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Revision 1.398 by root, Mon Apr 2 18:39:54 2012 UTC

…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
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);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
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_loop (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
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity 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
…		…
118	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
119	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
120	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
121	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
122	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
123	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
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 (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
134	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	144	time differences (e.g. delays) throughout libev.
136		145
137	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
138		147
139	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	149	and internal errors (bugs).
…		…
164		173
165	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
166		175
167	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
168	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
169	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>.
170		180
171	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
172		182
173	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
174	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
175	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 >>).
176		192
177	=item int ev_version_major ()	193	=item int ev_version_major ()
178		194
179	=item int ev_version_minor ()	195	=item int ev_version_minor ()
180		196
…		…
191	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
192	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
193	not a problem.	209	not a problem.
194		210
195	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
196	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
197		214
198	assert (("libev version mismatch",	215	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
201		218
…		…
212	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
214		231
215	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
216		233
217	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
218	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
219	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
220	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
221	(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
222	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
223		241
224	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
225		243
226	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
227	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
228	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
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
231		249
232	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
233		251
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
235		253
236	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
237	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
238	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
239	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
…		…
265	}	283	}
266		284
267	...	285	...
268	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
269		287
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg))
271		289
272	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
273	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
274	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
275	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
…		…
287	}	305	}
288		306
289	...	307	...
290	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
291		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
292	=back	323	=back
293		324
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		326
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
299		330
300	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
301	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
302	not.	333	do not.
303		334
304	=over 4	335	=over 4
305		336
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		338
308	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
309	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
310	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
311	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".
312		349
313	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
314	function.	351	function (or via the C<EV_DEFAULT> macro).
315		352
316	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
317	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
318	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).
319		357
320	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,
321	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
322	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
323	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
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	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.
326		382
327	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
328	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>).
329		385
330	The following flags are supported:	386	The following flags are supported:
…		…
345	useful to try out specific backends to test their performance, or to work	401	useful to try out specific backends to test their performance, or to work
346	around bugs.	402	around bugs.
347		403
348	=item C<EVFLAG_FORKCHECK>	404	=item C<EVFLAG_FORKCHECK>
349		405
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	406	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	407	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		408
354	This works by calling C<getpid ()> on every iteration of the loop,	409	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	410	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	411	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	412	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
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_NOSIGNALFD>	430	=item C<EVFLAG_SIGNALFD>
376		431
377	When this flag is specified, then libev will not 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 is	433	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	434	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	435	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	436	handling with threads, as long as you properly block signals in your
		437	threads that are not interested in handling them.
		438
		439	Signalfd will not be used by default as this changes your signal mask, and
		440	there are a lot of shoddy libraries and programs (glib's threadpool for
		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.
382		457
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		459
385	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
386	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,
…		…
411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413		488
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
416	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
417	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
418	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
419	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
420		498
421	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
422	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
423	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
424	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
425	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
426	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
427	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
428	hard to detect.	508	and is of course hard to detect.
429		509
430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
431	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
432	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
433	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
434	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
435	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
436	events to filter out spurious ones, recreating the set when required.	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
		520	not least, it also refuses to work with some file descriptors which work
		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...
437		526
438	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
439	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
440	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
441	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
…		…
478		567
479	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
480	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
481	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
482	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
483	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
484	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
485	cases	574	drops fds silently in similarly hard-to-detect cases
486		575
487	This backend usually performs well under most conditions.	576	This backend usually performs well under most conditions.
488		577
489	While nominally embeddable in other event loops, this doesn't work	578	While nominally embeddable in other event loops, this doesn't work
490	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
…		…
507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
508		597
509	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,
510	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)).
511		600
512	Please note that Solaris event ports can deliver a lot of spurious
513	notifications, so you need to use non-blocking I/O or other means to avoid
514	blocking when no data (or space) is available.
515
516	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
517	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
518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
519	might perform better.	604	might perform better.
520		605
521	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
522	notifications, this backend actually performed fully to specification
523	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
524	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.
525		620
526	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
527	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
528		623
529	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
530		625
531	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
532	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
533	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
534		629
535	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).
536		639
537	=back	640	=back
538		641
539	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,
540	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
541	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
542	()> will be tried.	645	()> will be tried.
543		646
544	Example: This is the most typical usage.
545
546	if (!ev_default_loop (0))
547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
548
549	Example: Restrict libev to the select and poll backends, and do not allow
550	environment settings to be taken into account:
551
552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
553
554	Example: Use whatever libev has to offer, but make sure that kqueue is
555	used if available (warning, breaks stuff, best use only with your own
556	private event loop and only if you know the OS supports your types of
557	fds):
558
559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
560
561	=item struct ev_loop *ev_loop_new (unsigned int flags)
562
563	Similar to C<ev_default_loop>, but always creates a new event loop that is
564	always distinct from the default loop. Unlike the default loop, it cannot
565	handle signal and child watchers, and attempts to do so will be greeted by
566	undefined behaviour (or a failed assertion if assertions are enabled).
567
568	Note that this function I<is> thread-safe, and the recommended way to use
569	libev with threads is indeed to create one loop per thread, and using the
570	default loop in the "main" or "initial" thread.
571
572	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.
573		648
574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575	if (!epoller)	650	if (!epoller)
576	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
577		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
578	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
579		659
580	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
581	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
582	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
583	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
584	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
585	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
587		667
588	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
589	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
590	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
591		671
592	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
593	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.
594	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>
595	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
596		680
597	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
598		682
599	Like C<ev_default_destroy>, but destroys an event loop created by an
600	earlier call to C<ev_loop_new>.
601
602	=item ev_default_fork ()
603
604	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
605	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
606	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
607	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
608	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
609	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
610		693
611	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
612	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
613	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
614		700
615	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
616	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		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	...
619	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
620
621	=item ev_loop_fork (loop)
622
623	Like C<ev_default_fork>, but acts on an event loop created by
624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
625	after fork that you want to re-use in the child, and how you do this is
626	entirely your own problem.
627		715
628	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
629		717
630	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
631	otherwise.	719	otherwise.
632		720
633	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
634		722
635	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
636	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
637	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
638		726
639	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
640	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
641	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
642		731
643	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
644		733
645	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
646	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
647		736
648	Outside C<ev_loop>, 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
649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
650	in which case it is higher.	739	in which case it is higher.
651		740
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
654		745
655	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
656		747
657	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
658	use.	749	use.
…		…
667		758
668	=item ev_now_update (loop)	759	=item ev_now_update (loop)
669		760
670	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
671	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
672	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
673		764
674	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
675	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
676	the current time is a good idea.	767	the current time is a good idea.
677		768
…		…
679		770
680	=item ev_suspend (loop)	771	=item ev_suspend (loop)
681		772
682	=item ev_resume (loop)	773	=item ev_resume (loop)
683		774
684	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
685	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
686		777
687	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
688	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
689	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
690	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
693		784
694	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
695	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
696	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
697	occured while suspended).	788	occurred while suspended).
698		789
699	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
700	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
701	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
702		793
703	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
704	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
705		796
706	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
707		798
708	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
709	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
710	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
711		804
712	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
713	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
714		808
715	Please note that an explicit C<ev_unloop> is usually better than	809	Please note that an explicit C<ev_break> is usually better than
716	relying on all watchers to be stopped when deciding when a program has	810	relying on all watchers to be stopped when deciding when a program has
717	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
718	that automatically loops as long as it has to and no longer by virtue	812	that automatically loops as long as it has to and no longer by virtue
719	of relying on its watchers stopping correctly, that is truly a thing of	813	of relying on its watchers stopping correctly, that is truly a thing of
720	beauty.	814	beauty.
721		815
		816	This function is also I<mostly> exception-safe - you can break out of
		817	a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		818	exception and so on. This does not decrement the C<ev_depth> value, nor
		819	will it clear any outstanding C<EVBREAK_ONE> breaks.
		820
722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	821	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
723	those events and any already outstanding ones, but will not block your	822	those events and any already outstanding ones, but will not wait and
724	process in case there are no events and will return after one iteration of	823	block your process in case there are no events and will return after one
725	the loop.	824	iteration of the loop. This is sometimes useful to poll and handle new
		825	events while doing lengthy calculations, to keep the program responsive.
726		826
727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	827	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
728	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
729	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
730	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
731	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
732	iteration of the loop.	832	iteration of the loop.
733		833
734	This is useful if you are waiting for some external event in conjunction	834	This is useful if you are waiting for some external event in conjunction
735	with something not expressible using other libev watchers (i.e. "roll your	835	with something not expressible using other libev watchers (i.e. "roll your
736	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	836	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
737	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
738		838
739	Here are the gory details of what C<ev_loop> does:	839	Here are the gory details of what C<ev_run> does (this is for your
		840	understanding, not a guarantee that things will work exactly like this in
		841	future versions):
740		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- If a fork was detected (by any means), queue and call all fork watchers.	848	- If a fork was detected (by any means), queue and call all fork watchers.
744	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	852	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
752	- Sleep if the I/O and timer collect interval say so.	858	- Sleep if the I/O and timer collect interval say so.
		859	- Increment loop iteration counter.
753	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	862	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
756	- Queue all expired timers.	863	- Queue all expired timers.
757	- Queue all expired periodics.	864	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	866	- Queue all check watchers.
760	- Call all queued watchers in reverse order (i.e. check watchers first).	867	- Call all queued watchers in reverse order (i.e. check watchers first).
761	Signals and child watchers are implemented as I/O watchers, and will	868	Signals and child watchers are implemented as I/O watchers, and will
762	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	870	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
764	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
765	continue with step *.	872	continue with step LOOP.
		873	FINISH:
		874	- Reset the ev_break status iff it was EVBREAK_ONE.
		875	- Decrement the loop depth.
		876	- Return.
766		877
767	Example: Queue some jobs and then loop until no events are outstanding	878	Example: Queue some jobs and then loop until no events are outstanding
768	anymore.	879	anymore.
769		880
770	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
771	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
772	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
774		885
775	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
776		887
777	Can be used to make a call to C<ev_loop> return early (but only after it	888	Can be used to make a call to C<ev_run> return early (but only after it
778	has processed all outstanding events). The C<how> argument must be either	889	has processed all outstanding events). The C<how> argument must be either
779	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	890	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
780	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	891	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
781		892
782	This "unloop state" will be cleared when entering C<ev_loop> again.	893	This "break state" will be cleared on the next call to C<ev_run>.
783		894
784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	895	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		896	which case it will have no effect.
785		897
786	=item ev_ref (loop)	898	=item ev_ref (loop)
787		899
788	=item ev_unref (loop)	900	=item ev_unref (loop)
789		901
790	Ref/unref can be used to add or remove a reference count on the event	902	Ref/unref can be used to add or remove a reference count on the event
791	loop: Every watcher keeps one reference, and as long as the reference	903	loop: Every watcher keeps one reference, and as long as the reference
792	count is nonzero, C<ev_loop> will not return on its own.	904	count is nonzero, C<ev_run> will not return on its own.
793		905
794	If you have a watcher you never unregister that should not keep C<ev_loop>	906	This is useful when you have a watcher that you never intend to
795	from returning, call ev_unref() after starting, and ev_ref() before	907	unregister, but that nevertheless should not keep C<ev_run> from
		908	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796	stopping it.	909	before stopping it.
797		910
798	As an example, libev itself uses this for its internal signal pipe: It	911	As an example, libev itself uses this for its internal signal pipe: It
799	is not visible to the libev user and should not keep C<ev_loop> from	912	is not visible to the libev user and should not keep C<ev_run> from
800	exiting if no event watchers registered by it are active. It is also an	913	exiting if no event watchers registered by it are active. It is also an
801	excellent way to do this for generic recurring timers or from within	914	excellent way to do this for generic recurring timers or from within
802	third-party libraries. Just remember to I<unref after start> and I<ref	915	third-party libraries. Just remember to I<unref after start> and I<ref
803	before stop> (but only if the watcher wasn't active before, or was active	916	before stop> (but only if the watcher wasn't active before, or was active
804	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
805	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
806	in the callback).	919	in the callback).
807		920
808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	921	Example: Create a signal watcher, but keep it from keeping C<ev_run>
809	running when nothing else is active.	922	running when nothing else is active.
810		923
811	ev_signal exitsig;	924	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	927	ev_unref (loop);
815		928
816	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
817		930
818	ev_ref (loop);	931	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
839	overhead for the actual polling but can deliver many events at once.	952	overhead for the actual polling but can deliver many events at once.
840		953
841	By setting a higher I<io collect interval> you allow libev to spend more	954	By setting a higher I<io collect interval> you allow libev to spend more
842	time collecting I/O events, so you can handle more events per iteration,	955	time collecting I/O events, so you can handle more events per iteration,
843	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	956	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
844	C<ev_timer>) will be not affected. Setting this to a non-null value will	957	C<ev_timer>) will not be affected. Setting this to a non-null value will
845	introduce an additional C<ev_sleep ()> call into most loop iterations. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
846	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
847	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
848		962
849	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
850	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
852	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
858	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
859	as this approaches the timing granularity of most systems. Note that if	973	as this approaches the timing granularity of most systems. Note that if
860	you do transactions with the outside world and you can't increase the	974	you do transactions with the outside world and you can't increase the
861	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
862	need to poll once per transaction and the I/O collect interval is 0.01,	976	need to poll once per transaction and the I/O collect interval is 0.01,
863	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
864		978
865	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
867	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
868	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		991
878	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
879		993
880	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
882	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
883		1001
884	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
885		1003
886	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1005	are pending.
888		1006
889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
890		1008
891	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
892	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
893	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
894	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
895		1013
896	If you want to reset the callback, use C<ev_invoke_pending> as new	1014	If you want to reset the callback, use C<ev_invoke_pending> as new
897	callback.	1015	callback.
