ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.316 by root, Fri Oct 22 09:34:01 2010 UTC vs.
Revision 1.420 by root, Sun Jul 1 19:58:12 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) throw ())
236		253
237	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
266	}	283	}
267		284
268	...	285	...
269	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
270		287
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		289
273	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	305	}
289		306
290	...	307	...
291	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
292		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
293	=back	323	=back
294		324
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		326
297	An event loop is described by a C<struct ev_loop *> (the C<struct> is	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	I<not> optional in this case unless libev 3 compatibility is disabled, as	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	libev 3 had an C<ev_loop> function colliding with the struct name).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
300		330
301	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created event loops	332	supports child process events, and dynamically created event loops which
303	which do not.	333	do not.
304		334
305	=over 4	335	=over 4
306		336
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		338
309	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
313		349
314	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
315	function.	351	function (or via the C<EV_DEFAULT> macro).
316		352
317	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
320		357
321	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
327		382
328	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		385
331	The following flags are supported:	386	The following flags are supported:
…		…
366	environment variable.	421	environment variable.
367		422
368	=item C<EVFLAG_NOINOTIFY>	423	=item C<EVFLAG_NOINOTIFY>
369		424
370	When this flag is specified, then libev will not attempt to use the	425	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	426	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	427	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	428	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		429
375	=item C<EVFLAG_SIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will attempt to use the	432	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	434	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	435	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	436	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	437	threads that are not interested in handling them.
383		438
384	Signalfd will not be used by default as this changes your signal mask, and	439	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	440	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	441	example) that can't properly initialise their signal masks.
		442
		443	=item C<EVFLAG_NOSIGMASK>
		444
		445	When this flag is specified, then libev will avoid to modify the signal
		446	mask. Specifically, this means you have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
387		457
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		459
390	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		490
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	492	kernels).
423		493
424	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
428		498
429	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	508	and is of course hard to detect.
437		509
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	520	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
447		526
448	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
488		567
489	It scales in the same way as the epoll backend, but the interface to the	568	It scales in the same way as the epoll backend, but the interface to the
490	kernel is more efficient (which says nothing about its actual speed, of	569	kernel is more efficient (which says nothing about its actual speed, of
491	course). While stopping, setting and starting an I/O watcher does never	570	course). While stopping, setting and starting an I/O watcher does never
492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	571	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
493	two event changes per incident. Support for C<fork ()> is very bad (but	572	two event changes per incident. Support for C<fork ()> is very bad (you
494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	573	might have to leak fd's on fork, but it's more sane than epoll) and it
495	cases	574	drops fds silently in similarly hard-to-detect cases
496		575
497	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
498		577
499	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
500	everywhere, so you might need to test for this. And since it is broken	579	everywhere, so you might need to test for this. And since it is broken
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		597
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
521		600
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	604	might perform better.
530		605
531	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
535		620
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
538		623
539	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
540		625
541	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		629
545	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		639
547	=back	640	=back
548		641
549	If one or more of the backend flags are or'ed into the flags value,	642	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	643	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	644	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	645	()> will be tried.
553		646
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
581		648
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	650	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
585		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
586	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
587		659
588	Destroys the default loop (frees all memory and kernel state etc.). None	660	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	661	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	662	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	663	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	664	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		666	for example).
594		667
595	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
598		671
599	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	679	and C<ev_loop_destroy>.
603		680
604	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
605		682
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610
611	This function sets a flag that causes subsequent C<ev_run> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
612	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
613	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
614	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
615	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
616	functions, and it will only take effect at the next C<ev_run> iteration.
617		688
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	689	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	690	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	692	during fork.
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	697	call it at all (in fact, C<epoll> is so badly broken that it makes a
627	difference, but libev will usually detect this case on its own and do a	698	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	699	costly reset of the backend).
629		700
630	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
631	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
634	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
635
636	=item ev_loop_fork (loop)
637
638	Like C<ev_default_fork>, but acts on an event loop created by
639	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
640	after fork that you want to re-use in the child, and how you keep track of
641	them is entirely your own problem.
642		715
643	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
644		717
645	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	719	otherwise.
…		…
657	prepare and check phases.	730	prepare and check phases.
658		731
659	=item unsigned int ev_depth (loop)	732	=item unsigned int ev_depth (loop)
660		733
661	Returns the number of times C<ev_run> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
662	times C<ev_run> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
663		736
664	Outside C<ev_run>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	739	in which case it is higher.
667		740
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
669	etc.), doesn't count as "exit" - consider this as a hint to avoid such	742	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
671		745
672	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
673		747
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	749	use.
…		…
690		764
691	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
692	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
693	the current time is a good idea.	767	the current time is a good idea.
694		768
695	See also L<The special problem of time updates> in the C<ev_timer> section.	769	See also L</The special problem of time updates> in the C<ev_timer> section.
696		770
697	=item ev_suspend (loop)	771	=item ev_suspend (loop)
698		772
699	=item ev_resume (loop)	773	=item ev_resume (loop)
700		774
…		…
718	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
719		793
720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
721	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
722		796
723	=item ev_run (loop, int flags)	797	=item bool ev_run (loop, int flags)
724		798
725	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
726	after you have initialised all your watchers and you want to start	800	after you have initialised all your watchers and you want to start
727	handling events. It will ask the operating system for any new events, call	801	handling events. It will ask the operating system for any new events, call
728	the watcher callbacks, an then repeat the whole process indefinitely: This	802	the watcher callbacks, and then repeat the whole process indefinitely: This
729	is why event loops are called I<loops>.	803	is why event loops are called I<loops>.
730		804
731	If the flags argument is specified as C<0>, it will keep handling events	805	If the flags argument is specified as C<0>, it will keep handling events
732	until either no event watchers are active anymore or C<ev_break> was	806	until either no event watchers are active anymore or C<ev_break> was
733	called.	807	called.
		808
		809	The return value is false if there are no more active watchers (which
		810	usually means "all jobs done" or "deadlock"), and true in all other cases
		811	(which usually means " you should call C<ev_run> again").
734		812
735	Please note that an explicit C<ev_break> is usually better than	813	Please note that an explicit C<ev_break> is usually better than
736	relying on all watchers to be stopped when deciding when a program has	814	relying on all watchers to be stopped when deciding when a program has
737	finished (especially in interactive programs), but having a program	815	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	816	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	817	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	818	beauty.
741		819
		820	This function is I<mostly> exception-safe - you can break out of a
		821	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		822	exception and so on. This does not decrement the C<ev_depth> value, nor
		823	will it clear any outstanding C<EVBREAK_ONE> breaks.
		824
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	825	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
743	those events and any already outstanding ones, but will not wait and	826	those events and any already outstanding ones, but will not wait and
744	block your process in case there are no events and will return after one	827	block your process in case there are no events and will return after one
745	iteration of the loop. This is sometimes useful to poll and handle new	828	iteration of the loop. This is sometimes useful to poll and handle new
746	events while doing lengthy calculations, to keep the program responsive.	829	events while doing lengthy calculations, to keep the program responsive.
…		…
755	This is useful if you are waiting for some external event in conjunction	838	This is useful if you are waiting for some external event in conjunction
756	with something not expressible using other libev watchers (i.e. "roll your	839	with something not expressible using other libev watchers (i.e. "roll your
757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	840	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
758	usually a better approach for this kind of thing.	841	usually a better approach for this kind of thing.
759		842
760	Here are the gory details of what C<ev_run> does:	843	Here are the gory details of what C<ev_run> does (this is for your
		844	understanding, not a guarantee that things will work exactly like this in
		845	future versions):
761		846
762	- Increment loop depth.	847	- Increment loop depth.
763	- Reset the ev_break status.	848	- Reset the ev_break status.
764	- Before the first iteration, call any pending watchers.	849	- Before the first iteration, call any pending watchers.
765	LOOP:	850	LOOP:
…		…
798	anymore.	883	anymore.
799		884
800	... queue jobs here, make sure they register event watchers as long	885	... queue jobs here, make sure they register event watchers as long
801	... as they still have work to do (even an idle watcher will do..)	886	... as they still have work to do (even an idle watcher will do..)
802	ev_run (my_loop, 0);	887	ev_run (my_loop, 0);
803	... jobs done or somebody called unloop. yeah!	888	... jobs done or somebody called break. yeah!
804		889
805	=item ev_break (loop, how)	890	=item ev_break (loop, how)
806		891
807	Can be used to make a call to C<ev_run> return early (but only after it	892	Can be used to make a call to C<ev_run> return early (but only after it
808	has processed all outstanding events). The C<how> argument must be either	893	has processed all outstanding events). The C<how> argument must be either
809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	894	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	895	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		896
812	This "unloop state" will be cleared when entering C<ev_run> again.	897	This "break state" will be cleared on the next call to C<ev_run>.
813		898
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	899	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		900	which case it will have no effect.
815		901
816	=item ev_ref (loop)	902	=item ev_ref (loop)
817		903
818	=item ev_unref (loop)	904	=item ev_unref (loop)
819		905
…		…
840	running when nothing else is active.	926	running when nothing else is active.
841		927
842	ev_signal exitsig;	928	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	929	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	930	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	931	ev_unref (loop);
846		932
847	Example: For some weird reason, unregister the above signal handler again.	933	Example: For some weird reason, unregister the above signal handler again.
848		934
849	ev_ref (loop);	935	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	936	ev_signal_stop (loop, &exitsig);
…		…
870	overhead for the actual polling but can deliver many events at once.	956	overhead for the actual polling but can deliver many events at once.
871		957
872	By setting a higher I<io collect interval> you allow libev to spend more	958	By setting a higher I<io collect interval> you allow libev to spend more
873	time collecting I/O events, so you can handle more events per iteration,	959	time collecting I/O events, so you can handle more events per iteration,
874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	960	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
875	C<ev_timer>) will be not affected. Setting this to a non-null value will	961	C<ev_timer>) will not be affected. Setting this to a non-null value will
876	introduce an additional C<ev_sleep ()> call into most loop iterations. The	962	introduce an additional C<ev_sleep ()> call into most loop iterations. The
877	sleep time ensures that libev will not poll for I/O events more often then	963	sleep time ensures that libev will not poll for I/O events more often then
878	once per this interval, on average.	964	once per this interval, on average (as long as the host time resolution is
		965	good enough).
879		966
880	Likewise, by setting a higher I<timeout collect interval> you allow libev	967	Likewise, by setting a higher I<timeout collect interval> you allow libev
881	to spend more time collecting timeouts, at the expense of increased	968	to spend more time collecting timeouts, at the expense of increased
882	latency/jitter/inexactness (the watcher callback will be called	969	latency/jitter/inexactness (the watcher callback will be called
883	later). C<ev_io> watchers will not be affected. Setting this to a non-null	970	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
929	invoke the actual watchers inside another context (another thread etc.).	1016	invoke the actual watchers inside another context (another thread etc.).
930		1017
931	If you want to reset the callback, use C<ev_invoke_pending> as new	1018	If you want to reset the callback, use C<ev_invoke_pending> as new
932	callback.	1019	callback.
933		1020
934	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1021	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
935		1022
936	Sometimes you want to share the same loop between multiple threads. This	1023	Sometimes you want to share the same loop between multiple threads. This
937	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
938	each call to a libev function.	1025	each call to a libev function.
939		1026
940	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
941	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
942	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
943	I<release> and I<acquire> callbacks on the loop.	1030	I<release> and I<acquire> callbacks on the loop.
944		1031
945	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
946	suspended waiting for new events, and C<acquire> is called just	1033	suspended waiting for new events, and C<acquire> is called just
947	afterwards.	1034	afterwards.
…		…
962	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
963	document.	1050	document.
964		1051
965	=item ev_set_userdata (loop, void *data)	1052	=item ev_set_userdata (loop, void *data)
966		1053
967	=item ev_userdata (loop)	1054	=item void *ev_userdata (loop)
968		1055
969	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
970	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
971	C<0.>	1058	C<0>.
972		1059
973	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,
974	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
975	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
976	any other purpose as well.	1063	any other purpose as well.
…		…
1087		1174
1088	=item C<EV_PREPARE>	1175	=item C<EV_PREPARE>
1089		1176
1090	=item C<EV_CHECK>	1177	=item C<EV_CHECK>
1091		1178
1092	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1179	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1093	to gather new events, and all C<ev_check> watchers are invoked just after	1180	gather new events, and all C<ev_check> watchers are queued (not invoked)
1094	C<ev_run> has gathered them, but before it invokes any callbacks for any	1181	just after C<ev_run> has gathered them, but before it queues any callbacks
		1182	for any received events. That means C<ev_prepare> watchers are the last
		1183	watchers invoked before the event loop sleeps or polls for new events, and
		1184	C<ev_check> watchers will be invoked before any other watchers of the same
		1185	or lower priority within an event loop iteration.
