2;
1327	}
1328		1413
1329	In this case getting the pointer to C<my_biggy> is a bit more	1414	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	1415	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	1416	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	1417	about to be invoked, so it is not normally pending inside the watcher
1333	programmers):	1418	callback.
1334		1419
1335	#include <stddef.h>	1420	The watcher might or might not be active while it is pending (for example,
		1421	an expired non-repeating timer can be pending but no longer active). If it
		1422	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1423	but it is still property of the event loop at this time, so cannot be
		1424	moved, freed or reused. And if it is active the rules described in the
		1425	previous item still apply.
1336		1426
1337	static void	1427	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)	1428	via C<ev_feed_event>), in which case it becomes pending without being
1339	{	1429	active.
1340	struct my_biggy big = (struct my_biggy *)
1341	(((char *)w) - offsetof (struct my_biggy, t1));
1342	}
1343		1430
1344	static void	1431	=item stopped
1345	t2_cb (EV_P_ ev_timer *w, int revents)	1432
1346	{	1433	A watcher can be stopped implicitly by libev (in which case it might still
1347	struct my_biggy big = (struct my_biggy *)	1434	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1348	(((char *)w) - offsetof (struct my_biggy, t2));	1435	latter will clear any pending state the watcher might be in, regardless
1349	}	1436	of whether it was active or not, so stopping a watcher explicitly before
		1437	freeing it is often a good idea.
		1438
		1439	While stopped (and not pending) the watcher is essentially in the
		1440	initialised state, that is, it can be reused, moved, modified in any way
		1441	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1442	it again).
		1443
		1444	=back
1350		1445
1351	=head2 WATCHER PRIORITY MODELS	1446	=head2 WATCHER PRIORITY MODELS
1352		1447
1353	Many event loops support I<watcher priorities>, which are usually small	1448	Many event loops support I<watcher priorities>, which are usually small
1354	integers that influence the ordering of event callback invocation	1449	integers that influence the ordering of event callback invocation
…		…
1481	In general you can register as many read and/or write event watchers per	1576	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	1577	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	1578	descriptors to non-blocking mode is also usually a good idea (but not
1484	required if you know what you are doing).	1579	required if you know what you are doing).
1485		1580
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	1581	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	1582	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	1583	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	1584	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	1585	with a relatively standard program structure. Thus it is best to always
1497	this situation even with a relatively standard program structure. Thus	1586	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.	1587	preferable to a program hanging until some data arrives.
1500		1588
1501	If you cannot run the fd in non-blocking mode (for example you should	1589	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	1590	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	1591	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	1592	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	1593	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	1594	use C<SIGALRM> and an interval timer, just to be sure you won't block
1507	indefinitely.	1595	indefinitely.
1508		1596
1509	But really, best use non-blocking mode.	1597	But really, best use non-blocking mode.
1510		1598
…		…
1538		1626
1539	There is no workaround possible except not registering events	1627	There is no workaround possible except not registering events
1540	for potentially C<dup ()>'ed file descriptors, or to resort to	1628	for potentially C<dup ()>'ed file descriptors, or to resort to
1541	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1629	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1542		1630
		1631	=head3 The special problem of files
		1632
		1633	Many people try to use C<select> (or libev) on file descriptors
		1634	representing files, and expect it to become ready when their program
		1635	doesn't block on disk accesses (which can take a long time on their own).
		1636
		1637	However, this cannot ever work in the "expected" way - you get a readiness
		1638	notification as soon as the kernel knows whether and how much data is
		1639	there, and in the case of open files, that's always the case, so you
		1640	always get a readiness notification instantly, and your read (or possibly
		1641	write) will still block on the disk I/O.
		1642
		1643	Another way to view it is that in the case of sockets, pipes, character
		1644	devices and so on, there is another party (the sender) that delivers data
		1645	on its own, but in the case of files, there is no such thing: the disk
		1646	will not send data on its own, simply because it doesn't know what you
		1647	wish to read - you would first have to request some data.
		1648
		1649	Since files are typically not-so-well supported by advanced notification
		1650	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1651	to files, even though you should not use it. The reason for this is
		1652	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1653	usually a tty, often a pipe, but also sometimes files or special devices
		1654	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1655	F</dev/urandom>), and even though the file might better be served with
		1656	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1657	it "just works" instead of freezing.
		1658
		1659	So avoid file descriptors pointing to files when you know it (e.g. use
		1660	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1661	when you rarely read from a file instead of from a socket, and want to
		1662	reuse the same code path.
		1663
1543	=head3 The special problem of fork	1664	=head3 The special problem of fork
1544		1665
1545	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1666	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	1667	useless behaviour. Libev fully supports fork, but needs to be told about
1547	it in the child.	1668	it in the child if you want to continue to use it in the child.
1548		1669
1549	To support fork in your programs, you either have to call	1670	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,	1671	()> 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	1672	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1552	C<EVBACKEND_POLL>.
1553		1673
1554	=head3 The special problem of SIGPIPE	1674	=head3 The special problem of SIGPIPE
1555		1675
1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1676	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	1677	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	1775	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1656	monotonic clock option helps a lot here).	1776	monotonic clock option helps a lot here).
1657		1777
1658	The callback is guaranteed to be invoked only I<after> its timeout has	1778	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	1779	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	1780	might introduce a small delay, see "the special problem of being too
		1781	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	1782	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	1783	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).	1784	longer true when a callback calls C<ev_run> recursively).
1664		1785
1665	=head3 Be smart about timeouts	1786	=head3 Be smart about timeouts
1666		1787
1667	Many real-world problems involve some kind of timeout, usually for error	1788	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,	1789	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1743		1864
1744	In this case, it would be more efficient to leave the C<ev_timer> alone,	1865	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	1866	but remember the time of last activity, and check for a real timeout only
1746	within the callback:	1867	within the callback:
1747		1868
		1869	ev_tstamp timeout = 60.;
1748	ev_tstamp last_activity; // time of last activity	1870	ev_tstamp last_activity; // time of last activity
		1871	ev_timer timer;
1749		1872
1750	static void	1873	static void
1751	callback (EV_P_ ev_timer *w, int revents)	1874	callback (EV_P_ ev_timer *w, int revents)
1752	{	1875	{
1753	ev_tstamp now = ev_now (EV_A);	1876	// calculate when the timeout would happen
1754	ev_tstamp timeout = last_activity + 60.;	1877	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1755		1878
1756	// if last_activity + 60. is older than now, we did time out	1879	// if negative, it means we the timeout already occured
1757	if (timeout < now)	1880	if (after < 0.)
1758	{	1881	{
1759	// timeout occurred, take action	1882	// timeout occurred, take action
1760	}	1883	}
1761	else	1884	else
1762	{	1885	{
1763	// callback was invoked, but there was some activity, re-arm	1886	// callback was invoked, but there was some recent
1764	// the watcher to fire in last_activity + 60, which is	1887	// activity. simply restart the timer to time out
1765	// guaranteed to be in the future, so "again" is positive:	1888	// after "after" seconds, which is the earliest time
1766	w->repeat = timeout - now;	1889	// the timeout can occur.