…		…
900		1018
901	Sometimes you want to share the same loop between multiple threads. This	1019	Sometimes you want to share the same loop between multiple threads. This
902	can be done relatively simply by putting mutex_lock/unlock calls around	1020	can be done relatively simply by putting mutex_lock/unlock calls around
903	each call to a libev function.	1021	each call to a libev function.
904		1022
905	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1023	However, C<ev_run> can run an indefinite time, so it is not feasible
906	wait for it to return. One way around this is to wake up the loop via	1024	to wait for it to return. One way around this is to wake up the event
907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
908	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
909		1027
910	When set, then C<release> will be called just before the thread is	1028	When set, then C<release> will be called just before the thread is
911	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1030	afterwards.
913		1031
…		…
916		1034
917	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
918	C<release> and C<acquire> (that's their only purpose after all), no	1036	C<release> and C<acquire> (that's their only purpose after all), no
919	modifications done will affect the event loop, i.e. adding watchers will	1037	modifications done will affect the event loop, i.e. adding watchers will
920	have no effect on the set of file descriptors being watched, or the time	1038	have no effect on the set of file descriptors being watched, or the time
921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
922	to take note of any changes you made.	1040	to take note of any changes you made.
923		1041
924	In theory, threads executing C<ev_loop> will be async-cancel safe between	1042	In theory, threads executing C<ev_run> will be async-cancel safe between
925	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
926		1044
927	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
928	document.	1046	document.
929		1047
930	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
931		1049
932	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
933		1051
934	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
936	C<0.>	1054	C<0>.
937		1055
938	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
939	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
940	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
941	any other purpose as well.	1059	any other purpose as well.
942		1060
943	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
944		1062
945	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
946	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
947	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
948	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
959		1077
960	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
961	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
962	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
963		1081
964	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
965	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
966	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
967		1086
968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
969	{	1088	{
970	ev_io_stop (w);	1089	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
972	}	1091	}
973		1092
974	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
975		1094
976	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
977		1096
978	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
981		1100
982	ev_loop (loop, 0);	1101	ev_run (loop, 0);
983		1102
984	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
985	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
986	stack).	1105	stack).
987		1106
988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
989	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
990		1109
991	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
992	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
993	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
994	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
995	is readable and/or writable).	1114	and/or writable).
996		1115
997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
998	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
999	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1023	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1024		1143
1025	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
1026	writable.	1145	writable.
1027		1146
1028	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1029		1148
1030	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1031		1150
1032	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1033		1152
…		…
1051		1170
1052	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1053		1172
1054	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1055		1174
1056	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1057	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
1058	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
1059	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
1060	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
1061	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1062	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1063		1182
1064	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1065		1184
1066	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1067		1186
1068	=item C<EV_FORK>	1187	=item C<EV_FORK>
1069		1188
1070	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1071	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
1072		1195
1073	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1074		1197
1075	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1076		1199
…		…
1123		1246
1124	ev_io w;	1247	ev_io w;
1125	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1250
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1252
1130	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
1131	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
1132	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
1133	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
1146		1269
1147	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
1148		1271
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1273
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1275
1153	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1155		1278
1156	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
1157	whole section.	1280	whole section.
1158		1281
1159	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1160		1283
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1285
1163	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
1164	the watcher was active or not).	1287	the watcher was active or not).
1165		1288
1166	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1192		1315
1193	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1194	(modulo threads).	1317	(modulo threads).
1195		1318
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1320
1198	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1199		1322
1200	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1233	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1234		1357
1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1236	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1237		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
1238	=back	1375	=back
1239		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1240		1379
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1242		1381
1243	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1244	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1245	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1246	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1247	member, you can also "subclass" the watcher type and provide your own
1248	data:
1249		1386
1250	struct my_io	1387	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1388
1258	...	1389	=item initialiased
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1390
1262	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1263	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1264		1394
1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1266	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1268	...	1398	C<ev_TYPE_init> again.
1269	}
1270		1399
1271	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1272	instead have been omitted.
1273		1401
1274	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1275	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1276		1407
1277	struct my_biggy	1408	=item pending
1278	{
1279	int some_data;
1280	ev_timer t1;
1281	ev_timer t2;
1282	}
1283		1409
1284	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1285	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1286	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1287	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1288	programmers):	1414	callback.
1289		1415
1290	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1291		1422
1292	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1293	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1294	{	1425	active.
1295	struct my_biggy big = (struct my_biggy *)
1296	(((char *)w) - offsetof (struct my_biggy, t1));
1297	}
1298		1426
1299	static void	1427	=item stopped
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1301	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1302	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1304	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1305		1441
1306	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1307		1443
1308	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1352		1488
1353	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1354	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1355	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1356	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1357	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1358	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1359	workable.	1495	workable.
1360		1496
1361	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1362	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1376	{	1512	{
1377	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1380		1516
1381	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1385	}	1521	}
1386		1522
…		…
1436	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1437	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1438	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1439	required if you know what you are doing).	1575	required if you know what you are doing).
1440		1576
1441	If you cannot use non-blocking mode, then force the use of a
1442	known-to-be-good backend (at the time of this writing, this includes only
1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1444	descriptors for which non-blocking operation makes no sense (such as
1445	files) - libev doesn't guarentee any specific behaviour in that case.
1446
1447	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1448	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1449	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1450	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1451	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1452	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1455		1584
1456	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1457	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1458	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1459	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1460	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1461	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1462	indefinitely.	1591	indefinitely.
1463		1592
1464	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1465		1594
…		…
1493		1622
1494	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1498	=head3 The special problem of fork	1660	=head3 The special problem of fork
1499		1661
1500	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1501	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1502	it in the child.	1664	it in the child if you want to continue to use it in the child.
1503		1665
1504	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1505	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1669
1509	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1510		1671
1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1512	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1515		1676
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1518	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1519		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1520		1719
1521	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1522		1721
1523	=over 4	1722	=over 4
1524		1723
…		…
1556	...	1755	...
1557	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1757	ev_io stdin_readable;
1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1560	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1562		1761
1563		1762
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1764
1566	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1574		1773
1575	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1576	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1577	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
1578	same loop iteration then the ones with earlier time-out values are invoked	1778	iteration then the ones with earlier time-out values are invoked before
1579	before ones of the same priority with later time-out values (but this is	1779	ones of the same priority with later time-out values (but this is no
1580	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1581		1781
1582	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1583		1783
1584	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1585	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1660		1860
1661	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1662	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1663	within the callback:	1863	within the callback:
1664		1864
		1865	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1666		1868
1667	static void	1869	static void
1668	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1669	{	1871	{
1670	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		1874
1673	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1674	if (timeout < now)	1876	if (after < 0.)
1675	{	1877	{
1676	// timeout occured, take action	1878	// timeout occurred, take action
1677	}	1879	}
1678	else	1880	else
1679	{	1881	{
1680	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1685	}	1888	}
1686	}	1889	}
1687		1890
1688	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1689	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1690	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1691	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1692	re-schedule the timer to fire at that future time, to see if maybe we have
1693	a timeout then.
1694		1895
1695	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1696	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1697		1905
1698	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1699	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1700	libev to change the timeout.	1908	libev to change the timeout.
1701		1909
1702	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1703	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1704	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1705		1914
		1915	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		1918
1710	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1712		1921
		1922	if (activity detected)
1713	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1714		1932
1715	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1716	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1717
1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
1719	callback :) - just change the timeout and invoke the callback, which will
1720	fix things for you.
1721		1935
1722	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1723		1937
1724	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1725	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1752	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1753	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1754	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1755	overkill :)	1969	overkill :)
1756		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1757	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1758		2009
1759	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1760	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1761	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1762	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1763	lots of events in one iteration.	2014	lots of events in one iteration.
1764		2015
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1766	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1772		2023
1773	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1775	()>.	2026	()>.
		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
1776		2060
1777	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1778		2062
1779	When you leave the server world it is quite customary to hit machines that	2063	When you leave the server world it is quite customary to hit machines that
1780	can suspend/hibernate - what happens to the clocks during such a suspend?	2064	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1824	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1825	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1826		2110
1827	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1828		2112
1829	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out, and restarts it again if it is
1830	repeating. The exact semantics are:	2114	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2115	timeout to the C<repeat> value and calling C<ev_timer_start>.
1831		2116
		2117	The exact semantics are as in the following rules, all of which will be
		2118	applied to the watcher:
		2119
		2120	=over 4
		2121
1832	If the timer is pending, its pending status is cleared.	2122	=item If the timer is pending, the pending status is always cleared.
1833		2123
1834	If the timer is started but non-repeating, stop it (as if it timed out).	2124	=item If the timer is started but non-repeating, stop it (as if it timed
		2125	out, without invoking it).
1835		2126
1836	If the timer is repeating, either start it if necessary (with the	2127	=item If the timer is repeating, make the C<repeat> value the new timeout
1837	C<repeat> value), or reset the running timer to the C<repeat> value.	2128	and start the timer, if necessary.
		2129
		2130	=back
1838		2131
1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2132	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1840	usage example.	2133	usage example.
1841		2134
1842	=item ev_timer_remaining (loop, ev_timer *)	2135	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2136
1844	Returns the remaining time until a timer fires. If the timer is active,	2137	Returns the remaining time until a timer fires. If the timer is active,
1845	then this time is relative to the current event loop time, otherwise it's	2138	then this time is relative to the current event loop time, otherwise it's
1846	the timeout value currently configured.	2139	the timeout value currently configured.
1847		2140
1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2141	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2142	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1850	will return C<4>. When the timer expires and is restarted, it will return	2143	will return C<4>. When the timer expires and is restarted, it will return
1851	roughly C<7> (likely slightly less as callback invocation takes some time,	2144	roughly C<7> (likely slightly less as callback invocation takes some time,
1852	too), and so on.	2145	too), and so on.
1853		2146
1854	=item ev_tstamp repeat [read-write]	2147	=item ev_tstamp repeat [read-write]
…		…
1883	}	2176	}
1884		2177
1885	ev_timer mytimer;	2178	ev_timer mytimer;
1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2179	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1887	ev_timer_again (&mytimer); /* start timer */	2180	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2181	ev_run (loop, 0);
1889		2182
1890	// and in some piece of code that gets executed on any "activity":	2183	// and in some piece of code that gets executed on any "activity":
1891	// reset the timeout to start ticking again at 10 seconds	2184	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2185	ev_timer_again (&mytimer);
1893		2186
…		…
1919		2212
1920	As with timers, the callback is guaranteed to be invoked only when the	2213	As with timers, the callback is guaranteed to be invoked only when the
1921	point in time where it is supposed to trigger has passed. If multiple	2214	point in time where it is supposed to trigger has passed. If multiple
1922	timers become ready during the same loop iteration then the ones with	2215	timers become ready during the same loop iteration then the ones with
1923	earlier time-out values are invoked before ones with later time-out values	2216	earlier time-out values are invoked before ones with later time-out values
1924	(but this is no longer true when a callback calls C<ev_loop> recursively).	2217	(but this is no longer true when a callback calls C<ev_run> recursively).
1925		2218
1926	=head3 Watcher-Specific Functions and Data Members	2219	=head3 Watcher-Specific Functions and Data Members
1927		2220
1928	=over 4	2221	=over 4
1929		2222
…		…
1964		2257
1965	Another way to think about it (for the mathematically inclined) is that	2258	Another way to think about it (for the mathematically inclined) is that
1966	C<ev_periodic> will try to run the callback in this mode at the next possible	2259	C<ev_periodic> will try to run the callback in this mode at the next possible
1967	time where C<time = offset (mod interval)>, regardless of any time jumps.	2260	time where C<time = offset (mod interval)>, regardless of any time jumps.
1968		2261
1969	For numerical stability it is preferable that the C<offset> value is near	2262	The C<interval> I<MUST> be positive, and for numerical stability, the
1970	C<ev_now ()> (the current time), but there is no range requirement for	2263	interval value should be higher than C<1/8192> (which is around 100
1971	this value, and in fact is often specified as zero.	2264	microseconds) and C<offset> should be higher than C<0> and should have
		2265	at most a similar magnitude as the current time (say, within a factor of
		2266	ten). Typical values for offset are, in fact, C<0> or something between
		2267	C<0> and C<interval>, which is also the recommended range.
1972		2268
1973	Note also that there is an upper limit to how often a timer can fire (CPU	2269	Note also that there is an upper limit to how often a timer can fire (CPU
1974	speed for example), so if C<interval> is very small then timing stability	2270	speed for example), so if C<interval> is very small then timing stability
1975	will of course deteriorate. Libev itself tries to be exact to be about one	2271	will of course deteriorate. Libev itself tries to be exact to be about one
1976	millisecond (if the OS supports it and the machine is fast enough).	2272	millisecond (if the OS supports it and the machine is fast enough).
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2353	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2354	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2355	potentially a lot of jitter, but good long-term stability.
2060		2356
2061	static void	2357	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2358	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2359	{
2064	... its now a full hour (UTC, or TAI or whatever your clock follows)	2360	... its now a full hour (UTC, or TAI or whatever your clock follows)
2065	}	2361	}
2066		2362
2067	ev_periodic hourly_tick;	2363	ev_periodic hourly_tick;
…		…
2090		2386
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2387	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2388
2093	Signal watchers will trigger an event when the process receives a specific	2389	Signal watchers will trigger an event when the process receives a specific
2094	signal one or more times. Even though signals are very asynchronous, libev	2390	signal one or more times. Even though signals are very asynchronous, libev
2095	will try it's best to deliver signals synchronously, i.e. as part of the	2391	will try its best to deliver signals synchronously, i.e. as part of the
2096	normal event processing, like any other event.	2392	normal event processing, like any other event.