		1186
1095	received events. Callbacks of both watcher types can start and stop as	1187	Callbacks of both watcher types can start and stop as many watchers as
1096	many watchers as they want, and all of them will be taken into account	1188	they want, and all of them will be taken into account (for example, a
1097	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1189	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1098	C<ev_run> from blocking).	1190	blocking).
1099		1191
1100	=item C<EV_EMBED>	1192	=item C<EV_EMBED>
1101		1193
1102	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1194	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1103		1195
1104	=item C<EV_FORK>	1196	=item C<EV_FORK>
1105		1197
1106	The event loop has been resumed in the child process after fork (see	1198	The event loop has been resumed in the child process after fork (see
1107	C<ev_fork>).	1199	C<ev_fork>).
		1200
		1201	=item C<EV_CLEANUP>
		1202
		1203	The event loop is about to be destroyed (see C<ev_cleanup>).
1108		1204
1109	=item C<EV_ASYNC>	1205	=item C<EV_ASYNC>
1110		1206
1111	The given async watcher has been asynchronously notified (see C<ev_async>).	1207	The given async watcher has been asynchronously notified (see C<ev_async>).
1112		1208
…		…
1134	programs, though, as the fd could already be closed and reused for another	1230	programs, though, as the fd could already be closed and reused for another
1135	thing, so beware.	1231	thing, so beware.
1136		1232
1137	=back	1233	=back
1138		1234
		1235	=head2 GENERIC WATCHER FUNCTIONS
		1236
		1237	=over 4
		1238
		1239	=item C<ev_init> (ev_TYPE *watcher, callback)
		1240
		1241	This macro initialises the generic portion of a watcher. The contents
		1242	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1243	the generic parts of the watcher are initialised, you I<need> to call
		1244	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1245	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1246	which rolls both calls into one.
		1247
		1248	You can reinitialise a watcher at any time as long as it has been stopped
		1249	(or never started) and there are no pending events outstanding.
		1250
		1251	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1252	int revents)>.
		1253
		1254	Example: Initialise an C<ev_io> watcher in two steps.
		1255
		1256	ev_io w;
		1257	ev_init (&w, my_cb);
		1258	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1259
		1260	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1261
		1262	This macro initialises the type-specific parts of a watcher. You need to
		1263	call C<ev_init> at least once before you call this macro, but you can
		1264	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1265	macro on a watcher that is active (it can be pending, however, which is a
		1266	difference to the C<ev_init> macro).
		1267
		1268	Although some watcher types do not have type-specific arguments
		1269	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1270
		1271	See C<ev_init>, above, for an example.
		1272
		1273	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1274
		1275	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1276	calls into a single call. This is the most convenient method to initialise
		1277	a watcher. The same limitations apply, of course.
		1278
		1279	Example: Initialise and set an C<ev_io> watcher in one step.
		1280
		1281	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1282
		1283	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1284
		1285	Starts (activates) the given watcher. Only active watchers will receive
		1286	events. If the watcher is already active nothing will happen.
		1287
		1288	Example: Start the C<ev_io> watcher that is being abused as example in this
		1289	whole section.
		1290
		1291	ev_io_start (EV_DEFAULT_UC, &w);
		1292
		1293	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1294
		1295	Stops the given watcher if active, and clears the pending status (whether
		1296	the watcher was active or not).
		1297
		1298	It is possible that stopped watchers are pending - for example,
		1299	non-repeating timers are being stopped when they become pending - but
		1300	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1301	pending. If you want to free or reuse the memory used by the watcher it is
		1302	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1303
		1304	=item bool ev_is_active (ev_TYPE *watcher)
		1305
		1306	Returns a true value iff the watcher is active (i.e. it has been started
		1307	and not yet been stopped). As long as a watcher is active you must not modify
		1308	it.
		1309
		1310	=item bool ev_is_pending (ev_TYPE *watcher)
		1311
		1312	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1313	events but its callback has not yet been invoked). As long as a watcher
		1314	is pending (but not active) you must not call an init function on it (but
		1315	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1316	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1317	it).
		1318
		1319	=item callback ev_cb (ev_TYPE *watcher)
		1320
		1321	Returns the callback currently set on the watcher.
		1322
		1323	=item ev_set_cb (ev_TYPE *watcher, callback)
		1324
		1325	Change the callback. You can change the callback at virtually any time
		1326	(modulo threads).
		1327
		1328	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1329
		1330	=item int ev_priority (ev_TYPE *watcher)
		1331
		1332	Set and query the priority of the watcher. The priority is a small
		1333	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1334	(default: C<-2>). Pending watchers with higher priority will be invoked
		1335	before watchers with lower priority, but priority will not keep watchers
		1336	from being executed (except for C<ev_idle> watchers).
		1337
		1338	If you need to suppress invocation when higher priority events are pending
		1339	you need to look at C<ev_idle> watchers, which provide this functionality.
		1340
		1341	You I<must not> change the priority of a watcher as long as it is active or
		1342	pending.
		1343
		1344	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1345	fine, as long as you do not mind that the priority value you query might
		1346	or might not have been clamped to the valid range.
		1347
		1348	The default priority used by watchers when no priority has been set is
		1349	always C<0>, which is supposed to not be too high and not be too low :).
		1350
		1351	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1352	priorities.
		1353
		1354	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1355
		1356	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1357	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1358	can deal with that fact, as both are simply passed through to the
		1359	callback.
		1360
		1361	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1362
		1363	If the watcher is pending, this function clears its pending status and
		1364	returns its C<revents> bitset (as if its callback was invoked). If the
		1365	watcher isn't pending it does nothing and returns C<0>.
		1366
		1367	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1368	callback to be invoked, which can be accomplished with this function.
		1369
		1370	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1371
		1372	Feeds the given event set into the event loop, as if the specified event
		1373	had happened for the specified watcher (which must be a pointer to an
		1374	initialised but not necessarily started event watcher). Obviously you must
		1375	not free the watcher as long as it has pending events.
		1376
		1377	Stopping the watcher, letting libev invoke it, or calling
		1378	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1379	not started in the first place.
		1380
		1381	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1382	functions that do not need a watcher.
		1383
		1384	=back
		1385
		1386	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1387	OWN COMPOSITE WATCHERS> idioms.
		1388
1139	=head2 WATCHER STATES	1389	=head2 WATCHER STATES
1140		1390
1141	There are various watcher states mentioned throughout this manual -	1391	There are various watcher states mentioned throughout this manual -
1142	active, pending and so on. In this section these states and the rules to	1392	active, pending and so on. In this section these states and the rules to
1143	transition between them will be described in more detail - and while these	1393	transition between them will be described in more detail - and while these
…		…
1145		1395
1146	=over 4	1396	=over 4
1147		1397
1148	=item initialiased	1398	=item initialiased
1149		1399
1150	Before a watcher can be registered with the event looop it has to be	1400	Before a watcher can be registered with the event loop it has to be
1151	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1401	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1152	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1402	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1153		1403
1154	In this state it is simply some block of memory that is suitable for use	1404	In this state it is simply some block of memory that is suitable for
1155	in an event loop. It can be moved around, freed, reused etc. at will.	1405	use in an event loop. It can be moved around, freed, reused etc. at
		1406	will - as long as you either keep the memory contents intact, or call
		1407	C<ev_TYPE_init> again.
1156		1408
1157	=item started/running/active	1409	=item started/running/active
1158		1410
1159	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1411	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1160	property of the event loop, and is actively waiting for events. While in	1412	property of the event loop, and is actively waiting for events. While in
…		…
1188	latter will clear any pending state the watcher might be in, regardless	1440	latter will clear any pending state the watcher might be in, regardless
1189	of whether it was active or not, so stopping a watcher explicitly before	1441	of whether it was active or not, so stopping a watcher explicitly before
1190	freeing it is often a good idea.	1442	freeing it is often a good idea.
1191		1443
1192	While stopped (and not pending) the watcher is essentially in the	1444	While stopped (and not pending) the watcher is essentially in the
1193	initialised state, that is it can be reused, moved, modified in any way	1445	initialised state, that is, it can be reused, moved, modified in any way
1194	you wish.	1446	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1447	it again).
1195		1448
1196	=back	1449	=back
1197
1198	=head2 GENERIC WATCHER FUNCTIONS
1199
1200	=over 4
1201
1202	=item C<ev_init> (ev_TYPE *watcher, callback)
1203
1204	This macro initialises the generic portion of a watcher. The contents
1205	of the watcher object can be arbitrary (so C<malloc> will do). Only
1206	the generic parts of the watcher are initialised, you I<need> to call
1207	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1208	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1209	which rolls both calls into one.
1210
1211	You can reinitialise a watcher at any time as long as it has been stopped
1212	(or never started) and there are no pending events outstanding.
1213
1214	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1215	int revents)>.
1216
1217	Example: Initialise an C<ev_io> watcher in two steps.
1218
1219	ev_io w;
1220	ev_init (&w, my_cb);
1221	ev_io_set (&w, STDIN_FILENO, EV_READ);
1222
1223	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1224
1225	This macro initialises the type-specific parts of a watcher. You need to
1226	call C<ev_init> at least once before you call this macro, but you can
1227	call C<ev_TYPE_set> any number of times. You must not, however, call this
1228	macro on a watcher that is active (it can be pending, however, which is a
1229	difference to the C<ev_init> macro).
1230
1231	Although some watcher types do not have type-specific arguments
1232	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1233
1234	See C<ev_init>, above, for an example.
1235
1236	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1237
1238	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1239	calls into a single call. This is the most convenient method to initialise
1240	a watcher. The same limitations apply, of course.
1241
1242	Example: Initialise and set an C<ev_io> watcher in one step.
1243
1244	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1245
1246	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1247
1248	Starts (activates) the given watcher. Only active watchers will receive
1249	events. If the watcher is already active nothing will happen.
1250
1251	Example: Start the C<ev_io> watcher that is being abused as example in this
1252	whole section.
1253
1254	ev_io_start (EV_DEFAULT_UC, &w);
1255
1256	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1257
1258	Stops the given watcher if active, and clears the pending status (whether
1259	the watcher was active or not).
1260
1261	It is possible that stopped watchers are pending - for example,
1262	non-repeating timers are being stopped when they become pending - but
1263	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1264	pending. If you want to free or reuse the memory used by the watcher it is
1265	therefore a good idea to always call its C<ev_TYPE_stop> function.
1266
1267	=item bool ev_is_active (ev_TYPE *watcher)
1268
1269	Returns a true value iff the watcher is active (i.e. it has been started
1270	and not yet been stopped). As long as a watcher is active you must not modify
1271	it.
1272
1273	=item bool ev_is_pending (ev_TYPE *watcher)
1274
1275	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1276	events but its callback has not yet been invoked). As long as a watcher
1277	is pending (but not active) you must not call an init function on it (but
1278	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1279	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1280	it).
1281
1282	=item callback ev_cb (ev_TYPE *watcher)
1283
1284	Returns the callback currently set on the watcher.
1285
1286	=item ev_cb_set (ev_TYPE *watcher, callback)
1287
1288	Change the callback. You can change the callback at virtually any time
1289	(modulo threads).
1290
1291	=item ev_set_priority (ev_TYPE *watcher, int priority)
1292
1293	=item int ev_priority (ev_TYPE *watcher)
1294
1295	Set and query the priority of the watcher. The priority is a small
1296	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1297	(default: C<-2>). Pending watchers with higher priority will be invoked
1298	before watchers with lower priority, but priority will not keep watchers
1299	from being executed (except for C<ev_idle> watchers).
1300
1301	If you need to suppress invocation when higher priority events are pending
1302	you need to look at C<ev_idle> watchers, which provide this functionality.
1303
1304	You I<must not> change the priority of a watcher as long as it is active or
1305	pending.
1306
1307	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1308	fine, as long as you do not mind that the priority value you query might
1309	or might not have been clamped to the valid range.
1310
1311	The default priority used by watchers when no priority has been set is
1312	always C<0>, which is supposed to not be too high and not be too low :).
1313
1314	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1315	priorities.
1316
1317	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1318
1319	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1320	C<loop> nor C<revents> need to be valid as long as the watcher callback
1321	can deal with that fact, as both are simply passed through to the
1322	callback.
1323
1324	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1325
1326	If the watcher is pending, this function clears its pending status and
1327	returns its C<revents> bitset (as if its callback was invoked). If the
1328	watcher isn't pending it does nothing and returns C<0>.
1329
1330	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1331	callback to be invoked, which can be accomplished with this function.
1332
1333	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1334
1335	Feeds the given event set into the event loop, as if the specified event
1336	had happened for the specified watcher (which must be a pointer to an
1337	initialised but not necessarily started event watcher). Obviously you must
1338	not free the watcher as long as it has pending events.
1339
1340	Stopping the watcher, letting libev invoke it, or calling
1341	C<ev_clear_pending> will clear the pending event, even if the watcher was
1342	not started in the first place.
1343
1344	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1345	functions that do not need a watcher.