		1890	ev_timer_set (w, after, 0.);
1767	ev_timer_again (EV_A_ w);	1891	ev_timer_start (EV_A_ w);
1768	}	1892	}
1769	}	1893	}
1770		1894
1771	To summarise the callback: first calculate the real timeout (defined	1895	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	1896	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	1897	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	1898	(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		1899
1778	Note how C<ev_timer_again> is used, taking advantage of the	1900	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.	1901	timed out, and need to do whatever is needed in this case.
		1902
		1903	Otherwise, we now the earliest time at which the timeout would trigger,
		1904	and simply start the timer with this timeout value.
		1905
		1906	In other words, each time the callback is invoked it will check whether
		1907	the timeout cocured. If not, it will simply reschedule itself to check
		1908	again at the earliest time it could time out. Rinse. Repeat.
1780		1909
1781	This scheme causes more callback invocations (about one every 60 seconds	1910	This scheme causes more callback invocations (about one every 60 seconds
1782	minus half the average time between activity), but virtually no calls to	1911	minus half the average time between activity), but virtually no calls to
1783	libev to change the timeout.	1912	libev to change the timeout.
1784		1913
1785	To start the timer, simply initialise the watcher and set C<last_activity>	1914	To start the machinery, simply initialise the watcher and set
1786	to the current time (meaning we just have some activity :), then call the	1915	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:	1916	now), then call the callback, which will "do the right thing" and start
		1917	the timer:
1788		1918
		1919	last_activity = ev_now (EV_A);
1789	ev_init (timer, callback);	1920	ev_init (&timer, callback);
1790	last_activity = ev_now (loop);	1921	callback (EV_A_ &timer, 0);
1791	callback (loop, timer, EV_TIMER);
1792		1922
1793	And when there is some activity, simply store the current time in	1923	When there is some activity, simply store the current time in
1794	C<last_activity>, no libev calls at all:	1924	C<last_activity>, no libev calls at all:
1795		1925
		1926	if (activity detected)
1796	last_activity = ev_now (loop);	1927	last_activity = ev_now (EV_A);
		1928
		1929	When your timeout value changes, then the timeout can be changed by simply
		1930	providing a new value, stopping the timer and calling the callback, which
		1931	will agaion do the right thing (for example, time out immediately :).
		1932
		1933	timeout = new_value;
		1934	ev_timer_stop (EV_A_ &timer);
		1935	callback (EV_A_ &timer, 0);
1797		1936
1798	This technique is slightly more complex, but in most cases where the	1937	This technique is slightly more complex, but in most cases where the
1799	time-out is unlikely to be triggered, much more efficient.	1938	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		1939
1805	=item 4. Wee, just use a double-linked list for your timeouts.	1940	=item 4. Wee, just use a double-linked list for your timeouts.
1806		1941
1807	If there is not one request, but many thousands (millions...), all	1942	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	1943	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	1970	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	1971	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	1972	off after the first million or so of active timers, i.e. it's usually
1838	overkill :)	1973	overkill :)
1839		1974
		1975	=head3 The special problem of being too early
		1976
		1977	If you ask a timer to call your callback after three seconds, then
		1978	you expect it to be invoked after three seconds - but of course, this
		1979	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1980	guaranteed to any precision by libev - imagine somebody suspending the
		1981	process with a STOP signal for a few hours for example.
		1982
		1983	So, libev tries to invoke your callback as soon as possible I<after> the
		1984	delay has occurred, but cannot guarantee this.
		1985
		1986	A less obvious failure mode is calling your callback too early: many event
		1987	loops compare timestamps with a "elapsed delay >= requested delay", but
		1988	this can cause your callback to be invoked much earlier than you would
		1989	expect.
		1990
		1991	To see why, imagine a system with a clock that only offers full second
		1992	resolution (think windows if you can't come up with a broken enough OS
		1993	yourself). If you schedule a one-second timer at the time 500.9, then the
		1994	event loop will schedule your timeout to elapse at a system time of 500
		1995	(500.9 truncated to the resolution) + 1, or 501.
		1996
		1997	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1998	501" and invoke the callback 0.1s after it was started, even though a
		1999	one-second delay was requested - this is being "too early", despite best
		2000	intentions.
		2001
		2002	This is the reason why libev will never invoke the callback if the elapsed
		2003	delay equals the requested delay, but only when the elapsed delay is
		2004	larger than the requested delay. In the example above, libev would only invoke
		2005	the callback at system time 502, or 1.1s after the timer was started.
		2006
		2007	So, while libev cannot guarantee that your callback will be invoked
		2008	exactly when requested, it I<can> and I<does> guarantee that the requested
		2009	delay has actually elapsed, or in other words, it always errs on the "too
		2010	late" side of things.
		2011
1840	=head3 The special problem of time updates	2012	=head3 The special problem of time updates
1841		2013
1842	Establishing the current time is a costly operation (it usually takes at	2014	Establishing the current time is a costly operation (it usually takes
1843	least two system calls): EV therefore updates its idea of the current	2015	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	2016	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	2017	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1846	lots of events in one iteration.	2018	lots of events in one iteration.
1847		2019
1848	The relative timeouts are calculated relative to the C<ev_now ()>	2020	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2026	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1855		2027
1856	If the event loop is suspended for a long time, you can also force an	2028	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	2029	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1858	()>.	2030	()>.
		2031
		2032	=head3 The special problem of unsynchronised clocks
		2033
		2034	Modern systems have a variety of clocks - libev itself uses the normal
		2035	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2036	jumps).
		2037
		2038	Neither of these clocks is synchronised with each other or any other clock
		2039	on the system, so C<ev_time ()> might return a considerably different time
		2040	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2041	a call to C<gettimeofday> might return a second count that is one higher
		2042	than a directly following call to C<time>.
		2043
		2044	The moral of this is to only compare libev-related timestamps with
		2045	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2046	a second or so.
		2047
		2048	One more problem arises due to this lack of synchronisation: if libev uses
		2049	the system monotonic clock and you compare timestamps from C<ev_time>
		2050	or C<ev_now> from when you started your timer and when your callback is
		2051	invoked, you will find that sometimes the callback is a bit "early".
		2052
		2053	This is because C<ev_timer>s work in real time, not wall clock time, so
		2054	libev makes sure your callback is not invoked before the delay happened,
		2055	I<measured according to the real time>, not the system clock.
		2056
		2057	If your timeouts are based on a physical timescale (e.g. "time out this
		2058	connection after 100 seconds") then this shouldn't bother you as it is
		2059	exactly the right behaviour.
		2060
		2061	If you want to compare wall clock/system timestamps to your timers, then
		2062	you need to use C<ev_periodic>s, as these are based on the wall clock
		2063	time, where your comparisons will always generate correct results.