2097		2393
2098	If you want signals to be delivered truly asynchronously, just use	2394	If you want signals to be delivered truly asynchronously, just use
2099	C<sigaction> as you would do without libev and forget about sharing	2395	C<sigaction> as you would do without libev and forget about sharing
2100	the signal. You can even use C<ev_async> from a signal handler to	2396	the signal. You can even use C<ev_async> from a signal handler to
…		…
2108		2404
2109	When the first watcher gets started will libev actually register something	2405	When the first watcher gets started will libev actually register something
2110	with the kernel (thus it coexists with your own signal handlers as long as	2406	with the kernel (thus it coexists with your own signal handlers as long as
2111	you don't register any with libev for the same signal).	2407	you don't register any with libev for the same signal).
2112		2408
2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
2115	sotpping it again), that is, libev might or might not block the signal,
2116	and might or might not set or restore the installed signal handler.
2117
2118	If possible and supported, libev will install its handlers with	2409	If possible and supported, libev will install its handlers with
2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2410	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2120	not be unduly interrupted. If you have a problem with system calls getting	2411	not be unduly interrupted. If you have a problem with system calls getting
2121	interrupted by signals you can block all signals in an C<ev_check> watcher	2412	interrupted by signals you can block all signals in an C<ev_check> watcher
2122	and unblock them in an C<ev_prepare> watcher.	2413	and unblock them in an C<ev_prepare> watcher.
2123		2414
		2415	=head3 The special problem of inheritance over fork/execve/pthread_create
		2416
		2417	Both the signal mask (C<sigprocmask>) and the signal disposition
		2418	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2419	stopping it again), that is, libev might or might not block the signal,
		2420	and might or might not set or restore the installed signal handler (but
		2421	see C<EVFLAG_NOSIGMASK>).
		2422
		2423	While this does not matter for the signal disposition (libev never
		2424	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2425	C<execve>), this matters for the signal mask: many programs do not expect
		2426	certain signals to be blocked.
		2427
		2428	This means that before calling C<exec> (from the child) you should reset
		2429	the signal mask to whatever "default" you expect (all clear is a good
		2430	choice usually).
		2431
		2432	The simplest way to ensure that the signal mask is reset in the child is
		2433	to install a fork handler with C<pthread_atfork> that resets it. That will
		2434	catch fork calls done by libraries (such as the libc) as well.
		2435
		2436	In current versions of libev, the signal will not be blocked indefinitely
		2437	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2438	the window of opportunity for problems, it will not go away, as libev
		2439	I<has> to modify the signal mask, at least temporarily.
		2440
		2441	So I can't stress this enough: I<If you do not reset your signal mask when
		2442	you expect it to be empty, you have a race condition in your code>. This
		2443	is not a libev-specific thing, this is true for most event libraries.
		2444
		2445	=head3 The special problem of threads signal handling
		2446
		2447	POSIX threads has problematic signal handling semantics, specifically,
		2448	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2449	threads in a process block signals, which is hard to achieve.
		2450
		2451	When you want to use sigwait (or mix libev signal handling with your own
		2452	for the same signals), you can tackle this problem by globally blocking
		2453	all signals before creating any threads (or creating them with a fully set
		2454	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2455	loops. Then designate one thread as "signal receiver thread" which handles
		2456	these signals. You can pass on any signals that libev might be interested
		2457	in by calling C<ev_feed_signal>.
		2458
2124	=head3 Watcher-Specific Functions and Data Members	2459	=head3 Watcher-Specific Functions and Data Members
2125		2460
2126	=over 4	2461	=over 4
2127		2462
2128	=item ev_signal_init (ev_signal *, callback, int signum)	2463	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2143	Example: Try to exit cleanly on SIGINT.	2478	Example: Try to exit cleanly on SIGINT.
2144		2479
2145	static void	2480	static void
2146	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2481	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2147	{	2482	{
2148	ev_unloop (loop, EVUNLOOP_ALL);	2483	ev_break (loop, EVBREAK_ALL);
2149	}	2484	}
2150		2485
2151	ev_signal signal_watcher;	2486	ev_signal signal_watcher;
2152	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2487	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2153	ev_signal_start (loop, &signal_watcher);	2488	ev_signal_start (loop, &signal_watcher);
…		…
2539		2874
2540	Prepare and check watchers are usually (but not always) used in pairs:	2875	Prepare and check watchers are usually (but not always) used in pairs:
2541	prepare watchers get invoked before the process blocks and check watchers	2876	prepare watchers get invoked before the process blocks and check watchers
2542	afterwards.	2877	afterwards.
2543		2878
2544	You I<must not> call C<ev_loop> or similar functions that enter	2879	You I<must not> call C<ev_run> or similar functions that enter
2545	the current event loop from either C<ev_prepare> or C<ev_check>	2880	the current event loop from either C<ev_prepare> or C<ev_check>
2546	watchers. Other loops than the current one are fine, however. The	2881	watchers. Other loops than the current one are fine, however. The
2547	rationale behind this is that you do not need to check for recursion in	2882	rationale behind this is that you do not need to check for recursion in
2548	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2883	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2549	C<ev_check> so if you have one watcher of each kind they will always be	2884	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2717		3052
2718	if (timeout >= 0)	3053	if (timeout >= 0)
2719	// create/start timer	3054	// create/start timer
2720		3055
2721	// poll	3056	// poll
2722	ev_loop (EV_A_ 0);	3057	ev_run (EV_A_ 0);
2723		3058
2724	// stop timer again	3059	// stop timer again
2725	if (timeout >= 0)	3060	if (timeout >= 0)
2726	ev_timer_stop (EV_A_ &to);	3061	ev_timer_stop (EV_A_ &to);
2727		3062
…		…
2805	if you do not want that, you need to temporarily stop the embed watcher).	3140	if you do not want that, you need to temporarily stop the embed watcher).
2806		3141
2807	=item ev_embed_sweep (loop, ev_embed *)	3142	=item ev_embed_sweep (loop, ev_embed *)
2808		3143
2809	Make a single, non-blocking sweep over the embedded loop. This works	3144	Make a single, non-blocking sweep over the embedded loop. This works
2810	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3145	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2811	appropriate way for embedded loops.	3146	appropriate way for embedded loops.
2812		3147
2813	=item struct ev_loop *other [read-only]	3148	=item struct ev_loop *other [read-only]
2814		3149
2815	The embedded event loop.	3150	The embedded event loop.
…		…
2875	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3210	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2876	handlers will be invoked, too, of course.	3211	handlers will be invoked, too, of course.
2877		3212
2878	=head3 The special problem of life after fork - how is it possible?	3213	=head3 The special problem of life after fork - how is it possible?
2879		3214
2880	Most uses of C<fork()> consist of forking, then some simple calls to ste	3215	Most uses of C<fork()> consist of forking, then some simple calls to set
2881	up/change the process environment, followed by a call to C<exec()>. This	3216	up/change the process environment, followed by a call to C<exec()>. This
2882	sequence should be handled by libev without any problems.	3217	sequence should be handled by libev without any problems.
2883		3218
2884	This changes when the application actually wants to do event handling	3219	This changes when the application actually wants to do event handling
2885	in the child, or both parent in child, in effect "continuing" after the	3220	in the child, or both parent in child, in effect "continuing" after the
…		…
2901	disadvantage of having to use multiple event loops (which do not support	3236	disadvantage of having to use multiple event loops (which do not support
2902	signal watchers).	3237	signal watchers).
2903		3238
2904	When this is not possible, or you want to use the default loop for	3239	When this is not possible, or you want to use the default loop for
2905	other reasons, then in the process that wants to start "fresh", call	3240	other reasons, then in the process that wants to start "fresh", call
2906	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3241	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2907	the default loop will "orphan" (not stop) all registered watchers, so you	3242	Destroying the default loop will "orphan" (not stop) all registered
2908	have to be careful not to execute code that modifies those watchers. Note	3243	watchers, so you have to be careful not to execute code that modifies
2909	also that in that case, you have to re-register any signal watchers.	3244	those watchers. Note also that in that case, you have to re-register any
		3245	signal watchers.
2910		3246
2911	=head3 Watcher-Specific Functions and Data Members	3247	=head3 Watcher-Specific Functions and Data Members
2912		3248
2913	=over 4	3249	=over 4
2914		3250
2915	=item ev_fork_init (ev_signal *, callback)	3251	=item ev_fork_init (ev_fork *, callback)
2916		3252
2917	Initialises and configures the fork watcher - it has no parameters of any	3253	Initialises and configures the fork watcher - it has no parameters of any
2918	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3254	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2919	believe me.	3255	really.
2920		3256
2921	=back	3257	=back
2922		3258
2923		3259
		3260	=head2 C<ev_cleanup> - even the best things end
		3261
		3262	Cleanup watchers are called just before the event loop is being destroyed
		3263	by a call to C<ev_loop_destroy>.
		3264
		3265	While there is no guarantee that the event loop gets destroyed, cleanup
		3266	watchers provide a convenient method to install cleanup hooks for your
		3267	program, worker threads and so on - you just to make sure to destroy the
		3268	loop when you want them to be invoked.
		3269
		3270	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3271	all other watchers, they do not keep a reference to the event loop (which
		3272	makes a lot of sense if you think about it). Like all other watchers, you
		3273	can call libev functions in the callback, except C<ev_cleanup_start>.
		3274
		3275	=head3 Watcher-Specific Functions and Data Members
		3276
		3277	=over 4
		3278
		3279	=item ev_cleanup_init (ev_cleanup *, callback)
		3280
		3281	Initialises and configures the cleanup watcher - it has no parameters of
		3282	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3283	pointless, I assure you.
		3284
		3285	=back
		3286
		3287	Example: Register an atexit handler to destroy the default loop, so any
		3288	cleanup functions are called.
		3289
		3290	static void
		3291	program_exits (void)
		3292	{
		3293	ev_loop_destroy (EV_DEFAULT_UC);
		3294	}
		3295
		3296	...
		3297	atexit (program_exits);
		3298
		3299
2924	=head2 C<ev_async> - how to wake up another event loop	3300	=head2 C<ev_async> - how to wake up an event loop
2925		3301
2926	In general, you cannot use an C<ev_loop> from multiple threads or other	3302	In general, you cannot use an C<ev_loop> from multiple threads or other
2927	asynchronous sources such as signal handlers (as opposed to multiple event	3303	asynchronous sources such as signal handlers (as opposed to multiple event
2928	loops - those are of course safe to use in different threads).	3304	loops - those are of course safe to use in different threads).
2929		3305
2930	Sometimes, however, you need to wake up another event loop you do not	3306	Sometimes, however, you need to wake up an event loop you do not control,
2931	control, for example because it belongs to another thread. This is what	3307	for example because it belongs to another thread. This is what C<ev_async>
2932	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3308	watchers do: as long as the C<ev_async> watcher is active, you can signal
2933	can signal it by calling C<ev_async_send>, which is thread- and signal	3309	it by calling C<ev_async_send>, which is thread- and signal safe.
2934	safe.
2935		3310
2936	This functionality is very similar to C<ev_signal> watchers, as signals,	3311	This functionality is very similar to C<ev_signal> watchers, as signals,
2937	too, are asynchronous in nature, and signals, too, will be compressed	3312	too, are asynchronous in nature, and signals, too, will be compressed
2938	(i.e. the number of callback invocations may be less than the number of	3313	(i.e. the number of callback invocations may be less than the number of
2939	C<ev_async_sent> calls).	3314	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2940		3315	of "global async watchers" by using a watcher on an otherwise unused
2941	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3316	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2942	just the default loop.	3317	even without knowing which loop owns the signal.
2943		3318
2944	=head3 Queueing	3319	=head3 Queueing
2945		3320
2946	C<ev_async> does not support queueing of data in any way. The reason	3321	C<ev_async> does not support queueing of data in any way. The reason
2947	is that the author does not know of a simple (or any) algorithm for a	3322	is that the author does not know of a simple (or any) algorithm for a
2948	multiple-writer-single-reader queue that works in all cases and doesn't	3323	multiple-writer-single-reader queue that works in all cases and doesn't
2949	need elaborate support such as pthreads.	3324	need elaborate support such as pthreads or unportable memory access
		3325	semantics.
2950		3326
2951	That means that if you want to queue data, you have to provide your own	3327	That means that if you want to queue data, you have to provide your own
2952	queue. But at least I can tell you how to implement locking around your	3328	queue. But at least I can tell you how to implement locking around your
2953	queue:	3329	queue:
2954		3330
…		…
3038	trust me.	3414	trust me.
3039		3415
3040	=item ev_async_send (loop, ev_async *)	3416	=item ev_async_send (loop, ev_async *)
3041		3417
3042	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3418	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3043	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3419	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3420	returns.
		3421
3044	C<ev_feed_event>, this call is safe to do from other threads, signal or	3422	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3045	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3423	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3046	section below on what exactly this means).	3424	embedding section below on what exactly this means).
3047		3425
3048	Note that, as with other watchers in libev, multiple events might get	3426	Note that, as with other watchers in libev, multiple events might get
3049	compressed into a single callback invocation (another way to look at this	3427	compressed into a single callback invocation (another way to look at
3050	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3428	this is that C<ev_async> watchers are level-triggered: they are set on
3051	reset when the event loop detects that).	3429	C<ev_async_send>, reset when the event loop detects that).
3052		3430
3053	This call incurs the overhead of a system call only once per event loop	3431	This call incurs the overhead of at most one extra system call per event
3054	iteration, so while the overhead might be noticeable, it doesn't apply to	3432	loop iteration, if the event loop is blocked, and no syscall at all if
3055	repeated calls to C<ev_async_send> for the same event loop.	3433	the event loop (or your program) is processing events. That means that
		3434	repeated calls are basically free (there is no need to avoid calls for
		3435	performance reasons) and that the overhead becomes smaller (typically
		3436	zero) under load.