1346
1347	=back
1348
1349
1350	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1351
1352	Each watcher has, by default, a member C<void *data> that you can change
1353	and read at any time: libev will completely ignore it. This can be used
1354	to associate arbitrary data with your watcher. If you need more data and
1355	don't want to allocate memory and store a pointer to it in that data
1356	member, you can also "subclass" the watcher type and provide your own
1357	data:
1358
1359	struct my_io
1360	{
1361	ev_io io;
1362	int otherfd;
1363	void *somedata;
1364	struct whatever *mostinteresting;
1365	};
1366
1367	...
1368	struct my_io w;
1369	ev_io_init (&w.io, my_cb, fd, EV_READ);
1370
1371	And since your callback will be called with a pointer to the watcher, you
1372	can cast it back to your own type:
1373
1374	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1375	{
1376	struct my_io *w = (struct my_io *)w_;
1377	...
1378	}
1379
1380	More interesting and less C-conformant ways of casting your callback type
1381	instead have been omitted.
1382
1383	Another common scenario is to use some data structure with multiple
1384	embedded watchers:
1385
1386	struct my_biggy
1387	{
1388	int some_data;
1389	ev_timer t1;
1390	ev_timer t2;
1391	}
1392
1393	In this case getting the pointer to C<my_biggy> is a bit more
1394	complicated: Either you store the address of your C<my_biggy> struct
1395	in the C<data> member of the watcher (for woozies), or you need to use
1396	some pointer arithmetic using C<offsetof> inside your watchers (for real
1397	programmers):
1398
1399	#include <stddef.h>
1400
1401	static void
1402	t1_cb (EV_P_ ev_timer *w, int revents)
1403	{
1404	struct my_biggy big = (struct my_biggy *)
1405	(((char *)w) - offsetof (struct my_biggy, t1));
1406	}
1407
1408	static void
1409	t2_cb (EV_P_ ev_timer *w, int revents)
1410	{
1411	struct my_biggy big = (struct my_biggy *)
1412	(((char *)w) - offsetof (struct my_biggy, t2));
1413	}
1414		1450
1415	=head2 WATCHER PRIORITY MODELS	1451	=head2 WATCHER PRIORITY MODELS
1416		1452
1417	Many event loops support I<watcher priorities>, which are usually small	1453	Many event loops support I<watcher priorities>, which are usually small
1418	integers that influence the ordering of event callback invocation	1454	integers that influence the ordering of event callback invocation
…		…
1545	In general you can register as many read and/or write event watchers per	1581	In general you can register as many read and/or write event watchers per
1546	fd as you want (as long as you don't confuse yourself). Setting all file	1582	fd as you want (as long as you don't confuse yourself). Setting all file
1547	descriptors to non-blocking mode is also usually a good idea (but not	1583	descriptors to non-blocking mode is also usually a good idea (but not
1548	required if you know what you are doing).	1584	required if you know what you are doing).
1549		1585
1550	If you cannot use non-blocking mode, then force the use of a
1551	known-to-be-good backend (at the time of this writing, this includes only
1552	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1553	descriptors for which non-blocking operation makes no sense (such as
1554	files) - libev doesn't guarantee any specific behaviour in that case.
1555
1556	Another thing you have to watch out for is that it is quite easy to	1586	Another thing you have to watch out for is that it is quite easy to
1557	receive "spurious" readiness notifications, that is your callback might	1587	receive "spurious" readiness notifications, that is, your callback might
1558	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1588	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1559	because there is no data. Not only are some backends known to create a	1589	because there is no data. It is very easy to get into this situation even
1560	lot of those (for example Solaris ports), it is very easy to get into	1590	with a relatively standard program structure. Thus it is best to always
1561	this situation even with a relatively standard program structure. Thus	1591	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1562	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1563	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1592	preferable to a program hanging until some data arrives.
1564		1593
1565	If you cannot run the fd in non-blocking mode (for example you should	1594	If you cannot run the fd in non-blocking mode (for example you should
1566	not play around with an Xlib connection), then you have to separately	1595	not play around with an Xlib connection), then you have to separately
1567	re-test whether a file descriptor is really ready with a known-to-be good	1596	re-test whether a file descriptor is really ready with a known-to-be good
1568	interface such as poll (fortunately in our Xlib example, Xlib already	1597	interface such as poll (fortunately in the case of Xlib, it already does
1569	does this on its own, so its quite safe to use). Some people additionally	1598	this on its own, so its quite safe to use). Some people additionally
1570	use C<SIGALRM> and an interval timer, just to be sure you won't block	1599	use C<SIGALRM> and an interval timer, just to be sure you won't block
1571	indefinitely.	1600	indefinitely.
1572		1601
1573	But really, best use non-blocking mode.	1602	But really, best use non-blocking mode.
1574		1603
…		…
1602		1631
1603	There is no workaround possible except not registering events	1632	There is no workaround possible except not registering events
1604	for potentially C<dup ()>'ed file descriptors, or to resort to	1633	for potentially C<dup ()>'ed file descriptors, or to resort to
1605	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1634	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1606		1635
		1636	=head3 The special problem of files
		1637
		1638	Many people try to use C<select> (or libev) on file descriptors
		1639	representing files, and expect it to become ready when their program
		1640	doesn't block on disk accesses (which can take a long time on their own).
		1641
		1642	However, this cannot ever work in the "expected" way - you get a readiness
		1643	notification as soon as the kernel knows whether and how much data is
		1644	there, and in the case of open files, that's always the case, so you
		1645	always get a readiness notification instantly, and your read (or possibly
		1646	write) will still block on the disk I/O.
		1647
		1648	Another way to view it is that in the case of sockets, pipes, character
		1649	devices and so on, there is another party (the sender) that delivers data
		1650	on its own, but in the case of files, there is no such thing: the disk
		1651	will not send data on its own, simply because it doesn't know what you
		1652	wish to read - you would first have to request some data.
		1653
		1654	Since files are typically not-so-well supported by advanced notification
		1655	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1656	to files, even though you should not use it. The reason for this is
		1657	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1658	usually a tty, often a pipe, but also sometimes files or special devices
		1659	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1660	F</dev/urandom>), and even though the file might better be served with
		1661	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1662	it "just works" instead of freezing.
		1663
		1664	So avoid file descriptors pointing to files when you know it (e.g. use
		1665	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1666	when you rarely read from a file instead of from a socket, and want to
		1667	reuse the same code path.
		1668
1607	=head3 The special problem of fork	1669	=head3 The special problem of fork
1608		1670
1609	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1671	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1610	useless behaviour. Libev fully supports fork, but needs to be told about	1672	useless behaviour. Libev fully supports fork, but needs to be told about
1611	it in the child.	1673	it in the child if you want to continue to use it in the child.
1612		1674
1613	To support fork in your programs, you either have to call	1675	To support fork in your child processes, you have to call C<ev_loop_fork
1614	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1676	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1615	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1677	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1616	C<EVBACKEND_POLL>.
1617		1678
1618	=head3 The special problem of SIGPIPE	1679	=head3 The special problem of SIGPIPE
1619		1680
1620	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1681	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1621	when writing to a pipe whose other end has been closed, your program gets	1682	when writing to a pipe whose other end has been closed, your program gets
…		…
1719	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1780	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1720	monotonic clock option helps a lot here).	1781	monotonic clock option helps a lot here).
1721		1782
1722	The callback is guaranteed to be invoked only I<after> its timeout has	1783	The callback is guaranteed to be invoked only I<after> its timeout has
1723	passed (not I<at>, so on systems with very low-resolution clocks this	1784	passed (not I<at>, so on systems with very low-resolution clocks this
1724	might introduce a small delay). If multiple timers become ready during the	1785	might introduce a small delay, see "the special problem of being too
		1786	early", below). If multiple timers become ready during the same loop
1725	same loop iteration then the ones with earlier time-out values are invoked	1787	iteration then the ones with earlier time-out values are invoked before
1726	before ones of the same priority with later time-out values (but this is	1788	ones of the same priority with later time-out values (but this is no
1727	no longer true when a callback calls C<ev_run> recursively).	1789	longer true when a callback calls C<ev_run> recursively).
1728		1790
1729	=head3 Be smart about timeouts	1791	=head3 Be smart about timeouts
1730		1792
1731	Many real-world problems involve some kind of timeout, usually for error	1793	Many real-world problems involve some kind of timeout, usually for error
1732	recovery. A typical example is an HTTP request - if the other side hangs,	1794	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1807		1869
1808	In this case, it would be more efficient to leave the C<ev_timer> alone,	1870	In this case, it would be more efficient to leave the C<ev_timer> alone,
1809	but remember the time of last activity, and check for a real timeout only	1871	but remember the time of last activity, and check for a real timeout only
1810	within the callback:	1872	within the callback:
1811		1873
		1874	ev_tstamp timeout = 60.;
1812	ev_tstamp last_activity; // time of last activity	1875	ev_tstamp last_activity; // time of last activity
		1876	ev_timer timer;
1813		1877
1814	static void	1878	static void
1815	callback (EV_P_ ev_timer *w, int revents)	1879	callback (EV_P_ ev_timer *w, int revents)
1816	{	1880	{
1817	ev_tstamp now = ev_now (EV_A);	1881	// calculate when the timeout would happen
1818	ev_tstamp timeout = last_activity + 60.;	1882	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1819		1883
1820	// if last_activity + 60. is older than now, we did time out	1884	// if negative, it means we the timeout already occurred
1821	if (timeout < now)	1885	if (after < 0.)
1822	{	1886	{
1823	// timeout occurred, take action	1887	// timeout occurred, take action
1824	}	1888	}
1825	else	1889	else
1826	{	1890	{
1827	// callback was invoked, but there was some activity, re-arm	1891	// callback was invoked, but there was some recent
1828	// the watcher to fire in last_activity + 60, which is	1892	// activity. simply restart the timer to time out
1829	// guaranteed to be in the future, so "again" is positive:	1893	// after "after" seconds, which is the earliest time
1830	w->repeat = timeout - now;	1894	// the timeout can occur.
		1895	ev_timer_set (w, after, 0.);
1831	ev_timer_again (EV_A_ w);	1896	ev_timer_start (EV_A_ w);
1832	}	1897	}
1833	}	1898	}
1834		1899
1835	To summarise the callback: first calculate the real timeout (defined	1900	To summarise the callback: first calculate in how many seconds the
1836	as "60 seconds after the last activity"), then check if that time has	1901	timeout will occur (by calculating the absolute time when it would occur,
1837	been reached, which means something I<did>, in fact, time out. Otherwise	1902	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1838	the callback was invoked too early (C<timeout> is in the future), so	1903	(EV_A)> from that).
1839	re-schedule the timer to fire at that future time, to see if maybe we have
1840	a timeout then.
1841		1904
1842	Note how C<ev_timer_again> is used, taking advantage of the	1905	If this value is negative, then we are already past the timeout, i.e. we
1843	C<ev_timer_again> optimisation when the timer is already running.	1906	timed out, and need to do whatever is needed in this case.
		1907
		1908	Otherwise, we now the earliest time at which the timeout would trigger,
		1909	and simply start the timer with this timeout value.
		1910
		1911	In other words, each time the callback is invoked it will check whether
		1912	the timeout occurred. If not, it will simply reschedule itself to check
		1913	again at the earliest time it could time out. Rinse. Repeat.
1844		1914
1845	This scheme causes more callback invocations (about one every 60 seconds	1915	This scheme causes more callback invocations (about one every 60 seconds
1846	minus half the average time between activity), but virtually no calls to	1916	minus half the average time between activity), but virtually no calls to
1847	libev to change the timeout.	1917	libev to change the timeout.
1848		1918
1849	To start the timer, simply initialise the watcher and set C<last_activity>	1919	To start the machinery, simply initialise the watcher and set
1850	to the current time (meaning we just have some activity :), then call the	1920	C<last_activity> to the current time (meaning there was some activity just
1851	callback, which will "do the right thing" and start the timer:	1921	now), then call the callback, which will "do the right thing" and start
		1922	the timer:
1852		1923
		1924	last_activity = ev_now (EV_A);
1853	ev_init (timer, callback);	1925	ev_init (&timer, callback);
1854	last_activity = ev_now (loop);	1926	callback (EV_A_ &timer, 0);
1855	callback (loop, timer, EV_TIMER);
1856		1927
1857	And when there is some activity, simply store the current time in	1928	When there is some activity, simply store the current time in
1858	C<last_activity>, no libev calls at all:	1929	C<last_activity>, no libev calls at all:
1859		1930
		1931	if (activity detected)
1860	last_activity = ev_now (loop);	1932	last_activity = ev_now (EV_A);
		1933
		1934	When your timeout value changes, then the timeout can be changed by simply
		1935	providing a new value, stopping the timer and calling the callback, which
		1936	will again do the right thing (for example, time out immediately :).