1859		2064
1860	=head3 The special problems of suspended animation	2065	=head3 The special problems of suspended animation
1861		2066
1862	When you leave the server world it is quite customary to hit machines that	2067	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?	2068	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	2112	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.	2113	do stuff) the timer will not fire more than once per event loop iteration.
1909		2114
1910	=item ev_timer_again (loop, ev_timer *)	2115	=item ev_timer_again (loop, ev_timer *)
1911		2116
1912	This will act as if the timer timed out and restart it again if it is	2117	This will act as if the timer timed out, and restarts it again if it is
1913	repeating. The exact semantics are:	2118	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2119	timeout to the C<repeat> value and calling C<ev_timer_start>.
1914		2120
		2121	The exact semantics are as in the following rules, all of which will be
		2122	applied to the watcher:
		2123
		2124	=over 4
		2125
1915	If the timer is pending, its pending status is cleared.	2126	=item If the timer is pending, the pending status is always cleared.
1916		2127
1917	If the timer is started but non-repeating, stop it (as if it timed out).	2128	=item If the timer is started but non-repeating, stop it (as if it timed
		2129	out, without invoking it).
1918		2130
1919	If the timer is repeating, either start it if necessary (with the	2131	=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.	2132	and start the timer, if necessary.
		2133
		2134	=back
1921		2135
1922	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2136	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1923	usage example.	2137	usage example.
1924		2138
1925	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2139	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
…		…
2047		2261
2048	Another way to think about it (for the mathematically inclined) is that	2262	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	2263	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.	2264	time where C<time = offset (mod interval)>, regardless of any time jumps.
2051		2265
2052	For numerical stability it is preferable that the C<offset> value is near	2266	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	2267	interval value should be higher than C<1/8192> (which is around 100
2054	this value, and in fact is often specified as zero.	2268	microseconds) and C<offset> should be higher than C<0> and should have
		2269	at most a similar magnitude as the current time (say, within a factor of
		2270	ten). Typical values for offset are, in fact, C<0> or something between
		2271	C<0> and C<interval>, which is also the recommended range.
2055		2272
2056	Note also that there is an upper limit to how often a timer can fire (CPU	2273	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	2274	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	2275	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).	2276	millisecond (if the OS supports it and the machine is fast enough).
…		…
2173		2390
2174	=head2 C<ev_signal> - signal me when a signal gets signalled!	2391	=head2 C<ev_signal> - signal me when a signal gets signalled!
2175		2392
2176	Signal watchers will trigger an event when the process receives a specific	2393	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	2394	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	2395	will try its best to deliver signals synchronously, i.e. as part of the
2179	normal event processing, like any other event.	2396	normal event processing, like any other event.
2180		2397
2181	If you want signals to be delivered truly asynchronously, just use	2398	If you want signals to be delivered truly asynchronously, just use
2182	C<sigaction> as you would do without libev and forget about sharing	2399	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	2400	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	2419	=head3 The special problem of inheritance over fork/execve/pthread_create
2203		2420
2204	Both the signal mask (C<sigprocmask>) and the signal disposition	2421	Both the signal mask (C<sigprocmask>) and the signal disposition
2205	(C<sigaction>) are unspecified after starting a signal watcher (and after	2422	(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,	2423	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.	2424	and might or might not set or restore the installed signal handler (but
		2425	see C<EVFLAG_NOSIGMASK>).
2208		2426
2209	While this does not matter for the signal disposition (libev never	2427	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	2428	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	2429	C<execve>), this matters for the signal mask: many programs do not expect
2212	certain signals to be blocked.	2430	certain signals to be blocked.
…		…
2225	I<has> to modify the signal mask, at least temporarily.	2443	I<has> to modify the signal mask, at least temporarily.
2226		2444
2227	So I can't stress this enough: I<If you do not reset your signal mask when	2445	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	2446	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.	2447	is not a libev-specific thing, this is true for most event libraries.
		2448
		2449	=head3 The special problem of threads signal handling
		2450
		2451	POSIX threads has problematic signal handling semantics, specifically,
		2452	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2453	threads in a process block signals, which is hard to achieve.
		2454
		2455	When you want to use sigwait (or mix libev signal handling with your own
		2456	for the same signals), you can tackle this problem by globally blocking
		2457	all signals before creating any threads (or creating them with a fully set
		2458	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2459	loops. Then designate one thread as "signal receiver thread" which handles
		2460	these signals. You can pass on any signals that libev might be interested
		2461	in by calling C<ev_feed_signal>.
2230		2462
2231	=head3 Watcher-Specific Functions and Data Members	2463	=head3 Watcher-Specific Functions and Data Members
2232		2464
2233	=over 4	2465	=over 4
2234		2466
…		…
3008	disadvantage of having to use multiple event loops (which do not support	3240	disadvantage of having to use multiple event loops (which do not support
3009	signal watchers).	3241	signal watchers).
3010		3242
3011	When this is not possible, or you want to use the default loop for	3243	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	3244	other reasons, then in the process that wants to start "fresh", call
3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3245	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	3246	Destroying the default loop will "orphan" (not stop) all registered
3015	have to be careful not to execute code that modifies those watchers. Note	3247	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.	3248	those watchers. Note also that in that case, you have to re-register any
		3249	signal watchers.
3017		3250
3018	=head3 Watcher-Specific Functions and Data Members	3251	=head3 Watcher-Specific Functions and Data Members
3019		3252
3020	=over 4	3253	=over 4
3021		3254
3022	=item ev_fork_init (ev_signal *, callback)	3255	=item ev_fork_init (ev_fork *, callback)
3023		3256
3024	Initialises and configures the fork watcher - it has no parameters of any	3257	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,	3258	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3026	believe me.	3259	really.
3027		3260
3028	=back	3261	=back
3029		3262
3030		3263
		3264	=head2 C<ev_cleanup> - even the best things end
		3265
		3266	Cleanup watchers are called just before the event loop is being destroyed
		3267	by a call to C<ev_loop_destroy>.
		3268
		3269	While there is no guarantee that the event loop gets destroyed, cleanup
		3270	watchers provide a convenient method to install cleanup hooks for your
		3271	program, worker threads and so on - you just to make sure to destroy the
		3272	loop when you want them to be invoked.
		3273
		3274	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3275	all other watchers, they do not keep a reference to the event loop (which
		3276	makes a lot of sense if you think about it). Like all other watchers, you
		3277	can call libev functions in the callback, except C<ev_cleanup_start>.
		3278
		3279	=head3 Watcher-Specific Functions and Data Members
		3280
		3281	=over 4
		3282
		3283	=item ev_cleanup_init (ev_cleanup *, callback)
		3284
		3285	Initialises and configures the cleanup watcher - it has no parameters of
		3286	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3287	pointless, I assure you.
		3288
		3289	=back
		3290
		3291	Example: Register an atexit handler to destroy the default loop, so any
		3292	cleanup functions are called.