3056		3437
3057	=item bool = ev_async_pending (ev_async *)	3438	=item bool = ev_async_pending (ev_async *)
3058		3439
3059	Returns a non-zero value when C<ev_async_send> has been called on the	3440	Returns a non-zero value when C<ev_async_send> has been called on the
3060	watcher but the event has not yet been processed (or even noted) by the	3441	watcher but the event has not yet been processed (or even noted) by the
…		…
3093		3474
3094	If C<timeout> is less than 0, then no timeout watcher will be	3475	If C<timeout> is less than 0, then no timeout watcher will be
3095	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3476	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3096	repeat = 0) will be started. C<0> is a valid timeout.	3477	repeat = 0) will be started. C<0> is a valid timeout.
3097		3478
3098	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3479	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3099	passed an C<revents> set like normal event callbacks (a combination of	3480	passed an C<revents> set like normal event callbacks (a combination of
3100	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3481	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3101	value passed to C<ev_once>. Note that it is possible to receive I<both>	3482	value passed to C<ev_once>. Note that it is possible to receive I<both>
3102	a timeout and an io event at the same time - you probably should give io	3483	a timeout and an io event at the same time - you probably should give io
3103	events precedence.	3484	events precedence.
3104		3485
3105	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3486	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3106		3487
3107	static void stdin_ready (int revents, void *arg)	3488	static void stdin_ready (int revents, void *arg)
3108	{	3489	{
3109	if (revents & EV_READ)	3490	if (revents & EV_READ)
3110	/* stdin might have data for us, joy! */;	3491	/* stdin might have data for us, joy! */;
3111	else if (revents & EV_TIMEOUT)	3492	else if (revents & EV_TIMER)
3112	/* doh, nothing entered */;	3493	/* doh, nothing entered */;
3113	}	3494	}
3114		3495
3115	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3496	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3116		3497
3117	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3118
3119	Feeds the given event set into the event loop, as if the specified event
3120	had happened for the specified watcher (which must be a pointer to an
3121	initialised but not necessarily started event watcher).
3122
3123	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3498	=item ev_feed_fd_event (loop, int fd, int revents)
3124		3499
3125	Feed an event on the given fd, as if a file descriptor backend detected	3500	Feed an event on the given fd, as if a file descriptor backend detected
3126	the given events it.	3501	the given events.
3127		3502
3128	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3503	=item ev_feed_signal_event (loop, int signum)
3129		3504
3130	Feed an event as if the given signal occurred (C<loop> must be the default	3505	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3131	loop!).	3506	which is async-safe.
3132		3507
3133	=back	3508	=back
		3509
		3510
		3511	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3512
		3513	This section explains some common idioms that are not immediately
		3514	obvious. Note that examples are sprinkled over the whole manual, and this
		3515	section only contains stuff that wouldn't fit anywhere else.
		3516
		3517	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3518
		3519	Each watcher has, by default, a C<void *data> member that you can read
		3520	or modify at any time: libev will completely ignore it. This can be used
		3521	to associate arbitrary data with your watcher. If you need more data and
		3522	don't want to allocate memory separately and store a pointer to it in that
		3523	data member, you can also "subclass" the watcher type and provide your own
		3524	data:
		3525
		3526	struct my_io
		3527	{
		3528	ev_io io;
		3529	int otherfd;
		3530	void *somedata;
		3531	struct whatever *mostinteresting;
		3532	};
		3533
		3534	...
		3535	struct my_io w;
		3536	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3537
		3538	And since your callback will be called with a pointer to the watcher, you
		3539	can cast it back to your own type:
		3540
		3541	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3542	{
		3543	struct my_io *w = (struct my_io *)w_;
		3544	...
		3545	}
		3546
		3547	More interesting and less C-conformant ways of casting your callback
		3548	function type instead have been omitted.
		3549
		3550	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3551
		3552	Another common scenario is to use some data structure with multiple
		3553	embedded watchers, in effect creating your own watcher that combines
		3554	multiple libev event sources into one "super-watcher":
		3555
		3556	struct my_biggy
		3557	{
		3558	int some_data;
		3559	ev_timer t1;
		3560	ev_timer t2;
		3561	}
		3562
		3563	In this case getting the pointer to C<my_biggy> is a bit more
		3564	complicated: Either you store the address of your C<my_biggy> struct in
		3565	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3566	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3567	real programmers):
		3568
		3569	#include <stddef.h>
		3570
		3571	static void
		3572	t1_cb (EV_P_ ev_timer *w, int revents)
		3573	{
		3574	struct my_biggy big = (struct my_biggy *)
		3575	(((char *)w) - offsetof (struct my_biggy, t1));
		3576	}
		3577
		3578	static void
		3579	t2_cb (EV_P_ ev_timer *w, int revents)
		3580	{
		3581	struct my_biggy big = (struct my_biggy *)
		3582	(((char *)w) - offsetof (struct my_biggy, t2));
		3583	}
		3584
		3585	=head2 AVOIDING FINISHING BEFORE RETURNING
		3586
		3587	Often you have structures like this in event-based programs:
		3588
		3589	callback ()
		3590	{
		3591	free (request);
		3592	}
		3593
		3594	request = start_new_request (..., callback);
		3595
		3596	The intent is to start some "lengthy" operation. The C<request> could be
		3597	used to cancel the operation, or do other things with it.
		3598
		3599	It's not uncommon to have code paths in C<start_new_request> that
		3600	immediately invoke the callback, for example, to report errors. Or you add
		3601	some caching layer that finds that it can skip the lengthy aspects of the
		3602	operation and simply invoke the callback with the result.
		3603
		3604	The problem here is that this will happen I<before> C<start_new_request>
		3605	has returned, so C<request> is not set.
		3606
		3607	Even if you pass the request by some safer means to the callback, you
		3608	might want to do something to the request after starting it, such as
		3609	canceling it, which probably isn't working so well when the callback has
		3610	already been invoked.
		3611
		3612	A common way around all these issues is to make sure that
		3613	C<start_new_request> I<always> returns before the callback is invoked. If
		3614	C<start_new_request> immediately knows the result, it can artificially
		3615	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3616	for example, or more sneakily, by reusing an existing (stopped) watcher
		3617	and pushing it into the pending queue:
		3618
		3619	ev_set_cb (watcher, callback);
		3620	ev_feed_event (EV_A_ watcher, 0);
		3621
		3622	This way, C<start_new_request> can safely return before the callback is
		3623	invoked, while not delaying callback invocation too much.
		3624
		3625	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3626
		3627	Often (especially in GUI toolkits) there are places where you have
		3628	I<modal> interaction, which is most easily implemented by recursively
		3629	invoking C<ev_run>.
		3630
		3631	This brings the problem of exiting - a callback might want to finish the
		3632	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3633	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3634	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3635	other combination: In these cases, C<ev_break> will not work alone.
		3636
		3637	The solution is to maintain "break this loop" variable for each C<ev_run>
		3638	invocation, and use a loop around C<ev_run> until the condition is
		3639	triggered, using C<EVRUN_ONCE>:
		3640
		3641	// main loop
		3642	int exit_main_loop = 0;
		3643
		3644	while (!exit_main_loop)
		3645	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3646
		3647	// in a modal watcher
		3648	int exit_nested_loop = 0;
		3649
		3650	while (!exit_nested_loop)
		3651	ev_run (EV_A_ EVRUN_ONCE);
		3652
		3653	To exit from any of these loops, just set the corresponding exit variable:
		3654
		3655	// exit modal loop
		3656	exit_nested_loop = 1;
		3657
		3658	// exit main program, after modal loop is finished
		3659	exit_main_loop = 1;
		3660
		3661	// exit both
		3662	exit_main_loop = exit_nested_loop = 1;
		3663
		3664	=head2 THREAD LOCKING EXAMPLE
		3665
		3666	Here is a fictitious example of how to run an event loop in a different
		3667	thread from where callbacks are being invoked and watchers are
		3668	created/added/removed.
		3669
		3670	For a real-world example, see the C<EV::Loop::Async> perl module,
		3671	which uses exactly this technique (which is suited for many high-level
		3672	languages).
		3673
		3674	The example uses a pthread mutex to protect the loop data, a condition
		3675	variable to wait for callback invocations, an async watcher to notify the
		3676	event loop thread and an unspecified mechanism to wake up the main thread.
		3677
		3678	First, you need to associate some data with the event loop:
		3679
		3680	typedef struct {
		3681	mutex_t lock; /* global loop lock */
		3682	ev_async async_w;
		3683	thread_t tid;
		3684	cond_t invoke_cv;
		3685	} userdata;
		3686
		3687	void prepare_loop (EV_P)
		3688	{
		3689	// for simplicity, we use a static userdata struct.
		3690	static userdata u;
		3691
		3692	ev_async_init (&u->async_w, async_cb);
		3693	ev_async_start (EV_A_ &u->async_w);
		3694
		3695	pthread_mutex_init (&u->lock, 0);
		3696	pthread_cond_init (&u->invoke_cv, 0);
		3697
		3698	// now associate this with the loop
		3699	ev_set_userdata (EV_A_ u);
		3700	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3701	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3702
		3703	// then create the thread running ev_run
		3704	pthread_create (&u->tid, 0, l_run, EV_A);
		3705	}
		3706
		3707	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3708	solely to wake up the event loop so it takes notice of any new watchers
		3709	that might have been added:
		3710
		3711	static void
		3712	async_cb (EV_P_ ev_async *w, int revents)
		3713	{
		3714	// just used for the side effects
		3715	}
		3716
		3717	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3718	protecting the loop data, respectively.
		3719
		3720	static void
		3721	l_release (EV_P)
		3722	{
		3723	userdata *u = ev_userdata (EV_A);
		3724	pthread_mutex_unlock (&u->lock);
		3725	}
		3726
		3727	static void
		3728	l_acquire (EV_P)
		3729	{
		3730	userdata *u = ev_userdata (EV_A);
		3731	pthread_mutex_lock (&u->lock);
		3732	}
		3733
		3734	The event loop thread first acquires the mutex, and then jumps straight
		3735	into C<ev_run>:
		3736
		3737	void *
		3738	l_run (void *thr_arg)
		3739	{
		3740	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3741
		3742	l_acquire (EV_A);
		3743	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3744	ev_run (EV_A_ 0);
		3745	l_release (EV_A);
		3746
		3747	return 0;
		3748	}
		3749
		3750	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3751	signal the main thread via some unspecified mechanism (signals? pipe
		3752	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3753	have been called (in a while loop because a) spurious wakeups are possible
		3754	and b) skipping inter-thread-communication when there are no pending
		3755	watchers is very beneficial):
		3756
		3757	static void
		3758	l_invoke (EV_P)
		3759	{
		3760	userdata *u = ev_userdata (EV_A);
		3761
		3762	while (ev_pending_count (EV_A))
		3763	{
		3764	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3765	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3766	}
		3767	}
		3768
		3769	Now, whenever the main thread gets told to invoke pending watchers, it
		3770	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3771	thread to continue:
		3772
		3773	static void
		3774	real_invoke_pending (EV_P)
		3775	{
		3776	userdata *u = ev_userdata (EV_A);
		3777
		3778	pthread_mutex_lock (&u->lock);
		3779	ev_invoke_pending (EV_A);
		3780	pthread_cond_signal (&u->invoke_cv);
		3781	pthread_mutex_unlock (&u->lock);
		3782	}
		3783
		3784	Whenever you want to start/stop a watcher or do other modifications to an
		3785	event loop, you will now have to lock:
		3786
		3787	ev_timer timeout_watcher;
		3788	userdata *u = ev_userdata (EV_A);
		3789
		3790	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3791
		3792	pthread_mutex_lock (&u->lock);
		3793	ev_timer_start (EV_A_ &timeout_watcher);
		3794	ev_async_send (EV_A_ &u->async_w);
		3795	pthread_mutex_unlock (&u->lock);
		3796
		3797	Note that sending the C<ev_async> watcher is required because otherwise
		3798	an event loop currently blocking in the kernel will have no knowledge
		3799	about the newly added timer. By waking up the loop it will pick up any new
		3800	watchers in the next event loop iteration.
		3801
		3802	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3803
		3804	While the overhead of a callback that e.g. schedules a thread is small, it
		3805	is still an overhead. If you embed libev, and your main usage is with some
		3806	kind of threads or coroutines, you might want to customise libev so that
		3807	doesn't need callbacks anymore.
		3808
		3809	Imagine you have coroutines that you can switch to using a function
		3810	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3811	and that due to some magic, the currently active coroutine is stored in a
		3812	global called C<current_coro>. Then you can build your own "wait for libev
		3813	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3814	the differing C<;> conventions):
		3815
		3816	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3817	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3818
		3819	That means instead of having a C callback function, you store the
		3820	coroutine to switch to in each watcher, and instead of having libev call
		3821	your callback, you instead have it switch to that coroutine.
		3822
		3823	A coroutine might now wait for an event with a function called
		3824	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3825	matter when, or whether the watcher is active or not when this function is
		3826	called):
		3827
		3828	void
		3829	wait_for_event (ev_watcher *w)
		3830	{
		3831	ev_cb_set (w) = current_coro;
		3832	switch_to (libev_coro);
		3833	}
		3834
		3835	That basically suspends the coroutine inside C<wait_for_event> and
		3836	continues the libev coroutine, which, when appropriate, switches back to
		3837	this or any other coroutine.
		3838
		3839	You can do similar tricks if you have, say, threads with an event queue -
		3840	instead of storing a coroutine, you store the queue object and instead of
		3841	switching to a coroutine, you push the watcher onto the queue and notify
		3842	any waiters.
		3843
		3844	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3845	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3846
		3847	// my_ev.h
		3848	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3849	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3850	#include "../libev/ev.h"
		3851
		3852	// my_ev.c
		3853	#define EV_H "my_ev.h"
		3854	#include "../libev/ev.c"
		3855
		3856	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3857	F<my_ev.c> into your project. When properly specifying include paths, you
		3858	can even use F<ev.h> as header file name directly.