		1937
		1938	timeout = new_value;
		1939	ev_timer_stop (EV_A_ &timer);
		1940	callback (EV_A_ &timer, 0);
1861		1941
1862	This technique is slightly more complex, but in most cases where the	1942	This technique is slightly more complex, but in most cases where the
1863	time-out is unlikely to be triggered, much more efficient.	1943	time-out is unlikely to be triggered, much more efficient.
1864
1865	Changing the timeout is trivial as well (if it isn't hard-coded in the
1866	callback :) - just change the timeout and invoke the callback, which will
1867	fix things for you.
1868		1944
1869	=item 4. Wee, just use a double-linked list for your timeouts.	1945	=item 4. Wee, just use a double-linked list for your timeouts.
1870		1946
1871	If there is not one request, but many thousands (millions...), all	1947	If there is not one request, but many thousands (millions...), all
1872	employing some kind of timeout with the same timeout value, then one can	1948	employing some kind of timeout with the same timeout value, then one can
…		…
1899	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1975	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1900	rather complicated, but extremely efficient, something that really pays	1976	rather complicated, but extremely efficient, something that really pays
1901	off after the first million or so of active timers, i.e. it's usually	1977	off after the first million or so of active timers, i.e. it's usually
1902	overkill :)	1978	overkill :)
1903		1979
		1980	=head3 The special problem of being too early
		1981
		1982	If you ask a timer to call your callback after three seconds, then
		1983	you expect it to be invoked after three seconds - but of course, this
		1984	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1985	guaranteed to any precision by libev - imagine somebody suspending the
		1986	process with a STOP signal for a few hours for example.
		1987
		1988	So, libev tries to invoke your callback as soon as possible I<after> the
		1989	delay has occurred, but cannot guarantee this.
		1990
		1991	A less obvious failure mode is calling your callback too early: many event
		1992	loops compare timestamps with a "elapsed delay >= requested delay", but
		1993	this can cause your callback to be invoked much earlier than you would
		1994	expect.
		1995
		1996	To see why, imagine a system with a clock that only offers full second
		1997	resolution (think windows if you can't come up with a broken enough OS
		1998	yourself). If you schedule a one-second timer at the time 500.9, then the
		1999	event loop will schedule your timeout to elapse at a system time of 500
		2000	(500.9 truncated to the resolution) + 1, or 501.
		2001
		2002	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2003	501" and invoke the callback 0.1s after it was started, even though a
		2004	one-second delay was requested - this is being "too early", despite best
		2005	intentions.
		2006
		2007	This is the reason why libev will never invoke the callback if the elapsed
		2008	delay equals the requested delay, but only when the elapsed delay is
		2009	larger than the requested delay. In the example above, libev would only invoke
		2010	the callback at system time 502, or 1.1s after the timer was started.
		2011
		2012	So, while libev cannot guarantee that your callback will be invoked
		2013	exactly when requested, it I<can> and I<does> guarantee that the requested
		2014	delay has actually elapsed, or in other words, it always errs on the "too
		2015	late" side of things.
		2016
1904	=head3 The special problem of time updates	2017	=head3 The special problem of time updates
1905		2018
1906	Establishing the current time is a costly operation (it usually takes at	2019	Establishing the current time is a costly operation (it usually takes
1907	least two system calls): EV therefore updates its idea of the current	2020	at least one system call): EV therefore updates its idea of the current
1908	time only before and after C<ev_run> collects new events, which causes a	2021	time only before and after C<ev_run> collects new events, which causes a
1909	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2022	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1910	lots of events in one iteration.	2023	lots of events in one iteration.
1911		2024
1912	The relative timeouts are calculated relative to the C<ev_now ()>	2025	The relative timeouts are calculated relative to the C<ev_now ()>
…		…
1918	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2031	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1919		2032
1920	If the event loop is suspended for a long time, you can also force an	2033	If the event loop is suspended for a long time, you can also force an
1921	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2034	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1922	()>.	2035	()>.
		2036
		2037	=head3 The special problem of unsynchronised clocks
		2038
		2039	Modern systems have a variety of clocks - libev itself uses the normal
		2040	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2041	jumps).
		2042
		2043	Neither of these clocks is synchronised with each other or any other clock
		2044	on the system, so C<ev_time ()> might return a considerably different time
		2045	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2046	a call to C<gettimeofday> might return a second count that is one higher
		2047	than a directly following call to C<time>.
		2048
		2049	The moral of this is to only compare libev-related timestamps with
		2050	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2051	a second or so.
		2052
		2053	One more problem arises due to this lack of synchronisation: if libev uses
		2054	the system monotonic clock and you compare timestamps from C<ev_time>
		2055	or C<ev_now> from when you started your timer and when your callback is
		2056	invoked, you will find that sometimes the callback is a bit "early".
		2057
		2058	This is because C<ev_timer>s work in real time, not wall clock time, so
		2059	libev makes sure your callback is not invoked before the delay happened,
		2060	I<measured according to the real time>, not the system clock.
		2061
		2062	If your timeouts are based on a physical timescale (e.g. "time out this
		2063	connection after 100 seconds") then this shouldn't bother you as it is
		2064	exactly the right behaviour.
		2065
		2066	If you want to compare wall clock/system timestamps to your timers, then
		2067	you need to use C<ev_periodic>s, as these are based on the wall clock
		2068	time, where your comparisons will always generate correct results.
1923		2069
1924	=head3 The special problems of suspended animation	2070	=head3 The special problems of suspended animation
1925		2071
1926	When you leave the server world it is quite customary to hit machines that	2072	When you leave the server world it is quite customary to hit machines that
1927	can suspend/hibernate - what happens to the clocks during such a suspend?	2073	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1971	keep up with the timer (because it takes longer than those 10 seconds to	2117	keep up with the timer (because it takes longer than those 10 seconds to
1972	do stuff) the timer will not fire more than once per event loop iteration.	2118	do stuff) the timer will not fire more than once per event loop iteration.
1973		2119
1974	=item ev_timer_again (loop, ev_timer *)	2120	=item ev_timer_again (loop, ev_timer *)
1975		2121
1976	This will act as if the timer timed out and restart it again if it is	2122	This will act as if the timer timed out, and restarts it again if it is
1977	repeating. The exact semantics are:	2123	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2124	timeout to the C<repeat> value and calling C<ev_timer_start>.
1978		2125
		2126	The exact semantics are as in the following rules, all of which will be
		2127	applied to the watcher:
		2128
		2129	=over 4
		2130
1979	If the timer is pending, its pending status is cleared.	2131	=item If the timer is pending, the pending status is always cleared.
1980		2132
1981	If the timer is started but non-repeating, stop it (as if it timed out).	2133	=item If the timer is started but non-repeating, stop it (as if it timed
		2134	out, without invoking it).
1982		2135
1983	If the timer is repeating, either start it if necessary (with the	2136	=item If the timer is repeating, make the C<repeat> value the new timeout
1984	C<repeat> value), or reset the running timer to the C<repeat> value.	2137	and start the timer, if necessary.
1985		2138
		2139	=back
		2140
1986	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2141	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1987	usage example.	2142	usage example.
1988		2143
1989	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2144	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1990		2145
1991	Returns the remaining time until a timer fires. If the timer is active,	2146	Returns the remaining time until a timer fires. If the timer is active,
…		…
2111		2266
2112	Another way to think about it (for the mathematically inclined) is that	2267	Another way to think about it (for the mathematically inclined) is that
2113	C<ev_periodic> will try to run the callback in this mode at the next possible	2268	C<ev_periodic> will try to run the callback in this mode at the next possible
2114	time where C<time = offset (mod interval)>, regardless of any time jumps.	2269	time where C<time = offset (mod interval)>, regardless of any time jumps.
2115		2270
2116	For numerical stability it is preferable that the C<offset> value is near	2271	The C<interval> I<MUST> be positive, and for numerical stability, the
2117	C<ev_now ()> (the current time), but there is no range requirement for	2272	interval value should be higher than C<1/8192> (which is around 100
2118	this value, and in fact is often specified as zero.	2273	microseconds) and C<offset> should be higher than C<0> and should have
		2274	at most a similar magnitude as the current time (say, within a factor of
		2275	ten). Typical values for offset are, in fact, C<0> or something between
		2276	C<0> and C<interval>, which is also the recommended range.
2119		2277
2120	Note also that there is an upper limit to how often a timer can fire (CPU	2278	Note also that there is an upper limit to how often a timer can fire (CPU
2121	speed for example), so if C<interval> is very small then timing stability	2279	speed for example), so if C<interval> is very small then timing stability
2122	will of course deteriorate. Libev itself tries to be exact to be about one	2280	will of course deteriorate. Libev itself tries to be exact to be about one
2123	millisecond (if the OS supports it and the machine is fast enough).	2281	millisecond (if the OS supports it and the machine is fast enough).
…		…
2237		2395
2238	=head2 C<ev_signal> - signal me when a signal gets signalled!	2396	=head2 C<ev_signal> - signal me when a signal gets signalled!
2239		2397
2240	Signal watchers will trigger an event when the process receives a specific	2398	Signal watchers will trigger an event when the process receives a specific
2241	signal one or more times. Even though signals are very asynchronous, libev	2399	signal one or more times. Even though signals are very asynchronous, libev
2242	will try it's best to deliver signals synchronously, i.e. as part of the	2400	will try its best to deliver signals synchronously, i.e. as part of the
2243	normal event processing, like any other event.	2401	normal event processing, like any other event.
2244		2402
2245	If you want signals to be delivered truly asynchronously, just use	2403	If you want signals to be delivered truly asynchronously, just use
2246	C<sigaction> as you would do without libev and forget about sharing	2404	C<sigaction> as you would do without libev and forget about sharing
2247	the signal. You can even use C<ev_async> from a signal handler to	2405	the signal. You can even use C<ev_async> from a signal handler to
…		…
2266	=head3 The special problem of inheritance over fork/execve/pthread_create	2424	=head3 The special problem of inheritance over fork/execve/pthread_create
2267		2425
2268	Both the signal mask (C<sigprocmask>) and the signal disposition	2426	Both the signal mask (C<sigprocmask>) and the signal disposition
2269	(C<sigaction>) are unspecified after starting a signal watcher (and after	2427	(C<sigaction>) are unspecified after starting a signal watcher (and after
2270	stopping it again), that is, libev might or might not block the signal,	2428	stopping it again), that is, libev might or might not block the signal,
2271	and might or might not set or restore the installed signal handler.	2429	and might or might not set or restore the installed signal handler (but
		2430	see C<EVFLAG_NOSIGMASK>).
2272		2431
2273	While this does not matter for the signal disposition (libev never	2432	While this does not matter for the signal disposition (libev never
2274	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2433	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2275	C<execve>), this matters for the signal mask: many programs do not expect	2434	C<execve>), this matters for the signal mask: many programs do not expect
2276	certain signals to be blocked.	2435	certain signals to be blocked.
…		…
2289	I<has> to modify the signal mask, at least temporarily.	2448	I<has> to modify the signal mask, at least temporarily.
2290		2449
2291	So I can't stress this enough: I<If you do not reset your signal mask when	2450	So I can't stress this enough: I<If you do not reset your signal mask when
2292	you expect it to be empty, you have a race condition in your code>. This	2451	you expect it to be empty, you have a race condition in your code>. This
2293	is not a libev-specific thing, this is true for most event libraries.	2452	is not a libev-specific thing, this is true for most event libraries.
		2453
		2454	=head3 The special problem of threads signal handling
		2455
		2456	POSIX threads has problematic signal handling semantics, specifically,
		2457	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2458	threads in a process block signals, which is hard to achieve.
		2459
		2460	When you want to use sigwait (or mix libev signal handling with your own
		2461	for the same signals), you can tackle this problem by globally blocking
		2462	all signals before creating any threads (or creating them with a fully set
		2463	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2464	loops. Then designate one thread as "signal receiver thread" which handles
		2465	these signals. You can pass on any signals that libev might be interested
		2466	in by calling C<ev_feed_signal>.
2294		2467
2295	=head3 Watcher-Specific Functions and Data Members	2468	=head3 Watcher-Specific Functions and Data Members
2296		2469
2297	=over 4	2470	=over 4
2298		2471
…		…
2674	Apart from keeping your process non-blocking (which is a useful	2847	Apart from keeping your process non-blocking (which is a useful
2675	effect on its own sometimes), idle watchers are a good place to do	2848	effect on its own sometimes), idle watchers are a good place to do
2676	"pseudo-background processing", or delay processing stuff to after the	2849	"pseudo-background processing", or delay processing stuff to after the
2677	event loop has handled all outstanding events.	2850	event loop has handled all outstanding events.
2678		2851
		2852	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2853
		2854	As long as there is at least one active idle watcher, libev will never
		2855	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2856	For this to work, the idle watcher doesn't need to be invoked at all - the
		2857	lowest priority will do.
		2858
		2859	This mode of operation can be useful together with an C<ev_check> watcher,
		2860	to do something on each event loop iteration - for example to balance load
		2861	between different connections.
		2862
		2863	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2864	example.