		3293
		3294	static void
		3295	program_exits (void)
		3296	{
		3297	ev_loop_destroy (EV_DEFAULT_UC);
		3298	}
		3299
		3300	...
		3301	atexit (program_exits);
		3302
		3303
3031	=head2 C<ev_async> - how to wake up an event loop	3304	=head2 C<ev_async> - how to wake up an event loop
3032		3305
3033	In general, you cannot use an C<ev_run> from multiple threads or other	3306	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	3307	asynchronous sources such as signal handlers (as opposed to multiple event
3035	loops - those are of course safe to use in different threads).	3308	loops - those are of course safe to use in different threads).
3036		3309
3037	Sometimes, however, you need to wake up an event loop you do not control,	3310	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>	3311	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.	3313	it by calling C<ev_async_send>, which is thread- and signal safe.
3041		3314
3042	This functionality is very similar to C<ev_signal> watchers, as signals,	3315	This functionality is very similar to C<ev_signal> watchers, as signals,
3043	too, are asynchronous in nature, and signals, too, will be compressed	3316	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	3317	(i.e. the number of callback invocations may be less than the number of
3045	C<ev_async_sent> calls).	3318	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
3046		3319	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	3320	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3048	just the default loop.	3321	even without knowing which loop owns the signal.
3049		3322
3050	=head3 Queueing	3323	=head3 Queueing
3051		3324
3052	C<ev_async> does not support queueing of data in any way. The reason	3325	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	3326	is that the author does not know of a simple (or any) algorithm for a
…		…
3145	trust me.	3418	trust me.
3146		3419
3147	=item ev_async_send (loop, ev_async *)	3420	=item ev_async_send (loop, ev_async *)
3148		3421
3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3422	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	3423	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3424	returns.
		3425
3151	C<ev_feed_event>, this call is safe to do from other threads, signal or	3426	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	3427	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3153	section below on what exactly this means).	3428	embedding section below on what exactly this means).
3154		3429
3155	Note that, as with other watchers in libev, multiple events might get	3430	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	3431	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>,	3432	this is that C<ev_async> watchers are level-triggered: they are set on
3158	reset when the event loop detects that).	3433	C<ev_async_send>, reset when the event loop detects that).
3159		3434
3160	This call incurs the overhead of a system call only once per event loop	3435	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	3436	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.	3437	the event loop (or your program) is processing events. That means that
		3438	repeated calls are basically free (there is no need to avoid calls for
		3439	performance reasons) and that the overhead becomes smaller (typically
		3440	zero) under load.
3163		3441
3164	=item bool = ev_async_pending (ev_async *)	3442	=item bool = ev_async_pending (ev_async *)
3165		3443
3166	Returns a non-zero value when C<ev_async_send> has been called on the	3444	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	3445	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);	3500	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3223		3501
3224	=item ev_feed_fd_event (loop, int fd, int revents)	3502	=item ev_feed_fd_event (loop, int fd, int revents)
3225		3503
3226	Feed an event on the given fd, as if a file descriptor backend detected	3504	Feed an event on the given fd, as if a file descriptor backend detected
3227	the given events it.	3505	the given events.
3228		3506
3229	=item ev_feed_signal_event (loop, int signum)	3507	=item ev_feed_signal_event (loop, int signum)
3230		3508
3231	Feed an event as if the given signal occurred (C<loop> must be the default	3509	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3232	loop!).	3510	which is async-safe.
3233		3511
3234	=back	3512	=back
		3513
		3514
		3515	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3516
		3517	This section explains some common idioms that are not immediately
		3518	obvious. Note that examples are sprinkled over the whole manual, and this
		3519	section only contains stuff that wouldn't fit anywhere else.
		3520
		3521	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3522
		3523	Each watcher has, by default, a C<void *data> member that you can read
		3524	or modify at any time: libev will completely ignore it. This can be used
		3525	to associate arbitrary data with your watcher. If you need more data and
		3526	don't want to allocate memory separately and store a pointer to it in that
		3527	data member, you can also "subclass" the watcher type and provide your own
		3528	data:
		3529
		3530	struct my_io
		3531	{
		3532	ev_io io;
		3533	int otherfd;
		3534	void *somedata;
		3535	struct whatever *mostinteresting;
		3536	};
		3537
		3538	...
		3539	struct my_io w;
		3540	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3541
		3542	And since your callback will be called with a pointer to the watcher, you
		3543	can cast it back to your own type:
		3544
		3545	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3546	{
		3547	struct my_io *w = (struct my_io *)w_;
		3548	...
		3549	}
		3550
		3551	More interesting and less C-conformant ways of casting your callback
		3552	function type instead have been omitted.
		3553
		3554	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3555
		3556	Another common scenario is to use some data structure with multiple
		3557	embedded watchers, in effect creating your own watcher that combines
		3558	multiple libev event sources into one "super-watcher":
		3559
		3560	struct my_biggy
		3561	{
		3562	int some_data;
		3563	ev_timer t1;
		3564	ev_timer t2;
		3565	}
		3566
		3567	In this case getting the pointer to C<my_biggy> is a bit more
		3568	complicated: Either you store the address of your C<my_biggy> struct in
		3569	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3570	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3571	real programmers):
		3572
		3573	#include <stddef.h>
		3574
		3575	static void
		3576	t1_cb (EV_P_ ev_timer *w, int revents)
		3577	{
		3578	struct my_biggy big = (struct my_biggy *)
		3579	(((char *)w) - offsetof (struct my_biggy, t1));
		3580	}
		3581
		3582	static void
		3583	t2_cb (EV_P_ ev_timer *w, int revents)
		3584	{
		3585	struct my_biggy big = (struct my_biggy *)
		3586	(((char *)w) - offsetof (struct my_biggy, t2));
		3587	}
		3588
		3589	=head2 AVOIDING FINISHING BEFORE RETURNING
		3590
		3591	Often you have structures like this in event-based programs:
		3592
		3593	callback ()
		3594	{
		3595	free (request);
		3596	}
		3597
		3598	request = start_new_request (..., callback);
		3599
		3600	The intent is to start some "lengthy" operation. The C<request> could be
		3601	used to cancel the operation, or do other things with it.
		3602
		3603	It's not uncommon to have code paths in C<start_new_request> that
		3604	immediately invoke the callback, for example, to report errors. Or you add
		3605	some caching layer that finds that it can skip the lengthy aspects of the
		3606	operation and simply invoke the callback with the result.
		3607
		3608	The problem here is that this will happen I<before> C<start_new_request>
		3609	has returned, so C<request> is not set.
		3610
		3611	Even if you pass the request by some safer means to the callback, you
		3612	might want to do something to the request after starting it, such as
		3613	canceling it, which probably isn't working so well when the callback has
		3614	already been invoked.