3134		3859
3135		3860
3136	=head1 LIBEVENT EMULATION	3861	=head1 LIBEVENT EMULATION
3137		3862
3138	Libev offers a compatibility emulation layer for libevent. It cannot	3863	Libev offers a compatibility emulation layer for libevent. It cannot
3139	emulate the internals of libevent, so here are some usage hints:	3864	emulate the internals of libevent, so here are some usage hints:
3140		3865
3141	=over 4	3866	=over 4
		3867
		3868	=item * Only the libevent-1.4.1-beta API is being emulated.
		3869
		3870	This was the newest libevent version available when libev was implemented,
		3871	and is still mostly unchanged in 2010.
3142		3872
3143	=item * Use it by including <event.h>, as usual.	3873	=item * Use it by including <event.h>, as usual.
3144		3874
3145	=item * The following members are fully supported: ev_base, ev_callback,	3875	=item * The following members are fully supported: ev_base, ev_callback,
3146	ev_arg, ev_fd, ev_res, ev_events.	3876	ev_arg, ev_fd, ev_res, ev_events.
…		…
3152	=item * Priorities are not currently supported. Initialising priorities	3882	=item * Priorities are not currently supported. Initialising priorities
3153	will fail and all watchers will have the same priority, even though there	3883	will fail and all watchers will have the same priority, even though there
3154	is an ev_pri field.	3884	is an ev_pri field.
3155		3885
3156	=item * In libevent, the last base created gets the signals, in libev, the	3886	=item * In libevent, the last base created gets the signals, in libev, the
3157	first base created (== the default loop) gets the signals.	3887	base that registered the signal gets the signals.
3158		3888
3159	=item * Other members are not supported.	3889	=item * Other members are not supported.
3160		3890
3161	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3891	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3162	to use the libev header file and library.	3892	to use the libev header file and library.
…		…
3181	Care has been taken to keep the overhead low. The only data member the C++	3911	Care has been taken to keep the overhead low. The only data member the C++
3182	classes add (compared to plain C-style watchers) is the event loop pointer	3912	classes add (compared to plain C-style watchers) is the event loop pointer
3183	that the watcher is associated with (or no additional members at all if	3913	that the watcher is associated with (or no additional members at all if
3184	you disable C<EV_MULTIPLICITY> when embedding libev).	3914	you disable C<EV_MULTIPLICITY> when embedding libev).
3185		3915
3186	Currently, functions, and static and non-static member functions can be	3916	Currently, functions, static and non-static member functions and classes
3187	used as callbacks. Other types should be easy to add as long as they only	3917	with C<operator ()> can be used as callbacks. Other types should be easy
3188	need one additional pointer for context. If you need support for other	3918	to add as long as they only need one additional pointer for context. If
3189	types of functors please contact the author (preferably after implementing	3919	you need support for other types of functors please contact the author
3190	it).	3920	(preferably after implementing it).
		3921
		3922	For all this to work, your C++ compiler either has to use the same calling
		3923	conventions as your C compiler (for static member functions), or you have
		3924	to embed libev and compile libev itself as C++.
3191		3925
3192	Here is a list of things available in the C<ev> namespace:	3926	Here is a list of things available in the C<ev> namespace:
3193		3927
3194	=over 4	3928	=over 4
3195		3929
…		…
3205	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	3939	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3206		3940
3207	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	3941	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3208	the same name in the C<ev> namespace, with the exception of C<ev_signal>	3942	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3209	which is called C<ev::sig> to avoid clashes with the C<signal> macro	3943	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3210	defines by many implementations.	3944	defined by many implementations.
3211		3945
3212	All of those classes have these methods:	3946	All of those classes have these methods:
3213		3947
3214	=over 4	3948	=over 4
3215		3949
3216	=item ev::TYPE::TYPE ()	3950	=item ev::TYPE::TYPE ()
3217		3951
3218	=item ev::TYPE::TYPE (struct ev_loop *)	3952	=item ev::TYPE::TYPE (loop)
3219		3953
3220	=item ev::TYPE::~TYPE	3954	=item ev::TYPE::~TYPE
3221		3955
3222	The constructor (optionally) takes an event loop to associate the watcher	3956	The constructor (optionally) takes an event loop to associate the watcher
3223	with. If it is omitted, it will use C<EV_DEFAULT>.	3957	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3256	myclass obj;	3990	myclass obj;
3257	ev::io iow;	3991	ev::io iow;
3258	iow.set <myclass, &myclass::io_cb> (&obj);	3992	iow.set <myclass, &myclass::io_cb> (&obj);
3259		3993
3260	=item w->set (object *)	3994	=item w->set (object *)
3261
3262	This is an B<experimental> feature that might go away in a future version.
3263		3995
3264	This is a variation of a method callback - leaving out the method to call	3996	This is a variation of a method callback - leaving out the method to call
3265	will default the method to C<operator ()>, which makes it possible to use	3997	will default the method to C<operator ()>, which makes it possible to use
3266	functor objects without having to manually specify the C<operator ()> all	3998	functor objects without having to manually specify the C<operator ()> all
3267	the time. Incidentally, you can then also leave out the template argument	3999	the time. Incidentally, you can then also leave out the template argument
…		…
3300	Example: Use a plain function as callback.	4032	Example: Use a plain function as callback.
3301		4033
3302	static void io_cb (ev::io &w, int revents) { }	4034	static void io_cb (ev::io &w, int revents) { }
3303	iow.set <io_cb> ();	4035	iow.set <io_cb> ();
3304		4036
3305	=item w->set (struct ev_loop *)	4037	=item w->set (loop)
3306		4038
3307	Associates a different C<struct ev_loop> with this watcher. You can only	4039	Associates a different C<struct ev_loop> with this watcher. You can only
3308	do this when the watcher is inactive (and not pending either).	4040	do this when the watcher is inactive (and not pending either).
3309		4041
3310	=item w->set ([arguments])	4042	=item w->set ([arguments])
3311		4043
3312	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4044	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3313	called at least once. Unlike the C counterpart, an active watcher gets	4045	method or a suitable start method must be called at least once. Unlike the
3314	automatically stopped and restarted when reconfiguring it with this	4046	C counterpart, an active watcher gets automatically stopped and restarted
3315	method.	4047	when reconfiguring it with this method.
3316		4048
3317	=item w->start ()	4049	=item w->start ()
3318		4050
3319	Starts the watcher. Note that there is no C<loop> argument, as the	4051	Starts the watcher. Note that there is no C<loop> argument, as the
3320	constructor already stores the event loop.	4052	constructor already stores the event loop.
3321		4053
		4054	=item w->start ([arguments])
		4055
		4056	Instead of calling C<set> and C<start> methods separately, it is often
		4057	convenient to wrap them in one call. Uses the same type of arguments as
		4058	the configure C<set> method of the watcher.
		4059
3322	=item w->stop ()	4060	=item w->stop ()
3323		4061
3324	Stops the watcher if it is active. Again, no C<loop> argument.	4062	Stops the watcher if it is active. Again, no C<loop> argument.
3325		4063
3326	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4064	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3338		4076
3339	=back	4077	=back
3340		4078
3341	=back	4079	=back
3342		4080
3343	Example: Define a class with an IO and idle watcher, start one of them in	4081	Example: Define a class with two I/O and idle watchers, start the I/O
3344	the constructor.	4082	watchers in the constructor.
3345		4083
3346	class myclass	4084	class myclass
3347	{	4085	{
3348	ev::io io ; void io_cb (ev::io &w, int revents);	4086	ev::io io ; void io_cb (ev::io &w, int revents);
		4087	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3349	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4088	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3350		4089
3351	myclass (int fd)	4090	myclass (int fd)
3352	{	4091	{
3353	io .set <myclass, &myclass::io_cb > (this);	4092	io .set <myclass, &myclass::io_cb > (this);
		4093	io2 .set <myclass, &myclass::io2_cb > (this);
3354	idle.set <myclass, &myclass::idle_cb> (this);	4094	idle.set <myclass, &myclass::idle_cb> (this);
3355		4095
3356	io.start (fd, ev::READ);	4096	io.set (fd, ev::WRITE); // configure the watcher
		4097	io.start (); // start it whenever convenient
		4098
		4099	io2.start (fd, ev::READ); // set + start in one call
3357	}	4100	}
3358	};	4101	};
3359		4102
3360		4103
3361	=head1 OTHER LANGUAGE BINDINGS	4104	=head1 OTHER LANGUAGE BINDINGS
…		…
3400	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4143	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3401		4144
3402	=item D	4145	=item D
3403		4146
3404	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4147	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3405	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4148	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3406		4149
3407	=item Ocaml	4150	=item Ocaml
3408		4151
3409	Erkki Seppala has written Ocaml bindings for libev, to be found at	4152	Erkki Seppala has written Ocaml bindings for libev, to be found at
3410	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4153	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3411		4154
3412	=item Lua	4155	=item Lua
3413		4156
3414	Brian Maher has written a partial interface to libev	4157	Brian Maher has written a partial interface to libev for lua (at the
3415	for lua (only C<ev_io> and C<ev_timer>), to be found at	4158	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3416	L<http://github.com/brimworks/lua-ev>.	4159	L<http://github.com/brimworks/lua-ev>.
3417		4160
3418	=back	4161	=back
3419		4162
3420		4163
…		…
3435	loop argument"). The C<EV_A> form is used when this is the sole argument,	4178	loop argument"). The C<EV_A> form is used when this is the sole argument,
3436	C<EV_A_> is used when other arguments are following. Example:	4179	C<EV_A_> is used when other arguments are following. Example:
3437		4180
3438	ev_unref (EV_A);	4181	ev_unref (EV_A);
3439	ev_timer_add (EV_A_ watcher);	4182	ev_timer_add (EV_A_ watcher);
3440	ev_loop (EV_A_ 0);	4183	ev_run (EV_A_ 0);
3441		4184
3442	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4185	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3443	which is often provided by the following macro.	4186	which is often provided by the following macro.
3444		4187
3445	=item C<EV_P>, C<EV_P_>	4188	=item C<EV_P>, C<EV_P_>
…		…
3458	suitable for use with C<EV_A>.	4201	suitable for use with C<EV_A>.
3459		4202
3460	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4203	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3461		4204
3462	Similar to the other two macros, this gives you the value of the default	4205	Similar to the other two macros, this gives you the value of the default
3463	loop, if multiple loops are supported ("ev loop default").	4206	loop, if multiple loops are supported ("ev loop default"). The default loop
		4207	will be initialised if it isn't already initialised.
		4208
		4209	For non-multiplicity builds, these macros do nothing, so you always have
		4210	to initialise the loop somewhere.
3464		4211
3465	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4212	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3466		4213
3467	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4214	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3468	default loop has been initialised (C<UC> == unchecked). Their behaviour	4215	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3485	}	4232	}
3486		4233
3487	ev_check check;	4234	ev_check check;
3488	ev_check_init (&check, check_cb);	4235	ev_check_init (&check, check_cb);
3489	ev_check_start (EV_DEFAULT_ &check);	4236	ev_check_start (EV_DEFAULT_ &check);
3490	ev_loop (EV_DEFAULT_ 0);	4237	ev_run (EV_DEFAULT_ 0);
3491		4238
3492	=head1 EMBEDDING	4239	=head1 EMBEDDING
3493		4240
3494	Libev can (and often is) directly embedded into host	4241	Libev can (and often is) directly embedded into host
3495	applications. Examples of applications that embed it include the Deliantra	4242	applications. Examples of applications that embed it include the Deliantra
…		…
3575	libev.m4	4322	libev.m4
3576		4323
3577	=head2 PREPROCESSOR SYMBOLS/MACROS	4324	=head2 PREPROCESSOR SYMBOLS/MACROS
3578		4325
3579	Libev can be configured via a variety of preprocessor symbols you have to	4326	Libev can be configured via a variety of preprocessor symbols you have to
3580	define before including any of its files. The default in the absence of	4327	define before including (or compiling) any of its files. The default in
3581	autoconf is documented for every option.	4328	the absence of autoconf is documented for every option.
		4329
		4330	Symbols marked with "(h)" do not change the ABI, and can have different
		4331	values when compiling libev vs. including F<ev.h>, so it is permissible
		4332	to redefine them before including F<ev.h> without breaking compatibility
		4333	to a compiled library. All other symbols change the ABI, which means all
		4334	users of libev and the libev code itself must be compiled with compatible
		4335	settings.
3582		4336
3583	=over 4	4337	=over 4
3584		4338
		4339	=item EV_COMPAT3 (h)
		4340
		4341	Backwards compatibility is a major concern for libev. This is why this
		4342	release of libev comes with wrappers for the functions and symbols that
		4343	have been renamed between libev version 3 and 4.
		4344
		4345	You can disable these wrappers (to test compatibility with future
		4346	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4347	sources. This has the additional advantage that you can drop the C<struct>
		4348	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4349	typedef in that case.
		4350
		4351	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4352	and in some even more future version the compatibility code will be
		4353	removed completely.
		4354
3585	=item EV_STANDALONE	4355	=item EV_STANDALONE (h)
3586		4356
3587	Must always be C<1> if you do not use autoconf configuration, which	4357	Must always be C<1> if you do not use autoconf configuration, which
3588	keeps libev from including F<config.h>, and it also defines dummy	4358	keeps libev from including F<config.h>, and it also defines dummy
3589	implementations for some libevent functions (such as logging, which is not	4359	implementations for some libevent functions (such as logging, which is not
3590	supported). It will also not define any of the structs usually found in	4360	supported). It will also not define any of the structs usually found in
3591	F<event.h> that are not directly supported by the libev core alone.	4361	F<event.h> that are not directly supported by the libev core alone.