		2865
2679	=head3 Watcher-Specific Functions and Data Members	2866	=head3 Watcher-Specific Functions and Data Members
2680		2867
2681	=over 4	2868	=over 4
2682		2869
2683	=item ev_idle_init (ev_idle *, callback)	2870	=item ev_idle_init (ev_idle *, callback)
…		…
2694	callback, free it. Also, use no error checking, as usual.	2881	callback, free it. Also, use no error checking, as usual.
2695		2882
2696	static void	2883	static void
2697	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2884	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2698	{	2885	{
		2886	// stop the watcher
		2887	ev_idle_stop (loop, w);
		2888
		2889	// now we can free it
2699	free (w);	2890	free (w);
		2891
2700	// now do something you wanted to do when the program has	2892	// now do something you wanted to do when the program has
2701	// no longer anything immediate to do.	2893	// no longer anything immediate to do.
2702	}	2894	}
2703		2895
2704	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2896	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2706	ev_idle_start (loop, idle_watcher);	2898	ev_idle_start (loop, idle_watcher);
2707		2899
2708		2900
2709	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2901	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2710		2902
2711	Prepare and check watchers are usually (but not always) used in pairs:	2903	Prepare and check watchers are often (but not always) used in pairs:
2712	prepare watchers get invoked before the process blocks and check watchers	2904	prepare watchers get invoked before the process blocks and check watchers
2713	afterwards.	2905	afterwards.
2714		2906
2715	You I<must not> call C<ev_run> or similar functions that enter	2907	You I<must not> call C<ev_run> or similar functions that enter
2716	the current event loop from either C<ev_prepare> or C<ev_check>	2908	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
2744	with priority higher than or equal to the event loop and one coroutine	2936	with priority higher than or equal to the event loop and one coroutine
2745	of lower priority, but only once, using idle watchers to keep the event	2937	of lower priority, but only once, using idle watchers to keep the event
2746	loop from blocking if lower-priority coroutines are active, thus mapping	2938	loop from blocking if lower-priority coroutines are active, thus mapping
2747	low-priority coroutines to idle/background tasks).	2939	low-priority coroutines to idle/background tasks).
2748		2940
2749	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2941	When used for this purpose, it is recommended to give C<ev_check> watchers
2750	priority, to ensure that they are being run before any other watchers	2942	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2751	after the poll (this doesn't matter for C<ev_prepare> watchers).	2943	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2944	watchers).
2752		2945
2753	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2946	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2754	activate ("feed") events into libev. While libev fully supports this, they	2947	activate ("feed") events into libev. While libev fully supports this, they
2755	might get executed before other C<ev_check> watchers did their job. As	2948	might get executed before other C<ev_check> watchers did their job. As
2756	C<ev_check> watchers are often used to embed other (non-libev) event	2949	C<ev_check> watchers are often used to embed other (non-libev) event
2757	loops those other event loops might be in an unusable state until their	2950	loops those other event loops might be in an unusable state until their
2758	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2951	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2759	others).	2952	others).
		2953
		2954	=head3 Abusing an C<ev_check> watcher for its side-effect
		2955
		2956	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2957	useful because they are called once per event loop iteration. For
		2958	example, if you want to handle a large number of connections fairly, you
		2959	normally only do a bit of work for each active connection, and if there
		2960	is more work to do, you wait for the next event loop iteration, so other
		2961	connections have a chance of making progress.
		2962
		2963	Using an C<ev_check> watcher is almost enough: it will be called on the
		2964	next event loop iteration. However, that isn't as soon as possible -
		2965	without external events, your C<ev_check> watcher will not be invoked.
		2966
		2967
		2968	This is where C<ev_idle> watchers come in handy - all you need is a
		2969	single global idle watcher that is active as long as you have one active
		2970	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2971	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2972	invoked. Neither watcher alone can do that.
2760		2973
2761	=head3 Watcher-Specific Functions and Data Members	2974	=head3 Watcher-Specific Functions and Data Members
2762		2975
2763	=over 4	2976	=over 4
2764		2977
…		…
3072	disadvantage of having to use multiple event loops (which do not support	3285	disadvantage of having to use multiple event loops (which do not support
3073	signal watchers).	3286	signal watchers).
3074		3287
3075	When this is not possible, or you want to use the default loop for	3288	When this is not possible, or you want to use the default loop for
3076	other reasons, then in the process that wants to start "fresh", call	3289	other reasons, then in the process that wants to start "fresh", call
3077	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3290	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3078	the default loop will "orphan" (not stop) all registered watchers, so you	3291	Destroying the default loop will "orphan" (not stop) all registered
3079	have to be careful not to execute code that modifies those watchers. Note	3292	watchers, so you have to be careful not to execute code that modifies
3080	also that in that case, you have to re-register any signal watchers.	3293	those watchers. Note also that in that case, you have to re-register any
		3294	signal watchers.
3081		3295
3082	=head3 Watcher-Specific Functions and Data Members	3296	=head3 Watcher-Specific Functions and Data Members
3083		3297
3084	=over 4	3298	=over 4
3085		3299
3086	=item ev_fork_init (ev_signal *, callback)	3300	=item ev_fork_init (ev_fork *, callback)
3087		3301
3088	Initialises and configures the fork watcher - it has no parameters of any	3302	Initialises and configures the fork watcher - it has no parameters of any
3089	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3303	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3090	believe me.	3304	really.
3091		3305
3092	=back	3306	=back
3093		3307
3094		3308
		3309	=head2 C<ev_cleanup> - even the best things end
		3310
		3311	Cleanup watchers are called just before the event loop is being destroyed
		3312	by a call to C<ev_loop_destroy>.
		3313
		3314	While there is no guarantee that the event loop gets destroyed, cleanup
		3315	watchers provide a convenient method to install cleanup hooks for your
		3316	program, worker threads and so on - you just to make sure to destroy the
		3317	loop when you want them to be invoked.
		3318
		3319	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3320	all other watchers, they do not keep a reference to the event loop (which
		3321	makes a lot of sense if you think about it). Like all other watchers, you
		3322	can call libev functions in the callback, except C<ev_cleanup_start>.
		3323
		3324	=head3 Watcher-Specific Functions and Data Members
		3325
		3326	=over 4
		3327
		3328	=item ev_cleanup_init (ev_cleanup *, callback)
		3329
		3330	Initialises and configures the cleanup watcher - it has no parameters of
		3331	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3332	pointless, I assure you.
		3333
		3334	=back
		3335
		3336	Example: Register an atexit handler to destroy the default loop, so any
		3337	cleanup functions are called.
		3338
		3339	static void
		3340	program_exits (void)
		3341	{
		3342	ev_loop_destroy (EV_DEFAULT_UC);
		3343	}
		3344
		3345	...
		3346	atexit (program_exits);
		3347
		3348
3095	=head2 C<ev_async> - how to wake up an event loop	3349	=head2 C<ev_async> - how to wake up an event loop
3096		3350
3097	In general, you cannot use an C<ev_run> from multiple threads or other	3351	In general, you cannot use an C<ev_loop> from multiple threads or other
3098	asynchronous sources such as signal handlers (as opposed to multiple event	3352	asynchronous sources such as signal handlers (as opposed to multiple event
3099	loops - those are of course safe to use in different threads).	3353	loops - those are of course safe to use in different threads).
3100		3354
3101	Sometimes, however, you need to wake up an event loop you do not control,	3355	Sometimes, however, you need to wake up an event loop you do not control,
3102	for example because it belongs to another thread. This is what C<ev_async>	3356	for example because it belongs to another thread. This is what C<ev_async>
…		…
3104	it by calling C<ev_async_send>, which is thread- and signal safe.	3358	it by calling C<ev_async_send>, which is thread- and signal safe.
3105		3359
3106	This functionality is very similar to C<ev_signal> watchers, as signals,	3360	This functionality is very similar to C<ev_signal> watchers, as signals,
3107	too, are asynchronous in nature, and signals, too, will be compressed	3361	too, are asynchronous in nature, and signals, too, will be compressed
3108	(i.e. the number of callback invocations may be less than the number of	3362	(i.e. the number of callback invocations may be less than the number of
3109	C<ev_async_sent> calls).	3363	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3110		3364	of "global async watchers" by using a watcher on an otherwise unused
3111	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3365	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3112	just the default loop.	3366	even without knowing which loop owns the signal.
3113		3367
3114	=head3 Queueing	3368	=head3 Queueing
3115		3369
3116	C<ev_async> does not support queueing of data in any way. The reason	3370	C<ev_async> does not support queueing of data in any way. The reason
3117	is that the author does not know of a simple (or any) algorithm for a	3371	is that the author does not know of a simple (or any) algorithm for a
…		…
3209	trust me.	3463	trust me.
3210		3464
3211	=item ev_async_send (loop, ev_async *)	3465	=item ev_async_send (loop, ev_async *)
3212		3466
3213	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3467	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3214	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3468	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3469	returns.
		3470
3215	C<ev_feed_event>, this call is safe to do from other threads, signal or	3471	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3216	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3472	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3217	section below on what exactly this means).	3473	embedding section below on what exactly this means).
3218		3474
3219	Note that, as with other watchers in libev, multiple events might get	3475	Note that, as with other watchers in libev, multiple events might get
3220	compressed into a single callback invocation (another way to look at this	3476	compressed into a single callback invocation (another way to look at
3221	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3477	this is that C<ev_async> watchers are level-triggered: they are set on
3222	reset when the event loop detects that).	3478	C<ev_async_send>, reset when the event loop detects that).
3223		3479
3224	This call incurs the overhead of a system call only once per event loop	3480	This call incurs the overhead of at most one extra system call per event
3225	iteration, so while the overhead might be noticeable, it doesn't apply to	3481	loop iteration, if the event loop is blocked, and no syscall at all if
3226	repeated calls to C<ev_async_send> for the same event loop.	3482	the event loop (or your program) is processing events. That means that
		3483	repeated calls are basically free (there is no need to avoid calls for
		3484	performance reasons) and that the overhead becomes smaller (typically
		3485	zero) under load.
3227		3486
3228	=item bool = ev_async_pending (ev_async *)	3487	=item bool = ev_async_pending (ev_async *)
3229		3488
3230	Returns a non-zero value when C<ev_async_send> has been called on the	3489	Returns a non-zero value when C<ev_async_send> has been called on the
3231	watcher but the event has not yet been processed (or even noted) by the	3490	watcher but the event has not yet been processed (or even noted) by the
…		…
3286	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3545	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3287		3546
3288	=item ev_feed_fd_event (loop, int fd, int revents)	3547	=item ev_feed_fd_event (loop, int fd, int revents)
3289		3548
3290	Feed an event on the given fd, as if a file descriptor backend detected	3549	Feed an event on the given fd, as if a file descriptor backend detected
3291	the given events it.	3550	the given events.
3292		3551
3293	=item ev_feed_signal_event (loop, int signum)	3552	=item ev_feed_signal_event (loop, int signum)
3294		3553
3295	Feed an event as if the given signal occurred (C<loop> must be the default	3554	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3296	loop!).	3555	which is async-safe.
3297		3556
3298	=back	3557	=back
		3558
		3559
		3560	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3561
		3562	This section explains some common idioms that are not immediately
		3563	obvious. Note that examples are sprinkled over the whole manual, and this
		3564	section only contains stuff that wouldn't fit anywhere else.
		3565
		3566	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3567
		3568	Each watcher has, by default, a C<void *data> member that you can read
		3569	or modify at any time: libev will completely ignore it. This can be used
		3570	to associate arbitrary data with your watcher. If you need more data and
		3571	don't want to allocate memory separately and store a pointer to it in that
		3572	data member, you can also "subclass" the watcher type and provide your own
		3573	data:
		3574
		3575	struct my_io
		3576	{
		3577	ev_io io;
		3578	int otherfd;
		3579	void *somedata;
		3580	struct whatever *mostinteresting;
		3581	};
		3582
		3583	...
		3584	struct my_io w;
		3585	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3586
		3587	And since your callback will be called with a pointer to the watcher, you
		3588	can cast it back to your own type:
		3589
		3590	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3591	{
		3592	struct my_io *w = (struct my_io *)w_;
		3593	...
		3594	}
		3595
		3596	More interesting and less C-conformant ways of casting your callback
		3597	function type instead have been omitted.