		3615
		3616	A common way around all these issues is to make sure that
		3617	C<start_new_request> I<always> returns before the callback is invoked. If
		3618	C<start_new_request> immediately knows the result, it can artificially
		3619	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3620	for example, or more sneakily, by reusing an existing (stopped) watcher
		3621	and pushing it into the pending queue:
		3622
		3623	ev_set_cb (watcher, callback);
		3624	ev_feed_event (EV_A_ watcher, 0);
		3625
		3626	This way, C<start_new_request> can safely return before the callback is
		3627	invoked, while not delaying callback invocation too much.
		3628
		3629	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3630
		3631	Often (especially in GUI toolkits) there are places where you have
		3632	I<modal> interaction, which is most easily implemented by recursively
		3633	invoking C<ev_run>.
		3634
		3635	This brings the problem of exiting - a callback might want to finish the
		3636	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3637	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3638	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3639	other combination: In these cases, C<ev_break> will not work alone.
		3640
		3641	The solution is to maintain "break this loop" variable for each C<ev_run>
		3642	invocation, and use a loop around C<ev_run> until the condition is
		3643	triggered, using C<EVRUN_ONCE>:
		3644
		3645	// main loop
		3646	int exit_main_loop = 0;
		3647
		3648	while (!exit_main_loop)
		3649	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3650
		3651	// in a modal watcher
		3652	int exit_nested_loop = 0;
		3653
		3654	while (!exit_nested_loop)
		3655	ev_run (EV_A_ EVRUN_ONCE);
		3656
		3657	To exit from any of these loops, just set the corresponding exit variable:
		3658
		3659	// exit modal loop
		3660	exit_nested_loop = 1;
		3661
		3662	// exit main program, after modal loop is finished
		3663	exit_main_loop = 1;
		3664
		3665	// exit both
		3666	exit_main_loop = exit_nested_loop = 1;
		3667
		3668	=head2 THREAD LOCKING EXAMPLE
		3669
		3670	Here is a fictitious example of how to run an event loop in a different
		3671	thread from where callbacks are being invoked and watchers are
		3672	created/added/removed.
		3673
		3674	For a real-world example, see the C<EV::Loop::Async> perl module,
		3675	which uses exactly this technique (which is suited for many high-level
		3676	languages).
		3677
		3678	The example uses a pthread mutex to protect the loop data, a condition
		3679	variable to wait for callback invocations, an async watcher to notify the
		3680	event loop thread and an unspecified mechanism to wake up the main thread.
		3681
		3682	First, you need to associate some data with the event loop:
		3683
		3684	typedef struct {
		3685	mutex_t lock; /* global loop lock */
		3686	ev_async async_w;
		3687	thread_t tid;
		3688	cond_t invoke_cv;
		3689	} userdata;
		3690
		3691	void prepare_loop (EV_P)
		3692	{
		3693	// for simplicity, we use a static userdata struct.
		3694	static userdata u;
		3695
		3696	ev_async_init (&u->async_w, async_cb);
		3697	ev_async_start (EV_A_ &u->async_w);
		3698
		3699	pthread_mutex_init (&u->lock, 0);
		3700	pthread_cond_init (&u->invoke_cv, 0);
		3701
		3702	// now associate this with the loop
		3703	ev_set_userdata (EV_A_ u);
		3704	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3705	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3706
		3707	// then create the thread running ev_run
		3708	pthread_create (&u->tid, 0, l_run, EV_A);
		3709	}
		3710
		3711	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3712	solely to wake up the event loop so it takes notice of any new watchers
		3713	that might have been added:
		3714
		3715	static void
		3716	async_cb (EV_P_ ev_async *w, int revents)
		3717	{
		3718	// just used for the side effects
		3719	}
		3720
		3721	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3722	protecting the loop data, respectively.
		3723
		3724	static void
		3725	l_release (EV_P)
		3726	{
		3727	userdata *u = ev_userdata (EV_A);
		3728	pthread_mutex_unlock (&u->lock);
		3729	}
		3730
		3731	static void
		3732	l_acquire (EV_P)
		3733	{
		3734	userdata *u = ev_userdata (EV_A);
		3735	pthread_mutex_lock (&u->lock);
		3736	}
		3737
		3738	The event loop thread first acquires the mutex, and then jumps straight
		3739	into C<ev_run>:
		3740
		3741	void *
		3742	l_run (void *thr_arg)
		3743	{
		3744	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3745
		3746	l_acquire (EV_A);
		3747	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3748	ev_run (EV_A_ 0);
		3749	l_release (EV_A);
		3750
		3751	return 0;
		3752	}
		3753
		3754	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3755	signal the main thread via some unspecified mechanism (signals? pipe
		3756	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3757	have been called (in a while loop because a) spurious wakeups are possible
		3758	and b) skipping inter-thread-communication when there are no pending
		3759	watchers is very beneficial):
		3760
		3761	static void
		3762	l_invoke (EV_P)
		3763	{
		3764	userdata *u = ev_userdata (EV_A);
		3765
		3766	while (ev_pending_count (EV_A))
		3767	{
		3768	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3769	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3770	}
		3771	}
		3772
		3773	Now, whenever the main thread gets told to invoke pending watchers, it
		3774	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3775	thread to continue:
		3776
		3777	static void
		3778	real_invoke_pending (EV_P)
		3779	{
		3780	userdata *u = ev_userdata (EV_A);
		3781
		3782	pthread_mutex_lock (&u->lock);
		3783	ev_invoke_pending (EV_A);
		3784	pthread_cond_signal (&u->invoke_cv);
		3785	pthread_mutex_unlock (&u->lock);
		3786	}
		3787
		3788	Whenever you want to start/stop a watcher or do other modifications to an
		3789	event loop, you will now have to lock:
		3790
		3791	ev_timer timeout_watcher;
		3792	userdata *u = ev_userdata (EV_A);
		3793
		3794	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3795
		3796	pthread_mutex_lock (&u->lock);
		3797	ev_timer_start (EV_A_ &timeout_watcher);
		3798	ev_async_send (EV_A_ &u->async_w);
		3799	pthread_mutex_unlock (&u->lock);
		3800
		3801	Note that sending the C<ev_async> watcher is required because otherwise
		3802	an event loop currently blocking in the kernel will have no knowledge
		3803	about the newly added timer. By waking up the loop it will pick up any new
		3804	watchers in the next event loop iteration.
		3805
		3806	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3807
		3808	While the overhead of a callback that e.g. schedules a thread is small, it
		3809	is still an overhead. If you embed libev, and your main usage is with some
		3810	kind of threads or coroutines, you might want to customise libev so that
		3811	doesn't need callbacks anymore.
		3812
		3813	Imagine you have coroutines that you can switch to using a function
		3814	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3815	and that due to some magic, the currently active coroutine is stored in a
		3816	global called C<current_coro>. Then you can build your own "wait for libev
		3817	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3818	the differing C<;> conventions):
		3819
		3820	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3821	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3822
		3823	That means instead of having a C callback function, you store the
		3824	coroutine to switch to in each watcher, and instead of having libev call
		3825	your callback, you instead have it switch to that coroutine.