3592		4362
3593	In standalone mode, libev will still try to automatically deduce the	4363	In standalone mode, libev will still try to automatically deduce the
3594	configuration, but has to be more conservative.	4364	configuration, but has to be more conservative.
		4365
		4366	=item EV_USE_FLOOR
		4367
		4368	If defined to be C<1>, libev will use the C<floor ()> function for its
		4369	periodic reschedule calculations, otherwise libev will fall back on a
		4370	portable (slower) implementation. If you enable this, you usually have to
		4371	link against libm or something equivalent. Enabling this when the C<floor>
		4372	function is not available will fail, so the safe default is to not enable
		4373	this.
3595		4374
3596	=item EV_USE_MONOTONIC	4375	=item EV_USE_MONOTONIC
3597		4376
3598	If defined to be C<1>, libev will try to detect the availability of the	4377	If defined to be C<1>, libev will try to detect the availability of the
3599	monotonic clock option at both compile time and runtime. Otherwise no	4378	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3663	be used is the winsock select). This means that it will call	4442	be used is the winsock select). This means that it will call
3664	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4443	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3665	it is assumed that all these functions actually work on fds, even	4444	it is assumed that all these functions actually work on fds, even
3666	on win32. Should not be defined on non-win32 platforms.	4445	on win32. Should not be defined on non-win32 platforms.
3667		4446
3668	=item EV_FD_TO_WIN32_HANDLE	4447	=item EV_FD_TO_WIN32_HANDLE(fd)
3669		4448
3670	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4449	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3671	file descriptors to socket handles. When not defining this symbol (the	4450	file descriptors to socket handles. When not defining this symbol (the
3672	default), then libev will call C<_get_osfhandle>, which is usually	4451	default), then libev will call C<_get_osfhandle>, which is usually
3673	correct. In some cases, programs use their own file descriptor management,	4452	correct. In some cases, programs use their own file descriptor management,
3674	in which case they can provide this function to map fds to socket handles.	4453	in which case they can provide this function to map fds to socket handles.
		4454
		4455	=item EV_WIN32_HANDLE_TO_FD(handle)
		4456
		4457	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4458	using the standard C<_open_osfhandle> function. For programs implementing
		4459	their own fd to handle mapping, overwriting this function makes it easier
		4460	to do so. This can be done by defining this macro to an appropriate value.
		4461
		4462	=item EV_WIN32_CLOSE_FD(fd)
		4463
		4464	If programs implement their own fd to handle mapping on win32, then this
		4465	macro can be used to override the C<close> function, useful to unregister
		4466	file descriptors again. Note that the replacement function has to close
		4467	the underlying OS handle.
3675		4468
3676	=item EV_USE_POLL	4469	=item EV_USE_POLL
3677		4470
3678	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4471	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3679	backend. Otherwise it will be enabled on non-win32 platforms. It	4472	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3715	If defined to be C<1>, libev will compile in support for the Linux inotify	4508	If defined to be C<1>, libev will compile in support for the Linux inotify
3716	interface to speed up C<ev_stat> watchers. Its actual availability will	4509	interface to speed up C<ev_stat> watchers. Its actual availability will
3717	be detected at runtime. If undefined, it will be enabled if the headers	4510	be detected at runtime. If undefined, it will be enabled if the headers
3718	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4511	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3719		4512
		4513	=item EV_NO_SMP
		4514
		4515	If defined to be C<1>, libev will assume that memory is always coherent
		4516	between threads, that is, threads can be used, but threads never run on
		4517	different cpus (or different cpu cores). This reduces dependencies
		4518	and makes libev faster.
		4519
		4520	=item EV_NO_THREADS
		4521
		4522	If defined to be C<1>, libev will assume that it will never be called
		4523	from different threads, which is a stronger assumption than C<EV_NO_SMP>,
		4524	above. This reduces dependencies and makes libev faster.
		4525
3720	=item EV_ATOMIC_T	4526	=item EV_ATOMIC_T
3721		4527
3722	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4528	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3723	access is atomic with respect to other threads or signal contexts. No such	4529	access is atomic and serialised with respect to other threads or signal
3724	type is easily found in the C language, so you can provide your own type	4530	contexts. No such type is easily found in the C language, so you can
3725	that you know is safe for your purposes. It is used both for signal handler "locking"	4531	provide your own type that you know is safe for your purposes. It is used
3726	as well as for signal and thread safety in C<ev_async> watchers.	4532	both for signal handler "locking" as well as for signal and thread safety
		4533	in C<ev_async> watchers.
3727		4534
3728	In the absence of this define, libev will use C<sig_atomic_t volatile>	4535	In the absence of this define, libev will use C<sig_atomic_t volatile>
3729	(from F<signal.h>), which is usually good enough on most platforms.	4536	(from F<signal.h>), which is usually good enough on most platforms,
		4537	although strictly speaking using a type that also implies a memory fence
		4538	is required.
3730		4539
3731	=item EV_H	4540	=item EV_H (h)
3732		4541
3733	The name of the F<ev.h> header file used to include it. The default if	4542	The name of the F<ev.h> header file used to include it. The default if
3734	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4543	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3735	used to virtually rename the F<ev.h> header file in case of conflicts.	4544	used to virtually rename the F<ev.h> header file in case of conflicts.
3736		4545
3737	=item EV_CONFIG_H	4546	=item EV_CONFIG_H (h)
3738		4547
3739	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4548	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3740	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4549	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3741	C<EV_H>, above.	4550	C<EV_H>, above.
3742		4551
3743	=item EV_EVENT_H	4552	=item EV_EVENT_H (h)
3744		4553
3745	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4554	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3746	of how the F<event.h> header can be found, the default is C<"event.h">.	4555	of how the F<event.h> header can be found, the default is C<"event.h">.
3747		4556
3748	=item EV_PROTOTYPES	4557	=item EV_PROTOTYPES (h)
3749		4558
3750	If defined to be C<0>, then F<ev.h> will not define any function	4559	If defined to be C<0>, then F<ev.h> will not define any function
3751	prototypes, but still define all the structs and other symbols. This is	4560	prototypes, but still define all the structs and other symbols. This is
3752	occasionally useful if you want to provide your own wrapper functions	4561	occasionally useful if you want to provide your own wrapper functions
3753	around libev functions.	4562	around libev functions.
…		…
3758	will have the C<struct ev_loop *> as first argument, and you can create	4567	will have the C<struct ev_loop *> as first argument, and you can create
3759	additional independent event loops. Otherwise there will be no support	4568	additional independent event loops. Otherwise there will be no support
3760	for multiple event loops and there is no first event loop pointer	4569	for multiple event loops and there is no first event loop pointer
3761	argument. Instead, all functions act on the single default loop.	4570	argument. Instead, all functions act on the single default loop.
3762		4571
		4572	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4573	default loop when multiplicity is switched off - you always have to
		4574	initialise the loop manually in this case.
		4575
3763	=item EV_MINPRI	4576	=item EV_MINPRI
3764		4577
3765	=item EV_MAXPRI	4578	=item EV_MAXPRI
3766		4579
3767	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4580	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3775	fine.	4588	fine.
3776		4589
3777	If your embedding application does not need any priorities, defining these	4590	If your embedding application does not need any priorities, defining these
3778	both to C<0> will save some memory and CPU.	4591	both to C<0> will save some memory and CPU.
3779		4592
3780	=item EV_PERIODIC_ENABLE	4593	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4594	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4595	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3781		4596
3782	If undefined or defined to be C<1>, then periodic timers are supported. If	4597	If undefined or defined to be C<1> (and the platform supports it), then
3783	defined to be C<0>, then they are not. Disabling them saves a few kB of	4598	the respective watcher type is supported. If defined to be C<0>, then it
3784	code.	4599	is not. Disabling watcher types mainly saves code size.
3785		4600
3786	=item EV_IDLE_ENABLE	4601	=item EV_FEATURES
3787
3788	If undefined or defined to be C<1>, then idle watchers are supported. If
3789	defined to be C<0>, then they are not. Disabling them saves a few kB of
3790	code.
3791
3792	=item EV_EMBED_ENABLE
3793
3794	If undefined or defined to be C<1>, then embed watchers are supported. If
3795	defined to be C<0>, then they are not. Embed watchers rely on most other
3796	watcher types, which therefore must not be disabled.
3797
3798	=item EV_STAT_ENABLE
3799
3800	If undefined or defined to be C<1>, then stat watchers are supported. If
3801	defined to be C<0>, then they are not.
3802
3803	=item EV_FORK_ENABLE
3804
3805	If undefined or defined to be C<1>, then fork watchers are supported. If
3806	defined to be C<0>, then they are not.
3807
3808	=item EV_ASYNC_ENABLE
3809
3810	If undefined or defined to be C<1>, then async watchers are supported. If
3811	defined to be C<0>, then they are not.
3812
3813	=item EV_MINIMAL
3814		4602
3815	If you need to shave off some kilobytes of code at the expense of some	4603	If you need to shave off some kilobytes of code at the expense of some
3816	speed (but with the full API), define this symbol to C<1>. Currently this	4604	speed (but with the full API), you can define this symbol to request
3817	is used to override some inlining decisions, saves roughly 30% code size	4605	certain subsets of functionality. The default is to enable all features
3818	on amd64. It also selects a much smaller 2-heap for timer management over	4606	that can be enabled on the platform.
3819	the default 4-heap.
3820		4607
3821	You can save even more by disabling watcher types you do not need	4608	A typical way to use this symbol is to define it to C<0> (or to a bitset
3822	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4609	with some broad features you want) and then selectively re-enable
3823	(C<-DNDEBUG>) will usually reduce code size a lot.	4610	additional parts you want, for example if you want everything minimal,
		4611	but multiple event loop support, async and child watchers and the poll
		4612	backend, use this:
3824		4613
3825	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4614	#define EV_FEATURES 0
3826	provide a bare-bones event library. See C<ev.h> for details on what parts	4615	#define EV_MULTIPLICITY 1
3827	of the API are still available, and do not complain if this subset changes	4616	#define EV_USE_POLL 1
3828	over time.	4617	#define EV_CHILD_ENABLE 1
		4618	#define EV_ASYNC_ENABLE 1
		4619
		4620	The actual value is a bitset, it can be a combination of the following
		4621	values:
		4622
		4623	=over 4
		4624
		4625	=item C<1> - faster/larger code
		4626
		4627	Use larger code to speed up some operations.
		4628
		4629	Currently this is used to override some inlining decisions (enlarging the
		4630	code size by roughly 30% on amd64).
		4631
		4632	When optimising for size, use of compiler flags such as C<-Os> with
		4633	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4634	assertions.
		4635
		4636	=item C<2> - faster/larger data structures
		4637
		4638	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4639	hash table sizes and so on. This will usually further increase code size
		4640	and can additionally have an effect on the size of data structures at
		4641	runtime.
		4642
		4643	=item C<4> - full API configuration
		4644
		4645	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4646	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4647
		4648	=item C<8> - full API
		4649
		4650	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4651	details on which parts of the API are still available without this
		4652	feature, and do not complain if this subset changes over time.
		4653
		4654	=item C<16> - enable all optional watcher types
		4655
		4656	Enables all optional watcher types. If you want to selectively enable
		4657	only some watcher types other than I/O and timers (e.g. prepare,
		4658	embed, async, child...) you can enable them manually by defining
		4659	C<EV_watchertype_ENABLE> to C<1> instead.
		4660
		4661	=item C<32> - enable all backends
		4662
		4663	This enables all backends - without this feature, you need to enable at
		4664	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4665
		4666	=item C<64> - enable OS-specific "helper" APIs
		4667
		4668	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4669	default.
		4670
		4671	=back
		4672
		4673	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4674	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4675	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4676	watchers, timers and monotonic clock support.
		4677
		4678	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4679	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4680	your program might be left out as well - a binary starting a timer and an
		4681	I/O watcher then might come out at only 5Kb.
		4682
		4683	=item EV_API_STATIC
		4684
		4685	If this symbol is defined (by default it is not), then all identifiers
		4686	will have static linkage. This means that libev will not export any
		4687	identifiers, and you cannot link against libev anymore. This can be useful
		4688	when you embed libev, only want to use libev functions in a single file,
		4689	and do not want its identifiers to be visible.
		4690
		4691	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4692	wants to use libev.
		4693
		4694	This option only works when libev is compiled with a C compiler, as C++
		4695	doesn't support the required declaration syntax.
		4696
		4697	=item EV_AVOID_STDIO
		4698
		4699	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4700	functions (printf, scanf, perror etc.). This will increase the code size
		4701	somewhat, but if your program doesn't otherwise depend on stdio and your
		4702	libc allows it, this avoids linking in the stdio library which is quite
		4703	big.
		4704
		4705	Note that error messages might become less precise when this option is
		4706	enabled.
3829		4707
3830	=item EV_NSIG	4708	=item EV_NSIG
3831		4709
3832	The highest supported signal number, +1 (or, the number of	4710	The highest supported signal number, +1 (or, the number of
3833	signals): Normally, libev tries to deduce the maximum number of signals	4711	signals): Normally, libev tries to deduce the maximum number of signals
3834	automatically, but sometimes this fails, in which case it can be	4712	automatically, but sometimes this fails, in which case it can be
3835	specified. Also, using a lower number than detected (C<32> should be	4713	specified. Also, using a lower number than detected (C<32> should be
3836	good for about any system in existance) can save some memory, as libev	4714	good for about any system in existence) can save some memory, as libev
3837	statically allocates some 12-24 bytes per signal number.	4715	statically allocates some 12-24 bytes per signal number.
3838		4716
3839	=item EV_PID_HASHSIZE	4717	=item EV_PID_HASHSIZE
3840		4718
3841	C<ev_child> watchers use a small hash table to distribute workload by	4719	C<ev_child> watchers use a small hash table to distribute workload by
3842	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4720	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3843	than enough. If you need to manage thousands of children you might want to	4721	usually more than enough. If you need to manage thousands of children you
3844	increase this value (I<must> be a power of two).	4722	might want to increase this value (I<must> be a power of two).