		3598
		3599	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3600
		3601	Another common scenario is to use some data structure with multiple
		3602	embedded watchers, in effect creating your own watcher that combines
		3603	multiple libev event sources into one "super-watcher":
		3604
		3605	struct my_biggy
		3606	{
		3607	int some_data;
		3608	ev_timer t1;
		3609	ev_timer t2;
		3610	}
		3611
		3612	In this case getting the pointer to C<my_biggy> is a bit more
		3613	complicated: Either you store the address of your C<my_biggy> struct in
		3614	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3615	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3616	real programmers):
		3617
		3618	#include <stddef.h>
		3619
		3620	static void
		3621	t1_cb (EV_P_ ev_timer *w, int revents)
		3622	{
		3623	struct my_biggy big = (struct my_biggy *)
		3624	(((char *)w) - offsetof (struct my_biggy, t1));
		3625	}
		3626
		3627	static void
		3628	t2_cb (EV_P_ ev_timer *w, int revents)
		3629	{
		3630	struct my_biggy big = (struct my_biggy *)
		3631	(((char *)w) - offsetof (struct my_biggy, t2));
		3632	}
		3633
		3634	=head2 AVOIDING FINISHING BEFORE RETURNING
		3635
		3636	Often you have structures like this in event-based programs:
		3637
		3638	callback ()
		3639	{
		3640	free (request);
		3641	}
		3642
		3643	request = start_new_request (..., callback);
		3644
		3645	The intent is to start some "lengthy" operation. The C<request> could be
		3646	used to cancel the operation, or do other things with it.
		3647
		3648	It's not uncommon to have code paths in C<start_new_request> that
		3649	immediately invoke the callback, for example, to report errors. Or you add
		3650	some caching layer that finds that it can skip the lengthy aspects of the
		3651	operation and simply invoke the callback with the result.
		3652
		3653	The problem here is that this will happen I<before> C<start_new_request>
		3654	has returned, so C<request> is not set.
		3655
		3656	Even if you pass the request by some safer means to the callback, you
		3657	might want to do something to the request after starting it, such as
		3658	canceling it, which probably isn't working so well when the callback has
		3659	already been invoked.
		3660
		3661	A common way around all these issues is to make sure that
		3662	C<start_new_request> I<always> returns before the callback is invoked. If
		3663	C<start_new_request> immediately knows the result, it can artificially
		3664	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3665	for example, or more sneakily, by reusing an existing (stopped) watcher
		3666	and pushing it into the pending queue:
		3667
		3668	ev_set_cb (watcher, callback);
		3669	ev_feed_event (EV_A_ watcher, 0);
		3670
		3671	This way, C<start_new_request> can safely return before the callback is
		3672	invoked, while not delaying callback invocation too much.
		3673
		3674	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3675
		3676	Often (especially in GUI toolkits) there are places where you have
		3677	I<modal> interaction, which is most easily implemented by recursively
		3678	invoking C<ev_run>.
		3679
		3680	This brings the problem of exiting - a callback might want to finish the
		3681	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3682	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3683	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3684	other combination: In these cases, C<ev_break> will not work alone.
		3685
		3686	The solution is to maintain "break this loop" variable for each C<ev_run>
		3687	invocation, and use a loop around C<ev_run> until the condition is
		3688	triggered, using C<EVRUN_ONCE>:
		3689
		3690	// main loop
		3691	int exit_main_loop = 0;
		3692
		3693	while (!exit_main_loop)
		3694	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3695
		3696	// in a modal watcher
		3697	int exit_nested_loop = 0;
		3698
		3699	while (!exit_nested_loop)
		3700	ev_run (EV_A_ EVRUN_ONCE);
		3701
		3702	To exit from any of these loops, just set the corresponding exit variable:
		3703
		3704	// exit modal loop
		3705	exit_nested_loop = 1;
		3706
		3707	// exit main program, after modal loop is finished
		3708	exit_main_loop = 1;
		3709
		3710	// exit both
		3711	exit_main_loop = exit_nested_loop = 1;
		3712
		3713	=head2 THREAD LOCKING EXAMPLE
		3714
		3715	Here is a fictitious example of how to run an event loop in a different
		3716	thread from where callbacks are being invoked and watchers are
		3717	created/added/removed.
		3718
		3719	For a real-world example, see the C<EV::Loop::Async> perl module,
		3720	which uses exactly this technique (which is suited for many high-level
		3721	languages).
		3722
		3723	The example uses a pthread mutex to protect the loop data, a condition
		3724	variable to wait for callback invocations, an async watcher to notify the
		3725	event loop thread and an unspecified mechanism to wake up the main thread.
		3726
		3727	First, you need to associate some data with the event loop:
		3728
		3729	typedef struct {
		3730	mutex_t lock; /* global loop lock */
		3731	ev_async async_w;
		3732	thread_t tid;
		3733	cond_t invoke_cv;
		3734	} userdata;
		3735
		3736	void prepare_loop (EV_P)
		3737	{
		3738	// for simplicity, we use a static userdata struct.
		3739	static userdata u;
		3740
		3741	ev_async_init (&u->async_w, async_cb);
		3742	ev_async_start (EV_A_ &u->async_w);
		3743
		3744	pthread_mutex_init (&u->lock, 0);
		3745	pthread_cond_init (&u->invoke_cv, 0);
		3746
		3747	// now associate this with the loop
		3748	ev_set_userdata (EV_A_ u);
		3749	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3750	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3751
		3752	// then create the thread running ev_run
		3753	pthread_create (&u->tid, 0, l_run, EV_A);
		3754	}
		3755
		3756	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3757	solely to wake up the event loop so it takes notice of any new watchers
		3758	that might have been added:
		3759
		3760	static void
		3761	async_cb (EV_P_ ev_async *w, int revents)
		3762	{
		3763	// just used for the side effects
		3764	}
		3765
		3766	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3767	protecting the loop data, respectively.
		3768
		3769	static void
		3770	l_release (EV_P)
		3771	{
		3772	userdata *u = ev_userdata (EV_A);
		3773	pthread_mutex_unlock (&u->lock);
		3774	}
		3775
		3776	static void
		3777	l_acquire (EV_P)
		3778	{
		3779	userdata *u = ev_userdata (EV_A);
		3780	pthread_mutex_lock (&u->lock);
		3781	}
		3782
		3783	The event loop thread first acquires the mutex, and then jumps straight
		3784	into C<ev_run>:
		3785
		3786	void *
		3787	l_run (void *thr_arg)
		3788	{
		3789	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3790
		3791	l_acquire (EV_A);
		3792	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3793	ev_run (EV_A_ 0);
		3794	l_release (EV_A);
		3795
		3796	return 0;
		3797	}
		3798
		3799	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3800	signal the main thread via some unspecified mechanism (signals? pipe
		3801	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3802	have been called (in a while loop because a) spurious wakeups are possible
		3803	and b) skipping inter-thread-communication when there are no pending
		3804	watchers is very beneficial):
		3805
		3806	static void
		3807	l_invoke (EV_P)
		3808	{
		3809	userdata *u = ev_userdata (EV_A);
		3810
		3811	while (ev_pending_count (EV_A))
		3812	{
		3813	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3814	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3815	}
		3816	}
		3817
		3818	Now, whenever the main thread gets told to invoke pending watchers, it
		3819	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3820	thread to continue:
		3821
		3822	static void
		3823	real_invoke_pending (EV_P)
		3824	{
		3825	userdata *u = ev_userdata (EV_A);
		3826
		3827	pthread_mutex_lock (&u->lock);
		3828	ev_invoke_pending (EV_A);
		3829	pthread_cond_signal (&u->invoke_cv);
		3830	pthread_mutex_unlock (&u->lock);
		3831	}
		3832
		3833	Whenever you want to start/stop a watcher or do other modifications to an
		3834	event loop, you will now have to lock:
		3835
		3836	ev_timer timeout_watcher;
		3837	userdata *u = ev_userdata (EV_A);
		3838
		3839	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3840
		3841	pthread_mutex_lock (&u->lock);
		3842	ev_timer_start (EV_A_ &timeout_watcher);
		3843	ev_async_send (EV_A_ &u->async_w);
		3844	pthread_mutex_unlock (&u->lock);
		3845
		3846	Note that sending the C<ev_async> watcher is required because otherwise
		3847	an event loop currently blocking in the kernel will have no knowledge
		3848	about the newly added timer. By waking up the loop it will pick up any new
		3849	watchers in the next event loop iteration.
		3850
		3851	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3852
		3853	While the overhead of a callback that e.g. schedules a thread is small, it
		3854	is still an overhead. If you embed libev, and your main usage is with some
		3855	kind of threads or coroutines, you might want to customise libev so that
		3856	doesn't need callbacks anymore.
		3857
		3858	Imagine you have coroutines that you can switch to using a function
		3859	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3860	and that due to some magic, the currently active coroutine is stored in a
		3861	global called C<current_coro>. Then you can build your own "wait for libev
		3862	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3863	the differing C<;> conventions):
		3864
		3865	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3866	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3867
		3868	That means instead of having a C callback function, you store the
		3869	coroutine to switch to in each watcher, and instead of having libev call
		3870	your callback, you instead have it switch to that coroutine.
		3871
		3872	A coroutine might now wait for an event with a function called
		3873	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3874	matter when, or whether the watcher is active or not when this function is
		3875	called):
		3876
		3877	void
		3878	wait_for_event (ev_watcher *w)
		3879	{
		3880	ev_set_cb (w, current_coro);
		3881	switch_to (libev_coro);
		3882	}
		3883
		3884	That basically suspends the coroutine inside C<wait_for_event> and
		3885	continues the libev coroutine, which, when appropriate, switches back to
		3886	this or any other coroutine.
		3887
		3888	You can do similar tricks if you have, say, threads with an event queue -
		3889	instead of storing a coroutine, you store the queue object and instead of
		3890	switching to a coroutine, you push the watcher onto the queue and notify
		3891	any waiters.
		3892
		3893	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3894	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3895
		3896	// my_ev.h
		3897	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3898	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3899	#include "../libev/ev.h"
		3900
		3901	// my_ev.c
		3902	#define EV_H "my_ev.h"
		3903	#include "../libev/ev.c"
		3904
		3905	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3906	F<my_ev.c> into your project. When properly specifying include paths, you
		3907	can even use F<ev.h> as header file name directly.
3299		3908
3300		3909
3301	=head1 LIBEVENT EMULATION	3910	=head1 LIBEVENT EMULATION
3302		3911
3303	Libev offers a compatibility emulation layer for libevent. It cannot	3912	Libev offers a compatibility emulation layer for libevent. It cannot
3304	emulate the internals of libevent, so here are some usage hints:	3913	emulate the internals of libevent, so here are some usage hints:
3305		3914
3306	=over 4	3915	=over 4
		3916
		3917	=item * Only the libevent-1.4.1-beta API is being emulated.
		3918
		3919	This was the newest libevent version available when libev was implemented,
		3920	and is still mostly unchanged in 2010.
3307		3921
3308	=item * Use it by including <event.h>, as usual.	3922	=item * Use it by including <event.h>, as usual.
3309		3923
3310	=item * The following members are fully supported: ev_base, ev_callback,	3924	=item * The following members are fully supported: ev_base, ev_callback,
3311	ev_arg, ev_fd, ev_res, ev_events.	3925	ev_arg, ev_fd, ev_res, ev_events.
…		…
3317	=item * Priorities are not currently supported. Initialising priorities	3931	=item * Priorities are not currently supported. Initialising priorities
3318	will fail and all watchers will have the same priority, even though there	3932	will fail and all watchers will have the same priority, even though there
3319	is an ev_pri field.	3933	is an ev_pri field.
3320		3934
3321	=item * In libevent, the last base created gets the signals, in libev, the	3935	=item * In libevent, the last base created gets the signals, in libev, the
3322	first base created (== the default loop) gets the signals.	3936	base that registered the signal gets the signals.
3323		3937
3324	=item * Other members are not supported.	3938	=item * Other members are not supported.
3325		3939
3326	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3940	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3327	to use the libev header file and library.	3941	to use the libev header file and library.
3328		3942
3329	=back	3943	=back
3330		3944
3331	=head1 C++ SUPPORT	3945	=head1 C++ SUPPORT
		3946
		3947	=head2 C API
		3948
		3949	The normal C API should work fine when used from C++: both ev.h and the
		3950	libev sources can be compiled as C++. Therefore, code that uses the C API
		3951	will work fine.
		3952
		3953	Proper exception specifications might have to be added to callbacks passed
		3954	to libev: exceptions may be thrown only from watcher callbacks, all
		3955	other callbacks (allocator, syserr, loop acquire/release and periodic
		3956	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3957	()> specification. If you have code that needs to be compiled as both C
		3958	and C++ you can use the C<EV_THROW> macro for this:
		3959
		3960	static void
		3961	fatal_error (const char *msg) EV_THROW
		3962	{
		3963	perror (msg);
		3964	abort ();
		3965	}
		3966
		3967	...
		3968	ev_set_syserr_cb (fatal_error);
		3969
		3970	The only API functions that can currently throw exceptions are C<ev_run>,
		3971	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3972	because it runs cleanup watchers).
		3973
		3974	Throwing exceptions in watcher callbacks is only supported if libev itself
		3975	is compiled with a C++ compiler or your C and C++ environments allow
		3976	throwing exceptions through C libraries (most do).
		3977
		3978	=head2 C++ API
3332		3979
3333	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3980	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3334	you to use some convenience methods to start/stop watchers and also change	3981	you to use some convenience methods to start/stop watchers and also change
3335	the callback model to a model using method callbacks on objects.	3982	the callback model to a model using method callbacks on objects.