		3826
		3827	A coroutine might now wait for an event with a function called
		3828	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3829	matter when, or whether the watcher is active or not when this function is
		3830	called):
		3831
		3832	void
		3833	wait_for_event (ev_watcher *w)
		3834	{
		3835	ev_cb_set (w) = current_coro;
		3836	switch_to (libev_coro);
		3837	}
		3838
		3839	That basically suspends the coroutine inside C<wait_for_event> and
		3840	continues the libev coroutine, which, when appropriate, switches back to
		3841	this or any other coroutine.
		3842
		3843	You can do similar tricks if you have, say, threads with an event queue -
		3844	instead of storing a coroutine, you store the queue object and instead of
		3845	switching to a coroutine, you push the watcher onto the queue and notify
		3846	any waiters.
		3847
		3848	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3849	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3850
		3851	// my_ev.h
		3852	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3853	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3854	#include "../libev/ev.h"
		3855
		3856	// my_ev.c
		3857	#define EV_H "my_ev.h"
		3858	#include "../libev/ev.c"
		3859
		3860	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3861	F<my_ev.c> into your project. When properly specifying include paths, you
		3862	can even use F<ev.h> as header file name directly.
3235		3863
3236		3864
3237	=head1 LIBEVENT EMULATION	3865	=head1 LIBEVENT EMULATION
3238		3866
3239	Libev offers a compatibility emulation layer for libevent. It cannot	3867	Libev offers a compatibility emulation layer for libevent. It cannot
3240	emulate the internals of libevent, so here are some usage hints:	3868	emulate the internals of libevent, so here are some usage hints:
3241		3869
3242	=over 4	3870	=over 4
		3871
		3872	=item * Only the libevent-1.4.1-beta API is being emulated.
		3873
		3874	This was the newest libevent version available when libev was implemented,
		3875	and is still mostly unchanged in 2010.
3243		3876
3244	=item * Use it by including <event.h>, as usual.	3877	=item * Use it by including <event.h>, as usual.
3245		3878
3246	=item * The following members are fully supported: ev_base, ev_callback,	3879	=item * The following members are fully supported: ev_base, ev_callback,
3247	ev_arg, ev_fd, ev_res, ev_events.	3880	ev_arg, ev_fd, ev_res, ev_events.
…		…
3253	=item * Priorities are not currently supported. Initialising priorities	3886	=item * Priorities are not currently supported. Initialising priorities
3254	will fail and all watchers will have the same priority, even though there	3887	will fail and all watchers will have the same priority, even though there
3255	is an ev_pri field.	3888	is an ev_pri field.
3256		3889
3257	=item * In libevent, the last base created gets the signals, in libev, the	3890	=item * In libevent, the last base created gets the signals, in libev, the
3258	first base created (== the default loop) gets the signals.	3891	base that registered the signal gets the signals.
3259		3892
3260	=item * Other members are not supported.	3893	=item * Other members are not supported.
3261		3894
3262	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3895	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3263	to use the libev header file and library.	3896	to use the libev header file and library.
…		…
3282	Care has been taken to keep the overhead low. The only data member the C++	3915	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	3916	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	3917	that the watcher is associated with (or no additional members at all if
3285	you disable C<EV_MULTIPLICITY> when embedding libev).	3918	you disable C<EV_MULTIPLICITY> when embedding libev).
3286		3919
3287	Currently, functions, and static and non-static member functions can be	3920	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	3921	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	3922	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	3923	you need support for other types of functors please contact the author
3291	it).	3924	(preferably after implementing it).
		3925
		3926	For all this to work, your C++ compiler either has to use the same calling
		3927	conventions as your C compiler (for static member functions), or you have
		3928	to embed libev and compile libev itself as C++.
3292		3929
3293	Here is a list of things available in the C<ev> namespace:	3930	Here is a list of things available in the C<ev> namespace:
3294		3931
3295	=over 4	3932	=over 4
3296		3933
…		…
3306	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3943	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3307		3944
3308	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3945	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>	3946	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	3947	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3311	defines by many implementations.	3948	defined by many implementations.
3312		3949
3313	All of those classes have these methods:	3950	All of those classes have these methods:
3314		3951
3315	=over 4	3952	=over 4
3316		3953
…		…
3449	watchers in the constructor.	4086	watchers in the constructor.
3450		4087
3451	class myclass	4088	class myclass
3452	{	4089	{
3453	ev::io io ; void io_cb (ev::io &w, int revents);	4090	ev::io io ; void io_cb (ev::io &w, int revents);
3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4091	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4092	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3456		4093
3457	myclass (int fd)	4094	myclass (int fd)
3458	{	4095	{
3459	io .set <myclass, &myclass::io_cb > (this);	4096	io .set <myclass, &myclass::io_cb > (this);
…		…
3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4147	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3511		4148
3512	=item D	4149	=item D
3513		4150
3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4151	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>.	4152	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3516		4153
3517	=item Ocaml	4154	=item Ocaml
3518		4155
3519	Erkki Seppala has written Ocaml bindings for libev, to be found at	4156	Erkki Seppala has written Ocaml bindings for libev, to be found at
3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4157	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3568	suitable for use with C<EV_A>.	4205	suitable for use with C<EV_A>.
3569		4206
3570	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4207	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3571		4208
3572	Similar to the other two macros, this gives you the value of the default	4209	Similar to the other two macros, this gives you the value of the default
3573	loop, if multiple loops are supported ("ev loop default").	4210	loop, if multiple loops are supported ("ev loop default"). The default loop
		4211	will be initialised if it isn't already initialised.
		4212
		4213	For non-multiplicity builds, these macros do nothing, so you always have
		4214	to initialise the loop somewhere.
3574		4215
3575	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4216	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3576		4217
3577	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4218	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	4219	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3723	supported). It will also not define any of the structs usually found in	4364	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.	4365	F<event.h> that are not directly supported by the libev core alone.
3725		4366
3726	In standalone mode, libev will still try to automatically deduce the	4367	In standalone mode, libev will still try to automatically deduce the
3727	configuration, but has to be more conservative.	4368	configuration, but has to be more conservative.
		4369
		4370	=item EV_USE_FLOOR
		4371
		4372	If defined to be C<1>, libev will use the C<floor ()> function for its
		4373	periodic reschedule calculations, otherwise libev will fall back on a
		4374	portable (slower) implementation. If you enable this, you usually have to
		4375	link against libm or something equivalent. Enabling this when the C<floor>
		4376	function is not available will fail, so the safe default is to not enable
		4377	this.
3728		4378
3729	=item EV_USE_MONOTONIC	4379	=item EV_USE_MONOTONIC
3730		4380
3731	If defined to be C<1>, libev will try to detect the availability of the	4381	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	4382	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3862	If defined to be C<1>, libev will compile in support for the Linux inotify	4512	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	4513	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	4514	be detected at runtime. If undefined, it will be enabled if the headers
3865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4515	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3866		4516
		4517	=item EV_NO_SMP
		4518
		4519	If defined to be C<1>, libev will assume that memory is always coherent
		4520	between threads, that is, threads can be used, but threads never run on
		4521	different cpus (or different cpu cores). This reduces dependencies
		4522	and makes libev faster.