3845		4723
3846	=item EV_INOTIFY_HASHSIZE	4724	=item EV_INOTIFY_HASHSIZE
3847		4725
3848	C<ev_stat> watchers use a small hash table to distribute workload by	4726	C<ev_stat> watchers use a small hash table to distribute workload by
3849	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4727	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3850	usually more than enough. If you need to manage thousands of C<ev_stat>	4728	disabled), usually more than enough. If you need to manage thousands of
3851	watchers you might want to increase this value (I<must> be a power of	4729	C<ev_stat> watchers you might want to increase this value (I<must> be a
3852	two).	4730	power of two).
3853		4731
3854	=item EV_USE_4HEAP	4732	=item EV_USE_4HEAP
3855		4733
3856	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4734	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3857	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4735	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3858	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4736	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3859	faster performance with many (thousands) of watchers.	4737	faster performance with many (thousands) of watchers.
3860		4738
3861	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4739	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3862	(disabled).	4740	will be C<0>.
3863		4741
3864	=item EV_HEAP_CACHE_AT	4742	=item EV_HEAP_CACHE_AT
3865		4743
3866	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4744	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3867	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4745	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3868	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4746	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3869	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4747	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3870	but avoids random read accesses on heap changes. This improves performance	4748	but avoids random read accesses on heap changes. This improves performance
3871	noticeably with many (hundreds) of watchers.	4749	noticeably with many (hundreds) of watchers.
3872		4750
3873	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4751	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3874	(disabled).	4752	will be C<0>.
3875		4753
3876	=item EV_VERIFY	4754	=item EV_VERIFY
3877		4755
3878	Controls how much internal verification (see C<ev_loop_verify ()>) will	4756	Controls how much internal verification (see C<ev_verify ()>) will
3879	be done: If set to C<0>, no internal verification code will be compiled	4757	be done: If set to C<0>, no internal verification code will be compiled
3880	in. If set to C<1>, then verification code will be compiled in, but not	4758	in. If set to C<1>, then verification code will be compiled in, but not
3881	called. If set to C<2>, then the internal verification code will be	4759	called. If set to C<2>, then the internal verification code will be
3882	called once per loop, which can slow down libev. If set to C<3>, then the	4760	called once per loop, which can slow down libev. If set to C<3>, then the
3883	verification code will be called very frequently, which will slow down	4761	verification code will be called very frequently, which will slow down
3884	libev considerably.	4762	libev considerably.
3885		4763
3886	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4764	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3887	C<0>.	4765	will be C<0>.
3888		4766
3889	=item EV_COMMON	4767	=item EV_COMMON
3890		4768
3891	By default, all watchers have a C<void *data> member. By redefining	4769	By default, all watchers have a C<void *data> member. By redefining
3892	this macro to a something else you can include more and other types of	4770	this macro to something else you can include more and other types of
3893	members. You have to define it each time you include one of the files,	4771	members. You have to define it each time you include one of the files,
3894	though, and it must be identical each time.	4772	though, and it must be identical each time.
3895		4773
3896	For example, the perl EV module uses something like this:	4774	For example, the perl EV module uses something like this:
3897		4775
…		…
3950	file.	4828	file.
3951		4829
3952	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4830	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3953	that everybody includes and which overrides some configure choices:	4831	that everybody includes and which overrides some configure choices:
3954		4832
3955	#define EV_MINIMAL 1	4833	#define EV_FEATURES 8
3956	#define EV_USE_POLL 0	4834	#define EV_USE_SELECT 1
3957	#define EV_MULTIPLICITY 0
3958	#define EV_PERIODIC_ENABLE 0	4835	#define EV_PREPARE_ENABLE 1
		4836	#define EV_IDLE_ENABLE 1
3959	#define EV_STAT_ENABLE 0	4837	#define EV_SIGNAL_ENABLE 1
3960	#define EV_FORK_ENABLE 0	4838	#define EV_CHILD_ENABLE 1
		4839	#define EV_USE_STDEXCEPT 0
3961	#define EV_CONFIG_H <config.h>	4840	#define EV_CONFIG_H <config.h>
3962	#define EV_MINPRI 0
3963	#define EV_MAXPRI 0
3964		4841
3965	#include "ev++.h"	4842	#include "ev++.h"
3966		4843
3967	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4844	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3968		4845
3969	#include "ev_cpp.h"	4846	#include "ev_cpp.h"
3970	#include "ev.c"	4847	#include "ev.c"
3971		4848
3972	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4849	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3973		4850
3974	=head2 THREADS AND COROUTINES	4851	=head2 THREADS AND COROUTINES
3975		4852
3976	=head3 THREADS	4853	=head3 THREADS
3977		4854
…		…
4028	default loop and triggering an C<ev_async> watcher from the default loop	4905	default loop and triggering an C<ev_async> watcher from the default loop
4029	watcher callback into the event loop interested in the signal.	4906	watcher callback into the event loop interested in the signal.
4030		4907
4031	=back	4908	=back
4032		4909
4033	=head4 THREAD LOCKING EXAMPLE	4910	See also L<THREAD LOCKING EXAMPLE>.
4034
4035	Here is a fictitious example of how to run an event loop in a different
4036	thread than where callbacks are being invoked and watchers are
4037	created/added/removed.
4038
4039	For a real-world example, see the C<EV::Loop::Async> perl module,
4040	which uses exactly this technique (which is suited for many high-level
4041	languages).
4042
4043	The example uses a pthread mutex to protect the loop data, a condition
4044	variable to wait for callback invocations, an async watcher to notify the
4045	event loop thread and an unspecified mechanism to wake up the main thread.
4046
4047	First, you need to associate some data with the event loop:
4048
4049	typedef struct {
4050	mutex_t lock; /* global loop lock */
4051	ev_async async_w;
4052	thread_t tid;
4053	cond_t invoke_cv;
4054	} userdata;
4055
4056	void prepare_loop (EV_P)
4057	{
4058	// for simplicity, we use a static userdata struct.
4059	static userdata u;
4060
4061	ev_async_init (&u->async_w, async_cb);
4062	ev_async_start (EV_A_ &u->async_w);
4063
4064	pthread_mutex_init (&u->lock, 0);
4065	pthread_cond_init (&u->invoke_cv, 0);
4066
4067	// now associate this with the loop
4068	ev_set_userdata (EV_A_ u);
4069	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4070	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4071
4072	// then create the thread running ev_loop
4073	pthread_create (&u->tid, 0, l_run, EV_A);
4074	}
4075
4076	The callback for the C<ev_async> watcher does nothing: the watcher is used
4077	solely to wake up the event loop so it takes notice of any new watchers
4078	that might have been added:
4079
4080	static void
4081	async_cb (EV_P_ ev_async *w, int revents)
4082	{
4083	// just used for the side effects
4084	}
4085
4086	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4087	protecting the loop data, respectively.
4088
4089	static void
4090	l_release (EV_P)
4091	{
4092	userdata *u = ev_userdata (EV_A);
4093	pthread_mutex_unlock (&u->lock);
4094	}
4095
4096	static void
4097	l_acquire (EV_P)
4098	{
4099	userdata *u = ev_userdata (EV_A);
4100	pthread_mutex_lock (&u->lock);
4101	}
4102
4103	The event loop thread first acquires the mutex, and then jumps straight
4104	into C<ev_loop>:
4105
4106	void *
4107	l_run (void *thr_arg)
4108	{
4109	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4110
4111	l_acquire (EV_A);
4112	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4113	ev_loop (EV_A_ 0);
4114	l_release (EV_A);
4115
4116	return 0;
4117	}
4118
4119	Instead of invoking all pending watchers, the C<l_invoke> callback will
4120	signal the main thread via some unspecified mechanism (signals? pipe
4121	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4122	have been called (in a while loop because a) spurious wakeups are possible
4123	and b) skipping inter-thread-communication when there are no pending
4124	watchers is very beneficial):
4125
4126	static void
4127	l_invoke (EV_P)
4128	{
4129	userdata *u = ev_userdata (EV_A);
4130
4131	while (ev_pending_count (EV_A))
4132	{
4133	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4134	pthread_cond_wait (&u->invoke_cv, &u->lock);
4135	}
4136	}
4137
4138	Now, whenever the main thread gets told to invoke pending watchers, it
4139	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4140	thread to continue:
4141
4142	static void
4143	real_invoke_pending (EV_P)
4144	{
4145	userdata *u = ev_userdata (EV_A);
4146
4147	pthread_mutex_lock (&u->lock);
4148	ev_invoke_pending (EV_A);
4149	pthread_cond_signal (&u->invoke_cv);
4150	pthread_mutex_unlock (&u->lock);
4151	}
4152
4153	Whenever you want to start/stop a watcher or do other modifications to an
4154	event loop, you will now have to lock:
4155
4156	ev_timer timeout_watcher;
4157	userdata *u = ev_userdata (EV_A);
4158
4159	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4160
4161	pthread_mutex_lock (&u->lock);
4162	ev_timer_start (EV_A_ &timeout_watcher);
4163	ev_async_send (EV_A_ &u->async_w);
4164	pthread_mutex_unlock (&u->lock);
4165
4166	Note that sending the C<ev_async> watcher is required because otherwise
4167	an event loop currently blocking in the kernel will have no knowledge
4168	about the newly added timer. By waking up the loop it will pick up any new
4169	watchers in the next event loop iteration.
4170		4911
4171	=head3 COROUTINES	4912	=head3 COROUTINES
4172		4913
4173	Libev is very accommodating to coroutines ("cooperative threads"):	4914	Libev is very accommodating to coroutines ("cooperative threads"):
4174	libev fully supports nesting calls to its functions from different	4915	libev fully supports nesting calls to its functions from different
4175	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4916	coroutines (e.g. you can call C<ev_run> on the same loop from two
4176	different coroutines, and switch freely between both coroutines running	4917	different coroutines, and switch freely between both coroutines running
4177	the loop, as long as you don't confuse yourself). The only exception is	4918	the loop, as long as you don't confuse yourself). The only exception is
4178	that you must not do this from C<ev_periodic> reschedule callbacks.	4919	that you must not do this from C<ev_periodic> reschedule callbacks.
4179		4920
4180	Care has been taken to ensure that libev does not keep local state inside	4921	Care has been taken to ensure that libev does not keep local state inside
4181	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4922	C<ev_run>, and other calls do not usually allow for coroutine switches as
4182	they do not call any callbacks.	4923	they do not call any callbacks.
4183		4924
4184	=head2 COMPILER WARNINGS	4925	=head2 COMPILER WARNINGS
4185		4926
4186	Depending on your compiler and compiler settings, you might get no or a	4927	Depending on your compiler and compiler settings, you might get no or a
…		…
4197	maintainable.	4938	maintainable.
4198		4939
4199	And of course, some compiler warnings are just plain stupid, or simply	4940	And of course, some compiler warnings are just plain stupid, or simply
4200	wrong (because they don't actually warn about the condition their message	4941	wrong (because they don't actually warn about the condition their message
4201	seems to warn about). For example, certain older gcc versions had some	4942	seems to warn about). For example, certain older gcc versions had some
4202	warnings that resulted an extreme number of false positives. These have	4943	warnings that resulted in an extreme number of false positives. These have
4203	been fixed, but some people still insist on making code warn-free with	4944	been fixed, but some people still insist on making code warn-free with
4204	such buggy versions.	4945	such buggy versions.
4205		4946
4206	While libev is written to generate as few warnings as possible,	4947	While libev is written to generate as few warnings as possible,
4207	"warn-free" code is not a goal, and it is recommended not to build libev	4948	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4243	I suggest using suppression lists.	4984	I suggest using suppression lists.
4244		4985
4245		4986
4246	=head1 PORTABILITY NOTES	4987	=head1 PORTABILITY NOTES
4247		4988
		4989	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4990
		4991	GNU/Linux is the only common platform that supports 64 bit file/large file
		4992	interfaces but I<disables> them by default.
		4993
		4994	That means that libev compiled in the default environment doesn't support
		4995	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4996
		4997	Unfortunately, many programs try to work around this GNU/Linux issue
		4998	by enabling the large file API, which makes them incompatible with the
		4999	standard libev compiled for their system.
		5000
		5001	Likewise, libev cannot enable the large file API itself as this would
		5002	suddenly make it incompatible to the default compile time environment,
		5003	i.e. all programs not using special compile switches.
		5004
		5005	=head2 OS/X AND DARWIN BUGS
		5006
		5007	The whole thing is a bug if you ask me - basically any system interface
		5008	you touch is broken, whether it is locales, poll, kqueue or even the
		5009	OpenGL drivers.
		5010
		5011	=head3 C<kqueue> is buggy
		5012
		5013	The kqueue syscall is broken in all known versions - most versions support
		5014	only sockets, many support pipes.
		5015
		5016	Libev tries to work around this by not using C<kqueue> by default on this
		5017	rotten platform, but of course you can still ask for it when creating a
		5018	loop - embedding a socket-only kqueue loop into a select-based one is
		5019	probably going to work well.
		5020
		5021	=head3 C<poll> is buggy
		5022
		5023	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5024	implementation by something calling C<kqueue> internally around the 10.5.6
		5025	release, so now C<kqueue> I<and> C<poll> are broken.
		5026
		5027	Libev tries to work around this by not using C<poll> by default on
		5028	this rotten platform, but of course you can still ask for it when creating
		5029	a loop.
		5030
		5031	=head3 C<select> is buggy
		5032
		5033	All that's left is C<select>, and of course Apple found a way to fuck this
		5034	one up as well: On OS/X, C<select> actively limits the number of file
		5035	descriptors you can pass in to 1024 - your program suddenly crashes when
		5036	you use more.
		5037
		5038	There is an undocumented "workaround" for this - defining
		5039	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5040	work on OS/X.
		5041
		5042	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5043
		5044	=head3 C<errno> reentrancy
		5045
		5046	The default compile environment on Solaris is unfortunately so
		5047	thread-unsafe that you can't even use components/libraries compiled
		5048	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5049	defined by default. A valid, if stupid, implementation choice.
		5050
		5051	If you want to use libev in threaded environments you have to make sure
		5052	it's compiled with C<_REENTRANT> defined.
		5053
		5054	=head3 Event port backend
		5055
		5056	The scalable event interface for Solaris is called "event
		5057	ports". Unfortunately, this mechanism is very buggy in all major
		5058	releases. If you run into high CPU usage, your program freezes or you get
		5059	a large number of spurious wakeups, make sure you have all the relevant
		5060	and latest kernel patches applied. No, I don't know which ones, but there
		5061	are multiple ones to apply, and afterwards, event ports actually work
		5062	great.
		5063
		5064	If you can't get it to work, you can try running the program by setting
		5065	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5066	C<select> backends.
		5067
		5068	=head2 AIX POLL BUG
		5069
		5070	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5071	this by trying to avoid the poll backend altogether (i.e. it's not even
		5072	compiled in), which normally isn't a big problem as C<select> works fine
		5073	with large bitsets on AIX, and AIX is dead anyway.
		5074
4248	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5075	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5076
		5077	=head3 General issues
4249		5078
4250	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5079	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4251	requires, and its I/O model is fundamentally incompatible with the POSIX	5080	requires, and its I/O model is fundamentally incompatible with the POSIX
4252	model. Libev still offers limited functionality on this platform in	5081	model. Libev still offers limited functionality on this platform in
4253	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5082	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4254	descriptors. This only applies when using Win32 natively, not when using	5083	descriptors. This only applies when using Win32 natively, not when using
4255	e.g. cygwin.	5084	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5085	as every compiler comes with a slightly differently broken/incompatible
		5086	environment.
4256		5087
4257	Lifting these limitations would basically require the full	5088	Lifting these limitations would basically require the full
4258	re-implementation of the I/O system. If you are into these kinds of	5089	re-implementation of the I/O system. If you are into this kind of thing,
4259	things, then note that glib does exactly that for you in a very portable	5090	then note that glib does exactly that for you in a very portable way (note
4260	way (note also that glib is the slowest event library known to man).	5091	also that glib is the slowest event library known to man).
4261		5092
4262	There is no supported compilation method available on windows except	5093	There is no supported compilation method available on windows except
4263	embedding it into other applications.	5094	embedding it into other applications.
4264		5095
4265	Sensible signal handling is officially unsupported by Microsoft - libev	5096	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4293	you do I<not> compile the F<ev.c> or any other embedded source files!):	5124	you do I<not> compile the F<ev.c> or any other embedded source files!):
4294		5125
4295	#include "evwrap.h"	5126	#include "evwrap.h"
4296	#include "ev.c"	5127	#include "ev.c"
4297		5128
4298	=over 4
4299
4300	=item The winsocket select function	5129	=head3 The winsocket C<select> function
4301		5130
4302	The winsocket C<select> function doesn't follow POSIX in that it	5131	The winsocket C<select> function doesn't follow POSIX in that it
4303	requires socket I<handles> and not socket I<file descriptors> (it is	5132	requires socket I<handles> and not socket I<file descriptors> (it is
4304	also extremely buggy). This makes select very inefficient, and also	5133	also extremely buggy). This makes select very inefficient, and also
4305	requires a mapping from file descriptors to socket handles (the Microsoft	5134	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4314	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5143	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4315		5144
4316	Note that winsockets handling of fd sets is O(n), so you can easily get a	5145	Note that winsockets handling of fd sets is O(n), so you can easily get a
4317	complexity in the O(n²) range when using win32.	5146	complexity in the O(n²) range when using win32.
4318		5147
4319	=item Limited number of file descriptors	5148	=head3 Limited number of file descriptors
4320		5149
4321	Windows has numerous arbitrary (and low) limits on things.	5150	Windows has numerous arbitrary (and low) limits on things.
4322		5151
4323	Early versions of winsocket's select only supported waiting for a maximum	5152	Early versions of winsocket's select only supported waiting for a maximum
4324	of C<64> handles (probably owning to the fact that all windows kernels	5153	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4339	runtime libraries. This might get you to about C<512> or C<2048> sockets	5168	runtime libraries. This might get you to about C<512> or C<2048> sockets
4340	(depending on windows version and/or the phase of the moon). To get more,	5169	(depending on windows version and/or the phase of the moon). To get more,
4341	you need to wrap all I/O functions and provide your own fd management, but	5170	you need to wrap all I/O functions and provide your own fd management, but
4342	the cost of calling select (O(n²)) will likely make this unworkable.	5171	the cost of calling select (O(n²)) will likely make this unworkable.
4343		5172
4344	=back
4345
4346	=head2 PORTABILITY REQUIREMENTS	5173	=head2 PORTABILITY REQUIREMENTS
4347		5174
4348	In addition to a working ISO-C implementation and of course the	5175	In addition to a working ISO-C implementation and of course the
4349	backend-specific APIs, libev relies on a few additional extensions:	5176	backend-specific APIs, libev relies on a few additional extensions:
4350		5177
…		…
4356	Libev assumes not only that all watcher pointers have the same internal	5183	Libev assumes not only that all watcher pointers have the same internal
4357	structure (guaranteed by POSIX but not by ISO C for example), but it also	5184	structure (guaranteed by POSIX but not by ISO C for example), but it also
4358	assumes that the same (machine) code can be used to call any watcher	5185	assumes that the same (machine) code can be used to call any watcher
4359	callback: The watcher callbacks have different type signatures, but libev	5186	callback: The watcher callbacks have different type signatures, but libev
4360	calls them using an C<ev_watcher *> internally.	5187	calls them using an C<ev_watcher *> internally.
		5188
		5189	=item pointer accesses must be thread-atomic
		5190
		5191	Accessing a pointer value must be atomic, it must both be readable and
		5192	writable in one piece - this is the case on all current architectures.
4361		5193
4362	=item C<sig_atomic_t volatile> must be thread-atomic as well	5194	=item C<sig_atomic_t volatile> must be thread-atomic as well
4363		5195
4364	The type C<sig_atomic_t volatile> (or whatever is defined as	5196	The type C<sig_atomic_t volatile> (or whatever is defined as
4365	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5197	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4388	watchers.	5220	watchers.
4389		5221
4390	=item C<double> must hold a time value in seconds with enough accuracy	5222	=item C<double> must hold a time value in seconds with enough accuracy
4391		5223
4392	The type C<double> is used to represent timestamps. It is required to	5224	The type C<double> is used to represent timestamps. It is required to
4393	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5225	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4394	enough for at least into the year 4000. This requirement is fulfilled by	5226	good enough for at least into the year 4000 with millisecond accuracy
		5227	(the design goal for libev). This requirement is overfulfilled by
4395	implementations implementing IEEE 754, which is basically all existing	5228	implementations using IEEE 754, which is basically all existing ones.
		5229
4396	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5230	With IEEE 754 doubles, you get microsecond accuracy until at least the
4397	2200.	5231	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5232	is either obsolete or somebody patched it to use C<long double> or
		5233	something like that, just kidding).
4398		5234
4399	=back	5235	=back
4400		5236
4401	If you know of other additional requirements drop me a note.	5237	If you know of other additional requirements drop me a note.
4402		5238
…		…
4464	=item Processing ev_async_send: O(number_of_async_watchers)	5300	=item Processing ev_async_send: O(number_of_async_watchers)
4465		5301
4466	=item Processing signals: O(max_signal_number)	5302	=item Processing signals: O(max_signal_number)
4467		5303
4468	Sending involves a system call I<iff> there were no other C<ev_async_send>	5304	Sending involves a system call I<iff> there were no other C<ev_async_send>
4469	calls in the current loop iteration. Checking for async and signal events	5305	calls in the current loop iteration and the loop is currently
		5306	blocked. Checking for async and signal events involves iterating over all
4470	involves iterating over all running async watchers or all signal numbers.	5307	running async watchers or all signal numbers.
4471		5308
4472	=back	5309	=back
4473		5310
4474		5311
		5312	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5313
		5314	The major version 4 introduced some incompatible changes to the API.
		5315
		5316	At the moment, the C<ev.h> header file provides compatibility definitions
		5317	for all changes, so most programs should still compile. The compatibility
		5318	layer might be removed in later versions of libev, so better update to the
		5319	new API early than late.
		5320
		5321	=over 4
		5322
		5323	=item C<EV_COMPAT3> backwards compatibility mechanism
		5324
		5325	The backward compatibility mechanism can be controlled by
		5326	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5327	section.
		5328
		5329	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5330
		5331	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5332
		5333	ev_loop_destroy (EV_DEFAULT_UC);
		5334	ev_loop_fork (EV_DEFAULT);
		5335
		5336	=item function/symbol renames
		5337
		5338	A number of functions and symbols have been renamed:
		5339
		5340	ev_loop => ev_run
		5341	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5342	EVLOOP_ONESHOT => EVRUN_ONCE
		5343
		5344	ev_unloop => ev_break
		5345	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5346	EVUNLOOP_ONE => EVBREAK_ONE
		5347	EVUNLOOP_ALL => EVBREAK_ALL
		5348
		5349	EV_TIMEOUT => EV_TIMER
		5350
		5351	ev_loop_count => ev_iteration
		5352	ev_loop_depth => ev_depth
		5353	ev_loop_verify => ev_verify
		5354
		5355	Most functions working on C<struct ev_loop> objects don't have an
		5356	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5357	associated constants have been renamed to not collide with the C<struct
		5358	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5359	as all other watcher types. Note that C<ev_loop_fork> is still called
		5360	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5361	typedef.
		5362
		5363	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5364
		5365	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5366	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5367	and work, but the library code will of course be larger.
		5368
		5369	=back
		5370
		5371
4475	=head1 GLOSSARY	5372	=head1 GLOSSARY
4476		5373
4477	=over 4	5374	=over 4
4478		5375
4479	=item active	5376	=item active
4480		5377
4481	A watcher is active as long as it has been started (has been attached to	5378	A watcher is active as long as it has been started and not yet stopped.
4482	an event loop) but not yet stopped (disassociated from the event loop).	5379	See L<WATCHER STATES> for details.
4483		5380
4484	=item application	5381	=item application
4485		5382
4486	In this document, an application is whatever is using libev.	5383	In this document, an application is whatever is using libev.
		5384
		5385	=item backend
		5386
		5387	The part of the code dealing with the operating system interfaces.
4487		5388
4488	=item callback	5389	=item callback
4489		5390
4490	The address of a function that is called when some event has been	5391	The address of a function that is called when some event has been
4491	detected. Callbacks are being passed the event loop, the watcher that	5392	detected. Callbacks are being passed the event loop, the watcher that
4492	received the event, and the actual event bitset.	5393	received the event, and the actual event bitset.
4493		5394
4494	=item callback invocation	5395	=item callback/watcher invocation
4495		5396
4496	The act of calling the callback associated with a watcher.	5397	The act of calling the callback associated with a watcher.
4497		5398
4498	=item event	5399	=item event
4499		5400
4500	A change of state of some external event, such as data now being available	5401	A change of state of some external event, such as data now being available
4501	for reading on a file descriptor, time having passed or simply not having	5402	for reading on a file descriptor, time having passed or simply not having
4502	any other events happening anymore.	5403	any other events happening anymore.
4503		5404
4504	In libev, events are represented as single bits (such as C<EV_READ> or	5405	In libev, events are represented as single bits (such as C<EV_READ> or
4505	C<EV_TIMEOUT>).	5406	C<EV_TIMER>).
4506		5407
4507	=item event library	5408	=item event library
4508		5409
4509	A software package implementing an event model and loop.	5410	A software package implementing an event model and loop.
4510		5411
…		…
4518	The model used to describe how an event loop handles and processes	5419	The model used to describe how an event loop handles and processes
4519	watchers and events.	5420	watchers and events.
4520		5421
4521	=item pending	5422	=item pending
4522		5423
4523	A watcher is pending as soon as the corresponding event has been detected,	5424	A watcher is pending as soon as the corresponding event has been
4524	and stops being pending as soon as the watcher will be invoked or its	5425	detected. See L<WATCHER STATES> for details.
4525	pending status is explicitly cleared by the application.
4526
4527	A watcher can be pending, but not active. Stopping a watcher also clears
4528	its pending status.
4529		5426
4530	=item real time	5427	=item real time
4531		5428
4532	The physical time that is observed. It is apparently strictly monotonic :)	5429	The physical time that is observed. It is apparently strictly monotonic :)
4533		5430
4534	=item wall-clock time	5431	=item wall-clock time
4535		5432
4536	The time and date as shown on clocks. Unlike real time, it can actually	5433	The time and date as shown on clocks. Unlike real time, it can actually
4537	be wrong and jump forwards and backwards, e.g. when the you adjust your	5434	be wrong and jump forwards and backwards, e.g. when you adjust your
4538	clock.	5435	clock.
4539		5436
4540	=item watcher	5437	=item watcher
4541		5438
4542	A data structure that describes interest in certain events. Watchers need	5439	A data structure that describes interest in certain events. Watchers need
4543	to be started (attached to an event loop) before they can receive events.	5440	to be started (attached to an event loop) before they can receive events.
4544		5441
4545	=item watcher invocation
4546
4547	The act of calling the callback associated with a watcher.
4548
4549	=back	5442	=back
4550		5443
4551	=head1 AUTHOR	5444	=head1 AUTHOR
4552		5445
4553	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5446	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5447	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4554		5448

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