3336		3983
…		…
3346	Care has been taken to keep the overhead low. The only data member the C++	3993	Care has been taken to keep the overhead low. The only data member the C++
3347	classes add (compared to plain C-style watchers) is the event loop pointer	3994	classes add (compared to plain C-style watchers) is the event loop pointer
3348	that the watcher is associated with (or no additional members at all if	3995	that the watcher is associated with (or no additional members at all if
3349	you disable C<EV_MULTIPLICITY> when embedding libev).	3996	you disable C<EV_MULTIPLICITY> when embedding libev).
3350		3997
3351	Currently, functions, and static and non-static member functions can be	3998	Currently, functions, static and non-static member functions and classes
3352	used as callbacks. Other types should be easy to add as long as they only	3999	with C<operator ()> can be used as callbacks. Other types should be easy
3353	need one additional pointer for context. If you need support for other	4000	to add as long as they only need one additional pointer for context. If
3354	types of functors please contact the author (preferably after implementing	4001	you need support for other types of functors please contact the author
3355	it).	4002	(preferably after implementing it).
		4003
		4004	For all this to work, your C++ compiler either has to use the same calling
		4005	conventions as your C compiler (for static member functions), or you have
		4006	to embed libev and compile libev itself as C++.
3356		4007
3357	Here is a list of things available in the C<ev> namespace:	4008	Here is a list of things available in the C<ev> namespace:
3358		4009
3359	=over 4	4010	=over 4
3360		4011
…		…
3370	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4021	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3371		4022
3372	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4023	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3373	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4024	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3374	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4025	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3375	defines by many implementations.	4026	defined by many implementations.
3376		4027
3377	All of those classes have these methods:	4028	All of those classes have these methods:
3378		4029
3379	=over 4	4030	=over 4
3380		4031
…		…
3470	Associates a different C<struct ev_loop> with this watcher. You can only	4121	Associates a different C<struct ev_loop> with this watcher. You can only
3471	do this when the watcher is inactive (and not pending either).	4122	do this when the watcher is inactive (and not pending either).
3472		4123
3473	=item w->set ([arguments])	4124	=item w->set ([arguments])
3474		4125
3475	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4126	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3476	method or a suitable start method must be called at least once. Unlike the	4127	with the same arguments. Either this method or a suitable start method
3477	C counterpart, an active watcher gets automatically stopped and restarted	4128	must be called at least once. Unlike the C counterpart, an active watcher
3478	when reconfiguring it with this method.	4129	gets automatically stopped and restarted when reconfiguring it with this
		4130	method.
		4131
		4132	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4133	clashing with the C<set (loop)> method.
3479		4134
3480	=item w->start ()	4135	=item w->start ()
3481		4136
3482	Starts the watcher. Note that there is no C<loop> argument, as the	4137	Starts the watcher. Note that there is no C<loop> argument, as the
3483	constructor already stores the event loop.	4138	constructor already stores the event loop.
…		…
3513	watchers in the constructor.	4168	watchers in the constructor.
3514		4169
3515	class myclass	4170	class myclass
3516	{	4171	{
3517	ev::io io ; void io_cb (ev::io &w, int revents);	4172	ev::io io ; void io_cb (ev::io &w, int revents);
3518	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4173	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3519	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4174	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3520		4175
3521	myclass (int fd)	4176	myclass (int fd)
3522	{	4177	{
3523	io .set <myclass, &myclass::io_cb > (this);	4178	io .set <myclass, &myclass::io_cb > (this);
…		…
3574	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4229	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3575		4230
3576	=item D	4231	=item D
3577		4232
3578	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4233	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3579	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4234	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3580		4235
3581	=item Ocaml	4236	=item Ocaml
3582		4237
3583	Erkki Seppala has written Ocaml bindings for libev, to be found at	4238	Erkki Seppala has written Ocaml bindings for libev, to be found at
3584	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4239	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3587		4242
3588	Brian Maher has written a partial interface to libev for lua (at the	4243	Brian Maher has written a partial interface to libev for lua (at the
3589	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4244	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3590	L<http://github.com/brimworks/lua-ev>.	4245	L<http://github.com/brimworks/lua-ev>.
3591		4246
		4247	=item Javascript
		4248
		4249	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4250
		4251	=item Others
		4252
		4253	There are others, and I stopped counting.
		4254
3592	=back	4255	=back
3593		4256
3594		4257
3595	=head1 MACRO MAGIC	4258	=head1 MACRO MAGIC
3596		4259
…		…
3632	suitable for use with C<EV_A>.	4295	suitable for use with C<EV_A>.
3633		4296
3634	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4297	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3635		4298
3636	Similar to the other two macros, this gives you the value of the default	4299	Similar to the other two macros, this gives you the value of the default
3637	loop, if multiple loops are supported ("ev loop default").	4300	loop, if multiple loops are supported ("ev loop default"). The default loop
		4301	will be initialised if it isn't already initialised.
		4302
		4303	For non-multiplicity builds, these macros do nothing, so you always have
		4304	to initialise the loop somewhere.
3638		4305
3639	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4306	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3640		4307
3641	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4308	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3642	default loop has been initialised (C<UC> == unchecked). Their behaviour	4309	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3787	supported). It will also not define any of the structs usually found in	4454	supported). It will also not define any of the structs usually found in
3788	F<event.h> that are not directly supported by the libev core alone.	4455	F<event.h> that are not directly supported by the libev core alone.
3789		4456
3790	In standalone mode, libev will still try to automatically deduce the	4457	In standalone mode, libev will still try to automatically deduce the
3791	configuration, but has to be more conservative.	4458	configuration, but has to be more conservative.
		4459
		4460	=item EV_USE_FLOOR
		4461
		4462	If defined to be C<1>, libev will use the C<floor ()> function for its
		4463	periodic reschedule calculations, otherwise libev will fall back on a
		4464	portable (slower) implementation. If you enable this, you usually have to
		4465	link against libm or something equivalent. Enabling this when the C<floor>
		4466	function is not available will fail, so the safe default is to not enable
		4467	this.
3792		4468
3793	=item EV_USE_MONOTONIC	4469	=item EV_USE_MONOTONIC
3794		4470
3795	If defined to be C<1>, libev will try to detect the availability of the	4471	If defined to be C<1>, libev will try to detect the availability of the
3796	monotonic clock option at both compile time and runtime. Otherwise no	4472	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3881		4557
3882	If programs implement their own fd to handle mapping on win32, then this	4558	If programs implement their own fd to handle mapping on win32, then this
3883	macro can be used to override the C<close> function, useful to unregister	4559	macro can be used to override the C<close> function, useful to unregister
3884	file descriptors again. Note that the replacement function has to close	4560	file descriptors again. Note that the replacement function has to close
3885	the underlying OS handle.	4561	the underlying OS handle.
		4562
		4563	=item EV_USE_WSASOCKET
		4564
		4565	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4566	communication socket, which works better in some environments. Otherwise,
		4567	the normal C<socket> function will be used, which works better in other
		4568	environments.
3886		4569
3887	=item EV_USE_POLL	4570	=item EV_USE_POLL
3888		4571
3889	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4572	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3890	backend. Otherwise it will be enabled on non-win32 platforms. It	4573	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3926	If defined to be C<1>, libev will compile in support for the Linux inotify	4609	If defined to be C<1>, libev will compile in support for the Linux inotify
3927	interface to speed up C<ev_stat> watchers. Its actual availability will	4610	interface to speed up C<ev_stat> watchers. Its actual availability will
3928	be detected at runtime. If undefined, it will be enabled if the headers	4611	be detected at runtime. If undefined, it will be enabled if the headers
3929	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4612	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3930		4613
		4614	=item EV_NO_SMP
		4615
		4616	If defined to be C<1>, libev will assume that memory is always coherent
		4617	between threads, that is, threads can be used, but threads never run on
		4618	different cpus (or different cpu cores). This reduces dependencies
		4619	and makes libev faster.
		4620
		4621	=item EV_NO_THREADS
		4622
		4623	If defined to be C<1>, libev will assume that it will never be called
		4624	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4625	above. This reduces dependencies and makes libev faster.
		4626
3931	=item EV_ATOMIC_T	4627	=item EV_ATOMIC_T
3932		4628
3933	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4629	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3934	access is atomic with respect to other threads or signal contexts. No such	4630	access is atomic with respect to other threads or signal contexts. No
3935	type is easily found in the C language, so you can provide your own type	4631	such type is easily found in the C language, so you can provide your own
3936	that you know is safe for your purposes. It is used both for signal handler "locking"	4632	type that you know is safe for your purposes. It is used both for signal
3937	as well as for signal and thread safety in C<ev_async> watchers.	4633	handler "locking" as well as for signal and thread safety in C<ev_async>
		4634	watchers.
3938		4635
3939	In the absence of this define, libev will use C<sig_atomic_t volatile>	4636	In the absence of this define, libev will use C<sig_atomic_t volatile>
3940	(from F<signal.h>), which is usually good enough on most platforms.	4637	(from F<signal.h>), which is usually good enough on most platforms.
3941		4638
3942	=item EV_H (h)	4639	=item EV_H (h)
…		…
3969	will have the C<struct ev_loop *> as first argument, and you can create	4666	will have the C<struct ev_loop *> as first argument, and you can create
3970	additional independent event loops. Otherwise there will be no support	4667	additional independent event loops. Otherwise there will be no support
3971	for multiple event loops and there is no first event loop pointer	4668	for multiple event loops and there is no first event loop pointer
3972	argument. Instead, all functions act on the single default loop.	4669	argument. Instead, all functions act on the single default loop.
3973		4670
		4671	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4672	default loop when multiplicity is switched off - you always have to
		4673	initialise the loop manually in this case.
		4674
3974	=item EV_MINPRI	4675	=item EV_MINPRI
3975		4676
3976	=item EV_MAXPRI	4677	=item EV_MAXPRI
3977		4678
3978	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4679	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4014	#define EV_USE_POLL 1	4715	#define EV_USE_POLL 1
4015	#define EV_CHILD_ENABLE 1	4716	#define EV_CHILD_ENABLE 1
4016	#define EV_ASYNC_ENABLE 1	4717	#define EV_ASYNC_ENABLE 1
4017		4718
4018	The actual value is a bitset, it can be a combination of the following	4719	The actual value is a bitset, it can be a combination of the following
4019	values:	4720	values (by default, all of these are enabled):
4020		4721
4021	=over 4	4722	=over 4
4022		4723
4023	=item C<1> - faster/larger code	4724	=item C<1> - faster/larger code
4024		4725
…		…
4028	code size by roughly 30% on amd64).	4729	code size by roughly 30% on amd64).
4029		4730
4030	When optimising for size, use of compiler flags such as C<-Os> with	4731	When optimising for size, use of compiler flags such as C<-Os> with
4031	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4732	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4032	assertions.	4733	assertions.
		4734
		4735	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4736	(e.g. gcc with C<-Os>).
4033		4737
4034	=item C<2> - faster/larger data structures	4738	=item C<2> - faster/larger data structures
4035		4739
4036	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4740	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4037	hash table sizes and so on. This will usually further increase code size	4741	hash table sizes and so on. This will usually further increase code size
4038	and can additionally have an effect on the size of data structures at	4742	and can additionally have an effect on the size of data structures at
4039	runtime.	4743	runtime.
4040		4744
		4745	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4746	(e.g. gcc with C<-Os>).
		4747
4041	=item C<4> - full API configuration	4748	=item C<4> - full API configuration
4042		4749
4043	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4750	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4044	enables multiplicity (C<EV_MULTIPLICITY>=1).	4751	enables multiplicity (C<EV_MULTIPLICITY>=1).
4045		4752
…		…
4075		4782
4076	With an intelligent-enough linker (gcc+binutils are intelligent enough	4783	With an intelligent-enough linker (gcc+binutils are intelligent enough
4077	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4784	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4078	your program might be left out as well - a binary starting a timer and an	4785	your program might be left out as well - a binary starting a timer and an
4079	I/O watcher then might come out at only 5Kb.	4786	I/O watcher then might come out at only 5Kb.
		4787
		4788	=item EV_API_STATIC
		4789
		4790	If this symbol is defined (by default it is not), then all identifiers
		4791	will have static linkage. This means that libev will not export any
		4792	identifiers, and you cannot link against libev anymore. This can be useful
		4793	when you embed libev, only want to use libev functions in a single file,
		4794	and do not want its identifiers to be visible.
		4795
		4796	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4797	wants to use libev.
		4798
		4799	This option only works when libev is compiled with a C compiler, as C++
		4800	doesn't support the required declaration syntax.