		4523
		4524	=item EV_NO_THREADS
		4525
		4526	If defined to be C<1>, libev will assume that it will never be called
		4527	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4528	above. This reduces dependencies and makes libev faster.
		4529
3867	=item EV_ATOMIC_T	4530	=item EV_ATOMIC_T
3868		4531
3869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4532	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	4533	access is atomic and serialised with respect to other threads or signal
3871	type is easily found in the C language, so you can provide your own type	4534	contexts. No such type is easily found in the C language, so you can
3872	that you know is safe for your purposes. It is used both for signal handler "locking"	4535	provide your own type that you know is safe for your purposes. It is used
3873	as well as for signal and thread safety in C<ev_async> watchers.	4536	both for signal handler "locking" as well as for signal and thread safety
		4537	in C<ev_async> watchers.
3874		4538
3875	In the absence of this define, libev will use C<sig_atomic_t volatile>	4539	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.	4540	(from F<signal.h>), which is usually good enough on most platforms,
		4541	although strictly speaking using a type that also implies a memory fence
		4542	is required.
3877		4543
3878	=item EV_H (h)	4544	=item EV_H (h)
3879		4545
3880	The name of the F<ev.h> header file used to include it. The default if	4546	The name of the F<ev.h> header file used to include it. The default if
3881	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4547	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
…		…
3905	will have the C<struct ev_loop *> as first argument, and you can create	4571	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	4572	additional independent event loops. Otherwise there will be no support
3907	for multiple event loops and there is no first event loop pointer	4573	for multiple event loops and there is no first event loop pointer
3908	argument. Instead, all functions act on the single default loop.	4574	argument. Instead, all functions act on the single default loop.
3909		4575
		4576	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4577	default loop when multiplicity is switched off - you always have to
		4578	initialise the loop manually in this case.
		4579
3910	=item EV_MINPRI	4580	=item EV_MINPRI
3911		4581
3912	=item EV_MAXPRI	4582	=item EV_MAXPRI
3913		4583
3914	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4584	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4011		4681
4012	With an intelligent-enough linker (gcc+binutils are intelligent enough	4682	With an intelligent-enough linker (gcc+binutils are intelligent enough
4013	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4683	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	4684	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.	4685	I/O watcher then might come out at only 5Kb.
		4686
		4687	=item EV_API_STATIC
		4688
		4689	If this symbol is defined (by default it is not), then all identifiers
		4690	will have static linkage. This means that libev will not export any
		4691	identifiers, and you cannot link against libev anymore. This can be useful
		4692	when you embed libev, only want to use libev functions in a single file,
		4693	and do not want its identifiers to be visible.
		4694
		4695	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4696	wants to use libev.
		4697
		4698	This option only works when libev is compiled with a C compiler, as C++
		4699	doesn't support the required declaration syntax.
4016		4700
4017	=item EV_AVOID_STDIO	4701	=item EV_AVOID_STDIO
4018		4702
4019	If this is set to C<1> at compiletime, then libev will avoid using stdio	4703	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	4704	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:	4848	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4165		4849
4166	#include "ev_cpp.h"	4850	#include "ev_cpp.h"
4167	#include "ev.c"	4851	#include "ev.c"
4168		4852
4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4853	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4170		4854
4171	=head2 THREADS AND COROUTINES	4855	=head2 THREADS AND COROUTINES
4172		4856
4173	=head3 THREADS	4857	=head3 THREADS
4174		4858
…		…
4225	default loop and triggering an C<ev_async> watcher from the default loop	4909	default loop and triggering an C<ev_async> watcher from the default loop
4226	watcher callback into the event loop interested in the signal.	4910	watcher callback into the event loop interested in the signal.
4227		4911
4228	=back	4912	=back
4229		4913
4230	=head4 THREAD LOCKING EXAMPLE	4914	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		4915
4368	=head3 COROUTINES	4916	=head3 COROUTINES
4369		4917
4370	Libev is very accommodating to coroutines ("cooperative threads"):	4918	Libev is very accommodating to coroutines ("cooperative threads"):
4371	libev fully supports nesting calls to its functions from different	4919	libev fully supports nesting calls to its functions from different
…		…
4467	=head3 C<kqueue> is buggy	5015	=head3 C<kqueue> is buggy
4468		5016
4469	The kqueue syscall is broken in all known versions - most versions support	5017	The kqueue syscall is broken in all known versions - most versions support
4470	only sockets, many support pipes.	5018	only sockets, many support pipes.
4471		5019
4472	Libev tries to work around this by not using C<kqueue> by default on	5020	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	5021	rotten platform, but of course you can still ask for it when creating a
4474	a loop.	5022	loop - embedding a socket-only kqueue loop into a select-based one is
		5023	probably going to work well.
4475		5024
4476	=head3 C<poll> is buggy	5025	=head3 C<poll> is buggy
4477		5026
4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5027	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4479	implementation by something calling C<kqueue> internally around the 10.5.6	5028	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4498		5047
4499	=head3 C<errno> reentrancy	5048	=head3 C<errno> reentrancy
4500		5049
4501	The default compile environment on Solaris is unfortunately so	5050	The default compile environment on Solaris is unfortunately so
4502	thread-unsafe that you can't even use components/libraries compiled	5051	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,	5052	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4504	isn't defined by default.	5053	defined by default. A valid, if stupid, implementation choice.
4505		5054
4506	If you want to use libev in threaded environments you have to make sure	5055	If you want to use libev in threaded environments you have to make sure
4507	it's compiled with C<_REENTRANT> defined.	5056	it's compiled with C<_REENTRANT> defined.
4508		5057
4509	=head3 Event port backend	5058	=head3 Event port backend
4510		5059
4511	The scalable event interface for Solaris is called "event ports". Unfortunately,	5060	The scalable event interface for Solaris is called "event
4512	this mechanism is very buggy. If you run into high CPU usage, your program	5061	ports". Unfortunately, this mechanism is very buggy in all major
		5062	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	5063	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	5064	and latest kernel patches applied. No, I don't know which ones, but there
4515	ones, but there are multiple ones.	5065	are multiple ones to apply, and afterwards, event ports actually work
		5066	great.
4516		5067
4517	If you can't get it to work, you can try running the program by setting	5068	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	5069	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4519	C<select> backends.	5070	C<select> backends.
4520		5071
4521	=head2 AIX POLL BUG	5072	=head2 AIX POLL BUG
4522		5073
4523	AIX unfortunately has a broken C<poll.h> header. Libev works around	5074	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	5075	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	5076	compiled in), which normally isn't a big problem as C<select> works fine
4526	with large bitsets, and AIX is dead anyway.	5077	with large bitsets on AIX, and AIX is dead anyway.
4527		5078
4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5079	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4529		5080
4530	=head3 General issues	5081	=head3 General issues
4531		5082
…		…
4533	requires, and its I/O model is fundamentally incompatible with the POSIX	5084	requires, and its I/O model is fundamentally incompatible with the POSIX
4534	model. Libev still offers limited functionality on this platform in	5085	model. Libev still offers limited functionality on this platform in
4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5086	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4536	descriptors. This only applies when using Win32 natively, not when using	5087	descriptors. This only applies when using Win32 natively, not when using
4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5088	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4538	as every compielr comes with a slightly differently broken/incompatible	5089	as every compiler comes with a slightly differently broken/incompatible
4539	environment.	5090	environment.
4540		5091
4541	Lifting these limitations would basically require the full	5092	Lifting these limitations would basically require the full
4542	re-implementation of the I/O system. If you are into this kind of thing,	5093	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	5094	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	5188	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	5189	assumes that the same (machine) code can be used to call any watcher
4639	callback: The watcher callbacks have different type signatures, but libev	5190	callback: The watcher callbacks have different type signatures, but libev
4640	calls them using an C<ev_watcher *> internally.	5191	calls them using an C<ev_watcher *> internally.
4641		5192
		5193	=item pointer accesses must be thread-atomic
		5194
		5195	Accessing a pointer value must be atomic, it must both be readable and
		5196	writable in one piece - this is the case on all current architectures.
		5197
4642	=item C<sig_atomic_t volatile> must be thread-atomic as well	5198	=item C<sig_atomic_t volatile> must be thread-atomic as well
4643		5199
4644	The type C<sig_atomic_t volatile> (or whatever is defined as	5200	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	5201	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	5202	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4671		5227
4672	The type C<double> is used to represent timestamps. It is required to	5228	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	5229	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	5230	good enough for at least into the year 4000 with millisecond accuracy
4675	(the design goal for libev). This requirement is overfulfilled by	5231	(the design goal for libev). This requirement is overfulfilled by
4676	implementations using IEEE 754, which is basically all existing ones. With	5232	implementations using IEEE 754, which is basically all existing ones.
		5233
4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5234	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5235	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5236	is either obsolete or somebody patched it to use C<long double> or
		5237	something like that, just kidding).
4678		5238
4679	=back	5239	=back
4680		5240
4681	If you know of other additional requirements drop me a note.	5241	If you know of other additional requirements drop me a note.
4682		5242
…		…
4744	=item Processing ev_async_send: O(number_of_async_watchers)	5304	=item Processing ev_async_send: O(number_of_async_watchers)
4745		5305
4746	=item Processing signals: O(max_signal_number)	5306	=item Processing signals: O(max_signal_number)
4747		5307
4748	Sending involves a system call I<iff> there were no other C<ev_async_send>	5308	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	5309	calls in the current loop iteration and the loop is currently
		5310	blocked. Checking for async and signal events involves iterating over all
4750	involves iterating over all running async watchers or all signal numbers.	5311	running async watchers or all signal numbers.
4751		5312
4752	=back	5313	=back
4753		5314
4754		5315
4755	=head1 PORTING FROM LIBEV 3.X TO 4.X	5316	=head1 PORTING FROM LIBEV 3.X TO 4.X
4756		5317
4757	The major version 4 introduced some minor incompatible changes to the API.	5318	The major version 4 introduced some incompatible changes to the API.
4758		5319
4759	At the moment, the C<ev.h> header file tries to implement superficial	5320	At the moment, the C<ev.h> header file provides compatibility definitions
4760	compatibility, so most programs should still compile. Those might be	5321	for all changes, so most programs should still compile. The compatibility
4761	removed in later versions of libev, so better update early than late.	5322	layer might be removed in later versions of libev, so better update to the
		5323	new API early than late.
4762		5324
4763	=over 4	5325	=over 4
		5326
		5327	=item C<EV_COMPAT3> backwards compatibility mechanism
		5328
		5329	The backward compatibility mechanism can be controlled by
		5330	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5331	section.
		5332
		5333	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5334
		5335	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5336
		5337	ev_loop_destroy (EV_DEFAULT_UC);
		5338	ev_loop_fork (EV_DEFAULT);
4764		5339
4765	=item function/symbol renames	5340	=item function/symbol renames
4766		5341
4767	A number of functions and symbols have been renamed:	5342	A number of functions and symbols have been renamed:
4768		5343
…		…
4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5362	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	5363	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>	5364	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4790	typedef.	5365	typedef.
4791		5366
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>	5367	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4799		5368
4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5369	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5370	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4802	and work, but the library code will of course be larger.	5371	and work, but the library code will of course be larger.
…		…
4808		5377
4809	=over 4	5378	=over 4
4810		5379
4811	=item active	5380	=item active
4812		5381
4813	A watcher is active as long as it has been started (has been attached to	5382	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).	5383	See L<WATCHER STATES> for details.
4815		5384
4816	=item application	5385	=item application
4817		5386
4818	In this document, an application is whatever is using libev.	5387	In this document, an application is whatever is using libev.
		5388
		5389	=item backend
		5390
		5391	The part of the code dealing with the operating system interfaces.
4819		5392
4820	=item callback	5393	=item callback
4821		5394
4822	The address of a function that is called when some event has been	5395	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	5396	detected. Callbacks are being passed the event loop, the watcher that
4824	received the event, and the actual event bitset.	5397	received the event, and the actual event bitset.
4825		5398
4826	=item callback invocation	5399	=item callback/watcher invocation
4827		5400
4828	The act of calling the callback associated with a watcher.	5401	The act of calling the callback associated with a watcher.
4829		5402
4830	=item event	5403	=item event
4831		5404
…		…
4850	The model used to describe how an event loop handles and processes	5423	The model used to describe how an event loop handles and processes
4851	watchers and events.	5424	watchers and events.
4852		5425
4853	=item pending	5426	=item pending
4854		5427
4855	A watcher is pending as soon as the corresponding event has been detected,	5428	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	5429	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		5430
4862	=item real time	5431	=item real time
4863		5432
4864	The physical time that is observed. It is apparently strictly monotonic :)	5433	The physical time that is observed. It is apparently strictly monotonic :)
4865		5434
4866	=item wall-clock time	5435	=item wall-clock time
4867		5436
4868	The time and date as shown on clocks. Unlike real time, it can actually	5437	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	5438	be wrong and jump forwards and backwards, e.g. when you adjust your
4870	clock.	5439	clock.
4871		5440
4872	=item watcher	5441	=item watcher
4873		5442
4874	A data structure that describes interest in certain events. Watchers need	5443	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.	5444	to be started (attached to an event loop) before they can receive events.
4876		5445
4877	=item watcher invocation
4878
4879	The act of calling the callback associated with a watcher.
4880
4881	=back	5446	=back
4882		5447
4883	=head1 AUTHOR	5448	=head1 AUTHOR
4884		5449
4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5450	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5451	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4886		5452

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