4080		4801
4081	=item EV_AVOID_STDIO	4802	=item EV_AVOID_STDIO
4082		4803
4083	If this is set to C<1> at compiletime, then libev will avoid using stdio	4804	If this is set to C<1> at compiletime, then libev will avoid using stdio
4084	functions (printf, scanf, perror etc.). This will increase the code size	4805	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4228	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4949	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4229		4950
4230	#include "ev_cpp.h"	4951	#include "ev_cpp.h"
4231	#include "ev.c"	4952	#include "ev.c"
4232		4953
4233	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4954	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4234		4955
4235	=head2 THREADS AND COROUTINES	4956	=head2 THREADS AND COROUTINES
4236		4957
4237	=head3 THREADS	4958	=head3 THREADS
4238		4959
…		…
4289	default loop and triggering an C<ev_async> watcher from the default loop	5010	default loop and triggering an C<ev_async> watcher from the default loop
4290	watcher callback into the event loop interested in the signal.	5011	watcher callback into the event loop interested in the signal.
4291		5012
4292	=back	5013	=back
4293		5014
4294	=head4 THREAD LOCKING EXAMPLE	5015	See also L</THREAD LOCKING EXAMPLE>.
4295
4296	Here is a fictitious example of how to run an event loop in a different
4297	thread than where callbacks are being invoked and watchers are
4298	created/added/removed.
4299
4300	For a real-world example, see the C<EV::Loop::Async> perl module,
4301	which uses exactly this technique (which is suited for many high-level
4302	languages).
4303
4304	The example uses a pthread mutex to protect the loop data, a condition
4305	variable to wait for callback invocations, an async watcher to notify the
4306	event loop thread and an unspecified mechanism to wake up the main thread.
4307
4308	First, you need to associate some data with the event loop:
4309
4310	typedef struct {
4311	mutex_t lock; /* global loop lock */
4312	ev_async async_w;
4313	thread_t tid;
4314	cond_t invoke_cv;
4315	} userdata;
4316
4317	void prepare_loop (EV_P)
4318	{
4319	// for simplicity, we use a static userdata struct.
4320	static userdata u;
4321
4322	ev_async_init (&u->async_w, async_cb);
4323	ev_async_start (EV_A_ &u->async_w);
4324
4325	pthread_mutex_init (&u->lock, 0);
4326	pthread_cond_init (&u->invoke_cv, 0);
4327
4328	// now associate this with the loop
4329	ev_set_userdata (EV_A_ u);
4330	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4331	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4332
4333	// then create the thread running ev_loop
4334	pthread_create (&u->tid, 0, l_run, EV_A);
4335	}
4336
4337	The callback for the C<ev_async> watcher does nothing: the watcher is used
4338	solely to wake up the event loop so it takes notice of any new watchers
4339	that might have been added:
4340
4341	static void
4342	async_cb (EV_P_ ev_async *w, int revents)
4343	{
4344	// just used for the side effects
4345	}
4346
4347	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4348	protecting the loop data, respectively.
4349
4350	static void
4351	l_release (EV_P)
4352	{
4353	userdata *u = ev_userdata (EV_A);
4354	pthread_mutex_unlock (&u->lock);
4355	}
4356
4357	static void
4358	l_acquire (EV_P)
4359	{
4360	userdata *u = ev_userdata (EV_A);
4361	pthread_mutex_lock (&u->lock);
4362	}
4363
4364	The event loop thread first acquires the mutex, and then jumps straight
4365	into C<ev_run>:
4366
4367	void *
4368	l_run (void *thr_arg)
4369	{
4370	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4371
4372	l_acquire (EV_A);
4373	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4374	ev_run (EV_A_ 0);
4375	l_release (EV_A);
4376
4377	return 0;
4378	}
4379
4380	Instead of invoking all pending watchers, the C<l_invoke> callback will
4381	signal the main thread via some unspecified mechanism (signals? pipe
4382	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4383	have been called (in a while loop because a) spurious wakeups are possible
4384	and b) skipping inter-thread-communication when there are no pending
4385	watchers is very beneficial):
4386
4387	static void
4388	l_invoke (EV_P)
4389	{
4390	userdata *u = ev_userdata (EV_A);
4391
4392	while (ev_pending_count (EV_A))
4393	{
4394	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4395	pthread_cond_wait (&u->invoke_cv, &u->lock);
4396	}
4397	}
4398
4399	Now, whenever the main thread gets told to invoke pending watchers, it
4400	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4401	thread to continue:
4402
4403	static void
4404	real_invoke_pending (EV_P)
4405	{
4406	userdata *u = ev_userdata (EV_A);
4407
4408	pthread_mutex_lock (&u->lock);
4409	ev_invoke_pending (EV_A);
4410	pthread_cond_signal (&u->invoke_cv);
4411	pthread_mutex_unlock (&u->lock);
4412	}
4413
4414	Whenever you want to start/stop a watcher or do other modifications to an
4415	event loop, you will now have to lock:
4416
4417	ev_timer timeout_watcher;
4418	userdata *u = ev_userdata (EV_A);
4419
4420	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4421
4422	pthread_mutex_lock (&u->lock);
4423	ev_timer_start (EV_A_ &timeout_watcher);
4424	ev_async_send (EV_A_ &u->async_w);
4425	pthread_mutex_unlock (&u->lock);
4426
4427	Note that sending the C<ev_async> watcher is required because otherwise
4428	an event loop currently blocking in the kernel will have no knowledge
4429	about the newly added timer. By waking up the loop it will pick up any new
4430	watchers in the next event loop iteration.
4431		5016
4432	=head3 COROUTINES	5017	=head3 COROUTINES
4433		5018
4434	Libev is very accommodating to coroutines ("cooperative threads"):	5019	Libev is very accommodating to coroutines ("cooperative threads"):
4435	libev fully supports nesting calls to its functions from different	5020	libev fully supports nesting calls to its functions from different
…		…
4600	requires, and its I/O model is fundamentally incompatible with the POSIX	5185	requires, and its I/O model is fundamentally incompatible with the POSIX
4601	model. Libev still offers limited functionality on this platform in	5186	model. Libev still offers limited functionality on this platform in
4602	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5187	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4603	descriptors. This only applies when using Win32 natively, not when using	5188	descriptors. This only applies when using Win32 natively, not when using
4604	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5189	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4605	as every compielr comes with a slightly differently broken/incompatible	5190	as every compiler comes with a slightly differently broken/incompatible
4606	environment.	5191	environment.
4607		5192
4608	Lifting these limitations would basically require the full	5193	Lifting these limitations would basically require the full
4609	re-implementation of the I/O system. If you are into this kind of thing,	5194	re-implementation of the I/O system. If you are into this kind of thing,
4610	then note that glib does exactly that for you in a very portable way (note	5195	then note that glib does exactly that for you in a very portable way (note
…		…
4704	structure (guaranteed by POSIX but not by ISO C for example), but it also	5289	structure (guaranteed by POSIX but not by ISO C for example), but it also
4705	assumes that the same (machine) code can be used to call any watcher	5290	assumes that the same (machine) code can be used to call any watcher
4706	callback: The watcher callbacks have different type signatures, but libev	5291	callback: The watcher callbacks have different type signatures, but libev
4707	calls them using an C<ev_watcher *> internally.	5292	calls them using an C<ev_watcher *> internally.
4708		5293
		5294	=item pointer accesses must be thread-atomic
		5295
		5296	Accessing a pointer value must be atomic, it must both be readable and
		5297	writable in one piece - this is the case on all current architectures.
		5298
4709	=item C<sig_atomic_t volatile> must be thread-atomic as well	5299	=item C<sig_atomic_t volatile> must be thread-atomic as well
4710		5300
4711	The type C<sig_atomic_t volatile> (or whatever is defined as	5301	The type C<sig_atomic_t volatile> (or whatever is defined as
4712	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5302	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4713	threads. This is not part of the specification for C<sig_atomic_t>, but is	5303	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4738		5328
4739	The type C<double> is used to represent timestamps. It is required to	5329	The type C<double> is used to represent timestamps. It is required to
4740	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5330	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4741	good enough for at least into the year 4000 with millisecond accuracy	5331	good enough for at least into the year 4000 with millisecond accuracy
4742	(the design goal for libev). This requirement is overfulfilled by	5332	(the design goal for libev). This requirement is overfulfilled by
4743	implementations using IEEE 754, which is basically all existing ones. With	5333	implementations using IEEE 754, which is basically all existing ones.
		5334
4744	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5335	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5336	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5337	is either obsolete or somebody patched it to use C<long double> or
		5338	something like that, just kidding).
4745		5339
4746	=back	5340	=back
4747		5341
4748	If you know of other additional requirements drop me a note.	5342	If you know of other additional requirements drop me a note.
4749		5343
…		…
4811	=item Processing ev_async_send: O(number_of_async_watchers)	5405	=item Processing ev_async_send: O(number_of_async_watchers)
4812		5406
4813	=item Processing signals: O(max_signal_number)	5407	=item Processing signals: O(max_signal_number)
4814		5408
4815	Sending involves a system call I<iff> there were no other C<ev_async_send>	5409	Sending involves a system call I<iff> there were no other C<ev_async_send>
4816	calls in the current loop iteration. Checking for async and signal events	5410	calls in the current loop iteration and the loop is currently
		5411	blocked. Checking for async and signal events involves iterating over all
4817	involves iterating over all running async watchers or all signal numbers.	5412	running async watchers or all signal numbers.
4818		5413
4819	=back	5414	=back
4820		5415
4821		5416
4822	=head1 PORTING FROM LIBEV 3.X TO 4.X	5417	=head1 PORTING FROM LIBEV 3.X TO 4.X
4823		5418
4824	The major version 4 introduced some minor incompatible changes to the API.	5419	The major version 4 introduced some incompatible changes to the API.
4825		5420
4826	At the moment, the C<ev.h> header file tries to implement superficial	5421	At the moment, the C<ev.h> header file provides compatibility definitions
4827	compatibility, so most programs should still compile. Those might be	5422	for all changes, so most programs should still compile. The compatibility
4828	removed in later versions of libev, so better update early than late.	5423	layer might be removed in later versions of libev, so better update to the
		5424	new API early than late.
4829		5425
4830	=over 4	5426	=over 4
		5427
		5428	=item C<EV_COMPAT3> backwards compatibility mechanism
		5429
		5430	The backward compatibility mechanism can be controlled by
		5431	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5432	section.
		5433
		5434	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5435
		5436	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5437
		5438	ev_loop_destroy (EV_DEFAULT_UC);
		5439	ev_loop_fork (EV_DEFAULT);
4831		5440
4832	=item function/symbol renames	5441	=item function/symbol renames
4833		5442
4834	A number of functions and symbols have been renamed:	5443	A number of functions and symbols have been renamed:
4835		5444
…		…
4854	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5463	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4855	as all other watcher types. Note that C<ev_loop_fork> is still called	5464	as all other watcher types. Note that C<ev_loop_fork> is still called
4856	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5465	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4857	typedef.	5466	typedef.
4858		5467
4859	=item C<EV_COMPAT3> backwards compatibility mechanism
4860
4861	The backward compatibility mechanism can be controlled by
4862	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4863	section.
4864
4865	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5468	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4866		5469
4867	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5470	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4868	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5471	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4869	and work, but the library code will of course be larger.	5472	and work, but the library code will of course be larger.
…		…
4876	=over 4	5479	=over 4
4877		5480
4878	=item active	5481	=item active
4879		5482
4880	A watcher is active as long as it has been started and not yet stopped.	5483	A watcher is active as long as it has been started and not yet stopped.
4881	See L<WATCHER STATES> for details.	5484	See L</WATCHER STATES> for details.
4882		5485
4883	=item application	5486	=item application
4884		5487
4885	In this document, an application is whatever is using libev.	5488	In this document, an application is whatever is using libev.
4886		5489
…		…
4922	watchers and events.	5525	watchers and events.
4923		5526
4924	=item pending	5527	=item pending
4925		5528
4926	A watcher is pending as soon as the corresponding event has been	5529	A watcher is pending as soon as the corresponding event has been
4927	detected. See L<WATCHER STATES> for details.	5530	detected. See L</WATCHER STATES> for details.
4928		5531
4929	=item real time	5532	=item real time
4930		5533
4931	The physical time that is observed. It is apparently strictly monotonic :)	5534	The physical time that is observed. It is apparently strictly monotonic :)
4932		5535
4933	=item wall-clock time	5536	=item wall-clock time
4934		5537
4935	The time and date as shown on clocks. Unlike real time, it can actually	5538	The time and date as shown on clocks. Unlike real time, it can actually
4936	be wrong and jump forwards and backwards, e.g. when the you adjust your	5539	be wrong and jump forwards and backwards, e.g. when you adjust your
4937	clock.	5540	clock.
4938		5541
4939	=item watcher	5542	=item watcher
4940		5543
4941	A data structure that describes interest in certain events. Watchers need	5544	A data structure that describes interest in certain events. Watchers need
…		…
4943		5546
4944	=back	5547	=back
4945		5548
4946	=head1 AUTHOR	5549	=head1 AUTHOR
4947		5550
4948	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5551	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5552	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4949		5553

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines